JP5582466B2 - Optical film and composite polarizing plate - Google Patents

Description

  The present invention relates to an optical film and a composite polarizing plate using the same.

  In recent years, low-power consumption, low-voltage, lightweight, and thin liquid crystal display devices are rapidly spreading as information display devices such as mobile phones, portable information terminals, computer monitors, and televisions. Further, along with the development of liquid crystal technology, various modes of liquid crystal displays have been proposed, and the conventional problems of liquid crystal display devices such as response speed, contrast, and narrow viewing angle are being solved. However, it is still pointed out that the viewing angle is narrower than that of a cathode ray tube (CRT), and various attempts have been made to expand the viewing angle.

  As one of such liquid crystal display devices, there is a vertical alignment (VA) mode liquid crystal display device in which rod-like liquid crystal molecules having positive or negative dielectric anisotropy are aligned perpendicularly to a substrate. In the non-driven state of the VA mode liquid crystal cell, since the liquid crystal molecules are aligned perpendicular to the substrate, the polarization state of incident light passes through the liquid crystal layer without change. Therefore, if linear polarizing plates are arranged on the front and back of the liquid crystal cell so that the absorption axes thereof are orthogonal to each other, the front surface of the liquid crystal display device using the same is almost completely black and exhibits a high contrast ratio.

  However, in the oblique viewing field of a liquid crystal display device in which only a linear polarizing plate is arranged in such a VA mode liquid crystal cell, the apparent absorption axis angle is deviated from orthogonal, and rod-like liquid crystal molecules in the liquid crystal cell are birefringent. The expression causes light leakage, and the contrast ratio is significantly reduced.

  In order to eliminate this oblique light leakage, it is necessary to dispose an optical film that compensates for the disturbed polarization state between the liquid crystal cell and the polarizing plate. So far, a laminated composite type polarizing plate in which an optical film is laminated via a pressure-sensitive adhesive (adhesive) on a linear polarizing plate comprising a protective film made of a triacetyl cellulose film on both sides of a polarizing film. The board is on the market.

  In addition, a composite polarizing plate using a film having the function of the optical film as a protective film laminated on the polarizing film is also on the market. In this configuration, since one triacetyl cellulose film and one pressure-sensitive adhesive layer, which are protective films, can be reduced from the laminated composite polarizing plate, the cost can be reduced and the thickness can be reduced. Further, by using an optical film made of a resin having a small photoelastic coefficient, there is an advantage that a deterioration in display quality called white spot can be suppressed.

  For example, Patent Documents 1 and 2 describe that at least one of the polarizing plate protective films is formed of a birefringent film. Patent Documents 3 and 4 describe that a protective film for a polarizing plate is composed of a cyclic olefin resin having a small photoelastic coefficient.

  When a birefringent film is used as a protective film for a polarizing plate, in order to solve the problems such as white spots described above, a photoelasticity of a material having a small birefringence accompanying deformation of the film, that is, the cyclic olefin resin, etc. A material having a small coefficient may be selected. However, although there is a general theory that there is no correlation between photoelasticity and orientation birefringence, when a material with a small photoelastic coefficient is selected to suppress white spots, most materials have low orientation birefringence at the same time. Since the expression of the retardation value due to stretching is too low, it was necessary to use a relatively thick film in order to express the desired retardation value.

  Therefore, Patent Documents 5 and 6 propose an optical film (retardation film) using a polypropylene-based resin capable of reducing the film thickness because the photoelastic coefficient is small and the expression rate of the retardation value is high. However, a retardation film using a polypropylene-based resin is subject to in-plane retardation value fluctuations over time, such that the in-plane retardation value gradually increases even after heat stretching treatment after stretching, In some cases, the in-plane retardation value is difficult to stabilize.

JP-A-8-43812 Japanese Patent Laid-Open No. 9-325216 JP 7-287123 A JP 2002-221619 A JP 2007-316603 A JP 2009-134257 A

  An object of the present invention is to provide an optical film that exhibits a desired retardation value even when the film thickness is small and has a small in-plane retardation value variation over time, and a composite polarizing plate using the same. is there.

According to the present invention, it is composed of a resin film containing a polypropylene resin and an alicyclic saturated hydrocarbon resin, the in-plane retardation value R ₀ is in the range of 40 to 500 nm, and the retardation in the thickness direction. in the range value R _th of 20 to 500 nm, the in-plane slow axis direction of the refractive indices n _x of the resin film, the refractive index n _y in-plane fast axis direction, a refractive index in the thickness direction n when is _z, wherein: the optical film Nz coefficient _{= (n x -n z) /} Nz coefficient defined by (n _x -n _y) is in the range of 0.9 to 3 is provided. The optical film of the present invention preferably has a thickness of 35 μm or less.

  The optical film of the present invention is preferably composed of a stretched film of a resin composition containing a polypropylene resin and an alicyclic saturated hydrocarbon resin. Moreover, it is preferable that this resin composition contains 0.1-30 weight% of alicyclic saturated hydrocarbon resin. The softening point of the alicyclic saturated hydrocarbon resin is preferably in the range of 110 to 145 ° C.

  The polypropylene resin is preferably made of a copolymer of propylene and ethylene containing 10% by weight or less of ethylene units, or substantially made of a propylene homopolymer.

  Moreover, according to this invention, a composite polarizing plate provided with a polarizing film and the said optical film of this invention laminated | stacked on the single side | surface of this polarizing film is provided. The composite polarizing plate of the present invention may further include a transparent protective layer on the surface opposite to the surface on which the optical film is laminated. Moreover, it is preferable that an optical film is laminated | stacked on a polarizing film through the hardened | cured material layer of an active energy ray hardening epoxy adhesive.

  According to the present invention, it is possible to provide an optical film and a composite polarizing plate in which the in-plane retardation value variation over time after production is sufficiently suppressed. By applying such a composite polarizing plate including an optical film having a small in-plane retardation value variation with time, the stability of the display performance of the liquid crystal display device can be improved.

It is a schematic sectional drawing which shows a preferable example of the composite polarizing plate of this invention.

<Optical film>
The optical film of the present invention is a birefringent resin film containing a polypropylene resin and an alicyclic saturated hydrocarbon resin. Typically, as will be described in detail later, a polypropylene resin and an alicyclic ring are typically used. It is a stretched film that expresses a retardation produced by uniaxially stretching or biaxially stretching a raw film containing a group saturated hydrocarbon resin.

The in-plane retardation value R ₀ of the optical film of the present invention is in the range of 40 to 500 nm, preferably 50 to 300 nm, and the retardation value R _{th in the} thickness direction is in the range of 20 to 500 nm, preferably 25 to 400 nm. Range. The Nz coefficient is in the range of 0.9-3. When the optical film of the present invention is a uniaxially stretched film, the Nz coefficient is preferably in the range of 0.9-2. On the other hand, in the case of a biaxially stretched film, the Nz coefficient is preferably in the range of 1.0 to 3. Even in the case of a biaxially stretched film, the Nz coefficient may approach 1 if the longitudinal and lateral stretch ratios differ greatly.

Incidentally, the in-plane slow axis direction of the refractive index of the film n _x, the refractive index n _y in-plane fast axis direction (direction orthogonal with the slow axis and the plane), the refractive index in the thickness direction n _z When the thickness is d, the in-plane retardation value R ₀ , the thickness direction retardation value R _th , and the Nz coefficient are defined by the following equations (I), (II), and (III), respectively.

_{R 0 = (n x -n y} ) × d (I)
R _th = [(n _x + _ny ) / 2−n _z ] × d (II)
_{Nz = (n x -n z)} / (n x -n y) (III)
From these formulas (I) to (III), the relationship between the Nz coefficient, the in-plane retardation value R ₀ , and the thickness direction retardation value R _th is expressed by the following formula (IV):
Nz = _Rth / _R0 + 0.5 (IV)
Can be expressed as

Polypropylene resin, the phase difference is easily expressed by stretching, i.e., the difference between n _x and n _y or difference between n _x or n _y and n _z are likely to increase in the above formula. Therefore, in the optical film of the present invention, while exhibiting the desired retardation characteristics, the thickness can be 35 μm or less, and further 30 μm or less. Thinning can be achieved. However, the thickness of the optical film is preferably 5 μm or more, and more preferably 8 μm or more. If the thickness is less than 5 μm, wrinkles and the like are likely to occur in the film, and handling properties at the time of winding and bonding may be reduced.

(Alicyclic saturated hydrocarbon resin)
The alicyclic saturated hydrocarbon resin constituting the optical film of the present invention is a resin classified as a petroleum resin. The petroleum resin is a thermoplastic resin obtained by polymerizing and solidifying a cracked oil fraction generated by thermal decomposition of petroleum, for example, an aliphatic petroleum resin using a C5 fraction as a raw material; a C9 fraction as a raw material. Aromatic petroleum resin; copolymerized petroleum resin obtained by copolymerizing two kinds of C5 fraction and C9 fraction; and aliphatic petroleum resin, aromatic petroleum resin, or copolymerized petroleum Examples thereof include hydrogenated petroleum resins obtained by hydrogenating resins.

  In the present invention, an alicyclic saturated hydrocarbon resin is particularly used among the above petroleum resins. The alicyclic saturated hydrocarbon resin is typically a hydrogenated petroleum resin obtained by hydrogenating an aromatic petroleum resin. The alicyclic saturated hydrocarbon resin has a high effect of suppressing fluctuation of the in-plane retardation value with time, is colorless and transparent, and has advantageous characteristics as an optical film material that is excellent in weather resistance.

  The alicyclic saturated hydrocarbon resin used in the present invention preferably has a softening point of 110 ° C. or higher and 145 ° C. or lower. More preferably, it is 115 degreeC or more and 135 degreeC or less. When the softening point is lower than 110 ° C, the heat resistance of the optical film tends to be lowered. When the softening point is higher than 145 ° C, the stretchability of the original film is deteriorated, and the productivity of the optical film is lowered. It is in.

  A commercial item can also be used as an alicyclic saturated hydrocarbon resin. Examples of such commercially available products include “Arcon” series manufactured by Arakawa Chemical Industries, Ltd. The “Arcon” series is a hydrogenated petroleum resin obtained by hydrogenating an aromatic petroleum resin.

  The optical film of the present invention can contain an alicyclic saturated hydrocarbon resin in the range of 0.1 to 30% by weight, preferably in the range of 3 to 20% by weight. Containing. If the content of the alicyclic saturated hydrocarbon resin is less than 0.1% by weight, the effect of suppressing the fluctuation of the in-plane retardation value over time cannot be sufficiently obtained, and if it exceeds 30% by weight, the optical film There is a concern that bleedout of the alicyclic saturated hydrocarbon resin may occur over time.

(Polypropylene resin)
The polypropylene resin constituting the optical film of the present invention may be a resin consisting essentially of a propylene homopolymer, or a resin consisting of a copolymer of propylene and another copolymerizable comonomer. Also good. The homopolymer of propylene is advantageous in that the film rigidity and yield strength can be further increased because the degree of crystallinity is higher than the copolymer of propylene and other copolymerizable comonomers. . Therefore, it becomes possible to further improve the handleability in the optical film preparation step and the polarizing plate formation step by using a resin consisting essentially of a propylene homopolymer as the polypropylene resin.

  Here, the “substantially propylene homopolymer” is a polymer having a propylene unit content of 100% by weight, or about 0.6% by weight or less for the purpose of improving the productivity of the raw film. Propylene / ethylene copolymers containing ethylene units in the range are also included.

  The polypropylene resin composed of a copolymer of propylene and another copolymerizable comonomer is preferably one in which propylene is the main component and one or two or more types of comonomer copolymerizable therewith are copolymerized in a small amount. . Specifically, the polypropylene resin comprising such a copolymer is a resin containing a comonomer unit in a range of, for example, 20% by weight or less, preferably 10% by weight or less, more preferably 7% by weight or less. be able to. The comonomer unit content in the copolymer is at least more than 0.6% by weight, preferably 1% by weight or more, more preferably 3% by weight or more. By setting the content of the comonomer unit to 1% by weight or more, processability and transparency can be significantly improved. On the other hand, when the content of the comonomer unit exceeds 20% by weight, the melting point of the polypropylene resin is lowered and the heat resistance tends to be lowered. In addition, when setting it as the copolymer of 2 or more types of comonomer, and propylene, it is preferable that the total content of the unit derived from all the comonomer contained in the copolymer is the said range.

  The comonomer copolymerized with propylene can be, for example, an unsaturated hydrocarbon such as ethylene or an α-olefin having 4 to 20 carbon atoms. Specific examples of the α-olefin include the following.

1-butene, 2-methyl-1-propene (above C ₄ );
1-pentene, 2-methyl-1-butene, 3-methyl-1-butene (above C ₅ );
1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3- Dimethyl-1-butene (above C ₆ );
1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl-1-butene (above C ₇ );
1-octene, 5-methyl-1-heptene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene, 2,3,4-trimethyl- 1-pentene, 2-propyl-1-pentene, 2,3-diethyl-1-butene (above C ₈ );
1-nonene (C ₉ ); 1-decene (C ₁₀ ); 1-undecene (C ₁₁ ); 1-dodecene (C ₁₂ ); 1-tridecene (C ₁₃ ); 1-tetradecene (C ₁₄ ); Pentadecene (C ₁₅ ); 1-hexadecene (C ₁₆ ); 1-heptadecene (C ₁₇ ); 1-octadecene (C ₁₈ ); 1-nonadecene (C ₁₉ ) and the like.

  Among the α-olefins, α-olefins having 4 to 12 carbon atoms are preferable. Specifically, 1-butene, 2-methyl-1-propene; 1-pentene, 2-methyl-1-butene, 3 -Methyl-1-butene; 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1 -Pentene, 3,3-dimethyl-1-butene; 1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl -1-butene; 1-octene, 5-methyl-1-heptene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene, 2,3 , 4-Trimethyl-1-pentene 2-propyl-1-pentene, 2,3-diethyl-1-butene; 1-nonene; 1-decene; 1-undecene; 1-dodecene, and the like. From the viewpoint of copolymerizability, 1-butene, 1-pentene, 1-hexene and 1-octene are preferable, and 1-butene and 1-hexene are more preferable.

  The copolymer may be a random copolymer or a block copolymer. Preferred copolymers include propylene / ethylene copolymers and propylene / 1-butene copolymers. In the propylene / ethylene copolymer and propylene / 1-butene copolymer, the ethylene unit content and the 1-butene unit content are, for example, those of “Polymer Analysis Handbook” (1995, published by Kinokuniya Shoten) Infrared (IR) spectrum measurement can be performed by the method described on page 616.

  From the viewpoint of increasing the transparency and workability of the optical film, the copolymer is preferably a random copolymer of propylene mainly composed of propylene and the unsaturated hydrocarbon, and a random copolymer of propylene and ethylene. More preferably, it is a polymer. As described above, the content of the ethylene unit in the propylene / ethylene random copolymer is preferably 1 to 20% by weight, more preferably 1 to 10% by weight, and 3 to 7% by weight. Is more preferable.

  The stereoregularity of the polypropylene resin may be any of isotactic, syndiotactic and atactic, but syndiotactic or isotactic polypropylene resin is preferably used from the viewpoint of heat resistance of the optical film. It is done.

  The polypropylene resin used in the optical film of the present invention has a melt flow rate (MFR) measured at a temperature of 230 ° C. and a load of 21.18 N in accordance with JIS K 7210, particularly 0.1 to 200 g / 10 min. It is preferably in the range of 0.5 to 50 g / 10 minutes. By using a polypropylene resin having an MFR in this range, a raw film for producing an optical film having a uniform resin composition and film thickness can be obtained without imposing a large load on the extruder.

The polypropylene resin constituting the optical film of the present invention can be produced by a method of homopolymerizing propylene or a method of copolymerizing propylene and another copolymerizable comonomer using a known polymerization catalyst. . Examples of known polymerization catalysts include the following.
(1) a Ti—Mg-based catalyst comprising a solid catalyst component containing magnesium, titanium, and halogen as essential components;
(2) a catalyst system in which a solid catalyst component containing magnesium, titanium, and halogen as essential components is combined with an organoaluminum compound and, if necessary, a third component such as an electron donating compound,
(3) Metallocene catalysts.

  Examples of the solid catalyst component containing magnesium, titanium, and halogen as essential components in the catalyst systems (1) and (2) above include, for example, JP-A-61-218606, JP-A-61-287904, Examples include the catalyst system described in Kaihei 7-216017. As the organoaluminum compound in the catalyst system of (2) above, triethylaluminum, triisobutylaluminum, a mixture of triethylaluminum and diethylaluminum chloride, tetraethyldialumoxane and the like are preferably used, and the electron donating compound is cyclohexylethyl. Dimethoxysilane, tert-butylpropyldimethoxysilane, tert-butylethyldimethoxysilane, dicyclopentyldimethoxysilane and the like are preferably used.

  Examples of the metallocene catalyst (3) include catalyst systems described in Japanese Patent No. 2587251, Japanese Patent No. 2627669, Japanese Patent No. 2668732, and the like.

  Among the above catalyst systems, the catalyst system of the above (2) can be most generally used in the present invention.

  Polypropylene resins are, for example, solution polymerization methods using an inert solvent typified by hydrocarbon compounds such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, and liquid monomers as solvents. It can be produced by a bulk polymerization method to be used or a gas phase polymerization method in which a gaseous monomer is polymerized as it is. Polymerization by these methods may be carried out batchwise or continuously.

<Method for producing optical film>
The optical film of the present invention is produced by producing a raw film from a resin composition containing a polypropylene resin and an alicyclic saturated hydrocarbon resin, and stretching the obtained raw film to develop a retardation. Can be obtained.

(Preparation of raw film)
The raw film is produced by forming a resin composition containing a polypropylene resin and an alicyclic saturated hydrocarbon resin. The method for preparing the resin composition is not particularly limited as long as at least the alicyclic saturated hydrocarbon resin is uniformly dispersed in the obtained resin composition. For example, a polypropylene resin is prepared. Examples thereof include a method of adding an alicyclic saturated hydrocarbon resin to the polymerization reaction mixture during or immediately after the polymerization reaction in the polymerization step. The alicyclic saturated hydrocarbon resin may be added as a solution dissolved in a solvent, or may be pulverized into a powder form so that it can be easily dispersed, added as a powder, or heated and melted. May be added.

  The resin composition can also be obtained by a method of melt melting and kneading after adding the alicyclic saturated hydrocarbon resin while melt kneading the polypropylene resin. These melt-kneading can be performed using, for example, a kneader such as a ribbon blender, a mixing roll, a Banbury mixer, a roll, various kneaders, a single-screw extruder, or a twin-screw extruder. The resin composition thus obtained may be subjected to a molding process into a raw film without being cooled after being melt-kneaded, or after being cooled into a molded article such as a pellet body. This may be heated again to be used for forming a raw film. Moreover, after cooling, it can also shape | mold into a raw fabric film by methods, such as press molding, with a cooling state.

  The content of the alicyclic saturated hydrocarbon resin in the resin composition is usually in the range of 0.1 to 30% by weight, preferably 3 to 20% by weight when the weight of the resin composition is 100% by weight. %. If the content of the alicyclic saturated hydrocarbon resin is less than 0.1% by weight, the effect of suppressing the fluctuation of the in-plane retardation value over time cannot be sufficiently obtained, and if it exceeds 30% by weight, the optical film There is a concern that bleedout of the alicyclic saturated hydrocarbon resin may occur over time.

  The said resin composition may contain a well-known additive in the range which does not inhibit the effect of this invention. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an antifogging agent, and an antiblocking agent. The resin composition can contain one or more additives.

  Examples of antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, hindered amine light stabilizers, and the like, and for example, phenolic antioxidant mechanisms in one molecule. It is also possible to use a composite antioxidant having a unit having both a phosphorus-based antioxidant mechanism and a phosphorus-based antioxidant mechanism. Examples of the UV absorber include UV absorbers such as 2-hydroxybenzophenone and hydroxyphenylbenzotriazole, and benzoate UV blockers. The antistatic agent may be polymer type, oligomer type or monomer type. Examples of the lubricant include higher fatty acid amides such as erucic acid amide and oleic acid amide, higher fatty acids such as stearic acid, and salts thereof. As the anti-blocking agent, fine particles having a spherical shape or a shape close thereto can be used regardless of inorganic type or organic type.

  Further, the nucleating agent may be either an inorganic nucleating agent or an organic nucleating agent. Examples of the inorganic nucleating agent include talc, clay, calcium carbonate and the like. Examples of the organic nucleating agent include metal salts such as aromatic carboxylic acid metal salts and aromatic phosphoric acid metal salts, high-density polyethylene, poly-3-methylbutene-1, polycyclopentene, and polyvinylcyclohexane. It is done. Among these, organic nucleating agents are preferable, and the above metal salts and high density polyethylene are more preferable. The addition amount of the nucleating agent is preferably within a range of 0.01 to 3% by weight with respect to 100% by weight of the polypropylene resin contained in the resin composition, and is 0.05 to 1.5% by weight. More preferably within the range.

  An original film can be obtained by forming the resin composition by any method. This raw film is transparent and has substantially no in-plane retardation. Examples of film forming methods include 1) a method of extruding a resin composition in a molten state (which may be once made into a pellet and then heated to a molten state), and 2) a resin composition containing a solvent. Casting a product (a solvent may be separately added to the resin composition) on a flat plate, removing the solvent to form a film, and 3) a method of press molding the resin composition Can do. By these methods, an original film of a resin composition having substantially no in-plane retardation can be obtained.

  As an example of a preferable method for producing a raw film, a film forming method by extrusion will be described in detail. In extrusion molding, the resin composition is melt-kneaded by rotation of a screw in an extruder and extruded from a T die into a sheet. The temperature of the extruded molten sheet can be about 180 to 300 ° C. When the temperature of the molten sheet is lower than 180 ° C., the spreadability is not sufficient, the thickness of the obtained raw film becomes non-uniform, and there is a possibility that the film has uneven retardation. Moreover, when the temperature of a molten sheet exceeds 300 degreeC, degradation and decomposition | disassembly of resin will occur easily, a bubble may arise in a molten sheet, and a carbide | carbonized_material may be contained.

The extruder may be a single screw extruder or a twin screw extruder. For example, in the case of a single screw extruder, L / D, which is the ratio of the screw length L to the diameter D, is about 24 to 36, the space volume V ₁ of the thread groove in the resin supply section, and the thread groove in the resin metering section. It is preferable to use a screw of a compression ratio V ₁ / V _2, which is a ratio to the space volume V ₂ , of about 1.5 to 4 and having a full flight type, a barrier type, or a Maddock type kneading part. . From the viewpoint of suppressing deterioration and decomposition of the resin composition and uniformly melting and kneading, a barrier type having an L / D of 28 to 36 and a compression ratio V ₁ / V ₂ of 2.5 to 3.5 It is more preferable to use a screw.

  Moreover, in order to suppress deterioration and decomposition | disassembly of a resin composition as much as possible, it is preferable to make the inside of an extruder into nitrogen atmosphere or a vacuum. Furthermore, in order to remove the volatile gas generated by the deterioration or decomposition of the resin composition, it is also preferable to provide an orifice of 1 mmφ to 5 mmφ at the tip of the extruder to increase the resin pressure at the tip of the extruder. Increasing the resin pressure at the tip of the extruder at the orifice means increasing the back pressure at the tip, thereby improving the stability of extrusion. The diameter of the orifice to be used is more preferably 2 mmφ or more and 4 mmφ or less.

  The T-die used for extrusion preferably has no fine steps or scratches on the surface of the flow path of the resin composition, and the lip portion is plated with a material having a low friction coefficient with the molten resin composition. Alternatively, a sharp edge shape that is coated and further polished to a lip tip of 0.3 mmφ or less is preferable. Examples of the material having a small friction coefficient include tungsten carbide type and fluorine type special plating. By using such a T-die, it is possible to suppress the generation of the eyes, and at the same time, it is possible to suppress the die line, so that a raw film having excellent appearance uniformity can be obtained. In the T die, the manifold has a coat hanger shape and preferably satisfies the following condition (1) or (2), and more preferably satisfies the condition (3) or (4).

(1) When the lip width of the T die is less than 1500 mm: the thickness direction length of the T die> 180 mm,
(2) When the lip width of the T die is 1500 mm or more: the thickness direction length of the T die> 220 mm,
(3) When the lip width of the T die is less than 1500 mm: the length in the height direction of the T die> 250 mm,
(4) When the lip width of the T die is 1500 mm or more: Length in the height direction of the T die> 280 mm.

  By using a T-die that satisfies such conditions, the flow of the molten resin composition inside the T-die can be adjusted, and the lip portion can be extruded while suppressing thickness unevenness. It is possible to obtain an original film which is excellent in accuracy and made more uniform at a level where the in-plane retardation is extremely low.

  In addition, it is preferable to attach a gear pump via an adapter between an extruder and a T die from a viewpoint of suppressing the extrusion fluctuation | variation of a resin composition. In order to remove foreign substances in the resin composition, it is preferable to attach a leaf disk filter.

  The molten sheet extruded from the T-die is between a metal cooling roll (also called a chill roll or a casting roll) and a touch roll including an elastic body that rotates in pressure contact with the circumferential direction of the metal cooling roll. It is pinched and cooled and solidified by both rolls to form a raw film. The touch roll may be one in which an elastic body such as rubber is directly on the surface, or may be one in which the surface of the elastic body roll is covered with an outer cylinder made of a metal sleeve. When using a touch roll in which the surface of the elastic roll is covered with an outer cylinder made of a metal sleeve, cooling is usually performed by directly sandwiching a molten sheet of the resin composition between the metal cooling roll and the touch roll. . On the other hand, in the case of using a touch roll whose surface is an elastic body, a biaxially stretched film of a thermoplastic resin may be interposed between the molten sheet of the resin composition and the touch roll to sandwich the pressure.

  When the molten sheet of the resin composition is sandwiched between the metal cooling roll and the touch roll as described above and cooled and solidified, both the cooling roll and the touch roll have their surface temperatures lowered, and the molten sheet The surface temperature of both rolls is preferably adjusted to a range of 0 ° C. or higher and 30 ° C. or lower. When these surface temperatures exceed 30 ° C, it takes time to cool and solidify the molten sheet, so that the crystal component in the molten sheet grows, and the transparency of the resulting raw film may be lowered. . The surface temperature of both rolls is more preferably less than 30 ° C, still more preferably less than 25 ° C. On the other hand, if the surface temperature of both rolls is less than 0 ° C., dew condensation occurs on the surface of the metallic cooling roll, and water droplets adhere to the surface of the roll, which may deteriorate the appearance of the raw film.

  Since the surface state of the metal cooling roll to be used is transferred to the surface of the original film, if the surface is uneven, the thickness accuracy of the resulting original film may be lowered. Therefore, the surface of the metal cooling roll is preferably as close to a mirror surface as possible as the film can be peeled off. Specifically, the roughness of the surface of the metal cooling roll is preferably 0.4 S or less, more preferably 0.05 S to 0.2 S, expressed as a standard sequence of the maximum height.

  The touch roll that forms the nip portion with the metal cooling roll has a surface hardness of 65 to 80 as a value measured by a spring type hardness test (A type) defined in JIS K 6301. It is preferable that it is 70-80. By using such a surface hardness touch roll, it becomes easy to maintain a uniform linear pressure applied to the molten sheet, and a bank (resin) of the molten sheet is provided between the metal cooling roll and the touch roll. It becomes easy to form into a film without causing a stagnation.

  The pressure (linear pressure) when sandwiching the molten sheet is determined by the pressure for pressing the touch roll against the metal cooling roll. The linear pressure is preferably 50 N / cm or more and 300 N / cm or less, and more preferably 100 N / cm or more and 250 N / cm or less. By setting the linear pressure within the above range, it becomes easy to produce a raw film while maintaining a constant linear pressure without forming a bank.

  When sandwiching a biaxially stretched film of a thermoplastic resin together with a molten sheet of a resin composition between a metal cooling roll and a touch roll, the thermoplastic resin constituting the biaxially stretched film is a molten sheet and Any resin that does not strongly heat-seal can be used. Specific examples include polyester, polyamide, polyvinyl chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and polyacrylonitrile. Among these, polyesters that have little dimensional change due to humidity, heat, and the like are most preferable. The thickness of the biaxially stretched film is usually about 5 to 50 μm, preferably 10 to 30 μm.

  The distance (air gap) from the lip of the T die to the pressure between the metal cooling roll and the touch roll is preferably 200 mm or less, and more preferably 160 mm or less. The molten sheet extruded from the T-die is stretched from the lip to the roll, and orientation tends to occur. By shortening the air gap as described above, a raw film having a smaller orientation can be obtained. The lower limit value of the air gap is determined by the diameter of the metal cooling roll to be used, the diameter of the touch roll, and the tip shape of the lip to be used, and is usually 50 mm or more.

  The processing speed of the raw film is determined by the time required for cooling and solidifying the molten sheet. When the diameter of the metal cooling roll to be used is increased, the distance at which the molten sheet is in contact with the cooling roll becomes longer, so that production at a higher speed is possible. Specifically, when a 600 mmφ metal cooling roll is used, the processing speed is about 5 to 20 m / min at the maximum.

  The raw film obtained by being sandwiched between a metal cooling roll and a touch roll and cooled and solidified is usually wound into a roll by a winder after slitting the end as necessary. Under the present circumstances, in order to protect the surface until it uses a raw film, you may wind in the state which bonded the surface protection film which consists of another thermoplastic resin to the single side | surface or both surfaces. When the molten sheet is sandwiched between a metallic cooling roll and a touch roll together with a biaxially stretched film made of a thermoplastic resin, the biaxially stretched film can be used as one surface protective film.

(Production of optical film)
The optical film of this invention can be obtained by extending | stretching the said raw film and expressing a phase difference. The stretching method is not particularly limited, and longitudinal uniaxial stretching, lateral uniaxial stretching, sequential biaxial stretching, simultaneous biaxial stretching, or the like can be employed.

  The uniaxial stretching in the machine direction is a method in which the raw film of the resin composition is preheated in the machine direction by a series of heating rolls and subsequently or simultaneously stretched by the difference in peripheral speed between the heating rolls to produce a longitudinally stretched film. is there. In the uniaxial stretching in the transverse direction, both ends of the raw film are fixed with two rows of chucks or pins aligned in the flow direction, and the two rows of chucks are heated in a heating furnace including a preheating portion, a stretching portion, and a heat treatment portion. This is a method for producing a transversely stretched film by stretching in the transverse direction by widening the interval. In sequential biaxial stretching, the raw film is preheated in the machine direction by a series of heating rolls and subsequently or simultaneously stretched longitudinally due to the difference in peripheral speed between the heating rolls. Both ends are fixed by two rows of chucks or pins aligned along the flow direction, and the two rows of chucks are widened in a heating furnace consisting of a preheating section, a stretching section and a heat treatment section, and then stretched in the transverse direction. This is a method for producing a biaxially stretched film. In the simultaneous biaxial stretching, both ends of the raw film are respectively fixed by two rows of chucks or pins arranged in the flow direction, and the two rows are formed in a heating furnace including a preheating portion, a stretching portion, and a heat treatment portion. This is a method for producing a biaxially stretched film by stretching simultaneously in the longitudinal direction and the transverse direction by widening the chuck interval and the individual chuck intervals in the row.

  In any of the stretching methods, the optical film obtained by stretching is subjected to corona treatment or the like as necessary on the surface or slit at both ends, and is usually wound into a roll by a winder. At this time, the surface protective film for temporarily protecting the surface of the optical film may be wound up in a state of being bonded to one side or both sides, and the film with the pressure-sensitive adhesive layer may be wound on one side or through the pressure-sensitive adhesive layer. You may wind up in the state bonded on both surfaces.

<Composite polarizing plate>
FIG. 1 is a schematic sectional view showing a preferred example of the composite polarizing plate of the present invention. As shown in FIG. 1, the composite polarizing plate 100 of the present invention includes a polarizing film 101 and an optical film 102 according to the present invention laminated on one surface of the polarizing film 101. The composite polarizing plate 100 of the present invention may further include a transparent protective layer 103 on the surface opposite to the surface on which the optical film 102 is laminated. The optical film 102 and the transparent protective layer 103 can be bonded to the polarizing film 101 using an adhesive. In this case, the optical film 102 and the transparent protective layer 103 are bonded to the adhesive layer (the adhesive layers 104 and 105 in FIG. 1). ) To the polarizing film 101. According to the composite polarizing plate of the present invention, the stability of the display performance of the liquid crystal display device can be improved by using the optical film of the present invention in which the in-plane retardation value variation over time is suppressed. Moreover, since the composite polarizing plate of this invention uses the optical film of this invention, thickness reduction is achieved.

  In the composite polarizing plate of the present invention, the optical film 102 functions as a wave plate or a viewing angle compensation film. The angle formed by the slow axis of the optical film 102 and the absorption axis of the polarizing film 101 is appropriately selected according to the function of the optical film 102. For example, in the case of a wave plate, the angle is 5 to 85 °. In the case of a compensation film, it is substantially 0 ° or substantially 90 °.

(Polarizing film)
As the polarizing film 101, a film obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film and imparting a predetermined polarizing property can be used. As the dichroic dye, iodine or a dichroic organic dye is used. Specifically, as the polarizing film 101, specifically, an iodine polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol resin film, a dye polarizing film in which a dichroic organic dye is adsorbed and oriented on a polyvinyl alcohol resin film, etc. Can be used.

  The polyvinyl alcohol resin constituting the polarizing film 101 can be obtained by saponifying a polyvinyl acetate resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and other monomers copolymerizable therewith is used. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may be used.

  The polarizing film 101 is usually a humidity adjusting step for adjusting the moisture of the polyvinyl alcohol-based resin film, a step of uniaxially stretching the polyvinyl alcohol-based resin film, a dichroic dyeing of the polyvinyl alcohol-based resin film with a dichroic dye. It is manufactured through a step of adsorbing and orienting the dye, a step of treating the polyvinyl alcohol resin film on which the dichroic dye is adsorbing and orienting with an aqueous boric acid solution, and a washing step of washing off the aqueous boric acid solution. Uniaxial stretching can be performed before dyeing, during dyeing, or during boric acid treatment after dyeing. Moreover, uniaxial stretching may be performed in these several steps. The method of uniaxial stretching may be a method of stretching uniaxially between rolls having different peripheral speeds, or a method of stretching uniaxially using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 4 to 8 times. The thickness of the finally obtained polarizing film 101 can be, for example, about 1 to 50 μm.

(Transparent protective layer)
Examples of the transparent protective layer 103 include (meth) acrylic resins such as methyl methacrylate resins, chain polyolefin resins such as polypropylene resins, cyclic polyolefin resins, polyvinyl chloride resins, cellulose resins, and styrene resins. , Acrylonitrile / butadiene / styrene copolymer resin, acrylonitrile / styrene copolymer resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, poly Transparent protective film made of butylene terephthalate resin, polyethylene terephthalate resin, polysulfone resin, polyethersulfone resin, polyarylate resin, polyamideimide resin, polyimide resin, etc. can be used. That. The thickness of a transparent protective film is 20-200 micrometers normally, Preferably it is 20-120 micrometers.

  The transparent protective layer 103 may be a coating-type transparent protective layer formed by applying and curing a resin composition containing a curable compound that can be cured by irradiation with active energy rays or heating. As a curable compound, the epoxy compound mentioned later can be used conveniently. The thickness of the coating type transparent protective layer is, for example, 0.1 to 10 μm, and preferably 1 to 5 μm. When the transparent protective layer 103 is a coating-type transparent protective layer, the transparent protective layer 103 can be directly laminated on the polarizing film 101 without interposing the adhesive layer 105.

(Adhesive layer)
Examples of the adhesive that forms the adhesive layers 104 and 105 responsible for bonding with the optical film 102 and the transparent protective layer include, for example, epoxy-based, acrylic-based, urethane-based, cyanoacrylate-based, or acrylamide-based adhesives. Or in combination. Even if any of these is used, good adhesive force can be obtained, but among them, epoxy adhesives are particularly preferably used because they exhibit particularly excellent adhesive force. The adhesive that bonds the optical film 102 and the polarizing film 101 and the adhesive that bonds the transparent protective layer 103 and the polarizing film 101 may be the same or different, It is preferable to use the same type from the viewpoint of simplifying the manufacturing process of the composite polarizing plate and reducing the types of materials used.

  As said epoxy-type adhesive agent, the adhesive agent which consists of curable resin composition containing the epoxy compound hardened | cured by irradiation of an active energy ray is mentioned. In this case, the polarizing film and the optical film can be bonded by irradiating the coating layer of the adhesive with active energy rays and curing the curable epoxy compound contained in the adhesive. The resulting adhesive layer is composed of a cured product layer of an active energy ray-curable epoxy adhesive. Curing of the epoxy compound by irradiation with this active energy ray is preferably performed by cationic polymerization. The epoxy compound used for the adhesive usually has at least two epoxy groups in the molecule. In the present specification, the active energy ray is a concept including visible light, ultraviolet rays, X-rays, electron beams, and the like.

  From the viewpoint of weather resistance, refractive index, cationic polymerizability, and the like, the epoxy compound contained in the curable epoxy resin composition as an adhesive is preferably one that does not contain an aromatic ring in the molecule. An adhesive using an epoxy compound that does not contain an aromatic ring in the molecule is described in, for example, JP-A-2004-245925. Examples of such epoxy compounds that do not contain an aromatic ring in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds.

  A hydrogenated epoxy compound can be obtained by subjecting an aromatic polyhydroxy compound, which is a raw material for an aromatic epoxy resin, to selective hydrogenation under pressure in the presence of a catalyst, followed by glycidyl etherification. . Examples of aromatic epoxy resins include bisphenol-type epoxy resins such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and bisphenol S diglycidyl ether; phenol novolac epoxy resins, cresol novolac epoxy resins, and hydroxy Examples include novolak-type epoxy resins such as benzaldehyde phenol novolac epoxy resins; glycidyl ethers of tetrahydroxyphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and polyfunctional epoxy resins such as epoxidized polyvinylphenol. For example, aromatic polyhydroxy compounds such as bisphenols, which are raw materials for these aromatic epoxy resins, are subjected to the nuclear hydrogenation reaction as described above, and then reacted with epichlorohydrin to obtain a hydrogenated epoxy compound. It is done. Among them, as the hydrogenated epoxy compound, hydrogenated bisphenol A glycidyl ether is preferable.

  The alicyclic epoxy compound means an epoxy resin having at least one epoxy group bonded to the alicyclic ring in the molecule. The “epoxy group bonded to the alicyclic ring” means a bridged oxygen atom —O— in the structure represented by the following formula, wherein m is an integer of 2 to 5.

A compound in which one or a plurality of hydrogen atoms in (CH ₂ ) _m in the above formula are bonded to another chemical structure can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, those having an oxabicyclohexane ring (m = 3 in the above formula) and an oxabicycloheptane ring (m = 4 in the above formula) exhibit excellent adhesion. Are preferably used. Although the alicyclic epoxy compound used preferably below is specifically illustrated, it is not limited to these compounds.

3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
Ethylene bis (3,4-epoxycyclohexanecarboxylate),
Bis (3,4-epoxycyclohexylmethyl) adipate,
Bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
Diethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
Ethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro- [5.2.2.5.2.2] henicosane (3,4-epoxycyclohexanespiro-2 ', 6 '-Dioxane spiro-3'',5''-dioxanespiro-3''', 4 '''-epoxycyclohexane)
3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,
4-vinylcyclohexene dioxide,
Bis-2,3-epoxycyclopentyl ether,
Dicyclopentadiene dioxide etc.

  Moreover, as an aliphatic epoxy compound, the polyglycidyl ether of an aliphatic polyhydric alcohol or its alkylene oxide addition product can be mentioned. More specifically, 1,4-butanediol diglycidyl ether; 1,6-hexanediol diglycidyl ether; glycerin triglycidyl ether; trimethylolpropane triglycidyl ether; polyethylene glycol diglycidyl ether; propylene Diglycidyl ether of glycol; Polyglycidyl of polyether polyol obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol or glycerin Examples include ether.

  In the adhesive comprising the curable resin composition, the epoxy compound may be used alone or in combination of two or more. The epoxy equivalent of the epoxy compound used for the adhesive is usually in the range of 30 to 3,000 g / equivalent, preferably 50 to 1,500 g / equivalent. When the epoxy equivalent is less than 30 g / equivalent, the flexibility of the composite polarizing plate after curing may be reduced, or the adhesive strength may be reduced. On the other hand, if it exceeds 3,000 g / equivalent, the compatibility with other components contained in the adhesive may be lowered.

  From the viewpoint of reactivity, cationic polymerization is preferably used as the curing reaction of the epoxy compound. For that purpose, it is preferable that the curable epoxy resin composition which is an adhesive agent contains a cationic polymerization initiator. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates an epoxy group polymerization reaction. Regardless of the type of cationic polymerization initiator, it is preferable from the viewpoint of workability that latency is imparted. Hereinafter, a cationic polymerization initiator that generates a cationic species or a Lewis acid by irradiation of active energy rays and initiates a polymerization reaction of an epoxy group is referred to as a “photo cationic polymerization initiator”.

  The method of curing the adhesive by irradiating active energy rays using a cationic photopolymerization initiator enables curing at room temperature, reducing the need to consider the distortion due to heat resistance or expansion of the polarizing film, and the optical film And it is advantageous in that the transparent protective layer and the polarizing film can be favorably bonded. In addition, since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with an epoxy compound.

  Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; and iron-allene complexes. These photocationic polymerization initiators may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferable because they have ultraviolet absorption characteristics even in a wavelength region of 300 nm or more, and thus can provide a cured product having excellent curability and good mechanical strength and adhesive strength. Used.

  These photocationic polymerization initiators can be easily obtained as commercial products. For example, “Kayarad PCI-220” and “Kayarad PCI-620” (Nippon Kayaku Co., Ltd. , "UVI-6990" (manufactured by Union Carbide), "Adekaoptomer SP-150" and "Adekaoptomer SP-170" (manufactured by ADEKA, Inc.), "CI-5102", "CIT-" 1370 ”,“ CIT-1682 ”,“ CIP-1866S ”,“ CIP-2048S ”and“ CIP-2064S ”(manufactured by Nippon Soda Co., Ltd.),“ DPI-101 ”,“ DPI-102 ”,“ DPI ” -103 "," DPI-105 "," MPI-103 "," MPI-105 "," BBI-101 "," BBI- 02 ”,“ BBI-103 ”,“ BBI-105 ”,“ TPS-101 ”,“ TPS-102 ”,“ TPS-103 ”,“ TPS-105 ”,“ MDS-103 ”,“ MDS-105 ” , “DTS-102” and “DTS-103” (manufactured by Midori Chemical Co., Ltd.), “PI-2074” (manufactured by Rhodia), and the like.

  The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of epoxy compounds, Preferably it is 1 weight part or more, Preferably it is 15 weight part or less.

  The curable epoxy resin composition that is an adhesive may further contain a photosensitizer or a photosensitization aid as necessary. By using a photosensitizer, the reactivity of cationic polymerization is improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes. The photosensitizer is preferably contained in the range of 0.1 to 20 parts by weight in 100 parts by weight of the curable epoxy resin composition. In addition, the use of a naphthalene-based photosensitization aid as the photosensitization aid improves the curability of the adhesive composition as compared with the case where it is not blended. The naphthalene-based photosensitization aid is preferably contained within a range of 0.1 to 5 parts by weight in 100 parts by weight of the curable epoxy resin composition.

  Furthermore, the curable epoxy resin composition may contain a compound that promotes cationic polymerization, such as an oxetane compound or a polyol compound.

  After applying the adhesive comprising the curable epoxy resin composition containing the epoxy compound as described above to the polarizing film, the optical film, the adhesive surface of the transparent protective layer, or both adhesive surfaces, the adhesive is applied. The composite polarizing plate can be obtained by pasting on the processed surface and curing the uncured adhesive layer by irradiating active energy rays. As an adhesive coating method, for example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used.

  The adhesive composed of the curable epoxy resin composition can basically be used as a solventless adhesive that does not substantially contain a solvent component, but each coating method has an optimum viscosity range. Therefore, a solvent may be included for viscosity adjustment. It is preferable to use a solvent that dissolves the epoxy resin composition well without degrading the optical performance of the polarizing film. For example, hydrocarbons represented by toluene, esters represented by ethyl acetate, and the like. And organic solvents such as

  Although the light source used for irradiation of active energy rays is not particularly limited, for example, an ultraviolet light source such as a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a black light lamp, or a metal halide lamp is preferably used. The irradiation intensity and irradiation amount of the active energy ray are such that the cationic photopolymerization initiator can be sufficiently activated and do not adversely affect the cured adhesive layer, polarizing film, optical film, and transparent protective layer. Adjust as appropriate.

  When using the adhesive which consists of a curable epoxy resin composition, the thickness of the adhesive bond layer after hardening is 0.1-50 micrometers normally, Preferably it is 0.5-20 micrometers, More preferably, it is 1-10 micrometers.

(Other parts)
The composite polarizing plate of this invention may have the adhesive layer laminated | stacked on the optical film. In the case where the composite polarizing plate is applied to a liquid crystal display device, this pressure-sensitive adhesive layer can be suitably used, for example, for bonding with a liquid crystal cell.

  As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, those using a base polymer such as an acrylic ester, methacrylic ester, butyl rubber, or silicone can be used. Among them, one or more (meth) acrylates selected from butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. A pressure-sensitive adhesive containing a polymer or copolymer having a main structural unit as a base polymer is preferably used. In the base polymer, a polar monomer is usually copolymerized together with the main structural unit. Examples of the polar monomer include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, Mention may be made of monomers having a carboxyl group, a hydroxyl group, an amino group, an epoxy group and the like, such as glycidyl (meth) acrylate. The pressure-sensitive adhesive usually contains one or more crosslinking agents in addition to the base polymer. Examples of the crosslinking agent include divalent or polyvalent metal salts that form a carboxylic acid metal salt with a carboxyl group, and polyisocyanate compounds that form an amide bond with a carboxyl group.

  The thickness of the pressure-sensitive adhesive layer can be about 3 to 50 μm. When the pressure-sensitive adhesive layer is applied to the composite polarizing plate, the optical film surface may be subjected to a surface treatment such as a corona treatment. Moreover, when forming an adhesive layer, it is normal to cover the adhesive layer surface with a peeling film etc. until the time of use of a composite polarizing plate.

When the composite polarizing plate is applied to a liquid crystal display device such as a VA mode, a viewing angle compensation film can be laminated on the optical film. In this case, the pressure-sensitive adhesive layer used for bonding with the liquid crystal cell can be provided on the viewing angle compensation film. The viewing angle compensation film, and a film having a retardation in a thickness direction satisfy a relation of _{n x = n y <n z} .

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples,% and part representing the content are based on weight unless otherwise specified. In addition, the thickness, retardation value, and in-plane retardation value variation of the optical film were measured by the following method.

[Measurement of optical film thickness]
It measured using digital micrometer MH-15M (made by Nikon Corporation).

[Measurement of retardation value of optical film]
Measurement was performed at a measurement wavelength of 590 nm using a phase difference measurement device KOBRA-WR (manufactured by Oji Scientific Instruments).

[Measurement of in-plane retardation value fluctuation of optical film]
In the same manner as the measurement of the retardation value, in-plane retardation values were measured immediately after production and 21 days after production. The in-plane retardation value fluctuation ΔR ₀ is expressed by the following formula (V) from the in-plane retardation value R ₀ 1 immediately after manufacturing and the in-plane retardation value R ₀ 2 21 days after manufacturing:
ΔR ₀ = (R ₀ 2−R ₀ 1) × 140 / R ₀ 1 (V)
Sought by. As shown in the equation (V), the in-plane retardation value variation ΔR ₀ is 140 / R to the difference between R ₀ 2 and R ₀ 1 in order to eliminate the influence of the magnitude of the in-plane retardation value. by applying a ₀ 1, the variation rate of the in-plane retardation value in-plane retardation value immediately after production was obtained by converting in the case of 140 nm.

<Example 1>
90 parts of polypropylene resin (“Nobrene FS2011DG3” manufactured by Sumitomo Chemical Co., Ltd., MFR = about 2.3 g / 10 min, ethylene content = about 0.5%), and alicyclic saturated hydrocarbon resin (Arakawa Chemical Industries ( Co., Ltd. “Alcon P-125”, softening point 125 ° C.) 10 parts is melt kneaded using a single screw extruder, then melt extruded at a resin temperature of 250 ° C., and rapidly cooled with a 20 ° C. cooling roll. Thus, a raw film having a thickness of 40 μm was obtained. This raw film was stretched uniaxially with a tenter transverse stretching machine. Stretching is performed at a line speed of 5 m / min, first through a preheating zone in which the temperature is adjusted to 144 ° C., and then in the stretching zone in which the temperature is adjusted to 134 ° C., the final draw ratio is 5 times. It was done. The in-plane retardation value R ₀ 1, thickness direction retardation value R _th , Nz coefficient and thickness immediately after production of the obtained stretched film (optical film) were measured. Further, as the stability evaluation of the in-plane retardation value, the in-plane retardation value R ₀ 2 21 days after the production was measured, and the in-plane retardation value variation ΔR ₀ was obtained by the above formula (V).

<Example 2>
Except that the amount of the polypropylene resin and alicyclic saturated hydrocarbon resin used is 80 parts and 20 parts, respectively, and the temperature of the preheating zone and the stretching zone of the tenter transverse stretching machine is adjusted to 139 ° C. and 129 ° C., respectively. An optical film was produced in the same manner as in Example 1, and the retardation characteristics and thickness were measured.

<Example 3>
90 parts of polypropylene resin (“Nobrene FS2011DG3” manufactured by Sumitomo Chemical Co., Ltd., MFR = about 2.3 g / 10 min, ethylene content = about 0.5%), and alicyclic saturated hydrocarbon resin (Arakawa Chemical Industries ( Co., Ltd. “Alcon P-125”, softening point 125 ° C.) 10 parts was melt kneaded with a twin screw granulator to obtain pellets, and then melt extrusion at a resin temperature of 250 ° C. using a single screw extruder. This was followed by quenching with a 20 ° C. cooling roll to obtain a 110 μm thick raw film. This raw film is preheated and then stretched 1.5 times in the longitudinal direction at a stretching temperature of 138 ° C. due to the difference in roll peripheral speed of the longitudinal stretching machine, followed by a line speed of 2 m / min. The film is passed through a preheating zone adjusted to 149 ° C., followed by transverse stretching in a drawing zone adjusted to a temperature of 139 ° C. so that the final draw ratio is 4.4 times. ) About the obtained optical film, retardation characteristics and thickness were measured in the same manner as in Example 1.

<Example 4>
The amount of the polypropylene resin and alicyclic saturated hydrocarbon resin used is 80 parts and 20 parts, respectively, the stretching temperature by the longitudinal stretching machine is 133 ° C., the preheating zone of the tenter transverse stretching machine and the temperature of the stretching zone are 144 respectively. An optical film was produced in the same manner as in Example 3 except that the temperature was adjusted to ° C and 134 ° C, and the retardation characteristics and thickness were measured.

<Comparative Example 1>
Melting polypropylene resin made of propylene / ethylene random copolymer (“Noblen W151” manufactured by Sumitomo Chemical Co., Ltd., MFR = about 2.5 g / 10 min, ethylene content = about 5%) using a twin screw extruder. The mixture was kneaded, melt-extruded at a resin temperature of 250 ° C., and rapidly cooled with a 20 ° C. cooling roll to obtain a 40 μm-thick original film. This raw film was stretched uniaxially with a tenter transverse stretching machine. Stretching is performed at a line speed of 5 m / min, first through a preheating zone in which the temperature is adjusted to 136 ° C., and then in the stretching zone in which the temperature is adjusted to 126 ° C., the final draw ratio is 4 times. It was done. About the obtained stretched film (optical film), the retardation characteristics and thickness were measured in the same manner as in Example 1.

<Comparative example 2>
A 110 μm-thick original fabric film obtained by the same method as in Comparative Example 1 was preheated, and then stretched 1.7 times in the longitudinal direction at a stretching temperature of 125 ° C. due to the difference in the peripheral speed of the longitudinal stretching machine. First, the film was passed through a preheating zone whose temperature was adjusted to 136 ° C. at a line speed of 2 m / min by a stretching machine, and then the final stretching ratio was 3.0 times in a stretching zone whose temperature was adjusted to 126 ° C. Thus, transverse stretching was performed to obtain a stretched film (optical film). About the obtained optical film, retardation characteristics and thickness were measured in the same manner as in Example 1.

  The retardation characteristics and thicknesses of the optical films of Examples 1 to 4 and Comparative Examples 1 to 2 are summarized in Table 1.

As shown in Table 1, the optical films of Examples 1 and 2 have the same stretching type and have comparatively different stretching types and thicknesses as well as the optical film of Comparative Example 1 having the same thickness. Compared with the optical film 2, the in-plane retardation value variation ΔR ₀ is small, and the stability of the in-plane retardation value is excellent. Similarly, the optical films of Examples 3 to 4 have the same stretching format and the same thickness as that of Comparative Example 2, but also the optical film of Comparative Example 1 having a different stretching format and thickness. However, the in-plane retardation value variation ΔR ₀ is small, and the stability of the in-plane retardation value is excellent.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 composite polarizing plate, 101 polarizing film, 102 optical film, 103 transparent protective layer, 104, 105 adhesive layer.

Claims (9)

It consists of a resin film containing a polypropylene resin and an alicyclic saturated hydrocarbon resin classified as a petroleum resin ,
The in-plane retardation value R ₀ is in the range of 40 to 500 nm, and the thickness direction retardation value R _th is in the range of 20 to 500 nm.
Plane slow axis direction of the refractive indices n _x of the resin film, the refractive index n _y in-plane fast axis direction, and the refractive index in the thickness direction is n _z, wherein: Nz coefficient = (n _{x -n z) / (n x -n} y) Nz coefficient defined by is in the range of 0.9 to 3, an optical film. The optical film according to claim 1, which has a thickness of 35 μm or less. It consists of a stretched film of a resin composition containing a polypropylene resin and an alicyclic saturated hydrocarbon resin classified as a petroleum resin ,
The optical film according to claim 1, wherein the resin composition contains 0.1 to 30% by weight of the alicyclic saturated hydrocarbon resin.   The optical film according to any one of claims 1 to 3, wherein a softening point of the alicyclic saturated hydrocarbon resin is in a range of 110 to 145 ° C.   The optical film according to any one of claims 1 to 4, wherein the polypropylene resin is a copolymer of propylene and ethylene containing 10% by weight or less of ethylene units.   The optical film according to claim 1, wherein the polypropylene resin is substantially composed of a homopolymer of propylene.   A composite polarizing plate comprising a polarizing film and the optical film according to claim 1 laminated on one side of the polarizing film.   The composite polarizing plate according to claim 7, further comprising a transparent protective layer on a surface opposite to a surface on which the optical film is laminated.   The said optical film is a composite polarizing plate of Claim 7 or 8 laminated | stacked on the said polarizing film through the hardened | cured material layer of an active energy ray curable epoxy adhesive.

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