JPH09133923A - Anisotropic high-polymer film, liquid crystal display device formed by using the same and production of anistropic high-polymer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an anisotropic high-polymer film for an oriented film which may be produced without the execution of a rubbing treatment, etc., and with which the occurrence of unequalness and domains is suppressed by forming the film in which the side chains are crosslinked to each other to constitute networks and the uncrossed side chains are isotropically distributed. SOLUTION: The anisotropic high-polymer film utilized as the oriented film 24 of a liquid crystal display device 10 has the structure in which the side chains of the respective high polymers are crosslinked. The film is so formed that the crosslinked parts of the side chains have anisotropy and that the non-crosslinked parts are isotropically distributed without deviation. The side chains are so crosslinked as to have the anisotropy in the manner described above, by which the orientation of liquid crystals 16 at the time of using the anisotropic high-polymer film as the oriented film 24 is made possible. In addition, the non-crosslinked parts are isotropically distributed, by which the unequalness of the orientation of the liquid crystals 16 is lessened and the occurrence of the domains is suppressed. The ratio of the uncrosslinking at the side chains is preferably below 20%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel anisotropic polymer film suitable for an alignment film provided in a liquid crystal display device and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, various displays such as a television and an image device connected to a computer are required to be lighter, thinner, and have lower power consumption. Under such circumstances, the emergence of an excellent liquid crystal display device is desired as a device for realizing a flat display that satisfies the above requirements. The liquid crystal display device is provided with an alignment film having a tilt formed on the surface and a pretilt angle set in order to align the liquid crystal in a certain direction. As a method for producing an alignment film, a rubbing treatment in which a polymer resin film such as a polyimide resin film formed on a substrate is rubbed in one direction with a cloth, or silicon dioxide (SiO ₂ ) is used.
There is known a method of forming by oblique vapor deposition.

However, in the case of an alignment film formed by using a rubbing process, when rubbing with a cloth or the like to produce this alignment film, dust is generated or static electricity is generated. There's a problem. Further, the method using the oblique vapor deposition has a problem that the manufacturing cost is high and it is difficult to form it in a large area, which is not suitable for a relatively large liquid crystal display device.

Therefore, in recent years, in order to solve such a problem, a method of manufacturing an alignment film by using a transfer method has come into the limelight. The method for producing an alignment film by this transfer method is a method of transferring an uneven shape to the surface of a film by pressing a transfer mold having an uneven pattern to be transferred formed on the surface of a resin film formed on a substrate while heating. To form. In general, the surface shape of the alignment film manufactured by this transfer mold is a shape in which a large number of convex shapes are repeatedly formed in parallel on a substrate.

However, in the liquid crystal display device using the alignment film having only the concavo-convex shape formed by the transfer method, the interface regulating force against the liquid crystal is weak, and an external force or heat is applied, so that a sufficient pretilt angle is obtained. (Generally, 1 ° or more) is not maintained, and so-called domain may occur.

Further, instead of the above-mentioned rubbing treatment or transfer method using a transfer type, a method of manufacturing an alignment film by utilizing polarized ultraviolet rays has been studied. For example, a polymer compound (polyvinyl cinnamate) represented by the following chemical reaction formula is uniformly applied on a substrate to form a film, and then ultraviolet rays polarized in a specific direction are irradiated at room temperature.
Then, the double bond of the polarization axis direction and the carbon double bond are parallel to each other and the distance from other adjacent double bonds is about 4Å or less to cleave to form a cyclobutane ring. The groups are arranged in a direction orthogonal to the polarization axis direction. And in a liquid crystal cell that uses an alignment film that uses this anisotropic network polymer, the liquid crystal molecules will be aligned in the direction orthogonal to the polarization axis (see "Surface-Induced Parallel Alignment of Liquid").
Crystals by Linearly Polymerized Photopolymers "Jp
n. J. Appl. Phys., 31,2155 (1992), TYMaruvsii, YA
Reznikov Mol. Mat., 3 (1993) 161).

[0007]

Embedded image This method is a non-contact method in which the resin film applied to the substrate is in contact with other members, which is indispensable for rubbing treatment, etc., so there are advantages such as no generation of static electricity and mixing of impurities. is there.

[0008]

However, the resin applied to this method is low in photosensitivity, and it is difficult to sufficiently and uniformly carry out the reaction by ultraviolet irradiation, and the resin is sufficiently aligned as an alignment film for liquid crystal display devices. In order to carry out the above, it was necessary to lengthen the irradiation time of the polarized ultraviolet light, and it took a long time for the manufacturing process. In other words, if the alignment treatment is completed in an industrially appropriate time, the liquid crystal of the manufactured liquid crystal display device will not be sufficiently aligned and the contrast will be poor. In addition, since a uniform reaction is not performed, when a liquid crystal display device is formed, unevenness or domains are generated on the screen.

The present invention has been made to solve the above-mentioned problems, and can be manufactured without rubbing treatment.
Another object of the present invention is to provide a liquid crystal display device having an alignment film in which unevenness and domains are suppressed, an anisotropic polymer film therefor, and a manufacturing method thereof.

[0010]

The anisotropic polymer membrane of the present invention is crosslinked with side chains to form a network, the crosslinked side chains have anisotropy, and the uncrosslinked side chains are It is characterized by being isotropically distributed.

The invention according to claim 2 is the anisotropic polymer film according to claim 1, which has a photocrosslinkable functional group in a side chain. The invention according to claim 3 has the repeating structural unit represented by the following chemical formula, and is the anisotropic polymer film according to claim 1.

Embedded image In the invention according to claim 4, the proportion of uncrosslinked side chains is 2
It is 0% or less, It is an anisotropic polymer film of Claim 1 characterized by the above-mentioned.

The liquid crystal display device of the present invention is characterized by having an alignment film formed of the anisotropic polymer film according to the first aspect. The invention according to claim 6 is characterized in that projections having long sides and short sides and having a substantially triangular cross section are repeatedly formed on the surface of the alignment film.
It is the described liquid crystal display device. The invention according to claim 7 is a ridge-shaped concavo-convex row in which the surface of the alignment film is formed by repeatedly forming convex portions composed of long side portions and short side portions along the first direction,
The height is lower than that of the ridge-shaped concave-convex row, and the valley-shaped concave-convex row formed along the same direction as the ridge-shaped concave-convex row is alternately formed adjacent to each other and repeatedly formed along the first direction. A shape having a concave-convex row having a long unit length and a concave-convex row having a repeating unit length shorter than the repeating unit length of the concave-convex row along the first direction along a second direction substantially orthogonal to the first direction. The liquid crystal display device according to claim 5, wherein

The method for producing an anisotropic polymer film according to the eighth aspect of the present invention comprises a step of forming a thermoplastic polymer film having a photocrosslinkable functional group on the surface of a substrate, and the step of forming the thermoplastic polymer film. And a step of irradiating polarized light while maintaining the temperature 10 ° C. or lower lower than the glass transition temperature and lower than the thermal decomposition temperature of the thermoplastic polymer film.
The invention according to claim 9 comprises the step of forming a thermosetting polymer film having a photocrosslinkable functional group on the surface of the substrate, and the thermosetting polymer film having a temperature not lower than 10 ° C lower than its glass transition temperature and a heat treatment. And a step of irradiating polarized light while maintaining the temperature below the thermosetting temperature of the curable polymer film.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In an anisotropic polymer film of the present invention used as an alignment film of a liquid crystal display device, each polymer has a structure in which a side chain is crosslinked, and the side chain has a crosslinked portion. Has anisotropy, and the non-crosslinked portion is isotropically distributed without bias. By thus cross-linking so that the side chains have anisotropy, it becomes possible to align the liquid crystal when the anisotropic polymer film is used as an alignment film, and the cross-linking is performed. The isotropic distribution of the non-existing portion reduces unevenness in the alignment of the liquid crystal and suppresses the generation of domains.

Furthermore, it is desirable that the proportion of uncrosslinked side chains is 20% or less, in other words, the proportion of uncrosslinked side chains is 1/4 or less of the proportion of crosslinked side chains. By doing so, it becomes possible to more sufficiently align the liquid crystal, and thus the uneven alignment of the liquid crystal is reduced,
Generation of domains is suppressed. The proportion of uncrosslinked in this side chain is more preferably 5 to 0%.

The cross-linking reaction of this anisotropic polymer film is preferably carried out by light, especially ultraviolet light, and therefore, one having a photo-crosslinkable functional group in its side chain is desirable. Among them, those having a repeating structural unit represented by the above chemical formula are preferable. Such a polymer may be a thermoplastic polymer or a thermosetting polymer, and examples of the thermoplastic polymer having a photocrosslinkable functional group include those having the following structural formula.

Embedded image Similarly, examples of the thermosetting polymer having a photocrosslinkable functional group include those having the following structural formula.

Embedded image

Such an anisotropic polymer film is used as an alignment film, and a liquid crystal display device equipped with the alignment film is
The occurrence of screen irregularities and domains is reduced. In addition, since the rubbing process is not performed in the manufacturing process, it is possible to avoid problems caused by the generation of static electricity and the inclusion of impurities.

Further, with the alignment film having the shape described in claim 7, the pretilt angle can be increased, the alignment property is high, and disclination hardly occurs. In particular, by making the cross-sectional shape of the convex portion asymmetrical, the in-plane uniformity of the pretilt angle of the liquid crystal is improved and the contrast is further improved.

Further, since the unevenness along the first direction and the unevenness along the second direction are formed, a flat surface parallel to the substrate is not present on the alignment film, and the entire surface of the alignment film is removed. A pretilt angle can be formed, rise of the liquid crystal when an electric field is applied, responsiveness is improved, contrast is increased, and unevenness of the liquid crystal screen can be further prevented. Further, since a large pretilt angle is formed on the entire surface of the alignment film, the liquid crystal can be sufficiently activated at a low voltage.

The shape of such an alignment film can be easily formed by utilizing a transfer method and can be reliably manufactured with good reproducibility.

Further, it is desirable that the irradiation of light is carried out under the temperature condition of 10 ° C. lower than the glass transition temperature of the alignment film material, and after the irradiation, it is cooled to room temperature (about 25 ° C.). 1 from the glass transition temperature of the alignment film material
By irradiating light under the condition of 0 ° C lower temperature,
The crosslinking reaction can be carried out uniformly, and the uncrosslinked portions of the side chains can be distributed isotropically. It should be noted that the temperature at the time of irradiating this light ray needs to be lower than its thermal decomposition temperature if the polymer film is a thermoplastic resin, and lower than its thermal curing temperature if the polymer film is a thermosetting resin. is there. In the case of a thermoplastic resin, the film is deteriorated above its thermal decomposition temperature, and in the case of a thermosetting resin, the film is cured at a portion other than the photocrosslinkable functional group of the side chain above the thermosetting temperature, This is because the side chains of the unreacted portion are left unnecessarily.

[0022]

【Example】

Example 1 The alignment film made of the anisotropic polymer film of the present invention can be applied to various liquid crystal display devices having the alignment film. An example of the liquid crystal display device is shown in FIG. The illustrated color liquid crystal display device 10 includes a pair of substrates 1 facing each other.
2, 14, liquid crystal 16 enclosed between them, liquid crystal driving element 18 formed on one substrate 12, and transparent electrode (pixel electrode) 20 connected to the liquid crystal driving element 18.
(20a, 20b, 20c), a counter electrode 22 formed on the other substrate 14 so as to face the transparent electrode 20, alignment films 24 and 24 for holding the liquid crystal 16, and a pair of substrates 1
2 and 14, polarization filters (lower polarization filter 26, upper polarization filter 28) formed, and color filters 30 (30r, 30g, 30b) formed on the substrate 14 are generally configured.

As the substrates 12 and 14, those used in general liquid crystal display devices can be applied, and various substrates such as ceramics can be applied in addition to glass substrates. A shape corresponding to a liquid crystal display device as a product is also used, and an arbitrary shape such as a flat rectangular shape is used. The liquid crystal 16 changes the orientation state of molecules by applying a voltage. For example, in the TN type liquid crystal shown as an example in FIG. 1, the molecules which are twisted by 90 ° when no voltage is applied are used. By applying a voltage, the column stands upright and the twist is eliminated. Although not shown in FIG. 1, both alignment films 2
A spacer made of fine particles or the like is interposed between the Nos. 4 and 24, and the spacer keeps the gap in which the liquid crystal is sealed at a predetermined gap.

A thin film transistor (TFT) or the like is applied to the liquid crystal drive element 18, and the voltage applied to the liquid crystal is controlled by the drive signal. The transparent electrode 20 forms a pair with the counter electrode 22 formed on the other substrate 14 and applies a voltage from the liquid crystal driving element 18 to the liquid crystal 16. Generally, an ITO film (indium oxide film) or the like is applied. .
The liquid crystal driving element 18 and the transparent electrode 20 (20a, 20
b, 20c) is provided for each pixel,
The counter electrode 22 is generally configured as a common electrode common to each pixel.

The alignment film 24 is for aligning the liquid crystal 16 in a predetermined direction, and a polymer film represented by the chemical formula is irradiated with ultraviolet rays polarized in a predetermined direction.

[Chemical 6]

The polarization filters 26 and 28 are films having a function of emitting linearly polarized light. In the illustrated liquid crystal display device 10, the lower filters 26 and the upper filters 28 formed on the substrates 12 and 14 are It is provided so that the polarization directions thereof are relatively different by 90 °. The color filter 30 is used in a color liquid crystal display device, and normally, three color filters of red, green, and blue are used for each pixel to form a set. In a color liquid crystal display device, various colors are expressed by combining these three colors.

In the color liquid crystal display device shown in FIG. 1, first, a light beam from below the polarizing filter 26 passes through the lower polarizing filter 26 as a backlight. At this time, only the light beam polarized in the lateral direction of FIG. 1 passes through the lower polarization filter 26. In the example shown in FIG. 1, the transparent electrode 20 is controlled by controlling the liquid crystal driving elements 18, 18, ....
no electric current is applied to the transparent electrode 20a and the transparent electrode 20b.
The voltage is applied only to the liquid crystal above c.

In this state, the lower polarization filter 26
Only the polarized light rays on the transparent electrodes 20a and 20b are transmitted through the glass substrate 12 and the alignment film 24.
The polarization direction is converted and transmitted through the upper polarization filter 28. At this time, the transparent electrodes 20a, 20b,
The color filter 30r that transmits only red and the color filter 30 that transmits only green so as to face 20c.
g, by providing the color filter 30b that transmits only blue light, blue light rays do not pass above the upper polarization filter 28, only red light rays and green light rays pass therethrough, and as a result, yellow light rays are transmitted. Will be displayed.

In the alignment film of this embodiment, the polymer represented by the above chemical formula is added to a solvent (for example, cyclohexanone) in an amount of 4%.
A wt% dissolved solution is applied on the substrate 12 having the transparent electrode 20, the solvent is removed to form a film, and then polarized ultraviolet light polarized in a predetermined direction is irradiated to impart anisotropy to the film surface. It is manufactured by doing. In this embodiment, the irradiation of the ultraviolet rays is 10 ° C. higher than the glass transition temperature of the polymer material on which the film is formed.
Perform at a temperature above the low temperature.

The coating of the polymer compound material used for the alignment film in the present invention on the substrate is not particularly limited, but spin coating, screen printing method, offset printing method or the like is applied. In addition, a polymer compound film is formed by drying by baking treatment, if necessary, such as by removing the solvent. At this time, the polymer compound film may be further pre-baked and baked if necessary. To perform pre-baking and baking, for example, after heating the substrate at 80 ° C. for about 1 minute, 1
It can be performed by heating at about 80 ° C. for 1 hour.
Further, the substrate may be preheated to about 80 ° C., screen printed, coated with the solution, and then baked.

When the solution is applied by the screen printing method, the printing stage is directed through the screen installed on the substrate in the longitudinal direction, the lateral direction or the oblique direction of the substrate at a predetermined speed, for example, 10 cm / It can be done by moving at a speed of 2 seconds. The thickness of the polymer compound film formed by coating the polymer compound unique to the present invention is 0.
About 1 μm is preferable.

[Example 2] In the production of the alignment film of Example 1, the transfer method of pressing the transfer mold against the surface of the film may be used in addition to the irradiation of polarized ultraviolet light. When used in combination with the transfer method, the polarization direction of the polarized ultraviolet light to be irradiated needs to be substantially orthogonal to the first direction in which the convex portions previously formed by the transfer mold are repeated. That is, referring to FIG. 2 showing an example of the shape of the alignment film, the first protrusions 36, 36, ... Each having a long side portion 32 and a short side portion 34 and having a substantially triangular cross section are repeatedly formed. 1
Ultraviolet rays having a polarization direction along a second direction which is substantially orthogonal to the direction of are irradiated. This direction is easily adjusted by changing the direction of the polarizing plate that generates polarized ultraviolet light.

As shown in FIG. 3, the surface of the alignment film formed by the transfer mold has a long side portion 32 'and a short side portion 34'.
And a ridge-like concavo-convex row 38 formed by repeatedly forming a convex portion 36 ′ consisting of the ridge-like concavo-convex row 38, which is lower than the ridge-like concavo-convex row 38 The valley-shaped concave-convex rows 40 to be formed are alternately formed adjacent to each other, and the concave-convex rows having a long repeating unit length U formed along the first direction and the second concave-convex rows that are substantially orthogonal to the first direction. And a concave-convex row having a repeating unit length U ′ shorter than the repeating unit length U of the concave-convex row along the first direction, the polarized light is polarized along the second direction. Irradiate with ultraviolet rays.

The repeating unit length U of the unevenness along the first direction is preferably 1 μm or more and 50 μm or less, and the repeating unit length U ′ along the second direction is preferably 0.1 μm or more and 3 μm or less. More preferably, the unit length U is 1 μm or more and 20 μm or less, and the repeating unit length U ′ is 0.1 μm or more and 1.2 μm or less. Furthermore, as shown in FIG. 4, it is desired that the inclination angle θ of the ridgeline of the long side portion 32 be 1 ° or more and 20 ° or less.

Further, as shown in FIG. 4, it is desirable that each of the convex and concave portions 36 along the first direction has a substantially triangular shape whose left and right are asymmetric. That is, the ratio r ₂ / r ₁ of the right and left angles of the apex angle divided by the perpendicular drawn from the apex of the convex portion 36.
Has a shape that does not become 1. As the shape of the convex portion 36, various shapes such as a shape similar to a sin wave, a comb shape, and a triangular shape can be considered. In the case of a triangular shape, the top may be rounded or flatly cut. Convex part 36
In the case of a triangular shape, it is desirable that the ratio r ₂ / r ₁ of the right and left angles of the apex angle divided by the perpendicular drawn from the apex of the triangle is 1.2 or more and 89 or less.

In the transfer method, for example, a manufacturing apparatus as shown in FIG. 5 can be applied. The manufacturing apparatus 42 shown in FIG.
Is roughly configured by including a pedestal 46 as a holding mechanism for the substrate 12, an upper plate 44 as a transfer mechanism vertically provided above the pedestal 46, and an ultraviolet irradiation mechanism 48. The pedestal 46 is for mounting the substrate 12, and the smooth polymer compound film 2 before the unevenness is formed on the upper surface of the substrate 12 mounted on the pedestal 44.
4 'is formed.

The upper plate 44, which is a transfer mechanism, moves up and down by a moving mechanism (not shown) to move the polymer compound film 24 '.
The concave portion 50 is formed on the lower surface of the concave portion 50, and the transfer mold 52 is mounted in the concave portion 50. In addition, a concavo-convex pattern in which a concavo-convex pattern to be formed on the upper surface of the alignment film 24 is formed on the lower surface of the transfer mold 52. Further, a protruding stopper 54 is formed in the peripheral portion of the recess 50, and the stopper 54 comes into contact with the upper surface of the pedestal 46 to stop the lowering of the upper plate 44. Therefore, when the stopper 54 of the upper plate 44 contacts the upper surface of the pedestal 46, the upper plate 4
4 has stopped descending, and the transfer compound 52 polymer compound film 24 '
Is stopped, and an uneven pattern having a specified depth is formed on the upper surface of the polymer compound film 24 '. The polarized ultraviolet irradiation mechanism 48 also includes an ultraviolet light source 56 that emits ultraviolet light.
And a polarizer 58 that polarizes the ultraviolet light emitted from the ultraviolet light source 56, and irradiates the polymer compound film 24 'with the polarized ultraviolet light.

In order to manufacture an alignment film using this manufacturing apparatus 42, first, the substrate 12 on which the polymer compound film 24 'made of the compound unique to the present invention is formed is placed on the pedestal 46. Then, the upper plate 44 is lowered. Then
Since the transfer mold 52 is pressed onto the upper surface of the polymer compound film 24 ', the uneven pattern on the lower surface of the transfer mold 52 is transferred onto the upper surface of the polymer compound film 24' to form the uneven pattern as shown in FIGS. The aligned film 24 thus obtained is obtained. After that, the polarized ultraviolet ray irradiation mechanism 48 irradiates ultraviolet rays polarized in the second direction of the concavo-convex pattern formed on the polymer compound film to cure.

[Test Example 1] The reaction ratio of the carbon double bond in polyvinyl cinnamate to the polarized ultraviolet rays irradiated was tested. In the test, first, polyvinyl cinnamate was uniformly formed on a germanium substrate, and an infrared spectroscope (“FTS-60A” manufactured by BIO-RAD) was used to double bond carbon (stretching vibration: Infrared absorption intensity at 1640 cm ^-1 (Ire
f) was measured. Then, polarized ultraviolet rays are irradiated under the condition that the film temperature is 90 ° C. After that, the infrared measurement is again performed to measure the infrared absorption intensity (I) of the unreacted carbon double bond. From these results, the ratio of double bonds of the reacted carbon, that is, (Iref-I) / Iref · 100 was calculated and shown in FIG. From FIG. 6, it can be seen that when the irradiation energy of polarized ultraviolet rays is 60 J / cm ² or more, most of the carbon double bonds have reacted. That is, when the irradiation energy of polarized UV is 60 J / cm ² or more, the infrared absorption intensity of the unreacted carbon double bond is so small that it cannot be measured by this measuring device. It is understood that it does not exist. In addition, when a liquid crystal display device was manufactured using an anisotropic polymer film in which the ratio of reacted carbon double bonds was 80% or more, and the alignment state of the liquid crystal was observed with a polarizing microscope, there were no domains and the alignment state was Was good.

Test Example 2 Using polyvinyl cinnamate (thermal decomposition temperature: 292 ° C.), the irradiation energy of polarized ultraviolet rays was changed to prepare an alignment film. The ultraviolet absorption intensity of this alignment film was measured using an ultraviolet spectroscope (“HITACHI 330” manufactured by Hitachi, Ltd.). Further, from the absorption intensity of the carbon double bond (absorption intensity: 274 nm), the dichroic ratio of the unreacted carbon double bond (absorption intensity of the carbon double bond existing in the polarization direction of polarized UV and the same polarization direction) The ratio to the absorption intensity of the carbon double bond existing in the direction orthogonal to the was determined.
The film temperature condition for irradiation with polarized ultraviolet rays is 90 ° C., which is the glass transition temperature of polyvinyl cinnamate.
Then, 30 ° C., which is lower than that temperature by 10 ° C. or more, was set.
The measurement result is shown in FIG. 7.

It can be seen from FIG. 7 that the dichroic ratio decreases as the irradiation intensity of polarized ultraviolet light increases when polarized ultraviolet light is irradiated under the condition that the film temperature is 30 ° C. This indicates that a large amount of unreacted carbon double bonds remain in the direction orthogonal to the polarization direction of polarized ultraviolet light, and the proportion of carbon double bonds present in the polymer is biased. With such an alignment film, domains are likely to occur. On the other hand, it is shown that when the film is irradiated with polarized ultraviolet light under the condition that the film temperature is 90 ° C., the dichroic ratio is 1 regardless of the intensity of the polarized ultraviolet light. This indicates that the unreacted carbon double bonds are distributed isotropically. Therefore, by performing sufficient energy irradiation, most of the carbon double bonds can be reacted and the orientation of the liquid crystal can be improved. In addition, by increasing the film temperature at the time of irradiation with polarized ultraviolet light, side chains having unreacted double bonds can be distributed isotropically. In the liquid crystal display device having such an alignment film, unevenness and domains do not occur on the screen, and the contrast (display quality) is improved.

Test Example 3 An alignment film was prepared using polyvinyl cinnamate, and a liquid crystal display device having a liquid crystal cell using the alignment film was manufactured. At this time, polarized ultraviolet rays were irradiated under the conditions of the film temperature of 30 ° C. and 90 ° C. The alignment state of the liquid crystal (“K-15” manufactured by Merck Japan Ltd.) was measured for the liquid crystal display device. Fig. 8 shows the measurement results.
Shown in As shown in FIG. 9, the measurement is carried out by irradiating the liquid crystal cell with infrared light that has passed through an infrared polarizer so that the incident direction is vertical, and performing infrared measurement using the infrared spectroscope. In the obtained infrared spectrum, it was 2229 cm ^-1
Observe the stretching vibration peak of the cyano group (-CN) in the vicinity. The absorption intensity corresponds to the amount of liquid crystal molecules aligned in the polarization direction of the infrared polarizer. Therefore, the orientation distribution of the liquid crystal molecules can be obtained by changing the angle of the infrared polarizer for measurement. In FIG. 8, the circumferential direction represents the angle formed by the polarization direction of the infrared polarizer and the polarization direction of the polarized ultraviolet light irradiated, and the radial direction represents the maximum infrared absorption intensity of the cyano group of the liquid crystal material (K-15). The value is calculated by taking the absorption intensity as 100%. From Figure 8, by polarized UV irradiation,
It can be seen that the liquid crystal molecules are aligned in a direction substantially orthogonal to the polarization direction of polarized ultraviolet light.

[Test Example 4] Among the liquid crystal display devices manufactured in Test Example 3, the ones irradiated with polarized ultraviolet light of 120 J / cm ² showed the dichroic ratio of the liquid crystal (orthogonal to the polarization direction of the polarized ultraviolet light to be irradiated). The ratio of the infrared absorption intensity of the stretching vibration of the cyano group of the liquid crystal material existing in the direction of polarization to the infrared absorption intensity of the carbon double bond existing in the polarization direction was measured), and the alignment state of the liquid crystal was observed with a polarizing microscope. . As a result, it was determined that the polarized ultraviolet rays were radiated under the condition that the film temperature was 30 ° C.
The dichroic ratio was 2.54, and the value obtained by irradiation with polarized ultraviolet light at a film temperature of 90 ° C. was 3.57. It is generally said that domains having a dichroic ratio of 3 or less are likely to occur, and if the film temperature during irradiation of polarized ultraviolet light is 30 ° C., the film temperature during irradiation of polarized ultraviolet light is The occurrence of domains was more noticeable than that of 90 ° C.

Test Example 5 With respect to the polymer film having two kinds of photo-crosslinkable functional groups shown in FIG. 10, an alignment film using the same with respect to the film temperature at the time of irradiation with polarized ultraviolet rays (120 J / cm ² ). The change in the dichroic ratio of the liquid crystal (“K-15” manufactured by Merck Japan Ltd.) of the liquid crystal display device equipped with was measured.
FIG. 10 shows the measurement results. It is clear from FIG. 10 that whichever anisotropic polymer is used, the dichroic ratio of the liquid crystal is improved as the film temperature during polarized ultraviolet irradiation is increased. In particular, it can be seen that the dichroic ratio of the liquid crystal can be at least 3 or more if the film temperature at the time of irradiation with polarized ultraviolet rays is at least 10 ° C. lower than the glass transition temperature of the polymer material.

[Test Example 6] Polarized ultraviolet rays were irradiated using the polymers having 14 kinds of photocrosslinkable functional groups shown in Tables 1 and 2 to prepare an alignment film. At that time, the ultraviolet ray of each anisotropic polymer has a film temperature of 30 ° C. (film temperature A), a temperature 10 ° C. lower than the glass transition temperature (film temperature B), and a glass transition temperature (film temperature C). Irradiated under conditions. A liquid crystal display device having each alignment film was manufactured, and the dichroic ratio of the liquid crystal was measured. The measurement results are also shown in Tables 1 and 2.

[0046]

[Table 1]

[Table 2] From Tables 1 and 2, when the polarized ultraviolet light is irradiated under the condition that the film temperature is 30 ° C., the dichroic ratio is less than 3, but the film temperature is 10 ° C. lower than the glass transition temperature and the glass. It can be seen that the dichroic ratio can be increased to 3 or more by irradiating polarized ultraviolet light under the condition of the transition temperature.

[0047]

EFFECT OF THE INVENTION The anisotropic polymer film of the present invention can suppress the unevenness of liquid crystal alignment and the generation of domains when used as an alignment film of a liquid crystal display device. Further, in the alignment film in the liquid crystal display device according to the seventh aspect, it is possible to control the pretilt angle, and thus it is possible to increase the order parameter. Therefore, the orientation is high, and disclination can be prevented. In addition, since there is no flat portion on the alignment film, a pretilt angle can be formed on the entire surface of the alignment film, the rise of the liquid crystal when an electric field is applied, the response is improved, and the contrast is increased. It is possible to prevent the occurrence of unevenness of the liquid crystal screen. Further, since a large pretilt angle is formed on the entire surface of the alignment film, the liquid crystal can be sufficiently activated at a low voltage.

In addition, since the manufacturing is performed by polarized ultraviolet irradiation, unlike the manufacturing method by rubbing treatment or oblique evaporation, there is no problem of dust generation or static electricity generation, and the manufacturing cost can be reduced. Further, by irradiating polarized ultraviolet rays under a specific temperature condition, it becomes possible to carry out the cross-linking reaction uniformly with high efficiency, and the non-cross-linking part of the side chain can be distributed isotropically. The occurrence of image unevenness and domains is reduced, and the contrast is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a liquid crystal display element.

FIG. 2 is a perspective view showing an example of an alignment film of the present invention.

FIG. 3 is a perspective view showing an example of an alignment film of the present invention.

FIG. 4 is a partial side view of an uneven row.

FIG. 5 is a side view showing an example of an alignment film manufacturing apparatus.

FIG. 6 is a graph showing the ratio of reacted carbon double bonds to polarized UV irradiation energy in Test Example 1.

7 is a graph showing the dichroic ratio of unreacted carbon double bond to polarized UV irradiation energy in Test Example 2. FIG.

8 is a graph showing the alignment state of the liquid crystal in Test Example 3. FIG. 8 (a) shows the state of FIG.
In (b), polarized ultraviolet rays are irradiated under the condition that the film temperature is 90 ° C.

FIG. 9 is a diagram showing a method for measuring an alignment state of liquid crystal.

FIG. 10 is a graph showing the dichroic ratio of liquid crystal to the film temperature during irradiation of polarized ultraviolet light in Test Example 5.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 12 Substrate 14 Substrate 16 Liquid crystal 20 Transparent electrode 24 Alignment film 32 Long side part 34 Short side part 36 Convex part 52 Transfer type

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuru Kano 1-7 Yukiya Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Tatsuo Uchida 2-11 Takasago, Miyagino-ku, Sendai-shi, Miyagi

Claims (9)

[Claims] 1. An anisotropic method in which side chains are crosslinked to form a network, the crosslinked side chains have anisotropy, and the uncrosslinked side chains are isotropically distributed. Polymer film. 2. The anisotropic polymer film according to claim 1, which has a photocrosslinkable functional group in a side chain. 3. The anisotropic polymer film according to claim 1, which has a repeating structural unit represented by the following chemical formula. Embedded image 4. The anisotropic polymer film according to claim 1, wherein the proportion of uncrosslinked side chains is 20% or less. 5. A liquid crystal display device, comprising an alignment film made of the anisotropic polymer film according to claim 1. 6. The liquid crystal display device according to claim 5, wherein a convex portion having a long side portion and a short side portion and having a substantially triangular cross section is repeatedly formed on the surface of the alignment film. 7. A ridge-shaped irregularity row in which a convex portion composed of a long side portion and a short side portion is repeatedly formed along a first direction on the surface of the alignment film, and a height higher than that of the ridge-shaped irregularity row. Is low, the valley-shaped irregularity row formed along the same direction as the ridge-shaped irregularity row,
A series of concavo-convex rows that are alternately formed adjacent to each other and that are formed along the first direction and have a long repeating unit length, and along a first direction that is along a second direction that is substantially orthogonal to the first direction. 6. The liquid crystal display device according to claim 5, wherein the liquid crystal display device has a shape having an uneven line having a repeating unit length shorter than the repeating unit length of the uneven line. 8. A step of forming a thermoplastic polymer film having a photocrosslinkable functional group on the surface of a substrate, and the thermoplastic polymer film having a glass transition temperature of 10 ° C.
The method for producing an anisotropic polymer film, comprising the step of irradiating polarized light while maintaining the temperature above a low temperature and below the thermal decomposition temperature of the thermoplastic polymer film. 9. A step of forming a thermosetting polymer film having a photocrosslinkable functional group on the surface of a substrate, and the thermosetting polymer film having a glass transition temperature of 10 ° C.
And a step of irradiating polarized light while maintaining the temperature above a low temperature and below the thermosetting temperature of the thermosetting polymer film.