JPH07120754A - Lighting module - Google Patents

Abstract

PURPOSE:To provide a lighting module capable of lighting a display element with uniform illuminating light without the dispersion of illuminating light from a light emitting element which is made incident on a light transmission plate on the lighting surface of the light transmission plate. CONSTITUTION:In this lighting module, one or more pairs of light emitting elements 1 are arranged to be opposed to the opposed end faces of the light transmission plate 6 consisting of light transmissive resin, and the display element is lighted with light from the light emitting element 1 which is made incident from the side surface 6b of the light transmission plate 6 from the lighting surface 6a of the light transmission plate 6 formed in parallel with the optical axis direction of the light emitting element 1. A recessed reflection part 7 is formed nearly in the center part of the surface 6c of the light transmission plate 6 on an opposite side to the lighting surface 6a thereof, and a part between the edge part and the deepest part 8 of the reflection part 7 is formed to be a projected curved surface 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light transmissive display device,
In particular, the present invention relates to an illumination module suitable for illuminating a light transmissive liquid crystal display device.

[0002]

2. Description of the Related Art In general, various display devices using a liquid crystal display element having a light-transmitting property are displayed by reflected light in the same environment as a normal reflection type liquid crystal display device under a bright environment. It functions to recognize the contents, and when the surroundings are darker than a certain degree, such as at night, the contents can be recognized by the illumination light of the illumination module, which is the illumination light source installed behind the liquid crystal display element. It is configured to do.

Known illumination modules include an LED type using a light emitting diode (LED) element as a light emitting element and an EL type using an electroluminescence (EL) element as a light emitting element. LED
The type includes a backlight type illumination module that directly illuminates the display element by arranging the LED element behind the display element, and a light guide plate behind the display element and the LED.
The elements are arranged on both sides of the light guide plate, and L which enters the light guide plate
There is a sidelight type illumination module that indirectly illuminates a display element with light from an ED element. Among them, the sidelight type illumination module is useful for making the product thinner, and is an illumination module that has been widely used in recent years.

A conventional sidelight type illumination module will be described below. 4 and 5 are views showing a sidelight type illumination module. In this illumination module, as shown in FIG. 4, a pair of printed wiring boards 2 each having two LED elements 1 mounted thereon are arranged with their surfaces on which the LED elements 1 are mounted facing each other. Base printed wiring board 3 is arranged between wiring boards 2. As shown in FIG. 4, holes 4 are formed at two locations on both sides of the base printed wiring board 3, and the connecting leg portions 2a of each printed wiring board 2 are inserted into the holes 4 so that these printed wiring boards are Board 2 and base printed wiring board 3 have holes 4
It is fixed by the solder 5 on the periphery. A combination of the printed wiring board 2 and the base printed wiring board 3 constitutes a U-shaped angle member, and a light guide plate 6 made of a light transmissive resin is mounted and supported on the base printed wiring board 3.

The display element is arranged on the front surface of the light guide plate 6 of the illumination module and is indirectly illuminated by the light of the LED element 1 as follows. That is, the light of the LED element 1 is incident from the side surface 6b of the light guide plate 6, and the incident light is formed in parallel with the optical axis direction of the LED element 1 and the illumination surface 6 of the light guide plate 6 is formed.
The display element is illuminated with the illumination light from a. Generally, the LED element 1 is composed of a chip-shaped package element, and as shown in FIGS. 4 and 5, the LED element 1 has the highest light amount distribution on the upper surface 1a of the package. 1 is arranged so as to introduce light from the upper surface 1a of the optical fiber 1 to the side surface 6b of the light guide plate 6.

[0006]

When the display element is illuminated by the illumination module as described above, the brightness of the illumination light of the LED element 1 incident on the light guide plate 6 varies depending on the position on the light guide plate 6. . That is, in FIG. 5, there is a problem that a large difference in brightness inevitably occurs between a region B of the light guide plate 6 close to the LED element 1 and a region C far from the LED element 1. This problem is caused by the thickness T of the light guide plate 6.
Is remarkable, especially when the thickness T is 1.5 mm or less. In recent years, it has been required to reduce the size and thickness of the product. Therefore, an effective solution is desired.

In order to avoid such a problem, various measures have been taken so that the illumination light of the LED element 1 incident on the light guide plate 6 is diffused. That is, a fluorescent paint or a white paint, that is, a paint having a high light reflectance is applied to the portion 3a on the base printed wiring board 3 where the light guide plate 6 is arranged, and the bottom surface 6c of the light guide plate 6 is finely treated by a hairline treatment. For example, a method of providing scratches to diffusely reflect light, a method of forming a diffusion surface on the bottom surface portion 6c of the light guide plate 6 by matting, and the like are used. However, even with these methods,
Since the illumination light is not sufficiently incident / diffused on the area C in FIG. 5 and the variation in brightness between the areas B and C still remains, it is a disadvantage that the character identification is deteriorated and the eyes are tired. There is.

The present invention has been made in view of the above circumstances, and a display element is provided by uniform illumination light without the illumination light of the light emitting element incident on the light guide plate varying on the illumination surface of the light guide plate. It is an object of the present invention to provide an illumination module that can illuminate.

[0009]

In the illumination module according to claim 1, a pair of light emitting elements are arranged as a light source so as to face each other, and a light guide plate made of a light transmissive resin is disposed between the pair of light emitting elements. In the illumination module, the light of the light emitting element incident from the side surface of the light guide plate illuminates the display element from the illumination surface of the light guide plate formed in parallel with the optical axis direction of the light emitting element. On the surface opposite to the illuminating surface of the light plate, a concave reflecting portion is formed in the substantially central portion of the surface, and the reflecting portion is formed into a convex curved surface between the edge portion and the deepest portion. This is the means for solving the above problems.

According to a second aspect of the present invention, in the illumination module according to the first aspect, the distance between the surface of the light guide plate opposite to the illuminated surface and the deepest part of the reflection part is the light guide plate. It is about 10% of the width and the length of the reflecting portion in the optical axis direction is about 60% of the length of the light guide plate in the optical axis direction.

According to a third aspect of the present invention, there is provided the illumination module according to the first or second aspect, wherein the reflecting portion formed on the light guide plate has a depth of 5 times the thickness of the light guide plate.
% To 20% was set as the means for solving the above problems.

An illumination module according to a fourth aspect is the illumination module according to any one of the first to third aspects, in which the optical axis of the light emitting element is the center line of the thickness of the light guide plate and the reflection part. Positioning it between the center line of the thickness of the light guide plate at the deepest part was the means for solving the above problems.

An illumination module according to a fifth aspect is the illumination module according to any one of the first to fourth aspects, wherein the deepest part of the reflection part is formed as a concave curved surface continuous from the convex curved surface of the reflection part. This is the means for solving the above problems.

[0014]

In the illumination module according to the first aspect, the light guide plate is arranged between the pair of light emitting elements, and the light of the light emitting elements enters from the side surface of the light guide plate. Part of the light that entered the light guide plate
The light is reflected by the curved surface of the reflecting portion formed in the substantially central portion of the surface opposite to the illuminated surface, and the reflected light is emitted from the central portion of the illuminated surface. When a concave curved surface is formed between the edge portion and the deepest portion of the reflecting portion, the light irradiated on the reflecting portion is scattered. On the other hand, when a convex curved surface is formed between the edge part and the deepest part of the reflection part, the entire light irradiated to the reflection part is condensed at a predetermined position of the light guide plate. In addition, since at least the surface of the reflecting portion is coated with a paint having a high light reflectance, the reflectance of light becomes high on the curved surface of the reflecting portion.

In the illumination module according to the second aspect of the present invention, the light incident from the side surface of the light guide plate and applied to the reflecting portion is condensed on the central portion of the illumination surface.

In the illumination module according to a third aspect of the present invention, the depth of the reflecting portion formed on the light guide plate is 5% to 20% of the thickness of the light guide plate.
It is within the range of%. The depth of the reflection part is 5% of the thickness of the light guide plate.
In the following cases, there is almost no light reflected by the curved surface of the reflecting portion. Further, when the depth of the reflection portion is 20% or more of the thickness of the light guide plate, the reflection portion is deep, so that the reflected light is not concentrated on the central portion of the illumination surface but scattered on the entire illumination surface.

In the illumination module according to the fourth aspect, the optical axis of the light emitting element is located between the center line of the thickness of the light guide plate and the center line of the thickness of the light guide plate at the deepest part of the reflection part. When the optical axis of the light emitting element is in the above range, light reflected by the curved surface of the reflecting portion is appropriately obtained, but when it is out of the above range, less reflected light is obtained by the curved surface of the reflecting portion.

In the illumination module according to the fifth aspect, the light emitted from the light-emitting element to the deepest part is appropriately scattered by the concave curved surface and dispersed over the entire illumination surface, so that the illuminance on the entire illumination surface is stable without uneven distribution. To do.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an illumination module according to the present invention will be described below with reference to the drawings. The same components as those in the above drawings are designated by the same reference numerals. 1 to 3 are views showing an embodiment of the present invention. In this illumination module, as shown in FIG. 1, a pair of printed wiring boards 2 each having two LED elements (light emitting elements) 1 as a light source mounted thereon are arranged such that the surfaces on which the LED elements 1 are mounted face each other. It is arranged. A base printed wiring board 3 is arranged between the pair of printed wiring boards 2, and holes 4 are formed at two locations on both sides of the base printed wiring board 3. As shown in FIG. 1, the coupling leg portions 2a of the printed wiring board 2 are inserted into the holes 4, respectively, and the base printed wiring board 3 with the solder 5 around the holes 4 is inserted.
And the pair of printed wiring boards 2 are fixed. The pair of the printed wiring board 2 and the base printed wiring board 3 are combined to form a U-shaped angle member, and the light guide plate 6 made of a light transmissive resin is provided on the base printed wiring board 3.
Is installed and supported. The base printed wiring board 3
Since various shapes can be used, the shape is not specified.

The light guide plate 6 has a thickness T of 0.5 mm to
It is about 1.5 mm and, as shown in FIG.
b faces the LED element 1, and an illumination surface 6a for illuminating the display element is formed parallel to the optical axis direction of the LED element 1. On the surface 6c on the side opposite to the illuminated surface 6a, a curved reflecting portion 7 is formed at a substantially central portion of the surface 6c. The reflecting portion 7 has a concave shape having a deepest portion 8 at the center, and a convex curved surface 9 is formed between a portion equidistant from the deepest portion 8 and the deepest portion 8. There is. The convex curved surface 9 has a shape that forms a part of a spherical surface having a constant radius of curvature in a cross-sectional view.

The depth of the reflecting portion 7 is preferably within the range of 5% to 20% of the thickness T of the light guide plate 6. In addition, the formation area of the reflection portion 7 is 20 times the area of the surface 6c of the light guide plate 6.
% To 80% is preferable. Further, it is preferable in terms of molding that the convex curved surface 9 has a constant radius of curvature, which is preferable. Then, a white paint (paint having a high light reflectance) is applied to the entire surface 6c including the convex curved surface 9 of the reflecting portion 7. The optical axis of the LED element 1 on the printed wiring board 2 is between the center line of the thickness T of the light guide plate 6 and the center line of the thickness t of the light guide plate 6 in the deepest part 8 of the reflection part 7. It is arranged to be located.

As shown in FIG. 3, the deepest portion 8 is formed as a concave curved surface continuous with the convex curved surface 9.

When a light transmissive liquid crystal display device is illuminated using the illumination module of this embodiment, as shown in FIG.
The light of the LED element 1 enters from the side surface 6b of the light guide plate 6, and the light entering the light guide plate 6 becomes illumination light, and illuminates a light transmissive liquid crystal display device (not shown) arranged in front of the illumination surface 6a. . At this time, a part of the light incident on the light guide plate 6 is reflected by the reflection portion 7, travels in the direction of the arrow, and is emitted from the illumination surface 6a. In the reflection of the incident light on the reflection part 7, the incident light irradiated on the convex curved surface 9 is reflected at a reflection angle equal to the incident angle. However, since the convex curved surface 9 is concave with respect to the illumination surface 6a, the reflection direction of the reflected light is Are condensed at a ratio according to the radius of curvature of the convex curved surface 9. The reflecting portion 7 has a condensing position of incident light at a central portion of the illuminated surface 6a, and holds the candela value at the central portion of the illuminated surface 6a, so that the illuminated light can be uniformly spread over the entire illuminated surface 6a. You can

Further, the illumination module of this embodiment has a surface 6
Since the incident light scattered in the c direction is guided to the central portion of the illuminated surface 6a without being dispersed to the outside of the illuminated surface 6a, the illuminated surface 6a
It is efficient and easy to make the illumination light uniform.
Further, since the converging position can be easily set by molding the convex curved surface 9, even when the LED elements 1 are not arranged on both sides of the light guide plate 6, the converging position is set to the purpose of the illumination surface 6a. By setting the position to the position, the illumination light to the illumination surface 6a can be easily made uniform, and the degree of freedom in designing the illumination module is improved. In addition, since the reflected light of the deepest part 8 of the illuminated surface 6a is reflected by the concave curved surface of the deepest part 8 without being converged, the illuminated surface 6a
The whole a is illuminated with a constant illuminance.

An experimental example in which the illumination module having the above-mentioned structure is manufactured and the illumination light on the illumination surface 6a of the light guide plate 6 is measured will be described below. Experimental Example The light guide plate 6 has a width W of 40 mm, a length D of 30 mm, and a thickness T.
Was formed to have a thickness of 1.5 mm. Reflector 7 on surface 6c of light guide plate 6
Has a depth of 0.3 mm (the thickness of the light guide plate 6 is 1.
20% of 5 mm), diameter is 30 mm (5 of area of surface 6c)
9%). Then, a white paint was applied to the entire surface 6c of the light guide plate. Further, the two LED elements 1 on each printed wiring board 2 were formed so that the distance X between them was 10 mm and the distance Y between the two printed wiring boards 2 was 44 mm. As the LED element 1, a chip-shaped package element, which is a yellow-green LED element having a high brightness type color tone, is used. The LED element 1 was energized by passing a current of 10 mA.

The reference illumination module is an illumination module manufactured under the same conditions as described above except that the thickness T of the light guide plate 6 is 3.0 mm and the reflecting portion 7 is not formed on the surface 6c. In this case, the photometric value (candela value) targeting the entire illuminated surface 6a is set to 1.0. Then, when the candela value of the illuminated surface 6a of the light guide plate 6 is measured by the illumination module of the above-mentioned experimental example, the area B in FIG.
5 and the area C was 0.70. As a comparative experiment, the thickness T of the light guide plate 6 is 3.0 mm and 1.5.
The candela value of the illuminated surface 6a was measured for each of the illuminated modules under the same conditions as in the experimental example except that the reflective portion 7 was not formed on the surface 6c of the light guide plate 6. When the thickness T of the light guide plate 6 was 3.0 mm, the area B in FIG. 2 was 1.35 and the area C was 0.85. When the thickness T of the light guide plate 6 was 1.5 mm, the area B in FIG. 2 was 1.30 and the area C was 0.42. From the above experimental example, in the illumination module of the present embodiment, even when the thickness T of the light guide plate 6 is made thin, the candela value on the illuminated surface 6a is the same as that of the light guide plate 6.
It can be seen that the thickness T can be obtained to the same extent as when the thickness T is large, and the illumination module has little variation in illumination light.

As the structure of the illumination module, in addition to the structure shown in FIGS. 1 to 3, a base printed wiring board 3 and a printed wiring board 2 on which the LED element 1 is mounted are provided as a flexible printed wiring board. Alternatively, the U-shaped angle member may be formed by integrally coupling the two with each other and bending and fixing the flexible printed wiring board portion.

[0028]

In the illumination module according to the first aspect of the present invention, the light guide plate made of a light-transmissive resin is disposed between the pair of light emitting elements that are arranged to face each other, and the light of the light emitting element is incident from the side surface of the light guide plate. Is an illumination module configured to illuminate a display element from an illuminating surface of a light guide plate formed parallel to the optical axis direction of the light emitting element, in the surface opposite to the illuminating surface of the light guide plate, the surface is A concave reflection part is formed in the substantially central part of the above, and the reflection part is formed in a convex curved surface between the edge part and the deepest part. Therefore, a part of the light of the light emitting element that has entered from the side surface of the light guide plate is reflected by the curved surface of the reflection part and is also reflected or dispersed by the paint with high light reflectance applied on the surface of the reflection part or at a predetermined position. Since the light is focused on, uniform illumination light can be obtained without variations in brightness on the entire illuminated surface. Further, since the display element is illuminated with uniform illumination light, the display device has good character discrimination and eye strain does not occur.

An illumination module according to a second aspect is the illumination module according to the first aspect, wherein a distance between a surface of the light guide plate opposite to the illuminated surface and the deepest part of the reflection part is the light guide plate. It is about 10% of the width, and the length of the reflecting portion in the optical axis direction is about 6 of the length of the light guide plate in the optical axis direction.
It is characterized by being 0%. Therefore, the reflecting portion focuses the incident light reflected by the concave curved surface almost at the center of the illuminating surface and efficiently raises the candela value at the center of the illuminating surface.

According to a third aspect of the present invention, in the illumination module according to the first or second aspect, the depth of the reflecting portion is within a range of 5% to 20% of the thickness of the light guide plate. Therefore, the light reflected by the reflecting section is appropriately obtained,
Since the reflected light is concentrated on the central part of the illuminating surface, the central part of the illuminating surface far from the light emitting element becomes bright, and the entire illuminating surface has uniform brightness.

The illumination module according to claim 4 is the illumination module according to any one of claims 1 to 3, wherein the optical axis of the light emitting element is the center line of the thickness of the light guide plate and the thickness of the light guide plate at the deepest part of the reflection part. Since it is located between the center line and the center line, the incident light is appropriately reflected by the reflecting portion with a desired light amount. Therefore, the brightness of the central portion of the illuminated surface is increased by the reflected light, and the brightness of the illuminated surface does not vary.

According to a fifth aspect of the present invention, in the illumination module according to any of the first to fourth aspects, the deepest part of the reflecting portion is formed as a concave curved surface continuous from the convex curved surface of the reflecting portion. Therefore, even in the deepest part of the reflection part, the light can be dispersed without being converged, and the entire illumination surface can be illuminated with a stable illuminance.

[Brief description of drawings]

FIG. 1 is a sectional view taken along line AB in FIG. 2 of an illumination module shown as an embodiment of the present invention.

FIG. 2 is a plan view of the illumination module.

FIG. 3 is an enlarged cross-sectional view showing the deepest part of the reflection part of the illumination module.

FIG. 4 is a cross-sectional view of the conventional illumination module taken along the line AB in FIG.

FIG. 5 is a plan view of the illumination module.

[Explanation of symbols]

 1 LED element 6 Light guide plate 6a Illuminated surface 7 Reflection part 8 Deepest part 9 Convex curved surface

Claims (5)

[Claims] 1. A pair of light emitting elements are arranged as a light source so as to face each other, a light guide plate made of a light transmissive resin is arranged between the pair of light emitting elements, and the light emitting element enters from a side surface of the light guide plate. Of the light, in an illumination module configured to illuminate the display element from the illumination surface of the light guide plate formed parallel to the optical axis direction of the light emitting element, on the surface opposite to the illumination surface of the light guide plate. The illumination module is characterized in that a concave reflection portion is formed substantially in the center of the surface, and the reflection portion is formed into a convex curved surface between the edge portion and the deepest portion. 2. The illumination module according to claim 1, wherein a distance between a surface of the light guide plate opposite to an illuminated surface and a deepest part of the reflection part is about 10% of a width of the light guide plate. The illumination module is characterized in that the length of the reflecting portion in the optical axis direction is about 60% of the length of the light guide plate in the optical axis direction. 3. The illumination module according to claim 1 or 2, wherein an immersion amount of a reflection portion formed on the light guide plate is
An illumination module, which is in a range of 5% to 20% of the thickness of the light guide plate. 4. The illumination module according to claim 1, wherein an optical axis of the light emitting element has a center line of a thickness of the light guide plate and a thickness of the light guide plate at a deepest portion of the reflection section. An illumination module, characterized in that it is located between the center line of Saano. 5. The illumination module according to any one of claims 1 to 4, wherein the deepest part of the reflection part is formed as a concave curved surface continuous from the convex curved surface of the reflection part. .