JP2011242593A - Optical film, polarizing plate, image display device and producing method of optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin optical film which is capable of keeping display image quality of a display such as a liquid crystal display device at a high grade over a long period of time, is excellent in brittleness, has a small haze value and a small curl value, and is suitable as a protective film for polarizing films.SOLUTION: In an optical film having a cellulose acylate film containing at least one kind of layered inorganic compound, a thickness of the cellulose acylate film is 20 to 70 μm, the layered inorganic compound is contained at a ratio of 1 to 50 mass% based on the total solid content of the cellulose acylate film, and the layered inorganic compound is localized in the thickness direction of the cellulose acylate film.

Description

  The present invention relates to an optical film, a polarizing plate, an image display device, and an optical film manufacturing method.

Liquid crystal display devices have low power consumption, and their use is expanding year by year as space-saving image display devices.
Conventionally, a large viewing angle dependency of an image has been a major drawback of a liquid crystal display device. However, in recent years, high viewing angle liquid crystal modes such as a VA mode and an IPS mode have been put into practical use. Demand for liquid crystal display devices is rapidly expanding even in markets where demand is high.
Along with this, higher performance has begun to be demanded for polarizing plates used in liquid crystal display devices.

In the polarizing plate, a polarizing plate protective film is generally bonded to both surfaces or one surface of a polarizing film having polarizing ability via an adhesive layer. As a material of the polarizing film, polyvinyl alcohol (hereinafter sometimes referred to as “PVA”) is mainly used, and the PVA film is uniaxially stretched and then dyed with iodine or a dichroic dye, or A polarizing film is formed by stretching after dyeing and further crosslinking with a boron compound. As a protective film, in addition to being optically transparent and having low birefringence, and having a smooth surface, it has an appropriate water vapor permeability (moisture permeability), and it is easy for water vapor to escape during the preparation of a polarizing plate for a short time. Cellulose triacetate (hereinafter sometimes referred to as “TAC”) has been widely used because of its high productivity at the time of producing a polarizing plate, such as being able to be dried at a low temperature. However, these polarizing plates have a problem that, when used for a long period of time, the transmittance of the entire screen in black display increases, the color changes, and a frame-like light leak occurs.
It is known that the increase in the transmittance and the cause of the frame-shaped light leakage are greatly affected by the amount of water vapor transmitted from the outside through the protective film.

  On the other hand, recently, polarizing plates mainly for notebook PCs have been in the trend of thinning, and there is an increasing demand for thinning protective films. When TAC is thinned as a protective film, the water vapor permeability increases, so that the productivity of the polarizing plate is further improved, but the durability as the polarizing plate is further deteriorated. Further, the thin film causes problems such as an increase in curl when a hard coat layer or the like is applied.

  As a technique for solving the problem relating to the increase in moisture permeability due to thinning, Patent Document 1 reports that a sheet made of norbornene resin is useful as a protective film for a polarizing film. However, a sheet made of a norbornene resin has a problem that the moisture permeability is sufficiently small and it is difficult to receive a change in humidity, but the productivity is low.

In addition, it has been reported that a protective film in which a layer containing a vinylidene chloride copolymer, polyvinyl alcohol, ethylene polyvinyl alcohol copolymer, a layered inorganic compound or a hydrophobic compound is provided on the surface of a cellulose triacetate film has been reported.
For example, Patent Documents 2 and 3 report that the wet heat property of the polarizing plate is improved by using a protective film provided with a layer containing a vinylidene chloride copolymer.
Patent Document 4 reports that water vapor permeability is reduced by using a protective film provided with a liquid crystal polymer containing a hydrophobic compound (thermotropic liquid crystal polymer).
In Patent Document 5, in addition to the layer containing the vinylidene chloride copolymer reported in Patent Documents 2 and 3, a layer in which a layered inorganic compound is dispersed in a resin layer component composed of a vinyl alcohol polymer is provided. It has been reported that by using a protective film, the water vapor transmission rate at 60 ° C. and 95% relative humidity is 300 g / m ² · day or less.
In any of the methods reported in Patent Documents 2, 3, 4, and 5 described above, in order to apply a low moisture-permeable layer on the protective film TAC, the TAC and the low moisture-permeable layer are used. Since the coefficients of thermal expansion are different, there is a problem that stress is generated between the layers and the curl is large.

  Patent Document 6 reports that the wet heat property of a polarizing plate is improved by using, as an adhesive, a layer in which a layered inorganic compound is dispersed in a resin layer component made of a vinyl alcohol polymer. However, in this case, since it is necessary to apply an adhesive of about 1 to 5 μm, there is a problem that it takes time to dry the polarizing plate and productivity is lowered. Further, it is known that the vinyl alcohol polymer can improve the crystallinity of the resin by drying at a high temperature, thereby improving the moisture resistance and water resistance. Although there is no description regarding water vapor permeability in Patent Document 6, even if a layer in which a layered inorganic compound is dispersed in a resin layer component made of a vinyl alcohol polymer is used as an adhesive, from the viewpoint of heat resistance of the polarizing film. Since there is a problem that the resin layer cannot be dried at a sufficiently high temperature, it is expected that a required level of moisture permeability cannot be achieved.

JP-A-10-101907 JP-A-62-161103 JP 2001-215331 A JP 2000-094613 A JP 2008-15500 A JP 2003-307623 A

  As described above, the thin film polarizing plate protective film is required to have appropriate moisture permeability from the viewpoint of productivity of the polarizing plate, durability in long-term use, and maintenance of high quality. On the other hand, when a large amount of an inorganic compound is contained in the resin, the haze of the resin layer increases or the brittleness is expected to deteriorate, for example, when the resin layer is rolled, the surface is cracked. .

  An object of the present invention is to provide a thin optical film suitable for a protective film for a polarizing film, which can maintain the display image quality of a display such as a liquid crystal display device for a long period of time, has excellent brittleness, has a small haze value and curl value. Is to provide a film. Another object of the present invention is a polarizing plate that is excellent in durability and can maintain the display image quality of a display such as a liquid crystal display device for a long period of time, and an image display device using the optical film or polarizing plate. Is to provide.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by the following optical film, and have completed the present invention.

[1]
An optical film having a cellulose acylate film having a multilayer structure including a layer containing at least one layered inorganic compound, wherein the cellulose acylate film has a thickness of 20 to 70 μm, and the layered inorganic compound is the cellulose acylate. An optical film that is contained in a proportion of 1 to 50% by mass with respect to the total solid content in the rate film, and in which the layered inorganic compound is localized in the thickness direction of the cellulose acylate film.
[2]
The optical film according to [1], wherein the multilayer structure has a base layer and a surface layer, and the layered inorganic compound is localized on the surface layer.
[3]
The optical film according to [2], wherein the surface layer has a thickness of 1 to 10 μm.
[4]
The optical film according to [2] or [3], wherein the surface layer is laminated on both sides of the base layer.
[5]
The optical film according to any one of [1] to [4], wherein the layered inorganic compound is organically treated.
[6]
The optical film according to any one of [1] to [5], wherein the moisture permeability at 60 ° C. and 95% relative humidity is 500 g / m ² · day to 2500 g / m ² · day.
[7]
The optical film according to any one of [1] to [6], which has a layer having at least a hard coat property on one surface of the cellulose acylate film.
[8]
A polarizing plate having a polarizing film and protective films on both sides of the polarizing film, wherein at least one of the protective films is the optical film according to any one of [1] to [7].
[9]
The image display apparatus which has an optical film of any one of [1]-[7], or a polarizing plate of [8].
[10]
A method for producing an optical film having a multilayer cellulose acylate film including a layer containing at least one layered inorganic compound,
A dope containing the layered inorganic compound and cellulose acylate is cast on a support to form a cast film, and the cast film is peeled off from the support and dried to form the cellulose acylate film. The manufacturing method of an optical film including the process to form.
[11]
The multilayer structure is a multilayer structure having a base layer and a surface layer,
A base layer dope containing the cellulose acylate substantially free of the layered inorganic compound and a surface layer dope containing the layered inorganic compound and the cellulose acylate are simultaneously or sequentially arranged on the support in this order. The film according to [10] or [11], wherein the film is formed by casting the film onto the support, peeling the cast film from the support, and drying to form the cellulose acylate film. Manufacturing method of optical film.
[12]
The method for producing an optical film according to [11], wherein the base layer dope and the surface layer dope are simultaneously cast on the support in this order to form the cast film.

  According to the present invention, both the haze value and the curl value are low, excellent in brittleness, an optical film having appropriate moisture permeability as a polarizing plate protective film, and a polarizing plate using the same, and using the polarizing plate, It is possible to provide a liquid crystal display device capable of maintaining high quality display images over a long period of time in various environments.

It is sectional drawing which shows an example of a cellulose acylate film typically. It is sectional drawing which shows an example of a cellulose acylate film typically. It is a figure which shows typically the solution film forming apparatus using a casting drum. It is a figure which shows typically the solution film forming apparatus using a casting band. Diagram showing a multi-manifold type co-casting die It is a figure which shows typically a feed block type co-casting die. It is a figure which shows typically the curl measuring method of an optical film.

  Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to these. In the present specification, when a numerical value represents a physical property value, a characteristic value, etc., the description “(numerical value 1) to (numerical value 2)” means “(numerical value 1) or more and (numerical value 2) or less”. . In the present specification, the description “(meth) acrylate” means “at least one of acrylate and methacrylate”. The same applies to “(meth) acrylic acid”, “(meth) acryloyl” and the like.

(Optical film)
The optical film of the present invention has a cellulose acylate film having a multilayer structure including a layer containing at least one layered inorganic compound, the thickness of the cellulose acylate film is 20 to 70 μm, and the layered inorganic compound is It is contained at a ratio of 1 to 50% by mass with respect to the total solid content in the cellulose acylate film, and the layered inorganic compound is localized in the thickness direction of the cellulose acylate film.
As described above, a specific amount of the layered inorganic compound is localized in the thickness direction of the cellulose acylate film in the thin cellulose acylate film, thereby setting the haze value of the cellulose acylate film to 1% or less, Both curl values are low, the brittleness is excellent, and moisture permeability suitable as a polarizing plate protective film can be imparted.

FIG. 1 is a schematic view showing an example of the cellulose acylate film of the present invention.
A cellulose acylate film 101 shown in FIG. 1 has a multilayer structure including a layer 102 and a layer 103, and the layer 102 contains a layered inorganic compound. “The layered inorganic compound is localized in the thickness direction of the cellulose acylate film” means that the cellulose acylate film 101 substantially does not contain the layer 102 containing the layered inorganic compound in the film thickness direction. It means having. Here, that the layer 103 does not substantially contain the layered inorganic compound means that the ratio of the layered inorganic compound in the layer 103 is less than 1.0% by mass with respect to the total solid content of the layer 103.
The ratio of the layer 102 containing the layered inorganic compound and the layer 103 containing substantially is not particularly limited, but the ratio of the layered inorganic compound in the cellulose acylate film 101 is the total solid of the cellulose acylate film 101 as described above. It is made to become the range of 1-50 mass% with respect to a minute.

In the optical film of the present invention, it is preferable that the layered inorganic compound is localized in the surface layer in a multilayer structure having a base layer and a surface layer for reasons such as improvement of brittleness, reduction of curling and haze, and improvement of moisture permeability. . Here, the “surface layer” is a layer whose one surface is the outermost surface of the cellulose acylate film, and the “base layer” refers to a layer adjacent to the “surface layer”. (However, in the case where the multilayer structure of the cellulose acylate film is a two-layer structure composed of one “surface layer” and one “base layer”, the “base layer” also has one surface (the side in contact with the “surface layer”). In this case, the layer containing the layered inorganic compound is referred to as the “surface layer”, and the layered inorganic compound is not substantially contained as the “base layer”. In addition, “the layered inorganic compound is localized in the surface layer” means that, of the base layer and the surface layer, the surface layer contains the layered inorganic compound, and the base layer substantially does not contain the layered inorganic compound. (That is, the ratio of the layered inorganic compound in the base layer is less than 1.0% by mass with respect to the total solid content of the base layer).
In addition, it is preferable to provide functional layers, such as a hard-coat layer mentioned later, an anti-glare layer, and an antireflection layer, on the surface layer containing the said layered inorganic compound. That is, the optical film of the present invention preferably has a base layer, a surface layer, and a functional layer in this order.
FIG. 2 is a schematic view showing an example of a cellulose acylate film having a multilayer structure having a base layer and a surface layer. A cellulose acylate film 201 shown in FIG. 3 has a three-layer structure including one base layer 203 and surface layers 202 and 204 on both sides thereof. And at least one of the surface layers 202 and 204 contains a layered inorganic compound, and the base layer 203 substantially does not contain a layered inorganic compound. For reasons such as improvement of brittleness, reduction of curling and haze, improvement of moisture permeability, etc., it is more preferable that both the surface layers 202 and 204 contain a layered inorganic compound.
These multi-layered cellulose acylate films can be produced by simultaneously or sequentially casting a plurality of cellulose acylate solutions (dope) corresponding to each layer, as will be described later. The form of the multilayer structure is not limited to the form shown in FIGS. Also,

1-19 micrometers is preferable and, as for the film thickness of the layer containing a layered inorganic compound, 1-10 micrometers is more preferable.
In the multilayer structure including the base layer and the surface layer, the thickness of the surface layer is preferably 1 to 18 μm, and more preferably 1 to 10 μm. In the case of a multilayer structure of three or more layers, the film thicknesses of the two surface layers may be the same or different from each other. 1-69 micrometers is preferable and, as for the film thickness of a base layer, 4-58 micrometers is especially preferable.
It is preferable that the film thicknesses of the surface layer and the base layer be in the above ranges from the viewpoint of obtaining an optical film having excellent brittleness and appropriate moisture permeability as a polarizing plate protective film.

Hereinafter, the optical film of the present invention will be described in more detail.
<Cellulose acylate film>
The optical film of the present invention has a cellulose acylate film containing at least one layered inorganic compound.

<Cellulose acylate>
The cellulose acylate film in the present invention contains cellulose acylate. As the cellulose acylate, an ester of cellulose and a carboxylic acid having 2 to 22 carbon atoms is preferable. For example, cellulose alkylcarbonyl ester, alkenylcarbonyl ester, cycloalkylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester, etc., each of which may further have a substituted group.
The ester of cellulose and a carboxylic acid having 2 to 22 carbon atoms is obtained by acylating the hydroxyl group of cellulose, and the acyl group as the substituent is from an acetyl group having 2 carbon atoms to 22 carbon atoms. Any of them may be used, and may be an aliphatic acyl group or an aromatic acyl group, and is not particularly limited. Preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, cyclohexanecarbonyl, adamantanecarbonyl, phenylacetyl, benzoyl, naphthylcarbonyl, (meth) acryloyl, cinnamoyl groups and the like. Among these, more preferred acyl groups are propionyl, butanoyl, pentanoyl, hexanoyl, cyclohexanecarbonyl, phenylacetyl, benzoyl, naphthylcarbonyl, and the like.

As the cellulose acylate suitably used in the present invention, those in which the degree of substitution of cellulose with a hydroxyl group satisfies the following mathematical formulas (1) and (2) are preferable.
Formula (1): 2.3 ≦ SA ′ + SB ′ ≦ 3.0
Formula (2): 0 ≦ SA ′ ≦ 3.0
Here, SA ′ is the substitution degree of the acetyl group substituting the hydrogen atom of the hydroxyl group of cellulose, and SB ′ is the substitution degree of the acyl group having 3 to 22 carbon atoms substituting the hydrogen atom of the hydroxyl group of cellulose. Represents. In the following description, SA represents an acetyl group substituting the hydrogen atom of the hydroxyl group of cellulose, and SB represents an acyl group having 3 to 22 carbon atoms substituting the hydrogen atom of the hydroxyl group of cellulose.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of hydroxyl groups esterified at each of the 2-position, 3-position and 6-position (100% esterification at each position is substitution degree 1). In the present invention, the total sum of substitution degrees of SA and SB (SA ′ + SB ′) is more preferably 2.6 to 3.0, and particularly preferably 2.70 to 3.00. Further, the substitution degree (SA ′) of SA is more preferably 1.4 to 3.0, and particularly 2.3 to 2.9.

Moreover, in this invention, it is preferable that the carbon atom number of the acyl group which has substituted the hydrogen atom of the hydroxyl group of the cellulose which is said SB is 3 or 4. It is preferable that the degree of substitution substituted with the acyl group having the number of carbon atoms satisfies the following mathematical formula (3) in addition to the mathematical formulas (1) and (2).
Formula (3): 0 ≦ SB ”≦ 1.2
Here, SB ″ represents the degree of substitution of the acyl group having 3 or 4 carbon atoms that replaces the hydrogen atom of the hydroxyl group of cellulose.

The degree of substitution can be obtained by calculating the degree of binding of fatty acids bound to hydroxyl groups in cellulose. As a measuring method, it can measure based on ASTM-D817-91 and ASTM-D817-96. The state of substitution of the acyl group with the hydroxyl group is measured by ¹³ C NMR method.

  The cellulose acylate film is preferably composed of cellulose acylate in which the polymer component constituting the film substantially satisfies the above mathematical formulas (7) and (8). “Substantially” means 55% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more) of the total polymer components. The cellulose acylate may be used alone or in combination of two or more.

  The degree of polymerization of the cellulose acylate preferably used in the present invention is a viscosity average degree of polymerization of 200 to 700, preferably 230 to 550, more preferably 230 to 350, and particularly preferably a viscosity average degree of polymerization of 240 to 320. The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538.

The number average molecular weight Mn of the cellulose acylate is preferably in the range of 7 to 25 × 10 ⁴ , and more preferably in the range of 8 to 15 × 10 ⁴ . The weight average molecular weight of the cellulose acylate Mw is preferably from 7 to 200 × 10 ^4, and more preferably 8 to 45 × 10 ^4. The ratio of the cellulose acylate to the mass average molecular weight Mw, Mw / Mn, is preferably 1.0 to 5.0, more preferably 1.0 to 3.0. In addition, the average molecular weight and molecular weight distribution of a cellulose acylate can be measured using a high performance liquid chromatography, Mn and Mw can be calculated using this, and Mw / Mn can be calculated.

<Layered inorganic compound>
The layered inorganic compound in the present invention is an inorganic compound having a structure in which unit crystal layers are laminated and exhibiting a property of swelling or cleaving by coordinating or absorbing a solvent between the layers.
Examples of such inorganic compounds include swellable hydrous silicates such as smectite group clay minerals (montmorillonite, saponite, hectorite, etc.), palm curite group clay minerals, kaolinite group clay minerals, phyllosilicates (mica). Etc.). In addition, a synthetic layered inorganic compound is also preferably used, and examples of the synthetic layered inorganic compound include synthetic smectite (hectorite, saponite, stevensite, etc.), synthetic mica and the like.
Among these layered inorganic compounds, smectite, montmorillonite and mica are preferable, montmorillonite and mica are more preferable, mica is more preferable, and synthetic mica is more preferable from the viewpoint of adjustment of moisture permeability, improvement of brittleness, and prevention of coloring. Particularly preferred. As a layered inorganic compound that can be used as a commercial product, MEB-3 (synthetic mica aqueous dispersion manufactured by Corp Chemical Co., Ltd.), ME-100 (synthetic mica manufactured by Corp Chemical Co., Ltd.), S1ME (manufactured by Corp Chemical Co., Ltd.) Synthetic mica), SWN (Synthetic smectite manufactured by Corp Chemical Co., Ltd.), SWF (Synthetic smectite manufactured by Corp Chemical Co., Ltd.), Kunipia F (Purified bentonite manufactured by Kunimine Chemical Industry Co., Ltd.), Bengel (Hojun Co., Ltd.) Purified bentonite), Bengel HV (refined bentonite manufactured by Hojun Co., Ltd.), Wenger FW (purified bentonite manufactured by Hojun Co., Ltd.), Bengel Bright 11 (purified bentonite manufactured by Hojun Co., Ltd.), Wenger Bright 23 (Hojung) Purified bentonite (Co., Ltd.), Wengel Bright 25 (Ho Interview emissions K.K. purified bentonite), Wenger A (HOJUN Co., Ltd. purified bentonite), Wenger 2M (HOJUN Co., Ltd. purified bentonite) and the like can be used.

<Organized layered inorganic compound>
In the present invention, the layered inorganic compound is made organic from the viewpoints of improving dispersibility in an organic solvent and improving swelling and cleavage after addition to the solvent to improve moisture permeability and improving brittleness. Preferably it has been treated. The organic treatment of the layered inorganic compound means that the organic agent is captured between the unit crystal layers by treating the crystal surface of the unit crystal layer and the hydroxyl group on the crystal end face with the organic agent.
Examples of the layered inorganic compound subjected to the organic treatment include a layered inorganic compound subjected to an organic treatment with an organic agent such as an alkylamine described below.
Further, for the purpose of further strengthening the strength of the cellulose acylate film and reducing moisture permeability, the organic acylation treatment may be performed with an organic agent containing a polymerizable group.
Examples of organically treated layered inorganic compounds that can be used as commercial products include Somasif MAE, MTE, MEE, MPE (all synthetic mica manufactured by Coop Chemical Co., Ltd.), Lucentite SAN, STN, SEN, SPN (all COP Chemical). Synthetic smectite manufactured by Co., Ltd.) and the like.

  In addition, layered inorganic compounds that have not been organically treated, such as Lucentite ME-100 (synthetic mica manufactured by Corp Chemical Co., Ltd.) and Lucentite SWN (synthetic smectite manufactured by Corp Chemical Co., Ltd.), are commercially available. It is also preferable to perform an organic treatment with an agent.

  The organic agent is preferably a quaternary ammonium salt and is not particularly limited, but a quaternary ammonium salt represented by the following general formula (1) is more preferable.

In the general formula (1), Ra is _{- (CH 2) m H,} - (CH 2) m RcH, or _- represents a _{(CH 2 Rc) m H,} m is an integer of 2 or more, Rc is any group or may or may not, Rb represents a -CH _3. n represents an integer of 0 to 3. A ⁻ represents Cl ⁻ or Br ⁻ .

In the said General formula (1), 0-3 are preferable, 0-2 are more preferable, and 0-1 are still more preferable. It is preferable from the viewpoint of dispersibility that n is in this range. When there are a plurality of Ras, all groups may have the same structure or different structures.
m is 2 or more, and at least one group in Ra is particularly preferably m or more, more preferably 8 or more, and still more preferably 8 to 30. The larger m is, the better the dispersibility is improved. Moreover, it is preferable also from the point of the ratio of the organic substance with respect to a layered inorganic compound that m exists in the said range.

Ra also preferably has a structure that increases the interaction between molecules, and examples thereof include —OH, —CH ₂ CH ₂ O—, —CHO (CH) ₃ —, and the like.

  Examples of the quaternary ammonium salt used in the organic treatment including the quaternary ammonium salt represented by the general formula (1) include, for example, dimethyldioctadecylammonium bromide, trimethyloctadecylammonium chloride, benzyltrimethylammonium chloride, dimethylbenzyloctadecylammonium. Bromide, trioctylmethylammonium chloride, polyoxypropylenetrimethylammonium chloride, di (polyoxypropylene) dimethylammonium chloride, di (polyoxyethylene) dodecylmethylammonium chloride, tri (polyoxypropylene) methylammonium chloride, tri (polyoxy) And propylene) methylammonium bromide.

  As a method of using an organically treated layered inorganic compound, a method in which the organically treated layered inorganic compound is sufficiently dispersed in an organic solvent and a cellulose acylate solution (dope) is added to the dispersion. In addition, a method of adding a solution in which a layered inorganic compound subjected to organic treatment is dispersed in an organic solvent is added to the dope solution.

  The layered inorganic compound is preferably finely divided from the viewpoint of moisture permeability adjustment, brittleness and haze. The layered inorganic compound subjected to the fine particle treatment is usually plate-shaped or flat-shaped, and the planar shape is not particularly limited, and may be an amorphous shape. The average particle radius (planar average particle radius) of the layered inorganic compound subjected to the fine particle treatment is, for example, preferably 0.1 to 10 μm, more preferably 0.5 to 8 μm, and particularly preferably 0.8 to 6 μm. The average particle radius is the number of particles having that value among the particle radius distribution values measured by a general particle size distribution meter, for example, a light scattering type particle size distribution meter ("Microtrack UPA" manufactured by Nikkiso Co., Ltd.). The largest particle size. By setting it as the above range, a sufficient moisture permeability adjusting effect can be obtained, and an increase in haze value and an increase in surface roughness can be prevented.

<Dispersion treatment of layered inorganic compound>
When the layered inorganic compound is localized in the thickness direction of the cellulose acylate film in a state where the layers are swollen or cleaved, the moisture permeability path length can be increased and the moisture permeability can be reduced. Therefore, in order to obtain a state in which each layer of the layered inorganic compound is swollen or cleaved, it is preferable to perform the organic treatment or dispersion treatment. The dispersion treatment is preferably carried out by high-pressure dispersion treatment a plurality of times in the solution. The treatment pressure is preferably 10 MPa or more, more preferably 20 MPa or more. There is no specific designation as a solvent.

  In this invention, content of the layered inorganic compound in a cellulose acylate film is 1-50 mass% with respect to the total solid in a cellulose acylate film. If it is this range, a water vapor transmission rate can be reduced to a desired range, without causing a raise of a haze value. More preferably, it is 3-48 mass%.

<Plasticizer>
In the present invention, a plasticizer may be used to impart flexibility to the cellulose acylate film, improve dimensional stability, and improve moisture resistance.

  In the present invention, a plasticizer having an octanol / water partition coefficient (log P value) of 0 to 10 is particularly preferably used. If the log P value of the compound is 10 or less, the compatibility with the cellulose acylate is good, there is no problem such as cloudiness or powder blowing of the film, and if the log P value is greater than 0, the hydrophilicity is high. Since it does not become too high, adverse effects such as deterioration of the water resistance of the cellulose acylate film are unlikely to occur. As the logP value, a more preferable range is 1 to 8, and a particularly preferable range is 2 to 7.

  The octanol / water partition coefficient (log P value) can be measured by a flask soaking method described in Japanese Industrial Standard (JIS) Z7260-107 (2000). Further, the octanol / water partition coefficient (log P value) can be estimated by a computational chemical method or an empirical method instead of the actual measurement. As a calculation method, the Crippen's fragmentation method [J. Chem. Inf. Comput. Sci. 27, 21 (1987)], Viswanadhan's fragmentation method [J. Chem. Inf. Comput. Sci. 29, 163 (1989)], Broto's fragmentation method [Eur. J. et al. Med. Chem. -Chim. Theor. 19 (71) (1984)] is preferably used, and the Crippen's fragmentation method is more preferable. When the log P value of a certain compound varies depending on the measurement method or calculation method, it is preferable to determine whether or not the compound is within the scope of the present invention by the Crippen's fragmentation method.

  Examples of the plasticizer that is preferably added include low-molecular to oligomeric compounds having a molecular weight of about 190 to 5,000 within the above physical properties. For example, phosphoric acid esters, carboxylic acid esters, polyol esters, and the like are used.

  Examples of phosphate esters include triphenyl phosphate (TPP), tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of the phthalic acid ester include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diphenyl phthalate, diethyl hexyl phthalate and the like. Examples of the citrate ester include O-acetyl triethyl citrate, O-acetyl tributyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.
These preferred plasticizers are liquid except for TPP (melting point: about 50 ° C.) at 25 ° C., and the boiling point is 250 ° C. or higher.

  Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, methyl phthalyl methyl glycolate, propyl phthalyl Examples include propyl glycolate, butyl phthalyl butyl glycolate, and octyl phthalyl octyl glycolate.

  JP-A-5-194788, JP-A-60-250053, JP-A-4-227941, JP-A-6-16869, JP-A-5-271471, JP-A-7-286068, JP-A-5-5047. No. 11, JP-A-11-80381, JP-A-7-20317, JP-A-8-57879, JP-A-10-152568, JP-A-10-120824, etc. are also preferably used. It is done. According to these publications, there are many preferable descriptions regarding not only examples of plasticizers but also their usage or characteristics, and they are preferably used in the present invention.

  Other plasticizers include (di) pentaerythritol esters described in JP-A No. 11-124445, glycerol esters described in JP-A No. 11-246704, diglycerol esters described in JP-A No. 2000-63560, Citric acid esters described in JP-A No. 11-92574, substituted phenyl phosphate esters described in JP-A No. 11-90946, ester compounds containing an aromatic ring and a cyclohexane ring described in JP-A No. 2003-165868 are preferably used. .

  A polymer plasticizer having a resin component having a molecular weight of 10,000 to 100,000 is also preferably used. For example, polyesters and / or polyethers described in JP-A-2002-22956, polyester ethers, polyester urethanes or polyesters described in JP-A-5-97073, copolyester ethers described in JP-A-2-292342, Examples thereof include an epoxy resin or a novolac resin described in JP-A No. 2002-146044.

  These plasticizers may be used alone or in admixture of two or more. The addition amount of the plasticizer is preferably 2 to 30 parts by mass, particularly 5 to 20 parts by mass with respect to 100 parts by mass of the cellulose acylate.

<Ultraviolet absorber>
In order to improve the light resistance of the film itself or to prevent deterioration of the image display member such as a polarizing plate or a liquid crystal compound of a liquid crystal display device, an ultraviolet absorber (ultraviolet ray inhibitor) is further added to the cellulose acylate film. Is preferred.

  As the ultraviolet absorber, one having an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal and having as little absorption of visible light having a wavelength of 400 nm or more as possible from the viewpoint of good image display properties is used. It is preferable. In particular, the transmittance at a wavelength of 370 nm is desirably 20% or less, preferably 10% or less, and more preferably 5% or less. Examples of such ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and ultraviolet absorbing groups as described above. Examples thereof include, but are not limited to, polymer ultraviolet absorbing compounds. Two or more kinds of ultraviolet absorbers may be used.

  In this invention, the usage-amount of a ultraviolet absorber is 0.1-5.0 mass parts with respect to 100 mass parts of cellulose acylates used for a cellulose acylate film, Preferably it is 0.5-4.0 mass parts, More preferably Is 0.8 to 2.5 parts by mass.

<Other additives>
Furthermore, in the solution (dope) for forming the cellulose acylate film, other various additives (for example, an antioxidant (for example, an antioxidant, a peroxide decomposing agent, a radical) in accordance with the use in each preparation step. Inhibitors, metal deactivators, acid scavengers, amines, etc.), optical anisotropy control agents, release agents, antistatic agents, infrared absorbers, etc.) can be added. But you can. That is, the melting point and boiling point are not particularly limited. Furthermore, as an infrared absorber, the thing as described in Unexamined-Japanese-Patent No. 2001-194522 can be used, for example.

  These additives may be added at any time in the dope preparation step, but may be added in the final preparation step of the dope preparation step by adding a preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when a cellulose acylate film is formed from a multilayer, the kind and addition amount of the cellulose acylate / additive of each layer may be different. For example, it is described in Japanese Patent Application Laid-Open No. 2001-151902 and the like, but these are conventionally known techniques. These details including the ultraviolet absorbers described above are the materials described in detail on pages 16 to 22 of the Japan Society for Invention and Innovation Technical Bulletin No. 2001-1745 (issued on March 15, 2001, Japan Institute of Invention). Preferably used.

  It is preferable that the usage-amount of these additives is suitably used in the range of 0.001-20 mass% in the whole composition which comprises a cellulose acylate film.

<Solvent>
Next, the organic solvent which dissolves the material forming the cellulose acylate film will be described. Examples of the organic solvent to be used include conventionally known organic solvents. For example, those having a solubility parameter in the range of 17 to 22 are preferable. Solubility parameters are described, for example, in J. Org. Brandrup, E.I. “Polymer Handbook (4th. Edition)” such as H and the like described in VII / 671 to VII / 714. Lower aliphatic hydrocarbon chloride, lower aliphatic alcohol, ketone having 3 to 12 carbon atoms, ester having 3 to 12 carbon atoms, ether having 3 to 12 carbon atoms, fat having 5 to 8 carbon atoms Group hydrocarbons, aromatic hydrocarbons having 6 to 12 carbon atoms, fluoroalcohols (for example, described in paragraph No. [0020] of JP-A-8-143709, paragraph No. [0037] of JP-A-11-60807) Compound) and the like.

The cellulose acylate film is preferably dissolved in an organic solvent in an amount of 10 to 30% by mass, more preferably 13 to 27% by mass, and particularly preferably 15 to 25% by mass. The methods for preparing these concentrations may be prepared so as to have a predetermined concentration at the stage of dissolution, or prepared in advance as a low concentration solution (for example, 9 to 14% by mass) and then in a concentration step described later. You may adjust to a high concentration solution. Furthermore, it is good also as a solution of the predetermined | prescribed low concentration by adding various additives later as a solution of the material which forms a high concentration cellulose acylate film beforehand.
One kind or two or more kinds of solvents may be used.

<Preparation of dope>
Regarding the preparation of the cellulose acylate solution (dope), the dissolution method is not particularly limited as described above, and it is carried out by a room temperature dissolution method, a cooling dissolution method, or a high temperature dissolution method, and further by a combination thereof. To be implemented. Regarding these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP 2000-53784, JP 11-322946, JP 11-322947, JP 2-276830, JP 2000-273239, JP 11-71463, JP 04-259511, JP JP-A Nos. 2000-273184, 11-323017, and 11-302388 describe methods for preparing cellulose acylate solutions. These techniques for dissolving cellulose acylate in an organic solvent can be applied as appropriate within the scope of the present invention. About these details, especially a non-chlorine type | system | group solvent system, it implements by the method described in detail on the 22-25th pages of the above-mentioned technical numbers 2001-1745. Further, the cellulose acylate dope solution is usually subjected to solution concentration and filtration, and similarly described in detail on page 25 of the above-mentioned official technical number 2001-1745. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.

(Optical film manufacturing method)
The present invention also relates to a method for producing an optical film.
The method for producing an optical film of the present invention is a method for producing an optical film having a multilayer structure cellulose acylate film including a layer containing at least one layered inorganic compound, the layered inorganic compound and the thermoplastic resin. And forming a layer containing the layered inorganic compound by peeling the cast film from the support and drying the cast film. .
By the above manufacturing method, an optical film that is excellent in brittleness and has a small haze value and curl value and is suitable as a protective film for a polarizing film can be obtained.

In the method for producing an optical film of the present invention, the dope containing a layered inorganic compound and cellulose acylate is cast on a support to form a cast film, and the cast film is peeled from the support. And dried to form the cellulose acylate film.
3 and 4 are diagrams showing an example of a solution film forming apparatus that performs casting. FIG. 3 shows an example in which a casting drum is used as a support, and in particular, by cooling the drum, the dope can be cooled to gel or contacted with the gel while it is in contact with the support. It can be peeled off at the right time, resulting in high productivity. FIG. 4 shows an example in which an endless belt is used as a support. This is a method in which the solvent is dried after the solvent is dried to a certain concentration while the dope is in contact with the belt.
In the solution casting apparatus shown in FIG. 3 and FIG. 4, the dope by the stirrer 11 is prepared in advance, and the dope is transferred to the stock tank 14 through the filter 13 by the transfer pump 12. The dope is finally prepared for casting while being transferred from the stock tank 13 by the pumps 15a to 15c. The finally prepared dope is cast on a support on a casting band 18 or a casting drum 19 by a casting die 17 to form a casting film. While being transferred from the stock tank 13 to the casting die 17, an additional solvent or additive can be added to the dope by the additive injection pumps 16a and / or 16c. In the present invention, the layered inorganic compound may be added to the stirrer 11 or may be added to the dope being transferred by the additive injection pump 16a and / or 16c, but the additive injection pump 16a and / or 16c. It is preferable to put into the dope being transferred. It is preferable to stir the layered inorganic compound separately in an organic solvent before adding the dope from the viewpoint of swelling or cleaving the layers of the layered inorganic compound.

In order to form a cellulose acylate film having a multilayer structure having a base layer and a surface layer, a lamination casting method such as a co-casting method (multilayer simultaneous casting) or a sequential casting method can be used. In the case of manufacturing by the co-casting method or the sequential casting method, first, a plurality of dopes including a surface layer dope and a base layer dope are prepared.
The surface layer dope preferably contains a layered inorganic compound and cellulose acylate. The content of cellulose acylate in the surface dope is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, and particularly preferably 15 to 65% by mass with respect to the total solid content of the dope. The amount of the layered inorganic compound in the surface layer dope is preferably 10 to 90% by mass, more preferably 20 to 85% by mass, and particularly preferably 25 to 80% by mass with respect to the total solid content of the dope. When two surface layers are provided, the amount of the layered compound in the surface layer dope may be the same or different in the two layers.
It is preferable that the base layer dope substantially does not contain a layered inorganic compound and contains only cellulose acylate. “Substantially no layered inorganic compound” means that the ratio of the layered inorganic compound in the base layer dope is less than 1.0 mass% with respect to the total solid content of the base layer dope. The content of cellulose acylate in the base layer dope is preferably 40 to 95% by mass, more preferably 50 to 90% by mass, and particularly preferably 70 to 90% by mass with respect to the total solid content of the dope.
The solid concentration of the surface layer and base layer dope is preferably 10 to 30% by mass.

  The co-casting method is a casting gussa (casting die) in which a plurality of dopes (three layers or more) may be simultaneously extruded from another slit on a casting support (band or drum). The dope is extruded from each of the layers, and each layer is cast at the same time. After being appropriately dried, it is peeled off from the support and dried to form a thermoplastic resin layer. As the casting die, either the multi-manifold type shown in FIG. 5 or the feed block type shown in FIG. 6 can be used. Further, an apparatus provided with a decompression chamber (member 19 in FIGS. 3 and 4) in the dope protrusion is preferable.

  In the sequential casting method, a first casting dope is first extruded from a casting gear on a casting support, and then dried or dried without being dried or dried. The dope is extruded from a casting gieser and casted. Thereafter, the third and subsequent dopes are successively cast and laminated, peeled off from the support at an appropriate time, and dried to form a thermoplastic resin layer. The casting method. Further, the substrate may be stretched in a certain direction during the period from drying to coating. Specifically, for example, the substrate may be stretched by about 0.9 to 1.5 times in the longitudinal direction and / or the transverse direction. preferable.

  Furthermore, in the co-casting method, it is preferable that the dope containing the above-described layered inorganic compound forms the outermost layer of the optical film. Specifically, during casting, the dope is preferably placed on the support surface or the air interface side, and more preferably placed on the air interface side from the viewpoint of peelability. Further, the temperature of the support is preferably 20 ° C. or lower so as not to be leveled at the beginning of casting, and it is also preferable that the temperature of the support is 0 ° C. or lower so as to be cooled and gelled after casting.

  When forming an optical film using a plurality of dopes by co-casting, the thickness of the surface dope (total thickness in the case of being on both sides) is preferably 1 to 10 μm, and more preferably 2 to 5 μm. When the thickness is 1 μm or more, it is easy to form a uniform layer. Further, when the thickness is 10 μm or less, the interface of the dope is stable and the surface shape is rarely damaged. Here, the thickness of the dope refers to the thickness after the solvent is volatilized. In addition, the terms surface layer dope and base layer dope represent a state in which a thermoplastic resin is dissolved in a solvent and forms a surface layer and a base layer adjacent to each other through a casting die, and the solvent has evaporated. It does not necessarily indicate that an interface is present in the cellulose acylate film later.

(Film thickness of cellulose acylate film)
The film thickness of the cellulose acylate film in the present invention is 20 to 70 μm. 70 μm or less is preferable from the viewpoint of obtaining moisture permeability suitable for a polarizing plate protective film and maintaining the quality of the polarizing plate over a long period of time, and being 20 μm or more prevents curling when a hard coat layer is applied. From the viewpoint of More preferably, it is 30 micrometers-60 micrometers.

(Other layers of optical film)
In the present invention, another functional layer can be further provided on the cellulose acylate film. Examples of the functional layer include a hard coat layer, an antiglare layer, an antireflection layer (a low refractive index layer, a medium refractive index layer, a high refractive index layer, etc.) described below.

<Layer with hard coat properties>
In order to impart the physical strength of the optical film, the optical film of the present invention is preferably provided with a layer having hard coat properties on one surface of the cellulose acylate film. Examples of the layer having hard coat properties include a hard coat layer described below and an antiglare layer for the purpose of imparting antiglare properties in addition to imparting physical strength.

<Hard coat layer>
More preferably, a low refractive index layer is provided on the hard coat layer, and an intermediate refractive index layer and a high refractive index layer are provided between the hard coat layer and the low refractive index layer to constitute an antireflection film. More preferably. The hard coat layer may be composed of a laminate of two or more layers.

The refractive index of the hard coat layer is preferably 1.48 to 2.00, more preferably 1.49 to 1.90, more preferably 1 from the optical design for obtaining an antireflection film. More preferably, it is 50-1.80.
By providing at least one low refractive index layer on the hard coat layer, when the refractive index is too small, the antireflection property is lowered, and when it is too large, the color of reflected light tends to be strong.

The thickness of the hard coat layer gives sufficient strength to the film, and from the viewpoint of curling prevention, is preferably about 0.5 μm to 50 μm, more preferably 1 to 20 μm, further preferably 2 to 15 μm, and more preferably 3 to 10 μm. Particularly preferred.
Further, the strength of the hard coat layer is preferably 2H or more, more preferably 3H or more, and further preferably 4H or more in the pencil hardness test.
In particular, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of an ionizing radiation curable compound. For example, a coating composition containing an ionizing radiation-curable polyfunctional monomer or polyfunctional oligomer is coated on a cellulose acylate film, and the polyfunctional monomer or polyfunctional oligomer is formed by a crosslinking reaction or a polymerization reaction. Can do.
The functional group of the ionizing radiation-curable polyfunctional monomer or polyfunctional oligomer is preferably a light, electron beam, or radiation polymerizable group, and among them, a photopolymerizable functional group is preferable.
Examples of the photopolymerizable functional group include unsaturated polymerizable functional groups such as a (meth) acryloyl group, a vinyl group, a styryl group, and an allyl group. Among them, a (meth) acryloyl group is preferable.

Further, instead of or in addition to the above-mentioned monomer having a polymerizable unsaturated group, a crosslinkable functional group may be introduced into the binder.
Examples of the crosslinkable functional group include isocyanate group, epoxy group, aziridine group, oxazoline group, aldehyde group, carbonyl group, hydrazine group, carboxyl group, methylol group and active methylene group.
Further, vinylsulfonic acid, acid anhydride, cyanoacrylate derivative, melamine, etherified methylol, ester and urethane, and metal alkoxide such as tetramethoxysilane can also be used as a monomer having a crosslinked structure.
A functional group that exhibits crosslinkability as a result of the decomposition reaction, such as a block isocyanate group, may be used.
That is, in the present invention, the crosslinkable functional group may not react immediately but may exhibit reactivity as a result of decomposition.
The binder having these crosslinkable functional groups can form a crosslinked structure by heating after coating.

  The hard coat layer contains matte particles having an average particle size of 1.0 to 10.0 μm, preferably 1.5 to 7.0 μm, such as inorganic compound particles or resin particles, for the purpose of imparting internal scattering properties. May be.

  For the purpose of controlling the refractive index of the hard coat layer, a high refractive index monomer, inorganic particles, or both can be added to the binder of the hard coat layer. In addition to the effect of controlling the refractive index, the inorganic particles also have the effect of suppressing cure shrinkage due to the crosslinking reaction. In the present invention, a polymer formed by polymerizing the polyfunctional monomer and / or the high refractive index monomer after the formation of the hard coat layer, and the inorganic particles dispersed therein are referred to as a binder.

When the optical film of the present invention is used on the surface of a liquid crystal display device, a reflection image of a surrounding object may be reflected on the surface, and the visibility of the display image may be reduced. The surface of the layer may be provided with unevenness to impart the ability to scatter light on the surface (antiglare property).
The hard coat layer may be a light scattering layer imparted with light scattering properties on the surface and / or inside (if the surface is imparted with scattering properties, it corresponds to the following antiglare layer).

<Anti-glare layer>
The antiglare layer is formed for the purpose of contributing to the film antiglare properties due to surface scattering and preferably hard coat properties for improving the scratch resistance of the film. Therefore, in the present invention, it can be used as one embodiment of a layer having hard coat properties.

  As a method for imparting antiglare properties, a method of laminating and forming a mat-shaped shaping film having fine irregularities on the surface as described in JP-A-6-16851, JP-A-2000-206317 The method of forming by curing shrinkage of ionizing radiation curable resin due to the difference in ionizing radiation dose as described in the above, the mass ratio of the good solvent to the translucent resin by drying as described in JP-A-2000-338310 A method of forming concavo-convex on the coating film surface by gelling the light-transmitting fine particles and the light-transmitting resin by gelation, as described in JP-A-2000-275404, by external pressure Method for imparting surface irregularities, Method for imparting surface irregularities by external pressure as described in JP 2000-275404 A, JP 2005-195819 A As described in the report, a method of forming surface irregularities using phase separation in the process of evaporation of a solvent from a mixed solution of a plurality of polymers is known, and these known methods can be used. it can.

[Translucent particles]
One preferred embodiment of the antiglare layer that can be used in the present invention contains a binder capable of imparting hard coat properties, translucent particles for imparting antiglare properties, and a solvent as essential components. Surface irregularities are formed by the protrusions of the light-transmitting particles themselves or the protrusions formed of an aggregate of a plurality of particles. The antiglare layer preferably has antiglare properties and hard coat properties.

Specific examples of the translucent particles include inorganic compound particles such as silica particles and TiO ₂ particles; resin particles such as acrylic particles, crosslinked acrylic particles, polystyrene particles, crosslinked styrene particles, melamine resin particles, and benzoguanamine resin particles. Is preferred. Of these, crosslinked styrene particles, crosslinked acrylic particles, and silica particles are preferred. The shape of the mat particles can be either spherical or irregular.

Two or more kinds of mat particles having different particle diameters may be used in combination. It is possible to impart anti-glare properties with mat particles having a larger particle size and to impart other optical characteristics with mat particles having a smaller particle size. For example, when an anti-glare antireflection film is attached to a high-definition display of 133 ppi or higher, a problem in display image quality called “glare” may occur.
“Glitter” is derived from the fact that pixels are enlarged or reduced due to unevenness present on the surface of the antiglare and antireflection film, resulting in loss of brightness uniformity, but the particle size is smaller than the matte particles that impart antiglare properties. Thus, the use of mat particles different from the refractive index of the binder can greatly improve the performance.

The mat particles, matting particle amount in the formed antiglare layer is preferably contained 10 to 1000 mg / ^{m 2,} it is more preferably contained 100 to 700 mg / ^{m 2.}

  The film thickness of the antiglare layer is preferably 1 to 20 μm, and more preferably 2 to 10 μm. Within the above range is preferable from the viewpoint of hard coat properties, curling, and brittleness.

  The strength of the antiglare layer is preferably H or more, more preferably 2H or more, and further preferably 3H or more in a pencil hardness test.

<Antireflection layer>
The optical film of the present invention is preferably provided with an antireflection layer on the hard coat layer for the purpose of reducing the reflectance. The antireflection layer has at least a low refractive index layer, and if necessary, at least one of a medium refractive index layer and a high refractive index layer on the hard coat layer side, and the low refractive index layer. It is more preferable in terms of reflectance reduction to provide an antireflection layer comprising a plurality of layers provided in this order.
In addition, although an antireflection layer can be provided without providing a hard coat layer, it is preferable to interpose a hard coat layer in order to improve the physical strength of the protective film. The hard coat layer may have a laminated structure of two or more layers.

[High refractive index layer and medium refractive index layer]
When the optical film of the present invention is provided with a high refractive index layer and a medium refractive index layer and optical interference is used together with a low refractive index layer described later, the antireflection property can be enhanced.
In the present specification, the high refractive index layer and the medium refractive index layer may be collectively referred to as a high refractive index layer. In the present invention, “high”, “medium”, and “low” in the high refractive index layer, medium refractive index layer, and low refractive index layer represent the relative refractive index relationship between the layers. In terms of the relationship with the cellulose acylate film, the refractive index preferably satisfies the relationship of cellulose acylate film> low refractive index layer, high refractive index layer> cellulose acylate film.
In the present specification, the high refractive index layer, the middle refractive index layer, and the low refractive index layer may be collectively referred to as an antireflection layer.

  In order to construct an antireflection layer by constructing a low refractive index layer on the high refractive index layer, the refractive index of the high refractive index layer is preferably 1.55 to 2.40, and 1.60. To 2.20 is more preferable, 1.65 to 2.10 is more preferable, and 1.80 to 2.00 is particularly preferable.

  When an antireflective film is prepared by coating a medium refractive index layer, a high refractive index layer, and a low refractive index layer in order from the optical film, the refractive index of the high refractive index layer is 1.65 to 2.40. Preferably, it is 1.70-2.20. The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.55-1.80.

Specific examples of the inorganic particles used in the high refractive index layer and the medium refractive index layer include TiO ₂ , ZrO ₂ , Al ₂ O ₃ , In ₂ O ₃ , ZnO, SnO ₂ , Sb ₂ O ₃ , ITO and SiO _2. Etc. TiO ₂ and ZrO ₂ are particularly preferable in terms of increasing the refractive index. The surface of the inorganic filler is preferably subjected to silane coupling treatment or titanium coupling treatment, and a surface treatment agent having a functional group capable of reacting with a binder species on the filler surface is preferably used.

The content of inorganic particles in the high refractive index layer is preferably 10 to 90 mass%, more preferably 15 to 80 mass%, and more preferably 15 to 75 mass% with respect to the mass of the high refractive index layer. More preferably. Two or more kinds of inorganic particles may be used in combination in the high refractive index layer.
When the low refractive index layer is provided on the high refractive index layer, the refractive index of the high refractive index layer is preferably higher than the refractive index of the transparent substrate film.
The high refractive index layer contains an ionizing radiation curable compound containing an aromatic ring, an ionizing radiation curable compound containing a halogenated element other than fluorine (for example, Br, I, Cl, etc.), and atoms such as S, N, P, etc. A binder obtained by a crosslinking or polymerization reaction such as an ionizing radiation curable compound is also preferably used.

  The film thickness of the high refractive index layer can be appropriately designed depending on the application. When using a high refractive index layer as an optical interference layer described later, 30 to 200 nm is preferable, 50 to 170 nm is more preferable, and 60 to 150 nm is still more preferable.

  The haze of the high refractive index layer is preferably as low as possible when it does not contain particles that impart an antiglare function. It is preferably 5% or less, more preferably 3% or less, still more preferably 1% or less. The high refractive index layer is preferably constructed directly on the transparent substrate film or via another layer.

[Low refractive index layer]
In order to reduce the reflectance of the optical film of the present invention, it is preferable to use a low refractive index layer.
The refractive index of the low refractive index layer is preferably 1.20 to 1.46, more preferably 1.25 to 1.46, and still more preferably 1.30 to 1.40.
The thickness of the low refractive index layer is preferably 50 to 200 nm, and more preferably 70 to 100 nm.
The haze of the low refractive index layer is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. The specific strength of the low refractive index layer is preferably H or more, more preferably 2H or more, and further preferably 3H or more in a pencil hardness test under a 500 g load.
In order to improve the antifouling performance of the optical film, the contact angle of the surface with respect to water is preferably 90 degrees or more, more preferably 95 degrees or more, and further preferably 100 degrees or more.
Preferred embodiments of the composition of the low refractive index layer include (1) a composition containing a fluorine-containing polymer having a crosslinkable or polymerizable functional group, and (2) a hydrolysis condensate of a fluorine-containing organosilane material. And (3) a composition containing a monomer having two or more ethylenically unsaturated groups and inorganic fine particles having a hollow structure.

(Physical properties of optical film)
<Moisture permeability>
The measurement method of moisture permeability is "Polymer Physical Properties II" (Polymer Experiment Course 4, Kyoritsu Shuppan), pages 285-294: Measurement of vapor permeation (mass method, thermometer method, vapor pressure method, adsorption amount method) The method described in can be applied.
In the present invention, it is preferable to calculate according to JIS Z-0208 except that the humidity control condition is changed to 60 ° C. and 95% RH. At this time, the operation of taking out and weighing the cup placed in the thermo-hygrostat at an appropriate time interval is repeated, and the mass increase per unit time is obtained for each of two consecutive weighings, and it is constant within 5%. It is preferable to continue evaluation until
Moreover, in order to exclude the influence by moisture absorption etc. of a sample, it is preferable to measure the value of moisture permeability by measuring a blank cup in which no hygroscopic agent is put.

The moisture permeability of the optical film of the present invention at 60 ° C. and 95% relative humidity is preferably 500 g / m ² · day or less and 2500 g / m ² · day or less.
If the moisture permeability of the optical film of the present invention is in this range, the performance as a polarizing plate (polarization degree, orthogonal single plate transmittance) will not be deteriorated, and the polarizing film will change due to changes in temperature and humidity during long-term use. It is possible to suppress the occurrence of unevenness in the display image due to the size change.

<Haze value>
The haze value of the cellulose acylate film in the optical film of the present invention (that is, the haze value when no other layer such as a hard coat layer is provided) is 1.0% or less in order to improve the transparency of the optical film. 0.01% or more and 1.0% or less is preferable, and 0.01% or more and 0.5% or less is more preferable.

<Hydrophilic treatment of optical film surface>
When creating a polarizing plate using the optical film of the present invention as at least one of the two protective films of the polarizing film, the optical film is a surface of the optical film opposite to the hard coat layer, That is, it is preferable to improve the adhesiveness on the adhesive surface by hydrophilizing the surface to be bonded to the polarizing film. The hydrophilized surface is effective for improving the adhesiveness with the adhesive layer mainly composed of polyvinyl alcohol. As the hydrophilic treatment, the following saponification treatment is preferably performed.

[Saponification]
(1) Method of immersing in alkaline solution This is a technique in which a protective film for polarizing plate is immersed in an alkaline solution under appropriate conditions, and all surfaces having reactivity with alkali on the entire surface of the film are saponified. It is preferable from the viewpoint of cost because it does not require any equipment. The alkaline liquid is preferably a sodium hydroxide aqueous solution. A preferred concentration is 0.5 to 3 mol / L, particularly preferably 1 to 2 mol / L. The liquid temperature of a preferable alkali liquid is 30-75 degreeC, Most preferably, it is 40-60 degreeC.
The combination of the saponification conditions is preferably a combination of relatively mild conditions, but can be set according to the material and configuration of the optical film and the target contact angle. After being immersed in the alkaline solution, it is preferable to sufficiently wash with water or neutralize the alkaline component by immersing in a dilute acid so that the alkaline component does not remain in the film.

By saponification treatment, the surface of the cellulose acylate film opposite to the surface having the antiglare layer or antireflection layer is hydrophilized.
The protective film for polarizing plate is used by adhering the hydrophilic surface of a cellulose acylate film to a polarizing film.
The hydrophilized surface is effective for improving the adhesiveness with the adhesive layer mainly composed of polyvinyl alcohol.
In the saponification treatment, the lower the contact angle with respect to the surface of the cellulose acylate film opposite to the side having the antiglare layer or the low refractive index layer, the better from the viewpoint of adhesiveness to the polarizing film. At the same time, since it is damaged by alkali from the surface having the antiglare layer and the low refractive index layer to the inside, it is important to set the reaction conditions to the minimum necessary. When the contact angle of water on the opposite cellulose acylate film surface as described above is used as an index of damage to each layer due to alkali, particularly when the cellulose acylate film is triacetylcellulose, preferably 10 degrees to 50 degrees, more preferably 30 degrees to 50 degrees, still more preferably 40 degrees to 50 degrees. If it is this range, it is preferable when adhesiveness with a polarizing film and the said damage are suppressed and physical strength is ensured.

(2) Method of applying alkaline solution As a means for avoiding damage to each film in the above-mentioned immersion method, the alkaline solution is applied only to the surface opposite to the surface having the antiglare layer or the low refractive index layer under appropriate conditions. An alkaline solution coating method of coating, heating, washing with water and drying is preferably used. The application in this case means that an alkaline solution or the like is brought into contact only with the surface to be saponified, and in addition to the application, it may be carried out by spraying or contacting a belt containing the solution. Including. By adopting these methods, a separate facility and process for applying an alkaline solution are required, which is inferior to the immersion method (1) from the viewpoint of cost. On the other hand, since the alkali solution contacts only the surface to be saponified, the opposite surface can have a layer using a material that is weak against the alkali solution. For example, vapor deposition films and sol-gel films have various effects such as corrosion, dissolution, and peeling due to alkali solution, so it is not desirable to use the immersion method. Is possible.

  In any of the saponification methods (1) and (2), since each layer can be formed after being unwound from a roll-shaped support, a series of steps are added in addition to the above-described antiglare antireflection film production process. You may carry out by operation of. Furthermore, the polarizing plate can be produced more efficiently than the same operation with a single wafer by continuously performing the bonding step with the polarizing plate comprising the support that has been unwound in the same manner.

(3) Method of protecting and saponifying the antiglare layer and the antireflection layer with a laminate film As in the case of (2), when the antiglare layer and / or the low refractive index layer has insufficient resistance to an alkaline solution In addition, after forming the final layer, after laminating the laminate film on the surface on which the final layer has been formed and then immersing it in an alkali solution, only the surface of the triacetyl cellulose opposite to the surface on which the final layer has been formed is hydrophilized, Thereafter, the laminate film can be peeled off. Even in this method, only the surface opposite to the surface on which the final layer of the triacetyl cellulose film is formed is subjected to the hydrophilization treatment necessary for the polarizing plate protective film without damaging the antiglare layer and the low refractive index layer. be able to. Compared with the method (2), there is an advantage that a laminate film is generated as waste, but a device for applying a special alkaline solution is unnecessary.

(4) Method of immersing in alkaline solution after forming up to antiglare layer Up to antiglare layer is resistant to alkaline solution, but when low refractive index layer is insufficiently resistant to alkaline solution, after forming up to antiglare layer It is also possible to soak both surfaces in an alkali solution to hydrophilize both surfaces, and then form a low refractive index layer on the antiglare layer. Although the manufacturing process becomes complicated, there is an advantage that the interlayer adhesion between the antiglare layer and the low refractive index layer is improved particularly when the low refractive index layer has a hydrophilic group such as a fluorine-containing sol-gel film.

(5) Method of forming a coating on a previously saponified triacetyl cellulose film Saponification is performed by, for example, pre-immersing a triacetyl cellulose film in an alkali solution, and coating is performed directly on one side or through another layer. A layer may be formed. In the case of saponification by dipping in an alkaline solution, interlayer adhesion between the coating layer and the triacetyl cellulose surface hydrophilized by saponification may deteriorate. In such a case, after saponification, only the surface on which the coating layer is to be formed is treated with corona discharge, glow discharge, etc. to remove the hydrophilic surface and then form an antiglare layer or other layer. Can be dealt with. Further, when the antiglare layer or other layers have a hydrophilic group, the interlayer adhesion may be good.

  Below, the polarizing plate using the optical film of this invention and the liquid crystal display device using this polarizing plate are demonstrated.

(Polarizer)
The polarizing plate of this invention has a polarizing film and a protective film for polarizing plates. The optical film of the present invention may be used as a protective film on at least one side of a polarizing film, and an optical compensation film is preferably used as a protective film on the side opposite to the optical film of the present invention. An optical film having an optical compensation layer formed thereon is also preferred. Further, it is also preferable to use an optical compensation film attached on the opposite protective film via an adhesive.

<Polarizing film>
The polarizing film of the present invention is preferably composed of polyvinyl alcohol (PVA) and a dichroic molecule. However, as described in JP-A-11-248937, PVA and polyvinyl chloride are dehydrated and dechlorinated. Thus, a polyvinylene polarizing film in which a polyene structure is generated and oriented may be used.

  PVA is a polymer material obtained by saponifying polyvinyl acetate, but may contain components copolymerizable with vinyl acetate such as unsaturated carboxylic acid, unsaturated sulfonic acid, olefins, and vinyl ethers. A modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group or the like may also be used.

The dichroic molecule is preferably a higher-order iodine ion such as I3- or I5- or a dichroic dye. Among them, higher-order iodine ions are particularly preferably used in the present invention. Higher-order iodine ions were obtained by dissolving iodine in an aqueous potassium iodide solution as described in “Applications of Polarizing Plates” by Nagata Ryo, CMC Publishing and Industrial Materials, Vol. 28, No. 7, p39-p45. PVA can be immersed in a liquid and / or boric acid aqueous solution, and can be produced in a state of being adsorbed and oriented in PVA.
When a dichroic dye is used as the dichroic molecule, an azo dye is preferable, and among them, a bisazo dye and a trisazo dye are more preferable. The dichroic dye is preferably a water-soluble dye. For this reason, a hydrophilic substituent such as a sulfonic acid group, an amino group or a hydroxyl group is introduced into the dichroic molecule, so that a free acid, an alkali metal salt, an ammonium salt or an amine is introduced. It is preferably used as a salt.

<Preparation of polarizing plate>
The optical film of the present invention can constitute a polarizing plate by being bonded to at least one surface of a polarizing film. The other surface of the polarizing film is preferably laminated with a protective film for polarizing plate having a moisture permeability of 800 to 3000 g / m ² · day, more preferably 1000 to 1700 g / m ² · day. Usually used TAC is preferably used.
A normal cellulose acetate film may be used, but a cellulose acetate film manufactured by a solution casting method and stretched in the width direction in the form of a roll film at a stretching ratio of 10 to 100% may be used.
Furthermore, in the polarizing plate of the present invention, an optical compensation film having an optically anisotropic layer made of a liquid crystalline compound while the other protective film may be the optical film of the present invention.

Of the two protective films of the polarizing film, the film other than the optical film of the present invention is preferably an optical compensation film having an optical compensation layer comprising an optical anisotropic layer. The optical compensation film (retardation film) can improve the viewing angle characteristics of the liquid crystal display screen.
A known film can be used as the optical compensation film, but the optical compensation film described in JP-A-2001-100042 is preferable in terms of widening the viewing angle.

  When used with a liquid crystal display device or the like, the optical film of the present invention is preferably disposed on the viewing side opposite to the liquid crystal cell.

(Liquid crystal display device)
The optical film and polarizing plate of the present invention can be advantageously used in a liquid crystal display device and the like, and is preferably used as the outermost layer of the display.
The liquid crystal display device has a liquid crystal cell and two polarizing plates arranged on both sides thereof, and the liquid crystal cell carries a liquid crystal between two electrode substrates. Furthermore, one optically anisotropic layer may be disposed between the liquid crystal cell and one polarizing plate, or two optically anisotropic layers may be disposed between the liquid crystal cell and both polarizing plates.

  The liquid crystal cell is preferably a TN (Twisted Nematic) mode, a VA (Vertically Aligned) mode, an OCB (Optically Compensated Bend) mode, an IPS (In-phase switching) mode, or an ECB (Electrically controlled rebending mode).

Hereinafter, other uses of the optical film and the polarizing plate of the present invention will be described.
<Brightness enhancement film>
As the brightness enhancement film, a polarization conversion element having a function of separating light emitted from a light source (backlight) into transmitted polarized light, reflected polarized light, or scattered polarized light is used. Such a brightness enhancement film can improve the output efficiency of linearly polarized light by using retroreflected light from reflected polarized light or scattered polarized light backlight.
An example is an anisotropic reflective polarizing film. Examples of the anisotropic reflective polarizing film include an anisotropic multiple thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction. An example of the anisotropic multi-thin film is DBM manufactured by 3M (see, for example, JP-A-4-268505).
An example of the anisotropic reflective polarizing film is a composite of a cholesteric liquid crystal layer and a λ / 4 plate. An example of such a composite is PCF manufactured by Nitto Denko (see JP-A-11-231130, etc.).
An example of the anisotropic reflective polarizing film is a reflective grid polarizing film. As a reflective grid polarizing film, a metal grid reflective polarizing film (see US Pat. No. 6,288,840, etc.) that finely processes metal and emits reflected polarized light even in the visible light region, metal fine particles in a polymer matrix. Examples thereof include those stretched by being inserted (see JP-A-8-184701, etc.).

Moreover, an anisotropic scattering polarizing film is mentioned. An example of the anisotropic scattering polarizing film is 3M DRP (see US Pat. No. 5,825,543).
Furthermore, there is a polarizing element that can perform polarization conversion in one pass. For example, the one using smectic C * can be mentioned (see JP 2001-201635 A). An anisotropic diffraction grating is used.
The polarizing plate of the present invention can be used together with a brightness enhancement film. When a brightness enhancement film is used, it is more preferable that the polarizing plate and the brightness enhancement film are in close contact with each other in order to prevent moisture from entering the polarizing plate and suppress light leakage. The adhesive for bonding the polarizing plate and the brightness enhancement film is not particularly limited. For example, acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate / vinyl chloride copolymer, modified polyolefin, epoxy-based, fluorine-based, natural rubber, synthetic rubber and other rubber-based polymers Can be appropriately selected and used. In particular, it is preferable to use a material that is excellent in optical transparency, exhibits appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and is excellent in weather resistance, heat resistance, and the like.

<Touch panel>
The optical film of the present invention can be applied to touch panels described in JP-A-5-127822 and JP-A-2002-48913.

<Organic EL device>
The optical film of the present invention can be used as a substrate (base film) such as an organic EL element or a protective film.
When the optical film of the present invention is used for an organic EL device or the like, JP-A-11-335661, JP-A-11-335368, JP-A-2001-192651, JP-A-2001-192652, JP-A-2001-192653. JP, 2001-335776, JP, 2001-247859, JP, 2001-181616, JP, 2001-181617, JP, 2002-181816, JP, 2002-181617, JP, 2002-056776, etc. The contents described in each publication can be applied. Moreover, it is preferable to use together with the content of each gazette of Unexamined-Japanese-Patent No. 2001-148291, Unexamined-Japanese-Patent No. 2001-221916, and Unexamined-Japanese-Patent No. 2001-231443.

    EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to a following example.

[Production of optical film]
In the dope formulation shown in Table 1 below, each dope is prepared, and the base layer dope and the surface layer dope are cast simultaneously so as to have the configuration shown in Table 2, and the cellulose acylate films in the optical films 1 to 24 are manufactured. did. The cellulose acylate films of the optical films 1 to 24 are cast so that the dope for the surface layer 1 is mirror-finished and cooled to −10 ° C. on the drum side using the casting apparatus shown in FIG. While volatilizing, the gel was formed by cooling, and the web (casting film) was peeled off. It was dried with hot air at 100 ° C. until the residual solvent amount was 10% by mass, and then dried with hot air at 140 ° C. for 10 minutes.

The materials used are shown below.
Cellulose triacetate: Degree of acetyl substitution 2.86, Viscosity average degree of polymerization 310
UV absorber: benzotriazole UV absorber (20/80% by weight mixture of TINUVIN326 / TINUVIN328, each manufactured by Ciba Japan Co., Ltd.)
MAE, MEE, MPE: Organically treated layered inorganic compound, synthetic mica manufactured by Co-op Chemical Co., Ltd., trade names Sofushima MAE, MEE, MPE
ME-100: layered inorganic compound not subjected to organic treatment, synthetic mica manufactured by Coop Chemical Co., Ltd., trade name Lucentite ME-100
SAN, STN, SEN: Organically treated layered inorganic compound, synthetic smectite manufactured by Co-op Chemical Co., Ltd., trade name Lucentite SAN, STN, SEN

  The base layer dope was prepared with a mixed solvent of methylene chloride: methanol 90:10 mass ratio so that the solid content concentration of the base layer dope was 23% by mass and the solid content concentration of the surface layer dope was 18% by mass.

<Preparation of coating solution for hard coat layer>
<< Preparation of Sol Solution 1 >>
In a 1,000 ml reaction vessel equipped with a thermometer, a nitrogen inlet tube and a dropping funnel, 187 g (0.80 mol) of acryloxyoxypropyltrimethoxysilane, 27.2 g (0.20 mol) of methyltrimethoxysilane, 320 g of methanol ( 10 mol) and 0.06 g (0.001 mol) of KF were added, and 15.1 g (0.86 mol) of water was slowly added dropwise at room temperature with stirring. After completion of the dropwise addition, the mixture was stirred at room temperature for 3 hours, and then heated and stirred for 2 hours under methanol reflux.
Then, 120 g of sol solution 1 was obtained by distilling off the low boiling point under reduced pressure and further filtering. As a result of GPC measurement of the substance thus obtained, the mass average molecular weight was 1,500, and among the components higher than the oligomer component, the component having a molecular weight of 1000 to 20000 was 30%.
Moreover, from the measurement result of ¹ H-NMR, the structure of the obtained substance was the following structure.

Furthermore, the condensation rate α as determined by ²⁹ Si-NMR was 0.56. From this analysis result, it was found that the silane coupling agent sol was mostly composed of a linear structure.
From the gas chromatography analysis, the raw material acryloxypropyltrimethoxysilane had a residual rate of 5% or less.

  The following composition was placed in a mixing tank, stirred to dissolve each component, and filtered through a polypropylene filter having a pore size of 30 μm to prepare a hard coat layer coating solution.

[Composition of coating liquid for hard coat layer]
・ PET-30 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 40.0g
・ DPHA ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 10.0g
・ Irgacure 184 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 2.0g
-SX-350 (30%) ... 2.0g
・ Cross-linked acrylic-styrene particles (30%) ... 13.0g
・ FP-13 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 0.06g
・ Sol solution 1 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 11.0g
・ Toluene 38.5g

The compounds used are shown below.
PET-30: A mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by Nippon Kayaku Co., Ltd.)
DPHA: Mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd.)
・ Irgacure 184: Polymerization initiator (Ciba Specialty Chemicals Co., Ltd.)
SX-350: average particle size 3.5 μm cross-linked polystyrene particles (refractive index 1.60, manufactured by Soken Chemical Co., Ltd., 30% by weight toluene dispersion, used after dispersion for 20 minutes at 10,000 rpm with a Polytron disperser)
Crosslinked acrylic-styrene particles: average particle size 3.5 μm (refractive index 1.55, manufactured by Soken Chemical Co., Ltd., 30% by weight toluene dispersion, used after dispersion at 10,000 rpm for 20 minutes with a Polytron disperser)
FP-13: Fluorosurfactant (used after dissolving as a 10% by mass solution of MEK. In the following formula, the composition ratio (60:40) represents a molar ratio.)

<Preparation of coating solution for low refractive index layer>
Thermally crosslinkable fluorine-containing polymer having a refractive index of 1.44 containing polysiloxane and hydroxyl group (JTA113, solid content concentration 6%, manufactured by JSR Corporation) 13 g, colloidal silica dispersion MEK-ST-L (trade name, average) Particle size 45 nm, solid content concentration 30%, manufactured by Nissan Chemical Co., Ltd.) 1.3 g, sol solution 10.65 g, methyl ethyl ketone 4.4 g, cyclohexanone 1.2 g were added, and after stirring, polypropylene having a pore size of 1 μm A low refractive index layer coating solution was prepared by filtering with a filter manufactured by the manufacturer. The refractive index of the layer formed with this coating solution was 1.45.

<< Coating of hard coat layer >>
The cellulose acylate films for optical films 1 to 24 prepared as described above are unwound in roll form, and the coating liquid 1 for hard coat layer is applied to the cellulose acylate film on the backup roll using a coater having a slot die. It was directly extruded onto the surface (surface 1 side) and applied. After coating at a transfer speed of 30 m / min, drying at 30 ° C. for 15 seconds and 90 ° C. for 20 seconds, and further using a 160 W / cm air-cooled metal halide lamp (made by Eye Graphics Co., Ltd.) under a nitrogen purge. The coating layer was cured by irradiating ultraviolet rays with an irradiation amount of 90 mJ / cm ² to form a 6 μm thick anti-glare hard coat layer and wound up.

<< Coating of low refractive index layer >>
On the surface on which the hard coat layer of the film on the backup roll is applied using a coater having a slot die, the film on which the hard coat layer is formed is unrolled in a roll form. It was extruded and applied directly to.
After drying at 120 ° C. for 150 seconds and further drying at 140 ° C. for 8 minutes, an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) with 240 W / cm in an atmosphere with an oxygen concentration of 0.1% by nitrogen purge Then, an ultraviolet ray having an irradiation amount of 300 mJ / cm ² is irradiated to form a low refractive index layer having a thickness of 100 nm, wound, and a low refractive index layer is further formed on the optical film on which the hard coat layer is formed. Films 1 to 24 were produced.

<Alkali treatment>
The optical films 1 to 24 on which the hard coat layer and the low refractive index layer were formed were immersed in an aqueous 1.5 mol / L sodium hydroxide solution at 55 ° C. for 120 seconds, and then washed with water and dried.

<Evaluation of optical film>
The following evaluation was performed about the produced optical films 1-24. The evaluation results are shown in Table 3.

<Measurement of moisture permeability>
The moisture permeability of the optical film was calculated according to JIS Z-0208 except that the humidity control condition was changed to 60 ° C. and 95% RH. At this time, the operation of taking out and weighing the cup placed in the thermo-hygrostat at an appropriate time interval is repeated, and the mass increase per unit time is obtained for each of two consecutive weighings, and it is constant within 5%. Evaluation continued until.
Moreover, in order to exclude the influence by the moisture absorption etc. of a sample, the blank cup which does not put a hygroscopic agent was measured, and the value of moisture permeability was correct | amended.

<Measurement of haze>
The total haze of the optical film (that is, the cellulose acylate film) before the hard coat layer was applied was measured and evaluated using a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.

<Measurement of brittleness (cracking resistance)>
The optical film sample after coating the hard coat layer and the low refractive index layer was cut into 35 mm × 120 mm, left to stand at a temperature of 25 ° C. and a relative humidity of 60% for 3 hours, and then cracked when rolled into a cylinder. The curvature diameter at which it began to occur was measured to evaluate surface cracks.
The crack resistance of the optical film was evaluated according to the following criteria based on the diameter of curvature at which cracks occur when the coated layer (hard coat layer and low refractive index layer) side is rolled outward.
○: The radius of curvature at which cracks are generated is less than 4 mm. Δ: The radius of curvature at which cracks are generated is from 4 mm to less than 7 mm. X: The radius of curvature at which cracks are generated is 7 mm or more.

<Measurement of curl>
The optical film after the hard coat layer and the low refractive index layer are coated is cut into a size of 5 mm × 150 mm so that the direction perpendicular to the coating direction is the long side. The straight line connecting both ends (the length of A in FIG. 7) was measured as a curl value, and evaluated according to the following criteria.
○: curl value less than 20 mm Δ: curl value of 20 mm or more and less than 40 mm ×: curl value of 40 mm or more, which is problematic in practice.

<Preparation of polarizing plate>
Each of optical films 1 to 24 (alkaline-treated) and the following norbornene resin film are immersed in an aqueous solution containing 120 parts by weight of a polyvinyl alcohol film containing 1 part by weight of iodine, 2 parts by weight of potassium iodide, and 4 parts by weight of boric acid. And it adhered and protected on both surfaces of the polarizing film produced by extending | stretching 4 times at 50 degreeC, Then, it was made to dry at 90 degreeC after that, and the polarizing plates 1-24 were produced. A PVA adhesive was used for adhesion between the sample and polyvinyl alcohol, and an isocyanate adhesive was used for adhesion between the norbornene resin film and polyvinyl alcohol.
Norbornene-based resin film: Norbornene-based resin film (manufactured by Nippon Zeon Co., Ltd .: trade name ZEONOR: thickness 60 μm) uniaxially stretched was used. The thickness was 54 μm, the in-plane retardation Re was 55 nm, and the thickness direction retardation Rth was 120 nm.

<Evaluation of polarizing plate>
The produced polarizing plates 1-24 were evaluated as follows. The evaluation results are shown in Table 3.

<Discoloration of polarizing plate>
An adhesive was applied to the norbornene-based resin film side of the polarizing plate, and the side having the adhesive was attached to a glass plate. The polarizing plate attached to the glass plate is exposed to a condition of 23 ° C. and 95% RH for 5 days, then left to stand at 25 ° C. and 60% RH for 1 day, and transmitted to a sample that has not been exposed to 23 ° C. and 95% RH for 5 days. The presence or absence of light color change was visually evaluated as follows.
○: The difference in color is not visible visually. Δ: The color difference is slightly visible. ×: The color difference is clearly visible.

<Polarizing plate durability>
An adhesive was applied to the norbornene-based resin film side of the polarizing plate, and the side having the adhesive was attached to a glass plate. The polarizing plate attached to the glass plate was exposed for 1 day at 50 ° C. and 90% RH, and then left for 1 day at 25 ° C. and 60% RH. Samples that have not been exposed to 50 ° C. and 90% RH for one day have transmittance Ii measured in an arrangement in which the polarizing plate transmission axes are orthogonal to each other, and samples that have been exposed to 50 ° C. and 90% for one day have an arrangement in which the polarizing plate transmission axes are orthogonal to each other. With the measured transmittance Io, the transmittance change (difference between Io and Ii) was evaluated as follows.
○: Change in transmittance less than 0.001% Δ: Change in transmittance from 0.001% to 0.005% ×: Change in transmittance greater than 0.005%

From Table 3, the optical film of the present invention can maintain the display image quality of a display such as a liquid crystal display device for a long period of time, is excellent in brittleness, has a small haze value and curl value, and is used as a protective film for a polarizing film. It turns out that it is a suitable thin optical film.
Furthermore, film no. 4 and no. Compared with the case where the layered inorganic compound is contained only in the surface layer on one side of the base layer (No. 20), the layered inorganic compound is contained in any of the surface layers on both sides of the base layer (No. 4). ) Has lower moisture permeability and a smaller curl value. In addition, film No. 4 and no. Comparison with No. 21 shows that when an organically treated layered inorganic compound is used (No. 4), it is excellent in brittleness. Furthermore, no. 4 and no. Comparison with 22-24 shows that when mica is used as the layered inorganic compound (No. 4), the moisture permeability is low and the brittleness is excellent.

  Moreover, the same effect was acquired even if the dope seed | species D of Table 1 was changed into the dope seed | species E and F. FIG.

DESCRIPTION OF SYMBOLS 11 Stirrer 12 Transfer pump 13 Filter 14 Stock tank 15a Surface layer casting liquid pump 15b Base layer casting liquid pump 15c Surface layer casting liquid pump 16a Additive injection pump (solvent, layered inorganic compound, etc.)
16c Additive injection pump (solvent, layered inorganic compound, etc.)
17 Casting die 18 Casting band 19 Decompression chamber 20 Casting drum 30 Casting die 32 Manifold 33 Feed block

Claims (12)

  An optical film having a cellulose acylate film having a multilayer structure including a layer containing at least one layered inorganic compound, wherein the cellulose acylate film has a thickness of 20 to 70 μm, and the layered inorganic compound is the cellulose acylate. An optical film that is contained in a proportion of 1 to 50% by mass with respect to the total solid content in the rate film, and in which the layered inorganic compound is localized in the thickness direction of the cellulose acylate film.   The optical film according to claim 1, wherein the multilayer structure has a base layer and a surface layer, and the layered inorganic compound is localized on the surface layer.   The optical film according to claim 2, wherein the surface layer has a thickness of 1 to 10 μm.   The optical film according to claim 2, wherein the surface layer is laminated on both sides of the base layer.   The optical film according to claim 1, wherein the layered inorganic compound is organically treated. The optical film according to any one of claims 1 to 5, wherein the moisture permeability at 60 ° C and 95% relative humidity is 500 g / m ² · day to 2500 g / m ² · day.   The optical film of any one of Claims 1-6 which has a layer which has a hard-coat property at least on one surface of the said cellulose acylate film.   The polarizing plate which has a protective film on both sides of a polarizing film and this polarizing film, Comprising: At least one protective film is a polarizing plate which is an optical film of any one of Claims 1-7.   The image display apparatus which has the optical film of any one of Claims 1-7, or the polarizing plate of Claim 8. A method for producing an optical film having a multilayer cellulose acylate film including a layer containing at least one layered inorganic compound,
A dope containing the layered inorganic compound and cellulose acylate is cast on a support to form a cast film, and the cast film is peeled off from the support and dried to form the cellulose ester film. The manufacturing method of the optical film including the process to do. The multilayer structure is a multilayer structure having a base layer and a surface layer,
A base layer dope containing the cellulose acylate substantially free of the layered inorganic compound and a surface layer dope containing the layered inorganic compound and the cellulose acylate are simultaneously or sequentially arranged on the support in this order. The optical film according to claim 10, further comprising a step of casting the cast film to form the cast film, peeling the cast film from the support, and drying to form the cellulose acylate film. Manufacturing method.   The method for producing an optical film according to claim 11, wherein the base layer dope and the surface layer dope are simultaneously cast in this order on the support to form the cast film.

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