JPH09202871A - Adhesive for planar light source and planar light source using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive for planar light source which can very efficiently produce planar light sources excellent in brightness, scarcely causing deviation between a reflection sheet and a photoconductive plate and a planar light source produced by using this adhesive. SOLUTION: An adhesive containing a white powder comprising barium sulfate and titanium oxide in an amount of 5-60 pts.wt. per 100 pts.wt. of the solid component of the adhesive is applied to one surface of a reflection sheet 3 so that the adherent part 1 on the surface may form a random pattern and a photoconductive plate 2 is stuck to the face to which the adhesive containing the white powder is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an adhesive for surface light source bodies and an adhesive for surface light source bodies that can be used for various surface light source bodies such as liquid crystal backlights, lighting displays, lighting signs, and lighting bodies. The present invention relates to the manufactured surface light source body.

[0002]

2. Description of the Related Art A surface light source body is formed by laminating a light guide plate and a reflection sheet. Light from a light source such as a fluorescent lamp is introduced from a side edge of the light guide plate, and the light is emitted from the surface of the light guide plate.
It has a lighting function. Conventionally, a surface light source panel used for a surface light source body is an ink in which a binder is mixed with titanium oxide, which is a photorefractive material, on one surface of a light guide plate made of a transparent resin substrate having good light transmittance such as acrylic resin. It was manufactured by screen-printing with, to form a pattern such as spots, and thereby forming an irregular reflection surface. However, when screen-printing, the diameter of particles such as titanium oxide contained in the ink is usually several microns to several tens of microns, which causes clogging of the screen, resulting in poor reproducibility of printing and non-uniformity. There is a problem of becoming. If the printing is uneven, the brightness of the surface light source becomes uneven, so that the acrylic resin plate that is the object to be printed must be discarded and the product yield is deteriorated. In particular, when the acrylic resin plate is large, the weight is large and the workability is poor, so the printing failure rate becomes large, and when the printing fails, the large acrylic resin plate must be discarded altogether, and the product yield is high. There was a problem of getting worse. For this reason, the printing process of the acrylic resin plate for the surface light source body in an actual factory uses a relatively small one such as for a liquid crystal backlight.

Further, the screen printing has a problem that printing cannot be performed when the light guide plate has a complicated curved surface. In addition, when the surface light source is fixed because the reflection sheet is not fixed to the light guide plate, the reflection sheet is easily peeled off, which makes it difficult to fix the reflection sheet and the light guide plate so as not to shift. there were. Therefore, in order to eliminate the above-mentioned drawbacks, a transparent pressure-sensitive adhesive is attached to one surface of the reflection sheet such that the sticky portion of the surface of the transparent pressure-sensitive adhesive has an arbitrary spaced pattern, and further, this reflection sheet There is proposed a transparent surface light source body prepared by sticking a light guide plate on the surface on which the transparent adhesive is adhered. However, this surface light source has a problem that the brightness is not sufficient.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art. A surface light source body that is less likely to be displaced between the reflection sheet and the light guide plate and has excellent brightness is provided. An object of the present invention is to provide an adhesive for a surface light source that can be manufactured extremely efficiently and a surface light source using the adhesive for a surface light source.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a white powder made of a mixture of barium sulfate powder and titanium oxide powder is used as an adhesive. A high-luminance surface light source body can be manufactured by providing a reflection pattern with an adhesive for surface light source bodies mixed with 5 to 60 parts by weight with respect to 100 parts by weight of solid content, and reflecting the light. The inventors have found that the above can be solved, and have completed the present invention based on the findings.

That is, according to the present invention, a white powder composed of a mixture of barium sulfate powder and titanium oxide powder is used as an adhesive,
An adhesive for surface light source bodies, characterized in that 5 to 60 parts by weight are mixed with 100 parts by weight of the solid content of the adhesive. In addition, the present invention provides a white powder-containing pressure-sensitive adhesive obtained by mixing 5 to 60 parts by weight of a white powder composed of a mixture of barium sulfate powder and titanium oxide powder into 100% by weight of the adhesive solid content. It is characterized in that a sticky portion of the surface is attached to one surface of a reflection sheet so that it has an arbitrary pattern, and a light guide plate is attached to the surface to which the white powder-containing adhesive is attached. And a surface light source body. Hereinafter, the present invention will be described in detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The pressure-sensitive adhesive for surface light source body of the present invention comprises 5-60 parts by weight of white powder comprising a mixture of barium sulfate powder and titanium oxide powder, based on 100 parts by weight of the adhesive solid content. It is a white powder containing pressure sensitive adhesive. As the pressure-sensitive adhesive that can be used in the present invention, various transparent pressure-sensitive adhesives can be used. Specific examples of the adhesive include acrylic resin-based adhesives, synthetic rubber-based adhesives,
Examples thereof include silicone resin-based adhesives and vinyl resin-based adhesives. These adhesives can be used alone or in combination of two or more. Among these adhesives, acrylic resin-based adhesives are preferable.

If necessary, a tackifier, a softening agent, an antiaging agent, an ultraviolet absorber, etc. may be added to the above-mentioned pressure-sensitive adhesive. Examples of the tackifier include rosin resins, terpene phenol resins, terpene resins, aromatic hydrocarbon-modified terpene resins, petroleum resins, coumarone-indene resins, styrene resins, phenol resins, and xylene resins. Examples of the softener include process oil, liquid rubber, plasticizer, and the like. Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers. Examples of the light stabilizer include hindered amine light stabilizers. The mixing ratio of the barium sulfate powder and the titanium oxide powder in the white powder is preferably 4: 1 to 2: 5, and particularly 2: 1 to
1: 2 is preferable.

The average particle size of the white powder is 0.1 to 1
The range of μm is preferable, and the range of 0.2 to 0.8 μm is particularly preferable. The particle size distribution of the white powder is 0.02
The range of 5 μm is preferable, and the range of 0.05 to 2 μm is particularly preferable. The content ratio of the white powder to the adhesive is preferably 10 to 50 parts by weight, and more preferably 20 to 40 parts by weight with respect to 100 parts by weight of the solid content of the adhesive. The white powder is
It is preferable to disperse the adhesive in the adhesive so as not to cause secondary aggregation.

Next, the surface light source body of the present invention will be described.
The surface light source body of the present invention has a white powder-containing pressure-sensitive adhesive obtained by mixing 5 to 60 parts by weight of white powder composed of a mixture of barium sulfate powder and titanium oxide powder with respect to 100 parts by weight of solid adhesive. Is adhered to one surface of the reflection sheet so that the sticky part has an arbitrary spaced pattern, and the light guide plate is further adhered to the surface to which the white powder-containing adhesive is adhered. As the reflection sheet used, various types can be used as long as they are introduced in the surface light source device, but a white sheet having a reflectance of 95% or more is preferable.
Specific examples of the reflective sheet include, for example, a low-foamed film of white polyester resin, a low-foamed film of white polystyrene resin, a low-foamed film of white ABS resin, a film of silver-deposited white polyester resin film, and a low-lightness of white polycarbonate resin. Examples thereof include a foamed film, a low foamed film made of a resin having a good optical transparency, or a film obtained by mixing the above-mentioned film or a resin having a good optical transparency with titanium oxide, zirconium oxide, barium sulfate or the like.

The width and length of the reflecting sheet may be appropriately selected according to various conditions such as the surface light source body. The reflection sheet is
A continuous strip is preferred, but a strip cut to an appropriate length may be used. The thickness of the reflection sheet may be appropriately selected and determined, but normally the thickness of 25 to 2000 μm is used, and preferably 100 to 500 μm. An adhesive layer for sticking to other members may be provided on the surface of the reflective sheet on which the white powder-containing adhesive is not attached, and a release sheet may be provided on the adhesive layer. May be.

The white powder-containing pressure-sensitive adhesive is attached to the reflection sheet so that the pressure-sensitive adhesive portions of the pressure-sensitive adhesive surface are separated and have an arbitrary pattern. The distant pattern is a pattern in which elements constituting the pattern such as dots, lines, and surfaces are arranged at an arbitrary distance, and examples thereof include various patterns such as stripes, spots, and meshes. . Preferable ones of these patterns are, for example, JP-A-3-118594 and JP-A-3118594.
The pattern described in Japanese Patent Publication No. 256590, that is, the area ratio is increased stepwise in parallel from the light source in the direction of the separation plane, preferably in the range of 20 to 60%,
Preferably, in order to eliminate the non-uniformity of brightness due to reflected light, a pattern composed of parallel pattern parts with a maximum ratio at an intermediate position from the end of the non-light source side, or this parallel pattern part and the parallel pattern itself. There is also a pattern formed so as to present a halftone dot pattern on the light source side with the opposite end to the light source as the base, and an adjustment pattern portion that slightly reduces the area ratio of the parallel pattern. . The thickness of the adhered white powder-containing pressure-sensitive adhesive is not particularly limited, but is usually 5 to 100.
The range is μm, preferably 10 to 50 μm, and particularly preferably 15 to 30 μm.

Next, as a preferred embodiment of the method for producing a reflection sheet for a surface light source used in the surface light source body of the present invention, for example, an adhesive containing white powder is screen-printed on the reflection sheet so as to have a predetermined pattern. Method, a method of applying a white powder-containing adhesive to the entire surface of the reflection sheet and performing a treatment such as etching to remove unnecessary white powder-containing adhesive, a method of applying the white powder-containing adhesive to the entire surface of the reflection sheet. , A method of deactivating the adhesiveness of unnecessary adhesive parts, applying a white powder-containing adhesive to the entire surface of the reflection sheet, and applying a non-adhesive substance in a predetermined pattern on the surface of the white powder-containing adhesive layer. Examples thereof include a method of applying or printing and a method of sticking an adhesive layer having a predetermined pattern on the reflection sheet.

Examples of the non-adhesive substance include vinyl acetate, vinyl chloride, polystyrene, methyl methacrylate, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, silicone resin, polyvinyl alcohol, and other synthetic resins. , Starch, printing ink, paint, etc., and examples of the substance that deactivates the tackiness of the pressure-sensitive adhesive portion include 2-ethylhexyl acrylate, acrylic acid having a carboxyl group in butyl acrylate, or 2-hydroxyethyl having a hydroxyl group. When an acrylic pressure-sensitive adhesive obtained by copolymerizing methacrylate or the like is used as the white powder-containing pressure-sensitive adhesive, reaction-curable resins such as triisocyanate and butylated melamine resin can be used.
When a continuous reflection sheet is used as the reflection sheet, it can be continuously fed to a screen printing machine and continuously screen printed, and the reflection sheet for a surface light source can be manufactured extremely efficiently.

The surface of the white powder-containing pressure-sensitive adhesive may be covered with a release sheet such as release paper. Instead of using the release sheet, a release agent may be applied to the back surface of the reflection sheet, and the reflection sheet may be rolled and stored. In this way, the surface of the white powder-containing pressure-sensitive adhesive can be protected and the surface can be prevented from being soiled.

Since the above-mentioned reflection sheet for surface light source body uses a thin sheet, it has good workability during production, can be produced extremely efficiently, has a good product yield, and has a complicated curved surface. It can be easily applied to a light guide plate, the reflection sheet and the light guide plate can be easily fixed, and a shift is unlikely to occur. Further, the surface light source body can be efficiently manufactured by using the reflection sheet.

The light guide plate is a transparent substrate having a good light transmittance, such as an acrylic resin plate, a polycarbonate resin plate,
An amorphous polyolefin resin plate, a glass plate, etc. are mentioned. The thickness of the light guide plate may be appropriately selected, but is usually 0.3 to 30 mm, preferably 0.5 to
It is 20 mm. Further, a diffusion film may be further stacked on the surface of the light guide plate. The surface light source of the present invention can be efficiently manufactured by attaching a light guide plate to the surface of the reflection sheet for surface light source to which the white powder-containing pressure-sensitive adhesive is attached. The light source of the surface light source body is provided at the edge of the light guide plate.

[0018]

EXAMPLES Next, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples. Example 1 Precipitable barium sulfate and titanium oxide were mixed in a weight ratio of 2: 3 and pulverized to obtain a white powder (particle size distribution: 0.2 to 1.0 μm) having an average particle size of 0.7 μm. Obtained. Next, acrylic adhesive (manufactured by Diabond Industry Co., Ltd., DB554
In 1), 26.5 parts by weight of the white powder was mixed with 100 parts by weight of the solid content of the adhesive, and 0.25 parts by weight of a curing agent (Coronate HL, manufactured by Nippon Polyurethane Co., Ltd.), and 10 parts by weight of xylene. The parts were mixed to prepare a white powder-containing pressure-sensitive adhesive. Next, this white powder-containing adhesive was used as a reflection sheet (trade name: E60L, manufactured by Toray Industries, Inc., polyethylene terephthalate film, thickness 188 μm, size 162 mm).
It was adhered to the central part of (× 241 mm) in a size of 20 mm × 20 mm (the thickness of the white powder-containing pressure-sensitive adhesive layer: 20 μm).
m). Next, an acrylic resin light guide plate (162 mm × 241 mm × 3 m) was placed on the surface on which the white powder-containing adhesive was pasted.
m) was adhered to produce a surface light source panel. At the side edge of this surface light source panel, a slim fluorescent tube with a diameter of 3 mm (2
4,000 cd / cm ² ) was installed and light was applied. Then, a luminance meter (Minolta LS100) was installed at a position 1 m away from the white powder-containing pressure-sensitive adhesive surface, and the luminance was measured. Table 1 shows the results.

Examples 2 to 10 The luminance was measured in the same manner as in Example 1 except that the content of the white powder in the adhesive in Example 1 was changed to the ratio shown in Table 1. Table 1 shows the results.

Comparative Examples 1 and 2 The luminance was measured in the same manner as in Example 1 except that the content of the white powder in the adhesive in Example 1 was changed to the ratio shown in Table 1. Table 1 shows the results.

[0021]

[Table 1]

Example 11 Using the white powder-containing pressure-sensitive adhesive prepared in Example 1, a reflective sheet (E60L, Toray Co., Ltd., E60L, thickness 188 μm, width 400 mm) was screen-printed to form a reflective sheet. Φ3mm so that the diameter gradually increases in the width direction
~ Adhesive dots with φ4.5 mm circles arranged at a distance,
Printing was performed so as to be spaced apart in the length direction of the reflection sheet. A light guide plate made of an acrylic resin having a thickness of 20 mm was stuck on the surface of the obtained reflection sheet on which the white powder-containing pressure-sensitive adhesive was stuck to produce a surface light source panel. The sectional view of the obtained surface light source body panel was shown in FIG. Adhesive dots 1 (thickness: 50 μm) in which circles of φ3 mm to φ4.5 mm are arranged at intervals.
Is printed so as to be spaced apart in the length direction of the reflection sheet 3, and the acrylic resin light guide plate 2 having a thickness of 20 mm is provided on the surface of the reflection sheet 3 on which the white powder-containing pressure-sensitive adhesive is adhered. It is attached. FIG. 2 is a plan view of the surface light source panel viewed from above the light guide plate 2. Φ25 mm on the side edge of this surface light source panel on the φ3 mm adhesive dot side
The fluorescent tube was installed and illuminated. The brightness of this surface light source was extremely higher than that of the surface light source manufactured using a transparent adhesive.

[0023]

According to the present invention, it is possible to manufacture a surface light source body which is less likely to be displaced between the reflection sheet and the light guide plate and which is excellent in brightness, with extremely high efficiency.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a reflection sheet for a surface light source body that is an embodiment of the present invention.

FIG. 2 is a plan view of a reflection sheet for a surface light source body of FIG.

[Explanation of symbols]

 1 Adhesive dot 2 Light guide plate 3 Reflective sheet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Kinase 43-7 Yamato-cho, Itabashi-ku, Tokyo Lintec Daiwa Dormitory No. 215 (72) Inventor Shigeo Ogawa 542-13 Tsuchiya, Omiya-shi, Saitama (72) Inventor Tadamasa Fujimura 1-24-15 Ebisu, Shibuya-ku, Tokyo Inside Prestige Co., Ltd.

Claims (6)

[Claims] 1. A white powder composed of a mixture of barium sulfate powder and titanium oxide powder is used as the adhesive, and the solid content of the adhesive is 100.
An adhesive for surface light source bodies, characterized in that 5 to 60 parts by weight are mixed with respect to parts by weight. 2. The pressure-sensitive adhesive for a surface light source according to claim 1, wherein the mixing ratio of the white powder barium sulfate powder and the titanium oxide powder is 4: 1 to 2: 5 by weight. 3. The white powder has an average particle size of 0.1 to 1 μm,
The pressure-sensitive adhesive for a surface light source according to claim 1 or 2, which has a particle size distribution of 0.02 to 5 µm. 4. A white powder-containing pressure-sensitive adhesive obtained by mixing 5 to 60 parts by weight of white powder composed of a mixture of barium sulfate powder and titanium oxide powder with 100 parts by weight of the solid content of the pressure-sensitive adhesive. The adhesive sheet is attached to one surface of the reflection sheet so that the adhesive portion has an arbitrary pattern, and the light guide plate is attached to the surface to which the white powder-containing adhesive is attached. A surface light source to be used. 5. The surface light source body according to claim 4, wherein the mixing ratio of the white powder barium sulfate powder and the titanium oxide powder is 4: 1 to 2: 5 by weight. 6. The white powder has an average particle size of 0.1 to 1 μm,
The surface light source body according to claim 4 or 5, wherein the particle size distribution is 0.02 to 5 µm.