JP2000313757A - Production of film phase plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a film phase plate which is capable of controlling the phase difference at an optional place, comprising removing the in-plane unevenness in phase difference, and improving production yield. SOLUTION: This method for producing a film phase plate comprises at least either one of the following steps: contacting an organic gas, organic vapor or steam with the surface of a film phase plate, irradiating the surface of a film phase plate consisting mainly of a polymer with light, heating the surface of a film phase plate consisting mainly of a polymer, and partially applying pressure to the surface of a film phase plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase compensator used for a liquid crystal display device, and more particularly to a film phase plate.

[0002]

2. Description of the Related Art In general, linearly polarized light incident on a liquid crystal display element propagates in the liquid crystal layer in the form of elliptically polarized light, and its polarization state varies depending on the wavelength of transmitted light. The phase compensator has a function of changing the polarization state and controlling the polarization state for each wavelength light at the emission end of the liquid crystal display element.

More specifically, it has the following three functions.

(1) The liquid crystal display element controls the transmitted light intensity I by changing the birefringence Δn of a liquid crystal layer sandwiched between two polarizing plates by applying a voltage V. For example,
The light transmission light intensity I in the ECB type liquid crystal display element is given by the following equation (1): I = I ₀ sin ² (2θ) sin ² (πdΔn, where I ₀ is the incident light intensity.
(V) / λ) (EPRaynes, DKRowe
ll and I, A. Shanks: Mol. Cryst. Liq. Cryst. Lett., 34,
p.105 (1976); D. Meyerhofer, Appl. Phys. Lett., 29,
p.691 (1976)).

Here, θ is the angle between the incident polarization direction and the direction of oscillation of the ordinary light in the cell, d and Δn (V) are the thickness of the liquid crystal layer and the birefringence of the liquid crystal layer when voltage V is applied, respectively, and λ is It represents the wavelength of the incident light.

At this time, a uniaxial medium is used as a phase compensator,
By arranging the principal axis of the phase compensator parallel or perpendicular to the optical principal axis direction of the liquid crystal layer, the cell voltage −
The transmittance characteristic can be shifted to a high voltage side or a low voltage side.

(2) In a liquid crystal display element utilizing a birefringent mode such as the STN mode, when the incident linearly polarized light propagates through the liquid crystal layer, the liquid crystal layer phase difference dΔn differs for each wavelength, so that light A problem arises in that the polarization state of the transmitted light at the emission end is different and the display is colored.

At this time, except that the directions of twist are opposite, liquid crystal cells having the same characteristics and structure are arranged so that the orientation directions of liquid crystal molecules on the adjacent substrate surface are orthogonal to each other. The coloring phenomenon can be completely eliminated (Okumura Osamu, Nagata Mitsuo, Wada Keishi: Technical Report of the Institute of Television Engineers of Japan, 11 (27), p.79 (1987), K. Katoh,
Y.Endo, M.Akatsuka, M.Ohgawara and K.Sawada: Jap.
J.Appl.Phys.vol.26, No.11, Nov., 1987, pp..L1784-
L1786; N.Kimura, T.Shinomiya, K.Yamamoto, Y.Ichim
ura: SID'88 Digest p.49 (1988)).

(3) In the liquid crystal display device, not only display characteristics in front of the panel but also display characteristics (performance) in oblique directions are important. Lighting in a liquid crystal display element from a diagonal direction or light leakage in a diagonal direction during black display is caused by a change in the effective crossing angle of the polarizing plate due to the oblique viewing angle of the crossing angle of the polarizing plate (for example, two polarizing plates in front). Even if the axes are perpendicular to each other, the effective crossing angle of the axes of the polarizing plates becomes larger than 90 degrees as the viewing angle is increased in the azimuth of 45 degrees, and the birefringence of the liquid crystal layer. This is due to the viewing angle dependence of the rate.

That is, the biaxial anisotropy of the liquid crystal layer is represented by a birefringent ellipsoid. When the principal axis nx is inclined with respect to the cell substrate surface, the liquid crystal layer is asymmetric with respect to the cell front. Optical characteristics. In addition, even when the nx axis is perpendicular to the cell substrate surface, the effective liquid crystal layer phase difference from an oblique direction becomes larger as the viewing angle is gradually inclined from the front, and the display quality deteriorates. I will do it.

The phase compensation layer has the function of reducing the viewing angle dependence of the birefringence of the liquid crystal layer.

As the phase compensation layer for compensating the phase difference of the display liquid crystal cell, the use of a compensation liquid crystal cell has been preferred and commercialization has been carried out. It was replaced by a film phase plate due to the difficulty of the process and increased costs. Behind this are advances in film manufacturing technology and technologies for controlling the orientation of molecules in the film.

Although the history as a phase conversion element typified by a λ / 4 plate is old, research on a film phase plate for a liquid crystal display element has been actively promoted in the achromatic color of an STN mode liquid crystal display element. Since the beginning of work on film phase plates (Nagae, Square, Komura, "Phase plate type black and white super TN liquid crystal panel", Technical Report of the Institute of Television Engineers of Japan, vol.
12, no.32, pp.29-34, August 1988, I. Fukuda, Y. Kota
ni, and T. Uchida: Rec.Int'l.Display Res.Conf.,
p.159 (1988), Ichiro Fukuda, Isao Kotani, Tatsuo Uchida: IEICE Technical Report, 88 (350), p.17 (198
9)).

In the transition from the compensating liquid crystal cell to the film phase plate, it is important to match the wavelength dispersion characteristics of the refractive index anisotropy Δn in each of the liquid crystal cell and the film phase plate. The Δn wavelength dispersion in the film phase plate depends on the polymer material used, and various films such as polyvinyl alcohol, polycarbonate, acrylic, and polyester have been developed for the above purpose.

Further, by combining a material having a small wavelength dispersion characteristic such as polypropylene or polyvinyl alcohol and a material having a large wavelength dispersion characteristic such as polycarbonate in an orthogonal arrangement, the wavelength dispersion which increases Δn on the long wavelength side can be obtained. Film phase plates with properties have also been developed (Tatsuki Nagatsuka, Yasuo Fujimura, Hiroyuki Yoshimi, "Phase difference film for STN-LCD": IEICE technical report EID91-4
3, p.29-34 (1991)).

More recently, it has become possible to make the optical characteristics of a film phase plate have the same temperature dependence as a liquid crystal cell (Toyokazu Okada, "Optical Film for LCD", Journal of the Institute of Image Information and Television Engineers, vol. 51, No.4, pp.431-434 (199
7)).

On the other hand, with respect to the control of the refractive index of the film phase plate in the three-dimensional direction, it has become possible with the progress of manufacturing technology. Specifically, a) positive uniaxial (nx> ny = nz), b) negative uniaxial orientation (nx = nz>) by a polymer film stretching technique.
ny), c) positive biaxial orientation (nx>ny> nz), d) perfect biaxial orientation (nx = ny> nz), e) vertical orientation (nz> nx = ny),
f) Orientation in the thickness direction (nx>nz> ny) (Y. Fujimura, TN)
agatsuka, H. Yoshimi, S. Umemoto and T. Shimomura, SI
D'92 Digest, 397 (1992)). A technique has also been developed for arbitrarily controlling the viewing angle dependence of film retardation by laminating a stretched film having a positive birefringence and a stretched film having a negative birefringence (Yasuo Fujimura, Nagatsuka Tatsuki, Hiroyuki Yoshimi, "Polarizers, Retarders", Electronic Materials, November 1991, pp.53-57; Y.Fujimur
a, T. Nagatsuka, H. Yoshimi and T. Shimomura, SID'91 D
igest, 739 (1991)). We have also developed a film phase plate for twisted nematic (TN) type liquid crystal display devices by fixing the orientation after twisting the liquid crystal molecules in the polymer.
It has been put into practical use (J. Mukai et al ,. SID'94 Digest,
p.241 (1994)).

More recently, rod-like low-molecular liquid crystals (Y. Inoue, T. Kurita, E. Yoda, T. Kaminade, T. Toyoo)
ka Y. Kobori, Proceedings of the 5th International
Display Workshops, FMC2-4, pp.255-258, 1998) and discotic liquid crystal molecules are arranged in a hybrid form.
A fixed film has also been developed, and has been put to practical use in TN-type liquid crystal display devices for the purpose of increasing the viewing angle.

The characteristics required for the film phase plate include adjusting the degree of the wavelength dispersion of the refractive index anisotropy (the temperature characteristic is reduced) in order to match the respective optical characteristics of the liquid crystal cell and the film phase plate. ), Conforming the refractive index distribution in the three-dimensional direction to that of the liquid crystal cell, uniformity of phase difference value (± 2% or less in terms of film thickness unevenness), heat resistance, moisture heat resistance, High permeability,
Workability is improved.

A general uniaxial film phase plate is produced by using a polycarbonate resin as a main raw material by a longitudinal stretching method between rolls, a roll rolling method, or a transverse tenter stretching method. In a biaxial film phase plate, a desired phase plate can be obtained by adjusting the balance and timing between longitudinal stretching and transverse stretching. In addition, in the case of a phase plate of a type in which a low-molecular liquid crystal compound is formed by aligning and fixing a low-molecular liquid crystal compound in a polymer, a polyimide alignment film is formed on a support in advance, and rubbing treatment is performed. The above polymer is applied and subjected to photopolymerization in a predetermined orientation state to fix the orientation.

[0021]

Problems relating to the film phase plate present the following problems.

(1) The refractive index anisotropy Δn of the liquid crystal composition and its wavelength dispersion characteristics can be freely adjusted to some extent under certain restrictions, but from the viewpoint of the optical design of the panel, Δn is optional. Is not always possible. Under such circumstances, it is difficult to match the wavelength dispersion characteristics of the phase difference dΔn between the liquid crystal layer and the film phase plate in a practical sense.

(2) Along with the development of film phase plate manufacturing technology, generally high-precision (± 2% or less) film thickness control (phase difference control) is possible, but the phase difference is 50 nm.
For the following low retardation films, in-plane unevenness of retardation may be a problem.

(3) When manufacturing by roll-to-roll,
The optical characteristics are different between the central portion and the end portion (peripheral portion) of the film, and the production yield cannot be greatly increased.

(4) Although the characteristics of the film phase plate have been remarkably improved by the technique for fixing the orientation of the low-molecular compound, the arrangement cannot be controlled as arbitrarily as the molecular arrangement of the liquid crystal layer in the compensating liquid crystal cell. .

(5) The phase difference cannot be changed for each RGB pixel.

[0027] Of the above-mentioned problems, the present invention aims at solving the respective problems (2), (3) and (5).

[0028]

According to the present invention, as a first solution, an organic gas or an organic vapor is brought into contact with the surface of a film phase plate mainly composed of a polymer. A method for producing a film phase plate characterized by modifying the characteristics of the film phase plate is used. As a second solution, a water vapor is brought into contact with the surface of the film phase plate mainly composed of a polymer. The method for producing a film phase plate is characterized in that the characteristics of the film phase plate are modified by using the method described above. The method for producing a film phase plate is characterized by modifying the characteristics of the film phase plate by performing irradiation. As a fourth solution, a polymer mainly comprises a polymer. By heating the surface of the film phase plate, the method of manufacturing the film phase plate is characterized by modifying the characteristics of the film phase plate. As a fifth solution, a polymer mainly comprises A method for manufacturing a film phase plate, wherein a property of the film phase plate is modified by partially performing a pressure treatment on a surface of the film phase plate to be formed. As the modification of the film phase plate, a method of contacting an organic gas or an organic vapor on the surface of the film phase plate, a method of contacting water vapor, a method of performing light irradiation, a method of heat-treating the surface of the film phase plate, and A method for producing a film phase plate, comprising modifying the characteristics of a film phase plate by two or more methods selected from a method of performing a partial pressure treatment. It is those who are.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. The measurement of the film phase difference is performed by a micro birefringence measuring device ADR-150L manufactured by Oak Manufacturing Co., Ltd.
C (measuring temperature: 25 ° C.).

Example 1 A film phase plate A0 was prepared by stretching a retardation film (100 nm retardation) manufactured by Nitto Denko Corporation in two directions, a main axis direction and a direction orthogonal to the main axis direction. When the in-plane distribution of the phase difference Δnd of the film phase plate A0 was measured with respect to light having a wavelength of 633 nm, the result shown in FIG. 2 was obtained. The measurement spot diameter at this time was 1 mm, and measurement was performed at 10 mm intervals.
As is clear from FIG. 2, the phase difference around the film phase plate is larger than the phase difference at the center of the film phase plate, and in-plane unevenness of the phase difference occurs. FIG. 3 shows a phase difference distribution in a section taken along the line YY ′ in FIG.

Next, the film phase plate A0 is irradiated with ultraviolet light having a wavelength of 365 nm through an ultraviolet light ND filter whose transmittance distribution is shown in FIG.
Was prepared. The irradiation energy at this time is 800 mJ / c
m ² . FIG. 1 shows an outline of the irradiation system.

That is, the ultraviolet light 12 emitted from the UV light source 11 is converted into a parallel light by the lens group 13, passes through the ND filter 14, and then enters the film phase plate 15.
At this time, the surface layer of the film phase plate 15 is modified according to the magnitude of the ultraviolet light energy and becomes isotropic, so that the phase difference of the light irradiation portion is reduced.

The in-plane distribution of the phase difference of the film phase plate A1 is as shown in FIG. 5, and the in-plane uniformity is greatly improved.
For example, the yield in the production of film phase plates is improved,
Its practical value is extremely large.

The modification of the surface according to this example was only on the very surface layer of the film phase plate, and no decrease in the film transmittance was observed.

In this experiment, the entire surface of the film phase plate was irradiated with ultraviolet light. However, when a portion having a large phase difference exists only partially in the plane, the ultraviolet light was spot-irradiated to irradiate the phase difference. In-plane unevenness can be eliminated.

(Example 2) Ultraviolet light having a wavelength of 365 nm was applied to an arton film phase plate 72 (having a phase difference of 30 nm) manufactured by JSR Corporation through a mask 71 having a plurality of openings of 300 μm × 100 μm shown in FIG. 30 seconds, 45
Irradiation while changing the irradiation position to seconds and 60 seconds (Step 1
10 μm) to produce a film phase plate B1. The irradiation energy at this time was 330 mJ / cm ² and 22 mJ / cm ² , respectively.
The values were 0 mJ / cm ² and 60 mJ / cm ² . FIG. 7 shows an outline of the process in the present invention.

FIG. 8 is a schematic diagram for explaining the position of irradiation with ultraviolet light, and FIG. 9 shows the distribution of the phase difference when viewed along the XX 'section in FIG. As is clear from FIG. 9, according to the present embodiment, the phase difference of the film phase plate can be changed corresponding to each of the red, green, and blue pixels, that is, the phase difference for each color light can be made uniform. Yes, its practical value is great.

Example 3 A film phase plate C0 was prepared by forming a film of norbornene resin manufactured by JSR Corporation by injection molding, and repeating the stretching operation between rolls. The in-plane distribution of the phase difference Δnd of the film phase plate C0 was
When measured with respect to light of 3 nm, the results shown in Table 1 were obtained. Here, the units of the phase difference and the (x, y) coordinates are nm and mm, respectively. As is clear from Table 1, it can be seen that a portion having a large phase difference exists in the plane of the film phase plate. In the measurement of the present retardation, data was acquired by associating the film retardation measurement location (x, y) with the value of the retardation.

Next, the film phase plate C0 was set in a thermal printer, and based on the data, only portions having a large phase difference were heated in accordance with the size to obtain a film phase plate C1. At this time, the temperature of the heating unit was 180 ° C., and the glass transition temperature (171 ° C.) of the resin used in this example was used.
° C) or higher.

Thereafter, the in-plane distribution of the phase difference Δnd in the film phase plate C1 was measured, and the results shown in Table 2 were obtained. As is clear from (Table 1) and (Table 2), according to the present invention, the variation of the in-plane phase difference can be reduced, and its practical value is large.

In this embodiment, the surface of the film is modified by heat conduction (randomization of surface polymer orientation) by bringing the printer head portion into direct contact with the surface of the film phase plate. Needless to say, a specific portion of the film surface may be heated to perform surface modification.

[0042]

[Table 1]

[0043]

[Table 2]

Example 4 A mask shown in FIG. 6 was adhered to a film phase plate (having a phase difference of 200 nm) manufactured by Nitto Denko Corporation.
This was allowed to stand for 0 second to obtain a film phase plate D1. Then, when the in-plane distribution of the phase difference of the film phase plate D1 in the XX ′ direction of FIG. 8 was measured by the same method as in Example 2, the result of FIG. 10 was obtained. It is also possible to control the phase difference for each pixel by the method of the present embodiment, which proves to be extremely effective for realizing a high-quality liquid crystal display device.

In this example, toluene was used as the organic solvent. However, similar effects were observed when other ketones such as acetone and methyl ethyl ketone and alcohols such as methanol, ethanol and propyl alcohol were used.

Similar results were obtained when water vapor was used in place of the organic solvent. Particularly, the effect was remarkable in a high-temperature water vapor atmosphere at 100 ° C. or higher or a pressurized atmosphere.

[0047]

As is clear from the above, according to the present invention, the in-plane variation of the phase difference of the film phase plate can be reduced and the yield in the production of the film phase plate can be improved. Its practical value is extremely high, for example, it is possible to control the film phase difference and to provide a high-performance liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram for explaining one embodiment of a method for producing a film phase plate of the present invention.

FIG. 2 is a view showing an in-plane distribution of retardation of a film phase plate before a process of manufacturing the film phase plate of the present invention.

FIG. 3 is a view showing a distribution of a phase difference in one cross section of the film phase plate before the film phase plate manufacturing process of the present invention is performed.

FIG. 4 is a view for explaining the transmittance distribution of an ND filter used in one embodiment of the method for producing a film phase plate of the present invention.

FIG. 5 is a view showing an in-plane distribution of retardation of the film phase plate after the film phase plate manufacturing process of the present invention is performed.

FIG. 6 is a view for explaining a mask pattern used in one embodiment of the method for producing a film phase plate of the present invention.

FIG. 7 is a process flow chart for explaining one embodiment of the method for producing a film phase plate of the present invention.

FIG. 8 is a view for explaining light-irradiated portions of a film phase plate produced by the method for producing a film phase plate of the present invention.

FIG. 9 is a diagram showing a distribution of retardation in one section of a film phase plate manufactured by the method of manufacturing a film phase plate of the present invention.

FIG. 10 is a view showing a distribution of a phase difference in one cross section of another film phase plate produced by the method for producing a film phase plate of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 UV light source 12 Ultraviolet light 13 Lens group 14 ND filter 15, 72 Film phase plate 71 Mask

Continued on the front page F term (reference) 2H049 BA06 BC03 BC05 BC22 4F073 AA14 BA06 BB01 CA53 DA08 DA09 GA01 GA05 HA02 HA05 HA11 4J002 AA001 BK001

Claims (14)

[Claims] 1. A method for producing a film phase plate, wherein the characteristics of the film phase plate are modified by bringing an organic gas or an organic vapor into contact with the surface of the film phase plate mainly composed of a polymer. 2. The method for producing a film phase plate according to claim 1, wherein said gas or said organic vapor is alcohol. 3. The method for producing a film phase plate according to claim 1, wherein said gas or said organic vapor is ketone. 4. A method for producing a film phase plate, comprising modifying the characteristics of the film phase plate by bringing water vapor into contact with the surface of the film phase plate mainly composed of a polymer. 5. A method for producing a film phase plate, comprising irradiating a surface of the film phase plate mainly composed of a polymer with light to thereby modify the characteristics of the film phase plate. 6. The method according to claim 5, wherein the main component of the irradiation light is light having a wavelength of 400 nm or less. 7. A method for producing a film phase plate, comprising heating a surface of a film phase plate mainly composed of a polymer to modify the characteristics of the film phase plate. 8. The method according to claim 7, wherein said heating means is by infrared irradiation. 9. The method according to claim 7, wherein said heating means is based on heat conduction from a high-temperature medium. 10. A method for producing a film phase plate, wherein the surface properties of the film phase plate are modified by partially subjecting the surface of the film phase plate mainly composed of a polymer to a pressure treatment. 11. A method of modifying the film phase plate, wherein a method of bringing an organic gas or an organic vapor into contact with the surface of the film phase plate, a method of contacting with water vapor, a method of irradiating light, and a heat treatment of the surface of the film phase plate. A method for producing a film phase plate, comprising modifying the properties of a film phase plate by two or more methods selected from a method and a method of partially performing a pressure treatment. 12. In the modification of the film phase plate, a mask is arranged so as to be in contact with the surface of the film phase plate or in a non-contact manner. A method for producing a film phase plate, comprising modifying characteristics of the film phase plate. 13. A film characterized in that, in the modification of the film phase plate, the characteristics of the film phase plate are partially modified by any one of claims 1 to 12. Phase plate manufacturing method. 14. The film phase plate according to claim 1, wherein, in the modification of the film phase plate, characteristics of the film phase plate are periodically changed in a plane thereof. A method for producing a film phase plate.