JP2002122733A - Phase contrast film and elliptical polarization film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase contrast film with a delay phase axis in a direction different from the longitudinal direction of a long polymer film. SOLUTION: When a gelatin layer 2 is formed on a long polymer film 3, the surface of the gelatin layer 2 is rubbed and a liquid-crystalline compound layer 1 is formed, the alignment direction (delay phase axis direction) of the liquid-crystalline compound layer 1 is different from the rubbing direction. (1) The phase contrast film is obtained, by successively forming the gelatin layer 2 and the liquid-crystalline compound layer 1 on the polymer film 3. (2) In the phase contrast film (1), the polymer film 3 is a film, based on a cellulose derivative. (3) In the phase contrast film (2), the cellulose derivative is triacetylcellulose.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a retardation film useful for an image display device, particularly a liquid crystal display device, and an elliptically polarizing film using the same.

[0002]

2. Description of the Related Art A retardation film produced by uniaxially stretching a polymer film is used for various displays, mainly liquid crystal displays. In the case of a liquid crystal display, for example, in order to perform black-and-white display in an STN-type liquid crystal display device, a retardation film having an appropriate retardation value and a polarizing film are provided. A so-called elliptically polarizing film having an absorption axis laminated at an angle is used. In the case of an organic EL display, for example, as an anti-reflection filter, a retardation film called a 波長 wavelength film and a polarizing film are set so that the slow axis of the retardation film and the absorption axis of the polarizing film become 45 °. A so-called circularly polarizing film laminated so as to be used is used. Thus, the retardation film is used for various displays in combination with the polarizing film.

However, these retardation films are:
When viewed from the front, the direction of the absorption axis of the polarizing film,
When the retardation films have different slow axis directions, a function of controlling polarized light is exhibited. Therefore, when producing the elliptically polarizing film as described above, it is necessary to laminate the polarizing film so that the absorption axis of the polarizing film and the slow axis of the retardation film are at different angles.

[0004]

The polarizing film is usually
It is obtained by uniaxially stretching a polyvinyl alcohol film impregnated with a dichroic dye. At this time, the absorption axis of the polarizing film coincides with the stretching direction. on the other hand,
The retardation film is also usually produced by uniaxially stretching a polymer film such as polycarbonate. At this time, the slow axis of the retardation film coincides with the stretching direction. Using the polarizing film and the retardation film thus produced, when producing an elliptically polarizing film as described above, one of the films had to be cut at a desired angle and laminated. . This means
This has complicated the work, reduced the production efficiency, and reduced the yield.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors formed a gelatin layer on a long polymer film, and rubbed the gelatin layer to obtain a liquid crystal compound. By forming the layer, it was found that the orientation direction (slow axis direction) of the liquid crystalline compound layer was different from the rubbing direction, and the present invention was achieved. That is, the present invention provides (1) a retardation film in which a gelatin layer and a liquid crystal compound layer are sequentially formed on a polymer film,
(2) The retardation film according to (1), wherein the polymer film is a film containing a cellulose derivative as a main component,
(3) The retardation film according to (2), wherein the cellulose derivative is triacetyl cellulose, and (4) the film containing the cellulose derivative as a main component is a film having a surface layer treated with alkali. Or (3)
The retardation film described in 1 above, (5) the gelatin layer is 0.1
(1) to (5), wherein the retardation film according to any one of (1) to (4), which has a thickness of ５5 μm, wherein (6) the gelatin layer is rubbed. The retardation film according to any one of the above (7), (7).
The liquid crystal compound layer is composed of a cured product of an ultraviolet curable or thermosetting liquid crystalline compound, the retardation film according to any one of (1) to (6), and (8) a long polymer film. After forming a gelatin layer, the surface of the gelatin layer is subjected to a rubbing treatment, and further, a liquid crystal compound layer is formed so that the orientation direction of the liquid crystal layer is different from the rubbing direction. (1) The method for producing a retardation film according to any one of (1) to (7), (9) Elliptical polarization comprising the retardation film according to any one of (1) to (7) and a polarizing film. The method for producing an elliptically polarizing film according to (9), wherein the film, the long retardation film produced by the method of (8) and the long polarizing film are laminated by roll-to-roll. , ( 1) (1) to an image display apparatus having a retardation film or elliptically polarizing film, according to any one of (10), related.

DETAILED DESCRIPTION OF THE INVENTION The retardation film of the present invention is shown in FIG.
As shown in the figure, the polymer film 3 has a structure in which a gelatin layer 2 and a liquid crystal compound layer 1 are sequentially laminated. The polymer film preferably has excellent transparency, smoothness, and processability. As such a polymer film, for example, a film containing a cellulose derivative as a main component is cited, and a film containing triacetyl cellulose as a main component is particularly preferably used. In these films, the surface layer may be made hydrophilic by an alkali treatment. The alkali treatment includes, for example, a method of immersing a film containing triacetyl cellulose as a main component in an aqueous solution of 1 to 3 N potassium hydroxide or sodium hydroxide at 30 ° C. to 50 ° C., and optionally immersing time. By changing
Desired hydrophilicity can be imparted. A film containing triacetyl cellulose as a main component that has been subjected to such treatment can improve the adhesion between the gelatin layer and the polymer film and the wettability of the aqueous gelatin solution when the gelatin layer is formed. It is particularly preferable because it can be used as a protective film for a polarizing element made of a polyvinyl alcohol film impregnated with a dye. Further, in addition to the above-described film mainly containing a cellulose derivative, a film mainly containing a cycloolefin polymer such as a norbornene derivative can be used. On such a film, a layer for improving the wettability of the above-mentioned gelatin aqueous solution and the adhesion to a polarizing element may be formed on the surface. The thickness of these plastic films is preferably about 30 to 200 μm in consideration of workability and the like when forming a liquid crystal layer.

The gelatin layer constituting the retardation film of the present invention is located between the polymer film and the liquid crystal compound layer, increases the adhesion at each interface, and forms the liquid crystal compound layer after rubbing. In this case, the liquid crystal compound layer has a role of causing the slow axis direction of the liquid crystal compound layer to be different from the rubbing direction. The gelatin layer is formed by continuously applying an aqueous solution of gelatin on a long polymer film and then drying by heating. The thickness of the gelatin layer is preferably 0.1 to 5 μm, in order to orient it in a direction different from the rubbing direction.
More preferably, the thickness is about 0.5 to 2 μm.

The rubbing treatment is performed on the gelatin layer constituting the retardation film of the present invention before forming the liquid crystal compound layer. In the rubbing treatment, for example, as shown in FIG. 2, a rubbing roll 4 made of a metal roll to which a rubbing cloth made of rayon, cotton, or the like is adhered is rotated at a high speed to convey a long polymer film 5 having a gelatin layer. This is achieved by contacting with each other. The degree of rubbing treatment is as follows: rubbing roll diameter, number of rotation of rubbing roll, contact length between rubbing roll and long polymer film,
Since it varies depending on the transport speed and transport tension of the film, the number of rubbing processes, and the like, it is appropriately determined.

The liquid crystalline compound used in the present invention includes a thermotropic liquid crystal which is a compound exhibiting liquid crystallinity in a certain temperature range, and a lyotropic liquid crystal which exhibits liquid crystallinity in a specific concentration range of a certain solution. In particular, a thermotropic liquid crystal is often used by mixing a plurality of liquid crystal compounds in order to exhibit liquid crystallinity in a wide temperature range. The liquid crystal compound may have a low molecular weight, a high molecular weight or a mixture thereof, and the liquid crystal state shown is preferably a nematic phase. Further, in order to fix the alignment state, the liquid crystal compound is preferably a compound which is polymerized or cross-linked by ultraviolet light or heat in the presence of a polymerization initiator or a cross-linking agent. As such a liquid crystal compound, a compound having a polymerizable group such as a (meth) acryloyl group, an epoxy group, or a vinyl group, or a compound having a crosslinkable functional group such as an amino group or a hydroxyl group is preferable. As such a compound, JP-A-200
A composition in which a nonionic fluoroalkyl-alkoxylate is added to a low-molecular liquid crystal compound comprising a mixture of liquid crystal compounds described in JP-A-0-98133 is exemplified.

As a method of forming the liquid crystalline compound layer of the present invention, the compound can be melted by heating and applied in a liquid or liquid crystal state to a rubbed gelatin layer as it is. In consideration of the properties and the uniformity of the coating film, it is preferable that the liquid crystalline compound is dissolved in an organic solvent and applied. As the organic solvent used when dissolving the liquid crystal compound, the compound can be dissolved, has excellent wettability on the substrate at the time of application, and does not disturb the orientation of the optically anisotropic compound after the solvent is removed. There is no particular limitation as long as it is an aromatic hydrocarbon such as toluene and xylene; ethers such as anisole, dioxane and tetrahydrofuran; methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, cyclopentanone,
-Pentanone, 3-pentanone, 2-hexanone, 3-
Ketones such as hexanone, 2-heptanone, 3-heptanone, 4-heptanone, 2,6-dimethyl-4-heptanone, alcohols such as n-butanol, 2-butanol, cyclohexanol, and isopropyl alcohol, methyl cellosolve, and acetic acid Examples include cellosolves such as methyl cellosolve and esters such as ethyl acetate, butyl acetate and methyl lactate. Further, the solvent may be a single solvent or a mixture. The concentration at which the compound is dissolved depends on the solvent solubility, wettability to the substrate, desired thickness after coating, etc., but is preferably 5 to 50% by weight, more preferably 10 to 50% by weight.
About 40% by weight is preferable.

In producing the retardation film of the present invention, for example, a gelatin aqueous solution is continuously applied on a long polymer film, and a gelatin layer is formed by heating and drying. Next, the surface of the gelatin layer is rubbed so that the rubbing direction coincides with the lengthwise direction of the film.
Next, a solution of the liquid crystalline compound dissolved using an appropriate solvent is applied onto the rubbed surface of the film, and then the solvent is removed by heating. Then, by cooling the liquid crystal compound to a temperature at which the liquid crystal compound is in a liquid crystal state, the liquid crystal compound is a rubbing direction according to various conditions such as rubbing conditions and the type and dissolution concentration of an organic solvent when the liquid crystal compound is dissolved. It can be oriented in different directions. Further, when the liquid crystal compound is polymerized or cross-linked by ultraviolet light or heat, the liquid crystal compound is polymerized or cross-linked by ultraviolet light or heat in the presence of a polymerization initiator or a cross-linking agent in an environment where the liquid crystal state is maintained. Layers can be formed. At this time, as shown in FIG. 3, the orientation direction 9 of the liquid crystal compound layer of the retardation film 10 of the present invention is different from the rubbing direction 8 (in this case, the length direction of the film coincides with the long direction). Orientation, and the orientation direction is
It differs depending on the rubbing conditions, the concentration of the solution of the liquid crystal compound, the type of solvent, the thickness of the liquid crystal compound layer to be formed, and the like, and is appropriately determined according to the intended orientation direction.
The method of applying the aqueous gelatin solution and the solution of the liquid crystal compound is not particularly limited. However, since the thickness of the liquid crystal compound layer after coating affects the optical characteristics (retardation value), a method of applying a uniform thickness can be used. Is preferred. Examples of such a coating method include a microgravure coating method, a gravure coating method, a wire bar coating method, a dip coating method, a spray coating method, and a meniscus coating method. The thickness of the liquid crystal compound layer varies depending on the desired retardation value, and the retardation value varies depending on the birefringence of the compound, but is preferably 0.05 to 10 μm, more preferably 0.1 to 10 μm. 5μ
m.

The thus obtained retardation film of the present invention and the polarizing film are adhered so that the slow axis direction of the retardation film and the absorption axis direction of the polarizing film make an appropriate angle. The elliptically polarizing film of the present invention can be obtained by laminating using an agent or an adhesive. In particular, by laminating with a roll-to-roll using a polarizing film having an absorption axis in the longitudinal direction and the retardation film of the present invention that is oriented at an angle from the longitudinal direction of the continuous polymer film, This is preferable because the step of cutting and pasting to the polarizing film can be omitted to continuously produce an elliptically polarizing film. Further, when the long polymer film is a film mainly composed of triacetyl cellulose 11 whose surface layer is alkali-treated, the alkali-treated triacetyl of the retardation film 10 of the present invention obtained as shown in FIG. Since the polarizing element 12 made of a polyvinyl alcohol film impregnated with a cellulose surface and a dichroic dye can be easily bonded with an adhesive made of an aqueous solution of polyvinyl alcohol, a thin elliptically polarizing film having a function as a protective film for the polarizing film. 13 can be obtained.

The retardation film and elliptically polarizing film of the present invention thus obtained can be used for various image display devices. For example, black and white display can be performed by using an STN liquid crystal display device. In addition, a circularly polarizing film can be used as an antireflection filter for a self-luminous display such as an organic EL display.

[0014]

The present invention will now be described more specifically with reference to examples. Example A film mainly composed of triacetyl cellulose whose surface layer has been alkali-treated (TD-8, manufactured by Fuji Photo Film Co., Ltd.)
0U), a 3% by weight aqueous solution of gelatin was applied by dip coating and dried at 100 ° C. to form a gelatin layer. Next, a rubbing roll having a roll diameter of 50 mm and a rubbing cloth made of rayon (YA-20-R: manufactured by Yoshikawa Kako Co., Ltd.) was wound on the gelatin layer surface of this film.
Rotation speed of rubbing roll: 200 m / min. , Contact length with the film: 20 mm, transport speed of the film: 10
m / min. , Transport tension of the film: 4 kgf / cm
The rubbing process was performed in the direction in which the rubbing direction coincided with the lengthwise direction of the film under the following conditions. Next, JP-A-2000-9
Liquid crystal compound according to 8133

[0015]

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42.3 parts by weight,

[0017]

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32.9 parts by weight and

[0019]

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18.8 parts by weight, 6 parts by weight of a photopolymerization initiator Irgacure 907 (manufactured by Ciba-Geigy), 0.1 part by weight of Florad FC-171 (manufactured by 3M) as a surfactant, and 174.7 parts by weight of toluene , Cyclohexanone 5
Dissolved in 8.3 parts by weight of the mixed solvent, the solid content concentration was about 30
A weight percent solution was prepared. This solution was rubbed on the surface of the gelatin layer of the film having a gelatin layer, using a microgravure coater, and transporting the film at a speed of 5 m / min. The coating is performed under such conditions that the film thickness after removing the solvent is about 1 μm, the solvent is removed by heating, air-cooled, and further cured by irradiating with a high-pressure mercury lamp (120 W / cm). A phase difference film was obtained.
The retardation value of the obtained retardation film was 135 nm, and the slow axis direction was 45 ° with respect to the longitudinal direction. Next, similarly to the retardation film of the present invention, using a film whose main layer is alkali-treated triacetyl cellulose as a main component, a polarized light composed of a uniaxially stretched polyvinyl alcohol film containing polyiodide ions as a dichroic dye. The element was sandwiched between rolls using a 4% by weight aqueous solution of polyvinyl alcohol so that the absorption axis direction of the polarizing element and the longitudinal direction of the retardation film of the present invention coincided with each other, and water was removed by heating. Thus, a circularly polarizing film of the present invention as shown in FIG. 4 was obtained by adhering to a polarizing element.

[0021]

The present invention relates to a retardation film in which a gelatin layer and a liquid crystal compound layer are sequentially formed on a polymer film, and a method for producing an elliptically polarizing film using this film. By using a film, an elliptically polarizing film can be efficiently produced and can be used for various displays.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a retardation film of the present invention.

FIG. 2 is a diagram illustrating an example of a rubbing process.

FIG. 3 is a diagram showing a relationship between a rubbing direction and an orientation direction of a liquid crystal compound layer.

FIG. 4 is a view showing a configuration of an elliptically polarizing film of the present invention.

[Explanation of symbols]

1: liquid crystal compound layer 2: gelatin layer 3: polymer film 4: rubbing roll 5: long polymer film having a gelatin layer 6: transport direction of the long polymer film 7: rotation direction of the rubbing roll 8: rubbing Direction 9: Orientation direction of liquid crystalline compound layer 10: Retardation film of the present invention 11: Triacetyl cellulose film whose surface layer has been alkali-treated 12: Polarizing element 13: Elliptic polarizing film of the present invention

Claims (11)

[Claims] 1. A retardation film in which a gelatin layer and a liquid crystal compound layer are sequentially formed on a polymer film. 2. The retardation film according to claim 1, wherein the polymer film is a film containing a cellulose derivative as a main component. 3. The retardation film according to claim 2, wherein the cellulose derivative is triacetyl cellulose. 4. The retardation film according to claim 2, wherein the film containing a cellulose derivative as a main component is a film having a surface layer treated with alkali. 5. The retardation film according to claim 1, wherein the gelatin layer has a thickness of 0.1 to 5 μm. 6. The retardation film according to claim 1, wherein the gelatin layer has been rubbed. 7. A liquid crystal compound layer comprising a cured product of an ultraviolet-curable or thermosetting liquid-crystalline compound.
The retardation film according to any one of the above items. 8. After a gelatin layer is formed on a long polymer film, the surface of the gelatin layer is subjected to a rubbing treatment, and further a liquid crystal compound layer is formed, whereby the orientation direction of the liquid crystal layer is rubbed. The method for producing a retardation film according to claim 1, wherein the direction is different from the direction. 9. An elliptically polarizing film comprising the retardation film according to claim 1 and a polarizing film. 10. The method for producing an elliptically polarizing film according to claim 9, wherein the long retardation film produced by the method of claim 8 and the long polarizing film are laminated by roll-to-roll. . 11. An image display device comprising the retardation film or the elliptically polarizing film according to claim 1.