JP2010061091A - Method and apparatus for manufacturing optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical film, which manufactures an optical film having no bright spot defect even when used for a display and preventing variation in strain deformation in the film by applying strain deformation in the film without producing scratch on a film surface, and stably stretches the film surface in an inclined direction, and to provide a manufacturing apparatus suitable for the manufacturing method. <P>SOLUTION: The method for manufacturing the optical film is provided that has a process 1 and a process 2 satisfying a specific condition, and manufactures the optical film by continuously conveying a resin film. In the process 1, difference between a refractive index in a thickness direction of the resin film and a refractive index in a direction orthogonal to a traveling direction is produced. In the process 2, adjustment is made so that a direction where the refractive index of the resin film is minimum is aligned with a direction inclined from a normal direction of the resin film surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and apparatus for producing an optical film suitable as an optical compensation film for a TN type liquid crystal display device.

  A twisted nematic (twisted nematic: hereinafter referred to as “TN”) type optical compensation film for a liquid crystal display device has a film surface in which the optical axis is inclined from the film surface direction for excellent field of view expansion. It is known that it is necessary within. For this reason, a liquid crystal compound is coated on a support film, and a rubbing treatment is performed so that the direction of liquid crystal molecules is inclined from the film surface direction and the optical axis is inclined from the film surface direction. .

  However, the optical compensation film for a TN type liquid crystal display device has a problem that its configuration and manufacturing method are complicated, productivity is low, and cost is high.

  For this reason, an optical compensation film that is an optical film that is excellent in productivity and in which the optical axis of a simple resin film that does not require a liquid crystal layer is inclined from the film surface direction has been proposed (see, for example, Patent Documents 1 and 2). .)

However, the achievement means for inclining the optical axis from the film surface direction sandwiches the film between two rollers having different peripheral speeds and applies a shearing force in the surface direction of the film, thereby giving distortion deformation to the film, Since the optical axis is tilted from the film surface direction, fine scratches are generated on the film surface due to slippage between the roller and the film, and when used in a liquid crystal display device, the scratches are conspicuous as bright spot defects. Further, the frictional force between the roller and the film is not stable, and it is difficult to control the shearing force. As a result, it is difficult to control the optical axis tilted from the film surface direction, which has not been put into practical use.
JP-A-6-222213 JP-A-7-333437

  The present invention has been made in view of the above-described problems and situations, and its solution is to give distortion to the film without causing scratches on the surface of the film. To provide an optical film manufacturing method that is capable of manufacturing an optical film that is free from defects and has a small variation in the amount of strain deformation in the film, and that can be stably stretched in the tilt direction on the film surface. . Moreover, it is providing the manufacturing apparatus suitable for the said manufacturing method.

The above-mentioned problem according to the present invention is solved by the following means.
1. It is a manufacturing method of an optical film which has a process 1 which satisfies the following condition 1 and a process 2 which satisfies the following condition 2, and manufactures an optical film by continuously conveying a resin film, wherein the thickness of the resin film in the step 1 A difference is generated between the refractive index in the vertical direction and the refractive index in the direction orthogonal to the traveling direction, and the direction in which the refractive index of the resin film is the smallest in the step 2 is inclined from the normal direction of the resin film surface. The method for producing an optical film is characterized in that the adjustment is performed so that the direction is adjusted.
Condition 1: Step 1 is a step in which the resin film is stretched x times in the direction orthogonal to the transport direction and y times in the transport direction, and the following conditional expression 1 is satisfied.
(Condition 1) 1.00 <x <2.50, 0.40 <y <1.00
Condition 2: Step 2 is a step in which a driving roller is brought into contact with one surface of the resin film and a follower rotating roller having a rotational load is brought into contact with the opposite surface of the resin film. The thickness d satisfies the following conditional expression 2.
(Condition 2) 0.40 × d <a <0.98 × d
2. In the step 2 in which the resin film uses two types of rollers, a driving roller A and a follower rotating roller B, the peripheral speed of the roller A is A1 (m / min), and the speed after the resin film is separated from the roller is P1. (M / min), the following conditional expression 3 is satisfied, The method for producing an optical film as described in 1 above, wherein
(Condition 3) 0.30 <P1 / A1 <1.00
3. 3. The method for producing an optical film as described in 1 or 2 above, wherein the driving roller and the follower rotating roller constitute a nip roller pair sandwiching the resin film.

  4). (1) to (3), wherein the resin film is heated or cooled before and after the portion (hereinafter also referred to as “contact portion”) where the resin film and the two types of rollers are in contact with each other. The manufacturing method of the optical film as described in any one.

  5. 5. The method for producing an optical film according to any one of 1 to 4, wherein a plurality of the driving rollers or following rotation rollers are provided, and the contact is performed at a plurality of locations on the film conveyance path.

  6). A driving roller that contacts one surface of the resin film and a follower rotating roller that contacts the opposite surface of the resin film and has a rotational load, and these two types of rollers serve as a means for conveying the resin film and are included in the resin film An apparatus for producing an optical film, which is a means for imparting strain deformation.

  7). 6. The apparatus for producing an optical film as described in 6 above, which is used for carrying out the method for producing an optical film according to any one of 1 to 5.

  By applying the above-described means of the present invention to strain deformation in the film without causing scratches on the surface of the film, there is no bright spot defect even when used in a display device, and the optical distortion is small in the amount of strain deformation in the film. An object of the present invention is to provide a method for producing an optical film capable of producing a film and capable of stably stretching the film surface in an inclined direction. Moreover, it is providing the manufacturing apparatus suitable for the said manufacturing method.

  This makes it possible to increase strength by stretching in the direction parallel to a generally known surface, and to provide various film properties that cannot be obtained by adjusting the optical axis and refractive index, and is useful for various optical films. It becomes. In particular, it is possible to provide a manufacturing method and a manufacturing apparatus suitable as a method for manufacturing an optical compensation film for a TN liquid crystal display device.

  The manufacturing method of the optical film of this invention is a manufacturing method of the optical film which has the process 1 which satisfy | fills the said conditions 1, and the process 2 which satisfies the said conditions 2, and conveys a resin film continuously and manufactures an optical film, In the step 1, a difference is generated between the refractive index in the thickness direction of the resin film and the refractive index in the direction orthogonal to the traveling direction, and the direction in which the refractive index of the resin film is the smallest in the step 2 is It adjusts so that it may become the direction inclined from the normal line direction of the said resin film surface. This feature is a technical feature common to the inventions according to claims 1 to 7.

  Hereinafter, the present invention, its components, and the best mode and mode for carrying out the present invention will be described in detail.

(Characteristics of the optical film production method of the present invention)
The method for producing an optical film of the present invention includes a step 1 that satisfies the following condition 1 and a step 2 that satisfies the following condition 2, and a method for producing an optical film by continuously conveying a resin film, In the step 1, a difference is generated between the refractive index in the thickness direction of the resin film and the refractive index in the direction orthogonal to the traveling direction, and the direction in which the refractive index of the resin film is the smallest in the step 2 is A method for producing an optical film, comprising adjusting the direction to be inclined from the normal direction of the resin film surface.
Condition 1: Step 1 is a step in which the resin film is stretched x times in the direction orthogonal to the transport direction and y times in the transport direction, and the following conditional expression 1 is satisfied.
(Condition 1) 1.00 <x <2.50, 0.40 <y <1.00
Condition 2: Step 2 is a step in which a driving roller is brought into contact with one surface of the resin film and a follower rotating roller having a rotational load is brought into contact with the opposite surface of the resin film. The thickness d satisfies the following conditional expression 2.
(Condition 2) 0.40 × d <a <0.98 × d
In the “stretching” in the above condition 1, reduction was expressed and included as stretching less than 1 time.

  In the present application, the “following rotating roller having a rotational load” is a rotating roller that freely rotates or forcibly rotates by contact pressure with the conveyed resin film, as shown in FIG. 1, and conveys the film by a driving roller. A rotating roller used to apply a force in the opposite direction so that the brake is applied on the film surface opposite to the film surface on which the force to be applied is applied. Various brakes can be used for the load required for rotation. As a point, it is important to have a structure in which the load torque does not fluctuate, and it is necessary to perform control so that a constant torque including the driving roller is obtained.

  Also, “giving distortion deformation to the resin film” means applying shearing force due to contact pressure with the roller or roller nip pressure to the resin film and optical properties such as refractive index in the resin film (“optical characteristics”). To cause distortion and deformation.

As an embodiment of the present invention, in the step 2 in which the resin film uses two types of rollers, the driving roller A and the following rotation roller B, the peripheral speed of the roller A is A1 (m / min), and the resin film is When the speed after separation from the roller is P1 (m / min), the production method preferably satisfies the following conditional expression 3.
(Condition 3) 0.30 <P1 / A1 <1.00
That is, it is preferable that the resin film does not slip between the driving roller and the contact portion of the two types of follower rollers. For this reason, it is preferable that the drive roller and the follower rotation roller constitute an nip roller pair that sandwiches the resin film. Accordingly, the resin film is prevented from slipping on the outer peripheral surfaces of the drive roller and the follower rotation roller, and thus the film surface is not scratched. Further, the stress transmitted from the drive roller and the follower roller to the film is stable, and the variation in the amount of distortion in the film is small.

  In this invention, the aspect which heats or cools the said resin film in the location (it calls a "contact part") where the said resin film and the said 2 types of roller contact, and the contact part is preferable. Strain deformation is likely to occur in the temperature range of 50 ° C above and below the glass transition temperature of the resin film, and heating is performed in front of the contact portion, so that the resin film temperature is close to the glass transition temperature. It is effective to increase the amount. Cooling is carried out after passing through the contact portion, and is effective for maintaining and fixing distortion deformation generated in the film to prevent it from changing.

  In addition, it is not preferable to maintain a temperature state equal to or higher than the glass transition temperature for a long time in a conveyance portion other than the contact portion because the generated strain deformation changes (including the disappearance phenomenon). In addition, in the pre-step of winding up the film after imparting strain deformation, the heat stabilization treatment at a high temperature above the glass transition temperature for a short time (1 to 20 minutes) makes it difficult for the strain deformation to fluctuate for a long time. This is a preferred embodiment.

  The glass transition temperature referred to here is an intermediate value determined according to JIS K7121 (1987) using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer) at a temperature rising rate of 20 ° C./min. The point glass transition temperature (Tmg).

  In the present invention, it is also preferable that a plurality of the driving rollers or following rotation rollers are provided, and the contact is performed at a plurality of locations on the film conveyance path.

  Forming a certain amount of strain deformation in multiple steps is superior in that the amount of variation can be reduced more stably than forming strain deformation once. In addition, when strain deformation is given in a plurality of times, a region to be heated in the film thickness direction is partially limited and the heating position is changed a plurality of times so that the strain deformation amount varies in the film thickness direction. It is possible and preferable.

  Accordingly, as a manufacturing apparatus used for carrying out the optical film manufacturing method of the present invention, basically, a driving roller that contacts one side of the resin film and a follower rotation that contacts the opposite surface of the resin film and has a rotational load. It is preferable that the apparatus for manufacturing an optical film has a roller, and these two types of rollers serve as a means for conveying the resin film and serve as a means for imparting strain deformation in the resin film.

  About the distortion deformation in the resin film which concerns on this invention, control of the deformation amount in a film is easy by the means shown to following (1)-(7), and the production stability by continuous conveyance of a film is favorable. is there.

  (1) The load amount of the rotational load of the following rotary roller is adjusted.

  (2) Adjust the film temperature of the part where the shear force is applied (contact part and its front and back).

  (3) The temperature state in the surface direction of the film is adjusted in (2) above. For example, the temperature difference from the non-heating (cooling) side by heating from one side is adjusted including the preheating time.

  (4) A follower rotating roller having a driving roller and a rotational load is used as a roller nip pair, and the number of roller nip pairs used is adjusted.

  (5) In the above (4), the rotational load amount of the following rotating roller is adjusted to be gradually increased or decreased with the plurality of roller nip pairs.

  (6) The roller temperature is changed by the plurality of roller nip pairs of the above (4) and (5), and the film temperature to be heated at the plurality of contact portions is adjusted.

  (7) The roller deformation amount is adjusted by selecting the roller material (metal, various rubbers).

  (8) A heating means is provided on one side of the film, and a cooling means is provided on the opposite side.

  Hereinafter, the technical features of preferred embodiments of the method for producing an optical film of the present invention will be described in more detail with reference to FIGS.

  FIGS. 2A to 2D are conceptual diagrams showing an arrangement example (positional interrelation example) of the driving roller and the follower rotating roller according to the present invention. In the case of the example shown in FIG. 2 (a), the roller does not nip, and the film is in close contact with the outer periphery of the roller, and the roller diameter can be reduced to form a small curved portion to give distortion deformation. Thus, distortion deformation different from that in FIG. 2B can be given. By changing the temperature of the plurality of rollers or changing the roller diameter, distortion deformation that cannot be obtained by the roller nip pair method can be given.

  In the case of the example shown in FIG. 2B, the mass of the roller can be used for the rotational load of the following rotary roller, and the variation in the roller width direction is reduced. The slip limit can be increased by the roller nip pressure, and a strong force can be transmitted by one pair of rollers, and the amount of deformation in the film by one pair of rollers can be increased.

  In the case of the example shown in FIG. 2C, the manufacturing process can be reduced by pairing a plurality of rollers with respect to one roller. The inside of the resin film on one surface of the resin film can be deformed by using the driving roller as a cooling roller and the follower rotating roller as a heating roller. In FIG. 2 (c), by setting the reverse roller arrangement in the first half and the second half, the deformation amount in the thickness direction of the resin film can be adjusted by deforming the inside of the resin film from both sides of the resin film.

  In the present invention, it is preferable that the resin film is in direct contact with the drive roller and the follower rotating roller. However, as shown in FIG. 2 (d), a film, a sheet, or a belt is interposed between the resin film and the roller. In addition, a method of applying strain deformation in the resin film is also included in the present invention.

<Roller material>
As materials constituting the roller according to the present invention, various commonly known materials can be used. Specifically, metal rollers such as stainless steel, chrome plating, titanium (not deformed), various rubbers (elastic deformation can be adjusted by rubber hardness), fluororesin (water repellent, oil repellent, etc.) Various types can be used.

<Rotational load on the following rotating roller>
Examples of the rotational load on the following rotating roller include increasing the nip force, utilizing the weight of the roller itself, using various roller brakes, adding another rotational pair to the roller, and setting the rotational load. It is done.

<Roller surface>
The surface state of the roller surface according to the present invention is a mirror surface state (0.01 to 2.0 nm having a very small surface roughness) and has a surface roughness of about 2 to 30 nm so as not to slip. The surface can be various surfaces such as 30 nm to 10 μm, such as having an effect of forming an uneven shape on the film surface (function of an antiglare film). It is preferable to select according to the use of the film.

<Heating and cooling>
In the present invention, various commonly known heating means such as an electric heater, a far infrared heater, and a heating medium can be used, and direct heating of the film (contact and non-contact), heating of the driving roller and the follower rotating roller can be performed. it can.

  For cooling, various commonly known cooling means such as cooling with a heat medium, air cooling, and use of a refrigerator can be used, and the film can be directly cooled (contact and non-contact), the driving roller, and the follower rotating roller can be cooled.

  The heating temperature varies depending on the purpose, but is preferably ± 100 ° C. of the glass transition temperature of the resin film. More preferably, it is ± 50 ° C. The cooling temperature is preferably in the range of room temperature to softening point temperature from the viewpoint of handleability.

(Resin film)
The resin of the resin film that can be used in the present invention is a thermoplastic resin (by heating, because it is difficult to control because it is an application of the present invention during curing). It can be used even if it is easily deformed and deformed), but a thermoplastic resin is preferable from the viewpoint of handleability. Examples of the thermoplastic resin include cellulose ester resin, polycarbonate resin, polyethersulfone resin, acrylic resin, and polysulfone. Examples thereof include resins, polyarylate resins, polyethylene resins, polystyrene resins, polyvinyl chloride resins, and alicyclic olefin polymers. Among these, as the thermoplastic resin, a cellulose ester resin, a polycarbonate resin, a cyclic olefin resin, and an acrylic resin are preferable. Further, polyamide resins, polyimide resins, polyester resins, polyether ketone resins, polyamides, which are polymer materials having a photoelastic coefficient of 60 × 10 ⁻⁸ cm ² / N or more described in JP-A-2004-212971. An imide resin and a polyesterimide resin can also be preferably used.

  Further, the resin film is simple and easy to handle as a single composition film, but may be a resin film having a laminated structure. As a laminated structure, the structure described in Unexamined-Japanese-Patent No. 2004-212971 which provided thin film layers, such as a polyimide resin, on the resin film surface is preferable.

  The resin film of the present invention is preferably handled as a long film. A form in which the resin film is wound up in a roll shape is unwound and wound up again after the production method of the present invention is applied. It is preferable to apply the production method of the present invention during the drying of the production or before the winding after the drying. On the other hand, although the manufacturing method of the present invention can be applied to a cut sheet film, it is inferior in terms of production efficiency as compared with a method of continuously treating a long film.

<Cellulose ester resin>
The cellulose ester resin that can be used in the present invention is selected from cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. It is preferable that there is at least one.

  Among these, particularly preferable cellulose esters include cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

  As the substitution degree of the mixed fatty acid ester, more preferable cellulose acetate propionate and lower fatty acid ester of cellulose acetate butyrate have an acyl group having 2 to 4 carbon atoms as a substituent, and the substitution degree of an acetyl group is X. When the substitution degree of propionyl group or butyryl group is Y, it is preferably a cellulose resin containing a cellulose ester that simultaneously satisfies the following formulas (I) and (II).

Formula (I) 2.6 ≦ X + Y ≦ 3.0
Formula (II) 1.0 ≦ X ≦ 2.5
Of these, cellulose acetate propionate is particularly preferably used. Among them, 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9 are preferable. The part not substituted with the acyl group is usually present as a hydroxyl group. These can be synthesized by known methods.

  Furthermore, the cellulose ester used in the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 5.0, Preferably it is 2.5-5.0, More preferably, the cellulose ester of 3.0-5.0 is used preferably.

  The cellulose ester raw material cellulose used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferred. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

  For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

  The cellulose ester resin according to the present invention was charged with 1 g in 20 ml of pure water (electric conductivity 0.1 μS / cm or less, pH 6.8), and had a pH of 6 when stirred in a nitrogen atmosphere at 25 ° C. for 1 hr. It is preferable that the electric conductivity is 1 to 100 μS / cm. If the pH is less than 6, the residual organic acid may accelerate cellulose degradation during heating and melting, and if the pH is higher than 7, hydrolysis may accelerate. In addition, when the electrical conductivity is 100 μS / cm or more, since a relatively large amount of residual ions are present, it is considered to be a factor for degrading cellulose during heating and melting.

<Polycarbonate resin>
In the present invention, various known polycarbonate resins can also 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 generally called polycarbonate is a generic name of a polymer material in which a polycondensation reaction is used in the synthesis method and the main chain is linked by a carbonic acid bond. , Phosgene, diphenyl carbonate and the like obtained by polycondensation. 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 selected as appropriate. Thus, an aromatic polycarbonate copolymer can be formed.

  In addition to 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-phenyl Ethane, 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-tri Mention may be made of a chill cyclohexane, and the like.

  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 aromatic polycarbonate used here has a viscosity average molecular weight of 10,000 or more and 200,000 or less, it is suitably used. A viscosity average molecular weight of 20,000 to 120,000 is particularly preferred. If a resin having a viscosity average molecular weight lower than 10,000 is used, the mechanical strength of the obtained film may be insufficient, and if it has a high molecular weight of 400000 or more, the viscosity of the dope becomes too high, which causes problems in handling. The viscosity average molecular weight can be measured by commercially available high performance liquid chromatography.

  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 calorimetric analyzer). For example, the baseline is unevenly determined by a temperature rising condition of 10 ° C./min with RDC220 manufactured by Seiko Instruments Inc. It is the temperature that begins to do.

  In the present invention, the solvent used in 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 amount of the linear or branched aliphatic alcohol having 1 to 6 carbon atoms is preferably 4 to 12 parts by mass. Using such a mixed solvent, by peeling the web with a higher residual solvent concentration than conventional, it is possible to suppress the generation of strong static electricity at the time of web peeling, thereby damaging the belt, film streaks and unevenness, The generation of minute scratches can be prevented.

  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 presumed 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 provides satisfactory peelability. As mentioned above, it is 4-14 mass parts with respect to a methylene chloride, Preferably it is 4-12 mass parts. 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.

  The present invention comprises the above methylene chloride and aliphatic alcohol in the dope composition, but other solvents 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 further has a low boiling point. 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 here include mixing the solvent without sacrificing solubility and stability, for example, improving the surface properties of the film formed by the solution casting method (leveling effect), evaporation rate and system These include viscosity adjustment and crystallization suppression effects. 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 (s) 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, and ethyl acetate and butyl acetate. Examples include ester solvents, 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 the aromatic polycarbonate solution dissolved in a certain solvent in advance, 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 the precipitation of the polymer. Therefore, the method of dissolving in the latter mixed solvent is preferable.

(Cyclic olefin resin)
In the present invention, it is also preferable to use a cyclic olefin resin. Examples of the cyclic olefin resin include norbornene resins, monocyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and hydrides thereof. Among these, norbornene-based resins can be suitably used because of their good transparency and moldability.

  Examples of the norbornene-based resin include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, a hydride thereof, and a norbornene structure. An addition polymer of a monomer having a monomer, an addition copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof.

  Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like. Can be used.

Examples of the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene) and tricyclo [4.3.0.1 ^2,5 ] deca-3,7-diene. (Common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4.0. 1 ^2,5 . ^{17, 10} ] dodec-3-ene (common name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different and a plurality may be bonded to the ring. Monomers having a norbornene structure can be used singly or in combination of two or more.

  Examples of the polar group include a hetero atom or an atomic group having a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of the polar group include a carboxyl group, a carbonyloxycarbonyl group, an epoxy group, a hydroxyl group, an oxy group, an ester group, a silanol group, a silyl group, an amino group, a nitrile group, and a sulfone group.

  Other monomers capable of ring-opening copolymerization with monomers having a norbornene structure include monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof, cyclic conjugated dienes such as cyclohexadiene, cycloheptadiene, and the like. And derivatives thereof.

  A ring-opening polymer of a monomer having a norbornene structure and a ring-opening copolymer of a monomer having a norbornene structure and another monomer copolymerizable with the monomer have a known ring-opening polymerization catalyst. It can be obtained by (co) polymerization in the presence.

  Examples of other monomers that can be addition copolymerized with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene, cyclopentene, And cycloolefins such as cyclohexene and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and the like. These monomers can be used alone or in combination of two or more. Among these, α-olefin is preferable and ethylene is more preferable.

  An addition polymer of a monomer having a norbornene structure and an addition copolymer of a monomer having a norbornene structure with another monomer copolymerizable with a monomer having a norbornene structure are prepared in the presence of a known addition polymerization catalyst. It can be obtained by polymerization.

  A hydrogenated product of a ring-opening polymer of a monomer having a norbornene structure, a hydrogenated product of a ring-opening copolymer of a monomer having a norbornene structure and another monomer capable of ring-opening copolymerization thereof, Hydrogenated products of addition polymers of monomers having a norbornene structure, and hydrogenated products of addition copolymers of monomers having a norbornene structure and other monomers capable of addition copolymerization with these A known hydrogenation catalyst containing a transition metal such as nickel or palladium is added to the polymer solution, and the carbon-carbon unsaturated bond is preferably hydrogenated by 90% or more.

Among norbornene-based resins, as repeating units, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane-7 , 9-diyl-ethylene structure, the content of these repeating units is 90% by mass or more based on the entire repeating units of the norbornene resin, and the content ratio of X and the content ratio of Y The ratio of X: Y is preferably 100: 0 to 40:60. By using such a resin, it is possible to obtain an optical compensation film (optical film) that has no dimensional change over a long period of time and is excellent in stability of optical characteristics.

  The molecular weight of the cyclic olefin resin used in the present invention is appropriately selected according to the purpose of use. Polyisoprene or polystyrene-converted weight average molecular weight (Mw) measured by gel permeation chromatography using cyclohexane (toluene if the polymer resin does not dissolve) as a solvent, usually 20,000 to 150,000. . Preferably it is 25,000-100,000, More preferably, it is 30,000-80,000. When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the film are highly balanced and suitable.

  The glass transition temperature of the cyclic olefin resin may be appropriately selected according to the purpose of use. From the viewpoint of durability and stretchability, it is preferably in the range of 130 to 160 ° C, more preferably 135 to 150 ° C.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the cyclic olefin resin is 1.2 to 3.5, preferably 1.5 to 3.0, from the viewpoint of relaxation time, productivity, and the like. More preferably, it is 1.8 to 2.7.

The cyclic olefin resin used in the present invention preferably has an absolute value of photoelastic coefficient of 10 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 7 × 10 ⁻¹² Pa ⁻¹ or less, and more preferably 4 × 10. It is particularly preferably ⁻¹² Pa ⁻¹ or less. The photoelastic coefficient C is a value represented by C = Δn / σ where birefringence is Δn and stress is σ. If the photoelastic coefficient of the cyclic olefin resin exceeds 10 × 10 ⁻¹² Pa ⁻¹ , the in-plane retardation of the stretched film may vary widely.

  In the present invention, it is preferable that the cyclic olefin resin does not substantially contain particles. Here, “substantially free of particles” means that even if particles are added to a film made of a cyclic olefin resin, the amount of increase in haze from the non-added state is allowed to be in the range of 0.05% or less. Means you can. In particular, the alicyclic polyolefin resin lacks affinity with many organic particles and inorganic particles. Therefore, when a cyclic olefin resin film to which particles exceeding the above range are added is stretched, voids are easily generated, and as a result, There is a risk that a significant decrease in haze occurs.

  In the present invention, by adding a load deflection temperature adjusting agent to the cyclic olefin resin, it is possible to obtain an optical compensation film having excellent stretchability as described above and improved changes in optical properties at high temperatures.

  This is because the difference between the glass transition temperature Tg (° C.) of the resin and the deflection temperature under load Tt (° C.) becomes large, so that the film can be stretched without applying excessive force even at low temperatures. It is considered that the unevenness of the retardation is greatly reduced and the thermal relaxation property of the retardation is improved.

  Specifically, the difference between Tg and Tt is Tg−Tt = 5 to 30 (° C.), more preferably 10 to 30 (° C.).

  In addition, you may select and mix suitably polymeric materials and oligomers other than said resin to a thermoplastic film. As the polymer material or oligomer, those excellent in compatibility with cellulose ester resin and the like are preferable, and the transmittance when formed into a film is 80% or more, more preferably 90% or more, and further preferably 92% or more. preferable. The purpose of mixing at least one of polymer materials and oligomers other than cellulose ester includes meanings for controlling viscosity at the time of heating and melting and improving film physical properties after film processing.

(Other additives)
The thermoplastic film according to the present invention may contain various compounds as additives depending on the purpose. For example, a plasticizer, an antioxidant, an acid scavenger, a light stabilizer, an ultraviolet absorber, an optical anisotropy control agent, a matting agent, an antistatic agent, a release agent, and the like can be contained.

  Among the additives, it is an optical anisotropy control agent that effectively contributes to the present invention, and in particular, the retardation increasing agent makes it easy to develop birefringence optically in an oblique direction from the intended plane. Therefore, it is preferable. The retardation increasing agent is preferably an aromatic compound having at least two aromatic rings. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the resin. And it is preferable to use in 0.05-15 mass parts, and it is still more preferable to use in 0.1-10 mass parts. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. Details thereof are described in JP-A No. 2004-109410, JP-A No. 2003-344655, JP-A No. 2000-275434, JP-A No. 2000-1111914, JP-A No. 12-275434, and the like.

(Matting agent)
In the optical film of the present invention, it is preferable to add fine particles as a matting agent in order to prevent the produced film from being scratched or having deteriorated transportability when handled.

  As fine particles, examples of inorganic compounds 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, Examples thereof include magnesium silicate and calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm. These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable. The content of these fine particles in the optical film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of an optical film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the haze of the optical film low. In the optical film of the present invention, it is preferable that the dynamic friction coefficient of at least one surface is 0.2 to 1.0.

(Method for producing thermoplastic resin film)
The method for producing the thermoplastic resin film according to the present invention may be a melt casting method or a solution casting method.

  In the melt casting method, a molding method by melt casting that is heated and melted without using a solvent (for example, methylene chloride, etc.) conventionally used in the solution casting method is a melt extrusion molding method, a press molding method, It can be classified into inflation method, injection molding method, blow molding method, stretch molding method and the like. Among these, in order to obtain a polarizing plate protective film having excellent mechanical strength and surface accuracy, the melt extrusion method is excellent.

  The film thickness variation of the optical film support is preferably ± 3%, more preferably ± 1%, and still more preferably ± 0.1%. Further, the smaller the number of various foreign substances in the film, the better. The better is zero (below the detection limit).

  In view of the recent increase in the size of liquid crystal displays, the width of the film is preferably 1 m or more as the optical film of the present invention for the purpose of expanding the field of view for TN liquid crystal. On the other hand, if it exceeds 4 m, the apparatus becomes large and difficult to convey, so the width of the optical film is preferably 1 to 4 m, particularly preferably 1.4 to 2.5 m.

<Stretching process in the direction parallel to the film surface>
The optical film of the present invention can be stretched in the direction parallel to the conventional film surface. The purpose of the stretching treatment can be performed for the purpose of improving the film flatness, increasing the film strength, and adjusting the retardation value.

  As the stretching direction, the longitudinal direction (MD) and the width direction (TD) are generally used, but the stretching direction may be oblique with respect to the longitudinal direction.

  Initially, the extending | stretching method of a longitudinal direction (MD) is demonstrated.

  One-stage or multi-stage MD stretching may be performed in the longitudinal direction. When stretching, assuming that the glass transition temperature of the film is Tg, the film is heated within the range of (Tg-30) to (Tg + 100) ° C., more preferably (Tg-20) to (Tg + 80) ° C. MD) or transverse direction (TD) is preferred. It is preferable to perform transverse stretching within the temperature range of (Tg-20) to (Tg + 20) ° C. and then heat-set. It is also preferable to perform relaxation treatment after the stretching step.

  The Tg of the optical film can be controlled by the material type constituting the film and the ratio of the constituting materials. The Tg when the film is dried is preferably 110 ° C. or higher, more preferably 120 ° C. or higher. This is because when the optical film according to the present invention is used in a liquid crystal display device, if the Tg of the film is lower than the above, molecules fixed inside the film due to the influence of the temperature and humidity of the use environment and the heat of the backlight. The orientation state of the film is affected, and there is a high possibility that the retardation value and the dimensional stability and shape of the film will greatly change. In addition, the shape of the film may not be maintained. Conversely, if the Tg of the film is too high, it becomes difficult to produce because it approaches the decomposition temperature of the film constituting material, and the presence of a volatile component or coloring may occur due to the decomposition of the material itself used when forming a film. Accordingly, the glass transition temperature is preferably 180 ° C. or lower, more preferably 150 ° C. or lower. At this time, the Tg of the film can be determined by the method described in JIS K7121.

  Next, the extending | stretching method of a lateral direction (TD) is demonstrated.

  In the case of TD stretching, it is preferable to perform transverse stretching while sequentially raising the temperature difference in the range of 1 to 50 ° C. in a stretching region divided into two or more, because the distribution of physical properties in the width direction can be reduced. Further, after transverse stretching, it is preferable that the film is held at a temperature not higher than the final TD stretching temperature and not lower than Tg−40 ° C. for 0.01 to 5 minutes because the distribution of physical properties in the width direction can be further reduced.

  The heat setting is performed at a temperature higher than the final TD stretching temperature and usually within 0.5 to 300 seconds within a temperature range of Tg-20 ° C. or less. Under the present circumstances, it is preferable to heat-fix, heating up sequentially in the range from which a temperature difference is set to 1-100 degreeC in the area | region divided into 2 or more.

  The heat-set film is usually cooled to Tg or less, and clip holding portions at both ends of the film are cut and wound. At this time, it is preferable to perform a relaxation treatment of 0.1 to 10% in the lateral direction and / or the longitudinal direction within a temperature range of not more than the final heat setting temperature and not less than Tg. In addition, it is preferable that the cooling is gradually performed from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. Means for cooling and relaxation treatment are not particularly limited, and can be performed by a conventionally known means. In particular, it is preferable to carry out these treatments while sequentially cooling in a plurality of temperature ranges from the viewpoint of improving the dimensional stability of the film. The cooling rate is a value obtained by (T1-Tg) / t, where T1 is the final heat setting temperature and t is the time until the film reaches Tg from the final heat setting temperature.

  More optimal conditions of these heat setting conditions, cooling, and relaxation treatment conditions vary depending on the type of additives such as cellulose ester and plasticizer constituting the film, so the physical properties of the obtained biaxially stretched film are measured and preferable characteristics are obtained. What is necessary is just to determine by adjusting suitably so that it may have.

  The in-plane retardation value (Ro) and the retardation value (Rt) in the thickness direction of the optical film according to the present invention are 0 ≦ Ro ≦ 200 nm and 30 ≦ Rt ≦ 400 nm when used as an optical compensation film. More preferably, 30 ≦ Ro ≦ 100 nm and 50 ≦ Rt ≦ 300 nm. Further, the variation of Rt and the width of distribution are preferably less than ± 10%, more preferably less than ± 5%. More preferably, it is less than ± 1%, and most preferably, there is no fluctuation of Rt.

  The retardation values Ro and Rt can be obtained by the following equations.

Ro = (nx−ny) × d
Rt = ((nx + ny) / 2−nz) × d
Here, d is the thickness (nm) of the film, the refractive index nx (also referred to as the maximum refractive index in the plane of the film, also the refractive index in the slow axis direction), ny (perpendicular to the slow axis in the film plane). Direction refractive index), and nz (the refractive index of the film in the thickness direction).

  The retardation values (Ro) and (Rt) can be measured using an automatic birefringence meter. For example, it can be obtained at a wavelength of 590 nm using KOBRA-21ADH (Oji Scientific Instruments) under an environment of 23 ° C. and 55% RH.

(Polarizer)
The optical film according to the present invention can be used as an optical film having both the function of an optical compensation film and the function of a polarizing plate protective film. The method for producing the polarizing plate is not particularly limited, and can be produced by a general method. it can. The obtained optical film is alkali-treated, and the optical film according to the present invention is bonded to at least one surface of a polarizer prepared by immersing and stretching the polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. . On the opposite side of the polarizer, as the following conventional polarizing plate protective film, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC8UCR-3, KC8UCR-4, KC12UR, KC8UXW-H, KC8UYW-HA, A cellulose ester film such as KC8UX-RHA (manufactured by Konica Minolta Opto Co., Ltd.) can be used.

  Further, instead of the alkali treatment, easy-adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be applied to perform polarizing plate processing.

(Display device)
By using the optical film produced by the method for producing an optical film of the present invention, various display devices having excellent visibility can be produced. The optical film according to the present invention is a reflective, transmissive, transflective LCD or TN, STN, OCB, HAN, VA (PVA, MVA), IPS, etc. Preferably used.

  In addition, the aromatic polycarbonate film is excellent in flatness and is preferably used in various display devices such as a plasma display, a field emission display, an organic EL display, an inorganic EL display, and electronic paper.

<Liquid crystal display device>
In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, a polarizing plate protective film to which the optical film according to the present invention is applied has high flatness and retardation uniformity. Excellent display properties can be obtained even if it is placed on the site. A polarizing plate protective film provided with a clear hard coat layer, an antiglare layer, an antireflection layer, or the like is preferably used for this portion of the polarizing plate protective film on the outermost display side of the liquid crystal display device. In the case of a polarizing plate protective film provided with an optical compensation layer, or a polarizing plate protective film provided with an appropriate optical compensation capability by stretching operation or the like, it is excellent in being disposed at a site in contact with the liquid crystal cell. Displayability is obtained. In particular, the use of the present invention for a multi-domain type liquid crystal display device, more preferably a multi-domain type liquid crystal display device with a birefringence mode, can further exhibit the effects of the present invention.

  Multi-domain is a method of dividing a liquid crystal cell that constitutes one pixel into a plurality of parts, and is suitable for improving the viewing angle dependency and the symmetry of image display. Various methods have been reported. “Okita, Yamauchi: Liquid Crystal, 6 (3), 303 (2002)”. The liquid crystal display cell is also shown in “Yamada, Yamabara: Liquid Crystal, 7 (2), 184 (2003)”, but is not limited thereto.

  The display quality of the display cell is preferably symmetrical with respect to human observation. Therefore, when the display cell is a liquid crystal display cell, it is possible to multiplex domains by giving priority to the symmetry on the observation side. A known method can be used to divide the domain, and can be determined in consideration of the properties of a known liquid crystal mode by a two-part dividing method, more preferably a four-part dividing method.

  The polarizing plate is composed of an MVA (Multi-domain Vertical Alignment) mode represented by a vertical alignment mode, in particular, a MVA mode divided into four, a known PVA (Patterned Vertical Alignment) mode multi-domained by an electrode arrangement, an electrode arrangement, It can be effectively used in a CPA (Continuous Pinwheel Alignment) mode that fuses the chiral ability. In addition, a proposal of an optically biaxial film is also disclosed in conformity to the OCB (Optical Compensated Bend) mode, and “T. Miyashita, T. Uchida: J. SID, 3 (1), 29 ( 1995) ", the effect of the present invention can be exhibited in display quality by the polarizing plate. If the effect of the present invention can be exhibited by using a polarizing plate, the arrangement of the liquid crystal mode and the polarizing plate is not limited.

  Since the liquid crystal display device has high performance as a device for colorization and moving image display, the display quality of the liquid crystal display device using the optical film according to the present invention, particularly a large liquid crystal display device, is less fatigued and faithful. Image display is possible.

<< TN type liquid crystal display device >>
A TN liquid crystal display device in which the optical film according to the present invention is particularly preferably used will be described.

  The TN liquid crystal display device is not particularly limited. Further, a light source may be further provided, and the light source is not particularly limited. However, for example, a planar light source that emits polarized light is preferable because light energy can be used effectively.

  An example of a TN type liquid crystal display device in which an optical film is particularly preferably used will be described with reference to FIGS. Each of the first polarizing plate 13 and the second polarizing plate 15 has a structure in which the polarizing films 2 and 10 are sandwiched between two polarizing plate protective films (the polarizing film 2 includes the first polarizing plate protective film 1 and the second polarizing plate 2). (The polarizing film 10 is sandwiched between the third polarizing plate protective film 9 and the fourth polarizing plate protective film 11).

  Ro and Rt of the 2nd polarizing plate protective film 3 and the 3rd polarizing plate protective film 9 exist in the range of 15 <= Ro <= 70, 70 <= Rt <= 200.

  The TN liquid crystal cell 14 has a liquid crystal layer 6 in a space sandwiched between two glass cell substrates 4 and 8. The average thickness of the liquid crystal layer 6 is the liquid crystal cell gap.

  The glass cell substrates 4 and 8 are provided with alignment layers 5 and 7 for aligning liquid crystals, and the alignment layers are rubbed. The twist angle of the liquid crystal coincides with the direction of the opposing rubbing process, that is, the angle formed by the rubbing axis, and the angle formed by the rubbing axis of the alignment film 5 (reference 0 °) and the rubbing axis of the alignment film 7 is 115 ± 22. °.

  The angle formed by the transmission axis of the first polarizing plate 13 (equal to the transmission axis of the polarizing film 2) and the rubbing axis of the liquid crystal alignment layer 5 is 3.5 ± 3 °, and the transmission axis of the second polarizing plate 15 The angle formed by (the same as the transmission axis of the polarizing film 10) and the rubbing axis of the liquid crystal alignment layer 7 is 3.5 ± 3 °.

  Note that the first polarizing plate and the second polarizing plate are arranged so as to be crossed Nicols (the transmission axes of each other form 90 °).

  The optical film of the present invention is preferably used as the second polarizing plate protective film 3 and the third polarizing plate protective film 9 having an optical compensation function and a polarizing plate protective function.

  Although not shown, a cellulose ester film having a polarizing plate protective function is used for the second polarizing plate protective film 3 and the third polarizing plate protective film 9, and the optical film of the present invention is used as an optical compensation film. The correspondence which installs in two places (both sides of a liquid crystal cell) between the 2nd polarizing plate protective film 3 and the glass cell substrate 4 and between the 2 polarizing plate protective film 9 and the glass cell substrate 8 is also a preferable correspondence.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” in the examples represents “part by mass”.

  In a reactor equipped with a thermometer, a stirrer and a reflux condenser, 152400 parts of ion-exchanged water and 84320 parts of 25% aqueous sodium hydroxide solution were added, and 9,9-bis (4-hydroxy-3 having a purity of 99.8% by HPLC analysis. -Methylphenyl) fluorene (hereinafter sometimes abbreviated as “biscresol fluorene”) 34848 parts, 2,2-bis (4-hydroxyphenyl) propane 9008 parts (hereinafter sometimes abbreviated as “bisphenol A”) and After dissolving 88 parts of hydrosulfite, 178400 parts of methylene chloride was added, and 18248 parts of phosgene was blown in at 60 ° C. for 15 minutes at 15-25 ° C. with stirring. After completion of the phosgene blowing, a solution obtained by dissolving 177.8 parts of p-tert-butylphenol in 2640 parts of methylene chloride and 10560 parts of a 25% aqueous sodium hydroxide solution were added. The reaction was terminated by stirring for a period of time. After completion of the reaction, the product is diluted with methylene chloride, washed with water, acidified with hydrochloric acid, washed with water, and when the conductivity of the aqueous phase is almost the same as that of ion-exchanged water, the methylene chloride phase is concentrated and dehydrated to remove polycarbonate. A solution with a concentration of 20% was obtained. The polycarbonate (copolymer A) obtained by removing the solvent from this solution had a molar ratio of biscresol fluorene to bisphenol A of 70:30 (polymer yield 97%). In addition, this polymer had an intrinsic viscosity of 0.674 and a Tg of 226 ° C.

  To 75 parts by mass of a mixed solvent of methylene chloride and ethanol containing 4 parts by mass of ethanol, 25 parts by mass of the polycarbonate was dissolved while stirring at 25 ° C. to obtain a transparent and viscous dope. The dope was cast on a 100 m stainless steel belt, which was blown with dry air and the dew point was controlled to 12 ° C. or less, and was peeled off. The residual solvent concentration at that time was 35%. From the fact that the peelability was good and the charge was small, no peeling step or peeling streaks were observed on the film surface by visual observation. Thereafter, when the residual solvent concentration was 2%, the width was maintained and dried. Then, it dried until the residual solvent density | concentration became 1% or less, and obtained the aromatic polycarbonate film. Ro = 28 nm, and the slow axis of the film was an angle with respect to the casting direction. The orientation angle was 0 °. The surface roughness Ra = 0.4 nm and the haze indicating light scattering was 0.9%. The film thickness was 125 μm.

Next, 50m prepare the film obtained by the above, according to the method disclosed in Japanese Patent Laid-Open No. 6-222213, the film in roll form is sandwiched in different roller R ₄ and roller R ₅ peripheral speeds shown in FIG. 5 did.

In FIG. 5, a roller R ₁ is a delivery roller, and R ₂ and R ₃ are nip rollers and residual heat rollers that do not have a drive system. R ₄ and R ₅ are rollers each having a drive system, and are rollers capable of arbitrarily controlling the peripheral speed difference. In addition, the pressure between R ₄ and R ₅ can be controlled by hydraulic pressure. R ₆ is a winding roller having a drive system, and the winding speed is controlled by a tension controller. A heater inside from R ₂ to the roller of R _5, and a temperature sensor is attached to the roller surface, and feeding back the temperature from the temperature sensor to the heater, the temperature control at ± 1 ° C. of accuracy by the PID control is doing.

  The molding conditions of the comparative optical compensation film are as follows.

Peripheral speed of roller R ₄ and roller R ₅ : 2.8 m / min, 1.9 m / min
Surface temperature of roller R ₄ and roller R ₅ : 145 ° C.
Roller _{R 4,} the force exerted on the sandwiched roller _{R 5} Film: 2000 kg
Roller _{R 4,} roll diameter of the roller _{R 5:} 150 mm
Distance between roller R ₄ and roller R ₅ : 123 μm
Next, the obtained film was subjected to transverse uniaxial stretching with a tenter to obtain a comparative optical compensation film N. The stretching conditions (stretching after roller treatment) are as follows.

Stretching temperature: 160 ° C
Stretch ratio: 7%
Film feed speed: 3m / min
A 50 m optical compensation film was prepared, and the 30 to 39 m central portion of the film was cut into 10 sheets every 1 m, and the inclination angle from the film surface was measured with a cobra. Further, scratches were counted for 10 sheets.

<Preparation of polarizing plate>
A 120 μm thick polyvinyl alcohol film was immersed in an aqueous solution containing 1 part of iodine, 2 parts of potassium iodide, and 4 parts of boric acid, and stretched 4 times at 50 ° C. to obtain a polarizing film. Next, Konica Minoltac KC8UX was immersed in a 2 mol / liter sodium hydroxide solution at 60 ° C. for 1 minute, further washed with water and dried, and then adhered to both sides of the polarizing film with a polyvinyl alcohol adhesive having a solid content of 2% by mass. Together, a polarizing plate was produced.

<Evaluation by liquid crystal display device>
A 15-inch display Multi Sync LCD1525J manufactured by NEC was used after removing the optical compensation film and the polarizing plate previously bonded.

About the optical compensation film of the said sheet | seat, it has arrange | positioned together with the polarizing plate on both surfaces of the liquid crystal cell. The viewing angle of the liquid crystal display device was measured by EZ-contrast 160D manufactured by ELDIM. The viewing angle was expressed in the range of the tilt angle from the normal direction with respect to the panel surface where the contrast ratio at the time of white display and black display of the liquid crystal cell is 10 or more. Table 1 shows the minimum and maximum minimum and maximum values of the viewing angle measured for the 10 sheets. Further, the number of bright spot defects was counted by visual evaluation of a viewing angle and a microscope and visual evaluation, and the numbers were shown in Table 1 as 1 m ² .

  Subsequently, using an apparatus conforming to the stretching apparatus disclosed in Japanese Patent Application Laid-Open No. 2008-44339, the film is stretched under the conditions shown in Table 1 in the transport direction and in the direction orthogonal to the transport direction to produce a raw film. As shown in FIG. 6, five driving rollers are arranged on the upper side of the film and five following rotating rollers are arranged on the lower side. That is, the film obtained as described above is sandwiched between the five roller pairs. Conveyance speed: It conveyed at 3 m / min, gave distortion deformation in the film, and produced optical compensation film AM and OT. The rotational load of the following rotary roller was adjusted so that the torque load of the drive motor was 500 N · m. In this way, an optical compensation film of 50 m was prepared, a film center part of 30 to 39 m was cut into 10 sheets every 1 m, and an inclination angle and an Rt value from the film surface were determined by an automatic birefringence meter: KOBRA-21ADH. (Oji Scientific Instruments Co., Ltd.) was used to measure on a film sample that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH.

  Further, 10 sheets were incorporated into the liquid crystal display device, and the viewing angle was evaluated. The number of bright spot defects and scratches was counted by a microscope and visual evaluation.

  The production stability was evaluated as follows based on whether or not continuous production of 100 m or more is possible.

○: Continuous production of 100 m or more is possible. X: Failure occurred at less than 100 m. Tables 1 and 2 show the above evaluation results.

  As is apparent from the results shown in Tables 1 and 2, the examples according to the present invention have fewer scratches and bright spot defects than the comparative examples, and the variation in the tilt angle is extremely small. It turns out that there is little nonuniformity when it is made.

Conceptual diagram showing the effect of the drive roller and follower rotation roller on the film The conceptual diagram which shows the example of arrangement | positioning of the drive roller and follower rotation roller which concern on this invention Conceptual diagram of a configuration example when the optical film according to the present invention is used as an optical compensation film and a polarizing plate protective film in a TN liquid crystal display Conceptual diagram showing the relationship between the twist angle, rubbing axis, and transmission axis of the liquid crystal of the polarizing plate The conceptual diagram which shows arrangement | positioning of the said roller in the apparatus which has a different circumferential speed roller The conceptual diagram which shows arrangement | positioning of the drive roller and a follower rotation roller in the Example of this invention.

Explanation of symbols

1R driving roller 2R following rotation roller B belt F resin film 1 first polarizing plate protective film 2 first polarizing film (3.5 ± 3 ° having transmission axis)
3 Second polarizing plate protective film 4 Viewing side glass cell substrate 5 Viewing side liquid crystal alignment layer (having a rubbing axis reference 0 °)
6 Liquid crystal layer (d: Liquid crystal cell gap)
7 Backlight side liquid crystal alignment layer (having rubbing axis 115 ± 22 °)
8 Backlight side glass cell substrate 9 Third polarizing plate protective film 10 Second polarizing film (having transmission axis 93.5 ± 3 °)
DESCRIPTION OF SYMBOLS 11 4th polarizing plate protective film 13 1st polarizing plate 14 TN type liquid crystal cell 15 2nd polarizing plate 16 Transmission axis (3.5 +/- 3 degree) of 1st polarizing plate
17 Rubbing axis of viewing side liquid crystal alignment layer (reference 0 °)
18 Back rubbing axis of the liquid crystal alignment layer (115 ± 22 °)
19 Transmission axis of second polarizing plate (93.5 ± 3 °)
R ₁ , R ₂ , R ₃ , R ₄ , R ₅ rollers

Claims (7)

It is a manufacturing method of an optical film which has a process 1 which satisfies the following condition 1 and a process 2 which satisfies the following condition 2, and manufactures an optical film by continuously conveying a resin film, wherein the thickness of the resin film in the step 1 A difference is generated between the refractive index in the vertical direction and the refractive index in the direction orthogonal to the traveling direction, and the direction in which the refractive index of the resin film is the smallest in the step 2 is inclined from the normal direction of the resin film surface. The method for producing an optical film is characterized in that the adjustment is performed so that the direction is adjusted.
Condition 1: Step 1 is a step in which the resin film is stretched x times in the direction orthogonal to the transport direction and y times in the transport direction, and the following conditional expression 1 is satisfied.
(Condition 1) 1.00 <x <2.50, 0.40 <y <1.00
Condition 2: Step 2 is a step in which a driving roller is brought into contact with one surface of the resin film and a follower rotating roller having a rotational load is brought into contact with the opposite surface of the resin film. The thickness d satisfies the following conditional expression 2.
(Condition 2) 0.40 × d <a <0.98 × d In the step 2 in which the resin film uses two types of rollers, a driving roller A and a follower rotating roller B, the peripheral speed of the roller A is A1 (m / min), and the speed after the resin film is separated from the roller is P1. The method for producing an optical film according to claim 1, wherein, when (m / min) is satisfied, the following conditional expression 3 is satisfied.
(Condition 3) 0.30 <P1 / A1 <1.00 The method for manufacturing an optical film according to claim 1, wherein the driving roller and the following rotation roller constitute a nip roller pair that sandwiches the resin film. 2. The resin film and the two types of rollers are in contact with each other (hereinafter also referred to as “contact part”) and before and after the contact part, the resin film is heated or cooled. 4. The method for producing an optical film according to any one of 3 above. 5. The optical film manufacturing method according to claim 1, wherein a plurality of the driving rollers or following rotation rollers are provided, and the contact is performed at a plurality of locations on the film conveyance path. Method. A driving roller that contacts one surface of the resin film and a follower rotating roller that contacts the opposite surface of the resin film and has a rotational load, and these two types of rollers serve as a means for conveying the resin film and are included in the resin film An apparatus for producing an optical film, which is a means for imparting strain deformation. It is used for implementation of the manufacturing method of the optical film as described in any one of Claims 1-5, The manufacturing apparatus of the optical film of Claim 6 characterized by the above-mentioned.

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