A VA liquid crystal display screen

Abstract

The present invention relates to the technical field of liquid crystal display screens, and specifically to a VA liquid crystal display screen, which includes a surface polarizer, a liquid crystal cell, and a bottom polarizer; the liquid crystal cell includes a surface ITO glass, an upper alignment film, a sealant edge, a liquid crystal layer, a lower alignment film, and a bottom ITO glass; the surface ITO glass and the bottom ITO glass are bonded by the sealant edge to form a closed space; the liquid crystal layer is arranged between the upper alignment film connected to the segmented electrode and the lower alignment film connected to the common electrode. By increasing the thickness of the liquid crystal layer and using a high-density friction cloth, the friction alignment ability is increased, and the reliability is improved. Since the cell thickness is increased, adjustments of liquid crystal and optical sheet compensation are required, and the best blackness effect is achieved at each non-selected state viewing angle. The VA liquid crystal display screen product with a newly designed combination of the present invention can achieve a better display effect and eliminate the problems of display black spots and haze.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid crystal display screens, and particularly relates to a VA liquid crystal display screen. Background Art

[0002] Current negative display liquid crystal display screens are mainly represented by the vertical alignment (VA) technology. VA is the abbreviation of the English word VERTICAL ALIGNMENT (vertical alignment). This technology was initially one of the mainstream TFT technologies, was first used in the high-end TFT industry, and was widely used in civilian luxury goods such as liquid crystal computers and liquid crystal TVs. Currently, monochrome liquid crystal display manufacturers have applied this VA display technology to monochrome liquid crystal display products by reference and obtained excellent display effects; it is especially suitable for applications in fields such as vehicle-mounted displays, smart home displays, and high-end displays. The products have advantages such as high contrast ratio, fast response speed, wide operating temperature, and wide viewing angle, and are deeply loved by consumers. Existing VA display screens mainly consist of a surface polarizer, a liquid crystal cell, and a bottom polarizer. The liquid crystal cell includes a surface ITO glass, an upper alignment film (PI layer), a sealant edge, a liquid crystal layer, a lower alignment film (PI layer), and a bottom ITO glass. After the electrodes on the surface ITO glass and the bottom ITO glass are energized, an electric field will be formed between the liquid crystal cells, and the liquid crystal will twist according to the rubbing direction to achieve the display effect.

[0003] Currently, for conventional VA liquid crystal display screens, in order to achieve a high contrast ratio effect, the liquid crystal cell thickness is generally selected to be relatively small, 3.5um. The alignment films (PI layers) of the upper and lower glasses are rubbed parallelly, so that the liquid crystal in the cell can be arranged orderly and form a good pretilt angle. When the LCD is connected to the drive circuit, the liquid crystal in the VA cell is driven by the electrodes in the cell and arranged and twisted orderly to form a display; however, due to the small liquid crystal cell thickness and the narrow tolerance of the rubbing process, the liquid crystal display screen is extremely prone to problems such as display black spots and haze, and at the same time, the problem of low manufacturing yield of conventional design products.

[0004] Therefore, it is necessary to study a liquid crystal display screen that can solve the problem of black spots and haze. Summary of the Invention

[0005] In order to solve the above problems, the present invention discloses a VA liquid crystal display screen, which can solve the problem of display black spots and haze.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A VA liquid crystal display screen includes a surface polarizer, a liquid crystal cell, and a bottom polarizer; the liquid crystal cell includes a surface ITO glass, an upper alignment film, a sealant edge, a liquid crystal layer, a lower alignment film, and a bottom ITO glass; the surface polarizer is attached to the surface ITO glass, the bottom polarizer is attached to the bottom ITO glass, and the surface ITO glass and the bottom ITO glass are bonded by a sealant edge to form a closed space; the liquid crystal layer is disposed between the upper alignment film and the lower alignment film, and a segmented electrode is connected to the upper alignment film, and a common electrode is connected to the lower alignment film.

[0008] Further, an ITO segmented electrode is etched on the surface ITO glass, and correspondingly, an ITO common electrode matching the ITO segmented electrode is etched on the bottom ITO glass.

[0009] Further, the cell gap D of the liquid crystal cell is 4.50 - 10.50 μm, which is larger than the thickness of the conventional design structure, and the purpose is to help increase the process tolerance and improve the yield.

[0010] Further, the liquid crystal material of the liquid crystal layer is selected as a negative liquid crystal, that is, the dielectric constant in the horizontal direction of the LC rod-shaped molecules is greater than the dielectric constant in the vertical direction: ΔΣ = Σ‖ - Σ⊥ is negative; the resistivity ρCl of the liquid crystal is 1.0×10 １0 Ω·cm to 1.0×10 16 Ω·cm.

[0011] Powder is sprayed in the liquid crystal layer to form support points to ensure uniform cell gap. The powder spraying density is 110 ± 20 particles.

[0012] Further, the refractive index anisotropy Δn of the negative liquid crystal is 0.030 - 0.135.

[0013] Further, the absorption axes of the surface polarizer and the bottom polarizer are matched in an orthogonal manner. The in-plane retardation Re of the polarizer compensation film is 45 - 225 nm, the film thickness retardation Rth of the polarizer compensation film is 0 - 55 nm, and the degree of polarization is greater than 99.9%.

[0014] According to the in-plane retardation Re and the film thickness retardation Rth of the polarizer compensation film and the birefringence of the liquid crystal layer, the final result is elliptical or spherical. When light is obliquely incident, the light generates a phase delay after passing through the liquid crystal layer and becomes elliptically polarized light. At this time, the analyzer cannot absorb all the outgoing light. At this time, the optical compensation film corrects the light with nz < nx = ny to generate a phase difference, so that the outgoing light is still linearly polarized light, and the analyzer absorbs all the outgoing light, so that a relatively perfect black state can also be obtained at the oblique viewing angle.

[0015] Further, the upper alignment film and the lower alignment film adopt PI with vertical alignment after the rubbing process.

[0016] Furthermore, the friction process is to use a friction wheel attached with a friction cloth to rub the PI surface.

[0017] Furthermore, the hair density of the friction cloth is 34,000 - 95,000 per cm², the material is soft, the wire diameter is 0.30 - 1.0 Denir, the hair length is 1.0 - 1.8 mm, and the inclination angle of the hair cloth is 35° - 45°.

[0018] Furthermore, the friction process parameters are as follows: the included angle between the upper and lower glass sheets is 0 - 100°, the friction press-in amount is 0.01 mm - 0.5 mm, the rotation speed range of the friction wheel is 300 - 1000 rpm, and the platform speed is 10 - 50 mm / sec.

[0019] Scheme description:

[0020] The main differences from the prior art are the cell thickness, friction process, liquid crystal refractive index, and polarizer. The design of the new scheme mainly increases the thickness of the liquid crystal layer, uses a high-density friction cloth, increases the friction orientation ability, and improves the reliability. Due to the increase in cell thickness, adjustments in liquid crystal and optical sheet compensation are required. The best blackness effect is achieved at all non-selected states, the light leakage rate is less than 0.1%, the display contrast at normal temperature in the selected state is greater than 1000, and reliability verifications such as working at 80°C for 1000 hours, 60°C * 90%RH * 1000 hours at high temperature and high humidity, and working at -30°C for 1000 hours do not show problems such as display black spots or haze.

[0021] Advantages of the present invention

[0022] The present invention discloses a VA liquid crystal display screen. By reasonably matching the thickness of the vertically aligned liquid crystal cell, friction parameters, liquid crystal, and polarizer materials, it is ensured that under normal driving force, the liquid crystal can form a stable arrangement, avoiding problems such as display black spots or haze, and improving the display performance of the product; due to the adjustment of the cell thickness, the yield rate is increased and the manufacturing cost is significantly reduced. Brief description of the drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 Schematic structural diagram of the present invention;

[0025] Figure 2 Relationship diagram between the cell thickness and contrast of the present invention;

[0026] Description of reference numerals: surface polarizer 1, bottom polarizer 11, surface ITO glass 2, bottom ITO glass 21, ITO segmented electrode 3, ITO common electrode 31, upper alignment film 4, lower alignment film 41, spacer 5, liquid crystal layer 6, sealant edge 7. Detailed implementation mode

[0027] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention. Therefore, the description of the specification is only for the purpose of illustration. Therefore, the practice of the inventive concept herein is not limited solely to the example embodiments described herein and the illustrations in the drawings. In addition, the drawings are not restrictive.

[0028] As Figure 1-2 shown:

[0029] Embodiment 1

[0030] A VA liquid crystal display screen includes a surface polarizer 1, a liquid crystal cell, and a bottom polarizer 11; the liquid crystal cell includes a surface ITO glass 2, an upper alignment film 4, a sealant edge 7, a liquid crystal layer 6, a lower alignment film, and a bottom ITO glass 21; the surface polarizer 1 is attached to the surface ITO glass 2, the bottom polarizer 11 is attached to the bottom ITO glass 21, and the surface ITO glass 2 and the bottom ITO glass 21 are bonded by a sealant edge 7 to form a closed space; the liquid crystal layer 6 is disposed between the upper alignment film 4 and the lower alignment film, and a segmented electrode is connected to the upper alignment film 4, and a common electrode is connected to the lower alignment film.

[0031] The surface ITO glass 2 is etched with an ITO segmented electrode 3, and correspondingly, the bottom ITO glass 21 is etched with an ITO common electrode 31 that matches the ITO segmented electrode 3.

[0032] The cell thickness D of the liquid crystal cell is 4.50 μm, which is larger than the thickness of the conventional design structure, and the purpose is to help increase the process tolerance and improve the yield.

[0033] The liquid crystal material of the liquid crystal layer 6 is selected as a negative liquid crystal, that is, the dielectric constant in the horizontal direction of the LC rod-shaped molecules is greater than the dielectric constant in the vertical direction: △ ∑ = ∑‖ - ∑⊥ is negative; the resistivity ρCl of the liquid crystal is 1.0 × 10 １0 Ω cm.

[0034] Powder is sprayed in the liquid crystal layer 6 to form support points to ensure uniform cell thickness, and the powder spraying density is 90 particles.

[0035] The refractive index anisotropy ∆n of the negative liquid crystal is 0.030.

[0036] The absorption axes of the surface polarizer 1 and the bottom polarizer 11 are in an orthogonal configuration. The in-plane retardation Re of the polarizer compensating film is 45, the film-thickness retardation Rth of the polarizer compensating film is 1 nm, and the degree of polarization is 99.91%.

[0037] According to the in-plane retardation Re and the film-thickness retardation Rth of the polarizer compensating film, the birefringence of the liquid crystal layer 6 finally forms an ellipse or a sphere. When light is obliquely incident, the light passing through the liquid crystal layer 6 generates a phase delay and becomes elliptically polarized light. At this time, the analyzer cannot absorb all the outgoing light. Then, the optical compensating film corrects the light with a phase difference nz < nx = ny, making the outgoing light still linearly polarized light, and the analyzer absorbs all the outgoing light, so that a relatively perfect black state can also be obtained at the oblique viewing angle.

[0038] The upper alignment film 4 and the lower alignment film adopt PI with vertical alignment after the rubbing process.

[0039] The rubbing process is to rub the surface of the PI with a rubbing wheel attached with a rubbing cloth.

[0040] The hair density of the rubbing cloth is 34000 pieces / cm², the material is soft, the wire diameter is 0.30 Denir, the hair length is 1.0 mm, and the inclination angle of the hair cloth is 35°.

[0041] The rubbing process parameters are as follows: the included angle between the upper and lower glass sheets is 1°, the rubbing press-in amount is 0.01 mm, the rotation speed range of the rubbing wheel is 300 rpm, and the platform speed is 10 mm / sec.

[0042] Example 2

[0043] A VA liquid crystal display screen includes a surface polarizer 1, a liquid crystal cell, and a bottom polarizer 11; the liquid crystal cell includes a surface ITO glass 2, an upper alignment film 4, a sealing rubber edge 7, a liquid crystal layer 6, a lower alignment film, and a bottom ITO glass 21; the surface polarizer 1 is attached to the surface ITO glass 2, the bottom polarizer 11 is attached to the bottom ITO glass 21, the surface ITO glass 2 and the bottom ITO glass 21 are bonded by a sealing rubber edge 7 to form a closed space; the liquid crystal layer 6 is disposed between the upper alignment film 4 and the lower alignment film, the upper alignment film 4 is connected with segmented electrodes, and the lower alignment film is connected with a common electrode.

[0044] ITO segmented electrodes 3 are etched on the surface ITO glass 2, and correspondingly, ITO common electrodes 31 matching the ITO segmented electrodes 3 are etched on the bottom ITO glass 21.

[0045] The cell gap D of the liquid crystal cell is 7 μm, which is larger than the thickness of the conventional design structure. The purpose is to help increase the process tolerance and improve the yield.

[0046] The liquid crystal material of the liquid crystal layer 6 is selected as a negative liquid crystal, that is, the dielectric constant in the transverse direction of the LC rod-shaped molecules is greater than the dielectric constant in the vertical direction: △∑ = ∑‖ - ∑⊥ is negative; the resistivity of the liquid crystal ρCl = 1.0×10 13 Ω·cm.

[0047] Powder is sprayed in the liquid crystal layer 6 to form support points to ensure the uniformity of the cell gap of the liquid crystal cell. The powder spraying density is 110 particles.

[0048] The refractive index anisotropy ∆n of the negative liquid crystal is 0.065.

[0049] The absorption axes of the surface polarizer 1 and the bottom polarizer 11 are matched in an orthogonal manner. The in-plane retardation Re of the polarizer compensating film is 115 nm, the film thickness retardation Rth of the polarizer compensating film is 25 nm, and the polarization degree is 99.95%.

[0050] According to the in-plane retardation Re and the film thickness retardation Rth of the polarizer compensating film and the birefringence of the liquid crystal layer 6, the final shape is elliptical or spherical. When light is obliquely incident, the light generates a phase delay after passing through the liquid crystal layer 6 and becomes elliptically polarized light. At this time, the analyzer cannot absorb all the outgoing light. At this time, the optical compensating film corrects the light with a phase difference nz < nx = ny, so that the outgoing light is still linearly polarized light, and the analyzer absorbs all the outgoing light, so that a relatively perfect black state can also be obtained at the oblique viewing angle.

[0051] The upper alignment film 4 and the lower alignment film adopt PI with vertical alignment after the rubbing process.

[0052] The rubbing process is to rub the surface of the PI with a rubbing wheel attached with a rubbing cloth.

[0053] The hair density of the rubbing cloth is 60000 roots / cm², the material is soft, the wire diameter is 0.65 Denir, the hair length is 1.4 mm, and the inclination angle of the hair cloth is 40°.

[0054] The rubbing process parameters are as follows: the included angle between the upper and lower glass sheets is 50°, the rubbing press-in amount is 0.25 mm, the rotation speed range of the rubbing wheel is 650 rpm, and the platform speed is 25 mm / sec.

[0055] Example 3

[0056] A VA liquid crystal display screen includes a surface polarizer 1, a liquid crystal cell, and a bottom polarizer 11; the liquid crystal cell includes a surface ITO glass 2, an upper alignment film 4, a sealant edge 7, a liquid crystal layer 6, a lower alignment film, and a bottom ITO glass 21; the surface polarizer 1 is attached to the surface ITO glass 2, the bottom polarizer 11 is attached to the bottom ITO glass 21, and the surface ITO glass 2 and the bottom ITO glass 21 are bonded by a sealant edge 7 to form a closed space; the liquid crystal layer 6 is disposed between the upper alignment film 4 and the lower alignment film, the upper alignment film 4 is connected with segmented electrodes, and the lower alignment film is connected with a common electrode.

[0057] ITO segmented electrodes 3 are etched on the surface ITO glass 2, and correspondingly, ITO common electrodes 31 matching the ITO segmented electrodes 3 are etched on the bottom ITO glass 21.

[0058] The cell gap D of the liquid crystal cell is 10.50 μm, which is larger than the thickness of the conventional design structure. The purpose is to help increase the process tolerance and improve the yield.

[0059] The liquid crystal material of the liquid crystal layer 6 is selected as a negative liquid crystal, that is, the dielectric constant in the horizontal direction of the LC rod-shaped molecules is greater than the dielectric constant in the vertical direction: △∑ = ∑‖ - ∑⊥ is negative; the resistivity ρCl of the liquid crystal is 1.0 × 10 16 Ω·cm.

[0060] Support points are formed by spraying powder in the liquid crystal layer 6 to ensure uniform cell gap, and the powder spraying density is 130 particles.

[0061] The refractive index anisotropy ∆n of the negative liquid crystal is 0.135.

[0062] The absorption axes of the surface polarizer 1 and the bottom polarizer 11 are matched in an orthogonal manner. The in-plane retardation Re of the polarizer compensating film is 225 nm, the film thickness retardation Rth of the polarizer compensating film is 55 nm, and the polarization degree is 99.99%.

[0063] According to the in-plane retardation Re and the film thickness retardation Rth of the polarizer compensating film and the birefringence of the liquid crystal layer 6, the final result is elliptical or spherical. When light is obliquely incident, the light generates a phase delay after passing through the liquid crystal layer 6 and becomes elliptically polarized light. At this time, the analyzer cannot absorb all the outgoing light. At this time, the optical compensating film corrects the light with a phase difference nz < nx = ny, so that the outgoing light is still linearly polarized light, and the analyzer absorbs all the outgoing light, so that a relatively perfect black state can also be obtained at the oblique viewing angle.

[0064] The upper alignment film 4 and the lower alignment film adopt PI with vertical alignment after the rubbing process.

[0065] The rubbing process is to rub the surface of the PI with a rubbing wheel attached with a rubbing cloth.

[0066] The hair density of the friction cloth is 95000 roots / cm², the material is soft, the wire diameter is 1.0 Denir, the hair length is 1.8 mm, and the inclination angle of the hair cloth is 45°.

[0067] The friction process parameters are as follows: the included angle between the upper and lower glass sheets is 100°, the friction press-in amount is 0.5 mm, the rotation speed range of the friction wheel is 1000 rpm, and the platform speed is 50 mm / sec.

[0068] The relevant experimental data of this technical solution are as follows:

[0069] The thickness of the liquid crystal cell

[0070] The upper and lower glass sheets are combined together. Through the central powder, the diameter of the powder determines the gap between the two glass sheets, that is, the thickness. The liquid crystal is injected into the gap between the two glass sheets, which is called the liquid crystal cell. The cell thickness of this liquid crystal is an important parameter affecting the entire device. According to the test data: when the cell thickness is less than 4.0 um, display fogging is likely to occur. The reason is that the smaller the cell thickness, the greater the torque required for the liquid crystal to twist. The torque is generated by the electric field. Under the condition of the same electric field, the liquid crystal with a large cell thickness is easy to twist and arrange neatly, and it is not easy to show black shadows.

[0071] The cell thickness cannot be too large either, which affects the contrast of the device. For the comparison of test data, see Figure 2 :

[0072] In the example, a cell thickness of 5.0 um is preferably selected.

[0073] 2. Friction parameters

[0074] The friction parameters include PI alignment film formation, friction cloth, and friction process parameters, etc.

[0075] According to the test comparison, PI with vertical alignment and high-density friction cloth are preferably selected. Considering reliability, process parameters with a pretilt angle close to 90 degrees are selected:

[0076] l Test data of PI film thickness and pretilt angle

[0077] In the example, the thickness of the PI layer is preferably 650 Å.

[0078] l Test data of PI curing and pretilt angle

[0079] In the example, 205 °C + 5 °C is used as the curing temperature.

[0080] l Test data of friction press-in amount (friction strength) and pretilt angle:

[0081] Due to the small friction strength and poor reliability, considering reliability, the friction press-in amount of 0.3 mm is preferably selected in the example.

[0082] 3. Matching of Liquid Crystal and Polarizer Materials

[0083] Select a negative liquid crystal as the liquid crystal material

[0084] The refractive index anisotropy ∆n is between 0.030 and 0.135

[0085] The retardation phase difference of the polarizer compensation value is Re 45~225nm, Rth 0~55nm

[0086] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0087] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. It should be noted that the technical features not described in detail in the present invention can all be realized by any existing technology.

Claims

1. A VA liquid crystal display screen, characterized in that, It includes a surface polarizer, a liquid crystal cell, and a bottom polarizer; the liquid crystal cell includes a surface ITO glass, an upper alignment film, a sealant edge, a liquid crystal layer, a lower alignment film, and a bottom ITO glass; the surface polarizer is attached to the surface ITO glass, the bottom polarizer is attached to the bottom ITO glass, and the surface ITO glass and the bottom ITO glass are bonded with a sealant to form a closed space; the liquid crystal layer is disposed between the upper alignment film and the lower alignment film, and a segmented electrode is connected to the upper alignment film, and a common electrode is connected to the lower alignment film; The cell thickness D of the liquid crystal cell is 4.50 - 10.50 μm; The liquid crystal material of the liquid crystal layer is a negative liquid crystal; The refractive index anisotropy Δn of the negative liquid crystal is 0.030 - 0.135; The absorption axes of the surface polarizer and the bottom polarizer are matched in an orthogonal manner, the in-plane retardation Re of the polarizer compensating film is 45 - 225 nm, the film thickness retardation Rth of the polarizer compensating film is 0 - 55 nm, and the degree of polarization is greater than 99.9%; 2. The VA liquid crystal display screen according to claim 1, characterized in that, ITO segmented electrodes are etched on the surface ITO glass, and correspondingly, ITO common electrodes matching the ITO segmented electrodes are etched on the bottom ITO glass; 3. The VA liquid crystal display screen according to claim 1, characterized in that, The upper alignment film and the lower alignment film adopt PI with vertical alignment after the rubbing process; 4. The VA liquid crystal display screen according to claim 3, characterized in that, The rubbing process is to rub the surface of the PI with a rubbing wheel attached with a rubbing cloth; 5. The VA liquid crystal display screen according to claim 4, characterized in that, The hair density of the friction cloth is 34,000 - 95,000 per cm 2 , with soft material, thread diameter of 0.30 - 1.0 Denir, hair length of 1.0 - 1.8 mm, and the inclination angle of the hair cloth being 35° - 45°.

6. The VA liquid crystal display screen according to claim 3, characterized in that, The rubbing process parameters are as follows: the included angle between the upper and lower glass sheets is 0 - 100°, the rubbing press-in amount is 0.01 mm - 0.5 mm, the rotation speed range of the rubbing wheel is 300 - 1000 rpm, and the platform speed is 10 - 50 mm / sec.

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