JP2001519547A - Liquid crystal cell - Google Patents

Abstract

(57) Abstract: The present invention relates to a liquid crystal cell provided with first and second layers, a liquid crystal disposed between these two layers, and two electrodes corresponding to the liquid crystal. In this case, at least one of the two electrodes is provided on the second layer as an electrode layer. Further, at least one polarizing layer is provided on the second layer, and illumination means is provided on the second layer on the side opposite to the liquid crystal. The invention is characterized in that the polarizing layer (49) is arranged in the second layer (21) on the side of the electrode layer (47) opposite to the lighting means (5).

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a first and a second layer, a liquid crystal disposed between the two layers, two electrodes associated with the liquid crystal, and a liquid crystal in the second layer. The invention relates to a liquid crystal cell having illumination means arranged on the opposite side.

[0002] Liquid crystal cells of this type are generally known. These liquid crystal cells are used to form a so-called LCD display unit in which individual liquid crystal cells are arranged in a matrix. Generally, a liquid crystal cell consists of a liquid crystal and two plates,
Liquid crystal is accommodated between the plates. Each of the two plates has a light-transmissive glass substrate as a support layer, on which a polarizing layer and an electrode layer are respectively mounted, wherein the polarizing layer and the liquid crystal in the support layer. Is on the other side. In the case of a liquid crystal cell using a so-called active matrix technique, a matrix composed of row lines and column lines is provided on a so-called active plate, and the transparent electrodes are controlled by these. At each intersection of a row and a column, a thin film transistor is arranged, which is connected to a pixel electrode belonging to the thin film transistor. This makes it possible to control all the pixels of the matrix individually. The liquid crystal is aligned by applying a control voltage to the electrodes,
Thereby, the light transmission characteristics of the liquid crystal change. In this case, by using both polarizing layers, light supplied from the backlight unit can be transmitted depending on the applied voltage.

[0005] A front plate located on the opposite side of the active plate supports a shadow mask called a so-called Black Matrix. The role of the black matrix is to cover the addressed liquid crystal cell area, for example the area between the pixel electrodes, thereby preventing unwanted transmission through that area and thus guaranteeing good contrast . However, a disadvantage of the black matrix is that the overall permeability of the cell is reduced. Depending on the design of the matrix consisting of row lines and column lines, the opening of the shadow mask, ie the ratio of light-transmitting areas to non-light-transmitting areas, is between 50% and 80%.

In particular, for relatively large liquid crystal display units, for example for use as computer monitors, so-called in-plane switching (IP)
S, "in-plane-switching") liquid crystal cells operating according to the method are increasingly used, for example in European Patent Application 0 509 025 B1.
Is disclosed. Unlike the liquid crystal cell structure described above, in the case of an IPS liquid crystal cell, both electrodes are arranged on an active plate, where the liquid crystal is oriented by a lateral electric field. The electrodes of this type of liquid crystal display unit are
It has an interdigital electrode structure. The advantage of an IPS cell lies in a significantly wider viewing angle range, for example as required for a computer monitor. However, a disadvantage of IPS cells is that the transmission value of one cell is relatively small. That is, on the one hand, the addressed area must be covered with a black matrix, and on the other hand, the transmissivity of each pixel itself is low due to the interdigital electrodes. Even if an interdigital electrode is formed by a transparent material, the transmittance is slightly increased. This is because the area in the electrode does not switch, and in the case of an IPS cell, the transmission state usually corresponds to the switched state. Typically, for IPS cells (considering black matrix and interdigitated electrodes) the aperture is about 30%.

Advantages of the Invention On the other hand, a liquid crystal cell having the configuration described in the characterizing portion of claim 1 has an advantage that luminous efficiency is significantly increased. This is achieved by providing a polarizing layer or polarizing filter on the side facing the liquid crystal in the black matrix and / or the electrode layer. This ensures that light reflected at the black matrix or electrode is not attenuated by absorption due to the polarizing filter. In this case, the light reflected on the second layer returns to the liquid crystal cell by the reflection on the illumination means again.

[0006] According to an advantageous embodiment of the invention, the liquid crystal cell is designed as an IPS cell, in which two electrodes lie in one plane. In such a liquid crystal cell having an aperture in the range of 30%, the luminous efficiency can be significantly increased.

[0007] According to one advantageous embodiment of the invention, the illuminating means comprises additional light reflecting means, which are used for back reflection. Thereby, the luminous efficiency can be further increased. This is because the reflecting means can be specially matched to a given situation. This has an advantageous effect on using the illumination means itself as a reflector, in terms of the luminous efficiency achievable based on the optimization of the reflection means.

According to an advantageous embodiment of the invention, the electrode or the black matrix has a surface that reflects well, at least on the side facing the illumination means. Thus, the component of light absorbed by the surface can be reduced, and the luminous efficiency can be significantly increased.

According to another advantageous embodiment of the invention, the surface of the electrode facing the liquid crystal is antireflection treated, so that reflection is prevented there. The advantage of this is that the contrast is not compromised even under ambient light.

[0010] According to one advantageous embodiment of the invention, the polarizing layer comprises Na 16 May 1996
381, in which a dichroic dye molecule is incorporated into the LPP / LCP layer combination.

According to one advantageous embodiment of the invention, the polarizing layer has an alignment layer for aligning adjacent liquid crystals. The advantage of such an arrangement is, in particular, that a separate alignment layer is omitted.

[0012] Furthermore, according to one advantageous embodiment of the invention, the polarizing layer is configured as a liquid-crystalline polymer layer containing dichroic dye molecules.

According to one advantageous embodiment of the invention, the second layer has a color filter, which is arranged between the electrode layer and the polarizing layer.

According to one advantageous embodiment of the invention, the liquid crystal is a Guest-Host
3.) It is based on liquid crystal or liquid crystal polymer compounds.

Particularly preferably, the liquid crystal cell according to the invention is an LCD display, for example a color LCD
It is used in displays (LCD = liquid crystal display), which are for example incorporated as monitors in the field of motor vehicles for portable computers and navigation systems.

Drawings Next, the present invention will be described in detail based on embodiments with reference to the drawings.

FIG. 1 is a schematic diagram for a basic explanation of the present invention.

FIG. 2 is a diagram showing the structure of the liquid crystal cell according to the first embodiment.

FIG. 3 is a diagram showing a structure of a liquid crystal cell according to the second embodiment.

FIG. 4 is a diagram showing a structure of a liquid crystal cell according to a third embodiment.

FIG. 5 is a basic configuration diagram of the LCD module.

Embodiment FIG. 5 illustrates a basic structure of a known LCD module (LCD = liquid crystal display). Modules of this kind are used, for example, in the field of motor vehicles, such as navigation systems, or as mobile communications and even computer monitors. The LCD module 1, which can be configured as a black-and-white display or a color display, has a casing 3, in which an illumination unit 5, a control unit 7, and a liquid crystal unit 9 are accommodated.

The lighting unit 5 has a lamp 11, a light guide 13 and a reflector 15 mounted on the side. The illumination unit 5 is configured such that the emitted light substantially travels in the direction of arrow P to uniformly illuminate the liquid crystal cell unit 9.

The liquid crystal unit 9 following the illumination unit 5 (as viewed from the radiation direction P) includes a first polarizing filter 19 in addition to the two sheets 17, and two layers 21, 21 for accommodating liquid crystal therebetween.
3 and a second polarizing filter 25.

The control unit 7 includes, besides the control electronics 27, the drive component 2
9 for controlling the liquid crystal cells of the liquid crystal cell unit 9 via the data lines 31.

The liquid crystal cell unit 9 is composed of a number of individual liquid phase cells, which are arranged in a matrix and can be controlled separately from each other. Control of the individual cells is performed in so-called TFT liquid crystal cells using thin film transistors, which are addressed via data lines 31 and apply voltages to the electrodes of the cells.

Next, the schematic structure of the liquid crystal cell according to the first embodiment will be described in detail with reference to FIG.

The liquid crystal cell 41 has a layered structure including a first layer 21 and a second layer 2.
3 and a liquid crystal 43 located between these two layers.

The first layer 21 has a glass substrate 45 used as a support, followed by an electrode layer 47, a polarizing layer 49, and an alignment layer 51 adjacent to the liquid crystal 43.

The electrode layer 47 has an integrated black matrix, a control transistor, and a line required for controlling the transistor. Here, these members are illustrated as a control unit 53 for simplicity. Furthermore, in the electrode layer,
An electrode 55 necessary for alignment of the liquid crystal is provided. In this embodiment, two electrodes required for controlling the liquid crystal cell are arranged in one plane. Here, a so-called IPS cell is targeted, in which case the individual electrodes are intersected in a comb shape (interdigital or interdigitated electrode structure). Such IP
A detailed description of the S-cell is disclosed in European Patent Application No. 0 509 025 B1, the disclosure of which is incorporated in its entirety. As shown in FIG. 2, the individual electrodes 55 are arranged in parallel with each other, and a free space 57 is formed between them. The free space 57 is translucent, while the electrodes 55 and the control unit 53 are non-translucent.

The second layer 23 has a similar structure, but does not include any actively controllable members. For this reason, the first layer 21 is also called an active layer. The second layer 23 also has a glass substrate 59, on which a color filter layer 61 and an orientation layer 63 are attached (for a color LCD module). Further, the second layer 23 has a polarizing layer, which is not drawn for clarity.
Advantageously, it can be designed as a component of the color filter 61.

The operation of the liquid crystal cell unit 41 is as follows.

When the liquid crystal cell is in an active state, light emitted from the lighting unit 5 (shown as a light beam 65) is transmitted through the second layer 23. This is because the polarization direction is turned in the direction corresponding to the polarization direction of the second polarizing layer in the second layer 23 during the passage of the liquid crystal. Light emitted from the lighting unit 5 penetrates only the translucent region of the first layer 21. In this embodiment, it is free space 5
There are only seven. On the lower surface of the electrode 55 and the black matrix integrated in this layer and the control unit 53, ie the surface facing the lighting unit 5, light is reflected back in the direction of the lighting unit 5 as indicated by the arrow 67. I do. This radiation 67 reflected at the electrode plane returns to the lighting unit 5 and then reflects again via the reflector 15 in the direction of the first layer 21. The advantage gained by this is that the reflected light can eventually be almost completely used for the transmission of the liquid crystal cell. Such a reflected light component is at least partially absorbed without passing through a polarizing filter. This is because the polarizing layer 49 is disposed on the other side of the electrode layer 47 with respect to the illumination unit 5.

In other words, the basic principle according to the present invention is that, on the one hand, the electrode is configured to reflect light, and on the other hand, the reflected light is at least partially absorbed irrespective of the polarizing layer. A display corresponding to this basic principle is shown in FIG. According to this figure,
The light emitted from the lighting unit 5 penetrates the liquid crystal cell unit 9 on the one hand, and is reflected there and returns to the lighting unit 5 on the other hand. This reflection component represented by reference numeral 69 is reflected again by the illumination unit 5 and returns to the liquid crystal cell unit 9.
This process can be continued multiple times as shown in FIG. This is because the radiation 69 reflected back from the liquid crystal cell unit 9 is not substantially attenuated.

FIG. 3 is a schematic diagram of a liquid crystal cell unit 71 according to the second embodiment. For the sake of clarity, the same layers as in the structure according to FIG. 2 have been given the same reference numbers and will therefore not be described again.

In contrast to the embodiment according to FIG. 2, the second layer 23 has an electrode layer 47, on which a transparent electrode (not shown) and a control unit 53 are provided. That is, in this case, the active layer or the driving layer is the layer 23 facing the viewer side B of the liquid crystal cell unit.

Instead of the electrode layer 47, the first layer 21 has a layer 73, which is a polarizing layer 49.
And the glass substrate 45. This layer 73 has a shadow mask 75 (black matrix) in addition to the transmissive electrodes, so that the region on the opposite side to the control unit 53 is made non-translucent. A light-transmitting region 77 is provided in a gap between each non-light-transmitting region of the shadow mask 75, and these regions can be used by, for example, attaching an appropriate optical material as a color filter.

The side of the shadow mask 75 facing the illumination unit 5 is configured to have extremely good light reflectivity. Thus, in this case as well, as already explained in connection with the embodiment according to FIG. 2, light is reflected back to the illumination unit 5 without attenuation by the polarizing filter, from which it is reflected again by suitable reflecting means towards the liquid crystal cell. Then, a configuration for returning to the original state is realized.

FIG. 4 shows still another embodiment of the liquid crystal cell unit 81. The structure of the liquid crystal cell unit 81 substantially corresponds to the structure of the embodiment shown in FIG.
Therefore, the members and layers with the same reference numerals are not described again.

The difference from the previous embodiment is that the electrode layer 47 is provided between the polarizing layer 49 and the glass substrate 45 in the first layer 21. Further, the layer 47 also includes the shadow mask 75 described above. On the other hand, the color filter layer is incorporated in the second layer 23 as the layer 83. The color filter layer 83 is located between the glass substrate 59 and the alignment layer 63.

In the case of this embodiment, the electrode 55 facing the lighting unit 5 and the control unit 53
Is light-reflective and is also configured as the surface of the shadow mask 75. Also in this case, the light is reflected in the direction of the illumination unit 5 and then reflected back toward the liquid crystal unit 81, thereby increasing the luminous efficiency.

Of course, other layer structures are also conceivable. According to the invention, the light is well reflected at the surface facing the irradiation unit 5 and that the reflected radiation must not pass through the polarizing filter, which would cause light attenuation. You only need to pay attention to).

As the polarizing layer, for example, a liquid crystal polymer layer containing dichroic dye molecules is used. Further, the polarizing layer may be constituted by a combination of LPP / LCP layers containing dichroic dye molecules. In this case, the polarizing layer can be used at the same time as an alignment layer for the liquid crystal, so that a separate alignment layer is omitted.

The shadow mask is advantageously manufactured from a metal having very good reflection properties. In the case of an IPS cell, the electrodes can also be made of a material having good reflection properties, but the surface facing the observer is antireflection treated by one or more dielectric intermediate layers.

In the above-described embodiments according to FIGS. 2 to 4, the second polarizing layer forming the second polarizing filter 25 is not shown for easy viewing. For example, the second
The layer 23 can be attached to the surface of the glass substrate opposite to the liquid crystal. Of course, it is also conceivable to provide the second polarizing layer on the glass substrate on the side facing the liquid crystal.

When the lighting unit 5 is operating according to the light guide method as shown in FIG. 5, care must be taken so that the reflected light does not enter the light guide and is absorbed. Therefore, a reflector is generally provided below the light guide that is not in optical contact with the light guide.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for a basic explanation of the present invention.

FIG. 2 is a diagram showing a structure of a liquid crystal cell according to a first embodiment.

FIG. 3 is a diagram showing a structure of a liquid crystal cell according to a second embodiment.

FIG. 4 is a diagram showing a structure of a liquid crystal cell according to a third embodiment.

FIG. 5 is a basic configuration diagram of an LCD module.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Gunther Haas, Germany Leonberg Zank Lorenz-Week 9 F-term (reference) 2H091 FA02Y FA08Y FA14Y FA35Y FA41Z FB02 FB11 FD04 FD08 GA02 GA06 HA08 LA16 2H092 GA14 JA24 JB05 JB07 J52 NA07 PA02 PA08 PA09 PA11 PA12 PA13 QA08

Claims (13)

[Claims] 1. A liquid crystal is disposed between a first layer and a second layer, an electrode layer is disposed on the first layer, and an interdigital electrode is disposed in the electrode layer. In a liquid crystal cell of the type in which the electrodes are arranged in a structure, an illuminating means (5) is arranged on the side of the first layer (21) opposite to the liquid crystal (43). An electrode (55) is provided on the facing surface in a reflective manner, and the light is reflected in the direction of the liquid crystal (43) by the lighting means (5) or the reflector (15). A liquid crystal cell, wherein a polarizing layer (49) is arranged on the side of the opposite electrode layer (47). 2. A liquid crystal is disposed between a first layer and a second layer, a mask layer is disposed on the first layer, and the first layer or the second layer is disposed on the first layer. In a liquid crystal cell in which an electrode layer is arranged in a layer and an electrode is arranged in an interdigital electrode structure in the electrode layer, the first layer (21) opposite to the liquid crystal (43) is formed. A lighting means (5) is arranged on the side of the mask layer (73), and a reflective shadow mask (7) is provided on a surface of the mask layer (73) facing the lighting means.
5) is provided, and light is reflected from the lighting means (5) or the reflector (15) in the direction of the liquid crystal (43), and the side of the mask layer (73) opposite to the lighting means (5). A liquid crystal cell, wherein a polarizing layer (49) is disposed on the liquid crystal cell. 3. A support layer (45) is provided on said first and second layers (21, 23).
, 59) are arranged. 4. The electrode according to claim 1, wherein the electrode (55) is subjected to an anti-reflection treatment on a surface opposite to the lighting means (5), for example, is subjected to an anti-reflection treatment by a dielectric intermediate layer. The liquid crystal cell according to claim 1. 5. The polarizing layer (49) is an LP containing dichroic dye molecules.
5. The semiconductor device according to claim 1, which is configured by a combination of P / LCP layers.
Item. 6. The liquid crystal cell according to claim 1, wherein the polarizing layer is an alignment layer for aligning adjacent liquid crystals. 7. The liquid crystal cell according to claim 1, wherein the polarizing layer is a liquid crystal polymer layer containing dichroic dye molecules. 8. The liquid crystal cell according to claim 1, wherein a color filter (61, 83) is arranged between said electrode layer (47) and said polarizing layer (49). 9. The liquid crystal cell according to claim 1, wherein the liquid crystal is configured as a guest-host liquid crystal or based on a liquid crystal polymer compound. 10. The use of a liquid crystal cell according to claim 1, for use in a liquid crystal display device, for example a color liquid crystal display device. 11. The method according to claim 1, wherein the second layer has a color filter, the color filter being arranged between the electrode layer and the polarizing layer.
0. The liquid crystal cell according to any one of 0. 12. The liquid crystal (43) is configured as a guest-host liquid crystal or based on a liquid crystal polymer compound.
12. The liquid crystal cell according to any one of items 1 to 11. 13. Use of a liquid crystal cell according to claim 1, for use in an LCD display, for example a color LCD display.