JPH1031115A - Diffusion sheetless plane light emitting device and production of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffusion sheetless plane light emitting device and production of the same with which the luminance loss of light emitted from a light transmission plate is reduced and further uniform planar light emission can be provided. SOLUTION: While using a transfer sheet 3 forming a light scattering layer 2 having a gradation pattern composed of dots in the size smaller than 300μm and having the number of lines more than 85 on a base film 1 at least, the transfer sheet 3 is arranged inside an injection molding metal die 4 so that the side of the light scattering layer 2 can be turned toward a cavity. Then, after the metal die is closed, fused transparent resin is injected into the metal die, and a transparent light transmission plate 5 is formed. At the same time, the light scattering layer 2 is integrated on the rear surface of the light transmission plate 5, the base film 1 is released after cooling, and a linear light source 6 is arranged on the side face of the light transmission plate 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffusion sheetless surface light emitting device and a method for manufacturing the same. INDUSTRIAL APPLICABILITY The diffusion sheetless surface light emitting device according to the present invention is suitable for a thin electric lighting, a thin and lightweight laptop personal computer, a word processor, a backlight of a liquid crystal TV, and the like.

[0002]

2. Description of the Related Art Conventionally, as a surface light emitting device of the edge light type, a line light source is arranged on a side surface of a transparent light guide plate, and an area ratio is set on a back surface of the light guide plate at a position farther from the line light source than near the line light source. In some cases, a light scattering layer is provided in a gradation pattern such that the light scattering layer becomes larger, and a diffusion sheet is disposed on the surface of the light guide plate.

The light scattering layer scatters and reflects light guided into the light guide plate from the linear light source, and directs a part of the light toward the surface of the light guide plate. Distribute the light evenly. In order to change the area ratio of the light scattering layer, the light scattering layer is formed of dots having an arbitrary shape, and the dot size is changed or the number of dots is changed depending on the position.

[0004]

However, in the above-described surface light emitting device, the light emitted from the surface of the light guide plate 5 without being totally reflected in the light guide plate 5, that is, the light emitted at an angle close to a perpendicular to the surface of the light guide plate is emitted. A part of the light travels in a direction having a large angle with respect to a perpendicular line due to diffusion in the diffusion sheet 11 or is reflected toward the light guide plate 5, so that the brightness is lost correspondingly ( See FIG. 8).

If the diffusion sheet 11 is omitted or the transmittance of the diffusion sheet 11 is increased, the luminance loss due to the diffusion sheet 11 can be eliminated or reduced, but a uniform surface light emission is obtained instead. There was a problem that can not be. The light scattering layer 2 provided on the back surface of a commercially available light guide plate used in an edge light type surface light emitting device has a minimum dot size of 300 μm and a coarse dot pitch. This is because a clear difference occurs between the light emission luminance near the upper part of each dot part and the light emission luminance around the same, and only the light emission near the upper part of the dot part becomes bright and conspicuous in a dot shape.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a diffusion sheetless surface light emitting device capable of obtaining uniform surface light emission with a small luminance loss of light emitted from a light guide plate, and a method of manufacturing the same.

[0007]

In order to achieve the above object, a surface light emitting device without a diffusion sheet according to the present invention has a linear light source disposed on a side surface of a transparent light guide plate, and a 300 μm light source disposed on the back surface of the light guide plate.
The light scattering layer was formed so as to have a gradation pattern composed of dots having a size of less than 85 and having a number of lines of 85 or more.

Further, in the method for manufacturing a surface light-emitting device without a diffusion sheet according to the present invention, at least a light scattering layer having a gradation pattern composed of dots having a size of less than 300 μm and having a line number of 85 or more is formed on a base film. Using a transfer sheet, place the transfer sheet in the injection mold so that the light scattering layer side faces the cavity, close the mold, and then inject the transparent resin into the mold to form the transparent light guide plate. At the same time as molding, the light scattering layer was integrated on the back surface of the light guide plate, the base film was peeled off after cooling, and a line light source was arranged on the side surface of the light guide plate.

Further, according to the method of manufacturing a surface light emitting device without a diffusion sheet of the present invention, a light reflecting layer is formed on a base film, and a transparent resin layer having a lower refractive index than the light guide plate is formed thereon. Using a transfer sheet formed with a light scattering layer having a gradation pattern of 85 lines or more consisting of dots with a size of less than 300 μm on the layer, and closing the mold, closing the mold and then melting the transparent resin in the mold To form a transparent light guide plate and at the same time a light reflection layer on the back of the light guide plate,
The transparent resin layer and the light scattering layer were integrated, the base film was peeled off after cooling, and a line light source was arranged on the side surface of the light guide plate.

In the method of manufacturing a surface light emitting device without a diffusion sheet according to the present invention, a transparent resin layer having a lower refractive index than that of the light guide plate is laminated on one surface of the light reflecting plate having reflectivity, and 300 μm is formed on the transparent resin layer. Using an insert sheet formed with a light scattering layer having a gradation pattern of dots having a size of less than 85 lines and having a number of lines of 85 or more, disposing the insert sheet in the injection mold so that the light scattering layer side faces the cavity. Then, after closing the mold, the molten transparent resin is injected into the mold, and a transparent light guide plate is formed, and at the same time, a light reflecting plate, a transparent resin layer, and a light scattering layer are integrated on the back surface of the light guide plate, After cooling, a line light source was arranged on the side surface of the light guide plate.

Further, in each of the above structures of the diffusion sheetless surface light-emitting device and the method of manufacturing the same, the gradation pattern of the light-scattering layer is formed such that dots having a size of 50 to 200 μm are formed and the number of lines is 120 to 250. Formed. In each configuration of the above manufacturing method, the light scattering layer was formed by any one of a gravure printing method, a flexographic printing method, and an inkjet method.

[0012]

FIG. 1 is a cross-sectional view showing one embodiment showing a manufacturing process of a diffusion sheetless surface light emitting device according to the present invention.
FIG. 2 is a cross-sectional view showing another embodiment of the transfer sheet used in the method of manufacturing a surface emitting device without a diffusion sheet according to the present invention.
FIG. 4 is a cross-sectional view showing a diffusion sheet-less surface light emitting device of the present invention obtained by using the transfer sheet of FIG. 2, and FIG. 4 shows an embodiment of an insert sheet used in a method of manufacturing a diffusion sheetless surface light emitting device of the present invention. FIG. 5 is a cross-sectional view showing a diffusion sheetless surface light emitting device of the present invention obtained using the insert sheet of FIG. 4, and FIG. 6 is obtained by directly forming a light scattering layer on a preformed light guide plate. FIG. 7 is a cross-sectional view showing an embodiment of the diffusion sheetless surface light emitting device of the present invention, and FIG. 7 is a cross-sectional view showing an embodiment of the diffusion sheetless surface light emitting device of the present invention in which the light guide plate has a wedge shape. 1 is a base film, 2 is a light scattering layer, 3
Is a transfer sheet, 4 is an injection mold, 5 is a light guide plate, 6 is a linear light source, 7 is a light reflection layer, 8 is a transparent resin layer, 9 is a light reflection plate,
Reference numeral 10 denotes an insert sheet.

In the method for manufacturing a diffusion sheetless surface light emitting device shown in FIG. 1, a light scattering layer 2 having a gradation pattern composed of dots having a size of less than 300 μm and having a line number of 85 or more is formed on a base film 1. Transfer sheet 3
(See FIG. 1a), the transfer sheet 3 is arranged in the injection mold 4 so that the light scattering layer 2 side faces the cavity (see FIG. 1b), and the transparent resin melted after the mold is closed is used. The light-scattering layer 2 is integrated with the back surface of the light guide plate 5 at the same time as the transparent light guide plate 5 is formed by injection into a mold, and the base film 1 is peeled off after cooling (see FIG. 1C). (See FIG. 1d).

The base film 1 of the transfer sheet 3 may be made of a resin sheet such as a polypropylene resin, a polyethylene resin, a polyamide resin, a polyester resin, a polyacryl resin, or a polyvinyl chloride resin.
It is possible to use a material used as a base film 1 of an ordinary transfer sheet, such as a metal foil such as an aluminum foil or a copper foil, a cellulosic sheet such as glassine paper, coated paper, cellophane, or a composite of the above sheets. it can.

The shape of the dots constituting the gradation pattern of the light scattering layer 2 is not particularly limited, and may be an arbitrary shape such as a round dot, a square dot, or a chain dot. The size of the dot is less than 300 μm.
In addition, the dot pitch is fine, and specifically, the number of lines is 85 lines or more. By using such a gradation pattern, it is possible to reduce the difference between the light emission luminance near the upper part of each dot portion on the light emission surface of the light guide plate and the light emission luminance around the dot part.
As a result, the light emission near the upper part of the dot portion becomes inconspicuous. In particular, the size of the dot is preferably in the range of 50 to 200 μm, and the number of lines is preferably in the range of 120 to 250 lines. If the size of the dot is larger than 200 μm, the difference between the light emission luminance near the upper part of each dot portion and the light emission luminance around it becomes large, and if the size of the dot is smaller than 50 μm, the printability of the dot deteriorates. On the other hand, if the number of lines is smaller than 120 lines, the difference between the light emission luminance near the upper portion of each dot portion and the light emission luminance around the dot portion becomes large, and if the line number is larger than 250 lines, it is difficult to change the gradation. As a method for forming the light scattering layer 2, there are a gravure printing method, a flexographic printing method, an ink jet method, and the like. These methods are suitable for setting the size of the dots constituting the light scattering layer 2 to less than 300 μm and making the gradation pattern 85 lines or more. The light scattering layer 2 is formed using an ink containing silica, titanium dioxide, nylon beads, calcium carbonate, or the like.

The transparent resin that becomes the light guide plate 5 after molding and cooling includes, for example, methacrylate polymer or copolymer such as polymethylpentene resin, hydroxyethyl methacrylate, polymethyl methacrylate, and acrylate polymer. Or a copolymer, acetyl cellulose, transparent cellulose resin such as acetyl butyl cellulose, polycarbonate resin, polystyrene resin,
Acrylic styrene resin, transparent vinyl chloride resin such as polyvinyl chloride, a copolymer of vinyl chloride and methacrylate, an ethylene-vinyl acetate copolymer, and the like can be used. The light guide plate 5 has a thickness of 1.
A rectangular plate of about 5 to 30 mm is preferred. Further, the thickness of the light guide plate 5 may be reduced as the distance from the linear light source 6 increases. Further, it is preferable that all side surfaces of the light guide plate 5 be finished to a smooth surface.

As the line light source 6, a cathode ray tube such as a hot cathode ray tube or a cold cathode ray tube having a diameter of about 2 to 3 mm is used. Also,
The shape of the linear light source 6 may be a straight shape, an L-shape extending over two adjacent sides, a U-shape extending over three adjacent sides, or the like. Further, a plurality of line light sources 6 may be arranged.

The diffusion sheetless surface light emitting device and the method of manufacturing the same according to the present invention are not limited to the above-described embodiment. For example, the light reflecting layer 7 on the base film 1
Is formed thereon, and a transparent resin layer 8 having a lower refractive index than the light guide plate is formed thereon. Light having a gradation pattern composed of dots having a size of less than 300 μm and having a line number of 85 or more is formed on the transparent resin layer 8. Transfer sheet 3 on which scattering layer 2 is formed
(See FIG. 2), the mold is closed, the molten transparent resin is injected into the mold, and the transparent light guide plate 5 is formed, and at the same time, the light reflection layer 7 and the transparent resin layer are formed on the back surface of the light guide plate 5. 8. The light scattering layer 2 may be integrated (see FIG. 3).

The light reflecting layer 7 reflects the light that cannot be returned to the light guide plate 5 among the light scattered and reflected by the light scattering layer 2 toward the light guide plate 5 so that the light can be used efficiently. .
As a material of the light reflection layer 7, an ink containing silica, titanium dioxide, mica, calcium carbonate, resin hollow beads, white pigment, silicon powder, or the like may be used. Examples of a method for forming the light reflection layer 7 include printing methods such as gravure printing and screen printing, and a coater method such as a roll coater.

The transparent resin layer 8 prevents light from being scattered and reflected by the light reflecting layer 7 toward the light exit surface of the light guide plate 5 in a portion where the light scattering layer 2 does not exist. Since the refractive index of the transparent resin layer 8 is lower than the refractive index of the light guide plate 5, light incident at an angle at which the light scattering layer 2 does not exist at the back surface interface of the light guide plate 5 is totally reflected at the interface. It does not reach the reflection layer 7. Examples of the material of the transparent resin layer 8 include transparent fluoroplastics such as polyvinylidene fluoride, poly (ethylene propylene), poly (chlorotrifluoroethylene), methacrylic acid such as polymethylpentene resin, hydroxyethyl methacrylate, and polymethyl methacrylate. Ester polymer or copolymer, acrylic acid ester polymer or copolymer, transparent cellulose resin such as acetylcellulose, acetylbutylcellulose, etc., polycarbonate resin, transparent vinyl chloride resin such as polyvinyl chloride, polyvinyl acetate resin, etc. Light guide plate 5 to be used
A material having a lower refractive index than that of the light guide plate 5 is selected according to the material. Examples of a method for forming the transparent resin layer 8 include a printing method such as gravure printing and screen printing, and a coater method such as a roll coater.

Further, a release layer may be provided to improve the releasability of the base film 1 of the transfer sheet 3, or an adhesive layer may be provided to increase the adhesion between the transfer layer and the light guide plate 5. The release layer is a layer which is formed entirely or partially on the surface of the base film 1 and which is separated from the base film 1 and left on the light guide plate 5 side when the base film 1 is separated after cooling. As the material of the release layer, polyacrylic resin, polyester resin, polyvinyl chloride resin,
Cellulose resin, rubber resin, polyurethane resin,
In addition to a polyvinyl acetate resin, a copolymer such as a vinyl chloride-vinyl acetate copolymer resin or an ethylene-vinyl acetate copolymer resin may be used. As the material of the adhesive layer, a heat-sensitive or pressure-sensitive resin suitable for the material of the light guide plate 5 is appropriately used. For example, when the material of the light guide plate 5 is a polyacrylic resin, a polyacrylic resin may be used. When the material of the light guide plate 8 is a polycarbonate-based resin, a polyacrylic resin, a polystyrene-based resin, a polyamide-based resin, or the like having an affinity for these resins may be used. As a method for forming the release layer and the adhesive layer, printing methods such as gravure printing and screen printing,
There is a coater method such as a roll coater.

In place of the transfer sheet 3, a transparent resin layer 8 having a lower refractive index than the light guide plate is laminated on one surface of the light reflecting plate 9 having reflectivity, and the transparent resin layer 8 has a size of less than 300 μm. Using the insert sheet 10 on which the light-scattering layer 2 formed of dots and having a gradation pattern of 85 lines or more is formed (see FIG. 4), the mold is closed, and then the molten transparent resin is injected into the mold. Then, at the same time as forming the transparent light guide plate 5, the light reflecting plate 9, the transparent resin layer 8, and the light scattering layer 2 are integrated on the back surface of the light guide plate 5, and the linear light source 6 is arranged on the side surface of the light guide plate 5 to form a diffusion sheet. A surface light emitting device may be manufactured (see FIG. 5). As a material of the light reflecting plate 9, a resin sheet or a metal plate such as aluminum is printed or coated with ink containing silica, titanium dioxide, mica, calcium carbonate, resin hollow beads, white pigment, silicon powder, etc. on one surface. It is good to use. In addition, a resin sheet containing a white pigment such as a white polyethylene terephthalate film can be used. Also, in the insert sheet 10, an adhesive layer similar to that of the transfer sheet 3 may be provided in order to increase the adhesive strength with the light guide plate 5.

The light scattering layer 2 may be formed directly on the back surface of the light guide plate 5 after the light guide plate 5 is formed by a gravure printing method, a flexographic printing method, or an ink jet method (see FIG. 6). Alternatively, the transfer may be performed after the light guide plate 5 is formed using the transfer sheet 3 on which the light scattering layer 2 is formed by the above method. In the case of these methods, glass can be used as the material of the light guide plate 5.

Further, a light source reflector may be arranged so as to cover the surface of the line light source 6 opposite to the light guide plate 5. The light source reflector reflects light from the surface of the line light source 6 opposite to the light guide plate 5 toward the light guide plate 5 so that the light can be used efficiently. As the material of the light source reflector, the same material as the light reflector 9 may be used. The distance between the linear light source 6 and the light source reflector may be kept uniform by interposing a spacer between them.

Further, a side reflection layer may be arranged on the side of the light guide plate 5 where the line light source 6 is not arranged. The side reflection layer reflects the light that has been emitted from the side surface of the light guide plate 5 and has not been returned to the light guide plate 5 side so that the light can be used efficiently. As the material of the side reflection layer, the same material as the light reflection layer 7 and the light reflection plate 9 may be used.

Further, the shape of the light guide plate 5 of the present invention is not limited to those having a uniform thickness as shown in the above-mentioned drawings. For example, an inclined surface portion may be formed on the back surface side of the light guide plate 5 such that the thickness decreases as the distance from the line light source 6 increases (see FIG. 7). Also, the slope may be curvilinear. Also, there may be parts that are not inclined

[0027]

[Example] A polyethylene terephthalate film was used as a base film, and nylon beads were 15% on the film.
A light having a gradation pattern by printing the contained mat ink by gravure printing using a gravure intaglio designed so that the dot diameter is 50 μm to 200 μm, the number of lines is 120, and the area density from the line light source is 20 to 70%. A scattering layer was formed to obtain a transfer sheet.

Next, the transfer sheet is placed in an injection molding mold having a cavity of 220 mm in length, 160 mm in width and 4 mm in thickness, and the molten polymethyl methacrylate resin is injected into the mold, and a transparent flat plate is formed. The light-scattering layer was integrated with the back surface of the light guide plate at the same time when the light guide plate was formed, and the base film was peeled off after cooling.

Finally, tube lengths 22 are provided on two opposite sides of the light guide plate.
When a cold cathode ray tube having a diameter of 5 mm and a diameter of 3.8 mm was arranged as a line light source and turned on, uniform surface light emission without luminance unevenness due to dots was obtained without a diffusion sheet, and the luminance was high.

[0030]

As described above, the diffusion sheetless surface light emitting device and the method of manufacturing the same according to the present invention have the following effects.

That is, by providing a light scattering layer having a gradation pattern having a dot size of less than 300 μm and having a line number of 85 lines or more and using no diffusion sheet, uniform surface emission can be achieved. And high brightness can be obtained.

Further, since no diffusion sheet is used, a thinner and less expensive surface emitting device can be provided.

In the case where the light reflecting layer or the light reflecting plate is integrated with the back surface of the light scattering layer at the same time as the formation of the light guide plate, the light reflecting layer and the light reflecting plate may be interposed between the light scattering layer and the light reflecting layer. By interposing a transparent resin layer having a lower refractive index than that of the light guide plate, light is scattered and reflected by the light reflection layer or the light reflection plate toward the emission surface side of the light guide plate in a portion where the light scattering layer does not exist. And uniform surface emission can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment showing a manufacturing process of a diffusion sheetless surface light emitting device according to the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the transfer sheet used in the method for manufacturing a diffusion sheetless surface light emitting device according to the present invention.

FIG. 3 is a cross-sectional view showing a diffusion sheetless surface emitting device of the present invention obtained using the transfer sheet of FIG. 2;

FIG. 4 is a cross-sectional view showing one embodiment of an insert sheet used in a method of manufacturing a diffusion sheetless surface light emitting device according to the present invention.

FIG. 5 is a sectional view showing a diffusion sheetless surface emitting device of the present invention obtained by using the insert sheet of FIG. 4;

FIG. 6 is a cross-sectional view showing an embodiment of a diffusion sheetless surface light emitting device of the present invention obtained by directly forming a light scattering layer on a light guide plate formed in advance.

FIG. 7 is a cross-sectional view showing an embodiment of a diffusion sheetless surface light emitting device of the present invention in which a light guide plate has a wedge shape.

FIG. 8 is a cross-sectional view showing a conventional surface emitting device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 base film 2 light scattering layer 3 transfer sheet 4 injection molding die 5 light guide plate 6 line light source 7 light reflection layer 8 transparent resin layer 9 light reflection plate 10 insert sheet 11 diffusion sheet

Claims (7)

[Claims] A light source is disposed on a side surface of a transparent light guide plate, and a light scattering layer having a gradation pattern composed of dots having a size of less than 300 μm and having a line number of 85 or more is formed on the back surface of the light guide plate. A diffusion sheetless surface light emitting device. 2. A gradation pattern of a light scattering layer,
It is composed of dots with a size of 50 to 200 μm and has a line frequency of 120 to 250
The diffusion sheetless surface light emitting device according to claim 1, wherein the surface light emitting device is a line. 3. A transfer sheet having at least a light-scattering layer formed of dots having a size of less than 300 μm and having a gradation pattern of 85 lines or more on a base film, wherein the light-scattering layer side faces the cavity. After placing the transfer sheet in the injection molding mold, closing the mold and injecting the molten transparent resin into the mold, forming a transparent light guide plate and simultaneously forming a light scattering layer on the back surface of the light guide plate. A method for manufacturing a surface light emitting device without a diffusion sheet, wherein the base film is separated after cooling, and a linear light source is arranged on a side surface of the light guide plate. 4. A light reflection layer is formed on a base film, a transparent resin layer having a lower refractive index than that of the light guide plate is formed thereon, and the transparent resin layer comprises dots having a size of less than 300 μm. Using a transfer sheet on which a light scattering layer having a gradation pattern of 85 lines or more was formed, the mold was closed, and then the molten transparent resin was injected into the mold to form a transparent light guide plate and at the same time a light guide plate Light reflection layer on the back of
A method for manufacturing a diffusion sheetless surface light emitting device, comprising: integrating a transparent resin layer and a light scattering layer; removing a base film after cooling; and arranging a linear light source on a side surface of the light guide plate. 5. A transparent resin layer having a lower refractive index than the light guide plate is laminated on one surface of the light reflecting plate having reflectivity, and the transparent resin layer is composed of dots having a size of less than 300 μm and has a line number of 85 or more. Using an insert sheet on which a light scattering layer having a gradation pattern is formed, disposing the insert sheet in an injection mold so that the light scattering layer side faces the cavity, and closing the mold to melt the transparent resin. Into a mold to form a transparent light guide plate, and at the same time integrate the light reflector, transparent resin layer, and light scattering layer on the back surface of the light guide plate, and arrange a line light source on the side surface of the light guide plate after cooling. A method for manufacturing a diffusion sheetless surface light emitting device. 6. A gradation pattern of a light scattering layer,
It is composed of dots with a size of 50 to 200 μm and has a line frequency of 120 to 250
The method for manufacturing a surface emitting device without a diffusion sheet according to any one of claims 3 to 5, which is a line. 7. The method according to claim 3, wherein the light scattering layer is formed by any one of a gravure printing method, a flexographic printing method, and an ink jet method.