JPH09230351A - Alignment layer treatment for alignment layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To harden an alignment layer at lowerer temp. in a shorter time than a conventional method and to increase the visual angle of a liquid crystal display while suppressing production of particles. SOLUTION: The alignment layer treatment includes the following processes. An alignment layer is applied on a glass substrate to form a substrate with an alignment layer (41). Then the alignment layer not hardened on the substrate is irradiated with at least either electron beams or UV rays to be hardened (42). After the hardening process, the film is subjected to alignment layer treatment by (1) rubbing and (2) by at least one of laser irradiation, ion beam irradiation and plasma irradiation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, in the manufacture of liquid crystal displays and the like, in which an alignment treatment for aligning liquid crystal molecules in a predetermined direction is performed. Regarding processing method.

[0002]

2. Description of the Related Art In order to align liquid crystal molecules on a surface of a substrate in a predetermined direction, an alignment film made of a high molecular organic material such as polyimide is applied to the surface of the substrate.

In this case, if the alignment film is simply applied to the surface of the substrate, the liquid crystal molecules are aligned in parallel with the surface of the substrate, and the liquid crystal molecules are aligned (or aligned) in a predetermined direction. Can not.

Therefore, conventionally, the alignment film has been subjected to the alignment treatment in the following steps.

An alignment film is applied on the substrate.

The alignment film is pre-baked at a predetermined temperature and time (for example, 80 to 100 ° C. for about 2 minutes).
Pre-baking before baking is, to put it simply, to make the film in a wet state uniform, to uniformly evaporate the solvent by uniform heating to obtain a uniform film surface, and to prevent bumping of the solvent to form an alignment film. This is to prevent problems such as cracks and peeling from occurring.

The alignment film after prebaking is baked at a predetermined temperature and time (for example, 200 to 250 ° C. for about 60 minutes). The firing is simply to react and cure the polymer organic material.

The alignment film is subjected to an alignment treatment by mechanically rubbing (rubbing) the surface of the alignment film after firing in a certain direction with a rubbing cloth made of nylon, rayon or the like.

[0009]

However, in the conventional method of curing the alignment film by firing as described above, the substrate with the alignment film is exposed to the above high temperature in the oven for a long time, As a result, there is a problem in that the color filter and the like formed on the substrate with the alignment film (more specifically, below the alignment film) before firing have adverse effects such as deformation and deterioration. In addition, since baking takes a long time, there is a problem that throughput (processing capacity per unit time) is low.

Further, in the method of subjecting the alignment film to the alignment treatment by rubbing as described above, since the alignment film is subjected to the alignment treatment in a constant direction and almost uniformly, the alignment direction of the liquid crystal molecules is constant and its pretilt angle ( The angle at which liquid crystal molecules rise from the surface of the alignment film) is almost uniform,
There is a problem that the viewing angle is narrow when a liquid crystal display is constructed.

In order to solve this, using the rubbing cloth as described above, the surface of the same alignment film is moved in different directions.
The rubbing process is performed by rubbing once to enable bidirectional alignment. By doing so, although the contrast is lowered, the viewing angle can be widened to some extent.

However, in the method in which the rubbing process is performed twice to widen the viewing angle, particles (dust) are generated during each rubbing process, so that a large amount of particles are generated, which results in a liquid crystal display. However, there is a problem that it becomes a factor of deteriorating the characteristics of, and eventually lowering the yield. For example, when particles are generated and adhere to the alignment film, display unevenness is caused thereby, display quality is deteriorated, and an electrically short-circuited portion is generated.

Therefore, the present invention provides an alignment treatment method for an alignment film, which can cure the alignment film at a lower temperature and in a shorter time than before, and can widen the viewing angle of a liquid crystal display while suppressing the generation of particles. The main purpose is to provide.

[0014]

In order to achieve the above-mentioned object, the alignment treatment method of the present invention performs at least one of electron beam irradiation and ultraviolet irradiation on an uncured alignment film provided on a substrate. And then subjecting the alignment film after curing to at least one of laser irradiation, ion beam irradiation, and plasma irradiation in addition to rubbing, to perform an alignment treatment. To do.

According to the above method, a chemical reaction such as a cross-linking reaction or a polymerization reaction occurs in the polymer constituting the alignment film due to the energy of the electron beam or the ultraviolet ray with which the uncured alignment film is irradiated, so that the firing is more than At low temperature and in a short time,
The alignment film can be cured.

In addition, in the alignment treatment, if at least one of laser irradiation, ion beam irradiation, and plasma irradiation is used in addition to rubbing, the alignment film has a plurality of alignment directions, and a plurality of alignment directions. Since it is possible to realize multi-domain orientation or random domain orientation dispersed in, it is possible to widen the viewing angle when a liquid crystal display is configured. Moreover, the rubbing is performed only once, and since the alignment film can be subjected to the alignment treatment by laser irradiation, ion beam irradiation or plasma irradiation in a non-contact manner, the generation of particles is very small. Therefore, the rubbing is performed twice compared with the conventional method. Can also reduce the generation of particles.

[0017]

1 is a process diagram showing an alignment treatment method according to an embodiment of the present invention. With reference to FIG. 2 and the like, the alignment treatment method includes a first step 41 of forming the alignment film-attached substrate 2 by applying the alignment film 6 on the glass substrate 4, and a step of forming the alignment film-attached substrate 2. In addition to rubbing, a second step 42 of curing the alignment film 6 by performing at least one of electron beam irradiation and ultraviolet irradiation on the cured alignment film 6 and then curing the alignment film 6 after curing. And at least one of laser irradiation, ion beam irradiation, and plasma irradiation is performed to perform an alignment treatment.
And The order of various processes in this third step 43 does not matter.

The substrate 2 with an alignment film is obtained by coating the surface of a glass substrate 4 with an alignment film 6 made of an organic polymer material such as polyimide. In the case of configuring a liquid crystal display, a transparent electrode made of ITO (tin-doped indium oxide) or the like is formed between the glass substrate 4 and the alignment film 6. Further, in the case of forming a color liquid crystal display, a color filter is formed under the alignment film 6.

The uncured alignment film 6 is cured by, for example, as shown in FIG. 2, electron beam 8 irradiation, ultraviolet ray 10 irradiation, or both.

The irradiation conditions of the electron beam 8 in this case are as follows, for example. Accelerating voltage: 150 kV or less, irradiation dose: 1 to 500 Mrad, irradiation atmosphere: in nitrogen gas. The reason for carrying out in a nitrogen gas atmosphere is to avoid the phenomenon that radicals generated in the alignment film by electron beam irradiation react with oxygen in the atmosphere and the surface of the alignment film is not completely cured.

The irradiation conditions of the ultraviolet rays 10 are as follows, for example. Wavelength: 200 to 250 nm, energy density: 30 J / cm ² or less, irradiation time: 10 seconds to 10 minutes.

When the uncured alignment film 6 is irradiated with an electron beam 8 or an ultraviolet ray 10, a chemical reaction such as a cross-linking reaction or a polymerization reaction occurs in the polymer constituting the alignment film 6 due to the energy of the irradiation, and firing is performed. The orientation film 6 can be cured at a lower temperature (eg, about room temperature) and in a shorter time (eg, 10 minutes or less). Therefore, even if a color filter or the like is formed on the substrate 2 with an alignment film, the color filter or the like is not adversely affected by deformation or deterioration due to heat. Moreover,
Since the processing time is shortened, the throughput is improved accordingly.

Further, in the case of electron beam irradiation or ultraviolet irradiation, since the alignment film 6 is cured by a chemical reaction due to the energy utilization thereof, bumping of the solvent unlike in the case of firing does not easily occur, and therefore, it is performed in the case of firing. Pre-baking can be omitted. As a result, the throughput is further improved by simplifying the process.

Alignment film 6 after being cured as described above
For example, referring to FIG. 3, the rubbing with respect to FIG.
Is moved in the direction of arrow A, for example, and the surface of the alignment film 6 is rubbed (rubbed) with the roll-shaped rubbing cloth 14 provided thereabove. The rubbing cloth 14 is made of, for example, nylon or rayon. The rubbing cloth 14 is normally rotated in the direction opposite to the movement of the moving table 12, as indicated by arrow B. The conditions of this rubbing process are as follows, for example. Table speed: 1
20 mm / sec or less, pushing amount: 0.7 mm or less, number of passes: 1-2 times.

Irradiation of the laser 16 or the ion beam 18 to the cured alignment film 6 may be performed almost directly above the alignment film 6 as shown in FIG. 4, or as shown in FIG. 5, for example. The irradiation may be performed at an irradiation angle θ of less than 90 degrees (that is, obliquely) with respect to the surface of the alignment film. In order to irradiate the entire surface of the alignment film 6 with the laser 16 or the ion beam 18, the laser 16 or the ion beam 18 may be scanned in the XY directions as needed. For oblique irradiation,
For example, as shown in FIG. 6, the rubbing direction D (this is shown in FIG.
It is preferable that the rubbing direction D and the irradiation direction E are different from each other by providing a predetermined azimuth angle φ between the irradiation direction E of the laser 16 or the ion beam 18). The reason is described below. When irradiating the laser 16 or the ion beam 18 from just above the alignment film 6, the azimuth angle φ does not exist, and therefore the rubbing direction is arbitrary.

The irradiation conditions of the laser 16 are as follows, for example. Wavelength: 248 nm (KrF laser) ~ 1
0.6 μm (CO ₂ laser), energy density: 50
0 mJ / cm ² or less, number of shots: 1 to 10 shots.

The irradiation conditions of the ion beam 18 are as follows, for example. Ion species: Inert gas ions such as helium, neon, argon, energy: 100-500
eV, beam current: 1 to 10 mA, irradiation time: 10 seconds to
3 minutes.

By irradiating the alignment film 6 with a laser 16, the alignment film 6 can be subjected to an alignment treatment. This is because the main chain or side chain of the polymer forming the alignment film 6 is cut by the energy of the laser 16 and aligned in a predetermined direction, and the liquid crystal molecules are aligned along it. Conceivable. Moreover, unlike rubbing, the alignment film 6 can be subjected to an alignment treatment without contact, so that the generation of particles can be prevented.

The alignment film 6 can also be subjected to the alignment treatment by irradiating the alignment film 6 with the ion beam 14. This is because the surface of the alignment film 6 is modified by irradiating with the ion beam 14, the main chains or side chains of the polymers forming the alignment film 6 are aligned in a certain direction, and the liquid crystal molecules are aligned along the same. It is considered that this is because, or a large number of minute groove-like things are formed on the surface of the alignment film 6 by the sputtering by the ion beam irradiation, and the liquid crystal molecules are aligned along it. Moreover,
Unlike the rubbing method, since the alignment film 6 can be subjected to the alignment treatment without contact, the generation of particles can be prevented.

Therefore, as described above, the irradiation angle θ of the laser 16 or the ion beam 18 is set to less than 90 degrees, and the irradiation direction E and the rubbing direction D are made different from each other by providing the azimuth angle φ. The alignment film 6 has two or more alignment directions different from each other, and can realize multi-domain alignment. As a result, the viewing angle of the liquid crystal display can be widened.

In that case, the smaller the irradiation angle θ,
The degree of orientational order (degree of indicating the proportion of liquid crystal molecules aligned in the same direction) and the pretilt angle (angle at which the liquid crystal molecules rise above the surface of the alignment film) obtained by irradiation with the laser 16 or the ion beam 18 are increased. Therefore, a clearer multi-domain alignment can be realized in combination with those obtained by rubbing.

When the laser 16 or the ion beam 18 is irradiated from almost directly above the alignment film 6, the degree of alignment order obtained thereby becomes small, but from a different point of view, this is because the alignment film has a large number of random alignments. It has a direction, and thus a random domain orientation can be realized. As a result, the liquid crystal molecules show a random orientation, and the degree of light scattering becomes stronger,
This can also widen the viewing angle of the liquid crystal display. However, since the pretilt angle in that case is small, it is necessary to use together with the rubbing having a large pretilt angle, and this is done in the present invention.

The plasma irradiation of the cured alignment film 6 is performed by using a plasma processing apparatus as shown in FIG. 7, for example. This plasma processing apparatus has a holder / electrode 22 inside a vacuum container 20 that is evacuated to a vacuum and a gas 26 is introduced.
And the electrode 24 are arranged so as to face each other, and high frequency power is supplied from a high frequency power supply 28 between them to generate plasma 30 by high frequency discharge. This holder and electrode 2
When the substrate 2 with an alignment film as described above is placed on the substrate 2,
Plasma 30 is incident on the alignment film 6. The gas 26 is an inert gas such as argon. The degree of vacuum in the vacuum container 20 is, for example, about 0.6 to 0.2 Torr. The applied high frequency power is, for example, about 100 to 300W.

The alignment treatment can be performed on the alignment film 6 also by making the plasma 30 incident on the alignment film 6.
This is due to the energy of the plasma 30 and the alignment film 6
It is considered that this is because the main chain or side chain of the polymer constituting the is cleaved so as to be aligned in a predetermined direction, and the liquid crystal molecules are aligned along it. Moreover, unlike rubbing, the alignment film 6 can be subjected to an alignment treatment without contact, so that the generation of particles can be prevented.

In addition to rubbing, if at least one of the above laser irradiation, ion beam irradiation and plasma irradiation is carried out, multi-domain alignment or random domain alignment can be realized by the above-mentioned action, so that the visual field can be improved. Although the angle can be widened, various processes can be performed by the alignment film 6 by performing a plurality of processes of laser irradiation, ion beam irradiation, and plasma irradiation in addition to rubbing, so that multi-domain alignment can be performed. Alternatively, the random domain alignment can be more strongly realized, and the viewing angle can be further widened.

Next, a more specific embodiment will be described.
As shown in FIG. 8, a twist angle 9 formed by using two upper and lower substrates 2 with an alignment film in which the rubbing direction D is different by 90 degrees
FIG. 9 shows the result of measuring the viewing angle of a 0-degree TN (twisted nematic) type cell set. This viewing angle shows a region having a contrast ratio of 10.

The viewing angle shown by the alternate long and short dash line in FIG. 9 is obtained when the alignment film 6 is subjected to the treatment of Example 1, and the viewing angle shown by the solid line is shown in FIG. The viewing angle shown by the broken line is obtained by the conventional method.

The processing conditions of Example 1 are as follows.

(1) Curing treatment: electron beam irradiation Accelerating voltage: 150 kV Irradiation dose: 20 Mrad Irradiation atmosphere: in nitrogen gas Irradiation angle: vertical Conveyor speed: 5 m / min

(2) Alignment treatment: laser irradiation after rubbing Rubbing table speed: 120 mm / sec Pushing amount: 0.5 mm Number of passes: 1 time Laser irradiation type: KrF laser Energy density: 60 mJ / cm ² Number of shots: 10 shots Angle θ: 45 degrees Azimuth angle φ: 90 degrees

The processing conditions of Example 2 are as follows.

(1) Curing treatment: UV irradiation Wavelength: 253 nm Energy density: 30 J / cm ² Irradiation angle: Vertical Irradiation time: 30 seconds

(2) Alignment treatment: laser irradiation followed by plasma irradiation, followed by rubbing laser irradiation Type: KrF laser Energy density: 60 mJ / cm ² Number of shots: 10 shots Irradiation angle: Vertical plasma irradiation Gas type: Argon Vacuum degree: 0. 4 Torr High frequency power: 150 W Rubbing table speed: 120 mm / sec Pushing amount: 0.5 mm Number of passes: 2 times

The processing conditions of the conventional method are as follows.

(1) Curing treatment: pre-baking and baking pre-baking temperature: 80 ° C. time: 120 seconds baking temperature: 250 ° C. time: 60 minutes

(2) Orientation treatment: rubbing Table speed: 120 mm / sec Pushing amount: 0.5 mm Number of passes: 1 time

From FIG. 9, the first embodiment is more advantageous than the conventional method.
It can be seen that the viewing angle of Example 2 is wider than that.

[0048]

Since the present invention is configured as described above, it has the following effects.

According to the alignment treatment method of the first aspect, a chemical reaction such as a crosslinking reaction or a polymerization reaction occurs in the polymer constituting the alignment film by the energy of the electron beam or the ultraviolet ray with which the uncured alignment film is irradiated. The alignment film can be cured at a lower temperature and in a shorter time than when firing is performed. Therefore, even if the color filter or the like is formed on the substrate with the alignment film, the color filter or the like is not adversely affected by heat such as deformation or deterioration. Moreover, since the processing time is shortened, the throughput is improved accordingly.

Further, in the case of electron beam irradiation or ultraviolet ray irradiation, since the alignment film is cured by a chemical reaction by utilizing those energy, bumping of the solvent unlike in the case of firing does not easily occur. Pre-baking can be omitted. As a result, the throughput is further improved by simplifying the process.

In addition, when at least one of laser irradiation, ion beam irradiation and plasma irradiation is used in addition to rubbing in the alignment treatment, the alignment film has a plurality of alignment directions and a plurality of alignment directions. Since it is possible to realize multi-domain orientation or random domain orientation dispersed in, it is possible to widen the viewing angle when a liquid crystal display is configured. Moreover, the rubbing is performed only once, and since the alignment film can be subjected to the alignment treatment by laser irradiation, ion beam irradiation or plasma irradiation in a non-contact manner, the generation of particles is very small. Therefore, the rubbing is performed twice compared with the conventional method. Can also reduce the generation of particles. As a result, for example, the factors that deteriorate the characteristics of the liquid crystal display are reduced, so that the yield of the liquid crystal display can be improved.

According to the alignment treatment method of the second aspect, by performing a plurality of treatments of laser irradiation, ion beam irradiation and plasma irradiation in addition to rubbing,
Since various alignment treatments can be performed with the alignment film,
The multi-domain orientation or the random domain orientation can be more strongly realized, and the viewing angle can be further widened.

[Brief description of drawings]

FIG. 1 is a process chart showing an alignment treatment method according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a state in which an alignment film is irradiated with an electron beam or ultraviolet rays.

FIG. 3 is a diagram showing an example of a state in which an alignment film is rubbed.

FIG. 4 is a diagram showing an example of a state in which an alignment film is irradiated with a laser or an ion beam.

FIG. 5 is a diagram showing another example of a state in which an alignment film is irradiated with a laser or an ion beam.

FIG. 6 is a plan view showing an azimuth angle φ of a laser or an ion beam with respect to a rubbing direction.

FIG. 7 is a cross-sectional view showing an example of a plasma processing apparatus.

FIG. 8 is an enlarged perspective view showing an example of a cell set constituting a liquid crystal display.

9 is a view showing a viewing angle range obtained by the method of the example and a viewing angle range obtained by the conventional method in the cell set shown in FIG.

[Explanation of symbols]

 2 substrate with alignment film 4 glass substrate 6 alignment film 8 electron beam 10 ultraviolet ray 14 rubbing cloth 16 laser 18 ion beam 30 plasma 41 to 43 steps

Claims (2)

[Claims] 1. An uncured alignment film provided on a substrate is irradiated with at least one of electron beams and ultraviolet rays to cure the alignment film, and then the alignment film after curing is cured. In addition to rubbing, at least one of laser irradiation, ion beam irradiation, and plasma irradiation is performed to perform an alignment treatment, and an alignment treatment method for an alignment film. 2. The alignment film according to claim 1, wherein the alignment film after the curing is subjected to a plurality of processes of laser irradiation, ion beam irradiation and plasma irradiation in addition to rubbing to perform the alignment process. Alignment treatment method.