CN114063337B

CN114063337B - Epitaxial alignment liquid crystal display

Info

Publication number: CN114063337B
Application number: CN202011106830.4A
Authority: CN
Inventors: 马耀东; 马凯
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-08-07
Filing date: 2020-10-16
Publication date: 2024-01-26
Anticipated expiration: 2040-10-16
Also published as: CN114063337A

Abstract

The present invention relates to a liquid crystal display, and more particularly to an Epitaxial Alignment Liquid Crystal Display (EALCD). The ultra-fast response time of the half-friction half-wave configuration enables the display to be addressed at the high frame rate of the next generation of information terminals.

Description

Epitaxial alignment liquid crystal display

Technical Field

Background

In 1968, williams from American Radio Company (RCA) found that nematic liquid crystals formed domain structures and had a light scattering phenomenon in the electric field. Heilmeir then developed a dynamic scattering mode, the first liquid crystal display in the world. Helfrich, schadt and Fergason have invented a Twisted Nematic (TN) in 1971, respectively. The combination of TN waveguide effect and integrated circuit forms a display device (TN-LCD), which opens up a wide prospect for the application of liquid crystal. Since then, the prior art liquid crystal display has made a breakthrough due to the development of large scale integrated circuits and the progress of liquid crystal materials. In 1983 to 1985, scheffer et al have successively proposed Super Twisted Nematic (STN) modes and adopted again AMLCD modes proposed in 1972 by Brody of West House corporation (Western House). Conventional TN-LCD technology has been shifted to STN-LCD and TFT-LCD technologies. Although the STN scan line can reach VGA level, there are some disadvantages such as response speed, viewing angle, and gray scale when the temperature increases. Therefore, active matrix displays are preferred for large panel, high information content, high color quality displays. TFT-LCDs have been widely used in direct-view televisions, large screen projection televisions, computer monitors, and certain military instrument displays. It is believed that TFT-LCD technology will have wider application.

Active matrix structures are of two types: the first is a Metal Oxide Semiconductor (MOS) on a silicon wafer as a substrate. The second is a Thin Film Transistor (TFT) fabricated on a glass substrate.

Monocrystalline silicon has limitations in its display size as a substrate due to many problems at the junctions of the various parts of the display unit or module assembly. Thus, the second TFT active matrix is promising. Early TFT displays were typically TFT-TN mode. The TFT substrate includes a compound semiconductor such as polysilicon and amorphous silicon.

In the past decade, for large panel displays (e.g., monitors and televisions), in-plane switching (IPS) mode and Vertical Alignment (VA) mode have been increasingly popular in the information industry due to their larger viewing angle and contrast than TFT-TN displays. However, the response time of both IPS and VA displays is not as fast as that of TN displays, although the latter is still not fast enough for the high frame rate display terminals required for 5G communication technology.

Disclosure of Invention

The invention mainly aims to realize an ultrafast TFT epitaxial orientation liquid crystal display.

Another object of the invention is to produce an indefinite-domain half-wave nematic liquid crystal display.

Another object of the present invention is to employ one side parallel rubbing layer and the other side parallel non-rubbing layer on the substrate of the liquid crystal display.

It is a further object of the invention to make a TFT addressed semi-blue band liquid crystal display.

Another object of the present invention is to suppress dispersion of liquid crystal by utilizing a twisted waveguide effect to achieve excellent color reproduction.

It is a further object of the invention to obtain a full color display using a color filter array.

It is still another object of the present invention to create a liquid crystal display having an excellent viewing angle.

Another object of the present invention is to achieve excellent fast switching speeds.

The final object of the invention is to realize an epitaxial alignment half-rubbing half-wave liquid crystal display.

Drawings

Fig. 1 shows a schematic structure of an Epitaxial Alignment Liquid Crystal Display (EALCD).

Fig. 2 shows a schematic reverse structure of the EALCD.

Fig. 3 shows the electro-optic curve of the EALCD.

Fig. 4 shows the electro-optic response time curve of the EALCD.

Fig. 5 shows the view angle of the EALCD.

Fig. 6 shows the viewing angle of the inverted EALCD.

Fig. 7 shows a photograph of the color representation of the EALCD.

Fig. 8 shows a grayscale photograph of the EALCD.

Fig. 9 shows a photograph of a map of the EALCD.

Fig. 10a shows a normal viewing picture of the EALCD.

Fig. 10b shows a 120 degree viewing angle of the EALCD.

Detailed Description

Referring first to fig. 1, an epitaxially oriented liquid crystal display structure is shown. The liquid crystal layer 130 includes at least one nematic parallel alignment domain 134 and at least one twisted nematic domain 133 in an off-field (field-off) region, which are located between the transparent front color filter substrate 111 having the transparent common electrode 113 and the transparent rear substrate 112 having the TFT active matrix electrode 114, to form a cell (cell) structure having a thickness in the range of 1-10 micrometers, more preferably in the range of 2.0-3.0 micrometers. The rubbed polyimide parallel alignment layer 131 deposited on the TFT layer with the TFT active matrix electrode 114 not only provides uniform molecular alignment for the liquid crystal, but also provides an optical index of the display cell structure to induce epitaxial liquid crystal alignment. On the other hand, the non-rubbed polyimide alignment layer 132 disposed on the color filter overcoat layer of the transparent common electrode 113 provides random alignment of liquid crystal molecules in indefinite two dimensions to promote liquid crystal epitaxy. The optical birefringence Δn of the nematic liquid crystal is predetermined so that the retardation ratio r=Δnd of the liquid crystal layer 130 satisfies the half-wave plate for visible light in the blue wavelength (for example, λ=450 nm). Where "d" is the cell gap (cell thickness). To obtain an epitaxial domain structure, a small amount of cholesteric twist material in the range of 0.5 to 1.0wt% is doped in the nematic liquid crystal.

As shown in fig. 1, the first liquid crystal layer adjacent to the rubbing alignment layer 131 (i.e., the start point of the epitaxial structure) is aligned in a uniform parallel manner, and the last liquid crystal layer adjacent to the non-rubbing alignment layer 132 exhibits an indefinite two-dimensional arrangement according to the twisting power of the liquid crystal and the retardation rate of the liquid crystal layer 130.

The optical axis of the linear polarizer 121 attached to the TFT substrate is 45 ° with respect to the rubbing direction of the alignment layer 131. Meanwhile, the optical axis of the linear polarizer 120 laminated on the color filter substrate is at 90 ° with respect to the linear polarizer 121. A conventional backlight illumination panel 140 is positioned at the bottom of the display cell structure.

When the backlight beam 141 from the illumination panel 140 passes through the linear polarizer 121, more than 40% of it will be converted to linear polarization. It will then modulate through the display cell structure in the cut-off region and be offset by about 90 ° by the combination of the 180 degree phase change effect of domain 133 and the light guiding effect of twisted domain 133, ultimately exiting cell structure 110 as polarized light 142. The polarized light will pass through the pre-polarizer 120 as light 144 without significant attenuation. On the other hand, when the backlight beam 141 from the illumination panel 140 passes through the linear polarizer 121, half thereof will be theoretically converted into linear polarization. It will then penetrate the display cell structure in the on-region without substantially changing its polarization state and finally exit the cell structure 110 as polarized light 143. Such light components will be completely blocked by the pre-polarizer 120.

As a result, the viewer 150 will see a full-color display image.

Turning now to fig. 2, an epitaxially oriented liquid crystal display structure is shown. The liquid crystal layer 130 includes at least one nematic parallel alignment domain 134 and at least one twisted nematic domain 233 in an outer field, which are positioned between the transparent front color filter substrate 111 having the transparent common electrode 113 and the transparent rear substrate 112 having the TFT active matrix electrode 114 to form the cell structure 110 having a thickness in a range of 1-10 micrometers, more preferably in a range of 2.0-3.0 micrometers. The rubbed polyimide parallel alignment layer 232 deposited on the color filter substrate 111 not only provides uniform molecular alignment for the liquid crystal, but also provides an optical index of the display cell structure. On the other hand, the non-rubbed polyimide alignment layer 231 with the TFT active matrix electrode 114 thereon provides an indefinite two-dimensional random alignment of liquid crystal molecules. The optical birefringence Δn of the nematic liquid crystal is predetermined so that the retardation ratio r=Δnd of the liquid crystal layer 130 satisfies the half-wave plate for visible light in the blue wavelength (for example, λ=450 nm). Where "d" is the cell gap. To obtain an epitaxial domain structure, a small amount of cholesteric twist material in the range of 0.5 to 1.0wt% is doped in the nematic liquid crystal.

As shown in fig. 2, the first liquid crystal layer adjacent to the rubbing alignment layer 232 (i.e., the start point of the epitaxial structure) is aligned in a uniform parallel manner, and the last liquid crystal layer adjacent to the non-rubbing alignment layer 231 exhibits an indefinite two-dimensional arrangement according to the twisting power of the liquid crystal and the retardation rate of the liquid crystal layer 130.

The optical axis of the linear polarizer 120 attached to the color filter substrate is at 45 ° with respect to the rubbing direction of the alignment layer 232. Meanwhile, the optical axis of the linear polarizer 121 stacked on the TFT substrate is at 90 ° with respect to the linear polarizer 120. A conventional backlight illumination panel 140 is positioned at the bottom of the display cell structure.

When the backlight beam 141 from the illumination panel 140 passes through the linear polarizer 121, more than 40% of it will be converted to linear polarization. It will then modulate through the display cell structure in the cut-off region and be offset by about 90 ° by the combination of the 180 degree phase change effect of domain 133 and the light guiding effect of twisted domain 233, ultimately exiting cell structure 110 as polarized light 142. The polarized light will pass through the pre-polarizer 120 as light 144 without significant attenuation. On the other hand, when the backlight beam 141 from the illumination panel 140 passes through the linear polarizer 121, half thereof will be theoretically converted into linear polarization. It will then penetrate the display cell structure in the on-region without substantially changing its polarization state and finally exit the cell structure 110 as polarized light 143. Such light components will be completely blocked by the pre-polarizer 120.

As a result, the viewer 150 will see a full color image from the display.

Example 1

EALCD was manufactured in TFT LCD production line and optically tested in optical laboratories. The display used was a full-color amorphous silicon TFT panel with a diagonal of 4.6 inches and a resolution of 640x 150. Table 1 discloses the main specifications of the display structure:

TABLE 1

Project	Specification of specification	Unit (B)
			Glass master size	400(H)x 500(V)x 1.0(D)	mm
Panel contour dimension	120.9(H)35.7(V)1.0(D)	mm
			Active screen size	115.2(H)*27.0(V)	mm
Resolution ratio	640(RGB)*150	Number of pixels
			Pixel driving element	Amorphous silicon TFT	-
Pixel size	60*180	Micron meter
			Pixel arrangement	RGB stripe	-

Rubbed parallel polyimide alignment layers are deposited on the color filter substrate with the rubbing direction perpendicular to the rectangular display (0 °). The optical orientations of the front linear polarizer and the rear linear polarizer were +45° and-45 °, respectively, with respect to the rubbing direction. As shown in fig. 2, the rubbing surface is a starting point of the epitaxial alignment liquid crystal display, in which the rear optical axis and the front optical axis of the display unit are predetermined by the rubbing direction. The non-rubbed polyimide deposited on the TFT substrate not only simplifies the production process but also improves the yield, providing an indefinite surface for the liquid crystal molecules. The epitaxial orientation is mainly governed by the rubbing direction and the distorting ability of the cholesteric material. In order to obtain achromatic display in the off state, the retardation rate should be precisely controlled during production; thus, cell gap uniformity is a critical issue for EALCD. Table 2 presents the measurement of the empty cell gap:

TABLE 2

Surprisingly, the uniformity of the cell gap at the 2.5 micron level is unexpectedly high, and the non-rubbing treatment on the TFT substrate achieves high yields. Further development schemes have been developed to achieve better optical performance using 2.0 microfabrication processes.

The uniformity of cell thickness allows the applicant to select nematic liquid crystal formulations. The liquid crystal has positive dielectric anisotropy and a suitable optical birefringence to meet the above-specified "r=Δnd" requirement. The invention provides a novel liquid crystal preparation with a polyfluoro functional group. The chemical structures of the series of compounds are shown in Table 3, and are characterized by low rotational viscosity, large dielectric anisotropy, good intersolubility and stability. As chiral dopant material, 0.5% S-811 was added to the nematic mixture. Note that the weight percentage of the liquid crystal may vary according to the electro-optic requirements of the EALCD.

TABLE 3 Table 3

Table 4 describes the properties of the liquid crystal mixtures with fast response times and low driving voltages.

TABLE 4 Table 4

The resulting retardation ratio was r=0.0975x2.54=2.43 μm or 243nm, which satisfies the half-wave plate of blue visible light, 243×2=486 nm. In order to obtain achromatic performance suppressing the ECB effect, the natural twist angle of the liquid crystal is designed to be about 15 °, as shown in fig. 2, which is attached to the non-rubbing alignment layer and is attributed to the twist domain 233. The combination of liquid crystal domains 134 and 233 developed by the half rubbing unit forms an epitaxial display structure, in other words, forms a controllable achromatic half wave plate, which is substantially independent of chromatic dispersion in the visible band. As shown in the following drawings, the novel EALCD has an ultra-fast switching speed, a large viewing angle, a high contrast ratio, various gray scales, and excellent color reproducibility.

Turning now to fig. 3, the electro-optic curves of an EALCD based on example 1 are shown. The curve is substantially achromatic at visible wavelengths. It should be readily appreciated that the drive voltages are similar to and compatible with those of conventional TN displays, and thus the currently available TN display driver ICs can be readily derived for use in the novel display. The normal white light electro-optic (EO) curve also shows unlimited gray-scale capability, as long as a suitable "gamma" linearity correction circuit similar to a TN display is introduced.

Turning now to fig. 4, a graph of the photo-response time of an EALCD based on example 1 is shown. It is apparent that the response time of the EALCD in the present invention is many times faster than that of the conventional TN, IPS, VA display. The total response time is 3.69ms including a rise time 2.414ms and a decay time of 1.276ms, which results in a frame rate of the display up to 270 frames per second. More importantly, by modifying the display cell structure and liquid crystal formulation, the response time can be further reduced without the physical limitations involved in other display modes. Laboratories have implemented optical shutters (shutters) with response times on the order of sub-milliseconds. The ultra-fast response time of EALCDs will enable many potential applications to be developed in the foreseeable future.

Turning now to fig. 5 and 6, the view angles of the EALCDs shown in fig. 1 and 2, respectively, are shown. It can be noted that the former has a larger viewing angle than the latter because the pre-non-rubbing alignment layer exhibits two-dimensional randomness to the liquid crystal domains. It should be readily understood in the art that the viewing angle can be further enlarged by employing an additional light compensation film (e.g., a negative C-plate), as with other liquid crystal displays.

Turning now to fig. 7, a photograph of a color representation of an EALCD based on example 1 is shown.

Turning now to fig. 8, a picture representing the gray scale of the EALCD based on example 1 is shown.

Turning now to fig. 9, a DVD map based on the EALCD of example 1 is shown.

Turning now to fig. 10a, a picture of a normal viewing image based on the EALCD of example 1 is shown.

Turning now to fig. 10b, a picture showing an image at a 120 degree viewing angle based on the EALCD of example 1 is shown.

In summary, the invention has the following characteristics:

1. the response speed has now reached 1 millisecond. By fine-tuning the display structure and the liquid crystal formulation, it is expected that 500 μs of display can be further realized in the near future. The display mode is superior to all the current LCD display modes (TN, IPS, VA, etc.), and is an ideal portable display product of 5G, 6G, etc. communication systems.

2. Compared with an organic light emitting display (AMOLE), the invention has the advantages of the traditional LCD display on the premise of the same response speed level, without the phenomenon of screen burning or screen flashing, and particularly the service life of the LCD display is not influenced by the half-life decay time of the former, so that the service life of the LCD display can reach or exceed 20 years.

3. Another feature of this display technology is its optical transparency: compared with various existing display technologies, the light transmittance and pixel density are doubled. Is the best display choice for interactive displays for teleconferencing, teaching, entertainment, video games, etc.

4. In terms of industrialization and economic feasibility, the production process of the display is basically matched with the existing TFT manufacturing process, part of the processes are simplified, the manufacturing precision is improved, and the cost is reduced. Mass production has been successfully achieved.

5. Under the guidance of a new epitaxial model, the invention breaks through the normal concept of the traditional liquid crystal display theoretical model. Some research projects are still underway to further improve the performance of rich displays.

Therefore, EALCD has important scientific value and will become an emerging new generation display technology.

Claims

1. An epitaxially oriented liquid crystal display comprising:

a. a front transparent conductive substrate having a non-rubbing alignment layer; and

b. a first polarizer layer; and

c. a liquid crystal layer having at least one parallel nematic domain region and at least one twist domain; and

d. a rear active matrix substrate having a rubbing alignment layer; and

e. a second polarizer layer; and

f. a back-lit panel is provided with a back-lit,

wherein the first polarizer is at a predetermined angle to the second polarizer, and the second polarizer maintains a predetermined angle to the rubbing direction of the rubbing alignment layer; wherein the backlight passes through the first polarizer, the liquid crystal parallel domains and the twist domains, and the second polarizer to form an optical on state; wherein backlight passing through the first polarizer and the homeotropic region is absorbed by the second polarizer, forming an optical cut-off state, such that a viewer will observe a display image.

2. The epitaxially oriented liquid crystal display of claim 1, wherein an angle between the first polarizer and the second polarizer is 90 degrees.

3. The epitaxial orientation liquid crystal display of claim 1, wherein an angle between the second polarizer and the rubbing direction is 45 degrees.

4. The epitaxially oriented liquid crystal display of claim 1, wherein the display is an indefinite-domain half-wave nematic liquid crystal display.

5. The epitaxial orientation liquid crystal display of claim 1 wherein the display has a twisted waveguide effect to suppress dispersion.

6. The epitaxial orientation liquid crystal display of claim 1 wherein the display further comprises a color filter array to obtain full color display.

7. The epitaxially oriented liquid crystal display of claim 1, wherein the display is an ultrathin cell structure having a thickness in the range of 1.0 to 10 microns.

8. The epitaxial orientation liquid crystal display of claim 1, wherein the display has a fast switching speed in the range of 1 to 4 milliseconds.

9. The epitaxial alignment liquid crystal display of claim 1, wherein the display is a half-rubbing half-wave display.

10. An epitaxially oriented liquid crystal display comprising:

a. a front transparent conductive substrate having a rubbing alignment layer; and

b. a first polarizer layer; and

d. a rear active matrix substrate having a non-rubbing alignment layer; and

e. a second polarizer layer; and

f. a back-lit panel is provided with a back-lit,

wherein the first polarizer forms a predetermined angle with the second polarizer and the rubbing direction of the rubbing alignment layer; wherein the backlight passes through the first polarizer, the liquid crystal parallel domains and the twist domains, and the second polarizer to form an optical on state; wherein backlight passing through the first polarizer and the homeotropic region is absorbed by the second polarizer, forming an optical cut-off state, such that a viewer will observe a display image.

11. The epitaxially oriented liquid crystal display of claim 10, wherein the non-rubbing alignment layer is located on a viewer side of the display.

12. The epitaxial alignment liquid crystal display according to claim 10, wherein a retardation ratio "r=Δnd" of the liquid crystal is in a range of 200nm to 250 nm.

13. The epitaxially oriented liquid crystal display of claim 10, wherein the twist-domains are chiral nematic liquid crystals, wherein the chiral material is in the range of 0.5% to 1.0%.

14. An epitaxially oriented liquid crystal display comprising:

b. a first polarizer layer; and

d. a rear conductive substrate having a non-rubbed alignment layer; and

e. a second polarizer layer is provided on the first polarizer layer,

wherein the first polarizer forms a predetermined angle with the second polarizer and the rubbing direction of the rubbing alignment layer; wherein light passes through the first polarizer, the liquid crystal parallel domains and the twist domains, and the second polarizer to form an optical on state; wherein light passing through the first polarizer and the homeotropic region is absorbed by the second polarizer, forming an optical cut-off state, such that a shutter display will be observed by a viewer.