JPS61166586A - Liquid crystal display unit - 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 Technical Field The present invention relates to a device structure for improving the display quality of a small liquid crystal display device, particularly a portable liquid crystal television.

<Prior Art> A color liquid crystal display panel has been developed as a display device that utilizes the electro-optical effect of liquid crystal for displaying television images. This color liquid crystal display panel consists of a large number of picture element electrodes arranged in a dot matrix, a liquid crystal layer that modulates light according to the voltage applied thereto, and coloring means arranged corresponding to the picture elements. Become. By applying a video signal according to the corresponding color to each picture element electrode, color CRT
It is possible to display an IJ sock image (any dot matrix containing intermediate colors that are additively mixed using the same principle as a cathode ray tube).

Generally, one of the following three methods is used to individually control each picture element.

(1) Simple matrix method A group of striped parallel electrodes is arranged on each of two substrates, and the substrates are bonded together so that they are perpendicular to each other, and liquid crystal is injected to form a display panel. . A row selection signal is sequentially applied to one row electrode. An image signal is applied to the other column electrode in synchronization with the row selection signal. Therefore, the intersection of the row electrode and the column electrode becomes a picture element, and the liquid crystal sandwiched between the two electrodes undergoes optical modulation for each picture element in response to the potential difference between the two electrodes.

Since the liquid crystal has a characteristic of responding to an effective value, the number of scanning lines cannot be set too large in view of crosstalk effects. Therefore, the following two methods have been developed to overcome these limitations.

(2) Addition of a nonlinear element A varistor, M I M (Meta 1/
This method adds a nonlinear element such as In5ulator/Metal) to suppress cross talk.

(3) Addition of switching elements In this method, a switching transistor is added to each picture element and driven individually. A drive voltage is applied during the selection period to charge the storage capacitor, which is maintained during the non-selection period.

Note that the liquid crystal itself is a capacitive load, and if its time constant is sufficiently larger than the driving repetition period, the storage capacitor can be omitted. As the switching transistor, a thin film transistor or a MOS-FET formed on a silicon wafer is used.

On the other hand, in a color liquid crystal panel, only the spectral region of one of the three primary colors is used in the spectrum of the incident light, and the remaining components are absorbed by the coloring means. Since the amount of light is further reduced by half, the display pattern becomes very dark in the reflective mode in which no illumination means is provided. For this reason, a light source such as an incandescent lamp, a fluorescent lamp, or an EL panel is provided as an illumination means, or measures are taken to guide ambient light to the back surface of the liquid crystal panel. When applying to portable equipment, there are severe restrictions on power supply capacity, and it is desirable to have a structure that uses ambient light in addition to internal illumination light.

As shown in FIG. 2, a liquid crystal display device having such a structure has a hood 2 that can be opened and closed and has a liquid crystal panel 1 therein, and is rotatably attached to one end of the hood 2. A mirror 4 is installed on the upper surface facing the liquid crystal panel 1 of the main body 6 of the device, and the display image of the liquid crystal panel 1 reflected by the mirror 4 is observed. There is a structure to do this. Particularly when using ambient light, the main body 6 of the device as shown in FIG.
An internal illumination light source 5, one end of which is rotatably connected to the panel, is rotated and placed below, and is used as a stand to tilt and support the liquid crystal panel 1, allowing ambient light to enter the liquid crystal panel. When ambient light enters the liquid crystal panel 1 in the 7-door 2 from the rear direction, this incident light 7 enters the liquid crystal panel 1.
Each picture element electrode undergoes modulation based on the optical characteristics of the liquid crystal by a driving voltage applied to the picture element electrodes inside, and a television image corresponding to the image signal is obtained on the output side. This television image is reflected by the mirror 4 of the main body 6 of the apparatus, and an observer 9 visually recognizes this reflected light 8, thereby obtaining image information. However, this method has the disadvantage that when the viewing direction approaches the perpendicular direction to the main body 6 of the device, the hood 2 that houses the liquid crystal panel 1 becomes an obstacle, making it impossible to observe the television image reflected on the mirror 4. There is.

<Object of the Invention> The present invention secures a good viewing field by using a Fresnel prism reflector as a reflector for reflecting image information in a liquid crystal display device that uses ambient light in order to reduce power consumption. Another object of the present invention is to provide a new and useful low power consumption liquid crystal display device that improves the quality of display patterns projected on a Fresnel prism.

Embodiment First, FIG. 3 shows an enlarged view of a reflecting mirror made of a Fresnel prism whose reflecting surface has an inclination angle of α, and the relationship between incident light and reflected light. This Fresnel prism has a serrated reflecting surface consisting of a vertical step surface and an inclined surface, and light is reflected by the inclined surface.

Light 7 incident on the reflecting mirror 10 at an incident angle of 00 is reflected on the reflecting surface 11
is tilted, the reflected light 13 is θo− with respect to the normal line.
It will be reflected at 2α. On the other hand, in a conventional mirror whose reflecting surface is horizontal, the reflected light 8 is also reflected in an oblique direction with respect to the incident light 7 from an oblique direction.In other words, the reflecting mirror 10 is a reflecting mirror made of a Fresnel prism instead of a smooth mirror. If 10 is used, the reflected light will be lifted by 2α.

FIG. 1 shows an embodiment in which a reflecting mirror 10 made of such a Fresnel prism is applied to a liquid crystal display device of a type that displays images using ambient light. A hood 2 in which a liquid crystal panel 1 for displaying television images and a light scattering plate 3 are installed is rotatably attached to the end of the main body 6 of the device at one end. When carrying the device, the hood 2 is attached to the main body 6 of the device. The hood 2 is opened and raised from the device main body 6 during display operation.

The liquid crystal panel 1 is composed of a transmissive display panel, and therefore, the light 7 incident from the back side is scattered by the light scattering plate 3 and then modulated when passing through the liquid crystal panel 1, and is reflected in the recessed portion of the device body 6. The light is irradiated onto a reflecting mirror 10 installed in the area. The reflecting mirror 10 is constituted by a Fresnel prism as shown in FIG. 3, and its reflected light 13 reaches the viewer 9, and the viewer 9 sees the television image displayed on the liquid crystal panel 1. Similarly, one end of the internal illumination light source 5 made of a surface light emitter is rotatably attached to the main body 6 of the device, and when displaying using natural light, this is rotated below the main body 6 of the device and serves as a stand. Support the whole thing. Further, during a display operation in the absence of natural light, the internal illumination light source 5 rotates to the rear side of the liquid crystal panel 1 of the hood 2 and comes into close contact with the hood 2, and irradiates the liquid crystal panel 1 with light from the rear side. The device main body 6 includes a power source, a video receiving circuit, a video display driving circuit, an audio control circuit, and the like. The mirror image of the liquid crystal panel 1 that is visually recognized by the observer 9 is at a position P with respect to the reflecting mirror 10.

The reflected light 13 from the reflecting mirror 10 that reaches the observer 9 is in a direction close to the normal direction of the reflecting mirror 10, and the opening angle of the hood 2 with respect to the apparatus main body 6 in this case is about 90 degrees. Therefore, even when the reflecting mirror 10 is observed from a substantially vertical direction, the viewing direction is not obstructed by the 7-door 2, and the television image can be satisfactorily observed. That is, by using the reflecting mirror 10 made of a Fresnel prism whose reflecting surface is raised toward the viewer, the reflected light is lifted in the vertical direction, making it possible to observe the apparatus main body 6 from directly in front of it.

However, in this method, as shown in Fig. 4, the light 7' incident from the observer side passes through the reflecting mirror 1 consisting of 7 Lennel prisms.
Since the reflected light is reflected by the vertical step surface that does not contribute to the display of 0 and enters the eyes of the observer 9, a display pattern other than the television image on the liquid crystal panel 1 appears, and the display quality of the television image deteriorates. become. Therefore, in the reflecting mirror 10 of this embodiment, the incident light that has passed through the liquid crystal panel is reflected by the mirror-treated inclined surface of the Fresnel prism, and the light that has entered from the viewer side is reflected by the black-treated vertical step surface of the 7-Resnel prism. The inclined surfaces of the Fresnel prism are treated with a mirror finish, and the vertical stepped surfaces are treated with a black color so that light can be absorbed by the light.

Hereinafter, a method for manufacturing the reflecting mirror 10 will be described in detail.

A Fresnel prism plate having a serrated surface as shown in FIG. 5 or 6 is produced by injection molding of acrylic resin, polycarbonate, etc., and a reflective film is formed on the serrated surface. Methods for forming the reflective film include a method in which a metal such as aluminum is evaporated from the front side of the Fresnel prism plate, and a method in which metal is deposited on the surface of the Fresnel prism plate by electroless plating. Regarding electroless plating, there is a method that utilizes silver mirror reaction. After a mirror surface is formed on the surface of the Fresnel prism plate by the above method, the portions 15 that do not contribute to display (vertical stepped surfaces or steep stepped surfaces) are treated with black, as shown in FIG. 7 or 8. A specific method for blackening is to deposit black film material 16 from an oblique direction as shown in FIG. 9, and blackening is applied only to portions 15 that do not contribute to display. Specifically, the black pigment is sublimated in a vacuum and deposited on the surface of the Fresnel prism plate.

Since the black pigment is deposited from an oblique direction, almost no black pigment is deposited on the portion 11 that contributes to display, and most of the black pigment is deposited on the portion 15 that does not contribute to display. Examples of the black pigment include carbon blank, graphite, and aniline black. Further, the inclination angle α of the reflective surface of the Fresnel prism is set in the range of about 10 to 30, as will be described later, and it is desirable to perform the deposition at the same angle α in the direction of oblique deposition. Another method is to mix the above-mentioned black pigment into acrylic resin or polycarbonate, and then injection mold it into the fifth layer.
A Fresnel prism plate as shown in the figure or FIG. 6 is manufactured. Thereafter, as shown in the IEIO diagram, gold such as aluminum is vapor-deposited only on the display pattern reflective inclined surface of the 7-Resnel prism to form the reflective surface 11.

In the above embodiment, the inclination angle of the reflective surface of the Fresnel prism is set to about 20 degrees, and the observation direction is raised about 40 degrees in the normal direction, thereby making it easy to observe directly in front. If the inclination angle of the Fresnel prism reflecting surface is too large, the image will be observed from a direction inclined toward the hood 2 side from the normal direction, and the hood will become an obstacle, making it impossible to observe the entire image reflected on the reflecting mirror. The angle of inclination of the reflecting surface of the Fresnel prism is desirably selected within the range of about 10 to 3 degrees. In addition, regarding mirror finishing to make a Fresnel prism a reflective mirror, if a reflective film is provided on the back surface of a 7-Resnel prism, the display quality of images viewed through the reflective mirror will deteriorate due to reflection between the front and back surfaces. do. Therefore, as described above, a reflective film is provided by forming a metal such as aluminum by vapor deposition on the serrated surface side of the Fresnel prism.

Effects> According to the present invention, images can be observed over a wide range by using a Fresnel prism, and the light incident from the observer side is reflected by the reflection plate made of the Fresnel prism, which is treated with black. A good image can be obtained without being absorbed in some areas and deteriorating the display quality of the image viewed through the reflective plate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a liquid crystal display device showing one embodiment of the present invention. FIG. 2 is a block diagram showing a conventional liquid crystal display device. FIG. 3 is an explanatory diagram illustrating the optical effect of the reflecting mirror used in the liquid crystal display device of FIG. 1. FIG. 4 is an explanatory diagram illustrating the path of light incident on the reflecting mirror. 5 and 6 are cross-sectional views showing details of the serrated surface of the reflector. FIGS. 7 and 8 are explanatory diagrams illustrating black processing of the reflecting mirror. FIG. 9 is an explanatory diagram illustrating a method of blackening a reflecting mirror. FIG. 10 is an explanatory diagram illustrating a mirror finishing method for a reflecting mirror. - 1...Liquid crystal panel 2...Hood 5...Internal illumination light source 6...Device body 7...Incoming light 9...
Observer 10...Reflecting mirror 11...Reflecting surface 13...
・Reflected light agent Patent attorney Aihiko Fukushi (and 2 others) Figure 3 q Figure 4 Figure 5 Mu Figure 6 Figure 8 Figure 10

Claims (1)

[Claims] 1. In a liquid crystal display device in which a display pattern displayed on a liquid crystal panel is reflected by a reflecting mirror made of a Fresnel prism formed into a serrated surface, the display pattern is reflected along the serrated surface of the Fresnel prism. 1. A liquid crystal display device characterized in that the inclined surfaces are mirror-treated surfaces, and the stepped surfaces connecting the inclined surfaces are blackened surfaces.