KR100978323B1 - Retardation film and process for producing the same - Google Patents

Abstract

As a retardation film mainly used for a liquid crystal display device and a manufacturing method thereof, a coloring film and a gray level inversion are reduced by a phase film having a birefringence characteristic to improve the viewing angle characteristic of a TN type liquid crystal display device.

LCD, Retardation Film, Birefringence, Coloration, Gradation Inversion, Viewing Angle

Description

Retardation film and its manufacturing method {RETARDATION FILM AND PROCESS FOR PRODUCING THE SAME}

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of birefringence of the 1st retardation film of this invention.

2 is a result of measuring birefringence of the retardation film (Example 1).

It is an example of the optical system at the time of attaching the said retardation film to a liquid crystal display device.

Fig. 4 is a calculation example of the optical compensation effect when the retardation film is attached and not attached by simulation of transmitted light using the 4 × 4 matrix method.

It is explanatory drawing of birefringence of the 2nd phase difference film of this invention.

6 is a result of measuring birefringence of the retardation film (Example 2).

It is an example of the optical system at the time of attaching the said retardation film to a liquid crystal display device.

Fig. 8 is a calculation example of the optical compensation effect when the retardation film is attached and not attached by the simulation of transmitted light using the 4 × 4 matrix method.

The present invention relates to a retardation film used to improve viewing angle characteristics of a liquid crystal display device and a method of manufacturing the same.

The retardation film is a film having a birefringence that transmits a linearly polarized light component oscillating in a direction perpendicular to each other and imparts a necessary phase difference between the two components. Such a retardation film is also utilized in the field of liquid crystal display, and in particular, a retardation film obtained by slant-oriented or bent-oriented liquid crystal material having negative birefringence has a viewing angle of a liquid crystal display device. It is used as an optical compensation film effective for magnification. Although a wide viewing angle enlargement effect can be acquired by such a retardation film, it is a fact that the optical compensation effect cannot fully be acquired depending on the direction which looks at a liquid crystal display device, and it cannot actually cope with the CRT.

In addition, such retardation films are subjected to rubbing and SiO musk deposition as described in JP-A-7-287119, JP-A-7-287120, and JP-A-10-278123. It is formed by arranging a liquid crystal material which is a negative refractive ellipsoid, such as a discotic liquid crystal, on an alignment film subjected to an alignment treatment by a method such as light irradiation or light irradiation. However, discotic liquid crystals have a structure similar to a triphenylene skeleton, and have a problem that the display becomes yellow in the left and right directions in the viewing angle when the wavelength dispersion is large or when the liquid crystal display device is mounted on the liquid crystal display device. . Moreover, in the method using such an alignment film, processes, such as the application drying process of an orientation material, the orientation treatment process of an alignment film, the application drying process of the liquid crystal material to arrange, and the process of arrangement | positioning the process of a liquid crystal material, become complicated, etc. There is also a problem.

As a method of solving the complexity of such a process, the method of expressing phase difference by light irradiation is mentioned. In this method, the optical sheet is irradiated with a polymer sheet containing an azobenzene moiety that is isomerized in JP-A-7-168020 or JP-A-7-207037. Although the retardation film which has axial property is proposed, since this film uses the photoisomerization of azobenzene, it is thought that the practicality is lacking in terms of heat resistance, photostability, and the like. Japanese Unexamined Patent Publication No. 11-160708 also discloses a method of irradiating light to a liquid crystalline alignment material expressing dichroic photoisomerization in which an azobenzene derivative is substituted, but only for confirming the expression of birefringence by light irradiation. There is no description about utility. In addition, Japanese Patent Application Laid-Open No. 11-183722 irradiates light to a film of a liquid crystalline material having a photoreactive substituent, and has a leading phase axis or a fast axis in the sheet plane or a slow phase that is slow in phase. A retardation film in which the inclination angle dependence of the retardation value when the lagging phase axis and the slow axis are set as the inclination axis is asymmetric with respect to the normal direction. However, the display becomes yellow in the left and right directions at the viewing angle when attached to the liquid crystal display device only by asymmetrical the inclination angle dependency of the phase difference value when the fast axis or the slow axis is the inclined axis with respect to the normal direction. There is a problem that the image quality is degraded, the optical compensation effect is not enough.

SUMMARY OF THE INVENTION The present invention provides a retardation film that improves the viewing angle characteristic of a TN type liquid crystal display, i.e., reduces coloring phenomenon and gray level inversion, and an industrial manufacturing method of the retardation film.

As shown in FIG. 1, the first retardation film of the present invention has biaxial refractive indices having main refractive indices nx, ny, and nz in the Z-axis direction parallel to the film plane, and in the Z-axis direction of the film plane normal direction, respectively. Rotate the ellipsoid by θ1 ° with the X-axis as the rotation axis, and rotate the θ2 ° with the Y-axis as the rotation axis, and change the main refractive index nx '(11a axis direction), ny' (11b axis direction), and nz '(11c axis direction). The branch has birefringence consisting of the biaxial index ellipsoid 11.

According to the first retardation film of the present invention, a biaxial index ellipsoid having main refractive indexes nx, ny, and nz in the X-axis, Y-axis, and Z-axis directions is rotated θ1 ° with the X-axis as the rotation axis, and the Y-axis as the rotation axis. Phase birefringence consisting of biaxial index ellipsoids having the main refractive indices nx ', ny', and nz 'in the direction rotated by θ2 °, thereby reducing coloring phenomenon and gray level inversion, and effective phase difference for expanding the viewing angle of the liquid crystal display device. Films may be provided.

In the TN type liquid crystal display device which consists of a liquid crystal cell which clamps the said retardation film between two electrode substrates, and two flat plate plates arrange | positioned at both sides, between a liquid crystal cell and a flat tube plate By attaching at least one sheet, color development and gradation inversion can be reduced, and the viewing angle characteristic of the TN type liquid crystal display can be improved.

It is preferable to produce the said 1st retardation film by the process including the operation which produces a film using the photosensitive material, and irradiates light in the direction inclined with respect to the film surface, or additionally heat-cools.

As shown in FIG. 5, in the second retardation film of the present invention, when the surface formed by the X axis and the Y axis is in the film plane, and the Z axis is in the thickness direction, the second retardation film is in the main refractive index nx and the Y axis direction in the X axis direction. The main refractive index ny and the first refractive index ellipsoid having the main refractive index nz in the Z-axis direction (where the relationship between the main refractive index of the first refractive ellipsoid is nx> ny≥nz) and the first refractive index ellipsoid are represented by the Y axis as the rotation axis. A second index ellipsoid having a main refractive index nx 'ny' nz 'in a direction rotated by an angle θ4 ° with the Z axis as a rotation axis (where the relationship between the main refractive indexes of the second index ellipsoid is nx'> ny'≥nz It has birefringence that forms all of them.

According to the second retardation film of the present invention, when the surface formed by the X-axis and the Y-axis is in the film plane, and the thickness direction is the Z-axis direction, the main refractive index nx in the X-axis direction, the main refractive index ny in the Y-axis direction, The index ellipsoid having the main refractive index nz in the Z-axis direction (where the relation between the main refractive index of the index ellipsoid is nx> ny ≥ nz) and the Y-axis rotated θ3 ° and the Z-axis rotated θ4 ° It has birefringence which forms all of the other index ellipsoids (where the relationship between the refractive indexes of the index ellipsoids is nx '> ny' ≥ nz ') with the main refractive index nx' in the direction, thereby reducing coloring phenomenon and gray level inversion. A retardation film effective for expanding the viewing angle of a display device can be provided.

A TN type liquid crystal display device comprising the retardation film comprising a liquid crystal cell in which a TN liquid crystal is sandwiched between two electrode substrates and two flat tube plates disposed on both sides thereof, wherein at least one of the retardation film is disposed between the liquid crystal cell and the flat plate. By attaching the medium, it is possible to reduce coloring phenomenon and gray level inversion, and to improve viewing angle characteristics of the TN type liquid crystal display device.

It is preferable to produce the said 2nd retardation film by the process including the operation which produces a film using the photosensitive material, and irradiates light in the direction inclined with respect to the film surface, or additionally heat-cools.

In the method for producing the second retardation film, the light irradiated in the direction inclined with respect to the film surface is light in which the full polarization component and the non-polarization component are mixed, and the electric field vibration direction of the full polarization component is the inclination of the irradiation light. It is preferable not to be parallel to the direction or its orthogonal direction.

Moreover, since the retardation film of this invention has the property which shows a birefringence characteristic different with a viewing direction, the direction of the slow axis of birefringence especially observed in the normal direction of a film surface is set as a reference axis, and the normal direction of a film surface The direction of the reference axis observed at was set to 0 ° with respect to the rotation about the film axis normal direction.

The invention will be clearly understood from the following description of the preferred embodiments with reference to the accompanying drawings. However, the examples and figures are for illustration and description only and should not be used to define the scope of the invention. The scope of the invention is defined by the appended claims. Like reference numerals in the drawings denote like parts in the accompanying drawings.

Below, the 1st phase difference film of this invention is demonstrated in detail.

As shown in FIG. 1, the first retardation film of the present invention has an X-, Y-, and Z-axis parallel to the film plane. Assuming the biaxial index ellipsoids of nx, ny, and nz, respectively, the main refractive index is rotated by an arbitrary rotation angle θ1 ° with the X axis as the rotation axis, and an optional rotation angle θ2 ° with the Y axis as the rotation axis. It is a retardation film which consists of biaxial refractive index ellipsoid which has nx '(11a axial direction), ny' (11b axial direction), and nz '(11c axial direction), and implements this 1st retardation film The retardation film in Example 1 is its typical film.

The birefringence measured by applying the Senarmont method is shown in FIG. The polarizer and the film which were arrange | positioned so that a transmission axis might become 45 degrees to a horizontal plane (incidence angle = O degree) were made into the azimuth angle O degree when the direction of the slow axis in a plane and the direction of a polarizer transmission axis orthogonally crossed. For this reason, when the film is rotated 55 ° about the normal axis of the horizontal plane to the right direction, on the contrary, when the film is rotated about -55 ° about the normal axis of the horizontal plane to the left, the azimuth angle is rotated 90 ° and the film is normal to the horizontal plane. The case of rotating the film by 55 ° about the axis is in the downward direction. On the contrary, when the film is rotated by -55 ° around the horizontal axis of the horizontal plane, the polarizer and the quarter wave plate are rotated 360 ° in each direction. The retardation is measured (the respective directions are names as appropriate directions when the retardation film of the present embodiment is mounted in combination with the liquid crystal display device). By this measuring method, knowledge regarding birefringence, such as the inclination direction of the axis and the magnitude of the phase difference, which becomes the maximum in the projected shape of the refractive index body of the retardation film in each of the directions in the vertical, vertical, left and right directions, can be obtained.                     

Based on this knowledge, it is possible to consider attaching the retardation film of the example to the liquid crystal display device in an optical arrangement as shown in Fig. 3 together with the film having negative birefringence.

In Fig. 3, reference numerals 31 and 31 'denote the first retardation film of the present invention, and reference numerals a and a' denote the direction of the slow axis when the retardation film is viewed from the front, and reference numerals 1 and 1 ' It is the direction of the main refractive index nx 'of the refractive index ellipsoid 11 in FIG. 1, and m and m' are the directions of the main refractive index ny '. Reference numeral 32 denotes a liquid crystal cell, reference numerals b and b 'denote pre-tilt directions, reference numerals 33 and 33' denote polarizing sheets, and c and c 'denote respective light transmission axis directions. have. When it mounted in this way, it was confirmed that a wide viewing angle characteristic is expressed not yellowish in the left-right direction (respective Q direction or P direction, respectively) of a liquid crystal display device.

In addition, in the simulation of transmitted light using the 4 × 4 matrix method, there is a good optical compensation effect when the retardation film of the present invention is mounted. The transmission axis of the polarizing plate is perpendicular to the display screen by 45 ° to the inside (back light source side). The transmitted light at the time of black display was confirmed by FIG. 4 which simulated the transmission light in the liquid crystal display which is attached to each of the and outside (display surface side).

4A and 4D show polarization states of light transmitted through the inner flat plate when the liquid crystal display device is viewed at 55 ° in the right direction and 55 ° in the left direction. 4B and 4E show the polarization states of light incident on the outer flat plate when the retardation film of the present invention and the negative birefringent film are mounted in the optical arrangement shown in FIG. 41 denotes the transmission axis of the outer flat plate.

From this figure, the light transmitted through the liquid crystal cell from the rear surface of the liquid crystal display device becomes a direction orthogonal to the transmission axis direction of the outer polarizing plate in a state relatively close to linearly polarized light, and a black color display is maintained so that good optical Compensation effects were shown in the simulation.

In addition, although the polarization state of the light which injects into the outer polarizing plate at the time of not mounting a retardation film and a negative birefringent film is shown to FIG.4 (C), (F), when it is not attached from a figure, the polarization state is largely disturbed, However, the black display is not maintained orthogonal to the transmission axis direction of the outer polarizing plate.

For producing the retardation film of the present invention, as the inventors described in Japanese Patent Application Laid-Open No. 11-l89665 and Japanese Patent Application No. 2000-400356, a material which generates birefringence by light irradiation and heat cooling can be used. have. These materials include substituents such as biphenyl, terphenyl, phenylbenzoate and azobenzene, which are frequently used as mesogene components of liquid crystalline polymers, cinnamoyl groups, chalcone groups, cinnamildene groups, and 6- (2- It has a side chain containing the structure which couple | bonded photosensitive groups, such as a furyl) acryloyl group (or derivatives thereof), and has hydrocarbon, acrylate, methacrylate, maleimide, N-phenylmaleimide, siloxane And a polymer having a structure such as a main chain in the main chain. The polymer may be a single polymer consisting of the same repeating unit or a copolymer of units having different side chains in structure, or may be copolymerized with units having side chains not containing photosensitive groups. Moreover, the compound which has a crystalline or liquid crystallinity which has many uses as a mesogenic component, and has substituents, such as a biphenyl, terphenyl, phenyl benzoate, azobenzene, also to mix is mentioned. The low molecular weight compound to mix is not limited to a single compound only, It is also possible to mix multiple types of compounds. Furthermore, the monomer which does not show liquid crystallinity without adding liquid crystallinity without impairing liquid crystallinity, or adding a crosslinking agent for improving alignment property and heat resistance to an extent to which liquid crystallinity is not impaired can also be copolymerized.

This material is applied onto a transparent substrate to produce a film. This board | substrate can be produced by irradiating two linearly polarized light in which the electric field oscillation surfaces orthogonally cross at each desired angle, and heat-cooling it. In this case, since the molecules in the film are to be oriented in the direction of the electric field oscillation of two linearly polarized light, the biaxial refractive ellipsoid having the main refractive indexes of nx, ny, and nz in the X, Y, and Z axes of the present invention. A phase difference film having birefringence composed of biaxial index ellipsoids having main refractive indexes of nx, ny ', and nz' in a direction of rotating θ1 ° with the X axis as the rotation axis and θ2 ° with the Y axis as the rotation axis. It can manufacture. The angle dependence of the phase difference by the cinnamon method of the retardation film thus prepared is X-axis, Y-axis, Z by fitting the optical simulation results for the layered medium having birefringence using the Muller method. A biaxial refractive index ellipsoid with nx, ny, and nz principal refractive index in the axial direction is rotated θ1 ° in the X axis and θ2 ° in the Y axis, and nx ', ny', and nz ' It is confirmed that it matches well with the case of the refractive index ellipsoid of axiality.                     

Here, the birefringence of the retardation film is measured as the inclination direction or the magnitude of the phase difference of the axis in which the refractive index in the up, down, left and right directions is maximum in the measuring method in FIG. It should adjust by optical characteristic determined according to thickness, inclination-angle, a kind of liquid crystal, etc. In many TN type liquid crystal display devices, the inclination direction of the axis in which the refractive index seen from the right direction is maximum in the measurement result of FIG. 2 is preferably about 45 ± 15 ° with respect to the horizontal direction in this viewing direction, and more preferably 45 ± 10 °. desirable. Moreover, as for the phase difference in this observation direction, about 50-250 nm is preferable. In addition, in order to enlarge the viewing angle in the up-down direction, the axis in which the index of refraction is maximum when viewed from the top direction has a smaller inclination than the direction of the reference axis seen in the direction, and the axis in which the index of refraction is maximum when viewed from the downward direction is in that direction. It is preferable that the inclination is larger than the direction of the reference axis. For adjusting the birefringence of the retardation film, it is effective to change the film thickness, the irradiation amount of the irradiation light, the degree of polarization, and the irradiation direction. Furthermore, it can also be combined with a negative birefringent film, a uniaxial stretched film, and a biaxially stretched film.

However, the manufacturing method of the retardation film of this invention is not limited to irradiating light to the material which generate | occur | produces birefringence by such light irradiation and heat cooling, What is necessary is just to have the birefringence mentioned above, and the biaxially stretched transparent resin rod May be cut at a desired inclination angle, stretched different circumferental sppeds that are conventionally used, oriented liquid crystal molecules on an alignment film, vapor deposition of inorganic materials, or a combination thereof.                     

The synthesis | combining method with respect to the raw material compound and low molecular weight compound of the photosensitive polymer used in Example 1 of the 1st retardation film of this invention is shown below.

(Monomer 1)

4-hydroxy-4'-hydroxyethoxybiphenyl was synthesized by heating 4, 4'-biphenyldiol and 2-chloroethanol under alkaline conditions. 1, 6-dibromohexane was reacted with this product under alkaline conditions to synthesize 4- (6-bromohexyloxy) -4'-hydroxyethoxybiphenyl. Subsequently, lithium methacrylate was reacted to synthesize 4-hydroxyethoxy-4 '-(6-methacryloyloxyhexyloxy) biphenyl. Finally, cinnamoyl chloride was added under basic conditions to synthesize monomer 1 shown in formula (1).

(Polymer 1)

The photosensitive polymer 1 was obtained by dissolving monomer 1 in tetrahydrofuran, and superposing | polymerizing by adding AIBN (azobisisobutylonitrile) as a reaction initiator. This polymer 1 showed liquid crystallinity in the temperature range of 47-75 degreeC.

(Low molecular weight compound 1)

4, 4'-biphenyldiol and 6-bromohexanol were reacted under alkaline conditions to synthesize 4,4'-bis (6-bromohexyloxy) biphenyl. Subsequently, the low molecular weight compound 1 shown in General formula (2) was synthesize | combined by carrying out process reaction with the succinic namoyl under basic conditions, and column-refining the product.

Example 1 is the Example which produced the 1st phase difference film of this invention.

(Example 1)

4.2 wt% of Polymer 1 and 0.8 wt% of Low Molecular Compound 1 were dissolved in dichloroethane and applied to a glass substrate (support) at a thickness of about 1 μm. Placing the coated surface to the substrate against a horizontal surface 40 inclined so that the irradiation surface, and the electric field vibration direction of the ultraviolet Castle linearly polarized light to ensure that the 45 ° relative to the inclined axis of a substrate and irradiated 10 OmJ / cm ^2, continuously linear 10 mJ / cm <^2> irradiation was made so that the electric-field vibration direction of polarized ultraviolet-ray might become -45 degree with respect to the inclination axis of a board | substrate. Moreover, the board | substrate was reversed and irradiated similarly, and after heating to 100 degreeC, it cooled to room temperature.

The retardation film obtained in this way was peeled off the polarizing sheet of EV-510 before the liquid crystal color television produced by Casio, and it stuck on the upper and lower sides of the liquid crystal cell, and attached the polarizing sheet (HEG1425DU by Nito Dengo) one by one up and down. The axis arrangement of each optical element was performed as in FIG. 3 described above. As a result of driving the liquid crystal color television with such a configuration, yellowing in the left and right directions did not occur, and the viewing angle characteristic was greatly improved, and the viewing angle enlargement effect was confirmed in the vertical direction.

(Comparative Example 1)

As in Example 1, 4.2 wt% of Polymer 1 and 0.8 wt% of Low Molecular Compound 1 were dissolved in dichloroethane and applied to a glass substrate (support) at a thickness of about 1 μm. The substrate is inclined at 60 degrees with respect to the horizontal plane, and the coated surface is disposed so as to be the irradiation surface, and the linearly polarized light is subjected to 100mJ / cm ² irradiation so that the direction of the electric field vibration is parallel to the inclination axis of the substrate. 10 mJ / cm <^2> irradiation was made so that the electric-field vibration direction of an ultraviolet-ray might become perpendicular | vertical with respect to the inclination axis of a board | substrate. In addition, the substrate was turned over and irradiated in the same manner, and then heated to 100 ° C., and then cooled to room temperature. A biaxial ellipsoid rotated using only the X axis of the biaxial ellipsoid as the rotation axis was inclined, and a retardation film having an inclination angle dependence of the retardation value in the case where the slow axis was the inclination axis was asymmetric with respect to the normal direction. The film was removed from the polarizing sheet of the liquid crystal color television EV-510 manufactured by Casio and pasted onto the upper and lower surfaces of the liquid crystal cell, and the upper and lower polarizing sheets (HEG1425DU manufactured by Nito Dengo) were attached one by one.

As a result of driving the liquid crystal color television in such a configuration, a deterioration in image quality with strong yellow color in the left and right directions occurred.

(Comparative Example 2)

The optical compensation film which bend-aligned the commercial discotic liquid crystal was peeled off the polarizing sheet of the liquid crystal color television EV-510 manufactured by Casio like Example 1, and it puts on the upper and lower surfaces of a liquid crystal cell one by one, and then polarizing sheet (Nito HEG1425DU) manufactured by Dengo was attached one by one.

As a result of driving the liquid crystal color television in such a configuration, there was a deterioration in image quality with strong yellow in the left and right directions.

From Example 1, a biaxial index ellipsoid having main refractive indices of nx, ny, and nz in the X-axis, Y-axis, and Z-axis directions of the present invention is rotated θ1 ° with the X-axis as the rotation axis, and the Y-axis as the rotation axis. Retardation film having birefringence consisting of biaxial index ellipsoids having main refractive indexes of nx ', ny', and nz 'in a direction rotated by 2 °, even in the left and right directions when mounted on a liquid crystal display device It has been proved that an optical compensatory sheet can be obtained which is not yellowish.

Next, the second retardation film of the present invention will be described.

As shown in FIG. 5, the birefringence of the second retardation film of the present invention has a first refractive index ellipsoid 12 having a main refractive index nx in the X-axis direction, a main refractive index ny in the Y-axis direction, and a main refractive index nz in the Z-axis direction. (Where the relationship between the main refractive index of the first index ellipsoid is nx> ny ≧ nz) and the first index ellipsoid is rotated by an angle of θ3 ° with the Y axis as the rotation axis, and rotated by an angle θ4 ° with the Z axis as the rotation axis. The second refractive index ellipsoid 13 having the main refractive index nx'ny'nz '(where the relationship between the main refractive indexes of the second refractive index ellipsoid is nx'> ny '≧ nz') is combined (combined). The retardation film in Example 2 of the present invention is a typical film thereof. The result of having measured the birefringence by the cinnamon method is shown in FIG. The measuring method of FIG. 6 is the same as that of FIG. 2 of Example 1 mentioned above.

Based on the knowledge regarding birefringence such as the inclination direction of the axis and the magnitude of the phase difference, which are the largest in the projected shape of the refractive index body of the second retardation film in each of the directions in the vertical, horizontal, left and right directions obtained in FIG. 6, It may be considered to mount the two retardation film to the liquid crystal display device in an optical arrangement as shown in FIG. 7 together with a film having negative birefringence characteristics. In Fig. 7, reference numerals 34 and 34 'denote second phase difference films of the present invention.

In the case of mounting in this way, it was confirmed that a wide viewing angle characteristic was expressed without being yellow in the left and right directions (Q direction or P direction, respectively) of the liquid crystal display device.

In addition, in the simulation of transmitted light using the 4 × 4 matrix method, there is a good optical compensation effect when the second retardation film of the present invention is mounted, so that the transmission axis of the polarizing plate is perpendicular to the display screen at 45 ° to the inside (backside). In the liquid crystal display device mounted on the light source side and the outside (display surface side), it was confirmed in FIG. 8 that simulated the transmitted light at the time of black display.

8A and 8D show polarization states of light transmitted through the inner polarizing plate when the liquid crystal display device is viewed at 55 ° in the right direction and 55 ° in the left direction. 8B and 8E show the polarization states of light incident on the outer polarizing plate when the second retardation film and the negative birefringent film of the present invention are mounted in the optical arrangement shown in FIG. 7.

From this figure, the light transmitted through the liquid crystal cell from the back of the liquid crystal display device is in a direction orthogonal to the transmission axis direction of the outer polarizing plate as it is relatively close to linearly polarized light. Appeared in the simulation.

On the other hand, in the polarization state of the light incident on the outer polarizing plate when the phase difference film and the negative birefringent film is not attached to (C) and (F) of FIG. 8, the polarization state is greatly disturbed when not attached and the transmission axis direction of the outer polarizing plate It is not orthogonal to and black display is not maintained.

As the material of the second retardation film, the same material as that described in the first retardation film described above is used. In addition, the monomer (1) shown in [Formula 1] synthesized in the same manner as in Example 1 and the low molecular compound (1) shown in Polymer (1) and [Formula 2] are used.

In this 2nd phase difference film, the said material is apply | coated on a transparent substrate and a film | membrane is produced. The substrate is inclined with respect to the horizontal plane, irradiated so that the electric field oscillation direction of the light and the fully polarized light component in which the full polarization component and the non-polarization component are mixed in the normal direction with respect to the horizontal plane does not become the inclination axis direction or the orthogonal direction, and heats and cools. This can be produced. In this case, since the molecules in the film are to be oriented in both the electric field vibration direction of the fully polarized component and the electric field vibration direction of the P wave of the non-polarized component, the surface formed by the X and Y axes of the present invention is in the film plane, Refractive index ellipsoid having a major refractive index nx in the X axis direction, a major refractive index ny in the Y axis direction, and a major refractive index nz in the Z axis direction when the thickness direction is set in the Z axis direction (where the relationship between the main refractive index of the index ellipsoid is nx> ny ≥ nz) and the other index ellipsoid having the main refractive index nx 'in the direction rotated θ3 ° with the Y-axis as the rotation axis and rotated θ4 ° with the Z-axis as the rotation axis (where the relationship between the main refractive index of the index ellipsoid is nx'> ny). Retardation film having birefringence combined with &quot; ≥ nz &quot;

However, the manufacturing method of the retardation film of this invention is not limited to light irradiation to the material which generate | occur | produces birefringence by irradiation of such light and heat cooling, If it has the birefringence mentioned above, the conventional circumferential speed drawing used conventionally, A process of orienting the liquid crystal component on the alignment film, depositing an inorganic substance, or a combination thereof may be used.

Example 2 is the Example which produced the 2nd phase difference film of this invention.

(Example 2)

4.2 wt% of Polymer 1 and 0.8 wt% of Low Molecular Compound 1 were dissolved in dichloroethane and applied to a glass substrate (support) at a thickness of about 1 μm. The substrate is inclined at an angle of 60 degrees with respect to the horizontal plane, and the coated surface is disposed so as to be an irradiation surface, and a polarization degree composed of a completely polarization component and a non-polarization component (where polarization degree is a completely polarization component / (completely polarization component + non-polarization component) × 100%) is 69.4% of ultraviolet rays, the electric field vibration direction of the fully polarized component is rotated by 15 ° with respect to the inclination axis of the glass substrate, 120mJ / cm ² irradiated from the vertical direction to the horizontal plane at room temperature, and then the substrate is turned over The same was investigated 120mJ / cm ² . Next, after heating to 100 degreeC, it cooled to room temperature.

The retardation film obtained in this way was peeled off the polarizing sheet of the liquid crystal color television EV-510 manufactured by Casio, and it stuck on the upper and lower sides of the liquid crystal cell, and then attached the polarizing sheet (HEG1425DU by Nito Dengo) one by one up and down. The axis arrangement of each optical element was the same as that of FIG. When the liquid crystal color television was driven by such a configuration, it did not appear yellow in the left-right direction, the viewing angle characteristic was greatly improved, and the viewing angle enlargement effect was also confirmed in the vertical direction.

(Comparative Example 3)

As in Example 2, 4.2 wt% of Polymer 1 and 0.8 wt% of Low Molecular Compound 1 were dissolved in dichloroethane and applied to a glass substrate (support) at a thickness of about 1 μm. The substrate is inclined at an angle of 60 degrees with respect to the horizontal plane, the coating surface is disposed so as to be an irradiation surface, and an ultraviolet ray having a degree of polarization of 69.4% consisting of a complete polarization component and a non-polarization component is inclined axis of the glass substrate. 120 mJ / cm ² irradiated at room temperature in the vertical direction with respect to the horizontal plane, and it was made to be parallel with respect to the horizontal surface, and the board | substrate was then reversed and 120 mJ / cm ² irradiated similarly. Next, after heating to 100 degreeC, by cooling to room temperature, the biaxial ellipsoid was inclined and the inclination-angle dependency of the phase difference value at the time of making the slow axis into the inclination axis produced the retardation film which is asymmetric with respect to a normal direction. The said film was peeled off the polarizing sheet of the liquid crystal color television EV-510 manufactured by Casio, and it attached to the upper and lower surfaces of the liquid crystal cell one by one, and then attached the polarizing sheet (HEG1425DU by Nito Dengo) one by one up and down.

As a result of driving the liquid crystal color television with such a configuration, a deterioration in image quality with strong yellow in the left and right directions occurred.

(Comparative Example 4)                     

Remove the polarizing sheet of the liquid crystal color television EV-510 manufactured by Casio in the same manner as in Example 2, attaching the optical compensation film in which the discotic liquid crystals were bent orientated on the upper and lower surfaces of the liquid crystal cell, and then attaching the polarizing sheet (Nitodengo Co., Ltd.). HEG1425DU) was attached one by one.

As a result of driving the liquid crystal color television in such a configuration, a deterioration in image quality with strong yellow color in the left and right directions occurred.

In Example 2, when the surface formed by the X-axis and the Y-axis of the present invention is in the film plane, and the thickness direction is the Z-axis direction, the main refractive index nX in the X-axis direction, and the main refractive index ny, Z in the Y-axis direction The direction of the refractive index ellipsoid having the main refractive index nz in the axial direction (where the relationship between the main refractive index of the index ellipsoid is nx> ny≥nz), and the Y axis rotated θ3 ° and the Z axis rotated θ4 °. Left and right when mounted on a liquid crystal display device by a birefringent retardation film in which another refractive index ellipsoid having a main refractive index nx '(where the relationship between the main refractive indexes of the refractive index ellipsoid is nx'> ny'≥nz ') is combined. It has been demonstrated that an optical compensatory sheet can be obtained which is not yellow in the direction.

As described above, according to the present invention, it is possible to improve the viewing angle characteristic of the TN type liquid crystal display by reducing the coloring phenomenon and the gray level inversion by the phase film having the birefringence characteristic.

Claims (5)

As a retardation film having birefringence, With respect to the coordinate system composed of the X axis, the Y axis parallel to the film plane, and the Z axis in the film plane normal direction, the principal refractive indices nx, ny, and nz (nx ≠ ny ≠ nz) are respectively determined in the axial directions of X, Y, and Z, respectively. Assuming that the biaxial index ellipsoid has a biaxial index ellipsoid, the index ellipsoid is rotated by an arbitrary rotation angle θ1 ° with the X axis as the rotation axis, and then rotated by an arbitrary rotation angle θ2 ° with the Y axis as the rotation axis. Refractive index of the ellipsoid has the birefringence characteristic of nx ', ny', nz ' Retardation film. As a method for producing a retardation film according to claim 1, A film is prepared using a photosensitive material, and is produced by a process including an operation of irradiating light in a direction inclined with respect to the film surface, or in addition, heating and cooling. The manufacturing method of retardation film. As a retardation film having birefringence, In the case where the surface formed by the X and Y axes is in the film plane and the Z axis is in the thickness direction, the first refractive index having the main refractive index nx in the X axis direction, the main refractive index ny in the Y axis direction, and the main refractive index nz in the Z axis direction The ellipsoid (the relationship between the main refractive index of the first index ellipsoid is nx> ny≥nz) and the first index ellipsoid are rotated by the angle θ3 ° with the Y axis as the rotation axis and rotated by the angle θ4 ° with the Z axis as the rotation axis. Direction has a birefringence formed by coexistence of a second refractive index ellipsoid having a main refractive index nx 'ny' nz '(the relationship between the main refractive indexes of the second refractive index ellipsoid is nx'> ny'≥nz '). Retardation film. As the method of manufacturing the retardation film according to claim 3, The retardation film is produced by a process comprising an operation of producing a film using a photosensitive material and irradiating light in a direction inclined with respect to the film surface, or in addition, heating and cooling. The manufacturing method of retardation film. In claim 4, The light irradiated in the direction inclined with respect to the said film surface is the light which a perfect polarization component and a non-polarization component mix, The electric field vibration direction of the said fully polarizing component is not parallel to the diagonal direction or the orthogonal direction of the said irradiation light, The manufacturing method of the retardation film.

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