JPH10199318A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make brightness distribution uniform and improve brightness by forming an optical boundary face at the end portion of a light incident face side of a light guide panel which extracts outward the light, led front a light incident face and shut-in, from the light emitting face on both sides of the light source and by leading the light to the effective region of the light guide panel with reflection of the light from the light source. SOLUTION: In the surface light source device, the top face of the guide light panel 12 formed of a transparent resin material having a large refractive index is the light emitting face 12a and the diffused pattern by means of dot printing, etc., of irregular working and diffusion reflection ink is formed in the bottom face. A reflection panel 13 formed of the material of a high surface reflective index such as a hard or relatively soft white plastic sheet is provided in the bottom face of the light guide panel 12. In addition, the central rectangle region of the light emitting face 12a is defined as the effective region R. This effective region R, when it is, for example, used as the surface light source device for a liquid crystal display device, is a region opposed against the region where picture elements of a liquid crystal display panel are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a surface light source device. Specifically, the present invention relates to a surface light source device used for a liquid crystal display device, a lighting device, and the like.

[0002]

[Prior art]

(First Conventional Example) A conventional surface light source device 1 is shown in an exploded perspective view of FIG. 1 and a sectional view of FIG. The surface light source device 1 includes a light guide plate 2 for confining light, a light emitting unit 3 and a reflection plate 4. The light guide plate 2 is formed of a transparent resin having a large refractive index such as a polycarbonate resin or a methacryl resin, and a diffusion pattern 5 is formed on the lower surface of the light guide plate 2 by uneven processing or dot printing of a diffuse reflection ink. . The light-emitting unit 3 is configured by mounting a so-called point light source 7 such as a plurality of light-emitting diodes (LEDs) on a circuit board 6, and faces the side surface (light incident surface 8) of the light guide plate 2. The reflection plate 4 is formed of, for example, a white resin sheet having a high reflectance, and has both sides adhered to the lower surface of the light guide plate 2 by a double-sided tape 9.

Further, in the surface light source device 1, a rectangular area excluding the four edges of the light emitting surface 10 of the light guide plate 2 is an effective area actually used for illumination of a liquid crystal or the like.

As shown in FIG. 2, light f emitted from the light emitting section 3 and guided from the light incident surface 8 to the inside of the light guide plate 2 is totally reflected inside the light guide plate 2 so that the light guide plate is reflected. 2 is trapped inside. The light f inside the light guide plate 2 is diffusely reflected when entering the diffusion pattern 5 and is reflected toward the light emitting surface 10 at an angle smaller than the critical angle of total reflection.
Is extracted from the light exit surface 10 to the outside. Further, the light f transmitted through the portion of the lower surface of the light guide plate 2 where the diffusion pattern 5 does not exist is reflected by the reflector 4 and returns to the inside of the light guide plate 2 again, so that loss of light amount from the lower surface of the light guide plate 2 is prevented.

[0005]

The surface light source device 1 using a point light source as described above has a point light source 7 for reducing power consumption.
And a linear light source was simulated. That is, a linear light source such as a cold cathode ray tube is imitated by arranging the point light sources 7 in a line. Therefore, in order to achieve lower power consumption, the number 7 of point light sources is reduced,
Preferably, it is desired to obtain the surface light source device 1 with high luminance and little luminance variation by using one point light source 7.

However, when the surface light source device 1 is caused to emit light by one point light source 7, the light f from the point light source 7 is totally reflected by the light incident surface 8 of the light guide plate 11, as shown in FIG. The coupling efficiency with the light guide plate 2 was poor, and the luminance of the surface light source device 1 was low. Further, the corner portion 11 (the shaded region in FIG. 3) of the light guide plate 2 was darkened over the corner portion of the effective region R, and a large luminance variation occurred in the surface light source device 1.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and has as its object to make the luminance distribution of the surface light source device uniform and improve the luminance.

[0008]

A surface light source device according to a first aspect of the present invention is provided with a light guide plate for confining light introduced from a light incident surface and extracting the light from a light exit surface to the outside, and is disposed on the light incident surface side of the light guide plate. A light source smaller than the width of the light incident surface of the light guide plate, and guides the light emitted from the light source from the light incident surface to the inside of the light guide plate, confine the light guide plate inside, and from the light exit surface of the light guide plate. In the surface light source device to be taken out, on both sides of the light source,
An optical boundary surface for reflecting light from a light source and guiding the light to an effective area of the light guide plate is formed at an end of the light guide plate on the light incident surface side. Here, the effective area is an area substantially used as a surface light source according to the use of the surface light source device, and the area differs depending on the specific use.

In the surface light source device according to the first aspect,
Optical boundaries are formed on both sides of the light source at the light incident surface side of the light guide plate, so light emitted from the light source toward the optical boundaries on both sides is reflected at the optical boundaries. By doing so, the light is collected in the effective area from outside the effective area. Therefore, the brightness of the surface light source device can be improved. Further, by directing the light reflected on the optical boundary surface to a region where the amount of light is insufficient, the luminance distribution of the surface light source device can be made uniform.

According to a second aspect of the present invention, in the surface light source device according to the first aspect, the optical boundary surface does not exceed a straight line connecting the light source and an edge of an effective area of the light guide plate. And

In the surface light source device according to the second aspect,
Since the optical boundary surface is provided so as not to exceed a straight line connecting the light source and the edge of the effective area of the light guide plate, the incidence of light from the light source into the effective area rather than by providing the optical boundary surface Is not disturbed.

According to a third aspect of the present invention, in the surface light source device, the light guide plate for confining the light introduced from the light incident surface and extracting the light from the light exit surface to the outside, and the light guide plate are disposed on the light incident surface side of the light guide plate. A light source smaller than the width of the light incident surface of the light guide plate is provided, and the light emitted from the light source is guided from the light incident surface to the inside of the light guide plate, confined inside the light guide plate, and from the light exit surface of the light guide plate to the outside. In the surface light source device to be taken out, in front of the light source,
It is characterized in that a void is formed in the light guide plate.

[0013] In the surface light source device according to the third aspect,
Since the cavity is formed in front of the light source, the light emitted from the light source toward the cavity is totally reflected or refracted at the boundary between the light guide plate and the cavity, so that the light is emitted inside the light guide plate. It is diffused and spreads throughout the light guide plate. In particular, since the light is totally reflected rearward at the boundary surface between the light guide plate and the empty space, the light reaches the corners of the light guide plate and the corners of the light guide plate are prevented from being darkened. Therefore, even when a light source smaller than the width of the light guide plate is used, the luminance distribution of the surface light source device can be made uniform.

According to a fourth aspect of the present invention, in the surface light source device according to the third aspect, the space penetrates the light guide plate.

According to a fifth aspect of the present invention, in the surface light source device of the third aspect, the space does not penetrate the light guide plate.

According to a sixth aspect of the present invention, in the surface light source device of the third aspect, the space has a triangular cross section.

The shape of the space may be as described in claims 4 to 6, but is not particularly limited. For example, if the void is not penetrated through the effective area, the leakage of light from the void in the thickness direction of the light guide plate is reduced, and the uniformity of the luminance distribution is reduced. do not do.
Further, if a void having a triangular cross section is provided, the direction of light reflected by the void can be controlled by changing the shape of the triangle, and the luminance of the surface light source device can be controlled. There is an excellent effect that the uniformity of distribution is further improved.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 4 is a perspective view showing a surface light source device 11 according to an embodiment of the present invention, and FIG. 5 is a plan view thereof.
In this surface light source device 11, an upper surface of a light guide plate 12 formed of a transparent resin material having a large refractive index serves as a light emitting surface 12a, and a lower surface thereof is formed with unevenness or dot printing of diffuse reflection ink. Thereby, a diffusion pattern (not shown) is formed. On the lower surface of the light guide plate 12, a reflection plate 13 formed of a material having a high surface reflectance, for example, a hard or relatively soft white plastic sheet is provided.
Is provided. The rectangular area at the center of the light emitting surface 12a is the effective area R. The effective region R is, for example, a region opposed to a region where pixels of a liquid crystal display panel are formed, when used as a surface light source device (backlight) of a liquid crystal display device. Further, a concave portion 16 for mounting a point light source 15 is provided at the center of the light incident surface 14 of the light guide plate 12, and V-shaped grooves 17 are recessed on both sides thereof.

The groove 17 is, as shown in FIG.
And a line segment L connecting the edge of the effective region R of the light guide plate 12 to the light guide plate 12. The boundary between the groove 17 and the air forms an optical boundary. As shown in FIG. 6, it is preferable that the inclination α of the line segment L with respect to the light incident surface 14 and the cut angle θ of the groove 17 with respect to the light incident surface 14 have a relationship of α> θ. Thereby, the groove 17 can be arranged near the point light source 15, and light outside the effective area R can be collected in the effective area R by the small groove 17.

The point light source 15 is a light source smaller than the width of the light guide plate 12, and is formed by resin-molding a light emitting element chip such as a light emitting diode (LED) chip mounted on a lead. Alternatively, a miniature light bulb or the like may be used as the point light source 15.

The light f emitted radially forward from the point light source 15 is directly introduced into the light guide plate 12 from the concave portion 16 as shown in FIG. Due to the function of the diffusion pattern on the lower surface of the light plate 12, light is emitted from the light emitting surface 12a with substantially uniform brightness except for the right and left corners Q on the light source side in the effective region R of the light guide plate 12.

Further, the light f outside the effective area R emitted from the point light source 15 toward the grooves 17 on both sides is indented into the groove 1.
7 is directed toward the corner Q by being totally reflected. At this time, since the groove 17 does not exceed the line segment L connecting the point light source 15 and the edge P of the effective area R of the light guide plate 12, the light is directly projected from the point light source 15 toward the corner Q of the effective area R. Light is not obstructed by the groove 17. Therefore, the surface light source device 10
Can be made uniform, and the brightness of the surface light source device 10 can be increased.

(Second Embodiment) FIG. 7 is a plan view showing a surface light source device 20 according to another embodiment of the present invention. In this surface light source device 20, a pair of left and right point light sources 21 and 22 are arranged side by side in the middle of each of the three grooves 17 and 17b.

That is, a third groove 17b is recessed in the center of the two grooves 17 on the light incident surface 14 of the light guide plate 12, and between the groove 17b and the grooves 17 on both sides thereof,
Two recesses 24, 2 for mounting point light sources 21, 22
5 are provided. The central groove 17 is recessed in an isosceles triangular shape, and the groove 17b is also a line segment L that connects the two point light sources 21 and 22 and the edge of the effective area R on the other point light source side. ′.

The light emitted from the two point light sources 21 and 22 to the other point light sources 21 and 22 respectively is totally reflected by the oblique side of the central groove 17b and is collected at the corner Q or the center. . On the other hand, as in the first embodiment, the light is collected at the corners Q by the grooves 17 on both sides, so that the uniformity of the luminance distribution of the surface light source device 20 can be kept good, and Are two point light sources 21 and 22, so that the surface light source device is further improved in luminance.

(Third Embodiment) FIG. 8 is a plan view showing a surface light source device 30 according to still another embodiment of the present invention. In the surface light source device 30, in the first embodiment, both left and right sides of the groove 17 of the light guide plate 12 are cut out. Thereby, the size and weight of the surface light source device 30 are realized while maintaining the same operation and effect as those of the first embodiment.

(Fourth Embodiment) FIG. 9 is a perspective view showing a surface light source device 40 according to still another embodiment of the present invention.
Reference numeral 0 is a longitudinal sectional view of the above, which is partially broken. In the surface light source device 40, the light guide plate 12 is formed with a generally conical or shell-shaped space 42 having a narrow end in front of the light emitting portion 41.

As shown in FIG. 10, the light emitting section 41 is formed by enclosing a point light source-like light emitting element 44 with an exterior member 43 made of a material having a high surface reflectance such as white resin. In the light emitting element 44, a minute light emitting element chip 46 such as an LED is die-bonded to the tip of one lead terminal 45, and the light emitting element chip 46 and the tip of the other lead terminal are connected by a bonding wire. And one lead terminal 45 and the other lead terminal are molded in a transparent sealing resin 47. As a result, only one surface (front surface) of the light emitting element 44 on the light emission side is the exterior member 4.
It is exposed from 3. Note that a miniature bulb or the like may be used as the light emitting element 44.

The light emitted from the light emitting element chip 46 in a direction other than the front surface, for example, in the rear direction, passes through the transparent sealing resin 47 and reaches the boundary surface between the transparent sealing resin 47 and the exterior member 43. Are reflected at this interface. The light reflected once or a plurality of times at the boundary surface with the exterior member 43 is emitted forward from the front surface of the light emitting element 44,
The light is introduced from the light incident surface 14 into the light guide plate 12. As described above, the light from the light emitting element 44 can be collected on the front surface and emitted by the light emitting section 41, so that the light emitting element 44
The light coupling efficiency between the light source and the light guide plate 12 can be increased, and the luminance of the surface light source device 40 can be improved.

Further, of the light introduced into the light guide plate 12, the light emitted from the light emitting portion 41 toward the space 42 is
As shown in FIG. 11, the light is diffused inside the light guide plate 12 by being totally reflected or refracted in various directions by the boundary surface of the substantially conical space 42 formed in front of the light emitting portion 41. , Spread over the entire light guide plate 12. In particular, the light guide plate 1
Since the light is totally reflected rearward at the boundary surface between the space 2 and the space 42, the light also reaches the corner Q of the effective area R and the corner Q is prevented from being darkened. Therefore, even when the light emitting portion 41 (point light source) smaller than the width of the light guide plate 12 is used, the luminance distribution of the surface light source device 40 can be made uniform.

(Fifth Embodiment) FIG. 12 is a perspective view showing a surface light source device 50 according to still another embodiment of the present invention, and FIG. In the surface light source device 50, the space 51 has a cylindrical shape penetrating the light guide plate 12. As shown in the present embodiment and the following embodiments, the shape of the space 51 is not particularly limited, and the influence on the luminance distribution differs depending on the shape.

As shown in FIG. 13, the light emitted from the light emitting section 41 is efficiently coupled to the light guide plate 12 in the same manner as in the fourth embodiment. Spread throughout. At this time, since the light is totally reflected rearward at the boundary surface between the light guide plate 12 and the space 51, it is possible to prevent the light from reaching the corner Q of the effective region R and darkening the corner Q. Can be.

(Sixth Embodiment) FIG. 14 is a perspective view showing a surface light source device 60 according to still another embodiment of the present invention, and FIG. In the surface light source device 60, the space 61 does not penetrate the light guide plate 12, that is, is a column that does not reach the light exit surface 12a in the fifth embodiment. As described above, if the space 61 does not reach the light emitting surface 12a,
Leakage of the light f from the space 61 in the thickness direction of the light guide plate 12 (indicated by a broken line in FIG. 15) is reduced, and a decrease in the uniformity of the luminance distribution can be prevented.

The light emitted from the light emitting section 41 is efficiently coupled to the light guide plate 12 as in the fourth embodiment, as shown in FIG. Spread throughout. At this time, the upper surface of the space 61 is
Since the light f is not exposed from the light exit surface 12a, the leakage of the light f from the cavity 61 in the thickness direction of the light guide plate 12 is reduced as compared with the fifth embodiment.

(Seventh Embodiment) FIG. 16 is a plan view showing a surface light source device 65 according to still another embodiment of the present invention.
FIG. 7 is a longitudinal sectional view of the same, partially broken away. In the surface light source device 65, in the fourth to sixth embodiments, the void 66 has a triangular cross section. If the apex of the void 66 having a triangular cross section is directed toward the light emitting part 41 and the base of the triangle is arranged so as to be orthogonal to the connection between the light emitting part 41 and the apex, the light from the light emitting part 41 can be efficiently used in the effective area. There is an excellent effect that the light gathers at the right and left corners Q on the light source side of R and the uniformity of the luminance distribution of the surface light source device 65 is further improved.

(Illuminating Device) FIG. 18 is a perspective view showing an illuminating device 71 using the surface light source device according to the present invention. In this lighting device 71, four point light sources 72 are used in order to increase the amount of light and increase the luminance. The lighting device 71 is used for indoor lighting, a tail lamp of an automobile, and the like. The same members as those in the second embodiment are denoted by the same reference numerals.

(Liquid Crystal Display) FIG. 19 is an exploded perspective view showing a liquid crystal display 81 using the surface light source device 80 according to the present invention. In the surface light source device 80, the light guide plate 1
2 is red (R) 82a, green (G) 82b, blue (B) 82c
A point light source 82 having three color light emitting elements is mounted. A diffusion sheet 83 is opposed to the light emitting surface 12a of the surface light source device 80, and a liquid crystal display panel 84 is opposed to the upper surface thereof. The liquid crystal display panel 84 includes two liquid crystal substrates (glass substrate, film substrate) on which transparent electrodes, TFTs, color filters, black matrices, etc. are formed.
A liquid crystal material is sealed between 85 and 86, and liquid crystal substrates 85 and 86 are sealed.
Polarizing plates 87 are arranged on both outer surfaces.

According to such a liquid crystal display device 81, the luminance distribution on the display surface can be made uniform, and the quality of the liquid crystal display device 81 can be improved.

(Electronic organizer provided with liquid crystal display device) The liquid crystal display device according to the present invention is a wireless information transmission device such as a mobile phone or a low power radio, a portable personal computer, an information processing device such as an electronic organizer or a calculator. It is preferable to be used for an apparatus or the like. FIG. 20 is a perspective view showing a mobile phone 89 having a liquid crystal display device 81 as shown in FIG. 19 according to the present invention for a display, and FIG. 21 is a functional block diagram thereof. A button switch 90 such as a numeric keypad for dial input is provided on the front of the mobile phone 89, a liquid crystal display device 81 is disposed above the button switch 90, and an antenna 91 is provided on the upper surface. When a dial or the like is input from the button switch 90, the input dial information or the like is transmitted from the antenna 91 to the base station of the telephone company through the transmission circuit 92. On the other hand, the inputted dial information etc.
3, the liquid crystal display device 81 is driven by the liquid crystal drive circuit 93, and dial information and the like are displayed on the liquid crystal display device 81.

FIG. 22 is a diagram showing an example of FIG.
FIG. 23 is a perspective view showing an electronic organizer 94 having a liquid crystal display device 81 as shown in FIG. 9 for a display, and FIG. 23 is a functional block diagram thereof. When the electronic notebook 94 opens the cover 95,
A key input section 96 and a liquid crystal display device 81 are provided, and a liquid crystal drive circuit 93, an arithmetic processing circuit 97, and the like are provided inside. When, for example, a numeric keypad or a kana key is input from the key input section 96, the input information is
3 and displayed on the liquid crystal display device 81. Then
When a control key such as an operation key is pressed, a predetermined process or operation is executed in the operation processing circuit 97, and the result is displayed on the liquid crystal driving circuit 9.
3 and displayed on the liquid crystal display device 81.

It should be noted that the present invention is not limited to the above-described embodiment, but can be modified within the scope of the present invention. For example, as the optical boundary surface, a hole may be provided instead of the groove, or a transparent refraction layer (light scattering layer) by printing or the like on the surface of the groove or on both sides of the point light source (light emitting portion) on the light incident surface. May be formed. Alternatively, the groove may be provided on a surface other than the light incident surface. Thus, light that has entered the periphery of the light guide plate outside the effective area can be more efficiently collected in the effective area, so that further improvement in uniformity and higher brightness can be realized.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a conventional surface light source device.

FIG. 2 is a longitudinal sectional view of the same.

FIG. 3 is a plan view showing an effective area of the light guide plate.

FIG. 4 is a perspective view showing a surface light source device according to an embodiment of the present invention.

FIG. 5 is a plan view of the same.

FIG. 6 is an explanatory view showing how light is collected at a corner by a groove.

FIG. 7 is a plan view illustrating a surface light source device according to another embodiment of the present invention.

FIG. 8 is a plan view showing a surface light source device according to still another embodiment of the present invention.

FIG. 9 is a perspective view showing a surface light source device according to still another embodiment of the present invention.

FIG. 10 is a longitudinal sectional view of the above, with a part cut away.

FIG. 11 is an explanatory diagram showing a state in which light is diffused throughout the light guide plate by an empty space.

FIG. 12 is a perspective view showing a surface light source device according to still another embodiment of the present invention.

FIG. 13 is a vertical cross-sectional view of the above, which is partially broken.

FIG. 14 is a perspective view showing a surface light source device according to still another embodiment of the present invention.

FIG. 15 is a vertical cross-sectional view of the above-mentioned partly broken part.

FIG. 16 is a plan view showing a surface light source device according to still another embodiment of the present invention.

FIG. 17 is a longitudinal sectional view of the above, with a part cut away.

FIG. 18 is a perspective view of a lighting device using the surface light source device of the present invention.

FIG. 19 is an exploded perspective view of a liquid crystal display device using the surface light source device of the present invention.

FIG. 20 is a perspective view showing a mobile phone provided with a liquid crystal display device according to the present invention for a display.

FIG. 21 is a block diagram showing a configuration for driving a liquid crystal display device in the mobile phone of the above.

FIG. 22 is a perspective view showing an electronic organizer provided with a liquid crystal display device according to the present invention for a display.

FIG. 23 is a block diagram showing a configuration for driving a liquid crystal display device in the above electronic organizer.

[Explanation of symbols]

 Reference Signs List 12 light guide plate 12a light emitting surface 14 light incident surface 15, 21, 22, 72, 82 point light source 17, 17b groove 41 light emitting portion 42, 51, 61, 66 void Q corner R effective area

Claims (6)

[Claims] 1. A light guide plate for confining light introduced from a light incident surface and extracting the light from the light exit surface to the outside, and the width of the light incident surface of the light guide plate disposed on the light incident surface side of the light guide plate. A surface light source device that comprises a light source that is smaller than the light source, guides light emitted from the light source from the light incident surface into the light guide plate, confine the light guide plate inside, and takes out the light from the light exit surface of the light guide plate to the outside. A surface light source device, wherein an optical boundary surface for reflecting light from a light source and guiding the light from a light source to an effective area of the light guide plate is formed at both ends of the light guide plate on the light incident surface side. 2. The surface light source device according to claim 1, wherein the optical boundary surface does not exceed a straight line connecting the light source and an edge of an effective area of the light guide plate. 3. A light guide plate for confining light introduced from a light incident surface and extracting the light from the light exit surface to the outside, and the width of the light incident surface of the light guide plate disposed on the light incident surface side of the light guide plate. A surface light source device that comprises a light source that is smaller than the light source, guides light emitted from the light source from the light incident surface into the light guide plate, confine the light guide plate inside, and takes out the light from the light exit surface of the light guide plate to the outside. A surface light source device, wherein a cavity is formed in a light guide plate at the front. 4. The surface light source device according to claim 3, wherein the space penetrates the light guide plate. 5. The surface light source device according to claim 3, wherein the space does not penetrate the light guide plate. 6. The surface light source device according to claim 3, wherein the space has a triangular cross section.