KR102179535B1 - Method of forming alignment layer and fabrication method of liquid crystal display using the same - Google Patents

Abstract

An embodiment of the present invention is to obtain a polydimethylsiloxane (hereinafter referred to as PDMS) having a predetermined pattern formed on one surface, contacting the surface on which the pattern of PDMS is formed on the UV cured film applied on the substrate, and contacting the PDMS. It is possible to provide a method for forming an alignment layer comprising the steps of forming an alignment layer by irradiating the UV cured layer with ultraviolet rays to cure it, and removing the PDMS in contact with the alignment layer to obtain an alignment layer having a pattern corresponding to the pattern of the PDMS. have.

Description

A method of forming an alignment layer and a method of manufacturing a liquid crystal display using the same {METHOD OF FORMING ALIGNMENT LAYER AND FABRICATION METHOD OF LIQUID CRYSTAL DISPLAY USING THE SAME}

The present invention relates to a method of forming an alignment layer and a method of manufacturing a liquid crystal display using the same, and more particularly, to a method of forming an alignment layer using fine pattern transfer of a UV cured layer and a method of manufacturing a liquid crystal display using the same.

Liquid crystal alignment technology is required to manufacture a liquid crystal display (LCD). The LCD transmits an image by converting an input electrical signal into visual information by using the characteristic of changing the light transmittance by varying the alignment state of the liquid crystal according to the applied voltage to the liquid crystal disposed between the polarizing plates.

Therefore, in flexible and liquid crystal displays, uniform liquid crystal alignment is a very important technique, and an alignment process of uniformly aligning liquid crystals on polyimide (hereinafter referred to as PI), which is an alignment film, is also very important.

As a conventional liquid crystal alignment method, there is typically a rubbing method, and the rubbing method is performed by treating the surface of a PI thin film. This is a method of aligning liquid crystals in one direction by scraping the surface of the PI thin film using a rubbing material such as cloth, and is a liquid crystal alignment method using a microgroove effect.

However, the rubbing method has a problem in that dust is generated in the alignment process or static electricity is easily generated in the alignment process due to the method of scraping the surface, and thus dust adheres to the surface of the alignment layer, causing display defects. In particular, in the case of a substrate having a TFT (Thin Film Transistor) element, circuit breakdown of the TFT element occurs due to generated static electricity, which causes a decrease in yield.

In addition, there is a problem in that it is difficult to perform a uniform rubbing treatment in a liquid crystal display, which is becoming more and more highly precise, because irregularities are formed on the surface of the substrate as the density of pixels increases.

On the other hand, as another means of aligning the liquid crystal in the liquid crystal cell, the ability to align the liquid crystal is imparted by irradiating a photosensitive thin film such as polyvinyl cinnamate, polyimide, azobenzene derivative, etc. formed on the surface of the substrate with polarized or non-polarized ultraviolet rays A photo-alignment method is known. In addition, an ion beam alignment method in which the surface of an organic or inorganic alignment layer is irradiated with argon ions for alignment is known.

However, the above-described methods are non-contact methods, unlike the rubbing method, and do not generate static electricity or dust, and achieve uniform liquid crystal alignment. However, most of the non-contact alignment methods have a limitation in that they cannot obtain uniform and well-aligned liquid crystal alignment characteristics because the anchoring energy that fixes the liquid crystal to the surface is weak.

In addition, high-brightness, high-performance, and high-resolution displays currently used due to the advancement of technology and the demands of users require stable orientation characteristics at high temperatures.

Korean Patent Publication No. 10-2014-0147354 (published on December 30, 2014)

An object of the present invention is to provide a method of forming an alignment layer capable of aligning liquid crystals uniformly aligned in a fine pattern and a method of manufacturing a liquid crystal display using the same.

Another object of the present invention is to provide a method of forming an alignment layer having high thermal stability and a method of manufacturing a liquid crystal display using the same.

Another object of the present invention is to provide a method of forming an alignment layer capable of reducing manufacturing cost by not generating static electricity or dust, thereby improving yield, and rapidly forming an alignment layer, and a method of manufacturing a liquid crystal display using the same.

A method for forming an alignment layer according to an exemplary embodiment of the present invention for achieving the above object includes the steps of obtaining polydimethylsiloxane (hereinafter referred to as PDMS) in which a predetermined pattern is formed on one surface; Contacting the surface on which the pattern of the PDMS is formed on the UV cured film applied on the substrate; Forming an alignment layer by irradiating and curing the UV cured layer in contact with the PDMS; And removing the PDMS in contact with the alignment layer to obtain an alignment layer on which a pattern corresponding to the pattern of the PDMS is formed. Includes.

Acquiring the PDMS may include obtaining a pattern master in which a pattern corresponding to a pattern formed on the PDMS is formed on one surface; Coating the uncured PDMS on the patterned surface of the pattern master; Curing the PDMS coated on the pattern master in a vacuum chamber; And separating from the pattern master the PDMS cured to form a pattern corresponding to the pattern of the pattern master. It may include.

In the step of obtaining the pattern master, the pattern master may be obtained by forming a pattern on a silicon wafer through a laser interference lithography process.

The pattern formed on the alignment layer may be a pattern in which grooves and protrusions are repeated at intervals of tens to hundreds of nm.

A method of manufacturing a liquid crystal display according to another exemplary embodiment of the present invention for achieving the above object includes forming an alignment layer on one surface of each of the first and second substrates; Bonding the first and second substrates apart by a predetermined distance so that the one surface on which the alignment layer is formed face each other; Injecting liquid crystal between the first and second substrates to form a liquid crystal layer; Forming a display panel by combining first and second polarizing plates on the other surfaces of the first and second substrates; And coupling a backlight unit to one surface of the display panel. Includes.

The forming of the alignment layer may include obtaining polydimethylsiloxane (hereinafter referred to as PDMS) in which a predetermined pattern is formed on one surface; Contacting the surface on which the pattern of the PDMS is formed on the UV cured film applied to one surface of the first and second substrates; Forming an alignment layer by irradiating and curing the UV cured layer in contact with the PDMS; And removing the PDMS in contact with the alignment layer to obtain an alignment layer in which a pattern corresponding to the pattern of the PDMS is formed. Includes.

Therefore, the alignment layer forming method and the liquid crystal display manufacturing method using the same according to an embodiment of the present invention transfer the pattern master micropatterned by a laser interference lithography process to PDMS, and transfer the PDMS back onto the UV cured layer, which is a culture layer. By using the method, it is possible to uniformly align the liquid crystal, improve the yield by not generating static electricity or dust, and reduce the manufacturing cost because it can be produced quickly. Therefore, it is possible to manufacture a high-brightness, high-resolution liquid crystal display. It is also possible to provide a liquid crystal display having high thermal stability.

1 shows a method of forming an alignment layer for a liquid crystal display according to an embodiment of the present invention.
2 shows an example of a method of manufacturing a pattern master of FIG. 1.
3 is a view showing a pattern of a UV cured film and an alignment film formed according to the method of forming the alignment layer of FIG. 1.
4 illustrates alignment characteristics of liquid crystals aligned by an alignment layer formed according to the alignment layer forming method of FIG. 1.
5 is a view for explaining the structure and manufacturing method of a liquid crystal display using an alignment layer according to an embodiment of the present invention.
6 shows thermal characteristics of a liquid crystal display according to an embodiment of the present invention.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the implementation of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the present invention will be described in detail by describing a preferred embodiment of the present invention with reference to the accompanying drawings. However, the present invention may be implemented in various different forms, and is not limited to the described embodiments. Further, in order to clearly describe the present invention, parts not related to the description are omitted, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components unless specifically stated to the contrary. In addition, terms such as "... unit", "... group", "module", and "block" described in the specification mean a unit that processes at least one function or operation, which is hardware, software, or hardware. And software.

1 shows a method of forming an alignment layer for a liquid crystal display according to an embodiment of the present invention, and FIG. 2 shows an example of a method of manufacturing a pattern master of FIG. 1.

Referring to FIG. 1, the method of forming an alignment layer according to the present embodiment may be performed according to steps (a) to (h).

First, step (a) is a step of acquiring the pattern master 110. Here, the pattern master 110 is used as a mold in which a predetermined pattern is formed on one surface to form a pattern for aligning the liquid crystal on the alignment layer.

As described above, since the conventional rubbing method scrapes the surface of the PI thin film as an alignment layer using a rubbing material such as cloth to form the pattern directly on the alignment layer, it is difficult to ensure the uniformity of the pattern, and dust is generated in the alignment process. Or, since static electricity is easily generated, there is a problem that dust adheres to the surface of the alignment layer and causes display defects.

In order to prevent this problem, in the method of forming an alignment layer according to the present embodiment, a separate pattern master 110 on which a predetermined pattern is formed is prepared. Here, the pattern master 110 may be implemented as, for example, a silicon wafer patterned so that grooves and protrusions are repeated at regular intervals on the upper surface.

Referring to FIG. 2, the pattern master 110 may be fabricated on a silicon wafer through a laser interference lithography (LIL) process.

Laser interference lithography does not require a mask/mold, enables large-area uniform pattern production, low cost of equipment, high productivity, and various substrates, as well as manufacturing cost due to the simplicity of the process and fast processing time. There is an advantage that can be reduced. In particular, laser interference lithography is easy to form nano-sized fine patterns.

That is, in the pattern master 110 of the present invention, a pattern is formed by a laser interference lithography process, where the pattern may be formed as a nano-pattern having a repeating period of grooves and protrusions in a range of tens to hundreds of nm, for example.

The laser interference lithography process is largely divided into a method using a Mach-Zender interferometer and a method using a Lloyd mirror interferometer. Lloyd's mirror interferometer has the advantage of being able to easily adjust the angle of incidence by rotating the stage. Accordingly, in this embodiment, it is assumed that the pattern master 110 is obtained by a laser interference lithography process using, for example, Lloyd's mirror interferometer.

As shown in FIG. 2, as an example, an argon ion (Ar-Ion) laser having a wavelength of 257 nm may be used as the laser. Further, the beam emitted from the laser is filtered by a spatial filter and incident on the stage.

The spatial filter includes a lens and a pinhole, the lens focuses a laser to focus on the pinhole, and the pinhole removes aberration caused by the lens.

The stage is arranged so that the Lloyd mirror and the silicon wafer have a predetermined angle, and is rotatable. The stage rotates to adjust the reflection angle of the Lloyd mirror, and the Lloyd mirror interferes with the light incident on the silicon wafer by reflecting the incident light onto the silicon wafer.

That is, the light reflected from the Lloyd mirror and the light incident on the silicon wafer interfere with each other due to a distance difference according to a path to form an interference pattern. In this case, the pattern may be formed as a nano-structured pattern.

At this time, the stage may control the angle of the Lloyd's mirror to adjust the pitch of the interference interval, and a pattern of tens to several hundred nanometers may be formed on the silicon wafer.

That is, the pattern master 110 illustrated in FIG. 1 may be obtained by implementing a silicon wafer on which a nano-sized fine pattern is formed by a laser interference lithography process.

Referring back to FIG. 1, when a pattern master 110 in which a nano-sized fine pattern is formed on one surface in step (a) is obtained, in step (b), polydimethylsiloxane is formed on the patterned surface of the pattern master 110. (Polydimethysiloxane: PDMS hereinafter) 120 is coated. PDMS may be coated on the surface on which the pattern is formed in the pattern master 110 through various methods such as spin-coating, roll coating, slit coating, and inkjet coating. In this case, the PDMS may be coated to have a sufficient thickness in consideration of being separated from the pattern master 110 later.

And as in step (c), the coated PDMS is cured. The curing of the PDMS 120 is cured by removing air in a vacuum chamber. In this case, the PDMS may be cured for 1 hour in an environment at room temperature (eg, 25° C.).

The PDMS 120 is a flexible transparent elastomer and may stably adhere to a relatively large area of the pattern master 110. In addition, since the interfacial free energy is low, when used as a mold for other polymers, adhesion does not occur well and separation is easy. In addition, it has the advantage of being very durable and can be reused repeatedly.

Accordingly, a pattern in which the pattern of the pattern master 110 is reversed is formed on the PDMS 120 cured on the pattern master 110 on which the fine pattern is formed, as in (c).

In step (d), the PDMS 120 on which the reverse reflection pattern is formed is separated from the pattern master 110. As described above, the PDMS 120 has flexibility and low interfacial free energy, so that it can be easily separated.

Meanwhile, in step (e), a UV curable polymer that can be cured by ultraviolet rays is applied on the substrate 130 to form a UV curable film 140. Here, the substrate 130 may be a glass substrate, for example. In addition, the UV cured film 140 may be formed by coating an ultraviolet curing polymer on the substrate 130 by spin-coating, roll coating, slit coating, inkjet coating, or the like.

In addition, a patterned PDMS 120 is disposed on the upper surface of the UV cured film 140 applied on the substrate 130. At this time, the PDMS 120 is disposed such that the surface on which the pattern is formed is in direct contact with the UV cured layer 140, so that the pattern of the PDMS 120 is imprinted on the UV cured layer 140.

Since the UV cured layer 140 before curing is a soft material such as PDMS, the pattern formed on the PDMS 120 is reversely transferred to the UV cured layer 140. The pattern formed on the PDMS 120 is formed by reverse transfer of the pattern of the pattern master 110, and the pattern of the UV cured film 150 is formed by reverse transfer of the pattern of the PDMS 120 again. The pattern of 150 is formed as a pattern to which the pattern of the pattern master 110 is transferred.

In step (f), ultraviolet (UV) rays are irradiated to the UV cured film 140 and the PDMS 120 on the substrate 130. Since the PDMS 120 is a transparent material, the irradiated ultraviolet rays (UV) are irradiated to the UV cured film 140 through the PDMS 120, and the UV cured film 140 is a state in which the pattern of the PDMS 120 is reversely transferred. It is cured at and formed as an alignment layer 150.

Thereafter, in step (g), when the UV cured layer 140 is cured to form the alignment layer 150 having a fine pattern, the PDMS 120 is separated from the alignment layer 150, and as a result, the alignment layer as shown in (e) is formed. Can be obtained.

The PDMS 120 is not only useful for transferring a large-area pattern because it has flexibility and excellent durability, but also has the advantage of being able to reuse it repeatedly because it has weak adhesion. That is, the alignment layer 150 can be easily formed at low cost.

In addition, liquid crystals aligned by the alignment layer 150 have horizontal alignment characteristics.

3 is a view showing a pattern of a UV cured film and an alignment film formed according to the method of forming the alignment layer of FIG. 1.

In FIG. 3 (a) is an image obtained by observing the pattern of the UV cured film 140 cured by transferring the pattern of the PDMS 120 with an atomic force microscope (AFM), and (b) is a pattern This is an image obtained by observing the pattern of the PDMS 120 to which the pattern of the master 110 is transferred by AFM.

Comparing (a) and (b) of Fig. 3, the pattern of the UV cured film 140 of (a) is reduced compared to the pattern of the PDMS 120 of (b), although the width between the groove and the protrusion is reduced. , It can be seen that the shape of the pattern was maintained and transferred. In particular, although the pattern is formed very uniformly, the width between the groove and the protrusion of the pattern is very large compared to the rubbing method or other conventional methods, and incident light can be prevented from leaking to the side. That is, a fine pattern of several tens of nanometers can be formed very precisely and uniformly.

4 illustrates alignment characteristics of liquid crystals aligned by an alignment layer formed according to the alignment layer forming method of FIG. 1.

4 shows the transmittance of the alignment layer formed according to the method of forming the alignment layer of FIG. 1 according to the incident angle of light, the blue line represents the transmittance of the alignment layer formed by the conventional rubbing method, and the red line is according to the present embodiment. It shows the transmittance of the formed alignment film.

As shown in FIG. 4, in the alignment layer formed according to the present embodiment, the grooves and protrusions of the fine pattern are formed very precisely and uniformly, so that light can be concentrated in a specific direction. That is, light leakage can be prevented and transmittance can be improved.

5 is a view for explaining the structure and manufacturing method of a liquid crystal display using an alignment layer according to an embodiment of the present invention.

Referring to FIG. 5, the liquid crystal display includes a liquid crystal display panel 200 and a backlight unit 300 that provides light to the liquid crystal display panel 100.

In addition, the liquid crystal display panel 200 includes a first substrate 210, a second substrate 212, a first alignment layer 214, a second alignment layer 216, a liquid crystal layer 218, a first polarizing plate 220, and 2 It may include a polarizing plate 222.

Referring to the method of manufacturing the liquid crystal display panel 200 of FIG. 5, first, a first alignment layer 214 and a second alignment layer 216 are formed on the first substrate 210 and the second substrate 212, respectively. Here, the first alignment layer 214 and the second alignment layer 216 may be formed according to steps (e) to (h) of FIG. 1.

That is, the UV curing polymer is applied on the first substrate 210 and the second substrate 212 to form the UV cured film 140, and the PDMS 120 with a pattern formed on the formed UV cured film 140 is disposed. The first alignment layer 214 and the second alignment layer 216 may be formed by irradiating UV radiation and curing after being transferred.

In addition, the first and second substrates 210 and 212 on which the first alignment layer 214 and the second alignment layer 216 are formed are interposed between the first alignment layer 214 and the second alignment layer 218. 216) are cemented in opposite directions. In this case, the liquid crystal layer 218 may be formed by being injected between the first substrate 210 and the second substrate 212 that are spaced apart and bonded at predetermined intervals.

Meanwhile, in the first and second substrates 210 and 212, the first and second polarizing plates 220 and 222 are disposed on opposite surfaces of the surfaces on which the first alignment layer 214 and the second alignment layer 216 are formed. Combine. In this case, the first polarizing plate 220 and the second polarizing plate 222 may be combined to have a polarization direction corresponding to the liquid crystal alignment direction of the corresponding alignment layers 214 and 216, respectively.

Also, although not shown, the liquid crystal of the liquid crystal layer 218 is divided into liquid crystal cells on the first substrate 210 and the second substrate 212, and a pixel electrode and a common electrode for driving the liquid crystal cell may be formed. The pixel electrode and the common electrode may be formed of indium tin oxide (ITO), which is a transparent conductive material.

In addition, between the first substrate 210 or the second substrate 212 and the first alignment layer 214 and the second alignment layer 216, a color filter layer for determining the color of the liquid crystal cell and light transmitted from each liquid crystal cell A black matrix layer may be further formed to block leakage into the adjacent cells.

When a liquid crystal display panel is manufactured, the backlight unit 300 is combined with the liquid crystal display panel 100 to manufacture a liquid crystal display.

6 shows thermal characteristics of a liquid crystal display according to an exemplary embodiment of the present invention.

6 illustrates the thermal characteristics of a liquid crystal display using an alignment layer formed according to an exemplary embodiment of the present invention, and shows the alignment of liquid crystals of the liquid crystal display at a temperature varying from 100°C to 200°C.

In the case of a liquid crystal display using the conventional rubbing method, it can be seen that the liquid crystals are uniformly aligned up to 180°C, while the liquid crystal display using the alignment layer according to the present embodiment shown in FIG. 6 exhibits thermal stability up to 120°C. have. That is, thermal stability can be maintained even at a high temperature of 180°C.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely exemplary, and those of ordinary skill in the art will appreciate that various modifications and other equivalent embodiments are possible therefrom.

Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

110: pattern master 120: polydimethylsiloxane (PDMS)
130: substrate 140: photocured film
150: alignment layer 200: liquid crystal display panel
210, 212: first and second substrates 214: liquid crystal layer
216, 218: first and second alignment layers 220, 222: first and second polarizing plates
300: backlight unit

Claims (8)

Obtaining polydimethylsiloxane (hereinafter referred to as PDMS) in which a predetermined pattern is formed on one surface;
Contacting the surface on which the PDMS pattern is formed so that the pattern of the PDMS is reversely transferred to the UV cured film of the soft material on the UV cured film of the soft material applied on the substrate;
Forming an alignment layer by irradiating and curing the UV cured layer of the flexible material in contact with the PDMS; And
Removing the PDMS in contact with the alignment layer to obtain an alignment layer in which a pattern corresponding to the pattern of the PDMS is formed; Including,
The step of obtaining the PDMS
Obtaining a pattern master in which a pattern corresponding to the pattern formed on the PDMS is formed on one surface;
Coating the uncured PDMS on the patterned surface of the pattern master;
Curing the PDMS coated on the pattern master in a vacuum chamber; And
Separating from the pattern master the PDMS, which is cured to form a pattern corresponding to the pattern of the pattern master; Alignment film forming method comprising a. delete The method of claim 1, wherein obtaining the pattern master comprises:
A method of forming an alignment layer to obtain the pattern master by forming a pattern on a silicon wafer through a laser interference lithography process. The method of claim 1, wherein the pattern formed on the alignment layer is
A method of forming an alignment layer in which grooves and protrusions are repeated at intervals of several tens to several hundreds of nm. Forming an alignment layer on one surface of each of the first and second substrates;
Bonding the first and second substrates apart by a predetermined distance so that the one surface on which the alignment layer is formed face each other;
Injecting liquid crystal between the first and second substrates to form a liquid crystal layer;
Forming a display panel by combining first and second polarizing plates on the other surfaces of the first and second substrates; And
Coupling a backlight unit to one surface of the display panel; Including,
Forming the alignment layer
Obtaining polydimethylsiloxane (hereinafter referred to as PDMS) in which a predetermined pattern is formed on one surface;
Contacting the surface on which the PDMS pattern is formed so that the pattern of the PDMS is reversely transferred to the UV cured film of the flexible material on the UV cured film of the soft material applied to one surface of the first and second substrates;
Forming an alignment layer by irradiating and curing the UV cured layer of the flexible material in contact with the PDMS; And
Removing the PDMS in contact with the alignment layer to obtain an alignment layer in which a pattern corresponding to the pattern of the PDMS is formed; Including,
The step of obtaining the PDMS
Obtaining a pattern master in which a pattern corresponding to the pattern formed on the PDMS is formed on one surface;
Coating the uncured PDMS on the patterned surface of the pattern master;
Curing the PDMS coated on the pattern master in a vacuum chamber; And
Separating from the pattern master the PDMS, which is cured to form a pattern corresponding to the pattern of the pattern master; Liquid crystal display manufacturing method comprising a. delete The method of claim 5, wherein obtaining the pattern master comprises:
A method of manufacturing a liquid crystal display for obtaining the pattern master by forming a pattern on a silicon wafer through a laser interference lithography process. The method of claim 5, wherein the pattern formed on the alignment layer is
A method of manufacturing a liquid crystal display in which grooves and protrusions are repeated at intervals of several tens to hundreds of nm.

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