JP3821956B2 - Light diffusion layer, optical element, and liquid crystal display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light diffusing layer and an optical element that can form a liquid crystal display device having excellent visibility and excellent ghost and glare prevention and non-glare properties.
[0002]
[Background]
In a display device such as a liquid crystal display device, a light diffusion layer is generally provided on the surface thereof. This light diffusing layer functions as a non-glare (anti-glare) layer that diffuses reflected light on the surface, and it is a ghost phenomenon in which external light such as fluorescent light and sunlight, and key borders are reflected on the screen. The purpose is to prevent obstruction. Conventionally, the light diffusing layer has been known to have a fine concavo-convex structure on the surface by a roughening method such as sandblasting or mixing of transparent particles.
[0003]
However, with the downsizing of pixels due to high definition and colorization of display devices, particularly liquid crystal display devices, glare that causes random intensity in display light becomes prominent, resulting in a problem that visibility is significantly reduced. It has become like this.
[0004]
[Technical Problem of the Invention]
An object of the present invention is to develop a light diffusion layer, an optical element, and a liquid crystal display device that are excellent in glare prevention and antiglare properties while maintaining a ghost prevention function.
[0005]
[Means for solving problems]
The present invention is composed of an ultraviolet curable resin film having a fine surface irregular structure, and the film is composed of a superimposed layer of a particle-containing ultraviolet curable resin layer, and the average particle size of the contained particles is different in the upper and lower layers of the superimposed layer. the light diffusion layer, wherein the thickness of each layer of the ultraviolet curable resin layer overlapping is 1～50Myu m, and shows a 5-40% of the light diffusing based on the haze in the interior superimposed layers, and the light An optical element having a diffusion layer on one side or both sides of an optical layer, and a liquid crystal display device having the light diffusion layer on the viewing side of the liquid crystal display element are provided.
[0006]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it can prevent a ghost in a liquid crystal display device etc., can also prevent glare, can obtain the light-diffusion layer and optical element which are excellent in anti-glare property, and can form the display apparatus excellent in visibility. . The reason for this is unclear, but the present inventors believe that the distortion of the display light is suppressed by the intra-layer diffusivity due to the multilayer structure described above.
[0007]
In other words, the above-mentioned glare problem due to the conventional light diffusion layer is such that the pixel size is reduced and the pitch becomes more compatible with the surface uneven structure of the light diffusion layer, and the display light that has passed through the pixel has a surface uneven structure of the light diffusion layer. It is considered that a distortion phenomenon such as refraction and diffusion is likely to occur, and a random strength difference is generated in display light from a pixel partitioned by a black matrix and converted into parallel light due to the distortion, thereby causing a glare phenomenon.
[0008]
On the other hand, in the light diffusing layer according to the present invention, the display light from the pixels that are collimated in the black matrix section is scattered based on the in-layer diffusibility due to the multilayer structure, and the difference in intensity of the display light is scattered. It seems that the glare phenomenon caused by is suppressed. Further, when the surface irregularities are miniaturized, it is considered that better visibility is achieved by making the area of the display light from each pixel uniform on the screen.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The light diffusing layer according to the present invention is composed of an ultraviolet curable resin film having a fine surface irregular structure, and the film is composed of a superimposed layer of particle-containing ultraviolet curable resin layers, and the average particle size of the contained particles in the upper and lower layers of the superimposed layer. There are different, the thickness of each layer of the ultraviolet curable resin layer overlapping is 1～50Myu m, and consists of an indication of 5-40% of the light diffusing based on the haze in the interior superimposed layers. Examples thereof are shown in FIGS. DESCRIPTION OF SYMBOLS 1 is a light-diffusion layer which consists of an ultraviolet curable resin film, 11 and 12 are the superposition layers of an ultraviolet curable resin layer, 13 and 14 are fine uneven structure surfaces, 2 is a transparent base material, 3 is an adhesion layer as needed It is.
[0010]
As shown in the figure, the light diffusing layer 1 may be formed as an independent layer such as a sheet made of an ultraviolet curable resin film itself composed of an overlapping layer of particle-containing ultraviolet curable resin layers 11 and 12, or a transparent substrate 2 It may consist of the light-diffusion sheet of the form which supported the ultraviolet curable resin film 1 on the one side or both surfaces through this. Further, according to the latter, it may be formed as a subordinate layer attached to the support base.
[0011]
Examples of UV curable resins that form resin films include UV polymerization initiators in monomers, oligomers, and polymers that can form polyester, acrylic, urethane, amide, silicone, and epoxy resins. In addition, an appropriate material such as a resin film that can be formed by a curing treatment by ultraviolet irradiation can be used.
[0012]
The ultraviolet curable resin that can be preferably used is, for example, an adhesive or transparency to the object to be attached, a hard coat property, or a compounded particle, such as one containing acrylic monomers or oligomers having 3 to 6 ultraviolet polymerizable functional groups as components. It has excellent dispersibility.
[0013]
Formation of an ultraviolet curable resin film having a fine surface irregularity structure can be achieved by, for example, dispersing transparent particles having different refractive indexes in an ultraviolet curable resin and applying it to a predetermined surface by an appropriate method such as a doctor blade method or a gravure roll coater method. Applying and curing the coated layer via ultraviolet irradiation to form a fine uneven structure reflecting unevenness by transparent particles on the surface, or the surface of the transparent substrate as appropriate by sandblasting, embossing roll, etching, etc. To an appropriate method such as a method of forming a fine concavo-convex structure by applying an ultraviolet curable resin film on the roughened surface and reflecting the unevenness of the roughened surface on the surface of the film. Can be done.
[0014]
In addition, the formation of the ultraviolet curable resin film comprising an overlapping layer of the particle-containing ultraviolet curable resin layer and having different average particle diameters of the contained particles in the upper and lower layers of the superimposed layer is, for example, the above-described particle-containing ultraviolet ray. On the cured resin layer, an ultraviolet curable resin containing particles having an average particle size different from that of the particles of the layer may be overcoated and cured by ultraviolet irradiation.
[0015]
Examples of particles to be contained in the ultraviolet curable resin layer include inorganic particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide, polymethyl methacrylate ( Appropriate ones such as crosslinked or uncrosslinked organic particles composed of various polymers such as PMMA) and polyurethane can be used.
[0016]
The particles that can be preferably used are excellent in transparency and do not dissolve in the ultraviolet curable resin before forming a cured film. The transparent particles that can be preferably used from the viewpoint of the formation of the surface roughness characteristics described above are those having an average particle size of 30 μm or less, especially 15 μm or less, particularly 0.1 to 10 μm.
[0017]
UV-curable resin layer overlapping is the thickness of each layer and 1～50Myu m, and as a combination for different average particle diameter of the contained particles in the upper and lower layers, based on the haze in the interior superimposed layers 5-40 %, And there is no particular limitation except that the number of layers of light overlapping is two or three or more. Further, the average particle size of the contained particles to be differentiated between the upper and lower layers can be determined as appropriate, but generally 0.2 μm or more from the viewpoint of preventing glare due to light diffusibility inside the overlapping layer due to the difference in particle size. In particular, a combination of average particle diameters different from 0.4 μm or more, particularly 0.6 μm or more is preferable.
[0018]
In addition, in the case of an ultraviolet curable resin film composed of two overlapping layers for the purpose of thinning the light diffusion layer, etc., a small particle layer containing particles having an average particle size of 0.1 to 1.0 μm or less, A combination with a large particle layer containing particles having an average particle diameter of more than 1.0 to 5 μm is particularly preferable from the viewpoint of preventing glare due to light diffusibility inside the superimposed layer.
[0019]
Furthermore, the light diffusing layer that is more preferable from the viewpoint of the formation of a clear image due to the prevention of glare, etc. has a light diffusibility inside the superposition layer of 10 to 35% based on the haze, and has fine irregularities on the surface. The surface roughness in the structure is a center line average roughness of 0.08 to 0.5 μm, especially 0.1 to 0.3 μm, an average peak-to-valley spacing of 20 to 80 μm, especially 25 to 60 μm. The interval between the peaks and valleys is preferably as constant as possible.
[0020]
On the other hand, as a transparent base material that supports the light diffusing layer composed of the above-mentioned ultraviolet curable resin film, for example, a polyester-based polymer such as polyethylene terephthalate or polyethylene naphthalate, a cellulose-based polymer such as cellulose diacetate or cellulose triacetate, or a polycarbonate-based material. Examples thereof include a film made of a transparent polymer such as a polymer or an acrylic polymer such as PMMA.
[0021]
Also, styrene polymers such as polystyrene and acrylonitrile / styrene copolymer (AS resin), polyethylene and polypropylene, polyolefins having cyclo or norbornene structure, olefin polymers such as ethylene / propylene copolymer, vinyl chloride polymers, nylon And a film made of a transparent polymer such as an amide polymer such as aromatic polyamide.
[0022]
Furthermore, imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers Examples thereof include a film made of a transparent polymer such as a polymer, an epoxy-based polymer, and a blend of the aforementioned polymers.
[0023]
In particular, a film made of a polymer having excellent transparency and having as little retardation as possible due to birefringence is preferably used. The thickness of the transparent substrate can be determined as appropriate, but generally it is 10 to 500 μm, especially 30 to 300 μm, especially 50 to 200 μm in terms of workability such as strength and handleability and thin layer properties. Is done.
[0024]
The thickness of each layer of superimposed UV-curable resin layer, from the viewpoint of formation of the light diffusion layer of the above noted properties,. 1 to 50.mu. m, in就3 0 .mu.m or less, are particularly 3 to 10 [mu] m. As shown in FIG. 2, the adhesive layer 3 provided as necessary is intended to adhere to other members such as an optical layer. For example, an acrylic, rubber or silicone adhesive or hot melt adhesive is used. It can be formed with an appropriate adhesive such as an agent, and is preferably excellent in transparency and weather resistance.
[0025]
The light diffusion layer according to the present invention can be used for various purposes according to the prior art. In particular, it can be preferably used for a display device in which pixels are arranged at a predetermined interval such as a liquid crystal display device. At the time of application, it can also be used as an optical element in which a light diffusion layer is provided on one side or both sides of the optical layer.
[0026]
Examples of the optical element according to the present invention are shown in FIGS. 4 is a polarizing plate, 5 is a retardation plate, and 6 is an elliptical polarizing plate made of a laminate of the polarizing plate 4 and the retardation plate 5. Therefore, the optical layer may be an appropriate one such as a polarizing plate, a retardation plate, or an elliptically polarizing plate made of a laminate thereof.
[0027]
Any appropriate polarizing plate may be used. By way of example, hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, ethylene / vinyl acetate copolymer partially saponified films, and dichroism such as iodine and dichroic dyes. Examples thereof include polarizing films such as those obtained by adsorbing a substance and stretched, dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. The thickness of the polarizing film is generally 5 to 80 μm, but is not limited thereto.
[0028]
Moreover, what provided the transparent protective layer which consists of a polymer coating layer, a laminate layer of a film, etc. for the purpose of protection, such as water resistance, is mention | raise | lifted on the one or both surfaces of the above-mentioned polarizing film. For the formation of the transparent protective layer, an appropriate polymer such as the exemplified polymer can be used as the above-mentioned transparent substrate, but a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property and the like can be preferably used.
[0029]
On the other hand, any appropriate retardation plate can be used. Incidentally, examples thereof include a stretched film and a liquid crystal polymer film by an appropriate method such as uniaxial or biaxial polymer film exemplified for the transparent substrate. The retardation film may be formed as a superposed body of two or more stretched films.
[0030]
The elliptically polarizing plate can be formed by laminating a polarizing plate and a retardation plate. In that case, the light diffusion layer is preferably provided at least on the polarizing plate side in view of practicality. Note that the polarizing plate and the retardation plate in the elliptically polarizing plate are preferably bonded and laminated through the above-described adhesive layer or the like from the viewpoint of stability of optical characteristics due to prevention of misalignment or the like.
[0031]
Further, the light diffusion layer in the optical element may be directly attached to the optical layer 4 as illustrated in FIG. 3, or is attached as a light diffusion sheet integrated with the transparent substrate 2 as illustrated in FIG. Also good. Also in the case of the light diffusion sheet, it is preferable that the optical diffusion layer is bonded and laminated to the optical layer through the above-described adhesive layer and the like from the viewpoint of stability of optical characteristics due to prevention of deviation and the like. The light diffusing layer preferably has a layer containing particles having a large average particle diameter as a surface for forming a fine concavo-convex structure on the surface from the viewpoint of non-glare properties.
[0032]
As described above, the light diffusing layer and the optical element according to the present invention are preferable for a display device in which distortion of display light through the pixel is a problem, and particularly for a liquid crystal display device in a personal computer such as a notebook type or a desktop type. Can be used. In particular, like a TFT-type or STN-type liquid crystal display element, pixels as a display unit are formed at a predetermined pitch by being equally spaced by a light-shielding portion (black matrix), and the pixel pitch is, for example, 50 to 500 μm. It can be preferably used for a liquid crystal display device.
[0033]
In the above, the light diffusing layer and the optical element are provided on the viewing side of the liquid crystal display device. In that case, the light diffusing layer is the outermost surface such as the outermost surface of the device from the viewpoint of glare prevention and non-glare action. It is preferable to be located at. The liquid crystal display device is not particularly limited except that at least one light diffusion layer or optical element according to the present invention is disposed, and can be formed as a conventional one.
[0034]
【Example】
Example 1
Viscosity adjustment by adding 15 parts of silica particles with an average particle size of 0.5 μm to an ultraviolet curable resin consisting of 100 parts (parts by weight) of an ultraviolet curable urethane acrylate monomer and 3 parts of a benzophenone photopolymerization initiator After adding a solvent to a solid content concentration of 50% by weight, the mixture was mixed with a high-speed stirrer. The mixed solution was applied to one side of a 50 μm thick triacetyl cellulose film with a bar coater, and the solvent was volatilized. After irradiation and curing to form a small particle layer having a thickness of 7 μm, a liquid mixture containing 10 parts of silica particles having an average particle diameter of 1.4 μm is prepared in accordance with the above, and this is applied onto the small particle layer. A large particle layer having a thickness of 7 μm was superposed to form a light diffusion sheet having a light diffusion layer.
[0035]
The light diffusing layer has a light diffusibility of 28% based on haze inside the superposed layer, and has a centerline average roughness (hereinafter the same) based on a stylus type surface roughness measuring instrument in a fine concavo-convex structure on the surface. The average crest / valley interval (hereinafter the same) according to the surface roughness curve was 0.12 μm and 42 μm.
[0036]
Comparative Example 1
A light diffusion sheet having a light diffusion layer was obtained in the same manner as in Example 1 except that a small particle layer containing silica particles having an average particle diameter of 0.5 μm was formed on a triacetyl cellulose film as a single layer with a thickness of 14 μm. . The light diffusion layer had an internal light diffusibility of 3% based on haze, a center line average roughness of the surface fine concavo-convex structure of 0.11 μm, and an average peak-valley interval of 44 μm.
[0037]
Comparative Example 2
A light diffusing sheet having a light diffusing layer was obtained in the same manner as in Example 1 except that a large particle layer containing silica particles having an average particle size of 1.4 μm was formed as a single layer on a triacetyl cellulose film with a thickness of 14 μm. . The light diffusing layer had an internal light diffusibility based on haze of 2%, a center line average roughness of the surface fine concavo-convex structure of 0.10 μm, and an average peak-valley interval of 45 μm.
[0038]
The light diffusion sheets obtained in Evaluation Test Example 1 and Comparative Examples 1 and 2 were placed on a liquid crystal display element (size 12.1 inches, resolution XGA) for a notebook personal computer, and a display image was visually confirmed. In that case, in the liquid crystal display device using the light diffusion sheet of Example 1, a very clear display image with little glare was obtained, but in Comparative Examples 1 and 2, the degree of glare was large and the display image was clear. It was inferior.
[Brief description of the drawings]
1 is a cross-sectional view of an example of a light diffusing layer. FIG. 2 is a cross-sectional view of another example of a light diffusing layer. FIG. 3 is a cross-sectional view of an example of an optical element. ]
1: Light diffusing layers 11 and 12 made of an ultraviolet curable resin film, 12: Superposed layers 13 and 14 of an ultraviolet curable resin layer, 2: Fine uneven structure surface 2: Transparent base material 4: Polarizing plate 5: Phase difference plate 6: Elliptical polarizing plate

Claims (6)

Made of ultraviolet curing resin film on the surface fine irregular structure, with its coating consists of a superimposed layers of the ultraviolet curable resin layer of the particles containing an average particle diameter of the contained particles in the upper and lower layers of the superimposed layers is different, superimposed UV curing thickness of each layer of the resin layer is 1~50μ m, and the light diffusion layer, characterized in that indicating the 5-40% of the light diffusing based on the haze in the interior superimposed layers. According to claim 1, have a large particle layer ultraviolet curable resin film contains an average particle size 1.0 super ~5μm particles with small particle layer containing the following particles having an average particle size 0.1~1.0μm A light diffusion layer in which the surface roughness of the surface fine concavo-convex structure is a center line average roughness of 0.08 to 0.5 μm and an average mountain-valley interval of 20 to 80 μm.   3. The light diffusing layer according to claim 1, wherein the light diffusing layer is supported on one side or both sides of the transparent substrate. An optical element comprising the light diffusion layer according to claim 1 on one side or both sides of the optical layer.   5. The optical element according to claim 4, wherein the optical layer is an elliptically polarizing plate made of a polarizing plate, a retardation plate, or a laminate thereof. The liquid crystal display device characterized by having a light diffusing layer according to one of claims 1 to 3 on the viewing side of the liquid crystal display device.

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