JP2007079214A - Polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate and a liquid crystal display device using the polarizing plate, which have high optical performance and improve light leakage at a peripheral portion of a screen due to temperature and humidity changes and continuous lighting of the liquid crystal display device.
The polarizer includes a polarizer, a protective film (1) provided on at least one surface of the polarizer, and an adhesive layer provided on the protective film (1). A polarizing plate having a rate of 0.15 MPa to 0.5 MPa and a thickness of the adhesive layer of 33 μm to 60 μm.
[Selection figure] None

Description

  The present invention relates to a polarizing plate in which light leakage caused by a change in temperature and humidity and a contraction stress of a polarizing plate in a peripheral portion of a screen in continuous lighting of a liquid crystal display device is improved, and a liquid crystal display device using the same.

  Liquid crystal display devices are widely used in monitors for personal computers and portable devices, and for television applications because of their various advantages such as low voltage and low power consumption, and enabling miniaturization and thinning. In such a liquid crystal display device, various modes have been proposed depending on the alignment state of the liquid crystal molecules in the liquid crystal cell. Conventionally, the liquid crystal display device is in an alignment state twisted by about 90 ° from the lower substrate to the upper substrate of the liquid crystal cell. The TN mode is the mainstream.

  In general, a liquid crystal display device includes a liquid crystal cell, an optical compensation sheet, and a polarizer. The optical compensation sheet is used for eliminating image coloring or expanding the viewing angle, and a stretched birefringent film or a film obtained by applying a liquid crystal to a transparent film is used.

  For example, Patent Document 1 discloses a technique in which a discotic liquid crystalline compound is applied on a triacetyl cellulose film and oriented, and a fixed optical compensation sheet is applied to a TN mode liquid crystal cell to widen the viewing angle. Yes. However, a liquid crystal display device for television that is expected to be viewed from various angles on a large screen has a strict requirement for viewing angle dependency, and even with the above-described method, the requirement cannot be satisfied. . Therefore, liquid crystal display devices different from the TN mode, such as an IPS (In-Plane Switching) mode, an OCB (Optically Compensatory Bend) mode, and a VA (Vertically Aligned) mode, have been studied. In particular, the VA mode is attracting attention as a liquid crystal display device for TV because of its high contrast and relatively high manufacturing yield.

  By the way, the cellulose acylate film is characterized by high optical isotropy (low retardation value) as compared with other polymer films. Therefore, it is common to use a cellulose acylate film for applications requiring optical isotropy, for example, for polarizing plates.

On the other hand, an optical anisotropy (high retardation value) is required for the optical compensation sheet (retardation film) of the liquid crystal display device. In particular, an optical compensation sheet for VA requires a front retardation (Re ₅₉₀ ) of 20 to 200 nm and a thickness direction retardation (Rth ₅₉₀ ) of 0 to 400 nm. Therefore, it is common to use a synthetic polymer film having a high retardation value such as a polycarbonate film or a polysulfone film as the optical compensation sheet.

  As described above, in the technical field of optical materials, when a polymer film requires optical anisotropy (high retardation value), a synthetic polymer film is used, and optical isotropy (low retardation value) is required. In some cases, it was common to use a cellulose acylate film.

  Patent Document 2 proposes a cellulose acetate film having a high retardation value that can be used for applications requiring optical anisotropy, overcoming conventional general techniques. In Patent Document 2, in order to achieve a high retardation value with cellulose triacetate, an aromatic compound having at least two aromatic rings, particularly a compound having a 1,3,5-triazine ring, is added and subjected to stretching treatment. ing. Cellulose triacetate is generally a polymer material that is difficult to stretch, and it is known that it is difficult to increase the birefringence, but it is necessary to increase the birefringence by simultaneously orienting the additives in the stretching process. To achieve a high retardation value. Since this film can also serve as a protective film for the polarizing plate, there is an advantage that an inexpensive and thin liquid crystal display device can be provided.

Patent Document 3 has an acyl group having 2 to 4 carbon atoms as a substituent, the substitution degree of acetyl group is A, and the substitution degree of propionyl group or butyryl group is B.
(Formula) 2.0 ≦ A + B ≦ 3.0
And (formula) A <2.4
An optical film containing a cellulose ester that simultaneously satisfies the above is disclosed.

  In Patent Document 4, a polarizing plate used in a VA mode liquid crystal display device, the polarizing plate has a polarizer and an optically biaxial mixed fatty acid cellulose ester film, and is disposed between the liquid crystal cell and the polarizer. A polarizing plate is disclosed in which the optically biaxial mixed fatty acid cellulose ester film is disposed.

  The method disclosed in the above-mentioned document is effective in that an inexpensive and thin liquid crystal display device can be obtained. However, in recent years, liquid crystal display devices are rapidly increasing in size and brightness, and light leakage at the periphery of the screen during black display due to contraction stress of the polarizing plate has become a problem. Although the polarizing plate tends to shrink due to changes in environmental temperature and humidity, it is fixed to the liquid crystal cell by the adhesive layer, so it is locally attached to the protective film of the polarizing plate, the adhesive layer, and the glass substrate of the liquid crystal cell (particularly the periphery of the screen). ), And light leakage occurs due to the change in birefringence due to the respective photoelasticity.

  When the liquid crystal cell with the polarizing plate attached was processed at high temperature, the water in the polarizing plate was released, resulting in significant shrinkage of the polarizing plate. The liquid crystal cell was taken out from the high temperature processing and from the high temperature processing to normal temperature and humidity. Immediately after that, light leakage occurs strongly. Thereafter, when the polarizing plate is left under normal temperature and humidity, the polarizing plate absorbs moisture and the contraction force of the polarizing plate decreases, so that light leakage also becomes weak. Even under normal temperature and humidity, when the backlight is continuously turned on, the temperature of the polarizing plate rises, and light leakage similar to that in the high temperature treatment occurs.

When a liquid crystal cell with a polarizing plate attached is processed under high temperature and high humidity, the polarizing plate absorbs moisture and is left at room temperature and humidity to release moisture in the polarizing plate. The shrinkage force increases. As this contraction force increases, light leakage increases.
Therefore, there is a demand for improvement in light leakage at the periphery of the screen due to such changes in temperature and humidity and continuous lighting.

  In the TN mode, the light leakage as described above has been improved by softening the pressure-sensitive adhesive layer that bonds the polarizing plate to the liquid crystal cell and relaxing the shrinkage stress applied to the optical compensation film. Patent Documents 5 to 7 disclose that the shrinkage stress is alleviated by increasing the creep value of the adhesive layer.

  In addition, it has been disclosed to reduce various elastic moduli of an adhesive layer for bonding a polarizing plate or an optical compensation film to a liquid crystal cell in order to reduce shrinkage stress. For example, the relaxation elastic modulus (Patent Document 8), the elastic modulus (Patent Documents 9 to 12), and the shear elastic modulus (Patent Document 13) can be mentioned.

  In order to make the pressure-sensitive adhesive layer relieve the shrinkage stress as described above, it is effective to reduce the gel fraction of the pressure-sensitive adhesive layer that bonds the polarizing plate or the optical compensation film to the liquid crystal cell as disclosed in Patent Document 14. It is believed that.

  Further, conventionally, the adhesive layer is softened in order to relieve the stress as described above, and the adhesive force of the adhesive layer is weakened in order to impart reworkability to the polarizing plate as disclosed in Patent Documents 15 to 17. I was designing.

  Further, in Patent Document 18, in the TN mode, in order to eliminate the light leakage as described above, it is only necessary to reduce the change in the optical characteristics of the optical compensation sheet and further reduce the temperature distribution generated in the optical compensation sheet. It is disclosed that the change in the optical characteristics is determined by the product of the photoelastic coefficient of the optical compensation sheet, the thickness, the virtual strain due to the change in environmental conditions, and the elastic modulus. Accordingly, it is disclosed that light leakage is remarkably reduced by lowering the photoelastic coefficient of the optical compensation sheet, reducing the thickness, reducing distortion due to changes in environmental conditions, and reducing the elastic modulus. That is, in the TN mode, it was considered that the elastic modulus of the protective film of the polarizing plate is small and the thin film thickness is effective in reducing light leakage.

Japanese Patent No. 2587398 European Patent Application No. 91656 JP 2002-71957 A JP 2003-270442 A JP 2001-272541 A JP 2003-50313 A JP 2001-350020 A JP-A-11-52133 JP 2001-272542 A JP 2000-321992 A JP 2000-162584 A JP 2000-155215 A JP 2001-272544 A JP 2000-155213 A JP-A-11-258419 JP 2000-9973 A JP 2004-78171 A JP 2002-139621 A

  An object of the present invention is to provide a polarizing plate and a liquid crystal display device using the polarizing plate, which have high optical performance and improve light leakage at the periphery of the screen due to temperature and humidity changes and continuous lighting of the liquid crystal display device. It is. In particular, it is to provide a polarizing plate and a liquid crystal display device using the polarizing plate, which have a high optical compensation function and improve light leakage at the periphery of the screen due to temperature and humidity changes and continuous lighting of the liquid crystal display device.

As a result of intensive studies, the present inventors have found that in the liquid crystal display device in which the absorption axes of the polarizing plates on the front and back of the liquid crystal cell are orthogonal to each other and the absorption axis is parallel to the side (long side or short side) of the liquid crystal cell. Unlike the polarizing plate of a liquid crystal display device in which the absorption axes of the polarizing plates on the front and back of the liquid crystal cell are orthogonal to each other and the absorption axis forms 45 degrees with the long side or the short side of the liquid crystal cell, The resulting light leakage at the periphery of the screen appears at the corner of the screen. The cause of the difference was also different, and it was discovered that the retardation produced by the photoelasticity on the protective film of the polarizing plate and the glass hardly affected, and only the retardation produced in the adhesive layer was the main cause and light leakage occurred. Accordingly, it was found that when the panel size of the display device is increased, if the adhesive layer is soft, the distortion generated in the adhesive layer increases and the leakage light increases remarkably. Therefore, it has been found that when the panel size is larger than 20 inches, the increase in leakage light can be suppressed if the adhesive layer is hardened to suppress distortion generated in the adhesive layer.
That is, the present invention is a polarizing plate and a liquid crystal display device having the following constitutions, thereby achieving the object of the present invention.

(1) A polarizer, a protective film (1) provided on at least one surface of the polarizer, and an adhesive layer provided on the protective film (1), and an elastic modulus of the adhesive layer Is a polarizing plate having a thickness of 0.15 MPa to 0.5 MPa and a thickness of the adhesive layer of 33 μm to 60 μm.
(2) The polarizing plate according to (1), wherein the size of the polarizing plate is 18 inches or more.
(3) The polarizing plate according to (1) or (2), wherein the direction of the absorption axis of the polarizing plate is substantially parallel or perpendicular to the side of the polarizing plate.
(4) The polarizing plate according to any one of (1) to (3), wherein the protective film (1) is stretched by 25% or more.
(5) The polarizing plate according to any one of (1) to (4), wherein the protective film (1) is biaxially stretched.
(6) The front retardation value (Reλ) and the retardation value (Rthλ) in the film thickness direction of the protective film (1) satisfy the following formulas (2) and (3): (1) to (5) The polarizing plate of any one.
Formula (2) 0 ≦ Re ₅₉₀ ≦ 200
Formula (3) 0 ≦ Rth ₅₉₀ ≦ 400
(In Equations (2) and (3), Reλ and Rth ₀ λ are, in order, a value at a wavelength λ nm, a front retardation value, and a retardation value in the film thickness direction (unit: nm).)
(7) The protective film (1) includes a mixed fatty acid ester of cellulose in which a hydroxyl group of cellulose is substituted with an acetyl group and an acyl group having 3 or more carbon atoms, the substitution degree A of the acetyl group and the carbon atom The polarizing plate according to any one of (1) to (6), wherein the substitution degree B of the acyl group having 3 or more satisfies the following mathematical formulas (4) and (5).
Formula (4): 2.0 ≦ A + B ≦ 3.0
Formula (5): 0 <B
(8) The polarizing plate according to (7), wherein the acyl group having 3 or more carbon atoms is a propionyl group or a butanoyl group.
(9) The polarizing plate according to (7) or (8), wherein the substitution degree of the hydroxyl group at the 6-position of the cellulose is 0.75 or more.
(10) Glucose in which the protective film (1) includes cellulose acylate obtained by substituting a hydroxyl group of glucose units constituting cellulose with an acyl group having 2 or more carbon atoms, and constituting the cellulose degree of substitution DS ₆ by substitution degree DS _2, 3-position of the hydroxyl group of the acyl group by substitution degree DS _3, 6 position hydroxyl group an acyl group by 2-position of the hydroxyl group an acyl group of the unit, the following equation (6) and (7 The polarizing plate according to any one of (1) to (9).
Formula (6): 2.0 ≦ DS ₂ + DS ₃ + DS ₆ ≦ 3.0
Formula (7): DS ₆ / (DS ₂ + DS ₃ + DS ₆ ) ≧ 0.315
(11) The polarizing plate according to (10), wherein the acyl group is an acetyl group.
(12) The polarizing plate according to any one of (1) to (11), wherein the protective film (1) contains one or more retardation enhancers.
(13) Any one of (1) to (12), wherein the protective film (1) contains one or more of a plasticizer, an ultraviolet absorber, a peeling accelerator, a dye, and a matting agent. The polarizing plate as described in.
(14) A liquid crystal display device having a liquid crystal cell and a polarizing plate, wherein at least one of the polarizing plates is the polarizing plate according to any one of (1) to (13).
(15) The protective film (1) of the polarizing plate according to any one of (1) to (13) is disposed so as to be positioned on the side of the liquid crystal cell. Liquid crystal display device.
(16) The liquid crystal cell is sandwiched between a pair of polarizing plates, the transmission axes of the pair of polarizing plates are arranged orthogonal to each other, and the transmission axis is substantially with respect to the side of the polarizing plate. The liquid crystal display device according to (14) or (15), which is orthogonal or parallel to each other.
(17) The liquid crystal display device according to any one of (14) to (16), wherein the liquid crystal cell is in a VA mode.

  The liquid crystal display device using the polarizing plate of the present invention improved the light leakage at the peripheral portion of the black display screen when the temperature and humidity changes or the liquid crystal display device is continuously lit.

Hereinafter, the contents of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
In the present specification, the description “(meth) acrylate” means “at least one of acrylate and methacrylate”. The same applies to “(meth) acrylic acid” and the like.
Furthermore, the side of the polarizing plate in the present specification refers to a side corresponding to the side of the rectangle when the polarizing plate is regarded as a rectangle, for example. In particular, in the case of having a long side and a short side, the longer side may be called the long side and the shorter side may be called the short side. Unless otherwise stated, either the long side or the short side may be used.

  Conventionally, in the liquid crystal display device in which the absorption axes of the polarizing plates on the front and back of the liquid crystal cell are orthogonal to each other and the absorption axis forms 45 degrees with the side of the liquid crystal cell as in the TN mode, the polarizing plate can be used for a long time. The internal stress caused by the dimensional change of the polarizing plate concentrates on the peripheral edge of the polarizing plate, causing light leakage at the periphery of the screen of the liquid crystal display device. This light leakage can alleviate the internal stress due to the dimensional change of the polarizing plate. Such relaxation has been realized by causing the adhesive layer to follow the dimensional change of the polarizing plate. However, as a result of intensive studies, the inventors of the present invention, as a result of VA mode, have polarized axes of the liquid crystal display device in which the absorption axes of the polarizing plates on the front and back of the liquid crystal cell are orthogonal to each other and the absorption axis is parallel to the sides of the liquid crystal cell In the plate, unlike in the case of the liquid crystal display device in which the absorption axis of the polarizing plate is 45 degrees with the side of the liquid crystal cell, such as the TN mode, light leakage at the periphery of the screen due to the contraction stress of the polarizer is Appears in the corner of the screen. The cause of the difference was also different, and it was discovered that the retardation produced by the photoelasticity on the protective film of the polarizing plate and the glass hardly affected, and only the retardation produced in the adhesive layer was the main cause and light leakage occurred. Accordingly, it has been found that when the panel size of the display device is increased, if the adhesive layer is soft, the distortion generated in the adhesive layer increases and the leakage light increases remarkably. Accordingly, it has been found that when the panel size is larger than 19 inches, the increase in leakage light can be suppressed by hardening the adhesive layer and suppressing the distortion generated in the adhesive layer.

(Adhesive layer)
First, the adhesive layer relating to the present invention will be described.
When the liquid crystal display device is left under high temperature, when the environment is changed from high temperature and high humidity to low temperature and low humidity, or when the backlight is continuously displayed, the dimensional change of the polarizing plate occurs. Accordingly, foaming of the adhesive layer and peeling from the adherend such as a liquid crystal cell are likely to occur. Conventional pressure-sensitive adhesive layers have been designed to withstand the use of the pressure-sensitive adhesive layer under the above severe conditions by increasing the molecular weight of the pressure-sensitive adhesive layer or increasing the degree of crosslinking.

  On the other hand, as described above, in the liquid crystal display device in which the absorption axis is substantially 45 degrees with the side of the liquid crystal cell as in the TN mode, light leakage at the periphery of the screen of the liquid crystal display device caused by the dimensional change of the polarizing plate. Has been improved by softening the adhesive layer and relieving internal stress due to dimensional changes of the polarizing plate, but in the polarizing plate of a liquid crystal display device in which the absorption axis is substantially parallel to the side of the liquid crystal cell, such as the VA mode. If the panel size is larger than 19 inches, light leakage at the periphery of the screen due to the contraction stress of the polarizer can be reduced if the adhesive layer is hardened to suppress distortion generated in the adhesive layer. It was found that the increase can be suppressed.

Therefore, in order to prevent foaming, peeling, and dimensional change of the polarizing plate that occur under severe conditions as described above, as a result of voluntary examination, the elastic modulus of the adhesive layer is set to 0.15 MPa to 0.5 MPa, and It has been found that the problem can be solved by setting the thickness of the adhesive layer to 33 μm to 60 μm.
Furthermore, in the pressure-sensitive adhesive layer of the present invention, three-dimensional crosslinking (gelation), glass transition temperature (Tg) when made into a homopolymer is low, that is, use of soft (meth) acrylic acid ester, molecular weight distribution (high molecular weight component and By adopting means such as the ratio of low molecular weight components, the balance between adhesion performance and hardness can be adjusted.
In particular, the balance between adhesion performance and hardness can be adjusted by the composition ratio of monomer components (low Tg compound and high Tg compound) constituting the copolymer and the degree of three-dimensional crosslinking (gel fraction).

Measurement of Tg As described above, Tg in the present invention refers to Tg in the case of a homopolymer unless otherwise specified. Here, the Tg was measured using a differential thermal scanning calorimeter (DSC2910, manufactured by TA Instruments). The polymer was put in an aluminum pan, the temperature was increased from −160 ° C. to + 100 ° C. at 10 ° C./min, and then the temperature was decreased from + 100 ° C. to −160 ° C. at 10 ° C./min, and Tg was obtained from the data of the temperature decrease process. .

(Meth) acrylic copolymer (A)
Below, the (meth) acrylic-type copolymer which is a preferable polymer used for the adhesion layer of this invention is demonstrated.
The (meth) acrylic copolymer in the present invention is a monomer having (a1) a repeating unit derived from a (meth) acrylic acid ester monomer having a Tg of less than −30 ° C. and (a2) a vinyl group having a Tg of −30 ° C. or more. It is preferable to have a repeating unit derived from (vinyl compound).
By adopting such a polymer, the cohesiveness of the pressure-sensitive adhesive layer can be increased, and the performance of the pressure-sensitive adhesive layer such as pressure-sensitive adhesiveness, water resistance, transparency, and workability can be further improved.

(A1) (Meth) acrylic acid ester monomer having Tg of less than −30 ° C. In the present invention, it is preferable to use a (meth) acrylic acid ester monomer having a Tg of less than −30 ° C. in order to relieve internal stress. Tg is more preferably less than −40 ° C., and further preferably less than −50 ° C. Examples of (meth) acrylic acid esters having a Tg of less than −30 ° C. include ethyl acrylate, propyl acrylate, n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, and n-nonyl. Acrylate, n-decyl acrylate, 2-methoxyethyl acrylate, ethoxymethyl acrylate, 2-ethoxyethyl acrylate, 3-ethoxypropyl acrylate, n-octyl methacrylate, n-nonyl methacrylate, n-decyl methacrylate, n-undecacil methacrylate , N-dodecyl methacrylate, n-dodecyl methacrylate and the like.
(A2) Monomer having a vinyl group with a Tg of −30 ° C. or higher (vinyl compound)
Examples of vinyl compounds having a Tg of −30 ° C. or higher include methyl acrylate, isobutyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, benzyl acrylate, n-undecyl acrylate, n-dodecyl acrylate, n-tridecyl acrylate, and n-tetra Decyl acrylate, n-pentadecyl acrylate, n-hexadecyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, cyclohexyl Methacrylate, benzyl methacrylate, n-heptyl methacrylate, n-tetradecyl methacrylate, n- Printer decyl methacrylate, (meth) acrylates such as n- hexadecyl methacrylate. Examples of other vinyl compounds include vinyl acetate, styrene, methyl styrene, vinyl toluene, acrylonitrile, (meth) acrylamide, and N-methyl acrylamide.

In the present invention, the repeating unit RU _S derived from the above (meth) acrylic acid ester having a Tg of less than −30 ° C. and a vinyl compound having a Tg of −30 ° C. or more is used. The ratio of unit RU _H is a mass ratio of monomer units, and RU _S is preferably 75 parts by mass or more, more preferably 85 parts by mass or more, and may be 100 parts by mass at the maximum. Further, RU _H is preferably 25 parts by mass or less, more preferably 15 parts by mass or less, and a minimum of 0 parts by mass may be provided.

(A3) Functional group-containing monomer having reactivity with respect to polyfunctional compound (B) Furthermore, in the (meth) acrylic copolymer (A) of the present invention, it reacts with polyfunctional compound (B). A functional group-containing monomer having a property may be included.
Examples of functional group-containing monomers include monomers containing carboxyl groups such as (meth) acrylic acid, β-carboxyethyl acrylate, itaconic acid, crotonic acid, maleic acid, maleic anhydride, and butyl maleate; 2-hydroxyethyl (meta ) Monomers containing hydroxyl groups such as acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, chloro-2-hydroxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate and allyl alicol; Amino groups such as aminomethyl (meth) acrylate, dimethylaminomethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate and vinylpyridine And the like monomers containing glycidyl (meth) acetoacetyl group, such as a monomer containing an epoxy group and acetoacetoxyethyl (meth) acrylates such as acrylate; monomers containing. These can be used alone or in combination.
Among these, a monomer containing a carboxyl group and a monomer containing a hydroxyl group are preferable.

  The content of the functional group-containing monomer is based on a total of 100 parts by mass of the (meth) acrylic acid ester monomer (a1) having a Tg of less than −30 ° C. and the vinyl compound (a2) having a Tg of −30 ° C. or more. Preferably it is 10 mass parts or less, More preferably, it is 0.5-10 mass parts.

  By copolymerizing the (meth) acrylic acid ester monomer (a1), the vinyl compound (a2), and the functional group-containing monomer (a3) having reactivity with respect to the polyfunctional compound in the amount as described above, A copolymer composition having better adhesion can be formed by combining with the polyfunctional compound (B).

(B) Polyfunctional compound It is preferable that the adhesion layer in this invention contains the polyfunctional compound (B) which has a reactive functional group.
The functional group of the polyfunctional compound reacts with the reactive functional group of the (meth) acrylic polymer (A), and has at least two functional groups in one molecule, preferably It has 2-4 pieces.

  Examples of such a polyfunctional compound (B) include isocyanate compounds, epoxy compounds, amine compounds, metal chelate compounds, and aziridine compounds.

  Examples of isocyanate compounds include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane trisene. Examples thereof include adducts such as isocyanate, polymethylene polyphenyl isocyanate, and polyols such as trimethylolpropane.

  Examples of the epoxy compound include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol. Diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine, N, N, N ′, N′-tetraglycidyl-m-xylenediamine and 1,3-bis (N, N′-diglycidyl Aminomethyl) cyclohexane and the like.

  Furthermore, examples of amine compounds include amino resins such as hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isophoronediamine, urea resin, melamine resin, and methylene resin. .

  Furthermore, examples of metal chelate compounds include compounds in which polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium are coordinated to acetylacetone or ethyl acetoacetate. And so on.

  Further, examples of the aziridine-based compound include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxide), N, N′-toluene-2,4-bis (1-aziridinecarboxamide), Triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tri-1-aziridinylphosphine oxide, N, N′-hexamethylene-1,6-bis (1-aziridinecarboxyde), tri Mention may be made of methylolpropane-tri-β-aziridinylpropionate and tetramethylolmethane-tri-β-aziridinylpropionate.

  In addition, dialdehydes, methylol polymers, acids, acid anhydrides, amino acids, and the like can be used.

  Such a polyfunctional compound (B) is preferably 0.005 to 5 parts by mass, more preferably 0.01 to 100 parts by mass with respect to 100 parts by mass of the high molecular weight (meth) acrylic copolymer (A). Used in an amount of 3 parts by weight. By using the polyfunctional compound (B) in such an amount, a more suitable three-dimensional crosslinked structure is formed with the high molecular weight (meth) acrylic copolymer. In addition, these polyfunctional compounds (B) can be used individually or in combination of 2 or more types.

Manufacture of (meth) acrylic copolymer Any known method can be employed for manufacturing the (meth) acrylic copolymer (A) constituting the adhesive layer in the present invention.

For example, a high molecular weight (meth) acrylic copolymer (A ¹ ) having a mass average molecular weight of 1,000,000 or more is from 0.01 to 1 part by mass of a polymerization initiator (azobisiso) relative to 100 parts by mass of the raw material monomer. Azo polymerization initiators such as vityronitrile and azobiscyclohexanecarbonitrile, peroxides such as benzoyl peroxide and acetyl peroxide, diphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one For example, a photopolymerization initiator such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, and the like, preferably by solution polymerization.

  In the case of the solution polymerization method, ethyl acetate, toluene, hexane, acetone or the like is used as a polymerization solvent, the reaction temperature is preferably 50 to 150 ° C., more preferably 50 to 110 ° C., the reaction time is preferably 3 to 15 hours, More preferably, it is 5 to 10 hours.

In addition, the low molecular weight (meth) acrylic (co) polymer (A ² ) having a polymerization average molecular weight of 100,000 or less is a block polymerization, solution polymerization, emulsion polymerization as in the case of the high molecular weight acrylic copolymer (A ¹ ). And synthesized by a method such as suspension polymerization, preferably by solution polymerization. However, in order to make the mass average molecular weight 100,000 or less, the amount of the polymerization initiator used is about 10 to 100 times that of the high molecular weight acrylic copolymer, and more preferably lauryl mercaptan, n-dodecyl mercaptan, n-octyl. Chain transfer agents such as mercaptans such as mercaptans, α-methylstyrene dimers and limonene are used.

Production of Adhesive Layer The adhesive layer in the present invention can be produced using a composition containing the (meth) acrylic copolymer (A) and the polyfunctional compound (B) produced as described above.
As (A), either the high molecular weight (meth) acrylic copolymer (A ¹ ) or the high molecular weight (meth) acrylic copolymer (A ² ) may be used, or both may be used. .
When both are used, the low molecular weight (meth) acrylic (co) polymer (A ² ) is preferably 20 to 200 with respect to 100 parts by mass of the high molecular weight (meth) acrylic copolymer (A ¹ ). It is a mass part, More preferably, it is 30-150 mass parts. The polyfunctional compound (B) is preferably 0.005 to 5 parts by mass, more preferably 0.005 parts by mass with respect to 100 parts by mass of the high molecular weight (meth) acrylic copolymer (A ¹ ). It contains in the range of 01-3 mass parts.

In order to relieve internal stress, in addition to using a (meth) acrylic acid ester having a low Tg, a three-dimensional crosslinked structure was prepared with a high molecular weight (meth) acrylate copolymer (A ¹ ). It can also be carried out by moving (sliding) the low molecular weight (meth) acrylate copolymer (A ² ) in the three-dimensional crosslinked structure. Specifically, it can be carried out according to the method described in Japanese Patent No. 3533589. In the present invention, the degree of relaxation of the internal stress is such that the (meth) acrylic copolymer (A ¹ ) having a high molecular weight (mass average molecular weight of 1 million or more) and a low molecular weight (mass average molecular weight is 100,000). The following can be adjusted by the introduction amount of the repeating unit derived from the functional group-containing monomer in the (meth) acrylic copolymer (A ² ). Preferably, the functional group distribution defined by the following formula (12) is preferably 0 to 15% by mass, and more preferably 0 to 10% by mass.
Formula (12)
Functional group distribution ratio = [mass of repeating unit derived from functional group-containing monomer in (meth) acrylic copolymer (A ² ) / functional group content in (meth) acrylic copolymer (A ¹ ) Mass of repeating unit derived from monomer] × 100

The degree of three-dimensional crosslinking (gel fraction) in the adhesive layer of the present invention is preferably 40% by mass to 90% by mass, more preferably 60% by mass to 90% by mass, and 70% by mass. More preferably, it is -90 mass%.
By setting it within the above-mentioned range, it is possible to adjust the balance between adhesion performance and relaxation more significantly, which is preferable. The degree of three-dimensional crosslinking can be adjusted by the amount of the polymerizable monomer having reactivity with the polyfunctional compound and the amount of the polyfunctional compound.

  The adhesive layer in the present invention is mainly composed of a composition of a (meth) acrylic copolymer comprising the (meth) acrylic copolymer (A) and the polyfunctional compound (B) as described above. In addition, the adhesive layer is usually blended with the adhesive layer in this type of field, weather resistance stabilizer, tackifier, plasticizer, softener, dye, pigment, silane coupling agent and conductive fine particles / light scattering properties. An inorganic filler such as fine particles can be blended.

The elastic modulus of the adhesive layer in the present invention is measured with a Tensilon (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a pulling rate of 10 mm / min and normal temperature and humidity at a width of 5 mm, a thickness of 1 mm, and a distance between chucks of 10 mm. Value.
In the present invention, the elastic modulus of the adhesive layer is 0.15 MPa to 0.5 MPa, preferably 0.20 MPa to 0.4 MPa, and more preferably 0.25 MPa to 0.35 MPa.
Moreover, in this invention, the film thickness of the adhesion layer is 33 micrometers-60 micrometers, and 34 micrometers-50 micrometers are more preferable.

(Protective film)
Next, the protective film of the present invention will be described.
The polarizing plate of the present invention has protective films on both sides of the polarizer. As the protective film, any protective film that is usually used as a protective film for a polarizing plate can be used. In the present invention, it is preferable to use a cellulose acylate film or a cycloolefin polymer. The protective films on both sides may be the same or different. For example, among the protective films on both sides of the polarizer, the aforementioned cellulose acylate film can be used on one side, and a cycloolefin-based polymer on the other side. Also, films having different compositions and different optical characteristics can be used. Furthermore, it is good also as a protective film by providing a polymer layer on a cellulose acylate film, a cycloolefin type polymer film, etc. For example, a polyimide layer can be provided on a cellulose acylate film to form a protective film. In the polarizing plate of the present invention, an adhesive layer is provided on at least one surface (one side of the polarizer) of the protective film (1) or the surface of the protective film via another functional layer.

Cellulose acylate film Next, a cellulose acylate film preferably used as a protective film in the present invention will be described.
The cellulose acylate film preferably used in the present invention can be formed using a specific cellulose acylate as a raw material. The cellulose acylate used for increasing the optical anisotropy and for decreasing the optical anisotropy may be used properly.

Cellulose acylate for increasing optical anisotropy First, cellulose acylate for increasing optical anisotropy will be described in detail. The cellulose acylate used here may be only one type or two or more types.

The cellulose acylate includes a mixed fatty acid ester of cellulose in which a hydroxyl group of cellulose is substituted with an acetyl group and an acyl group having 3 or more carbon atoms, and the degree of substitution A of the acetyl group and the number of carbon atoms is 3 or more. It is preferable that the substitution degree B of the acyl group satisfies the following formulas (4) and (5).
Formula (4): 2.0 ≦ A + B ≦ 3.0
Formula (5): 0 <B

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification has a degree of substitution of 1).

  In the present invention, the total substitution degree (A + B) of hydroxyl groups A and B is preferably 2.0 to 3.0, as shown in the above formula (4), and 2.2 to 2.9. It is more preferable that it is 2.40-2.85. Further, the substitution degree of B is preferably larger than 0, and more preferably 0.6 or more, as shown in the above formula (5). If (A + B) is 2.0 or more, the hydrophilicity becomes too strong and it is difficult to cause inconveniences such as being easily affected by environmental humidity.

  Further, B in the above formula (5) has a 6-position substitution degree with respect to the total substitution degree of preferably 0.28 or more, more preferably 0.30 or more, and further preferably 0.31 or more. Preferably, it is most preferably 0.32.

  Furthermore, the sum of the substitution degrees of A and B at the 6-position of cellulose acylate is preferably 0.75 or more, more preferably 0.80 or more, and further preferably 0.85 or more. preferable. These cellulose acylates can produce a solution for film preparation having excellent solubility and filterability, and a good solution can be produced even in a non-chlorine organic solvent. Furthermore, it becomes possible to produce a solution having a low viscosity and good filterability.

Further, when the cellulose acylate film is a protective film disposed on the liquid crystal cell side of the polarizing plate, the substitution degree of the hydroxyl group at the 2-position of the glucose unit constituting the cellulose by the acyl group is DS ₂ , and the acyl at the hydroxyl group at the 3-position When the degree of substitution with a group is DS ₃ and the degree of substitution with an acyl group of the hydroxyl group at the 6-position is DS ₆ , it is preferable that the following mathematical formulas (6) and (7) are satisfied.
Formula (6): 2.0 ≦ DS ₂ + DS ₃ + DS ₆ ≦ 3.0
Formula (7): DS ₆ / (DS ₂ + DS ₃ + DS ₆ ) ≧ 0.315
Satisfying the above formulas (6) and (7) is preferable because the solubility of the cellulose acylate film in the solvent is improved and the humidity dependence of the optical anisotropy is reduced.
Further, the acyl group is preferably an acetyl group in that saponification is likely to proceed, the elastic modulus is high, the dimensional change is small, the durability is high, and the cost is low.

  The acyl group having 3 or more carbon atoms is not particularly limited, and may be an aliphatic group or an aromatic hydrocarbon group. They are, for example, alkyl carbonyl esters, alkenyl carbonyl esters, aromatic carbonyl esters, aromatic alkyl carbonyl esters and the like of cellulose, and each may further have a substituent.

Preferred acyl groups having 3 or more carbon atoms include propionyl group, butanoyl group, keptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group and octadecanoyl group. , Isobutanoyl group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, preferred are propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, tert-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Particularly preferred are a propionyl group and a butanoyl group.
In the case of a propionyl group, the substitution degree B is preferably 1.3 or more.

  Specific examples of the mixed fatty acid cellulose acylate include cellulose acetate propionate and cellulose acetate butyrate.

Cellulose acylate for reducing optical anisotropy For reducing optical anisotropy, the acyl substitution degree of cellulose with a hydroxyl group is preferably 2.50 to 3.00, and 2.75 to 3.00. More preferably, it is more preferably 2.85 to 3.00.

  The acyl group substituted for the hydroxyl group of cellulose preferably has 2 to 22 carbon atoms. The acyl group having 2 to 22 carbon atoms is not particularly limited, and may be an aliphatic group or an aryl group. They are, for example, alkyl carbonyl esters, alkenyl carbonyl esters, aromatic carbonyl esters, aromatic alkyl carbonyl esters and the like of cellulose, and each may further have a substituent.

  As these preferable acyl groups, acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group , Isobutanoyl group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, acetyl group, propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, tert-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like are preferable, and acetyl group, propionyl group, butanoyl group are preferable. Groups are more preferred.

  Among the acyl substituents substituted on the hydroxyl group of cellulose described above, when it is substantially composed of at least two of an acetyl group, a propionyl group, and a butanoyl group, the total degree of substitution is 2.50 to 3.00. Preferably, it is 2.75 to 3.00, more preferably 2.85 to 3.00. If it exists in said range, the optical anisotropy of a cellulose acylate film can fully be reduced, and it is preferable.

Method for synthesizing cellulose acylate The basic principle of the method for synthesizing cellulose acylate is described in Ueda et al., Wood Chemistry, 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst.

  In order to obtain the cellulose acylate, specifically, a cellulose raw material such as cotton linter or wood pulp is pretreated with an appropriate amount of acetic acid, and then esterified by introducing it into a pre-cooled carboxylated mixed solution. Synthesize the rate (total of acyl substitution at the 2nd, 3rd and 6th positions is approximately 3.00).

  The carboxylated mixed solution generally contains acetic acid as a solvent, carboxylic anhydride as an esterifying agent, and sulfuric acid as a catalyst. The carboxylic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. After completion of the esterification reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess carboxylic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide).

  Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid) to obtain the desired degree of acyl substitution and polymerization. The cellulose acylate having a degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with a neutralizing agent as described above or in water or dilute sulfuric acid without neutralization. The cellulose acylate solution is charged (or water or dilute sulfuric acid is charged into the cellulose acylate solution), the cellulose acylate is separated, washed and stabilized, and the like. Can be obtained.

In the cellulose acylate film, the polymer component constituting the film is preferably substantially composed of the specific cellulose acylate.
Here, “substantially” means 55 mass% or more (preferably 70 mass% or more, more preferably 80 mass% or more) of the polymer component.

  The cellulose acylate is preferably used in the form of particles. It is preferable that 90% by mass or more of the particles to be used have a particle size of 0.5 to 5 mm. Moreover, it is preferable that 50 mass% or more of the particle | grains to be used have a particle size of 1-4 mm. The cellulose acylate particles preferably have a shape as close to a sphere as possible.

  The degree of polymerization of the cellulose acylate preferably used in the present invention is a viscosity average degree of polymerization, preferably 200 to 700, more preferably 250 to 550, still more preferably 250 to 400, and particularly preferably 250 to 350. . The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538.

  When the low molecular component is removed, the average molecular weight (polymerization degree) is increased, but the viscosity is lower than that of ordinary cellulose acylate. Therefore, the cellulose acylate from which the low molecular component is removed is useful. .

Cellulose acylate having a small amount of low molecular components can be obtained by removing low molecular components from cellulose acylate synthesized by a usual method. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass parts of cellulose acylates.
When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized.

  When cellulose acylate is used for film production, the moisture content is preferably 2% by mass or less, more preferably 1% by mass or less, and further preferably 0.7% by mass or less. preferable. In general, cellulose acylate contains water and is known to have a water content of 2.5 to 5% by mass. In this invention, in order to make the moisture content of a cellulose acylate into the said suitable range, it is necessary to dry, and the method will not be specifically limited if it is a method used as the target moisture content.

  The raw material cotton and the synthesis method of the cellulose acylate are described in detail in JIII Journal of Technical Disclosure No. 2001-1745 (issued on March 15, 2001, pages 7-12, JIII). And synthetic methods can be adopted.

  The cellulose acylate film preferably used in the present invention can be obtained by forming a film using a solution prepared by dissolving the specific cellulose acylate and, if necessary, an additive in an organic solvent.

Additives Examples of additives that can be used in the cellulose acylate solution in the present invention include plasticizers, ultraviolet absorbers, deterioration inhibitors, retardation (optical anisotropy) developing agents, and retardation (optical anisotropy). Property) lowering agent, wavelength dispersion adjusting agent, dye, fine particles, peeling accelerator, infrared absorber and the like. In the present invention, it is preferable to use a retardation developer. Moreover, it is preferable to use at least one of a plasticizer, an ultraviolet absorber and a peeling accelerator.

  They may be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, ultraviolet absorbers of 20 ° C. or lower and 20 ° C. or higher can be mixed and used, and plasticizers can also be mixed and used, for example, as described in JP-A-2001-151901.

Ultraviolet absorbers Any type of ultraviolet absorber can be selected according to the purpose. They can be used, and are preferably benzophenone, benzotriazole, and salicylic acid esters.

  Examples of benzophenone ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4-methoxybenzophenone, 2, 2′-di-hydroxy-4,4′-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4- (2-hydroxy-3- And methacryloxy) propoxybenzophenone.

  As the benzotriazole ultraviolet absorber, 2 (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2 (2′-hydroxy-5′-t-butylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-t-amylphenyl) benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5 Examples include chlorobenzotriazole, 2 (2′-hydroxy-5′-t-octylphenyl) benzotriazole, and the like.

  Examples of salicylic acid esters include phenyl salicylate, p-octylphenyl salicylate, and p-tert-butylphenyl salicylate.

  Among these exemplified ultraviolet absorbers, in particular, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4,4′-methoxybenzophenone, 2 (2′-hydroxy-3′-t-butyl- 5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5'-t-butylphenyl) benzotriazole, 2 (2'-hydroxy-3 ', 5'-di-t-amylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5-chlorobenzotriazole is particularly preferred.

  As the ultraviolet absorber, it is preferable to use a combination of a plurality of absorbers having different absorption wavelengths because a high blocking effect can be obtained in a wide wavelength range. From the viewpoint of preventing deterioration of the liquid crystal, the ultraviolet absorbent for liquid crystal is preferably excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, the absorption of visible light having a wavelength of 400 nm or more is small. Particularly preferred ultraviolet absorbers are the benzotriazole compounds, benzophenone compounds, and salicylic acid ester compounds mentioned above. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose ester is small.

  As for the UV absorber, JP-A-60-235852, JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, JP-A-6-107854. 118233, 6-148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, JP-A-2000-204173 These compounds can also be used.

  0.001-5 mass% is preferable with respect to a cellulose acylate, and, as for the addition amount of a ultraviolet absorber, 0.01-1 mass% is more preferable. If the addition amount is 0.001% by mass or more, the effect of addition can be sufficiently exerted, and if the addition amount is 5% by mass or less, it is preferable because bleeding out of the ultraviolet absorber to the film surface can be suppressed.

  Further, the ultraviolet absorber may be added simultaneously with dissolution of cellulose acylate, or may be added to the dope after dissolution. In particular, a mode in which an ultraviolet absorbent solution is added to the dope immediately before casting using a static mixer or the like is preferable because spectral absorption characteristics can be easily adjusted.

Deterioration preventing agent The deterioration preventing agent can prevent cellulose triacetate and the like from deteriorating and decomposing. Examples of the deterioration preventing agent include butylamine, hindered amine compounds (JP-A-8-325537), guanidine compounds (JP-A-5-271471), benzotriazole-based UV absorbers (JP-A-6-235819), and benzophenone-based compounds. There are compounds such as UV absorbers (JP-A-6-118233).

Plasticizer The plasticizer is preferably a phosphoric acid ester or a carboxylic acid ester. Examples of the phosphate ester plasticizer include triphenyl phosphate (TPP), tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, biphenyl diphenyl phosphate (BDP), trioctyl phosphate, tributyl phosphate and the like; Examples of the acid ester plasticizer include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP), diethyl hexyl phthalate (DEHP), O-acetyl citrate. Triethyl acid (OACTE), O-acetyl tributyl citrate (OACTB), acetyl triethyl citrate, acetyl tributyl citrate, oleic acid , Methyl ricinoleate, dibutyl sebacate, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc. The plasticizer used in the invention is more preferably selected from these exemplified plasticizers. Furthermore, the plasticizer is preferably (di) pentaerythritol esters, glycerol esters, diglycerol esters.

Peeling accelerators Examples of peeling accelerators include ethyl esters of citric acid.
Infrared Absorber Further, an infrared absorber is described in, for example, JP-A No. 2001-194522.

Addition time, etc. The time to add these additives may be added at any time in the dope preparation process, but it may be added to the final preparation process of the dope preparation process by adding the preparation step. Good. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested.

  Moreover, when a cellulose acylate film is a multilayer, the kind and addition amount of the additive of each layer may differ. For example, although described in Japanese Patent Application Laid-Open No. 2001-151902, these are conventionally known techniques.

  Furthermore, about an additive, what is described in detail in invention association public technical bulletin number 2001-1745 (issued on March 15, 2001, 16th page-, invention association) can be used suitably.

Retardation developing agent In the present invention, in the case of greatly developing optical anisotropy, it is preferable to use a retardation developing agent in order to realize a preferable retardation value. Examples of the retardation enhancer that can be used in the present invention include those composed of rod-like or discotic compounds. As the rod-like or discotic compound, a compound having at least two aromatic rings can be used.

  The addition amount of the retardation enhancer composed of the rod-shaped compound is preferably 0.1 to 30 parts by mass, and preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of the polymer component containing cellulose acylate. More preferred.

  The disk-shaped retardation developer is preferably used in a range of 0.05 to 20 parts by mass, and in a range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the polymer component containing the cellulose acylate. It is more preferable to use it, it is more preferable to use it in the range of 0.2-5 mass parts, and it is most preferable to use it in the range of 0.5-2 mass parts.

Since the discotic compound is superior to the rod-shaped compound in Rth retardation expression, it is preferably used when particularly large Rth retardation is required.
Two or more retardation developers may be used in combination.

  The retardation enhancer used in the present invention preferably has maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

Discotic Compound Hereinafter, the discotic compound will be described.
As the discotic compound, a compound having at least two aromatic rings can be used.
In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring.

  The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring.

Aromatic heterocycles generally have the most double bonds.
As a hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is more preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable, In particular, a 1,3,5-triazine ring is preferably used. Specifically, for example, a compound disclosed in JP 2001-166144 A is preferably used as the discotic compound.

  The number of aromatic rings contained in the discotic compound is preferably 2 to 20, more preferably 2 to 12, still more preferably 2 to 8, and most preferably 2 to 6. preferable.

  The bonding relationship between two aromatic rings can be classified into (a) when forming a condensed ring, (b) when directly connecting with a single bond, and (c) when connecting via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

  Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiant It includes emissions ring. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.

  The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.

  The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof.

Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
c ₁ : —CO—O—
c _2: -CO-NH-
c _3: - alkylene group -O-
c _4: -NH-CO-NH-
c _5: -NH-CO-O-
c _6: -O-CO-O-
c _7: -O- alkylene group -O-
c _8: -CO- alkenylene group -
c _9: -CO- alkenylene group -NH-
c _10: -CO- alkenylene group -O-
c ₁₁ : -alkylene group-CO-O-alkylene group-O-CO-alkylene group-
c _12: -O- alkylene group -CO-O- alkylene group -O-CO- alkylene group -O-
c _13: -O-CO- alkylene group -CO-O-
c _14: -NH-CO- alkenylene group -
c _15: -O-CO- alkenylene group -

The aromatic ring and the linking group may have a substituent.
Examples of substituents include halogen atoms (F, Cl, Br, I), hydroxyl groups, carboxyl groups, cyano groups, amino groups, nitro groups, sulfo groups, carbamoyl groups, sulfamoyl groups, ureido groups, alkyl groups, alkenyls. Group, alkynyl group, aliphatic acyl group, aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group An aliphatic substituted carbamoyl group, an aliphatic substituted sulfamoyl group, an aliphatic substituted ureido group, and a non-aromatic heterocyclic group.

  It is preferable that the alkyl group has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (for example, a hydroxy group, a carboxy group, an alkoxy group, an alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-methoxyethyl. A diethylaminoethyl group is included.

The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is more preferable. The alkenyl group may further have a substituent. Examples of the alkenyl group include a vinyl group, an allyl group, and a 1-hexenyl group.
The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of the alkynyl group include ethynyl group, 1-butynyl group and 1-hexynyl group.

The aliphatic acyl group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyl group include an acetyl group, a propanoyl group, and a butanoyl group.
The aliphatic acyloxy group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyloxy group include an acetoxy group.
The alkoxy group preferably has 1 to 8 carbon atoms. The alkoxy group may further have a substituent (for example, an alkoxy group). Examples of the alkoxy group (including a substituted alkoxy group) include a methoxy group, an ethoxy group, a butoxy group, and a methoxyethoxy group.

The alkoxycarbonyl group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include a methoxycarbonyl group and an ethoxycarbonyl group.
The alkoxycarbonylamino group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonylamino group include a methoxycarbonylamino group and an ethoxycarbonylamino group.

The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include a methylthio group, an ethylthio group, and an octylthio group.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include a methanesulfonyl group and an ethanesulfonyl group.

The aliphatic amide group preferably has 1 to 10 carbon atoms. Examples of the aliphatic amide group include an acetamide group.
The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamido group include a methanesulfonamido group, a butanesulfonamido group, and an n-octanesulfonamido group.

The number of carbon atoms of the aliphatic substituted amino group is preferably 1-10. Examples of the aliphatic substituted amino group include a dimethylamino group, a diethylamino group, and a 2-carboxyethylamino group.
The aliphatic substituted carbamoyl group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted carbamoyl group include a methylcarbamoyl group and a diethylcarbamoyl group.

The aliphatic substituted sulfamoyl group preferably has 1 to 8 carbon atoms. Examples of the aliphatic substituted sulfamoyl group include a methylsulfamoyl group and a diethylsulfamoyl group.
The aliphatic substituted ureido group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted ureido group include a methylureido group.
Examples of the non-aromatic heterocyclic group include a piperidino group and a morpholino group.

  The molecular weight of the retardation developer composed of a discotic compound is preferably 300 to 800.

Rod-shaped compound In the present invention, a rod-shaped compound having a linear molecular structure can be preferably used in addition to the aforementioned disk-shaped compound.

  The linear molecular structure means that the molecular structure of the rod-like compound is linear in the most thermodynamically stable structure. The most thermodynamically stable structure can be obtained by crystal structure analysis or molecular orbital calculation. For example, molecular orbital calculation is performed using molecular orbital calculation software (for example, “WinMOPAC2000” manufactured by Fujitsu Limited), and a molecular structure that minimizes the heat of formation of a compound can be obtained. The term “linear molecular structure” means that in the thermodynamically most stable structure obtained by calculation as described above, the angle of the main chain in the molecular structure is 140 ° or more.

As the rod-shaped compound, those having at least two aromatic rings are preferable, and as the rod-shaped compound having at least two aromatic rings, a compound represented by the following general formula (1) is preferable.
General formula (1)
Ar ¹ -L ¹ -Ar ²
In the general formula (1), Ar ¹ and Ar ² are each independently an aromatic group, and L ¹ is a divalent linking group.

  In the present specification, the aromatic group includes an aryl group (aromatic hydrocarbon group), a substituted aryl group, an aromatic heterocyclic group, and a substituted aromatic heterocyclic group. An aryl group and a substituted aryl group are more preferable than an aromatic heterocyclic group and a substituted aromatic heterocyclic group.

  The heterocycle of the aromatic heterocyclic group is generally unsaturated. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As a hetero atom, a nitrogen atom, an oxygen atom or a sulfur atom is preferable, and a nitrogen atom or a sulfur atom is more preferable.

  As the aromatic ring of the aromatic group, a benzene ring, a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, a thiazole ring, an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring and a pyrazine ring are preferable, and a benzene ring is particularly preferable. .

  Examples of the substituent of the substituted aryl group and the substituted aromatic heterocyclic group include a halogen atom (F, Cl, Br, I), a hydroxyl group, a carboxyl group, a cyano group, an amino group, an alkylamino group (for example, methyl Amino group, ethylamino group, butylamino group, dimethylamino group), nitro group, sulfo group, carbamoyl group, alkylcarbamoyl group (for example, N-methylcarbamoyl group, N-ethylcarbamoyl group, N, N-dimethylcarbamoyl group) ), Sulfamoyl group, alkylsulfamoyl group (for example, N-methylsulfamoyl group, N-ethylsulfamoyl group, N, N-dimethylsulfamoyl group), ureido group, alkylureido group (for example, N -Methylureido group, N, N-dimethylureido group, N, N, N'-trimethylureido group), An alkyl group (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, heptyl group, octyl group, isopropyl group, s-butyl group, t-amyl group, cyclohexyl group, cyclopentyl group), alkenyl group (for example, , Vinyl group, allyl group, hexenyl group), alkynyl group (for example, ethynyl group, butynyl group), acyl group (for example, formyl group, acetyl group, butyryl group, hexanoyl group, lauryl group), acyloxy group (for example, acetoxy group) Group, butyryloxy group, hexanoyloxy group, lauryloxy group), alkoxy group (for example, methoxy group, ethoxy group, propoxy group, butoxy group, pentyloxy group, heptyloxy group, octyloxy group), aryloxy group (for example, , Phenoxy group), alkoxycarbonyl group (eg , Methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, butoxycarbonyl group, pentyloxycarbonyl group, heptyloxycarbonyl group), aryloxycarbonyl group (for example, phenoxycarbonyl group), alkoxycarbonylamino group (for example, butoxycarbonylamino) Group, hexyloxycarbonylamino group), alkylthio group (for example, methylthio group, ethylthio group, propylthio group, butylthio group, pentylthio group, heptylthio group, octylthio group), arylthio group (for example, phenylthio group), alkylsulfonyl group (for example, , Methylsulfonyl group, ethylsulfonyl group, propylsulfonyl group, butylsulfonyl group, pentylsulfonyl group, heptylsulfonyl group, octylsulfonyl group , An amido group (e.g., acetamido group, butylamide group, hexylamide group, laurylamide group) and a non-aromatic Hajime Tamaki (e.g., morpholyl group, pyrazinyl group) include.

  Examples of the substituent of the substituted aryl group and the substituted aromatic heterocyclic group include a halogen atom, a cyano group, a carboxyl group, a hydroxyl group, an amino group, an alkyl-substituted amino group, an acyl group, an acyloxy group, an amide group, an alkoxycarbonyl group, Alkoxy groups, alkylthio groups and alkyl groups are preferred.

  The alkyl part and alkyl group of the alkylamino group, alkoxycarbonyl group, alkoxy group and alkylthio group may further have a substituent. Examples of the alkyl moiety and the substituent of the alkyl group include halogen atom, hydroxyl, carboxyl, cyano, amino, alkylamino group, nitro, sulfo, carbamoyl, alkylcarbamoyl group, sulfamoyl, alkylsulfamoyl group, ureido, alkylureido Group, alkenyl group, alkynyl group, acyl group, acyloxy group, acylamino group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, alkoxycarbonylamino group, alkylthio group, arylthio group, alkylsulfonyl group, amide group And non-aromatic heterocyclic groups. As the substituent for the alkyl moiety and the alkyl group, a halogen atom, hydroxyl, amino, alkylamino group, acyl group, acyloxy group, acylamino group, alkoxycarbonyl group and alkoxy group are preferable.

In the general formula (1), L ¹ is a divalent linking group selected from an alkylene group, an alkenylene group, an alkynylene group, —O—, —CO—, and a group thereof.

  The alkylene group may have a cyclic structure. As the cyclic alkylene group, cyclohexylene is preferable, and 1,4-cyclohexylene is particularly preferable. As the chain alkylene group, a linear alkylene group is more preferable than a branched alkylene group. The number of carbon atoms of the alkylene group is preferably 1-20, more preferably 1-15, still more preferably 1-10, even more preferably 1-8, 6 is most preferred.

  The alkenylene group and the alkynylene group preferably have a chain structure rather than a cyclic structure, and more preferably have a linear structure rather than a branched chain structure. The number of carbon atoms of the alkenylene group and the alkynylene group is preferably 2 to 10, more preferably 2 to 8, still more preferably 2 to 6, still more preferably 2 to 4, and most preferably 2 (vinylene group or ethynylene group).

  The arylene group preferably has 6 to 20 carbon atoms, more preferably 6 to 16, and still more preferably 6 to 12.

In the molecular structure of the general formula (1), the angle formed by Ar ¹ and Ar ² across L ¹ is preferably 140 ° or more.

As the rod-like compound, a compound represented by the following general formula (2) is more preferable.
General formula (2)
Ar ¹ -L ² -XL ³ -Ar ²
In the general formula (2), Ar ¹ and Ar ² are each independently an aromatic group.

The definition and examples of the aromatic group are the same as those of Ar ¹ and Ar ^{2 in} the general formula (1). L ² and L ³ are each independently a divalent linking group selected from an alkylene group, —O—, —CO— and a group consisting of a combination thereof.
The alkylene group preferably has a chain structure rather than a cyclic structure, and more preferably has a linear structure rather than a branched chain structure. The alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 8, more preferably 1 to 6, still more preferably 1 to 4, and 1 or 2 (methylene group or Most preferred is an ethylene group).
L ² and L ³ are particularly preferably —O—CO— or CO—O—.

  In the general formula (2), X is 1,4-cyclohexylene, vinylene or ethynylene.

  Specific examples of the compound represented by the general formula (1) or (2) include compounds described in [Chemical Formula 1] to [Chemical Formula 11] of JP-A No. 2004-109657.

In addition, a compound represented by the following general formula (3) is also preferable.
General formula (3)

(In the general formula ^{(3), R 1, R} 2, R 3, R 4, R 5, R 6, R 7, R 9 and R ¹⁰ each independently represent a hydrogen atom or a substituent, R ^1, At least one of R ² , R ³ , R ⁴ and R ⁵ represents an electron donating group, R ⁸ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or a carbon number. An alkynyl group having 2 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 12 carbon atoms, and 2 to 12 carbon atoms Represents an acylamino group, a cyano group or a halogen atom.)

  Of the retardation developing agents, specific examples of rod-like compounds that can be preferably used in the present invention are shown below.

Two or more rod-shaped compounds having a maximum absorption wavelength (λ _max ) shorter than 250 nm in the ultraviolet absorption spectrum of the solution may be used in combination.

The rod-like compound can be synthesized by a method described in the literature.
The literature includes “Mol. Cryst. Liq. Cryst.”, 53, p229 (1979), 89, p93 (1982), 145, p111 (1987), 170, p43 ( 1989), “J. Am. Chem. Soc.”, 113, p1349 (1991), 118, p5346 (1996), 92, p1582 (1970), “J. Org. Chem. ", 40, p420 (1975)," Tetrahedron ", 48, 16, p3437 (1992).

Compound for Reducing Reλ and Rthλ The protective film of the present invention may contain a compound for reducing Reλ and Rthλ (hereinafter referred to as “retardation reducing agent”). The retardation reducing agent is used when reducing the optical anisotropy of the protective film.
By using a compound that suppresses the cellulose acylate in the film from being oriented in the plane and in the film thickness direction, the optical anisotropy can be sufficiently reduced, and Re and Rth can be made zero or close to zero. . For this purpose, it is advantageous that the compound for reducing the optical anisotropy is sufficiently compatible with cellulose acylate, and the compound itself does not have a rod-like structure or a planar structure. Specifically, when a plurality of planar functional groups such as aromatic groups are provided, a structure having these functional groups in a non-planar rather than the same plane is advantageous.

Log P value When producing a cellulose acylate film having low optical anisotropy, as described above, the cellulose anion in the film is prevented from being oriented in the plane and in the film thickness direction, thereby reducing the optical anisotropy. Of the compounds to be produced, compounds having an octanol-water partition coefficient (log P value) of 0 to 7 are preferred. If the log P value of the compound is 7 or less, the compatibility with the cellulose acylate is good, and problems such as white turbidity and powder blowing of the film are less likely to occur.
Moreover, if the logP value of the compound is 0 or more, the hydrophilicity does not become too high and the water resistance of the cellulose acylate film is not deteriorated, which is preferable. A more preferable range for the log P value is 1 to 6, and a more preferable range is 1.5 to 5.

  The octanol-water partition coefficient (log P value) can be measured by a flask soaking method described in JIS Z-7260-107 (2000). Further, the octanol-water partition coefficient (log P value) can be estimated by a computational chemical method or an empirical method instead of the actual measurement.

  As a calculation method, Crippen's fragmentation method ("J. Chem. Inf. Comput. Sci.", 27, p21 (1987)), Viswanadhan's fragmentation method ("J. Chem. Inf. Comput. Sci."). ", 29, p163 (1989)), Broto's fragmentation method (" Eur. J. Med. Chem.-Chim. Theor. ", 19, p71 (1984)) and the like are preferably used. Crippen's fragmentation method ("J. Chem. Inf. Comput. Sci.", 27, p21 (1987)) is more preferable.

  When the log P value of a certain compound varies depending on the measurement method or calculation method, it is preferable to determine whether or not the compound is within the above range by the Crippen's fragmentation method.

Physical properties of compounds that reduce optical anisotropy The compounds that reduce optical anisotropy may or may not contain an aromatic group. In addition, the compound that decreases the optical anisotropy preferably has a molecular weight of 150 to 3000, more preferably 170 to 2000, and even more preferably 200 to 1000. A specific monomer structure may be used as long as these molecular weights are within the range, and an oligomer structure or a polymer structure in which a plurality of the monomer units are bonded may be used.

  The compound that reduces optical anisotropy is preferably liquid at 25 ° C. or a solid having a melting point of 25 to 250 ° C., more preferably liquid at 25 ° C. or a melting point of 25 to 200 ° C. It is a solid. Moreover, it is preferable that the compound which reduces optical anisotropy does not volatilize in the process of dope casting for cellulose acylate film production and drying.

  The addition amount of the compound that decreases the optical anisotropy is preferably 0.01 to 30% by mass of the cellulose acylate, more preferably 1 to 25% by mass, and 5 to 20% by mass. Is more preferable.

  The compound that decreases the optical anisotropy may be used alone, or two or more compounds may be mixed and used in an arbitrary ratio.

  The timing for adding the compound that decreases the optical anisotropy may be any time during the dope preparation process, or may be performed at the end of the dope preparation process.

  The compound that reduces the optical anisotropy is such that the average content of the compound in the portion from the surface on at least one side to 10% of the total film thickness is the average content of the compound in the central portion of the cellulose acylate film. It is preferable that it is 80 to 99% of. The abundance of the compound that reduces the optical anisotropy can be determined by measuring the amount of the compound at the surface and in the center, for example, by a method using an infrared absorption spectrum described in JP-A-8-57879. .

Specific Examples of Compounds that Reduce Optical Anisotropy Specific examples of compounds that reduce the optical anisotropy of cellulose acylate films that are preferably used in the present invention are shown below, but the present invention is not limited to these compounds.

Wavelength Dispersion Adjuster The cellulose acylate film may contain a compound that reduces wavelength dispersion. Specifically, at least one compound having absorption in the ultraviolet region of 200 to ₄₀₀ nm and lowering | Re ₄₀₀ -Re ₇₀₀ | and | Rth ₄₀₀ -Rth ₇₀₀ | of the film, relative to the solid content of cellulose acylate It is preferable to contain 0.01-30 mass%. By containing the wavelength dispersion adjusting agent, the wavelength dispersion of Re and Rth of the cellulose acylate film can be adjusted. Here, Re ₄₀₀ and Rth ₄₀₀ represent values at a wavelength λ = 400 nm, and Re ₇₀₀ and Rth ₇₀₀ represent values at a wavelength λ = 700 nm (both units: nm). As the addition amount of such a compound, the wavelength dispersion of Re and Rth of the cellulose acylate film can be adjusted by including 0.1 to 30% by mass.

  In general, the Re and Rth values of the cellulose acylate film have a wavelength dispersion characteristic that the longer wavelength side is larger than the shorter wavelength side. Therefore, it is required to smoothen the chromatic dispersion by increasing Re and Rth on the relatively small short wavelength side. On the other hand, a compound having absorption in the ultraviolet region of 200 to 400 nm has a wavelength dispersion characteristic in which the absorbance on the long wavelength side is larger than that on the short wavelength side. If this compound itself is isotropically present inside the cellulose acylate film, it is assumed that the birefringence of the compound itself, and thus the wavelength dispersion of Re and Rth, is large on the short wavelength side as well as the wavelength dispersion of absorbance. The

  Therefore, by using the above-described compound having absorption in the ultraviolet region of 200 to 400 nm and having a wavelength dispersion of Re and Rth of the compound itself large on the short wavelength side, Re of the cellulose acylate film, Rth wavelength dispersion can be prepared. For this purpose, the compound for adjusting the wavelength dispersion is required to be sufficiently uniformly compatible with the cellulose acylate. The absorption band range in the ultraviolet region of such a compound is preferably 200 to 400 nm, more preferably 220 to 395 nm, and even more preferably 240 to 390 nm.

In recent years, liquid crystal display devices such as televisions, notebook computers, and mobile portable terminals have been required to have excellent transmittance of optical members used in the liquid crystal display device in order to increase luminance with less power. In that respect, when a compound having absorption in the ultraviolet region of 200 to ₄₀₀ nm and reducing | Re ₄₀₀ -Re ₇₀₀ | and | Rth ₄₀₀ -Rth ₇₀₀ | of the film is added to the cellulose acylate film, spectral transmission is achieved. The rate is required to be excellent. In the cellulose acylate film preferably used in the present invention, the spectral transmittance at a wavelength of 380 nm is preferably 45% to 95%, and the spectral transmittance at a wavelength of 350 nm is preferably 10% or less.

  As described above, the wavelength dispersion adjusting agent preferably used in the present invention preferably has a molecular weight of 250 to 1000 from the viewpoint of volatility. More preferably, it is 260-800, More preferably, it is 270-800, Most preferably, it is 300-800. A specific monomer structure may be used as long as these molecular weights are within the range, and an oligomer structure or a polymer structure in which a plurality of the monomer units are bonded may be used.

  It is preferable that the wavelength dispersion adjusting agent does not volatilize during the dope casting and drying process for producing the cellulose acylate film.

Addition amount of wavelength dispersion adjusting agent The addition amount of the wavelength dispersion adjusting agent preferably used in the present invention is preferably 0.01 to 30% by mass with respect to the solid content of the cellulose acylate. More preferably, it is 20 mass%, and it is especially preferable that it is 0.2-10 mass%.

Method for Adding Wavelength Dispersion Adjusting Agent These wavelength dispersion adjusting agents may be used alone, or two or more compounds may be mixed and used in an arbitrary ratio.
Further, the timing of adding these wavelength dispersion adjusting agents may be any time during the dope preparation process, or may be performed at the end of the dope preparation process.

  Specific examples of the wavelength dispersion adjusting agent preferably used in the present invention include, for example, benzotriazole compounds, benzophenone compounds, compounds containing a cyano group, oxybenzophenone compounds, salicylic acid ester compounds, nickel complex compounds, and the like. However, the present invention is not limited only to these compounds.

Dye In the present invention, a dye for adjusting the hue may be added. The content of the dye is preferably 10 to 1000 ppm, more preferably 50 to 500 ppm, in terms of a mass ratio with respect to cellulose acylate. By containing the dye in this way, light piping of the cellulose acylate film can be reduced, and yellowness can be improved. These compounds may be added together with cellulose acylate and a solvent during the preparation of the cellulose acylate solution, or may be added during or after the solution preparation. Moreover, you may add to the ultraviolet absorber liquid added in-line. The dyes described in JP-A-5-34858 can be used.

Matting Agent Fine Particles It is preferable to add fine particles as a matting agent to the cellulose acylate film preferably used in the present invention. The fine particles used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and Mention may be made of calcium phosphate. As the fine particles, those containing silicon are preferable from the viewpoint of low turbidity, and silicon dioxide is particularly preferable.

  The silicon dioxide fine particles preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / L or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film. The apparent specific gravity is preferably 90 to 200 g / L or more, and more preferably 100 to 200 g / L or more. A higher apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  When silicon dioxide fine particles are used as the matting agent, the amount used is preferably 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the polymer component containing cellulose acylate.

  These fine particles usually form secondary particles having an average particle size of 0.1 to 3.0 μm, but are present as aggregates of primary particles in the film, and 0.1 to 3.0 μm on the film surface. Form irregularities. The average particle size of the secondary particles is preferably 0.2 μm to 1.5 μm, more preferably 0.4 μm to 1.2 μm, and most preferably 0.6 μm to 1.1 μm. If the average particle size is 1.5 μm or less, the haze will not be too strong, and if it is 0.2 μm or more, the effect of preventing squeezing will be sufficiently exhibited.

  The primary and secondary particle sizes of the fine particles are determined by observing the particles in the film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle size. Also, 200 particles are observed at different locations, and the average value is taken as the average particle size.

  As the fine particles of silicon dioxide, for example, commercially available products such as “Aerosil” R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, manufactured by Nippon Aerosil Co., Ltd.) can be used. . Zirconium oxide fine particles are commercially available under the trade names of “Aerosil” R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.), and can be used.

  Among these, “Aerosil 200V” and “Aerosil R972V” are fine particles of silicon dioxide having a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / L or more, and lower the turbidity of the optical film. This is particularly preferable because the effect of reducing the coefficient of friction is large while maintaining.

In the present invention, in order to obtain a cellulose acylate film containing particles having a small secondary average particle size, several methods are conceivable when preparing a dispersion of fine particles. For example, a fine particle dispersion prepared by stirring and mixing a solvent and fine particles is prepared in advance, and this fine particle dispersion is added to a small amount of a separately prepared cellulose acylate solution, dissolved by stirring, and further mixed with the main cellulose acylate dope solution. There is a way. This method is a preferable preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of cellulose ester to the solvent and dissolving with stirring, add the fine particles to this and disperse with a disperser. There is also a method of mixing. In the present invention, although not limited to these methods, the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, and 10 to 25% by mass. Is more preferable, and 15 to 20% by mass is most preferable.
A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved. The addition amount of the matting agent in the final cellulose acylate dope solution is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and 0.08 to 0.16 g per 1 m ^2. Most preferred.

  The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose ester.

  Next, the organic solvent in which cellulose acylate preferably used in the present invention is dissolved will be described.

  In the present invention, as the organic solvent, any of a chlorinated solvent containing a chlorinated organic solvent as a main solvent and a non-chlorinated solvent not containing a chlorinated organic solvent can be used.

Chlorine-based solvent In producing a cellulose acylate solution preferably used in the present invention, a chlorine-based organic solvent is preferably used as the main solvent. In the present invention, the type of the chlorinated organic solvent is not particularly limited as long as the object can be achieved as long as the cellulose acylate is dissolved and can be cast and formed into a film. These chlorinated organic solvents are preferably dichloromethane and chloroform. Particularly preferred is dichloromethane. In addition, there is no particular problem in mixing an organic solvent other than the chlorinated organic solvent. In that case, it is preferable to use at least 50% by mass of dichloromethane in the total amount of the organic solvent.

Other organic solvents used in combination with the chlorinated organic solvent in the present invention will be described below.
That is, as another preferable organic solvent, a solvent selected from esters, ketones, ethers, alcohols, hydrocarbons and the like having 3 to 12 carbon atoms is preferable. Esters, ketones, ethers and alcohols may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO—, and COO—) can also be used as a solvent. For example, other functional groups such as alcoholic hydroxyl groups can be used. You may have group simultaneously. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

  The alcohol used in combination with the chlorinated organic solvent may preferably be linear, branched or cyclic, and is preferably a saturated aliphatic hydrocarbon. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.

Examples of combinations of chlorinated organic solvents and other organic solvents include the following compositions, but are not limited thereto.
Dichloromethane / methanol / ethanol / butanol = 80/10/5/5 (parts by mass)
Dichloromethane / acetone / methanol / propanol = 80/10/5/5 (parts by mass)
Dichloromethane / methanol / butanol / cyclohexane = 80/10/5/5 (parts by mass)
Dichloromethane / methyl ethyl ketone / methanol / butanol = 80/10/5/5 (parts by mass)
Dichloromethane / acetone / methyl ethyl ketone / ethanol / isopropanol = 75/8/5/5/7 (parts by mass)
Dichloromethane / cyclopentanone / methanol / isopropanol = 80/7/5/8 (parts by mass)
Dichloromethane / methyl acetate / butanol = 80/10/10 (parts by mass)
Dichloromethane / cyclohexanone / methanol / hexane = 70/20/5/5 (parts by mass),
Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol = 50/20/20/5/5 (parts by mass),
Dichloromethane / 1, 3 dioxolane / methanol / ethanol = 70/20/5/5 (parts by mass),
Dichloromethane / dioxane / acetone / methanol / ethanol = 60/20/10/5/5 (parts by mass),
Dichloromethane / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane = 65/10/10/5/5/5 (parts by mass)
Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol = 70/10/10/5/5 (parts by mass),
Dichloromethane / acetone / ethyl acetate / ethanol / butanol / hexane = 65/10/10/5/5/5 (parts by mass)
Dichloromethane / methyl acetoacetate / methanol / ethanol = 65/20/10/5 (parts by mass),
Dichloromethane / cyclopentanone / ethanol / butanol = 65/20/10/5 (parts by mass).

Non-chlorine-based solvent Next, a non-chlorine-based organic solvent that is preferably used in preparing a cellulose acylate solution that is preferably used in the present invention will be described. In the present invention, the non-chlorine organic solvent is not particularly limited as long as the object can be achieved as long as the cellulose acylate is dissolved and can be cast and formed into a film. The non-chlorine organic solvent used in the present invention is preferably a solvent selected from esters, ketones and ethers having 3 to 12 carbon atoms. Esters, ketones and ethers may have a cyclic structure. A compound having two or more functional groups of an ester, a ketone and an ether (that is, —O—, —CO— and COO—) can also be used as a main solvent. It may have a functional group. In the case of the main solvent having two or more kinds of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone and methyl acetyl acetate. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

The above-mentioned non-chlorine organic solvent used for cellulose acylate is selected from the various viewpoints described above, and is preferably as follows.
That is, the non-chlorine solvent is preferably a mixed solvent containing the non-chlorine organic solvent as a main solvent, and is a mixed solvent of three or more different solvents, wherein the first solvent is methyl acetate, ethyl acetate, At least one selected from methyl formate, ethyl formate, acetone, dioxolane, and dioxane, or a mixture thereof, and the second solvent is selected from ketones having 4 to 7 carbon atoms or acetoacetate, The solvent is a mixed solvent selected from alcohols or hydrocarbons having 1 to 10 carbon atoms, more preferably alcohols having 1 to 8 carbon atoms. Note that when the first solvent is a mixed liquid of two or more kinds of solvents, the second solvent may not be provided. The first solvent is more preferably methyl acetate, acetone, methyl formate, ethyl formate, or a mixture thereof, and the second solvent is preferably methyl ethyl ketone, cyclopentanone, cyclohexanone, or methyl acetyl acetate. It may be a solvent.

  The alcohol as the third solvent may have a hydrocarbon chain that is linear, branched, or cyclic, and among them, a saturated aliphatic hydrocarbon chain is preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. In addition, as the alcohol, a fluorine-based alcohol in which part or all of the hydrogen in the hydrocarbon chain is substituted with fluorine is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like.

  Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.

  These alcohols and hydrocarbons as the third solvent may be used alone or in a mixture of two or more, and are not particularly limited. As the third solvent, preferred specific compounds include alcohol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and cyclohexanol, and hydrocarbons such as cyclohexane and hexane. Particularly preferred are methanol, ethanol, 1-propanol, 2-propanol and 1-butanol.

  The mixing ratio of the above three types of mixed solvents is that the first solvent is 20 to 95% by mass, the second solvent is 2 to 60% by mass, and the third solvent is 2 to 30% by mass in the total amount of the mixed solvent. %, Preferably the first solvent is 30 to 90% by mass, the second solvent is 3 to 50% by mass, and the third alcohol is 3 to 25% by mass. preferable. In particular, the first solvent is preferably 30 to 90% by mass, the second solvent is preferably 3 to 30% by mass, and the third solvent is an alcohol, and preferably 3 to 15% by mass.

  The non-chlorine organic solvent used in the present invention is described in detail in the Invention Association (published technical bulletin number 2001-1745, pages 12-16, issued on March 15, 2001, Invention Association). It is described in.

Preferred combinations of non-chlorine organic solvents of the present invention can include the following, but are not limited thereto.
Methyl acetate / acetone / methanol / ethanol / butanol = 75/10/5/5/5 (parts by mass),
Methyl acetate / acetone / methanol / ethanol / propanol = 75/10/5/5/5 (parts by mass),
Methyl acetate / acetone / methanol / butanol / cyclohexane = 75/10/5/5/5 (parts by mass),
Methyl acetate / acetone / ethanol / butanol = 81/8/7/4 (parts by mass)
Methyl acetate / acetone / ethanol / butanol = 82/10/4/4 (parts by mass),
Methyl acetate / acetone / ethanol / butanol = 80/10/4/6 (parts by mass)
Methyl acetate / methyl ethyl ketone / methanol / butanol = 80/10/5/5 (parts by mass),
Methyl acetate / acetone / methyl ethyl ketone / ethanol / isopropanol = 75/8/5/5/7 (parts by mass),
Methyl acetate / cyclopentanone / methanol / isopropanol = 80/7/5/8 (parts by mass),
Methyl acetate / acetone / butanol = 85/10/5 (parts by mass),
Methyl acetate / cyclopentanone / acetone / methanol / butanol = 60/15/14/5/6 (parts by mass),
Methyl acetate / cyclohexanone / methanol / hexane = 70/20/5/5 (parts by mass),
Methyl acetate / methyl ethyl ketone / acetone / methanol / ethanol = 50/20/20/5/5 (parts by mass),
Methyl acetate / 1,3-dioxolane / methanol / ethanol = 70/20/5/5 (parts by mass),
Methyl acetate / dioxane / acetone / methanol / ethanol = 60/20/10/5/5 (parts by mass),
Methyl acetate / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane = 65/10/10/5/5/5 (parts by mass),

Methyl formate / methyl ethyl ketone / acetone / methanol / ethanol = 50/20/20/5/5 (parts by mass),
Methyl formate / acetone / ethyl acetate / ethanol / butanol / hexane = 65/10/10/5/5/5 (parts by mass)
Acetone / methyl acetoacetate / methanol / ethanol = 65/20/10/5 (parts by mass),
Acetone / cyclopentanone / ethanol / butanol = 65/20/10/5 (parts by mass),
Acetone / 1,3-dioxolane / ethanol / butanol = 65/20/10/5 (parts by mass),
1,3-dioxolane / cyclohexanone / methyl ethyl ketone / methanol / butanol = 55/20/10/5/5/5 (parts by mass)
Etc.

Furthermore, a cellulose acylate solution prepared by the following method can also be used.
A method of preparing a cellulose acylate solution with methyl acetate / acetone / ethanol / butanol = 81/8/7/4 (parts by mass), adding 2 parts by mass of butanol after filtration and concentration,
A method of preparing a cellulose acylate solution with methyl acetate / acetone / ethanol / butanol = 84/10/4/2 (parts by mass), adding 4 parts by mass of butanol after filtration and concentration,
A method of preparing a cellulose acylate solution with methyl acetate / acetone / ethanol = 84/10/6 (parts by mass), adding 5 parts by mass of butanol after filtration and concentration,

  In addition to the non-chlorine organic solvent of the present invention, the dope used in the present invention may contain dichloromethane in an amount of 10% by mass or less based on the total amount of the organic solvent of the present invention.

Cellulose acylate solution characteristics The cellulose acylate solution is a solution in which cellulose acylate is dissolved in the organic solvent, and its concentration is in the range of 10 to 30% by mass from the viewpoint of suitability for film casting. More preferably, it is 13-27 mass%, Most preferably, it is 15-25 mass%.
A method for bringing the cellulose acylate solution into such a concentration range may be a predetermined concentration at the stage of dissolution, and will be described later after it is prepared in advance as a low concentration solution (for example, 9 to 14% by mass). You may adjust to a predetermined high concentration solution by a concentration process. Furthermore, after preparing a high concentration cellulose acylate solution in advance, various additives may be added to obtain a predetermined low concentration cellulose acylate solution, and any method is preferably used in the present invention. There is no particular problem if it is carried out so as to have a concentration.

Next, in the present invention, when the cellulose acylate solution is made 0.1 to 5% by mass with an organic solvent having the same composition, the aggregate molecular weight of the cellulose acylate in the diluted solution is 150,000 to 15 million. Is preferable from the viewpoint of solubility in a solvent. The associated molecular weight is more preferably 180,000 to 9 million. This associated molecular weight can be determined by a static light scattering method. In that case, it is preferable to melt | dissolve so that the inertial radius calculated | required simultaneously may be 10-200 nm. A more preferable radius of inertia is 20 to 200 nm. Furthermore, it is preferable to dissolve so that the second virial coefficient is −2 × 10 ⁻⁴ to + 4 × 10 ^−4, and more preferably, the second virial coefficient is −2 × 10 ⁻⁴ to + 2 × 10 ^−4. It is.

  Here, the definition of the associated molecular weight, the radius of inertia, and the second virial coefficient in the present invention will be described. These are measured using the static light scattering method according to the following method. Although the measurement is performed in a dilute region for the convenience of the apparatus, these measured values reflect the behavior of the dope in the high concentration region of the present invention.

  First, cellulose acylate is dissolved in a solvent used for the dope to prepare solutions of 0.1 mass%, 0.2 mass%, 0.3 mass%, and 0.4 mass%. In order to prevent moisture absorption, the cellulose acylate is dried at 120 ° C. for 2 hours, and is measured at 25 ° C. and 10% RH. The dissolution method is carried out according to the method employed at the time of dope dissolution (room temperature dissolution method, cooling dissolution method, high temperature dissolution method). Subsequently, these solutions and the solvent are filtered through a 0.2 μm Teflon filter (Teflon: registered trademark). Then, static light scattering of the filtered solution is measured at intervals of 10 ° from 30 ° to 140 ° at 25 ° C. using a light scattering measuring device “DLS-700” (manufactured by Otsuka Electronics Co., Ltd.). The obtained data is analyzed by the BERRY plot method. The refractive index necessary for this analysis is the value of the solvent determined by the Abbe refractive system, and the refractive index concentration gradient (dn / dc) is a differential refractometer “DRM-1021” (manufactured by Otsuka Electronics Co., Ltd.). ) And the solvent and solution used for the light scattering measurement.

Preparation of dope Next, preparation of a solution (dope) for casting and film formation of cellulose acylate will be described.
The method for dissolving cellulose acylate is not particularly limited, and may be a room temperature dissolution method, a cooling dissolution method or a high temperature dissolution method, or a combination thereof. With respect to these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP 2000-53784, JP 11-322946, JP 11-322947, JP 2-276830, JP 2000-273239, JP 11-71463, JP 04-259511, Special JP-A-2000-273184, JP-A-11-323017, JP-A-11-302388, and the like describe the methods for preparing a cellulose acylate solution.

  The above-described method for dissolving cellulose acylate in an organic solvent can be applied to the present invention as long as it is within the scope of the present invention. Details of these, especially non-chlorine solvent systems, are described in detail in the Japan Society for Invention and Innovation (Publication No. 2001-1745, pages 22-25, published on March 15, 2001, Japan Institute of Invention and Innovation). Can be carried out according to the method. Further, the cellulose acylate dope solution preferably used in the present invention is usually subjected to solution concentration and filtration. However, these are similarly disclosed in the JSIA published technical bulletin (Publication No. 2001-1745, page 25, (Invented on March 15, 2001, Invention Association). In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it carries out in a pressurized state.

It is preferable that the cellulose acylate solution has a viscosity and a dynamic storage elastic modulus within the ranges described below because it is easy to cast. These values are measured using 1 mL of the sample solution in a rheometer “CLS 500” and “Steel Cone” (both manufactured by TA Instruments) having a diameter of 4 cm / 2 °. The measurement conditions were measured by varying the range from 40 ° C. to −10 ° C. at 2 ° C./min with an Oscillation Step / Temperature Ramp, a static non-Newtonian viscosity n ^* (Pa · s) at 40 ° C., and a storage elasticity at 5 ° C. The rate G ′ (Pa) is obtained. Note that the sample solution is preliminarily kept at the measurement start temperature until the liquid temperature becomes constant, and then the measurement is started.

  In the present invention, the viscosity at 40 ° C. is 1 to 400 Pa · s, the dynamic storage elastic modulus at 15 ° C. is preferably 500 Pa or more, and more preferably the viscosity at 40 ° C. is 10 to 200 Pa · s. Therefore, the dynamic storage elastic modulus at 15 ° C. should be 100 to 1,000,000. Furthermore, the dynamic storage elastic modulus at low temperature is preferably as large as possible. For example, when the casting support is −5 ° C., the dynamic storage elastic modulus is preferably 10,000 to 1,000,000 Pa at −5 ° C. When the support is at −50 ° C., the dynamic storage elastic modulus at −50 ° C. is preferably 10,000 to 5 million Pa.

  In the present invention, since the above-mentioned specific cellulose acylate is used, it is characterized in that a high concentration dope can be obtained. A cellulose acylate having a high concentration and excellent stability can be obtained without resorting to a means of concentration. A rate solution is obtained. Further, in order to facilitate dissolution, the solution may be dissolved at a low concentration and then concentrated using a concentration means. The concentration method is not particularly limited. For example, the low-concentration solution is guided between the cylindrical body and the rotation trajectory of the outer periphery of the rotating blade rotating in the circumferential direction, and the temperature between the solution and the solution. A method of giving a difference and obtaining a high-concentration solution while evaporating the solvent (for example, JP-A-4-259511), until a heated low-concentration solution is blown into the container from the nozzle until the solution hits the inner wall of the container from the nozzle The solvent is flash evaporated between the container and the solvent vapor is withdrawn from the container and the concentrated solution is withdrawn from the container bottom (eg, US Pat. No. 2,541,012, US Pat. No. 2,858,229, US The method described in Japanese Patent No. 4,414,341, US Pat. No. 4,504,355, etc.) and the like.

  Prior to casting, the dope solution is preferably filtered off foreign matters such as undissolved matter, dust, and impurities using an appropriate filter medium such as a wire mesh or flannel. For filtration of the cellulose acylate solution, it is preferable to use a filter having an absolute filtration accuracy of 0.1 to 100 μm, and it is more preferable to use a filter having an absolute filtration accuracy of 0.5 to 25 μm. The thickness of the filter is preferably from 0.1 to 10 mm, more preferably from 0.2 to 2 mm. In that case, the filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, further 1.0 MPa or less, and particularly preferably 0.2 MPa or less. As the filter medium, conventionally known materials such as glass fibers, cellulose fibers, filter paper, fluororesins such as tetrafluoroethylene resin can be preferably used, and ceramics, metals and the like are particularly preferably used. The viscosity of the cellulose acylate solution immediately before film formation may be in a range that can be cast during film formation, and is usually prepared in a range of 10 Pa · s to 2000 Pa · s, preferably 30 Pa · s to 1000 Pa. · S is more preferable, and 40 Pa · s to 500 Pa · s is more preferable. The temperature at this time is not particularly limited as long as it is a temperature at the time of casting, but is preferably −5 to + 70 ° C., more preferably −5 to + 55 ° C.

Film Formation The cellulose acylate film preferably used in the present invention can be obtained by forming a film using the cellulose acylate solution (dope). As the film forming method and equipment, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film are used. The dope (cellulose acylate solution) prepared from the dissolving machine (kettle) is once stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope is sent from the dope discharge port to the pressurizing die through a pressurizing quantitative gear pump capable of feeding the dope with high accuracy by the number of rotations, for example, and the dope is run endlessly from the die (slit) of the pressurizing die The dope film (also referred to as a web) is peeled off from the metal support at a peeling point where the metal support is almost cast around the metal support. The both ends of the obtained web are sandwiched between clips, transported by a tenter while maintaining the width, dried, and then transported by a roll group of a drying device to finish drying, and wound to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. In the solution casting film forming method used for the functional protective film for electronic displays, in addition to the solution casting film forming apparatus, surface processing on films such as an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. Therefore, a coating device is often added. Although each manufacturing process is described briefly below, it is not limited to these.

  In producing a cellulose acylate film by the solvent cast method, first, the prepared cellulose acylate solution (dope) is cast on a drum or a band, and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 5 to 40% by mass. The surface of the drum or band is preferably finished in a mirror state. For the dope, a method of casting on a drum or band having a surface temperature of 30 ° C. or less is preferably employed, and the metal support temperature is particularly preferably in the range of −10 to 20 ° C. Further, in the present invention, JP 2000-301555 A, JP 2000-301558 A, JP 07-032391, JP 03-193316, JP 05-086212, JP 62-037113, JP The methods described in JP-A No. 02-276607, JP-A No. 55-014201, JP-A No. 02-111511, and JP-A No. 02-208650 can be used.

Multilayer Casting The cellulose acylate solution may be cast as a single layer liquid on a smooth band or drum as a metal support, or a plurality of cellulose acylate liquids of two or more layers may be cast. Good. When casting a plurality of cellulose acylate solutions, a solution containing cellulose acylate is cast from a plurality of casting openings provided at intervals in the traveling direction of the metal support, and the films are laminated while being laminated. For example, methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be applied. A film can also be formed by casting a cellulose acylate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, It can be carried out by the methods described in JP-A Nos. 61-104813, 61-158413, and 6-134933. Further, the cellulose described in JP-A-56-162617, a flow of a high-viscosity cellulose acylate solution is wrapped with a low-viscosity cellulose acylate solution, and the high-viscosity and low-viscosity cellulose acylate solutions are simultaneously extruded. An acylate film casting method may be used. Furthermore, it is also a preferred embodiment that the outer solution contains a larger amount of an alcohol component that is a poorer solvent than the inner solution, as described in JP-A-61-94724 and JP-A-61-94725. . Alternatively, two casting ports are used, and after the film formed on the metal support is peeled off by the first casting port, the second casting is performed on the side of the film that is in contact with the metal support surface. Thus, a film having a plurality of layers can also be produced, and examples thereof include a method described in Japanese Patent Publication No. 44-20235. The cellulose acylate solution to be cast may be the same solution or different cellulose acylate solutions, and is not particularly limited. In order to give a function to a plurality of cellulose acylate layers, a cellulose acylate solution corresponding to the function may be extruded from each casting port. Further, the cellulose acylate solution may be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorption layer, and a polarizing layer).

  In the conventional single-layer solution, in order to obtain the required film thickness, it is necessary to extrude a high-concentration and high-viscosity cellulose acylate solution, in which case the stability of the cellulose acylate solution tends to deteriorate. In many cases, a solid matter is generated, resulting in a failure or flatness. As a solution to this, by casting a plurality of cellulose acylate solutions from a plurality of casting ports relatively little by little, it becomes possible to extrude a highly viscous solution onto a metal support at the same time. In addition to producing an excellent planar film with improved properties, the use of a concentrated cellulose acylate solution can achieve a reduction in drying load and increase the production speed of the film.

  In the case of co-casting, the inner and outer thicknesses are not particularly limited, but preferably the outer side is preferably 1 to 50% of the total film thickness, and more preferably 2 to 30%. Here, in the case of co-casting of three or more layers, the total film thickness of the layer in contact with the metal support and the layer in contact with the air side is defined as the outer thickness. In the case of co-casting, a cellulose acylate film having a laminated structure can be produced by co-casting cellulose acylate solutions having different additive concentrations such as the plasticizer, ultraviolet absorber, and matting agent. For example, a cellulose acylate film having a structure of skin layer / core layer / skin layer can be produced. For example, the matting agent can be contained in the skin layer in a large amount or only in the skin layer. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer. It is also possible to change the type of plasticizer and ultraviolet absorber between the core layer and the skin layer. For example, the skin layer contains at least one of a low-volatile plasticizer and an ultraviolet absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. Furthermore, it is also a preferred embodiment that a peeling accelerator is contained only in the skin layer on the metal support side. Furthermore, it is also preferable to add more alcohol, which is a poor solvent, to the skin layer than the core layer in order to cool the metal support by the cooling drum method to gel the solution. The Tg of the skin layer and the core layer may be different, and the Tg of the core layer is preferably lower than the Tg of the skin layer. Further, the viscosity of the solution containing cellulose acylate during casting may be different between the skin layer and the core layer, and the viscosity of the skin layer is preferably smaller than the viscosity of the core layer. It may be smaller than the viscosity of the layer.

Casting method As a casting method of the solution, there is a method of uniformly extruding the prepared dope from a pressure die onto a metal support, and a doctor for adjusting the film thickness with a blade of the dope once cast on the metal support. Although there are a method using a blade and a method using a reverse roll coater which adjusts with a reverse rotating roll, a method using a pressure die is preferable. The pressure die includes a coat hanger type and a T die type, and any of them can be preferably used. In addition to the methods mentioned here, it can be carried out by various known methods for casting a cellulose triacetate solution, and each condition is set in consideration of differences in the boiling point of the solvent used. Thus, the same effects as those described in the respective publications can be obtained.

  The endlessly running metal support used for producing the cellulose acylate film preferably used in the present invention includes a drum whose surface is mirror-finished by chrome plating and a stainless steel belt whose surface is mirror-finished by surface polishing ( May be referred to as a band). One or more pressure dies may be installed above the metal support. Preferably 1 or 2 groups. When two or more are installed, the amount of dope to be cast may be divided into various ratios for each die, or the dope may be fed to the dies from each of a plurality of precision quantitative gear pumps. The temperature of the cellulose acylate solution used for casting is preferably −10 to 55 ° C., more preferably 25 to 50 ° C. In that case, all solution temperatures in the process may be the same or may be different in each part of the process. If they are different, the temperature may be a desired temperature just before casting.

Drying The drying of the dope on the metal support, which is related to the production of the cellulose acylate film, is generally performed with hot air from the surface side of the metal support (drum or belt), that is, from the surface of the web on the metal support. Contact method, method of applying hot air from the back of the drum or belt, contact the temperature controlled liquid from the back of the belt or drum opposite the dope casting surface, and heat the drum or belt by heat transfer to increase the surface temperature. Although there is a back surface liquid heat transfer method to be controlled, the back surface liquid heat transfer method is preferable. The surface temperature of the metal support before casting may be any number as long as it is not higher than the boiling point of the solvent used for the dope. However, in order to promote drying and to lose fluidity on the metal support, the temperature should be set to 1 to 10 ° C. lower than the boiling point of the lowest boiling solvent used. Is preferred. This is not the case when the cast dope is cooled and peeled off without drying.

Stretching treatment The protective film (particularly cellulose acylate film) preferably used in the present invention is preferably adjusted for retardation by a stretching treatment. In particular, when the in-plane retardation value of the cellulose acylate film is set to a high value, a method of positively stretching in the width direction, for example, JP-A-62-115035, JP-A-4-152125, A method of stretching the produced film described in JP-A-4-284211, JP-A-4-298310, and JP-A-11-48271 can be used.

The film is stretched at room temperature or under heating conditions. The heating temperature is preferably not higher than the glass transition temperature of the film. The film may be stretched uniaxially or longitudinally or biaxially, and biaxial stretching is preferred. Biaxial stretching may be simultaneous or sequential stretching. The stretching is preferably performed at 1 to 200%, more preferably 1 to 100%, and further preferably 1 to 50%. In the case of biaxial stretching, it is preferable to perform stretching in each range in each direction. Further, in the case of the polarizing plate in the liquid crystal display device in which the absorption axes of the polarizing plates on the front and back sides of the liquid crystal cell as in the VA mode are orthogonal to each other and the absorption axis is parallel to the side of the liquid crystal cell as in the present invention. The upper limit is preferably 200% or less. More preferably, it is preferable to perform stretching of 28 to 200%, particularly preferably 30 to 200%. Biaxial stretching is also preferable.
Moreover, it is also preferable to heat for 5 minutes or more at a high temperature exceeding Tg after stretching.

  In order to compensate for the optical anisotropy of the liquid crystal cell and to suppress light leakage when the polarizing plate is viewed obliquely, it is preferable to use a protective film having an in-plane retardation value of 30 nm or more. It is preferable to use a cellulose acylate film that has been stretched. In order to obtain the optical characteristics, specifically, the stretching ratio is preferably 10% or more, more preferably 15% or more.

  In order to suppress light leakage when the polarizing plate is viewed obliquely, it is necessary to arrange the transmission axis of the polarizer and the in-plane slow axis of the cellulose acylate film in parallel. Since the transmission axis of the roll film-like polarizer produced continuously is generally parallel to the width direction of the roll film, it is composed of the roll film-like polarizer and the roll film-like cellulose acylate film. In order to continuously bond the protective film, the in-plane slow axis of the roll film-shaped protective film needs to be parallel to the width direction of the film. Therefore, it is preferable to stretch more in the width direction. The stretching process may be performed in the middle of the film forming process, or the original fabric that has been formed and wound may be stretched. In the former case, stretching may be performed in a state containing a residual solvent, and the stretching can be preferably performed at a residual solvent amount of 2 to 30% by mass.

The film thickness of the cellulose acylate film preferably used in the present invention obtained after drying varies depending on the purpose of use, is preferably in the range of 5 to 500 μm, more preferably in the range of 20 to 300 μm, and in the range of 30 to 150 μm. Is more preferable. Moreover, it is preferable that it is 40-110 micrometers for optical use, especially for VA liquid crystal display devices. The film thickness may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap of the die base, the extrusion pressure from the die, the metal support speed, and the like so as to obtain a desired thickness.
Further, in the polarizing plate of the liquid crystal display device in which the absorption axes of the polarizing plates on the front and back of the liquid crystal cell as in the VA mode are orthogonal to each other and the absorption axis is parallel to the side of the liquid crystal cell as in the present invention, 20 to 200 μm. It is preferable that it is 35-200 micrometers, and it is especially preferable that it is 55-200 micrometers.
Of these, a thicker protective film is preferred because it increases the force of suppressing the shrinkage of PVA, which is a polarizing layer.

  The width of the cellulose acylate film obtained as described above is preferably 0.5 to 3 m, more preferably 0.6 to 2.5 m, and still more preferably 0.8 to 2.2 m. The length is preferably 100 to 10,000 m per roll, more preferably 500 to 7000 m, and still more preferably 1000 to 6000 m. When winding, it is preferable to give knurling to at least one end, the knurling width is preferably 3 mm to 50 mm, more preferably 5 mm to 30 mm, and the height is preferably 0.5 to 500 μm, more preferably 1 to 200 μm. is there. This may be a single push or a double push.

The variation in the Re ₅₉₀ value in the width direction of the film is preferably ± 5 nm, and more preferably ± 3 nm. Further, the variation of the Rth ₅₉₀ value in the width direction is preferably ± 10 nm, and more preferably ± 5 nm. Further, the variation in the Re value and the Rth value in the length direction is preferably within the range of the variation in the width direction.

Optical Properties of Cellulose Acylate Film In the present specification, Reλ and Rthλ represent in-plane retardation and retardation in the thickness direction at wavelength λ, respectively. Reλ is measured in “KOBRA 21ADH” (manufactured by Oji Scientific Instruments) by making light having a wavelength of λ nm incident in the normal direction of the film. Rthλ is incident with light having a wavelength of λnm from the direction inclined by + 40 ° with respect to the normal direction of the film, using Reλ and the in-plane slow axis (determined by “KOBRA 21ADH”) as the tilt axis (rotation axis). The retardation value measured and the retardation measured by injecting light having a wavelength of λ nm from the direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis) “KOBRA 21ADH” is calculated based on the retardation values measured in a total of three directions.

Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), polystyrene (1.59).
Further, by inputting the assumed average refractive index values and thicknesses, (refractive index in a slow axis direction) n _x by KOBRA 21ADH, (refractive index of the fast axis direction) n _y, n _z (thickness direction Is calculated). In addition, “KOBRA 21ADH” also calculates an angle β with respect to the film normal direction that minimizes the retardation value with respect to the light propagating through the film when the in-plane slow axis is the tilt axis.

It is preferable that the Reλ retardation value and the Rthλ retardation value satisfy the following formulas (2) and (3), respectively, in order to widen the viewing angle of a liquid crystal display device, particularly a VA mode liquid crystal display device. In particular, a cellulose acylate film is preferable when used for a protective film on the liquid crystal cell side of the polarizing plate.
Formula (2): 0 ≦ Re ₅₉₀ ≦ 200
Formula (3): 0 ≦ Rth ₅₉₀ ≦ 400
(In Equations (2) and (3), Reλ and Rthλ are, in order, a value at a wavelength λ nm, a front retardation value, and a retardation value in the film thickness direction (unit: nm).)

In order to reduce the influence of the optical anisotropy of the cellulose acylate film, Reλ and Rthλ of the cellulose acylate film disposed on the liquid crystal cell side preferably satisfy the formulas (8) to (11).
Formula (8): 0 ≦ Re ₅₉₀ ≦ 10
Formula (9): | Rth ₅₉₀ | ≦ 25
Formula (10): | Re ₄₀₀ −Re ₇₀₀ | ≦ 10
Formula (11): | Rth ₄₀₀ −Rth ₇₀₀ | ≦ 35
(In formulas (8) to (11), Reλ and Rthλ are a value at a wavelength λ nm, a front retardation value, and a retardation value in the film thickness direction (unit: nm) in this order.)

When the cellulose acylate film preferably used in the present invention is used in the VA mode, it is used only on one of the upper and lower sides of the cell (two-sheet type) in which two sheets are used on both sides of the cell. There are two types of forms (single sheet type).
In the case of the two-sheet type, Re ₅₉₀ is preferably 20 to 100 nm, and more preferably 30 to 70 nm. Rth ₅₉₀ is preferably 70 to 300 nm, and more preferably 100 to 200 nm.
In the case of a single sheet type, Re ₅₉₀ is preferably 30 to 150 nm, and more preferably 40 to 100 nm. Rth ₅₉₀ is preferably from 100 to 300 nm, more preferably from 150 to 250 nm.

  The variation of the slow axis angle in the film plane of the cellulose acylate film preferably used in the present invention is preferably in the range of −2 ° to + 2 ° with respect to the reference direction of the roll film, from −1 ° to More preferably, it is in the range of + 1 °, and most preferably in the range of -0.5 ° to + 0.5 °. Here, the reference direction is the longitudinal direction of the roll film when the cellulose acylate film is longitudinally stretched, and the width direction of the roll film when laterally stretched.

The cellulose acylate film preferably used in the present invention has a difference ΔRe (= Re _10% −Re _80% ) between the Re value at 25 ° C. and 10% RH and the Re value at 25 ° C. and 80% RH is 0. The difference between the Rth value at 25 ° C. and 10% RH and the Rth value at 25 ° C. and 80% RH is ΔRth (= Rth _10% −Rth _80% ) is 0 to 30 nm. It is preferable in order to reduce the color change with time of the apparatus.

Further, the cellulose acylate film preferably used in the present invention has an equilibrium water content of not more than 3.2% at 25 ° C. and 80% RH in order to reduce the color change with time of the liquid crystal display device.
The moisture content was measured by using a cellulose acylate film sample of 7 mm × 35 mm, a Karl Fischer method using a moisture measuring device and a sample drying apparatus (“CA-03”, “VA-05”, both Mitsubishi Chemical Corporation). Measure with It is calculated by dividing the amount of water (g) by the sample mass (g).

Furthermore, the cellulose acylate film preferably used in the present invention, 60 ° C., is 95% RH, 24 hours of moisture permeability (film thickness 80μm equivalent), is ^{400g / m 2 · 24hr~1800g / m} 2 · 24hr This is preferable in order to reduce the color change of the liquid crystal display device over time.

The moisture permeability decreases as the thickness of the cellulose acylate film increases, and increases as the thickness decreases. Therefore, it is necessary to provide and convert a reference film thickness in any film thickness sample. In the present invention, the film thickness was converted according to the following formula (13) with the standard film thickness set to 80 μm.
Formula (13)
Moisture permeability in terms of 80 μm = measured moisture permeability × measured film thickness μm / 80 μm

  The measurement method of moisture permeability is "Polymer Physical Properties II" (Polymer Experiment Course 4, Kyoritsu Shuppan), pages 285-294: Measurement of vapor permeation (mass method, thermometer method, vapor pressure method, adsorption amount method) The method described in can be applied.

  The glass transition temperature was measured by adjusting a cellulose acylate film sample (unstretched) 5 mm × 30 mm at 25 ° C. and 60% RH for 2 hours or more, and then measuring a dynamic viscoelasticity measuring device “Vibron: DVA-225” ( Measured at a distance between grips of 20 mm, a temperature rising rate of 2 ° C./minute, a measurement temperature range of 30 ° C. to 200 ° C., and a frequency of 1 Hz, using a logarithmic axis and a storage elastic modulus on the logarithmic axis. The temperature at which the storage elastic modulus shifts from the solid region to the glass transition region when the horizontal axis is the temperature (° C.) is a glass transition temperature Tg. did. Specifically, on the obtained chart, when the straight line 1 is drawn in the solid region and the straight line 2 is drawn in the glass transition region, the intersection of the straight line 1 and the straight line 2 decreases rapidly when the temperature rises. The glass transition temperature Tg (dynamic viscoelasticity) was determined because the film started to soften and the temperature started to shift to the glass transition region.

  The elastic modulus was measured by adjusting a cellulose acylate film sample 10 mm × 150 mm for 2 hours or more at 25 ° C. and 60% RH, and then tensile tester “Strograph-R2” (manufactured by Toyo Seiki Seisakusho) The chucking distance was 100 mm, the temperature was 25 ° C., and the stretching speed was 10 mm / min.

The measurement of the hygroscopic expansion coefficient is a value L _{80% obtained} by measuring the dimension of a film left at 25 ° C. and 80% RH for 2 hours or more with a pin gauge, and the dimension of a film left at 25 ° C. and 10% RH for 2 hours or more. Was obtained by the following formula (14) from the value L _10% measured with a pin gauge.
Formula (14)
(L _80% -L _10% ) / (80% RH-10% RH) × 10 ⁶

The cellulose acylate film preferably used in the present invention preferably has a haze in the range of 0.01 to 2%. Here, the haze can be measured as follows.
The haze is measured by measuring a cellulose acylate film sample 40 mm × 80 mm at 25 ° C. and 60% RH with a haze meter “HGM-2DP” (manufactured by Suga Test Instruments Co., Ltd.) according to JIS K-6714.

  Furthermore, the cellulose acylate film preferably used in the present invention preferably has a mass change in the range of 0 to 5% by mass when left for 48 hours under conditions of 80 ° C. and 90% RH.

  Furthermore, the cellulose acylate film preferably used in the present invention has a dimensional change when left for 24 hours under the conditions of 60 ° C. and 95% RH, and is allowed to stand for 24 hours under the conditions of 90 ° C. and 5% RH. The dimensional change when placed is small, and it is preferable that both are in the range of 0 to 5%.

The photoelastic coefficient is preferably 50 × 10 ⁻¹³ cm ² / dyne or less in order to reduce the color change with time of the liquid crystal display device.
As a specific measuring method, a tensile stress is applied to the major axis direction of a cellulose acylate film sample 10 mm × 100 mm, and the retardation at that time is measured with an ellipsometer “M150” (JASCO Corporation). The photoelastic coefficient was calculated from the amount of change in retardation with respect to stress.

Cycloolefin polymer Further, as the protective film, a cycloolefin polymer can be used instead of cellulose acylate. Examples of cycloolefin polymers include JP-A-1-132625, JP-A-1-132626, JP-A-1-240517, JP-A-63-145324, JP-A-63-264626, JP-A-63-264626. JP 63-218726, JP 2-133413, JP 60-168708, JP 61-120816, JP 60-115912, JP 62-252406 JP-A-60-252407, International Publication No. 2004 / 049011A1, Pamphlet of International Publication No. 2004 / 068226A1, Pamphlet of International Publication No. 2004 / 070463A1 may be used. Moreover, as commercially available cycloolefin polymers, ARTON (manufactured by JSR Corporation), ZEONOR (manufactured by ZEON Corporation), ZEONEX (manufactured by ZEON Corporation), ESINA (Sekisui Chemical Co., Ltd.) Can be used.
When it is desired to reduce the influence of the optical anisotropy of the cycloolefin polymer film, Re (λ) and Rth (λ) of the protective film (cycloolefin polymer film) disposed on the liquid crystal cell side are the same as those described above. It is preferable to satisfy the formulas (8) to (11).

(Polarizer)
Next, the polarizing plate according to the present invention will be described.
In the polarizing plate of the present invention, it is preferable that the thickness d ^{1 of the} protective film disposed on the liquid crystal cell side and the thickness d ^{2 of the} protective film disposed on the side opposite to the liquid crystal cell satisfy the following formula (15).
Formula (15)
0.3 × d ¹ ≦ d ² ≦ 1.3 × d ¹
By satisfying the above formula (15), when combining protective films having substantially the same elastic modulus and hygroscopic expansion coefficient, the curl of the polarizing plate is in the range of −30 mm to +15 mm, and a preferable result is obtained.

In the polarizing plate according to the present invention, the elastic modulus E ^{1 of the} protective film disposed on the liquid crystal cell side and the elastic modulus E ^{2 of the} protective film disposed on the opposite side of the liquid crystal cell satisfy the following formula (16). Is preferred. Thereby, when a protective film having substantially the same thickness and hygroscopic expansion coefficient is combined, the curl of the polarizing plate is in the range of −30 mm to +15 mm, and a preferable result is obtained.
Formula (16)
0.3 × E ¹ ≦ E ² ≦ 1.3 × E ¹

Further, the thickness d ¹ and elastic modulus E ^{1 of the} protective film disposed on the liquid crystal cell side, and the thickness d ² and elastic modulus E ^{2 of the} protective film disposed on the opposite side of the liquid crystal cell satisfy the following formula (17). It is preferable.
Formula (17)
0.3 × E ¹ × d ¹ ≦ E ² × d ² ≦ 1.3 × E ¹ × d ¹
By satisfy | filling numerical formula (17), also when combining the protective film from which thickness and elastic modulus differ, the curl of a polarizing plate becomes the range of -30 mm-+15 mm.

Furthermore, in the polarizing plate of the present invention, the hygroscopic expansion coefficient C ¹ of the protective film disposed on the liquid crystal cell side and the hygroscopic expansion coefficient C ^{2 of the} protective film disposed on the opposite side of the liquid crystal cell are expressed by the following formula (18). It is preferable to satisfy.
Formula (18)
0.3 × C ¹ ≦ C ² ≦ 1.3 × C ¹
By satisfying the above mathematical formula, the polarizing plate curl in the case where the humidity when the polarizing plate is bonded to the liquid crystal cell is higher than that during the preparation of the polarizing plate is in the range of −30 mm to +15 mm, and a preferable result is obtained.

  As the polarizer of the polarizing plate, an iodine-based polarizer, a dye-based polarizer using a dichroic dye, a polyene-based polarizer, or the like can be used. The iodine polarizer and the dye polarizer are preferably manufactured using a polyvinyl alcohol film.

When a cellulose acylate film is used for the protective film, the method for producing the polarizing plate is not particularly limited, and can be produced by a general method. For example, there is a method in which the obtained cellulose acylate film is treated with an alkali and bonded to both sides of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed. Examples of the adhesive used to bond the protective film-treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like.
In the case of using a cycloolefin polymer film as a protective film, the adhesive is not limited to polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, and vinyl latexes such as butyl acrylate, acrylic polymers, and epoxy polymers. Adhesives such as polymers, modified olefin polymers, styrene butadiene polymers, and special synthetic rubbers can be used.
A surface treatment may be performed in order to improve adhesiveness. Specific examples include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. It is also preferable to provide an undercoat layer as described in JP-A-7-333433. From the viewpoint of maintaining the flatness of the film, the temperature of the polymer film in these treatments is preferably Tg (glass transition temperature) or lower.

The polarizing plate of the present invention comprises a polarizer, a protective film (1) and a protective film (2) provided on both sides of the polarizer, and an adhesive layer provided on the protective film (1). Being done. Moreover, the adhesion layer may be provided also on the protective film (2). Furthermore, in the liquid crystal display device, the polarizing plate of the present invention is preferably arranged so that the protective film (1) side is on the liquid crystal cell side. Moreover, the polarizing plate of the present invention may be constituted by laminating a separate film on the adhesive layer surface and a protective film on the opposite surface of the polarizing plate from the separate film. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal cell. Moreover, a separate film is used in order to cover the adhesion layer for bonding a polarizing plate to a liquid crystal cell, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.
As described above, the adhesive layer was prepared by applying a solution of the composition containing the (meth) acrylic copolymer (A) and the polyfunctional compound (B) onto a separate film with a coater such as a die coater and drying. Then, it forms by transferring the whole separate film on a protective film. After the solution of the above composition is applied on a protective film and dried, the adhesive layer may be covered with a separate film.

  As shown in FIG. 1, when the above-described stretched protective film is used, the polarizer may be bonded so that the transmission axis 2 of the polarizer 11 and the slow axis 4 of the protective film coincide with each other. preferable.

  In addition, the polarizing plate produced under polarizing plate crossed Nicols has an orthogonal accuracy of 1 ° between the slow axis of the protective film (1) preferably used in the present invention and the absorption axis of the polarizer (axis orthogonal to the transmission axis). If it is within the range, the degree of polarization performance under the polarizing plate crossed Nicole will be lowered, causing light leakage, or insufficient black level and contrast will not be obtained when combined with a liquid crystal cell. Since it does not easily occur, the difference between the slow axis direction of the cellulose acylate film preferably used in the present invention and the transmission axis direction of the polarizing plate is preferably within 1 °, and within 0.5 °. More preferably.

  In general, the polarizing plate is attached to the liquid crystal cell by attaching the polarizing plate to a suction jig having a large number of holes, peeling off the separate film on the surface of the adhesive layer formed by coating the adhesive layer, The layer surface is brought into contact with the liquid crystal cell, and is applied by pressing with a roller. At this time, if the polarizing plate is curled so as to be concave on the liquid crystal cell side, the suction to the suction jig is not sufficiently performed, and the attachment angle to the suction jig is shifted, so that the sticking to the liquid crystal cell is not possible. The attachment angle is shifted and display characteristics as designed cannot be obtained. In addition, the polarizing plate may fall off from the suction jig during the pasting to the liquid crystal cell, and the pasting work cannot be continued, and the work may be interrupted.

  In order not to cause such a polarizing plate sticking failure, the curling amount of the polarizing plate is preferably in the range of −30 mm to +15 mm, more preferably in the range of −20 mm to +5 mm, and −10 mm to 0 mm. More preferably, it is set as the range. Here, the case of being concave on the surface (adhesive layer surface) side to be attached to the liquid crystal cell is called + (plus) curl, and the case of being convex is called-(minus) curl. The curl amount can be controlled by adjusting the relationship among the thickness, elastic modulus, and hygroscopic expansion coefficient of the protective film on the liquid crystal cell side and the protective film on the opposite side of the liquid crystal cell.

  The curl was measured after placing a polarizing plate of 230 mm x 305 mm on a flat table with the surface where the end is lifted down and leaving it in an environment of 25 ° C and 60% RH for 2 hours or longer. The height of the farthest position of the end of the polarizing plate is measured with respect to the surface of the table, and is defined as the curl amount. When a separate film and a protective film were attached, the measurement was performed with these films attached.

(Surface treatment of protective film)
The protective film in the present invention can achieve improved adhesion between the protective film and each functional layer (for example, the undercoat layer and the back layer) by performing a surface treatment as the case may be. As the surface treatment, for example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs in a low-pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferable. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail in the Journal of the Invention Association (Technology No. 2001-1745, pages 30 to 32, issued on March 15, 2001, Invention Association). Note that, in the plasma treatment at atmospheric pressure which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 Kgy is used under 10 to 1000 Kev, and more preferably irradiation energy of 20 to 300 Kgy is used under 30 to 500 Kev. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film.

Alkaline Saponification Treatment The alkali saponification treatment is preferably carried out by a method in which a cellulose acylate film is directly immersed in a saponification solution tank or a method in which a saponification solution is applied to the cellulose acylate film. Examples of the coating method include a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method. The solvent of the alkali saponification coating solution has good wettability in order to apply the saponification solution to the cellulose acylate film, and the surface of the cellulose acylate film surface is not formed by the saponification solution solvent without forming irregularities. It is preferred to select a solvent that remains good. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable. An aqueous solution of a surfactant can also be used as a solvent. The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the above solvent, and more preferably KOH or NaOH. The pH of the saponification coating solution is preferably 10 or more, and more preferably 12 or more. The reaction conditions at the time of alkali saponification are preferably 1 second to 5 minutes at room temperature, more preferably 5 seconds to 5 minutes, and particularly preferably 20 seconds to 3 minutes. After the alkali saponification reaction, it is preferable to wash the surface on which the saponification solution is applied with water or with an acid and then with water.

Moreover, the polarizing plate concerning this invention may provide an optically anisotropic layer on a protective film. When an optically anisotropic layer is provided on the protective film of the polarizing plate, the adhesive layer is further provided outside the optically anisotropic layer from the polarizer side.
The material of the optically anisotropic layer is not limited, such as a liquid crystal compound, a non-liquid crystal compound, an inorganic compound, and an organic / inorganic composite compound. As the liquid crystalline compound, a low molecular compound having a polymerizable group is aligned, and then the alignment is fixed by polymerization by light or heat, or the liquid crystalline polymer is heated and aligned and then cooled and aligned in a glassy state. You can use what you want to fix. As the liquid crystalline compound, those having a disk-like structure, those having a rod-like structure, and those having a structure showing optical biaxiality can be used. As the non-liquid crystalline compound, a polymer having an aromatic ring such as polyimide or polyester can be used.
Various methods, such as application | coating, vapor deposition, sputtering, can be used for the formation method of an optically anisotropic layer.

  Furthermore, the polarizing plate according to the present invention is preferably one in which at least one layer of a hard coat layer, an antiglare layer or an antireflection layer is provided on the surface of the protective film on at least one side of the polarizing plate. That is, as shown in FIG. 2, when the polarizing plate is used for a liquid crystal display device, a functional film 14 such as an antireflection layer is provided on the protective film 13 (TAC2) disposed on the side opposite to the liquid crystal cell. The functional film 14 is preferably provided with at least one layer of a hard coat layer, an antiglare layer or an antireflection layer. In addition, it is not necessary to provide each layer as a separate layer, for example, by providing an antireflection layer and a hard coat layer with an antiglare function, instead of providing two layers of an antireflection layer and an antiglare layer, You may make it function as an anti-glare antireflection layer.

Antireflective layer In the present invention, an antireflective layer in which at least a light scattering layer and a low refractive index layer are laminated in this order on the protective film of the polarizing plate, or a medium refractive index layer and a high refractive index layer on the protective film An antireflection layer in which low refractive index layers are laminated in this order is suitably provided. Preferred examples thereof are described below. In the former configuration, the specular reflectance is generally 1% or more, which is referred to as a low reflection (LR) film. In the latter configuration, it is possible to realize a mirror reflectivity of 0.5% or less, and this is called an Anti Reflection (AR) film.

LR film A preferred example of an antireflection layer (LR film) in which a light scattering layer and a low refractive index layer are provided on a protective film of a polarizing plate will be described.
The light scattering layer in the LR film preferably has mat particles dispersed therein, and the refractive index of the material other than the mat particles in the light scattering layer is preferably in the range of 1.50 to 2.00. The refractive index of the low refractive index layer in the LR film is more preferably in the range of 1.20 to 1.49. The light scattering layer in the LR film has both antiglare properties and hard coat properties, and may be a single layer or a plurality of layers, for example, two to four layers.

  The antireflection layer in the LR film has a surface irregularity shape, the centerline average roughness Ra is 0.08 to 0.40 μm, the 10-point average roughness Rz is 10 times or less of Ra, and the average irregularity distance Sm is 1 to 1. 100 μm, the standard deviation of the height of the convex part from the deepest part of the irregularities is 0.5 μm or less, the standard deviation of the average irregularity distance Sm with respect to the center line is 20 μm or less, and the surface with an inclination angle of 0-5 ° is 10% or more It is preferable to design so that sufficient anti-glare property and visual uniform matte feeling can be achieved.

Further, the ratio between the minimum value and the maximum value of the reflectance when the color of the reflected light under the C light source is in the range of a ^* value −2 to 2, b ^* value −3 to 3 and 380 nm to 780 nm. It is preferable that the color is 5 to 0.99 because the color of the reflected light becomes neutral. Furthermore, it is preferable that the b ^* value of the transmitted light under the C light source is 0 to 3 because the yellow color of white display when applied to a display device is reduced. Furthermore, if a 120 μm × 40 μm grid is inserted between the surface light source and the antireflection layer and the luminance distribution is measured on the film, the standard deviation of the luminance distribution is 20 or less. Since glare when the polarizing plate of the invention is applied is reduced, it is preferable.

  The antireflective layer in the LR film can suppress reflection of external light by setting the specular reflectance to 2.5% or less, the transmittance to 90% or more, and the 60 ° gloss to 70% or less as its optical characteristics. Is preferable. In particular, the specular reflectance is more preferably 1% or less, and most preferably 0.5% or less. Haze 20% to 50%, ratio of internal haze / total haze value 0.3 to 1, haze value after formation of low refractive index layer from haze value up to light scattering layer within 15%, comb width 0 .Transmission image clarity at 5 mm to 20% to 50%, vertical transmission light / transmission ratio in the direction of 2 ° tilt from vertical is 1.5 to 5.0, thereby preventing glare on a high-definition LCD panel. This is preferable because blurring of characters and the like is reduced.

The refractive index of the low refractive index layer in the LR film is preferably 1.20 to 1.49, more preferably 1.30 to 1.44. Furthermore, the low refractive index layer preferably satisfies the following formula (19) from the viewpoint of reducing the reflectance.
Formula (19)
( ^M / 4) λ × 0.7 <n ^L d ^L <(m / 4) λ × 1.3
(In Formula (19), m is a positive odd number, n ^L is the refractive index of the low refractive index layer, d ^L is the film thickness (nm) of the low refractive index layer, and λ is the wavelength, (The value is in the range of 500 to 550 nm.)

The material for forming the low refractive index layer in the LR film will be described below.
The low refractive index layer preferably contains a fluorine-containing polymer as a low refractive index binder.
As the fluorine polymer, a fluorine-containing polymer which is crosslinked by heat or ionizing radiation and having a dynamic friction coefficient of 0.03 to 0.20, a contact angle with water of 90 to 120 ° and a sliding angle of pure water of 70 ° or less is preferable. When the polarizing plate according to the present invention is mounted on an image display device, the lower the peel strength from a commercially available adhesive tape, the easier it is to peel off after sticking a seal or memo, which is preferable. Specifically, when measured with a tensile tester, the peel force is preferably 500 gf or less, more preferably 300 gf or less, and even more preferably 100 gf or less. Further, the higher the surface hardness measured with a microhardness meter, the harder it is to scratch, and the surface hardness is preferably 0.3 GPa or more, more preferably 0.5 GPa or more.

  Examples of the fluorine-containing polymer used in the low refractive index layer include hydrolysates and dehydration condensates of perfluoroalkyl group-containing silane compounds (for example, (heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane). In addition, a fluorine-containing copolymer having a fluorine-containing monomer unit and a structural unit for imparting crosslinking reactivity as structural components may be mentioned.

  Specific examples of the fluorine-containing monomer include, for example, fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, perfluorooctylethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole, etc.) , Part of (meth) acrylic acid or fully fluorinated alkyl ester derivatives (for example, “Biscoat 6FM”, manufactured by Osaka Organic Chemical Industry Co., Ltd.) or “M-2020”, manufactured by Daikin Industries, Ltd.), complete Alternatively, partially fluorinated vinyl ethers and the like can be mentioned, and perfluoroolefins are preferable, and hexafluoropropylene is particularly preferable from the viewpoint of refractive index, solubility, transparency, availability, and the like.

  As a structural unit for imparting crosslinking reactivity, a structural unit obtained by polymerization of a monomer having a self-crosslinkable functional group in the molecule in advance, such as glycidyl (meth) acrylate or glycidyl vinyl ether, a carboxyl group or a hydroxy group, Of monomers having amino groups, sulfo groups, etc. (for example, (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, allyl acrylate, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, maleic acid, crotonic acid, etc.) Structural units obtained by polymerization, structural units in which a crosslinkable reactive group such as a (meth) acryloyl group is introduced into these structural units by a polymer reaction (for example, by acting acrylic acid chloride on a hydroxy group) Can be introduced) And the like.

  In addition to the fluorine-containing monomer unit and the structural unit for imparting crosslinking reactivity, a monomer that does not contain a fluorine atom can be copolymerized as appropriate from the viewpoint of solubility in a solvent, film transparency, and the like. There are no particular limitations on the monomer units that can be used in combination. For example, olefins (ethylene, propylene, isoprene, vinyl chloride, vinylidene chloride, etc.), acrylic esters (methyl acrylate, methyl acrylate, ethyl acrylate, acrylic acid 2) -Ethylhexyl), methacrylates (methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene glycol dimethacrylate, etc.), styrene derivatives (styrene, divinylbenzene, vinyltoluene, α-methylstyrene, etc.), vinyl ethers (methyl) Vinyl ether, ethyl vinyl ether, cyclohexyl vinyl ether, etc.), vinyl esters (vinyl acetate, vinyl propionate, vinyl cinnamate etc.), acrylamides (Nt-butylacrylamide, N-cyclo) Hexyl acrylamide), methacrylamides, and acrylonitrile derivatives.

  As described in JP-A-10-25388 and JP-A-10-147739, a curing agent may be appropriately used in combination with the above polymer.

Light Scattering Layer The light scattering layer in the LR film is formed for the purpose of imparting to the film a light diffusibility due to at least one of surface scattering and internal scattering and a hard coat property for improving the scratch resistance of the film. Therefore, it is formed including a binder for imparting hard coat properties, matte particles for imparting light diffusibility, and inorganic fillers for increasing the refractive index, preventing crosslinking shrinkage, and increasing the strength as necessary. The In addition, by providing such a light scattering layer, the light scattering layer also functions as an antiglare layer, and the polarizing plate has an antiglare layer.

  The thickness of the light scattering layer is preferably 1 to 10 μm and more preferably 1.2 to 6 μm for the purpose of imparting hard coat properties. If the film thickness of the light scattering layer is not less than the lower limit, problems such as insufficient hardware properties are unlikely to occur, and if the thickness is not more than the upper limit, inconveniences such as curling and brittleness are deteriorated and workability is insufficient. Is preferable because it is difficult to cause.

  The binder of the light scattering layer is preferably a polymer having a saturated hydrocarbon chain or a polyether chain as the main chain, and more preferably a polymer having a saturated hydrocarbon chain as the main chain. The binder polymer preferably has a crosslinked structure. As the binder polymer having a saturated hydrocarbon chain as a main chain, a polymer of an ethylenically unsaturated monomer is preferable. As the binder polymer having a saturated hydrocarbon chain as the main chain and having a crosslinked structure, a (co) polymer of monomers having two or more ethylenically unsaturated groups is preferred. In order to make the binder polymer have a high refractive index, the monomer structure contains an aromatic ring or at least one atom selected from halogen atoms other than fluorine, sulfur atoms, phosphorus atoms, and nitrogen atoms. You can also choose.

  Examples of the monomer having two or more ethylenically unsaturated groups include esters of polyhydric alcohol and (meth) acrylic acid (for example, ethylene glycol di (meth) acrylate, butanediol di (meth) acrylate, hexanediol di ( (Meth) acrylate, 1,4-cyclohexanediacrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (Meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, pentaerythritol hexa (meth) acrylate, 1,2,3- Chlorohexane tetramethacrylate, polyurethane polyacrylate, polyester polyacrylate), modified ethylene oxide, vinylbenzene and derivatives thereof (for example, 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4 -Divinylcyclohexanone), vinyl sulfone (eg divinyl sulfone), acrylamide (eg methylenebisacrylamide) and methacrylamide. Two or more of these monomers may be used in combination.

  Specific examples of the high refractive index monomer include bis (4-methacryloylthiophenyl) sulfide, vinyl naphthalene, vinyl phenyl sulfide, 4-methacryloxyphenyl-4′-methoxyphenyl thioether, and the like. Two or more of these monomers may be used in combination.

  Polymerization of these monomers having an ethylenically unsaturated group can be performed by irradiation with ionizing radiation or heating in the presence of a photo radical initiator or a thermal radical initiator. Therefore, a coating solution containing a monomer having an ethylenically unsaturated group, a photo radical initiator or a thermal radical initiator, mat particles and an inorganic filler is prepared, and the coating solution is applied onto a protective film, and then ionizing radiation or heat is applied. It can harden | cure by the polymerization reaction by and can form an antireflection layer. As these photo radical initiators, known ones can be used.

  The polymer having a polyether as the main chain is preferably a ring-opening polymer of a polyfunctional epoxy compound. The ring-opening polymerization of the polyfunctional epoxy compound can be performed by irradiation with ionizing radiation or heating in the presence of a photoacid generator or a thermal acid generator. Therefore, a coating solution containing a polyfunctional epoxy compound, a photoacid generator or a thermal acid generator, matte particles and an inorganic filler is prepared, and the coating solution is applied on a protective film and then cured by ionizing radiation or heat polymerization reaction. Thus, an antireflection layer can be formed.

  Instead of, or in addition to, a monomer having two or more ethylenically unsaturated groups, a monomer having a crosslinkable functional group is used to introduce a crosslinkable functional group into the polymer, and this crosslinkable functional group reacts. A crosslinked structure may be introduced into the binder polymer.

Examples of the crosslinkable functional group include isocyanate group, epoxy group, aziridine group, oxazoline group, aldehyde group, carbonyl group, hydrazine group, carboxyl group, methylol group and active methylene group. Vinylsulfonic acid, acid anhydride, cyanoacrylate derivative, melamine, etherified methylol, ester and urethane, and metal alkoxide such as tetramethoxysilane can also be used as a monomer for introducing a crosslinked structure. A functional group that exhibits crosslinkability as a result of the decomposition reaction, such as a block isocyanate group, may be used. That is, in the present invention, the crosslinkable functional group may not react immediately but may exhibit reactivity as a result of decomposition.
These binder polymers having a crosslinkable functional group can form a crosslinked structure by heating after coating.

For the purpose of imparting antiglare properties, the light scattering layer is a matte particle having an average particle size larger than that of the filler particles, preferably 1 to 10 μm, more preferably 1.5 to 7.0 μm, such as inorganic compound particles or resin. Contains particles. Specific examples of the matte particles include, for example, inorganic particles such as silica particles and TiO ₂ particles, and resin particles such as acrylic particles, crosslinked acrylic particles, polystyrene particles, crosslinked styrene particles, melamine resin particles, and benzoguanamine resin particles. It is done. Of these, crosslinked styrene particles, crosslinked acrylic particles, crosslinked acrylic styrene particles, and silica particles are preferable. The shape of the mat particles can be either spherical or irregular.

  Further, two or more kinds of mat particles having different particle sizes may be used in combination. It is possible to impart anti-glare properties with mat particles having a larger particle size and to impart other optical characteristics with mat particles having a smaller particle size.

  Furthermore, the particle size distribution of the matte particles is most preferably monodispersed, and the particle sizes of the particles are preferably closer to each other. For example, when a particle having a particle size 20% or more larger than the average particle size is defined as a coarse particle, the proportion of the coarse particle is preferably 1% or less of the total number of particles, and 0.1% or less. More preferably, it is 0.01% or less. The matting particles having such a particle size distribution are obtained by classification after a normal synthesis reaction, and a matting agent having a more preferable distribution can be obtained by increasing the number of classifications or increasing the degree thereof.

The mat particles are contained in the light scattering layer so that the amount of mat particles in the formed light scattering layer is preferably 10 to 1000 mg / m ² , more preferably 100 to 700 mg / m ² .
The particle size distribution of the mat particles is measured by a Coulter counter method, and the measured distribution is converted into a particle number distribution.

The light scattering layer is made of an oxide of at least one metal selected from titanium, zirconium, aluminum, indium, zinc, tin, and antimony, in addition to the matte particles, in order to increase the refractive index of the layer. Thus, it is preferable that an inorganic filler having an average particle size of preferably 0.2 μm or less, more preferably 0.1 μm or less, and still more preferably 0.06 μm or less.
Conversely, in order to increase the difference in refractive index from the mat particles, it is also preferable to use a silicon oxide in order to keep the refractive index of the light scattering layer using the high refractive index mat particles low. The preferred particle size is the same as that of the inorganic filler described above.

Specific examples of the inorganic filler used in the light scattering layer include TiO ₂ , ZrO ₂ , Al ₂ O ₃ , In ₂ O ₃ , ZnO, SnO ₂ , Sb ₂ O ₃ , and a combination of ITO and SiO _2. Can be mentioned. TiO ₂ and ZrO ₂ are more preferable from the viewpoint of increasing the refractive index. It is also preferable that the surface of the inorganic filler is subjected to a silane coupling treatment or a titanium coupling treatment, and a surface treatment agent having a functional group capable of reacting with a binder species on the filler surface is preferably used.

  The addition amount of these inorganic fillers is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, and further preferably 30 to 75% by mass with respect to the total mass of the light scattering layer. .

  Such a filler does not scatter because the particle size is sufficiently smaller than the wavelength of light, and a dispersion in which the filler is dispersed in a binder polymer behaves as an optically uniform substance.

  The bulk refractive index of the mixture of the binder and the inorganic filler in the light scattering layer is preferably 1.50 to 2.00, and more preferably 1.51 to 1.80. In order to make the refractive index within the above range, the type and amount ratio of the binder and the inorganic filler may be appropriately selected. How to select can be easily known experimentally in advance.

  In order to ensure surface uniformity such as uneven coating, uneven drying, point defects, etc., the light scattering layer should be coated with either a fluorine-based or silicone-based surfactant, or both for forming the light scattering layer. Contained in the composition. In particular, a fluorine-based surfactant is preferably used because an effect of improving surface defects such as coating unevenness, drying unevenness, and point defects of the antireflection layer preferably used in the present invention appears in a smaller addition amount. The purpose is to increase productivity by giving high-speed coating suitability while improving surface uniformity.

AR Film Next, an antireflection layer (AR film) in which a middle refractive index layer, a high refractive index layer, and a low refractive index layer are laminated in this order on a protective film will be described.

An antireflection layer comprising at least a middle refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) in order on the protective film is designed to have a refractive index satisfying the following relationship. .
Refractive index of high refractive index layer> refractive index of medium refractive index layer> refractive index of protective film> refractive index of low refractive index layer

Further, a hard coat layer may be provided between the protective film and the medium refractive index layer. Further, it may be composed of a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer. For example, JP-A-8-122504, 8-110401, 10-300902, Examples thereof include an antireflection layer described in JP-A No. 2002-243906, JP-A No. 2000-11706 and the like.
Further, other functions may be imparted to each layer. For example, an antifouling low refractive index layer and an antistatic high refractive index layer (for example, JP-A Nos. 10-206603 and 2002-2002). 243906 publication etc.) etc. are mentioned.

  The haze of the antireflection layer is preferably 5% or less, more preferably 3% or less. Further, the surface strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K-5400.

High Refractive Index Layer and Medium Refractive Index Layer The antireflective layer having a high refractive index comprises a cured film containing at least an inorganic compound fine particle having a high refractive index having an average particle size of 100 nm or less and a matrix binder.

  The inorganic compound fine particles having a high refractive index are preferably inorganic compounds having a refractive index of 1.65 or more, more preferably those having a refractive index of 1.9 or more. Examples thereof include oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and composite oxides containing these metal atoms.

  In order to obtain such fine particles, the particle surface is treated with a surface treatment agent (for example, silane coupling agent, etc .: JP-A Nos. 1-1295503, 11-153703, 2000-9908). Anionic compounds or organometallic coupling agents: described in JP-A No. 2001-310432, etc., and a core-shell structure having high refractive index particles as a core (JP-A No. 2001-166104) And a specific dispersant combination (for example, described in JP-A-11-153703, US Pat. No. 6,210,858, JP-A-2002-277609, etc.) and the like.

Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.
More preferable materials include a polyfunctional compound-containing composition having at least two polymerizable groups of at least one of radically polymerizable and cationically polymerizable, a composition containing an organometallic compound containing a hydrolyzable group, And at least one composition selected from compositions containing the partial condensates thereof, for example, JP-A Nos. 2000-47004, 2001-315242, 2001-31871, 2001- And compounds described in Japanese Patent No. 296401.

  A curable film obtained from a colloidal metal oxide obtained from a hydrolyzed condensate of metal alkoxide and a metal alkoxide composition is also preferred. For example, it describes in Unexamined-Japanese-Patent No. 2001-293818.

  The refractive index of the high refractive index layer is preferably 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.

  The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70. The thickness of the medium refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.

Low Refractive Index Layer The low refractive index layer in the AR film is sequentially laminated on the high refractive index layer. The refractive index of the low refractive index layer is preferably 1.20 to 1.55, and more preferably 1.30 to 1.50.

  The low refractive index layer is preferably constructed as an outermost layer having scratch resistance and antifouling properties. As means for greatly improving the scratch resistance, imparting slipperiness to the surface is effective, and conventionally known means for thin film layers including introduction of silicone, introduction of fluorine, and the like can be applied.

The fluorine-containing compound is preferably a compound containing a crosslinkable or polymerizable functional group containing a fluorine atom in a range of 35 to 80% by mass, for example, paragraph numbers [0018] to [0026] of JP-A-9-222503. Examples thereof include the compounds described in paragraph Nos. [0019] to [0030] of JP-A-11-38202, paragraph numbers [0027] to [0028] of JP-A-2001-40284, JP-A 2000-284102, and the like.
The refractive index of the fluorine-containing compound is preferably 1.35 to 1.50, more preferably 1.36 to 1.47.

  The silicone compound is preferably a compound having a polysiloxane structure, containing a curable functional group or a polymerizable functional group in the polymer chain and having a crosslinked structure in the film. For example, reactive silicone (for example, “Silaplane” (manufactured by Chisso Corporation)), polysiloxane containing silanol groups at both ends (Japanese Patent Laid-Open No. 11-258403, etc.) and the like can be mentioned.

  The crosslinking or polymerization reaction of at least one of the fluorine-containing polymer and the siloxane polymer having a crosslinking or polymerizable group is performed simultaneously with the application of the coating composition for forming the outermost layer containing a polymerization initiator and a sensitizer. Alternatively, the low refractive index layer is preferably formed by light irradiation or heating after coating.

A sol / gel cured film is also preferred in which an organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent are cured by a condensation reaction in the presence of a catalyst.
For example, a polyfluoroalkyl group-containing silane compound or a partially hydrolyzed condensate thereof (Japanese Patent Laid-Open Nos. 58-142958, 58-147483, 58-147484, Japanese Patent Laid-Open Nos. 9-157582, 11) -106704), silyl compounds containing a poly (perfluoroalkyl ether) group which is a fluorine-containing long chain group (Japanese Patent Application Laid-Open Nos. 2000-117902, 2001-48590, 2002-53804). Etc.) and the like.

  The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as a filler (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as an additive other than the above. Low refractive index inorganic compounds, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820), silane coupling agents, slip agents, surfactants, and the like. .

  When the low refractive index layer is located below the outermost layer, the low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.). The coating method is preferable because it can be manufactured at a low cost.

  The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and further preferably 60 to 120 nm.

Hard coat layer The hard coat layer is provided on the surface of the protective film in order to impart physical strength to the protective film provided with the antireflection layer. In particular, it is preferably provided between the protective film and the high refractive index layer. The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a light and / or heat curable compound. The curable functional group in the curable compound is preferably a photopolymerizable functional group. Also preferred are hydrolyzable functional group-containing organometallic compounds and organoalkoxysilyl compounds.

Specific examples of these compounds are the same as those exemplified for the high refractive index layer.
Specific examples of the composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and WO 00/46617.

  The high refractive index layer can also serve as a hard coat layer. In such a case, it is preferable to form fine particles dispersed in the hard coat layer using the method described for the high refractive index layer.

  The hard coat layer can also serve as an antiglare layer containing particles having an average particle size of 0.2 to 10 μm and imparting an antiglare function (antiglare function).

  The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, and more preferably 0.5 to 7 μm.

  The surface strength of the hard coat layer is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K-5400. Further, in the Taber test according to JIS K-5400, the smaller the wear amount of the test piece before and after the test, the better.

Other layers of antireflection layer Further, a forward scattering layer, a primer layer, an antistatic layer, an undercoat layer, a protective layer and the like may be provided.

Antistatic Layer When an antistatic layer is provided, it is preferable to impart conductivity with a volume resistivity of 10 ⁻⁸ (Ωcm ⁻³ ) or less. The use of hygroscopic substances, water-soluble inorganic salts, certain surfactants, cationic polymers, anionic polymers, colloidal silica, etc. can give a volume resistivity of 10 ⁻⁸ (Ωcm ⁻³ ). There is a problem that dependency is large, and sufficient conductivity cannot be secured at low humidity. Therefore, a metal oxide is preferable as the conductive layer material. Some metal oxides are colored, but using these metal oxides as the conductive layer material is not preferable because the entire film is colored. Zn, Ti, Sn, Al, In, Si, Mg, Ba, Mo, W, or V can be used as the metal that forms the metal oxide without coloring, and a metal oxide containing these as main components is used. It is preferable.

Specific examples of the metal oxide include ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , WO ₃ , V ₂ O _5, etc. These composite oxides are good, and ZnO, TiO ₂ and SnO ₂ are particularly preferable. Examples of containing different atoms include, for example, additives such as Al and In for ZnO, addition of Sb, Nb and halogen elements for SnO ₂ , and Nb and Ta for TiO ₂ . Addition is effective.

Furthermore, as described in Japanese Patent Publication No. 59-6235, a material obtained by adhering the above metal oxide to other crystalline metal particles or fibrous materials (for example, titanium oxide) may be used. Note that the volume resistance value and the surface resistance value are different physical property values and cannot be simply compared. However, in order to secure conductivity of 10 ⁻⁸ (Ωcm ⁻³ ) or less in volume resistance value, The prevention layer should just have a surface resistance value of 10 ⁻¹⁰ (Ω / □) or less, more preferably 10 ⁻⁸ (Ω / □). The surface resistance value of the antistatic layer needs to be measured as a value when the antistatic layer is the outermost layer, and can be measured in the middle of forming the laminated film.

(Liquid crystal display device)
The liquid crystal display device of the present invention has at least the polarizing plate of the present invention. Preferably, it is a liquid crystal display device using a pair of polarizing plates one by one above and below the liquid crystal cell, and particularly preferably a liquid crystal display device using a pair of polarizing plates of the present invention one by one above and below the VA mode liquid crystal cell. It is. Moreover, it is preferable that at least one protective film of the polarizing plate is the protective film, that is, the cellulose acylate film or the cycloolefin polymer film. Furthermore, it is preferable that the protective film disposed on the liquid crystal cell side of the polarizing plate of the liquid crystal display device is a protective film that satisfies the mathematical formulas (6) and (7). Moreover, the aspect which provided the optically anisotropic layer on the protective film, and / or the aspect which provided the antireflection layer on the protective film are also preferable. With such a configuration, a light and thin liquid crystal display device can be obtained.
The panel size of the liquid crystal display device is preferably 18 inches or more, and more preferably 20 inches or more.

  Below, the example of the liquid crystal cell which can be set as a liquid crystal display device using the polarizing plate of this invention is given.

  The polarizing plate of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystals), AFLC (Anti-Ferroelectric Liquid Crystals), OCB (Opticly Liquid QuantNy). Various display modes such as HAN (Hybrid Aligned Nematic) can be given. Among these, it can use preferably for VA mode or OCB mode, and it is preferable to use for VA mode especially.

In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied.
The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). (2) Liquid crystal cell ("SID97, Digest of tech. Papers") (Proceedings) Vol. 28, in which the VA mode is multi-domained by protrusions (in the MVA mode) in order to enlarge the viewing angle. (1997) p.845), (3) liquid crystal cell of a mode (n-ASM mode, CPA mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied. Proceedings of the Japanese Liquid Crystal Society, p. 58-59 (1998), Sharp Technical Report No. 80, page 11), and (4) Multi-domain distribution by oblique electric field The liquid crystal cell of the causes SURVAIVAL mode (Monthly Display May issue, page 14 (1999)), the liquid crystal cell of the PVA mode is included ( "18th, IDRC Proceedings", p.383 (1998 years)).

  As shown in FIG. 3, the VA mode liquid crystal display device includes a liquid crystal cell (VA mode cell) and two polarizing plates (TAC1 (22), TAC2 (23, 33), and TAC3 (32) on both sides thereof. And a polarizer having a polarizer (21, 31) and an adhesive layer (not shown). The liquid crystal cell carries liquid crystal between two electrode substrates, although not particularly shown.

  In the embodiment of the transmissive liquid crystal display device of the present invention shown in FIG. 3, among the cellulose acylate films used as the protective film, the protective film TAC1 and the protective film TAC3 used on the liquid crystal cell side may be the same film. Different films may be used. TAC1 and TAC3 may be used as a protective film / optical compensation sheet.

  Although the protective film 13 (TAC2) of FIG. 3 is not particularly defined, a cell rate acylate film is preferable. Further, it is preferably thinner than the protective film. For example, 40-80 μm is preferable, and commercially available “KC4UX2M” (40 μm manufactured by Konica Caputo), “KC5UX” (60 μm manufactured by Konica Caputo), “TD80UL” (80 μm manufactured by Fuji Photo Film Co., Ltd.), etc. However, it is not limited to these.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

Production Example: Formation of Protective Film (TAC1, Cellulose Acylate Film) by Band Casting Machine (1) Cellulose Acylate Cellulose acylate as shown in Table 1 was prepared. Specifically, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, carboxylic acid serving as a raw material for the acyl substituent was added, and an acylation reaction was performed at 40 ° C. At this time, the kind of acyl group, the total substitution degree, and the 6-position substitution degree were adjusted by adjusting the amount of sulfuric acid catalyst, the amount of water, and the aging time. The aging temperature was 40 ° C. Moreover, it age | cure | ripened at 40 degreeC after acylation. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.

  In Table 1, CAP is an abbreviation for cellulose acetate propionate (cellulose ester derivative in which an acyl group is composed of an acetyl group and a propionyl group).

(2) Preparation of dope [1-1. Cellulose acylate solution]
The following composition was put into a mixing tank, stirred to dissolve each component, further heated to 90 ° C. for about 10 minutes, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm.

(Composition of cellulose acylate solution)
Cellulose acylate listed in Table 1 100.0 parts by mass Triphenyl phosphate 8.0 parts by mass Biphenyl diphenyl phosphate 4.0 parts by mass Methylene chloride 403.0 parts by mass Methanol 60.2 parts by mass

[1-2. Matting agent dispersion]
Next, the following composition containing the cellulose acylate solution prepared by the above method was charged into a disperser to prepare a matting agent dispersion.

(Composition of matting agent dispersion)
Silica particles (average particle size 16 nm) 2.0 parts by mass
"aerosil R972" (manufactured by Nippon Aerosil Co., Ltd.)
Methylene chloride 72.4 parts by mass Methanol 10.8 parts by mass The above cellulose acylate solution 10.3 parts by mass

[1-3. Retardation developer solution A]
Next, the following composition containing the cellulose acylate solution produced by the above method was put into a mixing tank and dissolved by stirring while heating to prepare a retardation developer solution A.

(Composition of retardation developer solution A)
Retardation developer (RP1) 20.0 parts by mass Methylene chloride 58.3 parts by mass Methanol 8.7 parts by mass The above cellulose acylate solution 12.8 parts by mass

100 parts by mass of the cellulose acylate solution, 1.35 parts by mass of the matting agent dispersion, and the retardation developer solution A were mixed in the proportions shown in Table 2 to prepare a dope for film formation. This dope was used for film production. The retardation developer solution A is shown in Table 2 in terms of parts by mass of the retardation developer when the cellulose acylate amount is 100 parts by mass.

(3) Casting The above dope was cast using a band casting machine. A film having a residual solvent amount of 25 to 35% by mass and peeled off from the band is a range from about 5 ° C. lower to about 5 ° C. higher than the glass transition temperature of the cellulose acylate film (hereinafter referred to as about Tg). Under the conditions of −5 to Tg + 5 ° C., the cellulose acylate film was formed by stretching in the machine direction and the width direction using a tenter at the stretch ratio shown in Table 2. Both ends were cut off in front of the winding part to make a width of 2000 mm and wound up as a roll film having a length of 4000 m. Table 2 shows the stretch ratio of the tenter. About the produced cellulose acylate film, Re ₅₉₀ value and Rth ₅₉₀ value at a wavelength of 590 nm were measured at 25 ° C. and 60% RH using a birefringence measuring apparatus “KOBRA 21ADH” (manufactured by Oji Scientific Instruments). For the calculation of the Rth ₅₉₀ value, 1.48 was input as the average refractive index.

[Preparation of polarizing plate]
Examples and Comparative Examples (Production of Polarizer)
A polyvinyl alcohol (PVA) film having a thickness of 80 μm is dyed by immersing it in an aqueous iodine solution having an iodine concentration of 0.05% by mass at 30 ° C. for 60 seconds, and then in an aqueous boric acid solution having a boric acid concentration of 4% by mass. The film was longitudinally stretched 5 times the original length during the second immersion, and then dried at 50 ° C. for 4 minutes to obtain a polarizer having a thickness of 20 μm.

(Surface treatment of cellulose acylate film)
The protective film produced in the production example and the commercially available cellulose acylate film “Fujitac TD80UL” (manufactured by Fuji Photo Film Co., Ltd.) (hereinafter sometimes referred to as “TAC2”) at a concentration of 1.5 mol / L at 55 ° C. After being immersed in an aqueous sodium hydroxide solution, the sodium hydroxide was sufficiently washed away with water. Then, after being immersed in a diluted sulfuric acid aqueous solution at a concentration of 0.005 mol / L for 1 minute for 1 minute, it was immersed in water to sufficiently wash away the diluted sulfuric acid aqueous solution. Finally, the sample was thoroughly dried at 120 ° C. The film thickness of TAC2 was 80 μm.

(Attaching the protective film to the polarizer)
TAC2 and TAC1 subjected to saponification treatment as described above were bonded together using a polyvinyl alcohol-based adhesive so as to sandwich the polarizer.

  At this time, since the polarizer and the protective films (TAC1 and TAC2) on both sides of the polarizer are produced in a roll form, the longitudinal directions of the roll films are parallel to each other and are continuously bonded. Further, as shown in FIG. 1, in the protective film 3 (TAC 1) disposed on the cell side of the polarizing plate, the transmission axis 2 of the polarizer 1 and the slow axis 4 of the protective film 3 are parallel to each other. .

(Preparation of (meth) acrylic copolymer (A) solution)
(Meth) acrylic acid ester (a1) having a composition ratio shown in Table 3 having a Tg of less than −30 ° C. when a homopolymer is used, and a compound having a vinyl group having a Tg of −30 ° C. or more when a homopolymer is used ( a2), a functional group-containing monomer (a3) reactive to a polyfunctional compound and a polymerization initiator are placed in a reaction vessel, and the reaction vessel is replaced with nitrogen gas. The reaction was carried out at the reaction temperatures and times shown in Table 3. (Meth) acrylic copolymer No. 1, 2, 3, 5 and 6 were diluted with ethyl acetate after the reaction to give a solid content concentration of 20% by mass to obtain a meth) acrylic copolymer solution. (Meth) acrylic copolymer No. About 4 and 7, it diluted with toluene after reaction, solid content concentration was 20 mass%, and the (meth) acrylic-type copolymer solution was obtained.
In Table 3, the composition ratio indicates parts by mass. BA is butyl acrylate, MA is methyl acrylate, AA is acrylic acid, BzA is benzyl acrylate, HEA is 2-hydroxyethyl acrylate, EAc is ethyl acetate, BPO is benzoyl peroxide, and AIBN is Azobisisobutyronitrile and LaSH indicate lauryl mercaptan, respectively.

[Measurement of mass average molecular weight]
The weight average molecular weight (Mw) in terms of styrene of each copolymer in the (meth) acrylic copolymer solution was determined by gel permeation chromatography (GPC). The measurement conditions are shown below. The results obtained are shown in Table 3.

Device name: HLC-8120 (manufactured by Tosoh Corporation)
Column: G7000HXL 7.8 mm ID × 30 cm 1 piece (manufactured by Tosoh Corporation)
GMHXL 7.8mmID × 30cm 2 pieces (manufactured by Tosoh Corporation)
G2500HXL 7.8mmID × 30cm 1 piece (manufactured by Tosoh Corporation)
Sample concentration: diluted with tetrahydrofuran to 1.5 mL / mL Mobile phase solvent: tetrahydrofuran Flow rate: 1.0 mL / min Column temperature: 40 ° C.

(Preparation of adhesive layer solution)
The (meth) acrylic copolymer (A) solution prepared in Synthesis Example 1 was mixed so as to have a solid content ratio shown in Table 4, and the polyfunctional compound (crosslinking agent) (B) shown in Table 4 was added. The mixture was added and sufficiently stirred to obtain an adhesive layer solution.

(Coating of adhesive layer)
The adhesive layer was applied as follows.
The adhesive layer solution shown in Table 4 was applied onto a 25 μm thick polyethylene terephthalate (PET) film using a die coater and then dried. Here, it adjusted so that the thickness of the adhesion layer after drying might be set to 30, 33, 60, and 70 micrometers, respectively. Next, the pressure-sensitive adhesive layer coated on the PET film was transferred to the protective film (TAC1) side provided on the surface of the polarizer and aged for 7 days at 25 ° C. and 60% RH. The adhesive layer solution was applied to form adhesive layers 1 to 20 in Table 4.
A PET separator was attached to the pressure-sensitive adhesive layer side of the polarizing plate produced as described above, and a PET protective film was attached to the side opposite to the pressure-sensitive adhesive layer.

[Measurement method of elastic modulus]
The PET film was placed on the adhesive layer provided on the PET film, and aged for 7 days at 25 ° C. and 60% RH. The pressure-sensitive adhesive layer is laminated to a thickness of about 1 mm, cut into a size of 20 mm length × 5 mm width, and stressed using the tensile tester under the conditions of a tensile speed of 10 mm / min and a distance between chucks of 10 mm. -The strain curve was calculated | required and the elasticity modulus was calculated | required. The ambient temperature during measurement was 25 ° C.
In Table 4, the composition ratio is shown in parts by weight. Tetrad X represents N, N, N ′, N′-tetraglycidyl-m-xylenediamine (manufactured by Mitsubishi Gas Chemical Co., Ltd.), and coronate. L represents tolylene diisocyanate tritrimethylolpropane adduct (manufactured by Tan Kogyo Co., Ltd.). In the (meth) acrylic copolymer (A), No. No. of the (meth) acrylic copolymer (A) in Table 3 respectively. It corresponds to.

  Table 4 summarizes the physical property values of the adhesive layers 1 to 20.

(Mounting on VA panel)
The polarizing plates produced in the examples and comparative examples are polarized on the backlight side so that the viewing side polarizing plates are 18 ", 20", 32 "in size and the absorption axis of the polarizer is parallel to the long side. Punched into a rectangle so that the absorption axis of the child is parallel to the short side, and polarizing plates prepared in Examples and Comparative Examples were pasted on the front and back sides of VA mode liquid crystal cells of 18, 20, and 32 inch sizes. After attaching the polarizing plate, it was held for 20 minutes at 50 ° C. and 5 kg / cm ² , and bonded, with the absorption axis of the polarizing plate on the viewing side in the horizontal direction of the panel. The absorption axis of the polarizing plate on the side was placed in the panel vertical direction, and the adhesive material surface was placed on the liquid crystal cell side.

[Light leakage by durability test]
The liquid crystal display device produced in the Example was subjected to an endurance test under the following conditions. It was kept in an environment of 60 ° C. and 90% RH for 200 hours, taken out in an environment of 25 ° C. and 60% RH, 24 hours later, the liquid crystal display device was displayed in black, and the light leakage intensity was evaluated. The results are shown in Table 5.

Evaluation of light leakage was performed as follows.
Light leakage occurrence situation Practical problem Light leakage No occurrence None 1
Very weak None 2
Weak None 3
Slightly strong Yes 4
Strong Yes 5
Very strong Yes 6

  From the results of the above examples and comparative examples, when the elastic modulus of the adhesive layer is 0.15 MPa to 0.5 MPa and the thickness of the adhesive layer is 33 μm to 60 μm, light leakage due to thermal distortion of the liquid crystal display device It was observed that

It is a schematic diagram which shows an example of the bonding method of the protective film and polarizer at the time of manufacture of the polarizing plate regarding this invention. It is a figure which shows typically an example of the cross-section of the polarizing plate of this invention. It is a figure which shows typically an example of the cross-section of the liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizer 2 Polarizer transmission axis 3 Protective film (TAC1)
4 Slow axis of protective film 11 Polarizer 12 Protective film (TAC1 or TAC3)
13 Protective film (TAC2)
14 Functional film 21 Polarizer 22 Protective film (TAC1)
23 Protective film (TAC2)
31 Polarizer 32 Protective film (TAC3)
33 Protective film (TAC2)
40 VA mode liquid crystal cell 50 Viewing side 60 Backlight side

Claims (17)

It has a polarizer, a protective film (1) provided on at least one surface of the polarizer, and an adhesive layer provided on the protective film (1). The polarizing plate which is 15 MPa-0.5 MPa, and the film thickness of the said adhesion layer is 33 micrometers-60 micrometers. The polarizing plate of Claim 1 whose size of the said polarizing plate is 18 inches or more. The polarizing plate according to claim 1 or 2, wherein the direction of the absorption axis of the polarizing plate is substantially parallel or perpendicular to the side of the polarizing plate. The polarizing plate according to any one of claims 1 to 3, wherein the protective film (1) is stretched by 25% or more. The polarizing plate according to claim 1, wherein the protective film (1) is biaxially stretched. The front retardation value (Reλ) and the retardation value (Rthλ) in the film thickness direction of the protective film (1) satisfy the following mathematical formulas (2) and (3). The polarizing plate as described.
Formula (2) 0 ≦ Re ₅₉₀ ≦ 200
Formula (3) 0 ≦ Rth ₅₉₀ ≦ 400
(In Equations (2) and (3), Reλ and Rth ₀ λ are, in order, a value at a wavelength λ nm, a front retardation value, and a retardation value in the film thickness direction (unit: nm).) The protective film (1) contains a mixed fatty acid ester of cellulose in which a hydroxyl group of cellulose is substituted with an acetyl group and an acyl group having 3 or more carbon atoms, and the substitution degree A of the acetyl group and the number of carbon atoms are 3 The polarizing plate according to claim 1, wherein the substitution degree B of the acyl group satisfies the following mathematical formulas (4) and (5).
Formula (4): 2.0 ≦ A + B ≦ 3.0
Formula (5): 0 <B The polarizing plate according to claim 7, wherein the acyl group having 3 or more carbon atoms is a propionyl group or a butanoyl group. The polarizing plate according to claim 7 or 8, wherein the substitution degree of the hydroxyl group at the 6-position of the cellulose is 0.75 or more. The protective film (1) contains a cellulose acylate obtained by substituting a hydroxyl group of a glucose unit constituting cellulose with an acyl group having 2 or more carbon atoms, and 2 of glucose units constituting the cellulose. The substitution degree DS ₂ of the hydroxyl group at the position with the acyl group, the substitution degree DS _{3 with} the acyl group of the hydroxyl group at the 3 position, and the substitution degree DS ₆ with the acyl group of the hydroxyl group at the 6 position satisfy the following formulas (6) and (7). The polarizing plate of any one of Claims 1-9.
Formula (6): 2.0 ≦ DS ₂ + DS ₃ + DS ₆ ≦ 3.0
Formula (7): DS ₆ / (DS ₂ + DS ₃ + DS ₆ ) ≧ 0.315 The polarizing plate according to claim 10, wherein the acyl group is an acetyl group. The polarizing plate according to any one of claims 1 to 11, wherein the protective film (1) contains one or more retardation enhancers. The polarizing plate according to any one of claims 1 to 12, wherein the protective film (1) contains one or more of a plasticizer, an ultraviolet absorber, a peeling accelerator, a dye, and a matting agent. . A liquid crystal display device comprising a liquid crystal cell and a polarizing plate, wherein at least one of the polarizing plates is the polarizing plate according to claim 1. The liquid crystal display device according to claim 14, wherein the protective film (1) for the polarizing plate according to any one of claims 1 to 13 is disposed so as to be positioned on the side of the liquid crystal cell. The liquid crystal cell is sandwiched between a pair of polarizing plates, the transmission axes of the pair of polarizing plates are arranged orthogonal to each other, and the transmission axis is substantially orthogonal to the sides of the polarizing plate. The liquid crystal display device according to claim 14, wherein the liquid crystal display device is parallel. The liquid crystal display device according to claim 14, wherein the liquid crystal cell is in a VA mode.

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