KR100319928B1 - Ferroelectric LCD panel and manufacturing method thereof by rubbing orientation of the orientation film - Google Patents

Abstract

The present invention uses a ferroelectric liquid crystal having spontaneous polarization instead of twisted nematic (TN) that responds to the orientation of liquid crystals with conventional dielectric anisotropy. And a method of manufacturing the same by adjusting the rubbing direction (Ferroelectric LCD panel and Manufacturing Method by rubbing orientation of the orientation film). The ferroelectric liquid crystal display panel according to the present invention calculates an angle at which the long axes of the liquid crystal molecules are arranged to the right and left sides based on the rubbing direction of the alignment layer while an electric field is applied in order to improve misalignment of the liquid crystal molecules by the top and bottom alignment layers. Then, by forming the rubbing direction of the alignment film of the upper and lower plates differently by the difference, high contrast and stable orientation are obtained.

Description

Ferroelectric LCD panel and manufacturing method by rubbing orientation of the orientation film

The present invention uses a ferroelectric liquid crystal having spontaneous polarization instead of twisted nematic (TN) that responds to the orientation of liquid crystals with conventional dielectric anisotropy. And a method for manufacturing the same by adjusting the rubbing direction.

1 is a vertical cross-sectional view of a general liquid crystal display panel displaying an image by using an alignment of liquid crystals. As shown, the ferroelectric liquid crystal display panel crosses each other on opposite surfaces of the first and second transparent substrates 1 and 11 and the first and second transparent substrates 1 and 11 which are disposed to face each other. The first and second alignment layers 3 and 3 stacked on each substrate so as to cover the first and second transparent electrodes 2 and 12 and the first and second transparent electrodes 2 and 12 arranged in a stripe direction. 13), ferroelectric liquid crystal 4 filling the inside of the liquid crystal cell between the first and second alignment films 3, 13, two first and second polarizing plates 5, 15 and the first surrounding the outside of the liquid crystal cell And a spacer 6 disposed between the second transparent substrates 1 and 11 to hold the gap of the liquid crystal cell. Here, if a ferroelectric LC having spontaneous polarization is used instead of the conventional twisted nematic (TN) as a liquid crystal material, a response speed of 500 times faster than that of a TN liquid crystal that responds with conventional dielectric anisotropy is possible. In addition, the response of the liquid crystal to the electric field direction of the up and down electrodes 2 and 12 moves in the vertical direction (X or Y direction) with respect to the electric field, so that the viewing angle is close to the CRT. In addition, gray scale display is possible and active driving is possible due to the low driving voltage. This ferroelectric liquid crystal is well described in J. applied Physics., Vol 59. No 7 p. 2355 (1986).

A conventional liquid crystal cell made by parallel and antiparallel rubbing using such a ferroelectric liquid crystal has a long axis of liquid crystal molecules (liquid crystal molecules based on the rubbing direction of the alignment layer, as shown in FIG. 3). ) Is different from the torsion angle β when the liquid crystal molecules are inclined in the left direction on the basis of the torsion angle α when the angle is tilted in the right direction and the rubbing direction of the alignment layer (α ≠ β). Even when the rubbing directions of the upper and lower alignment layers of the liquid crystal display panel are matched by the difference in the torsion angles based on the rubbing direction of the alignment layer, the alignment directions of the liquid crystal molecules by the alignment layers of the upper and lower plates are as shown in FIG. 4. Likewise, they are not matched by rotational symmetry (torsion). Due to such inconsistency, the liquid crystal display panel is found to have a fine image cracking phenomenon, and the contrast is reduced even by natural neglect for a long time.

In addition, the driving mode based on this alignment is completely different from the conventional ferroelectric liquid crystal (FLC) or antiferroelectric liquid crystal (AFLC) in the alignment method and the driving method, which makes it difficult to compare with the conventional method, but the conventional antiferroelectric liquid crystal (AFLC) In a liquid crystal having a phase transition to Iso-Smetic A-Sc * in the alignment method of the present invention, the twist angle is oriented by twisting the twist angle twice in the opposite direction to the Sc * on the SA (Smetic A). Although described in US Patent No. 5,559,620 and Japanese Patent Laid-Open No. 9-304794, it does not solve the above problem.

The present invention has been made to improve the above problems, the long axis of the liquid crystal molecules to the right and left with respect to the rubbing direction of the alignment film in the state in which the electric field is applied in order to improve the misalignment of the liquid crystal molecules by the top and bottom alignment film By calculating the angles to align and forming different rubbing directions of the alignment layers of the upper and lower plates by the difference, it is possible to prevent cracking of the fine phase due to the twist angle of the liquid crystal molecules due to the rubbing direction of the upper and lower alignment layers, and to reduce the contrast. It is an object of the present invention to provide a method for manufacturing a ferroelectric liquid crystal display panel by adjusting an orientation film rubbing direction that can be prevented.

1 is a vertical cross-sectional view of a general liquid crystal display panel displaying an image using an alignment of liquid crystals;

2 is an explanatory diagram showing a cone structure of liquid crystal molecules in a general ferroelectric liquid crystal display panel;

3 is a view showing a cone angle position of a liquid crystal in a general ferroelectric liquid crystal display panel when no full length is applied;

FIG. 4 is a view illustrating cone angle positions of liquid crystal molecules according to a rubbing direction of alignment layers formed on two transparent substrates in the ferroelectric liquid crystal display panel of FIG. 3;

5 is a view showing a liquid crystal alignment state in a state where no electric field is applied;

6 is a view showing a liquid crystal alignment state in a state where an electric field is applied;

FIG. 7 is a view showing cone angle positions of liquid crystal molecules according to a rubbing direction of alignment layers formed on two transparent substrates in the ferroelectric liquid crystal display panel according to the present invention, in which a torsion angle adjustment according to the rubbing direction of liquid crystal molecules is performed;

8 is a graph illustrating electro-optical characteristics of the ferroelectric liquid crystal display panel of FIG. 7.

<Description of the symbols for the main parts of the drawings>

1, 11. First transparent substrate and second transparent substrate 2, 12. First transparent electrode and second transparent electrode

3, 13. First alignment film and second alignment film 4. Ferroelectric liquid crystal

5, 15. First polarizer and second polarizer 6. Spacer

In order to achieve the above object, a ferroelectric liquid crystal display panel by adjusting an alignment layer rubbing direction according to the present invention includes: a first transparent substrate and a second transparent substrate disposed to face each other at regular intervals; First transparent electrodes and second transparent electrodes arranged on strips in directions crossing each other on opposite surfaces of the first transparent substrate and the second transparent substrate; A first alignment layer and a second alignment layer respectively coated on opposing surfaces of the first transparent substrate and the second transparent substrate on which the first transparent electrodes and the second transparent electrodes are formed; A ferroelectric liquid crystal injected between the first alignment layer and the second alignment layer; Spacers disposed between the first alignment layer and the second alignment layer to maintain a space in which the ferroelectric liquid crystal is injected between the first transparent substrate and the second transparent substrate; And a first polarizing plate and a second polarizing plate disposed on the outer side of the first transparent substrate and the second transparent substrate, respectively, the ferroelectric liquid crystal display panel comprising: the liquid crystal in the rubbing direction of the first alignment layer and the second alignment layer; In order for the left and right optical axes according to the arrangement of the molecules to the left or the right side to be coincident with each other, when the electric field is formed between the first transparent electrode and the second transparent electrode, the left-side twist of the liquid crystal molecules in the rubbing direction when they are oriented left When the angle is aligned with the right side, the difference between the right twist angle between the liquid crystal molecules and the rubbing direction is obtained, and the rubbing direction of the first alignment layer and the rubbing direction of the second alignment layer are twisted by the difference angle.

In the present invention, the ferroelectric liquid crystal is preferably a ferroelectric liquid crystal having a phase transition of Ch * -Sc *.

In addition, in order to achieve the above object, a method of manufacturing a ferroelectric liquid crystal display panel by adjusting an alignment film rubbing direction according to the present invention includes: a first transparent substrate and a second transparent substrate disposed to face each other at regular intervals; First transparent electrodes and second transparent electrodes disposed on the opposite surfaces of the first transparent substrate and the second transparent substrate, respectively, on a stripe in a direction crossing each other; A first alignment layer and a second alignment layer respectively coated on opposing surfaces of the first transparent substrate and the second transparent substrate on which the first transparent electrodes and the second transparent electrodes are formed; A ferroelectric liquid crystal injected between the first alignment layer and the second alignment layer; Spacers disposed between the first alignment layer and the second alignment layer to maintain a space in which the ferroelectric liquid crystal is injected between the first transparent substrate and the second transparent substrate; And a first polarizing plate and a second polarizing plate respectively disposed outside the first transparent substrate and the second transparent substrate, wherein the ferroelectric liquid crystal display panel comprises: (a) a liquid crystal with respect to a rubbing direction of the alignment layer; Obtaining a difference between the torsion angle when the long axis of the molecule is arranged to the left and the torsion angle when the major axis of the liquid crystal molecule is arranged to the right with respect to the rubbing direction of the alignment layer; And (b) applying the first alignment layer and the second alignment layer on the first transparent substrate and the second transparent substrate on which the first transparent electrode and the second transparent electrode are formed, respectively, and then apply the difference between the left and right twist angles. Rubbing the rubbing directions of the first and second alignment layers to be different; And (c) combining the first transparent substrate and the second transparent substrate such that the rubbing direction of the first alignment layer and the rubbing direction of the second alignment layer are shifted by the difference in the twist angle such that the alignment direction of the liquid crystal molecules coincides with the optical axis. And injecting and orientating the ferroelectric liquid crystal.

In the present invention, the step (a) includes (a-1) a sub-step of making a prototype of the ferroelectric liquid crystal display panel for calculating the torsional angle difference; (A-2) applying a predetermined voltage to form an electric field between the first and second electrodes of the prototype; (A-3) a substep of obtaining an angle at which the long axis of the liquid crystal molecules is arranged to the left with respect to the rubbing direction of the alignment layer while the predetermined voltage is applied; (A-4) a substep of obtaining an angle at which the major axes of the liquid crystal molecules are arranged to the right with respect to the rubbing direction of the alignment layer while the predetermined voltage is applied; And (a-5) calculating a difference of angles obtained in (a-3) substeps and (a-4) substeps so that the alignment direction of the liquid crystal molecules coincides with the optical axis. In the step (c), the liquid crystal injection formed by combining the first transparent substrate and the second transparent substrate such that the rubbing direction of the first alignment layer and the rubbing direction of the second alignment layer are shifted by a difference in the torsion angle. Injecting the ferroelectric liquid crystal mixture having spontaneous polarization at 120 ° C. into the space; (C-2) by cooling at a cooling rate of 1 ° C. per minute while applying a temperature of 2 ° C. higher than T _NC of the ferroelectric liquid crystal and a DC voltage between 2V and 3V between the first transparent electrode and the second transparent electrode. And sub-aligning the ferroelectric liquid crystal so that the optical axis due to the alignment of the liquid crystal molecules by the first alignment layer and the optical axis due to the alignment of the liquid crystal molecules by the second alignment layer are in the same direction.

Hereinafter, a method of manufacturing a ferroelectric liquid crystal display panel by adjusting an alignment film rubbing direction according to the present invention will be described in detail with reference to the drawings.

The method of manufacturing a ferroelectric liquid crystal display panel by adjusting the orientation direction of the alignment film according to the present invention uses a completely different principle to maintain alignment in a twisted state in a nematic state. In particular, as shown in FIG. 3, the fact that the left and right twist angles α and β of the liquid crystal molecules based on the rubbing direction of the alignment layer are different from each other is not easily observed or conceived, and as shown in FIG. When the rubbing directions of the first alignment layer and the second alignment layer respectively applied on the transparent substrate and the second transparent substrate coincide with each other, there is a mismatch in the left and right twist angles of the liquid crystal molecules by the first alignment layer and the second alignment layer. Based on this fact, the angles of the rubbing directions of the first alignment layer and the second alignment layer are misaligned, thereby correcting a mismatch between the left and right twist angles of the liquid crystal molecules according to the rubbing directions of the two alignment layers.

5 is a diagram illustrating a liquid crystal alignment state in a state where no electric field is applied, and FIG. 6 is a diagram illustrating a liquid crystal alignment state in a state where an electric field is applied. In the method of manufacturing the ferroelectric liquid crystal display panel by adjusting the alignment film rubbing direction according to the present invention, as shown in FIG. 4, the twist angle of the upper and lower substrates is determined from the angles α and β deviating from the optical axis of the liquid crystal with respect to the rubbing direction of the alignment film. By calculating the difference, the cone angle of the liquid crystal is calculated, and when producing a cell rubbing antiparallel from the cone angle, the extension direction of the optical axis of the liquid crystal is adjusted from β-α to the direction as shown in FIG. A high contrast liquid crystal cell can be obtained with (?-? =?). In addition, cells rubbed in parallel can also obtain the same result by the same principle.

The basic structure of the ferroelectric liquid crystal display panel by adjusting the rubbing direction of the alignment layer according to the present invention is shown in FIG. 1, and a method of manufacturing the same is performed by using a photoresist as a spacer on an electrode of one transparent substrate. The 1.6 μm spacer is attached to the substrate in a dot shape. Polyimide aligning agent (Nissan Chemical RN1199) was spin coated on the transparent substrate with spacers and baked for 5 minutes at 80 ° C, followed by rubbing and refired at 180 ° C for 1 hour. On the transparent electrode of the other transparent substrate, the polyimide aligning agent is spin coated, calcined at 80 ° C., rubbed, and then refired at 180 ° C. for 1 hour. An empty cell for vacuum injection is made by using an electrode A ferroelectric liquid crystal mixture having spontaneous polarization at 120 ° C. is injected into a completed vacuum cell, and a DC voltage of 2 to 3 volt is applied at a temperature higher than 2 ° C. of the liquid crystal TNC. The orientation is performed by cooling at a cooling rate of 1 ° C. per minute in. The alignment is such that the optical axes of the upper and lower transparent substrates are in the same direction as shown in Fig. 7, and the optical axis of the polarizer is the liquid crystal cell. It was consistent with the optical axis, to complete the cell as placing a polarizer (analyzer) on the other side of the polarizing plate.

Example 1

The cell of this example was attached to a substrate by using a photoresist as a spacer on one electrode and making the spacer a dot. A polyimide aligning agent (Nissan Chemical RN1199) was spin coated on the substrate with the spacer and baked at 80 ° C. for 5 minutes, and then calcined at 180 ° C. for 1 hour and rubbed. Polyimide was spin-coated on the other transparent electrode, calcined at 80 ° C., and then calcined at 180 ° C. for 1 hour, and a blank cell for vacuum injection was made using the upper and lower transparent electrodes. In order to maintain the cell gap, the spacer gap was maintained at 1.6 μm, and the thickness of the finished cell was maintained at 1.6 to 1.8 μm. -Sc *, T _NC 64 ℃) after injection was an orientation to a DC voltage per 1 ℃ cooled to a cooling rate applied in a state in 3volt T _NC 64 ℃ than 2 ℃ high 66 ℃. the experimental results of the above liquid crystal And In the case of using the aromatic film, the α and β values in Fig. 3 were 1.5 ° and 3.5 °, respectively, so that the rubbing directions of the two alignment films were shifted by about 2 ° to form a liquid crystal display panel in which the optical axes along the rubbing direction were matched. The polarizing plate was attached to the panel so that the optical axis of the polarizing plate and the optical axis (rubbing direction) of the liquid crystal were aligned, and the optical axis was perpendicular to the surface of the opposite electrode to complete the liquid crystal display panel. As a result of measuring the characteristics, the voltage-transmission curve showed gray scale as shown in Fig. 8. The response speed was 250 μsec and the contrast was 200 or more. , Left and right were respectively 150 ° or more.

Example 2

In Example 1, the cell was fabricated in the same manner, and the orientation and electro-optic characteristics of the cell fabricated with the rubbing direction torsion angle of the upper and lower substrates, γ as 0 °, + 1 °, -1 °, and -2 °, respectively The results were shown in Table 1 below.

Orientation and Contrast by Up and Down Rubbing Angle Torsion Torsion angle Orientation Contrast 0 ° Good, fine defect 150 ~ 200: 1 -1 ° Bad, striped defect 70--90: 1 + 1 ° Good 180 ~ 200: 1 -2 ° Bad, twisted defect 80: 1 or less + 2 ° Very good 500: 1 or more -4 ° Very bad 50: 1 or less + 4 ° Slightly defective 100-120: 1

Example 3

In Example 2, when the rubbing angle twist angle was between + 2 ° and + 1 °, an alignment state oriented to one side was obtained as shown in FIG. 6 without applying the electric field at the time of alignment of the liquid crystal.

As described above, in the ferroelectric liquid crystal display panel according to the present invention, in order to improve misalignment of liquid crystal molecules by the top and bottom alignment layers, the long axes of the liquid crystal molecules are shifted to the right and left sides based on the rubbing direction of the alignment layer while an electric field is applied. High contrast and stable orientation can be obtained by calculating the angle to arrange | positioning and forming the rubbing direction of the oriented film of an upper and lower plate differently by the difference.

Claims (5)

A first transparent substrate and a second transparent substrate disposed to face each other at regular intervals; First transparent electrodes and second transparent electrodes disposed on the opposite surfaces of the first transparent substrate and the second transparent substrate, respectively, on a stripe in a direction crossing each other; A first alignment layer and a second alignment layer respectively coated on opposing surfaces of the first transparent substrate and the second transparent substrate on which the first transparent electrodes and the second transparent electrodes are formed; A ferroelectric liquid crystal injected between the first alignment layer and the second alignment layer; Spacers disposed between the first alignment layer and the second alignment layer to maintain a space in which the ferroelectric liquid crystal is injected between the first transparent substrate and the second transparent substrate; And A first polarizing plate and a second polarizing plate respectively disposed outside the first transparent substrate and the second transparent substrate; In the ferroelectric liquid crystal display panel provided, An electric field is formed between the first transparent electrode and the second transparent electrode so that the left and right optical axes of the liquid crystal molecules aligned to the left or the right according to the rubbing directions of the first and second alignment layers are coincident with each other. When the liquid crystal molecules are aligned to the left when the liquid crystal molecules are aligned to the rubbing direction and the right torsion angle when the liquid crystal molecules are aligned to the right, the difference in the rubbing direction of the first alignment layer and the second direction A ferroelectric liquid crystal display panel, which is disposed so that the rubbing direction of the alignment layer is twisted. The method of claim 1, The ferroelectric liquid crystal panel is a ferroelectric liquid crystal display panel, characterized in that the ferroelectric liquid crystal having a phase transition of Ch *-Sc *. A first transparent substrate and a second transparent substrate disposed to face each other at regular intervals; First transparent electrodes and second transparent electrodes disposed on strips in directions crossing each other on opposite surfaces of the first transparent substrate and the second transparent substrate; A first alignment layer and a second alignment layer respectively coated on opposing surfaces of the first transparent substrate and the second transparent substrate on which the first transparent electrodes and the second transparent electrodes are formed; A ferroelectric liquid crystal injected between the first alignment layer and the second alignment layer; Spacers disposed between the first alignment layer and the second alignment layer to maintain a space in which the ferroelectric liquid crystal is injected between the first transparent substrate and the second transparent substrate; And In the method of manufacturing a ferroelectric liquid crystal display panel comprising a first polarizing plate and a second polarizing plate disposed on the outer side of the first transparent substrate and the second transparent substrate, respectively, (A) obtaining a difference in the torsion angle when the major axis of the liquid crystal molecules are arranged to the left with respect to the rubbing direction of the alignment layer and the difference in the torsion angle when the major axis of the liquid crystal molecule is arranged to the right with respect to the rubbing direction of the alignment layer; And (B) coating the first alignment layer and the second alignment layer on the first transparent substrate and the second transparent substrate, respectively, on which the first transparent electrode and the second transparent electrode are formed, and then apply the difference between the right and left twist angles. Rubbing the rubbing directions of the first alignment layer and the second alignment layer to be different; And (C) combining the first transparent substrate and the second transparent substrate such that the rubbing direction of the first alignment layer and the rubbing direction of the second alignment layer are shifted by the difference of the torsion angle such that the alignment direction of the liquid crystal molecules coincides with the optical axis. Injecting and orienting the ferroelectric liquid crystal; An alignment film manufacturing method of a ferroelectric liquid crystal display panel comprising a. The method of claim 3, Step (a), (A-1) a sub-step of making a prototype of the ferroelectric liquid crystal display panel for calculating the twist angle difference; (A-2) applying a predetermined voltage to form an electric field between the first and second electrodes of the prototype; (A-3) a substep of obtaining an angle at which the long axis of the liquid crystal molecules is arranged to the left with respect to the rubbing direction of the alignment layer while the predetermined voltage is applied; (A-4) a substep of obtaining an angle at which the major axes of the liquid crystal molecules are arranged to the right with respect to the rubbing direction of the alignment layer while the predetermined voltage is applied; And (A-5) a substep of calculating a difference between the angles obtained in (A-3) substeps and (A-4) substeps so that the alignment direction of the liquid crystal molecules coincides with the optical axis; An alignment film manufacturing method of a ferroelectric liquid crystal display panel comprising a. The method of claim 3, The (c) step, (C-1) spontaneously at 120 ° C. in a liquid crystal injection space formed by combining the first transparent substrate and the second transparent substrate such that the rubbing direction of the first alignment layer and the rubbing direction of the second alignment layer are shifted by a difference in the twist angle. A sub-step of injecting the ferroelectric liquid crystal mixture having polarization; (C-2) by cooling at a cooling rate of 1 ° C. per minute while applying a temperature of 2 ° C. higher than T _NC of the ferroelectric liquid crystal and a DC voltage between 2V and 3V between the first transparent electrode and the second transparent electrode. A sub-step of aligning the ferroelectric liquid crystal so that the optical axis due to the alignment of the liquid crystal molecules by the first alignment film and the optical axis due to the alignment of the liquid crystal molecules by the second alignment film are in the same direction; An alignment film manufacturing method of a ferroelectric liquid crystal display panel comprising a.