JP2000338485A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase illumination brightness by using a lamp box system as the illumination structure of a transmissive liquid crystal display element and to suppress temperature rising in the lamp box due to the heat generation caused by a light source for illumination. SOLUTION: In this device, a liquid crystal display element 1 is disposed on the front side of a frame-shaped holder 5 consisting of an insulating material, and a printed circuit board 13 on which the holder 5 and the liquid crystal display element 1 are mounted is provided. A light source 10 for illumination to transmissively illuminate the liquid crystal display element 1 from the rear side is disposed on the printed circuit board 13. A light case 9 to guide irradiating light rays of the light source 10 to the liquid crystal display element 1 is disposed on the holder 5. A ventilation part 12 communicated with the outside is disposed between the frame-shaped holder 5 and the light case 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device which is transmitted and illuminated by an incandescent light bulb which emits heat as a light source for illumination.

[0002]

2. Description of the Related Art In general, a liquid crystal display element of this type has a structure in which liquid crystal is sealed between opposing electrodes and the molecular arrangement direction of the liquid crystal is changed by selectively applying a voltage between the electrodes. Liquid crystal display devices that control transmission of light according to the relationship with the polarization axis of a polarizing plate provided are well known and widely used.

This liquid crystal display device can be classified into a reflection type using an external light beam and a transmission type using an irradiation light beam of an illumination light source provided behind, according to a difference in illumination method. When used as a display device, a transmissive liquid crystal display device that can display even in dark surroundings such as at night is suitable.

As an illumination structure of this transmissive liquid crystal display device, for example, a transparent electrode is formed on the opposite surface, and a liquid crystal display element consisting of two transparent substrates in which liquid crystal is sealed between the electrodes is provided behind the liquid crystal display element. In general, a light guide system in which a light guide plate made of a flat transparent polycarbonate resin or the like is provided, and a light source for illumination made of an incandescent lamp such as a tungsten lamp is provided on the back or side of the light guide plate.

[0005]

However, in recent years, in order to increase the illumination luminance, instead of the light guide method, the irradiation light of an illumination light source comprising an incandescent lamp provided behind a liquid crystal display element is directly or reflected by a reflector. A light box system in which the light is reflected on the liquid crystal display element and irradiated on the liquid crystal display element is being adopted.

An incandescent light bulb or the like used as a light source for illumination includes light emitted from a filament as a light-emitting member, which includes visible light and infrared light. When this infrared light is received from behind, a transparent resin located near the incandescent light bulb is used. The temperature of the light guide plate and the diffusion plate made of the liquid crystal rises to cause thermal deformation, adversely affecting the optical performance, and the temperature of the liquid crystal of the liquid crystal display element also increases, and the liquid crystal changes to a liquid state. However, there has been a problem that the voltage dependence characteristic of the period cannot be maintained.

In a conventional light box system, as shown in FIGS. 3 and 4, a plurality of terminal portions connected to the transparent electrode of the liquid crystal display element a and exposed to the outside are provided with clip-like electrode holding members. The liquid crystal display element a is mounted and fixed on a synthetic resin frame-shaped holder c, and the liquid crystal display element a is fixed to the frame-shaped holder c. The liquid crystal display element a
And an insertion hole d for receiving and guiding the lead pin b of
Frame-shaped holder c facing the display portion of the liquid crystal display element a
A light case e is formed on the rear side of the light case e so as to be continuous with the peripheral wall of the holder c and has a curved reflecting surface on the lower surface side. However, in order to suppress a rise in the temperature inside the holder c and the light case e due to the heat generated by the illumination light source f, the inside and the outside of the light case e are communicated below the side wall of the light case e. Vent holes g are provided at appropriate intervals.

A printed circuit board h incorporating a circuit for driving the liquid crystal display element a is disposed behind the light case e. Each lead pin 2 of the liquid crystal display element a is connected to the printed circuit board h. The illumination light source f is mounted on the printed circuit board h while being connected by soldering.

Therefore, the temperature rise inside the holder c and the light case e can be suppressed by the ventilation hole g provided at an appropriate position of the light case e. On the other hand, the illumination is provided by the ventilation hole g provided on the side wall of the light case e. There is a problem that light leaks out of the light case e, and the leaked light reduces the amount of light applied to the liquid crystal display element a, resulting in a decrease in illumination efficiency, There is also a problem that the above-mentioned leaked light rays affect the lighting effect of an external device.

Therefore, the present invention makes it possible to increase the illumination luminance by using a lamp box system as an illumination structure of a transmission type liquid crystal display element, and to suppress a rise in temperature in the lamp box due to heat generated by an illumination light source. It is an object to provide a liquid crystal display device.

[0011]

In order to achieve the above object, according to the present invention, a liquid crystal display element is provided on the front side of a frame-shaped holder made of an insulating material. A light board for mounting a liquid crystal display element and a light source for transmitting and illuminating the liquid crystal display element from behind on the printed circuit board, and guiding light emitted from the light source to the liquid crystal display element. Is provided in the holder, and a ventilation portion communicating with the outside is provided between the holder and the light case. In claim 2, in claim 1,
The liquid crystal display device according to claim 1, wherein the ventilation portion is provided so as to face a rear side of the liquid crystal display element. According to a third aspect of the present invention, in the liquid crystal display device according to the first or second aspect, the air passage is formed of a maze-shaped air passage. According to a fourth aspect of the present invention, in the first to third aspects, the liquid crystal display element is disposed on a front surface side of the frame-shaped holder via a diffusion plate that scatters an irradiation light beam of the irradiation light source. A liquid crystal display device characterized by the following. According to a fifth aspect of the present invention, there is provided the liquid crystal display device according to any one of the first to third aspects, wherein the liquid crystal display element is disposed on the front side of the frame-shaped holder via a color filter. According to a sixth aspect of the present invention, there is provided the liquid crystal display device according to the first to third aspects, wherein the liquid crystal display element is disposed on the front side of the frame-shaped holder via a diffusion plate and a color filter. It is. According to a seventh aspect of the present invention, in the first to sixth aspects, the light case is formed with an arc-shaped reflecting surface for reflecting and guiding the irradiation light of the illumination light source toward the liquid crystal display element. A liquid crystal display device characterized by the following.

[0012]

According to the first aspect of the present invention, the heat generated from the illumination light source is dissipated from the ventilation portion provided between the holder and the light case. According to the second aspect of the present invention, since the ventilation portion is formed behind the liquid crystal display element in the first aspect, the heat can be radiated from the upper side of the light case in which heat is easily trapped, and the temperature in the case can be reduced. The rise can be suppressed, whereby the operation of the liquid crystal display element can be stabilized and a good display can be achieved. According to a third aspect, in the first or second aspect, the vent portion is formed by maze-shaped ventilation, so that a temperature rise in the case can be suppressed, and at the same time, light from the illumination light source can be suppressed. Irradiation light can be suppressed from leaking from the inside to the outside of the light case, and illumination to the liquid crystal display element can be kept good. According to a fourth aspect, in the first to third aspects, the liquid crystal display element is disposed on the front surface side of the frame-shaped holder via a diffusion plate that scatters an irradiation light beam of an irradiation light source. Thus, the liquid crystal display element can be transmitted and illuminated. According to a fifth aspect, in the first to third aspects, the liquid crystal display element is disposed on the front side of the frame-shaped holder via a color filter, so that the background display color of the liquid crystal display element is changed. It is possible to provide a liquid crystal display device which can display an image by the color of the color filter and is easy to see. According to a sixth aspect, in the first to third aspects, the liquid crystal display element is disposed on the front side of the frame-shaped holder via a diffusion plate and a color filter, so that the background of the liquid crystal display element is provided. The display color can be displayed by the hue of the color filter, and the liquid crystal display element can be uniformly transmitted and illuminated by the diffusion plate. According to a seventh aspect of the present invention, in the first to sixth aspects, the light case is formed with an arc-shaped reflecting surface for reflecting and guiding the irradiation light of the illumination light source toward the liquid crystal display element. Thereby, the irradiation light from the illumination light source is reflected and guided toward the liquid crystal display element side by the reflection surface, so that the entire liquid crystal display element can be uniformly illuminated.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIGS. 1 to 4 show a first embodiment of the present invention, in which a liquid crystal is sealed between two electrode substrates made of a light-transmitting insulating substrate such as a glass substrate having a transparent electrode provided on the opposed inner surface. In this embodiment, a lead pin 2 having a clip-shaped electrode holding portion is connected and fixed to a plurality of terminal portions connected to the transparent electrode of the liquid crystal display device 1 and exposed to the outside. Have been.

In this embodiment, a desired translucent color portion is formed behind the liquid crystal display element 1 in accordance with each display section (not shown) of the liquid crystal display element 1, and a color filter 3 is provided. In addition, a diffusion plate 4 made of a synthetic resin such as white polycarbonate or white paper for diffusing light from an illumination light source, which will be described later, over a wide area on the back surface of the liquid crystal display element 1 is superimposed behind the color filter 3. It is arranged.

The liquid crystal display element 1, the color filter 3 and the diffusion plate 4, which are arranged in an overlapping manner, are supported on a frame-like holder 5 made of an insulating material, for example, made of synthetic resin. The holder 5 includes the liquid crystal display element 1
And a through hole 7 for receiving and guiding the lead pin 2 of the liquid crystal display element 1 is provided at a side edge of the mounting surface 6, and the mounting surface 6 on which the liquid crystal display element 1 is mounted. A light case 9 provided with a curved reflecting surface 8 on the lower surface side is formed continuously with the holder 5 at the rear of the location, and an illumination light source 10 is provided at the bottom of the light case 9.
Is provided.

Between the mounting surface 6 of the frame-shaped holder 5 located on the rear side of the liquid crystal display element 1 and the upper edge of the light case 9, the inside and the outside of the light case 9 communicate with each other. A ventilation portion 12 is provided. In this case, the peripheral wall side edge of one of the holders 5 is provided between the peripheral wall portion 5A facing the inside of the insertion hole 7 of the holder 5 and the peripheral wall portion 9A of the light case 9. The ventilation section 1 is formed by a maze-shaped ventilation path in
2 is formed, and at the side edge of the peripheral wall of the other holder 5, a part of six mounting surfaces of the holder 5 is cut out to form a side peripheral wall portion 5 </ b> B of the holder 5 and a side peripheral wall of the light case 9. A ventilation section 12 is formed by a maze-shaped ventilation path between the section 9B and the section 9B.

A printed circuit board 13 in which a circuit for driving the liquid crystal display element 1 is incorporated is provided behind the light case 9. Each lead pin 2 of the liquid crystal display element 1 is provided on the printed circuit board 13. While being connected by soldering, the illumination light source 10 is attached and fixed while being electrically routed.

In this embodiment, an incandescent lamp (tungsten lamp) with heat radiation is used as the illumination light source 10 in order to increase the luminance and reduce the cost. As the illumination light source 10, a light source formed of a light bulb such as a xenon lamp or a halogen lamp may be used.

In the first embodiment configured as described above, the illumination of the liquid crystal display device at night or the like is performed on the printed circuit board 1.
The light emitted from an illuminating light source 10 comprising an incandescent light bulb attached to the light source 3 is reflected directly toward the liquid crystal display element 1 or via the curved reflecting surface 8 of the light case 9 toward the liquid crystal display element 1. The irradiation light beam is guided indirectly.

At this time, by interposing the color filter 3 and the diffusion plate 4 behind the liquid crystal display element 1, the irradiation light from the illumination light source 10 is transmitted by the diffusion plate 4 and the color filter 3.
To the liquid crystal display element 1 through the
Is transmitted and illuminated, so that the background display color of the liquid crystal display element 1 can be displayed by the hue of the color filter 3, and the liquid crystal display element 1 is uniformly distributed by the diffusion plate 4.
Can be transmitted and illuminated directly, and can be illuminated directly without the intervention of a light guide plate, so that the illumination brightness can be increased.

In this embodiment, the temperature rise in the atmosphere partitioned by the holder 5 and the light case 9, that is, the temperature rise due to the heat of the illumination light source 9 itself, is reduced by the ventilation portion 12 provided in the light case 9. The heat is radiated to the outside of the light case 9 through the light source 9, thereby suppressing the heating of the color filter 3 and the diffusion plate 4, thereby eliminating the problem of adversely affecting the optical performance due to thermal deformation. It is also possible to solve the problem that the liquid crystal changes to the liquid state and cannot maintain the desired voltage-dependent characteristics.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. For example, in the above-described embodiment, the liquid crystal display element 1 A ventilation portion 12 communicating the inside and outside of the light case 9 is provided between the mounting surface 6 of the frame-shaped holder 5 and the upper edge of the light case 9. The width of the portion 12, the shape of the maze or the positional relationship thereof may be set so as not to cause a heat radiation effect or light leakage, and the rear side of the holder 5 is connected to the peripheral wall of the holder 5 and the lower surface side. A light case 9 having two curved reflecting surfaces 8 is formed, and an opening 11 for receiving two illumination light sources 10 is formed at the bottom of the light case 9 to constitute the entire liquid crystal display device. However, liquid crystal display The shape and size of the frame-shaped holder 5 and the light case 9 and the shape and size of the curved reflecting surface may be set in accordance with the size and length of the element 1. Needless to say, the installation position and the number may be arbitrarily determined and provided.

Further, in the above-described embodiment, the color filter and the diffusion plate are individually constructed and arranged.
Although the filter function and the diffusion plate function may be provided for both, the electric connection between the liquid crystal display element and the printed circuit board is electrically conducted by the lead pin in the embodiment as the electric connection. The liquid crystal display element and the printed circuit board may be connected by a flat cable or conductive rubber.

[0024]

As described in detail above, in the liquid crystal display device according to the present invention, a liquid crystal display element is disposed on the front side of a frame-shaped holder made of an insulating material, and the holder and the liquid crystal are provided. A printed circuit board on which a display element is mounted is provided, an illumination light source is provided on the printed circuit board for transmitting and illuminating the liquid crystal display element from behind, and a light case for guiding an irradiation light of the illumination light source to the liquid crystal display element is provided. Provided in the holder, by providing a ventilation portion that communicates with the outside between the frame-shaped holder and the light case, it is possible to radiate heat from the upper side of the light case where heat is easily trapped, It is possible to suppress a rise in temperature inside the device, thereby stabilizing the operation of the liquid crystal display element and enabling a good display, and to solve the conventional disadvantages. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the liquid crystal display device according to the first embodiment of FIG. 1 as viewed from a lateral direction.

FIG. 3 is a cross-sectional view of a liquid crystal display device showing a conventional example.

FIG. 4 is a cross-sectional view of the conventional liquid crystal display device of FIG. 3 viewed from a lateral direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display element 2 Lead pin 3 Color filter 4 Diffusion plate 5 Holder 6 Mounting surface 7 Insertion hole 8 Reflection surface 9 Light case 10 Lighting source 11 Opening hole 12 Vent section 13 Printed circuit board

Claims (7)

[Claims] 1. A liquid crystal display element is provided on the front side of a frame-shaped holder made of an insulating material, and a printed circuit board on which the holder and the liquid crystal display element are mounted is provided. An illumination light source for transmitting and illuminating the element from behind is provided, and a light case for guiding an irradiation light beam of the illumination light source to the liquid crystal display element is provided in the holder, and an outside communicates between the holder and the light case. A liquid crystal display device provided with a vent portion that performs ventilation. 2. The liquid crystal display device according to claim 1, wherein the ventilation portion is provided so as to face a rear side of the liquid crystal display element. 3. The liquid crystal display device according to claim 1, wherein the ventilation section comprises a maze-shaped ventilation path. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal display element is disposed on a front side of the frame-shaped holder via a diffusion plate that scatters the irradiation light of the irradiation light source. 4. The liquid crystal display device according to 3. 5. The liquid crystal display device according to claim 1, wherein the liquid crystal display element is disposed on a front side of the frame-shaped holder via a color filter. 6. The liquid crystal display device according to claim 1, wherein the liquid crystal display element is disposed on the front side of the frame-shaped holder via a diffusion plate and a color filter. 7. The light case according to claim 1, wherein the light case is formed with an arc-shaped reflecting surface for reflecting and guiding the irradiation light of the illumination light source toward the liquid crystal display element.
The liquid crystal display device according to claim 6.