METHOD FOR LIQUID CRYSTAL ALIGNMENT

Abstract

A method for liquid crystal alignment is provided, comprising step 1: coating liquid state alignment film material containing paramagnetic chain-like particles on a display region of a substrate; step 2: placing the substrate in a constant magnetic field, so that the paramagnetic chain-like particles are stably arranged in a direction of the magnetic field; step 3: removing the magnetic field; and step 4: adding liquid crystal material into the display region of the substrate, so that molecules of the liquid crystal material align in the orientation of the paramagnetic chain-like particles. According to the method of the present disclosure, the use of rubbing cloth can be avoided, and non-contact liquid crystal alignment can be realized.

Claims

1. A method for liquid crystal alignment, comprising: step 1: coating liquid state alignment film material containing paramagnetic chain-like particles on a display region of a substrate, step 2: placing the substrate in a constant magnetic field, so that the paramagnetic chain-like particles are stably aligned in a direction of the magnetic field, step 3: removing the magnetic field, and step 4: adding liquid crystal material into the display region of the substrate, so that molecules of the liquid crystal material align in the orientation of the paramagnetic chain-like particles.

2. The method according to claim 1, wherein in step 2, the liquid state alignment film material is further precured.

3. The method according to claim 2, wherein in step 2, the constant magnetic field is a uniform magnetic field.

4. The method according to claim 3, wherein the paramagnetic chain-like particles are copper complex containing [Cu(NH.sub.3).sub.4].sup.2+ or [Cu(H.sub.2O).sub.4].sup.2+.

5. The method according to claim 4, wherein in step 2, the substrate is pre-baked, so that the liquid state alignment film material is precured.

6. The method according to claim 5, wherein the liquid state alignment film material further comprises polyimide and N-methylpyrrolidone as carrier liquid for the paramagnetic chain-like particles.

7. The method according to claim 6, wherein a temperature of a pre-baking procedure is in a range from 80 to 100 C., and a magnetic strength of the uniform magnetic field is in a range from 0.1 to 1.5 T.

8. The method according to claim 6, wherein a mass content of the paramagnetic chain-like particles in the carrier liquid is in a range from 0.2 to 1%.

9. The method according to claim 5, wherein an additional step of removing paramagnetism of the paramagnetic chain-like particles is further performed between step 3 and step 4.

10. The method according to claim 7, wherein an additional step of removing paramagnetism of the paramagnetic chain-like particles is further performed between step 3 and step 4.

11. The method according to claim 8, wherein an additional step of removing paramagnetism of the paramagnetic chain-like particles is further performed between step 3 and step 4.

12. The method according to claim 9, wherein in the additional step, intensified baking is performed on the substrate at a higher temperature than the pre-baking, which is preferably in a range from 230 to 250 C.

Description

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0017] The present disclosure will be described in detail based on the examples in view of the accompanying drawings. In the drawings:

[0018] FIGS. 1-4 schematically show steps of a method according to the present disclosure.

[0019] In the drawings, same components are indicated with the same reference sign. The drawings are not drawn to actual scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The present disclosure will be described in detail in view of the accompanying drawings.

[0021] The method according to the present disclosure can be implemented by preparing liquid state alignment film material first. In an example, the liquid state alignment film material comprises N-methylpyrrolidone, polyimide and paramagnetic chain-like particles, in which N-methylpyrrolidone and polyimide are used as carrier liquid for the paramagnetic chain-like particles. Liquid state alignment film material comprising N-methylpyrrolidone and polyimide is well known to one skilled in the art, and thus will not be described in detail. The paramagnetic chain-like particles can be copper complex containing [Cu(NH.sub.3).sub.4].sup.2+ or [Cu(H.sub.2O).sub.4].sup.2+, which are also well known to one skilled in the art and will not be described in detail. The paramagnetic chain-like particles can be used as alignment guiding bodies for the molecules of the liquid crystal material. Polyimide can be used to form an alignment film on the substrate, which will be described in detail hereinafter.

[0022] As shown in FIG. 1, liquid state alignment film material is coated on a display region of a substrate 1. Because there is no magnetic field to guide paramagnetic chain-like particles 3, orientations of the paramagnetic chain-like particles 3 on the substrate 1 are chaotic.

[0023] Subsequently, the substrate 1 is placed in a constant magnetic field 4. Under the action of the magnetic field 4, the paramagnetic chain-like particles 3 are aligned in a direction of the magnetic field 4. In a preferred example, the constant magnetic field 4 is a uniform magnetic field 4 as shown in FIG. 2. Each point within a scope of the uniform magnetic field 4 has a same magnetic strength. It should be understood that the magnetic strength is a vector. In this case, value and direction of the magnetic strength of each point within the scope of the uniform magnetic field 4 are respectively the same. In this case, the direction of the magnetic field 4 is a predetermined direction of liquid crystal alignment. Therefore, in an example, each of a plurality of paramagnetic chain-like particles 3 is stably aligned in the direction of the magnetic field 4, i.e., stably aligned in the predetermined direction of liquid crystal alignment.

[0024] In a specific example, a magnetic strength of the uniform magnetic field is in a range from 0.1 to 1.5 T. Under the above condition, the paramagnetic chain-like particles 3 can fully overcome rotational resistance and thus align in the direction of the uniform magnetic field 4. In a specific example, a mass content of the paramagnetic chain-like particles 3 in the carrier liquid thereof is in a range from 0.2 to 1%. In this case, the paramagnetic chain-like particles 3 would not entangle with each other in a large scale; instead, each particle can rotate relatively independently. If the content of paramagnetic chain-like particles is further increased, mutual resistance during rotation of the paramagnetic chain-like particles 3 would be significantly increased, which may even cause failure of alignment of the paramagnetic chain-like particles 3 in the direction of the uniform magnetic field.

[0025] In another example, while substrate 1 coated with liquid state alignment film material is placed in the constant magnetic field 4, the liquid state alignment film material is further precured. For example, the substrate 1 is pre-baked, so that the liquid state alignment film material can be precured. In a specific example, a temperature of a pre-baking procedure is in a range from 80 to 100 C. After the liquid state alignment film material is precured, the already aligned paramagnetic chain-like particles 3 would not change status any more, thereby facilitating subsequent steps. Because paramagnetic chain-like particles 3 can turn rapidly under the uniform magnetic field 4 and a velocity of the precuring is relatively slow, precuring the liquid state alignment film material would not influence the alignment of the paramagnetic chain-like particles 3. On the contrary, the aligned sate of the paramagnetic chain-like particles 3 can be stabilized.

[0026] After the liquid state alignment film material is cured, the magnetic field 4 is removed.

[0027] After N-methylpyrrolidone in the liquid state alignment film material completely volatilizes, polyimide forms an alignment film 5 attached on the substrate 1. In this case, the paramagnetic chain-like particles 3 extend outside the alignment film 5 in form of combs 9. As shown in FIG. 3, because the paramagnetic chain-like particles 3 have already been aligned in the direction of the uniform magnetic field 4, the combs 9 extend roughly in parallel. That is, the extending direction of the combs 9 is the abovementioned direction of the uniform magnetic field 4.

[0028] Preferably, after the magnetic field 4 is removed, intensified baking is further performed on the substrate 1 at a temperature higher than the pre-baking. In a specific example, the temperature of the intensified baking is in a range from 230 to 250 C. The intensified baking can not only accelerate the volatilization of N-methylpyrrolidone, but also facilitate the polymerization of polyimide, whereby the alignment film 5 can be formed on the substrate 1 firmly. More importantly, intensified baking can destroy the paramagnetism of the paramagnetic chain-like particles 3, whereby the paramagnetic chain-like particles 3 can be prevented from being influenced from other magnetic field and being realigned, which would greatly influence the predetermined liquid crystal alignment, such as the orientation of molecules 8 of the liquid crystal material under the guidance of the combs 9.

[0029] At last, liquid crystal material is added into a display region of the substrate 1. Molecules 8 of the liquid crystal material can align in a predetermined direction under the guidance of the combs 9.

[0030] In this case, non-contact liquid crystal alignment procedure is realized.

[0031] Although the present disclosure has been described with reference to preferred embodiments, as long as there is no structural conflict, various embodiments as well as the respective technical features mentioned herein may be combined with one another in any manner. The present disclosure is not limited to the specific examples disclosed herein, but rather includes all the technical solutions falling within the scope of the claims.