JP2008242295A - Optical sheet, surface light source device, transmissive display device - Google Patents

Abstract

An optical sheet that is less likely to damage other optical sheets when stacked with other optical sheets, is easy to mold with a mold, and is unlikely to generate Newton rings, and a surface light source device including the optical sheet, A transmissive display device is provided.
In a light control sheet 15 having a lens shape in which a plurality of unit optical shapes 151 are arranged on the emission side, the vicinity of the apex T of the unit optical shape 151 is a rough surface 151a. The rough surface 151a has a fine convex shape formed by protruding a part of the diffusing material d having a fine particle shape. By adopting such a shape, it was possible to realize an optical sheet that is difficult to damage other optical sheets even when stacked with other optical sheets, is easy to mold with a mold, and hardly causes Newton rings.
[Selection] Figure 3

Description

  The present invention relates to an optical sheet formed by arranging a plurality of unit optical shapes on at least one surface, a surface light source device including the optical sheet, and a transmissive display device.

Conventionally, as an optical sheet used for a surface light source device or the like, there is one in which a plurality of unit optical shapes having a function of converging and diffusing light are arranged. As an example of such an optical sheet, a transparent film having a plurality of triangular prisms as disclosed in Patent Document 1 is known.
However, in the optical sheet in which a plurality of unit optical shapes are arranged as in the transparent film of Patent Document 1, when the unit is overlapped with another optical sheet and incorporated into a surface light source device or the like, the apex portion of the convex shape of the unit optical shape For example, there is a problem in that other stacked optical sheets are damaged.
In addition, when such an optical sheet is manufactured by extrusion molding, when the resin as a material adheres to the concave portion of the mold for shaping the unit optical shape, it is removed from the mold. In addition, there are problems that the unit optical shape is deformed, and the unit optical shape that is in close contact with the mold is released with a strong force, resulting in white line marks and the like.

Furthermore, in order to prevent scratches, Newton rings occur when a surface light source device is formed by laminating an optical sheet in which a plurality of unit optical shapes are arranged with a slight gap between other optical sheets. There was a problem that it was easy to do.
JP-A-63-318003

  An object of the present invention is to prevent damage to other optical sheets even when they are overlapped with other optical sheets, and to easily mold with a mold, and to prevent Newton rings from occurring, and a surface provided with the same A light source device and a transmissive display device are provided.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.
The invention of claim 1 is an optical sheet in which a plurality of unit optical shapes (151) are arranged on at least one surface, wherein the unit optical shape is a convex shape, and the vicinity of the apex (T) is a rough surface ( 151a) is an optical sheet (15).
According to a second aspect of the present invention, in the optical sheet according to the first aspect, the unit optical shape (151) is a plane side (151D) in which the cross-sectional shape in a cross section parallel to the normal line of the sheet surface is formed by a straight line. ) And a curved surface side (151U) formed by a curve, the optical sheet (15) is characterized in that it has an asymmetric shape.
A third aspect of the present invention is the optical sheet according to the first or second aspect, wherein the rough surface (151a) is formed by projecting a part of minute particles (d). This is an optical sheet (15).
According to a fourth aspect of the present invention, in the optical sheet according to the third aspect, the difference between the refractive index of the particles (d) and the refractive index of the material forming the unit optical shape (151) is 0.01 or less. It is an optical sheet (15) characterized by being.
The invention according to claim 5 is the optical sheet according to claim 3 or claim 4, wherein the particles (d) are contained on the opposite side in the thickness direction to the portion where the unit optical shapes (151) are arranged in plural. It is an optical sheet (15) characterized by having a part (15a) which is not made.
The invention of claim 6 is the optical sheet according to any one of claims 1 to 5, wherein the optical sheet is formed using a thermoplastic resin. .
The invention of claim 7 is a surface light source device (12, 13, 14, 15) comprising the optical sheet (15) according to any one of claims 1 to 6 and a light source unit (13). 16).
The invention of claim 8 is a transmissive display device (10) comprising the surface light source device (12, 13, 14, 15, 16) of claim 7 and a transmissive display section (11).

According to the present invention, the following effects can be obtained.
(1) An optical sheet in which a plurality of unit optical shapes are arranged on at least one surface, the unit optical shape is a convex shape, and the vicinity of the apex is a rough surface. When shaping the resin, it is possible to prevent the material resin or the like from coming into close contact with the mold, and it can be easily released from the mold. Accordingly, it is possible to prevent the deformation of the unit optical shape, white line marks, etc. that are likely to occur when the mold is released with a strong force, and the manufacture is also easy. Furthermore, Newton rings can be prevented from occurring when used in a surface light source device or the like.

(2) The unit optical shape is an asymmetric shape in which the cross-sectional shape in a cross section parallel to the normal line of the sheet surface has a plane side formed by a straight line and a curved surface side formed by a curve. The effect of increasing the luminance and the effect of gradual change in luminance can be obtained.

(3) Since the rough surface is formed by protruding a part of minute particles, even when the surface is overlapped with another optical sheet when used in a surface light source device or the like, It is hard to be damaged. In addition, since the rough surface can be formed by utilizing the shrinkage of the resin when the resin is cured and by utilizing a part of the particles protruding, the rough surface can be easily formed. Furthermore, the conditions of the rough surface (roughness, area of the rough surface portion, etc.) can be easily adjusted by the addition amount of the particles, the particle size, and the like.

(4) Since the difference between the refractive index of the particle and the refractive index of the material forming the unit optical shape is 0.01 or less, it is possible to reduce the diffusion due to the particle and suppress the decrease in the front luminance due to the diffusion. it can.

(5) Since there is a portion that does not contain particles on the opposite side in the thickness direction to the portion where a plurality of unit optical shapes are arranged, the moire reduction effect can be achieved while suppressing a decrease in front luminance due to the diffusion action of the particles. The effect of preventing damage to other optical sheets and the effect of facilitating release from the mold can be obtained.

(6) Since it is formed using a thermoplastic resin, it can be molded easily.

(7) Since the surface light source device includes the optical sheet according to the present invention and a light source unit, Newton's rings are unlikely to occur and a good light source without uneven brightness can be obtained.

(8) Since the transmissive display device includes the surface light source device according to the present invention and a transmissive display unit, color unevenness, luminance unevenness, and the like due to Newton rings do not occur, and a good image can be displayed.

The present invention provides an optical sheet that is less likely to damage other optical sheets when stacked with other optical sheets, is easy to mold with a mold, and is unlikely to generate Newton rings, and a surface light source device including the same The object of providing a transmissive display device is realized by making the vicinity of the apex of the unit optical shape formed on the optical sheet a rough surface.

(Embodiment)
FIG. 1 is a diagram showing an embodiment of a transmissive display device according to the present invention.
In addition, each figure shown below including FIG. 1 is the figure shown typically, and the magnitude | size and shape of each part are exaggerated suitably for easy understanding.
The terms plate, sheet, film, etc. are used, but these are generally used in the order of thickness, plate, sheet, film, and so on in this specification. I am using it. However, since there is no technical meaning in this proper use, the description in the scope of claims is unified and used as a description of a sheet. Accordingly, the terms “sheet”, “plate”, and “film” can be appropriately replaced. For example, the light control sheet may be a light control plate or a light control film.
The transmissive display device 10 according to the present embodiment includes an LCD (Liquid Crystal Display) panel 11, a reflector 12, an arc tube 13, a milky white plate 14, a light control sheet 15, a light diffusion sheet 16, and the like, and is formed on the LCD panel 11. It is a device that displays video information that is illuminated from the back. As the surface light source device (backlight) for illuminating the LCD panel from the back, the reflecting plate 12, the arc tube 13, the milky white plate 14, the light control sheet 15, and the light diffusion sheet 16 are applicable.

The LCD panel 11 is a transmissive display unit formed by a transmissive liquid crystal display element. In this embodiment, the LCD panel 11 can display a 32 inch diagonal (420 mm × 740 mm) and 768 × 1280 dots. In the LCD panel 11, the direction along the longitudinal direction of the arc tube 13 is used as a horizontal direction, and the direction in which the arc tubes 13 are arranged is used as a vertical direction.
The arc tube 13 is a cold cathode tube of a line light source that forms a light source part of the surface light source device. In this embodiment, 18 tubes are arranged in parallel at regular intervals of approximately 20 mm. A reflector 12 is provided on the back side of the arc tube 13.
The reflector 12 is provided over the entire surface of the arc tube 13 opposite to the milky white plate 14 (back side), and diffuses and reflects the illumination light traveling toward the rear side toward the milky white plate 14 (outgoing direction). , It has a function to make the incident light illuminance uniform.

The milky white plate 14 has a non-directional light diffusing action and is provided on the emission side (observation surface side) of the arc tube 13.
The light control sheet 15 is an optical sheet in which a plurality of unit optical shapes 151 are arranged on the exit side surface. In the present embodiment, the light control sheet 15 is provided on the exit side of the milky white plate 14. Details of the shape and the like of the light control sheet 15 will be described later.

The light diffusion sheet 16 is a sheet-like member that is provided between the light control sheet 15 and the LCD panel 11 and has a light diffusing action in which a fine convex shape is formed on the exit side surface. 220 μm.
As the diffusion sheet, there are a type in which the surface of the transparent substrate film is coated with a diffusion material, a type in which the diffusion material is kneaded into the substrate, a type in which the surface is roughened, and a combination thereof. .
Among these, the light diffusion sheet 16 used in this embodiment is a type in which the surface of the transparent substrate film is coated with a diffusion material. Specifically, a diffusion layer obtained by kneading fine beads in a binder is coated on a 188 μm thick transparent base material layer (film). The diffusion layer has a fine convex shape formed on the surface thereof by causing fine beads to protrude from the binder. The light diffusing sheet 16 used in this embodiment is a light diffusing film BS-702 manufactured by Eiwa Co., Ltd., and the haze value is 89.2% (manufacturer catalog value).

A diffusion sheet having a surface coated with a diffusion material (microbeads) exhibits a lens effect because the round portion of the top of the microbeads protrudes. Therefore, when diffused light with a wide viewing angle is incident, it exhibits a light condensing effect, and when diffused light with a narrow viewing angle is incident, it exhibits a diffusing effect. Has a different characteristic action.
Further, since the diffusion material is dispersed and coated, it does not have a periodic structure and moiré does not occur.
Furthermore, it is possible to adjust the lens effect (light collection and diffusion effect) by changing the amount of the diffusing material coated on the surface. When the amount of the diffusing material is small, the density of the diffusing material is small, so that the scattering effect due to the rough surface becomes larger than the lens effect, and the condensing effect for the diffused light having a wide viewing angle becomes small.
The kneading type or the rough surface type diffusion sheet is different from the light diffusion sheet 16 of the present embodiment in that only the diffusion effect is exhibited not by the lens effect but by the scattering effect and the refraction effect.

FIG. 2 is an enlarged view of a part of a cross section obtained by cutting the light control sheet 15 of the present embodiment along the cross section taken along the arrow SS shown in FIG. 1. In addition, in FIG. 2, it has shown as arrangement | positioning similar to the case where a use condition is cut | disconnected, and has shown so that the left side in a figure may become an output side (observation surface side).
As described above, the light control sheet 15 is an optical sheet having a lens shape formed by arranging a plurality of unit optical shapes 151 on the surface on the emission side. In the present embodiment, a plurality of unit optical shapes 151 are arranged and arranged so that the longitudinal direction thereof is parallel to the direction (horizontal direction) along the longitudinal direction of the arc tube 13.

The light control sheet 15 is formed of only a thermoplastic resin and is the same resin as the thermoplastic resin that forms the first layer 15a and the first layer not containing the diffusion material, and the diffusion material is kneaded. The second layer 15b is formed by two-layer extrusion molding, and a unit optical shape 151 is formed by a mold on the surface of the second layer 15b. Accordingly, the cured light control sheet 15 is formed by two-layer extrusion molding, but since the thermoplastic resin as the base is the same resin, it is substantially a single layer, with or without a diffusing material, It can be divided into a first layer 15a and a second layer 15b.
In the present embodiment, the first layer 15a does not contain a diffusing material. However, the present invention is not limited to this, and the amount of the diffusing material contained in the second layer 15b is very small. If there is, it may contain a diffusing material.

In this embodiment, the light control sheet 15 uses an MS (methacrylstyrene: copolymer of acrylic resin and styrene resin) resin having a refractive index of 1.53 as the thermoplastic resin. The thermoplastic resin used for the light control sheet 15 is not limited to MS resin, but is polycarbonate, MBS (methyl methacrylate / butadiene / styrene), PMMA (polymethyl methacrylate), styrene, AS (acrylonitrile / styrene), ABS ( Other thermoplastic resins having optical transparency such as (acrylonitrile, butadiene, styrene) may be used.
The diffusing material used for the light control sheet 15 has a minute particle shape (microbeads), and has a refractive index difference of 0.01 from the material forming the unit optical shape 151 (the thermoplastic resin used for the light control sheet 15). It is as follows. In the present embodiment, the diffusing material is formed using MS resin, the average particle diameter is 12 μm, and the refractive index is 1.53.

In the light control sheet 15 of the present embodiment, the ratio of the thickness of the first layer 15a (the layer of MS resin not including the diffusing material) and the second layer 15b (the layer of MS resin including the diffusing material). Is about 8: 2. The amount of the diffusion material kneaded in the second layer 15b is 15 parts by weight when the MS resin forming the second layer 15b is 100 parts by weight.
In the present embodiment, an example of using a diffusing material made of MS resin having a refractive index of 1.53 and an average particle diameter of 12 μm as a diffusing material has been shown. Glass beads having an average particle diameter of 8 μm may be used. Further, diffusing materials having different average particle diameters may be mixed and used, or diffusing materials having different refractive indexes may be mixed and used.

The shape of the unit optical shape 151 will be described by dividing it into an upper upper shape 151U and a lower lower shape 151D with the vertex T as a reference.
The lower shape 151D has a width in a direction parallel to the sheet surface from the position A to the vertex T, that is, a width WD in the vertical direction in the cross section shown in FIG. 2 (a cross section in a direction parallel to the normal to the sheet surface). = 0.09 mm plane (plane side), formed at an angle of 46 degrees with respect to the sheet surface.
In the cross section shown in FIG. 2, the upper shape 151U has a position B at a position of 0.189 mm upward in parallel with the sheet surface from the position A, and a radius R = 0.195 mm passing through the position B and the apex T. The cylindrical surface (curved surface side). Therefore, the width WU in the vertical direction of the upper shape 151U is 0.099 mm.
The sheet surface indicates a surface in the planar direction of the sheet when viewed as the entire sheet, and is used as the same definition in the following description and in the claims.

FIG. 3 is an enlarged view of the vicinity of the apex T of the unit optical shape 151 of the present embodiment (region C shown in FIG. 2).
The vicinity of the vertex T of the unit optical shape 151 is a rough surface 151a. The rough surface 151a is a fine convex shape formed by protruding part of the diffusion material d kneaded in the MS resin used for the light control sheet 15.
The rough surface 151a near the apex T of the unit optical shape 151 is adjusted by appropriately adjusting the molding temperature and molding pressure of the MS resin in which the diffusion material d is kneaded when the light control sheet 15 is extruded. The MS resin is not filled up to the vicinity corresponding to the apex T of the mold forming the optical shape 151. As a result, in the vicinity of the apex T, a part of the diffusing material d kneaded in the MS resin is protruded, and the rough surface 151a is formed by curing in this state.

According to the present embodiment, the rough surface 151a formed by projecting a part of the diffusing material d is formed in the vicinity of the vertex T of the unit optical shape 151, so that the plurality of unit optical shapes 151 are arranged. When another optical sheet is arranged close to the side, the other optical sheet can be prevented from being damaged. In addition, when the light control sheet 15 is transported in the manufacturing process, the surface on which the unit optical shape 151 of the light control sheet 15 is provided may not be protected by using a protective film for preventing damage.
Further, when the unit optical shape 151 is shaped by the mold, a minute space is formed by a part of the diffusion material d protruding between the mold and the vicinity of the apex of the unit optical shape 151. Therefore, when releasing from the mold after shaping, it can be easily released, and when the unit optical shape is deformed due to the resin being in close contact with the mold or when it is released with a strong force It is possible to prevent white line marks and the like that are easily generated.

Furthermore, according to the present embodiment, the light emitted from the vicinity of the vertex T, which is the portion where the light emission side of the light control sheet 15 is closest to the other optical sheet (in this embodiment, the light diffusion sheet 16), is diffused material d. The emission direction is diffused by. Further, the light reflected from the incident-side surface of the light control sheet 15 and returning to the vicinity of the vertex T is diffusely reflected by the rough surface 151a.
Therefore, even when another optical sheet such as the light diffusing sheet 16 is arranged close to the unit optical shape 151 side, Newton rings generated by interference of light reflected between two adjacent surfaces are prevented. It is possible to provide a surface light source device and a transmissive display device that are less prone to display defects such as luminance unevenness due to Newton rings, and can be easily manufactured.

(Deformation)
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the scope of the present invention.
(1) In this embodiment, the light control sheet 15 shows an example in which a plurality of one type of unit optical shapes 151 are arranged. However, the present invention is not limited to this, and for example, a plurality of types of unit optical shapes are arranged in combination. May be.

(2) In the present embodiment, the light control sheet 15 has a lens shape, and the unit optical shape 151 has an upper shape 151U and a lower shape 151D in the cross section parallel to the normal line of the sheet surface. Although the example which has an asymmetrical shape is shown, the unit optical shape is not limited to this, and the cross-sectional shape in a cross section parallel to the normal direction of the sheet surface may be symmetric. For example, the light control sheet may have a lenticular lens shape in which the unit optical shape is a partial shape of an elliptic cylinder. In addition, the unit optical shape is a unit prism shape whose cross-sectional shape in a cross section parallel to the normal line of the sheet surface is a substantially isosceles triangle shape, and a light control sheet having a prism shape in which a plurality of such unit prism shapes are arranged It is good. Furthermore, the light control sheet may be a sheet on which a lens array in which unit optical shapes are arranged in a two-dimensional direction (a so-called eyelet lens) is formed.

(3) In the present embodiment, an example in which the arc tube 13 that is a line light source is used as the light source unit of the surface light source device is shown. However, the present invention is not limited thereto, and for example, a plurality of point light sources such as LEDs (Light Emitting Diodes) are used. A lined light source unit may be used, or a light source unit that emits light such as organic EL (electroluminescence) or inorganic EL may be used.
It should be noted that the present embodiment and each modified embodiment can be used in appropriate combination, but detailed description thereof is omitted.

It is a figure which shows embodiment of the transmissive display apparatus by this invention. It is the figure which expanded and showed a part of cross section which cut | disconnected the light control sheet | seat 15 of embodiment by the arrow SS cross section shown in FIG. It is an enlarged view of the vertex T vicinity (area | region C shown in FIG. 2) of the unit optical shape 151 of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Transmission type display apparatus 11 LCD panel 12 Reflector 13 Light emission tube 14 Milky white board 15 Light control sheet 151 Unit optical shape 151a Rough surface 16 Light diffusion sheet T Vertex d Diffusion material

Claims (8)

An optical sheet in which a plurality of unit optical shapes are arranged on at least one surface,
The unit optical shape is a convex shape, and its apex is a rough surface,
An optical sheet characterized by The optical sheet according to claim 1,
The unit optical shape is an asymmetric shape in which a cross-sectional shape in a cross-section parallel to the normal line of the sheet surface has a flat surface formed by a straight line and a curved surface formed by a curve,
An optical sheet characterized by In the optical sheet according to claim 1 or 2,
The rough surface is formed such that a part of fine particles protrudes,
An optical sheet characterized by In the optical sheet according to claim 3,
The difference between the refractive index of the particles and the refractive index of the material forming the unit optical shape is 0.01 or less,
An optical sheet characterized by In the optical sheet according to claim 3 or claim 4,
On the opposite side in the thickness direction to the portion where the plurality of unit optical shapes are arranged, having a portion not containing the particles,
An optical sheet characterized by In the optical sheet according to any one of claims 1 to 5,
Formed using a thermoplastic resin,
An optical sheet characterized by The optical sheet according to any one of claims 1 to 6,
A light source unit;
A surface light source device comprising: A surface light source device according to claim 7;
A transmissive display;
A transmissive display device.

Images