KR101182309B1 - Method of manufacturing an Liquid Crystal Display Device - Google Patents

Abstract

The present invention provides a process for preparing a first substrate and a second substrate; Applying an alignment layer on at least one of the first substrate and the second substrate; Performing a rubbing process on the substrate on which the alignment layer is applied; Step of the alignment film is irradiated with the polarized UV 200nm to 300nm wavelength range onto a substrate with an energy density of 0.05J / cm ² to 0.7J / cm ² to the substrate surface; And a process for forming a liquid crystal layer between the first substrate and the second substrate.

According to the present invention, by performing a polarized UV irradiation process in addition to the rubbing process, even if the rubbing is not performed smoothly can be obtained uniformly aligned alignment film, in particular the present invention by a scan method using a linear UV light source By providing UV irradiation conditions in irradiating UV, the rubbing process is appropriately controlled by controlling the UV power density (P), the length (Ls) of the linear UV light source in the direction in which the substrate moves, and the moving speed (v) of the substrate. A uniform alignment film can be obtained while eliminating rubbing defects generated at the time.

Alignment film, light leakage

Description

Method of manufacturing an Liquid Crystal Display Device

1 is an exploded perspective view of a typical IPS mode liquid crystal display device.

2 and 3 is a view showing a problem of the conventional rubbing orientation method.

Figure 4 is a view showing a side chain decomposition of the alignment film by a polarized UV irradiation process according to the present invention.

5 is a view for explaining the conditions of the linear UV light source according to the present invention.

6A through 6E are schematic cross-sectional views illustrating a manufacturing process of a liquid crystal display device according to an exemplary embodiment of the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS OF THE DRAWINGS FIG.

100: first substrate 200: second substrate

120, 220: alignment film 300: rubbing roll

310: rubbing cloth 400: linear UV light source

500: liquid crystal layer

The present invention relates to a liquid crystal display device, and more particularly, to an alignment layer for the initial alignment of the liquid crystal in the liquid crystal display device.

Among the ultra-thin flat panel displays, where the display screen is only a few centimeters (cm) thick, the liquid crystal display has a low operating voltage, so it has low power consumption and can be used as a portable device. The applications range from spacecraft to aircrafts.

A liquid crystal display device generally includes a color filter substrate on which a color filter layer is formed, a thin film transistor substrate facing the color filter substrate and on which a thin film transistor is formed, and a liquid crystal layer formed between the two substrates.

In such a liquid crystal display device, the alignment direction of the liquid crystal layer is changed by applying a voltage, and the light transmittance is adjusted to reproduce an image. Therefore, an electrode is formed on the thin film transistor substrate and the color filter substrate for voltage application. A pixel electrode is disposed on the thin film transistor substrate and a common electrode is disposed on the color filter substrate, thereby forming a vertical electric field between the two substrates. (Twisted nematic (TN) mode) is also a case where a pixel electrode and a common electrode are arranged in parallel on a thin film transistor substrate to form a horizontal electric field (for example, an in-plane switching mode (IPS)).

1 is an exploded perspective view of a general IPS mode liquid crystal display device.

As can be seen in FIG. 1, the gate line 12 and the data line 14 cross each other in the thin film transistor substrate 10, and the thin film transistor T is formed in the intersection region of the thin film transistor T. Connected to the pixel electrode 16. In addition, the common electrode 25 is formed to be arranged in parallel with the pixel electrode 16. In addition, a light shielding layer 22 is formed on the color filter substrate 20 to prevent leakage of light, and color filter layers 24 of R, G, and B are formed therebetween, and planarization of the substrate is performed thereon. The overcoat layer 27 for this is formed. In this case, a horizontal electric field is formed between the pixel electrode 16 and the common electrode 25 formed on the thin film transistor substrate 10, thereby adjusting the alignment direction of the liquid crystal.

Both substrates 10 and 20 of the above structure are then bonded together to form one liquid crystal panel. At this time, a liquid crystal layer is formed between the two substrates 10 and 20.

On the other hand, if the liquid crystal layer is arbitrarily arranged between both substrates (10, 20) it is difficult to obtain a consistent molecular arrangement of the liquid crystal layer, although not shown, the liquid crystal on the thin film transistor substrate 10 and the color filter substrate 20 An alignment film for initial orientation of is formed.

An alignment film for the initial alignment of such liquid crystal is conventionally formed mainly using a rubbing alignment method.

In the rubbing orientation method, an organic polymer, such as polyimide, is coated on a substrate and cured, and then a rubbing roll wound with a rubbing cloth is rotated to rub the organic polymer in the thin film form, thereby fixing the ring direction of the organic polymer. It is made to align the process.

By the rubbing orientation method, the liquid crystal is aligned in the direction in which the rings of the organic polymer are aligned, and thus, the moving direction of the rubbing roll becomes the alignment direction of the liquid crystal.

However, the rubbing orientation method has the following disadvantages.

First, a problem of light leakage may occur when the arrangement of the rubbing cloth is disturbed.

2 is a schematic perspective view for showing a case where the arrangement of the rubbing cloth is disturbed.

As described above, since structures such as a thin film transistor, a color filter layer, and an electrode layer are formed on the substrate, as shown in FIG. 2, when the rubbing roll 30 rotates on the structure formed on the substrate 10 or 20. The arrangement may be disturbed in the part 32a of the rubbing cloth 32 wound on the rubbing roll 30. As such, when the rubbing cloth is disturbed, the region on the substrate rubbed by the disturbed rubbing cloth becomes unable to align the organic polymer. As a result, the alignment of the liquid crystal in the area is not uniform, resulting in light leakage.

Second, when the rubbing cloth does not come into contact with the substrate, light leakage may occur.

3 is a schematic perspective view illustrating a liquid crystal array in a case in which the rubbing cloth does not contact the substrate.

As described above, an electrode layer such as a pixel electrode and a common electrode is formed on the substrate. Therefore, as shown in FIG. 3, due to the step difference between the electrode layers on the substrate 10, a region A region in which the rubbing cloth 32 does not come into contact with the substrate is generated. In this case, the alignment of the liquid crystal is not uniform in the region (region A), resulting in light leakage.

As described above, the rubbing orientation method has a problem in that light leakage is generated because rubbing of the rubbing cloth is disturbed or the rubbing cloth does not come into contact with the substrate and rubbing is not performed smoothly.

The present invention is designed to solve the above problems,

An object of the present invention is to provide a method of manufacturing a liquid crystal display device that can solve the problem of light leakage caused by the rubbing process is not performed smoothly.

The present invention is a process for preparing a first substrate and a second substrate in order to achieve the above object; Applying an alignment layer on at least one of the first substrate and the second substrate; Performing a rubbing process on the substrate on which the alignment layer is applied; Irradiating the polarized UV on the substrate on which the alignment layer is applied; And forming a liquid crystal layer between the first substrate and the second substrate, wherein the polarized UV irradiation is performed by a scan method using a linear UV light source. Provided is a method of manufacturing a liquid crystal display device.

1. The first feature of the present invention is to solve the light leakage problem caused by the rubbing process through the UV irradiation process.

As can be seen in Figure 4, irradiating the polarized UV light on the alignment film is the bond of the side chains located in the polarization direction is decomposed and eventually only the side chains in the direction perpendicular to the polarization direction is left so that the liquid crystal can be aligned in that direction. Therefore, when the UV is irradiated by adjusting the polarization direction to the alignment layer that is not aligned after the rubbing process, a uniform liquid crystal alignment layer may be obtained, thereby solving the light leakage problem.

2. The second aspect of the present invention is to perform a scanning method using a linear UV light source in irradiating polarized UV.

As the size of the substrate increases in size, it is difficult to manufacture a UV light source corresponding to the size of the substrate, and the present invention allows UV irradiation using a linear UV light source.

3. A third aspect of the present invention is to provide UV irradiation conditions in irradiating UV by a scanning method using a linear UV light source. Hereinafter, the third feature will be described in more detail.

(1) First, the present invention provides a wavelength range of polarized UV and thus an energy density range.

Specifically, polarized UV having a wavelength range of 200nm to 300nm is preferably irradiated with an energy density of 0.05J / cm ² to 0.7J / cm ² to the substrate surface, polarized light having a wavelength range of 300nm to 400nm UV is preferably irradiated at an energy density of 0.2 J / cm ² to 2.8 J / cm ² .

As described above, when irradiated with polarized UV, the bonds of the side chains located in the polarization direction are decomposed and only the side chains in the direction perpendicular to the polarization direction remain so that the liquid crystal can be oriented in that direction. When is too small, the resolution of the side chain is poor to obtain the desired effect, and when the energy density of the irradiated UV is too large it may be decomposed to the unwanted side chain may adversely affect the orientation.

Accordingly, the present invention provides an optimal energy density range in each wavelength range.

(2) Next, the present invention provides a condition of a linear UV light source for applying an optimal energy density in the wavelength range.

Specifically, when the wavelength range is 200nm to 300nm, it is preferable to set the linear UV light source to satisfy 0.05J / cm ² ≤ (P × Ls) /V≤0.7J/cm ² , and in the case of 300nm to 400nm It is preferable to set a linear UV light source so as to satisfy 0.2 J / cm ² ? (P x Ls) / V? 2.8 J / cm ² .

Here, P means the UV power density (J / cm ² · s) of the linear UV light source means the UV power density after passing through the polarization system, Ls is a linear UV in the direction in which the substrate moves The length of the light source, and V means the moving speed of the substrate.

This will be described in more detail with reference to FIG. 5.

The total UV energy (Us) of the linear UV light source over time T is given by Equation 1 below.

Equation 1

Us = P × Ls × Ds × T

(here,

Us is the total UV energy of the linear UV light source, which means the total UV energy after passing through the polarization system.

P means the UV power density (J / cm ² · s) of the linear UV light source means the UV power density after passing through the polarization system (hereinafter referred to as UV power density for convenience),

Ls means the length of the linear UV light source in the direction in which the substrate moves,

Ds means the length of the linear UV light source in the direction perpendicular to the direction in which the substrate moves,

T means the time taken to process one substrate).

In the case where the wavelength range is 200 nm to 300 nm, the total UV energy (Ug) required by the substrate during the time T is given by Equation 2 below.

Equation 2

0.05 J / cm ² × Lg × Dg ≤ Ug ≤ 0.7 J / cm ² × Lg × Dg

Where Ug is the total UV energy needed to reliably decompose the alignment layer side chain,

Lg means the length of the substrate in the direction in which the substrate moves,

Dg means the length of the substrate in the direction perpendicular to the direction in which the substrate is moved).

Since Us = Ug must be satisfied, Substituting Equation 1 into Equation 2 is as follows.

Equation 3

0.05 J / cm ² × Lg × Dg ≤ P × Ls × Ds × T ≤ 0.7 J / cm ² × Lg × Dg

Here, since Dg = Ds is satisfied, a formula similar to Equation 4 is established.

Equation 4

0.05 J / cm ² ≤ P × Ls × T / Lg ≤0.7 J / cm ²

Since T / Lg = 1 / V (where V denotes a moving speed of the substrate) is satisfied, an equation such as Equation 5 is established.

Equation 5

0.05 J / cm ² ≤ (P × Ls) / V ≤ 0.7 J / cm ²

On the other hand, even in the case where the wavelength range is 300nm to 400nm, the same formula as Formula 6 is established through the same method.

Equation 6

0.2 J / cm ² ≤ (P × Ls) / V ≤ 2.8 J / cm ²

The present invention as described above in the case of a wavelength range of 200nm to 300nm is ^{0.05J / cm 2 ≤ (P ×} Ls) /V≤0.7J/cm 2, if the wavelength range of 300nm to 400nm is 0.2J / cm ² ≤ (P × Ls) /V≦2.8 J / cm ² to provide a linear UV light condition.

On the other hand, the UV irradiation conditions of the scanning method as described above can be applied to the batch exposure method.

However, in the case of the batch exposure method, since the substrate does not move, when the wavelength range is 200 nm to 300 nm, 0.05 J / cm ² ≤ P × Ls × T / Lg ≤ 0.7 J / cm ² as in Equation 4 above. The same equation holds, and in the case where the wavelength range is 300 nm to 400 nm, an equation such as 0.2 J / cm ² ? P × Ls × T / Lg? 2.8 J / cm ^{2 is} established.

 Where P is the UV power density, Ls is the length of one side of the linear UV light source, T is the time taken to process one substrate, and Lg is the length of one side of the substrate corresponding to Ls.

Example

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

6A through 6E are schematic cross-sectional views illustrating a manufacturing process of a liquid crystal display device according to an exemplary embodiment of the present invention.

First, as shown in FIG. 6A, a first substrate 100 and a second substrate 200 are prepared.

Although not shown, a gate line and a data line are formed on the first substrate 100 so as to cross each other to define a pixel area, and a gate electrode, a source electrode, and a drain electrode are formed at an intersection area of the gate line and the data line. A thin film transistor including a thin film transistor is formed, and a pixel electrode is formed in the pixel region so as to be connected to the drain electrode of the thin film transistor.

A light blocking layer is formed on the second substrate 200 to prevent light leakage, green, red, and blue color filter layers are formed on the light blocking layer, and a common electrode is formed on the color filter layer. have.

However, in the case of a so-called IPS (In-plane switching) mode liquid crystal display device, the common electrode is not formed on the second substrate 200, but is arranged in parallel with the pixel electrode on the first substrate 100 so as to be horizontal. Induce an electric field.

Thereafter, the alignment layer 120 is coated on the first substrate 100 as shown in FIG. 6B.

Although only the process of applying the alignment layer 120 on the first substrate 100 is illustrated in the drawing, the alignment layer may also be applied on the second substrate 200.

The alignment layer 120 may be any material as long as the alignment direction may be aligned by a rubbing process and a UV irradiation process, which will be described later. Preferably, polyimide, polyamic acid, and polyvinyl. Cinnamate, polyazobenzene, Polyethyleneimine, Polyvinyl alcohol, Polyamide, Polyethylene, Polystylene, Polyphenylenephthalamide , A polymer material selected from polyester, polyurethane, and polymethyl methacrylate is used.

The coating process of the alignment layer 120 may be performed through a process of printing the polymer material as described above and a process of curing the printed polymer material.

Thereafter, as illustrated in FIG. 6C, a rubbing process is performed on the first substrate 100 to which the alignment layer 120 is applied.

The rubbing process is performed by rotating the rubbing roll 300 to which the rubbing cloth 310 is attached in a desired orientation direction.

Thereafter, as illustrated in FIG. 6D, the first substrate 100 is irradiated with polarized UV by using a linear UV light source 400.

The polarized UV is irradiated by a scan method, but for this purpose, the first substrate 100 may be moved and the linear UV light source 400 may be fixed, but is not limited thereto. ) And move the linear UV light source 400.

The step of irradiating the polarized UV is when using polarized UV having a wavelength range of 200nm to 300nm and is preferably irradiated with an energy density of 0.05J / cm ² to 0.7J / cm ² with respect to the substrate surface, 300nm In the case of using polarized UV having a wavelength range of 400 nm to 400 nm, it is preferable to irradiate the substrate surface at an energy density of 0.2 J / cm ² to 2.8 J / cm ² .

When using a polarized UV having a wavelength range of 200nm and above 300nm is as described above ^{0.05J / cm 2 ≤ (P ×} Ls), UV power so as to satisfy the /V≤0.7J/cm ² density (P), It is preferable to carry out by controlling the length Ls of the linear UV light source in the direction in which the substrate moves and the moving speed V of the substrate.

When using the polarized UV having a wavelength range of 300nm to 400nm, UV power density (P), so as to satisfy 0.2J / cm ² ≤ (P × Ls) / V ≤ 2.8J / cm ² as described above It is preferable to control the length Ls of the linear UV light source and the moving speed V of the substrate in the direction in which the substrate moves.

The polarized UV irradiation process is preferably performed after the rubbing process, but is not limited thereto, and may also simultaneously perform the UV irradiation process and the rubbing process, and then perform the UV irradiation process first and then rubbing. It is also possible to carry out the process.

Since the polarized UV irradiation process is for aligning the alignment layer that is not aligned in the alignment direction even after the rubbing process, it is also possible to irradiate polarized UV only to the area, but irradiating polarized UV on the entire surface of the substrate may simplify the process. It is more preferable.

Since the alignment direction of the alignment layer by the rubbing process and the alignment direction of the alignment layer by the polarized UV irradiation process should coincide with each other, the polarization direction should be appropriately selected and performed during the polarized UV irradiation process.

The polarized UV irradiation process may be performed using partially polarized or linearly polarized UV.

Thereafter, as shown in FIG. 6E, the liquid crystal layer 500 is formed between the first substrate 100 and the second substrate 200 on which the alignment layers 120 and 220 are formed, thereby completing the liquid crystal display device.

The process of forming the liquid crystal layer 500 may be performed using a vacuum injection method or a liquid crystal dropping method.

In the vacuum injection method, a sealing material having an injection hole is formed on one of the two substrates 100 and 200, the two substrates 100 and 200 are bonded together, and then a liquid crystal is injected through the injection hole.

In the liquid crystal dropping method, a sealing material without an injection hole is formed on one of the two substrates 100 and 200, and after the liquid crystal is dropped on one of the two substrates 100 and 200, This is a method for bonding the substrates 100 and 200 together.

In addition, the present invention provides a method for manufacturing a liquid crystal display device in a batch exposure method by applying the above-described UV irradiation conditions of the scanning method.

In the case of the batch exposure method, since the substrate does not move, when the wavelength range is 200 nm to 300 nm, an expression such as 0.05 J / cm ² ≤ P × Ls × T / Lg ≤ 0.7 J / cm ^{2 is} established and the wavelength range is established. When 300 nm to 400 nm, an equation such as 0.2 J / cm ² ≦ P × Ls × T / Lg ≦ 2.8 J / cm ^{2 is} established.

 Where P is the UV power density, Ls is the length of one side of the linear UV light source, T is the time taken to process one substrate, and Lg is the length of one side of the substrate corresponding to Ls.

Other details are the same as the above-described scan method, and thus detailed description thereof will be omitted.

As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to the said embodiment, It is within the range which can be changed within the range apparent to those skilled in the art.

According to the present invention, by performing a polarized UV irradiation process in addition to the rubbing process, evenly aligned alignment film even if the rubbing of the rubbing cloth array or rubbing cloth is not in contact with the substrate does not perform smooth rubbing Can be obtained, and eventually, light leakage can be prevented.

In addition, the present invention is easy to apply even if the size of the substrate is increased by performing a scan method using a linear UV light source in irradiating the polarized UV.

In addition, the present invention by providing a UV irradiation conditions in the irradiation of UV by a scanning method using a linear UV light source, UV power density (P), the length of the linear UV light source (Ls) in the direction in which the substrate moves By appropriately controlling the moving speed V of the substrate and the substrate, it is possible to obtain a uniform alignment film while eliminating the rubbing defect generated during the rubbing process, thereby preventing generation of light leakage.

Claims (18)

Preparing a first substrate and a second substrate; Applying an alignment layer on at least one of the first substrate and the second substrate; Performing a rubbing process on the substrate on which the alignment layer is applied; Step of the alignment film is irradiated with the polarized UV 200nm to 300nm wavelength range onto a substrate with an energy density of 0.05J / cm ² to 0.7J / cm ² to the substrate surface; And And forming a liquid crystal layer between the first substrate and the second substrate, The process of irradiating the polarized UV is a manufacturing method of the liquid crystal display device, characterized in that performed by a scanning method using a linear UV light source. delete The method of claim 1, A step of irradiating the polarized UV is ^{0.05J / cm 2 ≤ (P ×} Ls) /V≤0.7J/cm linear UV light source in the direction in which the, UV power density (P), the substrate movement so as to satisfy the ² And controlling the length Ls and the moving speed v of the substrate. delete delete The method of claim 1, And the rubbing process and the polarized UV irradiation process are performed at the same time. The method of claim 1, And the rubbing process is performed before the polarized UV irradiation process. The method of claim 1, And the rubbing process is performed after the polarized UV irradiation process. The method of claim 1, And an alignment direction of the alignment layer by the rubbing process and an alignment direction of the alignment layer by the polarized UV irradiation process coincide with each other. The method of claim 1, The process of irradiating the polarized UV is a method of manufacturing a liquid crystal display device, characterized in that for irradiating partial or linearly polarized UV. The method of claim 1, The process of irradiating the polarized UV is a method of manufacturing a liquid crystal display device, characterized in that performed by moving the substrate and fixing a linear UV light source. The method of claim 1, The process of irradiating the polarized UV is a method of manufacturing a liquid crystal display device, characterized in that performed by fixing the substrate and moving a linear UV light source. The method of claim 1, The process of applying the alignment layer is polyimide, polyamic acid, polyvinylcinnamate, polyazobenzene, polyethyleneimine, polyvinyl alcohol, polyvinyl alcohol. Polyamide, Polyethylene, Polystylene, Polyphenylenephthalamide, Polyester, Polyurethane, and Polymethyl methacrylate A method of manufacturing a liquid crystal display device, characterized in that the coating of the selected polymer material. The method of claim 1, The process of forming a liquid crystal layer between the first substrate and the second substrate is Forming a sealing material without an injection hole on any one of the first substrate and the second substrate; Dropping liquid crystal onto any one of the first substrate and the second substrate; And And a step of bonding the first substrate and the second substrate together. Preparing a first substrate and a second substrate; Applying an alignment layer on at least one of the first substrate and the second substrate; Performing a rubbing process on the substrate on which the alignment layer is applied; Irradiating the polarized UV on the substrate on which the alignment layer is applied; And And forming a liquid crystal layer between the first substrate and the second substrate, A step of irradiating the polarized UV is a linear UV light source in a batch exposure method, the 200nm-polarized UV having a wavelength range of 300nm to an energy density of 0.05J / cm ² to 0.7J / cm ² to the substrate surface A method of manufacturing a liquid crystal display device, characterized by irradiating. 16. The method of claim 15, The process of irradiating the polarized UV is UV power density (P), length of one side of the linear UV light source (Ls) to satisfy 0.05J / cm ² ≤ P × Ls × T / Lg ≤ 0.7 J / cm ² And controlling the time (T) taken to process one substrate and the length (Lg) of one side of the substrate corresponding to Ls. delete delete

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