KR19980029985A - Reflective liquid crystal display device and manufacturing method thereof - Google Patents

Abstract

A reflective liquid crystal display device and its manufacturing method are disclosed. In the liquid crystal display device according to the present invention, a polymer-liquid crystal mixture in which a liquid crystal mixture and an ultraviolet curable polymer compound are mixed in a predetermined ratio is enclosed in each cell formed in the liquid crystal layer, and between the liquid crystal layer and the electrode for protecting the liquid crystal layer. A protective layer is interposed. According to the present invention, since the liquid crystal mixture in the liquid crystal layer uses a polymer-liquid crystal mixture layer surrounded by an ultraviolet curing polymer, it is possible to express two or more colors by patterning to implement two or more different colors separately. have.

Description

Reflective liquid crystal display device and its manufacturing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device and a manufacturing method thereof, and more particularly, to a reflective liquid crystal display device capable of displaying two or more colors and a method of manufacturing the same.

In addition to the low power consumption and low power consumption, the liquid crystal display device has been developed in various forms as an image display device due to its light and small structural advantages such as a plasma display panel or an electroluminescent effect device. It is also becoming very wide.

In the liquid crystal display devices currently in use, the liquid crystal display devices of the active matrix type using a simple matrix or thin film transistor (TFT) are applied with liquid crystals of TN (Twisted Nematic) type and STN (Super Twisted Nematic). At least one polarizer (ie, a polarizer) is required. However, in the liquid crystal display element, the polarizing plate shields light of up to 50% or more while controlling the polarization, thereby decreasing the light utilization efficiency for image display.

Therefore, in order to obtain an image of the required brightness, a high brightness background light source must be applied. However, in the case of a laptop type word processor or a computer using a battery or a storage battery as a power source, there is a problem in that it cannot be used continuously for a long time due to excessive power consumption of the power source.

Meanwhile, the general liquid crystal display device including the liquid crystal display device using the TN and STN liquid crystals has a structure in which the liquid crystal is filled between two glass plates, so that a cell gap, that is, a light control region, is formed for even image formation. It is necessary to strictly control and adjust the mutual gap between the glass plates. However, due to the limitations of the manufacturing process technology of the glass plate at present, it is difficult to supersize.

Conventionally, there has been a liquid crystal display device that does not use a polarizing plate, for example, CSM (Dynamic Scattering Mode) and CNT (Cholesteric) effect using a transition effect at the time of the development of the liquid crystal display device. Nematic transition type). Since the DSM liquid crystal display device has a slow response speed and a thicker thickness than other liquid crystal display devices, the use range is extremely narrow at present.

In the CNT liquid crystal display device, in the case of manufacturing a liquid crystal display device using a cholesteric-nematic liquid crystal mixture, the reflection wavelength (λ) is the average control ratio (n) of the nematic liquid crystal and the liquid crystal mixture pitch This is a product of (pitch) (p), i.e., an amount expressed by λ = n · p. Accordingly, a reflective liquid crystal display device may be implemented.

However, in the case described above, only monochrome display is possible and two or more colors cannot be displayed. That is, the cholesteric-nematic liquid crystal mixture used in the manufacture of the reflective liquid crystal display element cannot be patterned and thus cannot display two or more colors.

Accordingly, it is an object of the present invention to provide a reflective liquid crystal display device capable of displaying two or more colors.

Another object of the present invention is to provide a method of manufacturing the liquid crystal display device as described above.

FIG. 1 schematically illustrates a configuration of a reflective liquid crystal display device according to an exemplary embodiment of the present invention.

2 is a view showing a state of the liquid crystal layer when an electric field is applied to the liquid crystal display device according to the present invention.

3 is a view showing a state of the liquid crystal layer when no electric field is applied to the liquid crystal display device according to the present invention.

Explanation of symbols for the main parts of the drawings

10a, 10b: first and second substrates, 20a, 20b: first and second electrodes

30: liquid crystal layer, 32, 32a, 32b: liquid crystal mixture

34: ultraviolet curing polymer compound, 35: partition wall

40: protective layer

In order to achieve the above object, the present invention provides a second substrate including a first substrate on which a first electrode for driving a liquid crystal is formed, and a second electrode disposed to be spaced apart from the first substrate and opposing the first electrode. And a liquid crystal layer comprising a cell array in which cells each separated by a partition between the first electrode and the second electrode are arranged in a predetermined shape, wherein the liquid crystal layer is formed in the liquid crystal layer. Each cell is provided with a reflective liquid crystal display device characterized by encapsulating a liquid crystal mixture, which is a mixture of cholesteric liquid crystals and nematic liquid crystals, and a polymer-liquid crystal mixture in which UV-curable polymer compounds are mixed in a predetermined ratio.

Preferably, a protective layer for protecting the liquid crystal layer is interposed between the liquid crystal layer and the second electrode.

Preferably, the polymer-liquid crystal mixture comprises about 50-70% by weight of the liquid crystal mixture.

Also preferably, the partition is formed of polyimide, and the protective layer is formed of silicon oxide.

In order to achieve the above another object, the present invention, the first step of forming a partition for dividing the electrode into a predetermined region on the substrate on which the electrode is formed on the upper surface, the liquid crystal mixture and the ultraviolet curable polymer compound is mixed on the resultant A second step of coating the polymer-liquid crystal mixture, a third step of forming a cured polymer-liquid crystal mixture layer by irradiating UV on the coated polymer-liquid crystal mixture, and an insulating material on the polymer-liquid crystal mixture layer. Vapor deposition to form an insulating layer, a fifth step of forming a photoresist film defining only a necessary portion on the insulating layer, and the insulating layer and the polymer-liquid crystal mixture layer are wetted using the photoresist film as a mask. And a sixth step of removing by etching, and a seventh step of removing the photoresist film. It provides a method of producing crystal display device.

If necessary, the second to seventh steps may be repeated a predetermined number of times.

Preferably, in the second step, 10-25 wt% of aromatic urethane acrylate, 2-10 wt% of 2-hydroxyethyl methacrylate, 2-10 wt% of 2-ethyl as the polymer-liquid crystal mixture Compounds containing hexyl acrylate and from 50 to 70% by weight of the liquid crystal mixture are used. Or as the polymer-liquid crystal mixture, 10 to 25% by weight of aromatic urethane acrylate, 2 to 10% by weight of 2-hydroxyethyl methacrylate, 2 to 10% by weight of 2-ethylhexyl acrylate, 2 to 10 You may use the compound containing a weight% trimethylol propane triacrylate and 50-70 weight% liquid crystal mixture.

Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 schematically illustrates a configuration of a reflective liquid crystal display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a reflective liquid crystal display device according to a preferred embodiment of the present invention is spaced apart from a first substrate 10a having a first electrode 20a for driving a liquid crystal and the first substrate 10a. And a second substrate 10b including a second electrode 20b facing the first electrode 20a and the partition wall 35 between the first electrode 20a and the second electrode 20b. Cells separated by each other include a liquid crystal layer 30 including a cell array arranged in a predetermined shape. Each cell formed in the liquid crystal layer 30 is filled with a polymer-liquid crystal mixture in which a liquid crystal mixture 32 and an ultraviolet curable polymer compound 34 are mixed in a predetermined ratio, and the liquid crystal layer 30 and the second electrode ( A protective layer 40 for protecting the liquid crystal layer 30 is interposed between 20b).

Here, a mixture of cholesteric liquid crystal and nematic liquid crystal is used as the liquid crystal mixture. Here, the cholesteric liquid crystal and the cholesteric liquid crystal may be used to reflect light of a desired wavelength corresponding to each color, for example, red (R), green (G), and blue (B) when light is transmitted to the liquid crystal display. The composition ratio of the nematic liquid crystal can be adjusted.

As the ultraviolet curable polymer compound, aromatic urethane acrylate, 2-hydroxyethyl methacrylate and 2-ethylhexyl acrylate are mixed in a predetermined ratio. Consisting of compounds. If necessary, the polymer compound may further include trimethylol propane triacrylate.

In addition, in order to cure the polymer compound by ultraviolet rays, the polymer compound may further include a photoinitiator.

In addition, the liquid crystal mixture in the polymer-liquid crystal mixture is contained in an amount of about 50 to 70% by weight, preferably 60 to 70% by weight. In the present invention, by adjusting the pitch of the liquid crystal mixture mixed with the polymer compound, it is possible to adjust the value of the reflected wavelength, so that the wavelength corresponding to the desired color is reflected. Here, the higher the content ratio of the liquid crystal in the polymer-liquid crystal mixture, the lower the driving voltage of the liquid crystal display element.

In addition, the partition wall 35 separating each cell in the cell array of the liquid crystal layer 30 may be formed of polyimide, and the protective layer 40 may be formed of silicon oxide.

2 is a view showing a state of the liquid crystal layer when an electric field is applied to the liquid crystal display device according to the present invention. As shown in FIG. 2, in the liquid crystal display device according to the present invention, when a constant voltage V is applied between both electrodes, the spiral axes serving as the rotation centers of the liquid crystal molecules in the liquid crystal mixture 32a are the substrates 10a and 10b. It is perpendicular to the surface, and when light is incident, the wavelength according to the pitch of the liquid crystal mixture is reflected.

In the liquid crystal display device according to the present invention, since the liquid crystal mixture reflecting R, G, and B is patterned as a separate cell, each of R, G, and B can be reflected. Further, according to the present invention, when an electric field is applied to both electrodes of the liquid crystal display element, light is selectively reflected among R, G, and B, and thus color can be selectively displayed.

3 is a view showing a state of the liquid crystal layer when no electric field is applied to the liquid crystal display device according to the present invention. As shown in FIG. 3, when there is no voltage applied between both electrodes in the liquid crystal display according to the present invention, incident light is scattered, and when such scattered light passes through the liquid crystal mixture 32b and the polymer compound 34, the light is emitted. An absorbent plate (not shown) installed behind the substrate is reached and appears black.

Next, the method of manufacturing the liquid crystal display element which concerns on this invention which has the above structure is demonstrated in detail.

Referring to FIG. 1, a method of manufacturing a liquid crystal display device according to a preferred embodiment of the present invention is first coated with a transparent conductive film made of indium tin oxide (ITO) (In2O3) on a first substrate 10a. The conductive film is patterned to form the first electrode 20a for driving the liquid crystal. Thereafter, a barrier layer material layer formed of a predetermined material, for example, polyimide, is coated on the first electrode 20a, and then patterned to form the barrier rib 35.

Subsequently, in order to form one of R, G and B regions, for example, R region, the liquid crystal mixture 32 and the ultraviolet curable polymer compound 34 are mixed on the resultant in a predetermined ratio. The polymer-liquid crystal mixture is coated. As the polymer-liquid crystal mixture, about 10 to 25% by weight, preferably about 15 to 20% by weight of aromatic urethane acrylate, about 2 to 10% by weight, preferably about 3 to 7% by weight of 2-hydroxy Ethyl methacrylate, about 2 to 10% by weight, preferably about 4 to 8% by weight of 2-ethylhexyl acrylate, and about 50 to 70% by weight, preferably about 60 to 70% by weight of the liquid crystal mixture The compound containing can be used. Or as said polymer-liquid crystal mixture, about 10 to 25% by weight, preferably about 15 to 20% by weight of aromatic urethane acrylate, about 2 to 10% by weight, preferably about 3 to 7% by weight of 2- Hydroxyethyl methacrylate, about 2 to 10% by weight, preferably about 4 to 8% by weight of 2-ethylhexyl acrylate, about 2 to 10% by weight, preferably about 4 to 8% by weight of trimethylol It is also possible to use compounds comprising propane triacrylate and from about 50 to 70% by weight, preferably from about 60 to 70% by weight, of the liquid crystal mixture. In addition, the liquid crystal mixture is used by appropriately adjusting the mixing ratio of the cholesteric liquid crystal and the nematic liquid crystal in a conventional manner in order to obtain the reflected light having a desired wavelength corresponding to any one of R, G or B.

Thereafter, ultraviolet rays are irradiated to cure the polymer-liquid crystal mixture to form the polymer-liquid crystal mixture layer.

Thereafter, silicon oxide, for example, SiO 2, is deposited as an insulating material on the polymer-liquid crystal mixture layer to form an insulating layer. Thereafter, a photoresist film is formed on the insulating layer. The photoresist film is formed by wet etching the unnecessary portions exposed through the photoresist film, and the photoresist film is removed to remove only the necessary portions from the polymer-liquid crystal mixture layer. By leaving the insulating layer, a cell in the R region covered with a protective layer made of an insulating material is formed.

Then, to form the remaining two regions of the R region, the G region, and the B region, respectively, using the polymer-liquid crystal mixture having the above-described mixing ratio, coating, curing, forming a protective layer, and unnecessary formation of the polymer-liquid mixture described above. By repeating the partial removal step as many times as necessary, the cells constituting the G region and the B region, respectively, are sequentially formed. When the above steps are completed, the liquid crystal layer 30 and the protective layer 40 including the cell array including the cells of the R region, the G region, and the B region, each having different driving characteristics, are completed.

Thereafter, the second substrate 10b having the transparent second electrode 20b is assembled on the protective layer 40, and then the liquid crystal display device according to the present invention is completed by a conventional method.

Here, the barrier rib 35 and the protective layer 40 are formed to protect the liquid crystal contained in the polymer. That is, the partition wall 35 and the protective layer 40 are the liquid-crystal impregnated in the polymer in the required portion during the wet etching process for removing the unnecessary portion of the polymer-liquid crystal mixture layer and the protective layer during the above-described step is extracted It is formed to prevent the phenomenon. In addition, since the protective layer 40 is formed of an insulating layer such as silicon oxide, by providing an insulating effect between the opposite electrodes 20a and 20b of the liquid crystal display device, the electrical property is compensated for by preventing a short phenomenon. It may also serve to extend the life of the liquid crystal display element.

As described above, according to the reflective liquid crystal display device according to the preferred embodiment of the present invention, since the liquid crystal mixture in the liquid crystal layer uses a polymer-liquid crystal mixture layer surrounded by an ultraviolet curing polymer, two or more different colors are used. Patterning is possible to implement separately. Therefore, in the present invention, by adjusting the pitch of the liquid crystal mixture contained in the ultraviolet curable polymer, by adjusting the wavelength of the light reflected therefrom reflects the light having a wavelength corresponding to two or more colors to express each color A type liquid crystal display element can be provided.

Claims (15)

A first substrate having a first electrode for driving a liquid crystal, a second substrate including a second electrode disposed to be spaced apart from the first substrate, and facing the first electrode, the first electrode and the second electrode A reflective liquid crystal display device comprising a liquid crystal layer including a cell array in which cells separated by partition walls are arranged in a predetermined shape, wherein And each of the cells formed in the liquid crystal layer is filled with a liquid crystal mixture, a mixture of cholesteric liquid crystals and nematic liquid crystals, and a polymer-liquid crystal mixture in which UV-curable polymer compounds are mixed in a predetermined ratio. The reflective liquid crystal display device according to claim 1, wherein a protective layer for protecting the liquid crystal layer is interposed between the liquid crystal layer and the second electrode. The method of claim 1, wherein the ultraviolet curable polymer compound is an aromatic urethane acrylate (aromatic urethane acrylate), 2-hydroxyethyl methacrylate (2-hydroxyethyl methacrylate) and 2-ethylhexyl acrylate (2-ethylhexyl acrylate) Reflective liquid crystal display device comprising a. The reflective liquid crystal display device of claim 3, wherein the ultraviolet curable polymer compound further comprises trimethylol propane triacrylate. The reflective liquid crystal display device according to claim 3 or 4, wherein the ultraviolet curable polymer compound further comprises a photoinitiator. The reflective liquid crystal display of claim 1, wherein the polymer-liquid crystal mixture comprises about 50 to about 70 wt% of the liquid crystal mixture. The reflective liquid crystal display device of claim 1, wherein the barrier rib is formed of polyimide. The reflective liquid crystal display of claim 1, wherein the protective layer is formed of silicon oxide. A first step of forming a partition wall for dividing the electrode into a predetermined region on a substrate having an electrode formed on an upper surface thereof; Coating a polymer-liquid crystal mixture in which the liquid crystal mixture and the ultraviolet curable polymer compound are mixed on the resultant; Irradiating ultraviolet light onto the coated polymer-liquid crystal mixture to form a cured polymer-liquid crystal mixture layer; A fourth step of forming an insulating layer by depositing an insulating material on the polymer-liquid crystal mixture layer; Forming a photoresist film on the insulating layer, the photoresist film defining only a portion necessary; A sixth step of removing the insulating layer and the polymer-liquid crystal mixture layer by wet etching using the photoresist film as a mask; And a seventh step of removing the photoresist film. The first step is Forming a material layer for forming a partition by coating a predetermined material on a substrate having an electrode formed on the upper surface thereof; And forming a barrier rib by patterning the material layer for forming a barrier rib. The method of manufacturing a reflective liquid crystal display device according to claim 10, wherein the forming of the barrier rib material layer comprises using polyimide as the predetermined material. The method of claim 9, further comprising an eighth step of repeating the second to seventh steps a predetermined number of times. The method according to claim 9 or 12, wherein in the second step, 10-25 wt% of aromatic urethane acrylate, 2-10 wt% of 2-hydroxyethyl methacrylate, 2-10 as the polymer-liquid crystal mixture A method for producing a reflective liquid crystal display device, characterized by using a compound containing 2% by weight of 2-ethylhexyl acrylate and 50 to 70% by weight of the liquid crystal mixture. The method according to claim 9 or 12, wherein in the second step, 10-25 wt% of aromatic urethane acrylate, 2-10 wt% of 2-hydroxyethyl methacrylate, 2-10 as the polymer-liquid crystal mixture Manufacture of a reflective liquid crystal display device characterized by using a compound comprising 2% by weight of 2-ethylhexyl acrylate, 2 to 10% by weight of trimethylol propane triacrylate, and 50 to 70% by weight of a liquid crystal mixture. Way. The method of manufacturing a reflective liquid crystal display device according to claim 9 or 12, wherein the fourth step uses silicon oxide as the second insulating material.