JPH07110409A - Light transmission plate for edge light source type plane lamp - Google Patents

Abstract

PURPOSE:To provide the light transmission plate for an edge light source type plane lamp which is formable without providing the plate with an irregular reflection layer consisting of printing patterns changed in the density of fine dots, is excellent in yield and production efficiency and has the excellent uniformity of illuminance over the entire surface even in the case of obtaining a large light emitting surface. CONSTITUTION:This light transmission plate 1 is used to convert the light of a linear light source arranged on its flank to a surface light source and is the light transmission plate for the edge light source type plane lamp which consists of >=2 layers of the laminates of transparent substrates 11, 13 and of which the transparent substrate 11 on its exit side dispersedly contains light transmittable irregular reflection particles 12 having the refractive index at least on the surface thereof different from the refractive index of the transparent substrate 11. As a result, the light transmission plate is obtd. by forming the laminated composed of the transparent substrate 11 dispersedly contg. the irregular reflection particles and the mere transparent substrate 13. The light transmission plate is efficiently obtd. by a production system, such as injection molding system or casting polymn. system, with which mass production is easy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate for an edge light source type flat lamp which exhibits excellent brightness uniformity even when forming a large light emitting surface and is excellent in manufacturing efficiency.

[0002]

2. Description of the Related Art As shown in FIG. 2, a linear light source 2 such as a fluorescent lamp is arranged on a side surface of a light guide plate 1, light from the light source is received in the light guide plate and is directed to one side of the light guide plate as indicated by an arrow. Edge light source type flat lamps, which are adapted to be converted into surface light sources that emit light, are widely used as backlights of liquid crystal displays, illumination display lamps, and the like.

Conventionally, as the above-mentioned light guide plate, there has been known one in which a substrate (1) made of a homogeneous transparent body is provided with a diffuse reflection layer formed by pattern-printing dots of a reflective ink on the bottom surface. The irregular reflection layer is for emitting light to one side (front side) of the substrate so that the brightness of the entire surface becomes uniform,
In order to make the brightness on the entire light emitting surface uniform, the pattern is printed by a screen printing method or the like so that the dot density increases continuously (steplessly) as the distance from the light source increases.

However, in order to continuously change the dot density, it is necessary to change the area of each dot on the order of micron, so it is difficult to print each dot in a clearly divided state, and the light guide plate is obtained. In addition to the poor yield, it takes a lot of time and labor to produce a printing plate in which the dot density is continuously changed, and it is necessary to change the dot printing pattern for each size and shape of the light guide plate. There is a problem that the light plate is poor in manufacturing efficiency, and it is difficult to form a light guide plate having a large light emitting surface.

[0005]

According to the present invention, fine dots can be formed without providing a diffuse reflection layer consisting of a printed pattern in which the density is changed, and the yield and the manufacturing efficiency are excellent, and a large light emitting surface is obtained. The challenge is to develop a light guide plate for an edge light source type flat lamp, which has excellent uniformity of brightness on the entire surface.

[0006]

The present invention is a light guide plate for converting the light of a linear light source arranged on the side surface into a surface light source, which is composed of a laminate of two or more layers of transparent substrates, and A light guide plate for an edge light source type flat lamp, characterized in that the transparent substrate on the light emitting side contains dispersed diffuse reflection particles having a light transmittance different from that of the transparent substrate at least on the surface thereof.

[0007]

In the light guide plate having the above structure, the light incident on the transparent substrate on the light emitting side is diffusely reflected on the surface of the irregular reflection particles to emit the light from the plane of the substrate, and a large number of irregular reflection particles dispersed in the transparent substrate. The brightness of the entire light emitting surface is made uniform based on the distribution of, and in that case, the light from the linear light source of the side surface arrangement is mainly transmitted through the transparent substrate on the back surface on the light emission side to The light is efficiently transmitted to the end portions of the substrate so that the luminance of the entire light emitting surface can be made uniform even in the case of a large area plate. In addition, a transparent substrate containing diffusely-reflected particles dispersed therein can be easily formed by a mass-production-friendly manufacturing method such as an injection molding method or a casting polymerization method as well as a simple transparent substrate. Is.

[0008]

The light guide plate of the present invention comprises a laminate of two or more layers of transparent substrates, and the transparent substrate on the light emitting side has a light-transmitting diffused reflection whose refractive index at least on the surface is different from that of the transparent substrate. It is used for forming an edge light source type flat lamp which contains particles dispersedly and is arranged on the side surface of a linear light source so as to convert the light of the linear light source into a surface light source. FIG. 1 illustrates the light guide plate of the present invention, and FIG. 2 illustrates an edge light source type flat lamp. Reference numeral 1 is a light guide plate, 11 and 13 are transparent substrates, 12 is irregular reflection particles, and 2 is a linear light source.

As the transparent substrate, an appropriate transparent substrate can be used. Preferably, an acrylic resin such as polymethylmethacrylate or methacryl-styrene copolymer, polycarbonate, glass or the like is excellent in transparency. The thickness is arbitrary, but is generally 10 mm or less, preferably 10 μm to 7 mm, particularly 50 μm to 5 mm.

The light guide plate of the present invention is formed as a laminate of transparent substrates, and the number of layers is any number of 2 layers or 3 layers or more. In general, in the case of single-sided light emission, a two-layer laminated body is formed as illustrated in FIG. 1, and in the case of double-sided light emission, a three-layer laminated body is formed as illustrated in FIG.

The shape of the transparent substrate is generally a flat plate, but as shown in FIG. 4, the cross section of the laminated body as a light guide plate becomes farther from the linear light source 2 through a part or all of the laminated transparent substrates. It is also possible to use a taper shape in which the thickness gradually decreases. Such a tapered shape compensates for a decrease in light intensity due to the light-collecting effect based on the shape moving away from the linear light source, and advantageously acts to make the luminance uniform over the entire light emitting surface.

As shown in FIGS. 1 and 3, the diffused reflection particle 1 is used for the transparent substrate 11 on the light emitting side in the present invention.
Those containing 2 dispersedly are used. As the irregularly-reflecting particles, those having an excellent light-transmitting property, in particular, a wavelength range of a transmitted ray, and having a refractive index at least different from that of the transparent substrate containing the particles are used.

Therefore, as the irregular reflection particles, particles made of the same material as the transparent substrate and having a surface treated with a material having a refractive index different from that of the transparent substrate can also be used. Diffuse reflection particles that are generally used are powder of glass beads, thermoplastic resin, or thermosetting resin, but bubbles or the like can also function as diffuse reflection particles.

The transparent substrate containing the irregularly-reflecting particles dispersed therein can be formed by an appropriate method such as an injection molding method or a casting polymerization method using a transparent substrate-forming agent mixed with the irregularly-reflecting particles. In addition, a transparent substrate containing bubbles as diffusely-reflecting particles can be formed by a method of controlling a cooling rate such as abrupt cooling in the forming method according to the above.

The shape and particle size of the irregular reflection particles to be used can be appropriately determined according to the thickness of the transparent substrate in which they are contained, and the shape having a large surface area is advantageous in terms of irregular reflection on the particle surface. Also, 1/2 or less of the transparent substrate thickness,
In particular, particles having a particle size of 1/10 or less, particularly 0.1 to 500 μm are generally used. The content of diffuse reflection particles is
5-80% by weight is common.

The distribution of the diffused reflection particles on the transparent substrate may be uniform, or may be changed stepwise or continuously based on the distance from the linear light source. Moreover, the particle size of the irregular reflection particles may be changed stepwise or continuously based on the distance from the linear light source.

From the viewpoint of making the brightness of the entire light emitting surface uniform, it is preferable that the diffused reflection particles are densely distributed as the distance from the linear light source is increased and the particle size of the diffused reflection particles is reduced. The transparent substrate having such a distribution state can be formed by, for example, a method of sequentially laminating layers having different densities and particle diameters of diffuse reflection particles by a method such as an injection molding method or a casting polymerization method.

The laminated body of transparent substrates forming the light guide plate of the present invention can be formed simultaneously by, for example, a two-layer extrusion molding method,
It can be formed by an appropriate method such as a method of sequentially superimposing each layer, or a method of joining the layers formed by one layer with an adhesive or the like.

The edge light source type flat lamp can be obtained, for example, by arranging the linear light source 2 on the side surface of the light guide plate 1 of the present invention as illustrated in FIG. As the linear light source, for example, a fluorescent lamp such as a hot cathode lamp or a cold cathode lamp, an incandescent light bulb, an HID, an EL, an LED, or the like can be used appropriately. In particular, the cold cathode lamp can be preferably used from the viewpoints of life and thinning due to thin tube diameter. By the way, small cold cathode lamps with a tube diameter of 2.5 to 7 mm and a length of 50 to 300 mm are also commercially available. In FIG. 2, 5 is a reflective film made of metal foil or the like, and 6 is a cover.

A reflective layer may be provided on the light guide plate of the present invention, if necessary. Reference numeral 3 in FIGS. 2 and 4 is a reflective layer, which can be provided on the surface of the transparent substrate, particularly the transparent substrate that does not contain diffused reflection particles, on which light does not need to enter or exit. As the reflective layer, a suitable film such as a film made of polyester or the like having a diffused efficiency and a reflected light efficiency improved by a method of mixing a white pigment or a plastic film having a metal such as silver or aluminum deposited thereon can be used.

In the above description, the surface of the transparent substrate on which the reflective layer is provided, and in particular, the surface (bottom surface) facing the light emitting surface of the transparent substrate is a rough surface from the viewpoint of making the brightness of the entire light emitting surface uniform. It is advantageous to use a diffused reflection surface due to a change in the pattern, and it is also possible to use a diffused reflection layer by a conventional pattern printing.

Further, the light guide plate of the present invention may be provided with a diffusion layer if necessary. Reference numeral 4 in FIG. 2 denotes a diffusion layer, which can be provided on the light emitting surface of the transparent substrate as indicated by the arrow. As the diffusion layer, those in which particles for light diffusion are distributed on the surface of a plastic layer having excellent light transmittance such as polyester or polycarbonate, or those whose surface is roughened by embossing, and further those layers Appropriate ones such as a superposed one can be used.

The edge light source type flat lamp formed by using the light guide plate of the present invention can be used for various purposes such as a backlight of a liquid crystal display and an illumination lamp.

Example 1 100 parts of polymethylmethacrylate (parts by weight, the same applies hereinafter)
A pellet containing 30 parts of glass beads having a particle size of 50 to 500 μm and a pellet of polymethylmethacrylate were used in a two-layer extrusion molding method to have a thickness of about 1 mm and a width of 550.
mm, 400 mm long glass bead-containing plate and a polymethylmethacrylate plate having the same size and a thickness of about 2 mm are simultaneously formed, and the exposed surface of the polymethylmethacrylate plate is roughened with sandpaper. After that, a polyester solution containing 20% by weight of titania having an average particle size of 1 μm was applied to form a reflective layer to obtain a light guide plate.

Next, on the side surface in the width direction of the light guide plate, the tube diameter 3
Two cold-cathode lamps each having a length of 300 mm and a length of 300 mm were arranged in a V-shape, and a silver-deposited polyester-based reflective film was provided on the outside thereof to form an edge light source type flat lamp.

When the brightness of the above flat lamp was examined,
1 from the end on the cold cathode lamp side based on the length direction of the light guide plate
610 cd / m ² at 0 mm position, 595 c at 100 mm position
d / m ^2, located at 570 cd / m ^2, located at 545cd / m ^2, 400mm position of 300mm of 200mm at (end) 61
It was 5 cd / m ² . This is brightness uniformity comparable to that of a B5 plate having a size of a B5 plate provided with a diffuse reflection layer formed by pattern-printing dots of a conventional reflective ink. There was no difference in brightness in the width direction of the light guide plate.

[0027]

The light guide plate of the present invention can be obtained by forming a laminated body of a transparent substrate containing diffuse reflection particles dispersed therein and a simple transparent substrate, and is easy to mass-produce by an injection molding system or a casting polymerization system. Can be efficiently obtained by various manufacturing methods.
Therefore, it is possible to form fine dots without providing a diffused reflection layer consisting of a print pattern in which the density is changed, and it is excellent in yield and manufacturing efficiency. There is.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a light guide plate.

FIG. 2 is a sectional view illustrating an edge light source type flat lamp.

FIG. 3 is a cross-sectional view illustrating another light guide plate.

FIG. 4 is a sectional view illustrating still another light guide plate.

[Explanation of symbols]

 1: Light guide plate 11, 13: Transparent substrate 12: Diffuse reflection particles 2: Linear light source

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication G02F 1/1335 530 G09F 13/18 D 8621-5G

Claims (4)

[Claims] 1. A light guide plate for converting light of a linear light source arranged on a side surface into a surface light source, comprising a laminate of two or more layers of transparent substrates, and at least the transparent substrate on the light emission side thereof. A light guide plate for an edge light source type flat lamp, wherein diffused reflection particles having light transmissivity different from that of the transparent substrate are dispersed and contained in the surface thereof. 2. The light guide plate according to claim 1, wherein the distribution or / and the particle size of the irregular reflection particles is changed stepwise or continuously based on the distance from the linear light source. 3. The light guide plate according to claim 1, wherein the thickness of the light guide plate is gradually reduced as the distance from the linear light source increases. 4. An edge light source type flat lamp having a linear light source on a side surface of the light guide plate for an edge light source type flat lamp according to claim 1.