KR20050078468A - Liquid crystal display and manufacturing method thereof - Google Patents

Abstract

Disclosed are a liquid crystal display device having a refractive index anisotropic layer having a color filter function and a viewing angle compensation function, and a method of manufacturing the same. The liquid crystal layer is formed between the upper substrate and the lower substrate, and the refractive index anisotropic layer is formed between the front polarizer and the rear polarizer to compensate for the phase difference of light passing through the liquid crystal layer. Here, a cholesteric liquid crystal can be used for the refractive anisotropic layer. By forming the refractive index anisotropic layer having the function of the color filter and the viewing angle compensation, the process can be simplified by omitting the color filter and the overcoat process, and the wide viewing angle can be realized even if the liquid crystal display is not provided with a separate optical compensation film. .

Description

Liquid crystal display and its manufacturing method {LIQUID CRYSTAL DISPLAY AND MANUFACTURING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display and a method for manufacturing the same, and more particularly, to a liquid crystal display having a refractive index anisotropic layer having a function of color filters and viewing angle compensation, and a method for manufacturing the same.

First, as shown in FIG. 1, an array substrate 10 including a switching element, a pixel electrode layer 14, and a first alignment layer 16, which are sequentially formed on a first transparent substrate 12, and a second transparent substrate ( The color filter substrate 20 including the color pixel layer 24, the overcoating layer 26, the common electrode layer 28, and the second alignment layer 29 sequentially formed on the substrate 22, the array substrate 10, and the color On the upper surface of the liquid crystal layer 30 formed between the filter substrate 20, the first retardation film 42 and the rear polarizer 44 sequentially disposed on the rear surface of the array substrate 10, and the color filter substrate 20. The second phase difference film 46 and the front polarizing plate 48 are sequentially arranged.

As such, in the liquid crystal display device using the refractive anisotropy effect of the liquid crystal, the liquid crystal molecules of the liquid crystal layer 30 transition to a homogeneous alignment or a homeotropic alignment according to an applied voltage.

In particular, when the liquid crystal molecules maintain the vertical alignment state, when viewed from the front, the polarization axes of the front polarizer and the rear polarizer are orthogonal to each other so that light leakage does not occur. Light leakage occurs. In order to compensate for such light leakage, a compensation film such as a biaxial film or a uniaxial film is attached to the outside of the liquid crystal cell together with the polarizer.

Accordingly, the technical problem of the present invention has been made in view of the above, and the technical problem of the present invention is to provide a refractive index anisotropic layer having a function of color filter and viewing angle compensation in a liquid crystal display device defined by a color filter substrate and an array substrate. .

 In addition, another technical problem of the present invention is to provide a method of manufacturing the above-described liquid crystal display device.

According to an aspect of the present invention, a liquid crystal display device includes an upper substrate, a lower substrate, a front polarizer disposed on the upper substrate, a rear polarizer disposed under the lower substrate, and a liquid crystal formed between the upper substrate and the lower substrate. And a refractive index anisotropic layer formed between the front polarizer and the rear polarizer to serve as a color filter and a viewing angle compensation through the liquid crystal layer.

According to another aspect of the present invention, there is provided a method of manufacturing a color filter substrate for a liquid crystal display device, the method including: a liquid crystal display device including a color filter substrate accommodating a liquid crystal layer through incorporation with an array substrate. In the manufacturing method, (a) coating and orienting a UV curable liquid crystalline polymer material on a substrate, (b) fixing the alignment state through irradiation of UV light using a mask on the resultant of the step (a) to retard the phase difference Forming a refractive index anisotropic layer having a function, and adjusting the pitch of the cholesteric liquid crystal through irradiation of UV light to transmit light for each of the red, green, and blue wavelength bands, and (c) a common electrode layer on the refractive anisotropic layer. Forming an alignment layer on the common electrode layer. As another method, (a) the pitch is changed by adjusting the chiral component of the cholesteric liquid crystal, and then patterned and coated for each pixel, and then aligned to have selective reflection characteristics for each wavelength of red, green, and blue, Fixing the alignment state through irradiation of UV light to form a refractive index anisotropic layer having a phase difference function, (b) forming a common electrode layer on the refractive index anisotropic layer, and (c) forming an alignment layer on the common electrode layer. Steps. In addition, the refractive anisotropic layer may be formed between the upper substrate and the front polarizer rather than inside the liquid crystal cell, and the common electrode layer and the pixel electrode layer may be arranged together on the array substrate.

According to such a liquid crystal display and a manufacturing method thereof, the color filter and the overcoat are formed by forming a refractive index anisotropic layer having a function of color filter and viewing angle compensation through a UV or thermal curing process after coating the UV curable liquid crystal polymer material on the liquid crystal display. By omitting the process, the process can be simplified, and a wide viewing angle can be realized without providing a separate viewing angle compensation film outside the liquid crystal panel.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail with reference to attached drawing.

2 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

2, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal layer 300 formed between an array substrate 100, a color filter substrate 200, an array substrate 100, and a color filter substrate 200. The rear polarizer 410 formed under the array substrate 100 and the front polarizer 420 formed on the color filter substrate 200 are included.

The array substrate 100 includes a gate electrode 110, a gate electrode 110, and a gate insulating layer 112, a semiconductor layer 114, and an ohmic contact layer 116 formed on the transparent substrate 105. And a switching element TFT including a source electrode 120 and a drain electrode 130.

In addition, the array substrate 100 is formed on the passivation layer 140 and the passivation layer 140 exposing a part of the drain electrode 130 while covering the switching element TFT, and is thick to expose a part of the drain electrode 130. An organic insulating layer 144 is included.

In addition, the array substrate 100 includes a pixel electrode layer 150 connected to the drain electrode 130 through a first contact hole 141 formed by opening an organic insulating layer 144 and a portion of the passivation layer 140. And a first alignment layer 160 formed thereon. The pixel electrode layer 150 is a kind of transmission electrode that transmits light, and indium tin oxide (ITO), tin oxide (TO), or indium zinc oxide (IZO) is used.

Although not shown, a separate capacitor wiring may be formed in an area spaced from the switching element TFT by a predetermined distance, and the capacitor wiring and the pixel electrode layer 150 form a storage capacitor Cst. Such a storage capacitor formation method is called an independent wiring method.

Alternatively, a front gate method may be employed.

The color filter substrate 200 includes a transparent substrate 205, a black matrix layer 210, a refractive index anisotropic layer 220, a common electrode layer 240, and a second alignment layer 250.

The black matrix layer 210 is formed on the transparent substrate 205 and has a lattice shape that exposes a portion corresponding to the pixel electrode layer 150 formed on the array substrate 100.

The refractive index anisotropic layer 220 having a phase difference function is formed on the black matrix layer 210 to protect the black matrix layer 210 and compensate for the phase difference of light passing through the liquid crystal layer 300. If the liquid crystal display is of a transmissive type, light is artificial light provided by the backlight assembly. If the liquid crystal display is of a reflective type, light is natural light incident from the top of the color filter substrate. If the liquid crystal display is a reflection-transmissive type, the light is artificial light and natural light described above. In addition, the refractive anisotropic layer may be formed between the upper substrate and the front polarizer rather than inside the liquid crystal cell.

Specifically, the refractive anisotropic layer 220 is formed of an ultraviolet (UV) curable liquid crystal polymer material, and preferably is a cholesteric liquid crystal as shown in FIG. 3.

3 is a diagram schematically illustrating a molecular structure of a cholesteric liquid crystal.

As shown in Figure 3, the director changes gradually along the helical axis. This helical structure is characteristic of the cholesteric phase with its rotation period p. And this spiral axis coincides with the optical axis. That is, when a molecule forming a nematic phase has a chiral (chiral) structure in which the mirror symmetry is broken in the molecular structure, a nematic phase of a spiral structure may be displayed, which is called a cholesteric liquid crystal. . Locally, cholesteric liquid crystals, like nematic liquid crystal molecules, point in one direction, but macroscopically has a spiral axis perpendicular to the director, and the director has a characteristic of constantly rotating about this axis. Therefore, cholesteric liquid crystals have a spatial order because they are arranged regularly along the directional order and the helix axis.

 This cholesteric liquid crystal layer functions as a compensation film for improving the viewing angle.

The compensation effect of this compensation film is shown in FIG.

The method of forming the refractive anisotropic layer 220 using the cholesteric liquid crystal is as follows.

A refractive index anisotropic layer or work having a biaxial film function by coating and aligning the cholesteric liquid crystal to a desired thickness on the color filter substrate 200 and irradiating UV light to fix the alignment state of the cholesteric liquid crystal. A refractive index anisotropic layer having a uniaxial film function is formed.

For example, a biaxial film is formed by irradiating cholesteric liquid crystal with polarized UV light, and a C-plate film is formed by irradiating cholesteric liquid crystal with unpolarized UV light. In this case, the pitch of the cholesteric liquid crystal may be changed by adjusting the intensity of the UV light for each color of red, green, and blue using a mask in the process of irradiating UV light. As a method of adjusting the intensity, there is a method of electrically adjusting the intensity of the UV lamp or adjusting the exposure time while keeping the intensity constant. When the pitch of the cholesteric liquid crystal is changed by adjusting the intensity of UV light, the refractive anisotropic layer exhibits selective reflection characteristics according to the pitch. That is, by adjusting the pitch of the cholesteric liquid crystal to adjust the reflected wavelength region, it is possible to form a refractive index anisotropic layer that can realize red, green, and blue colors at the same time. In another method, the chiral component of the cholesteric liquid crystal is adjusted to change the pitch, and then patterned and coated for each pixel, and aligned to have selective reflection characteristics for each wavelength of red, green, and blue, and to irradiate UV light. It is also possible to use a method of fixing the alignment state through to form a refractive index anisotropic layer having a phase difference function.

As described above, the wavelength range reflected may be adjusted by adjusting the pitch of the cholesteric liquid crystal. This pitch is adjusted according to the amount of the component having chiral properties, and the pitch tends to decrease as the chiral component increases. In other words, it is possible to relatively increase the amount of the chiral component to achieve blue. This effect is shown in FIG.

The biaxial film has refractive index characteristics in which the refractive index nx in the x direction, the refractive index ny in the y direction, and the refractive index nz in the z direction are different from each other.

Meanwhile, uniaxial films are classified into A-plate films and C-plate films. The A-plate film has the same refractive index ny in the y direction and the refractive index nz in the z direction, but has a refractive index characteristic smaller than the refractive index nx in the x direction. When the UV curable liquid crystal having the refractive index characteristic of the A-plate film is irregularly arranged on the xy plane and has a thickness, the refractive index (nx) in the x direction and the refractive index (ny) in the y direction are the same, but the refractive index (nz) in the z direction is the same. Rather, it has a large refractive index characteristic, which is called a C-plate film.

The common electrode layer 240 is formed on the refractive index anisotropic layer 220 and receives a common electrode voltage Vcom from the outside. The arrangement of the liquid crystal molecules is determined by a potential difference between the common electrode voltage Vcom and a voltage applied to the pixel electrode layer 150 formed on the array substrate 100. The common electrode layer 240 may be arranged together with the pixel electrode layer 150 on the array substrate 100.

The second alignment layer 250 is formed on the common electrode layer 240 to uniformly align the liquid crystal. Of course, when not forming the common electrode layer 240 may be formed on the refractive index anisotropic layer 220. In addition, a λ / 4 plate (not shown) may be inserted between the color filter substrate 200 and the front polarizer 420. For example, the refractive index anisotropic layer 220 transmits 100% of red light, but 50% of green and blue light is reflected and 50% of circularly polarized light is transmitted in a red pattern. (Not shown) serves to convert circularly polarized light into linearly polarized light. The green and blue light in the linear polarization state are absorbed while passing through the polarizing plate 420, and thus the luminance of the green and blue light does not penetrate the pixel of the red pattern.

The liquid crystal layer 300 is formed between the array substrate 100 and the color filter substrate 200, and the potential difference applied between the pixel electrode layer 150 of the array substrate 100 and the common electrode layer 240 of the color filter substrate 200. Transition in response. The liquid crystal layer 300 may take a twisted nematic (TN) mode, may take an in-plane-switching (IPS) mode, employ a vertical alignment (VA) mode, and selectively compensated birefringence (OCB) mode. You can also take When the In-Plane-Switching (IPS) mode is used, the common electrode layer 240 may be arranged like the pixel electrode layer 150 on the array substrate 100 instead of the color filter substrate 200.

The rear polarizer 410 is disposed under the array substrate 100, and polarizes artificial light provided from the rear surface to provide the array substrate 100.

The front polarizer 420 is disposed on the color filter substrate 200, and polarizes and radiates artificial light passing through the array substrate 100, the liquid crystal layer 300, and the color filter substrate 200.

4A-4D are cross-sectional views of the color filter substrate at an intermediate stage of manufacturing the color filter substrate of FIG. 2 according to one embodiment of the invention.

First, as shown in FIG. 4A, a chromium (Cr) film is formed on one surface of the transparent substrate 205, and a positive photoresist is coated on the chromium (Cr) film. In addition, the photoresist is selectively exposed using a predetermined mask and then developed to form the light blocking layer 210 in a desired area.

Subsequently, as shown in FIG. 4B, a UV curable liquid crystalline polymer material such as cholesteric liquid crystal is coated and oriented on the entire surface of the transparent substrate 205. Subsequently, the alignment state is fixed through irradiation of UV light to form the refractive anisotropic layer 220 having a phase difference function.

Subsequently, as shown in FIG. 4C, the common electrode layer 240 having a transparent and electrically conductive like ITO is formed on the refractive index anisotropic layer 220.

Subsequently, as shown in FIG. 4D, the alignment layer 250 is formed on the entire surface of the common electrode layer 240 so that the liquid crystals are arranged in a predetermined direction. The alignment layer 250 may be formed of either an inorganic material or an organic material as long as it is a material capable of causing a predetermined pretilt on the liquid crystal molecules. As an inorganic material, metal oxides, such as silicon oxide (SiO) and magnesium oxide (MgO), magnesium fluoride, gold, etc. are used. In the case of using an inorganic material, since the deposition is performed in all directions, when the deposition angle is set, the alignment process is performed simultaneously with the formation of the alignment film.

As the organic material, a resin such as polyimide or polyvinyl alcohol, a chemical adsorption material such as a silane compound capable of chemisorbing onto a substrate, or a material capable of forming a thin film such as polyamic acid is used. When using an organic material, it is necessary to perform an orientation process. One example of the alignment treatment is performed by a method such as rubbing in the same direction on the array substrate 100 or irradiating polarized ultraviolet rays.

The alignment film 250 may be formed of a single layer made of the same material, but may be formed of a plurality of layers using two or more materials. For example, you may form an organic thin film on the thin film which consists of inorganic materials. At this time, when forming the alignment film 250 in plural layers, a vertical alignment agent such as lecithin may be used in addition to the organic material.

Through the process of FIGS. 4A to 4D described above, the color filter substrate 200 is completed, is coupled to the array substrate 100, and the liquid crystal between the color filter substrate 200 and the array substrate 200. By displaying 300, the liquid crystal panel is completed.

As described above, by applying a UV curable liquid crystal polymer material to the liquid crystal display device and irradiating and curing UV light to impart the function of the retardation film, even if the retardation film is not placed on the liquid crystal panel to pass through the liquid crystal layer The phase difference of light can be compensated for. As a result, the number of films for attaching the retardation film separately to the liquid crystal panel and the number of assembly processes can be reduced, thereby reducing the manufacturing cost of the liquid crystal display device.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

As described above, according to the present invention, a film having a color filter function and a viewing angle compensation function is formed on the liquid crystal display device to improve the viewing angle characteristics of the liquid crystal display device, reduce thickness and weight, and also manufacture costs. Can be saved.

1 is a diagram schematically illustrating a general liquid crystal display device.

2 is a diagram for describing a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a view for schematically explaining the molecular structure of the cholesteric liquid crystal.

4A to 4D are diagrams for describing a method of manufacturing the color filter substrate of FIG. 2.

5 is a graph showing the compensation effect of the refractive index anisotropic layer made of cholesteric liquid crystal.

6 is a graph showing reflection characteristics for each wavelength according to the pitch.

<Description of the symbols for the main parts of the drawings>

100: array substrate 140: protective film

144: organic insulating layer 150: pixel electrode layer

160: alignment layer 200: color filter substrate

210: black matrix layer 220: refractive anisotropic layer

240: common electrode layer 250, 260: alignment layer

300: liquid crystal layer 410, 420: polarizing plate

Claims (17)

Upper substrate, A lower substrate facing the upper substrate, A front polarizer disposed on the upper substrate, A rear polarizer disposed under the lower substrate, A liquid crystal layer formed between the upper substrate and the lower substrate, and An refractive index anisotropic layer formed between the front polarizer and the rear polarizer to have a color filter function and a viewing angle compensation function. Liquid crystal display comprising a.  In claim 1, The refractive index anisotropic layer is a liquid crystal display device made of a UV curable liquid crystal polymer material.  In claim 1, The refractive index anisotropic layer is a liquid crystal display device made of a cholesteric liquid crystal material.  The method of claim 2 or 3, And a [lambda] / 4 plate disposed between the upper substrate and the front polarizer.  The method according to any one of claims 1 to 3, And a refractive index anisotropic layer having a function of a color filter and viewing angle compensation on the upper substrate.  The method according to any one of claims 1 to 3, The upper substrate includes a common electrode layer, and the refractive index anisotropic layer is formed on the common electrode layer.  The method according to any one of claims 1 to 3, The lower substrate includes a pixel electrode layer, and the refractive index anisotropic layer is formed on the pixel electrode layer.  The method according to any one of claims 1 to 3, The lower substrate includes a common electrode and a pixel electrode layer, and the refractive anisotropic layer is formed on the common electrode and the pixel electrode layer.  The method according to any one of claims 1 to 3, The liquid crystal display device is any one of a VA, TN, IPS mode.  In the manufacturing method of the color filter substrate for liquid crystal display devices which accommodates a liquid crystal layer through coalescence with an array substrate, Coating a UV curable liquid crystalline polymer layer on the substrate, Orienting the polymer material layer, and UV light is irradiated to the polymer layer through a mask so that the polymer layer has a selective reflection characteristic for each wavelength of red, green, and blue, and the refractive index anisotropy having a phase difference function is fixed by fixing the alignment state of the polymer layer. Forming a layer The manufacturing method of the color filter substrate for liquid crystal display devices containing these. In claim 10, The said color filter is a cholesteric liquid crystal, The manufacturing method of the color filter substrate for liquid crystal display devices. In claim 10, The UV light is polarized UV light, and the refractive index anisotropic layer has a biaxial film function. In claim 10, The said UV light is unpolarized UV light, The said refractive index anisotropic layer has a C-plate film function, The manufacturing method of the color filter substrate for liquid crystal display devices. In the manufacturing method of the color filter substrate for liquid crystal display devices which accommodates a liquid crystal layer through coalescence with an array substrate, (a) adjusting the pitch of the chiral component of the cholesteric liquid crystal to form a first color filter corresponding to the first pixel group, (b) adjusting the pitch of the chiral component of the cholesteric liquid crystal to form a second color filter corresponding to the second pixel group, and (c) adjusting the pitch of the chiral component of the cholesteric liquid crystal to form a third color filter corresponding to the third pixel group Method for manufacturing color filter substrate for liquid crystal display device comprising a The method of claim 14, And the first, second and third color filters are red, green, and blue, respectively. The method of claim 14, Wherein each group of the color filters is formed of a film of different layers. The method of claim 14, The said refractive index anisotropic layer is a manufacturing method of the color filter substrate for liquid crystal display devices which is a C-plate film or a biaxial film.