JP2002148405A - Antireflection film and low reflection polarizing plate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection film which ensures a good display grade and superior scuffing and wear resistances, etc., of a display surface and a low reflection polarizing plate using the antireflection film. SOLUTION: A coating liquid for forming a glare-proof layer having 50 wt.% solid concentration is prepared by mixing 100 pts.wt. UV curable urethane acrylate resin, 15 pts.wt. fine silica particles having 1.3 μm average particle diameter and 5 pts.wt. UV polymerization initiator with toluene as a solvent. The coating liquid is applied to one face of a triacetylcellulose film 3 having 80 μm thickness, freed of the solvent by drying and cured by irradiation with UV to form a glare-proof layer 2 having a finely rugged surface structure. A coating liquid comprising fluorine-containing methyltrimethoxysilane having about 1 wt.% solid content is applied to the surface of the glare-proof layer 2 in such a way that about 100 nm average thickness is obtained after drying and curing, and the coating liquid is dried and cured at 90 deg.C in 50 hr to form an antireflection layer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display having an antireflection layer, which reduces surface reflected light, and has an antiglare property, so that an external image is not reflected by external light and has good visibility. The present invention relates to an antireflection film suitable for forming a display and a low reflection polarizing plate using the same.

[0002]

2. Description of the Related Art A liquid crystal display is one of various displays. In recent years, a demand for improved visibility has been further increased. In order to improve the visibility as a display device, for example, to achieve higher definition and higher image quality of a liquid crystal display, it is necessary to minimize reflection, reflection, and glare of external light on the display surface. In particular, for example, when a car navigation monitor, a video camera monitor, a mobile phone, a PHS, and various portable information terminals are used outdoors, since the external light is stronger than indoors, the reflection, reflection, glare, etc. of the external light are used. Therefore, the visibility of the display is significantly reduced as compared with the case where the display is used indoors. For this reason, anti-reflection treatment is indispensable for polarizing plates mounted on these devices. At the same time,
The scratch resistance, abrasion resistance, stain resistance and the like of the display surface are also indispensable. In particular, there is a problem that a scratch or the like on the display surface causes a permanent display defect and degrades the appearance quality. Scratch resistance is one of the important performances.

The antireflection layer formed by the conventional coating treatment is formed by curing a liquid obtained by dispersing and mixing metal oxide fine particles and the like in an organic or inorganic binder having a fluorine group by heat or ultraviolet rays. Was used.

On the other hand, the scratch resistance and abrasion resistance of only the antireflection layer have been evaluated so far. However, as a result of various studies on the case where the antireflection layer is formed into a laminated structure and evaluated from the overall structure, the present inventors have found that: It has been found that the difference in hardness between the upper layer and the lower layer also greatly affects the abrasion resistance and abrasion resistance of the outermost surface.

[0005]

SUMMARY OF THE INVENTION The present invention, when applied to a liquid crystal display or the like, provides an antireflection film having excellent display quality, as well as excellent scratch resistance and abrasion resistance on a display surface, and the use thereof. It is an object of the present invention to provide a low-reflection polarizing plate.

[0006]

Means for Solving the Problems To solve the above problems, the antireflection film of the present invention and a low reflection polarizing plate using the same are as follows.

(1) The antireflection film of the present invention has an antireflection layer provided on an antiglare layer provided on a transparent substrate film, and the surface hardness of the antireflection layer is 1.0 GPa or more. Features.

(2) In the antireflection film of the present invention, the surface hardness ratio of the antiglare layer and the antireflection layer is 1 or more (that is, antiglare layer surface hardness / antireflection layer surface hardness ≧).
1) is preferable.

(3) A low reflection polarizing plate of the present invention comprises a polarizing plate having the antireflection film according to any one of the above items (1) and (2).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As the transparent substrate film used for the antireflection film of the present invention, those having excellent transparency, mechanical strength, heat stability, moisture barrier properties and the like can be preferably used. Further, in many cases, the transparent substrate film is preferable as the optical anisotropy such as retardation is smaller. And usually
Since the antireflection film of the present invention is often used by being provided on the surface of a polarizing plate, the transparent base film for the antireflection film of the present invention can also serve as the transparent protective layer of the polarizing plate. Actually, when an antireflection film is provided on the surface of a polarizing plate, it is not necessary to increase the thickness of the display by also using the transparent protective layer of the polarizing plate as the transparent base film of the antireflection film of the present invention. It is preferable that the cause of deterioration of optical characteristics such as surface reflection loss due to the occurrence of different refractive index interfaces due to the increase is small. Therefore, as the transparent substrate film for the antireflection film of the present invention, a film made of the same polymer as the transparent protective layer of the polarizing plate described later can be used.

The fine uneven structure provided as an antiglare layer on the surface of the transparent substrate film may be formed by an appropriate method. For example, sandblasting, embossing rolls, those having a fine uneven structure on the surface by roughening treatment by an appropriate method such as chemical etching, those having a fine uneven structure on the surface by a transfer method using a mold, fine particles And the like.

More specifically, the fine uneven structure is
[A] The transparent substrate film (when formed on a polarizing plate, as described above, a transparent protective layer in the polarizing plate may be used. And the surface of the film itself is referred to as a “transparent substrate film”.
It can be formed as a layer or the like provided with a fine uneven structure by performing a roughening treatment by an appropriate method such as chemical etching. [B] Also, the fine uneven structure is an additional layer composed of a coating layer having fine unevenness of the resin layer with respect to the transparent base film, and [c] the surface of a polymer layer coated and applied on the transparent base film. A roughened surface to give a fine uneven structure, or [d] a transparent substrate film having a fine uneven structure formed on the surface by roughening the surface as in [a] above. Further, it can be formed as a layer provided with a polymer coating layer to such an extent that the fine uneven structure does not disappear.

The fine uneven structure is obtained by, for example, forming a fine uneven structure by roughening the surface of the transparent substrate film itself as shown in [a], and further filling the resin layer with the fine uneven structure. Two or more of the above-mentioned states, for example, a coating layer having a thickness such that the coating layer becomes flat and the surface of the coating layer is roughened as shown in [c] to form a composite layer having a fine uneven structure. May be formed as a composite layer such as a combination thereof.

From the viewpoint of the formability of the unevenness characteristics, the fine unevenness structure of the antiglare layer is preferably formed of a resin layer containing solid fine particles. Such a resin layer can be formed by, for example, dispersing and containing solid fine particles (hereinafter simply referred to as fine particles) in a resin solution, and applying the fine particles on a transparent substrate film. The coating method is not particularly limited.For example, a method of forming a coating film by coating on a transparent substrate film by an appropriate method such as a doctor blade method or a gravure roll coater method, or a resin film containing fine particles is separately provided. It may be formed in advance and formed by an appropriate method such as a method of bonding it on a transparent substrate film.

As the resin forming the resin layer, a polymer or the like exemplified in the transparent protective layer of the polarizing plate described later can be appropriately selected and used in consideration of its hardness and the like. A particularly preferred resin is an ultraviolet-curable resin. If a UV-curable resin is used, the layer composed of UV-cured resin containing fine particles can be efficiently processed by a simple processing operation such as embossing with a stamper when the coating layer is cured by UV irradiation. Can be formed. Further, by forming an ultraviolet curable resin layer on the surface of the roughened transparent substrate film, it is possible to easily reflect the surface irregularities of the transparent substrate film on the outermost surface.

Examples of the above-mentioned UV-curable resin include polyester, acrylic, urethane, amide, and the like.
An appropriate compound such as a compound obtained by blending an ultraviolet polymerization initiator with a monomer, oligomer, or polymer capable of forming a resin such as a silicone-based or epoxy-based resin so that a resin layer can be formed by curing treatment by ultraviolet irradiation can be used. .

The fine particles include, for example, crosslinked or uncrosslinked organic polymer particles made of various polymers such as polymethyl methacrylate (PMMA), polyurethane, polystyrene and melamine resin, silica, alumina, and the like.
Appropriate materials such as calcium oxide, and conductive inorganic particles such as titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide can be used.

The material for forming the antireflection layer is an ultraviolet-curable
Resin such as acrylic resin, colloidal silica in resin
A hybrid system in which inorganic fine particles such as
R) _ThreeAnd Si (OR)_FourOr RTi (OR)_ThreeAnd Ti
(OR)_Four(Where R is a lower alkyl group having 10 or less carbon atoms)
Show. ) Such as alkyl trialkoxysilanes and tetra
Alkoxysilane or alkyl titanium tetraalco
Metal alkoxy such as oxide and titanium tetraalkoxide
And a sol-gel system using a metal. However, anti-reflective
The refractive index of the material forming the stop layer is higher than that of the anti-glare layer.
Use a smaller one.

As the material for forming the antireflection layer as described above, a material containing a fluorine group-containing component for imparting surface antifouling properties can be selected. From the viewpoint of scratch resistance, those having a large content of inorganic components tend to be more excellent, and among them, sol-gel materials are preferable. The sol-gel system using a metal alkoxide is, for example, a metal alkoxide such as a lower alkoxide of silicon or a lower alkoxide of titanium (preferably alkoxides containing a fluorine group) as described above. And a gel formed by heat treatment to form a transparent glass layer. As a dispersion medium of such an alkoxide, water and / or a lower alcohol such as methanol or ethanol is used. An acid or alkali such as hydrochloric acid or ammonia is used as the hydrolysis catalyst used in accordance with the above. When gelling a metal alkoxide sol, it is common to add a hydrolysis catalyst, hydrolyze and heat treat.

In general, however, the lower the refractive index of the antireflection layer, the better, and the greater the difference in refractive index between the antireflection layer and the lower layer, the greater the antireflection effect. In order to obtain a suitable antireflection effect in the present invention, a material whose refractive index of the antireflection layer is the square root of the refractive index of the fine uneven structure which is the antiglare layer is preferable. However, in practice, finding a material having such a refractive index is generally difficult, as already known, and results in selecting a material that is as close as possible.
On the other hand, the thickness of the antireflection layer is determined by the design wavelength of the refractive index and incident light of Use material, for example a refractive index n ₁ is 1.51 of the substrate, the refractive index n ₂ of the antireflection layer 1. 38,
Assuming that the design wavelength of the light incident on the anti-reflection layer is 550 nm, the target thickness of the anti-reflection layer is calculated to be about 0.1 μm.

That is, specifically, the target thickness of the antireflection layer can be calculated by the following equation.

[0022]

## EQU1 ## d = (1 / n)_Two) × (λ / 4) where d is the target thickness of the antireflection layer (μm), and λ is the incident light
Design wavelength (μm), n _TwoIndicates the refractive index of the antireflection layer
And the refractive index n of the substrate (base)₁> n_TwoIs the case.

The anti-reflection layer can be formed on the fine uneven surface as an anti-glare layer by an appropriate method, but is preferably formed by applying a coating solution for forming an anti-reflection layer. For example, it can be formed by an appropriate method such as a doctor blade method, a gravure roll coater method, or a dipping method.

In order to maintain the required abrasion resistance and abrasion resistance of the display surface, the surface hardness of the antireflection layer must be 1.0 GPa.
It is necessary to be above. Surface hardness is 1.0 GPa
If it is above, it can withstand the abrasion resistance test at a load of 250 g with steel wool, which is a temporary evaluation standard.

Furthermore, in the present invention, the surface hardness ratio of the antiglare layer and the antireflection layer is 1 or more (that is, the surface hardness of the antiglare layer /
It is preferable that the surface hardness of the antireflection layer ≧ 1). Lower layer (in this case, an antiglare layer) and upper layer (in this case, an antireflection layer)
The hardness difference greatly affects the abrasion resistance and abrasion resistance of the outermost surface. For example, when there is a two-layer laminate, when a force is applied from above while the upper layer is hard and the lower layer is soft, the lower layer sinks, and accordingly, stress is generated in the upper layer. At this time, if the upper layer is hard and thin, cracks occur. As an extreme example, when a thin glass sheet is placed on a flexible rubber sheet and a force is applied from above the thin glass sheet, the thin glass sheet is broken. Therefore, it is preferable that at least the hardness of the lower layer is equal to or higher than the hardness of the upper layer.

The thus obtained antireflection film of the present invention can be usually laminated or combined with a polarizing plate to obtain a polarizing plate having an antireflection film. Although an appropriate polarizing plate can be used, the type thereof is not particularly limited. As a polarizer constituting the polarizing plate, for example, a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymer-based partially saponified film, iodine or dichroic A polarizing film such as a film obtained by adsorbing a dichroic substance such as a dye and stretching it, or a polyene-based oriented film such as a dehydrated polyvinyl alcohol or a dehydrochlorinated polyvinyl chloride. The thickness of the polarizing film is generally from 5 to 80 μm, but is not limited thereto.

As the polarizing plate, a polarizing plate consisting of a polarizer alone can be used. However, the polarizing plate is usually provided on one or both sides of the above-mentioned polarizer (polarizing film) for the purpose of protection such as water resistance. Those provided with a transparent protective layer composed of a coating layer of a polymer, a laminate layer of a film, and the like are preferably used. For the formation of the transparent protective layer, an appropriate material such as a transparent polymer can be used, but transparency and mechanical strength,
Those having excellent heat stability and moisture barrier properties can be preferably used. In many cases, the transparent protective layer is preferably as small as possible in optical anisotropy such as retardation. The thickness of the transparent protective layer is 1
The thickness is generally from 0 to 300 μm, but is not limited to this. As described above, the transparent protective layer of the polarizing plate can also serve as the transparent base film of the antireflection film of the present invention.

As the polymer forming the transparent protective layer, for example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulosic polymers such as cellulose diacetate and cellulose triacetate, and polymethyl methacrylate (PMM)
Acrylic polymers such as A), styrene polymers such as polystyrene and acrylonitrile / styrene copolymer (AS resin), and polycarbonate polymers are exemplified.

Also, polyolefin polymers such as polyethylene, polypropylene, polyolefin having a cyclocyclic or norbornene structure, polyolefin polymers such as ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, and imides such as polyimide Polymer, sulfone polymer such as polysulfone, other polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer,
Vinylidene chloride-based polymers, vinyl butyral-based polymers, arylate-based polymers, polyoxymethylene-based polymers, epoxy-based polymers, and blends of the above-mentioned polymers are also examples of the polymer forming the transparent protective layer.

The antireflection film of the present invention may be laminated on a polarizing plate. When the polarizing plate has a transparent protective layer as described above, the transparent protective layer is formed on the transparent base of the antireflection film of the present invention. The low reflection polarizing plate may be used also as a material film. Although the lamination method is not particularly limited, for example, the lamination may be performed via an adhesive or the like. Further, it may be provided on one side of the polarizing plate or on both sides.

The polarizing plate may be provided with an adhesive layer if necessary. The purpose of this adhesive layer is to adhere the polarizing plate to another member such as a liquid crystal cell. The adhesive layer can be formed of an appropriate adhesive such as an acrylic, rubber, or silicone adhesive or a hot-melt adhesive, and preferably has excellent transparency and weather resistance.

The polarizing plate according to the present invention may further comprise, if necessary, an optical functional layer selected from a reflective layer, a transflective layer and a retardation plate at least on the interlayer and / or the surface of the polarizing plate having a multilayer structure. It can be used for various applications such as a display device by being interposed and / or provided and laminated. If necessary,
Scratch resistance, durability, weather resistance, heat and humidity resistance, heat resistance, moisture resistance, moisture permeability, antistatic properties, conductivity, improved adhesion between layers,
It is also possible to perform processing for imparting various properties and functions such as improvement in mechanical strength, or insertion and lamination of a functional layer. Between the layers of the polarizing plate having a multilayer structure, for example, a hard coat layer, a primer layer, an adhesive layer, an adhesive layer, an antistatic layer, a conductive layer, a gas barrier layer, a water vapor blocking layer, a moisture blocking layer, or the like, Alternatively, these layers may be laminated on the polarizing plate surface. Also. At the stage of forming each layer of the polarizing plate, for example, conductive particles or an antistatic agent, various fine particles, a plasticizer, and the like may be added to each layer, and the mixing and the like may be improved as necessary.

FIG. 1 is a schematic cross-sectional view of an example of the antireflection film of the present invention in which an antiglare layer and an antireflection layer are provided on a transparent base film. In FIG. 1, reference numeral 3 denotes a transparent base film, 4 denotes fine particles, 2 denotes a fine uneven layer containing the fine particles, that is, an antiglare layer, and 1 denotes a surface hardness of 1.0 G
It is an antireflection layer of Pa or more. FIG. 2 is a schematic cross-sectional view of an example of a low-reflection polarizing plate having an anti-reflection film in which the anti-reflection film of the present invention is laminated on a polarizing plate;
In FIG. 2, reference numeral 6 denotes a polarizer, and a transparent protective layer 5 is provided on upper and lower surfaces of the polarizer 6. In this embodiment, the transparent protective layer 5 provided on the upper surface side of the polarizer 6 is formed as shown in FIG.
In this embodiment, the transparent base film 3 also serves as the antireflection film shown in FIG. Reference numeral 4 denotes fine particles, 2 denotes a fine uneven layer containing the fine particles, that is, an antiglare layer, and 1 denotes an antireflection layer having a surface hardness of 1.0 GPa or more.

[0034]

[Example 1] 100 parts of a urethane acrylate-based UV-curable resin (parts shown below are parts by weight), 15 parts of silica fine particles having an average particle diameter of 1.3 µm, and 5 parts of an ultraviolet polymerization initiator The mixture was mixed with toluene as a solvent to prepare a coating solution for forming an antiglare layer having a solid content of 50% by weight. On one side of a triacetyl cellulose film having a thickness of 80 μm, the coating solution for forming an antiglare layer is applied by a bar coater, dried with a solvent, and cured by irradiating ultraviolet rays to have an antiglare layer having a fine surface unevenness structure. A triacetyl cellulose film was obtained. On top of this, a coating solution composed of about 1% by weight of a solid component of a fluorine group-containing methyltrimethoxysilane,
The coating was applied to an average thickness of about 100 nm during drying and curing to obtain an antireflection film. The drying and curing conditions at this time are 90 ° C,
50 hours.

Example 2 100 parts of a urethane acrylate-based UV-curable resin, 5 parts of silica fine particles having an average particle size of 2.5 μm, and 5 parts of an ultraviolet polymerization initiator were mixed together with toluene as a solvent, and the solid content was adjusted. A 50% by weight coating solution for forming an antireflection layer was prepared. On one side of a triacetyl cellulose film having a thickness of 80 μm, the coating solution for forming an antiglare layer is applied by a bar coater, dried with a solvent, and cured by irradiating ultraviolet rays to have an antiglare layer having a fine surface unevenness structure. A triacetyl cellulose film was obtained. On top of this, a coating solution consisting of a fluorine-containing methyltrimethoxysilane of about 1% by weight of a solid component is dried and cured to have an average thickness of about 100 n.
m to obtain an antireflection film. Drying at this time
The curing conditions were 90 ° C. and 50 hours.

Example 3 100 parts of a urethane acrylate-based ultraviolet lightening type resin (parts indicated below are parts by weight), 15 parts of silica fine particles having an average particle diameter of 1.3 μm, and 1 part of an ultraviolet polymerization initiator The mixture was mixed with toluene as a solvent to prepare a coating solution for forming an antiglare layer having a solid content of 50% by weight. On one side of a triacetyl cellulose film having a thickness of 80 μm, the coating solution for forming an antiglare layer is applied by a bar coater, dried with a solvent, and cured by irradiating ultraviolet rays to have an antiglare layer having a fine surface unevenness structure. A triacetyl cellulose film was obtained. On top of this, a coating solution consisting of fluorine-containing methyltrimethoxysilane having a solid content of about 1% by weight was applied so as to have an average thickness of about 100 nm upon drying and curing to obtain an antireflection film. The drying and curing conditions at this time are 90
° C and 50 hours.

Comparative Example 1 The same operation as in Example 1 was performed to form an antireflection layer. The drying and curing conditions at this time were 60 ° C. and 50 hours.

Comparative Example 2 The same operation as in Example 2 was performed to form an antireflection layer. The drying and curing conditions at this time were 60 ° C. and 50 hours.

Table 1 below shows various measured values, evaluation results, and the like obtained in the above Examples and Comparative Examples. (Specular reflectance: Y value) Spectrophotometer “MPS manufactured by Shimadzu Corporation”
-2000 ", JISZ8701 2 degree field of view XY
The visibility is corrected (400 to 700 nm) by the Z system, and the specular reflectance Y value is measured. (Surface hardness) The indentation hardness obtained by a hardness measurement method using a thin film physical property evaluation apparatus “MHA-400” manufactured by NEC Corporation (a measurement method in which an indenter is pressed into a measurement sample in a perpendicular direction) is shown.

A specific measuring method is as follows. A triangular pyramid diamond indenter having a diagonal angle of 80 ° is measured with respect to a measurement sample at an indentation speed of 10.5 nm / sec.
Was determined. (Steel wool test) Using steel wool specified in # 0000, a load of 250 g was applied, and the state after 10 reciprocations was visually determined.

[0041]

[Table 1]

[0042]

According to the present invention, an antireflection film having good display quality, high surface hardness and excellent scratch resistance, and a polarizing plate having the same can be obtained. In addition, the antireflection layer can be formed by a wet coating method, which is a very simple method as compared with a forming method such as a vacuum deposition method.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of the antireflection film of the present invention.

FIG. 2 is a schematic cross-sectional view of an example of a low-reflection polarizing plate on which the antireflection film of the present invention is formed.

[Explanation of symbols]

 1: Anti-reflection layer 2: Fine uneven layer (anti-glare layer) 3: Transparent substrate film 4: Fine particles 5: Transparent protective layer 6: Polarizer

 ────────────────────────────────────────────────── ─── Continued on the front page F-term (reference) 2H042 BA02 BA03 BA12 BA13 BA15 BA20 2H049 BA02 BB65 BC22 2K009 AA02 AA12 BB28 CC03 CC09 CC24 CC42 CC45 DD02 DD12 DD15 4F100 AA20 AJ06 AK51 AK52 AR00A AR00B AR00C BA04 BA05 BA05 JK09 JK12 JK12C JN01A JN06A JN06C JN10 JN30B YY00A YY00B YY00C

Claims (3)

[Claims] 1. An antireflection layer is provided on an antiglare layer provided on a transparent substrate film, and the surface hardness of the antireflection layer is 1.
An antireflection film, which is 0 GPa or more. 2. The anti-reflection film according to claim 1, wherein the surface hardness ratio between the anti-glare layer and the anti-reflection layer is 1 or more. 3. A polarizing plate comprising the antireflection film according to claim 1.