JP2000330118A - Multi-domain liquid crystal display device with bump structural part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LCD with a wide visual angle. SOLUTION: The LCD is equipped with a pair of polarizing plates comprising a polarizer 100 and an analyzer 102. A pair of light transmissible substrates 104, 108 is formed between the pair of the polarizing plates. A compensator 106 is formed on the analyzer 102. A bump structural part 110 is formed on the upper side of the substrate. Liquid crystal molecules on the specified bump structural part are given a specified leaning direction so as to be imparted a larger pretilt angle. On at least one out of the pair of substrates the bump structural part is formed so as to impart the pretilt angle to the liquid crystal molecules filled between the pair of glass substrate. In this case, inclined surfaces are given to the bump structural part so as to make both edges of the bump structural part have heights different from each other. Alignment layers are formed on the pair of glass substrates and the bump structural part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display (L).
The present invention relates to a method of making a liquid crystal display (CD), and more particularly to a method of forming a wide viewing angle LCD.

[0002]

2. Description of the Related Art In recent years, personal information assistance devices (personal digital assistants, personal data assistants (PDAs)) and notebooks have made remarkable progress. The requirements for these portable display devices are light weight and low power consumption. As a display device that meets the above requirements and requires high pixel density and quality, a thin film transistor liquid crystal display device (TFT-LC
D: thin film transistor-liquid crystal display)
It has been known. In general, a TFT-LCD has a bottom plate on which a thin film transistor (TFT) and a pixel electrode are formed, and a top plate on which a color filter is formed. Liquid crystal is filled between the top plate and the bottom plate. Each unit pixel is provided with a capacitor,
This capacitor is configured for a TFT that functions as a switching element of a unit pixel. When a data voltage is applied to the TFT, the arrangement of the liquid crystal molecules changes, whereby the optical characteristics change and an image is displayed.

[0003]

Viewing angle and color performance are generally very important for LCD design.
In the LCD, a color filter (CF) plate is used for displaying a color portion of a screen. L
One trend in CD technology is to improve the viewing angle of LCDs. However, LCDs have been applied to large screen products with insufficient viewing angle and contrast ratio. S
ID97 Digest (SID'97 DIGEST) 845 pages-8
On page 48, K. Ohmuro, S. Kataoka, T. Sasaki and
The vertical mode (vertical-align) submitted by Y. Koike
ment-mode) There is a paper on LCD. In this document, a VA-LCD (vertically aligned LC) is achieved by optimizing an optical compensator (compensator compensator) and a cascade mode having a region division structure.
D) is realized. This cascade mode LCD has a wide viewing angle of 70 ° or more, fast response (<25 ms), and a high contrast ratio of 300 or more. However, there are still some problems. For example, the formation of a two-region structure requires a mask rubbing process, which is complex and expensive. In addition, the rubbing process causes a problem of ESD (Electrostatic Discharge) and also generates particles. Moreover, mask rubbing also causes sticking of images.

[0004]

SUMMARY OF THE INVENTION The present invention provides a wide viewing angle LCD.
The purpose is to provide.

According to the present invention, a bump structure (bump stratum) is provided on an LCD.
), the liquid crystal molecules have a pretilt angle
It is also intended to give a (pre-tilted angle).

[0006] The present invention provides a pair of lighters consisting of a polarizer and an analyzer.
polarizers). A pair of light-transmitting substrates is formed between the pair of polarizers. A compensator is formed in the analyzer. A bump structure is formed above the substrate. The liquid crystal molecules formed on the predetermined bump structure have a predetermined leaning direction to give a larger pretilt angle. A bump structure is formed on at least one of the pair of substrates, and a pretilt angle is given to liquid crystal molecules filled between the pair of glass substrates. At this time, the bump structure has an inclined surface (inclined surfac).
es) to make the heights of both ends of the bump structure different. An alignment layer is formed on the pair of glass substrates and the bump structure.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings. The present invention provides a method for increasing the viewing angle of a two-region homeotropic LCD with a compensator. It may be designed with a multi-region structure. In the present invention, a two-region structure is used as an example. In the present invention, a bump structure is employed to achieve the above object.
The detailed process will be described below.

FIG. 1 is a diagram showing a panel structure of a two-region homeotropic LCD having a compensator. This liquid crystal display device comprises a polarizer 100 and an analyzer 10
2 is provided. These polarizers and analyzers 102 are arranged such that the optical axes of the polarizer pair are mutually opposite. That is, when there is nothing in between, the light passing through the polarizer 100 is absorbed by the analyzer 102, and vice versa. Under the polarizer 100, a light-transmitting upper insulating substrate 1 such as glass
04 is formed. One (or more) compensator 106 is formed on the analyzer 102, or a compensator is formed on the pair of polarizers. This compensator 106 is used to reduce light leakage depending on the viewing angle. A lower substrate 108 is disposed on the compensator 104. The lower substrate is made of a light-transmitting material such as glass similar to the upper substrate 104. A translucent conductive layer including a thin film of indium tin oxide (ITO) is disposed on the bottom surface of the upper substrate 104 and the top surface (or the bump structure 110) of the lower substrate 108, respectively. , Orthogonal to each other. A bump structure 11 is provided on at least one of the pair of glass substrates.
0 is formed. In FIG. 1, the bump structure 110 is formed on the lower substrate 108. Bump structure 1
A detailed description of 10 will be given later.

On the surface of the upper substrate 104 and the bump structure 1
An alignment layer 112 is formed on each of the ten surfaces. Generally, the function of these alignment layers is to control the orientation of liquid crystal molecules. The alignment layer 112 is made of polyimide or polyimide acid. Liquid crystal molecules 114 are filled and confined between the upper substrate 104 and the lower substrate 108. The liquid crystal material 114 is preferably composed of negative homeotropic liquid crystal molecules. Negative homeotropic liquid crystal molecules constitute the tandem cell 10 together with the substrate.

The liquid crystal molecules 114 have a nematic alignment, and two domains (domains) 1 within one pixel.
2, 16 exist, and between these regions 12 and 16,
An overlap region 14 is created. Overlapping part 14
Direction of liquid crystal molecules projected on the substrate (azimuth: azimuthal)
Has an angle φ that is not equal to 90 degrees (greater or smaller than 180 degrees) with respect to the tilt direction of the liquid crystal molecules in the regions 12 and 16.

In the ON state, the color dispersion is small because the liquid crystal molecules are in a nematic alignment. The invention is also characterized by the advantage that the gray-scale viewing angles do not flip widely. FIG. 2 is a partial top view of a two-region VA (vertical aligned) mode LCD having a compensator. The tilt angle between the orientations of the liquid crystal molecules in regions 12 and 14 projected to the orientation of the substrate (where
Not equal to 80 degrees (greater or less than 180 degrees). In this embodiment, when no voltage is applied to the electrode (off state), the liquid crystal molecules in each region are oriented almost perpendicular to the surface of the substrate, and the angle is slightly inclined in advance from the normal line of the substrate. The substrate azimuth projection tilt angle between the alignment of the liquid crystal molecules in the two regions does not equal 180 degrees.

Making the liquid crystal molecules arranged in two regions in the regions 12 and 14 and the overlapping region 16 to have a pretilt angle before turning on greatly affects the response time of the liquid crystal molecules. The bump structure 110 according to the present invention has a region division V
It is used to achieve this response characteristic of the A-cell in a further way. FIG. 3 is a side view of the bump structure 110, and FIG. 4 is a diagram showing a three-dimensional image of the bump structure 110. The bump structure 110 can be made of a positive or negative photoresist.
Preferably, the bump structure 110 is shaped such that the top surface of the bump is leaned in a desired direction.
A larger pretilt angle is given to liquid crystal molecules formed above zero. For example, the bump structure 110 is connected to two side surfaces 1.
8, 20 and two inclined surfaces 22.
The side surfaces 18 and 20 of the bump structure have a triangular shape. In a preferred embodiment, the sides 18, 20 are formed at different heights H1 and H2, with H1 being higher than H2, so that the inclined surface 22 of the bump structure 110 can be inclined in a desired direction.
n). That is, the heights of both ends of the bump structure are made different. Each of the inclined surfaces 22 has its end portion on the side surface 1.
8, 20. The oblique angle of the inclined surface 22 with respect to the surface of the substrate is indicated by an angle α.

FIGS. 5A and 5B and FIGS. 6A and 6B show an embodiment of the present invention. The bump structure 110 can be formed on the surface of only one substrate or both substrates. Each figure shows a state in which the liquid crystal molecules formed on the bump structure 110 have a predetermined leaning direction and a larger pretilt angle. Obviously, the bump structure 110 can impart a larger pretilt angle to the liquid crystal molecules. The bump structure 110 may or may not be divided.

The formation of the bump structure 110 is as follows. In the first method, the bump structure 110 is formed using a multi-photomask. Turning to FIG. 7, a first negative photoresist 70 is applied to the substrate. Next, light is applied to the negative photoresist using a first photomask 72 having a first opening 74. This first negative photoresist 70 is developed in a conventional manner. As is known in the art, an exposed portion of the first negative photoresist 70 remains on the substrate. First photomask 72 and first negative photoresist 70
When the distance is increased, the outer shape of the first negative photoresist 70 at the time of development is inclined due to light interference. Next, referring to FIG. 8, a second negative photoresist 76 is formed.
Is applied on the substrate and the first negative photoresist. Next, the second negative photoresist 76 is exposed with a second photomask 78 having a second opening 80. The opening width of the second opening 80 is smaller than that of the first opening 74. Also, the second opening 80 is
Is spatially moved to a position on one side of the negative photoresist 70, and is aligned with the first negative photoresist. Similarly, the outer shape of the second negative photoresist after development is inclined. The above steps may be repeated several times as needed. Next, as shown in FIG. 9, a covering layer 82 is formed on the obtained structure, and a bump structure 110 having an inclined surface 22 is formed.

Further, the outer shape is smoothed using a photolithographic procedure. FIG. 10 shows the shape of the opening of the photomask. The shape of the opening is desirably trapezoidal. With this shape, the side surfaces 18, 2 of the bump structure 110 similar to a trapezoid
A shape of 0 is obtained. FIG. 11 shows a top view of the bump structure.

Using the photomask shown in FIG. 12, a bump structure can be constructed on a substrate. This photo mask is
It is divided into two main parts that are mirror images of each other. The opening of the mask increases in width from the center to the edge. That is,
Width T4 is wider than width T3, which is wider than width T2, which is also wider than T1. Also, the space between two adjacent openings decreases from the center to the edge, that is,
Space M1 is wider than M2, which is wider than M3. Space M3 is wider than M4. In the second method, light interference is introduced. The bump structure can be formed by one exposure.

There is a third method according to the present invention. This method uses one photomask and multiple exposure steps. A plurality of openings are formed in the photomask with equal widths.
The point of this method is to shift the photomask in a direction perpendicular to the normal of the photoresist surface after exposure,
The direction is shown in the drawing. After the multi-exposure, the exposed portion of the photoresist has an outer shape similar to a triangle.
This can be explained as follows.

The method of forming the bump structure includes the following steps: Step (a): exposing the photoresist using a photomask having openings formed; Step (b): exposing the surface of the photoresist. Shifting the photomask by the amount of the spacer along the direction perpendicular to the normal line; Step (c): repeating Step (a) and Step (b) a desired number of times;
(D): developing the photoresist; 1 to 6 are obtained by using the mask shown in FIG.

For clarity, the above method is an example.
To use five exposure steps. However, this
Not limited by limitations, ie any number of times
Exposure step can be performed. 13 to 17
With respect to the photo resist 102,
The first exposure is performed on the target 110. After this step t₁Second
is there. The photomask has a plurality of openings 104. Pho
The photoresist 110 is a positive photoresist, a negative photoresist.
Active photoresist, polyimide or polyamy
mie). Using negative photoresist
Sometimes the results are positive, as is known in the art.
An inverted structure is obtained when a photoresist is used. The present invention
Used positive photoresist as an example
You. Next, the photomask 102 is indicated by an arrow A1.
Shift to the spacer in the direction. Next, the second exposure step
And passed through the opening 104 of the photomask 102.
The positive photoresist 110 is exposed to light. same
The photomask 102 as in the last shift
Shift in space again. This step is t
_TwoComplete in seconds. Therefore, the second exposure is (t_Two-T₁)
Has been done for seconds. Similarly, the third, fourth and fifth exposure
To (t_Three-T_Two), (T_Four-T_Three) And (t_Five
-T_Four) Seconds. In the next step, Figure 15-17
The above procedure is repeated as shown. FIG.
The exposure part of the dist 110 is shown. Exposure of this exposed part
The light depth (de) is de (t_i) = (D / 5) x_iRepresented by
Where d is the thickness of the photoresist 110 and x_iIs i
Total shift space until the end of the second exposure step
Is. FIG. 17 shows the result after development. Most
The final bump structures 110 are adjacent to each other with an opening width of W / 2
Using a mask in which the spacer between the two openings is also W / 2
Complete. If each shift is about W / 10,
The total shift spacer (Δx) is about W / 2. this
Under the conditions, the bump structure is formed with the width W. FIG. 19 and FIG.
FIG. 20 shows that the total shift space is different.
And (Δx) <W / 2 and (Δx)> W / 2,
This is a bump structure portion having another external shape.

There is another approach similar to the last one. FIG.
Moving to 1, the photomask 100a is the same as in the last embodiment. The only difference is that this photomask 100a
Is moved at a constant speed (V) in the direction indicated by the arrow. The moving direction is also parallel to the substrate surface. As a result of FIG.
00a moves at a speed of V = (W / 2) / t. By adjusting the speed of the photomask 100a, FIG.
1, and the shape of the bump structure can be determined as shown in FIG.

While the preferred embodiment of the invention has been illustrated and described, various modifications can be made within the spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display (LCD) according to the present invention.

FIG. 2 is a top view of the liquid crystal display device according to the present invention.

FIG. 3 is a side view of the liquid crystal display device according to the present invention.

FIG. 4 is a view showing a bump structure according to the present invention.

FIG. 5 is a diagram showing an L having a bump structure according to the present invention;
It is a cross section of CD.

FIG. 6 is a perspective view showing an L having a bump structure according to the present invention;
It is a cross section of CD.

FIG. 7 is a cross-sectional view of a substrate showing a step of forming a bump structure according to the first method of the present invention.

FIG. 8 is a cross-sectional view of a substrate showing a step of forming a bump structure according to the first method of the present invention.

FIG. 9 is a cross-sectional view of a substrate showing a step of forming a bump structure according to the first method of the present invention.

FIG. 10 shows a photomask for forming a bump structure according to the first method of the present invention.

FIG. 11 is a top view of the bump structure according to the first embodiment of the present invention.

FIG. 12 is a diagram showing a design of a photomask for forming a bump structure according to the second method of the present invention.

FIG. 13 is a cross-sectional view of a substrate showing a step of forming a bump structure according to a third embodiment of the present invention.

FIG. 14 is a cross-sectional view of a substrate showing a step of forming a bump structure according to a third embodiment of the present invention.

FIG. 15 is a cross-sectional view of a substrate showing a step of forming a bump structure according to a third embodiment of the present invention.

FIG. 16 is a cross-sectional view of a substrate showing a step of forming a bump structure according to a third embodiment of the present invention.

FIG. 17 is a cross-sectional view of a substrate showing a step of forming a bump structure according to a third embodiment of the present invention.

FIG. 18 is a cross-sectional view of a substrate showing a shape of a bump structure formed by an embodiment of the method of the present invention.

FIG. 19 is a cross-sectional view of a substrate showing a shape of a bump structure formed by an embodiment of the method of the present invention.

FIG. 20 is a cross-sectional view of a substrate showing a shape of a bump structure formed by an embodiment of the method of the present invention.

FIG. 21 is a cross-sectional view of a substrate showing a step of forming a bump structure according to a third embodiment of the present invention.

[Explanation of symbols]

100 ... polarizer, 102 ... analyzer, 104 ...
Upper insulating substrate, 106: compensator, 108: lower insulating substrate.

Claims (16)

[Claims] 1. A structure of a liquid crystal display device, comprising: a pair of polarizers; one or more compensators formed on one or both of the pair of polarizers; A pair of light-transmitting substrates formed on the other of the polarizers; and a liquid crystal molecule formed on at least one of the pair of light-transmitting substrates and filled between the pair of light-transmitting substrates. A structure comprising: a bump structure to be provided; and an alignment layer on the bump structure and the pair of light-transmitting substrates. 2. The structure according to claim 1, wherein said bump structure has an inclined surface. 3. The structure according to claim 1, wherein a first height of a first end of the bump structure is different from a second height of a second end of the bump structure. 4. The bump structure having an inclined surface, wherein a first height of a first end of the bump structure is different from a second height of a second end of the bump structure. Item 2. The structure according to Item 1. 5. The bump structure is formed at different heights on its sides such that the bump structure is inclined in a desired direction.
The structure according to claim 1, wherein ends of the inclined surfaces are respectively connected to the side surfaces. 6. The structure according to claim 1, wherein the alignment layer is formed of polyimide or polyimide acid. 7. The structure according to claim 1, wherein the pair of polarizers comprises a polarizer and an analyzer. 8. The structure according to claim 1, wherein the liquid crystal molecules are aligned in a chiral nematic manner, and two regions are formed in one pixel, and an overlap portion is formed between the two regions. 9. The tilt direction (azimuth) of the liquid crystal molecules in the overlapping portion projected on the substrate has an angle greater than or less than 180 degrees with respect to the tilt direction of the liquid crystal molecules in the two regions. A structure according to claim 7. 10. A liquid crystal display device comprising: a pair of polarizers; one or more compensators formed on one or both of the pair of polarizers; a negative compensator and the pair of polarizers; A pair of light-transmitting substrates formed on the other of the polarizers; and a liquid crystal molecule formed on at least one of the pair of light-transmitting substrates and filled between the pair of light-transmitting substrates. A bump structure to be applied, wherein the bump structure comprises an inclined surface, and a first height of a first end of the bump structure is a second height of a second end of the bump structure. A structure comprising: a bump structure having a different height; and an alignment layer above the bump structure and above the pair of light-transmitting substrates. 11. The structure according to claim 10, wherein the bump structure further has a side surface. 12. The structure according to claim 10, wherein the alignment layer is made of polyimide or polyimide acid. 13. The structure according to claim 10, wherein said pair of polarizers comprises a polarizer and an analyzer. 14. The structure according to claim 10, wherein the liquid crystal molecules are aligned in a chiral nematic manner, and two regions are formed in one pixel, and an overlap portion is formed between the two regions. 15. A tilt direction (azimuth) of the liquid crystal molecules in the overlapping portion projected on the substrate has an angle greater than or less than 180 degrees with respect to the tilt direction of the liquid crystal molecules in the two regions. The structure according to claim 14. 16. A photomask for forming a bump structure, comprising two main portions that are mirror images of each other, wherein the width of an opening formed in the photomask increases from a center to an edge, A photomask in which a space between two adjacent openings decreases from the center toward the edge.