JP2006010724A - Light-diffusive antiglare film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-diffusive antiglare film having improved characteristics capable of attaining both an effect of reducing the reflection of a reflected image and an effect of suppressing white blur due to the enlargement of a viewing angle. <P>SOLUTION: An antiglare layer 11 dispersedly containing fine particles 10 having a cavity part in resin is formed on a transparent base film 1, and the surface 11a of the antiglare layer has a finely rugged structure, and a low-refractive index layer 12 having a refractive index of 1.20 to 1.50 is layered on the surface 11a. In the antiglare layer 11, the fine particle 10 having the cavity part is an organic and/or inorganic fine particle having an average particle diameter of 0.01 to 10μm, and having a refractive index of 1.40 to 1.80, and the antiglare layer 11 contains the fine particle 10 of 12 to 30wt.% per resin 100%wt. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a light diffusing anti-glare material used for manufacturing various optical elements such as a light diffusing anti-glare polarizing plate used in various image display devices such as a liquid crystal display (LCD) and an electroluminescence (EL) display device. It relates to film.

One of the various displays is a liquid crystal display. When pursuing ease of viewing as a display device such as wide viewing angle and high definition of a liquid crystal display, a decrease in contrast due to surface reflection on the surface of the liquid crystal display, that is, the surface of the polarizing plate cannot be ignored. In particular, in car navigation monitors and video camera monitors that are frequently used outdoors, the visibility is significantly reduced due to surface reflection.

For this reason, anti-reflection coatings are becoming indispensable for the polarizing plates mounted on these devices. For liquid crystal displays that are frequently used outdoors, there are polarizing plates that have undergone anti-glare treatment. The actual situation is being used.

The antiglare treatment is to blur the outline of the image reflected on the surface, thereby reducing the visibility of the reflected image and reducing the reflection of the reflected image when the display device is used. In general, the surface is roughened by an appropriate method such as sandblasting, embossing roll, chemical etching, etc., and the surface is given a fine uneven structure, the surface is given a fine uneven structure by a mold transfer method, etc., resin There are some in which fine particles are dispersed and added to the surface to give a fine concavo-convex structure on the surface, and the surface concavo-convex structure is designed to scatter reflected light in the visible light region.

Among these anti-glare treatments, the method of dispersing fine particles in the resin layer is desirable because it can easily give a fine uneven structure. For example, anti-glare with a fine concavo-convex structure on the surface by applying a dispersion liquid in which a radioactive curable resin, fine particles having an average particle size of 10 μm or less and a thixotropic agent are dispersed on a transparent substrate film and drying and curing. An example in which a layer is formed has been reported (see Patent Document 1). In addition, many examples of forming an antiglare layer by dispersing fine particles in a resin layer have been reported (see Patent Documents 2 and 3).

However, in these anti-glare treatments, it is difficult to widen the viewing angle. For this reason, it was not fully satisfactory in terms of the reflection reduction effect of the reflected image.

In order to realize a wide viewing angle of a liquid crystal display, it is known to provide a light diffusing film on the surface. In the light diffusing film, fine particles are dispersed and contained in a resin, and light diffusibility is imparted by a difference in refractive index between the resin and the fine particles. Since the refractive index difference is only 0.2 or less with ordinary fine particles, a method of improving the light diffusibility by increasing the addition ratio of the fine particles or increasing the thickness (see Patent Document 4), resin, A method of making the refractive index difference 0.4 or more by providing pores in the fine particles (see Patent Document 5) has also been reported.

However, these reports are only for the purpose of widening the viewing angle, and there is no particular mention that anti-glare property is obtained by imparting a fine uneven structure to the surface.

JP-A-10-219136 Japanese Patent Laid-Open No. 2002-202402 JP 2002-60735 A Japanese Patent Laid-Open No. 1-172801 JP-A-8-160206

As described above, in the prior art, no anti-glare function and a function for expanding the viewing angle have been found to effectively reduce the reflection of the reflected image. The appearance of a light diffusing antiglare film is strongly desired.

In addition, in the conventional anti-glare treatment, there is a problem that external light is scattered by the surface uneven structure, and the surface looks whitish and white blur occurs. Therefore, the appearance of a light diffusive anti-glare film that effectively reduces reflection of a reflected image while suppressing this white blur is desired.

The present invention provides a light diffusive anti-glare film that can meet such demands, that is, an improvement in characteristics that can achieve both a reflected image reduction effect and a white blur suppression effect by expanding the viewing angle. It is an object to provide a light diffusive antiglare film. Another object of the present invention is to provide an optical element such as a light diffusing anti-glare polarizing plate using the light diffusing anti-glare film, and an image display device equipped with the optical element.

As a result of intensive investigations to solve the above problems, the present inventors have provided an antiglare layer containing fine particles in a resin on a transparent substrate film to form a fine uneven structure on the surface. By making the fine particles have a space portion, the light is more easily scattered, the viewing angle is enlarged, and reflection of the reflected image can be effectively reduced. By laminating a layer with a lower refractive index, it is possible to suppress the white blur phenomenon that the external light is scattered by the fine uneven structure on the surface and the surface looks whitish, and the reflected image is reduced by expanding the viewing angle. The present invention has been completed by finding that a light diffusive antiglare film having improved properties that can achieve both a white blur suppression effect and a white blurring effect can be obtained.

That is, according to the present invention, an antiglare layer in which fine particles having a space portion are dispersed and contained in a resin is provided on a transparent base film, and the surface of the antiglare layer forms a fine uneven structure. The present invention relates to a light diffusing antiglare film characterized in that a low refractive index layer having a refractive index of 1.20 to 1.50 is laminated on the surface.

In particular, in the antiglare layer, the present invention has a configuration in which the fine particles having a space portion are 12 to 30 parts by weight per 100 parts by weight of the resin, and the fine particles having a space portion have an average particle diameter of 0.01 to 10 μm. , A configuration in which the refractive index is an organic or / and inorganic fine particles having a refractive index of 1.40 to 1.80, a configuration in which the resin is made of a thermosetting resin or a radiation curable resin having a refractive index of 1.40 to 1.70, The above-mentioned light diffusive antiglare film can be provided.

In the present invention, the low refractive index layer is formed of a sol-gel material containing a metal alkoxide and a silane coupling agent having a fluoroalkyl group. Can provide film.

Furthermore, the present invention can provide an optical element characterized in that the light diffusive anti-glare film having the above-described configuration is provided on one surface or both surfaces of the optical element body. Moreover, the image display apparatus characterized by mounting the light-diffusion anti-glare film of each said structure or the optical element of the said structure can be provided.

As described above, the present invention is configured to disperse and contain fine particles having a space portion in a resin, to provide an antiglare layer having a fine concavo-convex structure on the surface, and to further stack a low refractive index layer thereon. Thus, it is possible to provide a light diffusive antiglare film that can achieve both the effect of reducing reflection of reflected images and the effect of suppressing white blurring by expanding the viewing angle. Further, an optical element such as a light diffusing anti-glare polarizing plate using this film and an image display device equipped with this element can be provided.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of the light diffusing antiglare film of the present invention.

In FIG. 1, the light diffusive antiglare film A is provided with an antiglare layer 11 in which fine particles 10 having a space in a resin are dispersed on a transparent base film 1, and the surface of the antiglare layer. 11a forms a fine concavo-convex structure, and a low refractive index layer 12 having a refractive index of 1.20 to 1.50 is laminated on the surface 11a.

The transparent substrate film 1 is not particularly limited as long as it is a material having a high visible light transmittance and excellent transparency. The visible light transmittance is preferably 90% or more, and the haze value is preferably 1% or less. Moreover, an optically low birefringence thing is preferable.

Examples of the material having such characteristics include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, polycarbonate polymers, and acrylic polymers such as polymethyl methacrylate. .

Styrene polymers such as polystyrene and acrylonitrile / styrene copolymers, polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, olefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, nylon and aromatic polyamides Amide polymers such as are also used.

Furthermore, imide polymer, sulfone polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene Polymers and epoxy polymers are also used. Also, blends of the above polymers can be used.

The transparent substrate film 1 can be selected to have an appropriate thickness, but generally has a thickness of 10 to 500 μm, particularly 20 to 300 μm, from the viewpoints of workability such as strength and handleability and thin layer properties. Preferably, it is 30-200 micrometers.

Further, the transparent substrate film 1 is not particularly limited with respect to the refractive index, but in general, the refractive index is preferably in the range of 1.30 to 1.80, more preferably 1.40. It should be in the range of 1.70.

In the anti-glare layer 11, a resin that forms this layer can be used without particular limitation as long as it has sufficient strength as a film after the anti-glare layer is formed. Specific examples include thermoplastic resins, two-component mixed resins, thermosetting resins, and radiation curable resins (such as ultraviolet curable resins and electron beam curable resins). Among these, thermosetting resins and radiation curable resins having a refractive index of 1.40 to 1.70 are preferable because they can improve the hardness and scratch resistance of the antiglare layer 11. In particular, the use of an ultraviolet curable resin as the radiation curable resin is desirable because an antiglare layer can be easily and efficiently formed by a curing treatment by irradiation with ultraviolet rays.

There are various types of ultraviolet curable resins such as acrylic, polyester, urethane, amide, silicone, and epoxy. For example, as an acrylic ultraviolet curable resin, an acrylic monomer or oligomer having an ultraviolet polymerizable functional group, particularly having 2 or more, more preferably 3 to 6 functional groups, and a polymer added thereto. In this case, an ultraviolet polymerization initiator is used.

In the antiglare layer 11, as the fine particles to be dispersed and contained in the above resin, an organic substance and / or an inorganic substance having a space portion in the particles is used in order to enlarge the viewing angle due to good light diffusibility. The ratio of the space in the fine particles is not particularly limited, but it is usually desirable to occupy 5 to 50% by volume of the total fine particles. The formation method of a space part does not have limitation in particular, A well-known method can be used arbitrarily. The fine particles have an average particle diameter of 0.01 to 10 μm, preferably 0.1 to 8 μm, more preferably 1 to 5 μm, and a refractive index of 1.40 from the viewpoint of achieving antiglare properties. It should be in the range of 1.80.

For example, crosslinked or uncrosslinked organic fine particles made of a polymer such as PMMA (polymethyl methacrylate), polyurethane, polystyrene, melamine resin, etc. having a space inside the particles, glass, silica, alumina, calcium oxide, titania, zirconium oxide Inorganic fine particles such as zinc oxide, and conductive inorganic fine particles such as tin oxide, indium oxide, cadmium oxide, antimony oxide, and composites thereof are used. These fine particles can be produced by a known method, or commercially available products may be used as they are.

The antiglare layer 11 is obtained by mixing and dispersing the fine particles having the above-mentioned space in the above-described resin, and further, if necessary, a leveling agent, a thixotropic agent (for example, silica of 0.1 μm or less, mica, etc.), an antistatic agent. By adding an additive such as the above, a coating solution in which the mixture is uniformly mixed and dispersed is prepared, applied to the transparent substrate film 1, and after heating and drying, through a required curing process step such as irradiation with ultraviolet rays. Can be formed. Although the thickness of the glare-proof layer 11 is not restrict | limited, Usually, it is desirable that it is 1-20 micrometers, especially 2-10 micrometers.

When the antiglare layer 11 is formed in this manner, fine particles having a space on the surface protrude, and the protruding particle has a fine concavo-convex structure on the surface 11a of the antiglare layer with an average interval between the convex portions of 1 to 100 μm. Is granted. In addition, since the fine particles are dispersed and contained in the antiglare layer 11 and have a space portion therein, good light diffusibility is imparted, and the viewing angle is increased.

In order to express such an effect better, in the preparation of the coating solution, the amount of fine particles having a space is 12 to 30 parts by weight, preferably 15 to 25 parts by weight per 100 parts by weight of the resin. Is good. If the amount is less than 12 parts by weight, the above effect is hardly exhibited, and if it exceeds 30 parts by weight, problems such as transparency and strength are likely to occur.

In addition, although the fine uneven structure which contributes to anti-glare property can be easily formed on the anti-glare layer surface 11a by the above method, another method is added as necessary to form the fine uneven structure. You can also In other words, the surface is roughened by an appropriate method such as sand blasting, embossing roll, chemical etching, etc. to give the surface a fine concavo-convex structure, or a method using a mold transfer method to give the surface a fine concavo-convex structure. May be.

When the low refractive index layer 12 is laminated on the antiglare layer surface 11a, the antireflection effect causes the surface to appear whitish when the external light is scattered by the fine uneven structure of the antiglare layer surface 11a. It has a function of suppressing the phenomenon.

The refractive index of the low refractive index layer 12 is set lower than the refractive index of the antiglare layer 11 from the viewpoint of preventing reflection. The lower the refractive index, the better. However, if the refractive index is too low, the reflected light tends to be colored. For this reason, the refractive index of the low refractive index layer 12 is desirably in the range of 1.20 to 1.50, and particularly preferably in the range of 1.30 to 1.45.

The thickness of the low refractive index layer 12 is not particularly limited. Usually, it should be 0.05 to 0.3 μm, particularly 0.1 to 0.3 μm. From the viewpoint of reducing the reflectance, it is usually preferable that the value of thickness (nm) × refractive index be 140 nm or less.

Any material can be used for the low refractive index layer 12 as long as it has the above refractive index. For example, resin materials such as ultraviolet curable acrylic resins, hybrid materials in which inorganic fine particles such as colloidal silica are dispersed in the resin, sol-gel materials using metal alkoxides such as tetraethoxysilane and titanium tetraethoxide Etc. For each of the above materials, a material containing a fluorine group can be selected for imparting antifouling properties to the surface. From the aspect of scratch resistance, a low refractive index material having a high inorganic component content tends to be excellent, and a sol-gel material containing a metal alkoxide and a silane coupling agent having a fluoroalkyl group is particularly preferable. .

The low refractive index layer 12 can be formed by an appropriate method. For example, a solution containing a material for forming the low refractive index layer 12 on the surface of the antiglare layer 11 is prepared by using a doctor blade method, a gravure roll coater method, a dipping method, a spin coating method, a brush coating method, a flexographic printing method, a die coater, etc. The method of apply | coating by the appropriate | suitable method of this, drying and hardening is used preferably.

The conditions for drying and curing are not particularly limited. Usually, a condition of 60 to 150 ° C., preferably 70 to 130 ° C. and 100 hours or less, preferably 0.5 to 10 hours may be selected. These conditions are not limited to the above ranges and can be adjusted as appropriate. As a heating method, a method using a hot plate, an oven, a belt furnace, or the like can be appropriately employed.

In forming the low refractive index layer 12, the surface of the antiglare layer 11 may be modified in advance by subjecting it to discharge treatment and / or radiation irradiation treatment. By this surface modification, the adhesion at the interface between both layers is improved, and chemical resistance and the like can be improved. Examples of the discharge treatment and the radiation irradiation treatment include a corona discharge treatment, a plasma treatment, an ultraviolet irradiation treatment, and an electron beam irradiation treatment, and a corona discharge treatment and an ultraviolet irradiation treatment are particularly preferable.

2 and FIG. 3 use a polarizing plate as an optical element, and provide the light diffusing anti-glare film of the present invention on one side of the polarizing plate to form a light diffusing anti-glare polarizing plate.

In both figures, the light-diffusing anti-glare film A having the above-described configuration, that is, the anti-glare layer 11 in which fine particles 10 having a space portion are dispersed and contained on one side of a polarizing plate B which is an element body, and its A light diffusive antiglare film A in which a low refractive index layer 12 is laminated on the surface 11a of the fine concavo-convex structure is provided to constitute a light diffusive antiglare polarizing plate.

A polarizing plate B, which is an element body, includes a polarizer 21 and a transparent protective film 22, and FIG. 2 shows an example in which the transparent protective film 22 is provided on both sides of the polarizer 21, and FIG. 3 shows one side of the polarizer 21. An example in which a transparent protective film 22 is provided is shown. The light diffusing antiglare film A is provided with respect to the polarizing plate B with the transparent base film 1 side facing inward.

In the polarizing plate B, the polarizer 21 is not particularly limited, and various types can be used. For example, dichroic substances such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And polyene-based oriented films such as those obtained by uniaxial stretching, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic substance such as iodine is particularly suitable. The thickness of these polarizers 21 is not particularly limited, but is generally about 5 to 80 μm.

A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it is prepared by, for example, dying polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. Can do. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. By washing the polyvinyl alcohol-based film with water, dirt on the surface of the polyvinyl alcohol-based film and an antiblocking agent can be washed, and by swelling the polyvinyl alcohol-based film, there is an effect of preventing unevenness such as uneven coloring. The stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be performed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

The transparent protective film 22 is preferably excellent in transparency, mechanical strength, thermal stability, moisture shielding properties and the like. Further, in many cases, the better isotropic, that is, the smaller is the optical anisotropy such as phase difference. As a material, the same resin material as that of the transparent base film 1 constituting the light diffusive antiglare film A described above is used. Among them, a resin material such as triacetyl cellulose is most suitable. In addition, when providing the transparent protective film 22 on both sides of the polarizer 21, what consists of the same resin material may be used by the front and back, and what consists of a different resin material may be used. The thickness of the transparent protective film 22 is not particularly limited, but is generally about 10 to 300 μm.

When the transparent substrate film 1 constituting the light diffusing antiglare film A is made of a cellulose polymer such as triacetyl cellulose, a polycarbonate polymer, an acrylic polymer, a polyolefin having a cyclic or norbornene structure, this transparent substrate The film 1 can also serve as the transparent protective film 22 of the polarizing plate B.

For example, in the polarizing plate B shown in FIG. 2, the transparent protective film 22 on the light diffusing antiglare film A side is omitted, and the transparent base film 1 constituting the light diffusing antiglare film A functions as a transparent protective film. It is something that doubles up. This is close to FIG. 3 in which the transparent protective film 22 is provided only on one side of the polarizer 21 to configure the polarizing plate B.

In the polarizing plate B shown in FIGS. 2 and 3, the exposed surface of the transparent protective film 22 on the side opposite to the laminated side of the light diffusing antiglare film A is subjected to a treatment for the purpose of hard coat treatment or sticking prevention. be able to. The hard coat treatment is performed for the purpose of preventing scratches on the polarizing plate surface. For example, it can be formed by a method of adding a cured film excellent in hardness, sliding properties, etc. to the surface of the transparent protective film using an appropriate ultraviolet curable resin such as acrylic or silicone. In addition, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer. The hard coat treatment layer, the anti-sticking treatment layer, and the like can be provided on the transparent protective film 22 itself, or can be provided as an optical layer separately from the transparent protective film 22.

In the polarizing plate B, 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, etc. are inserted between the respective layers of the polarizing plate. Or may be laminated on the polarizing plate surface. Furthermore, at the stage of forming each layer of the polarizing plate, for example, conductive particles, antistatic agents, various fine particles, plasticizers, etc. may be added to and mixed with the material for forming each layer, and the characteristics may be appropriately improved. Good.

2 and 3 show an example in which the light diffusing anti-glare film A of the present invention is provided only on one surface of the polarizing plate B, but the light diffusing property of the present invention is provided on both surfaces of the polarizing plate B. An anti-glare film A can be provided to produce a light diffusing anti-glare polarizing plate.

In addition, as an optical element, in practice, an optical film in which other optical elements (optical layers) are laminated in addition to the polarizing plate B described above can be used. The optical layer is not particularly limited. For example, a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including a wave plate such as 1/2 or 1/4), a viewing angle compensation film, etc. One or more optical layers that may be commonly used for formation can be used.

In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflective plate or a semi-transmissive reflective plate is laminated on a polarizing plate, an elliptical polarizing plate or a circular polarizing plate in which a retardation plate is laminated on a polarizing plate, and a viewing angle compensation film on the polarizing plate. A laminated wide viewing angle polarizing plate and a polarizing plate in which a brightness enhancement film is laminated on the polarizing plate are preferred. In an elliptically polarizing plate, a polarizing plate with optical compensation, and the like, a light diffusing antiglare film A is provided on the polarizing plate side.

In addition, if necessary, various characteristics and functions such as scratch resistance, durability, weather resistance, moisture and heat resistance, heat resistance, moisture resistance, moisture permeability, antistatic properties, electrical conductivity, interlayer adhesion improvement, mechanical strength improvement, etc. It is also possible to perform a process for imparting a function, insertion of a functional layer, lamination, and the like.

The reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to produce a liquid crystal display device of the type that reflects incident light from the viewing side (display side) and displays it. The light source such as the above can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be produced by an appropriate method such as attaching a reflective layer made of metal or the like to one side of the polarizing plate via a transparent protective film. Specifically, a method of forming a reflective layer by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one surface of a transparent protective film matted as necessary.

Moreover, you may use a reflecting plate as a reflective sheet etc. which provided the reflecting layer in the appropriate film according to a transparent protective film instead of the system provided directly to the transparent protective film of a polarizing plate. The reflective layer is usually made of metal, and the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate, etc. prevents the reflectance from being lowered due to oxidation, and thus the long-term initial reflectance. From the standpoint of sustaining and avoiding the additional attachment of the protective layer, it is preferable.

The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device of a type that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be manufactured.

In other words, the transflective polarizing plate can be used to make a liquid crystal display device that can save energy when using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively bright atmosphere. is there.

Next, an elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

The elliptically polarizing plate compensates (prevents) the coloration (blue or yellow) caused by the birefringence of the liquid crystal layer of the Spirsist nematic (STN) type liquid crystal display device, and is effective when displaying black and white without the above coloration. Used. In addition, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which the image is color-displayed, and also has an antireflection function.

Specific examples of the above retardation plate include birefringence obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, and polyamide. Examples thereof include a film, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film.

The retardation plate may have an appropriate retardation according to the purpose of use, for example, for the purpose of compensating for coloring or viewing angle due to birefringence of various wave plates and liquid crystal layers. What laminated | stacked the above phase difference plates and controlled optical characteristics, such as phase difference, etc. may be used.

The above elliptical polarizing plate and other reflective elliptical polarizing plates are obtained by laminating a polarizing plate, a reflective polarizing plate and a retardation plate in an appropriate combination. These can also be formed by sequentially laminating them separately in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflective) polarizing plate and a retardation plate, as described above. An optical film such as an elliptically polarizing plate is preferable because it has excellent quality stability and stacking workability, and can improve the manufacturing efficiency of liquid crystal display devices.

The viewing angle compensation film is for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. Examples of the viewing angle compensation retardation plate include a retardation film, an alignment film such as a liquid crystal polymer, and a support in which an alignment layer such as a liquid crystal polymer is supported on a transparent substrate.

A normal retardation plate uses a birefringent polymer film that is uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film is biaxially stretched in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used.

Examples of the tilted alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, or a film obtained by obliquely aligning a liquid crystal polymer. Is mentioned.

The raw material polymer of the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloring due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good viewing. An appropriate one for the purpose is used.

In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optical compensation position in which a liquid crystal polymer alignment layer, particularly an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetyl cellulose film. A phase difference plate is preferably used.

What laminated | stacked the brightness enhancement film on the polarizing plate is normally provided and used for the back side of a liquid crystal cell. Brightness-enhancement film reflects the linearly polarized light with a predetermined polarization axis or circularly polarized light in a predetermined direction and transmits other light when natural light is incident due to backlight from a liquid crystal display device or the like, or reflection from the back side. It is. In the case where a brightness enhancement film is laminated on a polarizing plate, light from a light source such as a backlight is incident to obtain transmitted light in a predetermined polarization state, and light other than the predetermined polarization state is reflected without being transmitted. .

The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer provided on the rear side thereof and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. In addition to increasing the amount of light transmitted through the brightness enhancement film, supplying polarized light that is difficult to be absorbed by the polarizer to increase the amount of light that can be used in an image display device such as a liquid crystal display device, thereby improving the brightness Is.

When light is incident through the polarizer from the back side of the liquid crystal cell using a backlight or the like without using a brightness enhancement film, the light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost entirely in the polarizer. It is absorbed and does not pass through the polarizer. That is, although it depends on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and as a result, the amount of light that can be used in a liquid crystal image display device or the like is reduced, and the image becomes dark.

In the brightness enhancement film, light having a polarization direction that is absorbed by the polarizer is reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflection layer provided on the rear side thereof. Repeatedly re-entering the brightness enhancement film, and the brightness enhancement film transmits only the polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. To supply to the polarizer. For this reason, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

Examples of brightness enhancement films are those that transmit linearly polarized light with a predetermined polarization axis and reflect other light, such as dielectric multilayer thin films and multilayer laminates of thin film films with different refractive index anisotropies. , Cholesteric liquid crystal polymer alignment films and those whose alignment liquid crystal layer is supported on a film substrate, such as those that reflect either left-handed or right-handed circularly polarized light and transmit other light, etc. An appropriate one is used.

Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate as it is with the polarization axis aligned, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer. However, from the viewpoint of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable to make it enter into a polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light range includes, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm, and other retardation characteristics. Can be obtained by a method of superimposing, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

In addition, a cholesteric liquid crystal layer that has a reflection wavelength different from each other and has an arrangement structure in which two layers or three or more layers are overlapped to obtain a layer that reflects circularly polarized light in a wide wavelength range such as a visible light region. Based on this, transmission circularly polarized light in a wide wavelength range can be obtained.

Moreover, the polarizing plate may consist of what laminated | stacked the polarizing plate and the optical layer of 2 layers or 3 layers or more like the above-mentioned polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate having a combination of the above-described reflective polarizing plate, semi-transmissive polarizing plate, and retardation plate may be used.

In various optical elements as described above, the lamination of various optical layers on the polarizing plate and the lamination of the light diffusive antiglare film of the present invention on these optical elements are sequentially performed separately in the manufacturing process of liquid crystal display devices and the like. It can also be performed by a lamination method. However, those laminated in advance are preferable because they are excellent in quality stability and assembly work, and have the advantage of improving the manufacturing process of liquid crystal display devices and the like. For these lamination, an appropriate adhesive means such as a pressure-sensitive adhesive layer is used. When adhering a polarizing plate or other optical film, the optical axes thereof can be set to an appropriate arrangement angle in accordance with the target retardation characteristics.

As in the light diffusive antiglare polarizing plate shown in FIGS. 2 and 3, in an optical element provided with a light diffusive antiglare film on one side of the element main body such as a polarizing plate, the opposite surface of the element main body, that is, light diffusibility A pressure-sensitive adhesive layer to be bonded to other members such as a liquid crystal cell can be provided on the surface where the antiglare film is not provided (in FIG. 2 and FIG. 3, the exposed surface of the transparent protective film 22).

The pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer is not particularly limited. A polymer based on an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer can be appropriately selected and used. In particular, like acrylic pressure-sensitive adhesives, those excellent in optical transparency, exhibiting appropriate wettability, cohesiveness and adhesive properties, and having excellent weather resistance and heat resistance are preferred.

Moreover, in addition to the above characteristics, prevention of foaming and peeling phenomena due to moisture absorption, reduction of optical characteristics and liquid crystal cell warpage due to differences in thermal expansion, etc., as a result, production of liquid crystal display devices with high quality and excellent durability, etc. From the viewpoint, a pressure-sensitive adhesive layer having a low moisture absorption rate and excellent heat resistance is preferable.

In addition, such adhesive layers include natural and synthetic resins, especially tackifier resins, fillers made of glass fibers, glass beads, metal powders, other inorganic powders, pigments, coloring Various additives generally added to the pressure-sensitive adhesive layer, such as an agent and an antioxidant, may be contained. It may be a pressure-sensitive adhesive layer containing light particles and exhibiting light diffusibility.

The attachment of the adhesive layer to the optical element can be performed by an appropriate method. Specifically, a pressure-sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent consisting of a single solvent or a mixture of solvents such as toluene and ethyl acetate is prepared. There is a method of attaching directly on the optical element by an appropriate development method such as a casting method or a coating method, or a method of forming an adhesive layer on a separator according to the above and transferring it onto the optical element. is there. The pressure-sensitive adhesive layer may be provided as an overlapping layer having a different composition or type in each layer. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is usually 1 to 500 μm, preferably 5 to 200 μm, and particularly preferably 10 to 100 μm.

A separator is temporarily attached to the exposed surface of the pressure-sensitive adhesive layer for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesive layer in the usual handling state. The separator is based on thin film such as plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet, metal foil, and laminates of them. If necessary, silicone, long chain alkyl, fluorine, sulfide An appropriate one according to the prior art such as one treated with a release agent such as molybdenum can be used.

In the optical element of the present invention, each layer such as a polarizer, a transparent protective film, other optical layers, a pressure-sensitive adhesive layer that bonds the respective layers, or a pressure-sensitive adhesive layer on the exposed surface side described above is provided with salicylic acid. Ultraviolet absorbing ability can be imparted by a method such as treatment with an ultraviolet absorber such as an ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound.

In the present invention, an optical element such as a light diffusing anti-glare polarizing plate provided with a light diffusing anti-glare film on one side or both sides of the element body is preferably used for production of various devices such as a liquid crystal display device. The liquid crystal display device can be manufactured according to the conventional method. In other words, the liquid crystal display device can be generally manufactured by appropriately assembling components such as a liquid crystal cell, an optical element and, if necessary, a lighting system, and incorporating a drive circuit. It can be produced according to the above method except that it is used. As the liquid crystal cell, for example, any type such as a TN type, STN type, and π type can be used.

In the present invention, an appropriate liquid crystal display device such as a liquid crystal display device in which an optical element is disposed on one side or both sides of a liquid crystal cell, or a backlight or reflector used in an illumination system can be manufactured. In that case, the optical element according to the present invention can be installed on one or both sides of the liquid crystal cell. When optical elements are provided on both sides, they may be the same or different. Also, when manufacturing a liquid crystal display device, one or more layers of components such as a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight are arranged at appropriate positions. can do.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In each example, parts and percentages are by weight. The refractive index was measured with an Abbe refractometer manufactured by Atago Co., Ltd.

<Formation of antiglare layer>
Urethane acrylate-based ultraviolet curable resin ["Unidec 17806" manufactured by Dainippon Ink & Chemicals, Inc.], PMMA fine particles having a space part ["L-XX-07AA" manufactured by Sekisui Plastics Co., Ltd., Average particle size 4.9 μm, PMMA refractive index 1.49] 15 parts, UV polymerization initiator ["Irgacure 907" manufactured by Ciba Geigy Japan Ltd.], leveling agent [Dainippon Ink Chemical Co., Ltd. Of “Megafac F470N”] was dispersed in toluene to prepare a coating solution having a solid concentration of 40%.

Next, the coating solution prepared in this way was applied with a bar coater onto a triacetyl cellulose film (refractive index: 1.48) having a thickness of 80 μm as a transparent substrate film. The coating was heated at 90 ° C. for 3 minutes and dried. Thereafter, the film was cured by irradiation with ultraviolet rays to form an antiglare layer having a thickness of 8 μm and a refractive index of 1.52.

<Formation of low refractive index layer>
70 parts of tetraalkoxysilane ("Colcoat N103X" manufactured by Colcoat Co., Ltd.), 30 parts of a silane coupling agent having a fluoroalkyl structure and a polysiloxane structure ["JTA105" manufactured by JSR Corporation], isopropyl alcohol / butyl acetate / A coating solution having a solid content concentration of 2.0% was prepared by dispersing in a mixed solvent of methyl isobutyl ketone [70/18/12 (weight ratio)].

Next, the coating solution prepared in this way was applied with a bar coater on the antiglare layer formed on the transparent substrate film made of the acetylcellulose film. The coating film was heated at 120 ° C. for 3 minutes, dried and cured, and a low refractive index layer having a thickness of 0.1 μm and a refractive index of 1.43 was formed to obtain a light diffusing antiglare film. .

Comparative Example 1
The light diffusibility was the same as in Example 1 except that only the antiglare layer was formed on the transparent substrate film made of an acetylcellulose film and the formation of the low refractive index layer on the antiglare layer was omitted. An antiglare film was produced.

Comparative Example 2
In forming the antiglare layer, instead of 15 parts of PMMA fine particles having a space, PMMA particles having no space [XX-18AA manufactured by Sekisui Plastics Co., Ltd., average particle diameter of 5.0 μm, PMMA The antiglare film was produced in the same manner as in Example 1 except that 15 parts of the refractive index of 1.49] was used.

Comparative Example 3
An antiglare film is formed in the same manner as in Comparative Example 2 except that only the antiglare layer is formed on the transparent substrate film made of an acetylcellulose film and the formation of the low refractive index layer on the antiglare layer is omitted. Was made.

Regarding the light-diffusing anti-glare film prepared in Example 1 and Comparative Example 1 described above and the anti-glare film prepared in Comparative Examples 2 and 3, the diffusion method, haze value, image clarity, and surface roughness were as follows. Was evaluated. These results were as shown in Table 1.

<Diffusion angle measurement method>
A glass plate (thickness: 1.3 mm) made by MATSANAMI was bonded to the surface of each film where the surface treatment layer (antiglare layer or this and a low refractive index layer) was not formed, and used as a test piece. Using this test piece, a light diffusive anti-glare film or an anti-glare film was arranged perpendicular to the incident light with an OPTEC spectroscopic goniophotometer GP-3, and the scattered light profile was measured in all directions. The half width of the peak of the profile was defined as the diffusion angle.

<Measurement method of haze value>
Using a haze meter HGM-2DP manufactured by Suga Test Instruments Co., Ltd., measurement was performed so that the surface treatment layer (antiglare layer or this and a low refractive index layer) of each film faced the light source side.

<Measurement method of image clarity>
Measured so that the surface treatment layer (antiglare layer or this and a low refractive index layer) of each film faces the detector side by using a image clarity measuring device ICM-1 manufactured by Suga Test Instruments Co., Ltd. The image clarity at the time of.

<Measurement method of surface roughness>
A glass plate (thickness: 1.3 mm) made by MATSANAMI was bonded to the surface of each film where the surface treatment layer (antiglare layer or this and a low refractive index layer) was not formed, and used as a test piece. The test piece was measured using a high precision fine shape measuring instrument Surfcorder ET4000 manufactured by Kosaka Laboratory, and Ra (arithmetic average roughness) and Sm (average unevenness interval) described in JIS B0601-1994 were measured. Asked.

Table 1
┌────┬────┬────┬┬─────┬─────────────┐
│ │Diffusion angle │Haze value│ Image clarity │ Surface roughness │
│ │ │ │ ├──────┬──────┤
│ │ (degrees) │ (%) │ │Ra (μm) │ Sm (mm) │
├────┼────┼────┼─────┼──────┼──────┤
│ │ │ │ │ │ │
Example 1 | 1.60 | 30.3 | 13.2 | 0.50 | 0.120 |
│ │ │ │ │ │ │
├────┼────┼────┼─────┼──────┼──────┤
│ │ │ │ │ │ │
│Comparative Example 1│1.62│32.8│ 13.5│ 0.56 │ 0.111│
│ │ │ │ │ │ │
│Comparative Example 2│0.32│14.6│ 55.3│ 0.22 │ 0.130│
│ │ │ │ │ │ │
│Comparative Example 3│0.31│16.6│ 56.4│ 0.24│ 0.136│
│ │ │ │ │ │ │
└────┴────┴────┴─────┴──────┴──────┘

Next, with respect to the light diffusing anti-glare film prepared in Example 1 and Comparative Example 1 described above and the anti-glare film prepared in Comparative Examples 2 and 3, white blurring, reflectance and total light transmission are performed by the following methods. The rate was evaluated. These results were as shown in Table 2.

<Evaluation of white blur>
A black acrylic plate (thickness 1.0 mm) made by Nitto Resin Co., Ltd. is bonded to the surface of each film where the surface treatment layer (antiglare layer or this and low refractive index layer) is not formed, and the back surface A test piece with no reflection was produced. The test piece was visually checked for the phenomenon of white blur in an office environment in which a display is generally used, and evaluated according to the following criteria.
○: Almost no white blur
Δ: There is white blur but the effect on visibility is small
×: There is white blur

<Measurement method of reflectance>
A test piece similar to the case of evaluation of white blur was produced. The spectroscopic reflectance (specular reflectance + diffuse reflectance) was measured for this test piece with a U-4100 / high-sensitivity integrating sphere spectrophotometer manufactured by Hitachi, Ltd., and the total reflectance of the C light source / 2 ° field of view. (Y value) was obtained by calculation.

<Measurement method of total light transmittance>
Using a haze meter HGM-2DP manufactured by Suga Test Instruments Co., Ltd., measurement was performed so that the surface treatment layer (antiglare layer or this and a low refractive index layer) of each film faced the light source side.

Table 2
┌────┬─────┬─────┬────────┐
│ │ White blur │ Reflectance │ Total light transmittance │
│ │ │ (%) │ (%) │
├────┼─────┼─────┼────────┤
│ │ │ │ │
│Example 1│ ○ │ 2.6 │ 81.9 │
│ │ │ │ │
├────┼─────┼─────┼────────┤
│ │ │ │ │
│Comparative Example 1 │ × │ 4.4 │ 80.9 │
│ │ │ │ │
│Comparative Example 2│ ○ │ 2.5 │ 89.9 │
│ │ │ │ │
│Comparative Example 3│ × │ 4.5 │ 88.8 │
│ │ │ │ │
└────┴─────┴─────┴────────┘

From the results of Table 1 and Table 2, the light diffusive antiglare film of Example 1 is provided with an antiglare layer containing fine particles having spaces in the resin to form a fine uneven structure on the surface. Therefore, the light is more easily scattered, the viewing angle is widened, and reflection of the reflected image can be effectively reduced, and since the low refractive index layer is laminated on the antiglare layer, It can be seen that the white blur phenomenon in which the external light is scattered by the fine concavo-convex structure and the surface looks whitish can be suppressed, and the reflection reduction effect and the white blur suppression effect by expanding the viewing angle can be well achieved.

On the other hand, the light diffusive antiglare film of Comparative Example 1 that does not take the configuration of the present invention cannot suppress the white blur phenomenon due to scattering of external light in the fine uneven structure on the surface of the antiglare layer. In the antiglare films of Comparative Examples 2 and 3 that do not have a configuration, the viewing angle cannot be enlarged, so that the reflection of the reflected image cannot be effectively reduced, and it is difficult to satisfy both characteristics.

It is a schematic sectional drawing which shows an example of the light-diffusion anti-glare film of this invention. It is a schematic sectional drawing which shows an example of the light-diffusion anti-glare polarizing plate of this invention. It is a schematic sectional drawing which shows the other example of the light-diffusion anti-glare polarizing plate of this invention.

Explanation of symbols

A Light-diffusing anti-glare film 1 Transparent substrate film 10 Fine particles having a space portion 11 Anti-glare layer 11a Anti-glare layer surface (fine uneven structure)
12 Low refractive index layer B Polarizing plate 21 Polarizer 22 Transparent protective film

Claims (7)

On the transparent substrate film, an antiglare layer in which fine particles having a space portion are dispersed and contained in the resin is provided, and the surface of the antiglare layer forms a fine concavo-convex structure, and the refractive index is 1 on this surface. A light diffusive antiglare film, wherein a low refractive index layer of 20 to 1.50 is laminated.
The light diffusive antiglare film according to claim 1, wherein the fine particles having a space in the antiglare layer are 12 to 30 parts by weight per 100 parts by weight of the resin.
3. The fine particles having a space in the antiglare layer are organic or / and inorganic fine particles having an average particle diameter of 0.01 to 10 [mu] m and a refractive index of 1.40 to 1.80. Light diffusive antiglare film.
4. The light diffusing antiglare film according to claim 1, wherein the antiglare layer is made of a thermosetting resin or a radiation curable resin having a refractive index of 1.40 to 1.70.
The light diffusive antiglare film according to any one of claims 1 to 4, wherein the low refractive index layer is formed of a sol-gel material containing a metal alkoxide and a silane coupling agent having a fluoroalkyl group. .
An optical element, wherein the light diffusive antiglare film according to any one of claims 1 to 5 is provided on one side or both sides of an optical element body.
An image display device comprising the light diffusive antiglare film according to claim 1 or the optical element according to claim 6 mounted thereon.

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