JP4372338B2 - Light diffusing layer, light diffusing sheet and optical element - Google Patents

Description

【図面の簡単な説明】
【図１】本発明の光拡散性シートの断面図の一例である。
【図２】光拡散性シート表面の入射角６０°における受光角に対する光沢度分布を示すチャートである。
【図３】実施例１の光拡散性シートの光拡散層表面の光沢度分布である。
【符号の説明】
１：透明基板
２：樹脂皮膜層
３：微粒子
４：光拡散層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light diffusing layer used for suppressing deterioration of screen visibility in a liquid crystal display (LCD), EL, PDP, and the like, a light diffusing sheet having the light diffusing layer, and the light diffusing layer. The present invention relates to an optical element provided with a conductive sheet.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image display device such as an LCD is hindered in visibility of an image due to reflection of indoor lighting such as a fluorescent lamp, sunlight from a window, and an operator's shadow on a display device surface. Therefore, on the LCD surface, in order to improve the visibility of the image, the surface reflection light is diffused, regular reflection of external light is suppressed, and reflection of the external environment can be prevented (having anti-glare properties). A light diffusion layer having a concavo-convex structure is provided. As a method for forming the light diffusion layer, a method in which a resin film layer is formed by coating a resin in which fine particles are dispersed has become the mainstream because the structure can be easily refined and the productivity is good.
[0003]
However, in a high-haze light diffusion layer mounted on a high-definition (120 ppi or more) LCD or the like, surface scattering occurs, and the display screen becomes whitish during black display, so-called white blurring, so that the contrast of the screen display is reduced. Problems arise.
[0004]
For example, Japanese Patent Laid-Open No. 10-20103 discloses a light diffusing layer with improved antiglare properties and the like, focusing on the 60 ° glossiness of the surface of the light diffusing layer and setting it to 90% or less. However, in this publication, a large amount of particles having a small average particle diameter is used, and thus white blurring occurs. International Publication WO95 / 31737 also discloses that the 60 ° glossiness of the surface of the light diffusion layer is 90% or less, but the light diffusion layer described in the publication also has sufficiently improved white blurring. I can't say.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a light diffusing layer capable of suppressing white blurring while maintaining antiglare properties even when applied to a high-definition LCD. It is another object of the present invention to provide a light diffusing sheet having the light diffusing layer and an optical element provided with the light diffusing sheet.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by a light diffusion layer having the following characteristics, and have completed the present invention.
[0007]
That is, the present invention is a light diffusion layer composed of a resin film layer having a fine irregular shape formed on the surface.
The glossiness in the gloss distribution when the 60 ° specular glossiness of the surface of the fine concavo-convex shape is 70% or less and the light receiving angle with respect to the incident angle of 60 ° is changed by 1 ° in a range of 35 ° to 85 °. 1% ratio (b) / (a) is 0.05 or more 0.35 or less der acceptance angle spread (a) and gloss of 20% acceptance angle spread (b) is, and,
The ratio (x) / (y) between the glossiness (x) at a light receiving angle of 45 ° and the glossiness (y) at a light receiving angle of 60 ° with respect to an incident angle of 60 ° on the surface of the fine irregular shape is 0.003 or more and 0.05 or less. And
The resin film layer contains 6 to 20 parts by weight of organic fine particles having an average particle diameter of 1 to 10 μm with respect to 100 parts by weight of the resin forming the resin film layer, and the surface uneven shape of the resin film layer is the organic Formed by the system fine particles,
Light diffusion layer thickness of the resin coating layer is characterized 3~6μm der Rukoto relates.
[0008]
In the present invention, the 60 ° specular glossiness of the surface of the fine irregularities is set to 70% or less, so that reflection is prevented and antiglare property is good. The 60 ° specular gloss is preferably 50% or less from the viewpoint of antiglare properties. The 60 ° specular gloss is 20% or more.
[0009]
Further, by setting the ratio (b) / (a) of the light receiving angle spread in the gloss distribution to the above range, it is possible to control the reflected light diffusibility on the surface of the fine concavo-convex shape and to realize a display screen free from white blur. The ratio (b) / (a) is preferably 0.1 or more and 0.35 or less.
[0010]
In the light diffusing layer, the surface of the fine concavo-convex shape has a ratio (x) / (y) of a glossiness (x) at a light receiving angle of 45 ° and a glossiness (y) at a light receiving angle of 60 ° with respect to an incident angle of 60 °. Is preferably 0.003 or more and 0.05 or less.
[0011]
By setting the gloss ratio (x) / (y) in the above range, the reflected light diffusibility of the surface with fine irregularities can be controlled, and a display screen with less white blur can be realized. The ratio (x) / (y) is more preferably 0.006 or more and 0.05 or less.
[0012]
FIG. 2 shows an example of the glossiness distribution. The glossiness with respect to the light receiving angle at an incident angle of 60 ° follows a substantially normal distribution. FIG. 2A shows a light reception angle spread with a glossiness of 1%, and FIG. 2B shows a light reception angle spread with a glossiness of 20%. Further, (x) indicates the glossiness at a light receiving angle of 45 °, and (y) indicates the glossiness at a light receiving angle of 60 °. Note that (y) glossiness is the same as 60 ° specular glossiness.
[0013]
In the light diffusing layer, it is preferable that the resin film layer contains fine particles, and the uneven surface shape of the resin film layer is formed of fine particles. The fine particles contained in the resin film layer are preferably organic fine particles. Furthermore, it is preferable that the resin film layer is formed of an ultraviolet curable resin.
[0014]
By using fine particles, the gloss characteristics can be easily adjusted. Further, when organic fine particles are used as the fine particles, it is effective for forming the surface uneven shape having the gloss characteristics to suppress white blurring and further to suppress glare. In addition, the ultraviolet curable resin can efficiently form a resin film layer (light diffusion layer) by a simple processing operation by a curing treatment by ultraviolet irradiation.
[0015]
In the light diffusion layer according to the present invention, a low refractive index layer having a refractive index lower than the refractive index of the resin film layer is provided on the uneven surface of the resin film layer of the light diffusion layer. , Regarding. The antireflective function can be imparted by the low refractive index layer, and the blurring of the screen due to the irregular reflection of the image surface of a display or the like can be effectively suppressed.
[0016]
The present invention also relates to a light diffusing sheet, wherein the light diffusing layer is provided on at least one surface of a transparent substrate.
[0017]
Furthermore, the present invention relates to an optical element, wherein the light diffusing layer or the light diffusing sheet is provided on one side or both sides of the optical element.
[0018]
The light diffusing layer of the present invention can be used for various applications as a light diffusing sheet provided on a transparent substrate. For example, it is used for an optical element.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a light diffusing sheet in which a light diffusing layer 4 composed of a resin film layer 2 in which fine particles 3 are dispersed is formed on a transparent substrate 1, and the fine particles dispersed in the resin film layer 2. 3 forms an uneven shape on the surface of the light diffusion layer 4. In addition, in FIG. 1, although the case where the resin film layer 2 is one layer is shown, by separately forming a resin film layer containing fine particles between the resin film layer 2 and the transparent substrate 1, The light diffusion layer can also be formed by a plurality of resin film layers.
[0020]
Examples of the transparent substrate 1 include films made of transparent polymers such as 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. Is given. 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, etc. Examples thereof include films made of transparent polymers such as amide polymers. 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. In particular, those having a small optical birefringence are preferably used.
[0021]
The thickness of the transparent substrate 1 can be appropriately determined, but is generally about 10 to 500 μm from the viewpoints of workability such as strength and handleability, and thin layer properties. 20-300 micrometers is especially preferable, and 30-200 micrometers is more preferable.
[0022]
As long as the resin film layer 2 having a fine concavo-convex structure surface is formed on the transparent substrate 1, the formation method is not particularly limited, and an appropriate method can be adopted. For example, the surface of the film used for forming the resin film layer 2 is previously roughened by an appropriate method such as sand blasting, embossing roll, chemical etching, etc. A method of forming the surface of the material itself for forming the resin film layer 2 in a fine concavo-convex structure is exemplified. Further, there is a method in which a resin film layer is separately applied on the resin film layer 2 and a fine concavo-convex structure is imparted to the surface of the resin film layer by a transfer method using a mold or the like. Further, as shown in FIG. 1, there is a method in which fine concavo-convex structure is imparted by dispersing fine particles 3 in the resin film layer 2. These fine concavo-convex structure forming methods may be formed as a layer in which two or more methods are combined to combine the fine concavo-convex structure surfaces in different states. Among the methods for forming the resin film layer 2, a method of providing the resin film layer 2 containing the fine particles 3 in a dispersed manner is preferable from the viewpoint of the formability of the surface of the fine concavo-convex structure.
[0023]
Hereinafter, a method for providing the resin film layer 2 by dispersing the fine particles 3 will be described. As the resin for forming the resin film layer 2, fine particles 3 can be dispersed, and a resin having sufficient strength and transparency as a film after the resin film layer is formed can be used without particular limitation. Examples of the resin include thermosetting resins, thermoplastic resins, ultraviolet curable resins, electron beam curable resins, and two-component mixed resins. An ultraviolet curable resin that can efficiently form a light diffusion layer by a processing operation is preferable.
[0024]
Examples of the ultraviolet curable resin include polyester-based, acrylic-based, urethane-based, amide-based, silicone-based, and epoxy-based resins, and include ultraviolet curable monomers, oligomers, polymers, and the like. The UV curable resin preferably used includes, for example, those having an ultraviolet polymerizable functional group, and in particular, those containing an acrylic monomer or oligomer having 2 or more, particularly 3 to 6 functional groups. . Further, an ultraviolet polymerization initiator is blended in the ultraviolet curable resin.
[0025]
In addition, in formation of the resin film layer 2, additives, such as a leveling agent, a thixotropic agent, and an antistatic agent, can be contained. By forming a thixotropic agent (0.1 μm or less of silica, mica, etc.) in forming the resin film layer, the surface of the resin film layer (light diffusion layer) can be easily formed with a fine uneven structure by protruding particles. Can do.
[0026]
As the fine particles 3, those having transparency such as various metal oxides, glass, and plastic can be used without particular limitation. For example, inorganic fine particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide, polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, Examples thereof include crosslinked or uncrosslinked organic fine particles and silicone fine particles composed of various polymers such as benzoguanamine, melamine, and polycarbonate. These fine particles 3 can be used by appropriately selecting one kind or two or more kinds, but organic fine particles are preferred. The average particle diameter of the fine particles is 1 to 10 μm, preferably 2 to 5 μm.
[0027]
The method for producing the light diffusing sheet is not particularly limited, and an appropriate method can be adopted. For example, a resin film layer in which a resin containing fine particles 3 (for example, an ultraviolet curable resin: a coating solution) is applied on the transparent substrate 1, dried, and cured to exhibit an uneven shape on the surface. 2 to form the light diffusion layer 4. The coating solution is applied by an appropriate method such as phantom, die coater, casting, spin coating, phanten metalling, and gravure.
[0028]
In order to make the gloss characteristics of the surface of the formed light diffusion layer 4 within the above range, the average particle diameter and the ratio of the fine particles 3 contained in the coating liquid and the thickness of the resin film layer 2 are appropriately adjusted.
[0029]
Although the ratio of the fine particles 3 contained in the coating liquid is not particularly limited, it is preferably 6 to 20 parts by weight with respect to 100 parts by weight of the resin in terms of antiglare and white blurring. The thickness of the resin film layer 2 is not particularly limited, but is preferably about 3 to 6 μm, particularly 4 to 5 μm.
[0030]
A low refractive index layer having an antireflection function can be provided on the uneven surface of the resin film layer 2 that forms the light diffusion layer 4. The material of the low refractive index layer is not particularly limited as long as it has a refractive index lower than that of the resin film layer 2. For example, a low refractive index material such as fluorine-containing polysiloxane can be used. The thickness of the low refractive index layer is not particularly limited, but is preferably about 0.05 to 0.3 μm, particularly preferably 0.1 to 0.3 μm.
[0031]
Further, an optical element can be bonded to the transparent substrate 1 of the light diffusing sheet of FIG. 1 (not shown). Examples of the optical element include a polarizing plate, a retardation plate, an elliptical polarizing plate, a polarizing plate with optical compensation, and the like, and these can be used as a laminate. The optical element can be bonded through an appropriate adhesive layer having excellent transparency and weather resistance, such as an acrylic, rubber-based, or silicone-based pressure-sensitive adhesive, or a hot-melt adhesive, if necessary.
[0032]
As the polarizing plate, a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, an ethylene / vinyl acetate copolymer-based partially saponified film, or the like, which is stretched by adsorbing iodine, dye or the like, polyvinyl Examples thereof include polarizing films such as a dehydrated product of alcohol and a dehydrochlorinated product of polyvinyl chloride. Examples of the retardation plate include a uniaxial or biaxially stretched film of a polymer film exemplified for the transparent substrate and a liquid crystal polymer film. The retardation film may be formed as a superposed body of two or more stretched films. The elliptically polarizing plate and the polarizing plate with optical compensation can be formed by laminating a polarizing plate and a retardation plate. The elliptically polarizing plate and the polarizing plate with optical compensation have a light diffusion layer formed on the surface on the polarizing plate side.
[0033]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[0034]
Example 1
As fine particles, 20 parts by weight of acrylic (polymethylmethacrylate: PMMA) beads having an average particle diameter of 3 μm, 100 parts by weight of an ultraviolet curable resin (urethane acrylate monomer), 5 parts by weight of a benzophenone-based photopolymerization initiator, and a solid content thereof are 40 parts. A solution mixed with a solvent (toluene) weighed to give a weight percent was applied onto triacetylcellulose, dried at 120 ° C. for 5 minutes, and then cured by ultraviolet irradiation to a thickness of about 4 μm. A light diffusing sheet having a resin film layer on the surface of the fine concavo-convex structure was produced.
[0035]
Example 2
In Example 1, a light diffusing sheet was produced in the same manner as in Example 1 except that 12 parts by weight of polystyrene (PS) beads having an average particle diameter of 3.5 μm were used as the fine particles.
[0037]
Example 3
In Example 2, a low refractive index layer (material: fluorine-modified polysiloxane, refractive index: 1.39) lower than the refractive index (1.51) of the resin film layer is further formed on the uneven surface of the resin film layer. A light diffusing sheet was produced in the same manner as in Example 1 except that 1 μm was provided.
[0038]
Comparative Example 1
In Example 1, a light-diffusing sheet was produced in the same manner as in Example 1 except that 14 parts by weight of silica beads having an average particle diameter of 2.5 μm were used as the fine particles.
[0039]
About the light-diffusion layer of the light-diffusion sheet | seat obtained by the said Example and the comparative example, 60 degree specular glossiness was made from Suga Test Instruments Co., Ltd. (digital variable angle gloss meter UGV-5DP according to JISK7105-1981. ). Further, in the gloss distribution when the light receiving angle with respect to the incident angle of 60 ° is changed by 1 ° in the range of 35 ° to 85 °, the light receiving angle spread (a) with a glossiness of 1% and the light receiving angle with a glossiness of 20%. The spread (b) was measured using the above digital gonioglossmeter, and the ratio (b) / (a) was calculated from the obtained chart. In addition, the glossiness at a light receiving angle of 45 ° with respect to the incident light of 60 ° was measured using the digital variable glossmeter described above, and the ratio (x) / (y) was calculated from the obtained result. The measurement results are shown in Table 1. In Table 1, the values relating to the glossiness of Example 3 are the same as those of Example 2 (Example 3 without a low refractive index layer). FIG. 3 is a gloss distribution relating to the light diffusing sheet of Example 1.
[0040]
Adhering a polarizing plate (185 μm) to the light diffusing sheet obtained in the examples and comparative examples, and adhering it to the glass substrate, affixing a black tape on the surface opposite to the polarizing plate adhesion surface of the glass substrate, White blur (anti-blur) was visually evaluated according to the following criteria. In addition, the show-through write only in fluorescent light polarizing plates adhered to light-diffusing sheet was evaluated for the white blur and evaluated by the following criteria. The measurement results are shown in Table 1.
[0041]
(Anti-white blur)
◎… There is no white blur.
○… There is almost no white blur.
×… There is white blur.
(Reflection)
◎… There is no reflection.
○… There is almost no reflection.
×… There is no reflection.
[0042]
[Table 1]

[Brief description of the drawings]
FIG. 1 is an example of a cross-sectional view of a light diffusing sheet of the present invention.
FIG. 2 is a chart showing a gloss distribution with respect to a light receiving angle at an incident angle of 60 ° on the surface of a light diffusing sheet.
3 is a gloss distribution on the surface of the light diffusing layer of the light diffusing sheet of Example 1. FIG.
[Explanation of symbols]
1: Transparent substrate 2: Resin film layer 3: Fine particles 4: Light diffusion layer

Claims (5)

In the light diffusion layer consisting of a resin film layer with a fine irregular shape formed on the surface,
The glossiness in the gloss distribution when the 60 ° specular glossiness of the surface of the fine concavo-convex shape is 70% or less and the light receiving angle with respect to the incident angle of 60 ° is changed by 1 ° in a range of 35 ° to 85 °. 1% ratio (b) / (a) is 0.05 or more 0.35 or less der acceptance angle spread (a) and gloss of 20% acceptance angle spread (b) is, and,
The ratio (x) / (y) between the glossiness (x) at a light receiving angle of 45 ° and the glossiness (y) at a light receiving angle of 60 ° with respect to an incident angle of 60 ° on the surface of the fine irregular shape is 0.003 or more and 0.05 or less. And
The resin film layer contains 6 to 20 parts by weight of organic fine particles having an average particle diameter of 1 to 10 μm with respect to 100 parts by weight of the resin forming the resin film layer, and the surface uneven shape of the resin film layer is the organic Formed by the system fine particles,
Light diffusion layer thickness of the resin coating layer is characterized 3~6μm der Rukoto. Light diffusion layer according to claim 1, wherein the resin film layer is characterized in that it is formed by ultraviolet curing resin. 3. A light diffusing layer characterized in that a low refractive index layer having a refractive index lower than the refractive index of the resin coating layer is provided on the uneven surface of the resin coating layer of the light diffusing layer according to claim 1 or 2. . A light diffusing sheet, wherein the light diffusing layer according to any one of claims 1 to 3 is provided on at least one surface of a transparent substrate. An optical element, wherein the light diffusing layer according to any one of claims 1 to 3 or the light diffusing sheet according to claim 4 is provided on one side or both sides of the optical element.

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