KR100189839B1 - Stn-type lcd and orientation treating method of its liquid orientation film - Google Patents

Abstract

A super twisted nematic (STN) type liquid crystal display device is disclosed.

The disclosed liquid crystal display device includes a first substrate and a second substrate spaced apart by a predetermined distance from each other, a plurality of stripe-shaped first transparent electrodes disposed parallel to each other on an inner surface of the first substrate, and an inner surface of the second substrate. A plurality of stripe-shaped second transparent electrodes disposed in parallel to each other in an orthogonal direction to the array direction of the first transparent electrode, a first liquid crystal alignment film formed to cover the first transparent electrode on an inner surface of the first substrate, and a second substrate A second liquid crystal alignment layer formed to cover the second transparent electrode on an inner surface of the liquid crystal layer; and a liquid crystal injected between the first and second liquid crystal alignment layers and aligned in the alignment treatment direction of the first and second liquid crystal alignment layers; And two alignment treatment regions having different alignment treatment directions in the first and second liquid crystal alignment layers corresponding to each crossing region of the second transparent electrode. Thus, a wide viewing angle and an optimum contrast can be obtained.

Description

Super twisted nematic (STN) type liquid crystal display device and alignment processing method thereof

The present invention relates to a super twisted nematic liquid crystal display device capable of simultaneously obtaining optimum contrast in each of the pixels in the up and down directions, and to a method of aligning the liquid crystal alignment film thereof.

In general, liquid crystal display devices can be produced in various sizes ranging from the smallest to the large, and are widely used in the field of display devices because they have advantages in diversifying display patterns.

As one of the liquid crystal display devices, a super twisted nematic liquid crystal display device having a twist angle of about 180 ° to 260 ° has been introduced.

1 is a cross-sectional view showing a conventional super twisted nematic liquid crystal display device.

As illustrated, the first transparent electrode 5 and the second transparent electrode 15 on the stripe are formed on the mutually opposed inner surfaces of the first substrate 3 and the second substrate 17 disposed in parallel to each other. It is formed to intersect. In addition, the first liquid crystal alignment layer 7 and the second liquid crystal may be disposed on the inner surfaces of the first substrate 3 and the second substrate 17 to cover the first and second transparent electrodes 5 and 15. The alignment film 13 is formed, respectively. A super twisted nematic liquid crystal 11 is enclosed between the first and second liquid crystal alignment films 7 and 13. The circumference | surroundings of this liquid crystal 11 are sealed by the sealing material 9, such as frit glass and an organic adhesive material.

The two liquid crystal alignment layers 7 and 13 are used to orient the liquid crystal 11 in a predetermined direction, and are made of a polymer compound or an inorganic material, and a surface facing the liquid crystal 11 is an alignment direction of the liquid crystal 11. Orientation treatment is performed to determine this. This alignment treatment is performed by rubbing in a constant direction using a brush made of cotton or cloth, or by optical alignment using ultraviolet light. Accordingly, the liquid crystal 11 is aligned in the alignment treatment directions of the two liquid crystal alignment layers 7 and 13.

In addition, the first polarizing plate 1 and the second polarizing plate 19 are formed on the outer surfaces of the first substrate 3 and the second substrate 17, respectively. The polarization directions of the two polarizing plates 1 and 19 correspond to the twist angle of the liquid crystal 11. Therefore, only light oscillating in the main axis direction of the first polarizing plate 1 of the light irradiated from the light source (not shown) to the first polarizing plate 1 passes through the first polarizing plate 1, and the transmitted light is first The optical retardation (Δn · d) of the liquid crystal is changed according to the magnitude of the voltage applied through each of the first and second transparent electrodes 5 and 15, and transmitted through the second transparent electrode 15. Afterwards, the second polarizing plate 19 is partially transmitted along the polarization direction of the second polarizing plate 19.

In the conventional STN type liquid crystal display device, an example of an alignment treatment direction of each of the first liquid crystal alignment film 7 and the second liquid crystal alignment film 13 is shown in FIG. 2. Here, the arrow indicated by reference numeral 7a indicates the alignment treatment direction of the first liquid crystal alignment film 7, and the arrow indicated by reference numeral 13a indicates the alignment treatment direction of the second liquid crystal alignment film 13. The equicontrast curve in the case having such an orientation treatment direction is as shown in FIG. 3. Here, looking at the equi-contrast curve, the arrangement of the liquid crystal has a symmetry in the left and right direction (relative to the Y axis), while having an asymmetry in the up and down direction (relative to the X axis). As described above, the asymmetric isocontrast curve is obtained because the optical delay Δn · d of the liquid crystal changes according to the incident angle of light, and thus the light transmittance changes.

As described above, since the twist angle of the liquid crystal of the conventional STN type liquid crystal display device is about 180 ° to 260 °, a large amount of light transmission curve increases due to voltage application rather than a simple TN type liquid crystal display device in which a nonlinear device is not inserted. While it has the advantage of displaying information, it has a problem that the viewing angle is narrow.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described point, and has a first object to provide an STN type liquid crystal display device having a wide viewing angle characteristic.

Another object of the present invention is to provide an orientation processing method of an STN type liquid crystal display device in which the STN type liquid crystal is oriented such that the STN type liquid crystal has a symmetrical equal contrast curve.

1 is a cross-sectional view of a conventional STN type liquid crystal display device.

2 is a schematic view for explaining an orientation processing direction of a conventional STN type liquid crystal display device.

3 is a graph showing an iso contrast curve corresponding to the alignment direction of the conventional STN type liquid crystal display shown in FIG.

4 is a schematic view for explaining the orientation processing direction of the STN type liquid crystal display device according to the present invention.

5A to 5C are graphs showing a process of obtaining an equal contrast curve of an STN type liquid crystal display device according to the present invention;

6 is a flowchart showing a step of determining an orientation processing direction of a liquid crystal alignment film of an STN type liquid crystal display device according to the present invention;

Explanation of symbols for main parts of the drawings

1 ... 1st polarizing plate 3 ... 1st board | substrate 5 ... 1st transparent electrode

7.1st liquid crystal aligning film 9 ... sealing material 11 ... liquid crystal

13 second liquid crystal alignment layer 15 second transparent electrode 17 second substrate

19 ... second polarizer 20 ... first area 30 ... second area

40.Photoresist

In order to achieve the first object, the present invention, the first substrate and the second substrate spaced apart by a predetermined interval in parallel with each other, and a plurality of stripe-shaped first transparent electrode disposed in parallel to each other on the inner surface of the first substrate And a plurality of stripe-shaped second transparent electrodes disposed in parallel with each other in an orthogonal direction to the array direction of the first transparent electrode on an inner surface of the second substrate, and covering the first transparent electrode on an inner surface of the first substrate. A first liquid crystal alignment layer formed between the first liquid crystal alignment layer, a second liquid crystal alignment layer formed to cover the second transparent electrode on an inner surface of the second substrate, and the first and second liquid crystal alignment layers; In the STN type liquid crystal display device having liquid crystals oriented in the alignment treatment direction of the first and second liquid crystal alignment layers, different alignment treatments are applied to the first and second liquid crystal alignment layers corresponding to the cross regions of the first and second transparent electrodes. It provided that the two alignment treatment area having a flavor is characterized.

In order to achieve the second object, the present invention, the first substrate and the second substrate spaced apart by a predetermined interval in parallel with each other, and a plurality of stripe-like first transparent electrode disposed parallel to each other on the inner surface of the first substrate And a plurality of stripe-shaped second transparent electrodes disposed in parallel with each other in an orthogonal direction to the array direction of the first transparent electrode on an inner surface of the second substrate, and the first surface on an inner surface of each of the first and second substrates. And a pair of liquid crystal alignment layers formed to cover each of the second transparent electrodes, and a liquid crystal injected between the pair of liquid crystal alignment layers and oriented according to the alignment processing direction of each of the liquid crystal alignment layers. An alignment processing method comprising: aligning the liquid crystal alignment film corresponding to an intersection area of the first and second transparent electrodes in a first direction; Coating a photoresist on the aligned portion of the liquid crystal alignment layer; Exposing a portion of the liquid crystal alignment film by removing a portion of the photoresist by exposure; Aligning the liquid crystal alignment layer exposed in a second direction different from the first direction; Removing the remaining portion of the photoresist.

The STN type liquid crystal display device according to the present invention has a conventional structure as shown in FIG. However, in the alignment processing direction of the first liquid crystal alignment film (7 in FIG. 1) and the second liquid crystal alignment film (13 in FIG. 1), the conventional liquid crystal display device is different from the conventional STN type liquid crystal display device.

An orientation treatment direction of each of the first liquid crystal alignment layer 7 and the second liquid crystal alignment layer 13 according to the present invention is as shown in FIG. 4. That is, in order to secure X-axis symmetry and Y-axis symmetry of the alignment direction of the injected STN-type liquid crystal, the first and second liquid crystal alignment layers 7 and 13 of each pixel are divided into at least two alignment treatment regions, and then each alignment is performed. The alignment treatment is performed on the treatment region. Here, the alignment treatment is performed by a rubbing process in which a film is rubbed in a predetermined direction by using a brush made of cotton or cloth so that the liquid crystal is inclined, or by irradiating ultraviolet light.

4 shows an example in which two alignment treatment regions 20 and 30 are formed in the first and second liquid crystal alignment layers 7 and 13 of each pixel, wherein the twist angles of the STN type liquid crystals are 180 °, respectively. To 260 °. In FIG. 4, the white arrows 21 and 31 indicate the orientation directions of the first and second regions 20 and 30 on the first liquid crystal alignment film 7, respectively, and the black arrows 23 ( 33 shows the alignment treatment directions with respect to the first and second regions 20 and 30 on the second liquid crystal alignment layer 13, respectively.

As shown in FIG. 4, the alignment treatment direction 21 of the first region 20 of the first liquid crystal alignment layer 7 is opposite to the alignment treatment direction 31 of the second region 30. Similarly, the alignment treatment direction 23 of the first region 20 of the second liquid crystal alignment layer 13 is opposite to the alignment treatment direction 33 of the second region 30. Here, the alignment treatment directions 21 and 31 of the first liquid crystal alignment layer 7 may have a torsion angle of 180 degrees to 260 degrees with respect to the alignment treatment directions 23 and 33 of the second liquid crystal alignment layer 13, respectively. It can be seen that.

5A to 5C illustrate a process of obtaining an iso contrast curve in the case where each pixel is divided into two regions 20 and 30 and subjected to alignment as described above, and FIG. 5A illustrates a first region (see FIG. 20 shows an asymmetric isocontrast curve with respect to the X axis obtained by the alignment treatment directions 21 and 23 in FIG. 20, and FIG. 5B shows the alignment treatment directions 31 and 33 in the second region (30 in FIG. 4). Shows an isocontrast curve asymmetric with respect to the X-axis and symmetrical with the curve of FIG. 5B, which can be obtained by It shows a curve. Accordingly, as illustrated in FIG. 5C, by dividing each pixel into two regions 20 and 30, the asymmetric contrast with respect to the X axis may be corrected.

Referring to FIG. 6, a process of dividing the first and second liquid crystal alignment layers 7 and 13 into two areas is performed. For convenience of description, only the case of the first liquid crystal alignment layer 7 is illustrated in FIG. 6.

First, the first liquid crystal alignment layer 7 is formed on the first substrate 3 to cover the first transparent electrode 5 (S100).

Next, the surface of the first liquid crystal alignment film 7 facing the liquid crystal (FIG. 11) is aligned in the first direction, for example, in the direction of the arrow 31 in FIG. Rubbing in a constant direction using a brush made of cotton, cloth, or the like so as to be inclined is carried out using ultraviolet light. For example, in the case of performing alignment treatment using ultraviolet light, when the ultraviolet light monopolarized to the first liquid crystal alignment layer is irradiated, the alignment treatment direction is determined according to the single polarization direction, and the degree of inclination (pretilt) is proportional to the irradiation time of light Angle) is determined.

Then, the photoresist 40 is coated on the alignment-oriented liquid crystal alignment layer 7 (S120). Then, a mask (not shown) of a predetermined pattern is placed on the photoresist 40 and then exposed. For example, a portion of the first liquid crystal alignment layer 7 for alignment in the second direction different from the first direction, for example, the direction of the arrow 21 of FIG. 4, for example, the photoresist 40 of the first region 20 of FIG. 4. Remove) (S130)

In the same manner as described in step S110, the first region 20 of the first liquid crystal alignment layer 7 from which the photoresist 40 has been removed is aligned in a second direction. Is opposite to the first direction in step S110.

Finally, the photoresist 40 remaining in the second region 30 of the first liquid crystal alignment layer 7 is removed (S150).

Through this step, the first liquid crystal alignment layer 7 of each pixel may be aligned so that the alignment treatment directions of the first region 20 and the second region 30 are opposite to each other.

A process of aligning the second liquid crystal alignment layer (first FIG. 13) is as described with reference to FIG. 6, and the alignment treatment directions of the first region 20 and the second region 30 are indicated by the arrows of FIG. 4. 23, as indicated by 33.

Further, by repeating the above steps, the orientation processing direction can be selected for two or more regions for each pixel.

The STN type liquid crystal display device according to the present invention made as described above is provided with at least two alignment directions with respect to the liquid crystal of each pixel by the method described with reference to FIG. Can be obtained. Therefore, a wide viewing angle can be secured and the contrast characteristic of the image can be greatly improved.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible therefrom.

Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the claims.

Claims (8)

A first substrate and a second substrate spaced apart by a predetermined distance from each other, a plurality of stripe-shaped first transparent electrodes disposed parallel to each other on an inner surface of the first substrate, and the first surface on an inner surface of the second substrate; A plurality of stripe-shaped second transparent electrodes arranged parallel to each other in an orthogonal direction and an array direction of the transparent electrodes, a first liquid crystal alignment layer formed to cover the first transparent electrodes on an inner surface of the first substrate, and the second substrate A second liquid crystal alignment layer formed to cover the second transparent electrode on an inner surface of the second liquid crystal layer; and a liquid crystal injected between the first and second liquid crystal alignment layers and aligned in the alignment treatment direction of the first and second liquid crystal alignment layers; In the STN type liquid crystal display device, And at least two alignment treatment regions having different alignment treatment directions in the first and second liquid crystal alignment layers corresponding to the intersection regions of the first and second transparent electrodes. 2. The STN of claim 1, wherein two alignment treatment regions are formed in the first and second liquid crystal alignment layers corresponding to each cross region, and the alignment treatment directions of the two alignment treatment regions are opposite to each other. Type liquid crystal display device. The STN type liquid crystal display device according to claim 2, wherein the alignment treatment of the first and second liquid crystal alignment layers is performed by rubbing with a brush. The STN type liquid crystal display device according to claim 2, wherein the alignment treatment of the first and second liquid crystal alignment layers is performed by irradiating the first and second liquid crystal alignment layers with ultraviolet light having a single polarization component. A first substrate and a second substrate spaced apart by a predetermined distance from each other, a plurality of stripe-shaped first transparent electrodes disposed parallel to each other on an inner surface of the first substrate, and the first surface on an inner surface of the second substrate; A plurality of stripe-shaped second transparent electrodes arranged in parallel with each other in an orthogonal direction and an array direction of the transparent electrodes, and a pair of pairs formed to cover each of the first and second transparent electrodes on an inner surface of each of the first and second substrates; In the alignment processing method of the liquid crystal aligning film of the STN type liquid crystal display element provided with the liquid crystal aligning film and the liquid crystal injected between the pair of liquid crystal aligning films and orientated according to the alignment process direction of each said liquid crystal aligning film, Aligning the liquid crystal alignment layer in a first direction; Coating a photoresist on the aligned portion of the liquid crystal alignment layer; Exposing a portion of the liquid crystal alignment film by removing a portion of the photoresist by exposure; Aligning the exposed liquid crystal alignment layer in a second direction different from the first direction; Removing the remaining portion of the photoresist; alignment processing method of the liquid crystal alignment film of the STN type liquid crystal display device comprising a. The liquid crystal alignment film alignment method of claim 5, wherein the first direction and the second direction are opposite to each other. 7. The method of claim 6, wherein the alignment process is performed by rubbing with a brush on the liquid crystal alignment layer. 7. The method of claim 6, wherein the alignment process is performed by irradiating the liquid crystal alignment layer with ultraviolet light having a single polarization component.