JP2016114874A - Optical film, circular polarization plate and organic electroluminescence display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film, circular polarization plate and organic EL display, capable of preventing hue shift or ripple-like unevenness from occurring when displayed on an organic EL display.SOLUTION: An optical film manufactured by stretching a resin film is manufactured by using a resin having an in-plane phase difference variation rate (ΔRo) within a range of 10-20% when an uniaxial stretching having a stretching rate of 15% is performed at a glass transition temperature (Tg)+10°C and the glass transition temperature (Tg)+20°C and controlling the in-plane phase difference variation rate so as to satisfy optical characteristics of the requirements (1)-(3). The definitional equation: an in-plane phase difference variation rate (ΔRo)(%)=[{Ro(Tg+10°C)-Ro(Tg+20°C)}/Ro(Tg+10°C)]×100, the requirements:(1) 130 nm<Ro(550)<160 nm, (2) Nz<1.3, Nz=(n-n)/(n-n), (3) 0.7<DSP<1, DSP=Ro(450)/Ro (550).SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical film produced by stretching a resin film, and relates to an optical film, a circularly polarizing plate, and an organic electroluminescence film that can prevent hue deviation and ripple-like unevenness during display on an organic electroluminescence display device. The present invention relates to a luminescence display device.

Organic electroluminescence (organic EL) display devices have attracted attention because of increasing demands for viewing angle and display performance.
In an organic EL display device, a metal material having high light reflectivity is generally used as an electrode layer in order to efficiently extract light from the light emitting layer to the viewing side. For this reason, there is a problem that external light is reflected and reflections occur, and the contrast is greatly lowered in an environment with high illuminance.
A method of using a circularly polarizing element for preventing reflection of external light on a mirror surface is disclosed (see, for example, Patent Document 1), and an absorption linear polarizing plate and a λ / 4 retardation film are each provided with optical axes of The layers are laminated so as to intersect at 45 ° or 135 °. In this case, for monochromatic light, it is possible to adjust the phase difference to λ / 4 of the light wavelength, but for white light that is a composite wave in which light rays in the visible light range are mixed, There is a problem that a distribution occurs in the polarization state at each wavelength and the light is converted into colored polarized light. This originates in the material which comprises a phase difference plate having wavelength dispersion about a phase difference.
In order to solve such a problem, a broadband retardation plate capable of giving a uniform phase difference to light in a wide wavelength range is required.

  When a circularly polarizing element is manufactured using a broadband retardation plate capable of giving a uniform phase difference to light in a wide wavelength range and used for preventing reflection of external light, a hue shift occurs when displaying an organic EL display device. Ripples are easily generated. It is considered that the optical value of the film is likely to vary depending on the material used for the broadband retardation film.

In general, if the resin used for the retardation film has a large retardation variation rate, it is easily affected by subtle temperature unevenness and air flow unevenness in the stretching apparatus. The phase difference fluctuation rate indicates how much the phase difference fluctuates when the stretching temperature is changed. When the fluctuation is large, the phase difference fluctuation rate is large, and the phase difference value is sensitive to the stretching temperature. Will react.
In the case of a resin such as a commercially available polycarbonate or a conventional polycarbonate resin (see, for example, Synthesis Example 4 in Patent Document 2), the phase difference variation rate is large, and the phase difference changes greatly only by slightly changing the stretching temperature. Therefore, unevenness is likely to occur.
On the other hand, in the case of a conventional cellulose resin, the phase difference variation rate is small, the influence of the phase difference due to fluctuations in the stretching temperature is small, the phase difference is small, and unevenness is unlikely to occur. However, it is difficult to control the phase difference value within a preferable range, and when trying to obtain a uniform phase difference for light in a wide wavelength range, the phase difference value is insufficient or uniform for light in a wide wavelength range. There is a problem that a phase difference cannot be obtained.
If the phase difference variation rate is too small, it is difficult to obtain a phase difference value necessary for preventing external light reflection. Although the phase difference can be increased by lowering the stretching temperature, there is a problem that breakage tends to occur during stretching.

Japanese Patent Laid-Open No. 8-322138 JP 2013-3233 A

  The present invention has been made in view of the above-described problems and situations, and the solution to the problem is an optical film capable of preventing the occurrence of hue deviation and ripple-like unevenness during display of an organic electroluminescence display device, It is to provide a circularly polarizing plate and an organic electroluminescence display device provided with the optical film.

In order to solve the above-mentioned problems, the present inventor defines the phase difference variation rate within a specific range in the process of studying the cause of the above-described problems, and reduces the variation in the optical value of the film, thereby reducing the organic EL. The present inventors have found that it is possible to prevent hue deviation and ripple unevenness during display on a display device.
That is, the said subject which concerns on this invention is solved by the following means.
1. An optical film produced by stretching a resin film,
When the glass transition temperature (Tg) + 10 ° C. and the glass transition temperature (Tg) + 20 ° C. are uniaxially stretched at a stretching ratio of 15%, the in-plane retardation variation rate (ΔRo) defined by the following formula is 10 An optical film produced by using a resin in a range of ˜20% and controlled so as to satisfy the optical characteristics of the following requirements (1) to (3).
Definition formula: In-plane retardation variation rate (ΔRo) (%)
= [{Ro (Tg + 10 ° C.) − Ro (Tg + 20 ° C.)} / Ro (Tg + 10 ° C.)] × 100
Requirements:
(1) 130 nm <Ro (550) <160 nm
_{(2) Nz <1.3, Nz} = (n x -n z) / (n x -n y)
(3) 0.7 <DSP <1, DSP = Ro (450) / Ro (550)
[Significance of symbols in the above formula: Measurement environmental conditions: 23 ° C., 55% RH;
Ro (Tg + 10 ° C.): In-plane retardation value when the resin film is uniaxially stretched at Tg + 10 ° C., but the measurement light wavelength is 550 nm
Ro (Tg + 20 ° C.): In-plane retardation value when the resin film is uniaxially stretched at Tg + 20 ° C. However, the measurement light wavelength is 550 nm.
Ro (550): in-plane retardation value at a measuring wavelength 550 nm ro (450): the refractive index is maximized in the plane direction of the optical film: Measurement plane retardation value at wavelength 450 nm DSP: Wavelength dispersion _{n x} refractive index in the direction x n _y: in-plane direction of the optical film, the refractive index n _z in the direction y perpendicular to the direction _x: refractive index in the thickness direction z of the film; however, the measurement wavelength of the refractive index is 550nm ]

2. A circularly polarizing plate is prepared using the optical film, the circularly polarizing plate is attached to a mirror, and CIE1976L ^* a ^* b is spaced at 5 mm intervals in two directions parallel to the surface of the optical film and perpendicular to each other. ^* When the hue specified by the color system is measured, the absolute value of the difference in hue deviation defined by the following formula between adjacent measurement points is 0.5 or less, and the maximum hue 2. The optical film according to item 1, wherein the difference between the deviation width and the smallest hue deviation width is 3 or less.
Definition formula: hue deviation width = [(Δa ^* ) ² + (Δb ^* ) ² + (ΔL ^* ) ² ] ^1/2
However, Δa ^* = a ^* −a ^* (ave),
Δb ^* = b ^* −b ^* (ave),
ΔL ^* = L ^* −L ^* (ave)
[In the above formula, L ^* represents a value obtained by digitizing light and dark, and the larger the value, the brighter the color tone. L ^* (ave) represents the average value of all measured values of L ^* . a ^* represents a hue and saturation in the color system, and is a coordinate value indicating the position of the red-green transition line. a ^* (ave) represents an average value of all measured values of a ^* . b ^* represents a hue and saturation in the color system, and is a coordinate value indicating the position of the yellow-blue transition line. b ^* (ave) represents an average value of all measured values of b ^* . ]

  3. 3. The optical film according to item 1 or 2, wherein the uniaxial stretching is oblique stretching.

  4). The optical film according to any one of Items 1 to 3, wherein a cellulose ester resin, a cellulose ether resin, or a polycarbonate resin is contained as a component of the resin film.

  5. A circularly polarizing plate comprising the optical film according to any one of items 1 to 4.

  6). An organic electroluminescence display device comprising the circularly polarizing plate according to item 5.

By the above means of the present invention, an optical film capable of preventing occurrence of hue shift and ripple-like unevenness during display of an organic EL display device, a circularly polarizing plate provided with the optical film, and an organic EL display device are provided. can do.
The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
In order to satisfy the optical properties of the above requirements (1) to (3), it is necessary to appropriately control the stretching temperature and the stretching conditions. However, when the in-plane retardation variation rate exceeds 20%, the retardation is very easily affected by the stretching temperature. Therefore, even if the stretching temperature is appropriately controlled, the phase difference is caused by the slight deviation. It will fluctuate. When the in-plane retardation fluctuation rate is less than 10%, the retardation is hardly affected by the stretching temperature, but on the other hand, the development of retardation (ease of retardation due to stretching) tends to decrease. In some cases, appropriate stretching conditions cannot be achieved. That is, in order to obtain the phase difference of the above requirement (1), it is necessary to increase the stretching ratio, but if it is too large, the film will break during stretching.
In the case of a resin in which the in-plane retardation variation rate is in the range of 10 to 20%, the influence of retardation due to variation in stretching temperature is reduced, and the necessary retardation can be easily obtained. And stretching conditions can be appropriately controlled. Therefore, the dispersion of the phase difference value is reduced, the phase difference value is easily controlled within a preferable range, and it is presumed that the hue shift and the rippled unevenness can be prevented during the display of the organic EL display device. .

Schematic of a stretching apparatus applicable to the method for producing an optical film of the present invention The schematic diagram explaining the shrinkage ratio in the diagonal stretch of the optical film of this invention Schematic which showed an example of the rail pattern of the diagonal stretch apparatus applicable to the manufacturing method of the optical film of this invention Schematic which shows an example (example which extends | stretches diagonally after paying out from a long film original fabric roll) of the manufacturing method of the optical film of this invention. Schematic which shows an example (example which stretches diagonally continuously, without winding up a long film original fabric) of the manufacturing method of the optical film of this invention Schematic sectional view showing an example of the configuration of the organic EL display device of the present invention Schematic diagram of a stretching apparatus used in an embodiment of the present invention

The optical film of the present invention is an optical film produced by stretching a resin film, and was uniaxially stretched at a glass transition temperature (Tg) + 10 ° C. and a glass transition temperature (Tg) + 20 ° C. with a stretch ratio of 15%. When the in-plane retardation variation rate (ΔRo) defined by the following equation is within a range of 10 to 20%, and satisfies the optical characteristics of the above requirements (1) to (3) It is characterized by being controlled to the above. This feature is a technical feature common to the inventions according to claims 1 to 6.
As an embodiment of the present invention, from the viewpoint of expression of the effect of the present invention, a circularly polarizing plate is prepared using the optical film, the circularly polarizing plate is attached to a mirror, and parallel to the surface of the optical film, And when the hue defined by the CIE 1976 L ^* a ^* b ^* color system is measured at intervals of 5 mm in two directions perpendicular to each other, the difference in hue deviation width defined by the above formula between adjacent measurement points Is preferably 0.5 or less, and the difference between the maximum hue shift width and the minimum hue shift width is preferably 3 or less.
In addition, the fact that the uniaxial stretching is oblique stretching, when producing a circularly polarizing plate, it is possible to roll-to-roll the attachment of the polarizer and the optical film, and the production efficiency is improved. Is preferable.
Furthermore, it is preferable that a cellulose ester resin, a cellulose ether resin, or a polycarbonate resin is contained as a constituent component of the resin film because the in-plane retardation variation rate can be within an appropriate range.
The optical film of the present invention can be suitably used for a circularly polarizing plate.
The circularly polarizing plate of the present invention can be suitably used for an organic electroluminescence display device.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<Optical film>
The optical film of the present invention is an optical film produced by stretching a resin film, and was uniaxially stretched at a glass transition temperature (Tg) + 10 ° C. and a glass transition temperature (Tg) + 20 ° C. with a stretch ratio of 15%. When the in-plane retardation variation rate (ΔRo) defined by the following equation is within a range of 10 to 20%, and satisfies the optical characteristics of the following requirements (1) to (3) It is characterized by being controlled to the above.

Definition formula: In-plane retardation variation rate (ΔRo) (%)
= [{Ro (Tg + 10 ° C.) − Ro (Tg + 20 ° C.)} / Ro (Tg + 10 ° C.)] × 100 Requirements:
(1) 130 nm <Ro (550) <160 nm
_{(2) Nz <1.3, Nz} = (n x -n z) / (n x -n y)
(3) 0.7 <DSP <1, DSP = Ro (450) / Ro (550)

[Significance of symbols in the above formula: Measurement environmental conditions: 23 ° C., 55% RH;
Ro (Tg + 10 ° C.): In-plane retardation value when the resin film is uniaxially stretched at Tg + 10 ° C., but the measurement light wavelength is 550 nm
Ro (Tg + 20 ° C.): In-plane retardation value when the resin film is uniaxially stretched at Tg + 20 ° C. However, the measurement light wavelength is 550 nm.
Ro (550): in-plane retardation value at a measuring wavelength 550 nm ro (450): the refractive index is maximized in the plane direction of the optical film: Measurement plane retardation value at wavelength 450 nm DSP: Wavelength dispersion _{n x} refractive index in the direction x n _y: in-plane direction of the optical film, the refractive index n _z in the direction y perpendicular to the direction _x: refractive index in the thickness direction z of the film; however, the measurement wavelength of the refractive index is 550nm ]
Stretch rate (%) = [(length of film in stretch direction after stretching−length of film in stretch direction before stretching) / length of film in stretch direction before stretching] × 100

The optical film of the present invention is produced using a resin having the in-plane retardation variation rate in the range of 10 to 20%, and more preferably in the range of 10 to 15%. By setting the content within the range of 10 to 20%, the influence of the phase difference due to fluctuations in the stretching temperature is reduced. As a result, the dispersion of the phase difference is reduced, the phase difference value can be easily controlled within a preferable range, a uniform phase difference can be obtained even for light in a wide wavelength range, and further, when displaying on an organic EL display device In addition, it is possible to prevent occurrence of hue shift and ripple-like unevenness.
As the resin having the in-plane retardation variation rate within the above range, a cellulose derivative (cellulose ester resin, cellulose ether resin) or a polycarbonate resin described later is preferably contained.

  The in-plane retardation value Ro (550) defined in the present invention is characterized by being in the range of 130 to 160 nm (the above requirement (1)), and more preferably in the range of 135 to 145 nm. In the optical film of the present invention, when Ro (550) is in the range of 130 to 160 nm, the phase difference at a wavelength of 550 nm is approximately ¼ wavelength, and an optical film having such characteristics is used to obtain a circularly polarizing plate. For example, by providing this circularly polarizing plate in an organic EL display device, it is possible to improve performance stability in various usage environments.

Further, Nz (hereinafter also referred to as Nz coefficient) defined in the present invention is the refractive index in the direction x in which the refractive index is maximum in the in-plane direction of the optical film, and the direction x in the in-plane direction of the optical film. refractive index in the direction perpendicular to the refractive index in the thickness direction z of the optical film, when the _{n x,} n y, _{n z, respectively,} Nz ₌ with _{(n x -n z) / (} n x -n y) It is a defined value. That is, the value of the ratio (Rt / Ro + 0.5) between Ro and Rt (phase difference in the thickness direction).
In the present invention, the Nz coefficient is less than 1.3 (the above requirement (2)), and more preferably less than 1.0. An optical film having an Nz coefficient within this range can be easily manufactured by oblique stretching, and has excellent viewing angle characteristics when used in an organic EL display device.

  Further, Ro (450) / Ro (550) which is a value of the ratio between the retardation value Ro (450) and Ro (550) in the film plane, which is a guideline for wavelength dispersion characteristics (DSP) defined in the present invention, is obtained. , Within a range greater than 0.7 and less than 1 (requirement (3) above). More preferably, it is in the range of 0.75 to 0.89. If Ro (450) / Ro (550) is in the range of more than 0.7 and less than 1, when the circularly polarizing plate is produced, a wide band is obtained when the retardation exhibits an appropriate reverse wavelength dispersion characteristic. The antireflection effect can be obtained with respect to the light.

  As a means for controlling so as to satisfy the optical characteristics of the above requirements (1) to (3), for example, an additive is added, or the film forming method (casting method, The stretching temperature, the magnification, the film forming speed, etc.) can be changed.

In addition, a circularly polarizing plate is prepared using the optical film of the present invention, the circularly polarizing plate is attached to a mirror, and CIE1976L is spaced at 5 mm intervals in two directions parallel to the surface of the optical film and perpendicular to each other. ^{* A *} b ^* When the hue specified by the color system is measured, the absolute value of the difference in hue deviation defined by the following formula between adjacent measurement points is 0.5 or less, and The difference between the maximum hue shift width and the minimum hue shift width is preferably 3 or less.
Definition formula: hue deviation width = [(Δa ^* ) ² + (Δb ^* ) ² + (ΔL ^* ) ² ] ^1/2
However, Δa ^* = a ^* −a ^* (ave),
Δb ^* = b ^* −b ^* (ave),
ΔL ^* = L ^* −L ^* (ave)
[In the above formula, L ^* represents a value obtained by digitizing light and dark, and the larger the value, the brighter the color tone. L ^* (ave) represents the average value of all measured values of L ^* . a ^* represents a hue and saturation in the color system, and is a coordinate value indicating the position of the red-green transition line. a ^* (ave) represents an average value of all measured values of a ^* . b ^* represents a hue and saturation in the color system, and is a coordinate value indicating the position of the yellow-blue transition line. b ^* (ave) represents an average value of all measured values of b ^* . ]

In the present invention, by making the phase difference variation rate as small as within the above range, variations in optical values such as phase difference can be suppressed to some extent, but the difference in hue deviation width defined by the above equation When the absolute value is 0.5 or less and the difference between the maximum hue shift width and the minimum hue shift width is 3 or less, the optical value variation can be further reduced, and the ripples Unevenness becomes even less noticeable.
As a means for setting the absolute value of the difference in hue shift width defined by the above formula and the difference between the maximum hue shift width and the minimum hue shift width within the above range, the temperature and wind speed in the stretching apparatus must be finely adjusted. Control.
Specifically, it becomes possible to finely control the temperature and the wind speed by arranging a large number of hot air blowing nozzles in the stretching apparatus in the transport direction and the direction perpendicular to the transport direction.
As shown in FIG. 1, for example, five hot air nozzles N in the stretching apparatus 1 are provided at equal intervals in the transport direction (MD direction) and in the direction perpendicular to the transport direction (TD direction). It is preferable to provide a temperature sensor and a wind speed sensor individually.
And it is preferable to control so that the temperature fluctuation of blowing hot air may be +/- 1 degreeC with respect to setting temperature. Moreover, it is preferable to set a wind speed between 0.5-3 m / sec, and it is preferable to control the wind speed fluctuation | variation of blowing warm air so that it may become +/- 0.1 degreeC with respect to a setting wind speed. In FIG. 1, F indicates an optical film.

The resin used for the optical film of the present invention is not particularly limited as long as the in-plane retardation variation rate (ΔRo) is within a range of 10 to 20%. For example, a cellulose derivative (cellulose ester resin, Cellulose ether resin), polycarbonate resin, polyether sulfone resin, polyethylene terephthalate resin, polymethyl methacrylate resin, polysulfone resin, polyarylate resin, polyethylene resin, polyvinyl chloride resin, olefin polymer resin having an alicyclic structure (alicyclic ring) Formula olefin polymer resin).
Among these, polycarbonate resin, alicyclic olefin polymer resin, and cellulose derivative are preferable from the viewpoint of transparency and mechanical strength.
Among these, a cellulose derivative that can easily adjust the phase difference when an optical film is used is more preferable.
Hereinafter, the polycarbonate resin and the cellulose derivative will be described.

<Polycarbonate resin>
In the present invention, various known polycarbonate resins can be used. In the present invention, it is particularly preferable to use an aromatic polycarbonate. There is no restriction | limiting in particular about the said aromatic polycarbonate, and there will be no restriction | limiting in particular if it is an aromatic polycarbonate from which the various characteristics of a desired film are acquired.

In general, a polymer material collectively referred to as polycarbonate is a generic term for a polymer material in which a polycondensation reaction is used in its synthesis method and the main chain is linked by a carbonic acid bond. Among these, a phenol derivative, It means the one obtained by polycondensation from phosgene, diphenyl carbonate and the like.
Usually, an aromatic polycarbonate represented by a repeating unit having 2,2-bis (4-hydroxyphenyl) propane called bisphenol-A as a bisphenol component is preferably selected, and various bisphenol derivatives should be appropriately selected. Thus, an aromatic polycarbonate copolymer can be constituted.

  As this copolymerization component, besides this bisphenol-A, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 1, 1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) -2- Phenylethane, 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane, bis (4-hydroxyphenyl) diphenylmethane, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) -3,3,5-to It can be exemplified methyl cyclohexane.

  It is also possible to use an aromatic polyester carbonate partially containing terephthalic acid and / or isophthalic acid components. By using such a structural unit as a part of the structural component of the aromatic polycarbonate composed of bisphenol-A, the properties of the aromatic polycarbonate, such as heat resistance and solubility, can be improved. The present invention is also effective for coalescence.

  If the viscosity average molecular weight of the aromatic polycarbonate used here is in the range of 10,000 to 200,000, it is preferably used. A viscosity average molecular weight in the range of 20000 to 120,000 is particularly preferred. If the viscosity average molecular weight is in the range of 10,000 to 200,000, the mechanical strength of the resulting film will not be insufficient, and the viscosity of the dope will not be too high, causing problems in handling. The viscosity average molecular weight can be measured by commercially available high performance liquid chromatography or the like.

  The glass transition temperature of the aromatic polycarbonate according to the present invention is preferably 200 ° C. or higher in order to obtain a highly heat-resistant film, and more preferably 230 ° C. or higher. These can be obtained by appropriately selecting the copolymerization component. The glass transition temperature can be measured with a DSC apparatus (differential scanning calorimetry apparatus), for example, a baseline determined by SII NanoTechnology Co., Ltd .: RDC220 under a temperature rising condition of 10 ° C./min. Is the temperature at which it begins to deviate.

  In the present invention, the solvent used for the dope composition containing the aromatic polycarbonate is a mixed solvent containing 4 to 14 parts by mass of methylene chloride and a linear or branched aliphatic alcohol having 1 to 6 carbon atoms. It is preferable.

  The mixing amount of the linear or branched aliphatic alcohol having 1 to 6 carbon atoms is preferably in the range of 4 to 12 parts by mass. By using such a mixed solvent, the web is peeled off at a higher residual solvent concentration than before, thereby suppressing the generation of strong static electricity when the web is peeled off, thereby causing damage to the belt, film streaks, unevenness, and minuteness. Scratches can be prevented from occurring.

The type of alcohol added is limited by the solvent used. It is a necessary condition that the alcohol and the solvent are compatible. These may be added alone or in combination of two or more.
The alcohol in the present invention is preferably a linear or branched aliphatic alcohol having 1 to 6, preferably 1 to 4, more preferably 2 to 4 carbon atoms. Specific examples include methanol, ethanol, isopropanol, and tert-butanol. Of these, ethanol, isopropanol, and tertiary-butanol can achieve almost the same effect, but methanol has a slightly lower effect. Although the reason is not clear, it is assumed that the boiling point of the solvent, that is, the ease of flying during drying is related. Higher alcohols higher than that are not preferred because they have a high boiling point and are likely to remain after film formation.

  The amount of alcohol added must be carefully selected. These alcohols are completely poor in solubility in aromatic polycarbonate and are completely poor solvents. Therefore, it cannot be added too much and should be the minimum amount that can provide satisfactory peelability. As mentioned above, it is 4 to 14 parts by mass, preferably 4 to 12 parts by mass with respect to methylene chloride. When the addition amount is in the range of 4 to 14 parts by mass with respect to the amount of methylene chloride, the solubility of the solvent in the polymer and the dope stability are improved, and the effect of improving the peelability is increased.

  Although this invention is comprised in the dope composition with the said methylene chloride and aliphatic alcohol, another solvent can also be used. The remaining solvent is not particularly limited as long as it dissolves the aromatic polycarbonate at a high concentration and is compatible with alcohol, and is a low-boiling solvent. For example, as a solvent having a solubility in an aromatic polycarbonate, in addition to methylene chloride, halogen solvents such as chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene, 1,3-dioxolane, 1, Examples include cyclic ether solvents such as 4-dioxane and tetrahydrofuran, and ketone solvents such as cyclohexanone.

  When using other solvent, there is no limitation in particular and it may use it in consideration of an effect. The effects mentioned here include, for example, the improvement of the surface property (leveling effect) of the film formed by the solution casting method, the evaporation rate and the system by mixing the solvent within a range where the solubility and stability are not sacrificed. Viscosity adjustment and crystallization suppression effect. What is necessary is just to determine the kind and addition amount of the solvent to mix by the degree of these effects, and you may use 1 type, or 2 or more types as a solvent to mix.

  Other solvents preferably used include halogen solvents such as chloroform and 1,2-dichloroethane, hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone, ethyl acetate and butyl acetate. And ether solvents such as ethylene glycol dimethyl ether and methoxyethyl acetate.

  The dope composition according to the present invention may be prepared by any method as long as a transparent solution having a low haze is obtained as a result. A predetermined amount of alcohol may be added to an aromatic polycarbonate solution previously dissolved in a solvent, or the aromatic polycarbonate may be dissolved in a mixed solvent containing alcohol. However, as described above, since alcohol is a poor solvent, the method of adding the latter after the former may cause clouding of the dope due to precipitation of the polymer. Therefore, the method of dissolving in the latter mixed solvent is preferable.

《Cellulose derivative》
The cellulose derivative used in the present invention preferably has a glucose skeleton having a structure represented by the following general formula (1).

In the general formula (1), L ₂ , L ₃ and L ₆ each independently represent a single bond, —C (═O) — or — (Lw—O) _q —, or —CO—NH—. . Lw represents an alkylene group. q represents an integer of 0 to 10. R ₂ , R ₃ and R ₆ each independently represents a hydrogen atom, an aliphatic group or an aromatic group.

  Specific examples of the alkylene group represented by Lw include groups such as methylene, ethylene, 2-methylethylene, propylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, methylethylene, and ethylethylene. These groups may be further substituted with a substituent such as an alkyl group (methyl group, ethyl group, etc.). Lw is preferably a methylene group, an ethylene group, or a propylene group (methylethylene).

  q represents an integer of 0 to 10, preferably 0 to 3. When q is 0,-(Lw-O) q- represents a single bond.

Specific examples of the aliphatic group represented by R ₂ , R ₃ and R ₆ include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n- An octyl group, 2-ethylhexyl group, etc. are mentioned.

Specific examples of the aromatic group represented by R ₂ , R ₃ and R ₆ include phenyl group, p-tolyl group, naphthyl group, 2-furyl group, 2-thienyl group, 2-pyrimidinyl group, 2-benzothiazolyl. Group, 2-pyridyl group and the like.

n represents an average degree of polymerization and represents an integer of 10 to 2000. A plurality of L ₂ , L ₃ , L ₆ , R ₂ , R ₃ and R ₆ may be the same or different.
Moreover, in the cellulose derivative of the present invention, the glucose skeleton represented by the general formula (1) according to the present invention satisfies all the conditions defined by the following relational expressions (1-1) to (1-4). It is preferable to satisfy.

(1) Relational expression (1-1): 1.50 ≦ DSa ≦ 2.95
In DSa which defines the range in the relational expression (1-1), R ₂ , R ₃ and R ₆ are each an aliphatic group, and L ₂ -R ₂ , L ₃ -R ₃ and L ₆ -R ₆ represents the total average degree of substitution of aliphatic groups with respect to hydrogen atoms of the hydroxy groups at the 2nd, 3rd and 6th positions of 6; That is, it represents the total proportion of aliphatic groups in R ₂ , R ₃ and R ₆ of the glucose skeleton unit. However, in the present invention, L ₂ -R ₂ , L ₃ -R ₃ and L ₆ -R ₆ are also referred to as aliphatic groups.

(2) Relational expression (1-2): 0.00 <DSb ≦ 1.5
In the total average substitution degree DSb that defines the range in the above relational expression (1-2), R ₂ , R ₃ and R ₆ are each an aromatic group, L ₂ -R ₂ , L ₃ -R ₃ And the total average degree of substitution of the aromatic group with respect to the hydrogen atom of the 2-position, 3-position and 6-position hydroxy groups of L ₆ -R ₆ . That is, it represents the total ratio of aromatic groups in R ₂ , R ₃ and R ₆ of the glucose skeleton unit. However, in the present invention, L ₂ -R ₂ , L ₃ -R ₃ and L ₆ -R ₆ are also referred to as aromatic groups.

  Furthermore, the total average substitution degree DSb is preferably more than 0.00 and 0.5 or less from the viewpoint that the objective effect of the present invention can be expressed more.

(3) Relational expression (1-3): DSb (6th place) <DSb (2nd place) + DSb (3rd place)
In the above relational expression (1-3), the substitution degree of the aromatic group to the hydrogen atom of the hydroxy group of R ₂ , R ₃ and R ₆ of the glucose skeleton unit is shown, and the substitution degree of the aromatic group at the 6-position On the other hand, the total substitution degree at the 2nd and 3rd positions is large. That is, by setting the substitution degree of the aromatic group at the 2-position and the 3-position to be higher than the 6-position, extremely excellent reverse wavelength dispersion can be realized.

(4) Relational expression (1-4): 1.5 <DSa + DSb ≦ 3.0
In the above relational expression (1-4), the total average substitution degree DSa of the aliphatic groups with respect to the hydrogen atoms of the 2-, 3- and 6-position hydroxy groups and the hydrogen atoms of the 2-, 3- and 6-position hydroxy groups The sum of the total average substitution degrees DSa of the aromatic groups with respect to, that is, the total average substitution degree in R ₂ , R ₃ and R ₆ is more than 1.5 and 3.0 or less.

  In the cellulose derivative of the present invention, the average substitution degree DSh (6-position) of the hydrogen atom of the 6-position hydroxy group in the general formula (1) is preferably 0.20 or less.

  In the present invention, introduction of a substituent to the glucose skeleton is referred to as “substitution” or “esterification”. Further, the degree of substitution and the degree of esterification, the total average degree of substitution and the total average degree of esterification are treated as synonymous.

<< Method for producing cellulose derivative >>
In the method for producing a cellulose derivative of the present invention, the glucose skeleton having the structure represented by the general formula (1) and the glucose skeleton represented by the general formula (1) is represented by the relational expression (1-1). It is preferable to produce a cellulose derivative that satisfies all of the conditions specified by the relational expressions (1-4).

[Synthesis Method of Cellulose Derivative Having Structure Represented by General Formula (1)]
The cellulose derivative of the present invention can be produced by referring to a known method, for example, a method described in “Encyclopedia of Cellulose” pages 131 to 164 (Asakura Shoten, 2000).

  For example, a typical synthesis method of cellulose acetate is a liquid phase acetylation method using acetic anhydride (acetyl group donor), acetic acid (solvent), and sulfuric acid (catalyst). Specifically, a cellulose raw material such as wood pulp is pretreated with an appropriate amount of acetic acid, and then charged into a precooled acetylated mixed solution to form an acetic ester to synthesize cellulose acetate. After completion of the acetylation reaction, a neutralizing agent (for example, sodium, potassium, calcium, magnesium, iron, etc.) is used for hydrolysis of excess acetic anhydride remaining in the system and neutralization of a part of the esterification catalyst. An aqueous solution of aluminum, zinc or ammonium carbonate, acetate or oxide) is added. The obtained cellulose acetate is aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid) to obtain a cellulose acetate having a desired degree of acetyl substitution and degree of polymerization. Can be synthesized.

  As the raw material cotton of cellulose ester or cellulose ether used as a raw material, a known raw material can be used.

[Production of Cellulose Derivative A]
A cellulose derivative having a total average degree of substitution of aliphatic groups with respect to hydrogen atoms of 2-, 3- and 6-position hydroxy groups applied to the cellulose derivative production method a and the cellulose derivative production method b described below according to the present invention. A is obtained by substituting the hydroxy group at the 2-position, 3-position and 6-position of the glucose skeleton with an aliphatic group containing at least an acetyl group or an alkyl group within a range of a total average substitution degree of 1.0 to 3.0. The aliphatic group containing at least an acetyl group or an alkyl group is preferably prepared by hydrolysis until the total average substitution degree becomes DSa1. In L ₂ -R ₂ , L ₃ -R ₃ and L ₆ -R ₆ , L ₂ , L ₃ and L ₆ are not introduced, and an alkyl group is formed by an ether bond with each oxygen atom of each glucose skeleton. You may use the cellulose ether derivative A which formed the alkoxy group.

  An example of the production flow of the cellulose derivative A according to the present invention is shown below, but the present invention is not limited to the production method exemplified here.

An acetyl group in which L in the general formula (1) is C (═O) and R is CH ₃ in the step (2) with respect to the cellulose in the 2nd, 3rd and 6th positions shown in the step (1). All are acetylated to form triacetylcellulose (TAC). In the said process (2), it is preferable that the reaction temperature at the time of esterifying the hydrogen atom of the 2-position, 3-position, and 6-position hydroxy group of the cellulose derivative A with an acetyl group is 60 degreeC or more. Next, in step (3), a part of the acetyl group is hydrolyzed by hydrolysis (in the above example, the 2nd and 6th positions are hydrolyzed to be a hydroxy group), and the total average substitution degree of acetyl groups is in the range of DSa1. A cellulose derivative A (cellulose ester derivative) is produced.

  Moreover, in the said manufacturing method, the hydrogen atom of the hydroxyl group of 2nd-position, 3rd-position, and 6-position may be substituted by the alkyl group, and it is good also as a cellulose ether derivative.

  Table 1 below shows an example of cellulose derivative A.

[Production method a of cellulose derivative]
In the production method a, which is a specific method for producing the cellulose derivative of the present invention, the fat with respect to the hydrogen atoms of the 2-, 3- and 6-position hydroxy groups in the glucose skeleton having the structure represented by the general formula (1) Cellulose derivative A having a total average degree of group group substitution of DSa1, and then esterifying the hydroxy group at the 2-position, 3-position or 6-position of cellulose derivative A to an average degree of substitution DSa2 with an aliphatic acyl group, and further cellulose All of the hydroxy groups at the 2-position, 3-position or 6-position of the derivative A are substituted with aromatic acyl groups up to the total average substitution degree DSb, and are defined by the following relational expressions (2-1) to (2-3) A cellulose derivative is produced under the conditions satisfying the above conditions.

(1) Relational expression (2-1): DSa = DSa1 + DSa2
In the relational expression (2-1), the total substitution degree DSa of the aliphatic group with respect to the hydrogen atom of the hydroxyl group of R ₂ , R ₃ and R ₆ of the glucose skeleton unit is the 2-position, 3-position and 6 in the cellulose derivative A. The total average substitution degree DSa1 of the aliphatic group containing at least an acetyl group or an alkyl group with respect to the hydrogen atom of the hydroxy group at the position and the hydrogen atom of the hydroxy group at the 2-position, 3-position or 6-position of the cellulose derivative A as an aliphatic acyl group Is defined as the sum of the average degree of substitution DSa2 substituted.

(2) Relational expression (2-2): 0.00 <DSa2 <1.5
The range of the average substitution degree DSa2 substituted with the aliphatic acyl group for the cellulose derivative A is more than 0 and 1.5 or less.

(3) Relational expression (2-3): DSa2 (6th place)> DSa2 (2nd place) + DSa2 (3rd place)
In the relational expression (2-3), DSa is synonymous with the total average substitution degree DSa in the relational expression (1-1). The average degree of substitution DSa1 represents the total average degree of substitution of aliphatic groups with respect to the hydrogen atoms of the 2-position, 3-position and 6-position hydroxy groups of the cellulose derivative A. DSa2 represents the total average degree of substitution of aliphatic acyl groups for cellulose derivative A. DSa2 (2nd position), DSa2 (3rd position) and DSa2 (6th position) represent the average degree of substitution of each aliphatic acyl group for the hydrogen atom of the 2nd, 3rd and 6th hydroxy groups. That is, by setting the total substitution degree of the aliphatic groups at the 2-position and the 3-position to be lower than the substitution degree of the aliphatic group at the 6-position as described above, extremely excellent reverse wavelength dispersion can be realized. it can.

  In the above production, it is preferable that the reaction temperature when esterifying the hydroxyl group at the 2-position, 3-position or 6-position of the cellulose derivative A with an aliphatic acyl group is 60 ° C. or higher.

  When the reaction temperature at the time of esterification is 60 ° C. or higher, an aliphatic acyl group is easily introduced at the 6-position. On the other hand, when the temperature is lower than 60 ° C., the aliphatic acyl group is likely to be introduced at the 2-position and the 3-position.

  In the cellulose derivative produced by the above method, in the general formula (1), the average substitution degree DSh (6-position) of the hydrogen atom of the 6-position hydroxy group is preferably 0.20 or less.

(Production flow of cellulose derivative production method a)
Although the manufacturing method of the cellulose derivative in this invention is not specifically limited, A well-known method, for example, the method of Cellulose10; 283-296,2003 can be used. A preferred method for producing the cellulose derivative of the present invention is a method of esterifying cellulose derivative A by reacting acid chloride or acid anhydride in the presence of a base.

  As specific conditions for the esterification reaction, for example, pyridine, piperidine, triethylamine and the like can be used as the base. The reaction solvent is preferably a solvent that dissolves the cellulose derivative, and examples thereof include dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, dimethylimidazolidinone, acetone, and tetrahydrofuran.

  In the manufacturing method a of the cellulose derivative of this invention, a cellulose derivative can be manufactured with the manufacturing flow shown below using the cellulose derivative A prepared above.

  In the production method a, a cellulose derivative A having a total average degree of substitution of DSa1 of the aliphatic group (acetyl group) prepared by the method shown in the step (1) is prepared, and the hydroxy group of the cellulose derivative A is prepared in the step (2). Is esterified with an aliphatic acyl group to an average degree of substitution DSa2, and then, in step (3), the hydrogen atoms of the hydroxy group at the 2-position, 3-position or 6-position of the cellulose derivative A are total average with an aromatic acyl group. The cellulose derivative is produced by esterification to a substitution degree DSb.

  Moreover, in the said manufacturing method a, it may replace with the cellulose ester derivative illustrated above as a cellulose derivative A, and may use a cellulose ether derivative.

[Production method b of cellulose derivative]
In the cellulose derivative production method b applicable to the present invention, the hydrogen atom of the hydroxy group at the 2-position, 3-position or 6-position of the cellulose derivative A having a total average substitution degree of aliphatic groups of DSa1 is represented by an aromatic acyl group. , After esterifying until the sum of DSa1 and the degree of substitution of the aromatic acyl group becomes a total average substitution degree in the range of 2.9 to 3.0, a part of the esterified aromatic acyl group is In this method, hydrolysis is performed until the total average substitution degree becomes DSb.

(Production flow of cellulose derivative production method b)
In the manufacturing method b of the cellulose derivative of this invention, a cellulose derivative can be manufactured with the manufacturing flow shown below using the cellulose derivative A prepared above.

  In the production method b, a cellulose derivative A having a total average degree of substitution of DSa1 of the aliphatic group (acetyl group) prepared by the method shown in step (1) is prepared, and the hydroxy group of the cellulose derivative A is prepared in step (2). Is esterified with an aromatic acyl group until a total average substitution degree of 2.9 to 3.0 is obtained as the sum of DSa1 and the substitution degree of the aromatic acyl group. Finally, a part of the aromatic acyl group esterified in the step (3) is produced by hydrolysis until the total average substitution degree becomes DSb.

Although it does not specifically limit as a hydrolysis reaction of the cellulose derivative in this invention, A well-known method, for example, the method of Unexamined-Japanese-Patent No. 2008-1113630, can be used. Specific examples include acid hydrolysis with sulfuric acid, hydrochloric acid and the like, and hydrolysis methods with enzymes such as cellulase.
Moreover, in the said manufacturing method b, it may replace with the cellulose ester derivative illustrated above as a cellulose derivative A, and may use a cellulose ether derivative.

Below, an example of the specific manufacturing method of the compound example of the cellulose derivative which has a structure represented by General formula (1) is shown.
(Cellulose derivative: Synthesis of exemplary compound b-1)
<Synthesis of Intermediate b-1>
100 g of cellulose acetate (acetyl group substitution degree = 2.43, weight average molecular weight Mw: 160,000) was dissolved in 2 L of pyridine. To this, 1.0 g of dimethylaminopyridine was added, and 40.0 g of benzoyl chloride was added. Stir at 85 ° C. for 12 hours. After confirming that the substitution degree of the benzoyl group was 0.49 by ¹ H-NMR, heating was stopped and the mixture was allowed to cool. Methanol 500mL was added to the reaction solution, and it stirred at 50 degreeC for 1 hour.

  Subsequently, the reaction solution was added dropwise to a mixed solvent of 1 L of water and 1 L of methanol, and the precipitated solid content was separated by filtration and purified by continuous washing with methanol. The obtained solid was dried at 50 ° C. for 8 hours to obtain 122 g of Intermediate b-1.

<Synthesis of Exemplary Compound b-1>
122 g of intermediate b-1 was dissolved in 1 L of a mixed solvent of water: methanol (1:10), 100 mL of acetic acid was added thereto, and the mixture was stirred at 50 ° C. for 3 hours. After confirming that the substitution degree of the benzoyl group was 0.15 by ¹ H-NMR, heating was stopped and the mixture was allowed to cool. 1 L of water was added to the reaction solution, and the precipitated solid was separated by filtration and purified by continuous washing with methanol. The obtained solid content was dried at 50 ° C. for 8 hours to obtain 103 g of exemplary compound b-1.
^When the substitution position and average substitution degree of the benzoyl group were confirmed by ¹³ C-NMR, the substitution degree of the benzoyl group was 0.10 at the 2-position, the substitution degree at the 3-position was 0.04, and the substitution degree at the 6-position was 0.00. 01.

(Cellulose derivative: Synthesis of exemplary compound P-1)
Cellulose acetate (acetyl group substitution degree: 2.43; weight average molecular weight 160,000) 50 vacuum-dried at 60 ° C. for 12 hours in a 500 mL four-necked flask equipped with a cooling tube, a nitrogen introducing tube, a stirrer and a thermometer 50 0.0 g was added and 250 mL of pyridine was added to form a suspension, and then 6.3 g of phenyl isocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) was further added.
Next, nitrogen was introduced, the temperature was raised to 80 ° C. with stirring, and the mixture was reacted for 6 hours. Then, after cooling to 25 degreeC, the reaction liquid was dripped in ethanol 500mL, and precipitation was produced | generated. The product obtained by filtration from the precipitate was dissolved by adding 40 mL of acetone, and then dropped into 200 mL of methanol and 200 mL of pure water to cause precipitation.
30 mL of acetone was added to and dissolved in the product obtained by filtration from the precipitate, and then dropped into 400 mL of pure water to generate a precipitate. The product filtered off from the precipitate was washed with water and vacuum dried at 60 ° C. for 4 hours to obtain 48.0 g of Exemplified Compound P-1.
As a result of ¹ H-NMR analysis, the degree of carbamate substitution of P-1 was 0.10. The degree of substitution was determined by comparing the chemical shift (3.4 to 5.5 ppm) area of proton derived from the cellulose skeleton with the chemical shift (6.7 to 7.8 ppm) area of the proton of the phenyl group.
The content of methyl phenylcarbamate was 0.01% by mass as determined by gas chromatography.

[Measuring method of substitution degree of cellulose derivative having structure represented by general formula (1)]
In the present invention, the degree of substitution with each substituent of the glucose skeleton is determined by ¹ H-NMR or ¹³ using the method described in Cellulose Communication 6, 73-79 (1999) and Chality 12 (9), 670-674. It can be determined by C-NMR.

  The average degree of acetyl substitution can be measured with reference to the method of Tezuka (Tezuka, Carbohydr. Res., 273, 83 (1995)).

  That is, the residual hydroxy group of the cellulose derivative substituted with an acetyl group is propionylated with propionic anhydride in pyridine, the obtained sample is dissolved in deuterated chloroform, and the 13C-NMR spectrum is measured.

  The signal of the carbonyl carbon of the acetyl group appears in the region of 169 ppm to 171 ppm, the signals of the carbonyl carbon of the propionyl group appear in the same order in the region of 172 ppm to 174 ppm in the order of 2, 3, 6 from the high magnetic field. The distribution of acetyl groups in the original cellulose acetate can be determined from the abundance ratio of acetyl groups and propionyl groups at the corresponding positions.

Other substituents can be measured and calculated in the same manner.
[Various additives for optical film]
The optical film of the present invention can contain various additives for the purpose of imparting various functions.

  Additives that can be applied to the present invention are not particularly limited, and are, for example, a retardation increasing agent, a wavelength dispersion improving agent, a deterioration inhibitor, an ultraviolet absorber, a matting agent, a plasticizer, and the like within a range that does not impair the object effects of the present invention. An agent or the like can be used.

  Below, the typical additive applicable to the optical film of this invention is shown.

(UV absorber)
The optical film of the present invention can contain an ultraviolet absorber.

  Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like, but less benzotriazole compounds Compounds are preferred. In addition, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used. In the case where the optical film of the present invention is used as a protective film for a polarizing plate in addition to a retardation film, the ultraviolet absorber has an ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer and an organic EL device. In view of the display property of the organic EL element, it is preferable that the organic EL element has a characteristic that absorbs less visible light having a wavelength of 400 nm or more.

  Benzotriazole-based UV absorbers useful in the present invention include, for example, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t -Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-butyl Phenyl) -5-chlorobenzotriazole, 2- [2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl] benzotriazole, 2,2 -Methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2'-hydroxy-3) -T-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3 -[3-t-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-t-butyl-4-hydroxy-5- ( A mixture of 5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  Further, as a commercial product, “TINUVIN 109”, “TINUVIN 171”, “TINUVIN 326”, “TINUVIN 328” (above, trade name, manufactured by BASF Japan Ltd.) are preferable. Can be used.

  The addition amount of the ultraviolet absorber is preferably in the range of 0.1 to 5.0% by mass, and more preferably in the range of 0.5 to 5.0% by mass with respect to the cellulose derivative.

(Degradation inhibitor)
A degradation inhibitor such as an antioxidant, a peroxide decomposer, a radical polymerization inhibitor, a metal deactivator, an acid scavenger, and amines may be added to the optical film of the present invention. The deterioration inhibitor is described in, for example, JP-A-3-199201, JP-A-5-97073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The amount of the deterioration inhibitor added is a cellulose solution (dope) used for the production of an optical film from the viewpoint of suppressing the bleed-out of the deterioration inhibitor to the film surface because of the effect of the addition of the deterioration inhibitor. Is preferably in the range of 0.01 to 1% by mass, and more preferably in the range of 0.01 to 0.2% by mass. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (abbreviation: BHT) and tribenzylamine (abbreviation: TBA).

(Matting agent fine particles)
It is preferable to add fine particles as a matting agent to the optical film of the present invention. Examples of the matting agent fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, and magnesium silicate. And calcium phosphate. Among these matting agent fine particles, those containing silicon are preferable in terms of low turbidity (haze), and silicon dioxide is particularly preferable. The fine particles of silicon dioxide preferably have a primary average particle size in the range of 1 to 20 nm and an apparent specific gravity of 70 g / liter or more. The primary average particle size is preferably within the range of 5 to 16 nm from the viewpoint of reducing the haze of the optical film. The apparent specific gravity is further preferably in the range of 90 to 200 g / liter, particularly preferably in the range of 100 to 200 g / liter. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle size in the range of 0.05 to 2.0 μm. These secondary particles exist as an aggregate of primary particles in the optical film, and form irregularities of 0.05 to 2.0 μm on the optical film surface. The secondary average particle size is preferably in the range of 0.05 to 1.0 μm, more preferably in the range of 0.1 to 0.7 μm, and particularly preferably in the range of 0.1 to 0.4 μm. The primary particle size and the secondary particle size were determined by observing fine particles in the optical film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle size. Also, 200 particles are observed at different locations, and the average value is taken as the average particle size.

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

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and the friction coefficient is maintained while keeping the haze of the optical film low. This is particularly preferable because the effect of lowering is great.

  The matting agent fine particles are preferably prepared by the following method and applied to an optical film. That is, a matting agent fine particle dispersion in which a solvent and matting agent fine particles are stirred and mixed is prepared in advance, and this matting agent fine particle dispersion is added to various additive solutions prepared separately with a cellulose derivative concentration of less than 5% by mass. After stirring and dissolving, a method of further mixing with the main cellulose derivative dope solution is preferable.

  Since the surface of the matting agent fine particles is hydrophobized, when an additive having hydrophobicity is added, the additive is adsorbed on the surface of the matting agent fine particles, and the aggregate of the additive is formed using this as a core. Likely to happen. Therefore, by mixing a relatively hydrophilic additive with the matting agent fine particle dispersion in advance and then mixing a hydrophobic additive, aggregation of the additive on the surface of the matting agent can be suppressed. Is low, and light leakage in black display when incorporated in a liquid crystal display device is preferable.

  It is preferable to use an in-line mixer for mixing the matting agent fine particle dispersant and the additive solution and mixing the cellulose derivative dope liquid. Although the present invention is not limited to these methods, the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably within the range of 5 to 30% by mass, and within the range of 10 to 25% by mass. More preferably, it is in the range of 15 to 20% by mass. A higher dispersion concentration is preferable because turbidity with respect to the same amount of addition is reduced, and generation of haze and aggregates can be suppressed. The addition amount of the matting agent in the final cellulose derivative dope solution is preferably in the range of 0.001 to 1.0% by mass, more preferably in the range of 0.005 to 0.5% by mass. A range of 01 to 0.1% by mass is particularly preferable.

[Method for producing optical film containing cellulose derivative]
The method for producing the optical film of the present invention is not particularly limited, but a method for producing by the solvent casting method (solution casting method) is preferable. In the solvent cast method, an optical film is produced using a solution (dope) in which a cellulose derivative is dissolved in an organic solvent.

  The organic solvent used for the preparation of the dope includes ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and 1 to 6 carbon atoms. It is preferable to use a solvent selected from halogenated hydrocarbons.

  Ethers, ketones and esters may have a cyclic structure. A compound having two or more functional groups of ethers, ketones and esters (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have other functional groups such as alcoholic hydroxy groups. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms is preferably within the range of the above-mentioned preferable number of carbon atoms of the solvent having any functional group.

  Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole, phenetole and the like.

  Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone, and methylcyclohexanone.

  Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, pentyl acetate and the like.

  Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol, 2-butoxyethanol and the like.

  The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms in the halogenated hydrocarbon substituted with halogen is preferably in the range of 25 to 75 mol%, more preferably in the range of 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably within the range of mol%, particularly preferably within the range of 40 to 60 mol%. Methylene chloride is a representative halogenated hydrocarbon.

  For the preparation of the dope, it is preferable to use a mixed solvent of methylene chloride and alcohols, and the ratio of alcohols to methylene chloride is preferably in the range of 1 to 50% by mass, and in the range of 5 to 40% by mass. The range of 8 to 30% by mass is particularly preferable. As the alcohol, methanol, ethanol, and n-butanol are preferable, and two or more kinds of alcohols may be mixed and used.

  The dope can be prepared by a general method under a temperature of 0 ° C. or higher (room temperature or high temperature). The solution can be prepared by using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent.

  The concentration of the cellulose derivative in the dope is preferably in the range of 5 to 40% by mass, and more preferably in the range of 10 to 30% by mass. Various additives described above may be added to the organic solvent (main solvent).

  The dope can be prepared by stirring a cellulose derivative and an organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, the cellulose derivative and the organic solvent are placed in a pressure vessel and sealed, and stirred while being heated to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil.

  The heating temperature is usually 40 ° C or higher, preferably in the range of 60 to 200 ° C, more preferably in the range of 80 to 110 ° C.

  Each component may be roughly mixed in advance and then charged into the container. Moreover, you may put into a container sequentially. The container must be provided with a mechanism capable of stirring. An inert gas such as nitrogen gas can be injected to pressurize the container. Moreover, you may pressurize using the raise of the vapor pressure of the solvent by heating. Furthermore, after sealing the container, each component may be added under pressure.

  When heating, the method of heating from the outer peripheral part of a container is preferable. For example, a jacket type heating device can be used. Further, the entire container can be heated by providing a plate heater outside the container, or by installing a pipe on the outer periphery of the container and circulating the heated liquid in the pipe.

  It is preferable to provide a stirring blade inside the container and use this to stir. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.

  Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling, or is taken out and then cooled using a heat exchanger or the like.

  A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, the cellulose derivative can be dissolved in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a cellulose derivative with a normal melt | dissolution method, there exists an effect by which a rapid and uniform solution is obtained by applying the cooling melt | dissolution method.

  In the cooling dissolution method, first, a cellulose derivative is gradually added to an organic solvent with stirring at room temperature. The amount of the cellulose derivative is preferably adjusted so as to be contained in the mixture in the range of 5 to 40% by mass. The amount of the cellulose derivative is more preferably in the range of 10 to 30% by mass. Furthermore, you may add the above-mentioned arbitrary additive in a mixture.

  Next, the mixture is cooled within a range of −100 to −10 ° C. (preferably −80 to −10 ° C., more preferably −50 to −20 ° C., particularly preferably −50 to −30 ° C.). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). By cooling, the mixture of the cellulose derivative and the organic solvent is solidified.

  The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and particularly preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature.

  Furthermore, when this is heated within the range of 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., and still more preferably 0 to 50 ° C.), the cellulose derivative is dissolved in the organic solvent. . The temperature may be increased by simply leaving it at room temperature or in a warm bath.

  The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and even more preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is the value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. is there.

  A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.

  In the cooling dissolution method, it is preferable to use an airtight container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and pressure reduction, it is preferable to use a pressure-resistant container.

  An optical film having a cellulose derivative is produced from the prepared cellulose derivative solution (dope) by a solvent cast method.

(Solution casting method)
The optical film of the present invention is preferably manufactured by the solution casting method as described above. In the solution casting method, a step of preparing a dope by heating and dissolving a cellulose derivative and various additives satisfying the characteristics specified in the present invention in an organic solvent, and the prepared dope on a belt-shaped or drum-shaped metal support Includes a step of casting, a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or shrinking the peeled web, a step of drying, a step of winding up the finished film, etc. .

  The dope is cast on a drum or band and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is in the range of 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less.

  The drying method in the solvent cast method is described in U.S. Pat. Nos. 2,336,310, 2,367,603, 2,429,2078, 2,429,297, 2,429,978, 2,607,704, 2,273,069, and 2,739,070. Each specification, British Patent Nos. 640731 and 736892, and Japanese Patent Publication Nos. 45-4554, 49-5614, JP-A-60-176634, 60-203430, and 62- There is a description in each publication of No. 115035. Drying on the drum or band can be performed by blowing an inert gas such as air or nitrogen to the cast film.

  The prepared cellulose derivative solution (dope) can be cast into two or more layers to form a film. In this case, it is preferable to produce a cellulose derivative film by a solvent cast method. The dope is cast on a drum or band and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is in the range of 5 to 40%. The surface of the drum or band is preferably finished in a mirror state.

<Extension process>
As described above, the optical film (retardation film) of the present invention preferably has an in-plane retardation Ro (550) measured at a light wavelength of 550 nm in the range of 130 to 160 nm. By stretching the filmed optical film, the properties can be imparted.

  The stretching method applicable to the present invention is not particularly limited. For example, a method in which a circumferential speed difference is applied to a plurality of rollers and a longitudinal stretching is performed using a circumferential speed difference between the plurality of rollers therebetween. , Both ends of the web are fixed with clips and pins, and the distance between the clips and pins is extended in the longitudinal direction according to the direction of travel. The method of extending | stretching to both directions is employable individually or in combination.

  That is, the film may be stretched in the transverse direction, longitudinally, or in both directions with respect to the film forming direction, and when stretched in both directions, simultaneous stretching or sequential stretching may be used. May be. In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  As the stretching process, the film is usually stretched in the width direction (TD direction) and contracted in the transport direction (MD direction), but when contracted, it is easy to match the main chain direction when transported in an oblique direction. In addition, the phase difference effect is even greater. The shrinkage rate can be determined by the transport angle.

  FIG. 2 is a schematic diagram for explaining the shrinkage ratio in oblique stretching.

In Figure 2, when the oblique stretching the optical film F in the direction of the reference numerals A2, the optical film F shrinks to M ₂ by being obliquely bent. That is, when the gripping tool that grips the optical film F advances as it is without bending at the bending angle θ, it should advance by a length M ₁ ′ in a predetermined time. However, in reality, it bends at a bending angle θ and proceeds by M ₁ (where M ₁ = M ₁ ′). At this time, since the gripping tool advances by M ₂ in the film entering direction (direction orthogonal to the stretching direction (TD direction) A1), the optical film F has a length M ₃ (where M ₃ = M ₁ -M ₂₎ the fact that only shrinkage.

At this time, the shrinkage rate (%) is
Shrinkage rate (%) = (M ₁ −M ₂ ) / M ₁ × 100. If the bending angle is θ,
M ₂ = M ₁ × sin (π−θ), and the shrinkage rate is
Shrinkage rate (%) = (1-sin (π−θ)) × 100

  In FIG. 2, reference numeral 11 is the stretching direction (TD direction), reference numeral 13 is the transport direction (MD direction), and reference numeral 14 indicates the slow axis.

  In consideration of the productivity of the circularly polarizing plate, the optical film (retardation film) of the present invention has an orientation angle of 45 ° ± 2 ° with respect to the transport direction. This is preferable.

<Stretching with an oblique stretching device>
Next, the oblique stretching method of stretching in the 45 ° direction will be further described. In the method for producing an optical film of the present invention, an oblique stretching apparatus is preferably used as a method for imparting an oblique orientation to the optical film to be stretched.

  As an oblique stretching apparatus applicable to the present invention, the orientation angle of the film can be freely set by changing the rail pattern in various ways, and the orientation axis of the film can be oriented with high accuracy evenly in the left-right direction across the film width direction. It is preferable that the film stretching apparatus can control the film thickness and the in-plane retardation value with high accuracy.

  FIG. 3 is a schematic view showing an example of a rail pattern of an oblique stretching apparatus applicable to the production of the optical film of the present invention. In addition, FIG. 3 shown here is an example, Comprising: The extending | stretching apparatus applicable in this invention is not limited to this.

  In general, in the oblique stretching apparatus, as shown in FIG. 3, the feeding direction D1 of the long film original is different from the winding direction D2 of the stretched film after stretching, and has a feeding angle θi. ing. The feeding angle θi can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °. In the present specification, the term “long” refers to a film having a length of at least about 5 times the width of the film, preferably a film having a length of 10 times or more.

  The long film original is gripped at both ends by the left and right gripping tools (tenters) at the entrance of the oblique stretching apparatus (position A in the figure), and travels as the gripping tool travels. The left and right gripping tools are the left and right gripping tools Ci and Co at the entrance of the oblique stretching apparatus (position A in the figure) and facing the direction substantially perpendicular to the film traveling direction (feeding direction D1). The film travels on the asymmetric rails Ri and Ro, and the film gripped by the tenter is released at the position at the end of stretching (position B in the figure).

  At this time, as the left and right gripping tools facing each other at the entrance of the oblique stretching device (position A in the figure) travel on the left and right asymmetric rails Ri and Ro, the gripping tool Ci traveling on the Ri side becomes the Ro side. The positional relationship is advancing with respect to the gripping tool Co traveling.

  That is, at the entrance of the oblique stretching apparatus (the grip start position by the film gripping tool) A, the gripping tools Ci and Co that are opposed to the film feeding direction D1 are positioned at the end of the film stretching. In the state of B, the straight line connecting the grippers Ci and Co is inclined by an angle θL with respect to a direction substantially perpendicular to the film winding direction D2.

  According to the above method, the original film is stretched obliquely. Here, “substantially vertical” indicates that the angle is in a range of 90 ± 1 °.

  More specifically, in the method for producing the optical film of the present invention, it is preferable to perform oblique stretching using the tenter capable of oblique stretching described above.

  This stretching apparatus is an apparatus that heats a film raw fabric to an arbitrary temperature at which stretching can be performed and obliquely stretches the film. This stretching apparatus includes a heating zone, a pair of rails on the left and right on which a gripping tool for transporting the film travels, and a number of gripping tools that travel on the rails. Both ends of the film sequentially supplied to the inlet of the stretching apparatus are gripped by a gripping tool, the film is guided into the heating zone, and the film is released from the gripping tool at the outlet of the stretching apparatus. The film released from the gripping tool is wound around the core. Each of the pair of rails has an endless continuous track, and the gripping tool which has released the grip of the film at the outlet portion of the stretching apparatus travels outside and is sequentially returned to the inlet portion.

  In addition, the rail pattern of the stretching device has an asymmetric shape on the left and right, and the rail pattern can be adjusted manually or automatically depending on the orientation angle, stretching ratio, etc. given to the long stretched film to be manufactured. It has become. In the oblique stretching apparatus used in the present invention, it is preferable that the position of each rail portion and the rail connecting portion can be freely set, and the rail pattern can be arbitrarily changed (the ○ portion in FIG. 3 indicates an example of the connecting portion). ).

In the present invention, the gripping tool of the stretching apparatus travels at a constant speed with a constant interval from the front and rear gripping tools. Although the traveling speed of a holding | gripping tool can be selected suitably, it is 1-100 m / min normally. The difference in travel speed between the pair of left and right grippers is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the travel speed. This is because if there is a difference in the traveling speed between the left and right sides of the film at the exit of the stretching process, wrinkles and shifts will occur at the exit of the stretching process, so the speed difference between the left and right gripping tools is required to be substantially the same speed. Because.
In general stretching equipment, etc., there is a speed unevenness that occurs in the order of seconds or less depending on the period of the sprocket teeth driving the chain, the frequency of the drive motor, etc. This does not correspond to the speed difference described in the invention.

  In the stretching apparatus applicable to the present invention, a large bending rate is often required for the rail that regulates the locus of the gripping tool, particularly in a portion where the film is transported obliquely. For the purpose of avoiding interference between gripping tools due to sudden bending or local stress concentration, it is preferable that the trajectory of the gripping tool draws a curve at the bent portion.

  In the present invention, the long film original fabric is gripped in order by the right and left gripping tools at the entrance of the oblique stretching apparatus (position A in the drawing) and travels as the gripping tool travels. The left and right gripping tools facing the direction substantially perpendicular to the film traveling direction (feeding direction D1) at the entrance of the oblique stretching apparatus (position A in the figure) run on a rail that is asymmetrical to the preheating zone. Through a heating zone having a stretching zone and a heat setting zone.

  The preheating zone refers to a section that travels while maintaining a constant interval between the gripping tools that grip both ends at the entrance of the heating zone.

  The stretching zone refers to a section where the gap between the gripping tools gripping both ends starts to reach a predetermined distance. In the stretching zone, the oblique stretching as described above is performed, but the stretching may be performed in the longitudinal direction or the lateral direction before and after the oblique stretching as necessary. In the case of oblique stretching, there is contraction in the MD direction (fast axis direction) which is a direction perpendicular to the slow axis during bending.

In the optical film of the present invention, an optical modifier (for example, a compound represented by the above general formula (A) described above) deviated from the main chain of the cellulose derivative that is a matrix resin by performing a shrinkage treatment following the stretching treatment. ) In the direction perpendicular to the stretching direction (fast axis direction), thereby rotating the orientation state of the optical adjusting agent so that the main axis of the optical adjusting agent is aligned with the main chain of the cellulose derivative as the matrix resin. be able to. As a result, it is possible to increase the refractive index n _Y280 of the fast axis direction in the ultraviolet region 280 nm, can be a steep slope of n _y order chromatic dispersion in the visible light region.

  The heat setting zone refers to a section in which the gripping tools at both ends run in parallel with each other in a period in which the interval between the gripping tools after the stretching zone becomes constant again. You may pass through the area (cooling zone) by which the temperature in a zone is set to below the glass transition temperature Tg of the thermoplastic resin which comprises a film, after passing through a heat setting zone. At this time, in consideration of shrinkage of the film due to cooling, a rail pattern that narrows the gap between the opposing gripping tools in advance may be used.

  The temperature of each zone is the glass transition temperature Tg of the thermoplastic resin, the temperature of the preheating zone is in the range of Tg to Tg + 30 ° C., the temperature of the stretching zone is in the range of Tg to Tg + 30 ° C., and the temperature of the cooling zone is It is preferable to set within the range of Tg-30 ° C to Tg.

  In order to control thickness unevenness in the width direction, a temperature difference may be given in the width direction in the stretching zone. In order to give a temperature difference in the width direction in the stretching zone, a method of adjusting the opening degree of the nozzle for sending warm air into the temperature-controlled room so as to make a difference in the width direction, and controlling heating by arranging heaters in the width direction are known. Can be used.

  The length of the preheating zone, the stretching zone, the shrinking zone and the cooling zone can be appropriately selected. The length of the preheating zone is usually within a range of 100 to 150% with respect to the length of the stretching zone, and the length of the fixed zone. Is usually in the range of 50 to 100%.

  The stretch ratio (%) ((W−W0) / W0) in the stretching step is preferably in the range of 30 to 200%, more preferably in the range of 50 to 180%. When the stretching ratio is within this range, the thickness direction unevenness can be reduced. In the stretching zone of the oblique stretching apparatus, it is possible to further improve the uneven thickness in the width direction by making a difference in the stretching temperature in the width direction. W0 represents the width of the film before stretching, and W represents the width of the film after stretching. W0 represents the width of the film before stretching, and W represents the width of the film after stretching.

  As an oblique stretching method applicable in the present invention, in addition to the method shown in FIG. 3, the stretching methods shown in FIGS. 4 (a) to (c) and FIGS. 5 (a) and 5 (b) are mentioned. be able to.

FIG. 4 is a schematic view showing an example of a production method applicable to the present invention (an example in which the film is drawn from a long film original fabric roller and then obliquely stretched), and the long film original fabric once wound up in a roll shape. The pattern which extends | stretches and diagonally stretches is shown.
FIG. 5 is a schematic view showing an example of another manufacturing method applicable to the present invention (an example of continuous oblique stretching without winding a long film original fabric), and winding the long film original fabric. The pattern which performs a diagonal stretch process continuously, without showing is shown.

  4 and 5, reference numeral 15 denotes an oblique stretching device, 16 denotes a film feeding device, 17 denotes a transport direction changing device, 18 denotes a winding device, and 19 denotes a film forming device. In each figure, the code | symbol which shows the same thing may be abbreviate | omitted.

The film feeding device 16 is slidable and swivelable or slidable so that the film can be fed out at a predetermined angle with respect to the oblique stretching device inlet. It is preferable to be able to send
4A to 4C show patterns in which the arrangement of the film feeding device 16 and the transport direction changing device 17 is changed. 5A and 5B show patterns in which the film formed by the film forming apparatus 19 is directly fed to the stretching apparatus 15. FIG.
By configuring the film feeding device 16 and the conveyance direction changing device 17 in such a configuration, it becomes possible to further narrow the width of the entire manufacturing apparatus, and to finely control the film feeding position and angle. Thus, it becomes possible to obtain a long stretched film with small variations in film thickness and optical value. In addition, by making the film feeding device 16 and the conveyance direction changing device 17 movable, it is possible to effectively prevent the left and right clips from being caught in the film.

By arranging the winding device 18 so that the film can be pulled at a predetermined angle with respect to the outlet of the oblique stretching device, it is possible to finely control the film take-up position and angle, and variations in film thickness and optical value. It becomes possible to obtain a long stretched film having a small diameter. Therefore, it is possible to effectively prevent the film from being wrinkled and to improve the winding property of the film, so that the film can be wound up in a long length.
In the present invention, the take-up tension T (N / m) of the stretched film is adjusted within a range of 100 N / m <T <300 N / m, preferably 150 N / m <T <250 N / m. .

(Melting method)
An optical film (λ / 4 retardation film) containing a cellulose derivative may be formed by a melt film forming method in addition to the solution casting method described above. The melt film forming method is a molding method in which a composition containing an additive such as a cellulose derivative and a plasticizer is heated and melted to a temperature exhibiting fluidity, and then cast as a melt containing a fluid thermoplastic resin. is there.

  The molding method for heating and melting can be classified into, for example, a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, and a stretch molding method. Among these molding methods, the melt extrusion molding method is preferable from the viewpoint of mechanical strength and surface accuracy.

  The plurality of raw materials used in the melt extrusion method are usually preferably kneaded and pelletized in advance. Pelletization can be performed by a known method. For example, dry cellulose derivatives, plasticizers, and other additives are fed to an extruder with a feeder, kneaded using a single or twin screw extruder, and then from a die. It can be obtained by extruding into a strand, cooling with water or air, and cutting.

  The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. A small amount of additives such as matting agent fine particles and antioxidants are preferably mixed in advance in order to mix uniformly.

  The extruder used for pelletization preferably has a method of suppressing the shearing force and processing at the lowest possible temperature so that the resin can be pelletized so that the resin does not deteriorate (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. Of course, it is also possible to form the film as it is after it is not formed into pellets, and the raw material powder is put into the feeder as it is, supplied to the extruder, heated and melted.

  Using a single-screw or twin-screw type extruder, the melting temperature when extruding is within the range of 200 to 300 ° C., filtered through a leaf disk type filter or the like to remove foreign matter, and then from the T-die. The film is cast into a film, and the film is nipped with a cooling roller and an elastic touch roller, and solidified on the cooling roller.

  When introducing into the extruder from the supply hopper, it is preferable to carry out under vacuum or reduced pressure or in an inert gas atmosphere to prevent oxidative decomposition and the like.

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. A stainless steel fiber sintered filter is a product in which a stainless steel fiber body is intricately intertwined and compressed, and the contact points are sintered and integrated. The accuracy can be adjusted.

  Additives such as plasticizers and fine particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

  The film temperature on the touch roller side when the film is nipped between the cooling roller and the elastic touch roller is preferably in the range of Tg to Tg + 110 ° C. of the film. A known elastic touch roller can be used as the elastic touch roller having an elastic surface used for such a purpose. The elastic touch roller is also called a pinching rotary body, and a commercially available one can also be used.

  When peeling the film from the cooling roller, it is preferable to control the tension to prevent deformation of the film.

The film obtained as described above can be subjected to stretching and shrinkage treatment by stretching operation after passing through the step of contacting the cooling roller. As a method of stretching and shrinking, a known roller stretching device or oblique stretching device as described above can be preferably used.
The stretching temperature is usually preferably performed in the temperature range of Tg to Tg + 60 ° C. of the resin constituting the film.

  Before winding, the end may be slit and cut to the width to be the product, and knurling (embossing) may be applied to both ends to prevent sticking and scratching during winding. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the film has deform | transformed and cannot use as a product normally, the holding | grip part of the clip of both ends of a film is cut out and reused.

《Circularly polarizing plate》
Since the circularly polarizing plate of the present invention is produced using the optical film (λ / 4 retardation film) of the present invention, it can be applied to all the wavelengths of visible light by applying it to an organic EL display device described later. An effect of shielding the specular reflection of the metal electrode of the EL element can be exhibited. As a result, reflection during observation can be prevented and black expression can be improved.

  In addition, the circularly polarizing plate of the present invention preferably has an ultraviolet absorption function. It is preferable that the protective film on the viewing side has an ultraviolet absorbing function from the viewpoint that both the polarizer and the organic EL element can exhibit a protective effect against ultraviolet rays. Further, if the retardation film on the light emitter side also has an ultraviolet absorbing function, when used in an organic EL display device described later, deterioration of the organic EL element can be further suppressed.

In addition, the circularly polarizing plate of the present invention has an optical film (λ / 4 position) in which the angle of the slow axis (that is, the orientation angle θ) is adjusted to be “substantially 45 °” with respect to the longitudinal direction. By using the retardation film, it is possible to form an adhesive layer and bond the polarizer and the retardation film together by a consistent production line.
Specifically, after finishing the step of producing a polarizer by stretching a polarizing film, a step of laminating a polarizer and a retardation film can be incorporated during or after the subsequent drying step, Each can be continuously supplied, and can be connected in a production line that is consistent with the next process by winding in a roll state after bonding.
In addition, when bonding a polarizer and retardation film, a protective film can also be simultaneously supplied in a roll state and can also be bonded continuously. From the viewpoint of performance and production efficiency, it is preferable to simultaneously bond a retardation film and a protective film to a polarizer. That is, after finishing the step of producing a polarizer by stretching the polarizing film, during the subsequent drying step or after the drying step, the protective film and the retardation film are respectively bonded to both sides with an adhesive, It is also possible to obtain a rolled circularly polarizing plate.

  In the circularly polarizing plate of the present invention, the polarizer is preferably sandwiched between the optical film (λ / 4 retardation film) of the present invention and a protective film, and a cured layer is laminated on the viewing side of the protective film. preferable.

  The circularly polarizing plate can be provided in a liquid crystal display device or an organic EL image display device. By applying the circularly polarizing plate to an organic EL image display device as an example, an effect of shielding the specular reflection of a metal electrode of an organic EL light emitter. Is expressed.

(Protective film)
In the circularly polarizing plate, the polarizer is preferably sandwiched between the optical film of the present invention and the protective film.
As such a protective film, other cellulose ester-containing films are suitably used. For example, a commercially available cellulose ester film (for example, Konica Minoltack KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR , KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UAKC, 2UAH, KC4UAH, KC6UAH, Z TD60UL, Fujitac TD40UL, Fujitac R02, Fujitac R06, Fujifilm Corporation) Used properly. Although the thickness in particular of a protective film is not restrict | limited, It can be set as about 10-200 micrometers, Preferably it is the range of 10-100 micrometers, More preferably, it is the range of 10-70 micrometers.

(Polarizer)
A polarizer is an element that passes only light having a plane of polarization in a certain direction. Examples thereof include a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

  The polarizer can be obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing; or after dying a polyvinyl alcohol film and uniaxially stretching, and preferably by further performing a durability treatment with a boron compound. The thickness of the polarizer is preferably in the range of 5 to 30 μm, and more preferably in the range of 5 to 15 μm.

  Examples of the polyvinyl alcohol film include ethylene unit content of 1 to 4 mol%, polymerization degree of 2000 to 4000, and saponification degree of 99.0 to 99 described in JP2003-248123A, JP2003-342322A, and the like. 99 mol% ethylene-modified polyvinyl alcohol is preferably used. Moreover, it is preferable to produce a polarizing plate by the method of Unexamined-Japanese-Patent No. 2011-1000016, patent 4691205, and patent 4804589, and sticking it with the optical film of this invention.

(adhesive)
The bonding of the optical film of the present invention and the polarizer is not particularly limited, but can be performed using a completely saponified polyvinyl alcohol adhesive after saponifying the optical film. It can also be bonded using an actinic ray curable adhesive or the like. However, since the elastic modulus of the obtained adhesive layer is high and the deformation of the polarizing plate is easily suppressed, the bonding using the photocurable adhesive is possible. It is preferable to be a combination.

  Preferred examples of the photocurable adhesive include (α) a cationic polymerizable compound, (β) a photo cationic polymerization initiator, and (γ) a wavelength longer than 380 nm, as disclosed in JP2011-08234A. And a photo-curable adhesive composition containing each component of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, other photocurable adhesives may be used.

Hereinafter, an example of the manufacturing method of the polarizing plate using a photocurable adhesive agent is demonstrated.
The polarizing plate includes (1) a pretreatment step for easily adhering the surface of the optical film to which the polarizer is bonded, and (2) at least one of the adhesive surfaces of the polarizer and the optical film. (3) a bonding step of bonding the polarizer and the optical film through the obtained adhesive layer, and (4) a polarizer and the optical film through the adhesive layer. It can manufacture by the manufacturing method including the hardening process which hardens an adhesive bond layer in the bonded state. What is necessary is just to implement the pre-processing process of (1) as needed.

<Pretreatment process>
In the pretreatment step, an easy adhesion treatment is performed on the adhesive surface of the optical film with the polarizer. When bonding an optical film to both surfaces of a polarizer, easy adhesion processing is performed on the bonding surface of each optical film with the polarizer. Examples of the easy adhesion treatment include corona treatment and plasma treatment.

<Adhesive application process>
In the adhesive application step, the photocurable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the optical film. When the photocurable adhesive is directly applied to the surface of the polarizer or the optical film, the application method is not particularly limited. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting a photocurable adhesive between a polarizer and an optical film, the method of pressurizing with a roller etc. and spreading uniformly can also be utilized.

<Bonding process>
Thus, after apply | coating a photocurable adhesive agent, it uses for a bonding process.
In this bonding step, for example, when a photocurable adhesive is applied to the surface of the polarizer in the previous application step, an optical film is superimposed thereon. When a photocurable adhesive is applied to the surface of the optical film in the previous application step, a polarizer is superimposed thereon.
In addition, when a photocurable adhesive is cast between the polarizer and the optical film, the polarizer and the optical film are superposed in that state. In the case where the optical film is bonded to both surfaces of the polarizer, and the photocurable adhesive is used on both surfaces, the optical film is superimposed on the both surfaces of the polarizer via the photocurable adhesive. Usually, in this state, both sides (if the optical film is superimposed on one side of the polarizer, the polarizer side and the optical film side, and if the optical film is superimposed on both sides of the polarizer, The film is pressed with a roll or the like from the film side). As the material of the roll, metal, rubber or the like can be used. The rollers arranged on both sides may be made of the same material or different materials.

<Curing process>
In the curing step, the active energy ray is irradiated to the uncured photocurable adhesive to cure the adhesive layer containing the epoxy compound or the oxetane compound. Thereby, the overlapped polarizer and the optical film are bonded via the photocurable adhesive. When bonding an optical film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or an optical film side.
Moreover, when bonding an optical film on both surfaces of a polarizer, an active energy ray is applied from either one of the optical films in a state where the optical film is superimposed on both surfaces of the polarizer via a photocurable adhesive. It is advantageous to irradiate and simultaneously cure the photocurable adhesive on both sides.

  As the active energy ray, visible light, ultraviolet ray, X-ray, electron beam or the like can be used, and since it is easy to handle and has a sufficient curing speed, generally, an electron beam or ultraviolet ray is preferably used.

Any appropriate condition can be adopted as the electron beam irradiation condition as long as the adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably in the range of 5 to 300 kV, more preferably in the range of 10 to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and may be insufficiently cured. If the acceleration voltage exceeds 300 kV, the penetration force through the sample is too strong and the electron beam rebounds, There is a risk of damaging the polarizer.
The irradiation dose is in the range of 5 to 100 kGy, more preferably in the range of 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the adhesive becomes insufficiently cured, and when it exceeds 100 kGy, the transparent optical film and the polarizer are damaged, resulting in a decrease in mechanical strength and yellowing, thereby obtaining predetermined optical characteristics. I can't.

Arbitrary appropriate conditions can be employ | adopted for the irradiation conditions of an ultraviolet-ray, if it is the conditions which can harden the said adhesive agent. The dose of ultraviolet rays is preferably in the range of 50~1500mJ / cm ² in accumulated light quantity, and even more preferably in the range of 100 to 500 mJ / cm ^2.

  In the polarizing plate obtained as described above, the thickness of the adhesive layer is not particularly limited, but is usually in the range of 0.01 to 10 μm, and preferably in the range of 0.5 to 5 μm.

<< Organic EL display device >>
The organic EL display device of the present invention is manufactured by including the above-described circularly polarizing plate of the present invention.

  More specifically, the organic EL display device of the present invention includes a circularly polarizing plate using the optical film (retardation film) of the present invention and an organic EL element. Therefore, the organic EL display device is prevented from being reflected during observation, and the black expression is improved. The screen size of the organic EL display device is not particularly limited, and can be 20 inches or more.

Various configurations can be applied to the configuration of the organic EL element of the organic EL display device of the present invention. For example, the organic EL element may have the following layer structures (i) to (v). Further, the following light emitting layer is preferably composed of a blue light emitting layer, a green light emitting layer and a red light emitting layer.
Below, the typical example of a structure of an organic EL element is shown.

(I) Anode / hole injection transport layer / light emitting layer / electron injection transport layer / cathode (ii) Anode / hole injection transport layer / light emitting layer / hole blocking layer / electron injection transport layer / cathode (iii) Anode / Hole injection / transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron injection transport layer / cathode (iv) Anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / Cathode (v) Anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / cathode (vi) Anode / hole injection layer / hole transport layer / electron blocking Layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / cathode For the outline of the organic EL device applicable to the present invention, for example, JP2013-157634A and JP2013-168552A. JP, 2013-177361, JP 2013-187221, JP 2013-1. 1644, JP2013-191804, JP2013-225678, JP2013-235994, JP2013-243234, JP2013-243236, JP2013-242366 JP, 2013-243371, JP 2013-245179, JP 2014-003249, JP 2014-003299, JP 2014-013910, JP 2014-014933, The structure described in Unexamined-Japanese-Patent No. 2014-017494 etc. can be mentioned.

  FIG. 6 is a schematic explanatory diagram of the configuration of the organic EL display device of the present invention. The configuration of the organic EL display device of the present invention is not limited to that shown in FIG.

  As shown in FIG. 6, a metal electrode 102, a TFT 103, an organic light emitting layer 104, a transparent electrode (ITO, etc.) 105, an insulating layer 106, a sealing layer 107, a film on a transparent substrate 101 made of glass, polyimide, or the like. On the organic EL element B having 108 (which can be omitted), the above-described circularly polarizing plate C in which the polarizer 110 is sandwiched between the above-described retardation film 109 and the protective film 111 is provided to constitute the organic EL display device A.

  It is preferable that a hardened layer 112 is laminated on the protective film 111. The hardened layer 112 not only prevents scratches on the surface of the organic EL display device but also has an effect of preventing warpage due to the circularly polarizing plate. Further, an antireflection layer 113 may be provided on the cured layer. The thickness of the organic EL element itself is about 1 μm.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. Therefore, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device including an organic EL element having a transparent electrode on the surface side of an organic light emitting layer that emits light when a voltage is applied and a metal electrode on the back surface side of the organic light emitting layer, the surface side of the transparent electrode (visible) A polarizing plate can be provided on the side), and a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation film and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization function. In particular, if the retardation film is composed of a λ / 4 retardation film and the angle formed by the polarization direction of the polarizer and the retardation film is adjusted to 45 ° or 135 °, the mirror surface of the metal electrode is completely shielded. be able to.

  That is, the external light incident on the organic EL display device is transmitted only by the linearly polarized light component by the polarizer, and this linearly polarized light is generally elliptically polarized light by the retardation plate. When the angle formed by the polarization direction of the polarizer and the retardation film is 45 ° or 135 °, it becomes circularly polarized light.

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation film. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

[resin]
Resins [1] to [9] shown below were prepared.
<Resin [1]: Polycarbonate>
Panlite (registered trademark) K-1300Y manufactured by Teijin Limited
<Resin [2]: Polycarbonate>
Resin of Synthesis Example 1 described in Paragraph 0199 of JP2013-76982A <Resin [3]: Cellulose Ether>
Etcell MED70 manufactured by Dow Chemical Japan Co., Ltd.
<Resin [4]: Cellulose acetate propionate>
Cellulose acetate propionate (acetyl group substitution degree = 1.56, propionyl substitution degree = 0.09 average molecular weight Mw: 190,000)

<Resin [5]: Benzoate-substituted cellulose ester>
100 g of a cellulose derivative (acetyl group substitution degree: 2.43, average molecular weight Mw: 160,000) was dissolved in 2 L of pyridine. To this, 1.0 g of dimethylaminopyridine was added, and 20.0 g of benzoyl chloride was added. Stir at 85 ° C. for 12 hours. After confirming that the degree of substitution of the benzoyl group was 0.21 by ¹ H-NMR, heating was stopped and the mixture was allowed to cool. To the reaction solution, 500 ml of methanol was added and stirred at 50 ° C. for 1 hour.
Subsequently, the reaction solution was added dropwise to a mixed solvent of 1 L of water and 1 L of methanol, and the precipitated solid content was separated by filtration and purified by continuous washing with methanol. The obtained solid was dried at 50 ° C. for 8 hours to obtain 110 g of an intermediate.
110 g of the intermediate was dissolved in 1 L of a mixed solvent of water: methanol (1:10), 100 ml of acetic acid was added thereto, and the mixture was stirred at 50 ° C. for 3 hours. After confirming that the substitution degree of the benzoyl group was 0.09 by ¹ H-NMR, heating was stopped and the mixture was allowed to cool. 1 L of water was added to the reaction solution, and the precipitated solid was separated by filtration and purified by continuous washing with methanol. The obtained solid content was dried at 50 ° C. for 8 hours to obtain 98 g of a benzoate-substituted cellulose ester (resin [5]).
About the obtained benzoate substituted cellulose ester, when the substitution position and average substitution degree of the benzoyl group were confirmed by ¹³ C-NMR, the substitution degree of 2-position of the benzoyl group was 0.06, and the substitution degree of 3-position was 0.02. The substitution degree at the 6-position was 0.01.

<Resin [6]: Benzoate-substituted cellulose ester>
100 g of a cellulose derivative (acetyl group substitution degree: 2.43, average molecular weight Mw: 160,000) was dissolved in 2 L of pyridine. To this, 1.0 g of dimethylaminopyridine was added, and 40.0 g of benzoyl chloride was added. Stir at 85 ° C. for 12 hours. After confirming that the substitution degree of the benzoyl group was 0.49 by ¹ H-NMR, heating was stopped and the mixture was allowed to cool. To the reaction solution, 500 ml of methanol was added and stirred at 50 ° C. for 1 hour.
Subsequently, the reaction solution was added dropwise to a mixed solvent of 1 L of water and 1 L of methanol, and the precipitated solid content was separated by filtration and purified by continuous washing with methanol. The obtained solid was dried at 50 ° C. for 8 hours to obtain 122 g of an intermediate.
122 g of the intermediate was dissolved in 1 L of a mixed solvent of water: methanol (1:10), and 100 ml of acetic acid was added thereto, followed by stirring at 50 ° C. for 3 hours. After confirming that the substitution degree of the benzoyl group was 0.15 by ¹ H-NMR, heating was stopped and the mixture was allowed to cool. 1 L of water was added to the reaction solution, and the precipitated solid was separated by filtration and purified by continuous washing with methanol. The obtained solid content was dried at 50 ° C. for 8 hours to obtain 103 g of a benzoate-substituted cellulose ester (resin [6]).
About the obtained benzoate substituted cellulose ester, when the substitution position and average substitution degree of the benzoyl group were confirmed by ¹³ C-NMR, the substitution degree at the 2-position of the benzoyl group was 0.10, and the substitution degree at the 3-position was 0.04. The substitution degree at the 6-position was 0.01.

<Resin [7]: Carbamate-substituted cellulose ester>
Cellulose derivative vacuum-dried at 60 ° C. for 12 hours in a 500 mL four-necked flask equipped with a cooling tube, a nitrogen introducing tube, a stirrer, and a thermometer (acetyl group substitution degree = 2.43, average molecular weight Mw: 160,000) 50.0 g was added and 250 mL of pyridine was added to form a suspension, and then 6.3 g of phenyl isocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) was further added.
Next, nitrogen was introduced, the temperature was raised to 80 ° C. with stirring, and the mixture was reacted for 6 hours. Then, after cooling to 25 degreeC, the reaction liquid was dripped in ethanol 500mL, and precipitation was produced | generated. The product obtained by filtration from the precipitate was dissolved by adding 40 mL of acetone, and then dropped into 200 mL of methanol and 200 mL of pure water to cause precipitation.
30 mL of acetone was added to and dissolved in the product obtained by filtration from the precipitate, and then dropped into 400 mL of pure water to generate a precipitate. The product filtered off from the precipitate was washed with water and vacuum dried at 60 ° C. for 4 hours to obtain 48.0 g of a carbamate-substituted cellulose ester (resin [7]).
The degree of carbamate substitution was 0.10 as a result of ¹ H-NMR analysis. The degree of substitution was determined by comparing the chemical shift (3.4 to 5.5 ppm) area of proton derived from the cellulose skeleton with the chemical shift (6.7 to 7.8 ppm) area of the proton of the phenyl group.
The content of methyl phenylcarbamate was 0.01% by mass as determined by gas chromatography.

<Resin [8]: Benzoate-substituted cellulose ether>
100 g of cellulose derivative A (Exemplary compound VII described in Table 1, hydroxypropylmethylcellulose, methyl substitution = 1.80, hydroxypropyl substitution = 0.10, average molecular weight Mw: 180,000) was dissolved in 2 L of pyridine. To this was added 1.0 g of dimethylaminopyridine, 8.2 g of propionic acid chloride was added, and the mixture was stirred at 80 ° C. for 8 hours.
After confirming that the substitution degree of the propionyl group was 0.20 by ¹ H-NMR, heating was stopped and the mixture was allowed to cool. To this reaction solution, 500 ml of methanol was added and stirred at 50 ° C. for 1 hour. The reaction solution was added dropwise to a mixed solvent of 1 L of water and 1 L of methanol, and the precipitated solid was separated by filtration and purified by continuous washing with methanol. The solid content was dried at 50 ° C. for 8 hours to obtain 100 g of an intermediate.
About the obtained intermediate, when the substitution position and average substitution degree of the propionyl group were confirmed by ¹³ C-NMR, the substitution degree of the propionyl group was 0.03, the substitution degree of the 3-position was 0.02, The substitution degree at the 6-position was 0.15.
100 g of the intermediate prepared above was dissolved in 2 L of pyridine. Next, 1.0 g of dimethylaminopyridine was added, 15.0 g of benzoyl chloride was added, and the mixture was stirred at 75 ° C. for 12 hours. After confirming that the degree of substitution of the benzoyl group was 0.11 by ¹ H-NMR, heating was stopped and the mixture was allowed to cool. To the reaction solution, 500 ml of methanol was added and stirred at 50 ° C. for 1 hour. The reaction solution was dropped into a mixed solvent of 1.5 L of water and 0.5 L of methanol, and the precipitated solid was separated by filtration and purified by continuous washing with a mixed solvent of water: methanol (1: 1). The obtained solid was dried at 50 ° C. for 8 hours to obtain 95 g of benzoate-substituted cellulose ether (resin [8]).
About the obtained benzoate substituted cellulose ether, when the substitution position and average substitution degree of the benzoyl group were confirmed by ¹³ C-NMR, the substitution degree of the benzoyl group was 0.08 and the substitution degree of the third position was 0.02. The substitution degree at the 6-position was 0.01.

<Resin [9]: Modified polycarbonate>
9,9-bis (4-hydroxy-3-methylphenyl) fluorene
788 parts by mass 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane 296 parts by weight 1,4: 3,6-dianhydroglucitol 394 parts by mass Diphenyl carbonate 493 parts by mass Sodium hydroxide (catalyst) 6 × 10 ⁻⁴ parts by mass Each of the above materials was put into a reaction vessel, heated to 160 ° C. in a nitrogen atmosphere, and melted with stirring. Thereafter, the pressure in the reaction vessel was adjusted to 13.4 kPa in 30 minutes, and the temperature was raised to 180 ° C. in 60 minutes.
Next, the pressure was adjusted to 6.7 kPa in 30 minutes, the temperature was raised to 250 ° C. in 120 minutes, and the temperature was maintained for 30 minutes. Further, the pressure was reduced to 0.2 kPa or less over 60 minutes to remove the generated phenol.
After completion of the reaction, a catalyst amount of 2 moles of tetrabutylphosphonium dodecylbenzenesulfonate was added to deactivate the catalyst, and then extruded into water under nitrogen pressure from the bottom of the reaction vessel to obtain a resin [9]. .

[Preparation of fine particle additive solution]
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin to prepare a fine particle dispersion [1].
Next, with sufficient stirring in the dissolution tank containing methylene chloride, the fine particle dispersion [1] is slowly added in the following amount, and further dispersed with an attritor to produce a fine particle addition solution [2]. did.
99 parts by mass of methylene chloride Fine particle dispersion [1] 5 parts by mass

[Production of dope]
A dope [1] having the following composition was produced using the resin [1].
First, methylene chloride and ethanol were charged into the dissolution kettle. Resin [1] was added to a melting pot containing a solvent while stirring. This was completely dissolved with heating and stirring. Further, the fine particle addition solution [2] was added and sufficiently stirred to prepare a dope [1].
Methylene chloride 365 parts by mass Ethanol 50 parts by mass Resin [1] 90 parts by mass Particulate additive solution [2] 1 part by mass

[Production of Film [1]]
The dope [1] was cast into a film on a stainless steel metal belt support. The solvent was evaporated until the amount of residual solvent in the cast film was 75%, and then the film was peeled from the metal belt support with a peel tension of 130 N / m. The peeled film is transported to a tenter stretching apparatus, and the temperature is 15 ° C. higher than the Tg of the resin used for the dope [1], that is, 165 ° C. in the case of resin [1]. Direction) at a stretch rate of 100%. The residual solvent at the start of stretching was 15%.
In the tenter stretching apparatus, a hot air nozzle was provided by dividing into five in the transport direction (MD direction) and in the direction perpendicular to the transport (TD direction). The hot air nozzle was provided with a temperature sensor and a wind speed sensor, respectively, and the blown hot air was controlled so that the temperature was constant at 150 ± 1 ° C. and the wind speed was constant at 0.8 ± 0.1 m / sec.
Next, drying was terminated while the inside of the drying apparatus was conveyed by a number of rollers. The drying temperature was 130 ° C. and the transport tension was 100 N / m. As described above, a film [1] having a dry film thickness of 40 μm was obtained.

[Production of Films [2] to [9]]
Films [2] to [9] were produced in the same manner except that the resin [1] was changed to the resins [2] to [9] in the production of the film [1].

[Production of Film [10]]
In production of the film [7], the film was finished by drying without being stretched by a stretching apparatus to obtain a long film having a film thickness of 85 μm and a width of 1000 mm.
Then, the said long film was diagonally stretched with the extending | stretching apparatus 1 shown in FIG.
As shown in FIG. 7, the stretching apparatus 1 has a gripping tool travel support tool 2 on which a gripping tool (not shown) that grips the long film F travels on both sides of the long film F, and the gripping tool travel support is provided. The tool 2 is arranged so that a part thereof passes through the heating furnace 3.
The heating furnace 3 is divided into a preheating zone, a stretching zone 4 and a heat fixing zone in the furnace. In the stretching zone 4, a side wall 6 is provided along the gripping tool travel support 2 on both sides. The side wall 6 is made of stainless steel and has a height of 200 mm and a thickness of 10 mm. And provided integrally. In addition, the side wall 6 can block the convection of air generated by the traveling long film F, and can prevent the heat transfer from the long film F to the extra space. Therefore, the long film F is stretched in the stretching zone 4 in a state where there is no temperature unevenness and heat is applied sufficiently and uniformly. As a result, there is little variation in the width direction of the orientation angle of the obtained long film F, and a long stretched film with stable quality can be obtained.
The number of gripping tools provided on the gripping tool travel support tools 2 on both sides was the same (total of 800). The stretching apparatus 1 is configured so that the angle (stretching angle) formed by the feeding direction and the winding direction of the long film F can be arbitrarily changed. The total length of the inner gripping tool travel support tool 2 was 43 m. The overall length of the outer gripping tool travel support tool 2 was 43 m.
The end trimming process of the long stretched film discharged from the stretching apparatus 1 was performed, and the final long stretched film was adjusted to have a film width of 1600 mm. Thereafter, the film was wound with a take-up tension of 200 (N / m) by a winding device provided at the outlet to obtain a film [10]. At this time, the stretching angle was 45 ° and the stretching ratio was 100%. The traveling speed of the gripping tool at this time was 12 m / min.
The temperature conditions of the tenter oven when using the long film F were adjusted to 188 ° C for the preheating zone, 188 ° C for the stretching zone 4, 185 ° C for the heat setting zone, and 80 ° C for the cooling zone (not shown). .
In the stretching apparatus 1 as well, a hot air nozzle was provided by dividing into five in the transport direction (MD direction) and in the direction perpendicular to the transport (TD direction). The hot air nozzle was provided with a temperature sensor and a wind speed sensor, respectively, and controlled so that the temperature and the wind speed were constant.

[Production of Circular Polarizing Plate [1]]
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds. Subsequently, it was immersed in the 68 degreeC aqueous solution which consists of potassium iodide 6g, boric acid 7.5g, and water 100g. This was washed with water and dried to obtain a polarizer.
The film [1] prepared above was bonded using the following adhesive so that the slow axis of the film and the absorption axis of the polarizer were 45 °, and a protective film (Konica Minolta Tack was attached to the back side of the polarizer. KC4UY, thickness 40 μm, manufactured by Konica Minolta Co., Ltd.) was bonded together with an adhesive to produce a circularly polarizing plate [1].
The adhesive preparation and bonding method will be described in detail below.

<Preparation of adhesive>
Each of the following components was mixed and then defoamed to prepare an ultraviolet curable adhesive. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution. Below, the solid content of triarylsulfonium hexafluorophosphate is shown.
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries)
40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass

<Adhesion method>
The surface of the film [1] was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min.
Next, the UV curable adhesive prepared as described above is applied to the corona discharge treated surface of the film [1] with a bar coater so that the film thickness after curing is about 3 μm, and the UV curable adhesive layer is formed. Formed. The produced polarizer was bonded to the obtained ultraviolet curable adhesive layer.
Moreover, the protective film (Konica Minolta Tack KC4UY) was subjected to corona discharge treatment. The conditions for the corona discharge treatment were a corona output intensity of 2.0 kW and a line speed of 18 m / min.
The UV curable adhesive solution prepared above is applied to the corona discharge-treated surface of the protective film (Konica Minoltac KC4UY) with a bar coater so that the film thickness after curing is about 3 μm, and then the UV curable adhesive is used. An agent layer was formed.
A polarizer bonded to one side of the film [1] is bonded to the UV curable adhesive layer, and the film [1] / UV curable adhesive layer / polarizer / UV curable adhesive layer / A laminate in which a protective film was laminated was obtained.
From both sides of this laminate, using a UV irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems), UV light was applied so that the integrated light amount was 750 mJ / cm ^2. The UV curable adhesive layer was cured to produce a circularly polarizing plate [1].

[Production of Circular Polarizing Plates [2] to [10]]
In the production of the circularly polarizing plate [1], the circularly polarizing plates [2] to [2] to [10] were changed in the same manner except that the film [1] was changed to the films [2] to [10] and the stretching temperature was changed as shown in the following table. [10] was produced.

[Production of Organic EL Display Device [1]]
The obtained circularly polarizing plate [1] is bonded to the viewing side of an organic EL panel (product name 15EL9500, manufactured by LG Display Co.) via an acrylic pressure-sensitive adhesive (thickness 20 μm) to produce an organic EL display device [1]. did. In addition, the organic EL panel used for evaluation was used after peeling off the antireflection film bonded to the surface in advance.

[Production of Organic EL Display Devices [2] to [10]]
Organic EL display devices [2] to [10] were produced in the same manner except that the circularly polarizing plate [1] was changed to circularly polarizing plates [2] to [10] in the production of the organic EL display device [1]. .

[Evaluation method]
<Glass transition point (Tg)>
Using a differential scanning calorimeter (DSC-6220, manufactured by Seiko Instruments Inc.), the glass transition temperature (Tmg) was determined at a rate of temperature increase of 20 ° C./min and determined according to JIS K7121 (1987). Was the glass transition point (Tg), and the results are shown in the table below.

<In-plane retardation value (Ro (550)) and Nz>
The in-plane retardation value of the film obtained above is an in-plane retardation value (Ro) and Nz defined by the following formula (1) at a wavelength of 550 nm in an environment of a temperature of 23 ° C. and a relative humidity of 55%. Measurement was performed using Axoscan manufactured by Axometrics.
Specifically, after performing three-dimensional refractive index measurement at a wavelength of 550 nm in an environment of 23 ° C. and 55% RH and obtaining average values of refractive indices _nx , _ny , and _nz , In-plane retardation values Ro and Nz were calculated according to the equation.
Equation _{(1): Ro = (n} x -n y) × d
Equation _{(2): Nz = (n} x -n z) / (n x -n y)
In the formula (1) and (2), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the optical film. n _y, in-plane direction of the optical film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the optical film. d represents the thickness (nm) of the film.

<Chromatic dispersion value (DSP)>
The chromatic dispersion value (DSP) of the sample film obtained above is the above in-plane retardation value (Ro) at a wavelength of 450 nm and 550 nm in an environment of a temperature of 23 ° C. and a relative humidity of 55%, manufactured by Axometrics. It measured using Axoscan, Ro (450) was calculated | required by the following formula as an in-plane phase difference value in wavelength 450nm, and Ro (550) as an in-plane phase difference value in 550nm.
Formula (3): DSP = Ro (450) / Ro (550)

<In-plane retardation fluctuation rate>
The sample film was stretched under the following conditions using ORIENTEC RTC-1225A (manufactured by A & D Co., Ltd.), and the in-plane retardation value Ro was measured.
Sample size: 70 x 25 mm
Distance between chucks (air jaws): 50 mm
Stretch ratio: 15% in the 70 mm direction
Stretching temperature: Tg + 10 ° C. of sample film, Tg + 20 ° C.
In-plane retardation value when the sample film is stretched at Tg + 10 ° C .: Ro (Tg + 10 ° C.)
In-plane retardation value when stretched at Tg + 20 ° C. of sample film: Ro (Tg + 20 ° C.)
As a result, the in-plane retardation variation rate was calculated by the following equation.
In-plane phase difference fluctuation rate (ΔRo) (%)
= [{Ro (Tg + 10 ° C.) − Ro (Tg + 20 ° C.)} / Ro (Tg + 10 ° C.)] × 100

<Hue deviation>
CM-2500d (Konica Minolta Co., Ltd.) is attached at a 5 mm interval in the sample film transport direction (MD direction) and the direction perpendicular to the transport (TD direction) by attaching the circularly polarizing plate obtained above to a mirror. The hue defined by the CIE1976L ^* a ^* b ^* color system was measured under the following conditions. When the hue was measured, the absolute value of the difference in hue deviation defined by the following formula between adjacent measurement points, and the difference between the maximum hue deviation width and the minimum hue deviation width were calculated. The calculated results are shown in the following table.
Definition formula: hue deviation width = [(Δa ^* ) ² + (Δb ^* ) ² + (ΔL ^* ) ² ] ^1/2
However, Δa ^* = a ^* −a ^* (ave),
Δb ^* = b ^* −b ^* (ave),
ΔL ^* = L ^* −L ^* (ave)
[In the above formula, L ^* represents a value obtained by digitizing light and dark, and the larger the value, the brighter the color tone. L ^* (ave) represents the average value of all measured values of L ^* . a ^* represents a hue and saturation in the color system, and is a coordinate value indicating the position of the red-green transition line. a ^* (ave) represents an average value of all measured values of a ^* . b ^* represents a hue and saturation in the color system, and is a coordinate value indicating the position of the yellow-blue transition line. b ^* (ave) represents an average value of all measured values of b ^* . ]
(Measurement condition)
SCI (including regular reflection light)
Observation conditions: 10 degree field of view Observation light source: D65
Color value: L ^* a ^* b ^*

<Rippled unevenness>
The organic EL display device produced above was visually evaluated for unevenness.
(Evaluation criteria)
A: Unevenness was not confirmed on the screen by visual observation, and a sharp black color was obtained.
○: Although slight unevenness was confirmed on the screen by visual observation, a sharp black color was obtained.
(Triangle | delta): The nonuniformity was slightly confirmed on the screen by visual observation, and the black sharpness was falling.
X: Unevenness was confirmed on the screen by visual observation.

<Color change from front to diagonal direction>
About the organic electroluminescence display produced above, the change of color was evaluated visually.
A black image is displayed on the organic EL display device, and the image when viewed from the normal direction perpendicular to the screen,
Images were compared when viewed from a direction with an azimuth angle of 45 ° and an inclination of 60 ° from the normal.
A: Little change in color was observed by visual observation.
○: Slight changes in color that were not problematic for practical use were observed by visual observation.
(Triangle | delta): The change of the color was seen by visual observation.
X: Significant color change was observed by visual observation.

  As is clear from the results shown in Table 2, an organic EL display device using an optical film that satisfies the range of the phase difference variation rate of the present invention and satisfies the optical characteristics of the above requirements (1) to (3) is provided. It can be seen that hue deviation and ripple-like unevenness can be prevented as compared with the organic EL display device using the optical film of the comparative example.

DESCRIPTION OF SYMBOLS 1 Stretching apparatus 2 Grasping tool traveling support tool 3 Heating furnace 4 Stretching zone 6 Side wall 11 Stretching direction 13 Conveying direction 14 Slow axis D1 Feeding direction D2 Winding direction N Nozzle F Optical film (long film)
θi Bending angle (feeding angle)
Ci, Co gripper Ri, Ro Rail Wo Width of film before stretching W Width of film after stretching 16 Film feeding device 17 Transport direction changing device 18 Winding device 19 Film forming device A Organic RL display device B Organic EL element C Circularly polarizing plate 101 Transparent substrate 102 Metal electrode 103 TFT
DESCRIPTION OF SYMBOLS 104 Organic light emitting layer 105 Transparent electrode 106 Insulating layer 107 Sealing layer 108 Film 109 (lambda) / 4 phase difference film 110 Polarizer 111 Protective film 112 Hardened layer 113 Antireflection layer

Claims (6)

An optical film produced by stretching a resin film,
When the glass transition temperature (Tg) + 10 ° C. and the glass transition temperature (Tg) + 20 ° C. are uniaxially stretched at a stretching ratio of 15%, the in-plane retardation variation rate (ΔRo) defined by the following formula is 10 An optical film produced by using a resin in a range of ˜20% and controlled so as to satisfy the optical characteristics of the following requirements (1) to (3).
Definition formula: In-plane retardation variation rate (ΔRo) (%)
= [{Ro (Tg + 10 ° C.) − Ro (Tg + 20 ° C.)} / Ro (Tg + 10 ° C.)] × 100
Requirements:
(1) 130 nm <Ro (550) <160 nm
_{(2) Nz <1.3, Nz} = (n x -n z) / (n x -n y)
(3) 0.7 <DSP <1, DSP = Ro (450) / Ro (550)
[Significance of symbols and the like in the above formula: Measurement environmental conditions: 23 ° C., 55% RH;
Ro (Tg + 10 ° C.): In-plane retardation value when the resin film is uniaxially stretched at Tg + 10 ° C., but the measurement light wavelength is 550 nm
Ro (Tg + 20 ° C.): In-plane retardation value when the resin film is uniaxially stretched at Tg + 20 ° C. However, the measurement light wavelength is 550 nm.
Ro (550): in-plane retardation value at a measuring wavelength 550 nm ro (450): the refractive index is maximized in the plane direction of the optical film: Measurement plane retardation value at wavelength 450 nm DSP: Wavelength dispersion _{n x} refractive index in the direction x n _y: in-plane direction of the optical film, the refractive index n _z in the direction y perpendicular to the direction _x: refractive index in the thickness direction z of the film; however, the measurement wavelength of the refractive index is 550nm ] A circularly polarizing plate is prepared using the optical film, the circularly polarizing plate is attached to a mirror, and CIE1976L ^* a ^* b is spaced at 5 mm intervals in two directions parallel to the surface of the optical film and perpendicular to each other. ^* When the hue specified by the color system is measured, the absolute value of the difference in hue deviation defined by the following formula between adjacent measurement points is 0.5 or less, and the maximum hue 2. The optical film according to claim 1, wherein the difference between the deviation width and the smallest hue deviation width is 3 or less.
Definition formula: hue deviation width = [(Δa ^* ) ² + (Δb ^* ) ² + (ΔL ^* ) ² ] ^1/2
However, Δa ^* = a ^* −a ^* (ave),
Δb ^* = b ^* −b ^* (ave),
ΔL ^* = L ^* −L ^* (ave)
[In the above formula, L ^* represents a value obtained by digitizing light and dark, and the larger the value, the brighter the color tone. L ^* (ave) represents the average value of all measured values of L ^* . a ^* represents a hue and saturation in the color system, and is a coordinate value indicating the position of the red-green transition line. a ^* (ave) represents an average value of all measured values of a ^* . b ^* represents a hue and saturation in the color system, and is a coordinate value indicating the position of the yellow-blue transition line. b ^* (ave) represents an average value of all measured values of b ^* . ]   The optical film according to claim 1, wherein the uniaxial stretching is oblique stretching.   The optical film according to any one of claims 1 to 3, wherein a cellulose ester resin, a cellulose ether resin, or a polycarbonate resin is contained as a component of the resin film.   A circularly polarizing plate comprising the optical film according to any one of claims 1 to 4.   An organic electroluminescence display device comprising the circularly polarizing plate according to claim 5.

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