JPH0695108A - Backlight - Google Patents

Abstract

(57) [Summary] [Structure] A prism having a linear apex on the light emitting surface side of a light guide plate made of a translucent material that has a linear light source at the end and is partially covered with a light diffusing substance. A back light for a panel in which a large number of sheets made of a translucent material are arranged on the light emitting surface side so that the top edges are on the outside. [Effect] This backlight is small Thus, sufficient brightness can be obtained, and the backlight can be used with high power consumption-luminance conversion efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight for a panel which illuminates a transmissive or semi-transmissive panel from the back side.

[0002]

2. Description of the Related Art Recently, a liquid crystal display device having a backlight mechanism which is thin and easy to see has been used as a display device for a laptop or book type word processor, a computer or the like. For such a backlight, a one-lamp type edge light system in which a linear light source such as a fluorescent tube is provided at one end of a light-transmitting light guide plate as shown in FIG. 1, and as shown in FIG. A two-lamp type edge light system in which a linear light source such as a fluorescent tube is provided at two opposite ends of a light guide plate is often used. In the case of this edge light method, as shown in FIG. 2 or FIG. 4, one surface of the light guide plate is partially covered with a light diffusing substance having a refractive index higher than that of the material of the light guide plate, and almost the entire surface is covered. Many are arranged so as to be covered with a light diffusion reflector.

Particularly, in recent years, since the backlight is driven by a battery, further improvement of power consumption-luminance conversion efficiency is desired, and a light reflector for covering the linear light source is provided with a reflector having a high reflectance. It has been proposed to dispose the light guide plate or to dispose a reflection plate having a high reflectance on the surface of the light guide plate that is partially covered with the light diffusing substance.

However, although the power consumption-luminance conversion efficiency is improved by any of the above-mentioned methods, it is still not sufficient, and further improvement is desired.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a backlight which has high power consumption-luminance conversion efficiency and high luminance.

[0006]

As a result of various studies on the above points, the inventors of the present invention have found that a linear top edge is formed on the light emitting surface side of a translucent material partially covered with a light diffusing substance. Although a light transmissive prism sheet having a large number of is arranged, the directivity of light becomes stronger, and the power consumption-luminance conversion efficiency is high for the vicinity of the normal direction substantially dropped on the light emitting surface. I found it to be a light.

That is, according to the present invention, one wide surface of a light guide plate made of a translucent material is partially covered with a light diffusing substance having a refractive index higher than that of the light guide plate material, and the surface is mirror-finished or light-reflected. In a backlight for a panel, which is covered with a plate and has a linear light source near at least one side surface end of the light guide plate, a linear top edge is formed on the light exit surface side of the light guide plate at a fine interval on the same surface. A back light for a panel in which one or more sheets of a prism having a plurality of sheets made of a light-transmissive material are arranged on the light emitting surface side so that the apex surfaces are on the outer side. It is about.

Next, the present invention will be described in detail with reference to the drawings. FIG. 5 is a perspective view of an embodiment of an edge light system having a light source at one end of a light guide plate, and FIG. 6 is a sectional view thereof.
Similarly, FIG. 7 is a perspective view of an embodiment of an edge light system having light sources at two ends of the light guide plate, and FIG. 8 is a sectional view thereof.

In the figure, reference numeral 1 denotes a light guide plate, which may be any substance that allows light to pass efficiently, and is made of quartz, glass, translucent natural or synthetic resin such as acrylic resin. The light diffusing substance (6 in the figure) applied to the light guide plate is a pigment having a high refractive index and a large diffuse reflectance as compared with the material of the light guide plate, for example, paint containing titanium white, printing ink, or the like.
These are printed in dots on the surface of the light guide plate by a method such as screen printing.

Reference numeral 4 is a linear light source, and in a preferred embodiment,
A light reflector 5 having a gap (slit) for allowing light to enter the end portion of the light guide plate is covered with a gap of a certain width from the light source surface of the linear light source, and at least the light guide plate is covered. It is installed close to the one end face so that its central axis is substantially parallel to the end face of the light guide plate. The linear light source may be a fluorescent tube, a tungsten incandescent tube, an optical rod, an LED array, or the like, but a fluorescent tube is preferable, and from the viewpoint of power saving, the length of the uniform light emitting section excluding the electrode section is close to each other. It is preferable that the length is substantially equal to the length of the end portion of the light guide plate.

The mirror surface or the light diffusing reflection plate (3 in the figure) is arranged so as to cover almost the entire surface of the light guide plate coated with the light diffusing substance, but the remaining end surface of the light guide plate which is not in close proximity to the linear light source. It is more preferable to dispose so as to cover almost the entire surface of the portion in terms of light utilization efficiency and uniform planar light emission.

A sheet 2 made of a translucent material (hereinafter simply referred to as a sheet) 2 has a large number of straight apexes parallel to each other on the same surface at fine intervals. By arranging so that it is on the side opposite to the surface facing the light plate), the directivity of the light emitted from the light emitting surface of the backlight is changed, and the directivity in the vicinity of the normal direction dropped on the light emitting surface is made stronger. It is a thing. It may be arranged such that the linear apex portion is parallel to the central axis of the linear light source,
You may arrange so that it may become a right angle.

If necessary, the sheet-like pattern of the dot-like light diffusing substance (6 in the figure) printed on the surface of the light guide plate cannot be identified. A light diffusion plate (2 in the figure) may be arranged between the light guide plate and the light guide plate.

As described above, the present invention is characterized in that a sheet made of a translucent material having a shape satisfying a certain condition is arranged on the light emitting surface side of the backlight.

The above-mentioned conditions in the present invention will be described in more detail. The above-mentioned sheet (7 in the figure) is not particularly limited as long as it is made of a translucent material. For example, methacrylic acid ester, polycarbonate, poly Examples thereof include vinyl chloride, polystyrene, polyamide, polyester, polyethylene, polypropylene, and fiber-based resin glass.

As shown in FIG. 9, the shape of a prism having straight parallel ridges formed on the light output surface side of the sheet used in the present invention is parallel to each other, as shown in FIG. In this state, the apex ridge (8 in the figure) where the two optical planes intersect is linear, and a large number of linear prisms parallel to each other are present in the same plane at minute intervals (P in the figure). Is. The apex angles of these apexes formed on the sheet have portions of substantially the same shape. This means that the apex angles have substantially the same angle when cut under the same conditions centering on the apex. Means that.

In the present invention, the apex angle (9 in the figure) of the apex of the above-mentioned sheet is preferably 70 to 150 degrees. The more preferable range of the apex angle depends on the refractive index of the sheet material used and the light distribution characteristics of the planar light emitter used. For example, a material with a large refractive index (polycarbonate,
When a refractive index n = 1.59) is used, the apex angle is preferably 90 degrees rather than 70 degrees and 120 degrees rather than 90 degrees.
When the temperature exceeds 50 degrees, the effect of the present invention decreases, and the light distribution characteristics,
For example, when the light emitted from the planar light-emitting body is substantially concentrated within 45 degrees from the normal direction dropped on the light-emitting surface,
The vertical angle is preferably 100 to 140 degrees.

Further, it is particularly preferable to use the above-mentioned sheet prism in which the lengths of the respective hypotenuses from the apex are substantially equal in order to improve the effect of the present invention. In addition, the distribution state of a large number of linear prisms formed on the sheet makes it difficult for the light emitted from the surface to visually recognize the interval between the linear prisms. The ridge spacing is 10-100
It is preferably 0 μm. The thickness (t2 in the figure) of the linear prism portion of the sheet is determined by the apex angle of the apex ridge and the interval between the apex ridges described above. It is necessary to have a thickness (t1 in the figure) to maintain a proper positional relationship. This t1 is better to be thin in order to reduce the light transmittance and the thickness of the backlight. From the viewpoint of strength, the total thickness (T in the figure) of the sheet is 10 to 3000 μm, preferably 5
0 to 1000 μm is preferable. Further, the linear prisms formed on the same surface should have the same shape more effectively.

The method of molding the sheet used in the present invention is not particularly limited, and for example, a linear prism of substantially the same shape can be formed by a method such as die molding by hot pressing, embossing, template processing, or chemical treatment. Any method can be used as long as it can be molded so as to have a large number of fine particles in parallel with each other. It should be noted that although a slight sag occurs at the apex for manufacturing reasons, it may be within the range in which the effect of the present invention can be recognized.

In a liquid crystal display, the contrast becomes lower as the viewing angle from the normal direction lowered to the display surface becomes larger. Therefore, practically, the brightness in the vicinity of the normal direction is important. Further, since the viewfinder can be seen only from the normal direction dropped on the display surface, practically, the brightness in the vicinity of the normal direction is important.

In the present invention, as described above, when a sheet having a large number of linear prisms whose light emitting surface side is parallel to each other at fine intervals is arranged on the light emitting surface of the backlight, the directivity of light appears. . That is, when the brightness of the light emitted from the surface is measured in the direction of the normal line lowered to the light emitting surface,
Compared to the case where the sheet is not provided, the brightness is increased, an angle with respect to the normal line lowered to the light exit surface,
For example, the luminance measured similarly from the direction of 40 degrees has a larger reduction rate than the luminance measured in the normal direction (for example, almost 50% of the luminance measured in the normal direction).
It is understood that the above-mentioned light directivity appears.

Next, the operation of the present invention will be described in more detail with reference to the drawings. FIG. 10 is a diagram showing an example of ray tracing of a ray incident from an arbitrary point on the cross section of an arbitrary prism of the sheet in the case of using a sheet having a linear prism in the present invention.

When the apex angle of the prism is 2α (degrees), the refractive index of the sheet made of a translucent material is n, and the refractive index of air is 1, the critical angle θc (degrees) is θc = sin ^−1. (1 / n) 1) ray angle theta ₁ (incident in degrees), when emitted at the angle theta ₆ (degrees) (FIG. _{10 (a)) sinθ 1 =} n × sinθ 2 θ 3 = 90 ° -α −θ ₂ n × sin θ ₃ = sin θ ₄ (when θ ₃ ≦ θc) θ ₅ = 90 ° −α−θ ₄ θ ₆ = θ ₅ 2) A light beam is incident at an angle θ ₁ (degrees) and an angle θ _{When the} light is emitted at ₈ degrees (FIG. 10B) sin θ ₁ = n × sin θ ₂ θ ₃ = 90 ° −α−θ ₂ θ ₄ = θ ₃ (where θ ₃ > θc) θ ₅ = 2α _{-θ 4 n × sinθ 5 = sinθ} 6 ( although theta when _{5 ≦ θc) θ 7 = 90} ° -α-θ 6 θ 8 = -θ 7 to performing such calculations Therefore, if the refractive index of the material used for the sheet made of the translucent material and the apex angle of the prism are known, the incident angle of the light beam emitted from the light emitting surface of the backlight to the sheet made of the translucent material. The emission angle can be obtained from Although not shown in FIG. 10, depending on the above conditions, the incident light beam may be reflected twice or more inside the prism or may return to the light emitting surface of the backlight.

For example, as shown in FIG. 11, when the sheet is made of polycarbonate (refractive index n = 1.59) and the apex angle of the prism is 90 degrees, the incident angle is 0.
The light beam incident on the sheet at a time is totally reflected inside the prism and returned to the backlight. The light rays returned to the backlight are partially absorbed inside the backlight, partially reflected, and emitted again from the light emitting surface of the backlight.

Therefore, when the light emitted from the backlight is totally reflected inside the prism of the sheet and returned to the backlight again, the less light is absorbed inside the backlight, The higher the reflectance of light inside the backlight, that is, the more the surface other than the light emitting surface of the backlight is covered with the reflector having high reflectance, the more efficient the backlight becomes.

A light ray incident on the sheet at an incident angle of 30 degrees is emitted from the sheet at an emission angle of 0.5 degree, and a light ray incident on the sheet at an incident angle of 60 degrees is emitted at the emission angle. 25.7
Light is emitted from the sheet at a certain degree. Then, in this case, the light emitted from the light emitting surface of the backlight is substantially most concentrated within an angle of about 40 degrees from the normal direction dropped onto the light emitting surface, and as a result, the light is measured from the normal direction. The brightness is
The number is increased as compared with the case where the sheet is not provided.

Similarly, when the sheet is made of polycarbonate as shown in FIG. 12 and the apex angle of the prism is 120 degrees, the sheet is incident on the sheet at an incident angle of 0 degree. The emitted light is emitted from the sheet at an emission angle of 22.7 degrees,
A light ray that enters the sheet at an incident angle of 30 degrees has an exit angle of 1
A light beam emitted from the sheet at 1.2 degrees and a light beam incident on the sheet at an incident angle of 60 degrees exits from the sheet at an emission angle of 34.8 degrees. Then, the light emitted from the light emitting surface of the backlight in this case is substantially most concentrated within an angle of about 44 degrees from the normal direction dropped onto the light emitting surface, and as a result, the light is measured from the normal direction. The brightness increases as compared with the case where the sheet is not provided.

As described above, by controlling the apex angle of the prism of the sheet, it is possible to control the directivity of the light emitted from the light emitting surface of the planar light emitting body.

[0029]

EFFECTS OF THE INVENTION The present invention is comparatively small in size, can obtain sufficient brightness, and consumes less power in the direction normal to the light exit surface.
It can be used as a backlight with high luminance conversion efficiency.

[0030]

EXAMPLES Next, the present invention will be described in more detail with reference to Comparative Examples and Examples. A rectangular light guide plate (225 mm × 127 mm) having a thickness of 2.0 mm as shown in FIG.
A cold-cathode fluorescent tube (Normal tube manufactured by Harrison Electric Co., Ltd.) having a thickness of 8 mm is arranged, and a light diffusion film is laminated on the inner surface of a cylindrical aluminum reflector having a 2 mm slit in a portion in contact with the light guide plate. It was arranged so that the light emitted from the slit would enter the light guide plate from the end portion of the light guide plate. On the other hand, the light diffusing substance (paint containing titanium white) coated on the surface of the light guide plate has a circular dot pattern of 1.2.
It was screen-printed at a mm pitch and was prepared and used under the following conditions. The plots were made so that the coverage of the light diffusing substance was 6% at the minimum point (cold cathode fluorescent tube side), 80% at the maximum point, and these ratios were sequentially increased in the middle.

Further, one light diffusion film (Tsujimoto Denki Seisakusho D-204) was arranged on the light emitting surface side of the light guide plate. The surface brightness when an alternating voltage of 30 KHz is applied from the inverter to the cold-cathode tube and driven with a constant current, the viewing angle is 2 degrees by a brightness meter (Topcon BM-7), and the normal direction is lowered to the light emitting surface. On the other hand, when measured at a distance of 40 cm from the light emitting surface to the luminance meter, it was 192 cd / m ² (Comparative Example 1).

On the light diffusing film, a large number of commercially available linear prisms made of polycarbonate and having parallel apex angles of 90 ° are parallel to each other. The same apparatus and conditions as in Comparative Example 1 except that one sheet having a thickness of 360 μm processed to have an interval of 350 μm is arranged on the light emitting surface side of the backlight so that the linear prism is on the outside. The luminance measured according to Example 1 was 307 cd / m ² (Example 1).

Further, the brightness was measured by operating under the same apparatus and conditions as in Example 1 except that one linear prism was placed on the light emitting surface side of the backlight so that the linear prism was inside.
It was 5 cd / m ² (Comparative Example 2). Further, the brightness was 245 cd / m ² measured by operating under the same apparatus and conditions as in Example 1 except that a linear prism having a prism-shaped projection with an apex angle of 70 degrees was used (Example 2 ). Furthermore, the brightness measured at the same apparatus and conditions as in Example 1 was 330c except that the apex angle of the prismatic protrusion was 120 degrees.
It was d / m ² (Example 3).

Next, in order to examine the light distribution characteristics of the backlight, in Comparative Example 1, Example 1 and Example 2, an alternating voltage of 30 KHz was applied from the inverter to the cold cathode tube at a constant current. With respect to the surface luminance when driven, a luminance meter (Topcon BM-7) has a viewing angle of 2 degrees, and an angle with respect to a normal direction lowered to the light emitting surface from 0 degree to 7 degrees as shown in FIG.
The distance from the light emitting surface to the luminance meter is 40 cm
The value of the brightness when measured in FIG. From this figure, it can be seen that when the backlight of the present invention is used, the brightness is increased and the directivity of light is remarkable.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a one-light type edge light type backlight.

FIG. 2 is a cross-sectional view showing an example of a one-light type edge light type backlight.

FIG. 3 is a perspective view showing an example of a two-light type edge light type backlight.

FIG. 4 is a cross-sectional view showing an example of a two-light type edge light type backlight.

FIG. 5 is a perspective view of an embodiment of the present invention.

FIG. 6 is a cross-sectional view of one embodiment of the present invention.

FIG. 7 is a perspective view of an embodiment of the present invention.

FIG. 8 is a cross-sectional view of one embodiment of the present invention.

FIG. 9 is a perspective view of a sheet used in the present invention.

FIG. 10 is a diagram showing an example of ray tracing.

FIG. 11 is a diagram showing an example in which the prism vertical angle is 90 degrees.

FIG. 12 is a diagram showing an example in which the prism vertical angle is 120 degrees.

FIG. 13 is a conceptual diagram of a measuring method used in the present invention.

FIG. 14 is a diagram showing an angular distribution of emitted light brightness.

[Explanation of symbols]

 1: Light guide plate 2: Light diffusing plate 3: Reflecting plate 4: Linear light source 5: Reflector 6: Light diffusing substance 7: Sheet having linear prism 8: Linear apex ridge 9: Vertical angle of prism 10 : Backlight 11: Luminance meter 12: Angle with respect to the direction of the normal line lowered to the light emitting surface 13: Normal line lowered to the light emitting surface

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[Procedure amendment]

[Submission date] October 29, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

The above-mentioned conditions in the present invention will be described in more detail. The above-mentioned sheet (7 in the figure) is not particularly limited as long as it is made of a translucent material. For example, methacrylic acid ester, polycarbonate, polyvinyl chloride, polystyrene. , Polyamide, polyethylene terephthalate (PE
T) and other polyesters, polyethylene, polypropylene, fibrin resin , glass, and the like.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

The method of molding the sheet used in the present invention is not particularly limited, and for example, a linear prism of substantially the same shape can be formed by a method such as die molding by hot pressing, embossing, template processing, or chemical treatment. Any method can be used as long as it can be molded so as to have a large number of fine particles in parallel with each other. It should be noted that although a slight sag occurs at the apex for manufacturing reasons, it may be within the range in which the effect of the present invention can be recognized.
In addition, the same material as the base film or a different light-transmitting material (for example, an ultraviolet curing resin such as an acrylic resin) on the above-mentioned light-transmitting film (base film) is linearly printed by a method such as printing. You may shape | mold so that it may have many convex convex molds at a fine space | interval.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

Further, the brightness was measured by operating under the same apparatus and conditions as in Example 1 except that one linear prism was placed on the light emitting surface side of the backlight so that the linear prism was inside.
It was 5 cd / m ² (Comparative Example 2). Further, the brightness was 245 cd / m ² measured by operating under the same apparatus and conditions as in Example 1 except that a linear prism having a prism-shaped projection with an apex angle of 70 degrees was used (Example 2 ). Furthermore, the brightness measured at the same apparatus and conditions as in Example 1 was 330c except that the apex angle of the prismatic protrusion was 120 degrees.
It was d / m ² (Example 3). On the light diffusing film, a large number of linear convex portions made of an ultraviolet curing resin (acrylic resin) were formed on a PET base film having a thickness of 50 μm by a printing method, and the length of the bottom surface of the convex portion was 50 μm The height from the projection to the projection is 25 μm, and the interval between the projections is 50 μm.
Volatility measured by operating under the same apparatus and conditions as in Comparative Example 1 except that one sheet formed so as to have a thickness of μm was arranged on the light emitting surface side of the backlight so that the linear convex portion was on the outside. Was 235 cd / m ² (Example 4). ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

The mirror surface or the light reflecting plate, for example, the light diffusing reflecting plate (3 in the figure) is arranged so as to cover almost the entire surface of the light guiding plate coated with the light diffusing substance, but the linear light source of the light guiding plate is close to it. It is more preferable to dispose so as to cover almost the entire surface of the remaining end face portion which has not been performed in terms of light utilization efficiency and uniform planar light emission.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Reference numeral 7 denotes a sheet made of a translucent material (hereinafter, simply referred to as a sheet), which has a large number of linear apexes parallel to each other on the same surface at fine intervals, and the apex edge surface is outside (the light guide plate and By arranging it so that it is on the side opposite to the opposite surface), the directivity of the light emitted from the light emitting surface of the backlight is changed, and the directivity in the vicinity of the normal direction dropped on the light emitting surface is made stronger. is there. It may be arranged such that the linear apex portion is parallel to the central axis of the linear light source,
You may arrange so that it may become a right angle.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

[0030]

EXAMPLES Next, the present invention will be described in more detail with reference to Comparative Examples and Examples. As shown in FIG. 5 or 6 , a rectangular light guide plate (225 mm × 127 mm) having a thickness of 2.0 mm (1 in the figure) is provided with a cold cathode fluorescent tube (Harrison Electric Co., Ltd. ) having a thickness of 4.8 mm at the short end. ( Normal tube manufactured by Co., Ltd.) (4 in the figure) is placed, and a light diffusion film is laminated on the inner surface of a cylindrical aluminum reflector that has a slit of 2 mm in the portion in contact with the light guide plate. The light guide plate is arranged so that light enters the light guide plate from the end thereof. On the other hand, a light diffusing substance (paint containing titanium white) covering the surface of the light guide plate (6 in the figure)
Is a circular dot pattern screen-printed at a pitch of 1.2 mm, and was prepared and used under the following conditions.
The point where the light diffusing substance coverage is the minimum (cold cathode fluorescent tube side)
6%, 80% at the maximum point, and in the middle, these ratios were gradually increased.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

Further, one light diffusion film (Tsujimoto Denki Seisakusho D-204) (2 in the figure) was arranged on the light emitting surface side of the light guide plate. In addition, light is diffused to the surface side of the light guide plate that is coated with the light diffusion material.
A reflector (3 in the figure) was placed. The surface brightness of the cold cathode tube when it was driven with a constant current by applying an alternating voltage of 30 KHz from the inverter was measured with a brightness meter (Topcon BM-7) at a viewing angle of 2 degrees, with respect to the direction normal to the light exit surface. And measured at a distance of 40 cm from the light emitting surface to the luminance meter, 19
It was ² cd / m ² (Comparative Example 1). ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 7, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a one-light type edge light type backlight.

FIG. 2 is a cross-sectional view showing an example of a one-light type edge light type backlight.

FIG. 3 is a perspective view showing an example of a two-light type edge light type backlight.

FIG. 4 is a cross-sectional view showing an example of a two-light type edge light type backlight.

FIG. 5 is a perspective view of an embodiment of the present invention.

FIG. 6 is a cross-sectional view of one embodiment of the present invention.

FIG. 7 is a perspective view of an embodiment of the present invention.

FIG. 8 is a cross-sectional view of one embodiment of the present invention.

FIG. 9 is a perspective view of a sheet used in the present invention.

FIG. 10 is a diagram showing an example of ray tracing.

FIG. 11 is a diagram showing an example in which the prism vertical angle is 90 degrees.

FIG. 12 is a diagram showing an example in which the prism vertical angle is 120 degrees.

FIG. 13 is a conceptual diagram of a measuring method used in the present invention.

FIG. 14 is a diagram showing an angular distribution of emitted light brightness.

FIG. 15 is a diagram showing an angle distribution of emitted light brightness.

[Explanation of Codes] 1: Light guide plate 2: Light diffusing plate 3: Reflecting plate 4: Linear light source 5: Reflector 6: Light diffusing material 7: Sheet having linear prism 8: Linear apex 9: Prism apex angle 10: Backlight 11: Luminance meter 12: Angle with respect to the direction of the normal to the light emitting surface 13: Normal to the light emitting surface

Claims (3)

[Claims] 1. A wide surface of a light guide plate made of a translucent material is partially covered with a light diffusing substance having a refractive index higher than that of the light guide plate material, and the surface is covered with a mirror surface or a light reflecting plate. In a backlight for a panel having a linear light source adjacent to at least one side surface end portion of the light guide plate, a prism having linear vertexes on the same surface on the light emitting surface side of the light guide plate at fine intervals However, a sheet made of a translucent material having a large number of apexes in a state where the apexes are substantially parallel to each other so that the apex faces are on the outside.
A back light for a panel with one or more panels arranged on the light emitting surface side. 2. A seam having an apex with an apex angle of 70 to 150 degrees.
The backlight for a panel according to claim 1, wherein a backlight is used. 3. The distance between adjacent apexes is 10 to 10.
The backlight for a panel according to claim 1, wherein a sheet having a thickness of 1000 μm is used.