KR20050123372A - Liquid crystal display without back light - Google Patents

Abstract

The present invention provides a liquid crystal display device comprising a liquid crystal panel and a backlight, a light guide plate for guiding light incident from a fluorescent lamp at a lower portion of the liquid crystal panel, a diffuser plate for uniformizing light distribution, and collecting light into a viewing angle range. Omitting the backlight unit including the prism, replacing the light guide plate with the lower glass substrate of the liquid crystal panel, replacing the function of the diffuser with the light diffusion pattern of the lower glass substrate, and replacing the prism function with the polarizer. It relates to a liquid crystal display device that does not require. The liquid crystal display device of the present invention includes a light source for supplying light, a reflector for reflecting light emitted from the light source, and an upper surface of the liquid crystal display, the upper surface of which is parallel to the reflecting plate, and the lower surface of the liquid crystal display is further away from the light source. The lower glass substrate is formed to be inclined upward with respect to the reflecting plate to guide the light incident from the light source to convert the line light source into the surface light source, and the lower glass substrate so that the light incident from the light source and the light reflected from the reflecting plate are uniformly distributed throughout. The light diffusing pattern formed on the bottom and increasing in density as it moves away from the light source, and the lower polarizing plate which polarizes the light irradiated through the lower glass substrate in one direction and narrows the light irradiated through the lower glass substrate to the viewing angle range. It is configured to include.

Description

Liquid crystal display without back light

The present invention relates to a liquid crystal display device that does not require a backlight, and more particularly, to a liquid crystal panel including an upper substrate, a lower substrate, and a liquid crystal layer filled between both substrates, a light guide plate, a diffusion plate, and a prism. In the liquid crystal display device comprising a backlight, the light guide plate that omits the backlight and replaces the light guide plate is replaced by the lower substrate of the liquid crystal panel, and the function of the diffuser plate that scatters light is a light diffusion pattern formed on the bottom surface of the lower substrate. Instead, the present invention relates to a liquid crystal display device that does not require a backlight by replacing a prism function that collects light in a viewing angle range with a polarizer.

Recently, due to the rapid development of the information and communication field, the importance of the display industry for displaying desired information is increasing day by day, and until now, CRT (cathode ray tube) among information display devices can display various colors, and the brightness of the screen is increased. It has also enjoyed steady popularity so far because of its superiority.

However, there is an urgent need for the development of flat panel displays instead of CRTs, which are large in weight and volume due to the desire for large, portable and high resolution displays. Such flat panel display devices have a wide range of applications from computer monitors to display devices used in aircraft and spacecraft.

Currently produced or developed flat panel display devices include liquid crystal display (LCD), electro luminescent display (ELD), field emission display (FED), plasma display (plasma display). panel: PDP), etc. In order to become an ideal flat panel display, light weight, high brightness, high efficiency, high resolution, high speed response characteristics, low driving voltage, low power consumption, low cost, and color display characteristics are required. Among such flat panel display devices, the liquid crystal display device is in the spotlight because of its durability as well as its desire.

A liquid crystal display device is an image display device using optical anisotropy characteristics of liquid crystals. When light is irradiated onto a liquid crystal having polarization characteristics according to a voltage application state, the liquid crystal display device determines the amount of light that passes according to the alignment state of the liquid crystals according to the voltage application. It is a device that can control and express an image.

As described above, in order to configure the liquid crystal display device, a liquid crystal panel including a liquid crystal formed between two substrates and a driving circuit provided around the liquid crystal panel to apply a signal to the liquid crystal panel and control such a signal are required. Do.

In this case, since the liquid crystal panel does not emit light by itself, the reflective liquid crystal display device is restricted from being used in a dark space when it is reflected from the liquid crystal panel using external light such as sunlight.

Accordingly, the transmissive liquid crystal display device may solve a problem of space limitation by providing a separate backlight under the liquid crystal panel and irradiating parallel rays.

Hereinafter, a liquid crystal display of a general transmissive TN mode will be described with reference to the drawings.

1 is a schematic perspective view of a liquid crystal display of a general transmissive TN mode.

As shown in FIG. 1, the liquid crystal display device includes a liquid crystal panel 10 including an upper substrate 11, a lower substrate 12, and a liquid crystal layer 13 formed between the two substrates to express colors, and The first and second polarizing plates 14 and 15 are disposed above and below the liquid crystal panel 10 so as to be perpendicular to each other.

As will be described with reference to FIG. 2 of the liquid crystal panel 10, there is a backlight including a light guide plate, a reflecting plate, a diffusion plate, and a prism for transmitting light emitted from a light source such as a fluorescent lamp.

Here, the lower substrate 12 is also called an array substrate, and a thin film transistor (not shown), which is a switching element, and a pixel electrode (not shown) for displaying an image are formed in a matrix type.

The upper substrate 11 is also referred to as a color filter substrate, and has a black matrix for preventing light leakage to the outside of the pixel region, and colors of R (red), G (green), and B (blue) corresponding to the pixel electrodes. And a common electrode (not shown) on the black matrix and the color filter.

Pixel electrodes (not shown) and common electrodes (not shown) respectively formed on the lower substrate 12 and the upper substrate 11 are indium-tin oxides for transmitting light emitted from the backlight. -oxide: It is composed of transparent conductive metal such as ITO). In this case, in the IPS mode liquid crystal display, the common electrode is formed on the lower substrate.

The liquid crystal molecules 18 of the liquid crystal layer 13 formed between the upper substrate 11 and the lower substrate 12 are formed by the alignment layer (not shown) formed on the surfaces of the two substrates facing each other. The azimuth angles from 12) to the upper substrate 11 are twisted by 90 degrees.

In addition, the first and second polarizing plates 14 and 15 have a characteristic in which the polarization direction is vertical. That is, white light irradiated from the backlight is polarized in one direction by the first polarizing plate 14, and the light polarized by the first polarizing plate 14 is refracted by the lower substrate 12 and the liquid crystal layer 13. do.

At this time, as shown, the light incident on the liquid crystal layer 13 is refracted to be orthogonal to the direction polarized by the first polarizing plate 14 by rotating the azimuth angle by 90 degrees by the twisting of the liquid crystal molecules 18. . As such, the intensity of transmitted light may be adjusted by adjusting the azimuth or polar angle of the liquid crystal molecules 18 in the liquid crystal layer 13.

In addition, the white light refracted by the liquid crystal layer 13 passes through the upper substrate 11 having a color filter (not shown), which may display R, G, and B colors, and passes through the upper substrate 11. Light having a color is passed through the second polarizing plate 15 and represented as an image.

Accordingly, a general liquid crystal display device may implement an image by adjusting the intensity of transmitted light after expressing polarization and refraction using light irradiated from a backlight and expressing color.

On the other hand, the backlight for supplying parallel light in such a liquid crystal display device is a method of arranging a cylindrical fluorescent lamp, it is divided into a direct type and an edge type.

First, in the direct type, a fluorescent lamp is disposed on a plane. Since the shape of the fluorescent lamp appears on the liquid crystal panel, the gap between the fluorescent lamp and the liquid crystal panel 10 should be maintained, and light scattering is required for uniform distribution of light. Since the means must be arranged, there is a limit to thinning.

In addition, as the liquid crystal panel 10 becomes larger, the area of the light exit surface of the backlight also increases. When the direct backlight is enlarged, the light exit surface is not flat unless the light scattering means secures sufficient thickness. For this reason, the thickness of the light scattering means must be sufficiently secured.

On the other hand, in the edge type, a fluorescent lamp is installed on the outside and light is distributed to the entire liquid crystal panel by using a light guide plate, and the luminance may be lowered because the fluorescent lamp is installed on the side and light passes through the light guide plate.

In addition, high optical design and processing techniques for the light guide plate are required for uniform distribution of light intensity. As such, the direct type and edge type have their own disadvantages, and therefore the direct type type backlight is mainly used in a liquid crystal display device in which brightness is more important than the screen thickness. In an important liquid crystal display device, an edge type backlight is mainly used.

Recently, research and development on edge type backlights have been actively conducted due to consumption trends for ultra-thin, low weight, and low power consumption, such as wall-mounted TVs.

2 is a perspective view of a backlight according to the prior art. As shown in FIG. 2, the backlight of the prior art includes a fluorescent lamp 21, which is a light source, and a light guide plate 23 for irradiating forward the light incident from the side by the fluorescent lamp 21. And a reflecting plate 22 for reflecting the light exiting to the rear surface of the light guide plate 23 forward, and a diffusion plate for making the light incident from the light guide plate 23 into light having a uniform intensity ( 24, horizontal and vertical prism sheets 25 and 26 for increasing the brightness of light passing through the diffusion plate 24 and the light guide plate 23, and the horizontal and vertical prism sheets 25. It comprises a protective sheet 27 for protecting (26).

Here, the fluorescent lamp 21 emits white light, and may be located at both edges of one or four surfaces of the light guide plate 23, and a plurality of fluorescent lamps 21 may be disposed at both edges of the light guide plate 23, respectively.

In addition, the reflection plate 22 is used to reduce the loss portion when a part of the light in the light guide plate 23 through the opposite surface, the light exiting to the back of the light guide plate 23, the light guide plate 23. It serves to reflect in the direction of.

The light guide plate 23 serves to direct the path of light toward the front surface as the most important component in the backlight. The flat type as shown in the drawing and the fluorescent lamp 21 are not shown. There are two types of wedge-shaped, hexahedral shape, in which the lower surface is inclined and thinned in one direction as it is further away from the.

Since the light passing through the light guide plate 23 directly enters the eye, the backlight internal structure is directly reflected or the transmitted light is uneven throughout the entire surface. Accordingly, the light guide plate 23 is provided with a diffuser plate 24 to evenly distribute and supply light.

In addition, as the light luminance passing through the diffusion plate 24 is diffused in both the horizontal and vertical directions perpendicular to the plane, the light luminance rapidly drops. It is the horizontal and vertical prism sheets 25 and 26 for focusing this light again to increase the light brightness.

The horizontal and vertical prism sheets 25 and 26 have strip types of micro prisms formed on top of a base material (polyethylene terephtalate), and a set of two substantially horizontal and vertical sheets. Used as.

However, the above-described backlight unit of the related art has the following problems.

As such, the transmissive liquid crystal display device has a separate backlight under the liquid crystal panel, which not only increases the overall thickness of the liquid crystal display device but also increases the number of parts thereof, thereby acting as a significant obstacle to weight reduction and thinning of the liquid crystal display device. In addition, there is a problem that the failure rate and the production cost as a whole increases with the increase of the number of parts.

Accordingly, the present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to provide a backlight configuration such as a light guide plate, a diffuser plate and a prism for transmitting light emitted from a light source such as a fluorescent lamp. By omitting or replacing, it is possible to provide a liquid crystal display device that does not require a backlight for making the liquid crystal display device thinner and lighter.

According to a feature of the invention for achieving the above object, the present invention provides a light source for supplying light; A reflector reflecting light emitted from the light source; It is installed on the upper side of the reflecting plate, the upper surface is parallel to the reflecting plate and the lower surface is formed to be inclined upward with respect to the reflecting plate as it moves away from the light source unit to guide the light incident from the light source to convert the line light source into a surface light source Lower glass substrates; A light diffusion pattern formed on the bottom surface of the lower glass substrate such that light incident from the light source and light reflected from the reflector are uniformly distributed throughout the light source, and the density increases as the distance from the light source increases; A reflection plate capable of reflecting light between the lower glass substrate together with the light diffusion pattern; A lower polarizing plate which polarizes the light irradiated through the lower glass substrate in one direction and narrows the light irradiated through the lower glass substrate to a viewing angle range; A liquid crystal layer for controlling the amount of light passing according to the voltage applied state by showing polarization characteristics according to the voltage applied state; The upper glass substrate is formed on the liquid crystal layer and prevents light leakage, the upper glass substrate consisting of a color filter having a reddish green blue color, and the upper glass substrate is installed on the upper polarized light passing through the upper glass substrate in the other direction It is configured to include an upper polarizing plate.

According to the liquid crystal display device which does not require the backlight according to the present invention having such a configuration, there is an advantage that the liquid crystal display device can be made light and small.

Hereinafter, a preferred embodiment of a liquid crystal display device which does not require a backlight according to the present invention having the configuration as described above will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view of a configuration of a liquid crystal display device according to a preferred embodiment of the present invention.

As shown in FIG. 3, the liquid crystal display device 100 according to the present invention includes a liquid crystal panel 200 and a liquid crystal panel 200 in which a liquid crystal 130 layer is formed between lower and upper glass substrates 110 and 120. It is composed of a light source 300 for supplying light from the bottom.

The light source 300 may be installed in the lower portion of the liquid crystal panel 200 to emit light toward the front from the rear of the liquid crystal panel 200, or to emit light toward the front from the side of the liquid crystal panel 200. It may be installed on the side of the liquid crystal panel 200, but in the present embodiment is to be installed on the side of the liquid crystal panel 200.

In addition, the light source 300 may be installed only at one edge of the liquid crystal panel 200 or both edges, and the light source 300 may use a light emitting diode or a cold cathode fluorescent lamp having a small amount of heat, but the present invention. In the embodiment of the fluorescent lamp is described as being installed on both edges.

The lower portion of the liquid crystal panel 200 is provided with a reflecting plate 310 to prevent the light supplied from the fluorescent lamp 300 to escape to the lower portion of the liquid crystal panel 200.

The lower glass substrate 110 is parallel to the upper surface and the lower surface is formed to be inclined upward as the distance away from the light source is gradually thinner, the thickness of the thickest portion of the lower glass substrate 110 is 0.5 By forming it to 5 mm, it can manufacture within about 60% compared with the present thickness of a liquid crystal display device.

On the bottom surface of the lower glass substrate 110, various light diffusion patterns 112 are attached or engraved on the surface of the lower glass substrate to scatter and reflect light to the outside in order to emit light trapped in the interior due to the critical angle of incidence in the lower glass substrate. All. That is, the light incident from the fluorescent lamp 300 and converted into the surface light source from the lower glass substrate 110 is scattered in the light diffusion pattern 112 and is spread evenly over the entire surface. In addition, light that does not reach the light diffusion pattern continues to reflect light until it reaches the light diffusion pattern by the reflector. Although the light diffusion pattern 112 is formed by screen printing in the embodiment of the present invention, the shape of the light diffusion pattern 112 is pre-processed or molded into the mold for forming the lower glass substrate 110 or after the glass substrate ( The light diffusion pattern 112 may be formed by directly processing on the 110. The light diffusion pattern 112 is densely formed so that its density increases as it moves away from the fluorescent lamp 300.

Although not shown in the drawing, the lower glass substrate 110 includes a thin film transistor, which is a switching element, in a matrix form, and the upper glass substrate 120 has a black matrix and a color filter having a color to prevent light leakage.

The liquid crystal 130 is injected between the lower glass substrate 110 and the upper glass substrate 120 with the lower polarizing plate 140 interposed therebetween, and the upper polarizing plate 150 is installed on the upper glass substrate 120. .

Since the liquid crystal 130 exhibits polarization characteristics according to a voltage applied state, when light is irradiated onto the liquid crystal 130, the amount of light passing through the liquid crystal 130 is adjusted according to the alignment state of the liquid crystal 130 according to the voltage applied. Can be expressed.

The polarizers 140 and 150 mainly have a function of polarizing light in one direction, but do not include a prism sheet separately in the exemplary embodiment of the present invention because the polarizing plates 140 and 150 also perform a function of changing the light propagation path to increase the brightness of the light.

According to the liquid crystal display device configured as described above, the light generated from the fluorescent lamp 300 is guided to the lower glass substrate 110 to convert the linear light source into a bright light source and to be uniformized by the light diffusion pattern 112. The light incident from the substrate 110 to the liquid crystal 130 passes through the lower polarizer 140, changes the traveling path at a predetermined angle, and is linearly polarized in one direction and transmitted to the upper glass substrate 120.

As described above, the present invention provides a light guide plate, a diffusion plate, and a prism for transmitting light incident from a light source such as a fluorescent lamp in the lower part of the liquid crystal panel to reduce the thickness of the liquid crystal display device including the liquid crystal panel and the backlight. Omitting a backlight unit, replacing the function of the light guide plate with the lower glass substrate of the liquid crystal panel, replacing the function of the diffuser with the light diffusion pattern of the lower glass substrate, and replacing the function of the prism with the polarizer. It can be seen that the technical concept of the liquid crystal display that does not require the. Within the scope of the basic technical spirit of the present invention, many other modifications will be possible to those skilled in the art.

As described above, according to the configuration of the present invention, the following effects can be expected.

By omitting the backlight configuration consisting of a light guide plate, a diffusion plate, and a prism or replacing the glass substrate with a lower glass substrate, the liquid crystal display can be made lighter and thinner, the manufacturing process is shortened, and the productivity is increased, thereby increasing the mass production. It is possible to reduce the cost.

1 is a schematic perspective view of a liquid crystal display of a transmissive TN mode according to the prior art;

2 is a schematic perspective view of a backlight arrangement according to the prior art;

3 is a cross-sectional view of a liquid crystal display without a backlight according to the present invention.

** Description of Codes for Major Configurations of Drawings **

100: liquid crystal display 110: lower glass substrate

112: light diffusion pattern 120: upper glass substrate

130: liquid crystal 140: lower polarizing plate

150: upper polarizer 200: liquid crystal panel

300: light source 310: reflector

Claims (1)

A light source for supplying light; A reflector reflecting light emitted from the light source; It is installed on the upper side of the reflecting plate, the upper surface is parallel to the reflecting plate and the lower surface is formed to be inclined upward with respect to the reflecting plate as it moves away from the light source to guide the light incident from the light source to convert the line light source into a surface light source Lower glass substrates; A light diffusion pattern formed on the bottom surface of the lower glass substrate such that light incident from the light source and light reflected from the reflector are uniformly distributed throughout the light source, and the density increases as the distance from the light source increases; A lower polarizing plate which polarizes the light irradiated through the lower glass substrate in one direction and narrows the light irradiated through the lower glass substrate to a viewing angle range; A liquid crystal layer controlling the amount of light passing in accordance with the voltage applied state by showing polarization characteristics according to the voltage applied state; An upper glass substrate provided on the liquid crystal layer and composed of a black matrix for preventing light leakage and a color filter having a reddish greenish blue color; And an upper polarizing plate disposed on the upper glass substrate and configured to polarize light passing through the upper glass substrate in a different direction.