JP2021002059A - Optical film, transfer film, image display device, method for manufacturing optical film, and method for manufacturing transfer film - Google Patents

Abstract

To reduce decrease in a retardation with time in an optical film having a quarter-wave plate constituted by a laminated structure of a retardation layer made of a liquid crystal material.SOLUTION: An optical film includes layers of a linearly polarizing plate 15 and a quarter-wave plate 16. The quarter-wave plate 16 includes, first and second retardation layers 23, 22 sequentially disposed from the linearly polarizing plate 15 side: the first retardation layer 23 has a retardation of 80 nm or more and 230 nm or less and is disposed in such a manner that the slow axis direction thereof forms an angle of 10 degrees or more and 25 degrees or less with respect to the direction of the absorption axis of the linearly polarizing plate 15; and the second retardation layer 22 has a retardation of 65 nm or more and 120 nm or less and is disposed in such a manner that the slow axis direction thereof forms an angle of 45 degrees or more and 80 degrees or less with respect to the direction of the absorption axis of the linearly polarizing plate 15.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical film that constitutes a quarter wave plate by a laminated structure of retardation layers made of a liquid crystal material.

Conventionally, with respect to an image display device, a method has been proposed in which an optical film made of a circular polarizing plate is arranged on the panel surface (viewer side surface) of an image display panel, and the reflection of external light is reduced by this optical film. Here, this optical film is composed of a linear polarizing plate and a laminated 1/4 wave plate, and the external light directed to the panel surface of the image display panel is converted into linearly polarized light by the linear polarizing plate, followed by the 1/4 wave plate. Convert to circularly polarized light. Here, the external light due to this circular polarization is reflected by the surface of the image display panel or the like, but the rotation direction of the polarizing surface is reversed during this reflection. As a result, this reflected light is converted into linearly polarized light in the direction shaded by the linear polarizing plate by the 1/4 wave plate, and then shielded by the subsequent linear polarizing plate, as a result. Emission to the outside is significantly suppressed.

Regarding this optical film, Patent Document 1 and the like include a 1/2 wavelength phase difference layer that imparts a phase difference of 1/2 wavelength to transmitted light, and 1 / that imparts a phase difference of 1/4 wavelength to transmitted light. By stacking 4 wavelength retardation layers to form a 1/4 wave plate, a liquid crystal material with positive wavelength dispersion characteristics is used, and 1/4 wavelength is obtained due to the inverse dispersion characteristics with respect to the incident light from the linear polarizing plate. A method for making the board work has been proposed. Here, the inverse dispersion characteristic is a wavelength dispersion characteristic in which the phase difference in transmitted light is smaller toward the shorter wavelength side.

Regarding such an optical film, Patent Document 2 describes a device for improving the tint when observing from an oblique direction with respect to a laminated body of a 1/2 wavelength retardation layer, a 1/4 wavelength retardation layer, and a positive C plate. Has been proposed. Further, Patent Document 3 proposes a device for transferring a 1/4 wavelength retardation layer in a configuration for producing a laminate of a 1/2 wavelength retardation layer and a 1/4 wavelength retardation layer by a transfer method. .. According to the configuration disclosed in Patent Document 3, the alignment layer can reduce damage to the retardation layer in the manufacturing process.

Here, in the transfer method, for example, when a desired layer is formed on a base material, this layer is not directly formed on the base material, but can be once peeled off on a releasable support. After the transfer body is produced by laminating the layers, the layer formed on the support is finally laminated on the base material (base material to be transferred) according to the process, demand, etc. This is a method of forming a desired layer on the base material by adhering and laminating on the substrate and then peeling off the support.

By the way, the liquid crystal layer formed from the polymerizable liquid crystal which is this kind of retardation layer has a problem that the phase difference decreases with the passage of time. As one method for solving this problem, it is conceivable to apply the method disclosed in Patent Document 3, but the corresponding oriented layer may be peeled off from the retardation layer in the manufacturing process, which is still practically impossible. There are enough problems.

Japanese Unexamined Patent Publication No. 10-68816 Japanese Unexamined Patent Publication No. 2014-224738 Japanese Unexamined Patent Publication No. 2014-013291

The present invention has been made in view of such a situation, and it is intended to reduce a decrease in phase difference due to aging with respect to an optical film constituting a quarter wave plate by a laminated structure of retardation layers made of a liquid crystal material. The purpose.

The present inventor has conducted extensive research in order to solve the above problems, and compared with the case of the conventional laminated structure of 1/2 wavelength retardation layer and 1/4 wavelength retardation layer, the thickness of the retardation layer is thinner. We came up with the idea of forming a 1/4 wave plate by the laminated structure of the above, and came up with the present invention.

(1) A linear polarizing plate and a 1/4 wave plate are laminated,
The 1/4 wave plate is
The first and second retardation layers made of a liquid crystal material are sequentially provided from the linear polarizing plate side.
The first retardation layer is
With a phase difference of 80 nm or more and 230 nm or less,
It is arranged so that the slow phase axial direction forms an angle of 10 degrees or more and 25 degrees or less with respect to the absorption axis direction of the linear polarizing plate.
The second retardation layer is
With a phase difference of 65 nm or more and 120 nm or less,
An optical film arranged so that the slow axis direction forms an angle of 45 degrees or more and 80 degrees or less with respect to the absorption axis direction of the linear polarizing plate.

According to (1), a 1/4 wave plate is formed by laminating a first retardation layer and a second retardation layer, and the light emitted from the linear polarizing plate is subjected to a wide wavelength band. Therefore, a phase difference of 1/4 wavelength can be imparted due to the wavelength characteristic of inverse dispersion. Further, in this combination of retardation layers, the thickness of the retardation layers can be reduced as compared with the case of the conventional laminated structure of 1/2 wavelength retardation layers and 1/4 wavelength retardation layers. It is possible to reduce the decrease in the phase difference due to the change with time, and thereby it is possible to prevent the change in color by arranging it on the image display panel.

(2) In (1)
The 1/4 wave plate is
An optical film having a positive C plate on either the linear polarizing plate side, the side opposite to the linear polarizing plate, or between the first retardation layer and the second retardation layer.

According to (2), the viewing angle characteristic can be further improved.

(3) In (1) or (2)
At least the 1/4 wave plate
An optical film that is a transfer layer from a transfer film.

According to (3), an optical film can be efficiently produced by using the transfer method.

(4) In a transfer film provided with a support base material and a transfer layer,
The transfer layer is a 1/4 wave plate,
The 1/4 wave plate is
The first and second retardation layers made of a liquid crystal material are sequentially provided from the side opposite to the support base material.
The first retardation layer is
With a phase difference of 80 nm or more and 230 nm or less,
The second retardation layer is
With a phase difference of 65 nm or more and 120 nm or less,
A transfer film arranged so that the slow phase axial direction forms an angle of 30 degrees or more and 60 degrees or less with respect to the slow phase axial direction of the first retardation layer.

According to (4), the transfer layer is transferred to the linear polarizing plate to provide a phase difference of 1/4 wavelength with respect to the light emitted from the linear polarizing plate in a wide wavelength band due to the reverse dispersion wavelength characteristic. can do. Further, in this combination of retardation layers, the thickness of the retardation layers can be reduced as compared with the case of the conventional laminated structure of 1/2 wavelength retardation layer and 1/4 wavelength retardation layer. It is possible to reduce the decrease in the phase difference due to the change with time, and thereby it is possible to prevent the change in color by arranging it on the image display panel.

(5) In (4)
The support base material is a long transparent film material.
The first retardation layer is
The long transparent film material is formed so that the slow axis direction forms an angle of 10 degrees or more and 25 degrees or less with respect to the longitudinal direction or the width direction.
The second retardation layer is
A transfer film formed so that the slow axis direction forms an angle of 45 degrees or more and 80 degrees or less with respect to the longitudinal direction or the width direction of the long transparent film material.

According to (5), the long film shape allows efficient production by laminating with a linear polarizing plate.

(6) In (4) or (5)
The 1/4 wave plate is
A positive C plate is provided on either the support base material side, the side opposite to the support base material, or between the first retardation layer and the second retardation layer.

According to (6), the viewing angle characteristic can be further improved.

(7) An optical film in which the transfer layer of the transfer film according to any one of (4), (5), and (6) is laminated with a linear polarizing plate.

According to (7), it is possible to produce an optical film obtained by effectively avoiding a decrease in phase difference by the transfer method.

(8) An image display device in which the optical film according to any one of (1), (2), (3), and (7) is arranged on the panel surface of the image display panel.

According to (8), in a configuration in which an optical film having a 1/4 wave plate due to a laminated structure of retardation layers made of a liquid crystal material is arranged on an image display panel surface, it is possible to reduce a decrease in retardation due to aging. It is possible to reduce the time change of the color of the image display panel surface.

(9) A laminating step of laminating a 1/4 wave plate on a linear polarizing plate by a transfer method to produce an optical film is provided.
The 1/4 wave plate is
The first and second retardation layers made of a liquid crystal material are sequentially provided from the linear polarizing plate side.
The first retardation layer is
With a phase difference of 80 nm or more and 230 nm or less,
The second retardation layer is
With a phase difference of 65 nm or more and 120 nm or less,
The laminating step is
The first retardation layer is arranged so that the slow phase axial direction forms an angle of 10 degrees or more and 25 degrees or less with respect to the absorption axis direction of the linear polarizing plate.
A method for producing an optical film in which the second retardation layer is arranged so that the slow axis direction forms an angle of 45 degrees or more and 80 degrees or less with respect to the absorption axis direction of the linear polarizing plate.

According to (9), a 1/4 wave plate is formed by stacking with the first and second retardation layers, and is inversely dispersed with respect to the light emitted from the linear polarizing plate in a wide wavelength band. A phase difference of 1/4 wavelength can be imparted depending on the wavelength characteristics. Further, in this combination of retardation layers, the thickness of the retardation layers can be reduced as compared with the case of the conventional laminated structure of 1/2 wavelength retardation layers and 1/4 wavelength retardation layers. It is possible to reduce the decrease in the phase difference due to the change with time, and thereby it is possible to prevent the change in color by arranging it on the image display panel.

(10) In (9)
The laminating step is
A method for producing an optical film, comprising a laminating step relating to a 1/4 wave plate for producing a 1/4 wave plate by laminating the first and second retardation layers.

According to (10), damage to the second retardation layer can be reduced because the second retardation layer having a thin thickness can be formed into a laminated body at an early stage.

(11) In (9)
The laminating step is
The C plate laminating step of laminating the second retardation layer with the C plate and the 1/4 wave plate by laminating the laminated body of the second retardation layer and the C plate with the first retardation layer. A method for producing an optical film, which comprises a laminating step for a 1/4 wave plate.

According to (11), damage to the second retardation layer can be reduced because the second retardation layer having a thin thickness can be formed into a laminated body at an early stage.

(12) A process for producing the first retardation layer on the support base material of the first retardation layer, and a step for producing the first retardation layer.
A process for producing the second retardation layer on the support base material of the second retardation layer, and a process for producing the second retardation layer.
A laminating step of laminating the first retardation layer and the second retardation layer is provided.
The step of manufacturing the first retardation layer is
The first retardation layer was prepared by a retardation of 80 nm or more and 230 nm or less.
The step of manufacturing the second retardation layer is
The second retardation layer was prepared by a retardation of 65 nm or more and 120 nm or less.
The laminating step is
A method for producing a transfer film, which is laminated so that the slow-phase axial direction of the second retardation layer forms an angle of 30 degrees or more and 60 degrees or less in the slow-phase axial direction of the first retardation layer.

According to (12), the transfer layer is transferred to the linear polarizing plate to impart a phase difference of 1/4 wavelength to the light emitted from the linear polarizing plate in a wide wavelength band due to the wavelength characteristic of inverse dispersion. can do. Further, in this combination of retardation layers, the thickness of the retardation layers can be reduced as compared with the case of the conventional laminated structure of 1/2 wavelength retardation layers and 1/4 wavelength retardation layers. It is possible to reduce the decrease in the phase difference due to the change with time, and thereby it is possible to prevent the change in color by arranging it on the image display panel.

(13) The linear polarizing plate and the 1/4 wave plate are laminated,
The 1/4 wave plate is
The first and second retardation layers made of a liquid crystal material are sequentially provided from the linear polarizing plate side.
In the emitted light incident from the linear polarizing plate side and emitted from the 1/4 wave plate, the emitted light having wavelengths of 450 nm and 650 nm is a circle whose elliptic orientation is within 90 ° ± 15 ° and within 180 ± 10 °. An optical film that is polarized and whose emitted light having a wavelength of 550 nm is circularly polarized with an ellipticity of 0.9 or more.

According to (13), even when a 1/4 wave plate is manufactured by laminating thin retardation layers, reflection can be sufficiently suppressed in a wide wavelength band.

According to the present invention, it is possible to reduce a decrease in phase difference due to aging with respect to an optical film constituting a quarter wave plate by a laminated structure of retardation layers made of a liquid crystal material.

It is sectional drawing which shows the image display apparatus which concerns on 1st Embodiment of this invention. It is a figure which provides the explanation of the optical film applied to the image display device of FIG. It is sectional drawing which shows the transfer film which concerns on the optical film of FIG. It is a figure which provides the explanation of each transfer film used for the transfer film of FIG. It is a figure which provides the explanation of the manufacturing process of the transfer film of FIG. It is a chart which shows the examination result.

[First Embodiment]
[Optical film and image display device]
FIG. 1 is a diagram showing an image display device according to the first embodiment of the present invention. In the image display device 11, the optical film 13 is arranged on the panel surface (viewer side surface) of the image display panel 12. Here, the image display panel 12 is, for example, a liquid crystal display panel, and displays a desired color image. The image display panel 12 is not limited to the liquid crystal display panel, and various image display panels such as an image display panel using an organic EL can be widely applied.

The optical film 13 is an antireflection film that suppresses the reflection of foreign light coming to the image display panel 12 by the function of a circularly polarizing plate. Therefore, the optical film 13 is formed by laminating a linear polarizing plate 15 and a quarter wave plate 16. The optical film 13 is attached to the panel surface (viewer side surface) of the image display panel 12 by the adhesive layer 14 after peeling off a separator film (not shown) to expose the adhesive layer 14 with a pressure-sensitive adhesive. Be retained. Instead of the pressure-sensitive adhesive, the optical film 13 may be arranged with various adhesives or adhesives such as an ultraviolet curable resin. Further, the linear polarizing plate 15 and the quarter wave plate 16 are integrated via the adhesive layer 17. Here, although various adhesives such as an ultraviolet curable resin, a thermosetting resin, and a pressure-sensitive adhesive can be widely applied to the adhesive layer 17, an ultraviolet curable resin is used from the viewpoint of reducing the overall thickness. It is preferable to apply it, and in this case, it can be prepared with a thickness of about 1 μm.

The 1/4 wave plate 16 is composed of a laminate in which a first retardation layer 23 and a positive C plate 20 made of a liquid crystal material and a second retardation layer 22 made of a liquid crystal material are bonded by adhesive layers 19 and 20. Will be done.

Here, as shown in FIG. 2, the optical film 13 has slow axes of the first retardation layer 23 and the second retardation layer 22 with respect to the absorption axis of the linear polarizing plate 15 indicated by the arrows (arrows, respectively). (Indicated by) are arranged counterclockwise so as to form angles θ1 and θ2, which will be described later, respectively. Here, the optimum value for reducing the color change observed from an angle is that the smaller the angle of the slow axis of the first and second retardation layers, the smaller the phase difference and the second position of the first retardation layer. The phase difference of the phase difference layer tends to be small. However, if the angles θ1 and θ2 are too small, the phase difference change after the high temperature durability test can be suppressed, but the tint change cannot be reduced.

As a result, the optical film 13 sufficiently suppresses the reflection of external light in a wide wavelength band used for displaying a color image. From the viewpoint of effectively avoiding changes in the color of the display screen depending on the viewing direction and efficiently reflecting incident light in a wide wavelength band of the visible light region, the absorption axis of the linear polarizing plate 15 and the first phase difference. The angle θ1 formed by the slow axis of the layer 23 is preferably set to an angle of 10 degrees or more and 25 degrees or less, preferably 12 degrees or more and 23 degrees or less, and more preferably 14 degrees or more and 20 degrees or less. Similarly, the angle θ2 formed by the absorption axis of the linear polarizing plate 15 and the slow axis of the second retardation layer 22 is 45 degrees or more and 80 degrees or less, preferably 52 degrees or more and 74 degrees or less, more preferably 52 degrees. It is desirable to set the degree to 62 degrees or more. On the premise that the conditions of the angles θ1 and θ2 are satisfied, the slow axis direction of the second retardation layer 22 is 30 degrees or more and 60 degrees or less with respect to the slow axis direction of the first retardation layer 23. The angle is preferably set to be 38 degrees or more and 58 degrees or less, and more preferably 38 degrees or more and 48 degrees or less.

Similarly, the phase difference of the first retardation layer 23 is preferably 80 nm or more and 230 nm or less, preferably 90 nm or more and 220 nm or less, and more preferably 90 nm or more and 150 nm or less in transmitted light having a wavelength of 550 nm. Similarly, the phase difference of the second retardation layer 22 is preferably 65 nm or more and 120 nm or less, preferably 74 nm or more and 110 nm or less, and more preferably 74 nm or more and 95 nm or less in transmitted light having a wavelength of 550 nm.

When the 1/4 wave plate is formed by the laminated body of the first retardation layer 23 and the second retardation layer 22 in this way, the 1/2 wavelength retardation layer and the 1/4 wavelength retardation layer are laminated. The thickness of each retardation layer can be reduced as compared with the case of the structure. Thereby, in this embodiment, it is possible to reduce the decrease in the phase difference due to the change with time as compared with the conventional case. The reason why the decrease in the retardation can be reduced by reducing the thickness of the retardation layer in this way is that the thickness of the retardation layer is reduced so that the retardation layer is thicker than when the retardation layer is thicker. It is considered that this is because the liquid crystal material constituting the layer is sufficiently crosslinked.

The optical film 13 configured in this way has an elliptical orientation of 90 degrees ± in the emitted light having a wavelength of 450 nm and 650 nm in the emitted light incident from the linear polarizing plate 155 side and emitted from the 1/4 wave plate 16. It is circularly polarized light within 15 degrees and within 180 ± 10 degrees, and the emitted light having a wavelength of 550 nm is set to be circularly polarized light having an ellipticity of 0.9 or more. By being set in this way, the optical film 13 has a reverse dispersion wavelength characteristic with respect to the incident light of the linear polarizing plate in a wide wavelength band even when the 1/4 wavelength plate is formed by laminating thin retardation layers. It is possible to impart a phase difference to the transmitted light, and generally a laminated structure of a widened phase difference layer (for example, a laminated structure of a 1/2 wavelength retardation layer and a 1/4 wavelength retardation layer, which is 1 / The phase difference of the two-wavelength retardation layer is set to 275 nm, and this 1/2 wavelength retardation layer is arranged so that the slow axis forms an angle of 15 degrees with respect to the absorption axis of the linear polarizing plate, and is about 1/4 wavelength. Compared to this embodiment, the phase difference of the retardation layer is 135 nm, and the 1/4 wavelength retardation layer is arranged so that the slow axis forms an angle of 75 degrees with respect to the absorption axis of the linear polarizing plate). In such a configuration, the hues (a *, b *) when observed from the front tend to deviate from 0, but the change in color when observed from an angle is reduced. As a result, the color of the display screen can be reduced and the reflected light can be sufficiently suppressed in a wide wavelength band.

Here, the elliptical orientation related to elliptically polarized light is a case where the transmission axis direction of the linear polarizing plate 15 is 0 degrees. The measurement can be performed by KOBRA-21ADH Oji Measuring Instruments Co., Ltd.

The positive C plate 20 may be arranged between the linear polarizing plate 15 and the first retardation layer 23, or may be arranged on the image display panel 12 side of the second retardation layer 22. Further, if the change in color in the viewing angle direction can be sufficiently reduced in practice, the positive C plate 20 may be omitted. Further, instead of the optical compensation by the positive C plate, the optical compensation by the combination of the positive C plate and the negative C plate may be applied. Further, the first retardation layer 23, the second retardation layer 22, and the positive C plate 20 may have corresponding alignment layers integrally arranged.

Here, in the linear polarizing plate 15, for example, an optical functional layer having an optical function as a linear polarizing plate is produced by adsorbing and orienting iodine compound molecules on a film material made of polyvinyl alcohol (PVA), and the optical functional layer is referred to as, for example, TAC. It is configured to be sandwiched by a base material made of a transparent film made of (Triacetylcellulose) or the like. Although various adhesives such as ultraviolet curable resin, thermosetting resin, and pressure-sensitive adhesive can be widely applied to the adhesive layers 18 and 19, the ultraviolet curable resin is used from the viewpoint of reducing the overall thickness. It is preferable to apply it, and in this case, it can be prepared with a thickness of about 1 μm.

[Transfer]
In the optical film 13, the 1/4 wave plate 16 and the linear polarizing plate 15 are integrated by the adhesive layer 17, and the transfer method is applied to a series of processes related to the integration. Thereby, in this embodiment, the substrate to be transferred is a linear polarizing plate 15, and the layers (transfer layers) to be transferred are the first retardation layer 23, the adhesive layer 19, the positive C plate 20, and the adhesive layer 18. , A laminated body of the second retardation layer 22.

FIG. 3 is a diagram showing the configuration of the transfer film 21. On the support base material 26, the transfer film 21 has an orientation layer 25 related to the second retardation layer 22, a second retardation layer 22, an adhesive layer 18, a regular C plate 20, an adhesive layer 19, and a first. The retardation layer 23, the alignment layer 24 related to the first retardation layer 23, and the base material 27 are provided.

Here, in this embodiment, as shown in FIGS. 4A, 4B, and 4C, the transfer film 21 is formed on the support base material 26 with the orientation layer 25 relating to the second retardation layer 22. , The transfer film 31 formed by producing the second retardation layer 22, the transfer film 33 formed by forming the positive C plate 20 on the support base material 32, and the first retardation layer on the support base material 27. Using the transfer film 34 produced by producing the alignment layer 24 and the first retardation layer 23 according to 23, the first retardation layer 23, the positive C plate 20, and the second retardation layer 22 are subjected to a transfer method. Is laminated. Instead of laminating the first retardation layer 23, the positive C plate 20, and the second retardation layer 22 by a transfer method using each transfer film, all or part of this laminate is placed on the support base material. It may be produced by sequentially applying a coating liquid to the surface and performing an exposure treatment.

The transfer film 21 is obtained after the base material 27 is integrally peeled from the alignment layer 24 of the first retardation layer 23, then attached to the linear polarizing plate 15 by the adhesive layer 17 and held by the linear polarizing plate 15. The support 26 is integrally peeled from the alignment layer 25 of the second retardation layer 22, and as a result, the transfer layer 16 is laminated on the linear polarizing plate 15 by the transfer method.

Here, the support base materials 26, 32, and 27 support the corresponding transfer layer so that they can be peeled off, and after the transfer layer is adhered and laminated on the base material to be transferred, they are appropriately peeled off and removed at appropriate times. It is a base material. In this embodiment, a PET (Polyethylene terephthalate) film, which is a transparent film material, is applied, whereby the transfer films 21, 31, 33, and 34 are configured so that the optical properties can be inspected. The PET film is corona-treated as necessary, whereby the adhesive force is appropriately set. The support base materials 26, 32, and 27 may be coated with a resin film material made of a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, or polyethylene aphthalate, or a resin such as a polyolefin resin such as polypropylene or polymethylpentene. Good.

In this embodiment, a photo-alignment layer is applied to the alignment layers 25 and 24. Various photo-alignment layer materials capable of setting the orientation-regulating force by irradiation with polarized ultraviolet rays can be applied to the photo-alignment layer. More specifically, in this embodiment, for example, a photodimerization type material or an isomerization material is applied to the orientation layers 24 and 25. For this photodimerized material, see "M. Schadt, K. Schmitt, V. Kozinkov and V. Chigrinov: Jpn. J. Appl. Phys., 31, 2155 (1992)", "M. Schadt, H. Seiberle and A. Schuster: Nature, 381, 212 (1996) ”etc. can be used. Further, as the isomerization material, the constitution disclosed in Japanese Patent No. 5170468, International Publication No. WO13 / 191251, International Publication No. WO14 / 01688, etc. can be applied. Instead of the alignment layers 24 and 25 by the photo-alignment layer, an alignment layer prepared by rubbing treatment such as polyimide film and PVA, and an orientation layer prepared by transferring fine uneven shape by rabin treatment by shaping treatment are applied. You may.

The retardation layers 23 and 22 are produced by solidifying the liquid crystal material in a state of being oriented by the orientation regulating force of the alignment layers 25 and 24. Further, the C plate 20 is produced by solidifying a liquid crystal compound to which an additive that promotes vertical orientation is added. As this additive, for example, by using the additives described in JP-A-2005-173410, JP-A-2006-57051, and JP-A-2006-106662, the liquid crystal is vertically oriented without using a special alignment layer. be able to. The C plate 20 may be produced by producing a corresponding orientation layer.

Various liquid crystal materials applied to this type of optical film can be widely applied to the retardation layers 22 and 23 and the positive C plate 20. More specifically, the retardation layers 22, 23 and the positive C plate 20 contain a polymerizable liquid crystal composition. This polymerizable liquid crystal composition may contain an anti-blocking agent or the like in addition to a liquid crystal compound (hereinafter, also referred to as a “rod-like compound”) which is liquid crystal and has a polymerizable functional group in the molecule. Further, instead of the rod-shaped compound, a liquid crystal compound made of a discotic liquid crystal may be applied.

The rod-shaped compound has a refractive index anisotropy, and has a function of imparting desired retardation by regularly arranging the rod-shaped compounds by the orientation-regulating force of the corresponding alignment layer and the orientation-regulating force of the additive that promotes vertical alignment. Has. Examples of the rod-shaped compound include materials showing a liquid crystal phase such as a nematic phase and a smectic phase. However, the nematic phase is easily arranged in a regular manner as compared with a liquid crystal compound showing another liquid crystal phase. It is more preferable to use the rod-shaped compound shown.

Specific examples of the rod-shaped compounds used for the phase differences 22, 23 and the positive C plate in the present embodiment include compounds represented by the following formulas (1) to (16).

Further, as the liquid crystal compound by the discotic liquid crystal applied to the retardation layers 22 and 23, for example, the constitution disclosed in JP2012-042530A, JP2005-283670A and the like can be widely applied.

More specifically, for example, the following liquid crystal compounds disclosed in JP-A-2001-183643 and JP-A-9-073081 can be applied.

〔Manufacturing process〕
In the manufacturing process of the transfer film 21, the transfer film 31 is manufactured in the manufacturing process of the transfer film 31. Here, in the manufacturing process of the transfer film 31, the base material 26 is provided by the shape of the long film wound on the roll, and the coating liquid related to the alignment layer 25 is applied while the base material 26 is pulled out from the roll and conveyed. After the work, it is dried to prepare a material layer of the alignment layer 25. Then, the oriented layer 25 is produced by irradiating ultraviolet rays with linearly polarized light whose direction (direction of an angle θ2 with respect to the longitudinal direction or width direction of the base material) of FIG. 2 is the direction of the polarizing surface. Subsequently, the coating liquid for the retardation layer 22 is applied and dried, and then cured by irradiation with unpolarized ultraviolet rays, whereby the second retardation layer 22 is produced.

Further, in this manufacturing step, the transfer film 33 is manufactured in the manufacturing step of the transfer film 33. Here, in the manufacturing process of the transfer film 33, the base material 32 is provided by the shape of the long film wound on the roll, and the coating liquid related to the positive C plate 20 is applied while the base material 32 is pulled out from the roll and conveyed. After coating and drying, it is cured by irradiation with unpolarized ultraviolet rays, whereby a positive C plate 20 is produced and a transfer film 33 is produced.

Further, in the transfer film 34 manufacturing process, the base material 27 is pulled out from the roll and conveyed, and the coating liquid for the alignment layer 24 is applied and then dried to prepare the material layer of the alignment layer 24. After that, the oriented layer 24 is produced by irradiating ultraviolet rays with linearly polarized light whose direction (direction of an angle θ1 with respect to the longitudinal direction or width direction of the base material) described above with respect to FIG. 2 is the direction of the plane of polarization. Subsequently, the coating liquid for the retardation layer 23 is applied and dried, and then cured by irradiation with unpolarized ultraviolet rays, whereby the first retardation layer 23 is produced.

In this manufacturing step, as shown in FIG. 5 (A), the transfer films 31 and 33 are laminated by the adhesive layer 18, and then the base material 32 of the transfer film 33 is peeled off as shown in FIG. 5 (B). To do. Subsequently, as shown in FIG. 5C, the transfer film 34 is laminated by the adhesive layer 19 to produce the transfer film 21.

Instead of laminating the laminated body of the first retardation layer, the positive C plate, and the second retardation layer on the linear polarizing plate 15 by the transfer method in this way, the first retardation layer, the positive C plate, and the first The retardation layers of 2 may be sequentially laminated on the linear polarizing plate 15 by a transfer method. Further, the first retardation layer and the laminated body of the positive C plate may be laminated on the linear polarizing plate 15, and then the second retardation layer may be laminated. Further, after laminating the first retardation layer on the linear polarizing plate 15, the positive C plate and the laminate of the second retardation layer may be laminated. However, since the second retardation layer is extremely thin and easily damaged in the manufacturing process, when it is arranged on the linear polarizing plate, it is laminated with the positive C plate and the first retardation layer in advance. It is desirable to place it.

〔Study results〕
Samples of Examples and Comparative Examples were prepared and evaluated.

[Example 1]
[First retardation layer]
The following materials were mixed and dissolved, and reacted at 85 ° C. for 20 hours to produce a copolymer solution (solid content concentration: 20 wt%).
4- [6- (2-methacryloyloxyethylamino force rubonyloxy) hexyloxy] cinnamic acid methyl ester: 40.0 g
2-Hydroxyethyl methacrylate: 10.0 g
α, α'-azobisisobutyronitrile (polymerization catalyst): 1.2 g
Propylene glycol monomethyl ether acetate (solvent): 204.8 g

This copolymer solution was mixed and dissolved according to the following compounding ratio to prepare a composition for a photoalignment layer.
Copolymer solution: 5
Polyester polyol (adipic acid / diethylene glycol copolymer) (number average molecular weight 4,800): 0.8
Hexamethoxymethylmelamine (crosslinking agent): 1
P-luene sulfonic acid-hydrate (crosslink catalyst): 0.1
Propylene glycol monomethyl ether: 41.4

This composition for a photo-alignment layer is subjected to corona treatment of a PET film having a thickness of 50 μm (Toyobo, E5100: a film material having a corona-treated surface on one side and a smooth surface on which the other surface is not subjected to any corona treatment). The surface was die-coated with a dry thickness of 100 nm and dried at 110 ° C. to form a material layer of a photo-alignment layer.

Then, linearly polarized ultraviolet rays were irradiated with an integrated light amount of 20 mJ / cm ² to prepare an alignment layer 24 related to the first retardation layer 23.

Further, a composition for a retardation layer (coating liquid for the retardation layer) having the following composition is die-coated on the alignment layer 24 with a drying thickness of 0.7 μm, dried, and then irradiated with unpolarized ultraviolet rays. The retardation layer 23 of No. 1 was prepared, and the transfer film 34 related to the first retardation layer 23 was prepared by these.

The following (3-1) compound: 40 parts by weight The following (3-2) compound: 30 parts by weight The following (3-3) compound: 30 parts by weight Initiator (2-benzyl-2-dimethylamino-1- (4-Morphorinophenyl) -butanone-1): 5 parts by weight Fluorine-based surfactant: 0.01 parts by weight MEK: 400 parts by weight MIBK: 400 parts by weight Cyclohexanone: 100 parts by weight

From the transfer film 34 produced in this manner, the first retardation layer 23 was transferred to a glass plate via an adhesive sheet to prepare a glass plate with a liquid crystal layer, and the retardation was measured. The in-plane phase difference was 90 nm. When this glass plate with a liquid crystal layer was stored at 85 ° C. for 24 hours, the in-plane retardation was maintained at 87 nm, which caused a slight decrease in the retardation.

[Second retardation layer]
A transfer film 31 related to the second retardation layer 22 was produced in the same manner as the first retardation layer 23. However, the polarization direction of the polarized ultraviolet rays related to the alignment layer 25 is the direction corresponding to the slow axis direction of the second retardation layer 22 described above with respect to FIG. The dry thickness of the retardation layer composition was 0.73 μm.

Regarding the transfer film 31 related to the second retardation layer 22, a glass plate with a liquid crystal layer was produced in the same manner as in the first retardation layer 23, and the retardation was measured. The in-plane phase difference was 95 nm. When this glass plate with a liquid crystal layer was stored at 85 ° C. for 24 hours, the in-plane phase difference was 92 nm.

The slow-phase axial direction of the first retardation layer 23 in the transfer film 34 thus produced and the slow-phase axial direction of the second retardation layer 22 in the transfer film 31 form an angle of 38 degrees. Attached to a glass plate via an adhesive sheet, and using a phase difference measuring device (manufactured by KOBRA-21ADH Oji Measuring Instruments Co., Ltd.), incident light with linearly polarized light at wavelengths of 450 nm, 550 nm, and 650 nm (for the emitted light of the linear polarizing plate 15). The ellipticity with respect to the incident light having the corresponding polarization plane) and the elliptical azimuth angle with respect to the incident light (same as above) with linearly polarized light having wavelengths of 450 nm and 650 nm were measured and found to be 0.71, 0.93, and 0.71 respectively. The ellipticity, 78 degrees, and 172 degrees elliptical azimuth angles were measured, and good values were obtained. The elliptical azimuth was measured with the transmission axis direction of the linear polarizing plate set to 0 degrees.

[Transfer process]
The transfer film 34 related to the first retardation layer 23 is attached to the linear polarizing plate by an adhesive sheet in a direction in which the slow axis direction forms an angle of 14 degrees with respect to the absorption axis of the linear polarizing plate, and then oriented. The base material 27 was peeled off integrally with the layer 24, thereby producing a laminated body of the linear polarizing plate and the first retardation layer 23.

Further, the linear polarizing plate 15 and the first phase difference are formed through the adhesive sheet in a direction in which the slow axis direction of the second retardation layer 22 forms an angle of 52 degrees with respect to the absorption axis direction of the linear polarizing plate. After the second retardation layer 22 is attached to the laminated body of the layer 23, the base material 26 is peeled off integrally with the alignment layer 25 related to the second retardation layer 22, whereby the linear polarizing plate 15 and the first And a laminated body with the second retardation layers 23 and 22 were produced, and an optical film 13 which is an antireflection film using a circularly polarizing plate was produced.

The optical film 13 was evaluated by incorporating it into Galaxy S4 (manufactured by Samsung Electronics) using an adhesive layer. In the Galaxy S4, after removing the antireflection film and the like from the image display panel surface, an optical film to be evaluated was placed. When the display screen of the sample prepared in this manner was visually observed, it was observed in black color, whereby the first and second retardation layers were laminated with respect to the incident light from the linear polarizing plate in a wide wavelength band. It turned out that the body functions as a 1/4 wave plate.

When this sample was stored at 85 ° C. for 24 hours and then the change in color was observed, no change in color could be confirmed.

[Examples 2 to 13, Comparative Examples 1 and 2]
In the configuration of Example 1, Examples and Comparative Examples were created by changing the thicknesses of the first and second retardation layers 23 and 22 and the angles θ1 and θ2 related to the arrangement, and evaluated in the same manner as in Example 1. .. Note that Comparative Example 1 has a configuration in which the second retardation layer is omitted.

FIG. 6 is a chart showing the evaluation results of Examples 1 to 13 and Comparative Examples 1 and 2 together with the settings of the first and second retardation layers 23 and 22. In FIG. 6, as for the color of the mounted product, the degree to which the change in color cannot be perceived is set to "none", and although the change in color can be recognized by detailed observation, there are "some cases" that are practically sufficient. The one whose color changes to the extent that it is not practically used is regarded as "yes". In FIG. 6, the change in phase difference is indicated by ΔRe. In Comparative Example 1, although there was no change in color, the display screen was observed due to the reddish color, which proved to be still insufficient for practical use.

[Example 14]
[Positive C plate]
The following materials were mixed and dissolved to prepare a composition for an oriented layer.
Tricyclodecanedimethanol diacrylate (carbon content ratio = 4.5)
: 100 parts by weight Orientation control compound (FC-4430, manufactured by 3M Company): 5 parts by weight MEK: 157.5 parts by weight
2-Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one (initiator): 8 parts by weight

This composition for an alignment layer is die-coated on the corona surface of a PET film (Toyobo, E5100) having a thickness of 50 μm with a dry thickness of 2 μm, dried at 80 ° C., and then irradiated with ultraviolet rays with an integrated light intensity of 120 mJ / cm ^2. It was cured to prepare an orientation layer for the C plate.

Then, the composition for a retardation layer obtained by mixing and dissolving the following materials on the alignment layer is die-coated to a dry thickness of 1 μm, dried at 100 ° C. and oriented, and the integrated light intensity is 100 mW / cm ^2. A transfer film 33 provided with a positive C plate 20 was produced by irradiating with ultraviolet rays and curing.

The following (4-1) compound: 40 parts by weight The following (4-2) compound: 30 parts by weight The following (4-3) compound: 30 parts by weight
2-Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one (initiator): 5 parts by weight MEK: 300 parts by weight MIBK: 200 parts by weight Cyclohexanone: 100 parts by weight

For this transfer film 33, a glass plate with a liquid crystal layer was produced in the same manner as the retardation layer according to the above-described embodiment, and the retardation was measured. The out-of-plane phase difference was -100 nm. When this glass plate with a liquid crystal layer was stored at 85 ° C. for 24 hours, the out-of-plane phase difference was −99 nm.

[Transfer process]
The optical film 13 was produced by combining the C plate thus produced and the first and second retardation layers of Example 1. That is, after the transfer film 34 related to the first retardation layer 23 is attached to the linear polarizing plate by an adhesive sheet in a direction in which the slow axis direction forms an angle of 14 degrees with respect to the absorption axis of the linear polarizing plate 15. , The base material 27 was peeled off integrally with the alignment layer 24, thereby producing a laminated body of the linear polarizing plate and the first retardation layer 23.

Then, after laminating the C plate on the laminated body of the linear polarizing plate and the first retardation layer 23 via the adhesive layer, the base material is peeled off integrally with the alignment layer, whereby the linear polarizing plate, the first A laminate of the retardation layer 23 and the C plate was produced.

Further, depending on the direction in which the slow axis direction of the second retardation layer 22 forms an angle of 52 degrees with respect to the absorption axis direction of the linear polarizing plate, the linear polarizing plate 15 and the first phase difference are passed through the adhesive sheet. After the second retardation layer 22 is bonded to the laminated body of the layers 23 and the C plate, the base material 26 is peeled off integrally with the alignment layer 25 related to the second retardation layer 22, thereby providing the C plate. An optical film 13 which is an antireflection film using a circularly polarizing plate was produced.

The optical film 13 was evaluated in the same manner as in Examples 1 to 13. When the change in color was observed after storage at 85 ° C. for 24 hours, no change in color could be confirmed. Further, it was not possible to observe the change in color between the observation from the front direction and the observation from the oblique direction, and it was confirmed that the viewing angle characteristics were sufficiently improved by the positive C plate.

[Other Embodiments]
Although the specific configuration suitable for carrying out the present invention has been described in detail above, the present invention can be further modified and further combined with the above-described embodiments without departing from the spirit of the present invention. ..

That is, in the above-described embodiment, the case where the optical film is produced by the continuous processing of the long film material has been described, but the present invention is not limited to this, and can be widely applied to the case where the optical film is produced by the processing of a single sheet. it can.

Further, in the above-described embodiment, the case where the transfer layer is transferred to the linear polarizing plate formed by sandwiching the optical functional layer having an optical function as the linear polarizing plate between the base materials has been described, but the present invention is not limited to this. , The linear polarizing plate base material on the transfer layer side may be omitted, and the linear polarizing plate may be directly transferred to the optical functional layer of the linear polarizing plate.

Further, in the above-described embodiment, the case where the alignment layer is provided to prepare the retardation layer has been described, but the present invention is not limited to this, and the configuration of the alignment layer is omitted, for example, a photo-alignment liquid crystal having a photo-alignment function. It can also be widely applied when a retardation layer is formed by applying a photo-orientation method using a polymer.

11 Image display device 12 Image display panel 13 Optical film 14 Adhesive layer 15 Linear polarizing plate 16 1/4 wave plate (transfer layer)
17, 18, 19 Adhesive layer 20 Positive C plate
21, 31, 33, 34 Transfer film 22, 23 Phase difference layer 24, 25 Orientation layer 26, 27, 32 Base material

Claims (12)

A linear polarizing plate and a 1/4 wave plate are laminated,
The 1/4 wave plate is
The first and second retardation layers made of a liquid crystal material are sequentially provided from the linear polarizing plate side.
The first retardation layer is
With a phase difference of 80 nm or more and 230 nm or less,
It is arranged so that the slow phase axial direction forms an angle of 10 degrees or more and 25 degrees or less with respect to the absorption axis direction of the linear polarizing plate.
The second retardation layer is
With a phase difference of 65 nm or more and 120 nm or less,
The retarding axial direction is arranged so as to form an angle of 45 degrees or more and 80 degrees or less with respect to the absorption axis direction of the linear polarizing plate.
An optical film having a thickness of 1 μm or less for both the first retardation layer and the second retardation layer. The 1/4 wave plate is
The optical film according to claim 1, wherein a positive C plate is provided on either the linear polarizing plate side, the side opposite to the linear polarizing plate, or between the first retardation layer and the second retardation layer. At least the 1/4 wave plate
The optical film according to claim 1 or 2, which is a transfer layer from a transfer film. In a transfer film provided with a support base material and a transfer layer,
The transfer layer is a 1/4 wave plate,
The 1/4 wave plate is
The first and second retardation layers made of a liquid crystal material are sequentially provided from the side opposite to the support base material.
The first retardation layer is
With a phase difference of 80 nm or more and 230 nm or less,
The second retardation layer is
With a phase difference of 65 nm or more and 120 nm or less,
The first retardation layer is arranged so that the slow phase axial direction forms an angle of 30 degrees or more and 60 degrees or less with respect to the slow phase axial direction.
A transfer film having a thickness of 1 μm or less for both the first retardation layer and the second retardation layer. The support base material is a long transparent film material.
The first retardation layer is
The long transparent film material is formed so that the slow axis direction forms an angle of 10 degrees or more and 25 degrees or less with respect to the longitudinal direction or the width direction.
The second retardation layer is
The transfer film according to claim 4, wherein the slow axis direction is formed so as to form an angle of 46 degrees or more and 80 degrees or less with respect to the longitudinal direction or the width direction of the long transparent film material. The 1/4 wave plate is
Claim 4 or claim, wherein a positive C plate is provided on the support base material side, on the side opposite to the support base material, or between the first retardation layer and the second retardation layer. 5. The transfer film according to 5. An optical film in which the transfer layer of the transfer film according to any one of claims 4, 5, and 6 is laminated with a linear polarizing plate. An image display device in which the optical film according to any one of claims 1, 2, 3, and 7 is arranged on a panel surface of an image display panel. It is provided with a laminating step of laminating a 1/4 wave plate on a linear polarizing plate by a transfer method to produce an optical film.
The 1/4 wave plate is
The first and second retardation layers made of a liquid crystal material are sequentially provided from the linear polarizing plate side.
The first retardation layer is
With a phase difference of 80 nm or more and 230 nm or less,
The second retardation layer is
With a phase difference of 65 nm or more and 120 nm or less,
The laminating step is
The first retardation layer is arranged so that the slow phase axial direction forms an angle of 10 degrees or more and 25 degrees or less with respect to the absorption axis direction of the linear polarizing plate.
The second retardation layer is arranged so that the slow phase axial direction forms an angle of 45 degrees or more and 80 degrees or less with respect to the absorption axis direction of the linear polarizing plate.
A method for producing an optical film, wherein the thickness of the first retardation layer and the second retardation layer are both 1 μm or less. The laminating step is
The method for producing an optical film according to claim 9, further comprising a laminating step relating to a 1/4 wave plate for producing a 1/4 wave plate by laminating the first and second retardation layers. The laminating step is
The C plate laminating step of laminating the second retardation layer with the C plate and the 1/4 wave plate by laminating the laminated body of the second retardation layer and the C plate with the first retardation layer. The method for producing an optical film according to claim 9, further comprising a laminating step relating to a 1/4 wave plate for producing the above. The process of manufacturing the first retardation layer and the step of manufacturing the first retardation layer on the support base material of the first retardation layer,
A process for producing the second retardation layer on the support base material of the second retardation layer, and a process for producing the second retardation layer.
A laminating step of laminating the first retardation layer and the second retardation layer is provided.
The step of manufacturing the first retardation layer is
The first retardation layer was prepared by a retardation of 80 nm or more and 230 nm or less.
The step of manufacturing the second retardation layer is
The second retardation layer was prepared by a retardation of 65 nm or more and 120 nm or less.
The laminating step is
The second retardation layer is laminated in the slow axis direction of the first retardation layer so that the slow axis direction of the second retardation layer forms an angle of 30 degrees or more and 60 degrees or less.
A method for producing a transfer film, wherein the thickness of the first retardation layer and the second retardation layer are both 1 μm or less.

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