JP2001291415A - Backlight - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight having a good durability, which is capable of easily emitting light uniformly, has a little loss of light, and is capable of manufacturing at low cost. SOLUTION: The backlight 10 has a light guiding plate 9 and a light transmitting tube l adhered fixedly to an edge face of the light guiding plate 9 by an adhesive 8. A light is introduced from a light source unit 11 into the light transmitting tube 1, and the light is irradiated from a side circumferential surface of the light transmitting tube 1. The light transmitting tube 1 is provided, between a core 2 and a tubular clad 3 covering it, with a belt-like reflection layer 4 extended in a longer direction of the tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight used for a liquid crystal display or the like.

[0002]

2. Description of the Related Art Liquid crystal display devices are widely used as portable terminals as lightweight and thin display devices. Since a liquid crystal display does not have a self-luminous function, a flat light-emitting body (backlight) is usually used on the back of the liquid crystal.

[0003] In recent years, liquid crystal displays have been improved in definition and color, and it is necessary to increase the brightness of backlights. Also, in portable devices, it is necessary to reduce the size of the battery and prolong the pot life, so that low power consumption is desired. From that point, it is necessary to increase the brightness of the backlight. .

Conventionally, as a backlight for a liquid crystal display, a so-called edge light system in which light from a light source is incident on a transparent light guide plate from a side surface thereof has been known. In this method, light entering from the side surface of the light guide plate is reflected by dots formed on the back surface of the light guide plate, and as a result, light is emitted toward the upper surface of the light guide plate. In addition, a scattering light guide plate in which spherical fine particles are dispersed instead of a transparent light guide plate is also known. In this method, light is emitted toward the upper surface by refracting or reflecting light with the spherical fine particles. I have.

Conventionally, a cold cathode tube is often used as a light source of the backlight.

[0006]

A backlight using a cold-cathode tube as a light source has the following disadvantages. An inverter for driving a cold cathode tube is required. Since there are electrodes at both ends of the cold cathode tube, light is not emitted from both ends. Therefore, the vicinity of both ends of the backlight becomes dark. The cold-cathode tube has no directivity in the direction of light emission, requires a reflector (reflector), and is troublesome in mounting the reflector, which is expensive, and furthermore, the reflection loss at the reflector is considerable. large. The installation of the cold-cathode tube is troublesome, and requires a mounting member, which is costly. The durability of the cold cathode tube is not good. The cold-cathode tube has a slow lighting and extinguishing speed.

An object of the present invention is to solve such various problems and to provide a backlight which has excellent operation characteristics, is inexpensive, has good durability, and emits light uniformly over the whole.

[0008]

According to the present invention, there is provided a backlight comprising a light guide plate and a light source disposed on an end face of the light guide plate, the light source extending along the end face as the light source. A light transmission tube is provided.

With such a backlight, for example, by using a light emitting diode or the like as a light source of the light transmission tube, an inverter is not required and the turning on / off speed can be increased. In addition, this light transmission tube has good durability and can be easily fixed to the light guide plate by an adhesive or the like.

This optical transmission tube has a core and a tubular cladding, wherein a strip-like reflective layer is formed between the tubular cladding and the core along the longitudinal direction of the tubular cladding and passes through the core. It is preferable that the light be reflected and scattered by the reflection layer and emitted from the outer peripheral surface of the tubular cladding opposite to the side where the reflection layer is formed. This eliminates the need for a reflector. In addition, light leakage is significantly reduced due to the lens effect of the cladding.

The light transmission tube uses a three-color extruder, and a core material, a clad material, and a reflecting material are introduced into the three-color extruder, and the core material is formed into a cylindrical shape, and the reflecting material is formed into the cylindrical shape. It is inexpensive and suitable to simultaneously extrude a band shape on the outer peripheral surface of the core material and a tube shape covering the core material and the reflective material at the same time.

[0012] Since the light transmitting section of the light transmission tube extends over substantially the entire length, it is easy to uniformly emit light from the entire light guide plate. In order to fix the light transmission tube to the light guide plate, it is preferable to use a transparent adhesive.

By filling a gap between the light transmission tube and the light guide plate with a transparent adhesive, light loss can be significantly reduced.

It is preferable that a concave line is provided on the end surface of the light guide plate, and the light transmission tube is fitted and arranged so as to be in close contact with the concave line.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an optical transmission tube used in the backlight according to the embodiment, and FIG.
3 is a sectional view taken along the line III-III of FIG. 2, FIGS. 4 and 5 are perspective views of the backlight according to the embodiment, and FIG. 6 is a VI-VI of FIG. It is sectional drawing which follows a line. FIG. 7 is a perspective view of a light guide plate according to the embodiment, and FIG.
It is sectional drawing which follows the II-VIII line.

The backlight 10 has a light guide plate 9 and the light transmission tube 1 fixed to one end surface of the light guide plate 9 with a transparent adhesive 8. Light is introduced from the light source unit 11 into the light transmission tube 1, and the light is emitted from the side peripheral surface of the light transmission tube 1 into the light guide plate 9.

A light emitting diode is disposed in the light source unit 11. This light emitting diode may be one or one kind. In this embodiment, three light emitting diodes 12, 13, and 14 of red, blue, and yellow face the end face of the light transmission tube 1. Is provided. In FIG. 4, the light source unit 11 is provided only at one end of the light transmission tube 1, and in FIG. 5, the light source units 11 are provided at both ends of the light transmission tube 1.

The light transmission tube 1 has a band-shaped reflection layer 4 extending in the longitudinal direction of the tube between a core 2 and a tubular cladding 3 covering the core. The reflection layer 4 may be formed in a state in which the reflection layer 4 slightly penetrates into the core 3 from the surface of the core 3.

The reflection layer 4 is disposed on the side of the light transmission tube 1 opposite to the side from which light is to be emitted.
In this embodiment, the reflective layer 4 has a width that is about half the circumference of the core 2 of the light transmission tube 1, and light is hardly leaked from the reflective layer 4 side.

As the material (core material) constituting the core 2, a transparent material having a higher refractive index than the material (cladding material) constituting the tubular cladding 3 is used. Is appropriately selected and used depending on the purpose.

Specific examples of the core material include polystyrene,
Styrene / methyl methacrylate copolymer, (meth) acrylic resin, polymethylpentene, allyl glycol carbonate resin, spirane resin, amorphous polyolefin, polycarbonate, polyamide, polyarylate, polysulfone, polyallylsulfone, polyethersulfone, polyether Imide, polyimide, diallyl phthalate, fluororesin, polyester carbonate,
Transparent materials such as a norbornene-based resin (ARTON), an alicyclic acrylic resin (Optrez), a silicone resin, an acrylic rubber, and a silicone rubber can be used. .).

On the other hand, the clad material can be selected from transparent materials having a low refractive index, and examples thereof include organic materials such as plastics and elastomers.

Specific examples of the clad material include polyethylene, polypropylene, polymethyl methacrylate, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyethylene-vinyl acetate copolymer, polyvinyl alcohol, and polyethylene. -Polyvinyl alcohol copolymer, fluororesin, silicone resin, natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer, butyl rubber,
Halogenated butyl rubber, chloroprene rubber, acrylic rubber, ethylene-propylene-diene copolymer (EPD
M), acrylonitrile-butadiene copolymer, fluorine rubber, silicone rubber and the like.

Among the above-mentioned core materials and cladding materials, polystyrene, polycarbonate, styrene- (meth) acryl copolymers (core materials) are used as core materials in view of optical characteristics such as transparency and refractive index and coextrudability. MS polymer) and the like, and the clad material is (meth)
Acrylic polymers are preferred.

The reflection layer contains a white pigment or a scattering material (meta).
It is preferable to use an acrylic polymer.

Examples of the white pigment and the scattering material include organic polymer particles such as silicone resin particles and polystyrene resin particles, metal oxide particles such as Al ₂ O ₃ , TiO ₂ and SiO ₂ , and sulfate particles such as BaSO _4. And carbonate particles such as CaCO _3, etc., and one of these can be used alone or in combination of two or more.

In consideration of reflection efficiency, coextrusion workability, and the like, the average particle size of the particles of these white pigments and scattering materials is preferably about 0.1 to 200 μm, particularly preferably about 0.5 to 50 μm. The content in the reflective layer constituting material (reflective material) is about 0.5 to 20% by weight, particularly 1 to 10% by weight.
It is preferred that it is about.

Although the thickness of the reflection layer 4 is not particularly limited,
The thickness is preferably 0 to 200 μm, particularly preferably 50 to 100 μm. If the thickness is too small, the reflected light decreases and the luminance decreases.If the thickness is too large, the reflected light increases and the luminance increases. In some places, the brightness may be disadvantageously reduced.

Although the diameter of the core 2 is not particularly limited, it is usually about 2 to 30 mm, especially about 5 to 15 mm.
The wall thickness of the tubular cladding 3 is usually about 0.05 to 4 mm, especially about 0.2 to 2 mm.

In this light transmission tube, a reflective protective layer may be formed on the outer surface of the tubular cladding 3 so as to cover the peripheral surface that does not emit light (the peripheral surface on the side of the reflective layer 4). In the case of an optical transmission tube having such a reflective protective layer formed thereon, when there is a defect such as a pinhole in the reflective layer 4, light leaking to the back side of the reflective layer 4 through this defective portion or the reflective layer 4 has By reflecting the light leaking from the side portion with the reflective protective layer, the loss of light can be reduced, and the brightness on the opposite side of the reflective layer 4 can be further increased.

As a constituent material of the reflective protective layer, a material that does not transmit the light leaked from the reflective layer 4 to the outside, does not absorb the light, and reflects the light efficiently is preferable. And a metal foil or metal sheet of silver, aluminum, or the like, or a coating film in which the above-described scattering particles that scatter light are dispersed.

In order to manufacture this light transmission tube, for example, a three-color extruder having three screw portions is used, and a core material, a clad material, and a reflecting material containing a white pigment or a scattering material are introduced into the extruder. The core material may be extruded into a cylindrical shape, the reflective material may be extruded into a plurality of strips on the outer peripheral surface of the columnar core material, and the clad material may be extruded into a tube shape covering the core material and the reflective material.

According to this method, three types of materials having different refractive indices and physical properties can be simultaneously extruded, and a laminated structure having three types of functions can be formed at a time.
Moreover, since the respective materials are laminated in a softened state, an optical transmission tube having excellent adhesion between the respective layers can be efficiently manufactured.

When a reflective protective layer is formed, a metal foil or a metal sheet may be adhered after the extrusion molding, or a coating material in which scattering particles are dispersed may be applied. It is also possible to form a hydrophilic protective layer.

The optical transmission tube may be manufactured by a method other than the above.

By lighting one, two or three of the light emitting diodes 12, 13, and 14, the light transmission tube 1 is turned on.
Can emit light of various colors. When only one light emitting diode 12, 13, 14 of the light source unit 11 is turned on, light of the color of the diode is radiated, and when two diodes are turned on, a light of an intermediate color in which they are mixed is emitted. Light is emitted and white light is emitted by turning on the three diodes.

Of course, as described above, only one or one type of light emitting diode may be provided.

When the light source units 11 are provided at both ends of the light transmission tube 1, light with high luminance is emitted over the entire length of the light transmission tube 1. When the light transmission tube 1 is short, it is sufficient to provide the light source unit 11 only at one end of the light transmission tube 1, but when the light transmission tube 1 is long, it is preferable to provide it at both ends.

When the light source units 11 are provided at both ends of the light transmission tube 1, the light emission colors of the light source unit 11 at one end and the light source unit 11 at the other end may be different. For example, when red light is supplied from one end and blue light is supplied from the other end, red light is emitted near one end of the light transmission tube 1 and blue light is emitted near the other end. Near the middle of the tube 1, purple light is emitted. Therefore, a subtle hue and color tone can be expressed by one light transmission tube.

In this embodiment, the end surface of the light guide plate 9 is a flat surface. A transparent adhesive 8 is filled in a gap generated between the light transmission tube 1 and the peripheral surface of the light transmission tube 1 having a circular cross section. Thereby, the light emitted from the light transmission tube 1 is introduced into the light guide plate 9 with almost no leakage.

The light guide plate 9 is preferably made of a transparent synthetic resin such as an acrylic resin or polycarbonate.
As the adhesive 8, it is preferable to select an adhesive having a strong adhesive strength to both the light transmission tube 1 and the light guide plate 9, and for example, an epoxy adhesive is suitable.

In the present invention, in order to reduce the amount of the adhesive 8 used and to more reliably prevent light leakage,
As shown in FIG. 9, an arc-shaped or semicircular recess 7 may be provided on the end surface of the light guide plate 9A, and the light transmission tube 1 may be fitted into the recess 7 and fixed with an adhesive. The radius of curvature of the arc of the concave streak 7 is equal to the radius of curvature of the outer periphery of the optical transmission tube 1. Instead of manufacturing such a light guide plate 9A,
The light guide plate and the light transmission tube may be integrated by an insert molding method in which the light transmission tube 1 is placed in a mold (not shown) for forming the light guide plate 9A.

In the present invention, it is clear that a configuration accompanying the backlight may be added, such as disposing a prism sheet on the surface of the light guide plate.

[0044]

According to the backlight of the present invention, a light transmission tube is used as a light source disposed at the end face of the light guide plate, and light can be easily and uniformly emitted from the light guide plate, and the light loss can be reduced. Can also be reduced. Also,
By using the light emitting diode, the turning on / off speed can be increased and the amount of heat generated can be reduced. In addition, the light transmission tube has excellent durability, and has no risk of electric leakage even if it is cut, and is excellent in safety.
The backlight of the present invention is easy to manufacture and can be inexpensive.

[Brief description of the drawings]

FIG. 1 is a perspective view of an optical transmission tube used in an embodiment.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a perspective view showing a backlight according to the embodiment of the present invention.

FIG. 5 is a perspective view of a backlight according to another embodiment.

6 is a sectional view taken along the line VI-VI in FIG.

FIG. 7 is a perspective view of a backlight according to the embodiment.

FIG. 8 is a sectional view taken along line VIII-VIII in FIG.

FIG. 9 is a cross-sectional view of a main part of a backlight according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical transmission tube 2 Core 3 Tubular cladding 4 Reflection layer 8 Transparent adhesive 9 Light guide plate 10 Backlight 11 Light source unit

Claims (8)

[Claims] 1. A backlight comprising a light guide plate and a light source disposed on an end face of the light guide plate, wherein a light transmission tube extending along the end face is provided as the light source. Backlight. 2. The optical transmission tube according to claim 1, wherein the optical transmission tube is formed along a length direction of the tubular clad between the core, a tubular clad that encloses the core, and the tubular clad and the core. An optical transmission tube having a strip-shaped reflective layer, wherein light passing through the core is reflected and scattered by the reflective layer and emitted from the outer peripheral surface of the tubular cladding side opposite to the reflective layer forming side. The backlight. 3. The light transmission tube according to claim 2, wherein a core material, a clad material, and a reflecting material are introduced into the three-color extruder using a three-color extruder, and the core material is reflected in a cylindrical shape. A backlight comprising a light transmission tube formed by simultaneously extruding a material into a band shape on the outer peripheral surface of the cylindrical core material and simultaneously extruding a clad material into a tube shape covering the core material and the reflective material. 4. The backlight according to claim 2, wherein the reflection layer is made of a (meth) acryl-based polymer containing a white pigment or a scattering material. 5. The method according to claim 2, wherein the tubular cladding is made of a (meth) acrylic polymer, and the core is made of polystyrene, polycarbonate, or a styrene- (meth) acrylic copolymer. Backlight featured. 6. The backlight according to claim 1, wherein the light transmission tube is adhered to an end surface of the light guide plate by a transparent adhesive. 7. The backlight according to claim 6, wherein a transparent adhesive is filled between the light transmission tube and the light guide plate. 8. The backlight according to claim 1, wherein a recess is provided on an end surface of the light guide plate, and the light transmission tube is fitted in the recess. .