KR100477331B1 - Front light unit for reflection type liquid disply panel - Google Patents

Abstract

The present invention relates to a front light unit, which is an auxiliary light source used in a reflective liquid crystal panel, where an external light source can be used to view a displayed image without a separate light source, and in the absence of an external light source, display is performed by illumination of the front light unit. It is to be able to see the shape. The front light unit is installed above the reflective liquid crystal panel and is configured as elements such as a light source and a reflective light guide plate. The reflective light guide plate is completely transparent so that the display area can be seen, while the optical design in the form of a plurality of micro prisms on the upper surface allows the light incident from the light source to be uniformly distributed over the entire display area of the liquid crystal in a dark place. It is supposed to be. That is, the size of the product of the reflective liquid crystal panel according to the thickness of the reflective light guide plate is introduced into the shape (angle, pitch) of the upper surface of the reflective light guide plate and the top surface of the light guide plate to form the maximum brightness and uniformity. Optical design and manufacture.

Description

Front light unit for reflective liquid crystal display device {FRONT LIGHT UNIT FOR REFLECTION TYPE LIQUID DISPLY PANEL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device, and more particularly, to a front light unit for a reflective liquid crystal display device in which a light source and a reflective light guide plate are installed on an upper surface of a liquid crystal panel, so that a display image can be viewed even in a bright or dark place. It is about.

In general, a liquid crystal display device uses an electro-optic material whose optical properties change depending on an electric field, and a reflection type liquid crystal display device has been proposed as a device suitable for an information terminal due to low power consumption.

Such a reflective liquid crystal display device may display a display image without a separate light source in an external light source, and may display a display image by illumination of a front light unit even in an absence of an external light source.

As shown in FIG. 4, the front light unit used in the conventional reflective liquid crystal display device includes a flat or wedge-shaped reflective light guide plate 20 having a light source 10 disposed on one side of its front surface. have.

Here, the bottom surface of the light guide plate 20 is formed flat, and the top surface is formed with an alternating prism surface.

Accordingly, the light emitted from the light source 10 is guided to the light guide plate 20, and the guided light is reflected toward the liquid crystal display device 30 from the right prism surface of the light guide plate 20, and then the liquid crystal display device 30 Reflected by the reflecting plate 32 of the ()) is passed through the light guide plate 20 and finally reflected to the viewer's field of view. That is, the reflective light guide plate 20 is operated as a reflector and a light transmitting device.

In order to act as an ideal light transmitting device, the left prism face of the prism face should be nearly parallel to the bottom face. If the left and right prism surfaces form a large angle with respect to the bottom surface, the reflected light reflected from the liquid crystal display device 30 is refracted by the prism action and affects the display performance of the liquid crystal display device 30.

Therefore, in order to reflect the light traveling in the transverse direction from the reflective light guide plate 20 and to enter the liquid crystal display device almost vertically, each right prism surface is required to have an angle of about 45 ° with respect to the ground. .

As described above, when the overall shape is flat, the light guide plate 20 having the left prism face and the right prism face arranged alternately is brighter near the light source 10 and becomes darker as it moves away from the light source 10. For example, if the plurality of prisms forming the upper portion of the light guide plate 20 have a uniform prism shape, the amount of light reflected from each prism decreases as the prism is moved away from the light source 10, thereby providing uniform luminance from the light guide plate 20. Not suitable for getting

Meanwhile, in the conventional front light unit for a reflective liquid crystal display device for solving the above problems, as shown in FIG. 5, the upper surface of the light guide plate 20 meets the liquid crystal reading unit 23 and the light reflecting unit 24. The difference between the peaks and the bottoms, i.e., the height h of the prism, increases as the distance from the light source increases.

As a result, the reflectance of light in the light reflection part 24 increases almost linearly as it moves away from the light source, thereby compensating for the decrease in light intensity. As a result, the light guide plate 20 can obtain a substantially uniform luminance over the entire surface. Will be.

However, the conventional reflective light guide plate which obtains uniform brightness by the prism surface which changed the height h of prism as mentioned above had the problem that the manufacture was difficult.

That is, as the height h of the prism is changed, the shape of each prism must also be deformed, so that the angle α of the liquid crystal reading part 23 and the angle γ of the light reflection part 24 are continuous. It should be changed to, but it was inconvenient that the calculation process of such a deformed shape is not only complicated but also difficult to manufacture accordingly.

Disclosure of Invention The present invention has been made to solve the above problems, and an object thereof is to provide a front light unit for a reflective liquid crystal display device that is uniform in shape and uniform in brightness, and is easy to manufacture.

The present invention for achieving the above object, the light guide plate that reflects or passes through the light incident from the light source is formed on the bottom surface of the liquid crystal panel side is formed with a flat surface, the upper surface is arranged a large number of prism surface and uniform brightness The technical feature of the invention is that it is bent to have a predetermined radius of curvature with respect to the flat bottom surface.

Each prism of the prism surface is composed of a liquid crystal reading portion that rises with respect to the plane as it moves away from the light source, and a light reflection portion that descends with respect to the plane as it goes away from the light source, and the liquid crystal reading portion and the light reflection portion come into contact with each other. It forms a mountain shape, and each prism of the mountain shape is repeatedly arranged to form a prism surface.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual view illustrating a front light unit for a reflective liquid crystal display device according to an exemplary embodiment of the present invention, wherein a reflective light guide plate 200 is provided at one side of an observer of the liquid crystal panel 100, and The reflecting plate 300 is provided on the opposite side.

The liquid crystal panel 100 includes a pair of first and second glass substrates 102 and 103 disposed to face each other with an electro-optic liquid crystal 101 interposed therebetween, and a color filter layer formed to face the inner surface of the first glass substrate 102. And a pixel 106 opposed to the transparent electrode layer 105 and the second glass substrate 102.

The reflective plate 300 may be formed under the liquid crystal panel 100 or inside the liquid crystal panel 100, that is, under the pixel 106 or on the lower surface of the second glass substrate 102.

The light source 210 and the reflector 220 are disposed at one side of the viewer of the liquid crystal panel 100. The light source 210 is formed of a cold cathode tube (CCFL) or a light emitting diode terminal (LED), and the like, and the reflector 220 reflects light from the light source 210 toward the light guide plate 200 and is reflected by the reflector 220. The received light is incident into the light guide plate 200 at the left end of the drawing.

The polarization controller 400 and the light guide plate 200 for blocking the reflected light are stacked on the liquid crystal panel 100.

As shown in FIG. 2, the reflective light guide plate 200 is made of a transparent resin material, which is mainly composed of a single body having a plurality of prisms on a top surface and a flat surface on a bottom surface thereof, and a reverse phase is formed on a mold to produce an injection molding. In addition, the light guide plate 200 may be configured as a prism unit separate from the optical transparent resin.

That is, in the reflective light guide plate 200 which is integrated as described above, the bottom surface 203 forms a flat surface, and the upper surface of the reflective light guide plate 200 forms a prism surface with a large number of prisms arranged.

Each prism consists of a liquid crystal reader 204 gradually rising upward with respect to the plane as it moves away from the light source 210, and a light reflecting part 205 gradually descending with respect to the plane as it moves away from the light source 210. .

Here, the liquid crystal reading unit 204 and the light reflecting unit 205 contact each other to form an acid prism, and a plurality of prisms are repeatedly arranged to form a plurality of prisms forming the upper surface of the light guide plate 200.

The polarization regulator 400 is formed by stacking a linear polarizer 401 and a quarter wavelength (λ / 4) plate 402.

Here, the linear polarizer 401 forms linearly polarized light composed of x-components and y-components of the same intensity, respectively, and the quarter-wave plate 402 has a phase difference of λ / 4 between one of the x-components and the y-components. Puts. As a result, the light output from the polarization controller 400 and mirrored downward is blocked by the polarization controller 400 and does not reach the light guide plate 200.

As shown in FIG. 2, the light traveling through the light guide plate 200 from the left side to the right side is guided by the reflection of the liquid crystal reader 204 or the bottom surface 203, and is reflected by the light reflection unit 205 to reflect the liquid crystal panel. It is reflected toward (100).

Since the light reflecting portion 205 forms an angle of about 45 ° with respect to the horizontal plane, light traveling almost horizontally from left to right is reflected almost perpendicularly to the liquid crystal display.

On the other hand, the propagation of the light emitted from the light source 210 is not completely horizontal, and is reflected by the liquid crystal reading unit 204 and the bottom surface 203, so that the angle of the light reflection unit 205 is approximately 40 to 60 degrees. Is selected from the range of.

The light reflected from the reflective plate 300 through the liquid crystal panel 100 travels toward the polarization controller 400 and the reflective light guide plate 200. In the reflective light guide plate 200, the radius of curvature of the reflective light guide plate 200 is so large that the liquid crystal reader 204 which forms an almost horizontal surface forms an emission surface of the output light so that the display image of the liquid crystal can be viewed.

In order to obtain a better display performance in the liquid crystal display device, the luminance obtained by the light guide plate 200 is required to be uniform. Light emitted from the light source 210 provided on one side of the light guide plate 200 travels from the left side to the right side of the light guide plate 200.

If the shape of each prism forming a plurality of prisms of the light guide plate 200 is uniform, the incident angle of light incident on each prism becomes smaller toward the left side, and the amount of light reflected from the prism is determined by the prism from the light source 210. The farther it is, the smaller it becomes, and thus, uniform luminance cannot be obtained over the entire surface of the light guide plate 200.

On the other hand, the bottom 203 of the light guide plate 200 is a flat plane.

The upper surface of the light guide plate 200 is formed by repeating the liquid crystal reading unit 204 and the light reflecting unit 205. The vertex 206 and the bottom 207 of the prism are formed at the point where the liquid crystal reading portion 204 and the light reflection portion 205 contact each other. The liquid crystal reading unit 204 may not form a large angle with respect to the flat surface in order to pass all the light reflected from the reflecting plate 300 to the observer side. In other words, the liquid crystal reading unit 204 needs to be disposed substantially parallel to the bottom surface 203.

Therefore, when the liquid crystal reading portion 204 is disposed in parallel with the bottom surface 203, a plurality of prism shapes must be tapered to the left to form the prism. In this case, the light guide plate 200 looks like a wedge, and the wedge-shaped light guide plate 200 causes various problems.

In order to overcome the above problems, the liquid crystal reading unit 204 should be formed to be substantially horizontal with respect to the bottom surface 203, but as the distance from the light source 210 increases. For example, the liquid crystal reading portion 204 of each prism is preferably formed at an angle of about 0.5 to 3 degrees with respect to the horizontal plane.

On the other hand, the amount of light incident on each prism per unit area is not uniform. That is, the incident light amount gradually decreases from the left side to the right side of the drawing, and in order to obtain a uniform light amount in the reflective liquid crystal display, the light reflection unit 205 must be formed larger from the left side to the right side.

The method of increasing the light reflection portion 205 increases the difference (h) between the vertex 206 and the low point 207 from left to right, but this causes a change in the shape of each prism. Because of the manufacturing difficulties.

In addition, the average direction of the light incident on the light reflecting portion 205 also becomes smaller from left to right, so that light reflected from the light reflecting portion 205 is slightly inclined with respect to the vertical direction to the liquid crystal display (± 5). In order to obtain a bright and high contrast screen, the angle γ formed between the light reflecting unit 205 and the horizontal plane must be gradually increased. Also, the shape of each prism is changed so that the manufacturing problems described above can be achieved. Generates.

Here, the uniform prism shape gradually decreases the angle α formed with the liquid crystal reader 204 with respect to a horizontal horizontal line with respect to the bottom 203 at the apex of each prism from the left to the right, and the light reflecting portion 205 It can also be obtained by gradually increasing the angle (γ) forming a), but also there are manufacturing difficulties as described above.

Therefore, in order to simplify the fabrication while having a uniform prism shape, as shown in FIG. 3, the virtual surface 208 connecting the vertices 206 in the prism shape has a predetermined radius of curvature. The prism is made to form a curved surface. As a result, even with a prism having the liquid crystal reading unit 204 and the light reflecting unit 205 having the same shape, the length of the light reflecting unit 205 is increased, thereby obtaining uniform luminance.

That is, as described above, the angles α and γ formed by the horizontal plane parallel to the bottom surface 203 and the liquid crystal reading unit 204 and the light reflecting unit 205 are kept constant, and as a result, the vertices (see the above-mentioned peaks toward the right side) It is possible to obtain a structure in which the prism depth h formed between the 206 and the low point 207 is gradually increased, thereby obtaining a uniform amount of light with respect to an incident light amount gradually decreasing from left to right.

The virtual curved surface 208 may be formed to have a large curvature so that the light reflected from the reflector 300 may increase its transmittance at the liquid crystal reader 204.

Reflectivity in such curved multiple prisms increases almost linearly from left to right. Increasing the reflectance of the prism compensates for the decrease in the incident light intensity, so that the light guide plate 200 can obtain a substantially uniform luminance over the entire surface.

On the other hand, the pitch p between the prisms is constant, the range is preferably in the range of 50 to 500 microns, preferably 100 to 250 microns. The preferred prism depth h is suitably in the range of 1 to 15 microns.

In addition, the depth h of the prism should be adjusted to correspond to the intensity of light reflected by the light reflecting unit 205 and emitted vertically from the liquid crystal reading unit 204, and the range is at the position farthest from the light input unit. It is desirable to adjust the prism depth h so that the intensity of light has a range of 1.3 to 2 times the intensity of light at the position closest to the light input.

The angle α of the liquid crystal reading unit 204 formed in a horizontal plane parallel to the bottom surface 203 is in a range of 0.5 to 3 °, and the angle γ of the light reflecting unit 205 is 40 to 50 degrees. It is preferable to set it as ° range.

The entire light guide plate 200 may be formed as a transparent body such as an acrylic resin, but the prism unit 202 may be formed of a material having superior thermoplasticity to form a prism shape.

The present invention is not limited to the above-described embodiments, and various modifications can be made by those skilled in the art within the scope of the technical idea of the present invention.

As described above, in the reflective LCD according to the present invention, a line connecting the vertices of each prism constituting a plurality of prisms has a large curvature radius, that is, the shape of each prism, that is, a constant pitch p and a horizontal plane. Since the angles (α, γ) of the liquid crystal reading portion and the light reflecting portion with respect to are constant, the production is simplified.

In addition, since the lower point of the prism becomes deeper with respect to the horizontal plane and the length of the light reflection portion of the prism becomes longer as the distance from the light source increases, the present invention compensates that the light intensity decreases and the amount of light decreases as the distance from the light source increases. Uniform strength can be obtained over time.

1 is a conceptual diagram illustrating a front light unit for a reflective liquid crystal display device according to the present invention;

2 is an enlarged schematic view of a part of the front light unit according to the present invention;

3 is an enlarged cross-sectional view of a micro prism of the reflective light guide plate according to the present invention;

4 is a conceptual view illustrating a conventional front light unit for a reflective liquid crystal display device;

5 is a schematic view showing a conventional front light unit as shown in FIG.

       Explanation of symbols on the main parts of the drawings

100: liquid crystal panel 101: liquid crystal

102, 103: first and second glass substrate 104: color filter layer

105: transparent electrode layer 106: pixel

200: reflective light guide plate 203: bottom

204: liquid crystal reader 205: light reflection unit

206: peak 207: low

208: virtual reference plane 210: light source

220: reflector 300: reflector

400: polarization controller 401: linear polarizer

402: quarter-wave plate

Claims (5)

A light source 210 is installed on one side of the liquid crystal panel 100, and a bottom surface 203 forms a flat surface on one side of the light source, and a reflective light guide plate 200 having a plurality of prisms is repeatedly arranged on the top surface. In the reflective liquid crystal display device in which the reflective plate 30 is installed behind the liquid crystal panel 100 so that the displayed screen can be viewed even in a dark place. Each prism constituting the upper surface of the reflective light guide plate 20 includes a liquid crystal reading part 204 that rises with respect to the bottom surface 203 and a falling light reflection part 205 as the distance from the light source 210 increases. The virtual surface 208 connecting the vertices 206 of the liquid crystal reading unit 204 is formed to have a predetermined radius of curvature and forms a horizontal plane parallel to the bottom surface 203 so that the upper shape of each prism is the same. The angle α and the angle γ of the light reflecting portion 205 are formed uniformly, and the pitch p of each prism is formed uniformly, so that the vertex 206 and the low point of each prism move away from the light source. A front light unit for a reflective liquid crystal display device, characterized in that the prism depth (h) to be made deeper. delete The front light unit of claim 1, wherein the pitch (p) between the prisms is in a range of 50 to 500 microns. 4. The front light unit of claim 3, wherein the height h of the prism is in a range of 1 to 15 microns. 5. The angle α of the liquid crystal reading unit 204 forming a horizontal plane parallel to the bottom surface 203 is in a range of 0.5 to 3 °, and the angle γ of the light reflecting unit 205 is Frontlight unit for a reflective liquid crystal display device, characterized in that 40 to 50 ° range.