JPS63228188A - Liquid crystal display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention will be described in the following order.

A. Industrial field of application B9 Summary of the invention C1 Prior art [Figures 4 and 5] 09 Problems to be solved by the invention E9 Means for solving the problems F1 Effects G. Examples [First [Figures to Figures 3] H1 Effects of the invention (A, Industrial application field) The present invention relates to a liquid crystal display device, and particularly to a liquid crystal display device in which a light source for illuminating the liquid crystal display portion is arranged at a position offset from the back of the liquid crystal display portion. .

(B. Summary of the Invention) The present invention provides a liquid crystal display device in which a light source that illuminates the liquid crystal display portion is arranged at a position offset from the back of the liquid crystal display portion, the device is made thinner, and the light source illuminates the liquid crystal display portion. In order to reduce the loss of light and reduce the cost, a sag-like reflector is used as a means for guiding the light emitted from the light source to the liquid crystal display section.

(C, Prior Art) [Figures 4 and 5] Some liquid crystal display devices use a transmissive type liquid crystal display panel. This transmissive liquid crystal display device is widely used because it provides a bright display and is suitable for color display.

Incidentally, in the transmission type liquid crystal display device, a light source that illuminates the liquid crystal display section was initially placed behind the liquid crystal display section. FIG. 4 is a sectional view showing one of the conventional examples of such a liquid crystal display device, in which a is a box, b is a liquid crystal display panel fitted into a window C formed on the front of the box a, and d is a sectional view showing one of the conventional examples of such a liquid crystal display device. is a diffusion plate arranged behind the liquid crystal display panel b, e, e, e,
is a fluorescent lamp placed behind the diffuser plate d.

In such a liquid crystal display device, the liquid crystal display panel a can be uniformly illuminated from behind by the fluorescent lamps e, e, and e through the diffuser plate d. Although there may be a plurality of fluorescent lamps e arranged behind the diffuser plate d, for example two or three, there is also a case in which one U-shaped fluorescent lamp e is arranged.

By the way, in this way, there is a diffusion F behind the liquid crystal display pulse b.
id, and furthermore, fluorescent lights e, e, e are installed behind the diffuser plate d.
If it is provided, the thickness of the liquid crystal display device will become thicker,
It becomes difficult to meet the strong demand for thinner liquid crystal display devices. Further, when the light source e is placed behind the liquid crystal display panel b, there is a problem that the liquid crystal display panel b, which is made of a polymer compound and is extremely sensitive to heat, is easily heated by the light source e and deteriorates.

Therefore, the light source e is placed at a position offset from the back of the liquid crystal display panel b, and an appropriate reflecting means is placed behind the liquid crystal display panel b, and the light from the light source e is directed toward the liquid crystal display panel b by the reflecting means. A method has been proposed in which the liquid crystal display panel b is illuminated by reflection, and this is disclosed, for example, in Japanese Patent Laid-Open No. 123823/1983. Fig. 4 shows the liquid crystal display device disclosed to the public, and in the figure, a is the box of the liquid crystal display device, and b is the liquid crystal display panel placed in the window C formed in the front of the box a. , f is a wedge-shaped light guide placed behind the liquid crystal display panel b inside the box a, and e is a fluorescent lamp placed on the side of the conductor f inside the box a. As a matter of course, this fluorescent lamp e is located at a position offset from the back of the liquid crystal display panel b. In this specification, the term "side" refers not only to the left or right side but also to the upper or lower side.

- F The wedge-shaped light guide f has its base located on the side of the fluorescent lamp e, and the surface on the liquid crystal display panel b side goes toward the tip side, that is, as it gets farther from the fluorescent lamp e, the liquid crystal display panel b A Fresnel-shaped lens step is formed on the surface opposite to the liquid crystal display panel b.

In this liquid crystal display device, light emitted from the fluorescent lamp e enters the light guide f from the end face on the base side thereof. A part of the incident light is internally reflected at the lens step and directed toward the liquid crystal display panel b. In addition, the remainder of the light incident on the light guide f is once reflected internally by the surface of the light guide f on the side of the liquid crystal display panel b, and is directed toward the side opposite to the liquid crystal display panel b. The light is internally reflected again at the lens step formed in the front and illuminates the liquid crystal display panel b from behind.

According to a liquid crystal display device in which such a light source e is disposed at a position shifted from behind the liquid crystal display panel b, there is no risk that the liquid crystal display panel b will be heated in various ways by the light source e. The progress of deterioration due to
Furthermore, since the light source e is provided on the side of the light source e rather than behind the light guide f, the liquid crystal display device does not become so thick.

Note that it may also be possible to arrange the EL behind the liquid crystal display panel b and use it as a light source. However, when trying to increase the amount of light, EL deteriorates significantly and has a very short lifespan, making it completely impractical.

(D. Problem that the invention attempts to solve) By the way, the fifth problem
According to the liquid crystal display device shown in the figure, the optical path length of the light emitted from the fluorescent lamp e within the light guide f is relatively long, on the order of several centimeters or tens of centimeters. There is a problem that some of it is absorbed. This is because although the light guide f is made of glass or resin and is transparent, it absorbs light. Therefore, in order to obtain the amount of light necessary to illuminate the liquid crystal display panel b, the amount of light emitted by the fluorescent lamp must be increased. Increasing the amount of light emitted by the fluorescent lamp is not preferable because it increases the power consumption of the fluorescent lamp and requires increasing the size of the fluorescent lamp. Specifically, an increase in the power consumption of fluorescent lamps is undesirable because it hinders the long life of the battery, which is strongly required when a pocket television is constructed using a liquid crystal display device. Furthermore, increasing the size of fluorescent lamps is not preferable because it hinders the slimming down that is strongly required for pocket televisions and the like using liquid crystal display devices. Therefore, it is a problem that cannot be overlooked that the light emitted from the fluorescent lamp e is unnecessarily lost at the light guide f.

In addition, the light guide f needs to have a thickness of several millimeters to several centimeters, and cannot be said to be sufficiently thin, which is one of the factors that prevents further thinning of liquid crystal display devices. . Furthermore, the light guide f has a complicated shape and needs to be processed by molding, which increases the manufacturing cost to the point that it cannot be ignored. Therefore, it has been difficult to reduce the price of liquid crystal display devices.

The present invention has been made to solve these problems, and provides a liquid crystal display device in which a light source for illuminating the liquid crystal display section is arranged at a position offset from the back of the liquid crystal display section, the device being made thinner, The purpose of the present invention is to reduce the loss of light irradiated from a light source to a liquid crystal display section and to reduce the cost.

(E. Means for Solving the Problems) In order to solve the above-mentioned problems, the liquid crystal display device of the present invention uses a sag-like reflecting plate as a means for guiding the light emitted from the light source to the liquid crystal display section. It is characterized by

(F. Effect) According to the liquid crystal display device of the present invention, each light ray emitted from the light source to the side of the sag-like reflector can be reflected to the liquid crystal display section side by one reflective layer of the sag-like reflector. The distance through which each light beam passes through the transparent layer of the slant-shaped reflecting plate can be slightly longer than the thickness of the slant-shaped reflecting plate, for example, about 0.2 to 1 mm. Therefore, the amount of light lost within the sagging reflector can be greatly reduced. Further, the thickness of the sag-shaped reflecting plate is 0.2 to 1. It can be very easily made as thin as several mm. Therefore, it is possible to easily reduce the thickness of the liquid crystal display device. Furthermore, since the sag-like reflecting plate can be manufactured at a very low cost, it becomes easy to reduce the cost of the liquid crystal display device.

(G. Embodiment) [FIGS. 1 to 3] The liquid crystal display device of the present invention will be described in detail below according to the illustrated embodiment.

1 and 2 show one embodiment of the liquid crystal display device of the present invention.

In the drawing, 1 is a box-shaped housing of a liquid crystal display device, 2 is a window formed in the front of the housing 1, 3 is a liquid crystal display panel fitted into the window 2, and 4 is provided inside the housing 1. It is a sag-like reflecting plate and is arranged behind the liquid crystal display panel 3 so as to form a certain angle therewith. The slant-shaped reflective plate 4 is formed by alternately laminating transparent layers 5 and reflective layers 6 and slicing them thinly (for example, 0.2 to 0°6 mm) in a direction appropriately inclined from the laminating direction. It does not require mold forming processing, can be mass-produced easily, and can reduce manufacturing costs. In addition, the sudare-shaped reflecting plate 4 is manufactured by the Japanese Patent Publication Publication No. 56-176.
It can be manufactured by exactly the same method as the screen manufacturing method disclosed in Japanese Patent No. 49, and the manufacturing method is explained in detail and specifically in the above publication. Therefore, a detailed explanation of the method for manufacturing the sag-like reflecting plate 4 will be omitted.

Reference numeral 7 denotes a fluorescent lamp arranged on the side (lower side in this embodiment) of the sag-like reflector 4, and 8 is a flange placed on the opposite side of the sag-like reflector 4 of the fluorescent lamp 7. The light projected onto the side of the anti-sag reflection plate 4 is reflected back to the side of the anti-sag reflection plate 4. Although the reflector 8 is formed separately from the housing 1 in this embodiment, it may be formed integrally with the housing 1.

It has been mentioned that the slant-shaped reflector 4 of the liquid crystal display device is arranged behind the liquid crystal display panel 3 at a certain angle, but specifically, from the end closest to the fluorescent lamp 7 to the end farthest from the fluorescent lamp 7. They are arranged so as to be inclined away from the liquid crystal display panel 3 as one goes toward the liquid crystal display panel 3.

In this liquid crystal display device, the beam of light projected from the fluorescent lamp 7, including the light reflected by the deflector 8, enters the sag-shaped reflector plate 4 from the surface on the side opposite to the liquid crystal display panel 3. Then, the light passes through the transparent layer 5 of the sag-like reflector 4 and reaches the reflective layer 6, where it is reflected toward the liquid crystal display panel 3.

In such a liquid crystal display device, each light beam is incident on the transparent layer 5 at a slightly inclined angle from the stacking direction of the slant-like reflective plate 4, is reflected by the reflective layer 6, passes through the transparent layer 5, and is reflected by the transparent layer 5. The optical path length within the transparent body is about 1 mm or less, and the distance through the transparent body is much shorter than in the conventional case shown in FIG. Therefore, the loss of light caused by the transparent layer 5 is reduced, and the amount of light projected by the fluorescent lamp 7 required to illuminate the liquid crystal display panel 3 to a predetermined brightness is reduced. Therefore, a smaller fluorescent lamp 7 can be used, and the power consumption of the fluorescent lamp 7 can be further reduced.

Further, the thickness of the sag-like reflecting plate 4 is, for example, 0°2 to 0.6°.
The thickness of the liquid crystal display device is extremely thin, as it is placed at a slight angle behind the LCD panel 3, and the fluorescent lamp 7 is placed on the side of the sag-like reflector 4. It can be made thinner.

Furthermore, the sag-like reflecting plate 4 can be mass-produced by a simple method of alternately laminating transparent layers and reflective layers and then slicing without using molding, and can therefore be obtained at a very low cost. Therefore, the cost of the liquid crystal display device can be reduced.

In addition, since the fluorescent lamp 7, which is the light source, is arranged laterally from the rear side of the liquid crystal display panel 3, the liquid crystal display panel 3 is not heated to any extent by the fluorescent lamp 7. Deterioration of the liquid crystal display panel 3 due to heat can be reduced.

Here, we will discuss the second condition for effectively illuminating the liquid crystal display panel 3 without the light projected from the fluorescent lamp 7 onto the slant-shaped reflecting plate 4 passing through the sagging-shaped reflecting plate 4 and becoming wasted light. Consider this with reference to the figure.

In the figure, A is a liquid crystal display panel 3 with one reflective layer 6.
B is the end of the reflective layer 6 one layer below the reflective layer 6 on the side opposite to the liquid crystal display panel 3, and j is the straight line connecting A and B and the main surface of the sagging reflective plate 4. i is the angle between the incident light and the main surface of the slant-shaped reflector 4, and q is the angle between the reflected light reflected by the reflective layer 6 and the bottom surface 1a of the housing 1 (which is parallel to the liquid crystal display panel 3). θ is the angle of inclination of the liquid crystal display panel 4 with respect to the bottom surface 1a of the housing 1, and α is the angle formed by the reflective layer 6.
The angle formed by the front surface and the main surface of the liquid crystal display panel 4, P is the arrangement pitch of the reflective layers 6.6, . . . , and t is the thickness of the sagging reflective plate.

The conditions for preventing the incident light from passing through the sagging reflector 4 and becoming wasted light are as follows: % Formula % Here, the reflected light is perpendicular to the bottom surface 1a of the housing 1 (i.e., q=90' ), and when the direction of the main component of the incident light is parallel to the bottom surface 1a of the housing 1 (θ=i), the above formula (1) is satisfied.
becomes the following equation (2).

Psinj≦t −cos (j + [(yr/2)
-2θ]/2) ...... (2) This equation (2) becomes the following equation (3).

P≦t・0.7・([cos(j−〇)−sin(j−
〇)]/5inj) (3) If the angle θ with respect to the main surface of the liquid crystal display panel 4 is made approximately equal to the angle j (that is, j angle θ), the above formula (3 ) becomes the following equation (4).

P≦0.7t/sinθ −−−−・−(4
) On the other hand, the angle α of the reflective layer 6 with respect to the main surface of the sagging reflective plate 4 is expressed by the following equation (5).

α=(π/2)+(i10−9)/2 (5) Since q=90°, the above equation (5) becomes the following equation (6).

α=(π/4) + (i+θ)/2...
(6) By the way, the above-mentioned angle θ is determined automatically as the size of each member is determined in terms of design, but it can be set to about 10°, for example. Therefore, θ;
When calculated as 10゛, from the above formula (4), P≦4.0
It becomes 3t. From the above equation (6), αL=r55°.

If the size of the slant-shaped reflecting plate 4 is 4 inches diagonally, then t=Pxo, 187, and if the thickness of the slant-shaped reflecting plate 4 is assumed to be 0.5 mm, the reflection of the slant-shaped reflecting plate 4 The pitch of layers 6.6, . . . is 2.
This means that 67mm is better. In addition, if the thickness of the sag-shaped reflective plate 4 is set to 0.2 mm, the reflective layer 6.
6,..., a pitch of 1.07 mm is good.

In the embodiment L, a condensing lens 9 is provided between the fluorescent lamp 7 and the liquid crystal display panel 4, and the light projected from the fluorescent lamp 7 is condensed onto the liquid crystal display panel 4 by the lens 9. It's okay.

FIG. 3 shows another embodiment of the liquid crystal display device of the present invention.

In this embodiment, two panels having half the size of the liquid crystal display panel 3 are used.
A pair of slant-shaped reflecting plates 4a and 4b are arranged behind the liquid crystal display panel 3, so that the light projected from the fluorescent lamp 7.7 is reflected toward the liquid crystal display panel 3 side by the slant-shaped reflecting plates 4a and 4b. This is what I did. Specifically, a sag-like reflector 4a is arranged behind the upper half of the liquid crystal display panel 3,
A sag-like reflecting plate 4b is arranged behind the lower half of the liquid crystal display panel 3, and the sag-like reflecting plate 4a reflects light from the fluorescent lamp 7 arranged above it to the liquid crystal display panel 3. The slant-like reflector plate 4b is tilted so as to move away from the liquid crystal display panel 3 toward the bottom, and the slant-shaped reflector plate 4b directs light from the fluorescent lamp 7 placed below it to the liquid crystal display panel 3.
In order to reflect the light to the liquid crystal display panel 3, it is tilted so as to move away from the liquid crystal display panel 3 as it goes upward. That is, the two sagging-shaped reflecting plates 4a and 4b are arranged in a shape.

Note that a single U-shaped fluorescent lamp may be used as a light source instead of the two fluorescent lamps 7.7.

In addition, in each of the above embodiments, the sag-like reflecting plate 4.4a,
If the transparent layer 4b is made of a material that absorbs infrared rays, the amount of heating for the liquid crystal display panel 3 can be reduced. This is because some of the light beams projected from the fluorescent lamps 7 include infrared rays, so it was difficult to completely prevent the liquid crystal display panel 3 from being heated by the light source. If a transparent layer 4b that absorbs infrared rays is used, the liquid crystal display panel 3
Infrared rays can be blocked by the sag-like reflectors 4.4a and 4b, and deterioration of the liquid crystal display panel 3 can be more completely prevented (H, Effect of the Invention) As stated above, In the liquid crystal display device of the present invention, a slant-shaped reflecting plate formed by alternately laminating transparent layers and reflective layers and slicing them at a predetermined angle with respect to the lamination direction is arranged behind the liquid crystal display section, It is characterized by a light source placed on the side of the board.

Therefore, according to the liquid crystal display device of the present invention, each of the light beams emitted from the light source toward the side of the sag-like reflector can be reflected toward the liquid crystal display section side by one reflective layer of the sag-like reflector, The distance through which each light beam passes through the transparent layer of the slant-shaped reflecting plate can be as long as the thickness of the slant-shaped reflecting plate, for example, about 0.2 to 0.2 inches or slightly longer. Therefore, the amount of light lost within the sagging reflector can be greatly reduced.

Further, the thickness of the sag-like reflecting plate is, for example, 0.2 to 1. It can be very easily made as thin as several mm. Therefore, it is possible to easily reduce the thickness of the liquid crystal display device.

Furthermore, since the sag-like reflecting plate can be manufactured at a very low cost, it becomes easy to reduce the cost of the liquid crystal display device.

[Brief explanation of drawings]

1 and 2 show one embodiment of the liquid crystal display device of the present invention, FIG. 1 is a sectional view showing the entire liquid crystal display device, and FIG. 2 is an enlarged view of a part of the liquid crystal display device. 3 is a sectional view showing another embodiment of the liquid crystal display device of the present invention, FIG. 4 is a sectional view showing the first conventional example of the liquid crystal display device, and FIG. FIG. 2 is a sectional view showing a conventional example. Explanation of symbols 3...Liquid crystal display section, 4.4a, 4b...Sag-like reflecting plate, 5...Transparent layer, 6...Reflective layer, 7...Light source. Figure 2 Figure 3 Figure 7... Power source Figure 5

Claims (1)

[Claims] (1) A slant-shaped reflecting plate made by laminating transparent layers and reflective layers alternately and slicing them at a predetermined angle with respect to the lamination direction is placed behind the liquid crystal display section, and on the side of the slant-shaped reflecting plate. A liquid crystal display device characterized by arranging a light source in