JP2003077323A - Well-proportioned surface light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light emitting device having well-proportioned flat light emitting surface, useful for reducing the weight and the thickness of a backlight or a front light. SOLUTION: The well-proportioned surface light emitting device comprises at least a light source arranged at its one end side part, an another surface part opposite to one surface part enabled to emit light, perpendicular to the one end side part, and a light guide plate enabled to guide the light from various light sources to an emitting surface. One light emitting surface part is almost flat, and the other surface part has prism-shaped indentation. The incident light on the light guide plate has such a light distribution that the volume of the light traveling in the direction of one light emitting surface part and/or the other surface part having prism-shaped indentation is more than that traveling in parallel with the light guide plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source arranged in a liquid crystal display device, and more particularly, to a backlight illuminating device for illuminating the liquid crystal display device from the back side, and an auxiliary light source for displaying the liquid crystal display device. The present invention relates to a surface light emitting device having a high degree of uniformity suitable for a front light illuminating device arranged on the surface side.

[0002]

2. Description of the Related Art Liquid crystal display devices are widely used as display devices for liquid crystal televisions, computers, word processors, mobile phones, and other information devices. Since the liquid crystal display element is not a self-luminous device, a transmissive liquid crystal display device requires a backlight from behind, and a reflective liquid crystal display device can display by external light, but when external light is insufficient, it is an auxiliary light source. As a front light is required to illuminate the display surface.

Backlights and frontlights, which are illumination devices for liquid crystal displays, are required to be lightweight, thin, and have a uniform planar light source with good light utilization efficiency. As shown in FIG. 1, the thin planar light source propagates light incident from a light source 1 near one side surface of the light guide plate in a direction away from the light source while repeating total reflection at the interface between the light guide plate 2 and air. Let

In the backlight, the propagating light is reflected and refracted by the dots of the high refractive index particles printed on the back surface of the light guide plate to be emitted to the front surface. For the light emitted from the surface, a method of irradiating the transmissive liquid crystal display element with light in a desired direction using a lens film or a diffusion plate is adopted. However, in the method using printed dots, scattered light is obtained, so that light is diffused in an unnecessary direction, and the light utilization rate is likely to decrease. In addition, a lens film is needed to direct the light in the desired direction.

On the other hand, since the front light sees the display image through the light guide plate of the front light, the dot is visually recognized by the method of utilizing the reflection and refraction of light by the printing dot like the backlight, which is adopted. Can not. Therefore, a method of emitting light to the lower surface by reflection and refraction by the inclined surface of the prism-shaped unevenness provided on the front surface of the light guide plate is adopted. In this case, the prismatic irregularities include prisms of an isosceles triangle (Japanese Patent No. 3012462) and projection-shaped transmissive dots (Japanese Patent Laid-Open No. HEI-1).
No. 1-326898) has been proposed. But,
The prism-shaped concavo-convex structure has a drawback that a large amount of light is emitted toward the light source side, and the farther the light source is from the more difficult it is to emit light. For this reason, the pitch of the unevenness is shortened as the distance from the light source increases (Japanese Patent No. 2925530), or the distance from the light source increases.
The opposite surface is brought closer to the prismatic concave-convex structure surface (Patent No. 29)
11444) and other complicated methods have been proposed.

[0006]

DISCLOSURE OF THE INVENTION The surface emitting device of the present invention is intended to provide a prism-shaped concavo-convex structure having high light utilization efficiency in the backlight instead of the printing dots, and the front surface together with the backlight. It also solves the problem that a light is likely to occur in the prismatic concavo-convex structure, that is, it is difficult to obtain a uniform flat light source because the light emission from the light guide plate decreases as the distance from the light source increases, and a highly uniform surface illumination is provided. It is a thing.

[0007]

Means for Solving the Problems As a result of intensive research to solve the above-mentioned problems, the present inventors have found that, as a characteristic of a light guide plate having a prismatic concavo-convex structure, the defect that the darker the light source is, It has been found that the problem is solved by making a light beam having a biased distribution on either surface of the light guide plate rather than using a light beam having a distribution of many light beams in a direction parallel to the light guide plate as usual. Came to.

That is, in the invention of claim 1, the light source is provided at at least one side end portion, and the light source is disposed substantially perpendicular to the side end portion and has the other surface portion on the opposite side from which light can be emitted, A light guide plate capable of guiding light from the light source to the emission surface, one emission surface being a substantially flat surface, the other surface portion having a large number of prismatic concave-convex structures, and light incident on the light guide plate is parallel to the light guide plate. A surface emitting device having a high degree of uniformity, characterized in that there is more light distribution in the direction of the emission one surface portion and / or in the direction of the other surface portion having a prism-shaped concavo-convex structure than the direction light.

According to a second aspect of the present invention, the incident light is 10 to 50 toward the emission front surface side with reference to the direction parallel to the light guide plate.
2. The distribution according to claim 1, which has a distribution including more light directed in a direction within a range of 10 to 50 degrees toward the other surface portion having a prism-shaped concavo-convex structure within a range of degrees and / or in a direction parallel to the light guide plate. It is a surface emitting device.

According to a third aspect of the present invention, the incident light has a ridge having a triangular peak in section and a ridge having a valley between the light source disposed at one end of the light guide plate and the end of the light guide plate. 2. A planar film member, in which triangular prisms parallel to each other are arranged in a plane, is arranged so that the top edges thereof are parallel to the rod-shaped light source and the top portions are directed toward the light source to transmit light to give a distribution. Alternatively, it is the surface emitting device according to 2.

According to a fourth aspect of the present invention, a large number of prism-shaped concavo-convex structures on the other surface have triangular cross-sections of unequal sides, and triangular prisms or triangular grooves having ridges at the tops or valleys are substantially parallel to each other. The structure according to any one of claims 1 to 3, which is provided in
The surface emitting device according to the item.

According to a fifth aspect of the present invention, the triangles of the unequal side of the cross section of the prism-shaped concavo-convex structure on the other surface include a gentle slope and a steep slope, and the angle formed between the gentle slope and the bottom is 10 degrees or less, and the steep slope is the bottom. The surface emitting device according to any one of claims 1 to 4, wherein the angle formed with is an isosceles triangle of 30 to 60 degrees.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface emitting device is usually provided with a rod-shaped light source composed of a cold cathode tube, a light emitting diode, etc., which is installed near one end surface of a light guide plate, and the back surface is surrounded by a reflector plate. Light is incident from the side surface of the light guide plate. As shown in FIG. 1, the light incident on the light guide plate 2 made of a parallel flat plate which is transparent from the light source 1 is such that the light 01 parallel to the flat plate goes straight and the light 02 smaller than the critical angle of the parallel flat plate is emitted to the outside of the light guide plate. To be done. Lights 03 and 04 having a critical angle or more are guided while repeating total reflection on the upper and lower surfaces, without changing their directional angles.

Various methods are adopted to extract the light taken into the light guide plate 2. One of them is extracted by changing the direction by refraction / reflection by a printing dot containing particles having a high refractive index. However, with this method, it becomes scattered light and it is difficult to obtain light in a certain direction, and the light utilization efficiency is poor. In addition, it becomes opaque and is not suitable for the front light of a reflective liquid crystal display device.

As a method of remedying the above-mentioned drawbacks, a method of taking out with a light guide plate having a prismatic uneven structure has been proposed. As shown in FIG. 2, light is emitted to the surface (flat surface) 5 opposite to the structural surface 4 of the light guide plate 3. In this case, it is preferable that the light is emitted in the direction normal to the emission surface. In a preferred typical example, the prismatic concavo-convex structure is an isosceles triangle, and as shown in FIG. 3, it is composed of an angle α between a gentle slope and a bottom surface and an angle β between a steep slope and a bottom surface, and α is 10 degrees or less. It is said that a range of 30 to 60 degrees is suitable.

However, even when light is emitted by a light guide plate having a prism-shaped concavo-convex structure of unequal sides, a portion closer to the light source is likely to be emitted, and a portion farther from the light source is less likely to be emitted and is dark, and a uniform surface light source is obtained. I can't get it. Therefore, as the distance from the light source is increased, the prismatic concavo-convex structure is changed, the pitch is changed, the surface opposite to the prismatic concavo-convex surface is brought closer to the prismatic concavo-convex surface, and the like, but the structure is complicated, Moreover, there is a problem that the effect is not always sufficient.

On the other hand, a method (Japanese Patent Application Laid-Open No. 11-184386) in which incident light from a point light source is diffused and made incident and is narrowed down by a light guide having a microprism is being studied. The slope of the microprism is 5 to 15 degrees. It is valid. However, as a result of studying the light guide state of the light guide plate having the prismatic concavo-convex structure having the gentle slope and the steep slope, the present inventors have found that the angle of 10 degrees or less with respect to the surface parallel to the light guide plate on the steep slope side. The light received at is emitted at an angle close to the normal direction of the emission surface on the opposite surface side by total reflection efficiently, and light with a large angle of 30 degrees or 40 degrees with reference to the surface parallel to the light guide plate. Indicates that the probability of receiving light on a steep slope is small, and that the light received on a gentle slope has an angle of 2 with respect to the base angle of the gentle slope for every total reflection.
It was found that light with a small angle near a plane parallel to the light guide plate received less light on the gentle slope, and light with a large angle received on the gentle slope was high.

As a model case, when polycarbonate having a refractive index of 1.58 is used and prisms of an isosceles triangle having a gentle slope angle α = 2 ° and a steep slope angle β = 43 ° are arranged adjacent to each other, they are parallel to the light guide plate. The angle of incidence based on this plane is referred to as the parallel incidence angle, and the emission angle (parallel emission angle) and the light reception rate on a gentle slope and the light reception rate on a steep slope when the plane parallel to the light guide plate is used as a reference, as with the parallel incidence angle. Table 1 below shows a case of a typical angle.

[0019]

[Table 1]

All of the light received on the steep slope is emitted outside the light guide plate in the direction of the emission angle (emission horizontal angle). In this case, the light traveling direction is parallel to the light guide plate and the light traveling direction is 0 degrees, and the prism concave-convex surface side is indicated by plus and the opposite exit surface side is indicated by minus. For example, 22.70% of light with a parallel incident angle of 10 degrees
Is received on a steep slope, all of which are on the exit side 26 degrees 40
It means that the light is emitted in minutes. All the light received on the gentle slope is totally reflected and does not exit at that time. However, a part of the light immediately goes to the steep slope and goes to the minus direction, that is, the emitting surface side and is emitted. The ratio was defined as the gentle slope emission rate. For example, 77.30% of the light with an incident angle of 10 degrees is received on the gentle slope, and 11.06% of the light is emitted toward the steep surface again in the direction of -116 degrees.

In the calculation of the light receiving rate, it is calculated which slope receives the light incident on the steep slope or the gentle slope at an angle θ based on the angle parallel to the light guide plate. As shown in FIG.
The light irradiating the right part a'of the bottom face a hits a steep slope and the rest a "falls on a gentle slope. When the bottom face is a, a '/ a
Is the steep slope light receiving rate, and a ″ / a or 1−a ′ / a is the gentle slope light receiving rate.

When the size a of the steep slope is taken as the unit size 1, the following relationship is established.

[0023]

[Equation 1]

Similarly, the gentle slope emission rate is as shown in FIG.
Since the reflected light from the gentle slope b is received, the light received on the gentle slope b ′ part by the incident from the gentle slope side can hit the steep slope again, but the light received on the b ″ part does not go to the steep slope. When the gentle slope is b, it is the ratio of b ′ / b hitting the gentle slope and then being totally reflected again on the steep slope. , The light is emitted in the range of 92 ° to 43 ° with respect to the emission surface.If the size of the steep slope is set to 1 in the same manner as described above, the following relationship holds.

[0025]

[Equation 2]

As can be seen from the above table, it is useful to emit light in the direction normal to the emission surface as a surface light emitting device as a backlight or front light of a liquid crystal display device, and therefore emission to the emission surface side. Most of the incident light has a parallel incident angle of 0.
This is a part where light from 10 degrees to 10 degrees is received by the steep slope and emitted to the emission surface side. Table 2 shows the light reception and emission conditions from 0 degree to 10 degrees.

[0027]

[Table 2]

From 0 ° to 8 °, it can be seen that the light is emitted nearly 100% in the normal direction of the most preferable emission surface. In other words, the light is emitted at a position relatively close to the light source without repeating the reflection / refraction, which is the function of the light guide plate. On the other hand, in Table 1, light with a parallel incident angle of 10 degrees or more has a low light reception rate on a steep slope and therefore is rarely emitted. The light reception rate on a gentle slope is high, and light is guided with almost no emission. It can be inferred that it is possible to reduce the angle by 2 degrees with respect to the plane parallel to the light guide plate on the gentle slope and to convert the effective light from 0 degree to 10 degree at a place relatively far from the light source.

For the light guide plate, a usual transparent optical material can be used. Synthetic resins are suitable for accurately forming the prismatic uneven structure. Preferred synthetic resins include acrylic synthetic resins, polyesters, polycarbonates, transparent cyclic polyolefins, and the like. A method for manufacturing a light guide plate having a prismatic concavo-convex structure on one surface is arbitrary, but when a synthetic resin is used, a usual resin molding method can be adopted. If you need more,
A film or sheet having a prismatic concavo-convex structure may be separately manufactured and laminated with another synthetic resin plate. Various adhesives and pressure-sensitive adhesives can be selected and used for lamination.

The prismatic uneven structure preferably has a steep slope and a gentle slope. The steep slope receives the incident light and reflects on this slope, causing the light to be emitted to the opposite emission surface side. Therefore, it is designed so as to match the desired emitting direction, and is usually designed in consideration of the critical angle of the material used so that the light is emitted in the direction normal to the emitting surface. The gentle slope has a function of guiding light in the light guide plate while converting light having an incident angle unsuitable for emission. Therefore, the light guide plate is designed in consideration of how far the light needs to reach with respect to the thickness, and the inclination angle is large at a relatively short distance and small at a long distance. Normally, the steep slope angle is 30-60
The angle of the gentle slope is 10 degrees or less.

The steep slopes and the gentle slopes may be alternately arranged adjacent to each other or may be arranged intermittently, but from the viewpoint of effective use of the surfaces, they are preferably arranged adjacent to each other. In the case of disposing intermittently, the prism portion may be formed in a convex shape or a concave shape. The inclination angles of the steep slope and the gentle slope may each be a constant angle or may be changed as the distance from the light source increases. The alternating pitch of the steep slope and the gentle slope may be constant or may be gradually changed as the distance from the light source increases. When used for a front light, it is preferable that the inclination angle and pitch are as constant as possible so that the transmitted image on the liquid crystal display is not distorted.

The positions of the steep slope, the gentle slope, and the light source are preferably arranged so that the steep slope is likely to receive a light beam from the light source.
The ridgelines of a triangular prism or a trapezoidal prism having a steep slope and a gentle slope are parallel to each other, and in order for the steep slope to easily receive a light beam from a light source, it is most likely that the light beam and the ridgeline are orthogonal to each other. However, for the purpose of preventing the occurrence of interference fringes and the like with the liquid crystal display element, the light ray and the ridge line may be arranged so as to deviate from the optimum orthogonality.

In the front light, the surface opposite to the prismatic concavo-convex structure is the exit surface, which is a substantially flat surface. This flat surface may be parallel to the plane connecting the valleys of the prismatic concave-convex structure or may be inclined. In the case of tilting, a structure having a so-called wedge-shaped surface, which is closer to the light source, is preferable.

The light source for entering the light guide plate is a rod-shaped light source, which is installed close to the side end of the light guide plate, and an LED having a rod-shaped cold cathode tube or a rod-shaped light guide is used. The light incident on the light guide plate needs to be a light beam having a distribution in which the light in the direction of the emission one surface and / or the direction of the other surface of the prismatic uneven structure is larger than the light in the direction parallel to the light guide plate. .

Various methods can be used to create a ray having this distribution. One of them is a method of inclining the incident end surface of the light guide plate toward the emission one surface side of the light guide plate or the other surface side of the prism uneven structure. With this method, it is difficult to obtain a certain degree of accuracy in a thin light guide plate, and in order to show the uniformity, the amount of incident light exceeding the critical angle of the light guide plate increases and the light utilization efficiency deteriorates. The second method is a method in which a member having a prism structure on the surface is integrated with the side end portion of the light guide plate. In this case as well, the work accuracy is difficult at the thin side end. The third method is to insert a member having a prism structure between the rod-shaped light source and the side end of the light guide plate. This method is a preferable method because sufficient accuracy can be obtained simply by inserting a separately manufactured member having a highly precise prism structure in a planar shape.

A member having a preferable prism structure in a planar shape is a prism film or a sheet (hereinafter referred to as a prism film). The prism film is formed by arranging triangular prisms, each of which has a ridge having a triangular top in a cross section and a ridge having a valley in parallel to each other in parallel with each other. As shown in FIG. 6, the prism film 6 is inserted and arranged at the end on the side of the light guide plate so that the prism apex is parallel to the rod-shaped light source 1 and the apex faces the light source 1. If the triangle of the cross section of the prism film is equilateral, the light ray transmitted through this is refracted and has a distribution divided into two in the direction of the slope. A typical example is an isosceles triangle having an apex angle of about 90 degrees or an equilateral triangle having an apex angle of 60 degrees. In the case of unequal sides, the distribution is biased to one side, and as a typical example, a triangle having one side parallel to the light guide plate and the other side having a slope has a distribution biased to the side opposite to the slope.

In order to improve the uniformity, the distribution of the light rays incident on the light guide plate is in the direction parallel to the light guide plate in the range of 10 to 50 degrees toward the emission one surface side with reference to the direction parallel to the light guide plate. A distribution containing more light than the light, or a distribution containing more light directed in the direction of 10 to 50 degrees toward the other surface having the prismatic uneven structure, or 10 to 50 in both directions.
It is effective when the light beam has a distribution containing a large amount of light directed within the range of degrees.

The uniformity of the surface emitting device can be obtained by measuring the emitted light from each part of the surface light source in the maximum and minimum ratios. In particular, the difference between the emitted lights at different distances from the light source is important, and is greatly improved when a light beam having the above distribution is incident.

[0039]

EXAMPLES The present invention will be described in more detail based on the following examples, but it goes without saying that the present invention is not limited to these examples.

Examples 1 to 4 [Structure of light guide plate] A cyclic polyolefin "Arton" (manufactured by JSR Corporation) having a refractive index of 1.51 was used to obtain a thickness of 20.
As shown in FIG. 3, the prismatic unevenness of the light guide plate at 0 μm
The slope angle α of the gentle slope is 2.5 degrees, and the slope angle β of the steep slope is 45 degrees.
They had a cross section of 1 degree and were provided adjacent to each other with a pitch of 280 μm. On the other hand, 800 μm thick acrylic sheet “AR-C”
(Mitsubishi Rayon Co., Ltd.) refractive index 1.512 on one surface
A light guide plate was manufactured by bonding it to the opposite surface (flat surface) of the prismatic concave-convex surface with the adhesive "pol-A" (manufactured by Polatechno Co., Ltd.). The size of the light guide plate is 47.8 mm in height and 64. in width.
At 6 mm, the direction of the apex that intersects the gentle slope and the steep slope forms an angle of 7 degrees with the lateral direction of the light guide plate. The lateral end face of the light guide plate was polished vertically as an incident end face.

[Structure of Light Source] A rod-shaped light guide body having a white LED on both ends and having a quadrangular cross section was provided as a linear light source on the incident end surface of the light guide plate. Various prism films for providing distribution in the light direction are inserted and arranged between the rod-shaped light guide of the light source and the light guide plate having the prismatic concavo-convex structure, and the prism film is penetrated to enter the light guide plate. To do. As the types of prism films, four types of isosceles triangles having different apex angles and four different materials were used as described below.

Material: Polycarbonate, Vertical angle: 100
Degree, prism pitch: 50 μm, film thickness: 180
μm Material: Polycarbonate, Vertical angle: 90 °, Prism pitch: 50 μm, Film thickness: 190 μm Material: Polyethylene naphthalate, Vertical angle: 90 °, Prism pitch: 50 μm, Film thickness: 180 μm Material: Polycarbonate, Vertical angle: 66 ° , Prism pitch: 50 μm, film thickness: 180 μm

[Distribution in the emitting direction of the light source] The light source LED is turned on at a current of 15 mA and a voltage of 8.0 V, and a luminance meter (MITUTOYO BM5) is placed at a position of 600 mm in the emitting direction of the rod-shaped light guide of the light source for measurement. Measure at an angle of 0.1 degree. In order to obtain the distribution in the emission direction, the luminance meter is rotated in a plane perpendicular to the direction of the long edge of the inserted prism film, which is the same direction as the rod-shaped light guide of the LED, and the vertical direction of the rod-shaped light guide is set to 0 degree. As a result, the luminance in the emission direction was measured.

[Measurement of Uniformity] Aligned with the incident end face of the light guide plate having the prismatic uneven structure in the outgoing direction of the rod-shaped light guide,
Various prism films for providing the above-mentioned directional distribution of light are inserted and arranged between them, and the prismatic concave-convex surface is arranged on the front surface and the emission surface of the rear surface is arranged on the reflective liquid crystal display surface. Used as the front light of. L
After turning on the ED, a luminance meter was installed at 350 mm in the direction perpendicular to the display surface, and the measurement was performed in the same manner as the measurement of the distribution in the emission direction of the light source except the position of the luminance meter. In this case, the liquid crystal display element is 1
The measurement was performed twice in order to improve the luminance accuracy at three points of 2.0 mm, 23.9 mm and 35.9 mm. Then, the average luminance at three points was calculated, and the value obtained by dividing the lowest value at the three points by the highest value was calculated as the proportionality ratio and is shown in Table 3.

Comparative Example 1 Diffusion plate (commercial item: haze: 7) in place of the prism film
The measurement was performed in the same manner as in Examples 1 to 4 except that 4.3%, Tsujimoto PCMSA) was used. The results are shown in Table 3.

Comparative Example 1 The same operation and measurement as in Examples 1 to 4 were carried out except that the prism film was not used. The results are shown in Table 3.

[0047]

[Table 3]

From Table 3, it can be seen that the uniformity is greatly improved by inserting and disposing the prism film having the cross section of an isosceles triangle in the light source. The distribution of light emitted from the light source in this case is shown in FIG. This emitted light, that is, the incident light to the light guide plate is 1 degree from the 0 ° direction, that is, the direction parallel to the light guide plate.
It can be seen that the uniformity is improved in the case of a distribution in which a large amount of light directed in the direction of 0 degree or more is included.

[0049]

As described above, according to the surface emitting device of the present invention, surface illumination with a high degree of uniformity can be obtained only by disposing the prism film in the light source, so that the weight of the backlight or front light illuminating device can be reduced. It is very useful for thinning.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing how light is guided in a parallel-plate light guide plate.

FIG. 2 is a schematic diagram showing how light is emitted from a light guide plate having a prismatic uneven structure.

FIG. 3 is a cross-sectional view showing prismatic irregularities.

FIG. 4 is a calculation diagram of a light receiving ratio on a steep slope.

FIG. 5 is a calculation diagram of a ratio from a gentle slope to a steep slope.

FIG. 6 is a schematic view showing a state in which a prism film is arranged on a light source.

FIG. 7 shows a distribution in an emission direction when a light source and a prism film or a diffusion plate are provided.

[Explanation of symbols]

1 light source 2 Light guide plate consisting of parallel plates 3 Light guide plate with prism-shaped uneven structure 4 prismatic irregularities 5 Exit surface 6 Prism film

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09F 9/00 G09F 9/00 336C 336J 9/35 9/35 // G02F 1/13357 G02F 1/13357 F21Y 101: 02 F21Y 101: 02 103: 00 103: 00 (72) Inventor Takumi Kosugi 4-13-18 Anchi, Suminoe-ku, Osaka-shi, Osaka Prefecture Goyo Paper Co., Ltd. (72) Inventor Hiiragi Ohara Osaka, Osaka Prefecture 4-13-18, Anryu, Suminoe-ku, Yokohama (72) Inventor, Taizo Yasumoto 4-13-18, Anryu, Suminoe-ku, Osaka, Osaka (72) Inventor: Jun Hirose Gogo Paper Industry Co., Ltd. F-Term (Reference) 2H038 AA55 BA06 2H091 FA23Z FB02 FB03 FC14 FC29 FD07 FD16 FD22 LA03 LA12 LA18 5C094 AA03 AA15 AA55 BA43 ED01 FA04 HA08 5G435 AA01 AA18 BB12 BB15 BB16 EE22 EE23 EE27 FF06 FF08 FF12 LL07 LL08

Claims (5)

[Claims] 1. A light source is provided at at least one side end portion, and has one surface portion that is substantially perpendicular to the side end portion and that is capable of emitting light and the other surface portion that is opposite to the one end portion. It is composed of a light guide plate capable of emitting light, one emission surface is a substantially flat surface, and the other emission surface has a large number of prismatic concave-convex structures, and the light incident on the light guide plate is emitted from the light in the direction parallel to the light guide plate. A surface emitting device having a high degree of uniformity, characterized in that a large amount of light is distributed in the direction of one surface and / or the direction of the other surface having a prismatic uneven structure. 2. The incident light is in the range of 10 to 50 degrees toward the emission one surface side and / or with respect to the direction parallel to the light guide plate.
Or, to the other surface side having a large number of prismatic concave-convex structures,
2. The surface emitting device according to claim 1, wherein the surface emitting device has a distribution in which light directed in a direction within a range of .about.50 degrees is included more than in a direction parallel to the light guide plate. 3. The incident light has a ridge that forms a top and a valley that form a triangle in cross section between the light source disposed at one end of the light guide plate and the end of the light guide plate that are parallel to each other. The surface according to claim 1 or 2, wherein the planar film member in which triangular prisms are arranged in a plane is provided with the apex ridges parallel to the rod-shaped light source and with the apex facing the light source to allow light to pass therethrough. Light emitting device. 4. A large number of prism-shaped concavo-convex structures on the other surface,
The surface emission according to any one of claims 1 to 3, wherein the cross section is a triangle of unequal sides, and a triangular prism or a triangular groove having a ridge at a top or a valley is arranged in a plane substantially parallel to each other. apparatus. 5. The triangular unequal sides of the cross section of the prism-shaped concavo-convex structure on the other surface include a gentle slope and a steep slope, the gentle slope forms an angle with the bottom of 10 degrees or less, and the steep slope forms an angle with the bottom of 30 degrees. The surface emitting device according to any one of claims 1 to 4, which is an isosceles triangle of -60 degrees.