JPH1195219A - Formation of oriented film of liquid crystal cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for formation of oriented film of a liquid crystal cell which sufficiently progresses a dehydration reaction while maintaining temp. unequalness uniform over the entire part of the inside surfaces of coating films of oriented film forming materials in order to attain the imidization by baking of the coating films for the purpose of sufficiently assuring the intrinsic orientation function as the oriented films. SOLUTION: The respective coating films subjected to normal baking in the baking stage S4 are maintained within the prescribed vacuum degree to the extent of avoiding the occurrence of convection in a treating stage S5 of vacuum heating and a blowing stage S6 of drying gas. While the respective coating films are heated under prescribed heating conditions, the drying gas is blown to the inside surfaces of the respective coating films for the prescribed blowing time to the extent of allowing the removal of the moisture thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming an alignment film of a liquid crystal cell using various liquid crystals such as a smectic liquid crystal and a nematic liquid crystal.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal cell is constituted by sealing liquid crystal between both electrode substrates. Here, in order to align the liquid crystal, each alignment film of both electrode substrates is formed by imidizing a film made of polyamic acid and then performing a rubbing treatment. Here, in the liquid crystal cell, the formation of the alignment film is usually performed as follows.

That is, after cleaning each electrode substrate before forming an alignment film, a polyamic acid is applied to the inner surface of each electrode substrate in this state by printing in an atmospheric pressure atmosphere. After that, the coating film is pre-baked and then subjected to main baking.
Thereby, the coating film is imidized and formed as an alignment film. Then, the alignment film is subjected to a rubbing treatment from its liquid crystal side surface so as to exhibit an alignment function for aligning liquid crystal molecules in a certain direction.

[0004]

By the way, in the above-mentioned liquid crystal cell, in order for the alignment film to sufficiently exhibit its alignment function, it is necessary that the alignment film is sufficiently imidized. For this reason, the present inventors prepared a plurality of the above-mentioned alignment films and examined the relationship between the imidization of these alignment films and the alignment of the liquid crystal.

As a result, the liquid crystal side surface (hereinafter referred to as the inner surface) of the alignment film must be sufficiently and uniformly imidized, which is an essential condition for ensuring good alignment of the entire liquid crystal. I understood. Therefore, from such a viewpoint, when the problem of forming the alignment film by firing in an atmospheric pressure atmosphere as described above was examined,
The following became clear.

First, the above-described imidization reaction of the coating film by baking causes a dehydration reaction in the coating film. However, since the calcination is performed in an atmosphere at atmospheric pressure, the atmosphere contains moisture.
Therefore, depending on the atmosphere, the moisture in the coating film is hardly absorbed, and the desorption of moisture from the inner surface (the liquid crystal side surface) of the coating film does not sufficiently proceed. Therefore, imidization of the inner surface of the coating film does not proceed. as a result,
Insufficiency of imidization on the inner surface of the coating film causes insufficient alignment of the entire liquid crystal, which causes a problem of lowering display contrast of the liquid crystal cell.

Second, when the above-mentioned calcination is carried out in an atmosphere at atmospheric pressure as described above, since the mean free path of each molecule of air is short, mutual collision of the molecules becomes frequent and air Convection occurs. Accordingly, due to the contact of the convection air with the inner surface of the coating film, the temperature distribution on the inner surface of the coating film becomes uneven. Therefore, uneven firing occurs on the inner surface of the coating film.

[0008] This means that imidization is uneven over the entire inner surface of the coating film. As a result, the occurrence of unevenness in imidization on the inner surface of the coating film as described above causes unevenness in alignment of the entire liquid crystal, resulting in poor display contrast of the liquid crystal cell. In this regard, in more detail, in a region of the inner surface of the coating film where the imidization has progressed, the negatively polar carbonyl group becomes dominant and exerts an electric binding force on the liquid crystal molecules. However, in the region of the inner surface of the coating film where imidization has not progressed, in addition to the negative carbonyl group, a positive hydroxyl group and an amino group remain in a mixed state, and these groups are present in the liquid crystal. Disturb the orientation. As a result, the variation in the dark luminance of the liquid crystal cell is increased, and the display contrast is deteriorated.

In particular, in the case of an antiferroelectric liquid crystal, when no electric field is applied, the liquid crystal molecules are aligned in a fixed direction by the alignment regulating force on the inner surface of the alignment film, and a black display is maintained. The deterioration of contrast is remarkable. In contrast to this, according to Japanese Patent Application Laid-Open No. 54-68654, it is proposed that the coating film is fired in a vacuum or in an inert gas when imidizing the coating film.

However, when the coating film is fired while being left in a vacuum, the mean free path of each molecule of air becomes longer than in the atmospheric pressure due to the vacuum. Even if the temperature unevenness of the inner surface of the coating film can be reduced by suppressing the temperature, the component remaining near the inner surface of the coating film is usually almost water. For this reason, moisture is re-adsorbed to the inner surface of the coating film, thereby inhibiting imidization of the inner surface of the coating film.

Further, when the above-mentioned coating film is baked in an inert gas, the mean free path of each molecule of the inert gas is long because it is not in a vacuum. For this reason, convection of the inert gas is generated, causing temperature unevenness on the inner surface of the coating film. Therefore, imidization unevenness occurs on the inner surface of the coating film. According to Japanese Patent Application Laid-Open No. 4-278923, it is proposed that, when imidizing a coating film formed of an alignment film forming material, the coating film is thermally decomposed and polymerized by heat treatment in a constant vacuum. .

However, if the coating film is only heat-treated in a constant vacuum, moisture is re-adsorbed to the inner surface of the coating film as in the case of Japanese Patent Laid-Open No. 54-68654. Inhibits imidization of the inner surface of the coating film.
In view of the above, in view of the above, in order to sufficiently secure the original alignment function as an alignment film, the present invention employs imidization of a coating film of a material for forming an alignment film by firing, at least over the entire inner surface of the coating film. It is an object of the present invention to provide a method for forming an alignment film of a liquid crystal cell, which allows a dehydration reaction to sufficiently proceed while maintaining uniform temperature unevenness over a period of time.

[0013]

According to the first aspect of the present invention, each electrode substrate having a fired coating film is maintained in a vacuum atmosphere.
A dry gas is blown onto the inner surface of each coating film while heating the coating film to form each alignment film. As described above, by maintaining each coating film in a vacuum atmosphere, the generation of convection is suppressed, the temperature unevenness of the inner surface of each coating film is suppressed, and the drying gas is sprayed on the inner surface of each coating film. This promotes the removal of water from the inner surface.

[0014] This makes it possible to further promote and uniformize the imidization of the inner surface of each alignment film. as a result,
When such an alignment film is used, the display contrast of the liquid crystal cell can be satisfactorily ensured under the favorable alignment of the liquid crystal. According to the second aspect of the present invention, each electrode substrate having a pre-baked coating film is maintained in a vacuum atmosphere, and the inner surface of each of the coating films is dried while the respective coating films are fully baked. Is sprayed to form each alignment film.

Thus, the same operation and effect as the first aspect of the present invention can be achieved while simplifying the process of forming the alignment film. According to the third and fourth aspects of the present invention, each electrode substrate having a baked coating film is maintained in an atmosphere of a predetermined degree of vacuum that does not cause a convection phenomenon, and each coating film is maintained at a predetermined level. While heating under the above heating conditions, the respective alignment films are formed by blowing a dry gas onto the inner surfaces of the respective coating films for a predetermined spraying time for removing the moisture.

As described above, by maintaining each of the fired coating films in an atmosphere having a predetermined degree of vacuum, the occurrence of convection is prevented, and the occurrence of temperature unevenness on the inner surface of each of the coating films is prevented. By spraying a dry gas onto the inner surface of each of the coating films for a predetermined spraying time while heating the inner surface of the coating film under a predetermined heating condition, the water on the inner surface is completely removed.

As a result, the further imidization of the entire inner surface of each alignment film can be further promoted and uniformized. As a result, when such an alignment film is used, the display contrast of the liquid crystal cell can be satisfactorily secured while preventing the deterioration and unevenness of the liquid crystal cell under the favorable alignment of the whole liquid crystal.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a liquid crystal cell to which the present invention is applied. This liquid crystal cell has two electrode substrates 10, 2
0 is provided. These two electrode substrates 10 and 20 are overlapped with each other via an annular seal 30 and a partition 40, and an antiferroelectric liquid crystal or an antiferroelectric liquid crystal is provided between the two electrode substrates 10 and 20. The liquid crystal 50 is the seal 30
It is enclosed through.

Here, the electrode substrate 10 is configured such that an alignment film 12 is provided on the inner peripheral side of the seal 30 via a plurality of transparent electrodes and an insulating film 11 on the inner surface of a glass substrate. On the other hand, the electrode substrate 20 has a seal 30 on the inner surface of the glass substrate through a plurality of transparent electrodes (which constitute a matrix pixel together with the plurality of transparent electrodes) and an insulating film 21.
And an alignment film 22 is provided on the inner peripheral side of the substrate.

Next, a method of manufacturing the liquid crystal cell will be described with reference to FIGS. In the cleaning step S1, the electrode substrate 10 before the formation of the alignment film 12 (hereinafter, referred to as an electrode substrate 10A before the formation of the alignment film) and the electrode substrate 20 before the formation of the alignment film 22 (hereinafter, the electrode before the formation of the alignment film 12). Substrate 2
OA). Here, the electrode substrate 10A before forming the alignment film is formed by sequentially forming a plurality of transparent electrodes and an insulating film 11 on the inner surface of a glass substrate. The electrode substrate 20A before forming the alignment film is formed by sequentially forming a plurality of transparent electrodes and an insulating film 21 on the inner surface of a glass substrate.

After the cleaning step S1, in a printing step S2 of an alignment film forming material, a solution of polyamic acid, which is an alignment film forming material, is uniformly printed on the surface of the insulating film 11 on the alignment film 12 side by an offset printing machine. To form a coating film, and uniformly apply the solution of the polyamic acid to the surface of the insulating film 21 on the side of the alignment film 22 by printing using the offset printing machine. In addition, the polyamic acid has a chemical structural formula as shown by a symbol P in FIG.

Next, in the preliminary firing step S3, each of the electrode substrates 10A, 2A,
OA is accommodated in a firing furnace, and each of the coating films is temporarily fired at a predetermined temporary firing temperature (for example, 100 ° C.) for a predetermined temporary firing time in an atmosphere of atmospheric pressure. Further, the main firing step S
In 4, each of the preliminarily fired coating films is main fired at a predetermined main firing temperature (for example, 200 ° C.) for a predetermined main firing time in an atmosphere at atmospheric pressure.

As a result, each of the coating films is imidized, and the alignment films 12 and 22 (FIG. 1) are polyimide films.
And FIG. 3). Considering this from the chemical structural formula, the polyamic acid having the chemical structural formula P is
As shown in FIG. 5, after the water was removed, the chemical structural formula Q
It becomes an alignment film made of polyimide having the following. At this time,
The thickness of each of the alignment films 12 and 22 is, for example, 20 nm.

Thereafter, in order to promote and uniformize the inner surfaces of the alignment films 12 and 22, the treatment in the vacuum heating treatment step S5 and the dry gas blowing step S6 is performed as follows. First, in the vacuum heating process step S5, the electrode substrate 10A before forming an alignment film having the fully baked alignment film 12 is placed on a table 71 in a high-temperature vacuum chamber 70 with the polyimide film 12 facing upward, as shown in FIG. Place as shown.
Further, the electrode substrate 20A before alignment film formation having the alignment film film 22 that has been fully baked as described above is placed on the stage 7 in the high-temperature vacuum chamber 70.
3 is placed on each of the extension plates 72 extending upward in L-shape from both left and right end portions, with the alignment film 22 facing upward.

Next, the on-off valve 80a is opened, and the air in the high-temperature vacuum chamber 70 is discharged to the outside by the rotary pump 90 through the turbo molecular pump 80. This discharge is performed when the inside of the high-temperature vacuum chamber 70 has a predetermined degree of vacuum (for example, 10 ⁻²
Perform until r). Here, the predetermined degree of vacuum is 1
The reason for setting it to 0 ^-2 Torr is to extend the mean free path of the molecules of the air to such an extent that the air does not cause a convection phenomenon in the high-temperature vacuum chamber 70.

The turbo molecular pump 80 plays a role in sufficiently increasing the exhaust speed of the rotary pump 90. After the inside of the high-temperature vacuum chamber 70 is set to the predetermined degree of vacuum as described above, the inside of the high-temperature vacuum chamber 70 is heated to a predetermined heating temperature (for example, 200 ° C.) according to a predetermined temperature program. The heating temperature is maintained for a predetermined heating maintenance time (for example, 2 hours) by measuring the time set by a timer.

Next, in the drying gas spraying step S6, a drying gas spraying process is performed on each of the alignment films 12 and 22 as follows. In this process, the high-temperature vacuum chamber 70 is provided with a spray tube member 100, and the spray tube member 100 is provided with a pair of nozzles 101, 10
2 and a communication pipe 103. The spray pipe member 100 is hermetically inserted into the side wall 73 of the high-temperature vacuum chamber 70 by the communication pipe 103.

The pair of nozzles 101 and 102 are connected to the communication pipe 1
The nozzles 101 and 102 are bifurcated from the inner end of the nozzle No. 03 at the vertical position shown in FIG.
3 is inclined at the front end openings 101a and 102a of the inner surfaces of the alignment films 12 and 22 just above the right end in FIG. Further, as shown in FIG. 4, the nozzle 102 extends from the inner end of the communication tube 103 toward the right end in the inner surface of the alignment film 22 as shown in FIG. Reference numeral 101 extends from the inner end of the communication tube 103 toward the right end of the inner surface of the alignment film 12 in FIG.

Here, each of the nozzles 101 and 102 is shown in FIG.
The nozzles 101 and 102 have a flattened shape in the vertical direction in the figure.
Has an opening width corresponding to the vertical width shown in FIG. 4 among the inner surfaces of the alignment films 12 and 22. Then, the flow control valve 110 is opened, and an inert gas such as nitrogen or argon gas or air, which is sufficiently clean, is used as the gas G to form the drying bottle 120.
Pump inside. Then, the gas G is absorbed by the desiccant 121 such as silica gel filled in the drying bottle 120 to become moisture and becomes the dry gas Ga.

Next, the dry gas Ga passes through the communication pipe 103 of the spraying pipe member 100, and the nozzles 101, 10
2 and along the inner surface of each of the alignment films 12 and 22 are simultaneously sprayed from the right end to the left end as shown in FIGS. Thereby, the moisture on the entire inner surface of each of the alignment films 12 and 22 is sufficiently and uniformly adsorbed by the dry gas Ga.

At this time, the degree of vacuum inside the high-temperature vacuum chamber 70 also tends to decrease toward the atmospheric pressure side. However, since the turbo molecular pump 80 increases the exhaust speed of the gas in the high-temperature vacuum chamber 70, the high-temperature vacuum The degree of vacuum in the tank 70 does not reduce the predetermined degree of vacuum. Accordingly, the mean free path of the gas molecules of the drying gas is also maintained at a value corresponding to the predetermined degree of vacuum, so that convection of the drying gas does not occur. Therefore, a uniform temperature distribution can be maintained over the entire inner surfaces of the alignment films 12 and 22.

The temperature in the high-temperature vacuum chamber 70 also tends to be reduced by blowing the dry gas into the high-temperature vacuum chamber 70.
If the inside heating temperature is set high, the high-temperature vacuum chamber 70
Can be maintained at the predetermined heating temperature. Therefore, the degree of acceleration of the imidization of the entire inner surface of each of the alignment films 12 and 22 can be more uniformly promoted.

As described above, the temperature of the entire inner surface of each alignment film of the electrode substrates 10A and 20A before the formation of the alignment film is reduced to the above-mentioned predetermined heating temperature through both the vacuum heating processing step S5 and the drying gas blowing step S6. While maintaining, the entire inner surface of each alignment film is further promoted by the dehydration reaction from chemical structural formula P to chemical structural formula Q shown in FIG. Completely remove water.

As a result, the inner surfaces of the respective alignment films 12A and 22A are uniformly and further imidized over the entire surface. As a result, the entire inner surface of each of the alignment films 12 and 22 is
The carboxyl groups necessary for orienting the entire antiferroelectric liquid crystal 60 are uniformly formed in the same favorable state. After the process of the drying gas spraying step S6 is completed as described above, the partition 40 is formed on the inner surface of the alignment film of the electrode substrate 10 in the partition forming step S7. Next, a rubbing step S8
In step (1), a rubbing process is performed on each of the alignment films 12 and 22 of the electrode substrates 10A and 20A before forming the alignment film.

In this case, the dry gas spraying step S6
In the above, since the imidation of the entire inner surface of each of the alignment films 12 and 22 is promoted uniformly and further more than in the case of the main firing, the alignment treatment of the inner surface of each of the alignment films 12 and 22 is performed as follows.
It can be done uniformly and well over the entire inner surface. Thereby, each of the alignment films 12 and 22 is finally formed as a film exhibiting the original alignment function over the entire inner surface. The electrode substrates 10A and 20A before forming an alignment film having such alignment films 12 and 22 are the electrode substrates 10 and
Equivalent to 20.

After the rubbing step S8 as described above,
In the substrate cleaning step S9, the electrode substrates 10 and 20 are cleaned. Then, in the seal printing step S10, the seal 3 is formed on the outer peripheral edge of the inner surface of the alignment film 22 of the electrode substrate 20.
0 is formed in an annular shape by printing a sealant. Note that a liquid crystal injection port is formed in a part of the seal 30. Next, in a superposition step S11, the electrode substrate 20 is superposed on the electrode substrate 10 via the seal 30 and the partition wall 40. In this case, this superposition is performed by the alignment films 12 and 22.
In such a way that the rubbing directions are parallel.

Then, in a seal hardening step S12, both electrode substrates 10 and 20 are heated and pressurized to harden the seal 30 and secure a predetermined cell gap. After that, in the liquid crystal injection sealing step S13, the antiferroelectric liquid crystal 60 is liquefied by heating, filled through the liquid crystal injection port of the seal 30 and between the two electrode substrates 10 and 20, and then the liquid crystal injection port is sealed. I do. Thereby, the manufacture of the liquid crystal cell is completed.

At this time, as described above, each alignment film 12,
Since the imidization of the entire inner surface of the liquid crystal 22 is evenly and further promoted, the liquid crystal molecules of the antiferroelectric liquid crystal 60 are uniformly and well aligned over the entire surface. Therefore, the display contrast of the liquid crystal cell can be uniformly and satisfactorily secured over the entire display area of the liquid crystal cell. Incidentally, the effects of both the vacuum heating processing step S5 and the dry gas blowing step S6 described in the above embodiment were examined.

Here, as a target to be compared with each of the alignment films described in the above embodiment, each of the above-mentioned coating films is fully baked at 200 ° C. for 2 hours in a normal atmospheric pressure atmosphere, and the alignment film is It was adopted. Then, the contact angle θ of this alignment film with water
And the contact angle θ of each alignment film to water described in the above embodiment was calculated. The Wilhelmy method was used to calculate the contact angle using the micro balance 130 shown in FIG. That is, for example, a sample 140 of about 10 mm square is cut out from the electrode substrate 10A before forming an alignment film on which the alignment film is formed in a region including the alignment film. And the micro balance 13
The suspension is suspended at one end of the rod of No. 0 to balance with the weight 150 at the other end.

In this state, as shown in FIG. 7, the beaker 160 is moved upward, and the sample 140 is made to enter the water 161 in the beaker 160 from the water surface 161a. At this time, the load of the sample 140 was F, and the water 16
0 water surface 161a (that is, the sample 140
Assuming that σ is the force extruded by 60, the contact angle θ between water 160 and sample 140 at the time of intrusion is calculated by the following equation (1). This calculated contact angle θ is indicated by a point A in FIG.

[0041]

In the equation (1), L is the length of the water line of the sample 140 (the outer peripheral length of the sample 140 in contact with the uppermost portion of the water surface 161a in FIG. 7). Represents). Θ represents an angle between the load F and the surface tension σ.

As described above, a sample 140A having an alignment film is prepared by sintering at 200 ° C. for two hours in a normal atmospheric pressure atmosphere, and water 161 in a beaker 160 is prepared similarly to the sample 140. From the water surface 161a. Then, the contact angle θ between the water 160 at the time of intrusion and the sample 140A was calculated based on the equation (1). This calculated contact angle θ
Is indicated by point C in FIG.

By comparing the two calculated contact angles θ, it is found that Sample 1
It can be seen that the contact angle θ of 40A (see point C in FIG. 6) is smaller than that of the sample 140 (see point A in FIG. 6). This is for the following reason. The polyamic acid for forming the alignment film of the sample 140A is not sufficiently imidized only by main firing at 200 ° C. in an atmosphere of atmospheric pressure. Therefore, a hydroxyl group (OH) is formed on the inner surface of the alignment film.
And many amino groups (NH).

These hydroxyl groups and amino groups are basically
Because of the hydrophilic group, in the case of the orientation film of sample 140A that is insufficiently imidized, the sample 14A that is sufficiently imidized is not used.
The contact angle θ becomes smaller as shown in FIG. In other words, the sample 1 is smaller than the sample 140A.
It can be said that, in the case of No. 40, imidization of the inner surface of the alignment film is clearly advanced.

Accordingly, it can be seen that the effects of both the vacuum heating processing step S5 and the dry gas spraying step S6 described in the above embodiment are remarkably obtained. FIG. 6 also shows an example in which the heating temperature of the sample 140 in the processing step S5 is set to 250 ° C. In this case, the contact angle θ (see point B in FIG. 6) is further increased, and the orientation is increased. It can be said that the imidization of the inner surface of the film is further advanced.

Therefore, even if the heating temperature in the vacuum heating processing step S5 described in the above embodiment is higher than 200 ° C.
The same or more effects and advantages as those of the above embodiment can be achieved. The effects of both the vacuum heating processing step S5 and the drying gas spraying step S6 described in the above embodiment are described with respect to the alignment dark luminance (cd / m
m ² ). This is because the alignment dark luminance is deeply related to the display contrast of the liquid crystal cell, and the display contrast improves as the alignment dark luminance decreases.

Here, as a comparison with the liquid crystal cell having each alignment film described in the above embodiment, only the heating time in the vacuum heating processing step S5 described in the above embodiment was changed to 10 hours. The liquid crystal cell having the alignment film in the above case, and each of the above-mentioned coating films was placed at 200 ° C. in a normal atmospheric pressure atmosphere.
And a liquid crystal cell having an alignment film after the main baking for 2 hours. Each of these liquid crystal cells has the same configuration in which antiferroelectric liquid crystal is sealed. The thickness of the glass substrate constituting the electrode substrate of each liquid crystal cell is 1.1.
mm, and the thickness of the antiferroelectric liquid crystal layer is 1.8 μm.

The orientation dark luminance of the liquid crystal cell was measured by a luminance meter with the backlight turned on without applying a voltage to the antiferroelectric liquid crystal. By this measurement, the result shown in FIG. 8 was obtained. The alignment dark luminance of the liquid crystal cell having each alignment film described in the above embodiment is indicated by a point A in FIG. Processing step S of vacuum heating described in the above embodiment
The darkness of the alignment of the liquid crystal cell having the alignment film when only the heating time in 5 was changed to 10 hours is shown by a point B in FIG. In addition, each of the coating films is fully baked at 200 ° C. for 2 hours in a normal atmospheric pressure atmosphere, and the alignment dark luminance of the liquid crystal cell having the alignment film is shown by point C in FIG.

According to FIG. 8, the point A has a smaller orientation dark luminance than the point B, and the point B has a smaller orientation dark luminance than the point A. Therefore, the liquid crystal cell having each alignment film described in the above embodiment is better than the liquid crystal cell having the alignment film by firing each coating film at 200 ° C. for 2 hours in a normal atmospheric pressure atmosphere. It can be seen that the variation in luminance in the liquid crystal cell is significantly improved.

This is because, as described in the above embodiment, the vacuum heating processing step S5 and the drying gas blowing step S6
By performing both treatments, the promotion of imidization and uniformization of the entire inner surface of the alignment film are improved, and the density of carbonyl groups on the inner surface of the alignment film involved in the alignment is increased, thereby ensuring good alignment. Because you can. In the above embodiment, an example in which the respective processes of the main firing step S4, the vacuum heating step S5, and the drying gas blowing step S6 are sequentially performed has been described.
Instead of this, the respective processes of the main firing step S4, the vacuum heating step S5, and the drying gas spraying step S6 may be simultaneously performed in the main firing, vacuum heating, and spraying step S14 as shown in FIG. The same operation and effect as in the above embodiment can be achieved while simplifying the process.

In the above embodiment, the main firing step S4
Although the example of performing the process in the atmosphere of the atmospheric pressure has been described, the process of the main firing step S4 may be performed in a vacuum atmosphere instead. In implementing the present invention, when a predetermined degree of vacuum in the high-temperature vacuum layer 70 can be maintained, the turbo molecular pump 8 described in the above embodiment can be used.
0 may be abolished.

In the above embodiment, the high-temperature vacuum layer 70
The vacuum heating step S5 and the drying gas spraying step S6 are simultaneously performed on the two alignment films 12 and 22 housed therein, but instead of this, the vacuum heating step is separately performed on each of the alignment films 12 and 22. Each processing of S5 and the drying gas spraying step S6 may be performed. Further, each nozzle 10 of the spray pipe member 100 described in the above embodiment is used.
Each of the nozzles 101 and 102 has a shape capable of uniformly spraying a dry gas on the inner surface of each of the alignment films 12 and 22. Any shape may be used.

In practicing the present invention, the means for drying the gas G is not limited to the desiccant described in the above embodiment. For example, heating the gas G or dehydrating the gas G with sulfuric acid may be used. May be. Further, in carrying out the present invention, the liquid crystal used for the liquid crystal cell is not limited to the antiferroelectric liquid crystal described in the above embodiment, and a smectic liquid crystal such as a ferroelectric liquid crystal or a nematic liquid crystal may be employed. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a liquid crystal cell to which the present invention is applied.

FIG. 2 is a process chart showing a method for manufacturing the liquid crystal cell of FIG.

FIG. 3 is a schematic cross-sectional view of equipment for performing a vacuum heating process and a dry gas spraying process on both alignment films using a high-temperature vacuum chamber.

FIG. 4 is a plan view seen from the line 4-4 in FIG. 3;

FIG. 5 is a diagram showing a chemical structural formula representing a change from polyamic acid to polyimide.

FIG. 6 is a graph showing a contact angle θ as a parameter of imidization conditions for a polyamic acid coating film.

FIG. 7 is a schematic diagram for measuring a physical quantity related to a contact angle θ using a micro balance.

FIG. 8 is a graph showing the darkness of the orientation of a liquid crystal cell as a parameter of imidization conditions for a polyamic acid coating film.

FIG. 9 is a manufacturing process diagram of a liquid crystal cell showing a modification of the above embodiment.

[Explanation of symbols]

10, 20 ... electrode substrate, 10A, 20A ... electrode substrate before forming an alignment film, 11, 21 ... insulating film, 12, 22 ... alignment film,
50: antiferroelectric liquid crystal, 70: high vacuum tank, 100: spray tube member, 120: drying bottle, 121: silka gel, G
... Inert gas or air, Ga ... Dry gas, S3 ... Preliminary firing step, S4 ... Main firing step, S5 ... Vacuum heating step, S6 ...
Dry gas spraying process, S12: Main firing, vacuum heating,
Dry gas spraying process.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koji Iwaki 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation (72) Inventor Tadashi Hattori 1-1-1, Showa-cho, Kariya-shi, Aichi Co., Ltd. Inside DENSO

Claims (4)

[Claims] 1. An alignment film forming method for forming alignment films of both electrode substrates which are overlapped via a liquid crystal to form a liquid crystal cell, wherein an alignment film forming material is applied to an inner surface of each of the electrode substrates. Forming a coating film, baking each of the coating films, maintaining the electrode substrates each having the fired coating film in a vacuum atmosphere, and heating the respective coating films on the inner surface of each of the coating films. A method for forming an alignment film of a liquid crystal cell, wherein a dry gas is blown below to form each of the alignment films. 2. An alignment film forming method for forming respective alignment films of both electrode substrates which are overlapped via a liquid crystal to form a liquid crystal cell, wherein an alignment film forming material is applied to an inner surface of each of the electrode substrates. Forming a coating film, pre-baking each of the coating films, maintaining the electrode substrates each having the pre-baked coating film in a vacuum atmosphere, A method for forming an alignment film of a liquid crystal cell, wherein a dry gas is blown onto an inner surface of the film to form each of the alignment films. 3. An alignment film forming method for forming alignment films of both electrode substrates which are superposed via a liquid crystal to form a liquid crystal cell, wherein an alignment film forming material is applied to an inner surface of each of the electrode substrates. Forming a coating film, firing each of the coating films, maintaining each of the electrode substrates having the fired coating films within a predetermined degree of vacuum that does not cause a convection phenomenon, An alignment film of a liquid crystal cell forming each of the alignment films by blowing a dry gas for a predetermined spraying time for removing water from the inner surface of each coating film while heating under predetermined heating conditions. Forming method. 4. The alignment film forming material is a polyamic acid, the predetermined degree of vacuum is 10 ⁻² Torr or more, and the predetermined heating condition is a heating temperature in a range of 200 ° C. to 250 ° C. 4. The method of claim 3, wherein the heating time is about 2 hours to 10 hours, and the predetermined spray time is at least about 2 hours.