JP2001042782A - Display device - Google Patents

Abstract

(57) [Summary] [Problem] To make the surface of a liquid crystal display panel uniform brightness. A space is provided between a liquid crystal display panel and a substrate on which the light emitting elements are arranged by applying a white coat on a substrate facing the liquid crystal display panel to reflect light emitted from the light emitting elements. In addition, an LED sheet 5 having a diffusing means is provided, and a gray resin coat 8 is provided as a semi-transmissive means on a portion facing the light emitting element 6 to reduce light emitted directly from the light emitting element 6 to the liquid crystal display panel 2, Liquid crystal display panel 2
Make the surface brightness uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device equipped with a light-emitting device such as an LED (light-emitting diode) device used for a backlight of a liquid crystal display panel. It is about.

[0002]

2. Description of the Related Art As a display device 101 mounted on a conventional oil fan heater, as shown in FIG. 5, a large number of LED elements 105, which are light-emitting elements, are arranged on a printed board 106 at a constant pitch vertically and horizontally. A liquid crystal display 104 in which a white resin frame 104 serving also as a receiver for the liquid crystal display panel 102 is provided around the periphery thereof, and a diffusion sheet 103 is provided on the back side with a predetermined space above all the LED elements 105. A configuration in which a panel 102 is mounted is known.

When each LED element 105 emits light, most of the light hits the diffusion sheet 103 directly.
The remaining light is reflected by the white frame 104 and indirectly strikes the diffusion sheet 103, and the light is diffused by the diffusion sheet 103 so that the pictograms of the liquid crystal display panel 102 are projected.

[0004]

In a display device having a backlight function using LED elements as described above, the surface of the liquid crystal display panel directly above the LED elements is bright, and the space between the LED elements is large. The surface of the liquid crystal display panel directly above it becomes dark, and even if the diffusion sheet is effective, this phenomenon cannot be eliminated, and the difference in brightness and darkness appears as a stripe pattern on the surface of the liquid crystal display panel. I was In particular, when the distance between the upper surface of the LED element and the back side of the liquid crystal display panel becomes a certain distance (9 mm) or less,
This stripe pattern became remarkable, and there was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. In particular, when the distance between the upper surface of the LED element and the back side of the liquid crystal display panel is less than a predetermined distance (9 mm), the surface of the liquid crystal display panel is reduced. It is an object to provide a display device having uniform brightness.

[0006]

Means for Solving the Problems In order to solve the above problems, the present inventors have mainly taken the following two technical means. That is, as a first technical means, in the case of a light emitting element such as an LED element, the light is illuminated in the axial direction most brightly. Dimming the illumination of
The panel surface brightness just above the light emitting elements is made uniform.

In this case, the light semi-transmissive means may be of any form as long as it can be arranged in the space between the light emitting element and the liquid crystal display panel. Or a method of covering with a translucent resin sheet. If a sheet-like material is used, make the sheet material itself translucent,
Alternatively, any of the modes of applying a translucent printing layer to a transparent resin sheet can be adopted.

In the case where a plurality of light emitting elements arranged vertically and horizontally, that is, when the light transmissive means is provided on the upper surface of the light emitting element mounting portion, a transparent resin sheet covering the entirety of a large number of light emitting elements is formed in consideration of the manufacturing process. It is preferable to use a semi-transparent printing layer on the sheet just above the light emitting elements.

The position of the light transmissive means in the axial direction is not particularly limited as long as it is between the light emitting element and the liquid crystal display panel. In consideration of the amount of light reaching from the space to the liquid crystal display panel, a mode in which the light emitting element is disposed as close as possible to the light emitting element is preferable. In particular, when a resin sheet that covers the entire surface of the light emitting element mounting portion is employed, it is advantageous in that the area for applying the translucent printing layer is reduced.

When a resin sheet is used to cover the entire surface of the light emitting element mounting portion, the means for positioning the resin sheet in the sheet surface direction and height direction is not particularly limited.
For example, it is possible to employ any of a method of supporting the frame on a frame disposed around the liquid crystal display panel and a method of bonding the liquid crystal display panel to the upper surface of the light emitting element. However, adopting the method of bonding to the upper surface of the light emitting element is advantageous in that a frame having the same structure as that of the related art can be used because there is no need to form a sheet supporting portion on the frame.

When the resin sheet is bonded to the upper surface of the light emitting element, it is preferable that the upper surface of the light emitting element is a flat surface because the bonding area can be increased. As the light emitting element, an LED element can be exemplified, and since this LED element is obtained by molding a semiconductor chip with a transparent resin such as an epoxy resin, the upper surface of the resin can be easily formed into a flat surface.

As an adhesive for adhering the light emitting element to the resin sheet, a transparent glue is used because a part of the light from the light emitting element needs to be transmitted from the translucent printing layer to the liquid crystal display panel side. There is a need.

The relationship between the adhesive layer for the resin sheet and the translucent print layer is determined by forming the print layer and the adhesive layer on the back side of the resin sheet, or on the front side (liquid crystal display panel side) of the resin sheet. It is possible to adopt any of the modes of forming the printing layer and forming the adhesive layer on the back side of the resin sheet.However, in consideration of prevention of peeling of the printing layer, the printing layer is formed on the front side of the sheet and on the back side. An embodiment in which an adhesive layer is formed is preferred.

The printing layer is not particularly limited as long as it is of a semi-transmissive type. However, as a result of experiments by the present inventors, when the emission color of the LED element is green, the gray printing layer is used. The surface of the liquid crystal display panel having no unevenness was obtained by the application.

Next, as a second technical means, independently,
Alternatively, by forming a reflective coating layer on the surface of the substrate in combination with the first technical means, light from the light emitting element is reflected on the substrate surface, and the reflected light is irradiated on the back surface of the liquid crystal display panel. As a result, the brightness between light-emitting elements, which are likely to be dark portions, of the liquid crystal display panel is increased, and the striped pattern due to light and dark is eliminated.

As the reflection coat, either a mode in which a reflection printing layer is provided on the surface of the substrate or a mode in which a reflection sheet is adhered to the surface of the substrate can be adopted. As the color of the reflection coat layer, white having good reflection efficiency is preferable.

The light reflected by the reflection coat on the substrate is reflected directly or on the inner surface of the frame holding the liquid crystal display panel to reach the liquid crystal display panel. When the resin sheet is present, these lights are reflected. Reaches the liquid crystal display panel through the resin sheet. In this case, the transparent resin sheet may adopt either a mode in which an opening is formed between the semi-transmissive printing layers or a mode in which the transparent resin portion is left as it is. It is more preferable to include a small amount of a light diffusing agent in the portion to promote further diffusion of the reflected light.

The inner surface of the frame holding the liquid crystal display panel is preferably formed with a white coat layer or molded with a white resin material in order to increase the reflection efficiency. Further, the distance between the upper surface of the light emitting element and the liquid crystal display panel is not particularly limited. In particular, the first technical means is applied to a display device in which the distance between the two is small, for example, the distance between both is 9 mm or less. It is preferable to employ the second technical means. Further, in order to make the luminance uniform, in addition to the above technical means, a configuration in which a diffusion sheet is attached to the back surface of the liquid crystal display panel can be adopted.

[0019]

FIG. 1 is a structural view of a display device according to an embodiment of the present invention, FIG. 2 is an enlarged view of a main part thereof, and FIG.
FIG. 4 is a plan view of the sheet, and FIG. 4 is an enlarged sectional view of the LED sheet.

As shown in the figure, the display device 1 of the present embodiment
Is mounted on a heating device such as an oil fan heater, and includes a liquid crystal display panel 2 for displaying pictograms, and an LED element 6 for backlighting the liquid crystal display panel 2.
A printed board 7 on which the LED elements 6 are arranged at a constant pitch in the vertical and horizontal directions, a diffusion sheet 3 for diffusing the light of the LED elements 6, a frame 4 for receiving the liquid crystal display panel 2 and the diffusion sheet 3, and an LED element And an LED sheet 5 (resin sheet) for reflecting and diffusing the light from the LED.

In addition to the LED element mounting portion corresponding to the liquid crystal display panel 2, the printed circuit board 7 operates an operation switch for turning on / off the operation and an up / down switch for setting a room temperature and a timer. Switches, etc., and the LED element mounting part has an LED which is a light emitting element.
A large number of elements 6 are mounted and arranged at a constant pitch in the vertical and horizontal directions. The mounting surface (front surface) of the substrate 7 is the white resin sheet 1
0 (white reflective coat) to reflect the light from the LED element 6.

Each LED element 6 is formed by molding a semiconductor chip with a transparent resin such as an epoxy resin, and the upper surface of the resin is formed flat.

Around the LED element mounting portion, a rectangular frame 4 hollowed out on all sides of the LED element 6 is mounted, and the liquid crystal display panel 2 is formed in a concave portion 4a formed on the inner peripheral surface at the upper end thereof.
Further, the diffusion sheet 3 is placed and held so as to maintain a position at a constant height from the upper surface of the LED element 6. This frame 4
Is made of a white resin, and is further coated with a white resin on the inner surface side from the outer wall thereof so as to reflect light from the LED element 6.

The diffusion sheet 3 is in close contact with the back surface of the liquid crystal display panel 2 and is placed and held together with the liquid crystal display panel 2 in the outer peripheral recess 4a of the frame 4. The diffusion sheet 3 is a transparent resin sheet having a thickness of 1 mm (for example, a PC resin sheet).
In order to promote the light diffusion effect of the LED element 6, a small amount of a diffusing agent such as titanium-based fine particles is contained.

The LED sheet 5 is, as shown in FIG.
A transparent resin sheet (for example, a PC resin sheet) having a thickness of 0.5 to 1 mm disposed between the element 6 and the liquid crystal display panel 2 (including the diffusion sheet 3), and comprising a large number of LEDs
It is formed to have substantially the same diameter as the inner diameter of the frame 4 so as to cover the entire element 6. The LED sheet 5 contains a small amount of a diffusing agent such as titanium-based fine particles in order to promote the effect of diffusing light from the LED elements 6.

As shown in FIG. 3, a portion of the surface of the LED sheet 5 facing the LED element 6 is coated on its surface (liquid crystal display panel) with a gray resin coat 8 (semi-transparent) having substantially the same diameter as the LED element 6. Print layer). LED element 6
When the emission color of was green, an experiment was conducted with two colors of the resin coat 8 of white and gray, and the results were as shown in the following table.

[0027]

[Table 1]

As shown in Table 1, the gray color of the resin coat 8 was smaller than that of the white color and light transmission was small, and there was almost no unevenness.

As shown in FIG. 4, a transparent glue 9 as an adhesive means is applied to the rear surface of the LED sheet 5 opposite to the surface on which the resin coat 8 is formed, as shown in FIG.
It is adhered to the upper surface of the LED element 6. This transparent glue 9
Is designed so that the luminance of the LED element 6 does not decrease even if it adheres to the surface of the LED element 6.

The procedure for assembling the display device 1 having the above configuration is as follows.
The frame 4 is fitted around the LED element mounting portion of the printed circuit board 7 in which the D element 6 is incorporated and the white coat 10 is applied on the surface, and then the transparent water-like glue side of the LED sheet 5 is On the 6th side, the adhesive surface is adhered to the upper surface of the LED element 6. Next, when the diffusion sheet 3 and the liquid crystal display panel 2 are fitted into the recesses 4a of the frame 4, the display device 1 is completed.

Next, the operation will be described. When each LED element 6 emits light, the light is reflected directly on the white frame 4 and indirectly applied to the lower surface of the diffusion sheet 3. In this case, the light of each LED element 6 is diffused by the LED sheet 5 and spreads to the vicinity of the frame 4. At that time,
The brightness of the surface of the LED sheet 5 is highest immediately above each LED element 6, but the gray resin coat 8 reduces the brightness by absorbing a part of the light or reflecting the light downward.

The light reflected downward is reflected on the white resin coat 10 of the printed circuit board 7, and the light travels upward, and
Since the light passes through the diffusion sheet 3 through the transparent resin portion 5a of the ED sheet 5, the reflected light can be effectively used, and the luminance distribution becomes uniform on the surface of the liquid crystal display panel 2, thereby preventing the occurrence of unevenness. become.

[0033]

As is apparent from the above description, according to the present invention, since the light transmissive means is provided on the liquid crystal display panel side of the light emitting element, the light directly traveling from the light emitting element to the liquid crystal display panel is reduced, and Light unevenness on the display panel surface is eliminated. In addition, the reflective coating is applied to the substrate facing the liquid crystal display panel, so that the light emitted from the light emitting elements is reflected and radiated to the positions corresponding to the light emitting elements of the liquid crystal display panel, so that the brightness of the surface of the liquid crystal display panel is And the unevenness of light can be eliminated.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a display device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the same.

FIG. 3 is a plan view of the same LED sheet.

FIG. 4 is an enlarged sectional view of the same LED sheet.

FIG. 5 is a schematic structural diagram of a conventional display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Liquid crystal display panel 3 Diffusion sheet 4 Frame 5 LED sheet 6 LED element (light emitting element) 7 Printed circuit board 8 Gray resin coat 9 Transparent paste (adhesion means) 10 White resin coat

Claims (7)

[Claims] In a space between a liquid crystal display panel for displaying pictograms and a substrate on which light emitting elements are arranged as a backlight, light translucent means is provided at a portion facing the light emitting elements. Display device. 2. The display device according to claim 1, wherein said light semi-transmissive means is supported by a resin sheet covering a light emitting element mounting portion. 3. The display device according to claim 2, wherein said light semi-transmissive means is a gray color printed layer applied to a portion of said resin sheet facing the light emitting element. 4. The display device according to claim 2, wherein an adhesive layer is formed on a portion of the resin sheet facing the light emitting element, and an upper surface of the light emitting element is bonded to the resin sheet. 5. A display device comprising: a liquid crystal display panel for displaying pictograms; and a substrate on which light emitting elements are arranged as a backlight, wherein a reflection coating is applied to the substrate facing the liquid crystal display panel. Display device. 6. The display device according to claim 1, wherein said substrate is provided with a reflection coat. 7. The display device according to claim 5, wherein the reflection coat is a white reflection coat.