JP6756112B2 - Optical film and image display device - Google Patents

Description

The present invention relates to an optical film having a retardation layer that functions as an A plate, and an image display device using this optical film.

Conventionally, with respect to an image display device, a method of arranging an antireflection film which is an optical film functioning as a circular polarizing plate on the panel surface (viewer side surface) of an image display panel and reducing the reflection of external light by this antireflection film has been used. Proposed. Here, this antireflection film is composed of a linear polarizing plate and a 1/4 wave plate laminated, 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. Converts to circularly polarized light. Here, the external light due to this circular polarization is reflected by the panel surface of the image display panel or the like, but the rotation direction of the polarized surface is reversed at the time of 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. The emission to the outside is remarkably 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 of a laminated body of a 1/2 wavelength retardation layer, a 1/4 wavelength retardation layer, and a positive C plate when observed from an oblique direction. Has been proposed.

By the way, as disclosed in Reference 2, if a positive C plate is arranged on the 1/4 wave plate, a desired phase difference can be imparted to the transmitted light at various angles of view, which is sufficient. It is possible to secure the viewing angle characteristic and prevent reflection.

However, such a configuration has a problem that the configuration of the optical film becomes complicated. There is also a problem that the manufacturing process is complicated. Further, as the configuration becomes complicated and the manufacturing process becomes complicated, there is a problem that the occurrence of defects due to defects and the like increases and the quality deteriorates.

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

The present invention has been made in view of such a situation. Regarding an optical film provided with a retardation layer that functions as an A plate, while ensuring sufficient viewing angle characteristics, the configuration and process are simplified, and the quality is further improved. The purpose is to improve.

The present inventor has conducted extensive research to solve the above problems, and has one layer in which the NZ coefficient values NZ (450) and NZ (550) at wavelengths of 450 nm and 550 nm are NZ (450) <NZ (550). We came up with the idea of producing a retardation layer, and came up with the present invention.

(1) An optical film having a retardation layer on a transparent base material.
The retardation layer is
It is a one-layer retardation layer made of a polymerizable rod-shaped liquid crystal material.
When the values of the NZ coefficient represented by NZ = Rth / Re + 0.5 at wavelengths of 450 nm and 550 nm using the front phase difference Re and the thickness phase difference Rth are NZ (450) and NZ (550), NZ (450). ) <The optical film of NZ (550).

According to (1), the corresponding positive C plate is laminated on the A plate that imparts in-plane retardation by effectively avoiding the deterioration of color due to the wavelength characteristics of inverse dispersion by the one-layer retardation layer. It is possible to impart the same phase difference as the above to the transmitted light, thereby ensuring sufficient viewing angle characteristics. Further, by manufacturing this retardation layer from one layer, the configuration and process can be simplified, the occurrence of defects can be reduced, and the quality can be improved.

(2) In (1)
The retardation layer is
An optical film including a homeotropically oriented layer and a homogeneously oriented layer.

According to (2), with respect to an optical film provided with a retardation layer that functions as an A plate, the configuration and process are simplified and the quality is further improved while ensuring sufficient viewing angle characteristics. be able to.

(3) In (2)
An orientation layer is provided on the transparent substrate,
The retardation layer is
The polymerizable rod-shaped liquid crystal material is oriented by the orientation restricting force of the alignment layer to form the homogenius alignment layer.
An optical film in which the homeotropic alignment layer is formed on the opposite side of the alignment layer.

According to (3), a homogeneous alignment layer can be formed by the orientation regulating force of the alignment layer to secure sufficient viewing angle characteristics, the configuration and process can be simplified, and the quality can be further improved.

(4) In (2)
The transparent base material
It is a stretched film
The retardation layer is
The polymerizable rod-shaped liquid crystal material is oriented by the orientation restricting force of the transparent substrate to form the homogeneous alignment layer.
An optical film in which the homeotropic alignment layer is formed on the side opposite to the transparent substrate.

According to (4), by applying a biaxially stretched PET film or the like having an orientation regulating force in the horizontal direction to the base material, the alignment layer is omitted and a sufficient viewing angle characteristic is secured. , The process can be simplified and the quality can be further improved.

(5) In (2)
An orientation layer is provided on the transparent substrate,
The retardation layer is
The polymerizable rod-shaped liquid crystal material is oriented by the orientation restricting force of the alignment layer to form the homeotropic alignment layer.
An optical film in which the homogenius alignment layer is formed on the opposite side of the alignment layer.

According to (5), a homeotropically oriented layer can be formed by the orientation regulating force of the vertically oriented layer to secure sufficient viewing angle characteristics, and then the configuration and process can be simplified and the quality can be further improved. ..

(6) In any of (1) to (5),
In the measurement result of the phase difference value Re in which the phase advance axis of the phase difference layer is set as the reference axis and the angle of incidence on the phase difference layer is changed around the reference axis, the phase difference value Re is an extreme value. The angle of incidence is 10 degrees or less.
In the measurement result of the phase difference value Re in which the slow axis of the retardation layer is set as the reference axis and the angle of incidence on the retardation layer is changed around the reference axis, the phase difference value Re is an extreme value. An optical film having an incident angle of 10 degrees or less.

According to (6), the direction dependence of the optical characteristics due to the pre-tilt of the liquid crystal material can be sufficiently reduced, and the bias of the optical characteristics can be prevented.

(7) In any of (1), (2), (3), (4), (5), (6),
An optical film in which the front retardation Re of the retardation layer is 50 nm or more and 200 nm or less, and the NZ coefficient value NZ (550) at a wavelength of 550 nm is less than 1.0.

According to (7), it can be applied to an optical film having a 1/4 wavelength retardation layer to secure sufficient viewing angle characteristics, simplify the configuration and process, and further improve the quality.

(8) An image display device provided with the optical film according to any one of (1), (2), (3), (4), (5), and (7) on the panel surface of the image display panel.

According to (8), with respect to an image display device provided with an optical film having a retardation layer that functions as an A plate, the configuration and process are simplified and the quality is further improved while ensuring sufficient viewing angle characteristics. be able to.

According to the present invention, with respect to an optical film provided with a retardation layer that functions as an A plate, it is possible to simplify the configuration and process and further improve the quality while ensuring sufficient viewing angle characteristics.

It is a figure which shows the image display apparatus which concerns on 1st Embodiment of this invention. It is a figure which provides the explanation of the retardation layer. It is a figure which shows the transfer film applied to the optical film which concerns on the image display device of FIG. It is a flowchart which shows the manufacturing process of the transfer film of FIG. It is a figure which shows the image display apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the image display apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows the image display apparatus which concerns on 4th Embodiment of this invention. It is a chart which provides the explanation of an Example. It is a figure which shows the phase difference value and the wavelength dispersion of the Example of FIG. It is a chart which shows the Nz coefficient of the Example of FIG.

[First Embodiment]
[Image display device and optical film]
FIG. 1 is a cross-sectional view showing an image display device according to the first embodiment of the present invention. In the following, the front phase difference Re, the thickness phase difference Rth, and the NZ coefficient are values at a wavelength of 550 nm unless otherwise specified. The image display device 1 is arranged by sticking an optical film 3 made of an antireflection film on the panel surface (viewer side surface) of the image display panel 2 by using an adhesive layer or the like. As a result, the image display device 1 is configured to sufficiently prevent reflection by the optical film 3. Although the image display panel 2 is an image display panel using a self-luminous element such as an organic EL element, an image display panel such as a liquid crystal display panel may be applied instead.

The optical film 3 is formed by laminating a linear polarizing plate 4 and a 1/4 wave plate 5, thereby functioning as a circular polarizing plate and preventing reflection of external light. The linear polarizing plate 4 is formed by impregnating polyvinyl alcohol (PVA) with iodine or the like and then stretching it to form an optical functional layer that fulfills an optical function as a linear polarizing plate, and is a transparent film such as TAC (triacetyl cellulose). It is manufactured by sandwiching an optical functional layer with a base material made of a material.

The 1/4 wave plate 5 linearly polarizes a 1/4 wavelength retardation layer 7 that imparts an in-plane retardation of 1/4 wavelength to transmitted light from a transfer film described later by a transfer method together with an alignment layer 6. It is attached to the plate 4 and arranged. Note that only the 1/4 wavelength retardation layer 7 may be transferred. Here, in the transfer method, for example, when a desired layer is formed on a base material, this layer is not formed directly on the base material, but can be once peeled off on a releasable support. After the transfer body (transfer film) is produced by laminating the layers, the layer formed on the support is finally laminated with the base material (transferred) according to the process, demand, and the like. This is a method of forming a desired layer on the base material by adhering and laminating on the base material) and then peeling off the support.

The 1/4 wavelength retardation layer 7 is a one-layer retardation layer made of a liquid crystal material produced by curing one coating layer made of a polymerizable rod-shaped liquid crystal material, and is an in-plane retardation Re (in-plane retardation Re) at a wavelength of 550 nm. 550) is 50 nm or more and 200 nm or less, preferably 110 nm or more and 170 nm or less, and more preferably 120 nm or more and 150 nm or less.

The 1/4 wavelength retardation layer 7 uses NZ (450 nm) as the value of the NZ coefficient expressed by NZ = Rth / Re + 0.5 at wavelengths of 450 nm and 550 nm using the frontal retardation Re and the thickness retardation Rth at the wavelength λ. ) And NZ (550), NZ (450) <NZ (550) is set.

As a result, in the embodiment, the 1/4 wavelength retardation layer 7 made of the liquid crystal material produced by curing the one-layer coating layer made of the polymerizable rod-shaped liquid crystal material has a tint due to the wavelength characteristics of the inverse dispersion. The same phase difference as when a positive C plate corresponding to this A plate is laminated on an A plate that imparts an in-plane phase difference equivalent to 1/4 wavelength is imparted to transmitted light by effectively avoiding the deterioration of the above. This makes it possible to secure sufficient viewing angle characteristics. Further, by forming the 1/4 wavelength retardation layer 7 with a single coating film, the configuration and process can be simplified, the occurrence of defects can be reduced, and the quality can be improved.

At this time, the NZ coefficient NZ (550) at a wavelength of 550 nm is set to be less than 1, more preferably more than 0.2 and less than 0.8, and more than this, the viewing angle characteristics are sufficiently secured. It is configured to be able to.

In the optical film 3, the alignment layer 6 is an alignment layer (horizontal alignment layer) that exerts a horizontal orientation regulating force with respect to the liquid crystal compound related to the 1/4 wavelength retardation layer 7, and is composed of a photoalignment layer. To. Although the photoalignment layer can be produced using, for example, a photodimerization type material, not only the photodimerization type material but also various photoalignment layer materials can be widely applied. Specifically, the alignment layer 6 may be produced by a shaping treatment of a fine line-shaped uneven shape, or the surface of a resin layer such as polyimide may be subjected to a rubbing treatment to directly produce a fine line-shaped uneven shape to form an alignment layer. May be. The alignment layer 6 is formed so that the direction in which the alignment regulating force is expressed (the orientation direction of the liquid crystal compound according to the A plate layer 9 described later) with respect to the transmission axis direction of the linear polarizing plate 4 is an angle of 45 degrees. Will be done.

The 1/4 wavelength retardation layer 7 includes a polymerizable rod-shaped liquid crystal material used for producing a retardation layer functioning as an A plate and a polymerizable rod-shaped liquid crystal material used for producing a retardation layer functioning as a positive C plate. To prepare a coating liquid from a mixture mixed at a constant mixing ratio, and by coating, drying, and curing the coating liquid on the alignment layer 6, NZ (450) <NZ (550). ), Further produced with an NZ coefficient of less than 1.

Here, in the retardation layer 7, the polymerizable rod-shaped liquid crystal material used for producing the retardation layer that functions as the A plate and the polymerizable layer used for producing the retardation layer that functions as the positive C plate. By producing a rod-shaped liquid crystal material mixed with a constant mixing ratio, as shown in FIG. 2, the liquid crystal compound A is horizontally aligned in the vicinity of the alignment layer 6 due to the orientation restricting force of the alignment layer 6. A homogenius alignment layer is formed, and as a result, an A plate layer 9 that functions as an A plate is produced in the vicinity thereof, and the liquid crystal compound A is vertically oriented in the remaining portion, which is a portion away from the alignment layer 6. It is considered that the homeotropic alignment layer is formed, and thus the optical characteristics according to this embodiment can be ensured.

As a result, the optical film 3 can be produced by curing one layer of the coating film so that the NZ coefficient value NZ (λ) is NZ (450) <NZ (550), so that the deterioration of color is effective. In addition to ensuring sufficient viewing angle characteristics, the configuration and process can be simplified, the occurrence of defects can be reduced, and the quality can be improved.

The laminated structure of the A plate layer 9 and the regular C plate layer 8 is formed by simply coating, drying, and curing a mixture of two types of liquid crystal materials as in this embodiment, as well as a liquid crystal. It can be produced by utilizing the dipole moment of a molecule, and can also be produced by applying an electric field or a magnetic field, for example.

However, if the liquid crystal molecules related to the A plate layer 9 are oriented at an angle in the thickness direction, the optical characteristics are biased. Specifically, for example, when the in-plane phase difference is measured by changing the incident angle in the plane including the long axis direction (the phase advance axis direction) of the liquid crystal molecule, the in-plane phase difference is an extreme value (minimum value). Or the maximum value), the incident angle is different from 0 degrees, and it is biased to the positive side or the negative side of the incident angle. As a result, in the antireflection film, anisotropy is exhibited in the antireflection function, and the optical characteristics are deteriorated.

As a result of various studies, it was found that such an oblique tilt of the liquid crystal molecules related to the A plate layer 9 can be prevented by preventing the liquid crystal material from tilting diagonally at the interface with the alignment layer. Thereby, specifically, by adopting a configuration in which the tilt angle of the liquid crystal molecules at this interface is set to 0 degrees or 90 degrees, it is possible to prevent the optical characteristics from being biased. Therefore, it is desirable to apply a photo-alignment layer to the alignment layer 6 to prevent bias in optical characteristics.

More specifically, in the measurement result of the phase difference value Re in which the phase advance axis of the phase difference layer 7 is set as the reference axis and the angle of incidence on the phase difference layer 7 is changed around the reference axis, the phase difference value The incident angle at which Re is an extreme value is set to 10 degrees or less, preferably 5 degrees or less, and the slow axis of the retardation layer 7 is set as the reference axis so as to be around this reference axis. In the measurement result of the retardation value Re in which the angle of incidence on the retardation layer 7 is changed, the angle of incidence at which the extremum of the retardation value becomes an extreme value is set to 10 degrees or less, and is preferably 5 degrees or less. In this way, the bias of the optical characteristics can be sufficiently prevented. The phase advance axis of the retardation layer 7 is set as the reference axis, and the measurement result of the phase difference value Re obtained by changing the angle of incidence on the retardation layer 7 around the reference axis is the slow phase of the retardation layer 7. This is the measurement result of the retardation value Re in which the incident angle is changed in the vertical plane of the retardation layer including the axis. Further, the measurement result of the phase difference value Re in which the slow axis of the retardation layer 7 is set as the reference axis and the angle of incidence on the retardation layer 7 is changed around the reference axis is the phase advance of the retardation layer 7. It is a measurement result of the retardation value Re whose incident angle is changed in the vertical plane of the retardation layer including the axis.

Here, the polymerizable rod-shaped liquid crystal material applicable to the A plate is a liquid crystal material that is horizontally oriented by the orientation restricting force in the horizontal direction (the in-plane direction of the alignment layer) and has a polymerizable functional group in the molecule. Various rod-shaped liquid crystal compounds can be applied. Further, this rod-shaped liquid crystal compound has a refractive index anisotropy, and has a function of imparting a desired retardation property by regularly arranging the rod-shaped liquid crystal compound due to the orientation regulating force of the alignment layer 6. 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 compound used in the present embodiment include compounds represented by the following formulas (1) to (17), and these compounds are used alone or in admixture of a plurality of compounds and polymerized. can do.

On the other hand, the polymerizable rod-shaped liquid crystal material applicable to the positive C plate is a liquid crystal material that is vertically oriented by the orientation restricting force in the vertical direction (in the thickness direction of the alignment layer), and has polymerizable functionality in the molecule. Various rod-shaped liquid crystal compounds having a group can be applied.

Specifically, for example, the configuration disclosed in JP-A-2015-191143 can be applied. More specifically, RMM28B manufactured by Merck & Co., UCL-018 manufactured by DIC Corporation, and the like can be applied.

In the retardation layer made of a liquid crystal material (hybrid oriented liquid crystal material) that exhibits hybrid characteristics, the liquid crystal material is vertically oriented in the vicinity of the vertically aligned film, and the liquid crystal materials are gradually aligned as the distance from the vertically aligned film increases. It has the characteristic of falling (sleeping) in the horizontal direction. As a result, in the retardation layer made of the liquid crystal material showing the characteristics of the hybrid, it seems that the liquid crystal molecules are oriented in the same manner as described above with respect to FIG. However, in the retardation layer made of the hybrid liquid crystal material, when the in-plane phase difference is measured by swinging the angle in the long axis direction of the horizontally oriented liquid crystal molecules, the angle at which the in-plane phase difference shows the extreme value is the incident angle 0. The angle is biased from the direction of degrees, and the in-plane phase difference characteristic is biased in one direction. As a result, it becomes difficult to secure sufficient viewing angle characteristics in the retardation layer made of a liquid crystal material exhibiting hybrid characteristics.

However, in the retardation layer 7 of this embodiment, the incident angle at which the in-plane phase difference becomes an extreme value can be set to be approximately 0 degrees, and the positive and positive angles are centered on the direction of the incident angle of 0 degrees. The characteristics of the in-plane phase difference measured by swinging the angle in the negative incident angle direction can be made highly symmetric, and a sufficient viewing angle characteristic can also be ensured.

As a result, in the retardation layer made of the hybrid-oriented liquid crystal material, the incident angle at which the above-mentioned retardation value takes an extreme value becomes an angle larger than 10 degrees.

[Transfer film]
FIG. 3 is a cross-sectional view showing the structure of a transfer film used for producing the optical film 3. The transfer film 10 is formed by sequentially laminating an orientation layer 6 and a 1/4 wavelength retardation layer 7 on a base material 11 made of a transparent film material. By forming the 1/4 wavelength retardation layer 7 on the transfer film 10 and transferring it by the transfer method in this way, the thickness of the optical film 3 can be reduced.

Here, various transparent film materials used for producing a transfer film can be applied to the base material 11, and for example, a PET (polyethylene terephthalate) film or the like can be applied.

[Manufacturing method of optical film]
FIG. 4 is a flowchart showing a manufacturing process of the transfer film 10. In the optical film 3, the 1/4 wavelength retardation layer 7 of the transfer film 10 produced by this manufacturing process is bonded to the linear polarizing plate 4 with an adhesive such as an ultraviolet curable resin, and then the base material 11 is peeled off. As a result, the 1/4 wavelength retardation layer 7 is arranged on the linear polarizing plate 4 by the transfer method. After that, the pressure-sensitive adhesive layer, the separator film, and the like are laminated and cut to a desired size to produce the optical film 3. In the image display device 1, the separator film is peeled off from the optical film 3 to expose the adhesive layer, and the optical film 3 is arranged on the panel surface of the image display panel 2 by the adhesive layer.

In the transfer film 10, in the alignment layer preparation step SP2, the base material 11 is coated with the coating liquid for the alignment layer 6, dried, and then irradiated with linearly polarized ultraviolet rays, whereby the alignment layer 6 is formed. It is made.

In the subsequent liquid crystal material coating step SP3, the transfer film 10 is used for producing a polymerizable rod-shaped liquid crystal material used for producing a retardation layer that functions as an A plate and a retardation layer that functions as a positive C plate. A coating liquid is prepared from a mixture of the polymerized rod-shaped liquid crystal material to be produced and mixed at a constant mixing ratio, and the coating liquid is applied onto the alignment layer 6 and dried. Subsequently, in the curing step SP4, the coating film related to the 1/4 wavelength retardation layer 7 is cured by irradiation with unpolarized ultraviolet rays, whereby the 1/4 wavelength retardation layer 7 is produced.

[Second Embodiment]
FIG. 5 is a diagram showing an image display device according to a second embodiment of the present invention in comparison with FIG. An optical film 13 is applied to the image display device 21 instead of the optical film 3. Further, in the optical film 13, the optical film 15 is laminated on the linear polarizing plate 4 instead of the 1/4 wavelength retardation layer 7 and the alignment layer 6. The image display device 21 is configured in the same manner as the image display device 1 of the first embodiment, except that these configurations are different.

Here, the optical film 15 is formed by sequentially forming an alignment layer 6 and a 1/4 wavelength retardation layer 7 on the base material 22 from a transparent film material, and is optically anisotropic on the base material 22, similarly to the transfer film 10. For example, a TAC film material having a small property is applied, and the base material 22 is attached to the linear polarizing plate 4 and arranged. Thereby, in this embodiment, the positive C plate layer 8 is configured to be on the image display panel 2 side.

Even if the retardation layer is arranged integrally with the base material so that the positive C plate layer 8 is on the image display panel 2 side as in this embodiment, the same effect as that of the first embodiment can be obtained. ..

[Third Embodiment]
FIG. 6 is a diagram showing an image display device according to a third embodiment of the present invention in comparison with FIG. An optical film 33 is applied to the image display device 31 instead of the optical film 3. Further, in this optical film 33, a 1/2 wavelength retardation layer 34 is laminated on a 1/4 wavelength retardation layer 7 to form a 1/4 wave plate 5, and the 1/4 wavelength plate 5 is a linear polarizing plate 4. It is laminated on. The image display device 31 is configured in the same manner as the image display device 1 of the first embodiment, except that these configurations are different.

As a result, the optical film 33 according to this embodiment is produced by sequentially laminating the 1/2 wavelength retardation layer 34 and the 1/4 wavelength retardation layer 7 on the linear polarizing plate 4 by the transfer method. After laminating the 1/4 wavelength retardation layer 7 on the / 2 wavelength retardation layer 34 by the transfer method to prepare a laminate of the 1/2 wavelength retardation layer 34 and the 1/4 wavelength retardation layer 7, or transparent. A 1/4 wavelength retardation layer 7 and a 1/2 wavelength retardation layer 34 are sequentially manufactured on a base material made of a film material, and a laminate of these 1/4 wavelength retardation layers 7 and a 1/2 wavelength retardation layer 34 is formed. After the production, the laminate may be laminated on the linear polarizing plate by a transfer method. Further, as described above for the second embodiment in comparison with the first embodiment, instead of applying such a transfer method, the 1/2 wavelength retardation layer 34 and the 1/4 wavelength retardation layer 7 can be produced. The provided base materials may be integrally laminated.

Here, in this embodiment, in the laminated body of the 1/2 wavelength retardation layer 34 and the 1/4 wavelength retardation layer 7, the in-plane retardation of 1/4 wavelength is added to the transmitted light of the linear polarizing plate 4. The transmitted light is imparted and emitted toward the image display panel 2 by circularly polarized light. Further, at this time, by imparting an in-plane retardation of 1/4 wavelength by the laminated body of the 1/2 wavelength retardation layer 34 and the 1/4 wavelength retardation layer 7, reflection is sufficiently prevented in a wide wavelength band. It is configured to be able to.

Therefore, in this embodiment, when the optical film 33 is viewed from the front of the linear polarizing plate 4, the 1/2 wavelength retardation layer 34 and the 1/4 wavelength retardation layer 7 are relative to the absorption axis of the linear polarizing plate 4. Therefore, the slow axes of the 1/2 wavelength retardation layer 34 and the 1/4 wavelength retardation layer 7 are arranged so as to form angles θ1 and θ2 in the counterclockwise direction, respectively. Here, if the wavelength dispersion characteristics of the 1/2 wavelength retardation layer 34 and the 1/4 wavelength retardation layer 7 are the same, θ1 is 10 degrees or more and 20 degrees or less, more preferably 13 degrees or more and 17 degrees or less. And θ2 is 70 degrees or more and 80 degrees or less, and more preferably 72 degrees or more and 76 degrees or less.

The 1/2 wavelength retardation layer 34 is a one-layer retardation layer made of a liquid crystal material produced by curing a one-layer coating film made of a liquid crystal compound layer, and is an in-plane retardation Re (550) at a wavelength of 550 nm. ) Is 200 nm or more and 350 nm or less, more preferably 210 nm or more and 300 nm or less, and in this embodiment, the in-plane retardation Re (550) is produced by 220 nm or more and 280 nm or less, which is about 1/2 of the wavelength of 550 nm.

The 1/2 wavelength retardation layer 34 is made in the same manner as the 1/4 wavelength retardation layer 7, and NZ (450) <NZ (550), and the NZ coefficient is less than 1, which is more preferably 0. It is made to be greater than 2 and less than 0.8. Instead of this, the 1/2 wavelength retardation layer 34 may be configured to be the same as the retardation layer made of a liquid crystal material that functions as a conventional A plate.

Further, the 1/4 wave plate 5 has a laminated structure of the 1/4 wavelength retardation layer 7 and the 1/2 wavelength retardation layer 34, and the thickness direction retardation value Rth corresponding to the in-plane retardation of the 1/4 wavelength plate. (550) may be secured, and in this case, the 1/4 wavelength retardation layer 7 and the 1/2 wavelength retardation layer 34 may share the function as a positive C plate, for example, FIG. Although different from the configuration of 6, the 1/4 wavelength retardation layer is configured to be the same as the retardation layer made of a liquid crystal material that functions as a conventional A plate, and the 1/2 wavelength retardation layer 34 is formed by NZ (450) <. It may be made to be NZ (550), further preferably having an NZ coefficient of less than 1, more preferably more than 0.2 and less than 0.8.

When the 1/4 wave plate is formed by the laminated structure of the 1/4 wavelength retardation layer 7 and the 1/2 wavelength retardation layer 34 in this way, the polymerizable rod-shaped liquid crystal material used for producing the A plate and the polymerizable rod-shaped liquid crystal material The NZ coefficient of the 1/4 wavelength retardation layer 7 is adjusted by adjusting the mixing ratio so that the 1/4 wavelength retardation layer 7 is produced by mixing the polymer rod-shaped liquid crystal material used for producing the positive C plate. If it is configured to function as a negative A plate having a value of 0, the 1/2 wavelength retardation layer 34 is composed of the positive A plate according to the conventional configuration, and the 1/4 wavelength retardation layer according to the conventional configuration, 1/2 wavelength. It is possible to sufficiently improve the viewing angle characteristics by ensuring the same level of optical characteristics as the optical film due to the laminated structure of the retardation layer and the positive C plate.

According to the above configuration, a 1/4 wave plate is formed by a laminated structure of a 1/2 wavelength retardation layer and a 1/4 wavelength retardation layer, thereby ensuring sufficient viewing angle characteristics in a wide wavelength band. Therefore, the configuration and process can be simplified and the quality can be further improved.

[Fourth Embodiment]
FIG. 7 is a diagram showing an image display panel according to a fourth embodiment of the present invention. The image display panel 41 is a liquid crystal display panel based on an IPS (inplane switching) method or an FFS (fringe field switching) method, and is a transparent base material obtained by producing a transparent electrode, an alignment layer, or the like according to the IPS method or the FFS method. The liquid crystal cell 42 is manufactured by sandwiching the liquid crystal material. In the image display panel 41, linear polarizing plates 43 and 44 are arranged on both sides of the liquid crystal cell 42, respectively, and a backlight 46 is arranged on the side of one linear polarizing plate 43.

A 1/2 wave plate 45 is arranged between the linear polarizing plate 44 and the liquid crystal cell 42 on the opposite side of the backlight 46, and the optical compensation by the 1/2 wavelength plate sufficiently transmits transmitted light. It is configured to block light. In this embodiment, the structure of the 1/4 wave plate described above for the 1st embodiment and the 2nd embodiment of the 1/2 wave plate 45 sets the thickness of the retardation layer to the thickness corresponding to the 1/2 wavelength. And apply.

In this embodiment, even when applied to optical compensation of a liquid crystal display panel according to the IPS system, an optical film provided with a retardation layer that functions as an A plate is configured after ensuring sufficient viewing angle characteristics. , The process can be simplified and the quality can be further improved.

[Fifth Embodiment]
In this embodiment, by applying a stretched film, which is a transparent film material having a horizontal orientation regulating force, such as a biaxially stretched PET film, to the base material, the alignment layer 6 is omitted, and the above-described embodiment is adopted. It constitutes the transfer film and the optical film. This embodiment is configured in the same manner as the above-described embodiment, except that the configurations relating to the base material and the alignment layer are different.

As a result, in this embodiment, the liquid crystal material is horizontally oriented by the orientation restricting force of the transparent film material to produce a retardation layer.

Even if a stretched film, which is a transparent film material having a horizontal alignment regulating force, is applied to a transparent base material to omit the alignment layer as in this embodiment, the same effect as in the first to fourth embodiments is obtained. Can be obtained.

[Sixth Embodiment]
In this embodiment, instead of the horizontally oriented layer that exerts the orientation regulating force in the horizontal direction, the vertically oriented layer that expresses the orientation regulating force in the vertical direction is applied to the alignment layer. In this embodiment, the configuration is the same as that of the above-described embodiment except that the configuration relating to the orientation layer is different.

Here, as the vertically oriented layer, the oriented layer used for producing the C plate can be widely applied. When the vertically oriented layer is applied in this way, the liquid crystal material is vertically oriented in the vicinity of the interface with the vertically oriented layer, whereby a homeotropic oriented layer is formed on the oriented layer side, contrary to the configuration of FIG. It is considered that the regular C plate layer is formed, the homogenius oriented layer is formed at a portion away from the oriented layer, and the A plate layer is formed.

Even if the vertically oriented layer is applied in this way, the same effect as that of the above-described embodiment can be obtained.

[7th Embodiment]
In this embodiment, a transparent film material having a vertical alignment regulating force, such as a biaxially stretched PET film, is applied to the transparent substrate, the alignment layer 6 is omitted, and the transfer film and optics according to the above-described embodiment are omitted. Make up the film. This embodiment is configured in the same manner as the above-described embodiment, except that the configurations relating to the base material and the alignment layer are different.

Thereby, in this embodiment, a retardation layer having an NZ coefficient of less than 1 is produced so that the tilt angle at the interface with the transparent film material is 90 degrees.

Even if a transparent film material having a vertical alignment regulating force is applied to the base material and the alignment layer is omitted as in this embodiment, the same effect as in the first to sixth embodiments can be obtained. ..

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

That is, in the above-described embodiment, the case where the present invention is applied to an optical film related to antireflection and optical compensation has been described, but the present invention is not limited to this, and various optics having a retardation layer functioning as an A plate are provided. It can be widely applied to films.

FIG. 8 is a diagram for explaining an embodiment of the present invention. Examples 1 to 5 and Comparative Examples 1 to 4 are examples according to the first embodiment. In Examples 1 to 5, a PET film (E5100 manufactured by Toyobo Co., Ltd.) was applied to a base material, and an oriented layer was prepared by a photoaligned layer. For the photo-alignment layer, a photo-alignment film (solid content 4.5%) manufactured by JSR is coated with Miyabar # 3, dried at 120 ° C. for 1 minute, and then a sample is placed in a polarization exposure apparatus at a desired angle. An oriented layer was prepared by irradiating with polarized UV of 30 mj / cm ² .

Among the liquid crystal materials related to the retardation layer, the polymerizable rod-shaped liquid crystal material used for producing the retardation layer functioning as the A plate is a mixture of the rod-shaped compounds (11) and (17) described above at a mixing ratio of 1: 1. The mixture and the initiators, BASF Irgacure 907 and DIC Megafuck (F477), were dissolved in a 1: 1 mixed solvent of methyl ethyl ketone and methyl isobutyl ketone to prepare a 25% solution and applied. .. The polymerized rod-shaped liquid crystal material used to prepare the retardation layer that functions as a positive C plate is a 1: 1 mixture of RMM28B (Merck) and DIC Megafuck (F477) of methyl ethyl ketone and methyl isobutyl ketone. A 25% solution was prepared and applied by dissolving in a solvent. In Examples 1 to 5, these liquid crystal materials were mixed at a desired mixing ratio to prepare a coating liquid. In Examples 1 to 5 and Comparative Examples 1 to 4, each liquid crystal layer was prepared by applying the coating liquid of the above liquid crystal material with Miyabar # 6. The phase difference was measured using KOBRA-WR manufactured by Oji Measuring Instruments Co., Ltd. in a state where the retardation layer was transferred to a glass base material and the base material was peeled off.

In Example 1, the mixing ratio of the polymerizable rod-shaped liquid crystal material used for producing the retardation layer functioning as the A plate and the polymerization rod-shaped liquid crystal material used for producing the retardation layer functioning as the positive C plate is 1. : 3.5, and in Example 2, this mixing ratio was set to 1: 3.75. Further, in Examples 3 and 4 , the mixing ratios were set to 1: 1 and 1: 2, respectively, and in Examples 5 and 4 , the same base material and orientation layer as in Examples 1 to 4 were used. , A mixture of liquid crystal materials was applied, and the mixing ratios of the liquid crystal materials were set to 1: 3 and 1: 4, respectively.

Further, Comparative Example 1 is obtained by applying the same base material and orientation layer as in Examples 1 to 5. Comparative Example 1 is a polymerizable rod-shaped liquid crystal material used for producing a retardation layer that functions as an A plate, and the above-mentioned rod-shaped compounds (11) and (17) having positive dispersion wavelength characteristics are mixed at a mixing ratio of 1: 1. The mixture mixed in 1 and the initiators Irgacure 907 manufactured by BASF and Megafvck (F477) manufactured by DIC were dissolved in a 1: 1 mixed solvent of methyl ethyl ketone and methyl isobutyl ketone to prepare a 25% solution. , Miyaver # 3 was used for coating to prepare a 1/4 wavelength retardation layer. Further, RMM28B (manufactured by Merck) and Megafuck (F477) manufactured by DIC, which are polymer rod-shaped liquid crystal materials used for producing a retardation layer that functions as a positive C plate, are mixed with a 1: 1 mixed solvent of methyl ethyl ketone and methyl isobutyl ketone. A 25% solution was prepared by dissolving in, and a positive C plate layer was prepared using Miyaber # 2, and these 1/4 wavelength retardation layers and positive C plate layers were laminated. Comparative Example 2 was configured in the same manner as Comparative Example 1 except that a 1/4 wavelength retardation layer was prepared using PureAce_S-142 manufactured by Teijin Limited, which has a wavelength characteristic of inverse dispersion.

Further, in Comparative Example 3, the coating liquid was applied on the alignment layer by the photoalignment layer with Miyaber # 9, dried at a drying temperature of 65 ° C. for 5 minutes, and then irradiated with an H bulb manufactured by Fusion. It was prepared by immobilizing it by irradiating it with ultraviolet rays and curing it so that the amount was 380 mJ / cm ² . In addition, this coating liquid contains a mixture of compounds (1), ReM (1), and ReM (3) described in JP-A-2010-522892 at a blending ratio of 5: 3: 2 and 7: 3 of toluene / cyclohexanone. It was prepared by dissolving it in the mixed solvent of (1) and adjusting the solid content concentration to 21.5%.

In Comparative Examples 1 to 3, it can be confirmed that the retardation layer is produced by the frontal retardation Re at wavelengths of 450 nm and 550 nm due to the characteristics of forward dispersion and reverse dispersion, respectively, and thereby the wavelength dispersion Re ( 450) / Re (550) can be used to confirm the wavelength characteristics of normal dispersion and the wavelength characteristics of reverse dispersion.

Looking at the Nz coefficient, in Comparative Example 2 in which the A plate layer has the wavelength characteristic of inverse dispersion in Comparative Examples 1 to 3, NZ (450) <NZ (550), thereby NZ (450) <NZ. It can be seen that the characteristic of (550) makes it possible to impart a phase difference to the transmitted light due to the wavelength characteristic of inverse dispersion, and as a result, it is possible to sufficiently prevent a change in the color of the display screen on the image display panel.

On the other hand, in Examples 1 to 4, it can be confirmed that the retardation layer is produced due to the characteristics of inverse dispersion by the front retardation Re at wavelengths of 450 nm and 550 nm, and in Example 5, it is flat. It can be seen that the wavelength dispersion characteristics are ensured. Further, for NZ (450) and NZ (550), the relationship of NZ (450) <NZ (550) can be maintained as in Comparative Example 2, and thus the change in color can be sufficiently prevented. I understand. Further, in Comparative Example 4, it can be seen that this relationship cannot be maintained because the mixing ratio is remarkably biased. Further, it can be seen from this that various characteristics can be set by adjusting the mixing ratio.

9 and 10 are diagrams showing the measurement results in Examples 1 to 5 and Comparative Examples 1 to 4, and FIG. 9 shows front phase differences Re (450), Re (550) and wavelength dispersion Re (). It is a figure which shows 450) / Re (550), and FIG. 10 is a figure which shows the Nz coefficient.

According to FIGS. 9 and 10, in Examples 1 to 5, NZ (NZ) (similar to Comparative Example 2 in which the 1/4 wavelength retardation layer due to the inverse dispersion wavelength characteristic and the positive C plate layer are laminated) 450) It can be seen that the relationship of <NZ (550) can be secured. As a result, it is predicted that it can be arranged on the panel surface of the image display panel to reduce the change in color of the image display panel surface due to the change in the viewing angle, and to effectively avoid the deterioration of the antireflection characteristics due to the change in the viewing angle. To. According to the results of mounting and experimenting by actually arranging it on the image display panel, it was confirmed that the change in color of the image display panel surface and the deterioration of antireflection characteristics due to such a change in viewing angle can be effectively avoided. We were able to.

Specifically, a 1/4 wavelength retardation layer according to Examples and Comparative Examples is laminated on a linear polarizing plate by a transfer method to prepare an antireflection film, and an organic EL according to a portable information terminal (Galaxy S5 manufactured by Samsung Electronics Co., Ltd.) is used. The front reflection hue and the oblique reflection hue were observed by arranging them on the panel surface of the image display panel. The observation in the oblique direction was performed by changing the azimuth angle according to the polar angle of 60 degrees.

In the antireflection film using the 1/4 wavelength retardation layer of Example 5, both the front reflection hue and the oblique reflection hue are black with a blue tint, whereby the tint is sufficiently changed and deteriorated. It was confirmed that the above was prevented and a suitable hue could be secured. On the other hand, in the antireflection film using the 1/4 wavelength retardation layer of Comparative Example 1, the front reflection hue and the oblique reflection hue are red with a purple tint, which is due to a change in the viewing angle. It was confirmed that the change in hue itself was significantly deteriorated, although it could be prevented. On the other hand, in the antireflection film using the 1/4 wavelength retardation layer of Comparative Example 3, the front reflection hue is black with a blue tint, but the oblique reflection hue is tinted with green. It was blue, which confirmed the change in hue due to the change in viewing angle.

1, 21, 31 Image display device 2, 42 Image display panel 3, 13, 15, 33 Optical film 4, 43, 44 Linear polarizing plate 5 1/4 wave plate 6 Orientation layer 7 1/4 wavelength retardation layer 8 A Plate layer 9 Positive C plate layer 10 Transfer film 11, 22 Base material 34 1/2 wavelength retardation layer 42 Liquid crystal cell 45 1/2 wave plate 46 Backlight

Claims (8)

An optical film having a retardation layer on a transparent substrate.
The retardation layer is
It is a one-layer retardation layer made of a polymerizable rod-shaped liquid crystal material composed of a liquid crystal material used for producing a retardation layer functioning as an A plate and a liquid crystal material used for producing a retardation layer functioning as a positive C plate. ,
When the values of the NZ coefficient represented by NZ = Rth / Re + 0.5 at wavelengths of 450 nm and 550 nm using the front retardation Re and the thickness retardation Rth are NZ (450) and NZ (550), NZ (450). ) <NZ (550),
It has a homeotropic alignment layer and a homogenius alignment layer.
In the measurement result of the phase difference value Re in which the phase advance axis of the phase difference layer is set as the reference axis and the angle of incidence on the phase difference layer is changed around the reference axis, the phase difference value Re is an extreme value. The angle of incidence is 10 degrees or less.
In the measurement result of the phase difference value Re in which the slow axis of the retardation layer is set as the reference axis and the angle of incidence on the retardation layer is changed around the reference axis, the phase difference value Re is an extreme value. An optical film having an incident angle of 10 degrees or less. An orientation layer is provided on the transparent substrate,
The retardation layer is
The polymerizable rod-shaped liquid crystal material is oriented by the orientation restricting force of the alignment layer to form the homogenius alignment layer.
The optical film according to claim 1, wherein the homeotropic alignment layer is formed on the opposite side of the alignment layer. The transparent base material
It is a stretched film
The retardation layer is
The polymerizable rod-shaped liquid crystal material is oriented by the orientation restricting force of the transparent substrate to form the homogeneous alignment layer.
The optical film according to claim 1, wherein the homeotropic alignment layer is formed on the side opposite to the transparent substrate. An orientation layer is provided on the transparent substrate,
The retardation layer is
The polymerizable rod-shaped liquid crystal material is oriented by the orientation restricting force of the alignment layer to form the homeotropic alignment layer.
The optical film according to claim 1, wherein the homogenius alignment layer is formed on the opposite side of the alignment layer. Claim 1, claim 2, claim 3, claim 3, where the front retardation Re of the retardation layer is 50 nm or more and 200 nm or less, and the value NZ (550) of the NZ coefficient at a wavelength of 550 nm is less than 1.0. The optical film according to any one of 4. Claim 1, claim 2, claim 3, claim 3, where front retardation Re ( 450 ) and Re ( 550 ) at wavelengths 450 nm and 550 nm of the retardation layer are Re (450) <Re (550). The optical film according to any one of 4. The retardation layer is
It has the function of a 1/4 wavelength retardation layer with a negative A plate.
The optical film according to any one of claims 1, 2, 3, 3, 4, 5, and 6, which is laminated with a 1/2 wavelength retardation layer formed by a positive A plate. An image display device comprising the optical film according to any one of claims 1, 2, 3, 3, 4, 5, 5, and 7 on the panel surface of an image display panel.