JPH0372968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device, and particularly to a liquid crystal display device equipped with illumination means called a so-called backlight.

[Conventional technology]

In recent years, in this type of liquid crystal display device, as various properties of liquid crystal have been improved, the application fields of liquid crystal have expanded, including displays for toys, displays for clocks, displays for office equipment, displays for terminals, displays for terminals, and automobiles. With the application of lighting for business displays, etc., there has been a demand for long-time lighting, lighting with relatively large panels, decorative lighting, and efficient lighting.

2. Description of the Related Art Conventionally, for example, wristwatches have been put into practical use that are equipped with a backlight consisting of a small lamp on the back side of a liquid crystal display panel. However, in watches, the display is identified by lighting it for a very short time at night.
Backlights are minimally necessary only for telling the time, and are not fully satisfactory in terms of brightness, uniformity of light, decorativeness, lifespan, etc.

For example, FIGS. 3 and 4 show the liquid crystal display panel 1.
FIG. 2 is a vertical front view and a vertical side view showing an example of a conventional liquid crystal display device in which a light source 2 is arranged directly below.

The liquid crystal display panel 1 includes a liquid crystal 3 sandwiched between an upper electrode substrate 4 and a lower electrode substrate 5 with a spacer 6 interposed therebetween.
It is constructed by adding an upper polarizer 7 and a lower polarizer 8.

The light emitted from the light source 2 is reflected by the light scattering reflector 9 and illuminates the liquid crystal display panel 1 via the milky white light scatterer 10. Light source 2 is a fuse type,
These were tungsten lamps with linear shapes such as cylindrical or line filament types. Hereinafter, it will be abbreviated as a linear light source.

The light scattering body 10 was made of a milky white polycarbonate resin or a milky white acrylic resin, had a uniform thickness, and had a plate shape. Further, the reflector 9 was a metal plate made of Al or the like.

[Problems to be Solved by the Invention] However, in the above-mentioned liquid crystal display device, since the linear light source 2 is arranged directly below the liquid crystal display panel 1, the area close to the light source 2 is bright and the area away from the light source is bright. Distance areas may become dark and uneven illumination may occur, or a linear bright striped pattern may appear on the surface of the display panel along the linear light source.

FIG. 5 is a plan view of the display device showing a state in which uneven illumination of the backlight has occurred in the conventional liquid crystal display device with backlight shown in FIGS. 3 and 4. FIG. In FIG. 4, the illumination intensity is strong at the center part 1c of the liquid crystal display panel 1 in the direction intersecting the linear light source 2, and weak at the end part 1d. Therefore, the upper and lower parts 1d of the display of "AM 5:45" in Figure 5
is dark, and the center portion 1c is bright.

Although the above-mentioned illumination ram can be alleviated by moving the light source 2 away from the display panel 1, the brightness of the entire liquid crystal display panel decreases, and the illumination unevenness cannot be sufficiently eliminated. Further, there were other problems such as the overall thickness of the liquid crystal display device increasing and making it larger.

The present invention was proposed in view of the above problems, and an object of the present invention is to provide a liquid crystal display device that is small in size and can display images with uniform brightness over the entire liquid crystal display panel.

[Means to solve the problem]

In order to achieve the above object, the present invention has the following configuration. That is, a liquid crystal display panel;
In a liquid crystal display device comprising a linear light source disposed on the back side of the liquid crystal display panel substantially parallel to the liquid crystal display panel, a light beam from the linear light source is provided between the liquid crystal display panel and the linear light source. It has a function of scattering light while transmitting it, and has a function of scattering light while transmitting it, and on a surface substantially parallel to the liquid crystal display panel, varies the light scattering intensity in a direction orthogonal to the linear light source in a region close to the linear light source. It is characterized by the arrangement of opalescent light scatterers whose light scattering intensity is gradually greater than in other areas.

[Effect]

With the above configuration, the light emitted from the linear light source is scattered more or more widely in the area close to the linear light source than in other areas, making it possible to more uniformly illuminate the display panel.

〔Example〕

Hereinafter, a detailed explanation will be given based on the embodiment shown in the drawings.

1 and 2 are a longitudinal sectional front view and a longitudinal sectional side view showing one embodiment of a liquid crystal display device according to the present invention, and members having the same or similar functions as those in FIGS. 3 and 4 are the same. The reference numerals are given to omit further explanation.

In this embodiment, the thickness of the light scattering body 10 in the direction intersecting the longitudinal direction of the linear light source 2 is
The light scattering function of the light scattering body 10 in the area close to the light source 2 is made to be thicker in the vicinity of the light source 2, that is, in the center, and gradually thinner in the edge part away from the light source 2, so that the light scattering function of the light scattering body 10 in the area close to the light source 2 is gradually thinner than in other areas. It was made to grow larger.

With this configuration, the center of the light scattering body 10 is close to the linear light source 2 with strong emission intensity and is therefore exposed to strong light, and the end of the light scattering body 10 is far away from the linear light source 2. Because of this, the light that hits it directly is weak, but the center of the light scatterer 10 that hits the strong light is thicker, so the light is scattered widely and more and transmitted to the edges, and the light intensity at the center is slightly smaller. become weak. In addition, since the end portions of the light scattering body 10 are thin, light can pass through them well, and the light scattered at the center is transmitted, increasing the light intensity, so that the center portion of the light scattering body 10 and the ends thereof are transmitted. In this section, the illumination intensity is approximately averaged, producing a uniform light scattering intensity. Therefore, uneven illumination is eliminated, giving a sense of satisfaction to the viewer and having a great decorative effect even in relatively long-term illumination or constant illumination.

Furthermore, the present invention allows the illumination intensity to be averaged as described above without having to separate the light source 2 from the liquid crystal display panel 1 by a large distance as in the conventional method, so that the distance between the light source 2 and the display panel 1 can be shortened. In addition, since the shape of the light scattering body 10 is simply changed, a liquid crystal display device that provides a uniform illumination effect can be easily made thinner and smaller.

In the above embodiment, as shown in FIG. 1, the thickness of the light scattering body 10 in the direction parallel to the longitudinal direction of the linear light source 2 is thick at the center and thin at the ends. For example, if there is a non-light emitting part or a weak light emitting part 2b at the end of a linear light source, the backlight is strong in the center part 1a of the liquid crystal display panel 1 and the backlight is weak in the end part 1b. This is for the purpose of correction.

FIG. 6 shows an example of the display state in the conventional liquid crystal display device when a linear light source including the weak light emitting portion 2b etc. as described above is used. is strong, end 1
b is dark, so the "AM" and "3" parts are dark,
Since the "5:4" part is bright, the aesthetic appearance is spoiled.

In this case, if the linear light source 2 is moved away from the liquid crystal display panel 1, the illumination unevenness will be alleviated, but some light will still remain and the entire liquid crystal display device will become thicker.

Therefore, in this embodiment, the thickness of the light scattering body 10 in the direction parallel to the linear light source 2 is made thicker at the center and thinner at the ends, thereby eliminating uneven illumination in the direction parallel to the linear light source. It was designed to resolve this issue.

The reflector 9 is, for example, a metal plate made of Al, Fe, or stainless steel, or a metal plate plated, vapor-deposited, or sputtered with Al, Ni, Ag, etc., or made of polycarbonate resin, acrylic resin, etc. on the inside in the reflective direction. A transparent plastic light guide is formed, and the metal plate, metal foil, or laminate sheet of aluminum and plastic is attached to the outside by adhesive, mechanical attachment, mechanical pressure, etc., or a light guide made of Al, Ni, or Ag is formed. It is constructed by vapor-depositing or sputtering on a light object, or by mixing it with an adhesive or paint and painting it.

The reflector 9 is preferably provided on both ends of the linear light source 2 as shown in FIG. The illumination intensity near both ends of the linear light source can be increased.

Further, as the light source 2, a conventional tungsten lamp and various other linear light sources can be used, but preferably a cold cathode discharge tube can be used.

The reason is explained below.

As a means of illuminating a liquid crystal display panel, in order to take advantage of the thin characteristics of the display panel, it is necessary to satisfy the requirements of small size, thinness, low price, and low power consumption.
It has been said that tungsten lamps are good for such light sources, but the first problem with tungsten lamps is the color temperature.
It is around 2000°K and has slightly red emission spectral characteristics, and the transmission spectral characteristics of liquid crystals tend to emphasize red light, so when used as a backlight for liquid crystals, the appearance and color may deteriorate. Also the second
Although there are slight differences in the definition depending on the manufacturer,
50% to 80% of lamps have a lighting lifespan of tens of thousands of hours at most without breaking, and when used for long periods of time or constant lighting, it is necessary to have a structure that allows for easy lamp replacement, making the structure complex. This makes it disadvantageous for downsizing. Furthermore, if a socket or the like is used to facilitate lamp replacement, for example, the cost will increase accordingly. Furthermore, as the illumination area becomes larger and the number of lamps used increases, the probability that one of them will break and will have to be replaced increases, making it even more disadvantageous. Furthermore, in order to form a linear light source, the filament needs to be made into a linear shape, and the longer the filament is, the more strain it places on the structure, which further reduces the lifespan and reliability.

On the other hand, cold cathode discharge tubes have a short lifespan that is almost semi-permanent as long as they are used at the rated value, and when they are constantly lit, it takes more than tens of thousands of hours for the luminous intensity to be halved, making it necessary to replace the light source. It has the advantage of not causing any sexual problems. Secondly, the emitted light color is white, and when used as a backlight for a liquid crystal, the color tone harmonizes well with the liquid crystal, the lighting state of the liquid crystal is excellent, and the backlight has a great decorative effect. For this reason, it is especially suitable as a backlight for LCD color displays using color polarizing plates or color filters, and for guest-host type color displays.
Also suitable as a DTN type back light. For the above reasons, a cold cathode discharge tube is preferable as a light source for decorative liquid crystal lighting for constant lighting or long lighting.

Further, as shown in FIGS. 1 and 2, a transflector 11 may be provided between the liquid crystal display panel 1 and the light scattering body 10 as required. In this way, in the daytime state when the light source 2 is not turned on, the semi-transparent reflector 11 reflects the light incident from the panel 1 side, and when the light source 2 is turned on, the backlight is scattered and transmitted. Therefore, when the surroundings are bright, the light source 2 can be turned off to display without a backlight, and the light source 2 can be turned on only when it is dark, reducing the power consumption of the backlight. In addition, the semi-transparent reflector 11 itself has a light scattering effect, and the light scatterer 1
By using it in combination with 0, the unevenness of light can be further reduced. Furthermore, if the illuminance of the backlight is too strong, the intensity of the light illuminating the liquid crystal display panel 1 can be appropriately reduced by inserting the transflector 11.

[Effect of idea]

As explained above, the present invention provides that the light scattering function of the light scattering body in a region close to the linear light source in a direction perpendicular to the linear light source on a surface substantially parallel to the liquid crystal display panel is higher than that in other regions. The light emitted from the linear light source is scattered more or more widely in areas close to the linear light source than in other areas, making it possible to illuminate the display panel more uniformly. In addition, it is possible to prevent the display surface corresponding to the light source from becoming bright and conspicuous. Furthermore, since the illumination intensity on the display panel can be averaged without having to place the light source very far from the display panel, it is possible to provide a compact liquid crystal display device with good display performance.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of a liquid crystal display device according to the present invention, FIG. 2 is a longitudinal sectional side view thereof, FIG. 3 is a longitudinal sectional front view of a conventional liquid crystal display device, FIG. 4 is a longitudinal sectional side view thereof, and FIG. and FIG. 6 is a plan view showing an example of a display state of a conventional liquid crystal display device. 1 is a liquid crystal display panel, 2 is a linear light source, 9 is a reflector, and 10 is a light scatterer.

Claims (1)

[Scope of Claims] 1. A liquid crystal display device comprising a liquid crystal display panel and a linear light source disposed on the back side of the liquid crystal display panel substantially parallel to the liquid crystal display panel, comprising: between the light source and having a function of transmitting and scattering the light from the linear light source, and having different light scattering intensities in the direction orthogonal to the linear light source on a surface substantially parallel to the liquid crystal display panel. A liquid crystal display device characterized in that a milky white light scattering body is arranged such that light scattering intensity in a region close to the linear light source becomes gradually larger than in other regions.