JP2014115604A - Optical film, image display device and manufacturing method of optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film capable with further suppressed unevenness in film thickness of a retardation layer.SOLUTION: An optical film includes a transparent film base material 1; an alignment layer 2 formed on the transparent film base material 1, with a surface having an alignment regulating force; and a retardation layer 3 formed on the alignment layer 2 and aligned by the alignment regulating force of the surface of the alignment layer 2. In the retardation layer 3, volatility of film thickness per unit area is within 4.0%.

Description

  The present invention relates to an optical film, an image display device, and an optical film manufacturing method.

  In recent years, flat panel displays capable of three-dimensional display have been provided. Here, in order to perform three-dimensional display on a flat panel display, it is usually necessary to selectively provide a right-eye image and a left-eye image to the viewer's right eye and left eye in some manner. . As a method for selectively providing a right-eye image and a left-eye image, for example, a passive method is known. This passive three-dimensional display method will be described with reference to the drawings.

  FIG. 6 is a schematic diagram showing an example of a passive three-dimensional display using a liquid crystal display panel. In the example of FIG. 6, pixels that are consecutive in the vertical direction of the liquid crystal display panel are sequentially and alternately assigned to a right-eye pixel that displays a right-eye image and a left-eye pixel that displays a left-eye image. And driving with the image data for the left eye, thereby displaying the image for the right eye and the image for the left eye simultaneously. As a result, the screen of the liquid crystal display panel is alternately switched into a region for displaying an image for the right eye and a region for displaying an image for the left eye, for example, by a band-shaped region in which the short side is vertical and the long side is horizontal. It is divided.

  Furthermore, in the passive method, a pattern retardation film is placed on the panel surface of the liquid crystal display panel, and light emitted from the linearly polarized light from the right-eye and left-eye pixels is converted into circularly polarized light with different rotation directions for the right-eye and left-eye. To do. Therefore, in the pattern retardation film, two types of band-like regions in which the slow axis direction (direction in which the refractive index is maximum) are orthogonal to each other are sequentially formed corresponding to the setting of the region in the liquid crystal display panel. Thus, in the passive method, glasses equipped with corresponding polarizing filters are worn, and a right-eye image and a left-eye image are selectively provided to the viewer's right eye and left eye, respectively. Here, as the slow axis direction of the adjacent band-like region, a combination of +45 degrees and −45 degrees, or 0 degrees and +90 degrees with respect to the horizontal direction is usually employed. In the example of FIG. 6, the long side direction of the screen is shown as the horizontal direction according to the name in the normal image display device.

  This passive method can also be applied to a liquid crystal display device with a slow response speed, and can also display three-dimensionally with a simple configuration using a pattern retardation film and circularly polarized glasses.

  The pattern phase difference film according to this passive method requires a pattern-like phase difference layer that gives a phase difference to transmitted light corresponding to the allocation of pixels. With respect to this pattern retardation film, Patent Document 1 discloses a method of forming a retardation layer by forming a photo-alignment layer on a glass substrate with controlled alignment regulating force and patterning the alignment of liquid crystals with this photo-alignment layer. Is disclosed. Patent Document 2 discloses that a photo-alignment layer is prepared by exposing the entire surface to light and then using a mask, and aligning and curing the retardation layer by the alignment regulating force of the photo-alignment layer. Discloses a method for producing a patterned retardation film.

  By the way, the manufacturing process of a pattern phase difference film includes the process of apply | coating the liquid crystal material diluted with the solvent to a base material. In such a process, it was found that unevenness occurs in the film thickness of the retardation layer after curing due to the slight wind until the solvent dries.

  Unevenness in the film thickness of the retardation layer appears as unevenness in the color of the surface of the retardation layer, impairing the appearance of the retardation layer. Such color unevenness is also referred to as wind unevenness in this specification. Further, in an FPR (Film Patterned Retarder) pattern retardation film produced by directly bonding a retardation layer in which film thickness unevenness has occurred to a polarizing plate, the film thickness unevenness is between the retardation layer and the polarizing plate. It was visually recognized as interference fringes, which was one of the causes of damaging the quality of the pattern retardation film. Note that unevenness caused by interference fringes between the retardation layer and the polarizing plate is also referred to as interference unevenness in this specification.

  For example, Patent Literature 3 discloses a conventional technique for suppressing the unevenness of wind ripples or interference in the retardation layer. Patent Document 3 describes that interference unevenness is suppressed by transporting the liquid crystal material formed on the alignment layer to the heating zone without applying as much wind as possible. For this reason, the invention described in the cited document 1 defines the relative speed between the liquid crystal material conveyed in the manufacturing process of the pattern retardation film and the atmosphere.

JP 2005-49865 A JP 2012-42530 A JP-A-7-250249

  However, according to the inventors of the present invention, it has been found that the unevenness of the thickness of the retardation layer is caused not only by the velocity in the moving direction of the atmosphere but also by its fluctuation (hunting). For this reason, as described in Patent Document 3, there is a limit to suppressing the film thickness unevenness of the retardation layer only by controlling the relative speed between the surface of the liquid crystal material being transported and the atmosphere.

  This invention is made | formed in view of such a point, and it aims at providing the manufacturing method of the optical film, image display apparatus, and optical film which reduced the film thickness nonuniformity of the phase difference layer sufficiently.

  The inventors of the present invention have made extensive studies in order to solve the above-mentioned problems, obtained the knowledge that, in addition to the moving speed of the surface atmosphere related to the liquid crystal material being transported, the fluctuation of the moving speed is suppressed. The invention has been completed.

  Specifically, the present invention provides the following.

(1) a transparent film substrate;
An alignment layer formed on the transparent film substrate, the surface of which has an alignment regulating force;
A retardation layer formed on the alignment layer and aligned by an alignment regulating force on a surface of the alignment layer;
The variation rate per unit area of the thickness of the retardation layer is within 4.0%.

  According to (1), there is little unevenness in film thickness, and a high-quality optical film can be provided.

  (2) In (1), the variation in chromaticity b * represented by the L * a * b * color system, measured by irradiating the surface of the retardation layer with light having a wavelength of 550 nm, It is within 10% of the average value of chromaticity b *.

  According to (2), it is possible to provide an optical film in which the degree of color unevenness is within an allowable range for use.

  (3) In (1) or (2), the retardation layer includes a first region in which liquid crystal molecules are aligned in a first direction and a second region in which liquid crystal molecules are aligned in a second direction different from the first direction. The first region and the second region have a band shape in plan view and are alternately arranged.

  According to (3), a pattern retardation film having a right-eye region and a left-eye region can be configured.

  (4) An image display device in which the optical film according to any one of claims 1 to 3 is disposed on a surface of an image display panel.

  According to (4), it is possible to provide an image display apparatus in which a high-quality optical film is arranged with little film thickness unevenness.

(5) A method for producing an optical film including a retardation layer formed by curing a liquid crystal material, the coating step applying the liquid crystal material on an alignment layer;
A drying step of drying the solvent contained in the liquid crystal material applied in the application step,
In the environment where the liquid crystal material is transported from the coating process to the drying process, the average value of the moving speed of the atmosphere is ± 2 m / sec or less, and the fluctuation amount of the moving speed is 0.1 m / sec or less. .

  According to (5), there is little film thickness nonuniformity and a high quality optical film can be manufactured.

(6) In (5),
The drying step
The substrate formed by forming the alignment layer is heated by conveying the substrate to a heating zone by a guide roll that contacts the surface on the side where the alignment layer is not formed,
In the conveyance process to the heating zone, the guide roll is used to heat the base material from the surface side where the alignment layer is not formed.

  According to (6), the solvent can be actively scattered even in the process of transporting to the heating zone, thereby shortening the period during which wind ripple unevenness may occur and making it less susceptible to the influence of atmospheric flow. As a result, the wind pattern unevenness can be further reduced.

  (7) In (5) or (6), a solvent for diluting the liquid crystal material is a first solvent that evaporates at a first evaporation rate, and a second solvent that evaporates at a second evaporation rate that is faster than the first evaporation rate. Solvent.

  According to (7), by mixing a solvent having a high evaporation rate, the period during which the liquid crystal can cause film thickness unevenness can be shortened, and the occurrence of film thickness unevenness can be suppressed.

  (8) In (7), the first solvent contains methyl isobutyl ketone, and the second solvent contains methyl ethyl ketone.

  According to (8), a preferable solvent can be applied from the viewpoints of both the adhesion of the liquid crystal material and the suppression of film thickness unevenness.

  According to the present invention, it is possible to provide an optical film in which the film thickness unevenness of the retardation layer is sufficiently reduced, and a method for producing the optical film.

It is a figure which shows the image display apparatus which concerns on one Embodiment of this invention. It is a figure for demonstrating the manufacturing method of a pattern phase difference film. It is a figure explaining each process of FIG. It is a figure where it uses for description to the installation of the process of FIG. It is a table | surface which shows the evaluation result of an experiment example and a comparative example. It is a figure which shows the manufacturing process which concerns on 2nd Embodiment of this invention. It is a figure which shows the evaluation result of a pattern phase difference film. It is a figure which shows the passive three-dimensional display which uses a liquid crystal display panel.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an image display apparatus 100 according to an embodiment of the present invention. In the image display device 100, the pixels of the liquid crystal display panel 11 that are continuous in the vertical direction (the left and right directions are the corresponding directions in FIG. 1) are alternately displayed. Are distributed to the left-eye pixels for displaying the image, and are driven by the right-eye image data and the left-eye image data, respectively. As a result, the image display device alternately divides the display screen into a band-like region for displaying an image for the right eye and a band-like region for displaying an image for the left eye, so that the image for the right eye and the image for the left eye are divided. Display at the same time. In the image display device 100, a pattern retardation film 10 is disposed on a panel (viewer side surface) 11 of a liquid crystal display panel, and the pattern retardation film 10 corresponds to light emitted from pixels for right and left eyes, respectively. Give the phase difference. Thereby, the image display apparatus 100 displays a desired stereoscopic image by a passive method.

  Here, as for the pattern phase difference film 10, the orientation layer 2 and the phase difference layer 3 are produced in order on one surface of the transparent film base material 1 which consists of transparent films, such as TAC (triacetyl cellulose) and an acryl. In the pattern retardation film 10, the retardation layer 3 is formed of a liquid crystal material that is solidified (cured) while maintaining refractive index anisotropy, and the alignment of the liquid crystal material is patterned by the alignment regulating force of the alignment layer 2. To do. In FIG. 1, the orientation of the liquid crystal molecules is exaggerated by an elongated ellipse. By this patterning, the pattern retardation film 10 has a right width region (first region) A and a left eye region (second region) with a certain width corresponding to the pixel assignment in the liquid crystal display panel. ) B and B are sequentially formed in a band shape, and give phase differences corresponding to light emitted from the right-eye and left-eye pixels, respectively.

  After the photo-alignment material film is produced from the photo-alignment material, the pattern retardation film 10 is irradiated with ultraviolet rays by linearly polarized light by a so-called photo-alignment technique, and the alignment layer 2 is formed by the photo-alignment material film. It is formed. Here, the ultraviolet light applied to the photo-alignment material film is set so that the direction of polarization differs between the right-eye region A and the left-eye region B by 90 degrees, whereby the liquid crystal material provided in the retardation layer 3 , Liquid crystal molecules are aligned in the corresponding directions in the right-eye region A and the left-eye region B, and a phase difference corresponding to transmitted light is given.

  In addition, although various materials to which the photo-alignment technique can be applied can be applied as the photo-alignment material, in this embodiment, the alignment is not changed by ultraviolet irradiation after the alignment, for example, a light dimerization type. Use materials. This light dimerization type material is described in “M. Schadt, K. Schmitt, V. Kozinkov and. Chigrinov: Jpn. J. Appl. Phys., 31, 2155 (1992)”, “M. Seiberle and A. Schuster: Nature, 381,212 (1996) ", etc., for example, and already marketed under the trade name" ROP-103 "(Rolic technologies Ltd).

  In addition, as the liquid crystal material for forming the retardation layer 3, a conventionally known retardation layer material can be used. An example of such a material is a liquid crystal material that exhibits a nematic liquid crystal phase. As a liquid crystal material that exhibits a nematic liquid crystal phase, a conventionally known liquid crystal material may be used, and examples thereof include rod-like liquid crystal molecules, polymer liquid crystals, and polymerizable liquid crystal compounds.

[Method for producing optical film]
FIG. 2 is a diagram illustrating a manufacturing process of the pattern retardation film 10. In this manufacturing process, the transparent film substrate 1 wound around a roll is pulled out, and a photo-alignment material film is sequentially formed on the transparent film substrate 1 (step S201).

  Subsequently, in the manufacturing process of the present embodiment, polarized ultraviolet rays are irradiated onto the A region or the B region (referred to as the A region in FIG. 2), and the right eye region A or the left eye region B is exposed (step S202). Next, the entire surface of the photo-alignment material film including the right-eye area A and the left-eye area B is exposed (step S203). The alignment layer 2 is created by steps S202 and S203. The alignment layer 2 is a layer for imparting alignment regulating force to the retardation layer to be laminated later.

  Subsequently, in the present embodiment, a liquid crystal material is applied on the alignment layer 2 by a die or the like (step S204). As the liquid crystal material, the liquid crystal material described above was applied on the alignment layer 2 by diluting, for example, 100% methyl isobutyl ketone (MIBK) as a solvent. The applied liquid crystal material is dried by heating, and the solvent used for diluting the liquid crystal material is removed (step S205).

  Further, in the present embodiment, while the liquid crystal material applied on the alignment layer 2 is transported from the coating process of step S204 to the drying process of step S205, the moving speed of the atmosphere (hereinafter referred to as “wind speed” in the present embodiment). Is also ± 2 m / sec or less, and the speed variation is 0.1 m / sec or less. This specific configuration will be described later. The liquid crystal material is dried and then cured by irradiation with ultraviolet rays (step S206) to form the retardation layer 3 made of liquid crystal. After that, the pattern retardation film is subjected to an antireflection film creation process or the like as necessary, and then cut into a desired size in the cutting step.

  3A to 3E are diagrams for explaining each process shown in FIG. Fig.3 (a) has shown the transparent film base material 1 of the state pulled out from the roll. In the figure, for the transparent film substrate 1, the surface on the side on which the alignment layer is formed is indicated by reference numeral 1a. FIG. 3B shows a state in which the alignment layer 2 is formed on the surface 1a. As described with reference to FIG. 2, the alignment layer 2 is formed by selectively exposing the right eye region A or the left eye region B and then exposing the entire surface including the region A and the region B in this embodiment. Is done.

  The pattern retardation film 10 is coated with an ultraviolet curable liquid crystal material on the alignment layer 2 to form a liquid crystal material layer 3a (FIG. 3C). The liquid crystal material layer 3 a is heated to remove the solvent (FIG. 3D), and the liquid crystal molecules of the liquid crystal material layer 3 a are aligned in the direction of the alignment regulating force of the alignment layer 2. Subsequently, the liquid crystal material layer 3a is irradiated with polarized ultraviolet rays u, and the liquid crystal material is cured in an aligned state to form the retardation layer 3.

  FIG. 4 is a diagram illustrating a manufacturing process according to the retardation layer 3. In the process shown in FIG. 4, the base material 1 on which an alignment film is formed with a configuration not shown is conveyed in the direction of arrow C. In this process, the substrate 1 is transported in the course of transporting the die 107 for applying the coating liquid of the liquid crystal material layer 3A, the heating zone 108 by a drying furnace for drying the applied liquid crystal material, and the temperature can be adjusted. A temperature control drum 112 that is wound around a peripheral side surface, and a substrate 1 wound around the temperature control drum 112 is irradiated with ultraviolet light u to cure the liquid crystal material layer 3a, and the retardation layer 2 is formed. A take-up roll 114 for winding up the base material 1 is sequentially provided. In this step, the substrate 1 is conveyed from the heating zone 108 toward the temperature control drum 112 by the guide rollers 110 and 111. The temperature of the temperature control drum 112 is controlled by a water cooling method, and this manufacturing process prevents wrinkles from being generated on the transparent film substrate 1 due to heat during ultraviolet irradiation.

  In the facility shown in FIG. 4, the transparent film substrate 1 coated with the liquid crystal material is sent to the heating zone 108 from the region where the liquid crystal material is applied by the die 107 (hereinafter referred to as “zone”). A region including the line L between the two is covered with a cover (not shown) for reducing the movement of the atmosphere.

  In such an environment, the die 107 applies a coating liquid for the liquid crystal material layer 3 a onto the alignment layer 2. After application, the applied liquid crystal material is sent to the heating zone 108 and dried. In the present embodiment, the wind speed and the amount of variation thereof are measured using an anemometer in the line L covered by the cover.

  As a result of the above measurement, the wind speed of the environment in which the substrate 1 is conveyed by covering the line L with the cover is within ± 0.2 m / sec (−0.2 m / sec to 0 m / sec, 0 m / sec to +0.2 m / sec).

  In addition, the solvent for dilution is scattered and removed from the coating liquid, and after the coating liquid is applied, the solvent is removed by the scattering (the content of the solvent in the coating liquid is set in advance). The wind speed variation (hunting) σ was 0.10 m / sec or less (0 m / sec to 0.10 m / sec). The symbol “+” of the moving speed indicates the same direction (following wind) as the moving direction of the liquid crystal material layer 3a and the like. The symbol “−” of the moving speed indicates the direction (head wind) opposite to the moving direction of the liquid crystal material layer 3a and the like.

  The transparent film substrate 1 that has passed through the heating zone 108 is sent to a zone in which an ultraviolet irradiation device 109 that performs ultraviolet irradiation is provided, and the liquid crystal material is aligned by the alignment regulating force of the alignment film by irradiation with ultraviolet u. Is cured (solidified) to form a retardation layer, which is wound on a winding roll 114.

[quality evaluation]
Next, the inventors of the present invention evaluated the pattern retardation film of the present embodiment as follows.
(1) Visual observation A commercially available polarizing plate (HCL2-5618HCS, manufactured by Sanlitz Co., Ltd.) is bonded to both sides of the pattern retardation film cut to 1 m ^{2 so} that the bright light position of the crossed Nicol arrangement is obtained, and the liquid crystal in the dark room Installed on the backlight. And the part in which the color nonuniformity appeared on the surface was observed visually, and the grade of the color nonuniformity was evaluated in five steps (Lv1-Lv5). The evaluation criteria are such that Lv1 and Lv2 can be used, and Lv3 to 5 cannot be used (quality: Lv1>Lv2>Lv3>Lv4> Lv5).

(2) Retardation value, film thickness In the present embodiment, a phase difference Re (hereinafter referred to as “resonance difference”) is measured at 9 points in the pattern retardation film using a phase difference / optical axis measurement device (Axostep: manufactured by Axometrics). (Referred to as “in-plane retardation”). Further, the fluctuation rate of the film thickness was calculated with the refractive index difference being constant with the fluctuation value of the retardation value as a reference. As a result of the calculation, it is confirmed that the variation rate of the film thickness per unit area (1 m ² ) is within 4.0% (0% to 4.0%) in the pattern retardation film created in this embodiment. Was

(3) Color unevenness A black PET (polyethylene terephthalate) substrate is bonded to the back surface of the patterned retardation film constituted by the orientation layer 2 and the retardation layer 3 described above, and a spectroscope (UV-PC 2500: manufactured by Shimadzu Corporation). Was used, and the spectrum of C light source 2 degrees was applied from the surface side. Then, the chromaticity b * of 5 degree reflection was measured. The chromaticity b * is a parameter indicating chromaticity defined by the L * a * b * color system. As a result of the measurement, it was found that in the pattern retardation film of the present embodiment, the variation in chromaticity b * was within 10% (0% to 10%) of the average value of chromaticity b *.

[Experimental example]
Next, specific experimental examples 1 to 8 performed on the pattern retardation film of the present embodiment described above will be described.
(1) Experimental example 1
In Experimental Example 1, the pattern retardation film of the present embodiment was prepared by the procedure described in the following (a) to (d).
(A) A base material in which a photo-alignment layer material is coated on the back surface of a TAC original fabric (TD60UL-P) treated with AG (Anti Glare), 20 mJ / cm 2 of polarized UV light has an optical axis of 45 degrees Irradiation was performed to form an alignment layer.
(B) On the alignment layer, a nematic liquid crystal material to be a retardation layer was diluted with a solvent and applied by die coating. In Experimental Example 1, the solvent was 100% MIBK.
(C) The TAC original plate coated with the liquid crystal material was transported to the heating zone while keeping the average wind speed at +0.2 m / sec and the wind speed variation σ at 0.10 m / sec, and dried in the heating zone.
(D) The nematic liquid crystal material is irradiated with ultraviolet rays so as to have a thickness of 1 μm after completion, and aligned so that regions for the right eye and regions for the left eye are alternately arranged to form a retardation layer. Formed.

(2) Experimental example 2
Experimental Example 2 was performed in the same procedure as Experimental Example 1 except that the moving speed fluctuation amount σ in the procedure (c) was set to 0.09 m / sec or less in the procedure of Experimental Example 1 described above.
(3) Experimental example 3
Experimental Example 3 is the same as Experimental Example 1 except that the average wind speed in Procedure (c) is within +0.1 m / sec and the variation σ is 0.05 m / sec or less. The same procedure was performed.
(4) Experimental example 4
Experimental example 3 is the same as the experimental example 1 described above, except that the average wind speed in step (c) was −0.1 m / sec and the variation σ was 0.06 m / sec or less. The same procedure was used.

(5) Experimental example 5
Experimental example 5 is the same as the experimental example 1 described above except that the average wind speed in step (c) was −0.2 m / sec and the variation σ was 0.08 m / sec or less. The same procedure was used.
(6) Experimental example 6
Experimental Example 6 was performed in the same procedure as Experimental Example 1 except that the average of the wind speed in the procedure (c) was set within −0.2 m / sec.

(7) Experimental example 7
Experimental example 7 is a mixture of MIBK and MEK at a ratio of 7: 3 in the procedure of experimental example 1 described above, and the average wind speed of procedure (c) is -0.2 m. / Sec. The procedure (a) was performed in the same manner as in Experimental Example 1. MEK (methyl ethyl ketone) is a solvent having a higher evaporation rate than MIBK (specific evaporation rate of methyl ethyl ketone: 465, specific evaporation rate of methyl isobutyl ketone: 145), and is removed from the liquid crystal material faster than MIBK. For this reason, in Experimental Example 7, it is possible to reduce the time during which the liquid crystal material is in a state in which wind ripple unevenness or the like can occur, and to suppress wind ripple unevenness.

  Experimental Example 8 is a mixture of MIBK and MEK at a ratio of 6: 4 in the procedure of Experimental Example 7 described above, and the average wind speed of Procedure (c) is −0.2 m. / Sec. The procedure (a) was performed in the same manner as in Experimental Example 1.

[Experimental example]
In addition, the inventors of the present invention conducted an experiment for comparison with the results of Experimental Examples 1 to 8 described above. The procedure of Comparative Experimental Examples 1 to 4 for comparison is described below.
(1) Comparative Experiment Example 1
Comparative experiment example 1 is the same as the experiment example 1 described above except that the average wind speed in step (c) is set to within −0.3 m / sec and the movement speed variation σ is set to 0.20 m / sec or less. Was performed in the same procedure as in Experimental Example 1.
(2) Comparative experiment example 2
Comparative experiment example 2 is the same as the experiment example 1 described above except that the average wind speed in step (c) is within +0.4 m / sec and the variation σ of the moving speed is 0.30 m / sec or less. The procedure was the same as in Experimental Example 1.
(3) Comparative Experiment Example 3
Comparative experiment example 3 is the same as the experiment example 1 described above except that the average wind speed in step (c) is set to within −0.4 m / sec and the moving speed variation σ is set to 0.15 m / sec or less. Was performed in the same procedure as in Experimental Example 1.
(4) Comparative Experiment Example 4
In Comparative Experimental Example 4, among the procedures of Experimental Example 1, the solvent of Procedure (b) was mixed with MIBK and MEK at 6: 4 in the same manner as Experimental Example 8, and The average wind speed was set within −0.4 m / sec. The procedure (a) was performed in the same manner as in Experimental Example 1.

  FIG. 5 is a table showing evaluation results of Experimental Examples 1 to 8 and Comparative Experimental Examples 1 to 4 performed under the conditions described above. The evaluation was performed by the above-described visual observation, film thickness unevenness, and color unevenness (chromaticity b *). As is clear from FIG. 5, regarding color unevenness, Lv1 or Lv2 that can be used in all of Experimental Examples 1 to 8 of this embodiment is obtained. Moreover, it was confirmed that the variation rate of the film thickness obtained from the in-plane retardation is within 4.0% for all of Experimental Examples 1 to 8 of the present embodiment. If the variation rate of the film thickness is set within 4.0%, the color unevenness can be sufficiently suppressed and a high quality optical film can be provided.

  Furthermore, for all of Experimental Examples 1 to 8, it was confirmed that the variation rate of chromaticity b * indicating color unevenness was within 10% with respect to the average value of chromaticity b *. As a result, if the variation rate of the chromaticity b * indicating the color unevenness is within 10% of the average value of the chromaticity b *, the color unevenness is sufficiently suppressed by a more specific configuration and the high quality is achieved. The optical film can be provided. Note that, as in Experimental Example 8, even when the proportion of MEK in the solvent of Experimental Example 7 was increased from 30% to 40%, the film quality of the pattern retardation film was significantly different from that of Experimental Example 7. There wasn't.

  On the other hand, in Comparative Experimental Examples 1 to 4, the evaluation of Lv3 or Lv4, all of which cannot be used due to color unevenness, was obtained. In all of Comparative Experimental Examples 1 to 4, the variation rate of the film thickness obtained from the in-plane retardation is 4.0% or more, and the variation rate of the chromaticity b * is relative to the average value of the chromaticity b *. Of 10% or more. Further, from Comparative Experimental Example 4, even when MEK having a high evaporation rate is mixed with a solvent, when the average wind speed and the variation σ thereof are large, the quality of the pattern retardation film becomes a usable standard. I found that it was not enough.

[Second Embodiment]
As a result of further investigations, it has been found that, in the drying process of the coating liquid applied to the retardation layer, if the drying is set to be completed in a short time, the wind ripple unevenness can be further reduced. This means that by shortening the period during which the wind ripple unevenness may occur, it can be made less susceptible to the influence of the atmospheric flow, and as a result, the wind ripple unevenness can be reduced.

  Here, FIG. 6 is a diagram for explaining the manufacturing process according to the second embodiment in comparison with FIG. 4. In this manufacturing process, three coating rolls 200, 201, and 202 are provided in the conveyance process to the heating zone 108 after coating the coating liquid related to the retardation layer by the die 107. The base material 1 is conveyed by the guide rolls 200, 201, and 202. Each of the guide rolls 200, 201, and 202 is provided with a heater and a temperature sensor, and is configured such that the temperature of the peripheral side surface can be set to a desired temperature by the control of the controller 205 based on the temperature detection result by the temperature sensor.

  Thereby, in this embodiment, in addition to the control of the air flow on the surface of the base material described above with respect to the first embodiment, the back surface of the base material 1 (the surface on which the coating liquid is not applied) in the transport process to the heating zone The wind ripple unevenness is further reduced by controlling the temperature of the guide rolls 200, 201, and 202 that are in contact with the head). This embodiment has the same configuration as that of the first embodiment except that the configuration relating to the guide rolls 200, 201, and 202 is different.

  In addition to such a configuration, by applying a quick-drying solution to the diluted solution of the coating solution, it is possible to further reduce the unevenness of the wind pattern. In this embodiment, a mixed solution of MIBK and MEK is applied to the diluted solution. By doing so, it is possible to sufficiently ensure quick drying.

  In addition, when the base material 1 is heated from the back surface immediately after application to disperse the solvent, the liquid crystal material layer 3a can be formed with a sufficiently uniform film thickness, which is created by irradiation with ultraviolet rays. It was found that even in the retardation layer formed, the optical properties were improved by forming with a uniform film thickness.

  When the guide rolls 200, 201, 202 are heated, the permeability of the diluent to the base material 1 is also improved, so that the adhesion to the base material 1 through the alignment film is increased, thereby improving the reliability. It will be different. In addition, since the coating liquid dries in a shorter time, the occurrence of defects due to so-called repelling that repels the coating liquid is further suppressed, and this also improves the reliability.

  FIG. 7 is a diagram showing these evaluation results. The temperature of the guide roll and the peripheral side surface was set variously, and the nonuniformity of drying which becomes a wind pattern nonuniformity, the adhesive force with respect to the base material 1, orientation, and the defect by repelling were confirmed. The dry unevenness is clearly indicated by “×” and “△” when the interference unevenness due to the wind ripple unevenness is significant, and although it is a practically sufficient level, it can be observed in detail. The case where it can be done is indicated by “◯”, and the case where it cannot be seen even by detailed observation is indicated by “◎”.

In addition, the adhesion force is indicated by “◯” when it does not peel off in the 45 ° peel test specified in JISK5400, and indicated by “x” when this condition is not satisfied. The orientation is judged by measuring the amount of transmitted light at the extinction position with a pattern retardation film sandwiched between linearly polarizing plates arranged in a crossed Nicols state. However, a case where there is room for improvement from the viewpoint of securing a high-quality image that has been sunk further black is indicated by “◯”, and a case where a sufficiently high-quality image that has been sunk black can be secured is indicated by “◎”. Moreover, the defect of repellency is determined by the first and second criterion values for the number of defects having a diameter of 500 μm or more in a certain range (1 m ² ). A thing with "(triangle | delta)" was represented by "(triangle | delta)", and the thing with many defects was represented by "x".

  This measurement was performed at room temperature of 20 ° C to 25 ° C. Therefore, the guide rolls 200, 201, and 202 are generally held at 20 ° C. to 25 ° C. under the condition that the guide roll temperature is not set.

  It has been found that when the temperature of the guide rolls 200, 201, 202 is too high, the drying speed is remarkably increased so that drying unevenness corresponding to the arrangement of the guide rolls 200, 201, 202 occurs. As a result, it is desirable that the portion where the solvent is completely scattered is between the guide rolls where the guide roll is not in contact with the back surface. Further, when a temperature equal to or higher than the transition temperature of the liquid crystal material is applied to the retardation layer, the orientation of the retardation layer is lowered, so that the temperature of the guide rolls 200, 201, 202 is desired to be within a certain range. In the example of FIG. 5, it is desirable that it is 40 degreeC or more and about 70 degrees or less.

[Other Embodiments]
The specific configuration suitable for the implementation of the present invention has been described in detail above. However, the present invention can be variously combined with the above-described embodiment without departing from the spirit of the present invention. Various configurations can be changed.

  That is, in the above-described embodiment, by covering the line from the application of the liquid crystal material to the heating zone, the wind speed contacting the surface of the liquid crystal material and the fluctuation thereof are suppressed, but the present invention is not limited to this. Any method may be used as long as the average wind speed is ± 2 m / sec or less and the fluctuation amount is 0.1 m / sec or less.

  Moreover, although this embodiment demonstrated above applies the liquid crystal material which hardens | cures by irradiating an ultraviolet-ray, this invention is not applied to an ultraviolet-curable liquid crystal material, but irradiates with other energy rays. Thus, the present invention can be applied to a liquid crystal material that is cured by heating and a thermosetting liquid crystal material.

    In the above-described embodiment, the case where the solvent in which MEK and MIBK are mixed is applied to the diluent. However, the present invention is not limited to this, and various solvents having quick drying properties are applied to the diluent. be able to.

  In the above-described embodiment, the case where the alignment film is formed by performing the exposure process on the front surface after selectively exposing the right-eye area or the left-eye area is described, but the present invention is not limited thereto. On the contrary, after the front surface exposure process, the right eye area or the left eye area is selectively exposed to create an alignment film. When the alignment film is formed, the right eye area or the left eye area is selectively exposed and then unexposed. The present invention can be widely applied to the case where an alignment film is formed by selectively exposing the left eye region or the right eye region.

  In addition, the present embodiment is not limited to the pattern retardation film, but various optical films in which the liquid crystal on the entire surface is aligned in the same direction to form a retardation layer, and further, an alignment film is formed by rubbing traces. It can be widely applied to the case of creating.

DESCRIPTION OF SYMBOLS 1: Transparent film base material 2: Orientation layer 3: Retardation layer 3a: Liquid crystal material layer 10: Pattern retardation film 11: Liquid crystal display panel 100: Image display apparatus 107: Die 108: Heating zone 110: Roller 112: Temperature control Drum 113: UV irradiation device 200, 201, 202 Guide roll

Claims (8)

A transparent film substrate;
An alignment layer formed on the transparent film substrate, the surface of which has an alignment regulating force;
A retardation layer formed on the alignment layer and aligned by an alignment regulating force on a surface of the alignment layer;
A variation rate per unit area of the film thickness of the retardation layer is within 4.0%. The optical film according to claim 1,
The variation of the chromaticity b * represented by the L * a * b * color system measured by irradiating the surface of the retardation layer with light having a wavelength of 550 nm is the average value of the chromaticity b *. An optical film characterized by being within 10%. The optical film according to claim 1 or 2,
The retardation layer includes: a first region in which liquid crystal molecules are aligned in a first direction; and a second region in which liquid crystal molecules are aligned in a second direction different from the first direction. An optical film characterized in that two regions have a belt-like shape in plan view and are alternately arranged.   An image display device comprising the optical film according to claim 1 disposed on a surface of an image display panel. A method for producing an optical film including a retardation layer formed by curing a liquid crystal material,
An application step of applying the liquid crystal material on the alignment layer;
A drying step of drying the solvent contained in the liquid crystal material applied in the application step,
In the environment where the liquid crystal material is transported from the coating process to the drying process, the average value of the moving speed of the atmosphere is ± 2 m / sec or less, and the fluctuation amount of the moving speed is 0.1 m / sec or less. The manufacturing method of the optical film characterized by the above-mentioned. It is a manufacturing method of the optical film according to claim 5,
The drying step
The substrate formed by forming the alignment layer is heated by conveying the substrate to a heating zone by a guide roll that contacts the surface on the side where the alignment layer is not formed,
In the conveyance process to the said heating zone, the said base material is heated from the surface side of the side which has not created the said alignment layer with the said guide roll, The manufacturing method of the optical film characterized by the above-mentioned. It is a manufacturing method of the optical film according to claim 5 or 6,
The solvent for diluting the liquid crystal material includes a first solvent that evaporates at a first evaporation rate, and a second solvent that evaporates at a second evaporation rate that is faster than the first evaporation rate. Production method. It is a manufacturing method of the optical film according to claim 7,
The method for producing an optical film, wherein the first solvent contains methyl isobutyl ketone and the second solvent contains methyl ethyl ketone.

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