TWI468749B - An optical film, a polarizing plate and a liquid crystal display device using the same - Google Patents

Description

Optical film, polarizing plate using the same, and liquid crystal display device

The present invention relates to an optical film for improving hardness and usability, a polarizing plate using the optical film, and a liquid crystal display device.

The liquid crystal display device is in demand for use in liquid crystal televisions and liquid crystal displays of personal computers. Generally, a liquid crystal display device is formed by arranging a liquid crystal cell such as a transparent electrode, a liquid crystal layer, a color filter or the like on a glass plate with two polarizing plates provided on both sides thereof, and each polarizing plate is made of two optical films ( The polarizing plate protective film is composed of a polarizer (also called a polarizer and a polarizing film). This polarizing plate protective film is usually a cellulose triacetate film.

In addition, due to advances in technology in recent years, liquid crystal display devices have been accelerated and large-scale, and the use of liquid crystal display devices has also diversified. For example, it can be used as a display for advertisements that is installed on a large display on a street or a store or used in a public place where a display device called a digital signage is used.

This use is assumed to be used outdoors, and therefore, the polarizing plate protective film requires higher moisture resistance due to the problem of deterioration due to moisture absorption of the polarizing film. However, it is difficult to obtain sufficient moisture resistance of a cellulose ester film such as a cellulose triacetate film which has been conventionally used. When the film is thickened in order to obtain moisture resistance, there is a problem that the optical influence is increased. In recent years, since the thickness of the device is required to be thinned, there is a problem that the thickness of the polarizing plate itself is increased.

In addition, polymethyl methacrylate (hereinafter abbreviated as "PMMA") which is an acrylic resin which is a low-absorption optical film material exhibits excellent transparency and dimensional stability in addition to low humidity. Suitable for optical films.

However, as described above, with the increase in size of liquid crystal display devices and the expansion of outdoor applications, it is necessary to fully recognize images even outside the house. Therefore, it is necessary to increase the amount of backlight light, and when used under more severe conditions, it is required to have a high temperature. Heat resistance and long-term heat resistance.

However, the PMMA film has a problem of shape change due to lack of heat resistance, use at high temperatures, long-term use, and the like.

This problem is not only the physical properties of the film monomer, but also a polarizing plate or a display device using such a film is an important subject. In other words, in the liquid crystal display device, the polarizing plate is curled as the film is deformed, so that the entire panel is deformed.

The problem caused by the deformation of the film has a problem on the backlight side, and the phase difference in design due to deformation when the position of the identification side surface is used is changed, so that there is a problem that the viewing angle changes or the color tone changes.

Further, when the acrylic resin film is more likely to be broken or brittle than the cellulose ester film or the like, it is difficult to perform operations such as cutting (cutting), and it is difficult to stably manufacture optical for a large liquid crystal display device. film.

In view of the above-mentioned problems and the like, for example, Patent Document 1 proposes a technique for improving moisture resistance and heat resistance as an acrylic resin combined impact-resistant acrylic rubber-methyl methacrylate copolymer or butyl-modified ethylene-based fiber. Resin.

Patent Document 2 proposes a technique of mixing a plasticizer or controlling an optical property to mix a lower molecular weight acrylic resin with respect to a conventional cellulose ester film. Patent Document 3 proposes an optical film in which an acrylic resin having a relatively large molecular weight and a cellulose ester resin are melt-mixed, but this technique is incompatible with the compatibility of the acrylic resin and the cellulose ester resin, and lacks a general-purpose technique, and Insufficient hardness.

Further, it is proposed that the optical film is composed of a plurality of layers while imparting new characteristics or opposite characteristics. For example, Patent Document 4 proposes to provide an image in which a high contrast ratio can be displayed over a wide range of viewing angles by using an optical compensation film in which a concentration in a film surface layer of inorganic fine particles is larger than an average concentration in a film of the inorganic fine particles. Further, it is possible to reduce the color shift (change in color tone when viewed in an oblique direction), in particular, a VA mode liquid crystal display device, an optical compensation film that imparts such characteristics, and a technique for manufacturing a polarizing plate and an optical compensation film. These techniques are techniques for containing an additive in a layer relating to a part of the thickness direction of the layer of the same resin composition, but there is no mention of a technique for improving the properties by changing the resin composition.

Patent Document 5 proposes a core layer composed of a polymer soluble or dispersible in an organic solvent or water, and a surface layer composed of a cellulose derivative having a film thickness of 0.1 to 20 μm on at least one side of the core layer. Special protective film for polarizing plates, which provides low retardation, less optical distortion, less bright spots, good dimensional stability under high humidity, less curl, and good adhesion to glass substrates. The technique of using a protective film. This technique is a technique for providing a core layer characterized by a surface layer mainly composed of a cellulose derivative and a cellulose derivative and a compound having an ethylenic double bond and a photorecoupling initiator. This technique does not mention a property which is changed by the resin composition, and a technique of providing an optical film of a preferable characteristic by providing a plurality of layers having different resin compositions. Further, when an acrylic resin and a cellulose resin are used in particular, even if an optical film having a plurality of layers is provided, when a layer having a different resin ratio is provided, an interface is formed between layers due to a difference in resin composition, and an optical film cannot be obtained. The required optical properties.

[Advanced technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 5-119217

[Patent Document 2] JP-A-2003-12859

[Patent Document 3] JP-A-2008-88417

[Patent Document 4] JP-A-2008-262161

[Patent Document 5] JP-A-2001-21533

The present invention has been made in view of the above problems and problems, and an object of the present invention is to provide an optical film which improves the hardness and usability of a film. Further, a polarizing plate and a liquid crystal display device using the optical film are provided.

The above problems of the present invention are solved by the following means.

An optical film comprising at least two or more layers of resin layers different from each other, characterized in that (i) at least one layer constituting a layer of the surface of the optical film is 95:5 to 85:15 The mass ratio contains the acrylic resin (A) and the cellulose ester resin (B), and (ii) the layer other than the layer constituting the surface contains the acrylic resin (A) and the cellulose ester in a mass ratio of 80:20 to 50:50. Resin (B), (iii) The weight average molecular weight of the acrylic resin (A) is 80,000 or more, and (iv) the total substitution degree of the thiol group of the cellulose ester resin (B) is 2.0 to 3.0, and the carbon number is 3 to 7. The degree of substitution of the fluorenyl group is from 1.2 to 3.0, and the weight average molecular weight of the cellulose ester resin (B) is 75,000 or more.

2. The optical film according to the above item 1, wherein the thickness of the layer constituting the surface is 5 to 20% of the entire thickness of the optical film.

3. The optical film according to the above item 1 or 2, wherein, in the layer constituting the surface, the average particle diameter of 0.01 to 1% by mass is in the range of 50 to 300 μm with respect to the total mass of the layer constituting the surface. A fine particle of an inorganic compound or an organic compound.

4. The optical film according to any one of items 1 to 3 above which contains an antistatic agent.

The optical film according to any one of the preceding claims, wherein the optical film has a length in the width direction of at least 10 to 90%, and a portion including a center of the film width direction contains at least two The foregoing resin above the layer constitutes a different layer.

6. The optical film according to any one of the above items 1 to 5, wherein the layers having the different resin compositions are formed simultaneously at the time of film formation.

A polarizing plate characterized by using the optical film according to any one of items 1 to 6 above.

A liquid crystal display device characterized by using the optical film according to any one of the above items 1 to 6.

An optical film which improves the hardness and usability of the film can be provided by the means of the present invention. Further, a polarizing plate and a liquid crystal display device using the optical film can be provided.

[Formation of the Invention]

The optical film of the present invention is an optical film having at least two or more layers of resin compositions different from each other, wherein (i) at least one layer constituting the surface of the optical film is 95:5 to 85:15. The mass ratio contains the acrylic resin (A) and the cellulose ester resin (B), and (ii) the layer other than the layer constituting the surface contains the acrylic resin (A) and the cellulose ester in a mass ratio of 80:20 to 50:50. Resin (B), (iii) The weight average molecular weight of the acrylic resin (A) is 80,000 or more, and (iv) the total substitution degree of the thiol group of the cellulose ester resin (B) is 2.0 to 3.0, and the carbon number is 3 to 7. The degree of substitution of the fluorenyl group is from 1.2 to 3.0, and the weight average molecular weight of the cellulose ester resin (B) is 75,000 or more. This feature is a common technical feature of claims 1 to 8 of the patent application.

The optical film of the present invention can be applied to a polarizing plate. Therefore, it is also applicable to a liquid crystal display device.

Hereinafter, the present invention and its constituent elements and aspects for carrying out the invention will be described in detail.

[Summary of the composition of optical film]

The optical film of the present invention may be in various layers, and is characterized in that it has an optical film having at least two or more layers of resin compositions different from each other. In addition, its characteristics satisfy the following requirements (i) to (iv).

(i) At least one layer constituting the surface of the optical film contains the acrylic resin (A) and the cellulose ester resin (B) in a mass ratio of 95:5 to 85:15.

(ii) The layer other than the layer constituting the surface contains the acrylic resin (A) and the cellulose ester resin (B) in a mass ratio of 80:20 to 50:50.

(iii) The weight average molecular weight of the acrylic resin (A) is 80,000 or more.

(iv) the total degree of substitution of the thiol group of the cellulose ester resin (B) is 2.0 to 3.0, the degree of substitution of the fluorenyl group having 3 to 7 carbon atoms is 1.2 to 3.0, and the weight average of the cellulose ester resin (B) The molecular weight is 75,000 or more.

In the embodiment of the present invention, from the viewpoint of the effect of the present invention, the thickness of the layer constituting the surface is preferably 5 to 20% of the entire thickness of the optical film. The aspect of the layer constituting the surface is preferably a layer containing 0.01 to 1% by mass of an inorganic compound or an organic compound in an average particle diameter of 50 to 300 μm with respect to the total mass of the layer constituting the surface. . The optical film of the present invention preferably contains an antistatic agent.

In the present invention, in the range of at least 10 to 90% of the length in the width direction of the optical film, and the portion containing the center in the width direction of the film is preferably a layer containing at least two or more layers having different resin compositions. The layer in which the resin compositions are different from each other is preferably formed at the same time in film formation.

Each component will be described in detail below.

(acrylic resin (A))

The acrylic resin used in the present invention also includes a methacrylic resin. The resin is not particularly limited, but is preferably composed of 50 to 99% by mass of methyl methacrylate unit and 1 to 50% by mass of other monomer units copolymerizable therewith.

Other monomers copolymerizable include, for example, an alkyl methacrylate having an alkyl group having 2 to 18 carbon atoms, an alkyl group having an alkyl group having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, or the like. An aromatic vinyl compound such as an unsaturated group-containing dicarboxylic acid such as β-unsaturated acid, maleic acid, fumaric acid or itaconic acid, styrene or α-methylstyrene, acrylonitrile or the like α,β-unsaturated nitrile such as acrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, etc., which may be used alone or in combination of two or more kinds of monomers use.

Among them, from the viewpoint of heat decomposition resistance and fluidity of the copolymer, methacrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, and 2 are preferable. Ethylhexyl acrylate or the like, particularly preferably methacrylate or n-butyl acrylate.

The acrylic resin (A) used in the optical film of the present invention has a weight average molecular weight (Mw) of 80,000 or more from the viewpoint of improving the brittleness of the optical film and improving the transparency when it is compatible with the cellulose ester resin (B). When the weight average molecular weight (Mw) of the acrylic resin (A) is 80,000 or less, the brittleness cannot be sufficiently improved, and the compatibility with the cellulose ester resin (B) is inferior. The weight average molecular weight (Mw) of the acrylic resin (A) is more preferably in the range of 80,000 to 1,000,000, particularly preferably in the range of 100,000 to 600,000, and most preferably in the range of 150,000 to 400,000. The upper limit of the weight average molecular weight (Mw) of the acrylic resin (A) is not particularly limited, but from the viewpoint of production, 1,000,000 or less is a preferable form.

The weight average molecular weight of the acrylic resin of the present invention can be determined by gel permeation chromatography. The measurement conditions are as follows.

Solvent: dichloromethane

Column: Shodex K806, K805, K803G (Showa Electric (share) system connection 3)

Column temperature: 25 ° C

Sample concentration: 0.1% by mass

Detector: RI Model 504 (made by GL Science)

Pump: L6000 (Hitachi Manufacturing Co., Ltd.)

Flow rate: 1.0ml/min

Calibration curve: A calibration curve of 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 2,800,000 to 500 was used. It is preferred that 13 samples are used at substantially equal intervals.

The method for producing the acrylic resin (A) of the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization or solution polymerization can be used. As the polymerization initiator, a general peroxide-based or azo-based polymerization initiator may be used, and a redox system may also be used. The polymerization temperature may be 30 to 100 ° C for suspension or emulsion polymerization, and the polymerization may be carried out at 80 to 160 ° C in bulk or solution polymerization. In order to control the reduction viscosity of the obtained copolymer, an alkylthiol or the like may be used as a chain transfer agent to carry out polymerization. An example of the acrylic resin of the present invention and a method for producing the same will be described below.

A1: monomer mass ratio (MMA: MA = 98: 2), Mw70000

A2: monomer mass ratio (MMA: MA = 97: 3), Mw 160000

A3: monomer mass ratio (MMA: MA = 97: 3), Mw 350000

A4: monomer mass ratio (MMA: MA = 97: 3), Mw550000

A5: monomer mass ratio (MMA: MA = 97: 3), Mw 800000

A6: monomer mass ratio (MMA: MA = 97: 3), Mw930000

A7: monomer mass ratio (MMA: MA = 94: 6), Mw 1100000

MS1: monomer mass ratio (MMA: ST=60:40), Mw100000

MS2: monomer mass ratio (MMA: ST=40:60), Mw100000

MMA: Methyl methacrylate

MA: methacrylate

ST: Styrene

(Synthesis example of A8)

First, the methyl methacrylate/acrylamide-based copolymer suspension was adjusted as follows.

Methyl methacrylate 20 parts by mass

Acrylamide 80 parts by mass

Potassium persulfate 0.3 parts by mass

Ion exchange water 1500 parts by mass

The above components were put into a reactor, and the reactor was replaced with a nitrogen gas while maintaining a reaction at 70 ° C to completely convert the monomers into polymers. The resulting aqueous solution is used as a suspending agent. 0.05 parts by mass of the above-mentioned suspending agent was dissolved in 165 parts by mass of ion-exchanged water, and the solution supply capacity was 5 L, and a stainless steel pressure cooker equipped with a baffle plate and a pfauder type (a reverse impeller) type stirring blade was replaced with a nitrogen gas in the system. Stirring was performed at 400 rpm.

Next, the mixture of the following input compositions was added while stirring the reaction system.

Methacrylic acid 27 parts by mass

Methyl methacrylate 73 parts by mass

T-dodecanethiol 1.2 parts by mass

2,2'-azobisisobutyronitrile 0.4 parts by mass

After the addition, the temperature was raised to 70 ° C, and when the internal temperature reached 70 ° C, the point was taken as the polymerization start point, and then the polymerization was carried out for 180 minutes.

Then, the reaction system is cooled, the polymer is separated, washed, and dried according to a usual method to obtain a particulate copolymer. The copolymer had a polymerization ratio of 97% and a weight average molecular weight of 130,000.

To the copolymer, 0.2% by mass of an additive (NaOCH ₃ ) was added, and a 2-axis extruder (TEX30 (manufactured by Nippon Steel Co., Ltd., L/D = 44.5)) was used, and nitrogen gas was supplied from the supply hopper portion at a rate of 10 L/min. The pellet was subjected to intramolecular cyclization at a screw rotation number of 100 rpm, a raw material supply amount of 5 kg/hr, and a cylinder temperature of 290 ° C to prepare pellets, which were vacuum dried at 80 ° C for 8 hours to obtain an acrylic resin A8. The weight average molecular weight (Mw) of the acrylic resin A8 was 130,000, and the Tg was 140 °C.

A commercially available product can be used for the acrylic resin of the present invention. For example, there are Delpet 60N, 80N (made by Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (manufactured by Mitsubishi Rayon Co., Ltd.), KT75 (manufactured by Electrochemical Industry Co., Ltd.), and the like. Two or more kinds of acrylic resins may be used in combination.

(Cellulose ester resin (B))

The cellulose ester resin (B) of the present invention preferably has a total degree of substitution (T) of from 2,000 to 3.0, from the viewpoint of improving the brittleness or the transparency when it is compatible with the acrylic resin (A). The substitution degree of the thiol group of 3 to 7 is 1.2 to 3.0, and the substitution degree of the thiol group having 3 to 7 carbon atoms is 2.0 to 3.0. In other words, the cellulose ester resin of the present invention is a cellulose ester resin substituted with a fluorenyl group having 3 to 7 carbon atoms. Specifically, a propyl fluorenyl group, a butyl fluorenyl group or the like is preferably used, and a propyl fluorenyl group is particularly preferably used.

When the total degree of substitution of the thiol group of the cellulose ester resin (B) is less than 2.0, in other words, when the hydroxyl residue at the 2, 3, and 6 positions of the cellulose ester molecule is higher than 1.0, the acrylic resin (A) and the cellulose The ester resin (B) is not sufficiently compatible, and there is a problem of turbidity when used as an optical film. Further, even if the total degree of substitution of the fluorenyl group is 2.0 or more, when the degree of substitution of the fluorenyl group having 3 to 7 carbon atoms is less than 1.2, sufficient compatibility is not obtained, or brittleness is lowered. For example, even if the total substitution degree of the fluorenyl group is 2.0 or more, the substitution ratio of the fluorenyl group having 2 carbon atoms, that is, the thiol group is higher, and the degree of substitution of the fluorenyl group having 3 to 7 carbon atoms is less than 1.2, the compatibility is lowered. The turbidity rises. Further, even if the total substitution degree of the fluorenyl group is 2.0 or more, the degree of substitution of the fluorenyl group having 8 or more carbon atoms is high, and when the degree of substitution of the fluorenyl group having 3 to 7 carbon atoms is less than 1.2, the brittleness is deteriorated and the The desired characteristics.

The cellulose ester resin (B) of the present invention has a thiol substitution degree of a total degree of substitution (T) of 2.0 to 3.0, and a substitution degree of a ruthenium group having a carbon number of 3 to 7 of 1.2 to 3.0 is not problematic. However, the degree of substitution of the fluorenyl group having 3 to 7 carbon atoms, that is, an oxime group and a fluorenyl group having 8 or more carbon atoms is preferably 1.3 or less in total.

Further, the total degree of substitution (T) of the thiol group of the cellulose ester resin (B) is more preferably in the range of 2.5 to 3.0.

In the present invention, the above mercapto group may be an aliphatic mercapto group or an aromatic mercapto group. When it is an aliphatic fluorenyl group, it may be a straight chain or a branched chain, and may have a substituent. The carbon number of the fluorenyl group of the present invention is a substituent containing a fluorenyl group.

When the cellulose ester resin (B) has an aromatic fluorenyl group as a substituent, the number of substituents X substituted on the aromatic ring is preferably from 0 to 5. At this time, it is necessary to pay attention to the degree of substitution of the fluorenyl group having a carbon number of 3 to 7 containing a substituent of 1.2 to 3.0. For example, since the carbon number of the phenylhydrazine group is 7, when the carbon-containing substituent is present, the carbon number of the phenylhydrazine group is 8 or more, and it is not contained in the fluorenyl group having 3 to 7 carbon atoms.

Further, when the number of the substituents substituted on the aromatic ring is two or more, they may be the same or different from each other, and may be bonded to each other to form a condensed polycyclic compound (for example, naphthalene, anthracene, indane, phenanthrene, quinoline, or different). Quinoline, chromene, chroman, pyridazine, acridine, anthracene, anthracene, etc.).

The cellulose ester resin (B) as described above has a structure containing at least one of aliphatic fluorenyl groups having 3 to 7 carbon atoms, and can be used as a structure for the cellulose resin of the present invention.

The degree of substitution (T) of the cellulose ester resin (B) of the present invention is 2.0 to 3.0, and the degree of substitution of the fluorenyl group having 3 to 7 carbon atoms is 1.2 to 3.0.

Further, in addition to the fluorenyl group having 3 to 7 carbon atoms, that is, the sum of the substitution degrees of the fluorenyl group and the fluorenyl group having 8 or more carbon atoms is preferably 1.3 or less.

The cellulose ester resin (B) of the present invention is particularly preferably selected from the group consisting of cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, fiber At least one of the butyrate esters preferably has a fluorenyl group having 3 or 4 carbon atoms as a substituent.

Particularly preferred cellulose ester resins are cellulose acetate propionate or cellulose propionate.

The moiety that is not substituted by a thiol group usually exists in the form of a hydroxyl group. These can be synthesized by a known method.

Further, the degree of substitution of the ethyl thiol group or the degree of substitution of the other thiol group can be obtained by the method specified in ASTM-D817-96.

The weight average molecular weight (Mw) of the cellulose ester resin of the present invention is particularly preferably 75,000 or more, more preferably 75,000 to 300,000, and more preferably 100,000 to the viewpoint of compatibility with the acrylic resin (A) and improvement of brittleness. The range of 240000 is particularly good for 160,000 to 240,000. When the weight average molecular weight (Mw) of the cellulose ester resin is less than 75,000, the effect of improving heat resistance and brittleness is not good, and the effects of the present invention cannot be obtained. In the present invention, two or more kinds of cellulose resins may be used in combination.

The optical film of the present invention has an optical film having at least two or more layers of resin compositions different from each other, but it is required that (i) at least one layer constituting the surface of the optical film is contained in a mass ratio of 95:5 to 85:15. The acrylic resin (A) and the cellulose ester resin (B), (ii) the layer other than the layer constituting the surface contains the acrylic resin (A) and the cellulose ester resin in a mass ratio of 80:20 to 50:50 (B) ). Further, it is preferable to contain the acrylic resin (A) and the cellulose ester resin (B) in a compatible state.

The optical film of the present invention must contain the acrylic resin (A) and the cellulose ester resin (B) in a compatible state. The compatibility or complementarity of different resins can achieve the physical properties or qualities necessary for the optical film.

For example, whether or not the acrylic resin (A) and the cellulose ester resin (B) are in a compatible state can be determined by the glass transition temperature Tg.

For example, when the glass transition temperatures of the resins of the two are different, when the resins of the two are mixed, the glass transition temperature of the respective resins is also present, so that the glass transition temperature of the mixture is also two or more. However, when the resins of the two are compatible, the respective resins are used. The intrinsic glass transition temperature disappears and becomes one glass transition temperature, which becomes the glass transition temperature of the resin after the compatibility.

In addition, the term "glass transition temperature" as used herein refers to a midpoint glass obtained by a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer Co., Ltd.) at a temperature increase rate of 20 ° C/min, and obtained according to JIS K7121 (1987). Conversion temperature (Tmg).

Each of the acrylic resin (A) and the cellulose ester resin (B) is preferably a non-crystalline resin, and one of them may be a crystalline polymer or a part of a polymer having crystallinity, but the acrylic resin of the present invention (A) It is preferable to be compatible with the cellulose ester resin (B) to form a non-crystalline resin.

The weight average molecular weight (Mw) of the acrylic resin (A) or the weight average molecular weight (Mw) or the degree of substitution of the cellulose ester resin (B) in the optical film of the present invention is the difference in solubility of the solvent between the two resins. After the distinction is made, each is measured. When the resin is distinguished, it is distinguished by adding a resin in which the phase is dissolved in a solvent in which only one of them is dissolved, and then extracting the dissolved resin, and at this time, heating operation or reflux can be performed. The combination of these solvents can be combined in two or more steps to distinguish the resins. The dissolved resin is filtered with a resin remaining as an insoluble matter, and the solution containing the extract can be distinguished from the resin by a step of evaporating and drying the solvent. These differentiated resins can be defined by general structural analysis of the polymer. When the optical film of the present invention contains a resin other than the acrylic resin (A) and the cellulose ester resin (B), it can be distinguished by the same method.

Further, when the weight average molecular weight (Mw) of the resin after the compatibility is different, the high molecular weight substance can be first dissolved by gel permeation chromatography (GPC), and the lower the molecular weight is, the longer it takes to be dissolved. Therefore, it is easy to distinguish and the molecular weight can be measured.

Further, the molecular weight of the resin after the dissolution is measured by GPC, and the resin solution after each period of time is separately obtained, the solvent is distilled off, and the dried resin is quantitatively analyzed for structure, and each partition of different molecular weight is detected. The resin composition can respectively define a compatible resin. Further, each of the resins obtained in advance in the difference in solubility of the solvent was measured for molecular weight distribution by GPC, and each of the resins was detected.

In the present invention, "containing the acrylic resin (A) and the cellulose ester resin (B) in a compatible state" means mixing the respective resins (polymers), and as a result, they are in a compatible state, and do not contain the cellulose ester resin. (B) A precursor of an acrylic resin such as a monomer, a dimer or an oligomer is mixed, and then a state of a mixed resin is obtained by polymerization.

For example, after mixing a precursor of an acrylic resin such as a monomer, a dimer or an oligomer in the cellulose ester resin (B), the step of obtaining a mixed resin by polymerization is complicated in polymerization, and the method is produced. Resin, it is difficult to control the reaction, and molecular weight adjustment is also difficult. Moreover, when a resin is synthesized by such a method, a graft polymerization, a crosslinking reaction, or a cyclization reaction often occurs, and it is often insoluble in a solvent or melted by heating, so that it is difficult to mix acrylic acid in a resin. Since the resin is dissolved and the weight average molecular weight (Mw) is measured, it is difficult to control the physical properties, and it cannot be used as a resin capable of stably producing an optical film.

The optical film of the present invention may be composed of a resin other than the acrylic resin (A) or the cellulose ester resin (B) and an additive, without impairing the function of the optical film.

When a resin other than the acrylic resin (A) or the cellulose ester resin (B) is contained, the added resin may be in a compatible state or may be mixed in an insoluble state.

The total mass of the acrylic resin (A) and the cellulose ester resin (B) in the optical film of the present invention is preferably 55 mass% or more, more preferably 60 mass% or more, and particularly preferably 70 mass% or more.

When a resin other than the acrylic resin (A) and the cellulose ester resin (B) and an additive are used, it is preferred to adjust the amount of addition within a range that does not impair the function of the optical film of the present invention.

(acrylic particles (C))

The optical film of the present invention preferably contains acrylic particles.

The acrylic particles (C) of the present invention are acrylic components which are present in a particulate state (also referred to as an incompatible state) in an optical film containing the acrylic resin (A) and the cellulose ester resin (B) in a compatible state.

For example, the acrylic film (C) is prepared by dissolving the produced optical film in a predetermined amount, dissolving in a solvent, stirring, and sufficiently dissolving and dispersing, and then using a PTFE film having a pore diameter which does not reach the average particle diameter of the acrylic particles (C). The weight of the insoluble matter collected by the filter filtration and filtration is preferably 90% by mass or more of the acrylic particles (C) added to the optical film.

The acrylic particles (C) used in the present invention are not particularly limited, and are preferably acrylic particles (C) having a layer structure of two or more layers, and particularly preferably an acrylic-based particulate composite having a multilayer structure described below.

The multilayered acrylic granulated composite refers to a structure in which the innermost peripheral portion has the innermost hard layer polymer, the crosslinked soft layer polymer exhibiting rubber elasticity, and the outermost hard layer polymer are layered and overlapped. A particulate acrylic polymer.

In other words, the multilayer structure acrylic particulate polymer refers to a multilayer structure acrylic particulate polymer composed of an innermost hard layer, a crosslinked soft layer, and an outermost hard layer from the center portion toward the outer peripheral portion. It is preferable to use the multilayer structure of the three-layer core-shell structure to form an acrylic granular composite.

Preferred embodiments of the multilayer structure acrylic particulate composite used in the acrylic resin composition of the present invention include, for example, the following. For example, (a) from 80 to 98.9 mass% of methyl methacrylate, from 1 to 20% by mass of the alkyl acrylate having an alkyl group of from 1 to 8, and from 0.01 to 0.3% by mass of the polyfunctional grafting agent. The innermost hard layer polymer obtained by polymerizing the monomer mixture of the composition; (b) the alkyl acrylate having a carbon number of 4 to 8 from the alkyl group in the presence of the innermost hard layer polymer 75 to 98.5 a crosslinked soft layer polymer obtained by polymerizing a monomer mixture composed of a mass %, a polyfunctional crosslinking agent of 0.01 to 5% by mass, and a polyfunctional grafting agent of 0.5 to 5% by mass; (c) within the above-mentioned innermost In the presence of a polymer composed of a hard layer and a crosslinked soft layer, a single crystal composed of 80 to 99% by mass of methyl methacrylate and 1 to 20% by mass of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms The outermost hard layer polymer obtained by polymerization of the bulk mixture; has a three-layer structure, and the obtained three-layer structure polymer is the innermost hard layer polymer (a) 5 to 40% by mass, and the soft layer polymer (b) 30 to 60% by mass and the outermost hard layer polymer (c) 20 to 50% by mass, and an insoluble portion when distinguished by acetone, the insoluble portion having a methyl ethyl ketone swelling degree of 1.5 ~4.0 acrylic granular polymer.

Further, as disclosed in Japanese Patent Publication No. Sho 60-17406 or Japanese Patent Publication No. Hei No. 3-39095, the composition and particle diameter of each layer of the multilayered acrylic particulate composite are specified, and the multilayered structural acrylic composite is also used. The tensile modulus and the methyl ethyl ketone swelling degree of the acetone-insoluble portion are set within a specific range, whereby a balance of more sufficient impact resistance and stress whitening resistance can be achieved.

The innermost hard layer polymer (a) constituting the multilayer structure acrylic granulated composite is preferably an alkyl acrylate having a methyl methacrylate content of 80 to 98.9 mass% and an alkyl group having a carbon number of 1 to 8. A monomer mixture composed of 20% by mass and a polyfunctional grafting agent of 0.01 to 0.3% by mass is obtained by polymerization.

An alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, such as methacrylate, ethacrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2- As the ethylhexyl acrylate or the like, methacrylate and n-butyl acrylate are preferably used.

The ratio of the alkyl acrylate unit in the innermost hard layer polymer (a) is 1 to 20% by mass, and when the unit is less than 1% by mass, the thermal decomposition property of the polymer becomes large, and the unit exceeds 20% by mass. When the glass transition temperature of the innermost hard layer polymer (c) is lowered, and the impact resistance imparting effect of the three-layer structure acrylic type granular composite is lowered, it is not preferable.

The polyfunctional grafting agent is a polyfunctional monomer having different polymerizable functional groups, such as acrylic acid, methacrylic acid, maleic acid, allyl fumarate, etc., preferably using allyl group. Acrylate. The polyfunctional grafting agent is used to chemically bond the innermost hard layer polymer and the soft layer polymer. Therefore, the ratio of the innermost hard layer to be polymerized is 0.01 to 0.3% by mass.

The crosslinked soft layer polymer (b) constituting the acrylic granular composite is preferably an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms in the presence of the innermost hard layer polymer (a). A monomer mixture composed of 75 to 98.5% by mass, a polyfunctional crosslinking agent of 0.01 to 5% by mass, and a polyfunctional grafting agent of 0.5 to 5% by mass is polymerized.

The alkyl acrylate having an alkyl group having 4 to 8 carbon atoms is preferably n-butyl acrylate and 2-ethyl hexyl acrylate.

Further, these polymerizable monomers may be copolymerized with 25% by mass or less of other monofunctional monomers copolymerizable.

Other monofunctional monomers which can be copolymerized are, for example, styrene and substituted styrene derivatives. When the ratio of the alkyl acrylate having a carbon number of 4 to 8 to styrene is more than the current one, the lower the glass transition temperature of the polymer (b), the softer it is.

Further, from the viewpoint of the transparency of the resin composition, the refractive index at room temperature of the soft layer polymer (b) is closer to the innermost hard layer polymer (a), the outermost hard layer polymer (c), and the rigid thermoplastic acrylic resin. The better, consider the ratio of the two after considering these.

As the polyfunctional grafting agent, those enumerated as mentioned in the above-mentioned innermost hard layer polymer (a) can be used. The polyfunctional grafting agent used herein is for chemically bonding the soft layer polymer (b) to the outermost hard layer polymer (c), and the ratio of the innermost hard layer used for polymerization is resistant. The viewpoint of the impact imparting effect is preferably 0.5 to 5% by mass.

As the polyfunctional crosslinking agent, a generally known crosslinking agent such as a divinyl compound, a diallyl compound, a diacrylic compound or a dimethacrylic compound can be used, and polyethylene glycol diacrylate (molecular weight 200) is preferably used. ~600).

The polyfunctional crosslinking agent used herein is used to form a crosslinked structure during polymerization of the soft layer (b), and has an effect of imparting impact resistance. However, when the conventional polyfunctional grafting agent is used for the polymerization of the soft layer, the crosslinked structure of the soft layer (b) is formed to some extent, so that the polyfunctional crosslinking agent is not essential, but from the viewpoint of imparting impact resistance, The ratio of the polyfunctional crosslinking agent used in the polymerization of the soft layer is preferably from 0.01 to 5% by mass.

The outermost hard layer polymer (c) constituting the multilayer structure acrylic granular composite is preferably a methacrylic acid in the presence of the innermost hard layer polymer (a) and the soft layer polymer (b). A monomer mixture composed of 80 to 99% by mass of an ester and 1 to 20% by mass of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms is polymerized.

Among them, the alkyl acrylate may be used, and methacrylate and ethyl acrylate are preferably used. The proportion of the alkyl acrylate unit in the outermost hard layer (c) is preferably from 1 to 20% by mass.

Further, in the polymerization of the outermost hard layer (c), in order to improve the compatibility with the acrylic resin (A), in order to adjust the molecular weight, an alkyl mercaptan or the like may be used as a chain transfer agent for polymerization.

In particular, it is preferable that the outermost hard layer has a slope (slope) in which the molecular weight is gradually decreased from the inner side to the outer side, and the balance between the elongation and the impact resistance can be improved. The specific method is to divide the monomer mixture for forming the outermost hard layer into two or more, and sequentially increase the chain transfer dose per addition, and the molecular weight of the polymer forming the outermost hard layer can be made of a multilayer structure. The inner side of the acrylic granular composite is reduced to the outside.

The molecular weight formed at this time can be known by measuring the molecular weight of the polymer obtained by separately polymerizing each of the monomer mixtures used under the same conditions.

The particle diameter of the acrylic particles (C) which are suitably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 nm or less, more preferably 20 nm or more and 500 nm or less, and most preferably 50 nm or more and 400 nm or less.

In the acrylic granular composite in which the multilayer structure polymer is suitably used in the present invention, the mass ratio of the core to the shell is not particularly limited, but when the entire multilayer structure polymer is 100 parts by mass, the core layer is preferably 50 parts by mass. The above is 90 parts by mass or less, more preferably 60 parts by mass or more and 80 parts by mass or less. This core layer refers to the innermost hard layer.

Commercial products of the multilayer structure of the acrylic granular composite are, for example, "metablen" manufactured by Mitsubishi Rayon Co., Ltd., "kanes" manufactured by Kaneka Chemical Industry Co., Ltd., "Paraloid" manufactured by Kureha Chemical Industry Co., Ltd., and manufactured by Rohm and Haas Co., Ltd. "Acryloid", "staphiloid" manufactured by ganz Chemical Industry Co., Ltd., and "parapet SA" manufactured by Kuraray Co., Ltd., etc., may be used alone or in combination of two or more.

Further, in the acrylic particle (C) which is more suitably used in the present invention, a specific example of the graft copolymerized acrylic particle (c-1) which is more suitable is an unsaturated carboxylic acid ester in the presence of a rubbery polymer. A graft copolymer obtained by copolymerizing a monomer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, a monomer mixture composed of other vinyl monomers copolymerized therewith.

The rubbery polymer used for the acrylic particles (c-1) of the graft copolymer is not particularly limited, and a diene rubber, an acrylic rubber, a vinyl rubber or the like can be used. Specific examples are polybutadiene, styrene-butadiene copolymer, styrene-butadiene block copolymer, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyiso Pentadiene, butadiene-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene A copolymer, an ethylene-isoprene copolymer, and an ethylene-methyl acrylate copolymer. These rubbery polymers may be used alone or in combination of two or more.

Further, when the acrylic particles (C) are added to the optical film of the present invention, the refractive index of the mixture of the acrylic resin (A) and the cellulose ester resin (B) and the acrylic particles are from the viewpoint of obtaining a film having high transparency. The refractive index of C) is close to better. Specifically, the difference in refractive index between the acrylic particles (C) and the acrylic resin (A) is preferably 0.05 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less.

In order to satisfy such a refractive index condition, the composition ratio of each monomer unit of the acrylic resin (A) may be adjusted, and/or the composition ratio of the rubbery polymer or monomer used for the acrylic particle (C) may be adjusted. The method and the like reduce the refractive index difference, and an optical film excellent in transparency can be obtained.

Here, the refractive index difference means that the optical film of the present invention is sufficiently dissolved in a solvent soluble in the acrylic resin (A) to form a white turbid solution under appropriate conditions, and then separated into a solvent-soluble portion by centrifugation or the like. The insoluble portion (acrylic resin (A)) and the insoluble portion (acrylic acid particles (C)) were separately purified from the insoluble portion, and the difference between the measured refractive index (23 ° C, measurement wavelength: 550 nm) was shown.

In the present invention, the method of formulating the acrylic particles (C) in the acrylic resin (A) is not particularly limited, and it is preferred to add acrylic acid at 200 to 350 ° C after using the acrylic resin (A) and other optional components in advance. The particle (C) is simultaneously uniformly melt-kneaded by a uniaxial or biaxial extruder.

Further, a method in which a solution in which acrylic particles (C) are dispersed in advance is added to a solution (slurry) in which an acrylic resin (A) and a cellulose ester resin (B) are dissolved may be used or a method in which acrylic particles (C) and acrylic particles (C) and A method in which a solution obtained by dissolving and mixing other optional additives is subjected to inline addition or the like.

An example of the acrylic particles of the present invention and a method for producing the same are shown below.

<Modulating Acrylic Particles (C1)>

38.2 L of ion-exchanged water and 111.6 g of sodium dioctylsulfosuccinate were placed in a reactor equipped with a reflux condenser at an internal volume of 60 L, and stirred at 250 rpm while raising the temperature to 75 ° C under a nitrogen atmosphere to form a fact. The state affected by oxygen. After adding APS 0.36 g and stirring for 5 minutes, a monomer mixture composed of MMA 1657 g, BA 21.6 g, and ALMA 1.68 g was added in one portion, and the polymerization of the innermost hard layer was completed after detecting the onset heat peak for 20 minutes.

Next, 3.48 g of APS was added, and after stirring for 5 minutes, a monomer mixture composed of BA 8105 g, PEGDA (200) 31.9 g, and ALMA 264.0 g was continuously added over 120 minutes, and after completion of the addition, the polymerization of the soft layer was completed for 120 minutes.

Then, 1.32 g of APS was added, and after stirring for 5 minutes, the monomer mixture consisting of 2106 g of MMA and 201.6 g of BA was continuously added over 20 minutes, and after completion of the addition, the polymerization of the outermost hard layer 1 was completed for 20 minutes.

Next, 1.32 g of APS was added, and after 5 minutes, a monomer mixture composed of MMA 3148g, BA 201.6 g, and n-OM 10.1 g was continuously added over 20 minutes, and the addition was continued for 20 minutes. After heating to 95 ° C and holding for 60 minutes, the polymerization of the outermost hard layer 2 was completed.

The polymer latex obtained above was placed in a 3 mass% sodium sulfate warm aqueous solution, and subjected to repeated salting out and solidification, followed by dehydration and washing, followed by drying to obtain a three-layer structure of acrylic particles (C1). An average particle diameter of 100 nm was obtained by an absorbance method.

The above abbreviations are each of the following materials.

MMA: Methyl methacrylate

MA: methacrylate

BA: n-butyl acrylate

ALMA: allyl methacrylate

PEGDA: polyethylene glycol diacrylate (molecular weight 200)

n-OM: n-octyl mercaptan

APS: ammonium persulfate

Commercially available products can be used for the acrylic particles of the present invention. For example, there are metablen W-341 (C2) (manufactured by Mitsubishi Rayon Co., Ltd.), chemisnow MR-2G (C3), and MS-300X (C4) (manufactured by Suga Chemical Co., Ltd.).

In the optical film of the present invention, the acrylic resin particles (C) are preferably contained in an amount of from 0.5 to 30% by mass, more preferably from 1.0 to 15% by mass, based on the total mass of the resin constituting the film.

<antistatic agent>

The optical film of the present invention preferably contains an antistatic agent, and preferably contains 0.001 to 2.0 parts by mass of an antistatic agent based on 100 parts by mass of the resin constituting the film.

The antistatic agent is not particularly limited, and a known antistatic agent can be used, but is preferably selected from the group consisting of an anionic antistatic agent, a cationic antistatic agent, a nonionic antistatic agent, an amphoteric ionic antistatic agent, and a polymer prevention agent. At least one of the electrostatic agent and the conductive fine particles is more preferably conductive fine particles, and particularly preferably at least one selected from the group consisting of cerium oxide, indium oxide, tin oxide, ammonium oxide, and cerium oxide.

Examples of the anionic antistatic agent include fatty acid salts, higher alcohol sulfate salts, liquid fatty oil sulfate salts, aliphatic amines and aliphatic decyl sulfates, aliphatic alcohol phosphate salts, and dibasic groups. a sulfonate of a fatty acid ester, an aliphatic decyl sulfonate, an alkylallyl sulfonate, a naphthalene sulfonate of a formaldehyde solution condensation, etc., and a cationic antistatic agent such as an aliphatic amine Salts, grade 4 ammonium salts, alkyl pyridinium salts, and the like. Examples of the nonionic antistatic agent include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, and the like. The zwitterionic antistatic agent is, for example, an imidazoline derivative, a betaine-based higher alkylamino derivative, a sulfate derivative, a phosphate derivative, etc., and a specific compound agent is contained in "Mosticide" by Mikio Hideo. "The surface of the polymer has been upgraded." Fortunately, the book is supplemented with "Practical Notes for Plastics and Rubber Additives p333~p455", Chemical Industry Press, Special Edition No. 11-256143, Special Public Show No. 52-32572, and Special Kaiping No. 10-158484.

A preferred antistatic agent is, for example, an ionic polymer compound such as an anionic antistatic agent or a cationic antistatic agent. An ionic polymer compound such as an anionic polymer compound represented by Japanese Patent Publication No. Sho 49-23828, No. 49-23827, and No. 47-28937; Japanese Patent Publication No. 55-734, Japanese Patent Publication No. 50-54672, and special public display An ionene type polymer having a dissociation group in a main chain as described in No. 59-14735, No. 57-18175, No. 57-18176, No. 57-56059, etc.: Tegong Show No. 53-13223, the same 57 No. -15376, special public Zhao 53-45231, same as 55-145783, the same 55-65950, the same 55-67746, the same 57-11342, the same 57-19735, the special public Zhao 58-56858, special opening A cationic betaine-based polymer having a cationic dissociable group in the side chain described in each of the publications of the Japanese Patent Publication No. 62-27346, and a graft copolymer described in JP-A-H05-230161.

Further, in the optical film of the present invention, the branch conductive fine particles are particularly suitable, and the metal oxide is preferably, for example, ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, or the like. CeO ₂ , Sb ₂ O ₃ , MoO ₂ , V ₂ O ₅ , or the like, or a composite oxide thereof, is particularly preferably CeO ₂ , In ₂ O ₃ , SnO ₂ , Sb ₂ O ₃ , and SiO ₂ . Examples of the hetero atom include addition of Al or In to ZnO, addition of Nb or Ta to TiO ₂ , and addition of Sb, Nb, and a halogen element to SnO ₂ . The amount of such hetero atoms to be added is preferably in the range of 0.01 to 25 mol%, particularly preferably in the range of 0.1 to 15 mol%.

The average fine particle diameter of the conductive fine particles is preferably 100 nm or less, more preferably 5 to 100 nm. When the average fine particle diameter of the conductive fine particles is 100 nm or less, when it is contained in a resin material, it is preferable because it can provide sufficient antistatic properties without affecting the transparency of the resin material.

A particularly preferable antistatic agent is preferably one in which the surface specific resistance value is 1 × 10 ¹⁰ Ω or less from the relationship between the antistatic property and the added amount. The surface specific resistance value was measured by adjusting the sample in an atmosphere of 23 ° C and 50% RH for 24 hours, and then measuring it according to ASTM D257 using a super insulation meter.

In the present invention, a cationic conductive polymer described in JP-A-9-203810 or a 4-stage ammonium cation conductive polymer having a crosslink between molecules is used.

The dispersible granular polymer obtained by the special type of the cross-linked cationic conductive polymer can have a cationic component in the fine particles at a high concentration and a high density, and therefore has excellent conductivity and compatibility with the resin. High transparency was obtained, and even at a lower relative humidity, no deterioration in conductivity was observed.

The dispersible granular polymer of the cross-linked cationic conductive polymer for antistatic is generally used in the range of fine particle size of about 0.01 to 0.3 μm, preferably in the range of 0.05 to 0.15 μm.

In the present invention, each of the antistatic agents described above is preferably added in an amount of 0.001 to 2.0 parts by mass based on 100 parts by mass of the optical film of the present invention, and the amount of the antistatic agent added is 0.001 part by mass or more and 2.0 parts by mass. In the following, it is possible to effectively prevent dust from adhering to the resin material, and the light transmittance of the resin material can be maintained at a desired value. The amount of the antistatic agent added is preferably from 0.005 to 1.0 part by mass, more preferably from 0.01 to 0.5 part by mass, per 100 parts by mass of the polymer having an alicyclic structure.

In the present invention, the same effect can be obtained by providing the above-mentioned antistatic agent and a layer having a fluorine compound for general antifouling on a resin.

In order to obtain the performance of the optical film of the present invention, a layer (antistatic layer) containing at least one of an antistatic agent may be provided on the surface of the film.

The antistatic layer can be provided by applying the aforementioned mixture having an antistatic agent to the surface of the optical element, or by a method such as evaporation. Further, the thickness of the antistatic layer is preferably from 50 to 300 μm.

(matting agent)

In order to impart the smoothness, optical, and mechanical function of the optical film of the present invention, fine particles of an inorganic compound or fine particles of an organic compound may be added as a matting agent.

It is preferable to use a shape in which the shape of the matting agent is a spherical shape, a rod shape, a needle shape, a layer shape, a flat shape or the like.

The matting agent is oxidized by metal atoms such as cerium oxide, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, clay, talc, calcined calcium citrate, water and calcium citrate, aluminum silicate, magnesium citrate and calcium phosphate. Inorganic fine particles such as phosphates, citrates, carbonates, and the like.

The fine particles of the organic compound can be described, for example, in the starch described in the specification of the U.S. Patent No. 2,322,037, the starchy derivative described in the specification of the Belgian Patent No. 625,451, or the specification of the British Patent No. 981,198, and the like. The polystyrene or the polymethacrylate described in the Patent No. 330,158, the polyacrylonitrile described in the specification of the U.S. Patent No. 3,079,257, and the like described in the specification of U.S. Patent No. 3,022,169. Organic fine particles of carbonate.

In other words, examples of the fine particles of the organic compound, wherein the water-dispersible ethylene polymer is, for example, polymethacrylate, polymethyl methacrylate, polyacrylonitrile, acrylonitrile-α-methylstyrene copolymer, polyphenylene Ethylene, styrene-divinylbenzene copolymer, polyvinyl acetate, polyethylene carbonate, polytetrafluoroethylene, etc., cellulose derivatives such as methyl cellulose, cellulose acetate, cellulose Examples of the starch derivative such as acetate propionate or the like, such as carboxyl starch, carboxyl nitrophenyl starch, urea-formaldehyde-starch reactant, gelatin hardened by a known hardener, and coacervate hardening to form microcapsule hollow granules Hardened gelatin or the like can be suitably used.

Among the above inorganic fine particle fine particles or organic compound fine particles, cerium oxide is preferable because it can lower the haze value of the film. It is preferred that these fine particles are surface-treated by an organic substance to lower the haze value of the film.

It is preferred to carry out surface treatment with a halodecane, an alkoxydecane, a guanamine, a decane or the like. The larger the average particle diameter of the fine particles, the larger the smoothness effect, and conversely, the smaller the average particle diameter, the more excellent the transparency.

Further, the average particle diameter of the primary particles of the fine particles is in the range of 0.01 to 1.0 μm. The average particle diameter of the primary particles of the preferred fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm.

These fine particles are suitable for producing irregularities of 0.01 to 1.0 μm on the surface of the optical film.

Examples of the cerium oxide particles include AEROSIL 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600, NAX50, etc., manufactured by Japan AEROSIL Co., Ltd., and KE-P10 manufactured by Nippon Shokubai Co., Ltd. KE-P30, KE-P100, KE-P150, etc., preferably AEROSIL200V, R972V, NAX50, KE-P30, KE-P100. These fine particles may be used in combination of two or more kinds.

When two or more types are used in combination, they can be used in any ratio. At this time, fine particles having an average particle diameter or a different material such as AEROSIL 200V and R972V may be used in a mass ratio of 0.1:99.9 to 99.9:0.1.

The method of adding these matting agents is preferably added by a method such as kneading. Further, another form is a solid substance obtained by mixing and dispersing a matting agent previously dispersed in a solvent with a resin and/or a plasticizer and/or an antioxidant and/or an ultraviolet absorber to obtain a solvent which is volatilized or precipitated, and is used for The production process of the resin melt is preferably from the viewpoint that the matting agent can be uniformly dispersed in the resin.

To improve the mechanical, electrical, and optical properties of the film, the above matting agent may be added.

The addition of these fine particles can improve the smoothness of the obtained film, but the haze value after the addition increases, so the content is preferably 0.001 to 5% by mass, more preferably 0.005 to 1% by mass, still more preferably 0.01 to 0.5% by mass based on the resin. quality%.

When the optical film of the present invention has a haze value of more than 1.0%, it may have an influence as an optical material, and it is preferable that the haze value is less than 1.0%, more preferably less than 0.5%. The haze value can be measured by JIS-K7136.

<Other additives>

In order to enhance the fluidity and flexibility of the composition, the optical film of the present invention may be used in combination with a plasticizer. The plasticizer may, for example, be a phthalate type, a fatty acid ester type, a trimellitic acid ester type, a phosphate type, a polyester type or an epoxy type.

Among them, a polyester-based and phthalate-based plasticizer is preferably used. When the polyester-based plasticizer is superior to a phthalate-based plasticizer such as dioctyl phthalate, it has excellent non-migration property and extraction resistance, but has a slightly poor plasticizing effect and compatibility.

Therefore, the selection or combination of these plasticizers can be applied to a wide range of applications.

The polyester-based plasticizer is a reactant of a monovalent to tetravalent carboxylic acid and a monovalent to hexavalent alcohol, but mainly obtained by reacting a divalent carboxylic acid with a glycol. Representative divalent carboxylic acids are, for example, glutaric acid, itaconic acid, adipic acid, decanoic acid, sebacic acid, sebacic acid and the like.

In particular, when adipic acid, citric acid or the like is used, it is possible to obtain an excellent plasticizing property. The glycol may, for example, be a glycol such as ethylene, propylene, 1,3-butene, 1,4-butene, 1,6-hexene, neopentene, diethylene, triethylene or dipropylene. These divalent carboxylic acids and glycols may each be used singly or in combination.

The ester-based plasticizer may be in any form of ester, oligoester, polyester, etc., and the molecular weight may range from 100 to 10,000, and preferably from 600 to 3,000, the plasticizing effect is large.

Further, although the viscosity of the plasticizer is related to the molecular structure or molecular weight, when it is an adipic acid plasticizer, the relationship between compatibility and plasticization efficiency is preferably in the range of 200 to 5,000 MPa ‧ (25 ° C). Further, several polyester-based plasticizers may be used in combination.

The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass based on 100 parts by mass of the optical film of the present invention. When the amount of the plasticizer added exceeds 30 parts by mass, the surface is sticky and practically poor.

The optical film of the present invention may contain an ultraviolet absorber, and examples of the ultraviolet absorber to be used include a benzotriazole type, a 2-hydroxybenzophenone type, or a phenyl salicylate type. For example, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H - triazoles such as benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2 a benzophenone such as hydroxy-4-octyloxybenzophenone or 2,2'-dihydroxy-4-methoxybenzophenone.

Among these ultraviolet absorbers, the ultraviolet absorber having a molecular weight of 400 or more is less likely to volatilize at a high boiling point and is not easily scattered when formed at a high temperature, so that it can be effectively improved in weather resistance by being added in a small amount.

The ultraviolet absorber having a molecular weight of 400 or more is, for example, 2-(2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl)-2-benzotriazole, 2,2-Asia. Benzotriazole, bis(2,2, methyl bis[4-(1,1,3,3-tetrabutyl)-6-(2H-benzotriazol-2-yl)phenol] A hindered amine system such as 6,6-tetramethyl-4-piperidinyl sebacate or bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate And 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonic acid bis(1,2,2,6,6-pentamethyl-4 -piperidinyl ester), 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propenyloxy]ethyl]-4-[3-(3, a mixed system of hindered phenol and hindered amine structure in the molecule of 5-di-t-butyl-4-hydroxyphenyl)propanoxy]-2,2,6,6-tetramethylpiperidine These may be used alone or in combination of two or more. Among them, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2-benzotriazole and 2,2-methylenebis[4- (1,1,3,3-tetrabutyl)-6-(2H-benzotriazol-2-yl)phenol].

Further, the optical film of the present invention may contain various antioxidants in order to improve thermal decomposition properties and thermal coloring properties during molding processing. An antistatic agent is added to impart antistatic properties to the optical film.

As the optical film of the present invention, a flame-retardant acrylic resin composition to which a phosphorus-based flame retardant is added can also be used.

The phosphorus-based flame retardant used herein is, for example, selected from the group consisting of red phosphorus, triaryl phosphate, diaryl phosphate, monoaryl phosphate, arylphosphonic acid compound, arylphosphine oxide compound, condensed aryl phosphate One or a mixture of two or more of an ester, a halogenated alkyl phosphate, a halogen-containing condensed phosphate, a halogen-containing condensed phosphonate, and a halogen-containing phosphite.

Specifically, for example, triphenyl phosphate, 9,10-dihydro-9-ox-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris(β-chloroethyl)phosphate, tris(dichloro Propyl) phosphate, tris(tribromoneopentyl) phosphate, and the like.

According to the optical film of the present invention, it is possible to simultaneously achieve improvement in low moisture absorption, transparency, high heat resistance and brittleness which cannot be achieved by the conventional resin film.

In the present invention, the index of brittleness is judged based on whether or not it is "an optical film which does not cause ductile damage". An optical film which does not cause ductile damage and improves brittleness can be obtained, and even when a polarizing plate for a large liquid crystal display device is produced, cracking or cracking does not occur, and an optical film excellent in workability can be formed. A ductile failure system is defined as a fracture that occurs when a stress greater than the strength of a material is applied, and which is accompanied by a significant extension or contraction of the material before the final fracture. The section is characterized by the formation of numerous recesses called pockets.

In the present invention, whether or not the "optical film which does not cause ductile damage" is evaluated by the fact that even if a large stress is applied to bend the film into two pieces, no damage such as breakage occurs. Even when an optical film which does not cause ductile damage is applied even when such a large stress is applied, even when it is used as a polarizing plate for a large-sized liquid crystal display device, problems such as breakage during production can be sufficiently reduced, and even after one bonding Further, when the optical film is used, the optical film is not broken, and it can be sufficiently applied to the thinning of the optical film.

In the present invention, a tension softening point is used as an index of heat resistance. With the increase in the size of liquid crystal display devices, the increasing brightness of backlight sources, and the need for higher brightness in the application of digital signage for outdoor applications, optical films are required to withstand higher temperature environments, but when the tension softening point is 105 to 145 ° C It can be judged that it has sufficient heat resistance. It is especially suitable for control at 110~130 °C.

A specific measurement method for displaying the temperature at the tension softening point of the optical film, for example, using a universal tensile tester (RTC-1225A manufactured by ORIENTEC Co., Ltd.), and cutting the optical film into 120 mm (length) × 10 mm (width), and then pulling at a tension of 10 N The temperature was continuously increased at a temperature increase rate of 30 ° C / min, and the temperature at the point of reaching 9 N was measured three times, and the average value was obtained.

Further, from the viewpoint of heat resistance, the glass transition temperature (Tg) of the optical film is preferably 110 ° C or higher. More preferably, it is 120 ° C or more. Particularly preferred is 150 ° C or more.

The glass transition temperature is an intermediate point glass transition temperature (Tmg) determined by a differential scanning calorimeter (Model DSC-7 manufactured by Perkin Elmer Co., Ltd.) at a temperature increase rate of 20 ° C /min, in accordance with JIS K7121 (1987).

The index for determining the transparency of the optical film of the present invention is a haze value (turbidity). In particular, a liquid crystal display device used outside the house is required to have sufficient brightness and high contrast even in a bright place, and therefore the haze value must be 1.0% or less, more preferably 0.5% or less.

According to the optical film of the present invention containing the acrylic resin (A) and the cellulose ester resin (B), high transparency can be obtained, but when acrylic particles are used to improve other physical properties, the resin (acrylic resin) is lowered. A) The difference in refractive index between the cellulose ester resin (B) and the acrylic particles (C) prevents the haze value from rising.

Further, since the surface roughness also affects the haze value in the form of surface haze, the particle size and the addition amount of the acrylic particles (C) are controlled within the above range, and the surface roughness of the film contact portion at the time of film formation can be effectively reduced. .

Further, the hygroscopicity of the optical film of the present invention is evaluated by dimensional change with respect to change in humidity.

The following method can be used for the evaluation method of the dimensional change with respect to the humidity change.

In the casting direction of the produced optical film, mark (cross) at two places, and treat it at 60 ° C, 90% RH for 1000 hours, and measure the distance between the mark (cross) before and after the treatment using an optical microscope. Dimensional change rate (%). The dimensional change rate (%) is expressed by the following formula.

Dimensional change rate (%) = [(a1-a2)/a1] × 100

A1: distance before heat treatment

A2: distance after heat treatment

When an optical film is used as a protective film for a polarizing plate of a liquid crystal display device, the size of the optical film changes due to moisture absorption, and thus the optical film is unevenly distributed (color unevenness) or phase difference value, so that a problem of contrast reduction or color unevenness occurs. . In particular, when the polarizing plate protective film for a liquid crystal display device for outdoor use is used, the above problem is more remarkable. However, when the dimensional change rate (%) of the above conditions was less than 0.5%, it was evaluated as an optical film which showed sufficiently low hygroscopicity. More preferably, it is less than 0.3%.

Further, the optical film of the present invention has a defect of 5 μm or more in the surface of the film, preferably 1/10 cm square or less. More preferably, it is 0.5 /10 cm square or less, more preferably 0.1 /10 cm square.

The diameter of the defect means that the diameter is a circular shape, and the diameter is not determined by the following method, and the maximum diameter (diameter of the circumscribed circle) can be determined by the following method using a microscope to observe the defect.

The disadvantage is that when the defect is a bubble or a foreign matter, it refers to the size of the shadow when the defect is observed by the differential light of the microscope. The disadvantage is that when the surface shape such as transfer or scratch of the roller is changed, the size of the reflected light of the microscope can be differentially observed to confirm the size.

Further, when the size of the defect is not clearly observed when reflected light, it can be observed by vapor-depositing aluminum or platinum on the surface.

In order to obtain a film excellent in quality with such a defect frequency with better productivity, it is possible to use a high-precision filtration of the polymer solution before casting, or to improve the cleanliness of the periphery of the casting machine, or to set the casting in stages. The drying conditions are followed by drying with high efficiency and suppression of foaming.

When the number of the defects is more than one /10 cm square, for example, when tension is applied to the film during processing in the subsequent step, the film may be broken due to the defect, and the productivity may be remarkably lowered. Moreover, when the diameter of the defect is 5 μm or more, it can be visually confirmed by observation of a polarizing plate or the like, and a bright spot may be generated when used as an optical member.

Even when it is not visually confirmed, when a hard coat layer etc. are formed on this film, the coating agent cannot be formed uniformly, and it is a fault (uncoated). Disadvantages refer to voids (foaming defects) in a film produced by rapid evaporation of a solvent in a drying step of a solution film formation, or a film generated by a foreign matter in a film forming solution or a foreign matter mixed in a film forming film. Foreign matter (foreign foreign matter).

Further, when the optical film of the present invention is measured in accordance with JIS-K7127-1999, the elongation at break in at least one direction is preferably 10% or more, more preferably 20% or more.

The upper limit of the elongation at break is not particularly limited and is actually about 250%. In order to increase the elongation at break, it is possible to suppress disadvantages in the film due to foreign matter or foaming.

The thickness of the optical film of the present invention is preferably 20 μm or more. More preferably, it is 30 μm or more.

The upper limit of the thickness is not particularly limited, but the upper limit is 250 μm from the viewpoints of coatability, foaming, solvent drying and the like. Further, the film thickness can be appropriately selected depending on the use.

The light transmittance of the optical film of the present invention is preferably 90% or more, more preferably 93% or more. The actual upper limit is 99%. In order to achieve such excellent transparency as a total light transmittance, it is possible to avoid introduction of an additive or a copolymerized component that absorbs visible light, or to remove foreign matter in the polymer by high-precision filtration, or to reduce the inside of the film. Light diffuses or absorbs.

In addition, the surface roughness of the film surface can be reduced by reducing the surface roughness of the film contact portion (cooling roll, calender roll, roller, conveyor belt, coated substrate, transfer roll, etc.) at the time of film formation. Degree, or reduce the refractive index of the acrylic resin, reducing the light diffusion or reflection on the surface of the film.

When the optical film of the present invention satisfies the physical properties as described above, it is particularly suitably used as a polarizing plate protective film for a liquid crystal display device of a large liquid crystal display device or an outdoor use.

<Film film formation>

Hereinafter, an example of a film forming method of an optical film will be described, but the present invention is not limited thereto.

In the film forming method of the optical film of the present invention, for example, a production method such as a blow molding method, a T-die method, a calendering method, a cutting method, a casting method, an emulsification method, or a hot pressing method can be used, but from the viewpoint of suppressing coloring and suppressing foreign matter defects, From the viewpoint of suppressing optical defects such as mold marks and the like, it is preferred to form a film by a solution of a casting method.

The optical film of the present invention is an optical film having at least two or more layers of resin compositions different from each other, characterized in that (i) at least one layer constituting the surface of the optical film is 50:50 to 30:70. The mass ratio contains the acrylic resin (A) and the cellulose ester resin (B), and (ii) the layer other than the layer constituting the surface contains the acrylic resin (A) and the cellulose ester in a mass ratio of 80:20 to 50:50. Resin (B), (iii) The weight average molecular weight of the acrylic resin (A) is 80,000 or more, and (iv) the total substitution degree of the thiol group of the cellulose ester resin (B) is 2.0 to 3.0, and the carbon number is 3 to 7. The degree of substitution of the fluorenyl group is from 1.2 to 3.0, and the weight average molecular weight of the cellulose ester resin (B) is 75,000 or more. Therefore, a method for realizing such a feature is preferably a method of simultaneously forming a layer in which the resin compositions are different from each other in the film forming step described in detail below. For example, there is a method in which a plurality of different compositions of the resin are prepared in advance, and then a method of supplying the same, preparing a paste of the respective resin, and appropriately mixing a plurality of layers of the resin before casting, but uniforming from the glue The viewpoint of the nature is preferably a method of preliminarily preparing a plurality of layers of the resin which are different from each other and then supplied.

For example, the optical film of the present invention is obtained by using a plurality of slits having a plurality of slits, using a slit having a plurality of slits, directly casting on a casting belt for co-casting (casting step), followed by heating to remove After a part of the solvent (drying step on the casting tape), the film is peeled off from the casting tape, and the peeled film is dried (film drying step), and an optical film having a plurality of layers having different resin compositions of the present invention can be obtained. .

The surface side referred to in the present invention means a portion having a depth of 5% or more and 20% or less of the thickness of the film from the surface of the film.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a preferred embodiment of the apparatus for simultaneous casting and continuous casting of the present invention.

1a to 1c denote the glue liquid tanks respectively, 2a to 2c denote pumps, and 3 denote molds for co-casting. An enlarged cross-sectional view of the mold for co-casting is shown in Fig. 2, and has a die slit of four of 10, 11a, 11b, and 12.

The respective mortars for casting are supplied to the slits 10, 11a, and 11b, respectively, and a laminar flow is formed at the joining point, and the casting slit is supplied from the slit of 12 to the casting tape. 5 is a support for casting (belt), 4 is a rotating drum, and 7 is an optical film after peeling after moderately evaporating the solvent, and 6 is a drum for conveying the optical film.

For example, the glue A, the glue B, and the glue C having different resin compositions are filled in the slurry tanks 1a, 1b, and 1c, respectively, and the flow rates of the pumps 2a to 2c are changed, and the slits are supplied by the three slits for casting. Three-layer co-cast film.

It is preferable that the optical film has a length in the width direction of at least 10 to 90%, and a portion containing the center of the film in the width direction is preferably a layer containing at least two or more layers having different resin compositions.

(organic solvent)

When the optical film of the present invention is produced by a solution casting method, an organic solvent for forming a paste is not particularly limited as long as it can simultaneously dissolve the acrylic resin (A), the cellulose ester resin (B), and other additives. be usable.

For example, the chlorine-based organic solvent is dichloromethane, and the non-chlorine organic solvent is, for example, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxin. Alkane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1, 1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3 , 3-pentafluoro-1-propanol, nitroethane, etc., preferably using dichloromethane, methyl acetate, ethyl acetate or acetone.

In addition to the above organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the ratio of the alcohol in the dope is increased, the web is gelated and easily peeled off from the metal support, and when the proportion of the alcohol is small, the non-nitrogen-based organic solvent also promotes dissolution of the acrylic resin ( A), the function of the cellulose ester resin (B).

In particular, the acrylic resin (A), the cellulose ester resin (B) and the acrylic acid particles (C) are dissolved in at least 15 to 45% by mass in a straight chain or a branched chain containing methylene chloride and a carbon number of 1 to 4. The paste composition in the solvent of the aliphatic alcohol is preferred.

The linear or branched aliphatic alcohol having 1 to 4 carbon atoms is, for example, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol or tert-butanol. Among these, in view of the stability of the dope, the lower boiling point, and the good drying property, methanol is preferred.

A preferred film forming method of the optical film of the present invention will be described below.

1) Dissolution step

In an organic solvent mainly composed of a good solvent for the acrylic resin (A) or the cellulose ester resin (B), the acrylic resin (A), the cellulose ester resin (B), and if necessary, in a dissolution pot Acrylic particles (C) and other additives are stirred and dissolved to form a dope, or the acrylic resin (A), the cellulose ester resin (B) solution may be mixed with an acrylic particle (C) solution, and the like. The additive solution is a step of forming a dope of the main solution.

The dissolution of the acrylic resin (A) or the cellulose ester resin (B) can be carried out by a method of dissolving under normal pressure, a method of dissolving below the boiling point of the main solvent, or a method of performing pressure dissolution at a boiling point or higher of the main solvent, such as a special opening. In the method of dissolving by a cooling and dissolving method, as described in JP-A-11-21379 Various methods of dissolving are particularly preferred as a method of pressure-dissolving above the boiling point of the main solvent.

The acrylic resin (A) and the cellulose ester resin (B) in the dope preferably have a total range of 15 to 45% by mass. Adding an additive to the dope after dissolution or dissolution, dissolving and dispersing, filtering, defoaming with a filter material, and pumping to the next step by liquid feeding.

The filtration system is preferably a filter material having a particle diameter of 0.5 to 5 μm and a filtration time of 10 to 25 sec/100 ml.

In this method, agglomerates which are generated when the particles are dispersed or agglomerates which are generated when the main gel is added are used, and only agglomerates can be removed by using a filter medium having a particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec/100 ml. In the main dope, the concentration of the particles is very low compared to the additive liquid, so that the aggregates do not stick to each other during filtration, resulting in a rapid increase in filtration pressure.

Fig. 3 is a schematic view showing an example of a dope preparation step, a casting step, and a drying step of the preferred solution casting film forming method of the present invention.

If necessary, the acrylic particles are introduced into the pot 41 to remove the larger aggregates by the filter 44, and then the liquid is supplied to the storage pot 42. Thereafter, the acrylic particle addition liquid is added to the main dope dissolving pot 1x from the storage pot 42.

Thereafter, the main dope was filtered through a main filter 3x, and then a UV absorber addition liquid was added by a 16x connection.

In many cases, the main glue contains 10 to 50% by mass of the recycled material. The acrylic material may be contained in the return material, and in this case, the addition amount of the acrylic acid particle addition liquid is preferably controlled in accordance with the added amount of the recycled material.

The additive liquid containing acrylic particles preferably contains 0.5 to 10% by mass of the acrylic particles, more preferably 1 to 10% by mass, most preferably 1 to 5% by mass.

In the above range, it is preferred to add a liquid system with a low viscosity, which is easy to handle and easy to add to the main dope.

The regrind refers to an article in which the optical film is finely pulverized, and an article which is obtained by cutting the optical film and which cuts off both ends of the film or a scratch or the like, is used as a material of the optical film raw material other than the specification.

It is preferred to previously knead the acrylic resin, the cellulose ester resin and, if necessary, the acrylic particles to form granules.

2) Casting step

The glue is sent to the pressurizing die 30 through a liquid feeding pump (for example, a pressurized quantitative gear pump), and then the rubber slurry is cast by the pressurizing die slit to the endless metal strip 31 which is infinitely transferred, for example, a stainless steel belt, A casting step of a casting position on a metal support such as a rotating metal drum.

The shape of the slit of the die portion of the mold can be adjusted, and the pressurizing die having a uniform film thickness is preferable. The press mold can be used with a coat hanger die or a T die. The surface of the metal support becomes a mirror surface. In order to increase the film forming speed, two press molds may be provided on the metal support, and the amount of the glue may be divided and laminated. Alternatively, a laminated structure film can be obtained by a co-casting method in which a plurality of cements are simultaneously cast.

3) Solvent evaporation step

The step of heating the solvent on the casting support by ejecting the fiber web (the dope film formed by casting the dope onto the casting support is referred to as "web") to evaporate the solvent.

When the solvent is to be evaporated, there is a method of blowing from the side of the fiber web and/or a method of transferring heat from the inner surface of the support by liquid, a method of transferring heat from the surface by radiant heat, etc., but the inner liquid heat transfer method is dried. It is more efficient and therefore better. It is also possible to use a combination of these methods. It is preferred that the web on the cast support is dried on the support in an atmosphere of 40 to 100 ° C. When it is desired to maintain an atmosphere of 40 to 100 ° C, it is preferred to blow the hot air of this temperature onto the surface of the fiber web or by means of infrared rays or the like.

From the viewpoint of surface quality, moisture permeability, and peelability, it is preferred that the fiber web is peeled off from the support within 30 to 120 seconds.

4) Stripping step

The step of peeling the web after evaporating the solvent on the metal support at the peeling position. The stripped web is sent to the next step.

The temperature at the peeling position on the metal support is preferably from 10 to 40 ° C, more preferably from 11 to 30 ° C.

The amount of residual solvent in the peeling of the web on the metal support at the time of peeling is preferably in the range of 50 to 120% by mass, depending on the strength of the drying conditions and the length of the metal support, but the amount of residual solvent is more When the web is too soft, the flatness at the time of peeling is impaired, and the peeling tension tends to cause slack or straight strips. Therefore, the amount of residual solvent at the time of peeling is determined in consideration of economic speed and quality.

The residual solvent amount of the fiber web is defined by the following formula.

Residual solvent amount (%) = (mass before heat treatment of fiber web - mass after heat treatment of fiber web) / (mass after heat treatment of fiber web) × 100

Further, the heat treatment at the time of measuring the amount of residual solvent means heat treatment at 115 ° C for 1 hour.

When the metal support and the film are peeled off, the peeling tension is usually 196 to 245 N/m. However, when wrinkles are likely to occur during peeling, peeling is preferably performed at a tension of 190 N/m or less, and more preferably a peelable minimum tension of ~166.6 N. /m, then peeled off at a minimum tension of ~137.2 N/m, particularly preferably at a minimum tension of ~100 N/m.

In the present invention, the temperature at the peeling position on the metal support is preferably -50 to 40 ° C, more preferably 10 to 40 ° C, and most preferably 15 to 30 ° C.

5) Drying and stretching steps

After the peeling, the web is transported by a drying device 35 that transports the webs through a plurality of rolls arranged in a drying device, and/or a tenter stretching device 34 that grips both ends of the web by a jig, and the web is dried.

The drying means generally uses hot air to blow the two sides of the fiber web, or a microwave oven can be used to heat the hot air instead of heating. Too fast drying tends to damage the planarity of the finished film. The residual solvent may be about 8% by mass or less by drying at a high temperature. The overall drying is about 40~250 °C. It is especially good to dry at 40~160 °C.

When the tenter extension device is used, it is preferable to use a right and left holding means by the tenter to independently control the holding length of the film (the distance from the start of gripping to the end of gripping). In the tentering step, in order to improve the planarity, a section having a different temperature can also be deliberately produced.

The neutral region can be set so that there is no interference between the respective intervals in different temperature ranges.

The extension operation can be divided into multiple stages, and the two-axis extension can also be performed in the casting direction and the width direction. When biaxial stretching is performed, biaxial stretching or phased implementation can be performed simultaneously.

In this case, the stages may be extended in different directions, for example, or may be divided into multiple stages, and extensions in different directions may be applied to any of the stages. In other words, for example, the following extension steps are possible.

‧ Casting direction extension - width direction extension - casting direction extension - casting direction extension

‧Width direction extension - width direction extension - casting direction extension - casting direction extension

In addition, at the same time, when the two-axis is extended, the one side is extended, and the other side is relaxed and contracted. At the same time, the preferred stretching ratio of the 2-axis extension may be in the range of ×1.01 to 1.5 times in the width direction and the length direction.

The amount of residual solvent of the fiber web at the time of tenter stretching is preferably 20 to 100% by mass at the start of tenter stretching, and it is preferable to carry out tentering while drying at a residual solvent amount of the fiber web of 10% by mass or less. More preferably, it is 5% by mass or less.

The drying temperature for stretching is preferably 30 to 160 ° C, more preferably 50 to 150 ° C, and most preferably 70 to 140 ° C.

In the tentering step, the temperature distribution in the width direction of the atmosphere is small, and from the viewpoint of improving the uniformity of the film, the temperature distribution in the width direction of the tentering step is preferably within ±5 ° C, more preferably within ± 2 ° C. , preferably within ±1 °C.

6) Winding step

After the amount of the residual solvent in the fiber web is 2% by mass or less, the film is wound by the winder 37 in the form of an optical film, and the residual solvent amount is 0.4% by mass or less, whereby a film having good dimensional stability can be obtained. In particular, it is preferably wound at 0.00 to 0.10% by mass.

The winding method may be a method generally used, for example, a fixed torque method, a constant tension method, a taper tension method, a program tension control method in which internal stress is fixed, and the like.

The optical film of the present invention is preferably a long film, specifically, a film of a size of from 100 m to 5,000 m, usually provided in a cylindrical shape. Further, the width of the film is preferably from 1.3 to 4 m, more preferably from 1.4 to 2 m.

The film thickness of the optical film of the present invention is not particularly limited, but is preferably 20 to 200 μm, more preferably 25 to 100 μm, and particularly preferably 30 to 80 μm, for use in a polarizing plate protective film to be described later.

[Polarizer]

When the optical film of the present invention is used as a protective film for a polarizing plate, a polarizing plate can be produced by a general method. Preferably, an adhesive layer is provided on the inner surface side of the optical film of the present invention, and is bonded to at least one surface of a polarizer prepared by stretching in an iodine solution.

On the other hand, the optical film of the present invention, or other polarizing plate can be used to protect the film. For example, it is preferred to use a commercially available cellulose ester film (for example, Konica Minolta TAC KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UE, KC4UE, KC4FR-3, KC4FR) -4, KC4HR-1, KC8UY-HA, KC8UX-RHA, the above is made by Konica Minolta Opto Co., Ltd.).

The polarizer of the main constituent elements of the polarizing plate refers to an element which can pass only the light of the deflecting surface in a certain direction. The representative polarizing film which is known at present is a polyvinyl alcohol-based polarizing film, and the polarizing film has iodine-made polyvinyl alcohol. Film dyes and dichroic dyes.

The polarizer may be obtained by forming a film of a polyvinyl alcohol aqueous solution, and then uniaxially stretching and dyeing it, or uniaxially stretching after dyeing, and it is preferred to carry out durability treatment with a boron compound.

Preferably, the adhesive used in the adhesive layer is an adhesive which is used in at least a part of the adhesive layer at a storage modulus of from 0.5 × 10 ⁴ to 1.0 × 10 ⁹ Pa at 25 ° C, and is coated with an adhesive. A hardening type adhesive which forms a high molecular weight substance or a crosslinked structure by various chemical reactions is suitable.

Specific examples thereof include a urethane-based pressure-sensitive adhesive, an epoxy-based pressure-sensitive adhesive, a water-based polymer-isocyanate-based pressure-sensitive adhesive, a thermosetting acrylic adhesive, and the like, and a moisture-curing urethane adhesive. , polyether methacrylate type, ester type methacrylate type, oxidized polyether methacrylate and other anaerobic adhesives, cyanoacrylate type instant adhesives, acrylates and peroxides The second liquid type instant adhesive and the like.

The above-mentioned adhesive may be a one-liquid type or a two-liquid type in which two or more liquids are mixed before use.

The above-mentioned adhesive may be a solvent based on an organic solvent or a water-based or solvent-free type such as an emulsion type, a colloidal dispersion type, or an aqueous solution type which is a medium containing water as a main component. The concentration of the above-mentioned adhesive liquid can be appropriately determined depending on the film thickness after the adhesion, the coating method, the coating conditions, and the like, and is generally 0.1 to 50% by mass.

[Liquid Crystal Display Device]

When a polarizing plate to which the optical film of the present invention is bonded is assembled in a liquid crystal display device, various liquid crystal display devices having excellent visibility can be produced, and are particularly suitable for liquid crystal displays for outdoor use such as large liquid crystal display devices or digital signs. The polarizing plate of the present invention is bonded to the liquid crystal cell by the adhesion layer or the like.

The polarizing plate of the present invention is suitable for various types of driving such as reflective, transmissive, semi-transmissive LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type (including FFS mode). The way the LCD. In particular, a display device having a screen size of 30 吋 or more, more preferably 30 吋 to 54 吋, has no whitening at the periphery of the screen, and the effect can be maintained for a long period of time.

Moreover, the stain, the glare, or the unevenness are less uneven, and the eye does not get tired even if it is watched for a long time.

Example

The present invention will be specifically described below by way of examples, but the invention is not limited thereto.

Example 1 [Production of optical film] <Production of Optical Film 1> (Mixed with glue 1)

DIANAL BR85 (Mitsubishi Rayon Co., Ltd.) 65 parts by mass

Acrylic particles (C1) 5 parts by mass

Cellulose ester (cellulose acetate propionate thiol total substitution degree 2.75,

Ethyl thiol substitution degree 0.19, propyl thiol substitution degree 2.56, Mw=200000) 30 parts by mass

Dichloromethane 300 parts by mass

40 parts by weight of ethanol

The above composition was sufficiently dissolved by heating to prepare a dope 1.

Similarly, the dope 2 was produced in the same manner except that the resin composition was changed as described below.

(Mastic 2 composition)

DIANAL BR85 (Mitsubishi Rayon) 85 parts by mass

Acrylic particles (C1) 5 parts by mass

Cellulose ester (cellulose acetate propionate thiol total substitution degree 2.75, acetylation degree substitution degree 0.19, propyl thiol substitution degree 2.56, Mw=200000) 10 parts by mass

Dichloromethane 300 parts by mass

40 parts by weight of ethanol

(film formation of acrylic resin film)

The above-prepared dope 1 and 2 were uniformly cast on a stainless steel belt support at a temperature of 22 ° C and a width of 2 m using a belt casting apparatus (see Fig. 1). The solvent was evaporated on the stainless steel belt support until the amount of residual solvent became 100%, and peeled off from the stainless steel belt support at a peeling tension of 160 N/m. Next, the casting amount of the dope 1 and 2 is appropriately controlled to obtain a film having a desired layer thickness. The web of the peeled film was allowed to evaporate at 35 ° C, and was stretched 1.5 times in the width direction using a tenter while being dried at a drying temperature of 140 ° C. At this time, the amount of residual solvent at the start of tenter stretching was 10%. After stretching using a tenter, after relaxing at 130 ° C for 5 minutes, it was conveyed by a plurality of rolls through a drying zone of 100 ° C and 120 ° C, and at the same time drying was completed, and cut into a width of 1.5 m, and a width of 10 mm was applied to both ends of the film. The embossing process at a height of 5 μm was wound on a core having an inner diameter of 15.24 cm at an initial tension of 220 N/m and a final tension of 110 N/m to obtain an optical film 1 of the present invention.

<Production of Optical Films 2 to 13 of the Present Invention and Optical Films 1 to 7 of Comparative Examples>

In the production of the optical film 1 described above, the optical film 2 of the present invention was produced in the same manner except that the type and composition ratio of the acrylic resin (A) and the cellulose ester resin (B) were changed as shown in Tables 1 and 2. 13 and comparative examples of optical films 1 to 7. The ratio of DIANALBR85 to acrylic particles (C1) of acrylic resin is constant.

In the production of the optical film 1 of the present invention, except that the acrylic resin was changed to Delpet 80N manufactured by Asahi Kasei Chemicals Co., Ltd., the composition ratio of the acrylic resin (A) and the cellulose resin (B) was changed to that shown in Table 2, and the same. The optical films 14 to 20 of the present invention were produced. The ratio of Delpet 80N to acrylic particles (C1) of acrylic resin is constant.

Evaluation Method

The obtained optical film was evaluated as follows.

(bend evaluation)

The optical film was cut into a size of 100 mm (length) × 10 mm (width), and folded in the center portion in the longitudinal direction, and folded in half, and the evaluation was performed 10 times, and the number of folds was evaluated. The rupture evaluated here indicates that the rupture is separated into two or more fragments.

(pencil hardness)

For each of the optical films of Examples 1 to 20 and Comparative Examples 1 to 7 produced as described above, a test pencil specified in JIS S 6006 was used, and a pencil hardness evaluation method according to JIS K 5400 was used, and a load of 1 kg was used. The pencil of the hardness was drawn on the surfaces of the optical films of Examples 1 to 20 and Comparative Examples 1 to 7, and the pencil hardness was measured. The optical film of the present invention was evaluated on the side surface of the layer 2. The results obtained are shown in Tables 1 and 2 below.

As shown in Tables 1 and 2, the optical film of the present invention has high hardness and is less likely to be broken by bending, and it is possible to obtain characteristics which cannot be achieved when the resin composition in the thickness direction is uniform.

Example 2

In the preparation of the dope 2 of Example 1, in addition to the addition of the additional compound as shown in Table 3, an optical film which improved the adhesion and hardness of the optical film was provided in the same manner. A polarizing plate and a liquid crystal display using the optical film are provided.

Films 21 to 28 were produced. The antistatic agent described in the examples of P-1 and P-2 of the Japanese Patent Publication No. Hei 9-203810. The produced optical film was subjected to the bending evaluation of Example 1, the pencil hardness evaluation, and the following dirt adhesion test. The results obtained are shown in Table 3 below.

(dirt adhesion test)

The side of the a side of the film was brought close to the cigarette ash for 10 seconds until the height was 1 cm, and the adhesion of the dirt was observed.

○: No dirt was observed at all.

△: A little dirt adhered.

×: The dirt adhered significantly.

As described in Table 3, the optical film of the present invention using an antistatic agent or a matting agent has a characteristic optical film having high hardness, less cracking of the bend, and excellent stain adhesion.

Example 3

In the production of the optical film 1 of Example 1, except that the film of Comparative Example 1 was cast in a single layer at both end portions of the film, and the film holding method of the tenter portion was changed, the optical film was produced in the same manner. film. The optical film 30 of the present invention is a cookware method in which a metal block is held by an end portion of a film which is pressed up and down, and the optical film 31 is a pin-punched film end portion, and the film is held by a penetrating needle. Extend with a tenter. The transport properties of these films are shown in Table 4 below.

(transportability test)

The film was conveyed by setting the internal temperature of the tenter to 100 ° C, 130 ° C, and 150 ° C and an elongation of 1.5 times, and observing the film.

○: The film can be conveyed without cracking or deformation.

△: Although the film was not broken, it was deformed.

×: The film was broken and deformed and could not be transported.

As described in Table 4, the optical film of the present invention exhibits the transportability of both the cookware and the needle by the gripping means of the tenter.

(Feature evaluation of liquid crystal display device) <Production of polarizing plate>

A polarizing plate in which each optical film was used as a polarizing plate protective film was produced as follows.

The strip-shaped polyvinyl alcohol film having a thickness of 120 μm was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and a polarizing film was formed by stretching five times in the transport direction at 50° C.

Next, the optical film 1 produced in Example 1 was subjected to corona treatment using an acrylic adhesive, and then bonded to one side of the above polarizing film.

KC8UX manufactured by Konica Minolta Opto Co., Ltd., which is a phase difference film which was alkali-saponified, was bonded to the other surface of the polarizing film, and dried to prepare a polarizing plate. Similarly, a polarizing plate was produced using the optical films 2 to 13 of the present invention and the optical films 1 to 7 of the comparative examples.

The polarizing plate-based film using the optical film of the present invention is excellent in cuttability and easy to process.

<Production of Liquid Crystal Display Device>

The display characteristics of the optical film were evaluated using the respective polarizing plates produced above.

The polarizing plate prepared by the company's 32-inch TV 32H2000, which is bonded to the two sides, was peeled off, and the polarizing plate produced above was prevented from having the respective KC8UX on the glass surface side of the liquid crystal cell, and the absorption axis was oriented toward the pre-bonded polarized light. The plates are bonded in the same direction to produce a liquid crystal display device.

(display quality evaluation)

With respect to the liquid crystal display device produced as described above, various images were displayed, and the quality of the display image in an environment of 23 ° C and 55% RH was evaluated.

○: Good display

△: The displayed image lacks uniformity and has uneven spots (unevenness).

×: A part of the extreme color change.

(Color shift: heat resistance and moisture resistance evaluation of polarizing plate)

In the liquid crystal display device produced as described above, the display was black in an environment of 23 ° C and 55% RH, and was observed at an angle of 45° in the oblique direction. Next, the polarizing plate was also subjected to treatment at 60 ° C and 90% RH for 1,000 hours, and the color change was evaluated on the basis of the following criteria.

○: Completely colorless change.

△: A slight color change.

×: The color change is large.

A polarizing plate or a liquid crystal display device produced by using the optical film of the present invention has characteristics of excellent display quality and color shift.

1a~1d. . . Glue tank

2a~2c. . . Pump

3. . . Casting die

4. . . cylinder

5. . . Casting zone

6. . . roller

7. . . Resin film

10, 11a, 11b, 12. . . Mold seam

1x. . . Dissolving pot

3x, 6x, 12x, 15x. . . filter

4x, 13x. . . Storage tank

5x, 14x. . . Liquid pump

8x, 16x. . . catheter

10x. . . UV absorber is put into the pot

20. . . Confluence tube

twenty one. . . Mixer

30. . . mold

31. . . Metal support

32. . . Fiber web

33. . . Peeling position

34. . . Chuck device

35. . . Roll drying device

41. . . Particles into the pot

42. . . Storage tank

43. . . Pump

44. . . filter

Fig. 1 is a schematic view showing a resin film production apparatus capable of simultaneously casting a plurality of dopes.

[Fig. 2] Cross-sectional view of a mold for co-casting

Fig. 3 is a schematic view showing an example of a dope preparation step, a casting step, and a drying step of a solution casting film forming method.

1a~1c. . . Glue tank

2a~2c. . . Pump

3. . . Casting die

4. . . cylinder

5. . . Casting zone

6. . . roller

7. . . Resin film

Claims (8)

An optical film having at least two or more layers of resin layers different from each other, characterized in that (i) at least one layer constituting a layer of the surface of the optical film has a mass ratio of 95:5 to 85:15. The layer containing the acrylic resin (A) and the cellulose ester resin (B), (ii) the layer constituting the surface contains the acrylic resin (A) and the cellulose ester resin in a mass ratio of 80:20 to 50:50 ( B), (iii) the weight average molecular weight of the acrylic resin (A) is 80,000 or more, and (iv) the total substitution degree of the thiol group of the cellulose ester resin (B) is 2.0 to 3.0, and the carbon number is 3 to 7. The degree of substitution of the group is from 1.2 to 3.0, and the weight average molecular weight of the cellulose ester resin (B) is 75,000 or more. The optical film of claim 1, wherein the thickness of the layer constituting the surface is 5 to 20% of the entire thickness of the optical film. The optical film of claim 1 or 2, wherein the layer constituting the surface contains 0.01 to 1% by mass of the average particle diameter in the range of 50 to 300 μm with respect to the total mass of the layer constituting the surface. A fine particle of an inorganic compound or an organic compound. An optical film according to claim 1 or 2, which contains an antistatic agent. The optical film according to claim 1 or 2, wherein the optical film has a length in the width direction of at least 10 to 90%, and a portion including a center of the film width direction contains at least two or more layers. The resin is composed of different layers. An optical film as claimed in claim 1 or 2 wherein the aforementioned tree Layers having different lipid compositions from each other are simultaneously formed at the time of film formation. A polarizing plate characterized by using an optical film according to any one of claims 1 to 6. A liquid crystal display device characterized by using an optical film according to any one of claims 1 to 6.