JPH08338995A - Liquid crystal display panel and its production - Google Patents

Abstract

PURPOSE: To improve the display quality for an oblique visual field when the medium contrast is displayed and to improve the visual angle characteristics by forming minute oriented regions in such a manner that each region is uniform and sufficiently small. CONSTITUTION: A display electrode 13 and a first polymer film 16 are formed on a first substrate 11, while a counter electrode 14 and a second polymer film 17 are formed on the second substrate 12. Further, a sealing part 18 is formed to seal liquid crystal molecules 19 between the first substrate 11 and the second substrate 12. The polymer film 16 and the second polymer film 17 are not subjected to uniaxial orientation treatment such as rubbing so that these films have such a surface state that does not regulate the liquid crystal molecules 19 in one direction in the plane. Lots of minute oriented regions 1 are formed in one pixel in such a manner that meandering disclination lines 3 are produced in a rather aligned state on the borders of the minute oriented regions 1 and that the distance Ld between two disclination lines 3 adjacent to one minute oriented film 1 is almost uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display panel having improved viewing angle characteristics, and more particularly to a liquid crystal display panel having improved image quality in an oblique viewing field and a method for manufacturing the same.

[0002]

2. Description of the Related Art At present, liquid crystal display panels are being used in display screens for word processors, personal computers, etc., as the screen size and display capacity are increasing. As a means of this liquid crystal display panel, a twisted nematic (TN) type liquid crystal display panel is generally used in an active matrix system having switching elements such as a thin film diode (TFD) element and a thin film transistor (TFT) element, which are becoming mainstream recently. ing.
As shown in FIG. 4, this TN type liquid crystal display panel is provided with an alignment film 4 which is uniaxially regulated by rubbing.
6 and 47 are formed on the substrate, and the rubbing directions are orthogonal to each other between the upper and lower substrates 41 and 42, and the liquid crystal molecules 49 enclosed between the substrates are regularly arranged along the rubbing direction. The liquid crystal molecules are twisted by 90 degrees between them. Further, the liquid crystal molecules 49 have a predetermined pretilt angle 40 in the vertical direction of the substrate and are uniformly oriented in the same direction in the plane of the substrate. When a voltage is further applied, the rising direction of the liquid crystal molecules 49 becomes a constant direction according to the alignment direction and the pretilt angle.

As described above, in this TN type liquid crystal display panel, the liquid crystal molecules are constructed so as to rise in the same direction in the plane, so that the direction in which the observer looks at the liquid crystal display panel when displaying an image. There is a problem of viewing angle dependency that the halftone display of the image is reversed depending on the angle and the angle, and it cannot be recognized as a normal image.

In order to improve the problem of the viewing angle dependence, a large number of minute alignment regions, that is, regions in which the alignment directions of liquid crystal molecules are aligned in the minute regions are provided in one pixel, and the liquid crystal molecules are arranged between the alignment regions. Japanese Patent Application Laid-Open No. 6-194655 discloses a multi-domain method in which the rising directions are different. In this method, the rising directions of liquid crystal molecules when a voltage is applied are random and exist with equal probability in all directions, so the transmittance-voltage (TV) characteristics are the same in all directions, and As a result, a liquid crystal display panel having no viewing angle dependency can be obtained.

[0005]

However, in this multi-domain liquid crystal display panel, as shown in FIG. 3, when the voltage is applied, the fine alignment region 1 is formed.
Since the rising directions of the liquid crystal molecules are different between the two, a disclination line 3 is generated at the boundary 2 thereof, and the shape of each of the minute alignment regions 1 separated by the disclination line 3 is indefinite, and the size is also different. It's all different. When the distance (Ld) 4 between the two disclination lines 3 adjacent to the fine alignment region 1 is defined as the size of the fine alignment region 1, the size of the fine alignment region 1 is Ld.
4 is about 5 to 10 μm, and a large one is 50 to 1
The size is 00 μm or more, and a large number of minute alignment regions 1 having various sizes are mixed to form a multi-domain alignment. Further, since the fine alignment regions 1 have different rising directions of liquid crystal molecules, the transmittances of the fine alignment regions 1 are different when viewed from an arbitrary direction in an oblique visual field. From this, when the observer sees from an oblique field of view, if the minute alignment regions 1 are mixed in various sizes in the pixel, for example, a small minute alignment region that appears black and white when halftone display is performed. Since large visible micro-orientation regions are mixed, the balance between white and black is lost, and normal halftone display cannot be obtained. In addition, since the existence ratios of the shape and size of the minute alignment region 1 are different between pixels, a rough and ugly display state is visible to the naked eye, and in terms of display quality,
It's a big problem.

An object of the present invention is to solve the above-mentioned problems, to make the shape and size of the minute alignment region finer, and to obtain a good display quality when viewed from an oblique visual field. And a manufacturing method.

[0007]

In order to achieve the above object, the liquid crystal display panel of the present invention adopts the following means. A liquid crystal display panel of the present invention includes a first substrate having a display electrode, a second substrate having a counter electrode, liquid crystal molecules sandwiched between the first substrate and the second substrate, and a display electrode. And a pixel in which a counter electrode faces each other, and at least one of the first substrate and the second substrate has an alicyclic polymer film containing polyamide or polyimide or polyamic acid, and The polymer film has a surface state that does not regulate the alignment of liquid crystal molecules in a certain direction, and the pixel is provided with a plurality of minute alignment regions.

Further, the liquid crystal molecules used in the liquid crystal display panel constructed as described above are characterized by containing a halogen atom, preferably a chlorine atom.

A method of manufacturing a liquid crystal display panel according to the present invention comprises a first substrate having a display electrode and a second substrate having a counter electrode.
A polymer film having a surface state that does not regulate the alignment of liquid crystal molecules in a certain direction on at least one of the substrates, and injecting the liquid crystal molecules between the first substrate and the second substrate, An alternating voltage is applied to the liquid crystal molecules while heating so that the liquid crystal molecules are held in an isotropic liquid state.

The polymer film of the liquid crystal display panel manufactured by such a method for manufacturing a liquid crystal display panel is characterized in that the structure thereof contains an alicyclic polyamide, polyimide or polyamic acid.

The liquid crystal molecules of the liquid crystal display panel manufactured by such a method for manufacturing a liquid crystal display panel are characterized by containing a halogen atom, preferably a chlorine atom.

[0012]

In the liquid crystal display panel of the present invention, when liquid crystal molecules are aligned, at least one of the first substrate and the second substrate has an alicyclic polyamide or polyimide or polyamic acid in its structure. It has a polymer film containing, and it is possible to obtain a special alignment state in which the size of the fine alignment region is made uniform and fine by the interaction between the liquid crystal molecules and the polymer film. Further, in this case, the effect is improved by using liquid crystal molecules containing a halogen atom, preferably a chlorine atom.

Further, by carrying out a manufacturing method in which an alternating voltage is applied while keeping the liquid crystal molecules in an isotropic liquid state, the interaction between the liquid crystal molecules and the polymer film is changed from the state immediately after the injection, and the fine alignment is achieved. A uniform fine micro-alignment region is formed in which the distance between two disclination lines adjacent to each region is about 10 μm, and the existence ratio of the shape and size of the micro-alignment region is substantially the same between pixels. Therefore, the image display quality in the oblique view is very good.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A liquid crystal display panel according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing an alignment state of one pixel portion in the liquid crystal display panel of the present invention. FIG. 2 is a sectional view of the liquid crystal display panel of the present invention. First, the structure of the liquid crystal display panel of the present invention is shown in FIGS.
It will be explained using and.

The first substrate 11 has a display electrode 13 and a first electrode 13.
Polymer film 16 is provided, a counter electrode 14 and a second polymer film 17 are provided on the second substrate 12, and liquid crystal molecules are provided between the first substrate 11 and the second substrate 12. A seal portion 18 for enclosing 19 is provided. The first polymer film 16 and the second polymer film 17 do not undergo a uniaxial orientation process such as a rubbing process, and have a surface state that does not regulate the liquid crystal molecules 19 in a certain direction in the plane. . The liquid crystal molecules 19 are randomly aligned, and as shown in FIG.
A large number of micro-oriented regions 1 are formed in 5. further,
The first polymer film 16 and the second polymer film 17 are configured by using an alicyclic polymer film such as polyamic acid, polyimide, or polyamide. Here, the alicyclic compound may be bonded to any part of the polymer.
For example, even when a part of the main skeleton such as polyamic acid, polyimide, or polyamide is substituted with an alicyclic hydrocarbon group, or an alicyclic hydrocarbon group is bonded to the main skeleton or the end portion. Even if you are. Further, a polymer film in which a polymer such as an alicyclic polyamic acid or a polymer such as polyimide or polyamide and another polymer are blended or copolymerized may be used.

Next, a manufacturing method for obtaining the liquid crystal display panel according to the present invention will be described with reference to FIGS. On the first substrate 11 made of glass, indium tin oxide (ITO), which is a transparent conductive film, is formed with a thickness of 200 nm by a sputtering method or an evaporation method. Then, a photo-etching method in which a photosensitive resin is formed on the entire surface, an exposure and development process is performed using a photomask, the photosensitive resin is patterned, and ITO is patterned using the patterned photosensitive resin as an etching mask. Thus, the display electrode 13 is formed. Further, an alicyclic polymer material such as polyamic acid or polyimide or polyamide is applied on the display electrode 13 by a flexographic printing method to a thickness of 50 nm, and is baked. Then, the first polymer film 16 is provided without performing the uniaxial orientation regulating process such as the rubbing process. On the other hand, the second substrate 12 made of glass is provided with the counter electrode 14 made of a transparent conductive film formed by the same processing method as described above. Further, the second polymer film 17 is provided on the counter electrode 14 by the same manufacturing method as described above. In this embodiment, the first polymer film 16 and the second polymer film 17 are made of the same material, but different materials may be used for either one of the substrates. Also, the polymer film may not be provided. Then, the first substrate 11 and the second substrate 12
In order to bond the two to each other, a seal portion 18 made of an epoxy resin is formed on either one of the substrates by a screen printing method, the first substrate 11 and the second substrate 12 are overlapped with each other, and heat treatment is performed to form the seal portion 18 Cure.

Then, the first substrate 11 and the second substrate 12
A liquid crystal adjusted to have a predetermined chiral pitch by injecting a chiral agent into a fluorine-based liquid crystal material having a chlorine atom at its terminal is injected into the gap between and to provide 19 layers of liquid crystal molecules. The chlorine atom or fluorine atom in the liquid crystal molecule may be bonded to the main skeleton, or to the side chain or the terminal.

(Example 1) After that, an AC voltage generator was connected to the display electrode 13 and the counter electrode 14, and the liquid crystal molecules 19 were connected.
Is heated at a temperature higher than the temperature at which the liquid crystal phase changes to the isotropic liquid phase (N-I phase transition temperature), and while maintaining the state of the isotropic liquid, an AC voltage of 1.5 V at a frequency of 60 Hz is applied to 1
The liquid crystal molecule 19 layer is applied for 5 minutes. After that, the liquid crystal phase is cooled from the isotropic liquid phase, and the voltage application step is completed. In the liquid crystal display panel thus manufactured, the liquid crystal molecules 19 are oriented in a random direction in the plane on the first polymer film 16 and the second polymer film 17, and one pixel 15 A large number of micro-alignment regions 1 are formed inside, and a meandering disclination line 3 as shown in FIG. And the distance (Ld) between the two disclination lines 3 is about 10 μm, and the minute fine alignment regions 1 are evenly formed. Further, the existence ratio of the shape and size of the fine alignment regions 1 between the pixels 15 is almost the same. The same liquid crystal display panel was obtained.

(Examples 2 and 3) Subsequently, the voltage value applied to the liquid crystal molecules in the liquid crystal display panel prepared in the same manner as in Example 1 was changed. While the liquid crystal molecules are heated and kept in an isotropic liquid state, an AC voltage of 0.5 V with a frequency of 60 Hz is applied for 15 minutes in Example 2, and a frequency of 60 Hz is used in Example 3.
AC voltage of 2.5V is applied to the liquid crystal molecular layer for 15 minutes,
After that, the liquid crystal phase is cooled from the isotropic liquid phase, and the voltage application step is completed. The liquid crystal display panels prepared in Examples 2 and 3 are liquid crystal in which, similarly to Example 1, uniform and fine minute alignment regions are formed, and the abundance ratios of the shapes and sizes of the minute alignment regions are substantially the same between pixels. A display panel is obtained.

Here, it is preferable that the voltage application step is performed at a voltage value of 3 V or less applied to the liquid crystal molecules. When a voltage higher than that is applied, the minute alignment region becomes too fine, and the area occupied by the disclination line in the pixel increases, so that the display contrast decreases, which is a practical problem.

Next, as a conventional example, a liquid crystal display panel was manufactured by changing the material of the polymer film of the embodiment of the present invention and the liquid crystal material. For the polymer film, polyamic acid, polyimide, or polyamide having no alicyclic molecular skeleton in its structure was used, and the liquid crystal material was liquid crystal containing no halogen atom. Further, the step of applying an alternating voltage while heating the liquid crystal after injecting the liquid crystal was not performed. The liquid crystal molecules of the liquid crystal display panel prepared by the conventional example are oriented in random directions, and the disclination line 3 as shown in FIG.
And the distance (Ld) between the two disclination lines 3 adjacent to the minute alignment region is different at each place,
Forming minute alignment areas of various sizes in one pixel,
The abundance ratio of the shape and size of the minute alignment region was different between pixels.

Subsequently, the liquid crystal display panel obtained according to the embodiment of the present invention and the liquid crystal display panel obtained according to the conventional example were actually subjected to halftone image display and evaluated. As shown in FIG. 5, the display state of the halftone display was evaluated in an oblique view while arbitrarily changing the angle θ from the Z axis, which is the front direction of the liquid crystal display panel, in the viewing direction. When the rough display state was evaluated as ×, when the rough display state was not observed, it was evaluated as ◯, and the middle thereof was evaluated as Δ. Table 1 shows the results.

[0023]

[Table 1]

As shown in Table 1, in each of the liquid crystal display panels according to the examples of the present invention, since the fine alignment regions are uniform and formed fine enough, the angle θ from the Z axis is large,
That is, good halftone display was observed even when observed from an oblique view, and high-quality image display was obtained in a wide view angle.
In addition, in the liquid crystal display panel created by the conventional example, minute alignment regions are formed in various sizes, and the abundance ratios are different between pixels. However, the image display was rough and ugly, and satisfactory display quality was not obtained.

[0025]

As is clear from the above description, in the liquid crystal display panel of the present invention, since the respective fine alignment regions are formed uniformly and finely, the display quality particularly in the oblique viewing field in the halftone display. It is possible to obtain a liquid crystal display panel having a high viewing angle characteristic.

[Brief description of drawings]

FIG. 1 is a plan view showing an alignment state in one pixel of a liquid crystal display panel in an example of the present invention.

FIG. 2 is a cross-sectional view showing an arrangement state of liquid crystal molecules of a liquid crystal display panel in an example of the present invention.

FIG. 3 is a plan view showing an alignment state in one pixel of a liquid crystal display panel in a conventional example.

FIG. 4 is a cross-sectional view showing an arrangement state of liquid crystal molecules of a TN type liquid crystal display panel.

FIG. 5 is a schematic view showing a direction in which a liquid crystal display panel is observed.

Claims (7)

[Claims] 1. A first substrate having a display electrode, a second substrate having a counter electrode, liquid crystal molecules sandwiched between the first substrate and the second substrate, a display electrode and a counter electrode. And a pixel formed by facing each other, and at least one of the first substrate and the second substrate has an alicyclic polymer film containing polyamide or polyimide or polyamic acid. Is a liquid crystal display panel having a surface state that does not regulate the orientation of liquid crystal molecules in a certain direction, and the pixel is provided with a plurality of minute orientation regions. 2. The liquid crystal display panel according to claim 1, wherein the liquid crystal molecule contains a halogen atom. 3. The liquid crystal display panel according to claim 1, wherein the liquid crystal molecule contains a chlorine atom. 4. A polymer film having a surface state that does not regulate orientation of liquid crystal molecules in a certain direction on at least one of a first substrate having a display electrode and a second substrate having a counter electrode. Forming, injecting liquid crystal molecules between the first substrate and the second substrate, and applying an AC voltage to the liquid crystal molecules while heating the liquid crystal molecules so as to maintain the state of an isotropic liquid. A method for manufacturing a liquid crystal display panel, comprising: 5. The method for manufacturing a liquid crystal display panel according to claim 4, wherein the polymer film contains an alicyclic polyamide, polyimide, or polyamic acid. 6. The method for manufacturing a liquid crystal display panel according to claim 4, wherein the liquid crystal molecule contains a halogen atom. 7. The method of manufacturing a liquid crystal display panel according to claim 4, wherein the liquid crystal molecule contains a chlorine atom.