KR100321255B1 - Method for fabricating polymer-dispersed liquid crystal display - Google Patents

Abstract

PURPOSE: A method for fabricating a polymer-dispersed liquid crystal display is provided to allow light to be inputted even to the portion under a TFT line to improve reliability and contrast of the liquid crystal display. CONSTITUTION: Polymer-dispersed liquid crystal layer(4) is formed between two substrates(1,1') that respectively have a TFT layer(3) and a black matrix(2) and hardened with ultraviolet rays, so as to fabricate a polymer-dispersed liquid crystal display. A quartz block(11) having at least two faces is located on the substrate having the TFT layer and ultraviolet rays are incident on each face of the quartz block to form the polymer-dispersed liquid crystal. The bottom face of the quartz block has uneven surface.

Description

Manufacturing method of polymer dispersed liquid crystal display device

The present invention relates to a method for manufacturing a polymer dispersed liquid crystal display device, and more particularly, the light control function for controlling the transmission and blocking of light by electrical manipulation, and the reliability of long-term use are very excellent. A method of manufacturing a polymer dispersed liquid crystal display device capable of displaying.

The polymer dispersed liquid crystal display device manufactured according to the present invention is useful as a screen for screen blocking or dimming curtain in a building window or a show window, and a character or figure is displayed thereon and can be electrically changed within a quick response time. It can be applied to various displays such as billboards, guide boards, decorative displays, and the like.

The liquid crystal product business, which began with the application of liquid crystals to electronic desk clocks, developed rapidly due to active research and development.In the late 1970s, liquid crystals were applied to displays, and TN (twisted nematic) and STN (super twisted nematic) Active matrix driving method using TFT (Thin Film Transistor) driving device, which has been actively developed in recent years to provide a high-definition screen, has been in the spotlight. High resolution, low driving voltage, color expression close to natural color, wide viewing angle, etc. are being actively researched to realize a display capable of expressing a high quality screen with the human eye.

TN type (Twisted Nematic Liquid Crystal Display) or STN (Super Twisted Nematic Liquid Crystal Display) type liquid crystal display devices, which are mainstream in the field of display, have advantages such as low power consumption and low driving voltage. Although it is widely used as a device, the use of a polarizing plate reduces the light utilization efficiency, resulting in poor contrast, surface orientation is required, and as the pixel density increases, it becomes difficult to align the TFT around the thin film transistor (TFT) device. It is narrow around 20 degrees. Therefore, many efforts have been attempted to use a display using a transmission scattering mode of light without using polarization. That is, recently, liquid crystal displays of a light scattering mode polymer dispersed liquid crystal display (PDLCD) or a polymer network liquid crystal display (PNLCD) in which a liquid crystal is dispersed in a polymer have appeared.

The polymer dispersed liquid crystal display (PDLCD) is a principle that uses the difference between the refractive index of the liquid crystal and the polymer when the voltage is applied or the voltage is not applied, and more specifically, the refractive index of the transparent polymer resin is n _p , When the normal light refractive index of the liquid crystal is n _o and the ideal light refractive index is n _e , when no electric field is applied, the liquid crystal molecules become disordered and the refractive indexes of n _e and n _p are different so that incident light is scattered, so that the cell is opaque. When the electric field is applied, since the liquid crystals are arranged in the electric field direction, n _o and n _p coincide with each other, and incident light is transmitted, so that the cell is transparent. In this way, the polymer dispersed liquid crystal display device does not use a polarizing plate based on the principle of scattering and transmission of light, so that the use efficiency of light is higher than that of the conventional liquid crystal display device, and thus, it is possible to express images of high brightness, and the illumination angle is excellent. It becomes possible.

The first to be released as PDLCD (Polymer Dispersed Liquid Crystal Display) technology is NCAP (Microcapsule liquid crystal sphere such as J. Pegason, which is dispersed between transparent polymer resin by mechanical and physical method). Nematic Curveliner Aligned Phase) (US Pat. No. 4,435,047). This method evenly disperses the liquid crystal in gelatin, gum arabic, or polyvinyl alcohol aqueous solution, and then uniformly coated to a thickness of 5-20㎛ on the transparent conductive support, and then evaporated water to bond another transparent conductive support It is to prepare a polymer liquid crystal complex. In addition, the method by which J-Dan et al. Disperse | distributed and hardened | cured liquid crystal on the polymer resin continuum, such as an epoxy resin, is well known (Japanese Patent Laid-Open No. 61-502128).

Kumai et al., In Japanese Patent Application Laid-Open No. 3-107819, use a monomer and oligomer-based UV-curable polymer component to control liquid crystals uniformly on polymer resin by precise morphology control by spinodal phase separation from a mixture with liquid crystal. A method for preparing a dispersed liquid crystal polymer resin composite is introduced. The liquid crystal polymer composite obtained by this method is known to have very good driving voltage and contrast characteristics. On the other hand, Takatsu et al. (European Patent No. 313,053) propose a liquid crystal device having a low driving voltage and fast response speed in which a liquid crystal forms a continuous phase and a polymer resin formed from an ultraviolet curable resin has a three-dimensional network structure. As the level of the polymer liquid crystal complex is increased, an active matrix display device can be driven, and efforts have been actively made to commercialize it.

In the conventional display device of the liquid crystal / polymer composite film, as shown in FIG. 3, the off current of the TFT device 3 is increased by back light on one of the ITO substrates 1, thereby increasing the PDLCD. In order to prevent the contrast of the film from being lowered, a black matrix 2 that forms an inter-pixel shielding layer is provided, and a color filter 6 is provided for colorization, and the other ITO substrate 1 facing the black matrix 2 is provided. ') Is manufactured by stacking the TFT element layer 3 forming the active circuit portion on the inner surface, and then injecting the liquid crystal polymer resin composite 4 between the two ITO substrates 1 and 1' and curing them with ultraviolet (UV) light. .

When the display device of the liquid crystal / polymer composite film described above is manufactured by a conventional ultraviolet irradiation method that irradiates ultraviolet rays (UV) in a direction perpendicular to the panel, the ultraviolet ray transmittance is small on the color filter 6 side, and thus hardening is impossible. Ultraviolet rays should be irradiated. In this case, since ultraviolet rays (UV) do not reach the pixel portions below the TFT element layer 3 and the black matrix 2, there is a problem that the ultraviolet curable resin of this portion remains uncured. . The uncured portion of the liquid crystal and ultraviolet curable resin composition penetrates into the neighboring cured liquid crystal polymer composite over time to change the overall characteristics.

Accordingly, methods for curing the composition under the black matrix have been developed, such as a method for making a small hole in the middle of the black matrix (Japanese Patent Laid-Open No. 4-251220), as shown in FIG. There are known methods for investigating from the photographic direction (Yoshida et al., '93 EURODISPLAY Data Collection, FRANCE, 1993).

However, these methods still have the disadvantage that the manufacture of ultraviolet irradiation paper is not easy and complete curing is difficult. That is, when the display device of the liquid crystal polymer composite film is manufactured by the above-described methods, the liquid crystal quadrature is formed in the center portion of the pixel that is exposed to a lot of ultraviolet rays, so that the liquid crystal quadrature is large at the edge of the pixel where the light scattering is large but the amount of ultraviolet rays is relatively low. (Approximately 7 to 10 mm or more) formed, so that light scattering is drastically reduced. As a result, when the display device is driven, local differences and non-uniformity of contrast are caused, resulting in a sharp deterioration in image quality, and deterioration in purity due to residues of uncured parts.

An object of the present invention is to solve the problems as described above, by allowing light to enter the material below the TFT line to eliminate the uncured polymer, the degree of phase separation of the liquid crystal / polymer composite film is uniform and stable, the long-term usability of the panel The present invention provides a method for manufacturing a polymer dispersed liquid crystal display device having improved reliability and contrast.

The above object is to change the optical path of the ultraviolet light on the upper surface of the ITO substrate where the TFT element layer is patterned when curing the liquid crystal and ultraviolet curing resin mixture injected between two indium tin oxide (ITO) substrates with ultraviolet rays. By mounting a quartz block of a multi-sided surface formed with irregularities on the lower surface so as to emit light, the ultraviolet light can be irradiated from the upper side to the multi-sided surface. The liquid crystal polymer composite material is achieved by the present invention which results in an overall uniform phase separation form.

That is, the present invention injects a liquid crystal and a photocurable resin mixture between a substrate having opposite ITO (Indium Tin Oxide) positive electrode layers each including a TFT device layer and a black matrix, and hardens them with ultraviolet rays to produce a polymer dispersed liquid crystal display device. The method further comprises placing a quartz block having two or more multi-sided surfaces having irregularities formed on the lower surface of the upper ITO electrode substrate having the TFT device layer, and irradiating ultraviolet rays from each surface to form a liquid crystal polymer resin composite. It is to provide a method for producing a polymer dispersed liquid crystal display device.

Hereinafter, the present invention will be described in more detail with reference to the drawings of FIG. 1.

In the present invention, by placing the quartz block 12 of the multi-sided surface formed with irregularities on the lower surface of the upper ITO substrate (1 ') by irradiating ultraviolet rays from each surface to increase the ultraviolet intensity and to set the more efficient ultraviolet irradiation direction It is possible to obtain a polymer liquid crystal composite membrane 4 having a uniform degree of phase separation as a whole. Such a polymer liquid crystal composite film 4 has a high contrast value and can produce a liquid crystal display device of a liquid crystal polymer resin composite which is stable to aging change over time.

In the present invention, the opening diameter of the liquid crystal display device varies depending on the size and use of the display device panel, but generally has a size of about 50 μm to 300 μm, and quartz having two or more faces on the ITO substrate 1 ′. When the block 12 is placed and irradiated with ultraviolet (UV) light from each side, the ultraviolet (UV) light is uniformly lowered to the bottom of the TFT element 3 inside the panel for the liquid crystal display device into which a mixed solution of liquid crystal and ultraviolet curable resin is injected. Irradiation produces a liquid crystal display device of a liquid crystal polymer resin composite having a liquid crystal droplet phase separation degree is very uniform and stable to aging change over time.

The liquid crystals used in the present invention include nematic liquid crystals, smectic liquid crystals, ferroelectric liquid crystals, cholesteric liquid crystals, and the like, and may be used alone or in a mixed state.

In particular, mixed liquid crystals such as cholesteric liquid crystals and ferroelectric liquid crystals / cholesteric liquid crystals are added as dopants in the nematic liquid crystals, and twisting power is applied to the cholesteric liquid crystal phases such as focal conic structures. If so, the scattering properties of the liquid crystal polymer resin composite can be enhanced. When selecting a liquid crystal, it is desirable to have positive dielectric anisotropy, and it is necessary to use a composition that satisfies various required characteristics such as operating temperature range and operating voltage.

As the photocurable resin used in the present invention, a photocurable resin which is well mixed with a liquid crystal composition in an uncured state and mixed well, and which is not compatible with a liquid crystal after curing, is completely phase-separated into two components of a liquid crystal / polymer. As such a photocurable resin, a general photocurable resin which itself has a photoreactive property or where curing is induced by a material produced by light irradiation may be used, and a photocurable vinyl resin is suitable.

In order for the photocurable resin to be photopolymerized in a mixture state with the liquid crystal and to have stability such as phase separation structure and adhesiveness in an appropriate form, the polymer component is preferably used as a plurality of mixtures of monomers and oligomer compounds having a photocurable vinyl group.

Examples of the monomer having a photocurable vinyl group in the polymer composition include vinyl benzene-based compounds such as N-vinylpyridone, styrene and derivatives thereof, vinyl halide compounds such as vinyl chloride, monofunctional acrylate compounds, and polyfunctional acryl. Rate compounds and the like are used. In this case, the acrylate compound refers to an acryl or methacrylate compound of a hydrocarbon compound having a substituent such as a halogen group compound such as fluorine, a hydroxyl group or an aliphatic group or an aromatic group. These monomer compounds generally serve to improve compatibility with diluents and liquid crystals that reduce the viscosity of high viscosity oligomer compounds, and monomer compounds that exhibit appropriate compatibility according to the type and composition ratio of liquid crystals alone or in binary systems. It can be used in the above mixed state.

As the oligomeric compound, compounds such as polyester acrylate, epoxy acrylate, polyol acrylate, silicone acrylate and the like are used and are polyfunctional compounds having a bifunctional group or more.

A photocuring initiator for polymerizing the photocurable resin may be used such as benzoin ether, benzophenone, acetophenone, and the like, and may be used in an amount of 0.01 to 5% by weight of the polymer component. If the initiator content is high, the photocurable resin is polymerized before light irradiation, which is not good.

It is advantageous for the preparation of the liquid crystal polymer resin composite that the liquid crystal material has a composition ratio of 10% by weight or more and 99% by weight or less, preferably 30% by weight to 90% by weight of the total light control layer constituent material. If the magnification of the liquid crystal material is too small, it tends to be difficult to form a continuous phase of the liquid crystal and the polymer resin.

The liquid crystal polymer resin composite prepared under the above conditions is introduced between substrates in which transparent electrodes, such as In ₂ O ₃ -SnO ₂ (ITO) and SnO ₂ , are treated to form a liquid crystal display device. As the material of the substrate used, plastic such as glass or transparent polyester film may be used. A liquid crystal alignment film such as polyimide may be coated on one or both surfaces of the two substrates. At this time, the distance between the substrates is adjusted by a spacer having a diameter of about 5 to 50 μm (not shown in FIG. 1), and appropriately adjusted to 7 to 15 μm in consideration of contrast when voltage is applied or not applied. Do.

After introducing the liquid crystal polymer composition between the two substrates in this way, in the direction of two or more surfaces through the multi-faceted quartz block (glass) 11 having irregularities formed on the lower surface of the upper portion in the manner as shown in FIG. Irradiate ultraviolet (UV) light. At the time of ultraviolet curing, it is preferable to irradiate the surface of a board | substrate uniformly with the ultraviolet-ray which has a certain intensity, and ultraviolet irradiation can also be performed once or divided into several times. In this case, in order to reduce the degree of surface reflection at the interface between the quartz block 11 and the ITO substrate 1 ', oils such as ceda oil are preferably applied to the interface.

As a result, the liquid crystal display device of the conventional liquid crystal polymer resin composite remains uncured in the photocurable resin between the TFT element portion and the black matrix even when irradiated with ultraviolet rays in the manufacturing process. Although there is a problem such as a change in physical properties, the liquid crystal display device manufactured according to the present invention has a uniform and stable degree of phase separation of the liquid crystal polymer composite, so that the effect of improving the reliability and the contrast, such as long-term usability of the panel, can be obtained.

Due to such excellent characteristics, it is possible to manufacture a liquid crystal display device that can solve the transmission light loss caused by the polarizing plate, which is a disadvantage of the conventional liquid crystal display device. Meanwhile, the manufacturing process such as the alignment treatment process is shortened, thereby reducing the cost and increasing the yield. You can expect.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited by the following examples.

Example 1

A pair of ITO-attached TFT glass substrates (1, 1 ') were spread to make uniform thickness of the microfuel 10 占 퐉 spacer manufactured by Mitsui Doatsu Corporation. As a liquid crystal, 80 weight% of fluorine-type liquid-crystal TL-205 of BDH company, a photocurable resin composition are monomer 2-ethylhexyl acrylate, a urethane acrylate, CN-972 by Satomer Corporation as an oligomer, trimethylol propane triacrylate as a polyfunctional monomer ( TMPTA) was uniformly mixed with 19.8% by weight of a compound having a ratio of 7/2/1 and 0.2% by weight of Tarocure-1173 from Ciba-Geigyisa Inc. as a photopolymerization initiator, and injected into an isotropic liquid state at room temperature between the two substrates. After injection, apply Cedar oil on the upper substrate 1 'and place the quartz block 11 in the form of a triangular prism as shown in FIG. It was.

The liquid crystal cell obtained in this manner is uniform in the degree of phase separation of the liquid crystal polymer composite material in the opening and the degree of phase separation of the material between the TFT element layer 3 and the black matrix 2 as observed under a polarization microscope. Was formed. Such a cell has a voltage holding ratio of more than 95%, a light transmittance of 80% under an applied voltage of 7V, a high contrast ratio of more than 100 when projected on a screen, and a very uniform characteristic of the entire panel. In the case of the response speed, the sum of the rising time and the decaying time of the liquid crystal was 50 ms before. In the reliability evaluation, the contrast ratio and other driving characteristics of 100 or more were maintained after 500 repetitions even after 1000 hours at 80 ° C or in a heat cycle test in the range of -40 ° C to 80 ° C.

Comparative Example 1

In Example 1, the liquid crystal cell was manufactured in the same manner as in Example 1 except that the ultraviolet ray was irradiated for 3 minutes without using the quartz block during the ultraviolet irradiation.

The obtained liquid crystal cell exhibited a significant deterioration in physical properties such as a contrast ratio falling below 10.

Comparative Example 2

In Example 1, the liquid crystal cell was manufactured in the same manner as in Example 1 except that the ultraviolet rays were irradiated with ultraviolet rays for 3 minutes using a simple quartz block having no irregularities formed on the lower surface shown in FIG. Was prepared.

In the obtained liquid crystal cell, the contrast ratio was lowered to 80 or less, and the physical properties such as light leakage occurred in each pixel on the screen.

1 is a manufacturing principle of the polymer dispersed liquid crystal display device of the present invention,

2 is a structural diagram of a quartz block used in the present invention,

3 is a manufacturing principle of a conventional polymer dispersed liquid crystal display device,

4 is a manufacturing principle of a polymer dispersed liquid crystal display device for irradiating a conventional ultraviolet ray in an inclined direction.

* Description of the symbols for the main parts of the drawings *

1,1 ': ITO substrate 2: Black matrix

3: TFT 4: polymer / liquid crystal composite film

5: Cedar oil 6: color filter

10 substrate 11 quartz block

Claims (1)

A polymer dispersed liquid crystal display device is manufactured by injecting a liquid crystal and a photocurable resin mixture between two substrates including a TFT device layer and opposing indium tin oxide (ITO) positive electrode layers each having a black matrix, and curing them with ultraviolet rays. A quartz block having at least two facets with irregularities formed on the lower surface of the upper ITO electrode substrate having the TFT device layer is disposed, and the liquid crystal polymer composite is formed by irradiating ultraviolet rays from each surface. Method of manufacturing a polymer dispersed liquid crystal display device.