KR20040041237A - Method for Manufacturing Liquid Crystal Alignment Film For Liquid Crystal Displays - Google Patents

Abstract

PURPOSE: A method for manufacturing a liquid crystal alignment layer of a liquid crystal display is provided to supply a new liquid crystal alignment film capable of substituting for a polyimide. CONSTITUTION: After forming a vacuum within a chamber by a vacuum pump, inert gases such as helium and argon are induced within the quartz tube(4) wound an RF coil(2). When applying RF power, a plasma forming region(6) is produced within the quartz tube(4). A carbon gas is induced through a gas distribution ring(8) and a PLC(Polymer-Like Carbon) thin film in which hydrogen content on a glass substrate(10) placed on a substrate holder(12) exceeds 30 atom % is deposited. On the surface of the PLC thin film, an ionic beam of an ion gun is irradiated through a shutter, thereby obtaining a surface-treated PLD thin film.

Description

Method for manufacturing liquid crystal alignment film for liquid crystal display {Method for Manufacturing Liquid Crystal Alignment Film For Liquid Crystal Displays}

The present invention relates to a liquid crystal aligning film for a liquid crystal display, and more particularly, to solve a problem of the conventional liquid crystal aligning film by depositing a polymer-like carbon (PLC) thin film on a substrate and manufacturing the liquid crystal aligning film by surface treating the thin film with an ion beam. It's about doing.

In general, the conventional cathode ray tube (CRT) display device, despite the excellent characteristics, because of the disadvantage that the volume and weight rapidly increases as the screen is larger, the recent demand for high-definition, large screen and flat panel type It is inadequate for use in multimedia systems, and liquid crystal displays have been developed to improve this.

The liquid crystal display method injects a liquid crystal between two transparent electrode substrates and moves the liquid crystal by an electric field. Among the various flat panel display technologies developed to date, there are many applications and the widest market share. . In this liquid crystal display method, a liquid crystal alignment layer is formed on the substrate, and the liquid crystal is arranged to have a predetermined direction and a specific pretilt angle using the liquid crystal alignment layer. This method is a method of orienting liquid crystals by depositing an inorganic alignment layer such as SiO _x by the vapor deposition method. After forming an organic liquid crystal aligning film like polyimide from the method, the method of orienting a liquid crystal using a rubbing method etc. is mentioned. The rubbing method, which is the most typical liquid crystal alignment method, is a method of rubbing a surface of a polyimide film in a predetermined direction using a rubbing cloth to orient the liquid crystal, and is currently applied in most production lines due to a simple process.

However, since the rubbing method is a contact liquid crystal alignment method in which a polyimide film is directly rubbed using a rubbing cloth to form a liquid crystal alignment film, dust generated in the rubbing cloth and a multi-step cleaning process for removing the rubbing cloth are inevitably required, and an in-line (in-line) process has the disadvantage that it is impossible. In addition, the polyimide film most widely used as the liquid crystal alignment film of the rubbing method is easy to obtain a relatively uniform alignment film, and has the advantage of being stable even at a high temperature of about 200 ℃, acid anhydride and diamine compound in the polyimide film forming process After synthesis of polyamide acid to form a polyamide acid, and then heat-cured and imidized to go through a multi-step process to form a polyimide film has a disadvantage that affects the peripheral device due to the heat treatment process.

In addition, as a non-contact liquid crystal alignment method for overcoming the disadvantages of the rubbing method, an optical alignment method for surface-modifying polyimide using light such as UV has been developed, but until now it has not been commercialized because of lack of stability.

In addition, US Patent Nos. 6,020,946 and 6,061,114 disclose a liquid crystal alignment film by depositing a DLC thin film on a transparent substrate by PECVD with a bias voltage of -20 V to -300 V, and then subjecting the thin film to an atomic beam. The technique of obtaining is disclosed. However, in the patent, the DLC thin film is deposited with a high bias voltage applied, so that a thin film having a low hydrogen content (less than 30 atomic%) and an optical bandwidth of less than 1.5 eV is obtained, so that a high energy region (blue region) is obtained. Satisfactory transmittance could not be obtained at. Thus, the liquid crystal alignment film could be used only for the TN mode.

The present invention is to solve the above problems of the conventional liquid crystal display, to provide a new liquid crystal alignment film that can replace the polyimide used as a liquid crystal alignment film for a conventional liquid crystal display and a new liquid crystal alignment method for forming the same. .

In addition, an object of the present invention is to solve the problem of a DLC thin film deposited in a state where a conventional high bias voltage is applied.

1 is a schematic diagram of a remote-PECVD apparatus according to the present invention.

2 is a schematic diagram of an ion beam irradiation system according to the present invention.

3 is a graph showing that the thickness of a PLC thin film obtained according to the present invention decreases with ion beam irradiation.

4 is a graph showing that the optical bandwidth of the PLC thin film obtained according to the present invention decreases with ion beam irradiation.

5A and 5B are transmittance data of a PLC thin film deposited and ion beam treated under different process conditions according to the present invention.

6 is a graph showing that the pretilt angle of the PLC thin film liquid crystal alignment film obtained according to the present invention changes with ion beam irradiation time.

7 is a graph showing that the pretilt angle of the PLC thin film liquid crystal alignment film obtained according to the present invention changes with the ion beam irradiation angle.

The present invention relates to (a) depositing a PLC thin film having a hydrogen content of more than 30 atomic percent in a thin film by vacuum deposition on a substrate, and (b) surface treating the PLC thin film with an ion beam having an energy of 100 to 300 eV. Thereby, the manufacturing method of the liquid crystal aligning film for liquid crystal displays which forms a PLC thin film liquid crystal aligning film whose optical bandwidth is 1.5 eV or more is provided.

Here, during the surface treatment, the ion beam is preferably irradiated to the thin film at an angle of 10 ° ~ 70 °, and before the step (b) it is preferable that the PLC thin film further undergoes a plasma etching or ion beam etching step. Do.

Further, more preferably, the PLC thin film may be deposited by remote-PECVD.

All. In addition, the pretilt angle of the PLC thin film liquid crystal alignment film may change according to the ion beam treatment time, the pretilt angle of the PLC thin film liquid crystal alignment film may change according to the irradiation angle of the ion beam onto the PLC thin film of the substrate, Depending on the processing time of the ion beam and / or the angle of irradiation of the ion beam onto the PLC thin film of the substrate, a liquid crystal alignment film for TN mode, IPS mode or VA mode may be obtained.

Hereinafter, the present invention will be described in more detail based on the preferred embodiments of the present invention and the accompanying drawings. However, the scope of the present invention is not limited by the specific examples below, and the scope of the present invention will be limited only by the following claims.

The deposition of the PLC according to the present invention may be performed by a vacuum deposition method such as evaporation, sputtering, ion beam deposition, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), or the like. However, more preferably, the PLC thin film according to the present invention is deposited by remote-PECVD method. Unlike the conventional chemical vapor deposition method, the remote-PECVD method is separated from the plasma formation region and the region where the substrate is to be deposited to prevent thin film damage caused by accelerated ions, and the reaction path can be determined to compensate for the disadvantages of the general PECVD method. can do. Therefore, in the below-described embodiment of the present invention, the ion damage of the deposited PLC thin film is minimized by using the remote-PECVD method. In addition, the PLC thin film according to the present invention is deposited in the ground state is deposited because the sheath voltage is very low.

Since the thin film surface is hardly subjected to ion damage, a PLC thin film having a hydrogen content of more than 30 atomic percent in the thin film can be obtained. A schematic diagram of the deposition equipment is shown in FIG. 1.

A transparent glass substrate coated with ITO was used as a substrate for PLC thin film deposition, and was ultrasonically cleaned for 5 minutes in TCE, acetone, and alcohol solution before deposition, and then charged in a deposition chamber. The substrate loaded into the chamber was subjected to a pre-sputtering process for about 10 minutes using an inert gas plasma such as helium or argon. At this time, 10 ~ 500W RF power, preferably 10 ~ 100W RF power was used for plasma generation. After washing the physical and chemical substrates, the PLC thin film was deposited with a hydrocarbon gas such as acetylene and methane gas as a carbon gas source, and an inert gas such as helium or argon for plasma generation. At this time, the ratio of carbon gas / inert gas is preferably about 0.5 to about 10.

Referring to the drawings, after the vacuum is formed in the chamber by a vacuum pump, an inert gas such as helium or argon is introduced into the quartz tube 4 on which the RF coil 2 is wound, and the above-described RF power source Is applied, the above-mentioned plasma forming region 6 is formed in the quartz tube 4, and a carbon substrate such as acetylene is introduced through the gas dispersion ring 8, and the glass substrate mounted on the substrate holder 12 ( 10) Deposit PLC thin film with hydrogen content above 30 atomic%. For reference, reference numeral 14 is a magnet.

In addition, in the present invention, preferably, the ion beam by the Kaufman ion gun 20 schematically shown in FIG. 2 is irradiated onto the surface of the PLC thin film on the substrate 24 through the shutter 22. Processing was done. Thereby, a PLC thin film liquid crystal alignment film having an optical bandwidth of 1.5 eV or more can be obtained. An argon gas was introduced into the ion gun 20 to generate an ion beam having an energy of 100 to 300 eV, and the angle between the irradiated ion beam and the substrate was changed in a range of 10 ° to 70 °. Although the Kaufman type ion gun was used in the embodiment of the present invention because it was a laboratory-scale experiment, an end-hole type ion gun may be used on the mass production scale, or a scanning method of moving the substrate while the ion gun is fixed may be employed. The ion beam treatment time can be varied within the range of 10 seconds to 10 minutes.

In addition, before performing the surface treatment by the ion beam, plasma etching or ion beam etching may be performed on the surface of the PLC thin film.

The present inventors confirmed that when the PLC thin film having a hydrogen content of more than 30 atomic% in the thin film is deposited as described above and surface treated by ion beam, a PLC thin film liquid crystal alignment film having an optical bandwidth of 1.5 eV or more can be obtained. It was confirmed that the pretilt angle of the liquid crystal alignment film was changed in accordance with the processing time of the ion beam and / or the irradiation angle of the ion beam, so that the final liquid crystal alignment film was thus obtained for TN mode, IPS mode or VA mode. In the case of TN mode, it was obtained almost in full range. In the case of IPS mode, the irradiation angle was obtained when it was irradiated with high irradiation energy for a long time at an angle of 10 ° to 40 ° or 50 ° to 70 ° instead of around 45 °. In addition, VA mode was obtained when the thin film thickness was reduced by performing ion beam irradiation for a long time after performing plasma etching or ion beam etching before the ion beam surface treatment.

Example-Effect of Ion Beam Irradiation

1) Change of PLC Thin Film Thickness

Although the thickness of the PLC thin film deposited by the remote-PECVD method of the present invention for 10 minutes was 4.8 nm, when the deposited thin film was irradiated with an argon ion beam having an energy of 200 eV for 1 minute, the thickness was reduced to 3.1 nm. When irradiated for a minute, a value very similar to that when irradiated with 3.0 nm for 1 minute was obtained.

As a result of the ion beam treatment, the initial thickness decreases rapidly and then the thickness rarely decreases. The reason why the PLC thin film deposited according to the present invention is deposited in the ground state is greater than 30 atomic% in the PLC thin film. This is because it has a porous structure containing a considerable amount of hydrogen. That is, since the PLC thin film manufactured in the ground state has a very low sheath voltage, the deposited thin film surface is hardly subjected to ion damage. Therefore, the deposited thin film has a low density and high hydrogen content. Hydrogen present in the thin film retains sp ³ CH bonds or exists as HH bonds. Since double CH bonds are much weaker bonds than CC bonds, they can be effectively removed through heat treatment or ion beam (plasma) treatment.

Therefore, when the PLC thin film is manufactured in the ground state as in the present invention, a considerable amount is present in the thin film, and it is considered that the thickness of the thin film is reduced while hydrogen present in the thin film is released by ion beam irradiation. However, when irradiated for 2 minutes, the thickness of the film hardly changes. This means that while irradiating an ion beam for 1 minute, a large amount of hydrogen present in the thin film is released and no more hydrogen is released. The sp ³ CC structure in the thin film is changed to an sp ² CC structure by ion beam irradiation. I think because. Therefore, when the ion beam irradiation time is within 1 minute, a sudden thickness decrease occurs due to the change in hydrogen content, and when the ion beam irradiation time is 1 minute or more, the thickness change according to the ion beam irradiation time does not appear significantly.

2) Optical property change of PLC thin film

The light transmittance of the deposited PLC thin film and the light transmittance according to the ion beam irradiation time are shown in FIGS. 5A and 5B. The light transmittance of the deposited PLC thin film was very excellent because the thickness of the deposited thin film was very thin. The reason why the light transmittance decreases by ion beam irradiation is due to the optical bandwidth change shown in FIG. 4. According to the present invention, since the low sheath voltage of the PLC thin film deposited in the ground state is formed, a very low density thin film is formed while many CH bonds are formed, and thus the optical bandgap is included because it contains a lot of deposited sp ³ components. Very high value. When the thin film is manufactured in the high sheath voltage region, a thin film having a high sp ³ CC density is obtained, and the optical bandwidth of the thin film thus obtained has a value of less than about 1.5 eV.

When the ion beam was irradiated on the thin film, the optical bandwidth was rapidly decreased, and when the ion beam was irradiated for 5 minutes, the thin film had an optical bandwidth of about 1.5 eV. This is inside the film

It is thought that the sp ³ CH structure is changed to the sp ² CC structure as the hydrogen bond is removed by the ion beam.

The biggest feature of the present invention is to deposit a PLC thin film having a very high hydrogen content in the first ground state, and then ion-beam treat the PLC thin film to obtain a liquid crystal alignment film made of a PLC thin film having an optical bandwidth of 1.5 eV or more. The conventional DLC thin film similar to the PLC thin film of the present invention has an optical bandwidth of less than 1.5 eV, and thus has a problem in that light transmittance is poor in a high energy region (blue region), but as shown in FIGS. 5A and 5B in the present invention. It is also shown that the light transmittance property is slightly reduced (FIG. 5a) even in a high energy region, or that no decrease in transmittance is observed (FIG. 5b). The transmittance data of FIG. 5A and the data of the one-minute ion beam irradiation in FIG. 4B show that the liquid crystal alignment layer can be used in the TN mode, and when the ion beam is irradiated for five minutes in FIG. 5B, the thickness of the thin film becomes very thin. There is no degradation of transmittance near 350 nm, which shows that it can be used in VA mode. As described later, the data in FIG. 5B was obtained for a PLC thin film which was subjected to plasma etching or ion beam etching by introducing oxygen or hydrogen gas before the ion beam treatment.

Example-Cell Test (Pretilt)

When the TN cell was manufactured using a PLC thin film which was not deposited and irradiated with an ion beam as an alignment layer, the liquid crystal was not aligned. In the present invention, all the liquid crystal alignment layers are formed of PLC thin film.

After fabrication, the TN cell was prepared after irradiating an ion beam.

The PLC thin film irradiated with ion beam for 1 minute showed a pretilt angle of 3.5 degrees. To be used for TN cells, a pretilt angle of more than 2.5 degrees is required, which is a very good result.

In addition, when the pretilt angle near zero degrees, which was difficult to implement by the conventional rubbing method, was set to 5 minutes in the ion beam irradiation time according to the present invention, the pretilt angle showed a small value of less than 1 degree. A liquid crystal alignment film having such a pretilt angle can be used for an IPS cell. The above result is shown in FIG.

Therefore, when the incident angle of the ion beam is changed, the pretilt angle of the liquid crystal is shown to be changed, which is shown in FIG. When the incident angle of the ion beam was changed, the most preferable pretilt angle was obtained for the TN cell at 40 degrees to 50 degrees (preferably around 45 degrees). In addition, it can be seen that it is preferable to set the angle of incidence of the ion beam to about 10 degrees to 40 degrees or about 50 degrees to 70 degrees for use in the IPS cell.

In addition, in the case of the VA liquid crystal cell, the alignment film shown in 5b, after the treatment 2 minutes at 25W plasma etching conditions, the PLC thin film deposited by the remote -PECVD method with H ₂ plasma, ion beam irradiation angle of 200 eV, the ion beam irradiation time 20 seconds A 5-minute treatment resulted in a pretilt angle of 89 degrees to 94.9 degrees.

In addition, TN cells using a PLC thin film irradiated with an ion beam for 1 minute as a liquid crystal alignment film and thermal stability were compared with TN cells using a polyimide by a rubbing method as a liquid crystal alignment film. Confirmed to show.

As described above, the present invention enables the PLC thin film capable of a low temperature thin film process to use the ion beam process in order to solve the shortcomings of the polyimide used in the conventional liquid crystal display liquid crystal aligning film. By omitting the cleaning process to improve the efficiency of the manufacturing process.

In addition, the present invention can overcome the limitations and problems of the conventional DLC thin film having poor light transmittance characteristics in the blue region.

Claims (7)

(a) depositing a PLC thin film having a hydrogen content of more than 30 atomic percent in a thin film by vacuum deposition on a substrate; and (b) treating the PLC thin film with an ion beam having an energy of 100 to 300 eV, thereby providing optical bandwidth. A method for producing a liquid crystal alignment film for a liquid crystal display, wherein the PLC thin film liquid crystal alignment film is 1.5 eV or more. The method of claim 1, wherein the ion beam is irradiated to the thin film at an angle of 10 ° to 70 ° during the surface treatment. The method of claim 2, wherein the PLC thin film is further subjected to plasma etching or ion beam etching prior to step (b). The method according to any one of claims 1 to 3, wherein the PLC thin film is deposited by a remote-PECVD method. The method of manufacturing a liquid crystal display for liquid crystal display according to any one of claims 1 to 3, wherein the pretilt angle of the PLC thin film liquid crystal alignment film changes with the ion beam treatment time. 4. The liquid crystal alignment film for liquid crystal display according to any one of claims 1 to 3, wherein the pretilt angle of the PLC thin film liquid crystal alignment film changes according to the irradiation angle of the ion beam to the PLC thin film of the substrate. Way. The liquid crystal alignment film according to any one of claims 1 to 3, wherein a liquid crystal alignment film for TN mode, IPS mode or VA mode is obtained according to the processing time of the ion beam and / or the angle of irradiation of the ion beam to the PLC thin film of the substrate. The manufacturing method of the liquid crystal aligning film for liquid crystal displays characterized by the above-mentioned.