JPH09318945A - Planar surface illuminator and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar surface illuminator in particular excellent in luminance uniformity in the case of being used for the back illumination of a liquid crystal display device. SOLUTION: This planar surface illuminator is provided with a linear light emitting body 101, a light transmission body (light guide means) 102 on which the light emitted from the body 101 is made incident from a light entering end face, and a sheet-like light diffusing means 103 having a light diffusing and reflecting part 107 disposed on the surface of the body 102 where the light outgoes on a lower surface; and a part projecting from the light entering end face of the means 102 is provided on the means 103 and the part 107. Thus, the luminance irregularity occurring in the vicinity of the body 101 can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat lighting device used for back lighting of a liquid crystal display device for displaying characters and images, and more particularly to a flat lighting device having excellent brightness uniformity.

[0002]

2. Description of the Related Art A flat lighting device used for back lighting of a liquid crystal display device or the like, as shown in FIG. The outgoing light is converted into a desired outgoing light characteristic by using the light diffusing means 3 and the like. In general, a cold cathode fluorescent tube is often used for the linear light-emitting body 1, and a transparent resin such as PMMA is molded into a flat plate or a wedge shape for the light guide means, and a white surface is formed on the back surface in order to improve the emission light efficiency and the brightness uniformity. Concavities and convexities (not shown) formed by dot printing or molding are provided, and a reflection sheet 5 of white resin or the like is provided on almost the entire back surface of the light guide means. Further, in order to efficiently enter the light rays from the linear light-emitting body 1 to the end face of the light-guide means, the linear light-emitting body is covered with a reflecting member 6 made of a high-reflectance material such as a metal vapor deposition sheet, and the light-guide means direction is set. The structure that concentrates the light rays only on is often used.

The diffusing means is a means for providing unevenness on a transparent resin sheet and diffusing transmitted light rays, and the diffusing effect can be adjusted by the shape of the unevenness. In addition, it is also practiced to obtain a desired outgoing light characteristic by installing a light condensing means 4 in which a prism is formed in a sheet shape so as to overlap or replace the diffusing means and collect light rays in a specific direction.

[0004]

In the flat lighting device having the above-described structure, the brightness of the light emitted from the main surface of the light guide means 2 is made uniform by the white dots formed on the back surface of the transparent resin plate of the light guide means. It is performed by adjusting the density and area of printing (not shown). That is, by lowering the density and area of the portion near the linear light emitter and increasing the density and area of the far portion, a uniform luminance distribution is obtained regardless of the distance from the linear light emitter.

However, in the liquid crystal display device, a portion corresponding to a so-called frame outside the effective display area is being reduced due to the recent enlargement of the screen and downsizing of the entire device. Along with this, also in the back lighting device, the effective light emitting area where uniform brightness is required is expanded, and almost the entire area of the light guide means 2 is the effective light emitting area. as a result,
The area close to the end surface on the light guide means side where the light rays from the linear luminous body is incident has a higher brightness than the central part of the light guide means even though there is almost no white dot printing to suppress the brightness. It often goes into a state.

In order to reduce this uneven brightness, as shown in FIG. 7, a portion near the light incident side of the reflection sheet 5 arranged on the back surface of the light guiding means 2 or the light incident side of the diffusing means 3. A structure in which a light absorbing portion is provided in a portion near the side,
Specifically, a band-shaped pattern is printed with black ink 7 or a black adhesive tape is attached. However, there is a problem in that the installation of these light absorbing parts causes a total reduction in brightness. Further, in recent years, where a narrower frame is required, the distance from the effective display area to the linear luminous body is shorter than that of the conventional one, and the emitted light is reflected by the reflecting member 6 before entering the light guide means. There is a problem that the generated light rays are emitted from the display surface as shown by the arrow in the figure, and a strong luminance increase band is generated in the vicinity of the linear light emitter in the effective display area of the liquid crystal display device.

[0007]

In order to achieve this object, a flat lighting device of the present invention is provided with a linear light-emitting body and a light guide body into which light emitted from the linear light-emitting body enters from a light incident end surface. And a sheet-like light diffusing means having a light-scattering / reflecting portion provided on the light-emitting surface of the light guide on the lower surface, and the light-diffusing means and the light-scattering / reflecting portion include the light guide means input end surface. The light-scattering / reflecting portion can prevent the vicinity of the light-incident end face from having high brightness by providing a more protruding portion.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The flat lighting device of the present invention comprises a linear light-emitting body, a light guide body through which light emitted from the linear light-emitting body enters through a light-incident end surface, and a light beam emitted from the light guide body. A sheet-like light diffusing means having a light scattering / reflecting portion disposed on the surface on the lower surface, and the light diffusing means and the light scattering / reflecting portion having a portion protruding from the input end face of the light guiding means. Yes, since the portion of the light diffusing means or the condensing means exhibiting light scattering reflectivity is projected from the end surface of the light guide means,
It has an effect that a phenomenon in which the emitted light beam is not reflected by the reflection member 6 before entering the light guide means, does not propagate through the light guide means, and is directly emitted to the display surface does not occur.

Further, in the flat lighting device of the present invention, a linear light-emitting body, a light guide into which the light emitted from the linear light-emitting body is incident from the light incident end face, and a light emitting surface of the light guide. A sheet-like light diffusing means having a light absorbing portion disposed on the lower surface, and the light diffusing means and the light absorbing portion are provided with a portion projecting from the input end face of the light guiding means, and the emitted light beam is guided. It has an effect that the phenomenon of being reflected by the reflecting member 6 before propagating to the light means and not propagating in the light guide means and being directly emitted to the display surface does not occur.

Further, in the flat lighting device of the present invention, the linear luminous body and the linear luminous body having a light scattering reflection portion on a surface facing the linear luminous body around the linear luminous body. The light guide has a reflecting member that reflects light and a light guide body that allows the light emitted from the linear light-emitting body to enter from a light-incident end surface, and the light-scattering / reflecting portion has the light guide means near the input end surface of the light guide means. The reflecting member covers the body and acts in the same manner as the portion provided in the light diffusing means or the condensing means and exhibiting the light scattering reflectivity, and can eliminate the uneven brightness occurring near the linear light source.

Further, according to the present invention, a linear luminous body, a light guide body which receives light emitted from the linear luminous body from a light incident end surface, and a light emitting surface of the light guide body from the incident end surface. A sheet-like light diffusing means having a protruding portion, a reflecting member for reflecting the light of the linear light emitting body around the linear light emitting body, and a reflecting surface side of the reflecting member and the light diffusing means are bonded together. And a double-sided adhesive tape having a light-scattering property, wherein the adhesive or the double-sided tape is disposed on the light diffusing means such that at least a part of the adhesive or the double-sided tape projects from the input end face of the light guide means. Therefore, the adhesive or the double-sided adhesive tape acts in the same manner as the light absorbing portion provided on the light diffusing means or the light converging means, and the uneven brightness can be prevented.

Further, the present invention is a flat illuminating device having a condensing means for regulating the traveling direction of the light of the light guide body above the light emitting surface of the light guide body. Can be collected on the display. Further, the liquid crystal display device provided with the flat lighting device of the present invention as the back lighting has an action of preventing the band-shaped nonuniformity in which the brightness is increased in the vicinity of the linear light emitter even when the so-called frame portion outside the effective display area is thinned. Yes,
It is intended to obtain a high quality liquid crystal display device having a uniform luminance distribution.

An embodiment of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view of a flat lighting device which is an example of the embodiment. A cold cathode tube was used as the linear light-emitting body 101, and a light-guiding body formed by molding PMMA resin into a wedge shape was used as the light-guiding means 102. A reflection sheet 105 made of a white resin sheet is provided on the surface opposite to the emitted light side.
No light absorbing means such as black band printing is applied to the portion of the reflection sheet close to the cold cathode tube. In addition, the diffusing means 103, which is a resin sheet subjected to embossing, is arranged on the light emitting surface. Even if the light emitted from the light guiding means 102 is biased by the diffusing means 103, the diffusing means 10
After passing 2, the bias is eliminated and the entire liquid crystal panel is brightened. The plane dimension of the diffusing means is arranged on the light-entering surface side of the light guide body and is made larger than about 0.7 mm from the light guide body, and is projected from the end surface of the light guide body by about 0.7 mm or more. A silver vapor-deposited resin film was wrapped around the cold cathode tube 101 to form a reflecting member 106, and the reflecting member 106 was made to overlap the surface of the light diffusing means 103. A coating containing a white pigment is applied to the light guide body side surface of the portion of the diffusing means 103 near the cold cathode tube and the lower surface of the light diffusing means 103, and the scattering reflection surface 1 is formed.
07 was formed. The white pigment application surface is provided in a strip shape having a width of about 3 mm including the protruding portion of the diffusing means. Therefore, the light beam emitted from the cold cathode tube toward the upper side of the reflecting member 106 does not directly hit the reflecting member 106 but hits the white pigment surface and is scattered. Can be prevented. as a result,
It is possible to prevent a strong luminance rising zone from occurring on the linear luminous body side of the effective display area of the liquid crystal display device. The shape of the light-scattering / reflecting surface and the amount of protrusion of the diffusing means from the light guide are not limited to the above-mentioned values, but may be different optimum values depending on the thickness of the light guide, the diameter of the cold cathode tube, and the relative arrangement. It is desirable to do.

Further, in the case of a flat illuminating device which does not use a diffusing means but uses only a light converging means for regulating the traveling direction of the diffused light emitted from the light guide body, the dimensional change and the formation of the scattering reflection surface are performed by the diffusing means. The same effect can be obtained by performing the same operation on the light collecting means. Further, in the case of the structure in which the diffusing means and the condensing means are stacked, it is necessary to change the dimensions and form the scattering reflection surface on the side closer to the light guiding means.

(Embodiment 2) FIG. 2 is a cross-sectional view of a flat lighting device as an example of the embodiment. Linear light emitter 101
A cold cathode tube is used for the
A light guide formed by molding a resin into a wedge shape was used. A reflection sheet 105 made of a white resin sheet is provided on the surface opposite to the emitted light side. No light absorbing means such as black band printing is applied to the portion of the reflection sheet close to the cold cathode tube. In addition, the diffusing means 103, which is a resin sheet subjected to embossing, is arranged on the light emitting surface. The plane size of the diffusing means is arranged on the light entrance surface side of the light guide and is made larger than about 0.7 mm from the light guide, and is projected from the end surface of the light guide by about 0.7 mm or more. A silver vapor-deposited resin film was wrapped around the cold cathode tube 101 to form a reflecting member 106, and a part of the reflecting member 106 overlaps the upper surface of the light diffusing means 103. A light absorbing surface 107 was formed by applying gray paint containing a black pigment to the light guide body side surface of the portion of the diffusing means 103 near the cold cathode tube and the lower surface of the light diffusing means 103. The gray coating surface has a width of about 2 including the protruding portion of the diffusion means.
It is provided in a band shape of mm. Since the light beam generated from the cold cathode tube does not directly hit the reflecting member 106 and strikes the surface of the gray paint and is absorbed, when observed from the light exit side, it is possible to prevent a high brightness band near the cold cathode tube. As a result, it is possible to prevent a strong luminance rising band from being generated on the linear light emitter side of the effective display area of the liquid crystal display device. It should be noted that the shape of the light absorbing surface and the amount of protrusion of the diffusing means from the light guide are not limited to the above-mentioned values, and may be set to different optimum values depending on the thickness of the light guide, the diameter of the cold cathode tube, and the relative arrangement. Is desirable.

(Embodiment 3) FIG. 3 is a cross-sectional view of a flat lighting device as an example of the embodiment. Linear light emitter 101
A cold cathode tube is used for the
A light guide formed by molding a resin into a wedge shape was used. A reflection sheet 105 made of a white resin sheet is provided on the surface opposite to the emitted light side. No light absorbing means such as black band printing is applied to the portion of the reflection sheet close to the cold cathode tube. In addition, the diffusing means 103, which is a resin sheet subjected to embossing, is arranged on the light emitting surface. A white resin film made of expanded PET resin was wrapped around the cold cathode tube 101 to form a reflecting member 106. The surface of the reflection member 106 facing the linear light-emitting body 101 has a scattering reflection surface in a part of, and one end of this scattering reflection surface has a diffusing means 103 and a light guiding means 102.
The adhesive was fixed to the diffusion means while being inserted between the two. The insertion amount from the end surface of the light guide means was about 1.5 mm. The light rays emitted from the cold cathode tube are irradiated to the end surface of the light guide body, and the light ray that causes the high brightness band near the cold cathode tube is scattered and reflected in both the component in front of the end surface of the light guide body and the component incident on the light guide body. Therefore, when observed from the light emitting side, it is possible to prevent a high brightness band near the cold cathode tube. As a result, it is possible to prevent a strong luminance rising band from being generated on the linear light emitter side of the effective display area of the liquid crystal display device. The insertion amount of the reflecting member 106 from the light guide is not limited to the above-mentioned numerical value, and it is desirable to set it to an optimum value that varies depending on the thickness of the light guide, the diameter of the cold cathode tube, and the relative arrangement.

(Embodiment 4) FIG. 4 is a cross-sectional view of a flat lighting device which is an example of an embodiment. Linear light emitter 101
A cold cathode tube is used for the
A light guide formed by molding a resin into a wedge shape was used. A reflection sheet 105 made of a white resin sheet is provided on the surface opposite to the emitted light side. No light absorbing means such as black band printing is applied to the portion of the reflection sheet close to the cold cathode tube. In addition, the diffusing means 103, which is a resin sheet subjected to embossing, is arranged on the light emitting surface. The plane dimension of the diffusing means is made larger by about 0.7 mm than the light guide body on the light guide light entrance surface side, and is made to project from the end surface of the light guide body by about 0.7 mm. A silver vapor-deposited resin film was wrapped around the cold cathode tube 101 to form a reflecting member 106. Reflection member 106
Is a black double-sided tape with a width of 1.5 mm (No.
707) was used to hang and bond the light diffusing means 103 over the light guiding body from the portion protruding from the end surface of the light guiding body. as a result,
Since the light beam generated from the cold cathode tube does not directly hit the reflecting member 106 and strikes the black double-sided tape and is absorbed, it is possible to prevent a high brightness band near the cold cathode tube when observed from the light emitting side. As a result, it is possible to prevent a strong luminance rising band from being generated on the linear light emitter side of the effective display area of the liquid crystal display device. The width of the double-sided tape and the protrusion amount of the diffusing means from the light guide are not limited to the above-mentioned values, and may be set to different optimum values depending on the thickness of the light guide, the diameter of the cold cathode tube, and the relative arrangement. Is desirable. Also, the material and color of the double-sided tape are not limited to the above-mentioned types, and the same effect can be obtained by using an adhesive having a light-absorbing color tone such as black instead of the double-sided tape.

(Fifth Embodiment) FIG. 5 is a cross-sectional view of a liquid crystal display device using the flat lighting device shown in the first embodiment as back lighting. Diagonal 29 with drive circuit 112 connected
The cm type liquid crystal panel 110 is arranged on the light emitting surface of the flat illumination device and fixed by the frame 111. The light guide body 102 has a thickness of 3.0 at the end face facing the cold cathode tube 101.
mm, and the cold cathode tube had an outer diameter of 2.4 mm. The distance from the effective display area of the liquid crystal panel to the center of the cold cathode tube is 4.0 m.
In the case of m, if no measure against uneven brightness is applied to the reflection sheet 105 or the diffusing means 103, the maximum difference in brightness between the central part and the cold cathode tube side end is 50% in the effective display area of the liquid crystal panel.
Also reached. Therefore, as shown in (Embodiment 1), the diffusing means is projected from the end of the light guide body by 0.7 mm, and a scattering reflecting portion having a width of 3 mm is provided on the diffusing means by using white paint. Within the effective display area, the maximum difference in brightness between the central part and the end of the cold cathode tube was suppressed to 5%, and the average brightness was reduced by 6%. For comparison, when the diffusing means is made to have the same size as the diffusing means without protruding from the end of the light guide, the difference in brightness between the central part and the end of the cold cathode tube on the effective display area of the liquid crystal panel. Occurs at a maximum of 25%, indicating that the suppression of the brightness increase phenomenon is insufficient.

The same brightness uniformity effect is obtained by the second to fourth embodiments.
It can also be obtained when the flat illumination device shown in FIG.

[0020]

The flat lighting device of the present invention eliminates the uneven brightness caused in the vicinity of the linear light source by adding an extremely simple structure, and is particularly required in recent years by being used particularly in a liquid crystal display device. Even in a model in which the so-called frame portion around the display area is extremely narrow, it is of great industrial value to obtain a high display image quality with excellent brightness uniformity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a flat lighting device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a flat lighting device according to an embodiment of the present invention.

FIG. 3 is a sectional view of a flat lighting device according to an embodiment of the present invention.

FIG. 4 is a sectional view of a flat lighting device according to an embodiment of the present invention.

FIG. 5 is a sectional view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional flat lighting device.

FIG. 7 is a sectional view of a conventional flat lighting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Linear luminous body 2 Light guide means 3 Diffusing means 4 Condensing means 5 Reflecting sheet 6 Reflecting member 101 Linear luminous body 102 Light guiding means 103 Diffusing means 105 Reflecting sheet 106 Reflecting member 107 Scattering reflecting section 108 Light absorbing section 109 Black Double-sided tape 110 Liquid crystal panel 111 Frame 112 Drive circuit

Claims (6)

[Claims] 1. A linear light-emitting body, a light guide body on which light emitted from the linear light-emitter body enters from a light-incident end surface, and a light-scattering / reflecting portion arranged on a light-emitting surface of the light guide body. A flat illumination device comprising: a sheet-like light diffusing unit provided on a lower surface, the light diffusing unit and the light scattering / reflecting unit having a portion projecting from the input end face of the light guiding unit. 2. A lower surface of a linear light emitter, a light guide body into which light emitted from the linear light emitter enters through a light-incident end surface, and a light absorbing portion arranged on a light exit surface of the light guide body. A sheet-like light diffusing unit having the sheet diffusing unit, and the light diffusing unit and the light absorbing unit having a portion projecting from the light guide unit input end face. 3. A linear light-emitting body, and a reflection member for reflecting light of the linear light-emitting body, which has a light scattering reflection portion on a surface facing the linear light-emitting body around the linear light-emitting body. A flat light illuminating device, comprising: a light guide body that allows light emitted from the linear light emitter to enter from a light incident end surface, and the light scattering / reflecting portion overlaps the light guide body upper surface near the light guide means input end surface. 4. A linear light-emitting body, a light guide body on which light emitted from the linear light-emitting body enters through a light-incident end surface, and a light-projecting surface of the light guide body, the portion protruding from the incident end surface. A sheet-like light diffusing unit having the above, a reflecting member for reflecting the light of the linear luminous body around the linear luminous body, and a light scattering property for bonding the reflecting surface side of the reflecting member and the light diffusing unit. And a double-sided adhesive tape having a flat surface illumination arranged between the reflecting member and the light diffusing means such that at least a part of the adhesive or the double-sided tape projects from the input end face of the light guide means. apparatus. 5. A light condensing means for restricting a traveling direction of light of the light guide is provided above the light emitting surface of the light guide.
The flat lighting device according to any one of to 4. 6. A liquid crystal display device provided with the flat lighting device according to claim 1 as back lighting.