JPWO2011045991A1 - Optical film - Google Patents

Abstract

An object of the present invention is to improve retardation unevenness and alignment angle deviation in a thin film optical film caused by inferior heat resistance and brittleness peculiar to an acrylic resin. An object of the present invention is to contain an acrylic resin (A) having a weight average molecular weight Mw of 70,000 to less than 1,000,000, an acrylic resin (B) having a weight average molecular weight of 1,000,000 to 10,000,000, and a cellulose ester resin (C). And achieved by an optical film.

Description

  The present invention relates to an optical film used for a liquid crystal display device or the like.

  Polymethyl methacrylate (hereinafter abbreviated as PMMA), which is a representative of conventional acrylic resins, has been suitably used for optical films from the viewpoint of its excellent transparency, dimensional stability, low hygroscopicity, and the like.

  However, the PMMA film has poor heat resistance and has a problem that its shape changes when used under high temperatures or for long-term use.

  This problem is an important issue not only as a physical property of a single film but also in a polarizing plate and a display device using such a film. That is, in the liquid crystal display device, because the polarizing plate curls with the deformation of the film, the entire panel is warped, and the design phase difference changes even when used at the position on the viewing side surface. There has been a problem that the viewing angle fluctuates or the color changes.

  Patent Document 1 proposes a method of adding polycarbonate (hereinafter abbreviated as PC) to an acrylic resin in order to improve heat resistance. However, there is a limit to the solvent that can be used, and the compatibility between resins is insufficient. Therefore, it is easy to become cloudy and use as an optical film is difficult.

  On the other hand, PMMA films are inherently inferior in brittleness and have the property of being easily broken during production and use.

On the other hand, in order to improve both heat resistance and brittleness simultaneously, a method of blending a cellulose ester resin with a specific acrylic resin has been proposed. (Patent Document 2)
However, even in this method, when a thin film having a film thickness of 40 μm is manufactured, when the film is peeled off from the peeling roll, the film strength is weak and the film extends in the conveying direction. Since the force required for peeling is not uniform, when the film is stretched in the subsequent process, the retardation value is uneven (variation) and the optical slow axis direction (orientation angle) is largely misaligned. There was a problem caused by the lack.

JP-A-5-306344 International Publication No. 2009/047924 Pamphlet

  An object of the present invention is to improve retardation unevenness and misalignment of an orientation angle in a thin film optical film caused by inferior heat resistance and brittleness peculiar to an acrylic resin.

  The object of the present invention has been achieved by the following constitution.

  1. An optical film comprising an acrylic resin (A) having a weight average molecular weight Mw of 70,000 to less than 1,000,000, an acrylic resin (B) having a weight average molecular weight of 1,000,000 to 10,000,000, and a cellulose ester resin (C).

  2. 2. The optical film as described in 1 above, wherein the optical film contains a retardation control agent (D).

  3. 3. The optical film as described in 1 or 2 above, wherein the optical film contains acrylic particles (E).

  According to the present invention, a thin acrylic resin film having high heat resistance and improved brittleness can be provided.

It is the schematic of the apparatus which manufactures the optical film of this invention.

The optical film of the present invention contains an acrylic resin (A) having a weight average molecular weight Mw of 70,000 to less than 1,000,000, an acrylic resin (B) having a weight average molecular weight of Mw of 100 to 10,000,000, and a cellulose ester resin (C). And
<Acrylic resin (A) having a weight average molecular weight Mw of 70,000 or more and less than 1,000,000>
The acrylic resin (A) used in the present invention includes a methacrylic resin. Although it does not restrict | limit especially as resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable.

  Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Saturated acids, maleic acids, fumaric acids, unsaturated divalent carboxylic acids such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, and the like. These may be used alone or in combination of two or more.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

  The acrylic resin (A) used in the optical film of the present invention preferably has a weight average molecular weight (Mw) of 100,000 or more and less than 1,000,000 from the viewpoint of mechanical strength as a film and fluidity when producing the film.

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

Solvent: THF
Column: Shodex KF807L (two Showa Denko Co., Ltd. connected and used)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (Mw = 20,700,000 to 580, a calibration curve with 6 samples was used. 6 samples are preferably used at approximately equal intervals.

  There is no restriction | limiting in particular as a manufacturing method of the acrylic resin (A) in this invention, You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used.

  Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. Furthermore, in order to control the reduced viscosity of the produced copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

A commercially available thing can be used as an acrylic resin (A) of this invention. For example, Delpet 80N (Mw = 100000) (manufactured by Asahi Kasei Chemicals Corporation), Dianal BR52 (Mw = 85000), BR80 (Mw = 95000), BR85 (Mw = 280000), BR88 (Mw = 4800000), Metabrene P-700A (Mw = 500,000) (manufactured by Mitsubishi Rayon Co., Ltd.), Kane Ace PA10 (Mw = 800000) (manufactured by Kaneka Corporation) and the like can be mentioned.
<Acrylic resin (B) having a weight average molecular weight of 1 million to 10 million>
The acrylic resin (B) of the present invention has a monomer composition similar to that of the acrylic resin (A) of the present invention and has a large weight average molecular weight.

  The acrylic resin (B) of the present invention can be prepared by a known method, and commercially available products can also be used. For example, Kane Ace PA20 (Mw = 1000000), PA40 (Mw = 6000000), PA60 (Mw = 8000000) (manufactured by Kaneka Corporation), methabrene P-551A (Mw = 1500,000), P-530A (Mw = 3100000) ( Mitsubishi Rayon Co., Ltd.).

  In addition, the measurement method similar to the said acrylic resin (A) was used for the weight average molecular weight of an acrylic resin (B).

The difference in weight average molecular weight between the acrylic resins (A) and (B) is 100,000 or more and 9 million or less, and preferably 500,000 or more and 5 million or less.
<Cellulose ester resin (C)>
The cellulose ester resin (C) of the present invention may be substituted with either an aliphatic acyl group or an aromatic acyl group, but is preferably substituted with an acetyl group.

  When the cellulose ester resin of the present invention is an ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically acetyl, propionyl, butyryl, isobutyryl, valeryl, pivaloyl, hexanoyl, Examples include octanoyl, lauroyl, stearoyl and the like.

  In the present invention, the aliphatic acyl group is meant to include those further having a substituent. When the aromatic ring is a benzene ring in the above-described aromatic acyl group, the substituent of the benzene ring Are exemplified.

  When the cellulose ester resin is an ester with an aromatic acyl group, the number of substituents X substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, particularly preferably One or two.

  Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

  As the structure used in the cellulose resin of the present invention, the cellulose ester resin has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group. Used, these may be single or mixed acid esters of cellulose.

  As for the substitution degree of the cellulose ester resin of the present invention, the total substitution degree (T) of the acyl group is 2.00 to 3.00, and the substitution degree (ac) of the acetyl group is 0 to 2.50. More preferably, the acyl group substitution degree (r) other than the acetyl group is 1.50 to 2.90.

  The acyl group other than the acetyl group preferably has 3 to 7 carbon atoms.

  In the cellulose ester resin of the present invention, those having an acyl group having 2 to 7 carbon atoms as a substituent, that is, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate It is preferably at least one selected from benzoate and cellulose benzoate.

  Among these, particularly preferable cellulose ester resins include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

  More preferably, the mixed fatty acid is a lower fatty acid ester of cellulose acetate propionate or cellulose acetate butyrate and having an acyl group having 2 to 4 carbon atoms as a substituent.

  The portion that is not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96.

If the weight average molecular weight (Mw) of the cellulose ester resin of the present invention is 75000 or more, the object of the present invention can be achieved even if it is about 1000000, but considering productivity, it is 75000 to 280000. The thing of 100000-2400 is more preferable.
<Optical film>
It is preferable that the optical film does not cause ductile fracture in the present invention. Here, the ductile fracture is caused by applying a stress larger than the strength of a certain material, and is defined as a fracture accompanied by significant elongation or drawing of the material before the final fracture. The fracture surface is characterized by numerous indentations called dimples.

  Therefore, “an optical film in which ductile fracture does not occur” is characterized in that breakage such as breakage is not observed even when a large stress is applied to bend the film in two.

  The demand for the brittleness of optical films is increasing from the viewpoint of reworkability and productivity as optical films become larger and thinner with the recent increase in liquid crystal display devices, and the above ductile fracture does not occur. Is required.

  In order to form the optical film which does not cause ductile fracture of the present invention, it is achieved by selecting the material composition such as acrylic resin, cellulose ester, and other additives used as described above.

  The optical film of the present invention has a tension softening point of 105 ° C. or lower when considering use in a high-temperature environment such as a projector having a high haze and a high temperature such as a projector or a vehicle-mounted display device. It is preferable to set it as 145 degreeC, and it is more preferable to control to 110 to 130 degreeC.

  As a specific method for measuring the tension softening point temperature of the optical film, for example, a Tensilon tester (ORIENTEC, RTC-1225A) is used, and the optical film is cut into 120 mm (length) × 10 mm (width) and 10 N The temperature can be increased at a rate of temperature increase of 30 ° C./min while pulling with a tension of 30 ° C., and the temperature at 9 N is measured three times, and the average value can be obtained.

  The optical film of the present invention preferably has a glass transition temperature (Tg) of 110 ° C. or higher. More preferably, it is 120 ° C. or higher. Especially preferably, it is 150 degreeC or more.

  In addition, the glass transition temperature here is the intermediate | middle calculated | required according to JISK7121 (1987), using the differential scanning calorimeter (DSC-7 type | mold by Perkin Elmer), measured with the temperature increase rate of 20 degree-C / min. Point glass transition temperature (Tmg).

  In the optical film of the present invention, the number of defects within a film plane of 5 μm or more is 1/10 cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

  Here, the diameter of the defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope by the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

  The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

  In addition, when observing with reflected light, if the size of the defect is unclear, aluminum or platinum is deposited on the surface for observation.

  In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

  If the number of defects is greater than 1/10 cm square, for example, when the film is tensioned during processing in a later step, the film may break with the defects as a starting point, and productivity may be significantly reduced. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

  Moreover, even when it cannot be visually confirmed, when a hard coat layer or the like is formed on the film, the coating agent may not be formed uniformly, resulting in a defect (missing coating). Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. This refers to the foreign matter (foreign matter defect) in the film.

  In the measurement according to JIS-K7127-1999, the optical film of the present invention preferably has a breaking elongation in at least one direction of 10% or more, more preferably 20% or more.

  The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

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

  The upper limit of the thickness is not particularly limited, but in the case of forming a film by a solution casting method, the upper limit is about 250 μm from the viewpoint of applicability, foaming, solvent drying, and the like. The thickness of the film can be appropriately selected depending on the application.

  The optical film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve such excellent transparency expressed by the total light transmittance, it is necessary not to introduce an additive or a copolymer component that absorbs visible light, or to accurately filter foreign substances in the polymer. It is effective to reduce the diffusion and absorption of light inside the film.

  Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the acrylic resin.

  The optical film of the present invention is characterized in that the haze value (turbidity), which is one of the indices indicating transparency, is 1.0% or less. However, the luminance and contrast when incorporated in a liquid crystal display device are characteristic. From the point, it is preferably 0.5% or less.

  In order to achieve such a haze value, it is effective to remove foreign substances in the polymer by high-precision filtration and reduce the diffusion of light inside the film.

  In addition, the total light transmittance and haze value of the said optical film are the values measured according to JIS-K7361-1-1997 and JIS-K7136-2000.

  The optical film of the present invention can be preferably used as an optical film as long as the above physical properties are satisfied, but a film excellent in workability and heat resistance can be obtained by using the following composition. be able to.

  That is, from the viewpoint of achieving both workability and heat resistance, the optical film contains acrylic resin (A), (B) and cellulose ester resin in a mass ratio of 95: 5 to 30:70, and the cellulose ester resin. The total substitution degree (T) of the acyl group of (C) is 2.00 to 3.00, the acetyl group substitution degree (ac) is 0 to 2.50, and the number of carbon atoms of the acyl group other than the acetyl group is 3 to 7. And the weight average molecular weight (Mw) is preferably 75,000 to 280000.

  When the amount of the acrylic resin component is increased, for example, dimensional change under high temperature and high humidity is suppressed, and curling of the polarizing plate and warping of the panel when used as a polarizing plate can be remarkably reduced. Furthermore, in the composition in which the acrylic resin component is more than half, the above physical properties can be maintained for a longer time.

  The acrylic resin (A) and the cellulose ester resin (C) are preferably mixed at a mass ratio of 95: 5 to 30:70. The total amount of the acrylic resin (A) and the cellulose ester resin (C) is an acrylic resin. It is preferable that it is 99: 1-80: 20 with respect to (B).

  The optical film of the present invention may be configured to contain a resin other than the acrylic resins (A), (B), and the cellulose ester resin (C).

The total mass of acrylic resin (A), (B) and cellulose-ester resin (C) is 55-100 mass% of an optical film, Preferably it is 60-99 mass%.
<Phase difference control agent (D)>
In the present invention, the retardation control agent (D) can be added to the optical film. As the retardation control agent (D), compounds described in JP-A No. 2002-296421 and various ester plasticizers can be used. Hereinafter, preferred ester compounds will be described in detail.

  In the present invention, among various compounds described below, a compound having a structure in which aromatic rings are arranged in a plane when added and stretched as an additive is preferable.

  For this reason, a compound in which an aromatic ring is contained as a block in the main chain or at the terminal is preferred.

(Polyester polyol)
As the polyester polyol used in the present invention, a dehydration condensation reaction between a glycol having an average carbon number of 2 to 3.5 and a dibasic acid having an average carbon number of 4 to 5.5, or the glycol It is preferable to be produced by a conventional method by addition of a dibasic anhydride having an average carbon number of 4 to 5.5 and a dehydration condensation reaction.

《Glycol》
Examples of the glycol used in the polyester polyol include ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propanediol, 1,4-butylene glycol, and neopentyl. Glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, and the like. These may be used alone or in combination of two or more. For example, ethylene glycol or a mixture of ethylene glycol and diethylene glycol Is particularly preferably used.

  Regarding the above-mentioned glycol, it is preferable that the average number of carbon atoms of the glycol is in the range of 2 to 3.5 from the viewpoint of production of polyester polyol, compatibility with cellulose, transparency and the like.

  When a mixture of ethylene glycol and diethylene glycol is used as the glycol, the molar ratio of ethylene glycol / diethylene glycol is preferably 25 to 100/75 to 0, and for cellulose esters having excellent compatibility with cellulose esters. A modifier can be obtained. Furthermore, it is more preferably 25-40 / 75-60, and 60-95 / 40-5, and by adjusting to such a range, the crystallinity and melting point of the polyester polyol are close to conventional ones. Productivity is also improved.

《Dibasic acid》
Next, examples of the dibasic acid constituting the polyester polyol used in the present invention include succinic acid, glutaric acid, adipic acid, and sebacic acid.

  These can be used alone or in combination of two or more. For example, succinic acid or a mixture of succinic acid and terephthalic acid is particularly preferably used.

  Moreover, regarding the above-mentioned dibasic acid, it is preferable that the average number of carbon atoms of the dibasic acid is in the range of 4 to 5.5 from the viewpoint of production of polyester polyol, compatibility with cellulose, transparency, and the like. .

  When a mixture of succinic acid and terephthalic acid is used as the dibasic acid, the molar ratio of succinic acid / terephthalic acid is preferably 25-100 / 75-0 and has excellent compatibility with the cellulose ester. A cellulose ester modifier can be obtained.

  Furthermore, it is more preferably 25-40 / 75-60, and 60-95 / 40-5, and by adjusting to such a range, the crystallinity and melting point of the polyester polyol are close to conventional ones. Productivity is also improved.

  The glycol and dibasic acid constituting the polyester polyol used in the present invention include combinations other than the above, but the total of the average number of carbon atoms of the glycol and the average number of carbon atoms of the dibasic acid is 6-7. A combination of .5 is preferred.

  The polyester polyol obtained from the glycol and dibasic acid may have a number average molecular weight in the range of 1,000 or more and 200,000 or less, more preferably 1000 to 5000 basically polyester having a hydroxyl group (hydroxyl group) terminal, Those having a number average molecular weight of 1200 to 4000 are particularly preferably used.

  By using a polyester polyol having a number average molecular weight in such a range, a retardation control agent (cellulose ester modifier) excellent in compatibility with the cellulose ester can be obtained by solid phase reaction.

  In obtaining the effect of the present invention, the polyester polyol having a number average molecular weight of 1000 or more is preferably contained in the film in an amount of 2 to 30% by mass from the viewpoint of retardation development, compatibility, moisture permeability, and the like. More preferably, it is 10-20 mass%.

  Actually, the content of the polymer in the film depends on the type of polymer and the weight average molecular weight, and the performance such as dimensional stability, retentivity, and transmittance is within the range in which dope, web, and phase separation do not occur after film formation. It is decided accordingly.

  On the other hand, the content of the carboxyl group terminal in the polyester polyol used in the present invention is preferably 1/20 or less of the hydroxyl group (hydroxyl group) terminal from the viewpoint of the effect of the present invention. Furthermore, it is more preferable to stop at 1/40 or less.

  In producing the above-described polyester polyol, conventionally known esterification catalysts such as metal organic acid salts or metal chelate compounds such as titanium, zinc, lead and zirconium, or antimony oxide can be used.

  As such an esterification catalyst, for example, tetraisopropyl titanate, tetrabutyl titanate and the like are preferably used, and 0.0005 to 0.005 with respect to a total of 100 parts by mass of glycol (a) and dibasic acid (b) used. 02 parts by weight are preferably used.

  Polycondensation of the polyester polyol is performed by a conventional method.

  For example, a direct reaction of the above dibasic acid and glycol, the above dibasic acid or an alkyl ester thereof, for example, a polyesterification reaction or transesterification reaction between a dibasic acid methyl ester and a glycol, or a hot melt condensation method, Alternatively, it can be easily synthesized by any method of dehydrohalogenation reaction between acid chlorides of these acids and glycols, but polyester polyols whose number average molecular weight is not so large are preferably by direct reaction.

  The polyester polyol having a high distribution on the low molecular weight side has very good compatibility with the cellulose ester, and after forming the film, a water vapor permeability is small, and a cellulose ester film rich in transparency can be obtained.

  A conventional method can be used as a method for adjusting the molecular weight without particular limitation. For example, although it depends on the polymerization conditions, the amount of these monovalent compounds can be controlled by a method of blocking the molecular ends with a monovalent acid or monovalent alcohol. In this case, a monovalent acid is preferable from the viewpoint of polymer stability.

  For example, acetic acid, propionic acid, butyric acid, pivalic acid, benzoic acid and the like can be mentioned, but during the polycondensation reaction, such monovalent acid is not removed from the system but stopped and removed from the reaction system. Those which are easy to be distilled off when being removed from the system are selected, but these may be mixed and used.

  In the case of direct reaction, the number average molecular weight can also be adjusted by measuring the timing at which the reaction is stopped by the amount of water distilled off during the reaction. In addition, it can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged or by controlling the reaction temperature.

(Aromatic terminal ester plasticizer)
As the phase difference controlling agent according to the present invention, an aromatic terminal ester plasticizer represented by the following general formula (I) can be used.

Formula (I) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (I), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

  As the benzene monocarboxylic acid component of the aromatic terminal ester plasticizer, for example, benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, There are aminobenzoic acid, acetoxybenzoic acid and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the aromatic terminal ester plasticizer include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, and 1,3-butanediol. 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1 , 3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1,3-hexanediol There are 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are used as one kind or a mixture of two or more kinds. The

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Or it can be used as a mixture of two or more.

  Examples of the aryl glycol component having 6 to 12 carbon atoms of the aromatic terminal ester include hydroquinone, resorcin, bisphenol A, bisphenol F, and bisphenol. These glycols are used as one kind or a mixture of two or more kinds. Can be used.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds.

  Examples of the aryl dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The aromatic terminal ester plasticizer has a number average molecular weight of preferably 300 to 2000, more preferably 500 to 1500. The acid value is 0.5 mgKOH / g or less, the hydroxyl group (hydroxyl group) value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl group (hydroxyl group) value is 15 mgKOH / g or less. Those are preferred.

<< Acid value, hydroxyl group (hydroxyl group) value of aromatic terminal ester >>
“Acid value” refers to the number of milligrams of potassium hydroxide necessary to neutralize the acid (carboxyl group present at the molecular terminal) contained in 1 g of a sample. The acid value and the hydroxyl group (hydroxyl group) value are measured in accordance with JIS K0070.

  Although the specific compound of an aromatic terminal ester plasticizer is shown below, this invention is not limited to this.

  The content of the aromatic terminal ester plasticizer is preferably 1 to 20% by mass, and particularly preferably 3 to 11% by mass in the cellulose ester film.

(Polyhydric alcohol ester)
In the present invention, a polyhydric alcohol ester plasticizer can be further used as the retardation control agent.

  The polyhydric alcohol ester used in the present invention comprises an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  The polyhydric alcohol used in the present invention is represented by the following general formula (1).

General formula (1) R1- (OH) _n
In the formula, R1 represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic or phenolic hydroxyl group (hydroxyl group).

  Examples of preferable polyhydric alcohols include the following.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol.

  Of these, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used.

  Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferable in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used.

  It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10. The use of acetic acid is preferred because the compatibility with the cellulose ester is increased, and it is also preferred to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or derivatives thereof can be mentioned. In particular, benzoic acid is preferred.

  Although there is no restriction | limiting in particular in the molecular weight of a polyhydric alcohol ester, It is preferable that it is the range of molecular weight 300-1500, and it is further more preferable that it is the range of 350-750.

  A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  The specific compound of a polyhydric alcohol ester is shown below.

(Sugar ester compound)
The retardation control agent is preferably an optical film including a sugar ester compound obtained by esterifying a hydroxyl group (hydroxyl group) of a sugar compound in which 1 to 12 at least one structure selected from a furanose structure and a pyranose structure is bonded. .

  Examples of the sugar compound include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose and the like, and those having both a furanose structure and a pyranose structure are particularly preferable.

The ester compound is a monosaccharide (α-glucose, β-fructose) benzoate or a monosaccharide represented by the following general formula (A): —OR ₁₂ , —OR ₁₅ , —OR ₂₂ , —OR ₂₅ It is preferable that the benzoic acid ester of the polysaccharide of m + n = 2-12 produced | generated by dehydration condensation of arbitrary two or more places.

  The sugar ester compound is one in which part or all of the hydroxyl group (hydroxyl group) of the sugar compound is esterified or a mixture thereof.

  The benzoic acid in the above general formula may further have a substituent, for example, an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group have a substituent. You may have.

  Although the specific example of an esterified compound is given to the following, this invention is not limited to this.

  The optical film according to the present invention preferably contains 1 to 30% by mass of the sugar ester compound in the total amount of the resin constituting the optical film in order to suppress the fluctuation of the retardation value and stabilize the display quality.

  As a sugar ester compound, it is marketed as Monopet SB (Daiichi Kogyo Seiyaku Co., Ltd.).

(Other phase difference control agents)
As the phase difference controlling agent, those containing bisphenol A in the molecule are also preferred. A compound in which ethylene oxide or propylene oxide is added to both ends of bisphenol A can be used.

  For example, BP series such as New Pole BP-2P, BP-3P, BP-23P, BP-5P, BPE-20 (F), BPE-20NK, BPE-20T, BPE-40, BPE-60, BPE-100, There are BPE series (manufactured by Sanyo Chemical Co., Ltd.) such as BPE-180, and BPX series (manufactured by Adeka Co., Ltd.) such as Adeka polyether BPX-11, BPX-33, BPX-55.

  Diallyl bisphenol A, dimethallyl bisphenol A, tetrabromobisphenol A with bisphenol A substituted with bromine, oligomers and polymers obtained by polymerizing this, bisphenol A bis (diphenyl phosphate) substituted with diphenyl phosphate, etc. Can be used.

  Polycarbonate obtained by polymerizing bisphenol A, polyarylate obtained by polymerizing bisphenol A with a dibasic acid such as terephthalic acid, and an epoxy oligomer or polymer polymerized with an epoxy-containing monomer can also be used.

  Modiper CL130D or L440-G obtained by graft polymerization of bisphenol A and styrene, styrene acrylic, or the like can also be used.

  The optical film according to the present invention can also contain two or more retardation control agents. In this case, by optimizing the combination, elution of the phase difference controlling agent can be reduced.

Although the reason is not clear, elution is suppressed by the ability to reduce the amount added per type and the interaction between the two phase difference control agents and the acrylic resin (A) -containing composition. Seem.
<Acrylic particles (E)>
In the present invention, the optical film may contain acrylic particles (E).

  The acrylic particles (E) of the present invention are characterized by being present in the state of particles in the optical film with the acrylic resins (A) and (B) and the cellulose ester resin (C) (also referred to as incompatible state). is there.

  The acrylic particles (E) are obtained, for example, by collecting a predetermined amount of the produced optical film, dissolving in a solvent, stirring, and sufficiently dissolving / dispersing, so that the pore size is less than the average particle size of the acrylic particles (E). It is preferable that the weight of the insoluble matter filtered and collected using the PTFE membrane filter is 90% by mass or more of the acrylic particles (E) added to the optical film.

  The acrylic particles (E) used in the present invention are not particularly limited, but are preferably acrylic particles (E) having a layer structure of two or more layers, particularly the following multilayer structure acrylic granular composite. It is preferable.

  The multilayer structure acrylic granular composite is formed by laminating an innermost hard layer polymer, a cross-linked soft layer polymer exhibiting rubber elasticity, and an outermost hard layer polymer from the center to the outer periphery. This refers to a particulate acrylic polymer having a structure.

  Preferred embodiments of the multilayer structure acrylic granular composite used in the acrylic resin composition of the present invention include the following.

  (A) Monomer composed of 80 to 98.9% by mass of methyl methacrylate, 1 to 20% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 0.01 to 0.3% by mass of polyfunctional grafting agent An innermost hard layer polymer obtained by polymerizing the body mixture, (b) in the presence of the innermost hard layer polymer, 75 to 98.5% by mass of an alkyl acrylate having an alkyl group with 4 to 8 carbon atoms, A crosslinked soft layer polymer obtained by polymerizing a monomer mixture comprising a multifunctional crosslinking agent of 0.01 to 5% by mass and a multifunctional grafting agent of 0.5 to 5% by mass; (c) the innermost hard In the presence of a polymer comprising a layer and a crosslinked soft layer, a monomer mixture comprising 80 to 99% by mass of methyl methacrylate and 1 to 20% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is polymerized. Outermost hard layer weight And the obtained three-layer structure polymer is an innermost hard layer polymer (a) 5 to 40% by mass, a soft layer polymer (b) 30 to 60% by mass, and The outermost hard layer polymer (c) is composed of 20 to 50% by mass, has an insoluble part when fractionated with acetone, and an acrylic granular composite having a methyl ethyl ketone swelling degree of 1.5 to 4.0 at the insoluble part. .

  As disclosed in Japanese Patent Publication No. 60-17406 or Japanese Patent Publication No. 3-39095, not only the composition and particle size of each layer of the multilayer structure acrylic granular composite are defined, but also the multilayer structure acrylic granular composite. By setting the tensile modulus of the body and the degree of swelling of methyl ethyl ketone in the acetone-insoluble part within a specific range, it is possible to realize a further sufficient balance between impact resistance and stress whitening resistance.

  Here, the innermost hard layer polymer (a) constituting the multi-layer structure acrylic granular composite is 80 to 98.9% by mass of methyl methacrylate and 1 to 20% of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group. % And a polyfunctional grafting agent obtained by polymerizing a monomer mixture consisting of 0.01 to 0.3% by mass.

  Here, examples of the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like. And n-butyl acrylate are preferably used.

  The proportion of the alkyl acrylate unit in the innermost hard layer polymer (a) is 1 to 20% by mass. When the unit is less than 1% by mass, the thermal decomposability of the polymer is increased, while the unit is 20% by mass. If it exceeds 50%, the glass transition temperature of the innermost hard layer polymer (c) is lowered, and the impact resistance imparting effect of the three-layer structure acrylic granular composite is lowered.

  Examples of the polyfunctional grafting agent include polyfunctional monomers having different polymerizable functional groups, such as allyl esters of acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and allyl methacrylate is preferably used. .

  The polyfunctional grafting agent is used to chemically bond the innermost hard layer polymer and the soft layer polymer, and the ratio used during the innermost hard layer polymerization is 0.01 to 0.3% by mass. .

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

  Here, as the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group, n-butyl acrylate or 2-ethylhexyl acrylate is preferably used.

  In addition to these polymerizable monomers, it is possible to copolymerize 25% by mass or less of other monofunctional monomers capable of copolymerization.

  Other monofunctional monomers that can be copolymerized include styrene and substituted styrene derivatives. As the ratio of the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group and styrene increases, the glass transition temperature of the produced polymer (b) decreases as the former increases, that is, it can be softened.

  On the other hand, from the viewpoint of the transparency of the resin assembly, the refractive index of the soft layer polymer (b) at room temperature is set to the innermost hard layer polymer (a), the outermost hard layer polymer (c), and the hard heat. It is more advantageous to make it closer to the plastic acrylic resin, and the ratio between them is selected in consideration of these.

  For example, in applications where the coating layer thickness is small, it is not always necessary to copolymerize styrene.

  As the polyfunctional grafting agent, those mentioned in the item of the innermost layer hard polymer (a) can be used. The polyfunctional grafting agent used here is used to chemically bond the soft layer polymer (b) and the outermost hard layer polymer (c), and the proportion used during the innermost hard layer polymerization is impact resistance. 0.5-5 mass% is preferable from a viewpoint of the property provision effect.

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

  The polyfunctional cross-linking agent used here is used to generate a cross-linked structure at the time of polymerization of the soft layer (b) and develop an effect of imparting impact resistance. However, if the above-mentioned polyfunctional grafting agent is used during the polymerization of the soft layer, the polyfunctional crosslinking agent is not an essential component because the crosslinked structure of the soft layer (b) is generated to some extent. Is preferably 0.01 to 5% by mass from the viewpoint of imparting impact resistance.

  In the presence of the innermost hard layer polymer (a) and the soft layer polymer (b), the outermost hard layer polymer (c) constituting the multilayer structure acrylic granular composite is 80 to 99 masses of methyl methacrylate. % And an alkyl group having 1 to 20% by mass of an alkyl acrylate having 1 to 8 carbon atoms are preferably obtained by polymerizing a monomer mixture.

  Here, as the acrylic alkylate, those described above are used, and methyl acrylate and ethyl acrylate are preferably used. The ratio of the alkyl acrylate unit in the outermost hard layer (c) is preferably 1 to 20% by mass.

  Further, for the purpose of improving the compatibility with the acrylic resin (A) during the polymerization of the outermost hard layer (c), it is also possible to use an alkyl mercaptan or the like as a chain transfer agent in order to adjust the molecular weight.

  In particular, it is preferable to provide the outermost hard layer with a gradient such that the molecular weight gradually decreases from the inside toward the outside in order to improve the balance between elongation and impact resistance. As a specific method, the monomer mixture for forming the outermost hard layer is divided into two or more, and the molecular weight is increased from the inside by a method of sequentially increasing the amount of chain transfer agent added each time. It is possible to make it smaller toward the outside.

  The molecular weight formed at this time can also be examined by polymerizing the monomer mixture used each time under the same conditions and measuring the molecular weight of the obtained polymer.

  The particle diameter of the acrylic granular composite which is a multilayer structure polymer preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 nm or less, and more preferably 20 nm or more and 500 nm or less. More preferably, it is most preferably 50 nm or more and 400 nm or less.

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

  Examples of such commercially available multilayered acrylic granular composites include, for example, “Metablene” manufactured by Mitsubishi Rayon Co., “Kane Ace” manufactured by Kaneka Chemical Co., Ltd., “Paralloid” manufactured by Kureha Chemical Co., Ltd., Rohm and Haas “Acryloid” manufactured by KK, “Staffyroid” manufactured by Ganz Kasei Kogyo Co., Ltd., “Parapet SA” manufactured by Kuraray Co., Ltd., and the like can be used alone or in combination of two or more.

  Further, specific examples of acrylic particles (E-1) which are graft copolymers suitably used as acrylic particles (E) preferably used in the present invention include unsaturated carboxylic acids in the presence of a rubbery polymer. A monomer mixture comprising an acid ester monomer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith A polymerized graft copolymer may be mentioned.

  Although there is no restriction | limiting in particular in the rubbery polymer used for the acrylic particle (E-1) which is a graft copolymer, Diene type rubber, acrylic type rubber, ethylene type rubber, etc. can be used. Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer. , Butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, and ethylene-acrylic acid Examples thereof include a methyl copolymer. These rubbery polymers can be used alone or in a mixture of two or more.

  Moreover, since the transparency of the optical film of this invention can be obtained when each refractive index of acrylic resin (A), (B) and acrylic particle (E) is approximated, it is preferable. Specifically, the refractive index difference between the acrylic particles (E) and the acrylic resins (A) and (B) is preferably 0.05 or less, more preferably 0.02 or less, especially 0.01 or less. It is preferable.

  In order to satisfy such a refractive index condition, a method of adjusting the monomer unit composition ratio of acrylic resins (A) and (B) and / or a rubbery polymer used for acrylic particles (E) Alternatively, the refractive index difference can be reduced by a method of adjusting the composition ratio of monomers, and an optical film excellent in transparency can be obtained.

  Note that the difference in refractive index referred to here is a solution in which the optical film of the present invention is sufficiently dissolved in a solvent in which the acrylic resins (A) and (B) are soluble under suitable conditions, and this is centrifuged. By separating the solvent-soluble part and the insoluble part by the above operation, and purifying the soluble part (acrylic resins (A) and (B)) and the insoluble part (acrylic particles (E)), respectively, the measured refractive index was measured. The difference of (23 degreeC, measurement wavelength: 550nm) is shown.

  In the present invention, the method of blending the acrylic particles (E) with the acrylic resins (A) and (B) is not particularly limited, and after the acrylic resins (A) and (B) and other optional components are previously blended. Usually, at 200 to 350 ° C., a method of uniformly kneading with a single or twin screw extruder while adding acrylic particles (E) is preferably used.

  Further, a method in which acrylic particles (E) are dispersed in advance is added to and mixed with a solution (dope solution) in which acrylic resins (A), (B) and cellulose ester resin (C) are dissolved, and acrylic particles ( A method such as in-line addition of a solution obtained by dissolving and mixing E) and other optional additives can be used.

  A commercially available thing can also be used as an acrylic particle of this invention. For example, metabrene W-341 (E2) (manufactured by Mitsubishi Rayon Co., Ltd.), Chemisnow MR-2G (E3), MS-300X (E4) (manufactured by Soken Chemical Co., Ltd.) and the like can be mentioned.

  The optical film of the present invention preferably contains 0.5 to 45% by mass of acrylic particles (E) with respect to the total mass of the resin constituting the film.

<Other additives>
In the optical film of the present invention, a plasticizer can be used in combination in order to improve the fluidity and flexibility of the composition. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

  Of these, polyester and phthalate plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

  Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

  The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

  In particular, when adipic acid, phthalic acid or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

  The ester plasticizer may be any of ester, oligoester and polyester types, and the molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

  The viscosity of the plasticizer has a correlation with the molecular structure and molecular weight. In the case of an adipic acid plasticizer, the viscosity is preferably in the range of 200 to 5000 mPa · s (25 ° C.) in view of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

  The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the composition containing the acrylic resins (A) and (B).

  The composition containing the acrylic resins (A) and (B) of the present invention preferably contains an ultraviolet absorber, and as the ultraviolet absorber used, a benzotriazole-based, 2-hydroxybenzophenone-based or salicylic acid phenyl ester-based And the like. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone And benzophenones.

  Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

  In addition, since the transition from the thin coating layer to the substrate layer is particularly small and hardly precipitates on the surface of the laminate, the amount of contained UV absorber is maintained for a long time, and the durability of the weather resistance improvement effect is excellent. From the point of view, it is preferable.

  Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl L] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine and the like, hindered phenol and hindered amine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

  Furthermore, various antioxidants can be added to the acrylic resins (A) and (B) used in the optical film of the present invention in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to give the optical film antistatic performance.

  As the acrylic resin composition of the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

  Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

  Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl). Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

<Optical film formation>
An example of a method for producing an optical film will be described, but the present invention is not limited to this.

  As a method for forming the optical film of the present invention, production methods such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, and a hot press method can be used. From the standpoint of suppressing optical defects such as die lines and optical defects such as die lines, solution casting by casting is preferred.

(Organic solvent)
The organic solvent useful for forming the dope when the optical film of the present invention is produced by the solution casting method is acrylic resin (A), (B), cellulose ester resin (C), and other additives at the same time. Any material that can be dissolved can be used without limitation.

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy, and when the proportion of alcohol is small, acrylic resins (A) and (B) in a non-chlorine organic solvent system ) And also promote the dissolution of the cellulose ester resin (C).

  In particular, acrylic resin (A), (B), cellulose ester resin (C) and acrylic particles (E) are added to a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. 3) is preferably a dope composition in which at least 15 to 45 mass% in total is dissolved.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

  Hereinafter, the preferable film forming method of the optical film of the present invention will be described.

1) Dissolution Step In the organic solvent mainly composed of a good solvent for the acrylic resins (A) and (B) and the cellulose ester resin (C), the acrylic resins (A) and (B) and the cellulose ester resin ( C), in some cases, the acrylic particles (E), other additives are dissolved with stirring to form a dope, or the acrylic resin (A), (B), cellulose ester resin (C) solution is optionally In this step, an acrylic particle (E) solution and other additive solutions are mixed to form a dope that is a main solution.

  For dissolving the acrylic resins (A), (B) and the cellulose ester resin (C), a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, Various methods such as a method using a cooling dissolution method as described in JP-A-9-95544, JP-A-9-95557, or JP-A-9-95538, a method using a high pressure as described in JP-A-11-21379, etc. However, a method of pressurizing at a temperature equal to or higher than the boiling point of the main solvent is preferable.

  The total amount of the acrylic resins (A) and (B) and the cellulose ester resin (C) in the dope is preferably 15 to 45% by mass. An additive is added to the dope during or after dissolution to dissolve and disperse, then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  Filtration is preferably performed using a filter medium having a collected particle size of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  In this method, the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added are only aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

  FIG. 1 is a diagram schematically showing a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

  If necessary, large agglomerates are removed from the acrylic particle charging kettle 41 by the filter 44 and fed to the stock kettle 42. Thereafter, the acrylic particle additive solution is added from the stock kettle 42 to the main dope dissolving kettle 1.

  Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material. The return material may contain acrylic particles. In that case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the return material.

  The additive solution containing acrylic particles preferably contains 0.5 to 10% by mass of acrylic particles, more preferably 1 to 10% by mass, and 1 to 5% by mass. Most preferably.

  The above range is preferable because the smaller the acrylic particle content, the lower the viscosity and the easier the handling, and the higher the acrylic particle content, the smaller the addition amount and the easier the addition to the main dope.

  The return material is a product obtained by finely pulverizing the optical film, which is generated when the optical film is formed, and is obtained by cutting off both sides of the film, or by using an optical film original that has been speculated out due to scratches, etc. .

  In addition, an acrylic resin, a cellulose ester resin, and, in some cases, acrylic particles kneaded into pellets can be preferably used.

2) Casting process An endless metal belt 31, such as a stainless steel belt or a rotating metal drum, which feeds the dope through a liquid feed pump (for example, a pressurized metering gear pump) to the pressure die 30 and transfers it infinitely. This is a step of casting the dope from the pressure die slit to the casting position on the support.

  A pressure die that can adjust the slit shape of the die base and facilitates uniform film thickness is preferred. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

  To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

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

  In addition, it is preferable that the residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. When peeling off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be impaired, and slippage and vertical stripes are likely to occur due to peeling tension, so the balance between economic speed and quality The amount of residual solvent is determined.

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

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, when wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension that can be peeled to 166.6 N / m, and then peel at a minimum tension to 137.2 N / m, and particularly preferably peel at a minimum tension to 100 N / m.

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

5) Drying and stretching step After peeling, a drying device 35 that alternately conveys the web through a plurality of rolls arranged in the drying device and / or a tenter stretching device 34 that clips and conveys both ends of the web with a clip are used. And dry the web.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout the drying is generally carried out at 40-250 ° C. It is particularly preferable to dry at 40 to 160 ° C.

  When a tenter stretching apparatus is used, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

  It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  In addition, extending | stretching operation may be divided | segmented and implemented in multiple steps, and it is also preferable to implement biaxial stretching in a casting direction and a width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

  In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferable draw ratio of simultaneous biaxial stretching can be taken in the range of x1.01 to x1.5 times in both the width direction and the longitudinal direction.

  When the tenter is used, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and it is preferable to perform drying while applying the tenter until the residual solvent amount of the web becomes 10% by mass or less. More preferably, it is 5% by mass or less.

  30-150 degreeC is preferable, as for the drying temperature in the case of performing a tenter, 50-120 degreeC is more preferable, and 70-100 degreeC is the most preferable.

  In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C Is more preferable, and within ± 1 ° C. is most preferable.

6) Winding step This is a step of winding the optical film by the winder 37 after the residual solvent amount in the web is 2% by mass or less, and the dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. A film with good properties can be obtained.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  The optical film of the present invention is preferably a long film. Specifically, the optical film has a thickness of about 100 m to 5000 m and is usually provided in a roll shape. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2m.

Although there is no restriction | limiting in particular in the film thickness of the optical film of this invention, When using for the polarizing plate protective film mentioned later, it is preferable that it is 20-200 micrometers, it is more preferable that it is 25-100 micrometers, and it is 30-80 micrometers. It is particularly preferred.
<Polarizing plate>
The polarizing plate used in the present invention can be produced by a general method. It is preferable that an adhesive layer is provided on the back side of the optical film of the present invention, and is bonded to at least one surface of a polarizer produced by immersion and stretching in an iodine solution.

  The film may be used on the other surface, or another polarizing plate protective film may be used. For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KV8UY-HA, KV8UX-RHA, OP Etc.) are preferably used.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound.

As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. It is preferable to use a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded.

Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

  The pressure-sensitive adhesive may be a one-component type or a type that is used by mixing two or more components before use.

The pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The density | concentration of the said adhesive liquid should just be suitably determined with the film thickness after adhesion, the coating method, the coating conditions, etc., and is 0.1-50 mass% normally.
<Liquid crystal display device>
By incorporating the polarizing plate bonded with the optical film of the present invention into a liquid crystal display device, various liquid crystal display devices with excellent visibility can be produced. The polarizing plate according to the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

  The polarizing plate according to the present invention is a reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type, etc. Preferably used. In particular, in a large-screen display device having a screen size of 30 or more, especially 30 to 54, there is no white spot at the periphery of the screen, and the effect is maintained for a long time.

  In addition, there was little color unevenness, glare and wavy unevenness, and the eyes were not tired even during long-time viewing.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
The following acrylic resins (A) A1 to A6 and acrylic resins (B) B1 to B7 were prepared by known methods, and commercially available resins were obtained.
A1: (PMMA) Mw300000
A2: (PMMA) Mw 70000
A3: (PMMA) Mw85000
A4: (PMMA) Mw100,000
A5: Poly (MMA-St) mass ratio 90:10 Mw 280000
A6: poly (MMA-CHMI-St) mass ratio 90: 5: 5 Mw 90000
A7: Metabrene P-700 (PMMA) Mw 500,000 A8: Kane Ace PA10: Poly (MMA-BA) Mass ratio 70:30 Mw 800,000 B1: (PMMA) Mw 1,000,000 B2: (PMMA) Mw 1.15 million B3: Metabrene P-551A: Poly (MMA-MA) mass ratio 85:15 Mw 1,500,000 B4: methabrene P-530A: poly (MMA-BA) mass ratio 85:15 Mw 3,100,000 B5: Kaneace PA40: poly (MMA-BA) mass ratio 70:30 Mw 600 10,000 B6: Kane Ace PA60: Poly (MMA-BA) mass ratio 70:30 Mw 9 million B7: Poly (MMA-BA-St) mass ratio 80: 15: 5 Mw 3.1 million MMA: Methyl methacrylate St: Styrene CHMI: Cyclohexylmaleimide MA : Methyl acrylate BA: Buti As the acrylate cellulose ester resin (C), those shown in Table 1 were used.

<Preparation of optical film 1>
(Dope solution composition)
Acrylic resin A1 65 parts by weight Acrylic resin B4 5 parts by weight Cellulosic ester resin C1 30 parts by weight Methylene chloride 300 parts by weight Ethanol 40 parts by weight The above composition was sufficiently dissolved while heating to prepare a dope solution.

(Formation of acrylic resin film 1)
The produced dope solution was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m.

  The peeled acrylic resin web was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while being stretched 1.1 times in the width direction by a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%.

  After stretching with a tenter and relaxing at 130 ° C for 5 minutes, drying was completed while transporting the drying zone at 120 ° C and 130 ° C with a number of rolls, slitting to a width of 1.5 m, and 10 mm wide at both ends of the film. A knurling process having a thickness of 5 μm was performed, and the film was wound around a core having an inner diameter of 6 inches with an initial tension of 220 N / m and a final tension of 110 N / m.

  The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times.

  The residual solvent amount of the optical film 1 described in Tables 1 and 2 was 0.1%, the film thickness was 40 μm, and the winding length was 4000 m.

  Other optical films were the same as the optical film 1 except that the types and composition ratios of the acrylic resins (A) and (B) cellulose ester resin (C) were changed as shown in Tables 2 and 3 below. A sample was prepared.

"Evaluation method"
The following evaluation was implemented about the obtained optical film sample.

(Tension softening point)
The following evaluation was performed using a Tensilon tester (ORITC Corporation, RTC-1225A).

  An optical film conditioned for 24 hours in an air conditioning room at 23 ° C. and 55% RH is cut out at 120 mm (length) × 10 mm (width) under the same conditions, and pulled at a tension rate of 10 N at a rate of temperature increase of 30 ° C./min. The temperature was continuously increased, and the temperature at 9 N was measured three times, and the average was obtained.

(Brittleness = ductile fracture)
Brittleness was evaluated by the following ductile fracture test.

  An optical film conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH is cut out at 100 mm (length) × 10 mm (width) under the conditions of 5 ° C. and 22% RH. The film was folded once into a mountain fold and a valley fold so that the film was exactly overlapped at 0 mm and a folding angle of 180 °, and this evaluation was measured 10 times and evaluated as follows. In addition, "break" by evaluation here represents that it broke and separated into two or more pieces.

◎ ... Cannot be folded 10 times ○ ・ ・ ・ 1 fold in 10 △ ・ ・ ・ 2 folds in 10 ×× Bold 3 or more out of 10 (Characteristics as a liquid crystal display device) Evaluation)
<Preparation of polarizing plate>
A polarizing plate using the optical film of the present invention as a polarizing plate protective film was prepared as follows.

  A 120-μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the transport direction 5 times at 50 ° C. to produce a polarizer.

  Next, the optical film 1 subjected to alkali saponification treatment was bonded to one surface of the polarizer. Furthermore, KC8UCR-5 manufactured by Konica Minolta Opto Co., Ltd., which is a retardation film subjected to alkali saponification treatment, was bonded to the other surface of the polarizer and dried to prepare a polarizing plate. Similarly, a polarizing plate was prepared using other sample optical films.

<Production of liquid crystal display device>
(Screen unevenness)
Display characteristics of the optical film of the present invention were evaluated using the produced polarizing plate.

  The obtained polarizing plate carefully peels off the viewing side polarizing plate previously bonded to the Hitachi liquid crystal display device Woo W32L-H90, which is an IPS type liquid crystal display device, and matches the transmission axis of the polarizing plate originally applied. Then, a polarizing plate was attached so that the optical film of the present invention produced through the pressure-sensitive adhesive was on the viewing side, and a liquid crystal display device was produced.

Thereafter, in an environment of a temperature of 23 ° C. and a humidity of 55% RH, the backlight is continuously turned on for 5 hours, and the entire black display state is visually observed in a dark room to comprehensively judge retardation unevenness and misalignment of the orientation angle. The screen unevenness was visually evaluated.
(Screen unevenness)
A: No unevenness is observed in both the bright room and the dark room.
○: Not observed at all in the bright room, but slightly uneven in the dark room.
Δ: Not mindful in a bright room, but unevenness is observed in a dark room.
X: Unevenness is observed even in a bright room.

  The results of the above evaluation are shown in Tables 2 and 3.

  As is clear from Tables 2 and 3, it can be seen that the present invention has excellent brittleness even in a thin film of 40 μm, and image unevenness is small.

Example 2
In Example 1, samples having the same film thickness were prepared in the same manner except that the compounds shown in Table 4 were added as the retardation control agent (D) and acrylic particles (E), and the same evaluation was performed. The results are shown in Table 4.
D1: Aromatic terminal ester plasticizer exemplified compound (14)
D2: Sugar ester compound exemplified compound (3)
D3: Polyhydric alcohol ester exemplary compound (16)
D4: The following triazine compound

  As is apparent from Table 4, it can be seen that the present invention has excellent brittleness and small image unevenness even in a thin film of 40 μm.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter device 35 Roll dryer 41 Particle charging vessel 42 Stock tank 43 Pump 44 Filter

  2. The mixing ratio of the acrylic resin (A) and the cellulose ester resin (C) is 95: 5 to 30:70 by mass ratio, and the total amount of the acrylic resin (A) and the cellulose ester resin (C) is acrylic. 2. The optical film as described in 1 above, wherein the mass ratio of the resin (B) is 99: 1 to 80:20.

3. 3. The optical film as described in 1 or 2 above, wherein the optical film contains a retardation control agent (D).
4). 4. The optical film as described in any one of 1 to 3, wherein the optical film contains acrylic particles (E).

Claims (3)

  An optical film comprising an acrylic resin (A) having a weight average molecular weight Mw of 70,000 to less than 1,000,000, an acrylic resin (B) having a weight average molecular weight of 1,000,000 to 10,000,000, and a cellulose ester resin (C).   The optical film according to claim 1, wherein the optical film contains a retardation control agent (D).   The optical film according to claim 1, wherein the optical film contains acrylic particles (E).