KR100831961B1 - Optical film using the reactive mesogen and manufacturing of the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal polymer optical film and a method of manufacturing the same, wherein the optical crosslinkable liquid crystal is inclined to have an optical axis inclined with respect to the film surface. The diagonal alignment of the photocrosslinkable liquid crystal can be performed by inclining the ultraviolet light having predetermined conditions on the photosensitive polymer alignment layer coated on the substrate. The diagonally oriented photocrosslinked liquid crystal forms an inclination with the surface of the alignment layer from the first liquid crystal contacting the alignment layer, and thus the liquid crystals stacked on the alignment layer may have almost the same inclination. In addition, a chiral dopant may be introduced into the photocrosslinkable liquid crystal to realize an inclined spiral alignment structure. The liquid crystal optical film having the inclined alignment structure of the liquid crystal is excellent in the surface uniformity and productivity of the optical characteristics, such a film can be used as an optical compensation film to widen the viewing angle of the LCD.

Photocrosslinkable Liquid Crystal, Compensation Film, Liquid Crystal Display, Photo Alignment

Description

Optical film using the reactive mesogen and manufacturing of the same}

1 is a cross-sectional view showing the configuration of a splay oriented discotic liquid crystal film according to the prior art.

Figure 2 is a cross-sectional view showing the configuration of the splay-oriented anti-magnetic liquid crystal film according to the prior art.

3 is a cross-sectional view showing a configuration of a liquid crystal film having a non-uniform film thickness according to the prior art.

Figure 4 is a cross-sectional view showing the configuration of a tilted discotic liquid crystal film according to an embodiment of the present invention.

Figure 5 is a cross-sectional view showing the configuration of a tilted nematic liquid crystal film according to an embodiment of the present invention.

6 is a cross-sectional view showing a configuration of a liquid crystal film having a non-uniform film thickness according to the present invention.

7 is a cross-sectional view showing the configuration of an inclined and spirally oriented photocrosslinkable nematic liquid crystal film according to the present invention.

FIG. 8 is a cross-sectional view of a liquid crystal film having a configuration in which a spiral pitch of an inclined and spirally oriented photocrosslinkable nematic liquid crystal is laminated one or more times. FIG.

Fig. 9 is a sectional view of the helical alignment structure (one cycle) of the nematic liquid crystal according to the present invention seen from the upper layer.

10 is a cross-sectional view of a helical alignment structure (one cycle) of nematic liquid crystals according to the present invention.

11 is a perspective view showing a surface alignment treatment process using ultraviolet light for the inclined alignment according to the present invention.

** Description of Codes for Major Configurations of Drawings **

110: description

120: alignment film

130: liquid crystal layer

The present invention relates to an optical film using a photocrosslinkable liquid crystal and a method of manufacturing the same. More specifically, the ultraviolet ray is irradiated perpendicularly to the inclined direction irradiated with ultraviolet rays on the alignment layer, and the ultraviolet rays polarized with respect to the alignment layer are 10 ° to 80 °. By irradiating in the range of or by irradiating unpolarized ultraviolet rays in the range of 40 ° to 80 °, the first liquid crystal contacting the alignment film is inclined at the beginning, and the other liquid crystals arranged on top of the first are inclined alignment. The present invention relates to an optical film using a photocrosslinkable liquid crystal that is inclined at the same inclination and a manufacturing method thereof.

With the rapid development of the information society in recent years, it is possible to make thinner, lighter, lower power consumption, and a liquid crystal display (LCD), a flat panel display device having excellent characteristics such as resolution, color display, and image quality. Is being applied.

In general, a liquid crystal display device arranges two substrates on which the field generating electrodes are formed so that the surfaces on which the two electrodes are formed face each other, and injects a liquid crystal material between the two substrates to form a liquid crystal cell of a liquid crystal layer. The liquid crystal molecules are moved by an electric field generated by applying a voltage to the two electrodes, and thus the image is expressed by the transmittance of light which varies accordingly.

The liquid crystal cell is a twisted nematic LC cell. The liquid crystal molecules constituting the twisted nematic liquid crystal cell have an elongated rod shape and are twisted in a spiral with a constant pitch to arrange the long axis of the liquid crystal molecule. It has a twisted structure in which the direction is changed continuously.

In such a twisted nematic liquid crystal system, incident polarization shows different viewing angle characteristics depending on the arrangement of the long axis and short axis of the molecule. That is, since the viewing angle of the liquid crystal display is formed along the long axis of the liquid crystal molecules of the spiral structure, the viewing angle changes according to the viewing direction.

The liquid crystal display has a symmetrical viewing angle ranging from approximately +45 to -45 with respect to the horizontal direction, and the viewing angle is limited between -15 and 5 degrees with respect to the vertical direction, so that the image is inverted at the viewing angle in the vertical direction. There is a problem that the viewing angle is narrowed.

When the LCD is small, a small number of users will often look at the LCD from a limited angle, but as the LCD becomes larger, it is more likely that many users will see the LCD from different angles. Accordingly, the limited viewing angle characteristic of the liquid crystal display device is an important problem.

A general method for overcoming the limited viewing angle problem of the liquid crystal display device is to arrange an optical film having an o-plate characteristic having an inclined optical axis between the liquid crystal cell and the polarizing plate. In this case, a narrow viewing angle may be compensated by arranging the average optical axis of the twist-oriented liquid crystal in the liquid crystal cell driven by an electric field and the optical axis of the o-plate opposite to each other, and in general, at least one sheet may be disposed between the liquid crystal cell and the upper polarizing plate. The o-plate may be used to impart a compensation effect, and at least one o-plate may be used between the upper polarizer and the liquid crystal cell or between the lower polarizer and the liquid crystal cell to maximize the compensation effect.

Among the optical compensation films having the o-plate properties, there is a liquid crystal film using a splay-oriented photocrosslinkable liquid crystal. The liquid crystal film is an optical film prepared by splay-aligning liquid crystal molecules by coating a photocrosslinked liquid crystal (reactive mesogen) containing an additive on a horizontally aligned surface.

The photocrosslinkable liquid crystal refers to liquid crystal phase molecules having at least one or more photocrosslinkable functional groups such as acrylate, and generally, a mixture of a small amount of photoinitiator, and irradiated with ultraviolet rays to crosslink the photocrosslinkable liquid crystals to generate a liquid crystal polymer. The additive may play a role of causing inclination between liquid crystals.

Therefore, when the photocrosslinked liquid crystal, the photoinitiator, and the additive are mixed in a suitable solvent, the molten liquid crystal solution is coated on the horizontally aligned target surface to a predetermined thickness, and then the solvent is evaporated, the liquid crystals in contact with the target surface form a horizontal direction. The liquid crystal stacked in the thickness direction has a splay alignment structure which is arranged while making a predetermined inclination between the liquid crystals. When the solvent is evaporated and irradiated with ultraviolet rays to the liquid crystal coating film, the arranged liquid crystals are crosslinked with each other, thereby forming an o-plate having an average optical axis inclined by the splay arranged liquid crystals.

Such a liquid crystal film includes a discotic liquid crystal film splay oriented photocrosslinkable discotic liquid crystal as shown in FIG. 1, and a nematic liquid crystal film splay oriented photocrosslinkable nematic liquid crystal as shown in FIG. 2. .

In the case of the nematic liquid crystal, anisotropic characteristics (Nx ≠ Ny) having different refractive indices in the major axis and the minor axis are different, and in the case of the discotic liquid crystal, the refractive indexes in the major axis and the minor axis in the plate cannot be different. Therefore, since the refractive indexes in the major axis and the minor axis have the same characteristics (Nx = Ny), the liquid crystal films using these liquid crystals have different optical characteristics and compensation effects.

However, according to the conventional optical film as described above has the following problems.

In spite of the different optical properties described above, in both cases optical unevenness due to variation in coating thickness cannot be prevented. In the case of the liquid crystal film described above, when there is a slight deviation in the thickness of the liquid crystal coating, as shown in FIG. 3, since a change in the average optical axis is caused by the variation in the coating thickness, all the coatings having large and small thickness deviations exist. In the process, there is a problem that it is difficult to obtain uniform optical properties on all liquid crystal surfaces.

In addition, the liquid crystal film using the above-described splay alignment, the space between the left and right liquid crystals is increased by the inclination between the liquid crystals to be laminated, the packing effect of the upper liquid crystals to be laminated is reduced, the alignment state becomes unstable, and There is a problem that it is difficult to obtain a coating surface.

In addition, for the same reason as above, in the case of splay orientation, the average optical axis does not always exceed 45 ° because it is difficult to be completely oriented at 90 ° in the case of liquid crystal stacked on the uppermost layer away from the oriented surface or close to the air layer. If the average optical axis of 45 ° is required for efficient optical compensation of the liquid crystal cell, there is a fundamental problem.

On the other hand, an optical film using a photocrosslinkable liquid crystal has an alignment process in which the liquid crystal molecules are splay-oriented by coating the liquid crystal on the alignment-treated surface.

Generally, rubbing, vacuum evaporation of inorganic material, irradiation of ions or plasma beams on a substrate made of organic or inorganic materials in a vacuum state, and optical alignment using a photoalignment film are well known. Known.

In the case of the irradiation method using the ion or the plasma, it is possible to make the inclination orientation or the horizontal orientation in which the inclination angle of the orientation is basically adjusted by adjusting the irradiation angle of the beam.

In the case of the vacuum vapor deposition method of the inorganic material, when the photocrosslinkable liquid crystal is coated, a predetermined inclination orientation can be obtained, and the inclination angle of the liquid crystal alignment can be adjusted to the deposition angle of the inorganic material.

In the rubbing method, a polyimide (or polyamic acid) alignment layer having a long side branch is coated on a substrate, baked, and then rubbed. In this case, the alignment inclination angle of the liquid crystal may be adjusted by adjusting the alkyl side length of the alignment layer.

In the case of the optical alignment method, polarized ultraviolet rays are used to align the liquid crystal. In this case, linearly polarized light, partial polarized light, or elliptical polarized light may be used, and the liquid crystal is generally aligned in the polarized optical axis direction. Also in this case, oblique alignment can be induced by irradiating the polarized ultraviolet rays.

However, according to the conventional optical film manufacturing method as described above has the following problems.

Although the above-mentioned alignment method may be suitable as a general alignment, ie, an orientation method without photocrosslinkability, there exists a problem that it is not suitable for the orientation of a photocrosslinkable liquid crystal.

The photocrosslinkable liquid crystal has introduced two or more photocrosslinking functional groups connected by flexible linear alkyl branches by liquid crystal phase molecules. The photocrosslinked liquid crystal is larger in size than a typical liquid crystal without photocrosslinkability, and is generally solid at room temperature. A solution dissolved in an appropriate solvent should be used. Since the photocrosslinkable liquid crystal is required to have a high degree of crosslinking after evaporating the solvent, the length of the alkyl branch is generally long so that the photocrosslinkable functional group is sufficiently flexible.

Therefore, in order to align the liquid crystals having such a large size, there is a problem that it is difficult to obtain an alignment having the same level of uniformity under the same surface alignment conditions as compared to general liquid crystals.

In addition, the above-described alignment method is a method that can be applied in the manufacture of the liquid crystal cell, the production of the liquid crystal cell is a surface alignment treatment of the two substrates or the substrate coated with the alignment film by the alignment method described above, The surface-oriented surfaces face each other such that their orientations are opposite to each other, and the liquid crystals filled by the alignment forces of both alignment surfaces are aligned by filling the liquid crystals therebetween at predetermined intervals between opposing substrates. Going through.

Therefore, the above-mentioned alignment method utilizes the alignment force of both alignment surfaces, so it is thought that the liquid crystal alignment induction is easy and the diagonal alignment may be possible, but in fact, when the filled liquid crystal is a photocrosslinkable liquid crystal solution, the solvent is evaporated between the substrates. It's almost impossible, so it's not the right way. And since there are inefficiencies that two base materials and two orientation treatments are needed, it is not suitable at all as a manufacturing method of a liquid crystal film.

In addition, the beam irradiation method in the above method has a fundamental difficulty in controlling the inclination angle of the liquid crystal alignment broadly because the irradiation angle required for the surface alignment process should be at least 40 degrees in the normal direction of the irradiated surface. When performing a roll-to-roll continuous process for mass production, the beam irradiation method or the deposition method requiring vacuum may be regarded as having no productivity.

The rubbing method of polyimide requires a heat treatment of at least 150 degrees to several tens of minutes in order to fire the polyimide (or polyamic acid) alignment layer coated on the substrate, and thus a large limitation in using a substrate that is not affected by physical properties even at such high temperatures is required. In addition, there is a problem that the polyimide alignment layer itself is not high in transparency and is not suitable for an optical film application. In addition, the process that requires rubbing of the substrate itself is not efficient for the roll to roll continuous process. There is.

Therefore, the present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to have an optical property enhanced surface uniformity by the average optical axis does not change even if a variation in the thickness of the film occurs An optical film using a photocrosslinkable liquid crystal and a method of manufacturing the same are provided.

Another object of the present invention is to provide an optical film using a photocrosslinkable liquid crystal capable of diversifying the optical compensation effect by adjusting the inclination angle of the liquid crystal from 0 ° to 90 ° according to the alignment conditions and a method of manufacturing the same.

It is still another object of the present invention to provide an optical film using a photocrosslinked liquid crystal having an inclined spiral alignment structure of nematic liquid crystal similar to the optical properties of a discotic liquid crystal by adding a chiral dopant to the liquid crystal, and a method of manufacturing the same. .

According to a feature of the present invention for achieving the object as described above, the present invention, the photosensitive polymer alignment film coated on the substrate, and the photocrosslinkable liquid crystal polymerized by being aligned at a predetermined inclination on the alignment film It comprises a liquid crystal layer.

The first liquid crystal in contact with the alignment film is tilted with respect to the alignment film from the beginning, and the other liquid crystals stacked on top are inclined at the same inclination as the liquid crystal initially tilted.

The photocrosslinkable liquid crystal is a photocrosslinkable nematic liquid crystal.

The photocrosslinkable liquid crystal is a photocrosslinkable discotic liquid crystal.

The inclination angle of the photocrosslinkable liquid crystal is greater than 0 ° and smaller than 90 °.

The substrate is an optical film using a photo-crosslinked liquid crystal using a photo-crosslinked liquid crystal for Tri Acetyl Cellulose, Polycarbonate, PMMA, Cyclic Olefinic polymer, Poly Ether Sulfone and other LCD.

The photosensitive polymer is a polymer polymerized with vinyl cinnamoyl derivative (cinnamoyl) derivative side by side.

The photocrosslinkable nematic liquid crystal is an inclined helical which contains a chiral dopant in the photocrosslinkable nematic liquid crystal layer to form a predetermined inclination in the vertical direction on the alignment layer and to rotate at a predetermined average angle in the horizontal direction. It is cholesteric oriented.

The spirally twisted nematic liquid crystal has a refractive index characteristic of Nx = Ny when the twist becomes 360 ° (1 pitch), which is similar to the optical characteristic of the discotic liquid crystal.

The inclination angle of the inclined spiral liquid crystal is 60 ° or less.

The thickness of the said liquid crystal layer is 10 micrometers or less.

According to another feature of the invention, the present invention comprises the steps of preparing a substrate, dissolving a photosensitive polymer alignment layer material in a solvent and coating on the substrate, and after coating to remove the solvent to complete the alignment layer, Irradiating ultraviolet light on the alignment film to form an alignment liquid crystal, forming a photocrosslinkable liquid crystal solution, coating the photocrosslinkable liquid crystal solution on the photoalignment alignment film, and forming an oriented liquid crystal layer; And irradiating ultraviolet rays onto the liquid crystal layer to cure the liquid crystal.

The photo-alignment process by irradiating the alignment layer with ultraviolet rays comprises performing an alignment process on the surface of the alignment layer by irradiating the surface of the alignment layer with the ultraviolet rays vertically polarized with respect to the irradiated inclination direction in a range of 10 ° to 80 °. Investigate.

The polarized ultraviolet light is any one of linearly polarized light, partial polarized light, and circularly polarized ultraviolet light.

The photo-alignment treatment by irradiating the alignment layer with ultraviolet rays comprises performing an alignment process on the surface of the alignment layer by irradiating the surface of the alignment layer with 40 ° to 80 ° of unpolarized UV light perpendicular to the irradiation direction. Investigate in the scope.

The obliquely irradiated ultraviolet rays are collimated in parallel so as to irradiate light to a target at a predetermined angle.

According to the optical film using the photocrosslinkable liquid crystal which concerns on this invention which has such a structure, and its manufacturing method, there exists an advantage which has uniform optical characteristic also in the dispersion | variation in liquid crystal thickness.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of an optical film using a photocrosslinked liquid crystal according to the present invention having the configuration as described above and a method of manufacturing the same will be described in detail.

As shown in FIGS. 4 and 5, the optical film using the photocrosslinkable liquid crystal of the present invention includes a substrate 110, an alignment film 120 coated by a photosensitive polymer on the substrate, and an alignment film coated on the alignment film. And a liquid crystal layer 130 made of a photocrosslinkable liquid crystal.

A characteristic of the present embodiment relates to an optical characteristic in which the first liquid crystal in contact with the alignment film 120 is inclined at the beginning, and the other liquid crystals stacked on top are inclined at the same inclination as the first inclined alignment liquid crystal. Accordingly, even if there is a variation in the thickness of the coated liquid crystal layer 130, the optical axis of the liquid crystal has no change in optical properties, and the alignment stability between the stacked liquid crystals is improved.

According to the present embodiment, the photocrosslinkable liquid crystal includes both a photocrosslinkable nematic liquid crystal as shown in FIG. 4 and a photocrosslinkable discotic liquid crystal as shown in FIG. 5, and induces an inclination between the liquid crystals. There is a feature that does not use additives that cause tilt.

According to another feature of the present embodiment, the inclination angle can be variously adjusted from 0 ° to 90 ° according to the alignment conditions, and the required optical axis can be determined according to the application field of the optical film using the photocrosslinkable liquid crystal.

The substrate 110 may be both a film used as an optical film for LCD and a general carrier film, and glass or metal may be used as long as it has properties such as durability, wear resistance, transparency, and ultraviolet absorption. . In particular, in the case of using the optical film using the photocrosslinkable liquid crystal for LCD as a substrate, there is an advantage that the characteristics of the liquid crystal film formed by the present invention can be added to the optical properties of the substrate.

In the present invention, the photosensitive polymer used to form the photoalignment layer 120 on the substrate 110 is a vinyl polymerized polymer, which includes cinnamoyl derivatives as side chains.

The alignment layer 120 further includes a solvent for dissolving the photosensitive polymer in addition to the photosensitive polymer. The solvent is a solvent such as NMP, cyclopentanone, tolune, xylene, MED, cyclohexane, MC, acetone, cresol strong solvents are used.

In order to increase the ease of coating the solution according to the type of the subject, additives such as wetting agent, leveling agent may be further included.

In order to increase the adhesiveness between the substrate 110 and the alignment layer 120, an adhesion promoter or an adhesive component may be added. When the amount of the additive is less than 20%, the adhesion may be performed without significantly reducing the basic physical properties of the alignment layer. Can improve the sex.

Although the thickness of the alignment layer 120 is only a few nanometers (nm) may exhibit a sufficient orientation ability, but generally has a sufficient thickness because the projections that inhibit the flatness on the surface of the substrate 110 is present, approximately 20nm It is more preferable to form the thickness in the range of about 200 nm.

The alignment layer 120 coated with the photosensitive polymer is subjected to a photoalignment treatment. In the present invention, the surface alignment treatment is performed by obliquely irradiating ultraviolet rays of polarized or non-polarized light. Therefore, the alignment direction of the liquid crystal varies depending on the inclination direction of the ultraviolet rays to be irradiated.

At this time, when irradiating ultraviolet rays polarized perpendicularly to the inclination direction of the ultraviolet rays, if the inclination of the irradiation angle is too large, sufficient light quantity cannot be irradiated to the alignment layer, and when the inclination is close to the vertical, the inclination is not inclined as intended, as it is in the polarization direction. Since there is a tendency to be oriented, it is preferable that the irradiation angle of polarized ultraviolet rays is maintained in the range of 10 ° to 80 °.

Linearly polarized light, partial polarized light, elliptical polarized light and the like are used for the polarized ultraviolet light.

The elliptical polarization may be obtained by transmitting light through a medium having the characteristics of an a-plate, and the partial polarization may be obtained by inclining the traveling direction of the light and transmitting the light having a predetermined refractive index. It is well known that light can be obtained by transmitting light through a linear polarizer, but in order to efficiently pass a wavelength band corresponding to deep UV (DUV) of 250 nm to 400 nm, the polarizing medium is made of an inorganic material such as quartz. It is preferable to use one.

Even when non-polarized ultraviolet light is used, the alignment layer 120 may be inclined by inclined irradiation. The angle of inclination should be at least 40 ° in the vertical direction of the target surface. Even in this case, the liquid crystal is aligned in the direction of irradiation of ultraviolet rays.

In addition, the irradiated light is advantageous to collimate the light so that the entire surface of the irradiated object can receive light from a certain direction, and the higher the parallel light, the lower the irradiation angle.

The degree to which the photocrosslinkable liquid crystal is tilted with respect to the substrate 110 is controlled by the irradiation angle or the irradiation amount of ultraviolet rays, but the inclination angle tends to be lower as the irradiation angle and the irradiation amount are larger. On the contrary, if the irradiation amount is too small, the photomodification of the photoalignment film for inducing the surface orientation cannot be sufficiently induced. If the irradiation amount is too large, the processing time becomes long, so it is preferable to irradiate the light amount of about 0.1 to 10 J / cm 2.

The liquid crystal layer 130 is a coating layer in which a liquid crystal solution in which a photocrosslinkable liquid crystal is dissolved is coated on the alignment layer 120.

As described above, the photocrosslinkable liquid crystal is irrespective of nematic liquid crystal and discotic liquid crystal, and among nematic liquid crystal, rod-like nematic liquid crystal has one or more optical crosslinking functional groups such as at least one attrile each at both ends of the nematic liquid crystal molecule. It is included and photocrosslinked by ultraviolet with photoinitiator.

The discotic liquid crystal is a discotic liquid crystal molecule having a plate-like triphenyl structure and uses a discotic photocrosslinkable liquid crystal including at least two photocrosslinkable functional groups, and is optically crosslinked in the same manner as a nematic liquid crystal.

A small amount of photoinitiator is added to the liquid crystal solution. There are several kinds of photoinitiators that induce photoreaction efficiently according to the wavelength band. In the embodiment of the present invention, an effective photoinitiator is used in the wavelength range of 300 nm to 400 nm.

The solvent is an organic solvent having a relatively high solubility, such as PGMEA, xylene, toluene, is selected in consideration of the solvent resistance of the substrate 110 or the alignment layer 120, and can be used alone, but may be used in combination of two or more thereof. Can be.

As such, when the liquid crystals of the liquid crystal film are tilted, as shown in FIG. 6, there is no change in the optical axis due to the change in thickness, thereby ensuring uniformity of the plane.

As shown in FIG. 7, another embodiment of the present invention is to align sloping photocrosslinkable nematic (bar or rod) liquid crystals in a spirally cholesteric form, thereby splay-orienting or obliquely inclining an optical axis. It is to provide a liquid crystal film made of a photocrosslinkable nematic liquid crystal exhibiting an optical characteristic similar to that of an optical crosslinkable discotic liquid crystal having. This can be done by adding a chiral dopant in the preparation of the photocrosslinkable nematic liquid crystal solution by orienting the liquid crystals that are coated and stacked on the object surface in a spirally twisted shape. The twisted nematic liquid crystal has a twist of 360 ° (cycle, pitch) has a refractive index characteristic of Nx = Ny, which is similar to the optical characteristic of a discotic liquid crystal.

The inclined angle can be regarded as the main optical axis even in this inclined spiral alignment structure.

Spirally twisted nematic liquid crystals have a property of transmitting or reflecting circularly polarized light having a predetermined wavelength depending on the size of the pitch, and thus the pitch is sufficiently shortened in the application of an optical compensation film. There should be no selective reflection in the area.

In general, the discotic liquid crystal has a complicated manufacturing process due to the characteristics of its chemical structure, which is very expensive compared to the nematic liquid crystal, and thus the neat liquid crystal is used as shown in FIG. 8. Repeating a) can be realized an optical effect such as a discotic liquid crystal.

The helical alignment of the photocrosslinkable liquid crystal is basically a stable alignment structure, but the alignment structure having an inclination angle while maintaining this alignment structure has a large balance of the orientation control force of the surface orientation with respect to the interaction between liquid crystals in the thickness direction when the inclination angle is very large. Loss of orientation can result in loss of stability. This phenomenon may appear as a reverse display structure in which the inclination angle of the liquid crystal becomes smooth as it goes in the thickness direction, or the orientation itself loses uniformity. It is preferable to set it as follows.

Even in the above-described inclination orientation, the orientation of the inverse display structure in which the inclination angle of the liquid crystal in contact with air is very soft due to a weakening of the surface orientation control power of the liquid crystal as it goes in the thickness direction. This may result in a decrease in the average optical axis of the inclined alignment liquid crystal layer and thus cannot take advantage of the inclination alignment.

Therefore, in either case, the thickness of the liquid crystal coating cannot be made infinitely thick, and it is preferable that the thickness of the liquid crystal layer is about 10 micrometers or less after all the solvents have evaporated, and the liquid crystal satisfying most of the optical characteristics within this thickness range. Production of the film is possible.

As such, when the liquid crystal layer 130 is formed of a mixed solution of a photocrosslinkable nematic liquid crystal and a chiral dopant in an organic solvent, the dopant has a predetermined average angle (α). Since the optical crosslinkable nematic liquid crystal is rotated while maintaining the average angle α by the dopant, as shown in FIG. It looks like a plate, and as can be seen in FIG. 10, it can be seen that it has the same shape as the discotic liquid crystal molecules.

Hereinafter, a method of manufacturing an optical film using a photocrosslinkable liquid crystal using a photocrosslinkable liquid crystal according to the present invention having the above-described configuration will be described in detail with reference to the accompanying drawings.

First, in the optical film manufacturing method using the photocrosslinkable liquid crystal according to the present invention, the inclination alignment of the photocrosslinkable liquid crystal can be realized only by the one-side orientation of the alignment layer 120 and the alignment method for the one-side orientation. .

In general, the photo-alignment method is a method of coating a photosensitive polymer solution suitable for photo-alignment on a substrate, firing to form a photo-alignment layer, and then irradiating ultraviolet rays thereto to induce a predetermined photo-modification on the surface of the photo-alignment layer to perform surface alignment treatment. It is known as a process that can be applied to a liquid crystal cell with a two-sided orientation, and as a photoalignment film material that can be used here, polyvinyl containing photosensitive side branches such as polyimide, cinnamoyl derivative, coumarin derivative, chalcone derivative or azobenzene derivative , Polymethyl methacrylate, polymaleimide and the like are known.

According to an embodiment of the present invention, a photosensitive polymer alignment layer 120 including a cinnamoyl derivative as a photosensitive side chain as a vinyl polymerized polymer is formed on the substrate 110, and then polarized or non-coated on the surface. It is possible to obtain the inclined alignment structure of the photocrosslinked liquid crystal in which the polarized ultraviolet rays are inclinedly irradiated and the liquid crystal is also inclined at the same inclination.

Preparation step of substrate ;

The base 110, such as a film used as an optical film for LCD or a general carrier film, is prepared.

The optical film for LCD includes a plurality of polymer films, such as polycarbonate, PMMA, Cyclic Olefinic polymer, and Poly Ether Sulfone, which are used as optical films using other optical crosslinked liquid crystals such as triacetyl cellulose, retardation film, and the like used as a polarizing plate material. The carrier film includes a plurality of polymer films such as polyehtylene terephthalate and polysturene.

Dissolving the photosensitive polymer alignment layer material in a solvent to coat the substrate on a substrate ;

In order to form the photo-alignment layer 120 on the substrate 110, a photosensitive polymer including a cinnamoyl derivative as a photosensitive side branch as a vinyl polymerized polymer is dissolved in a solvent.

At this time, solvents such as NMP, cyclopentanone, tolune, xylene, MEK, cyclohexane, MC, acetone, cresol can be used. Most solvents can be used, and solvents of low surface tension such as butoxyethanol are mixed to improve the coating property. Mixed solvents can also be used.

In addition, a small amount of additives such as a wetting agent and a leveling agent may be added to increase the coating usability of the solution according to the type of the inspected object.

In addition, adhesive components such as an adhesion promoter or an acrylic polymer may be added to improve the adhesion between the alignment layer 120 and the substrate 110. When the amount is less than 20%, the basic physical properties of the alignment layer 120 are greatly reduced. The adhesiveness can be improved without making it.

At this time, the method of coating the solution may be a batch method or a continuous method such as a spin coating method, a roll coating method, a gravure method, an immersion pulling method, a die coating method, or the like.

After coating, removing the solvent to complete the alignment layer ;

Drying conditions may vary depending on the solvent used, but the coating film is dried for an appropriate time according to the process conditions while maintaining the coating film to receive heat of 50 ° or more using at least warm air, hot air, or radiant heat to form the alignment layer 120 through evaporation of the solvent. Do it.

In this case, the thickness of the alignment layer 120 after the solvent drying may exhibit sufficient alignment capability even if it is only a few nanometers. However, since projections that inhibit flatness generally exist on the substrate surface, it is preferable that the thickness of the alignment layer 120 has a sufficient thickness to completely apply it. It is common to form about 200 nm.

The method comprising the photo alignment treatment to the alignment film is irradiated with ultraviolet rays;

As shown in FIG. 11, the surface is aligned by irradiating ultraviolet rays to the surface of the alignment layer 120. At this time, when irradiating ultraviolet rays polarized perpendicularly to the inclination direction of the ultraviolet rays, if the inclination of the irradiation angle is too large, the amount of light cannot be irradiated to the alignment layer. If the inclination is close to the vertical, the polarization is not oriented tilted as intended. Since there is a tendency to be oriented in the direction as it is (not inclined orientation), it is preferable to irradiate the polarized ultraviolet rays with a slope of at least 10 ° to 80 °.

For the surface photomodification of the photoalignment layer 120, ultraviolet rays generally have a wavelength in the deep ultraviolet band of 250 nm to 400 nm, and both polarized and unpolarized ultraviolet rays such as linearly polarized light, partial polarized light, and elliptical polarized light can be used. Do. However, in the case of irradiating unpolarized ultraviolet rays, the inclination angle should be at least 40 ° in the vertical direction of the target surface.

In addition, it is advantageous to collimate the light so that the entire surface of the irradiated object can receive the light from a certain direction. The degree of parallel lightening may decrease the irradiation angle. The degree to which the photocrosslinkable liquid crystal is tilted with respect to the substrate 110 can be adjusted by the irradiation angle or the irradiation amount of ultraviolet rays. The collimated and polarized ultraviolet rays are inclined at 10 ° in the normal direction and aligned. When it is irradiated with the minimum amount of light required to obtain an oblique alignment of almost 90 °, the light is irradiated with colloidal ultraviolet rays (both polarized and non-polarized) to obtain an orientation close to 0 °.

When the photo-alignment layer 120 is irradiated with light, the atmosphere may be a nitrogen atmosphere or the substrate may be heated to increase the temperature of the alignment layer, thereby allowing surface light modification to proceed more quickly.

Preparing a photocrosslinkable liquid crystal solution ;

The photocrosslinkable liquid crystal is basically dissolved in a solvent having excellent solubility such as PGMEA, xylene, toluene, and coated, and the solution can be prepared by various methods such as mixing solvents of alcohol to control the coating property.

Photocrosslinkable liquid crystals having nematic (rod-like) properties include photocrosslinkable functional groups such as at least one attrile each at both ends of the nematic liquid crystal molecules, and are photocrosslinked together with a photoinitiator by ultraviolet light.

The photocrosslinkable liquid crystal having a discotic (plate) property is a discotic liquid crystal molecule having a plate-like triphenyl structure, which uses a discotic photocrosslinkable liquid crystal including at least two photocrosslinking functional groups, and is photocrosslinked in the above manner.

A small amount of photoinitiator is included in the liquid crystal solution, and there are various types of inducing photoreaction efficiently according to a wavelength band.

The organic solvent may be selected in consideration of solvent resistance of the substrate 110 or the alignment layer 120, and may be used alone, but may be used in combination of two or more thereof. It may vary depending on the thickness.

A chiral dopant is added to create a helical alignment structure of the photocrosslinkable nematic liquid crystal. In this case, the chiral dopant serves to help the nematic liquid crystal molecules have a helical twist power while maintaining a predetermined average angle α.

Spirally twisted nematic liquid crystals have the property of transmitting or reflecting circularly polarized light of a certain wavelength depending on the size of the pitch. Therefore, in the application of an optical compensation film, the pitch is sufficiently shorted in the visible region. It is better to avoid the selective reflection of.

According to the thickness direction of the coated liquid crystal layer 130, the alignment state of the liquid crystal layer, which is far from the alignment layer 120, receives less alignment control by the alignment layer, so that uniformity of alignment may be lowered. The thickness of the photocrosslinkable liquid crystal layer for obtaining the required optical properties is generally better than 10 micrometers.

Forming an oriented liquid crystal by coating a liquid crystal solution on the photo alignment treatment film ;

The liquid crystal solution is coated on the alignment layer 120 that is photoaligned. At this time, the method of coating the solution can be used in one-time batch or continuous method, such as spin coating method, roll coating method, gravure method, immersion impression method, die coating method, but before the liquid crystal is cured, the low molecular state and if possible thickness Since it is necessary to minimize the deviation, it is preferable to use a coating method capable of precise coating.

Liquid crystal having a predetermined fluidity in the liquid crystal solution coated on the alignment layer 120 starts to be aligned at the same time as the coating and it is necessary to adjust the drying conditions so that the alignment state can be optimally maintained as the solvent is dried. As a result, the temperature range is lower than the phase transition temperature at which the liquid crystal is transferred to the isotropic phase, and a temperature range between the minimum temperatures required for solvent drying should be selected. Other conditions may be determined depending on the solvent. When the drying temperature is higher than the above liquid crystal phase transition temperature, uniform alignment may be difficult.

Irradiating ultraviolet light onto the liquid crystal to cure the liquid crystal ;

Ultraviolet rays are irradiated onto the aligned liquid crystal using an ultraviolet lamp, and the liquid crystal layer 130 is formed by photopolymerization crosslinking of the liquid crystal.

In this case, the ultraviolet broadband is most preferably in the range of 300 nm to 400 nm. A photoinitiator capable of efficiently inducing photocrosslinking in the band may be used, and in the case of the ultraviolet lamp, many kinds of ultraviolet lamps having a high amount of light in the band may be used.

The photocrosslinking of the liquid crystal is more efficient in a nitrogen atmosphere, and the ultraviolet rays do not need to be polarized or parallelized, but it is preferable to irradiate at least 0.5J / cm 2 or more in order to achieve sufficient photocrosslinking of the liquid crystal.

The liquid crystal phase oriented in the present optical crosslinking process is crosslinked and polymerized while maintaining almost the arrangement thereof to form a liquid crystal polymer film having predetermined optical characteristics.

As described above, according to the configuration of the present invention, the following effects can be expected.

First, the liquid crystal film made of the tilted liquid crystal of the present invention has almost no change in the liquid crystal inclination according to the height in the thickness direction, so that there is almost no change in the main optical axis due to the change in the thickness of the liquid crystal polymer film. This has an excellent advantage.

Second, the inclination orientation employed in the optical compensation film of the present invention has an advantage that it is easy to obtain a uniform coating film compared to the splay alignment, and thus high productivity can be obtained.

Third, the inclined helical nematic liquid crystal alignment of the present invention by introducing a chiral dopant into the photocrosslinkable nematic liquid crystal can exhibit optical properties almost similar to that of a splay or diagonally aligned discotic liquid crystal. More economical effects are expected.

Claims (16)

materials; A photosensitive polymer alignment layer coated on the substrate; A photocrosslinked liquid crystal layer oriented on the alignment layer with a predetermined inclination to form a liquid crystal polymer; It is configured to include, The first liquid crystal in contact with the alignment film is firstly inclined with respect to the alignment film, and the other liquid crystals stacked on top are inclined at the same inclination as the first inclined alignment liquid crystal, wherein the optical film using the photocrosslinkable liquid crystal. delete The method of claim 1, The optical crosslinkable liquid crystal is an optical film using a photocrosslinkable liquid crystal, characterized in that the photocrosslinkable nematic liquid crystal. The method of claim 1, The optical crosslinkable liquid crystal is an optical film using a photocrosslinkable liquid crystal, characterized in that the photocrosslinkable discotic liquid crystal. The method according to claim 3 or 4, The inclination angle of the photocrosslinkable liquid crystal is greater than 0 ° and 90 ° small, the optical film using the photocrosslinkable liquid crystal. The method of claim 1, The substrate is an optical film using a photocrosslinkable liquid crystal, characterized in that the optical film selected from Tri Acetyl Cellulose, Polycarbonate, PMMA, Cyclic Olefinic polymer, Poly Ether Sulfone. The method of claim 1, The photosensitive polymer is an optical film using a photocrosslinkable liquid crystal, characterized in that the cinnamoyl derivative (cinnamoyl) derivative is included side by side and the vinyl polymerized polymer. The method of claim 3, wherein The photocrosslinkable nematic liquid crystal, A chiral dopant is contained in the photocrosslinkable nematic liquid crystal layer to form a predetermined inclination in the vertical direction on the alignment layer and to be twisted in a helical spiral form that is rotated at a predetermined average angle in the horizontal direction. An optical film using a photocrosslinkable liquid crystal. delete The method of claim 8, The inclination angle of the inclined spiral liquid crystal is 60 ° or less, the optical film using a photocrosslinkable liquid crystal. The method of claim 1, The thickness of the said liquid crystal layer is 10 micrometers or less, The optical film using the photocrosslinkable liquid crystal characterized by the above-mentioned. delete Preparing a substrate; Dissolving a photosensitive polymer alignment layer material in a solvent and coating it on the substrate; After coating, removing the solvent to complete the alignment layer; Irradiating ultraviolet light on the alignment layer to perform photo alignment; Preparing a photocrosslinkable liquid crystal solution; Forming an oriented liquid crystal layer by coating the photocrosslinkable liquid crystal solution on a photo alignment layer; Irradiating ultraviolet rays onto the liquid crystal layer to cure the liquid crystal; Including, Irradiating ultraviolet light to the alignment layer is a photo alignment process, While the surface of the alignment layer is irradiated with an ultraviolet ray by inclining the surface, the surface of the alignment layer is irradiated with ultraviolet rays vertically polarized with respect to the inclined direction to be irradiated in a range of 10 ° to 80 °, The obliquely irradiated ultraviolet rays are optically prepared using a photocrosslinkable liquid crystal, characterized in that the collimating (collimating) to irradiate light to a target at a predetermined angle. delete Preparing a substrate; Dissolving a photosensitive polymer alignment layer material in a solvent and coating it on the substrate; After coating, removing the solvent to complete the alignment layer; Irradiating ultraviolet light on the alignment layer to perform photo alignment; Preparing a photocrosslinkable liquid crystal solution; Forming an oriented liquid crystal layer by coating the photocrosslinkable liquid crystal solution on a photo alignment layer; Irradiating ultraviolet rays onto the liquid crystal layer to cure the liquid crystal; Including, Irradiating ultraviolet light to the alignment layer is a photo alignment process, While the surface of the alignment layer is irradiated with the ultraviolet rays by inclination, the surface is oriented, and irradiated with ultraviolet rays unpolarized perpendicularly to the inclined direction to be irradiated in the range of 40 ° to 80 °, The obliquely irradiated ultraviolet rays are optically prepared using a photocrosslinkable liquid crystal, characterized in that the collimating (collimating) to irradiate light to a target at a predetermined angle. delete

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