JP2017122905A - Optical film and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a sufficient viewing angle characteristic of an optical film including a phase difference layer functioning as an A plate, and simplify the configuration and step and improve quality of the optical film.SOLUTION: There is provided an optical film 10 including a phase difference layer 7 on a transparent base material 11, wherein the phase difference layer 7 is a single-layer phase difference layer formed of a polymerizable rod-like liquid crystal material; the NZ coefficient represented by NZ=Rth/Re+0.5 using the front phase difference Re and thickness phase difference Rth is less than 1; the tilt angle in an interface with a member on the transparent base material is 0 degree or 90 degrees.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical film including a retardation layer functioning as an A plate, and an image display device using the optical film.

  Conventionally, regarding an image display device, there is a method of disposing an antireflection film, which is an optical film functioning as a circularly polarizing plate, on the panel surface (viewer side surface) of an image display panel, and reducing the reflection of extraneous light with this antireflection film. Proposed. Here, this antireflection film is composed of a laminate of a linearly polarizing plate and a quarter wavelength plate, converts external light directed to the panel surface of the image display panel into linearly polarized light by the linearly polarizing plate, and continues to the quarter wavelength plate. To convert to circularly polarized light. Here, the extraneous light due to the circularly polarized light is reflected on the panel surface of the image display panel, but the rotation direction of the polarization plane is reversed during the reflection. As a result, contrary to the arrival time, this reflected light is converted into linearly polarized light in the direction shielded by the linear polarizing plate by the quarter wavelength plate, and then shielded by the subsequent linear polarizing plate. Outgoing emission is significantly suppressed.

  With regard to this optical film, Patent Document 1 and the like include a 1/2 wavelength retardation layer that imparts a phase difference of ½ wavelength to transmitted light, and a 1 / wavelength that imparts a phase difference of ¼ wavelength to transmitted light. By forming a quarter-wave plate by laminating the four-wavelength retardation layer, a quarter wavelength is obtained by the reverse dispersion characteristic with respect to the incident light from the linearly polarizing plate using a liquid crystal material having a positive wavelength dispersion characteristic. Methods have been proposed to make the plates work. Here, the reverse dispersion characteristic is a wavelength dispersion characteristic in which the phase difference in transmitted light is smaller as the wavelength is shorter.

  With regard to such an optical film, Patent Document 2 discloses a device for improving the tint during observation from an oblique direction with respect to a laminate of a ½ wavelength retardation layer, a ¼ wavelength retardation layer, and a positive C plate. Has been proposed.

  By the way, if the positive C plate is arranged on the quarter wavelength plate as disclosed in the cited document 2, a desired phase difference can be imparted to the transmitted light with various incident angles. Viewing angle characteristics can be secured to prevent reflection.

  However, when configured in this way, there is a problem that the configuration of the optical film becomes complicated. In addition, the manufacturing process is complicated. Further, since the configuration is complicated and the manufacturing process is complicated, there is a problem that the generation of defects due to defects and the like increases and the quality deteriorates.

JP-A-10-68816 JP 2014-224837 A

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

  In order to solve the above-mentioned problems, the present inventor has made extensive studies and made the retardation layer so that the NZ coefficient is less than 1, so that the alignment direction of the liquid crystal molecules in the vicinity of the alignment layer interface is slanted. The idea of not tilting was reached, and the present invention was conceived.

(1) An optical film provided with a retardation layer on a transparent substrate,
The retardation layer is
It is a single phase difference layer made of a polymerizable rod-like liquid crystal material,
The NZ coefficient represented by NZ = Rth / Re + 0.5 using the front phase difference Re and the thickness phase difference Rth is less than 1,
An optical film having a tilt angle of 0 degree or 90 degrees at the interface with the transparent substrate side member.
However, the front phase difference Re, the thickness phase difference Rth, and the NZ coefficient are values based on a wavelength of 550 nm.

  According to (1), the phase difference similar to that obtained by laminating the corresponding positive C plate on the A plate that gives the desired in-plane retardation can be given to the transmitted light by one phase difference layer. Thus, sufficient viewing angle characteristics can be secured. Further, by producing this retardation layer with one layer, the configuration and the process can be simplified, and the generation of defects can be further reduced to improve the quality. At this time, when the tilt angle at the interface of the retardation layer is 0 degree or 90 degrees, the direction dependency of the optical characteristics due to the pretilt of the liquid crystal material can be sufficiently reduced, and the deviation of the optical characteristics can be prevented.

(2) In (1),
The retardation layer is
An optical film comprising a homeotropic alignment layer and a homogeneous alignment layer.

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

(3) In (1) or (2),
The transparent substrate is
Stretched film,
The optical film whose interface with the said transparent base material side member is an interface with the said transparent base material.

  According to (3), by specifically aligning the polymerizable rod-like liquid crystal material using the alignment regulating force of the transparent base material to produce the retardation layer, it is possible to specifically prevent the deviation of optical characteristics. .

(4) In (1) or (2),
A photo-alignment layer is formed on the transparent substrate,
The optical film whose interface with the said transparent base material side member is an interface with the said photo-alignment layer.

  According to (4), by specifically aligning the polymerizable rod-like liquid crystal material with the photo-alignment layer to produce the retardation layer, it is possible to specifically prevent the deviation in optical characteristics.

(5) In (1) or (2),
A vertical alignment layer is formed on the transparent substrate,
The optical film whose interface with the said transparent base material side member is an interface with the said vertical alignment layer.

  According to (5), by specifically aligning the polymerizable rod-like liquid crystal material with the vertical alignment layer to produce the retardation layer, it is possible to specifically prevent the deviation of optical characteristics.

(6) In any one of (1), (2), (3), (4), (5),
In the measurement result of the phase difference value Re in which the fast axis of the retardation layer is set as a reference axis and the incident angle to the retardation layer is changed around the reference axis, the phase difference value Re is an extreme value. The incident angle is 10 degrees or less,
In the measurement result of the retardation value Re in which the slow axis of the retardation layer is set as a reference axis and the incident angle to the retardation layer is changed around the reference axis, the retardation value Re is an extreme value. An optical film having an incident angle of 10 degrees or less.

  According to (6), the optical film which avoids the bias | deviation of an optical characteristic more specifically regarding the optical characteristic which concerns on a phase difference value can be provided.

  (7) An image display device comprising the optical film according to any one of (1), (2), (3), (4), (5), and (6) on a panel surface of an image display panel.

  According to (7), with respect to the image display device including the optical film including the retardation layer functioning as the A plate, the structure and the process are simplified and the quality is further improved while ensuring a sufficient viewing angle characteristic. be able to.

  According to the present invention, regarding an optical film including a retardation layer functioning as an A plate, the structure and process can be simplified and the quality can be further improved 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 where it uses for description of a phase difference layer. It is a figure which shows the transfer film applied to the optical film which concerns on the image display apparatus 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 table | surface used for description of an Example.

[First Embodiment]
[Image display device and optical film]
FIG. 1 is a sectional view showing an image display apparatus 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 based on a wavelength of 550 nm, unless otherwise specified. The image display device 1 is arranged by attaching an optical film 3 made of an antireflection film to the panel surface (viewer side surface) of the image display panel 2 using an adhesive layer or the like. Thus, the image display device 1 is configured to sufficiently prevent reflection by the optical film 3. The image display panel 2 is an image display panel using a self-luminous element such as an organic EL element, but an image display panel such as a liquid crystal display panel may be applied instead.

  The optical film 3 is composed of a laminate of the linearly polarizing plate 4 and the quarter wave plate 5, thereby functioning as a circularly polarizing plate and preventing reflection of extraneous light. The linear polarizing plate 4 is formed by impregnating polyvinyl alcohol (PVA) with iodine or the like, and then stretched to form an optical functional layer that performs an optical function as a linear polarizing plate, and a transparent film such as TAC (triacetyl cellulose). The optical functional layer is sandwiched between base materials made of materials.

  The quarter-wave plate 5 is a linearly polarized light integrally formed with an alignment layer 6 by using a quarter-wave retardation layer 7 that imparts an in-plane retardation for a quarter wavelength to transmitted light from a transfer film described later by a transfer method. Affixed to the plate 4 and arranged. Only the quarter-wave retardation layer 7 may be transferred. Here, the transfer method means that, for example, when a desired layer is formed on a base material, the layer is not directly formed on the base material, but can be peeled once on a releasable support. After the layers are laminated to produce a transfer body (transfer film), the layer formed on the support is finally laminated on the substrate (transferred layer) according to the process, demand, etc. In this method, a desired layer is formed on the base material by bonding and laminating on the base material and then peeling off and removing the support.

  The quarter-wave retardation layer 7 is a single retardation layer made of a liquid crystal material prepared by curing a single coating layer made of a polymerizable rod-like liquid crystal material, and has an in-plane retardation Re (( 550) is 50 nm to 200 nm, preferably 110 nm to 170 nm, more preferably 120 nm to 150 nm.

  In addition, the ¼ wavelength retardation layer 7 has an NZ coefficient represented by NZ = Rth / Re + 0.5 using a front phase difference Re at a wavelength of 550 nm and a thickness phase difference Rth at a wavelength of 550 nm of less than 1. More preferably, it is more than 0.2 and less than 0.8.

  Accordingly, in the embodiment, in the one-quarter wavelength retardation layer 7 made of the liquid crystal material produced by curing one coating layer made of the polymerizable rod-like liquid crystal material, in-plane for a quarter wavelength. A phase difference similar to that obtained by laminating the positive C plate corresponding to the A plate on the A plate for imparting the phase difference can be imparted to the transmitted light, thereby ensuring a sufficient viewing angle characteristic. Further, by producing the quarter-wave retardation layer 7 with a single coating film, the configuration and the process can be simplified, and the generation of defects can be reduced to improve the quality.

  At this time, if the NZ coefficient is more than 0.2 and less than 0.8, the viewing angle characteristics can be sufficiently secured in practical use.

  In the optical film 3, the alignment layer 6 is an alignment layer (horizontal alignment layer) that expresses an alignment regulating force of horizontal alignment with respect to the liquid crystal compound related to the quarter-wave retardation layer 7, and is configured by a photo-alignment layer. The Note that the photo-alignment layer can be manufactured using, for example, a light-dimerization type material, but is not limited to the light-dimerization-type material, and various photo-alignment layer materials can be widely applied. Here, the alignment layer 6 is set so that the liquid crystal molecules of the retardation layer 7 at the interface with the alignment layer 6 are not inclined in the thickness direction, that is, the tilt angle of the liquid crystal molecules is set to 0 degree or 90 degrees. Possible orientation layers are applied. In this embodiment, since the alignment layer 6 is a horizontal alignment layer, a configuration in which the tilt angle of the liquid crystal molecules of the retardation layer 7 at the interface with the alignment layer 6 is set to 0 degree is applied to the alignment layer 6. Thereby, the photo-alignment layer is applied.

  The quarter-wave retardation layer 7 includes a polymerizable rod-like liquid crystal material used for producing a retardation layer that functions as an A plate, and a polymerizable rod-like liquid crystal material used for producing a retardation layer that functions as a positive C plate. The coating solution is prepared with a mixture mixed at a constant mixing ratio, and the coating solution is applied on the alignment layer 6 and dried and cured to produce the coating solution with an NZ coefficient of less than 1. Is done.

  Here, in the retardation layer 7 prepared by simply mixing the liquid crystal material of the A plate and the positive C liquid crystal material, coating, drying and curing, the NZ coefficient is thus less than 1. The reason for this is not clear, but as shown in FIG. 2, in the vicinity of the alignment layer 6, the liquid crystal compound A is horizontally aligned by the alignment regulating force of the alignment layer 6 to form a homogeneous alignment layer. An A plate layer 9 that functions as an A plate is produced in the vicinity, and the liquid crystal compound B is vertically aligned to form a homeotropic alignment layer in the remaining portion, which is further from the alignment layer 6. This is considered to be due to the production of the positive C plate layer 8 that functions as a positive C plate.

  As a result, the optical film 3 can produce a retardation layer 7 having a NZ coefficient of less than 1 by curing a single coating film, thereby ensuring a sufficient viewing angle characteristic and simplifying the structure and process. Furthermore, the occurrence of defects can be reduced and the quality can be improved.

  The laminated structure of the A plate layer 9 and the positive C plate layer 8 is not limited to the liquid crystal material prepared by simply coating, drying and curing a mixture of two types of liquid crystal materials as in this embodiment. It can be produced by utilizing the dipole moment of the molecule, for example, it can be produced by applying an electric field or a magnetic field.

  However, if the liquid crystal molecules related to the A plate layer 9 are tilted and aligned 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 major axis direction (the fast axis direction) of the liquid crystal molecules, the in-plane phase difference is an extreme value (minimum value). (Or the maximum value) is different from 0 degree and is biased to the positive side or the negative side of the incident angle. As a result, in the antireflection film, anisotropy appears in the antireflection function, and the optical characteristics deteriorate.

  As a result of various studies, it has been found that such an inclination of the liquid crystal molecules related to the A plate layer 9 can be prevented by preventing the liquid crystal material from inclining 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 degree or 90 degrees, it is possible to prevent the deviation of the optical characteristics. Thereby, in this embodiment, the optical alignment layer is applied to the alignment layer 6 to prevent the deviation of the optical characteristics.

  More specifically, in the measurement result of the phase difference value Re in which the fast axis of the phase difference layer 7 is set as the reference axis and the incident angle to the phase difference layer 7 is changed around the reference axis, The incident angle at which Re reaches an extreme value is preferably 10 degrees or less, preferably 5 degrees or less, and the slow axis of the retardation layer 7 is set as a reference axis, and the reference axis is set around this reference axis. In the measurement result of the phase difference value Re in which the incident angle to the phase difference layer 7 is changed, the incident angle at which the phase difference value becomes an extreme value is 10 degrees or less, and preferably 5 degrees or less. In this way, it is possible to sufficiently prevent the deviation in optical characteristics. The phase difference value Re obtained by setting the phase advance axis of the phase difference layer 7 as the reference axis and changing the incident angle to the phase difference layer 7 around the reference axis is obtained as the slow phase of the phase difference layer 7. It is a measurement result of phase difference value Re which changed an incidence angle in the perpendicular plane of a phase contrast layer containing an axis. Further, the phase difference value Re measured by setting the slow axis of the phase difference layer 7 as the reference axis and changing the incident angle to the phase difference layer 7 around the reference axis is obtained as the phase advance value of the phase difference layer 7. It is a measurement result of phase difference value Re by which an incident angle was changed in the perpendicular plane of a phase contrast layer containing an axis.

  Here, the polymerizable rod-shaped liquid crystal material applicable to the A plate is a liquid crystal material that is horizontally aligned by the alignment regulating force in the horizontal direction (the in-plane direction of the alignment layer), and has a polymerizable functional group in the molecule. Various rod-like liquid crystal compounds can be applied. Further, this rod-like liquid crystal compound has a refractive index anisotropy, and has a function of imparting desired retardation by being regularly arranged by the alignment regulating force of the alignment layer 6. Examples of the rod-like compound include materials exhibiting a liquid crystal phase such as a nematic phase and a smectic phase, but the nematic phase is easier to arrange regularly than liquid crystal compounds exhibiting other liquid crystal phases. It is more preferable to use the rod-shaped compound shown.

  As a specific example of the rod-shaped compound used in the present embodiment, for example, compounds represented by the following formulas (1) to (17) can be exemplified, and these compounds are used alone or mixed and polymerized for use. can do.

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

  Specifically, for example, the configuration disclosed in Japanese Patent Application Laid-Open No. 2015-191143 can be applied. More specifically, RMM28B manufactured by Merck, UCL-018 manufactured by DIC, or the like can be applied.

  The retardation layer made of a liquid crystal material (hybrid alignment liquid crystal material) exhibiting hybrid characteristics is aligned in the vertical direction in the vicinity of the vertical alignment film, and the liquid crystal material is gradually aligned as the distance from the vertical alignment film increases. It has the characteristic of falling (sleeping) in the horizontal direction. Thus, in the retardation layer made of a liquid crystal material exhibiting hybrid characteristics, it seems that liquid crystal molecules are aligned in the same manner as described above with reference to FIG. However, in the retardation layer made of a hybrid liquid crystal material, when the in-plane retardation is measured by changing the angle in the major axis direction of the horizontally aligned liquid crystal molecules, the angle at which the in-plane retardation exhibits an extreme value is 0. The angle is deviated from the direction of the angle, and the in-plane phase difference characteristic is deviated in one direction. As a result, it becomes difficult to ensure a sufficient viewing angle characteristic in a retardation layer made of a liquid crystal material exhibiting hybrid characteristics.

  However, in the retardation layer 7 of this embodiment, the angle at which the in-plane retardation shows an extreme value is set in the direction of the incident angle of 0 degree, and the positive and negative incident angle directions are centered on the direction of the 0 degree. The in-plane phase difference characteristic measured by changing the angle can be made highly symmetric, and this also ensures a sufficient viewing angle characteristic.

  In addition, by these, in the retardation layer made of the hybrid alignment liquid crystal material, the incident angle at which the above-described retardation value takes an extreme value becomes an angle larger than 10 degrees.

[Transfer film]
FIG. 3 is a cross-sectional view showing the configuration of a transfer film used for producing the optical film 3. The transfer film 10 is configured by sequentially laminating an alignment layer 6 and a quarter-wave retardation layer 7 on a base material 11 made of a transparent film material. Thus, the thickness of the optical film 3 can be reduced by producing the 1/4 wavelength phase difference layer 7 to the transfer film 10, and transferring by the transfer method.

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

[Method for producing optical film]
FIG. 4 is a flowchart showing the manufacturing process of the transfer film 10. In the optical film 3, after the quarter 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, the substrate 11 is peeled off. Thus, the quarter-wave retardation layer 7 is disposed on the linearly polarizing plate 4 by a transfer method. Then, an adhesive layer, a separator film, etc. are laminated | stacked and cut | disconnected to a desired magnitude | size, and the optical film 3 is produced. 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 disposed 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 SP <b> 2, the substrate 11 is coated with the coating liquid related to the alignment layer 6, dried, and then irradiated with linearly polarized ultraviolet rays. Produced.

  The manufacturing process of the transfer film 10 is used in the subsequent liquid crystal material coating process SP3 to produce a polymerizable rod-shaped liquid crystal material used for producing a retardation layer functioning as an A plate and a retardation layer functioning as a positive C plate. A coating liquid is prepared from a mixture obtained by mixing the polymerization rod-shaped liquid crystal material to be mixed at a certain mixing ratio, and this coating liquid is applied onto the alignment layer 6 and dried. Subsequently, in the curing step SP4, the coating film related to the quarter-wave retardation layer 7 is cured by irradiation with non-polarized ultraviolet rays, whereby the quarter-wave retardation layer 7 is produced.

  According to the above configuration, by providing a single retardation layer made of a polymerizable rod-like liquid crystal material having an NZ coefficient of less than 1 on the transparent substrate, the A plate and the positive plate can be formed in one retardation layer. The characteristics relating to the laminated structure of the C plate can be ensured, thereby ensuring the sufficient viewing angle characteristics, simplifying the configuration and the process, and further improving the quality. At this time, when the tilt angle at the interface of the retardation layer is 0 degree or 90 degrees, the direction dependency of the optical characteristics due to the pretilt of the liquid crystal material can be sufficiently reduced, and the deviation of the optical characteristics can be prevented.

  In addition, by providing a homeotropic alignment layer and a homogeneous alignment layer, the retardation layer has a more specific configuration, and with respect to an optical film including a retardation layer that functions as an A plate, after ensuring sufficient viewing angle characteristics. The structure and the process can be simplified, and the quality can be further improved.

  Further, by preparing a photo-alignment layer on a base material and orienting a polymerizable rod-like liquid crystal material with the photo-alignment layer to produce a retardation layer, it is possible to specifically prevent deviation of optical characteristics.

[Second Embodiment]
FIG. 5 is a diagram showing an image display apparatus according to the second embodiment of the present invention in comparison with FIG. In this image display device 21, the optical film 13 is applied instead of the optical film 3. Further, in this optical film 13, an optical film 15 is laminated on the linear polarizing plate 4 in place of the quarter-wave 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, like the transfer film 10, the optical film 15 is formed by sequentially forming the alignment layer 6 and the quarter-wave retardation layer 7 on the base material 22 made of a transparent film material. For example, a TAC film material having a low property is applied, and the base material 22 is bonded to the linearly polarizing plate 4 and disposed. Thus, 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 in 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. In this image display device 31, an optical film 33 is applied instead of the optical film 3. In addition, the optical film 33 is formed by laminating the ½ wavelength retardation layer 34 on the ¼ wavelength retardation layer 7 to form the ¼ wavelength plate 5, and is laminated on the linear polarizing plate 4. 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.

  The optical film 33 according to this embodiment is manufactured by sequentially laminating the ½ wavelength retardation layer 34 and the ¼ wavelength retardation layer 7 on the linearly polarizing plate 4 by the transfer method. The 1/4 wavelength phase difference layer 7 is laminated on the / 2 wavelength phase difference layer 34 by a transfer method to produce a laminate of the 1/2 wavelength phase difference layer 34 and the 1/4 wavelength phase difference layer 7, or transparent A quarter-wave retardation layer 7 and a half-wave retardation layer 34 are sequentially formed on a substrate made of a film material, and a laminate of the quarter-wave retardation layer 7 and the half-wave retardation layer 34 is formed. After the production, this laminate may be laminated on the linear polarizing plate by a transfer method. Further, as described above with respect to the second embodiment in comparison with the first embodiment, instead of applying such a transfer method, the half-wave retardation layer 34 and the quarter-wave retardation layer 7 are produced. You may make it laminate | stack the provided base material integrally.

  Here, in this embodiment, in the laminated body of the ½ wavelength retardation layer 34 and the ¼ wavelength retardation layer 7, an in-plane retardation for ¼ wavelength is given to the transmitted light of the linearly polarizing plate 4. The transmitted light is emitted toward the image display panel 2 by circularly polarized light. Further, at this time, by providing an in-plane retardation corresponding to ¼ wavelength by the laminated body of the ½ wavelength retardation layer 34 and the ¼ wavelength retardation layer 7, sufficient antireflection is achieved in a wide wavelength band. Configured to be able to.

  For this reason, in this embodiment, when the optical film 33 is viewed from the linear polarizing plate 4 side, the half-wave retardation layer 34 and the quarter-wave retardation layer 7 are formed with respect to the absorption axis of the linear polarizing plate 4. Thus, the slow axes of the ½ wavelength phase difference layer 34 and the ¼ wavelength phase difference layer 7 are arranged to form angles θ1 and θ2 counterclockwise, respectively. Here, if the chromatic dispersion characteristics of the ½ wavelength retardation layer 34 and the ¼ 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. Θ2 is not less than 70 degrees and not more than 80 degrees, and more preferably not less than 72 degrees and not more than 76 degrees.

  The half-wave retardation layer 34 is a single retardation layer made of a liquid crystal material prepared by curing a single coating film made of a liquid crystal compound layer, and has 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. In this embodiment, the in-plane retardation Re (550) is about 220 nm or more and 280 nm or less, which is about ½ of the wavelength 550 nm.

  The ½ wavelength phase difference layer 34 is produced in the same manner as the ¼ wavelength phase difference layer 7, and is produced so that the NZ coefficient is less than 1, more preferably more than 0.2 and less than 0.8. The Alternatively, the half-wave retardation layer 34 may be configured in the same manner as a retardation layer made of a liquid crystal material functioning as a conventional A plate (NZ coefficient is 1).

  The quarter-wave plate 5 is a laminated structure of the quarter-wave retardation layer 7 and the half-wave retardation layer 34, and has a thickness direction retardation value Rth corresponding to the in-plane retardation of the quarter-wave plate. (550) may be secured, and in this case, the quarter-wave retardation layer 7 and the half-wave retardation layer 34 may share the function as the positive C plate. Although the configuration is different from the configuration of 6, the 1/4 wavelength retardation layer is configured in the same manner as the retardation layer made of a liquid crystal material functioning as a conventional A plate, and the 1/2 wavelength retardation layer 34 has an NZ coefficient of less than 1. More preferably, it may be made to be more than 0.2 and less than 0.8.

  In this way, when a quarter wavelength plate is constituted by the laminated structure of the quarter wavelength retardation layer 7 and the half wavelength retardation layer 34, a polymerizable rod-like liquid crystal material used for producing the A plate, The quarter-wave phase difference layer 7 is prepared by mixing the polymer rod-shaped liquid crystal material used for the production of the positive C plate, and the NZ coefficient of the quarter-wave phase difference layer 7 is adjusted by adjusting the mixing ratio. If it is configured to function as a negative A plate having a value of 0, the ½ wavelength phase difference layer 34 is constituted by a positive A plate according to the conventional configuration, and a ¼ wavelength phase difference layer, ½ wavelength according to the conventional configuration. Optical characteristics comparable to those of an optical film having a layered structure of a retardation layer and a positive C plate can be secured, and viewing angle characteristics can be sufficiently improved.

  According to the above configuration, the quarter wavelength plate is configured by the laminated structure of the ½ wavelength retardation layer and the ¼ wavelength retardation layer, thereby ensuring sufficient viewing angle characteristics in a wide wavelength band. Thus, the structure and process can be simplified and the quality can be further improved.

[Fourth Embodiment]
FIG. 7 is a view showing an image display panel according to the fourth embodiment of the present invention. This image display panel 41 is a liquid crystal display panel using an IPS (in-plane switching) system or an FFS (fringe field switching) system, and is made of a transparent substrate, an alignment layer, and the like according to the IPS system or FFS system. Thus, the liquid crystal cell 42 is produced by sandwiching the liquid crystal material. In the image display panel 41, linear polarizing plates 43 and 44 are disposed on both surfaces of the liquid crystal cell 42, and a backlight 46 is disposed on one linear polarizing plate 43 side.

  On the opposite side of the backlight 46, a half-wave plate 45 is disposed between the linear polarizing plate 44 and the liquid crystal cell 42. The optical compensation by the half-wave plate sufficiently transmits transmitted light. It is configured to be shielded from light. In this embodiment, the configuration of the quarter-wave plate described above with respect to the first embodiment or the second embodiment is set on the half-wave plate 45, and the thickness of the retardation layer is set to a thickness corresponding to the half-wave. Applied.

  In this embodiment, even when applied to optical compensation of a liquid crystal display panel according to the IPS mode and the FFS mode, sufficient viewing angle characteristics are ensured for an optical film including a retardation layer functioning as an A plate. Thus, the structure and process can be simplified and the quality can be further improved.

[Fifth Embodiment]
In this embodiment, for example, a transparent film material having a horizontal alignment regulating force, such as a biaxially stretched PET film, is applied to a transparent substrate, the alignment layer 6 is omitted, and the transfer film and optical according to the above-described embodiment Construct a film. This embodiment is configured in the same manner as the above-described embodiment except that the configurations regarding 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 such that the tilt angle at the interface with the transparent film material is 0 degree.

  Even if a transparent film material having a horizontal alignment regulating force is applied to a substrate and the alignment layer is omitted as in this embodiment, the same effects as in the first to fourth embodiments can be obtained. .

[Sixth Embodiment]
In this embodiment, instead of the horizontal alignment layer that expresses the alignment regulating force in the horizontal direction, a vertical alignment layer that expresses the alignment regulating force in the vertical direction is applied to the alignment layer. This embodiment is configured in the same manner as the above-described embodiment except that the configuration regarding the alignment layer is different.

  Here, as the vertical alignment layer, an alignment layer used for manufacturing a C plate can be widely applied. When the vertical alignment layer is applied in this manner, the liquid crystal material of the retardation layer is aligned at a tilt angle of 90 degrees at the interface with the vertical alignment layer, thereby conversely to the configuration of FIG. It is considered that a homeotropic alignment layer is formed to form a positive C plate layer, and a homogeneous alignment layer is formed at a position far from the alignment layer to form an A plate layer.

  Even when the vertical alignment layer is applied in this manner, the same effects as those of the above-described embodiment can be obtained.

[Seventh Embodiment]
In this embodiment, for example, a transparent film material having a vertical alignment regulating force, such as a biaxially stretched PET film, is applied to a transparent substrate, the alignment layer 6 is omitted, and the transfer film and optical according to the above-described embodiment Construct a film. This embodiment is configured in the same manner as the above-described embodiment except that the configurations regarding the base material and the alignment layer are different.

  Thus, 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.

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

[Other Embodiments]
The specific configuration suitable for the implementation of the present invention has been described in detail above. However, the present invention is not limited to the scope of the present invention, and various combinations of the above-described embodiments, and further the configuration of the above-described embodiments. Can be variously changed.

  That is, in the above-described embodiment, the case where the present invention is applied to the optical film related to antireflection and optical compensation has been described. However, the present invention is not limited to this, and various optical systems including a retardation layer functioning as an A plate. Can be widely applied to film.

FIG. 8 is a diagram for explaining an embodiment of the present invention. Examples 1 and 2 are examples relating to the transfer film of the first embodiment, in which a photo-alignment layer is provided by applying a biaxially stretched PET film and a glass substrate to the base material 11, respectively. Example 3 is an example according to the optical film 15 of the second embodiment, in which a TAC film is applied to the substrate 22 and a photo-alignment layer is provided. The photo-alignment layers in Examples 1 to 3 were prepared by irradiating ultraviolet rays by linearly polarized light with a light amount of 30 mJ / cm ² , and the tilt angle at the interface with the alignment layer was 0 degree.

  Example 4 is an example according to the fifth embodiment, in which a biaxially stretched PET film is applied to a base material, and a liquid crystal material is horizontally oriented by the orientation regulating force of the base material to produce a retardation layer. Is. Thus, in Example 4, the tilt angle at the interface with the base material is 0 degree.

  Examples 5 and 6 are examples according to the sixth embodiment, in which a biaxially stretched PET film and a glass substrate are applied to a base material to produce a vertical alignment layer, and the alignment regulating force of this vertical alignment layer A liquid crystal material is vertically aligned to produce a retardation layer. Thus, in Examples 5 and 6, the tilt angle at the interface with the vertical alignment layer is 90 degrees.

  Examples 7 and 8 are examples according to the seventh embodiment, except that a stretched PET film material, which is a transparent film material stretched so as to develop an orientation regulating force in the vertical direction, is applied to a substrate. Thus, the configuration was the same as in Example 4. As a result, in Examples 7 and 8, the tilt angle at the interface with the substrate is 90 degrees.

  In the comparative example, a biaxially stretched PET film is applied to a base material, a polyimide resin layer is prepared on the base material, and then a rubbing treatment is performed, thereby producing an alignment layer by the rubbing treatment. Thereby, in the comparative example, the tilt angle at the interface with the alignment layer was 5 degrees. The tilt angle is measured by cutting a cross section of the prepared sample to produce a test sample using a thin film, placing the test sample on a polarizing microscope, and crossing the substrate surface at 0 degree under a polarizing plate crossed Nicol. This was carried out by examining the slow axis of the liquid crystal.

  In Examples 1 to 8 and Comparative Examples, (11) described in the rod-shaped compound is applied to the polymerizable rod-shaped liquid crystal material used for the production of the retardation layer functioning as the A plate, and functions as a positive C plate. RMM28B (manufactured by Merck & Co., Inc.) was applied to the polymerized rod-shaped liquid crystal material used for the production of the retardation layer, and these liquid crystal materials were mixed to prepare a coating liquid for the retardation layer.

  In these examples 1 to 8 and the comparative example, the fast axis and slow axis of the retardation layer are respectively set as the reference axis (rotation axis), and the incident angle to the retardation layer is changed around the reference axis. A phase difference value was measured, and an incident angle that was an extreme value was measured. For this measurement, for example, KOBRA-WR manufactured by Oji Scientific Instruments can be used. In addition, this measurement was performed in three places, respectively.

  In Examples 1-8, except for Example 8, the incident angle at which the extreme value is reached is 5 degrees at the maximum, and this prevents the deviation of the optical characteristics sufficiently. It can be seen that the incident angle is large and this causes a deviation in optical characteristics.

1, 21, 31 Image display device 2, 42 Image display panel 3, 13, 15, 33 Optical film 4, 43, 44 Linearly polarizing plate 5 1/4 wavelength plate 6 Alignment 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 wavelength plate 46 Backlight

Claims (7)

An optical film having a retardation layer on a transparent substrate,
The retardation layer is
It is a single phase difference layer made of a polymerizable rod-like liquid crystal material,
The NZ coefficient represented by NZ = Rth / Re + 0.5 using the front phase difference Re and the thickness phase difference Rth is less than 1,
An optical film having a tilt angle of 0 degree or 90 degrees at the interface with the transparent substrate side member.
However, the front phase difference Re, the thickness phase difference Rth, and the NZ coefficient are values based on a wavelength of 550 nm. The retardation layer is
The optical film according to claim 1, comprising a homeotropic alignment layer and a homogeneous alignment layer. The transparent substrate is
Stretched film,
The optical film according to claim 1, wherein an interface with the transparent substrate side member is an interface with the transparent substrate. A photo-alignment layer is formed on the transparent substrate,
The optical film according to claim 1, wherein an interface with the transparent substrate side member is an interface with the photo-alignment layer. A vertical alignment layer is formed on the transparent substrate,
The optical film according to claim 1, wherein an interface with the transparent substrate side member is an interface with the vertical alignment layer. In the measurement result of the phase difference value Re in which the fast axis of the retardation layer is set as a reference axis and the incident angle to the retardation layer is changed around the reference axis, the phase difference value Re is an extreme value. The incident angle is 10 degrees or less,
In the measurement result of the retardation value Re in which the slow axis of the retardation layer is set as a reference axis and the incident angle to the retardation layer is changed around the reference axis, the retardation value Re is an extreme value. The incident angle which becomes 10 degrees or less. The optical film in any one of Claim 1, Claim 2, Claim 3, Claim 4, and Claim 5. An image display device comprising the optical film according to any one of claims 1, 2, 3, 4, 5, and 6 on a panel surface of an image display panel.