JPH0996814A - Illumination device, back light and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the peeling of a light control plate and light transmission body even by a severe environmental test and to stabilize the adhesion state for a long period. SOLUTION: This illumination device includes a light transmission plate 2 which has flanks, a rear surface and a light exit surface, a light source which is disposed on the flank side of the light transmission plate 2, a condenser sheet 5 which is successively provided with plural lens-like projecting parts and prism-like projecting parts 5b on the front surface and rear surface, respectively and a transparent adhesive 4 which is applied on the light exit surface 2a of the light transmission plate 2 and adheres the condenser sheet 5 onto the light exit surface 2a of the light transmission plate 2 by press fitting the prism-like projecting part 5b side of the condenser sheet 5 up to the range tb of 5 to 50% in the application thickness ta thereof.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a lighting device, a backlight using the lighting device, and a liquid crystal display device using the backlight.

[0002]

2. Description of the Related Art Conventionally, a backlight of this type has a white ink printed on the back surface of a light guide plate to utilize the light diffuse reflection of the white portion, or a conical recess or V groove is formed on a molded light guide plate. The light is reflected by utilizing the inclined portion and is emitted to the front surface of the light guide plate. However, in this method, since diffused light is emitted to the front surface, high brightness cannot be obtained, so recently, light is incident from the side surface side of the light guide plate to connect a plurality of convex lens portions and prismatic convex portions. A resin condensing sheet that combines both front and back sides is attached on the light exit surface of the light guide plate, and light is guided from the prismatic convex side of this back surface into the sheet, and in the normal direction on the convex lens side surface. It has been proposed that a function of changing the direction of a light beam can obtain a brightness which is 3 to 8 times that of a conventional method. One example is the backlight described in US Pat. No. 5,396,350 and the drawings.

[0003]

However, in such a conventional backlight, since the light-condensing sheet is simply adhered to the light-exiting surface of the light guide member with an adhesive, it is necessary to perform a harsh environmental test. However, there is a problem in that the light-collecting sheet is peeled off so that light is not emitted, and a uniform light emitting surface cannot be obtained as a backlight.

Therefore, an object of the present invention is to provide a lighting device, a backlight, and a liquid crystal display, which can secure a bonded state for a long period of time without the light-condensing sheet and the light guide body being separated from each other even under a severe environmental test. The purpose is to provide a device.

[0005]

SUMMARY OF THE INVENTION In the present invention, the problem of the conventional backlight is that the light control plate is peeled off from the light guide plate in the reliability test because the adhesion of these bonding interfaces becomes a problem. This poor adhesion is due to the fact that the properties of the adhesive deteriorate from the end of the joint surface and the adhesive strength often decreases, causing peeling. To be done.

According to a first aspect of the present invention, a light guide having a side surface, a back surface, and a light exit surface; a light source disposed on the side surface of the light guide; a plurality of lens-shaped convex portions and prism-shaped convex portions; A light control plate having a front surface and a back surface connected to each other; applied on the light exit surface of the light guide and press-fitting the prism-shaped convex portion side of the light control plate up to a range of 5 to 50% of the applied thickness. And a transparent adhesive for adhering the light control plate to the light exit surface of the light guide.

Therefore, according to the present invention, the transparent adhesive coated on the light emitting surface of the light guide has a coating thickness of 5 to 50.
%, The prism-shaped convex portions of the light control plate are press-fitted and bonded, so that the bonding area can be increased. Therefore, the adhesive strength of the adhesive can be increased, and
It is possible to suppress the decrease in the adhesive strength of the adhesive.

According to a second aspect of the present invention, in addition to the first aspect of the invention, the transparent adhesive is formed in a wavy waveform on the light emitting surface of the light guide body, and is formed between the light emitting surface and the light emitting surface. It forms a void.

Therefore, according to the present invention, claim 1
In addition to being able to achieve the same effect as the invention described above, the light incident on the gap between the corrugated transparent adhesive and the light exit surface of the light guide has a refractive index between the air and the light guide. It is possible to suppress the scattering by causing almost total reflection on the light exit surface due to the difference of. Therefore, it is possible to prevent light leakage due to scattering of light on the light emitting surface, and thus it is possible to improve light emission efficiency.

[0010] The third aspect of the present invention is the first or second aspect.
In the invention described above, the transparent adhesive is applied only to the top ends of the prismatic convex portions of the light control plate.

Therefore, according to the present invention, since the transparent adhesive is applied only to the apexes of the prismatic convex portions of the light control plate, it is transparent as compared with the case where the transparent adhesive is applied to the entire light emitting surface of the light control plate. In addition to saving the amount of adhesive applied, in comparison with the case where a transparent adhesive is applied in spots on the light exit surface of the light guide where it is predicted that the prismatic protrusions will be located, The positioning can be performed accurately and easily.

The invention described in claim 4 is the first to third aspects of the present invention.
In any one of the inventions, the transparent adhesive is silicone-based and has a film thickness of 20 to 30 μm.

Therefore, according to the present invention, when the film thickness of the adhesive is too thick, the transmittance is lowered and the brightness of the display surface is lowered. If it is too thin, peeling occurs in the reliability test, and sufficient adhesive strength cannot be obtained. As a result of the experiment, the film thickness of the silicone adhesive is optimally 20 to 30 μm.

[0014] The invention according to claim 5 provides the invention according to claims 1 to 3.
In any one of the inventions, the transparent adhesive is acrylic and has a film thickness of 20 to 60 μm.

Therefore, according to the present invention, if the film thickness of the adhesive is too thick, the transmittance is lowered and the brightness of the display surface is lowered. If it is too thin, peeling occurs in the reliability test, and sufficient adhesive strength cannot be obtained. As a result of the experiment, the film thickness of the acrylic adhesive is optimally 20 to 60 μm.

The invention according to claim 6 is the invention according to claims 1 to 5.
In the invention described in any one of 1 to 3, the light control plate is further made of any one of polystyrene, polycarbonate, and methylpentene polymer.

The invention according to claim 7 is the invention according to claims 1 to 6.
The invention according to any one of the above, further comprising: a light diffuser disposed on the light control plate side; and a reflector disposed on the back side of the light guide.

Therefore, according to these inventions, since the light guide and the light control plate according to any one of claims 1 to 6 are provided, the invention according to any one of claims 1 to 6 is provided. The same operational effect as can be obtained.

The invention according to claim 8 is the invention according to claims 1 to 7.
And a case body that accommodates a light guide, a light source, a reflector, a light diffuser, and a light control plate;
The lighting unit is provided in the case body and supplies high-frequency power to the light source.

The invention according to claim 9 is the invention according to claims 1 to 8.
And a liquid crystal display unit that is illuminated by light from the illumination device.

Therefore, since the backlight according to claim 8 and the liquid crystal display device according to claim 9 have the illuminating device according to any one of claims 1 to 7, the same operational effects as those illuminating devices can be obtained. be able to.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. 1 to 6, the same or corresponding parts are designated by the same reference numerals.

FIG. 1 is an enlarged view of an essential part of FIG. 2, and FIG. 2 is a vertical sectional view of a first embodiment of the present invention. In these drawings, a lighting device 1 is a rectangular flat plate made of, for example, a transparent acrylic resin. For example, a pair of right and left straight fluorescent lamps 3a and 3b are arranged laterally on the left and right side surfaces of the light guide plate 2 formed in a shape.

On the light exit surface 2a of the light guide plate 2, a silicone-based or acrylic-based transparent adhesive 4 is applied approximately evenly in a required film thickness, and an assembly sheet 5 as a light control plate is adhered and fixed. ing.

The aggregate sheet 5 is made of PS (polystyrene), P
A sheet of synthetic resin such as C (polycarbonate) or TPX (methyl pentene polymer) is formed into a sheet shape, and a plurality of convex lens portions 6 in an arc shape convex upward in the figure are laterally formed on the upper surface 5a (surface) in the figure. While arranging at a predetermined pitch,
In the figure, a plurality of inverted trapezoidal wedge-shaped prism-shaped convex portions 7 are continuously arranged in a lateral direction at a predetermined pitch on a lower surface 5b (on the light emitting surface 2a side of the light guide plate 2). That is, the plurality of convex lens portions 6 and the plurality of prismatic convex portions 7 are integrally formed on the front and back surfaces 5a and 5b, respectively.

When the light collecting sheet 5 is adhered onto the light exit surface 2a of the light guide plate 2 with the transparent adhesive 4, first, the transparent adhesive 4 is applied onto the light exit surface 2a of the light guide plate 2 by a predetermined film. It is applied with a thickness of ta almost evenly.

Next, the light-condensing sheet 5 is placed on the transparent adhesive 4 with its prismatic convex portion 7 side facing, and the light-condensing sheet 5 and the light guide plate 2 are not shown in the drawing. The prismatic protrusions 7 are placed in the transparent adhesive 4 within a thickness of 5 to 5 of the film thickness ta as shown in FIG.
It is dried and solidified and fixed in a state of being press-fitted in the range of 0% tb. When the transparent adhesive 4 is of silicone type, the film thickness ta is preferably 20 to 30 μm, and when it is of acrylic type, the film thickness ta is preferably 20 to 60 μm. These film thickness ta
If the thickness is too thick, the light transmittance decreases and the brightness of the light emitting surface decreases, while if it is too thin, peeling occurs in the reliability test,
Sufficient mounting strength cannot be obtained. As a result of the experiment, the above optimum film thickness was obtained.

Since the illuminating device 1 is constructed in this way, the light from the pair of fluorescent lamps 3a and 3b is incident on the inside of the side surface of the light guide plate 2, and part of it is on the bottom surface of the light guide plate 2. The light is almost totally reflected and guided to the light exit surface 2a side, and further enters from the light exit surface 2a into the light-condensing sheet 5 from the back surface 5b side forming the plurality of prismatic convex portions 6,
The light passes through the light-condensing sheet 5 and is emitted from each lens-shaped convex portion 6 as substantially parallel light in the normal direction.

In this embodiment, each prismatic convex portion 7 of the light-condensing sheet 5 is placed in the transparent adhesive 4 and its film thickness ta is obtained.
5 to 50% of the range tb is press-fitted and the light exit surface 2 of the light guide plate 2 is pressed.
Since the light-condensing sheet 5 is adhered on a, the light-condensing sheet 5
It is possible to increase the area where each prismatic convex portion 7 and the transparent adhesive 4 come into contact with each other. For this purpose, the light collecting sheet 5
Since the adhesive force between the light guide plate 2 and the light exit surface 2a of the light guide plate 2 can be increased, the interface of this joint can be stabilized for a long period of time, and the light-condensing sheet 5 can be prevented from peeling off from the light guide plate light exit surface 2a. It can be effectively prevented for a period.

That is, when the inventors of the present invention conducted an environmental test on the lighting device 1, the pressure applied to the light guide plate 2 of the light collecting sheet 5 was changed in various ways to form the light collecting sheet 5 and the light guide plate 2. As a result of investigating the adhesion state, the prismatic convex portion 7 of the light collecting sheet 5
The present invention was completed by newly discovering that by press-fitting up to 5 to 50% of the film thickness ta of the transparent adhesive 4, it is possible to sufficiently withstand the environmental test.

FIG. 3 is a cross-sectional view of a main part of the second embodiment of the present invention. In this lighting device 1A, the transparent adhesive 4 is applied only to the top end surface of each prismatic convex portion 7 of the light collecting sheet 5. It is characterized by the fact that each of these prismatic convex portions 7 is attached to the transparent adhesive 4
The point that the light-condensing sheet 5 is adhered onto the light-exiting surface 2a of the light guide plate 2 by press-fitting in the range tb of 5 to 50% of the total film thickness ta is the same as in the above embodiment.

Therefore, according to this illuminating device 1A, the amount of the transparent adhesive 4 applied can be reduced as compared with the case where the transparent adhesive 4 is applied to almost the entire light exit surface 2a of the light guide plate 2.

Further, the transparent adhesive 4 is applied to the light exit surface 2a of the light guide plate.
The application amount of the adhesive 4 can be saved by applying the adhesive 4 in spots at the locations where the top ends of the respective prism-shaped convex portions 7 are expected to be located. There is a case where the application position and the position of each prismatic convex portion 7 are displaced. However, according to this embodiment, there is no such inconvenience, and such positioning can be performed accurately and easily.

FIG. 4 is a vertical cross-sectional view of a main part of a third embodiment of the present invention. In this illuminating device 1B, a transparent adhesive 4 for adhering a light-condensing sheet 5 on a light exit surface 2a of a light guide plate 2 is The light emitting surface 2a is formed in a wavy shape in the vertical direction in the figure, and each arcuate portion 4a that is convex upward in this waveform is provided in a wedge-shaped concave portion 7a between adjacent prism-shaped convex portions 7, The feature is that a plurality of small voids 8 are formed between each of the circular arc portions 4a and the light emitting surface 2a. Similar to each of the above-described embodiments, the light-condensing sheet 5 has the prism-shaped convex portions 7 pressed into the transparent adhesive 4 within a range tb of 5 to 50% of the total film thickness ta of the light guide plate 2. It is adhered on the light emitting surface 2a.

Since there is a difference between the air in each void 8 and the refractive index in the light guide plate 2, as shown in FIG. When light is incident, it is totally reflected by the light emitting surface 2a, and scattering can be suppressed. For this reason, it is possible to suppress the scattering of light on the light emitting surface 2a to other than the light emitting surface 5a of the light-condensing sheet 5 and improve the brightness on the light emitting surface 5a.

FIG. 5 is a vertical cross-sectional view showing one step of an example of a method for forming the transparent adhesive 4 in a corrugated form. This is the transparent adhesive 4 applied to the prismatic convex portion 7 side of the light collecting sheet 5.
In addition, it is characterized in that the adhesive 4 is formed into a corrugated shape by pressing a rubber-like roller or a rubber corrugated plate 10 through the protective cito 9. According to this, the transparent adhesive 4 can be accurately and easily formed into a corrugated shape.

FIG. 6 shows a lighting device 1 having such a configuration.
Backlight 1 including, for example, 1 of 1A and 1B
1 is an exploded perspective view of FIG. In the backlight 11, a reflection sheet 12 is stacked on the bottom surface of the light guide plate 2, while a light-condensing sheet 5 and a diffusion sheet 13 are sequentially stacked on the light exit surface 2a of the light guide plate 2 in this order to form a bottomed thin prismatic case. It is housed in the main body 14. The case main body 14 is integrally molded with a synthetic resin such as a polycarbonate resin, and the upper surface of the case is almost entirely opened.

Further, lamp covers A, B 16a, 16b housing, for example, L-shaped fluorescent lamps 15 are interposed between the side surface of the light guide plate 2 and the inner side wall of the case body 14. The fluorescent lamp 15 may be either a hot-cathode type or a cold-cathode type, but a cold-cathode type is preferable as a light source of a backlight because it has good rising characteristics and low power consumption. Inside the lamp covers A, B 16a, 16b, a silver sheet 1 whose back surface is formed with double-sided adhesive tape 1
7a and 17b are attached and formed on the reflecting surface. Reference numeral 18 is a conductive sheet attached to the L-shaped fluorescent lamp 15 to shield noise generated in the lamp 15.
Is the frame corner.

A lighting device (not shown) is electrically connected to the fluorescent lamp 15. From this lighting device, the fluorescent lamp 1 is connected.
High-frequency power is stably supplied to 5 to be lit stably. This lighting device is also mounted on the case body 14.

By providing the liquid crystal display panel 20 having a liquid crystal drive circuit (not shown) on the diffusion sheet 13, a liquid crystal display device can be constructed.

[0041]

As described above, the invention according to claim 1 of the present application provides a transparent adhesive coated on the light emitting surface of the light guide,
Since the prism-shaped convex portions of the light control plate are press-fitted and bonded to 5 to 50% of the coating thickness, the bonding area can be increased. Therefore, it is possible to increase the adhesive force of the adhesive between the light guide and the light control plate, and it is possible to suppress the decrease in the adhesive force of the adhesive.

According to the second aspect of the present invention, the same operational effect as that of the first aspect of the present invention can be obtained, and the gap between the corrugated transparent adhesive and the light exit surface of the light guide is obtained. The light incident on the light can be almost totally reflected on the light exit surface due to the difference in the refractive index between the air and the light guide, and scattering can be suppressed. Therefore, it is possible to prevent light leakage due to scattering of light on the light emitting surface, and thus it is possible to improve light emission efficiency.

According to the third aspect of the present invention, since the transparent adhesive is applied only to the apexes of the prism-shaped convex portions of the light control plate, it is compared with the case where the transparent adhesive is applied to the entire light emitting surface of the light control plate. In addition to saving the amount of transparent adhesive to be applied, it is possible to reduce the amount of transparent adhesive applied to spots on the light exit surface of the light guide where it is expected that prismatic convex parts will Positioning of the control plate can be performed accurately and easily.

The invention according to claim 4 is the same as claims 1 to 3.
In any one of the inventions, the transparent adhesive is silicone-based and has a film thickness of 20 to 30 μm.

Therefore, according to the present invention, when the film thickness of the adhesive is too thick, the transmittance is lowered and the brightness of the display surface is lowered. If it is too thin, peeling occurs in the reliability test, and sufficient adhesive strength cannot be obtained. As a result of the experiment, the film thickness of the silicone adhesive is optimally 20 to 30 μm.

The invention according to claim 5 is the same as claims 1 to 3.
In any one of the inventions, the transparent adhesive is acrylic and has a film thickness of 20 to 60 μm.

Therefore, according to the present invention, if the film thickness of the adhesive is too thick, the transmittance is lowered and the brightness of the display surface is lowered. If it is too thin, peeling occurs in the reliability test, and sufficient adhesive strength cannot be obtained. As a result of the experiment, the film thickness of the acrylic adhesive is optimally 20 to 60 μm.

According to the sixth and seventh aspects of the invention, the light guide according to any one of the first to fifth aspects of the invention and the light control plate are included. Therefore, any one of the first to fifth aspects of the invention is provided. It is possible to obtain the same operational effects as the invention described in one.

Since the backlight according to claim 8 and the liquid crystal display device according to claim 9 have the illuminating device according to any one of claims 1 to 7, the same operational effects as these illuminating devices can be obtained. You can

[Brief description of drawings]

FIG. 1 is an enlarged view of a main part of FIG.

FIG. 2 is a schematic vertical cross-sectional view of the lighting device according to the first embodiment of the present invention.

FIG. 3 is a schematic vertical sectional view of an illumination device according to a second embodiment of the present invention.

FIG. 4 is a schematic vertical cross-sectional view of an illumination device according to a third embodiment of the present invention.

5 is a vertical cross-sectional view of one step for forming the corrugated adhesive shown in FIG. 4 into a corrugated shape.

FIG. 6 is an exploded perspective view of a backlight or a liquid crystal display device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1, 1A, 1B Illuminating device 2 Light guide plate 2a Light emitting surface 3a, 3b Fluorescent lamp 4 Transparent adhesive 5 Light collecting sheet 5a Light collecting sheet front surface 5b Light collecting sheet back surface 6 Lens-shaped convex portion 7 Prism-shaped convex portion 8 Void 11 Backlight 12 Reflective Sheet 13 Light Diffusing Sheet 14 Case Body 15 L-shaped Fluorescent Lamp 20 Liquid Crystal Display Panel

Claims (9)

[Claims] 1. A light guide having a side surface, a back surface, and a light exit surface; a light source disposed on the side surface of the light guide; and a plurality of lens-shaped convex portions and prism-shaped convex portions on a front surface and a back surface. A light control plate, which is provided in series, is applied to the light exit surface of the light guide, and the prism-shaped convex portion side of the light control plate is press-fitted to the range of 5 to 50% of the applied thickness to guide the light control plate. An illuminating device comprising: a transparent adhesive that adheres to a light emitting surface of a light body. 2. The illuminating device according to claim 2, wherein the transparent adhesive is formed in a wavy shape on the light emitting surface of the light guide body to form a gap between the transparent adhesive and the light emitting surface. . 3. The illumination device according to claim 1, wherein the transparent adhesive is applied only to the top ends of the prismatic convex portions of the light control plate. 4. The lighting device according to claim 1, wherein the transparent adhesive is a silicone-based adhesive and has a film thickness of 20 to 30 μm. 5. The lighting device according to claim 1, wherein the transparent adhesive is acrylic and has a film thickness of 20 to 60 μm. 6. The lighting device according to claim 1, wherein the light control plate is made of polystyrene, polycarbonate, or methylpentene polymer. 7. A light diffuser disposed on the light control plate side; and a reflector disposed on the back side of the light guide body. The lighting device according to any one of claims. 8. The lighting device according to claim 1, a case body that accommodates a light guide, a light source, a reflector, a light diffuser, and a light control plate;
And a lighting means for supplying high-frequency power to the light source. 9. A liquid crystal display device, comprising: the illuminating device according to claim 1; and a liquid crystal display means illuminated by light from the illuminating device.