CN101840107A - Liquid crystal light valve (LCLV) with wide visual angle, high contrast ratio and rapid response - Google Patents

Abstract

The invention belongs to an optical switch device, in particular to a liquid crystal light valve with wide viewing angle, high contrast ratio and fast response. Its structure includes: two polarizers, two -a wave plates, two -c wave plates and a liquid crystal box, in which the two polarizers are polarizers and analyzers respectively; their positional relationship is polarizer, The first-a-wave plate, the first-c-wave plate, the liquid crystal cell, the second-c-wave plate, the second-a-wave plate and the analyzer, the light passes through the polarizer, the first-a-wave plate, and the first-a-wave plate in sequence One-c-wave plate, liquid crystal cell, second-c-wave plate, second-a-wave plate and analyzer. The liquid crystal light valve of the present invention uses an optical self-compensating bending (OCB) mode liquid crystal cell, and the liquid crystal molecules have an up-down symmetrical orientation in the thickness direction of the liquid crystal layer, and the liquid crystal cell has two -c wave plates and two -a wave plates as compensation films , the maximum contrast reaches 2300. The viewing angle is also very wide, the contrast ratio can reach 1000 in each direction of the polar angle range of 20°, and the contrast ratio of the horizontal direction can reach 200 in the polar angle range of plus or minus 60°. The response time is 1.9 milliseconds.

Description

Wide viewing angle, high contrast and fast response liquid crystal light valve

Technical field:

The invention belongs to an optical switch device, in particular to a liquid crystal light valve with wide viewing angle, high contrast ratio and quick response. An optical self-compensating bend (Optical Compensated Bend: OCB) mode liquid crystal cell, two -a wave plates, two -c wave plates and two polarizers are used to realize the optical switching effect.

Background technique:

Liquid Crystal Light Valve (LCLV) for short, is a spatial light modulator with real-time function made by utilizing the modulation characteristics of liquid crystal to light. It can be widely used in modern high-tech fields such as optical computing, pattern recognition, information processing, and display, with broad prospects. Since the writing light and the reading light of the liquid crystal light valve are independent of each other, the incoherent light can be easily converted into coherent light, so the liquid crystal light valve is an indispensable device in the coherent light real-time processing system. At the same time, the liquid crystal light valve can also increase the energy of the read light and realize the energy amplification of weak images, so it is also widely used in large-screen, high-brightness projection displays.

Most traditional liquid crystal light valves use twisted nematic liquid crystal cells, the response time is tens of milliseconds, the contrast ratio can reach about 200, and the viewing angle is relatively narrow. If it is used in projection display, only displaying text and black and white pictures can meet the needs. However, if it is used to demonstrate colorful photos and play video animations, it is best to choose a high-contrast projector with a ratio of 1000:1 or more. The shorter the response time, the better. There are traces similar to afterimages or procrastination, and most displays still require a wider viewing angle. Therefore, the traditional liquid crystal light valve made by twisted nematic liquid crystal cells cannot meet the requirements.

Invention content:

The object of the present invention is to solve the problems of viewing angle, contrast and response time of the traditional liquid crystal light valve, and provide a liquid crystal light valve with wide viewing angle, high contrast and fast response. The present invention adopts the OCB mode liquid crystal cell with the characteristics of fast response, and realizes the response time of 1.9 ms through film compensation and optimization of the OCB cell, the maximum contrast ratio reaches 2300, and the viewing angle is also very wide. The contrast ratio can reach 1000, and the contrast ratio in the horizontal direction can reach 200 in the polar angle range of plus or minus 60°.

Technical solution of the present invention is as follows:

A liquid crystal light valve with wide viewing angle, high contrast and fast response, its structure includes: two polarizers, two -a wave plates, two -c wave plates and a liquid crystal cell, wherein the two polarizers are polarizers respectively and the polarizer; the positional relationship is the polarizer, the first-a wave plate, the first-c wave plate, the liquid crystal cell, the second-c wave plate, the second-a wave plate and the polarizer, The light passes through the polarizer, the first-a wave plate, the first-c wave plate, the liquid crystal cell, the second-c wave plate, the second-a wave plate and the analyzer in sequence.

The two polarizers described above all use polarizers with a high degree of polarization.

The birefringence indices of the two -c wave plates and the two -a wave plates are the same, both being -0.0092 (589nm). The thickness of the two-a wave plates is in the range of 14-16 μm, and the thickness of the two-c-wave plates is in the range of 40-43 μm.

The liquid crystal cell described is an OCB mode liquid crystal cell, comprising: a glass substrate, an indium tin oxide (ITO) electrode, an orientation layer, a liquid crystal material, a sealing frame glue and a spherical resin powder; its positional relationship is: the outermost layer is two pieces Glass substrate, the inner surface of the glass substrate is an electrode, and then there is an alignment layer, and the middle is a liquid crystal material and a spacer. When no voltage is applied, the liquid crystal material is arranged along the direction that the alignment layer has been rubbed in advance, that is, the liquid crystal molecules are antiparallel. , when the low voltage is applied, the liquid crystal molecules are in a curved arrangement structure, and when the high voltage is applied, the liquid crystal molecules are arranged vertically to the surface of the substrate. The liquid crystal cell of this mode has the characteristics of fast response.

The two glass substrates are bonded together by a bezel sealant, and spherical resin powder matching the required thickness of the liquid crystal layer is placed in the liquid crystal to control the thickness of the liquid crystal layer.

The sealing frame glue is between two layers of glass substrates, forming a closed space with the upper and lower layers of glass substrates.

The thickness of the liquid crystal layer is 4 μm, and the parameters of the liquid crystal material are: ε _// =18.6, ε _⊥ =3.5, n _o =1.5, Δn=0.2, K ₁₁ =12.9pN, K ₃₃ =17.3pN, γ ₁ =0.134 Pa·s, the boundary is strongly anchored, and the pretilt angles of the liquid crystals at the upper and lower substrates are 5° and 175°, respectively.

The manufacturing method of the high-contrast and fast-response liquid crystal light valve described above, its steps are as follows:

Step 1, etching out the electrode pattern;

Step 2, alignment layer coating and curing;

Step 3, rubbing the alignment layer;

Step 4, spray spherical resin powder on the lower glass substrate, and print sealing frame glue on the upper glass substrate;

Step 5, attach the upper and lower glass substrates and cure the bezel sealant;

Step 6, pouring liquid crystal material and sealing;

Step 7, clean the glass surface and attach two -a wave plates, two -c wave plates, polarizer and analyzer. Finally, the liquid crystal light valve with wide viewing angle, high contrast ratio and fast response is obtained.

Compared with the prior art, the present invention has the following beneficial effects:

The characteristic of the liquid crystal light valve designed by the present invention is to use the optical self-compensating bending (OCB) mode liquid crystal cell, and the OCB mode has high electro-optical response speed because the liquid crystal molecules have an up-down symmetrical orientation in the thickness direction of the liquid crystal layer, so it is applied in liquid crystal The light valve can meet the requirements of response speed; in addition, two -c wave plates and two -a wave plates in the liquid crystal cell are used as compensation films, and the appropriate parameters are used to optimize the mode, so that the contrast of the liquid crystal light valve is very high, the maximum The contrast reaches 2300. The viewing angle is also very wide, the contrast ratio can reach 1000 in each direction of the polar angle range of 20°, and the contrast ratio of the horizontal direction can reach 200 in the polar angle range of plus or minus 60°. The response time is 1.9 milliseconds.

Description of drawings:

Fig. 1 is a schematic diagram of the appearance and structure of the liquid crystal light valve with wide viewing angle, high contrast ratio and fast response of the present invention;

Fig. 2 is a schematic diagram of the structure of the liquid crystal cell in the liquid crystal light valve with wide viewing angle, high contrast and fast response of the present invention;

FIG. 3 is a schematic diagram of the arrangement of liquid crystal molecules in the OCB mode liquid crystal cell under the conditions of no power supply, low voltage application and high voltage application respectively.

Fig. 4 is the contrast viewing angle diagram of the liquid crystal light valve with wide viewing angle, high contrast ratio and fast response of the present invention;

Fig. 5 is a response time chart of the liquid crystal light valve with wide viewing angle, high contrast ratio and fast response according to the present invention.

Detailed ways:

The manufacturing method of the high-contrast and fast-response liquid crystal light valve of the present invention is made according to the following steps:

Step 1, etching out the electrode pattern;

First coat the photosensitive adhesive on the ITO conductive glass, and then cover the photoresist mask (the photoresist mask is made on the film with a black and white pattern corresponding to the electrode pattern, and the photoresist in the transparent area is exposed to the action of light when exposed. Under the reaction), and then irradiated by ultraviolet light, the ITO electrode layer is selectively chemically etched, so that a pattern completely corresponding to the mask plate is obtained on the ITO conductive glass.

Step 2, alignment layer coating and curing;

Coating an alignment agent (polyamic acid solution) on the etched ITO conductive glass to form a uniform film layer. Then pre-baking, heating the solvent in the alignment material solution to volatilize it, leaving a solid alignment material film layer, and then curing it at 300-350°C for 1-2 hours, dehydrating and closing the ring to form a polyimide film, thus forming the required alignment film.

Step 3, rubbing the alignment layer;

Rub the flannelette on the alignment film in one direction, and the liquid crystal molecules in the liquid crystal layer will be arranged in parallel according to the direction of rubbing, so that a consistent orientation and the required tilt angle of the liquid crystal light valve can be obtained, and the pre-tilt of the liquid crystal at the upper and lower substrates The angles are 5° and 175°, respectively.

Step 4, the lower glass substrate is sprayed with spherical resin powder with a diameter of 4 μm, and the upper glass substrate is printed with sealant;

Spray spherical resin powder on the lower glass substrate with a powder sprayer to form a more uniform distribution to control the distance between the two glass substrates. On the upper glass substrate, screen printing method is used to screen the frame glue and conductive dispensing to control the distance between the two glass substrates. Make the size of the liquid crystal light valve and conduct the common electrode between the upper and lower substrates.

Step 5, attach the upper and lower glass substrates and cure the bezel sealant;

The upper and lower glass substrates are aligned and laminated on the alignment laminating machine, and the frame glue is cured at about 200°C by using a heat curing method to form a liquid crystal empty box.

Step 6, pouring liquid crystal material and sealing;

Place the empty box in a vacuumed liquid crystal perfusion airtight room, the gas in the box is drawn out from the seal, and then the injection hole (the gap in the sealing frame) is in contact with the liquid crystal. The material parameters of the liquid crystal: ε _// = 18.6, ε _⊥ = 3.5, n _o =1.5, Δn=0.2, K ₁₁ =12.9pN, K ₃₃ =17.3pN, γ ₁ =0.134Pa·s. Using the capillary phenomenon, most of the volume of the empty cell can be injected into the liquid crystal material, and then the inert gas such as fully dried argon and nitrogen is filled into the liquid crystal perfusion chamber, and the liquid crystal material is completely filled with the liquid crystal cell by the pressure of the inert gas. The sealant is used to bond the seal, and the sealant is properly shrunk and brought into the seal by freezing, and then cured by ultraviolet light.

Step 7, clean the glass surface and attach two -a wave plates, two -c wave plates and two polarizers (ie polarizer and analyzer).

Squeegee and clean to remove some sealing glue, liquid crystal and other dirt left on the surface of the liquid crystal cell. Then you can attach two -a wave plates, two -c wave plates and two polarizers. The birefringence index of -a wave plate and -c wave plate is -0.0092 (589nm), the thickness of both -a wave plates is in the range of 14～16μm, the azimuth angle of both -c wave plates is 0°, The thicknesses are all in the range of 40 to 43 μm. The polarizer adopts a high polarization degree polarizer, SKN-18243T produced by Polatechno Company. The azimuth angle of the polarizer is -41°, the azimuth angle of the analyzer is 49°, the azimuth angle of the first-a-wave plate is 45.3°, and the azimuth angle of the second-a-wave plate is 45.3°. Two biaxial compensation films and two polarizers finally get this liquid crystal light valve with wide viewing angle, high contrast and fast response.

The content not described in the above production methods is a known technology. For details, please refer to "Basics of Liquid Crystal Device Technology" published by Beijing University of Posts and Telecommunications Press and edited by Fan Zhixin.

The appearance structure of the liquid crystal light valve that the present invention makes is as shown in Figure 1, and light passes through polarizer 1, the first-a wave plate 2, the first-c wave plate 3, the liquid crystal cell 4, the second-c wave plate successively Plate 5, second-a wave plate 6, analyzer 7. The structure of the liquid crystal cell is shown in Figure 2. The outermost layer of the liquid crystal cell is a glass substrate 8, the inner surface of the glass substrate is an electrode 9, and the inner surface is an alignment layer 10, and the inside is a liquid crystal material 11 rubbed along the alignment layer 10 in advance. The two glass substrates 8 are bonded together by the sealant 12, and the spherical resin powder 13 with a diameter of 4 μm is placed in the liquid crystal to control the thickness of the liquid crystal layer. FIG. 3 is a schematic diagram of the arrangement of liquid crystal molecules in the OCB mode liquid crystal cell under the conditions of no power supply, low voltage application and high voltage application respectively. When no voltage is applied, the liquid crystal molecules are arranged antiparallel, as shown in Figure 3(a); when a low voltage is applied, they are arranged in a curved structure, as shown in Figure 3(b); when a high voltage is applied, they are arranged vertically to the surface of the substrate, as shown in Figure 3(a) 3(c).

The thickness of the liquid crystal layer is 4 μm, and the parameters of the liquid crystal material (MLC-2136 produced by Merck Company): ε _// =18.6, ε _⊥ =3.5, n _o =1.5, Δn=0.2, K ₁₁ =12.9pN, K ₃₃ =17.3 pN, γ ₁ =0.134Pa·s, the boundary is strongly anchored, and the pretilt angles of the liquid crystals at the upper and lower substrates are 5° and 175° respectively. The birefringence index of -a wave plate and -c wave plate is -0.0092 (589nm). Both are in the range of 40 to 43 μm. The polarizer adopts a high polarization degree polarizer (SKN-18243T produced by Polatechno Company). The azimuth angle of the liquid crystal layer plane is 0°, the azimuth angle of the polarizer 1 is -41°, the azimuth angle of the analyzer 7 is 49°, the azimuth angle of the first-a wave plate 2 is 45.3°, the second- The azimuth angle of the a-wave plate 6 is 45.3°.

First apply a low voltage U ₁ =1.2V, and the liquid crystal molecules are arranged in a curved structure. At this time, the liquid crystal cell is in a bright state, and the corresponding transmittance is the bright state transmittance. Then change the low voltage U ₁ =1.2V to the high voltage U ₂ =14V, the liquid crystal molecules are gradually arranged perpendicular to the direction of the substrate, at this time the transmittance of the liquid crystal cell gradually decreases, and finally the liquid crystal cell is in a dark state, and the corresponding transmittance The pass rate is the dark state transmittance. After changing the high voltage U ₂ =14V to the low voltage U ₁ =1.2V, due to the elastic force in the liquid crystal layer, the liquid crystal molecules will gradually return to the state of bending alignment, and the transmittance of the liquid crystal cell will gradually change. Increase, and finally the liquid crystal cell shows a bright state again. Contrast can be expressed by the ratio of bright state transmittance to dark state transmittance. The contrast viewing angle diagram of the liquid crystal light valve can be simulated by Mouse-LCD 2.6 software. , the area of 1. The results of the simulation software show that the maximum contrast ratio can reach 2300. It can also be seen from the figure that the viewing angle of the liquid crystal cell is very wide, the contrast ratio can reach 1000 in all directions within the polar angle range of 20°, and the contrast ratio in the horizontal direction can reach 200 within the polar angle range of plus or minus 60°. The time from 90% of the maximum transmittance to 10% is defined as the rise time; the time from 10% of the maximum transmittance to 90% is defined as the fall time. The sum of rise time and fall time is defined as response time. The response time diagram of the liquid crystal light valve can be obtained through simulation calculation, as shown in FIG. 5 . After changing the low voltage U ₁ =1.2V to the high voltage U ₂ =14V, the transmittance of the liquid crystal cell will gradually decrease, as shown in curve a. After changing the high voltage U ₂ =14V to the low voltage U ₁ =1.2V, the transmittance of the liquid crystal cell increases gradually, as shown in curve b. According to the definition of response time, it can be obtained from Figure 5 that the rise time is about 0.1ms, the fall time is about 1.8ms, and the total response time is about 1.9ms. The liquid crystal light valve satisfies the requirements of wide viewing angle, high contrast ratio and fast response liquid crystal light valve.

Figures 4 and 5 are based on the fact that the thickness of the two -a wave plates is 15 μm, and the thickness of the two -c wave plates is 40 μm. When the thickness of the two -a wave plates is in the range of 14-16 μm, and the thickness of the two -c-wave plates is in the range of 40-43 μm, the equal-contrast viewing angle diagram obtained from other data is basically unchanged, and the curve in the figure The results described for these data are also satisfied. Response time is the same.

What is not mentioned in the present invention is applicable to the prior art.

Claims (8)

1. A liquid crystal light valve with wide viewing angle, high contrast and fast response is characterized in that it comprises: two polarizers, two-a wave plates, two-c wave plates and a liquid crystal box, wherein the two polarizers are respectively It is polarizer and analyzer; its positional relationship is polarizer, first-a-wave plate, first-c-wave plate, liquid crystal cell, second-c-wave plate, second-a-wave plate and detector The light passes through the polarizer, the first-a-wave plate, the first-c-wave plate, the liquid crystal cell, the second-c-wave plate, the second-a-wave plate and the analyzer in sequence. 2. The liquid crystal light valve with wide viewing angle, high contrast ratio and fast response as claimed in claim 1, characterized in that the two polarizers are polarizers with high polarization degree. 3. as claimed in claim 1, the liquid crystal light valve of wide viewing angle, high contrast ratio and quick response is characterized in that the birefringence of described two-c wave plates and two-a wave plates is all the same, both It is -0.0092 (589nm). The thickness of the two-a wave plates is in the range of 14-16 μm, and the thickness of the two-c-wave plates is in the range of 40-43 μm. 4. The liquid crystal light valve with wide viewing angle, high contrast ratio and quick response as claimed in claim 1 is characterized in that said liquid crystal cell is a liquid crystal cell of OCB mode, comprising: glass substrate, indium tin oxide (ITO) electrodes, orientation Layer, liquid crystal material, sealing frame glue and spherical resin powder; the positional relationship is: the outermost layer is two glass substrates, the inner surface of the glass substrate is an electrode, and the inner surface is an alignment layer, and the middle is a liquid crystal material and a spacer. 5. The liquid crystal light valve with wide viewing angle, high contrast and fast response as claimed in claim 1, characterized in that the two glass substrates are bonded together by sealing frame glue, and placed in the liquid crystal to match the thickness of the required liquid crystal layer The spherical resin powder is used to control the thickness of the liquid crystal layer. 6. The liquid crystal light valve with wide viewing angle, high contrast ratio and fast response as claimed in claim 1, characterized in that said bezel sealant is placed between two glass substrates, forming a closed space with the upper and lower glass substrates. 7. The liquid crystal light valve with wide viewing angle, high contrast ratio and fast response as claimed in claim 1, characterized in that the thickness of the liquid crystal layer is 4 μm, and the parameters of the liquid crystal material: ε _// =18.6, ε _⊥ =3.5, n _o = 1.5, Δn = 0.2, K ₁₁ = 12.9pN, K ₃₃ = 17.3pN, γ ₁ = 0.134Pa·s, the boundary is strongly anchored, and the pretilt angles of the liquid crystals at the upper and lower substrates are 5° and 175° respectively. 8. the manufacture method of the liquid crystal light valve of high contrast and quick response as claimed in claim 1, it is characterized in that the steps are as follows: Step 1, etching out the electrode pattern; Step 2, alignment layer coating and curing; Step 3, rubbing the alignment layer; Step 4, spray spherical resin powder on the lower glass substrate, and print sealing frame glue on the upper glass substrate; Step 5, attach the upper and lower glass substrates and cure the bezel sealant; Step 6, pouring liquid crystal material and sealing; Step 7, clean the glass surface and attach two -a wave plates, two -c wave plates, polarizer and analyzer, and finally obtain the liquid crystal light valve with wide viewing angle, high contrast and fast response.

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