JP2011180257A - Optical film, coating liquid for producing the optical film, and method for producing the film and the coating liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film useful as a so-called "c-plate", comprising a mixture of resin and an inorganic layer compound which is not modified with an organic substance, wherein the inorganic layer compound not modified with an organic substance is sufficiently dispersed in the resin. <P>SOLUTION: The optical film includes an inorganic layer compound which is not modified with an organic substance, with the compound having a cation exchangeability of 90 to 120 meq/100 g, and a cellulose derivative having a substitution degree of hydroxyl groups of 2.1 to 3.0 and a number average molecular weight, in the range from 25,000 to 120,000. A coating liquid for producing the optical film, wherein the inorganic layer compound and the cellulose derivative are mixed in a polar organic solvent is provided; the coating liquid is produced by a method for dispersing the inorganic layer compound in a polar organic solvent and mixing the dispersion liquid with a polar organic solvent solution of the cellulose derivative; and the optical film is produced by applying the coating liquid on a substrate and drying. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical film composed of an inorganic layered compound not modified with an organic substance and a cellulose derivative, and a coating liquid for producing the optical film. Moreover, this invention relates also to the manufacturing method of the said optical film and the coating liquid for optical film manufacture.

  In recent years, low-power consumption, low-voltage, light-weight and thin liquid crystal displays are rapidly spreading as information display devices such as mobile phones, portable information terminals, computer monitors, and televisions. With the development of liquid crystal technology, various modes of liquid crystal displays have been proposed, and problems with liquid crystal displays such as response speed, contrast, and narrow viewing angle are being solved. However, it has been pointed out that the viewing angle is still 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 perpendicular to a substrate. In this vertical alignment mode, in the non-driven state, since the liquid crystal molecules are aligned perpendicular to the substrate, the light passes through the liquid crystal layer without changing the polarization. For this reason, by arranging the linearly polarizing plates so that the absorption axes are orthogonal to each other above and below the liquid crystal panel, almost complete black display can be obtained when viewed from the front, and a high contrast ratio can be obtained. .

  However, in such a VA mode liquid crystal display device having only a polarizing plate in a liquid crystal cell, the axial angle of the disposed polarizing plate is deviated from 90 ° when viewed obliquely. Light leakage occurs due to the birefringence of the rod-like liquid crystal molecules, and the contrast ratio varies significantly and the color tone changes depending on the viewing angle. Such a contrast ratio and a color change when the liquid crystal display device is viewed obliquely are referred to as “viewing angle characteristics”.

  In order to eliminate this problem of viewing angle characteristics, it is necessary to place an optical compensation film between the liquid crystal cell and the linear polarizing plate. Conventionally, a biaxial retardation film is provided between the liquid crystal cell and the upper and lower polarizing plates, respectively. The specification to arrange one by one, or the specification to arrange the uniaxial retardation film and the complete biaxial retardation film one by one above and below the liquid crystal cell, or both on one side of the liquid crystal cell is adopted. I came. For example, in claim 15, paragraph 0036 of Japanese Patent Application Laid-Open No. 2001-109090 (Patent Document 1), in a vertical alignment mode liquid crystal display device, an a plate (that is, a liquid crystal cell) It is described that a positive uniaxial retardation film) and a c-plate (ie a fully biaxial retardation film) are arranged.

A positive uniaxial retardation film is a film having an _Nz coefficient of approximately 1.0, and a complete biaxial retardation film is a film having an in-plane retardation value R _{0 of} approximately 0. . Here, the refractive index in the in-plane slow axis direction n _x of the film, the refractive index in the in-plane fast axis direction n _y of the film, the refractive index in the thickness direction of the film n _z, the thickness of the film d In this case, the in-plane retardation value R ₀ , the thickness direction retardation value R _th , and the N _z coefficient are defined by the following expressions (1) to (3), respectively.

_{R 0 = (n x -n y} ) × d (1)
R _th = [(n _x + _ny ) / 2−n _z ] × d (2)
N _z factor _{= (n x -n z) /} (n x -n y) (3)

Since the _{n z ≒ (nearly equal) n} y is a uniaxial film, the Nz coefficient ≒ 1.0. However, even with a uniaxial film, the Nz coefficient varies between about 0.8 and 1.5 depending on the stretching conditions. Further, since the n _x ≒ n _y is a perfectly biaxial film, the R ₀ ≒ 0. A completely biaxial film has a negative uniaxial property because only the refractive index in the thickness direction is different (small), and is also called a film in which the optical axis is in the normal direction. Also called a plate.

As the uniaxial retardation film, for example, a resin film stretched by free end longitudinal uniaxial stretching, fixed end lateral uniaxial stretching or the like is often used. A free-end uniaxially stretched film is obtained, for example, by a method of longitudinally uniaxially stretching in the longitudinal direction (flow direction) of the film, and usually 0.9 ≦ N _z coefficient ≦ 1.1. The fixed-end lateral uniaxially stretched film is obtained, for example, by a method of laterally uniaxially stretching with a tenter or the like, and usually 0.8 ≦ N _z coefficient ≦ 1.5, and often has some biaxiality, Since it can be said that the film generally has uniaxial optical characteristics, a film having an _Nz coefficient in this range is also referred to as a uniaxial retardation film in this specification.

  On the other hand, as a completely biaxial film (c plate), it is known to use a coating layer of an inorganic layered compound. For example, claims 1, 4 and 13 of JP 2008-15500 A (Patent Document 2) and claims 1, 2, 3, 4 and 5 of JP 2009-255671 A (Patent Document 3) include cellulose. It is disclosed that a coating layer containing polyvinyl alcohol and an inorganic layered compound is formed on a cellulose acylate film such as acetate to form a protective film for a polarizing plate. Claim of Japanese Patent No. 3060744 (Patent Document 4) 1. Paragraph 0022 discloses that the inorganic layered compound layer is a retardation film. Further, referring to paragraph 0023, etc., the inorganic layered compound that is not modified with an organic substance that can swell or disperse in water can be coated with polyvinyl. It is also disclosed that a retardation film is formed by mixing a hydrophilic resin such as alcohol to form a coating layer. Claim 1 of JP-A-10-10320 (Patent Document 5) also discloses that a retardation film is formed by forming a composition containing polyvinyl alcohol and an inorganic layered compound not modified with an organic substance. Yes.

  An optical film comprising a mixture of an inorganic layered compound not modified with an organic material and a hydrophilic resin disclosed in these documents often has a problem that the haze value of the optical film increases.

JP 2001-109909 A JP 2008-15500 A JP 2009-25671 A Japanese Patent No. 3060744 Japanese Patent Laid-Open No. 10-10320

  An object of the present invention is an optical film useful as a so-called c-plate comprising a mixture of an inorganic layered compound not modified with an organic substance and a resin, and the inorganic layered compound not modified with an organic substance is sufficiently dispersed in the resin. It is to provide an optical film.

  Another object of the present invention is to provide a coating liquid in which an inorganic layered compound not modified with an organic substance is dispersed in an organic solvent, which is useful for producing the above-described optical film. Another object of the present invention is to provide a method for producing the coating liquid advantageously, and further to provide a method for producing the optical film described above using the coating liquid obtained by the method. is there.

  The optical film of the present invention is not modified with an organic substance, has an inorganic layered compound having a cation exchange capacity of 90 to 120 meq / 100 g, a hydroxyl group substitution degree of 2.1 to 3.0, and a number average molecular weight of 2. It consists of cellulose derivatives in the range of 15,000 to 120,000.

  In the optical film of the present invention, the inorganic layered compound is preferably a smectite group mineral.

  The cellulose derivative in the present invention preferably has a weight ratio of the inorganic layered compound to the cellulose derivative in the film in the range of 0.5 to 5.0.

  In the optical film of the present invention, it is preferable that the in-plane retardation value is 0 to 5 nm and the thickness direction retardation value is 40 to 300 nm.

  The present invention further includes an inorganic layered compound that is not modified with an organic substance and has a cation exchange capacity of 90 to 120 meq / 100 g, a hydroxyl group substitution degree of 2.1 to 3.0, and a number average molecular weight of 25,000. Provided is a coating liquid for producing an optical film comprising a cellulose derivative in the range of 1,000 to 120,000 and a polar organic solvent.

  In the coating liquid of the present invention, the weight ratio of the inorganic layered compound to the cellulose derivative is in the range of 0.5 to 5.0, and the total concentration of the inorganic layered compound and the cellulose derivative is 3 to 15 with respect to the polar organic solvent. It is preferable to be in the range of% by weight.

  The present invention also provides an inorganic layered compound that is not modified with an organic substance and has a cation exchange capacity of 90 to 120 meq / 100 g, a hydroxyl group substitution degree of 2.1 to 3.0, and a number average molecular weight of 25,000. A method for producing a coating liquid for producing an optical film comprising a cellulose derivative in the range of 1,000 to 120,000 and a polar organic solvent, wherein the inorganic layered compound is dispersed in the polar organic solvent, and the dispersing step And a cellulose derivative mixing step of mixing the dispersion obtained in the above with a polar organic solvent solution of the cellulose derivative.

  The present invention further provides a method for producing an optical film comprising a coating step of coating the above-described coating liquid of the present invention on a substrate, and a drying step of removing the polar organic solvent after coating.

  According to the present invention, a film composed of a mixture of an inorganic layered compound not modified with an organic substance and a cellulose derivative is combined with a cellulose derivative despite the use of the inorganic layered compound not modified with an organic substance. Thus, an optical film that maintains transparency and has transparency suitable for optical applications is provided. According to such an optical film of the present invention, since an inorganic layered compound not modified with an organic substance is used, physical property deterioration caused by an organic modifier or the like, in particular, adhesive strength reduction when combined with an adhesive layer does not occur. The effect is played. In addition, there is an advantage that an optical film made thereof is inexpensive and high in productivity because it does not use a modified inorganic layered compound having a large number of processes and inferior in mass productivity.

[Optical film]
The optical film of the present invention is not modified with an organic substance, has an inorganic layered compound having a cation exchange capacity of 90 to 120 meq / 100 g, a hydroxyl group substitution degree of 2.1 to 3.0, and a number average molecular weight of 2. And a mixture of cellulose derivatives in the range of 15,000 to 120,000.

  In general, many composite materials in which an inorganic layered compound is dispersed in a resin are organically modified to increase the affinity with the resin and bring about dispersibility. Conversely, the inorganic layered compound is not modified such as modified. A composite material using is often inferior in transparency. Thus, although some kind of modified inorganic layered compound has been used for the transparent material, organic substances that modify the inorganic layered compound may be liberated and bleed out from the composite material. Although the mechanism of action of the pressure-sensitive adhesive layer of the retardation film comprising the inorganic layered compound and the pressure-sensitive adhesive layer, which is the subject of the present invention, is not clearly understood, the modifier is a modifier of the inorganic layered compound as described above. It is presumed that the compound is liberated and the pressure sensitive adhesive is modified. However, when an inorganic layered compound that is not modified with an organic substance is selected, it is difficult to use as an optical film because of poor transparency.

  In the present invention, although the above-described cellulose derivative and the inorganic layered compound not modified with an organic substance are used, the inorganic layered compound not modified with an organic substance exhibits sufficient dispersibility in the cellulose derivative and is suitable for optical applications. It has been found that it has suitable transparency, and uses an inorganic layered compound that is not modified with an organic substance. Therefore, the physical properties decrease due to the modifier compound described above, particularly when combined with an acrylic pressure-sensitive adhesive layer. There is an effect that no reduction occurs. In addition, the use of a modified inorganic layered compound having a large number of processes and inferior mass productivity is also advantageous in that the optical film made thereof is inexpensive and has high productivity.

  The inorganic layered compound used in the present invention is not modified with an organic substance or the like. An inorganic layered compound is a clay mineral in which a sheet-type structure formed by connecting metal ions such as sodium, magnesium, aluminum, potassium, calcium, and iron and silicic acid is formed in layers, and is a layered silicate mineral Is preferred.

  Examples of such inorganic layered compounds include, for example, smectite group minerals such as montmorillonite, saponite, hectorite, beidellite, stevensite, kaolinite, antigonite, monoclinic chrysotile stone, orthorhombic chrysotile stone, parachrysotile stone, lizard stone , Kaolinite minerals such as Amesite, Kelly, Gruna, and Nupoite, mica minerals such as muscovite, celadonite, Roscoe mica, Tobe mica, iron mica, phlogopite, nacre, clintonite, etc. It is done. These inorganic layered compounds may be used alone or in combination with a plurality of different types.

Trivalent aluminum in the crystal layer of such an inorganic layered compound is partially replaced by divalent magnesium or iron, and a portion having a negative permanent layer charge is generated on the crystal layer surface. In order to compensate for the charge, a cation of an alkali metal such as Na ⁺ or K ⁺ or an alkaline earth metal such as Ca ²⁺ or Mg ²⁺ is adsorbed on the portion having a permanent layer charge. A value indicating how many equivalents of this cation are held per 100 g of the inorganic layered compound is called a cation exchange capacity. Therefore, the cation exchange capacity represents the ability of the inorganic layered compound to retain cations on the layer surface.

  Such a cation exchange capacity can be measured by a known method. For example, “Cation test of soil cation exchange capacity (CEC)” described on page 361 of ammonium acetate solution leaching method and ground material test method and explanation (issued by Geotechnical Society, ISBN: 978-4-88644-083-9) "Method" etc. can be referred to.

  The cation exchange capacity of the inorganic layered compound used in the present invention is 90 to 120 meq / 100 g. From the viewpoint of dispersibility and optical properties, the cation exchange capacity is more preferably from 100 to 120 meq / 100 g. When an optical film is produced using an inorganic layered compound having a cation exchange capacity of less than 90 meq / 100 g, a desired thickness direction retardation value may not be obtained. When an optical film is produced using an inorganic layered compound having a cation exchange capacity exceeding 120 meq / 100 g, sufficient transparency as an optical film may not be obtained.

  Among these, an artificially synthesized layered silicate mineral is preferable, and synthetic smectite is more preferable. Synthetic smectite has a higher purity than natural products, has a small particle size, and has a narrow distribution, and is therefore relatively suitable as a constituent material for optical films.

  Even if it is a natural layered silicate mineral, it is generally less expensive than an artificially synthesized material if it is highly purified and has a sufficiently small particle size and can be used for optical film applications. Therefore, since it greatly contributes to the productivity improvement of the optical film, it is preferably used.

  Naturally-occurring inorganic layered compounds are produced by volcanic ash deposited on the seabed and lake bottom under erosion and weathering under elevated temperature and pressure. By mining and refining these, industrially usable inorganic layered compounds can be obtained.

  In order to synthesize smectite artificially, a mineral such as gel or feldspar having a composition close to the target inorganic layered compound is usually used as the starting material, and this starting material is hydrothermally reacted with sufficient thermal energy and reaction time. Although the method is employed, the cation exchange capacity of the inorganic layered compound can be controlled by changing the pressure and temperature of the hydrothermal reaction and the amount of the raw materials such as aluminum, magnesium and iron.

  The inorganic layered compound thus obtained can be easily obtained as a commercial product, for example, Kunipia (sold from Kunimine Industry Co., Ltd .: purified natural product bentonite), Smecton SA (Sold from Kunimine Industry Co., Ltd .: synthetic saponite), Wengel (sold from Hojun Co., Ltd .: purified natural bentonite), white bentonite (sold from Volclay Japan Co., Ltd .: purified natural bentonite), Veegum (sold from Vanderbilt: purified natural smectite), Lucentite (Coop Chemical) Co., Ltd .: Synthetic smectite), Micromica (Corp Chemical Co., Ltd .: Synthetic mica), Somasifu (Corp Chemical Co., Ltd .: Synthetic mica), Laponite (Sold from Rockwood Additives Co., Ltd .: Synthetic smectite) And the like.

(Cellulose derivative)
The cellulose derivative used in the present invention refers to a compound in which a part or all of the hydroxyl group is substituted with an alkanoyloxy group or an alkoxy group by esterification or etherification in the cellulose corresponding to the following formula (I). .

  For example, cellulose acetate (including what is called cellulose triacetate or cellulose diacetate), cellulose propionate, cellulose acetate propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, carboxymethylcellulose, hydroxyethyl Including methylcellulose, hydroxypropylmethylcellulose, methylcellulose and the like. Such cellulose derivatives may be used alone or in combination with a plurality of different types. Moreover, you may add and use additives, such as a small amount of plasticizers.

  And in this invention, the cellulose derivative in which the substitution degree of a hydroxyl group exists in the range of 2.1-3.0 is employ | adopted. Here, the substitution degree of the hydroxyl group in the cellulose derivative has the same meaning as the degree of substitution generally called (Degree of Substitution), and can also be called a unit ring (pyranose ring) of cellulose corresponding to the following formula (II): ) Means the ratio of three hydroxyl groups present per one being replaced by other groups.

  Since the cellulose has a structure in which a large number of unit rings (pyranose rings) corresponding to the formula (II) are bonded as shown in the above formula (I), the degree of substitution of the hydroxyl group is determined as an average value. Further, as can be seen from the above definition, since there are three hydroxyl groups in the unit ring (pyranose ring) of cellulose, the degree of substitution of hydroxyl groups in the cellulose derivative is 3 at the maximum. In the present invention, a cellulose derivative in which all of the hydroxyl groups are substituted or 70% or more of the hydroxyl groups are substituted and some of the hydroxyl groups remain as they are is used.

Such a substitution degree of a hydroxyl group can be measured by a known method. For example, regarding cellulose acetate, the degree of hydroxyl substitution can be determined by measuring ¹³ C-NMR after propionylating cellulose acetate. For the measurement method, the method of Tezuka et al. (Carbohydr. Res. 273 (1995) 83-91) can be referred to.

  When a cellulose derivative having a hydroxyl group substitution degree of less than 2.1 is used, the durability of the resulting optical film in a high temperature and high humidity environment tends to be insufficient. The substitution degree of the hydroxyl group in this cellulose derivative is preferably 2.4 or more.

  As the cellulose derivative, those having a number average molecular weight of 25,000 to 120,000 are adopted. When a cellulose derivative having a number average molecular weight of less than 25,000 is used, the mechanical strength of the resulting optical film tends to be weak. On the other hand, when a cellulose derivative having a number average molecular weight exceeding 120,000 is used, the inorganic layered compound tends to be difficult to disperse sufficiently in a coating liquid obtained by blending a compatible polymer and an inorganic layered compound. As a result, even in an optical film obtained using such a coating solution, the dispersion state of the inorganic layered compound is deteriorated, and the transparency tends to be lowered. The number average molecular weight of the cellulose derivative is preferably 25,000 or more and 95,000 or less. These number average molecular weights were measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve.

  The cellulose derivative used in the present invention may be a mixture of a low-substituted cellulose acetate and a high-substituted cellulose acetate. The substitution degree of the hydroxyl group of the low-substituted cellulose acetate is preferably 2.1 to 2.6, and the number average molecular weight is preferably 25,000 to 75,000. The degree of substitution of the hydroxyl group of the highly substituted cellulose acetate is preferably 2.8 to 3.0, and the number average molecular weight is preferably 65,000 to 95,000. The degree of substitution of hydroxyl groups in the mixture of low-substituted cellulose acetate and high-substituted cellulose acetate is preferably 2.4 or more. When the substitution degree of the hydroxyl group of the mixture of the low-substituted cellulose acetate and the high-substituted cellulose acetate is less than 2.4, the heat and humidity resistance of the optical film is lowered, and the optical film may be whitened.

  Although it does not specifically limit as a manufacturing method of a cellulose derivative, Usually, cellulose raw materials, such as a wood pulp with comparatively high alpha-cellulose content, are disaggregated and disintegrated, and then acetic acid, propionic acid, butyric acid, or a small amount A pretreatment activation step of spraying and mixing the acetic acid containing the acidic catalyst, and treating the activated cellulose with a mixed acid comprising acetic acid, propionic acid, butyric acid, etc., an anhydride thereof, and an acidic catalyst (for example, sulfuric acid). An esterification step for obtaining a primary cellulose ester, an aging step for hydrolyzing the primary cellulose ester to obtain a secondary cellulose ester having a desired substitution degree, and separating and purifying the obtained secondary cellulose ester from the reaction solution; A post-treatment step that is stabilized and dried is employed.

  The cellulose derivative thus obtained can be easily obtained as a commercial product. For example, LM-80 (manufactured by Daicel Chemical Industries, Ltd.), L-20, L-30, L-40, L-70 (Daicel Chemical Industry). (Manufactured by: Cellulose diacetate), LT-35, LT-55, LT-105 (manufactured by Daicel Chemical Industries, Ltd .: cellulose triacetate), TC-5 (manufactured by Shin-Etsu Chemical Co., Ltd .: hydroxypropyl methylcellulose), Metroles ( Shin-Etsu Chemical Co., Ltd .: methyl cellulose), Shin-Etsu AQOAT (Shin-Etsu Chemical Co., Ltd .: hydroxypropyl methylcellulose acetate succinate), Meserose (manufactured by Sakai Industrial Co., Ltd .: methyl cellulose), cellulose triacetate product number 181005 (manufactured by Aldrich: cellulose) Triacetate) And the like.

(Optical film)
In the optical film of the present invention, the weight ratio of the inorganic layered compound to the cellulose derivative is preferably in the range of 0.5 to 5. When the weight ratio of the inorganic layered compound to the cellulose derivative is less than 0.5, there is a tendency that a sufficient thickness direction retardation value cannot be obtained when an optical film is obtained. On the other hand, when the weight ratio exceeds 5, when they are mixed with an organic solvent to form a coating solution, the inorganic layered compound tends to be difficult to disperse sufficiently. Also in the obtained optical film, the dispersion state of the inorganic layered compound is deteriorated and the transparency tends to be lowered. The weight ratio of the inorganic layered compound to the cellulose derivative is more preferably in the range of 1 to 4.

  The optical film of the present invention may contain various additives for further improving the hydrophobicity, durability, plasticity, and cohesion, such as a lubricant, a crosslinking agent, and a plasticizer.

  The optical film of the present invention is a complete biaxial retardation film (c plate) by appropriately adjusting the thickness of the film or the blending ratio of the composition constituting the film to control the thickness direction retardation value. Can do. The retardation value is preferably 0 to 5 nm in the plane and 40 to 300 nm in the thickness direction. If the in-plane retardation value exceeds 5 nm, the value cannot be ignored, the negative uniaxiality in the thickness direction is impaired, and light leakage may occur when bonded to a liquid crystal cell in combination with a polarizing plate. . Further, the thickness direction retardation value is appropriately selected according to the use of the retardation film, particularly the characteristics of the liquid crystal cell to be bonded in combination with the polarizing plate, and is particularly limited as long as it is within the above range. Although it is not a thing, 50-270 nm is more preferable.

  This thickness direction retardation value can be controlled by the content of the clay mineral in the film and the thickness of the film. Therefore, the thickness of the film is not particularly limited as long as it is a thickness necessary for realizing the retardation required for the retardation film.

The refractive index anisotropy in the thickness direction is represented by the thickness direction retardation value R _th defined by the above formula (2), and is tilted by 40 degrees with the in-plane retardation value R ₀ and the slow axis as the tilt axis. Using the retardation value R ₄₀ , the thickness d of the film, and the average refractive index n ₀ of the film, _nx , n by numerical calculation from the above formula (1) and the following formulas (4) and (5) _y and _nz can be obtained and can be calculated by substituting these into equation (2).

_{R 40 = (n x -n y} ') × d / cos (φ) (4)
(N _x + _ny + _nz ) / 3 = n ₀ (5)
here,
φ = sin ⁻¹ [sin (40 °) / n ₀ ] (6)
_ny ′ = _ny × _nz / [ _ny ² × sin ² (φ) + _nz ² × cos ² (φ)] ^1/2 (7)

In the commercially available phase difference measuring apparatus, the numerical calculation shown here is automatically performed in the apparatus, and the in-plane retardation value R ₀ and the thickness direction retardation value R _th are automatically displayed. Many of them are included, and KOBRA-WR (manufactured by Oji Scientific Instruments Co., Ltd.) used in Examples described later is also like that.

  The internal haze value (the value obtained by subtracting the surface haze value from the total haze value) of the optical film of the present invention is preferably 1.5% or less. More preferably, it is 1% or less. If the internal haze value exceeds 1.5%, sufficient transparency as an optical film cannot be maintained.

  The pressure-sensitive adhesive that can be used in the present invention adheres to the surface of another substance simply by pressing it, and when it is peeled off from the adherend surface, it is removed without leaving any trace as long as the adherend has strength. It refers to a viscoelastic body, also called an adhesive. As such a pressure-sensitive adhesive, a conventionally known appropriate pressure-sensitive adhesive can be used without particular limitation, and examples thereof include acrylic, rubber-based, urethane-based, silicone-based, and polyvinyl ether-based pressure-sensitive adhesives. It is done.

[Coating liquid for optical film production]
The present invention also provides an inorganic layered compound not modified with an organic substance, a cellulose derivative having a hydroxyl group substitution degree of 2.1 to 3.0 and a number average molecular weight in the range of 25,000 to 120,000. A coating liquid containing a polar organic solvent is provided. Such a coating liquid of the present invention can be suitably used for the production of the optical film of the present invention described above.

  The polar organic solvent used in the coating liquid of the present invention is not particularly limited as long as it can swell the inorganic layered compound, and further can swell until it exhibits a colloidal shape or dissolves the cellulose derivative. Are, for example, formamide, N, N-dimethylformamide, dimethyl sulfoxide, N, N-dimethylacetamide, N-methylformamide, propylene carbonate, 1,3-dimethyl-2-imidazolidinone, 1,4-dioxane, tetrahydrofuran Acetone, methanol, ethanol, isopropyl alcohol, ethylene glycol, glycerin and the like are exemplified as preferable examples.

  Among the polar organic solvents, those having a relative dielectric constant of 30 or more are preferable, and typical examples of such preferable polar organic solvents include formamide, N, N-dimethylformamide, dimethyl sulfoxide, N, N-dimethylacetamide. , N-methylformamide, propylene carbonate and the like. In addition, a mixed solvent selected from a plurality of these can also be used.

  The solid content concentration in the coating solution is not particularly limited as long as the viscosity after preparation does not cause a practical problem, but it is 3 to 15 wt.% As a solid content concentration of an inorganic layered compound not modified with an organic substance and a cellulose derivative. %. The optimum solid content concentration is appropriately selected depending on the kind of each solid content such as the inorganic layered compound and cellulose derivative and the respective composition ratio.

  Moreover, this coating liquid may contain a viscosity modifier, a leveling agent, an antifoaming agent, etc. for improving the applicability | paintability at the time of coating on a base material.

  An apparatus used to disperse or dissolve the components of such a coating liquid composition is not particularly limited. For example, an ordinary stirring mixer, a homogenizer equipped with a stirring blade of a turbine type or the like is used. (Homogenizer), ball mill, bead mill, paint shaker, ultrasonic disperser and the like. Among these, a bead mill and a paint shaker are preferably used because they can efficiently finely disperse the inorganic layered compound not modified with an organic substance. These apparatuses may be used in combination with a plurality of different types depending on the dispersion state of the inorganic layered compound not modified with an organic substance and the degree of dissolution of a resin component such as a cellulose derivative or a polymer compatible with the cellulose derivative.

[Manufacturing method of coating liquid]
The present invention is also a method for producing a coating liquid comprising an inorganic layered compound, a cellulose derivative, and a polar organic solvent, the dispersion step of dispersing the inorganic layered compound in the polar organic solvent, and the dispersion obtained in the dispersion step The present invention also provides a method for producing a coating liquid comprising a cellulose derivative mixing step of mixing a liquid with a polar solvent solution of a cellulose derivative. Hereinafter, each process of the manufacturing method of the coating liquid of this invention is demonstrated.

  First, in the dispersion step, the inorganic layered compound is mixed with a polar organic solvent, and the inorganic layered compound is dispersed in the polar organic solvent. The polar organic solvent used here can swell the inorganic layered compound not modified with an organic substance as described above, and further can use a solvent that can swell until it exhibits a colloidal shape. It is as follows.

  Finally, in the cellulose derivative mixing step, the inorganic layered compound dispersion obtained as described above is mixed with a polar organic solvent solution of the cellulose derivative. Here, the polar organic solvent for dissolving the cellulose derivative may be the same type of polar organic solvent as that used in the dispersion step, or may be another polar organic solvent. It is the same polar organic solvent as the polar organic solvent used in the dispersion step. Through such steps, the coating liquid for producing an optical film of the present invention as described above is suitably produced.

[Method for producing optical film]
The present invention further provides a method for suitably producing the above-described optical film of the present invention. The manufacturing method of the optical film of this invention includes the application | coating process which apply | coats the coating liquid of this invention mentioned above on a base material, and the drying process which removes a polar organic solvent after application | coating. Through these steps, the above-described optical film of the present invention can be suitably produced.

  In the coating step, the method of coating the coating liquid on the substrate can be appropriately selected according to the physical properties and solid content concentration of the coating liquid, and is not particularly limited. For example, a die coater, A method of coating using an appropriate coating machine such as a comma coater, a reverse roll coater, a gravure coater, a rod coater, a wire bar coater, a doctor blade coater, or an air doctor coater can be employed.

  Also, in the drying process, as a method of removing the polar organic solvent and water by drying the coating liquid coated on the substrate, a method of introducing the substrate into a drying furnace immediately after coating is usually adopted. Is done. The drying temperature and drying time are not particularly limited as long as they are in a range sufficient to remove the solvent used. For example, the temperature is about 50 ° C. to 170 ° C., and the time is about 30 seconds to 30 minutes. You can select from a range in a timely manner.

  The substrate on which the coating liquid is applied is not particularly limited as long as it is a transparent substrate or film suitable for optical applications. For example, glass, cyclic olefin resin film, cellulose triacetate resin film, polyethylene terephthalate Resin film and the like. Such a substrate may be subjected to a release treatment in order to peel the optical film formed by applying a coating liquid and drying the substrate. In addition to the above, any optical functional film such as a polarizing plate, a retardation film, and a brightness enhancement film may be used.

  The resin film used as such a substrate can be easily obtained as a commercial product. For example, as a cyclic olefin resin film, Zeonoa film (manufactured by Nippon Zeon Co., Ltd.), Arton film (manufactured by JSR Corporation) Etc. Examples of the cellulose triacetate resin film include Fujitac TD (Fuji Film Co., Ltd.), Konica Minolta TAC Film KC (Konica Minolta Opto Co., Ltd.), and the like. Also, for example, as polyethylene terephthalate resin film, Diafoil (Mitsubishi Resin Co., Ltd.), Hostafan (Mitsubishi Resin Co., Ltd.), Fusion (Mitsubishi Resin Co., Ltd.), Teijin Tetron Film (Teijin DuPont Film Co., Ltd.) ), Melinex (manufactured by Teijin DuPont Film Co., Ltd.), Mylar (manufactured by Teijin DuPont Film Co., Ltd.), Teflex (manufactured by Teijin DuPont Film Co., Ltd.), Toyobo Ester Film (manufactured by Toyobo Co., Ltd.), Toyobo Espet Film ( Toyobo Co., Ltd., Cosmo Shine (Toyobo Co., Ltd.), Crisper (Toyobo Co., Ltd.), Lumirror (Toray Film Co., Ltd.), Embron (Unitika Ltd.), Emblet (Unitika Ltd.) Made), Skyroll (E - made cable Sea Co., Ltd.), Kofiru (manufactured by high case), Rui communication polyester film (manufactured by Rui with), Taiko polyester film (produced by Futamura Chemical Co., Ltd.) and the like.

  EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples, “%” and “part” representing the content or the amount used are based on weight unless otherwise specified.

  The catalog value of each manufacturer of an inorganic layered compound was adopted for the cation exchange capacity of the inorganic layered compound.

[Example 1]
(1) Preparation of smectite / N, N-dimethylacetamide dispersion As an inorganic layered compound, synthetic smectite that is not organically modified (high cation exchange capacity Lucentite SWN, manufactured by Coop Chemical Co., Ltd., cation exchange capacity = 110 meq / 100 g) Add 6.6 g to 96.1 g of N, N-dimethylacetamide, stir using 79 mL of zirconia beads (diameter: 0.8 mm) and a high-speed stirrer (Three-One Motor BL1200, manufactured by Shinto Kagaku Co., Ltd.). Dispersed to obtain a smectite dispersion.

(2) Preparation of Cellulose Acetate Solution N, N-dimethylacetamide 85 was added to 15 parts of cellulose acetate (cellulose tricetate LT-35, manufactured by Daicel Chemical Industries, Ltd.) having a hydroxyl group substitution degree of 2.88 and a number average molecular weight of 76000. A 15% strength highly substituted cellulose acetate solution was prepared.

(3) Preparation of coating solution To 102.7 g of the smectite and N, N-dimethylacetamide dispersion prepared in (1) above, 15% high-substituted cellulose acetate solution 22 prepared in (2) above. .2 g was added, and the mixture was further stirred for 2 hours with a high-speed stirrer for dispersion treatment. The obtained dispersion was filtered through a membrane filter having a pore size of 6 μm to prepare a coating solution. This coating liquid has the following composition when the whole is 100 parts.

・ High cation exchange capacity Lucentite SWN 5.2 parts ・ Highly substituted cellulose acetate with hydroxyl group substitution degree 2.88 2.6 parts ・ N, N-dimethylacetamide 92.2 parts

(4) Production and Evaluation of Retardation Film The coating liquid prepared in (3) above was applied on a 38 μm-thick polyethylene terephthalate film that had been subjected to a release treatment using an applicator, and 5 ° C. at 80 ° C. The film was dried for a minute to prepare a retardation film coated on a polyethylene terephthalate film. The retardation film side (coating layer side) was transferred to a 4 cm square glass plate via a pressure sensitive adhesive to prepare a retardation value measurement sample. The in-plane retardation value R ₀ and thickness direction retardation value R _th of this sample were measured with a monochromic light having a wavelength of 589 nm using a phase difference measuring device (KOBRA-WR, manufactured by Oji Scientific Instruments). It was measured by. As a result, the in-plane retardation value R ₀ = 0.2 nm and the thickness direction retardation value R _th = 133.2 nm.

  Further, the polyethylene terephthalate film as a base material was changed to a glass plate, and the others were applied in the same manner as above, and the above-mentioned coating solution was applied onto the glass plate and dried to prepare a retardation film. The internal haze value of the retardation film was 0.92% when the retardation film was immersed in a dimethyl phthalate solution and measured using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[Example 2]
(1) Preparation of smectite / N, N-dimethylacetamide dispersion As an inorganic layered compound, synthetic smectite which is not organically modified (low cation exchange capacity Lucentite SWN, manufactured by Corp Chemical Co., Ltd., cation exchange capacity = 101 meq / 100 g) Add 6.6 g to 96.1 g of N, N-dimethylacetamide, stir using 79 mL of zirconia beads (diameter: 0.8 mm) and a high-speed stirrer (Three-One Motor BL1200, manufactured by Shinto Kagaku Co., Ltd.). Dispersed to obtain a smectite dispersion.

(2) Preparation of cellulose acetate solution In the same manner as in Example 1 (2), a 15% strength highly substituted cellulose acetate solution was prepared.

(3) Preparation of coating solution 22.2 g of the highly substituted cellulose acetate solution prepared in (2) above was added to 102.7 g of the smectite and N, N-dimethylacetamide dispersion prepared in (1) above. The mixture was further stirred for 2 hours with a high-speed stirrer to carry out dispersion treatment. The obtained dispersion was filtered through a membrane filter having a pore size of 6 μm to prepare a coating solution. This coating liquid has the following composition when the whole is 100 parts.

・ Low cation exchange capacity Lucentite SWN 5.2 parts ・ Highly substituted cellulose acetate with hydroxyl group substitution degree 2.88 2.6 parts ・ N, N-dimethylacetamide 92.2 parts

(4) Production and evaluation of retardation film In the same manner as in Example 1 (4), a retardation film coated on a polyethylene terephthalate film and a retardation film coated on a glass plate were produced. The former was transferred to a glass plate through a pressure-sensitive adhesive in the same manner as in Example 1 (4), and the retardation value was measured. As a result, the in-plane retardation value R ₀ = 0.6 nm, the thickness direction retardation value. R _th = 78.4 nm. Moreover, about the latter, when the internal haze value was measured similarly to Example 1 (4), it was 0.28%.

[Example 3]
(1) Preparation of smectite / N, N-dimethylacetamide dispersion As an inorganic layered compound, synthetic smectite that is not organically modified (high cation exchange capacity Lucentite SWN, manufactured by Coop Chemical Co., Ltd., cation exchange capacity = 110 meq / 100 g) 3.3 g of synthetic smectite that is not organically modified (low cation exchange capacity Lucentite SWN, manufactured by Corp Chemical Co., Ltd., cation exchange capacity = 101 meq / 100 g) is added to 96.1 g of N, N-dimethylacetamide. In addition, 79 mL of zirconia beads (diameter: 0.8 mm) and a high-speed stirrer (Three-One Motor BL1200, manufactured by Shinto Kagaku Co., Ltd.) were used to disperse the smectite to obtain a smectite dispersion.

(2) Preparation of cellulose acetate solution In the same manner as in Example 1 (2), a 15% strength highly substituted cellulose acetate solution was prepared.

(3) Preparation of coating solution To 102.7 g of the smectite and N, N-dimethylacetamide dispersion prepared in (1) above, 15% high-substituted cellulose acetate solution 22 prepared in (2) above. .2 g was added, and the mixture was further stirred for 2 hours with a high-speed stirrer for dispersion treatment. The obtained dispersion was filtered through a membrane filter having a pore size of 6 μm to prepare a coating solution. This coating liquid has the following composition when the whole is 100 parts.

・ High cation exchange capacity Lucentite SWN 2.6 parts ・ Low cation exchange capacity Lucentite SWN 2.6 parts ・ Highly substituted cellulose acetate having a hydroxyl substitution degree of 2.88 2.6 parts ・ N, N-dimethylacetamide 92.2 parts

(4) Production and evaluation of retardation film In the same manner as in Example 1 (4), a retardation film coated on a polyethylene terephthalate film and a retardation film coated on a glass plate were produced. The former was transferred to a glass plate through a pressure-sensitive adhesive in the same manner as in Example 1 (4), and the retardation value was measured. As a result, the in-plane retardation value R ₀ = 0.5 nm, the thickness direction retardation value. R _th = 102.3 nm. Moreover, about the latter, when the internal haze value was measured similarly to Example 1 (4), it was 0.53%.

[Comparative Example 1]
(1) Preparation of smectite / N, N-dimethylacetamide dispersion 6.6 g of synthetic smectite that is an inorganic layered compound and is not organically modified (Laponite XLG, manufactured by Rockwood Additives Ltd., cation exchange capacity = 88 meq / 100 g) , 96.1 g of N, N-dimethylacetamide was added, and the mixture was stirred using 79 mL of zirconia beads (diameter: 0.8 mm) and a high-speed stirrer (Three-One Motor BL1200, manufactured by Shinto Kagaku Co., Ltd.) to disperse smectite and disperse smectite. A liquid was obtained.

(2) Preparation of Cellulose Acetate Solution N, N-dimethylacetamide 85 was added to 15 parts of cellulose acetate (cellulose tricetate LT-35, manufactured by Daicel Chemical Industries, Ltd.) having a hydroxyl group substitution degree of 2.88 and a number average molecular weight of 76000. A 15% strength highly substituted cellulose acetate solution was prepared.

(3) Preparation of coating solution To 102.7 g of the smectite and N, N-dimethylacetamide dispersion prepared in (1) above, 15% high-substituted cellulose acetate solution 22 prepared in (2) above. .2 g was added, and the mixture was further stirred for 2 hours with a high-speed stirrer for dispersion treatment. The obtained dispersion was filtered through a membrane filter having a pore size of 6 μm to prepare a coating solution. This coating liquid has the following composition when the whole is 100 parts.

・ Laponite XLG (synthetic smectite not organically modified) 5.2 parts ・ Highly substituted cellulose acetate having a hydroxyl group substitution degree of 2.88 2.6 parts ・ N, N-dimethylacetamide 92.2 parts

(4) Production and evaluation of retardation film In the same manner as in Example 1 (4), a retardation film coated on a polyethylene terephthalate film and a retardation film coated on a glass plate were produced. The former was transferred to a glass plate via a pressure-sensitive adhesive in the same manner as in Example 1 (4), and the retardation value was measured. As a result, the in-plane retardation value R ₀ = 0.9 nm, the thickness direction retardation value. R _th = 39.3 nm. Moreover, about the latter, when the internal haze value was measured similarly to Example 1 (4), it was 1.62%.

  The main conditions and results of Examples 1, 2, 3 and Comparative Example 1 are summarized in Table 1.

As shown in Table 1, the retardation films of Examples 1 to 3 using a smectite having a cation exchange ability within the range of 90 to 120 meq / 100 g used a smectite having a cation exchange ability outside the above range. It can be seen that the internal haze value is lower than that of the retardation film of Comparative Example 1. That is, it turns out that the retardation film of Examples 1-3 is excellent in transparency, even if it uses the inorganic layered compound which is not modified with organic substance. Moreover, it turns out that the retardation film of Examples 1-3 has sufficient in-plane retardation value _R0 and thickness direction retardation value _Rth .

Claims (8)

  An inorganic layered compound that is not modified with an organic substance and has a cation exchange capacity of 90 to 120 meq / 100 g, a hydroxyl group substitution degree of 2.1 to 3.0, and a number average molecular weight of 25,000 to 120,000. An optical film comprising a cellulose derivative in a range.   The optical film according to claim 1, wherein the inorganic layered compound is a smectite group mineral.   The optical film according to claim 1 or 2, wherein a weight ratio of the inorganic layered compound to the cellulose derivative is in the range of 0.5 to 5.   The optical film according to any one of claims 1 to 3, wherein the in-plane retardation value is 0 to 5 nm and the thickness direction retardation value is 40 to 300 nm.   An inorganic layered compound that is not modified with an organic substance and has a cation exchange capacity of 90 to 120 meq / 100 g, a hydroxyl group substitution degree of 2.1 to 3.0, and a number average molecular weight of 25,000 to 120,000. A coating liquid for producing an optical film comprising a cellulose derivative in a range and a polar organic solvent.   The weight ratio of the inorganic layered compound to the cellulose derivative is in the range of 0.5 to 5, and the total concentration of the inorganic layered compound and the cellulose derivative is in the range of 3 to 15% by weight with respect to the polar organic solvent. The coating liquid according to claim 5. An inorganic layered compound that is not modified with an organic substance and has a cation exchange capacity of 90 to 120 meq / 100 g, a hydroxyl group substitution degree of 2.1 to 3.0, and a number average molecular weight of 25,000 to 120,000. A method for producing a coating liquid for producing an optical film comprising a cellulose derivative in a range and a polar organic solvent,
A dispersion step of dispersing the inorganic layered compound in a polar organic solvent;
A method for producing a coating liquid, comprising a cellulose derivative mixing step of mixing the dispersion obtained in the dispersing step with a polar organic solvent solution of the cellulose derivative.   The manufacturing method of an optical film including the application | coating process which apply | coats the coating liquid of Claim 5 or 6 on a base material, and the drying process which removes the said polar organic solvent after application | coating.