CN105137677A - Blue-phase liquid crystal display device - Google Patents

Abstract

The present invention is a blue-phase liquid crystal display device, which is composed from top to bottom: an upper polarizer, a λ/2 biaxial film, an upper glass substrate, a blue-phase liquid crystal layer, and a protrusion with a high dielectric constant layer, an electrode layer, a lower glass substrate and a lower polarizer; the electrode layer is a Pixel electrode and a Common electrode that are sequentially distributed on the lower glass substrate at intervals; electrode or directly above the Common electrode. The present invention successfully solves the problems of high driving voltage and low light transmittance of the blue-phase liquid crystal display by introducing a trapezoidal high dielectric constant raised layer on the Pixel electrode and the Common electrode on the basis of the IPS display mode. The problem is that the driving voltage is reduced from 83V to about 14V, and the light transmittance is increased from 60% to 77%.

Description

A blue phase liquid crystal display device

technical field

The invention designs a device in the technical field of liquid crystal display, specifically a blue-phase liquid crystal display device with low driving voltage, high transmittance, simple and stable alignment, and can well eliminate the influence of misalignment.

Background technique

In recent years, with the in-depth research on blue-phase liquid crystals, people have discovered many revolutionary advantages of blue-phase liquid crystals, for example, no alignment layer is required, making the manufacturing process simple and greatly reducing production costs; sub-millisecond The response speed enables it to eliminate the tailing phenomenon of the liquid crystal display, and the picture becomes clearer and more stable; in the dark state, the blue phase liquid crystal can be regarded as an isotropic medium, so it can form a symmetrical viewing angle and high contrast . These excellent display performances presented by blue-phase liquid crystal displays are highly sought after by scholars, and are recognized as the next generation of displays.

Although the blue-phase liquid crystal display has many excellent display performances compared with other liquid crystal displays, the high driving voltage and low light transmittance are still two bottlenecks restricting the development and application of the blue-phase liquid crystal display. In order to realize the low-voltage drive of the blue-phase liquid crystal display, various scientific research workers and scholars have proposed various schemes. For example, double-sided electrode structure, wall electrode structure, elliptical bump electrode structure and so on. Although these protruding electrodes can reduce the driving voltage to a certain extent, they are relatively complicated in terms of manufacturing process. It is often necessary to use photolithography to fabricate a protruding structure, and then make a transparent conductive electrode material on the surface of the protruding structure, and then use photolithography to produce a protruding structure. The required electrode pattern is etched out by etching technology. Because in the process of manufacturing, the surface of the raised structure produced by photolithography technology cannot be guaranteed to be smooth, and there are often some defects in the film made on it, and the thickness of the produced electrode is too thin, usually around 0.1 micron , This will easily cause defects in the electrodes on the surface of the raised structure, which will lead to open circuit problems caused by electrode fractures. This is also a major reason why the blue-phase liquid crystal display has not yet been industrialized since the prototype appeared in 2008. Therefore, the manufacturing process is improved, the defects generated in the process are reduced, and a new technical method is proposed to obtain a low driving voltage.

Contents of the invention

The present invention aims at the deficiencies in the current technology, and proposes a blue-phase liquid crystal display device, which makes a trapezoidal high dielectric constant raised structure above the coplanar electrode in the blue-phase liquid crystal display driven by an in-plane electric field (IPS), Change the classic method of making electrodes on the raised structure in the previous technology, on the basis of the ordinary IPS liquid crystal display manufacturing process, manufacture a material layer with high dielectric constant, and obtain the patented structure of the present invention through one-time photolithography technology, the structure can be obtained by Adjust the dielectric constant of the bump layer, bump height, electrode spacing and other influencing factors to achieve low-voltage drive and high transmittance of the blue-phase liquid crystal display, so the manufacturing process is simple, and there is no electrode defect, while solving the problem of traditional blue-phase liquid crystal The problem of high display driving voltage and low light transmittance promotes the development and application of blue-phase liquid crystal displays.

Technical scheme of the present invention is:

A blue-phase liquid crystal display device, the composition of the device from top to bottom includes: an upper polarizer, a λ/2 biaxial film, an upper glass substrate, a blue-phase liquid crystal layer, a raised layer with a high dielectric constant, and an electrode layer, lower glass substrate and lower polarizer;

The electrode layer is a Pixel electrode and a Common electrode successively distributed on the lower glass substrate at intervals; the thickness of the Pixel electrode and the Common electrode is 0.08-0.12 μm, the width of the electrode is 1-5 μm, and the distance between the electrodes is 2-6 μm ;

The raised layer of high dielectric constant is covered on the lower glass substrate distributed with Pixel electrodes and Common electrodes, and the protrusions in the raised layer of high dielectric constant are located on the positive side of the Pixel electrodes or Common electrodes. Above, the width of the lower part of the section is 1/2 to 3/2 of the width of the electrode below;

In the raised layer with high dielectric constant, the part covering the lower glass substrate has a thickness of 0.1-0.3 μm;

The range of the high dielectric constant is 300-10000; preferably 300-3000.

Both the Pixel electrodes and the Common electrodes are transparent indium tin oxide (ITO) electrodes; the electrode thicknesses are both 0.1 μm. The top view of the electrode is a rectangle or a "zigzag" shape; the purpose of the "zigzag" electrode is to obtain a multi-domain structure, and the display effect is that the change of color with the viewing angle is not obvious.

The width of the protrusion is 1-5 μm, the length is the pixel length, the gap between the protrusions is 2-6 μm, and the height is 1-10 μm;

The thickness of the blue phase liquid crystal layer is 5 to 20 μm, and the light wavelength λ=550nm.

The parameters of the λ/2 biaxial film are n _x =1.511, _ny =1.5095, and _nz =1.51025; the thickness of the λ/2 biaxial film is 184 μm.

Said protrusion has a cross-sectional shape of rectangle, trapezoid, triangle or semi-ellipse.

Compared with the prior art, the beneficial effects of the present invention are: 1. On the basis of the IPS display mode, a trapezoidal high dielectric constant raised layer is introduced on the Pixel electrode and the Common electrode, successfully solving the problem of the blue phase liquid crystal display. The driving voltage is too high and the light transmittance is too low. Through the technical solution, the driving voltage of the blue-phase liquid crystal display is reduced from 83V to about 14V, and the light transmittance is increased from 60% to 70%. 2. Based on the trapezoidal high dielectric constant protrusions, a rectangular high dielectric constant protrusion was fabricated, and by adjusting the lateral width ratio of the protrusions to the electrodes, the maximum light transmission rate of the blue-phase liquid crystal display was achieved under the same parameter conditions. rate increased to 77.8%. More importantly, the fabrication of the structure is simpler and more stable than that of the conventional bump electrodes, and can well eliminate the influence of misalignment, making the bumps of the structure easier to realize in terms of process fabrication.

Other aspects and features of the present invention will become apparent from the following detailed description with reference to the accompanying drawings and the embodiments. It should be noted, however, that this drawing is designed for purposes of illustration only, and not as a setting of the scope of the invention, since it is given by reference.

Description of drawings

Fig. 1 is the structural diagram of the blue phase liquid crystal display that embodiment 1 proposes;

Fig. 2 is the comparison diagram of the voltage-transmittance curve of the traditional IPS blue-phase liquid crystal display of embodiment 1 and the blue-phase liquid crystal display of low driving voltage and high transmittance proposed by the present implementation;

FIG. 3 is a graph showing potential distribution and electric field direction distribution in the blue-phase liquid crystal display proposed in Embodiment 1 and the traditional IPS blue-phase liquid crystal display. Fig. 3 (a) is the blue-phase liquid crystal display proposed in this implementation; Fig. 3 (b) is the traditional IPS blue-phase liquid crystal display;

Fig. 4 is the impact diagram of the voltage-transmittance curve of the blue phase liquid crystal display that the size of embodiment 1 raised dielectric constant proposes to the present implementation; Fig. 4 (a) is raised layer dielectric constant to voltage-transmittance The influence figure of curve; Fig. 4 (b) is the influence figure of raised layer dielectric constant to driving voltage; Fig. 4 (c) is the influence figure of raised layer dielectric constant to light transmittance;

Fig. 5 is the influence diagram of the voltage-transmittance curve of the blue phase liquid display proposed by the embodiment 1 protrusion height;

FIG. 6 is a graph showing the influence of electrode parameters in Embodiment 1 on the voltage-transmittance curve of the blue-phase liquid crystal display proposed in this embodiment.

Fig. 7 is a structural diagram of the rectangular high dielectric constant protrusion proposed in the embodiment 2;

Fig. 8 is a comparison diagram of the voltage-transmittance curve of the trapezoidal high dielectric constant protrusion in embodiment 2 and the blue phase liquid crystal display proposed in this embodiment;

FIG. 9 is a graph showing potential distribution and electric field direction distribution in the blue-phase liquid crystal display proposed in Embodiment 2 and the blue-phase liquid crystal display with trapezoidal high dielectric constant protrusions. Fig. 9 (a) is the blue-phase liquid crystal display proposed in this implementation; Fig. 9 (b) is the raised blue-phase liquid crystal display of trapezoidal high dielectric constant;

Fig. 10 is a graph showing the influence of different bumps and electrode parameters in Embodiment 2 on the electro-optical curve of the blue-phase liquid crystal display proposed in this embodiment.

Fig. 11 is a graph showing the influence of misalignment in Embodiment 2 on the electro-optical curve of the blue-phase liquid crystal display proposed in this embodiment.

FIG. 12 is an iso-contrast perspective view of the blue-phase liquid crystal proposed in Embodiment 2. FIG. Fig. 12 (a) is the equal-contrast viewing angle diagram before the compensation of the blue-phase liquid crystal display proposed under the present implementation; Fig. 12 (b) is the equal-contrast viewing angle diagram after the compensation of the blue-phase liquid crystal display proposed under the present implementation;

Detailed ways

The following is a further description of the implementation of the present invention in conjunction with the accompanying drawings: this embodiment is implemented on the premise of the technical solution of the present invention, providing detailed implementation and specific operation process, but it does not mean that the scope of protection is limited thereto.

The material of the raised layer with a high dielectric constant in the present invention is a known material, and its material can be obtained by doping nanoparticles with a high dielectric constant into an insulating polymer material. The particles are inorganic materials such as graphene flakes, carbon black materials with a particle size of 10-50nm, metal nanoparticles with a particle size of about 10nm, and copper phthalocyanine with a particle size of about 40nm, which have been reported in many documents. Such as: Document 1 [J.Lu, etal, Synthesis and dielectric properties of novel high-Kpolymer composites containing in-situformed silver nanoparticles for embedded capacitor applications, J. Mater. Chem., Vol.16pp.1543-1548, 2006] provides the use of carbon black/Ag nanoparticles/epoxy resin materials Composition, when adding carbon black with a particle size of about 30nm, the weight ratio is 20%; when adding silver nanoparticles with a particle size of 13nm, the weight ratio is about 4%, the material with a dielectric constant of about 2000; in Document 2 [J.Y.Li, C.Huang, Q.M.Zhang, Enhanced electromechanical properties in all-polymer percolativecomposites. Appl. Phys. Lett., Vol.84pp.3124-3126, 2004] using o-CuPc (copper phthalocyanine) with a particle size of 40nm to fill polyurethane composites material, when the volume content of copper phthalocyanine is 3.5%, the dielectric constant of the composite material is as high as 4816; .], using epoxy resin composite material doped with nano-silver particles, when the silver particle size is 40nm, and the volume content is 22%, the material with a dielectric constant greater than 300 can also be obtained.

Example 1

A blue-phase liquid crystal display device according to the present invention is shown in Figure 1, and the composition of the device includes from top to bottom: an upper polarizer 1, a λ/2 biaxial film 2, an upper glass substrate 3, a blue phase A liquid crystal layer 4 , a raised layer with a high dielectric constant, an electrode layer, a lower glass substrate 8 and a lower polarizer 9 .

The electrode layer is Pixel electrodes 6 and Common electrodes 7 distributed sequentially on the lower glass substrate 8 at intervals;

The raised layer of high dielectric constant is covered on the lower glass substrate 8 distributed with Pixel electrodes 6 and Common electrodes 7, and the bumps 5 in the raised layer of high dielectric constant are located on the Pixel electrodes 6 Or directly above the Common electrode 7, the width of the lower part of its section is the same as the width of the Pixel electrode 6 or Common electrode 7 below it;

The high dielectric constant is specifically 2000;

The manufacturing process of the IPS electrode structure of the present invention is the same as the common IPS liquid crystal display manufacturing process. After the IPS electrode structure is manufactured, the high dielectric constant material is coated on the substrate surface of the IPS electrode structure and reused. The bump 5 structure is obtained by conventional photolithography technology.

The high dielectric constant protrusion 5 has a length of pixel size, and its top view is a rectangle with a trapezoidal cross-sectional shape, a height of 5 μm, a lower bottom width of 2 μm, and an upper top width of 1.5 μm; In the raised layer, the thickness of the non-bump 5 (that is, the material covering the lower glass substrate 8 and connected with the raised structure) is 0.2 μm;

The light transmission axis direction of the upper polarizer 1 is -45°, and the light transmission axis direction of the lower polarizer 9 is 45°.

The Pixel electrode 6 and the Common electrode 7 are transparent indium tin oxide (ITO) electrodes, the width is 2 μm, the length is the pixel length, and its top view is rectangular, and the thickness of all electrodes is 0.1 μm; Pixel electrode 6 and The spacing between Common electrodes 7 is 4 μm;

The thickness of the blue phase liquid crystal layer is 10 μm.

The Kerr constant of the blue phase liquid crystal is K=13.7nm/V ² , and the light wavelength λ=550nm.

The parameters of the λ/2 biaxial film are n _x =1.511, n _y =1.5095, and n _z =1.51025.

The thickness of the λ/2 biaxial film is 184 μm.

FIG. 2 shows the relationship between transmittance and voltage (electro-optical curve) of the blue-phase liquid crystal display with low driving voltage and high transmittance proposed by the present invention and the traditional IPS blue-phase liquid crystal display. Through comparison, it can be known that the driving voltage of the traditional IPS blue-phase liquid crystal display is 83V, and the maximum transmittance of light is 60%. However, the driving voltage of the blue-phase liquid crystal display with high dielectric constant protrusions proposed in this embodiment is 14V, and the maximum transmittance of light is 71%. The high dielectric constant value used here is 2000, and the driving voltage obtained by using it is low and the transmittance is high. In order to verify that the value of the dielectric constant can achieve better results, we performed simulation calculations on the driving voltage and transmittance under different dielectric constants, as shown in the descriptions of FIGS. 4 and 5 below.

FIG. 3 shows the distribution diagram of liquid crystal molecules and horizontal electric field in the blue-phase liquid crystal display with low driving voltage and high transmittance proposed by the present invention. Fig. 3(a) shows the distribution diagram of liquid crystal molecules and horizontal electric field in the high dielectric constant blue phase liquid crystal display in this embodiment. Fig. 3(b) shows the distribution diagram of liquid crystal molecules and horizontal electric field in the traditional IPS blue-phase liquid crystal display in this embodiment. By comparison, we can find that the introduction of the high dielectric constant raised layer, compared with the traditional IPS blue-phase liquid crystal display, is conducive to enhancing the horizontal electric field intensity (the density of the electric field line in the horizontal direction becomes larger), and it is also conducive to enhancing The electric field acts on the depth of the liquid crystal layer (the electric field line density in the horizontal direction above the protrusion becomes larger), so as to achieve the purpose of reducing the driving voltage and increasing the light transmittance.

Fig. 4 shows the relationship diagram of electro-optic curves of the blue-phase liquid crystal display with low driving voltage and high transmittance proposed by the present invention under different dielectric constants of the raised layer. It can be seen from Fig. 4(a) that the dielectric constant of the raised layer has a great influence on the electro-optical curve, especially in reducing the driving voltage (the dielectric constant of the traditional raised layer is 3.8, and the high dielectric constant is in this embodiment Below means that the dielectric constant is greater than 300). From FIG. 4( b ), it can be known that under the condition of other parameters being fixed, the larger the dielectric constant of the protrusion is, the lower the driving voltage of the blue phase liquid crystal display is. When the dielectric constant exceeds 2000, the driving voltage tends to be stable. From Figure 4(c), it can be seen that under the condition of other parameters, as the dielectric constant of the raised layer increases, the transmittance also increases. When the dielectric constant exceeds 1000, the transmittance increases with the dielectric constant The effect of the increase is not too great.

Fig. 5 shows the relationship diagram of electro-optic curves of the blue-phase liquid crystal display with low driving voltage and high transmittance under different protrusion heights proposed by the present invention. In this embodiment, the heights of the protrusions are respectively set to 1 μm, 3 μm and 5 μm. Through comparison, it can be seen that the higher the bump height, the lower the driving voltage. As the height of the protrusions increases, the transmittance also increases. Therefore, we can appropriately increase the height of the raised layer to reduce the driving voltage of the blue-phase liquid crystal display under the condition that the thickness of the liquid crystal cell allows.

FIG. 6 shows the relationship diagram of electro-optic curves under different electrode (protrusion) parameters of the blue-phase liquid crystal display with low driving voltage and high transmittance proposed by the present invention. By comparison, it can be seen that when the electrode gap (L) is constant, the larger the electrode width (W), the lower the light transmittance (by comparing the two curves of W=2μm, L=4μm and W=3μm, L=4μm); When the electrode width is constant, the larger the electrode spacing, the higher the driving voltage (compare the two curves of W=3 μm, L=4 μm and W=3 μm, L=6 μm). Therefore, W=2 μm, L=4 μm is a more reasonable electrode parameter setting, that is, the structural parameters of the raised structure are: the width of the lower bottom is 2 μm, and the gap between the lower bottom is 4 μm.

Example 2

The structure of this embodiment is shown in Figure 7, the other parts are the same as in Embodiment 1, the difference is: the cross-sectional shape of the protrusion structure is rectangular, and the width is much smaller than the electrode width, and the width of the protrusion in this embodiment is the same as The lateral ratio of the electrode width is 1/2, and the shape of the protrusion is rectangular, the purpose of which is to improve the transmittance of the liquid crystal display.

FIG. 8 shows the relationship between transmittance and voltage (electro-optic curve) of the blue-phase liquid crystal display proposed by the present invention and the blue-phase liquid crystal display with trapezoidal high dielectric constant protrusions in Example 1. Wherein the hollow circle line is the optimization result of embodiment 1, and the solid triangle line is the result of this embodiment, wherein the width and gap of the electrodes are respectively W=2 μm and L=4 μm, and the width of the raised structure in this embodiment is W ₁ = 1 μm. Through comparison, it can be known that the driving voltage of the blue-phase liquid crystal display in this embodiment is the same as that of the blue-phase liquid crystal display in Example 1, 18V, and the maximum transmittance is increased from 71% to 77.4%.

FIG. 9 shows distribution diagrams of liquid crystal molecules and horizontal electric fields in the blue-phase liquid crystal display with trapezoidal high dielectric constant protrusions and the blue-phase liquid crystal display proposed in this embodiment. Figure 9(a) shows the distribution diagram of liquid crystal molecules and horizontal electric field in the trapezoidal high dielectric constant raised blue phase liquid crystal display. FIG. 9( b ) shows the distribution diagram of liquid crystal molecules and horizontal electric field in the blue phase liquid crystal display proposed in this embodiment. By comparison, we can find that: setting the ratio of the protrusion to the lateral width of the electrode as 1/2 realizes that the horizontal electric field acts on the The depth of the liquid crystal layer (the density of the horizontal electric field lines above the protrusion becomes larger). Therefore, the purpose of increasing the light transmittance is achieved under the premise of maintaining the driving voltage unchanged.

FIG. 10 shows the relationship diagram of the electro-optic curve of the blue-phase liquid crystal display proposed by the present invention under misalignment. In this embodiment, the lateral width ratio of the protrusions to the electrodes is set to 1/2, and the offset positions of the protrusions are 0, 0.1 μm, 0.2 μm and 0.3 μm respectively. Through comparison, it can be known that within the range of 0.3 μm from the central position of the protrusion, the influence of misalignment on the electro-optical curve can be ignored. Therefore, compared with the traditional bump electrodes, the protrusions of this structure are not only simpler and more stable to manufacture, but also can well eliminate the influence caused by misalignment.

Fig. 11 shows the relationship diagram of the electro-optic curves of the blue phase liquid crystal display proposed by the present invention under different electrode parameters and different protrusion parameters. By comparison, it can be seen that when the electrode width and protrusion width are constant, the driving voltage and transmittance will increase as the electrode gap increases (comparison W=2μm, L=4μm, W ₁ =1μm, H= 3μm and W=2μm, L=6μm, W ₁ =1μm, H=3μm two curves); when the electrode spacing and protrusion width are constant, the wider the electrode width, the higher the driving voltage, and the transmittance also increases with It has decreased (compare the two curves of W=2μm, L=4μm, W ₁ =1μm, H=3μm and W=3μm, L=4μm, W ₁ =1μm, H=3μm); When the width and the electrode gap are constant, the driving voltage decreases as the bumps become wider, but the transmittance decreases accordingly (compared to W=2μm, L=4μm, W ₁ =1μm, H= 3μm and W=3μm, L=4μm, W ₁ =2μm, H=3μm two curves); therefore, weighing the driving voltage and transmittance, W=2μm, L=4μm, W ₁ =1μm, H=3μm It is a reasonable electrode and bump size.

FIG. 12 shows the viewing angle diagram of the blue-phase liquid crystal display with low driving voltage and high transmittance proposed by the present invention. Fig. 12(a) shows the iso-contrast diagram of the blue-phase liquid crystal display proposed in this embodiment before compensation; Fig. 12(b) shows the iso-contrast diagram of the blue-phase liquid crystal display proposed in this embodiment after compensation. By comparing the iso-contrast diagrams before and after compensation, it can be seen that the blue-phase liquid crystal display can display an iso-contrast diagram with an excellent viewing angle under the compensation of a simple λ/2 biaxial film. For example, before using the compensation film, the area with a contrast ratio greater than 1000:1 is within 20° polar angle, and the contrast ratio of almost the entire display area is greater than 10:1; after using the compensation film, the area with a contrast ratio greater than 1000:1 is within 60° Within polar angles, the contrast ratio over the entire display area is greater than 100:1.

Matters not covered in the present invention are known technologies.

Claims (8)

1. A blue-phase liquid crystal display device is characterized in that the composition of the device comprises successively from top to bottom: an upper polarizer, a λ/2 biaxial film, an upper glass substrate, a blue-phase liquid crystal layer, and a high dielectric constant bump layer, electrode layer, lower glass substrate and lower polarizer; The electrode layer is a Pixel electrode and a Common electrode successively distributed on the lower glass substrate at intervals; the thickness of the Pixel electrode and the Common electrode is 0.08-0.12 μm, the width of the electrode is 1-5 μm, and the distance between the electrodes is 2-6 μm ; The protrusion in the high dielectric constant protrusion layer is located directly above the Pixel electrode or Common electrode, and the width of the lower part of the section is 1/2 to 3/2 of the width of the lower electrode; The range of the high dielectric constant is 300-10000. 2 . The blue-phase liquid crystal display device according to claim 1 , wherein the thickness of the part covering the lower glass substrate in the raised layer with high dielectric constant is 0.1-0.3 μm. 3. blue phase liquid crystal display device as claimed in claim 1, it is characterized in that described Pixel electrode and Common electrode are transparent indium tin oxide (ITO) electrode; Electrode thickness is 0.1 μ m; The top view of electrode is rectangle or "Zhi" glyph. 4. The blue phase liquid crystal display device according to claim 1, characterized in that the width of the protrusion is 1-5 μm, the length is the pixel length, the gap between the protrusions is 2-6 μm, and the height is 1-10 μm. 5. The blue-phase liquid crystal display device according to claim 1, characterized in that the thickness of the blue-phase liquid crystal layer is 5 to 20 μm, and the light wavelength λ=550 nm. 6. The blue phase liquid crystal display device as claimed in claim 1, characterized in that the parameters of the described λ/2 biaxial film are n _x =1.511, _ny =1.5095, _nz =1.51025; the λ/2 2 The thickness of the biaxial film is 184 μm. 7. The blue-phase liquid crystal display device as claimed in claim 1, characterized in that the protrusion has a cross-sectional shape of rectangle, trapezoid, triangle or semi-ellipse. 8. The blue-phase liquid crystal display device according to claim 1, characterized in that said high dielectric constant is preferably 300-3000.