JPH10119067A - Manufacture of triacetylcellulose film having antigrare property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a triacetylcellulose film used as the protective film of a polarizing plate or the like with antiglare properties excellent in heat resistance. SOLUTION: At the manufacture of a film in a solution casting method, in which a dope prepared by dissolving a triacetylcellulose in a solvent is cast on a support 5 so as to obtain a film 7 by solidifying the triacetylcellulose through the evaporation of the solvent and then separate the obtained film 7 from the support 5, the surface, on which the dope is cast, of the support is made into an uneven surface 6 so as to form an unevenness simultaneously with the formation of a film on the surface of the formed film in order to obtain an antiglare triacetylcellulose film, the surface roughness of which lies within the range of 0.3-10μm by ten-point mean roughness Rz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a protective film for a polarizing plate used for a liquid crystal display or the like. In particular, it relates to a method for producing a protective film made of triacetyl cellulose having antiglare performance.

[0002]

2. Description of the Related Art A liquid crystal display using a polarizing plate is used for various purposes. It is preferable that the polarizing plate has an antiglare property so that the reflected light on the surface does not make the display difficult to see. Therefore, conventionally, an antiglare film having a mat-like surface has been further laminated or bonded on a polarizing plate.

[0003]

By the way, the polarizing plate is
Generally, both sides of a polarizing film made of polyvinyl alcohol film or the like in which iodine or a dye is adsorbed and oriented,
This is a configuration in which transparent resin layers are stacked. As a transparent resin layer, a protective film of a triacetyl cellulose film is often used. Therefore, if the surface of the triacetylcellulose film itself, which is a constituent material of the polarizing plate, is matted without using an antiglare film having a surface mat on the polarizing plate, the anti-glare film is separately provided. The need to use a glare film should be eliminated. However, the triacetyl cellulose film has a higher melting point and better heat resistance than a diacetyl cellulose film, etc., but even if the film surface can be processed into a mat shape by hot embossing, the surface irregularity shape under a high temperature environment Only those with dullness and reduced antiglare properties were obtained. There is also a method of applying a resin coating liquid containing a filler such as silica to form a matte surface, but a new coating step is required.

[0004]

Accordingly, the present invention provides a dope (solution) in which triacetyl cellulose is dissolved in a solvent,
In a method for producing a triacetylcellulose film by the so-called solution casting method, in which a film obtained by casting a solvent and evaporating and solidifying the solvent to separate the film from the support, the surface of the support on which the dope is cast is roughened. As the surface, the unevenness is formed on the film surface to be formed at the same time as the film is formed by the uneven surface, and the surface roughness is 0.3 μm ≦ Rz at ten point average roughness Rz.
A triacetyl cellulose film having an antiglare property and having an uneven surface of ≦ 10 μm on one side of the film was produced.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing triacetyl cellulose having antiglare properties of the present invention will be described in detail with reference to the drawings. First, FIG. 1 is a conceptual diagram showing one embodiment of the production method according to the present invention, FIG. 2 is a cross-sectional view showing one embodiment of an anti-glare triacetyl cellulose film obtained by the production method of the present invention, and FIG. FIG. 4 is a cross-sectional view of an antiglare triacetyl cellulose film obtained by a method of further providing a cured film on an uneven surface in order to improve abrasion resistance, as another embodiment of the production method of the present invention.

In the present invention, as shown in FIG. 2, the triacetylcellulose film 10 itself has an uneven surface 1 having a desired roughness on one side. The surface roughness of the uneven surface 1 is preferably in a range of 0.3 μm ≦ Rz ≦ 10 μm as a ten-point average roughness Rz. If the ten-point average roughness Rz is less than 0.3 μm, the surface roughness is too close to a plane to obtain sufficient anti-glare performance. Conversely, if the ten-point average roughness Rz is more than 10 μm, Although anti-glare performance can be obtained, the haze value is increased, and when a polarizing plate is used, the image quality of the display is deteriorated. The thickness of the triacetylcellulose film having antiglare properties for protecting the polarizing film is appropriately selected depending on the application, but is usually 10 to 5 times.
It is about 00 μm, preferably about 20 to 200 μm.

[0007] In the production method of the present invention, the surface irregularities of the desired roughness formed on the surface of the triacetylcellulose film can be obtained by forming the support surface on which the dope is cast by the solution casting method into an irregular surface, Will form. By the way, the solution casting method has conventionally been classified into a belt method using a rotating endless belt (film forming band) as a support for casting the dope and a drum method using a rotating drum as the support. In the invention, either method may be used. In either method, the uneven surface can be formed on the surface of the triacetylcellulose film obtained by forming a film by making the surface of the support an uneven surface. Figure 1 shows
It is a conceptual diagram which shows the manufacturing method by the solution casting method of a belt system. The manufacturing method of the present invention will be described with reference to the belt system shown in FIG. 1. A dope (solution) in which triacetyl cellulose is dissolved in a solvent is a support that is an endless belt that is rotated by a rotating drum 4 from a casting die 3. Uneven surface 6 of 5
The film 7 cast on the support 4 and obtained by evaporating and solidifying a part of the solvent on the support 4 is peeled off by a peeling roll 8,
The remaining solvent is further dried in the drying chamber 9 to obtain an anti-glare triacetyl cellulose film having desired irregularities on one surface. Note that the surface of the support is made uneven by a chemical etching method, a frost processing method, a sand blast method, or the like.

The dope cast on the support 5 is a solution in which triacetyl cellulose is dissolved in a solvent. Examples of the solvent include lower aliphatic hydrocarbon chlorides such as methylene chloride, methanol, ethanol, and the like. Lower aliphatic alcohols such as n-propyl alcohol and n-butyl alcohol, cyclohexanone, dioxane, toluene, ethyl acetate, methyl cellosolve and the like are appropriately used. Methylene chloride is a good solvent for triacetyl cellulose, but by appropriately using a poor solvent such as the lower aliphatic alcohol together with a good solvent, when the dope cast on the support is cooled, solidification is promoted. be able to.

Further, additives such as a plasticizer, a peeling accelerator, and an ultraviolet absorber can be appropriately added to the dope as a component contained in the film after drying. Examples of the plasticizer include phosphate plasticizers such as triphenyl phosphate and triethyl phosphate, phthalate plasticizers such as dimethyl phthalate and diethyl phthalate, and glycols such as methyl phthalyl ethyl glycolate and ethyl phthalyl ethyl glycolate. An acid ester plasticizer, a polymer plasticizer, or the like can be used. The release accelerator facilitates the release of the film obtained by solidifying the dope from the support, and for example, metal soap or the like is used. In addition, ultraviolet absorbers, benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber,
Alternatively, an ultraviolet absorbing polymer or the like is appropriately used.

[0010] Triacetyl cellulose (cellulose triacetate) is obtained by substituting about three of the three hydroxyl groups per cellulose unit with an acetyl group. Substituted acetylation degree 62.
From 5% to about 56% acetylation is usually used.

The anti-glare triacetyl cellulose film obtained by the above-mentioned production method is excellent in heat resistance, and its surface unevenness does not change even in a heat test at 100 ° C. for 500 hours. Shows excellent heat resistance without lowering the antiglare performance.

According to the production method of the present invention as described above, a triacetylcellulose film having an antiglare property can be obtained, but in order to improve the scratch resistance of the uneven surface of the film,
As shown in the anti-glare triacetyl cellulose film 10a illustrated in FIG. 3, a thermosetting resin or an ionizing radiation curable resin is further coated on the uneven surface 1 by a conventional gravure coating, roll coating, reverse roll coating, or the like. The cured film 2 may be provided by applying and curing by a known coating method. The thickness of the cured film is set to such an extent that the irregularities on the base surface are not buried and the antiglare performance is not lost, and depends on the surface roughness of the base, but is usually about 3 to 10 μm.

As the thermosetting resin, for example, polyurethane resin, acrylic urethane resin, unsaturated polyester resin, epoxy resin, melamine resin, acrylic melamine and the like can be used. Further, as the writing ionizing radiation curable resin, a conventionally known ionizing radiation curable resin which is cured by ionizing radiation such as ultraviolet rays or electron beams can be used. Specifically, a composition comprising a compound such as a prepolymer (including an oligomer) or a monomer having a radically polymerizable unsaturated group or a cationically polymerizable functional group in a molecule is used. Further, a polyene / thiol prepolymer based on a combination of polyene and polythiol is also used. Note that ionizing radiation means an electromagnetic wave or a charged particle beam having an energy quantum that can polymerize or crosslink a molecule, and is usually ultraviolet (UV).
Alternatively, an electron beam (EB) is used. As the prepolymer having a radical polymerizable unsaturated group, for example, polyester (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, melamine (meth) acrylate, and the like can be used. Means acrylate or methacrylate]. Examples of the monomer having a radically polymerizable unsaturated group include, for example, methyl (meth) acrylate,
Monofunctional monomers such as ethylhexyl (meth) acrylate and phenoxyethyl (meth) acrylate, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylpropane tri (meth) acrylate, and trimethylolpropane ethylene oxide tri Polyfunctional monomers such as (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth) acrylate are used. The compounding of the polyfunctional monomer
It is effective for improving the scratch resistance of the cured film. Further, as the prepolymer having a cationically polymerizable functional group, for example,
Bisphenol type epoxy resin, epoxy resin such as novolak type epoxy compound, fatty acid type vinyl ether,
A prepolymer of a vinyl ether resin such as an aromatic vinyl ether may be used. Examples of the thiol include polythiols such as trimethylolpropane trithioglycolate and pentaerythritol tetrathioglycolate. Examples of the polyene include those obtained by adding allyl alcohol to both ends of a polyurethane made of a diol and diisocyanate.

When the ionizing radiation-curable resin is cured with ultraviolet rays, a photopolymerization initiator is further added. As the photopolymerization initiator, in the case of a resin having a radical polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ethers can be used alone or in combination. In addition, as a photopolymerization initiator in the case of a resin having a cationically polymerizable functional group, an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metallocene compound, a benzoin sulfonic acid ester or the like is used alone or in combination. be able to. The addition amount of these photopolymerization initiators is based on 100 parts by weight of the ionizing radiation-curable resin.
It is about 0.1 to 10 parts by weight.

The ionizing radiation-curable resin may further contain various additives, if necessary. Examples of the additive include a thermoplastic resin such as a vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, an acrylic resin, and a cellulose resin, and an extender made of a fine powder such as silica and alumina. Further, a diluting solvent may be appropriately added.

As the ultraviolet light source for curing the ionizing radiation-curable resin, for example, a light source such as an ultra-high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a black light, and a metal halide lamp can be used. As the electron beam source, various electron beam accelerators such as Cockcroft-Walton type, Bande graph type, Resonant transformation type, Insulating core transformation type, Linear type, Dynamitron type and High frequency type are used.
0 to 1000 keV, preferably 100 to 300 keV
A device that irradiates an electron beam of about energy can be used.

[0017]

【Example】

Example 1 A dope composed of triacetyl cellulose, triphenyl phosphate, methylene chloride, methanol, and n-butanol was cast on an endless belt having an uneven surface. Evaporate the solvent component on an endless belt, solidify it, form a film, peel it off, and further evaporate and dry the remaining solvent component in a drying chamber to obtain a triacetyl cellulose film having the antiglare property of the present invention. Obtained. The surface roughness of the obtained film was 3 μm in terms of a ten-point average roughness Rz, and the antiglare property was evaluated by a specular glossiness of 60 ° (JIS Z8741). The specular glossiness Gs (60 °) = 23%, showing excellent anti-glare properties.

(Example 2) A polyester acrylate-based ultraviolet-curable resin was further applied on the uneven surface of the triacetyl cellulose film obtained in Example 1, and cured by irradiation with ultraviolet light to perform three-dimensional crosslinking. By forming a cured film having a thickness of 3 μm, an anti-glare triacetyl cellulose film of the present invention was obtained. The surface roughness of the obtained film was 2 μm in terms of a ten-point average roughness Rz, and the antiglare property was evaluated by a specular gloss of 60 ° in the same manner as in Example 1. The specular gloss Gs (60 °) = The anti-glare property was excellent at 47%.

[0019]

According to the present invention, a triacetylcellulose film having an antiglare property can be used as a film having surface irregularities simultaneously with film formation without the need for post-treatment after film formation. Can be easily obtained. Also,
Since the uneven shape of the surface unevenness is not formed by thermo-mechanical external stress such as hot pressing, return due to residual stress does not occur essentially, so it is excellent in heat resistance and even in high temperature environment The uneven shape is not dull, and the antiglare property does not decrease. Further, if a film having a configuration in which a cured film of a thermosetting resin or an ionizing radiation curable resin is provided on the uneven surface,
The abrasion resistance of the uneven surface is improved, the antiglare property is not reduced during long-term use, and the display is not difficult to see due to scratching.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing one embodiment of a method for producing a triacetyl cellulose film having antiglare properties of the present invention.

FIG. 2 is a cross-sectional view showing one embodiment of a triacetylcellulose film having antiglare properties obtained by the production method of the present invention.

FIG. 3 is a cross-sectional view showing another embodiment (with a cured film) of an anti-glare triacetyl cellulose film obtained in another embodiment of the production method of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Uneven surface of film 2 Cured film 3 Casting die 4 Rotating drum 5 Support (endless belt) 6 Uneven surface of support 7 Film 8 Peeling roll 9 Drying room 10, 10a Triacetylcellulose film having antiglare property

Claims (2)

[Claims] 1. A method for producing a triacetyl cellulose film, comprising: casting a dope in which triacetyl cellulose is dissolved in a solvent onto a support; and evaporating and solidifying the solvent to remove a film obtained from the support. A substrate having an uneven surface with a surface roughness of 0.3 μm ≦ Rz ≦ 10 μm with a ten-point average roughness Rz on one side using a support surface on which the dope is cast as an uneven surface. A method for producing an acetylcellulose film. 2. A thermosetting resin or an ionizing radiation-curable resin is applied to the uneven surface of the film obtained in claim 1,
A method for producing a triacetylcellulose film having an antiglare property, which is cured to provide a cured film.