JP2014106244A - Optical sheet, surface light source device, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet that allows anisotropic diffusion of light, simple production, and easy adjustment of diffusion characteristics, and a surface light source device and a display device equipped with the optical sheet.SOLUTION: An optical sheet includes a light diffusion layer configured to diffuse transmitted light. The light diffusion layer contains a diffusion agent that diffuse light. A high density part having relatively high density of the diffusion agent and a low density part having relatively low density of the diffusion agent are alternately juxtaposed along one direction parallel to a sheet surface. A surface light source device is equipped with the optical sheet, and a display device is equipped with the optical sheet.

Description

  The present invention relates to an optical sheet that controls and transmits transmitted light, and a surface light source device and a display device including the optical sheet.

  In display devices such as a plasma television, a liquid crystal display device, and a projection television, an optical sheet for modifying an image provided to the observer is disposed on the viewer side of a screen that displays the image. Some of these optical sheets control the path of image light emitted to the viewer side. Further, in a liquid crystal display device or the like, a surface light source device that provides light to a liquid crystal panel (hereinafter, referred to as “LCD”) on which information of an image is displayed is controlled in a path of light incident on the LCD. An optical sheet is disposed. The light incident on the LCD from the surface light source device is preferably as parallel as possible to the normal direction of the panel surface of the LCD. Thereby, the quality of the image light provided to the observer can be improved.

  As an optical sheet capable of controlling the path of incident light as described above, for example, in Patent Document 1, the diffusivity changes depending on the light incident direction, and the distribution of diffused light in the direction in which the diffusivity is maximized is incident. A diffusion film (optical sheet) that is asymmetric with respect to the direction is disclosed. Patent Documents 2 and 3 disclose an anisotropic light diffusion film (optical sheet) and an anisotropic light diffusion film composition for anisotropically diffusing incident light. Patent Document 4 discloses a light diffusion film having a first structure region for anisotropically diffusing incident light and a second structure region for isotropically diffusing incident light, The first structure region is a louver structure region in which a plurality of plate-like regions having different refractive indexes are alternately arranged in parallel along the film surface direction, and the second structure region is included in the medium object. Discloses a light diffusion film (optical sheet) characterized in that it is a column structure region in which a plurality of columnar objects having different refractive indexes are planted. Further, in Patent Document 5, the first scattering film that does not have the incident angle dependency on the haze value and scatters the incident light in the horizontal direction, and the haze value has the incident angle dependency, and the incident light is A light control film (optical sheet) formed by laminating a second scattering film that scatters in a vertical direction perpendicular to the horizontal direction is disclosed.

JP 2006-003506 A JP 2012-141591 A JP 2012-141592 A JP 2012-141593 A JP 2012-145893 A

  According to the optical sheets disclosed in Patent Documents 1 to 5, the light is diffused so that the angle (range) at which light is diffused differs between a specific direction (for example, the horizontal direction) and another direction (for example, the vertical direction). (Hereinafter, such an action is referred to as “anisotropic diffusion”). However, each technique has a complicated manufacturing method, and there is a problem in that it is not easy to change the design such as changing the direction and angle of light diffusion (hereinafter referred to as “diffusion characteristics”).

  Accordingly, the present invention provides an optical sheet that can diffuse light anisotropically, is easy to manufacture, and that allows easy adjustment of diffusion characteristics, and a surface light source device and a display device including the optical sheet. This is the issue.

  The present invention will be described below.

  The invention according to claim 1 is an optical sheet provided with a light diffusion layer for diffusing transmitted light, and the light diffusion layer contains a diffusing agent for diffusing light, and is parallel to the sheet surface. In the optical sheet, a high concentration portion having a relatively high concentration of the diffusing agent and a low concentration portion having a relatively low concentration of the diffusing agent are alternately arranged along the direction.

  According to a second aspect of the present invention, in the optical sheet according to the first aspect, in the parallel direction of the high density part and the low density part, the size of the high density part is larger than the size of the low density part. .

  The invention according to claim 3 is the optical sheet according to claim 1 or 2, wherein a light diffusion layer is formed on one surface side of the base material layer, and one of the high concentration portion and the low concentration portion is It is formed to have a plurality of parallel grooves on the base material layer, and the other of the high concentration portion and the low concentration portion is formed in the groove.

  According to a fourth aspect of the present invention, in the optical sheet according to the third aspect, the surface of the light diffusion layer opposite to the side on which the base material layer is provided is covered with a smooth surface so as to cover the light diffusion layer. A layer is formed.

  According to a fifth aspect of the present invention, in the optical sheet according to any one of the first to fourth aspects, the light sheet includes two light diffusion layers, the parallel direction of the high concentration portion of one light diffusion layer, and the other. Two light diffusion layers are laminated so that the parallel direction of the high concentration portion of the light diffusion layer intersects when viewed from the normal direction of the sheet surface.

  The invention according to claim 6 is the optical sheet according to claim 5, wherein the parallel direction of the high concentration portion of one light diffusion layer and the parallel direction of the high concentration portion of the other light diffusion layer are the sheet surface. It is characterized by being orthogonal when viewed from the normal direction.

  Invention of Claim 7 is a manufacturing method of the optical sheet in any one of Claim 1 thru | or 6, Comprising: One of a high concentration part and a low concentration part is parallelly arranged on a base material layer by predetermined spacing. A step of producing a prepared intermediate sheet, an excessive supply of the composition to be the other of the high-concentration part and the low-concentration part on the intermediate sheet, and scraping off the composition using a blade. And filling the composition into a recess formed between one of the high-concentration part and the low-concentration part arranged in parallel on the material layer.

  The invention according to claim 8 is a surface light source device including a light source and the optical sheet according to any one of claims 1 to 6 disposed on the viewer side from the light source.

  A ninth aspect of the present invention is a display device comprising: a video source; and the optical sheet according to any one of the first to sixth aspects, which is disposed closer to the viewer than the video source.

  According to the present invention, an optical sheet that can anisotropically diffuse light, is easy to manufacture, and can easily adjust diffusion characteristics, and a surface light source device and a display device including the optical sheet are provided. can do.

3 is a cross-sectional view in the thickness direction schematically showing the layer configuration of the optical sheet 10. FIG. 3 is an enlarged vertical sectional view showing a part of a light diffusion layer 12. FIG. 3 is a horizontal cross-sectional view of a high concentration portion 13. FIG. It is thickness direction sectional drawing which showed the layer structure of optical sheet 10 'roughly. 2 is a cross-sectional view in the thickness direction schematically showing the layer configuration of the optical sheet 20. FIG. It is the schematic which looked at the optical sheet 20 from the front (sheet surface normal line direction). 3 is an exploded perspective view schematically showing the display device 100. FIG.

  The above-described operation and gain of the present invention will be clarified from embodiments for carrying out the invention described below. Hereinafter, the present invention will be described based on embodiments shown in the drawings.

<Optical sheet>
The optical sheet of the present invention includes a light diffusion layer that diffuses transmitted light. FIG. 1 is a cross-sectional view in the thickness direction schematically showing the layer structure of an optical sheet 10 which is an embodiment of the optical sheet of the present invention. In the following description, the vertical direction in FIG. 1 is the vertical direction, and the back / near direction is the horizontal direction. In FIG. 1, for ease of viewing, some of the repeated symbols are omitted (the same applies to the following drawings).

  The optical sheet 10 is a laminated sheet having a base material layer 11 and a light diffusion layer 12. Each layer will be described below.

  The base material layer 11 is a layer that becomes a base material for forming the light diffusion layer 12 described in detail later. The main component of the material which comprises the base material layer 11 will not be specifically limited if it has translucency. The “main component” means a component that is contained in an amount of 50% by mass or more based on the entire material constituting the layer (the same applies hereinafter). Examples of the main component of the material constituting the base material layer 11 include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol copolymer, terephthalic acid-cyclohexanedimethanol-ethylene. Polyester resins such as glycol copolymers, polyamide resins such as nylon 6, polyolefin resins such as polypropylene and polymethylpentene, acrylic resins such as polymethyl methacrylate, styrene resins such as polystyrene and styrene-acrylonitrile copolymers Examples thereof include a resin, a cellulose resin such as triacetyl cellulose, an imide resin, and a polycarbonate resin. Among these, polycarbonate resin is preferable from the viewpoints of availability, cost, adhesion with ionizing radiation curable resin, and the like. In addition to the main components, other resins and various additives may be appropriately added to the resin constituting the base material layer 11. Examples of general additives include phenol-based antioxidants, lactone-based stabilizers, and the like. Moreover, you may add well-known additives, such as a ultraviolet absorber, a filler, a plasticizer, an antistatic agent, in these resins suitably as needed.

  Although the thickness of the base material layer 11 is not specifically limited, It is preferable that they are 50 micrometers or more and 200 micrometers or less, and it is more preferable that they are 75 micrometers or more and 125 micrometers or less.

  The light diffusion layer 12 includes a diffusing agent, and a high concentration portion 13 having a relatively high concentration of the diffusing agent and a low concentration portion 14 having a relatively low concentration of the diffusing agent along one direction parallel to the sheet surface. Are alternately arranged in parallel. The high concentration portion 13 and the low concentration portion 14 are configured to be able to diffuse the reached light. The light diffusion layer 12 has the cross section shown in FIG. 1 and extends to the back / near side of the drawing. That is, the high concentration portion 13 and the low concentration portion 14 are arranged so as to extend in one direction along the sheet surface with the cross section shown in FIG. 1, and along the sheet surface in a direction different from the one direction. A plurality of high concentration portions 13 are arranged. The low concentration portion 14 is disposed between the high concentration portions 13. Details are as follows.

  As described above, the high concentration portions 13 are arranged in parallel in the direction along the sheet surface at a predetermined interval, and a concave portion (groove) having a trapezoidal cross section is formed between the high concentration portions 13. The recesses in the present embodiment are grooves having a trapezoidal cross section whose width becomes wider from the base material layer 11 side to the opposite side in the cross section (sheet thickness direction cross section) shown in FIG. The low concentration part 14 is formed by filling the material constituting the part 14. Therefore, the low concentration portion 14 also has a trapezoidal cross section along the recess.

Of the trapezoidal cross section of the low concentration portion 14, the angle θ ₁ (see FIG. 1) of the hypotenuse constituting the leg portion with respect to the sheet surface normal is preferably 0 ° or more and 20 ° or less. The angle θ ₁ with respect to the sheet surface normal is less than 0 ° (in this embodiment, θ ₁ is negative means that in the cross section shown in FIG. 1, the side opposite to the width of the bottom of the base layer 11 side of the low concentration portion 14 If the low-concentration portion 14 is formed so that the bottom width of the mold becomes short, the mold used for forming the high-concentration portion 13 becomes difficult to manufacture. However, the mold release property of the molded material is deteriorated. On the other hand, if θ ₁ is too large, a desired effect described later by the light diffusion layer 12 may be reduced.

However, in the present invention, the shapes of the high concentration portion and the low concentration portion are not limited to the form illustrated in FIG. In the light diffusion layer, the high concentration portion and the low concentration portion may be formed alternately along one direction parallel to the sheet surface. Accordingly, in the cross section corresponding to the cross section shown in FIG. 1, the high concentration portion and the low concentration portion may be rectangular (when θ ₁ = 0 °), and the portion corresponding to the trapezoidal leg portion of the low concentration portion. Is curved (the tangent of the curve is preferably 0 ° or more and 20 ° or less similarly to θ _{1 in} each part) or broken line (each line constituting the broken line is 0 ° or more and 20 similarly to θ ₁ described above) It is preferable that the angle is less than or equal to °.

  In addition, it is preferable to have the base part 13a comprised with the material same as the high concentration part 13 between the low concentration part 14 and the base material layer 11. FIG. Assuming that the base portion 13a is not provided, that is, the low-concentration portion 14 is in contact with the base material layer 11, when the high-concentration portion 13 is formed using a mold as described later, There is a possibility that the adhesion between the layer 11 and the light diffusing layer 12 is deteriorated or the appearance of the optical sheet 10 is deteriorated.

  The pitch at which the high concentration portion 13 and the low concentration portion 14 are arranged in parallel is not particularly limited, but is preferably 10 μm or more and 200 μm or less. If the pitch is too narrow, processing becomes difficult because of the fine shape. On the other hand, if the pitch is too wide, the releasability of the material tends to decrease when the high-concentration portion 13 is molded with a mold.

  Of the trapezoidal cross section of the low concentration portion 14, the width opposite to the base material layer 11 (width of the opening of the groove between the high concentration portions 13) is not particularly limited, but is preferably 5 μm or more and 150 μm or less. If this width is too narrow, it becomes a fine shape, making processing difficult. On the other hand, if this width is too wide, the releasability of the material tends to decrease when the high-concentration portion 13 is formed with a mold.

  In the parallel direction of the high concentration portion 13 and the low concentration portion 14, the size of the high concentration portion 13 is preferably larger than the size of the low concentration portion 14. By making the size of the high concentration portion 13 larger than the size of the low concentration portion 14 in the parallel direction of the high concentration portion 13 and the low concentration portion 14, the transmitted light is diffused in the parallel direction of the high concentration portion 13 and the low concentration portion 14. The range in which the transmitted light is diffused in the direction in which the high concentration portion 13 and the low concentration portion 14 extend is easily narrowed. For example, when the parallel direction of the high density portion 13 and the low density portion 14 is the vertical direction of the display device, the vertical viewing angle is relatively narrow with respect to the horizontal direction, and the horizontal viewing angle is set to the vertical direction. On the other hand, since it can be made relatively wide, it is possible to distribute light within a practically necessary range for a general display device.

  As the material constituting the high-concentration portion 13 and the low-concentration portion 14, a material that diffuses while transmitting light can also be used. As such a material, a material obtained by mixing a transparent curable resin (hereinafter sometimes referred to as “binder”) and a transparent diffusing agent having a refractive index different from that of the curable resin is preferable.

  Moreover, as said curable resin, the photocurable resin composition which mix | blended the reactive dilution monomer (M1) and the photoinitiator (I1) with the photocurable prepolymer (P1) can be used, for example.

  Examples of the photocurable prepolymer (P1) include epoxy acrylate-based, urethane acrylate-based, polyether acrylate-based, polyester acrylate-based, and polythiol-based prepolymers.

  Examples of the reactive dilution monomer (M1) include vinyl pyrrolidone, 2-ethylhexyl acrylate, β-hydroxy acrylate, and tetrahydrofurfuryl acrylate.

  Examples of the photopolymerization initiator (I1) include hydroxybenzoyl compounds (2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, benzoin alkyl ether, etc.), benzoyl Formate compounds (such as methylbenzoylformate), thioxanthone compounds (such as isopropylthioxanthone), benzophenone compounds (such as benzophenone), phosphate compounds (1,3,5-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6) -Trimethylbenzoyl) -phenylphosphine oxide, etc.), benzyldimethyl ketal and the like. Among these, the irradiation device for curing the photocurable resin composition and the curability of the photocurable resin composition can be arbitrarily selected. From the viewpoint of preventing coloring of the light transmitting portion 116, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone and bis (2,4,6-trimethylbenzoyl) are preferable. ) -Phenylphosphine oxide.

  These photocurable prepolymer (P1), reactive diluent monomer (M1) and photopolymerization initiator (I1) can be used alone or in combination of two or more.

  Examples of the diffusing agent include crosslinked particles obtained by polymerizing monomers mainly composed of (meth) acrylic acid ester and styrene. Specific examples of the cross-linked particles include Gantz Pearl manufactured by Gantz Kasei Co., Ltd. The cross-linked particles can be controlled in refractive index by changing the mixing ratio of acrylic acid ester and styrene. For example, the refractive index can be made about 1.49 by increasing the acrylic ratio, and the refractive index can be made about 1.59 by increasing the styrene ratio. Also, urethane cross-linked particles can be used as the diffusing agent. Specific examples of the urethane crosslinked particles include Art Pearl manufactured by Negami Kogyo Co., Ltd. The diffusing agent can also be made into hollow particles.

  The ratio of the diffusing agent in the material constituting the high concentration part 13 is preferably 10 parts by mass or more and 30 parts by mass or less with 100 parts by mass of the binder used for the high concentration part 13. If the amount is less than 10 parts by mass, desired diffusion characteristics may not be obtained. If the amount exceeds 30 parts by mass, the diffusing agent may not be sufficiently dispersed in the material constituting the high concentration part 13.

  The proportion of the diffusing agent in the material constituting the low concentration portion 14 is desirably 50% or less of the same proportion in the high concentration portion 13. For example, when the proportion of the diffusing agent in the material constituting the high concentration part 13 is 30 parts by mass with 100 parts by mass of the binder used for the high concentration part 13, the diffusion occupied in the material constituting the low concentration part 14 The ratio of the agent is desirably 15 parts by mass or less based on 100 parts by mass of the binder used for the low concentration part 14. When the proportion of the diffusing agent in the material constituting the low concentration portion 14 exceeds 50% of the same proportion in the high concentration portion 13, the concentration difference of the diffusing agent between the high concentration portion 13 and the low concentration portion 14 is insufficient, There is a possibility that the light is hardly diffused anisotropically.

  In order to diffuse light anisotropically by the light diffusion layer 12, it is sufficient if there is a difference in the degree of light diffusion between the high concentration portion 13 and the low concentration portion 14. From this point of view, for example, the binder and / or diffusing agent used in the high concentration portion 13 may be different from the binder and / or diffusing agent used in the low concentration portion 14. That is, the high-concentration part only needs to be configured to have a greater degree of light diffusion than the low-concentration part. As a specific means, the high-concentration part and the low-concentration part include a binder and a diffusing agent. The refractive index difference between the two and the diffusing agent may be changed. For example, increasing the refractive index difference between the binder and the diffusing agent makes it easier to diffuse light. Therefore, the refractive index difference between the binder and the diffusing agent may be increased in the high concentration portion than in the low concentration portion. Also, by making the shape of the diffusing agent contained in the high concentration part more complicated than that of the diffusing agent contained in the low concentration part, the high concentration part can diffuse light more easily than the low concentration part. May be.

  Although the thickness of the light-diffusion layer 12 is not specifically limited, It is preferable that they are 10 micrometers or more and 200 micrometers or less. If the light diffusion layer 12 is too thin, there is a possibility that problems such as difficulty in processing the low concentration portion 14 may occur. On the other hand, if the light diffusing layer 12 is too thick, the production of a mold for forming the recesses between the high-concentration parts 13 and the releasability of the material from the mold are lowered, and the productivity may be deteriorated.

  Next, the path of light passing through the light diffusion layer 12 will be described. 2 and 3 schematically show examples of optical paths. FIG. 2 is an enlarged vertical sectional view showing a part of the light diffusion layer 12. FIG. 3 is a horizontal cross-sectional view of the high concentration portion 13 shown in FIG. The optical path examples shown in FIGS. 2 and 3 are conceptually shown, and do not strictly represent the degree of refraction and reflection.

  First, the light path in the vertical plane will be described with reference to FIG. The light path example L1 illustrated in FIG. 2 is light incident perpendicularly to the layer surface of the light diffusion layer 12. The optical path examples L <b> 2 and L <b> 3 are light obliquely incident on the layer surface of the light diffusion layer 12. L1 passes only through the high concentration portion 13 in the light diffusion layer 12, whereas L2 and L3 pass through the low concentration portion 14 in the light diffusion layer 12 as well. Since the low-concentration part 14 has a smaller amount of diffusing agent than the high-concentration part 13, the light transmitted through the low-concentration part 14 has a narrower range of diffusion than the light transmitted through the high-concentration part 13. Therefore, the range in which L2 and L3 passing through the low concentration portion 14 are diffused becomes narrow. In this way, it is possible to make light difficult to diffuse in the vertical direction (the parallel direction of the high concentration portion 13 and the low concentration portion 14).

  Next, the path of light in the horizontal plane will be described with reference to FIG. The light path example L4 illustrated in FIG. 2 is light that is incident perpendicularly to the layer surface of the light diffusion layer 12. The optical path examples L5 and L6 are light incident obliquely on the layer surface of the light diffusion layer 12. L4 passes through the high concentration portion 13 at the shortest distance, while L5 and L6 pass through the high concentration portion 13 at a distance longer than L4. Therefore, L5 and L6 are diffused with respect to L4. It becomes easy to be done. In this way, light can be easily diffused in the horizontal direction (the direction in which the high concentration portion 13 and the low concentration portion 14 extend).

  As described above, the light diffusing layer 12 is a range in which light transmitted in the direction in which the high concentration portion 13 and the low concentration portion 14 extend is diffused in the parallel direction of the high concentration portion 13 and the low concentration portion 14. In the direction in which the high concentration portion 13 and the low concentration portion 14 extend, the range in which the transmitted light is diffused relative to the parallel direction of the high concentration portion 13 and the low concentration portion 14 is relatively wide. can do. That is, light can be diffused anisotropically. In addition, according to the light diffusion layer 12, the diffusion characteristics can be adjusted by changing the width of the high-concentration part 13 and the low-concentration part 14 and the content of the diffusing agent. Therefore, according to the optical sheet 10 provided with the light diffusion layer 12, light can be anisotropically diffused, and the adjustment of the diffusion characteristics is easy. Furthermore, as will be described below, the optical sheet 10 can be easily manufactured.

  A method for manufacturing the optical sheet 10 will be described below.

  The light diffusion layer 12 can be formed by a method using a mold roll. That is, a mold roll is prepared in which irregularities capable of transferring the shape of the high concentration portion 13 of the light diffusion layer 12 are provided on the outer peripheral surface of the cylindrical roll. And the base material used as the base material layer 11 is inserted between a die roll and the nip roll arrange | positioned so as to oppose this. The mold roll and the nip roll are rotated while supplying the composition constituting the high-concentration part 13 between the base material and the mold roll. Thereby, the composition which comprises the high concentration part 13 is filled in the uneven part of the unevenness | corrugation formed in the surface of a metal mold | die roll, and this composition becomes what follows the uneven | corrugated surface shape of a metal mold | die roll.

  Light is irradiated from the base material side by a light irradiation device to the composition constituting the high concentration portion 13 sandwiched between the mold roll and the base material and filled therein. Thereby, the composition which comprises the high concentration part 13 can be hardened, and the shape can be fixed. And the base material layer 11 and the shape | molded high concentration part 13 are released from a metal mold | die roll with a mold release roll.

Next, the low concentration portion 14 can be formed by filling the concave portion formed between the high concentration portions 13 with the composition constituting the low concentration portion 14 and curing the composition. Specifically, the composition constituting the low-concentration portion 14 is excessively supplied to the recess, and the excess composition is scraped off by squeezing with a blade, and the recess is filled with the composition. An appropriate curing method is applied to the composition thus filled to cure the curable resin, and the low-concentration portion 14 can be formed.
As described above, the optical sheet 10 can be easily manufactured.

  Next, another embodiment of the optical sheet of the present invention will be described. FIG. 4 is a view for explaining the optical sheet 10 ′ according to the second embodiment, and is a view corresponding to FIG. 1 of the optical sheet 10 ′. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

  The optical sheet 10 ′ is different from the optical sheet 10 in that the optical sheet 10 ′ has a base portion 15 on the side opposite to the side where the base material layer 11 of the light diffusion layer 12 is provided. The optical sheet 10 and the optical sheet 10 'are the same in other respects.

  The covering layer 15 is provided for the purpose described below. When forming the low-concentration part 14 as described above, the excess of the composition constituting the low-concentration part 14 is squeezed with a blade or contracted when the composition is cured, thereby reducing the low concentration. The side opposite to the base material layer 11 of the portion 14 may be slightly depressed. The covering layer 15 is a layer provided in order to fill the depression of the low concentration portion 14 formed as described above or to prevent the depression. By making the surface of the coating layer 15 opposite to the light diffusing layer 12 a smooth surface, the appearance of the optical sheet 10 can be improved and unintended diffusion of transmitted light can be suppressed.

  A method for forming the coating layer 15 will be described below. As a method of forming the coating layer 15, for example, the following two methods are conceivable.

  In the first method, first, as described in the description of the manufacturing method of the optical sheet 10, a high density part 13 and a low density part 14 are formed, and a laminated sheet having a base material layer 11 and a light diffusion layer 12 is formed. create. Next, the composition (for example, the same composition as the composition which comprises the low concentration part 14) which comprises the coating layer 15 is supplied to the surface side opposite to the base material layer 11 of the said lamination sheet, and the surface is a mirror surface. The coating layer 15 can be formed by curing the composition while pressing the composition with the roll, and then pressing the composition.

  In the second method, first, the high concentration portion 13 is formed as described in the description of the method of manufacturing the optical sheet 10. Thereafter, the composition constituting the low-concentration part 14 is excessively supplied onto the high-concentration part 13, and the composition is cured after pressing the composition with a roll having a mirror surface. In this manner, the low concentration portion 14 can be formed, and the coating layer 15 integrated with the low concentration portion 14 can be formed using the same material as the low concentration portion 14. According to the second method, the coating layer 15 is formed with fewer steps than the first method and without the equipment for squeezing the composition constituting the low concentration portion 14 supplied in excess. can do.

  Next, a third embodiment of the optical sheet of the present invention will be described. FIG. 5 is a diagram schematically showing the layer structure of the optical sheet 20 according to the third embodiment.

  The optical sheet 20 includes a base material layer 11 (hereinafter sometimes referred to as “first base material layer 11”) and a light diffusion layer 12 (hereinafter sometimes referred to as “first light diffusion layer 12”). The pressure-sensitive adhesive layer 25, the base material layer 21 (hereinafter sometimes referred to as "second base material layer 21") and the light diffusion layer 22 (hereinafter referred to as "second light diffusion layer 22"). ). Since the 1st light-diffusion layer 12 and the 1st base material layer 11 are the same as that of the optical sheet 10 mentioned above, description is abbreviate | omitted.

  The second base material layer 21 has the same configuration as the first base material layer 11, and the second light diffusion layer 22 has the same configuration as the first light diffusion layer 12. The high-concentration portion 23 and the low-concentration portion 24 of the light diffusion layer 22 (only the high-concentration portion 23 appears in FIG. 5 but the low-concentration portion 24 does not appear) are the high-concentration portion 13 of the first light diffusion layer 12. In addition, they are arranged in a direction orthogonal to the low concentration portion 14. FIG. 6 shows the relationship between the low concentration portion 14 of the first light diffusion layer 12 and the low concentration portion 24 of the second light diffusion layer 22. FIG. 6 is a schematic view of the optical sheet 20 as viewed from the front (sheet surface normal direction).

  The pressure-sensitive adhesive layer 25 is a layer for bonding the first light diffusion layer 12 and the second base material layer 21. The material constituting the pressure-sensitive adhesive layer 25 is not particularly limited as long as the first light diffusion layer 12 and the second base material layer 21 can be bonded to each other, and known pressure-sensitive adhesives, adhesives, and photocuring properties are used. A resin, a thermosetting resin, or the like can be used. As a material constituting the pressure-sensitive adhesive layer 25, for example, an acrylic pressure-sensitive adhesive can be used, and more specifically, a pressure-sensitive adhesive combining an acrylic copolymer and an isocyanate compound can be used. However, the material constituting the pressure-sensitive adhesive layer 25 is preferably excellent in translucency and weather resistance due to the properties of the optical sheet 20.

  Although the thickness of the adhesive layer 25 is not specifically limited, It is preferable that they are 10 micrometers or more and 100 micrometers or less. By making the thickness of the pressure-sensitive adhesive layer 25 in the above range, it is easy to ensure the adhesion between the first base material layer 11 and the second light diffusion layer 22 while making the thickness of the pressure-sensitive adhesive layer 25 uniform. Become.

  In the first light diffusion layer 12 and the second light diffusion layer 22, the transmitted light is diffused in the direction in which the high concentration portion and the low concentration portion extend in the parallel direction of the high concentration portion and the low concentration portion, respectively. The range in which the transmitted light is diffused in the direction in which the high concentration portion and the low concentration portion extend is relatively wide in the direction in which the high concentration portion and the low concentration portion extend. it can. That is, the first light diffusion layer 12 and the second light diffusion layer 22 can each distribute light in a necessary direction. According to the optical sheet 20 provided with the first light diffusion layer 12 and the second light diffusion layer 22 as described above so that the parallel directions of the high concentration portion and the low concentration portion intersect in a plan view, A direction in which the high concentration portion 13 and the low concentration portion 14 of the first light diffusion layer 12 extend and the second light while suppressing a decrease in front luminance of the light source when being bonded to the observer side. It is considered that the viewing angle can be expanded in the direction in which the high concentration portion 23 and the low concentration portion 24 of the diffusion layer 22 extend (for example, the vertical direction and the horizontal direction).

  The optical sheet 20 is prepared by producing a laminated sheet including the first base material layer 11 and the first light diffusion layer 12 by the same method as the optical sheet 10 described above, and then the second sheet via the pressure-sensitive adhesive layer 25. It can manufacture by bonding the laminated sheet in which the 2nd light-diffusion layer 22 was formed in the one surface side of the base material layer 21. FIG. The second light diffusion layer 22 can be formed in the same manner as the first light diffusion layer 12. The pressure-sensitive adhesive layer 25 is formed on the other surface side of the first base material layer 11 before forming the first light diffusion layer 12 on the one surface side of the first base material layer 11. Alternatively, the first light diffusion layer 12 and the second base material layer 21 may be formed on the surface of the first light diffusion layer 12 or the second base material layer 21 when the first light diffusion layer 12 and the second base material layer 21 are bonded together. When the pressure-sensitive adhesive layer 25 is made of an ultraviolet curable resin or the like, the first light diffusion layer 12 and the second base material layer 21 are laminated through the pressure-sensitive adhesive layer 25 and then cured by irradiation with ultraviolet light or the like. You can do it.

  In the description of the optical sheet 20 so far, as shown in FIG. 6, in the front view of the optical sheet, the low concentration portion of the first light diffusion layer and the low concentration portion of the second light diffusion layer are respectively The embodiment in which the optical sheet is arranged in parallel with any one of the four sides has been described as an example. However, the present invention is not limited to such a form, and the low concentration portion of the first light diffusion layer and the low concentration portion of the second light diffusion layer are respectively in four sides of the optical sheet in the front view of the optical sheet. It may be arranged in parallel in an inclined direction. At this time, the crossing angle between the low concentration portion of the first light diffusion layer and the low concentration portion of the second light diffusion layer when the optical sheet is viewed from the front is not particularly limited. Or less, more preferably 90 °.

  Further, in the description of the optical sheet 20 thus far, the embodiment in which the first and second light diffusion layers and the second light diffusion layer are arranged so that the front and back surfaces thereof are in the same direction has been described as an example. The form is not limited, and either or both of the first light diffusing layer and the second light diffusing layer may be opposite to the illustrated form.

  In addition, in the explanation of the optical sheet of the present invention so far, an example in which a high concentration portion is formed on a base material layer and then a low concentration portion is formed in a recess (groove) between the high concentration portions is exemplified. Although described, the present invention is not limited to such a form. A portion corresponding to the high concentration portion of the embodiment exemplified so far can be a low concentration portion, and a portion corresponding to the low concentration portion of the embodiment exemplified so far can be a high concentration portion.

  Moreover, in the description of the optical sheet of the present invention so far, the embodiment in which the light diffusion layer is formed on the base material layer has been described as an example, but the present invention is not limited to such a form. The light diffusing layer can also be produced by alternately laminating the sheet constituting the high density part and the sheet constituting the low density part without using the base material layer and then cutting in the laminating direction.

<Surface light source device>
Next, the surface light source device of the present invention will be described. The optical sheet of the present invention described above can be applied to a surface light source device used for a liquid crystal display device or the like.

  The surface light source device of the present invention includes a light source and the above-described optical sheet of the present invention. As the light source, a backlight used in a normal surface light source device can be used. This includes, for example, a form in which light emitting sources are arranged substantially uniformly in a plane to form a planar light source, or a light emitting source is arranged on an edge and a reflecting surface is used to finally form a planar shape. Examples include an edge input type that emits light. In addition, the surface light source device of the present invention includes other members provided in a normal surface light source device. Examples of the other members include a diffusion sheet that transmits and diffuses light from a light source, and a prism sheet that increases front luminance.

<Display device>
Next, the display device of the present invention will be described. The optical sheet of the present invention described above can be applied to a display device. The display device exemplified below includes a video source and the optical sheet described above. Examples of the video source include a liquid crystal display and a PDP provided with the surface light source device. A display device can be configured by bonding the above-described optical sheet to the image light output side of the image source via an adhesive layer or the like.

  FIG. 7 is an exploded perspective view schematically showing a plasma television 100 which is a display device according to one embodiment. In FIG. 7, the upper right side of the drawing shows the observer side, and the lower left side of the drawing shows the back side. As can be seen from FIG. 7, the plasma television 100 includes a PDP unit 101 that is a video source unit inside a casing formed by a front casing 103 and a rear casing 102. The PDP unit 101 includes a PDP and an optical sheet from the back side of the plasma television 100 toward the viewer side, and the optical sheet is bonded to the PDP with an adhesive layer.

  The PDP is a plasma display panel that is a flat image source, and a plasma display panel that is used for a normal plasma television can be applied as it is. Accordingly, like a normal PDP, pixels each having three primary color phosphors as one unit are arranged in parallel vertically and horizontally, and an electrode for causing gas discharge to emit light is provided.

  When the optical sheet is arranged on the viewer side of the display device as described above, the optical sheet includes an antiglare layer, an antireflection layer, a hard coat layer, an antistatic layer, a polarizing filter layer, an antifouling layer, and the like. Preferably it is.

The anti-glare layer is a layer having a function capable of preventing glare when an observer looks at the screen, and is also referred to as an AG layer. An anti-glare layer can be comprised by the glare-proof film which can be normally obtained, for example.
The antireflection layer is a so-called anti-reflection layer and is also referred to as an AR layer. A film having a function capable of preventing reflection is disposed.
The hard coat layer is also called an HC layer. This is a layer in which a film having a function capable of imparting scratch resistance is provided in order to prevent the image display surface from being scratched.
The antistatic layer is also referred to as an antistatic (AS) layer. This is a layer in which a film having a function capable of preventing charging, that is, preventing static electricity from being charged, is disposed. A commonly available AS film can be applied to this.
The antifouling layer is a layer in which a film having a function capable of preventing the screen surface from being stained is disposed.
The polarizing filter layer is the same as the polarizing filter described above. You may arrange here as needed.

  In addition to the PDP unit 101, the plasma television 100 is provided with usual devices included in the plasma television. Examples thereof include various electric circuits and cooling means.

  Here, a plasma television is exemplified as the display device of the present invention. For example, a liquid crystal display (LCD), an electroluminescence display (FED), and a surface conduction electron-emitting device display (SED), which are generally known as video sources. Organic EL or the like can also be used.

  While the present invention has been described in connection with the most practical and preferred embodiments at the present time, the invention is not limited to the embodiments disclosed herein, but is claimed. The optical sheet, the surface light source device, and the display device with such changes are also included in the technical scope of the present invention. Must be understood as being.

10, 10 'optical sheet 11 base material layer (1st base material layer)
12 Light diffusion layer (first light diffusion layer)
13 High-concentration part 13a Base part 14 Low-concentration part 15 Coating layer 20 Optical sheet 21 Base material layer (second base material layer)
22 Light diffusion layer (second light diffusion layer)
23 High-concentration part 24 Low-concentration part 25 Adhesive layer 100 Plasma television (display device)

Claims (9)

An optical sheet having a light diffusion layer for diffusing transmitted light,
The light diffusing layer includes a diffusing agent that diffuses light, and a high concentration portion where the concentration of the diffusing agent is relatively high and the concentration of the diffusing agent are relative to each other along one direction parallel to the sheet surface. An optical sheet in which low density parts having a low density are alternately arranged in parallel.   The optical sheet according to claim 1, wherein a size of the high density portion is larger than a size of the low density portion in a parallel direction of the high density portion and the low density portion. The light diffusion layer is formed on one surface side of the base material layer,
One of the high concentration portion and the low concentration portion is formed to have a plurality of parallel grooves on the base material layer, and the other of the high concentration portion and the low concentration portion is formed in the groove. The optical sheet according to claim 1 or 2.   The optical sheet according to claim 3, wherein a coating layer having a smooth surface is formed on the side of the light diffusion layer opposite to the side on which the base material layer is provided so as to cover the light diffusion layer. Having two light diffusion layers;
The two layers are arranged such that the parallel direction of the high concentration part of one light diffusion layer and the parallel direction of the high concentration part of the other light diffusion layer intersect when viewed from the normal direction of the sheet surface. The optical sheet according to claim 1, wherein a light diffusion layer is laminated.   The parallel direction of the high concentration part of the one light diffusion layer and the parallel direction of the high concentration part of the other light diffusion layer are orthogonal to each other as viewed from the normal direction of the sheet surface. The optical sheet described. A method for producing an optical sheet according to any one of claims 1 to 6,
Producing an intermediate sheet in which one of the high-concentration part and the low-concentration part is arranged on the base material layer at a predetermined interval;
On the intermediate sheet, the composition to be the other of the high-concentration part and the low-concentration part was supplied excessively, and the composition was scraped off using a blade, and arranged in parallel on the base material layer. Filling the concave portion formed between one of the high-concentration portion and the low-concentration portion with the composition.   A surface light source device comprising: a light source; and the optical sheet according to claim 1 disposed on the viewer side with respect to the light source.   A display device comprising: an image source; and the optical sheet according to claim 1 disposed on an observer side of the image source.

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