JPH10104434A - Diffusion sheetless surface light emission device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffusion sheetless surface light emission device which has a small luminance loss of light emitted from a light guide plate and obtains a uniform surface light emission. SOLUTION: A transfer sheet 3 is used which has at least a light scatter layer 2 with a gradation pattern of 66 to 85 in the lines formed of dots of <=385μm on a base film 1 and the transfer sheet is arranged in a projection molding metal mold 4 so that the side of the light diffusion layer 2 faces the cavity; after the metal mold is clamped, molten resin is injected into the metal mold to form a transparent light guide plate 5 and at the same time, the light scatter layer 2 is united with the reverse surface of the light guide plate 5. After the transfer sheet is cooled, the base film 1 is peeled and a linear light source 6 is arranged on the flank of the light guide 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, a part of the light emitted at an angle close to the perpendicular to the surface of the light guide plate 5 is partially diffused between the diffuser sheet 11 and the perpendicular. Since the light travels in a direction having a large angle or is reflected on the light guide plate 5 side, the brightness is lost accordingly (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. That is, the commercially available light guide plate used in the edge light type surface light emitting device has a large dot of the light scattering layer on the back surface and a coarse dot pitch, and a dot having a large light scattering area and a dot with a coarse pitch are used as the light guide plate. This is because a clear difference is generated between the light emission luminance near the upper part of each dot portion on the emission surface and the light emission luminance around the dot part. That is, only the light emission near the upper part of the dot portion 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 which can easily emit light from a light guide plate with little luminance loss and can obtain uniform surface light emission, and a method of manufacturing the same.

[0007]

In order to achieve the above object, a diffusion sheetless surface light emitting device according to the present invention has a line light source disposed on a side surface of a transparent light guide plate and 385 μm on a back surface of the light guide plate.
It is composed of dots smaller than m and the number of lines is 66 or more and 85
It was configured such that a light scattering layer having a gradation pattern less than the line was formed.

[0008] In the above structure of the surface light emitting device without the diffusion sheet, the surface of the light guide plate may be a matte surface.

Further, the method for manufacturing a surface light-emitting device without a diffusion sheet according to the present invention is characterized in that the light-scattering layer having a gradation pattern composed of dots having a size of less than 385 μm and having a line number of 66 or more and less than 85 lines on the base film. Using at least the formed transfer sheet, the transfer sheet is arranged in the injection mold so that the light scattering layer side faces the cavity, and after the mold is closed, the molten transparent resin is injected into the mold, At the same time as forming a transparent light guide plate, integrate the light scattering layer on the back of the light guide plate, peel off the base film after cooling,
The linear light source was arranged on the side surface of the light guide plate.

Further, according to the method for manufacturing a surface light emitting device without a diffusion sheet according to 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 in which a light scattering layer having a gradation pattern of 66 lines or more and less than 85 lines formed of dots having a size of less than 385 μm on the layer, the transparent resin melted after closing the mold is used. Inject into a mold, mold a transparent light guide plate, and at the same time integrate the light reflection layer, transparent resin layer and light scattering layer on the back surface of the light guide plate, peel off the base film after cooling, and place a line light source on the side of the light guide plate Was arranged.

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 the light guide plate is laminated on one surface of the light reflecting plate having reflectivity, and 385 μm is formed on the transparent resin layer. Consisting of dots less than
Using an insert sheet having a light scattering layer having a gradation pattern of 6 lines or more and less than 85 lines, disposing the insert sheet in an injection mold so that the light scattering layer side faces the cavity, and closing the mold. After that, the molten transparent resin is injected into the mold to form a transparent light guide plate, and at the same time, the light reflection plate, the transparent resin layer, and the light scattering layer are integrated on the back surface of the light guide plate. The light source was arranged.

In each of the above-described manufacturing methods, the light scattering layer was formed by any one of a gravure printing method, a flexographic printing method, and an ink jet method.

In each configuration of the above-mentioned manufacturing method, a matte surface may be formed on the surface of the light guide plate by providing irregularities on the inner wall surface of the cavity of the injection mold.

FIG. 1 is a cross-sectional view showing one embodiment of a process for manufacturing a diffusion sheetless surface light emitting device according to the present invention, and FIG. FIG. 3 is a cross-sectional view showing a diffusion sheetless surface light emitting device of the present invention obtained by using the transfer sheet of FIG. 2, and FIG. 4 is a sectional view of a diffusion sheetless surface light emitting device of the present invention. FIG. 5 is a cross-sectional view showing an embodiment of an insert sheet used in the manufacturing method, 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. FIG. 7 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 plate. FIG. It is sectional drawing which shows an Example. 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 line light source, 7
Denotes a light reflecting layer, 8 denotes a transparent resin layer, 9 denotes a light reflecting plate, and 10 denotes an insert sheet.

The method for manufacturing a surface light-emitting device without a diffusion sheet shown in FIG. 1 uses a light-scattering layer having a gradation pattern comprising dots having a size of less than 385 μm and having a number of lines of 66 to less than 85 on the base film 1. The transfer sheet 3 on which the light scattering layer 2 faces the cavity is used (see FIG. 1b), and the transfer sheet 3 is disposed in the injection molding die 4 (see FIG. 1b). After closing, the molten transparent resin is injected into a mold to form the transparent light guide plate 5 and at the same time integrate the light scattering layer 2 on the back surface of the light guide plate 5 and peel off the base film 1 after cooling (see FIG. 1c). ), A line light source 6 is arranged on one side of the light guide plate 5 (FIG. 1d).
See).

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, a polyvinyl chloride resin, or the like.
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, a chain dot, or the like. Further, the size of the dots is reduced to less than 385 μm, and the dot pitch is also reduced to the number of lines of 66 to less than 85. With such a gradation pattern, it is possible to reduce the difference between the light emission luminance near the upper portion of each dot portion on the light emitting surface of the light guide plate 5 and the light emission luminance around the dot portion. As a result, the light emission near the upper part of the dot portion becomes inconspicuous. The reason why the dot pitch has a fineness limit of less than 85 lines is as follows. The pattern of the light scattering layer 2 has a line light source 6
In addition to the basic luminance non-uniformity correction that increases the area ratio at a position distant from the light source, the luminance non-uniformity partially generated by the length of the linear light source 6 and the size and shape of the housing into which the light guide plate 5 is incorporated is reduced. You may need to make corrections. However, when the dot pitch is 85 lines or more, the adjacent dots are too close to enlarge the dots to partially increase the output light amount, so that the correction width is reduced. 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 reduce the size of the dots constituting the light scattering layer 2 to 385.
less than μm and the gradation pattern is 66 lines or more and 85
It is suitable to be less than the line. Light scattering layer 2
The formation of silica, titanium dioxide, nylon beads,
An ink containing calcium carbonate or the like is used.

The transparent resin which becomes the light guide plate 5 after molding and cooling includes, for example, methacrylate polymer or copolymer such as polymethylpentene resin, hydroxyethyl methacrylate and 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. In addition, as the shape of the light guide plate 5, a rectangular plate material having a thickness of about 1.5 to 30 mm is preferable. Further, the thickness of the light guide plate 5 may be reduced as the distance from the linear light source 6 increases.

The light guide plate 5 preferably has a matte surface. First, interference of light generated between the light guide plate 5 and a smooth transparent film such as a lens sheet or a housing disposed on the surface thereof, or so-called Newton's ring causes external light to be scattered and reflected by the satin ground. This can be prevented by doing so. Second, the light guide plate 5 by the pear ground
This is because more internal light can be extracted and the luminance can be further improved.

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. The shape of the linear light source 6 may be straight, L-shaped over two adjacent sides, or U-shaped over three adjacent sides. 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 embodiments. For example, the light reflection 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. A gradation pattern composed of dots having a size of less than 385 μm and having a line number of 66 or more and less than 85 lines is formed on the transparent resin layer 8. After the mold is closed, the molten transparent resin is injected into the mold using the transfer sheet 3 on which the light scattering layer 2 having the light scattering layer 2 is formed. The light reflection layer 7, the transparent resin layer 8, and the light scattering layer 2 may be integrated on the back surface of the light plate 5 (see FIG. 3).

The light reflecting layer 7 reflects, to the light guide plate 5 side, of the light scattered and reflected by the light scattering layer 2 and which cannot return to the inside of 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 the portion where the light scattering layer 2 is not present. 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. Therefore, uniform surface emission can be achieved. 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, acrylate polymer or copolymer, acetyl cellulose, transparent cellulose resin such as acetyl butyl cellulose, polycarbonate resin, transparent polyvinyl chloride resin such as polyvinyl chloride,
A material having a lower refractive index than the light guide plate 5 is selected from polyvinyl acetate resin and the like according to the material of the light guide plate 5 to be used. 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.

Instead 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 a transparent resin layer 8 having a size of less than 385 μm is formed on the transparent resin layer 8. Using the insert sheet 10 on which the light-scattering layer 2 having a gradation pattern of 66 lines or more and less than 85 lines formed of dots is formed (see FIG. 4), the transparent resin melted after the mold is closed is closed. To form a transparent light guide plate 5 and, at the same time, integrate a light reflection plate 9, a transparent resin layer 8 and a light scattering layer 2 on the back surface of the light guide plate 5.
The light source 6 may be disposed on the side surface to produce a diffusion sheetless surface emitting device (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,
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.

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 each of the 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

[0030]

EXAMPLE A polyethylene terephthalate film was used as a base film, on which calcium carbonate was added.
% Of the matte ink having a dot diameter of 100 μm to 350 μm.
μm, number of lines 70, area density from line light source 25 to 69
% By gravure printing using a gravure intaglio designed so as to obtain a light scattering layer having a gradation pattern to obtain a transfer sheet.

Next, the transfer sheet is 220 mm long and 16 mm wide.
The molten polymethyl methacrylate resin was placed in an injection mold having a cavity of 0 mm and a thickness of 4 mm, and the molten polymethyl methacrylate resin was placed in the mold using a mold in which the surface of the mold opposite to the transfer sheet was matted. To form a transparent flat light guide plate, and at the same time, a light scattering layer was integrated on the back surface of the light guide plate. After cooling, the base film was peeled off.

Finally, a tube length 2 is provided on the two opposite sides of the light guide plate.
When a cold cathode ray tube having a diameter of 25 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.

[0033]

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 in which the size of the dots is less than 385 μm and the number of lines is 66 or more and less than 85 lines, the light emission luminance near the upper part of each dot portion on the emission surface of the light guide plate is provided. And the light emission luminance around the dot can be reduced, so that light emission in the vicinity of the upper part of the dot portion becomes inconspicuous, and uniform surface light emission can be obtained without using a diffusion sheet. Moreover, since a diffusion sheet is not used, the luminance loss of light emitted from the light guide plate is small, and high luminance can be obtained.

Further, since a diffusion sheet is not used, a thinner and less expensive surface emitting device can be provided.

[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] 1. A light-scattering layer having a linear light source disposed on a side surface of a transparent light guide plate and a gradation pattern comprising dots having a size of less than 385 μm and having a number of lines of 66 or more and less than 85 lines is provided on a back surface of the light guide plate. A diffusion sheetless surface light emitting device characterized by being formed. 2. The surface emitting device according to claim 1, wherein the surface of the light guide plate is a matte surface. 3. A transfer sheet having at least a light-scattering layer formed on a base film and having a gradation pattern consisting of dots having a size of less than 385 μm and having a number of lines of 66 or more and less than 85 lines, wherein the light-scattering layer side has a cavity. After placing the transfer sheet in the injection mold so that it faces the mold, the mold is closed, and then the molten transparent resin is injected into the mold to form a transparent light guide plate and simultaneously apply light to the back surface of the light guide plate. Integrate the scattering layer, peel off the base film after cooling,
A method for manufacturing a diffusion sheetless surface light emitting device, wherein a line light source is disposed on a side surface of a light guide plate. 4. A light reflection layer is formed on a base film, a transparent resin layer having a lower refractive index than the light guide plate is formed thereon, and the transparent resin layer is formed of dots having a size of less than 385 μm. Using a transfer sheet formed with a light scattering layer having a gradation pattern of 66 lines or more and less than 85 lines, injecting a molten transparent resin into the mold after closing the mold, and forming a transparent light guide plate. At the same time, a light-reflecting layer, a transparent resin layer and a light-scattering layer are integrated on the back surface of the light guide plate, the base film is peeled off after cooling, and a line light source is arranged on the side surface of the light guide plate. Manufacturing method. 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 385 μm and having a line number of 6
Using an insert sheet having a light scattering layer having a gradation pattern of 6 lines or more and less than 85 lines, disposing the insert sheet in an injection mold so that the light scattering layer side faces the cavity, and closing the mold. After that, the molten transparent resin is injected into the mold to form a transparent light guide plate, and at the same time, the light reflection plate, the transparent resin layer, and the light scattering layer are integrated on the back surface of the light guide plate. A method for manufacturing a diffusion sheetless surface light emitting device, comprising arranging a light source. 6. 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. 7. The method of manufacturing a surface emitting device without a diffusion sheet according to claim 3, wherein a matte surface is formed on the surface of the light guide plate by providing irregularities on the inner wall surface of the cavity of the injection molding die. .