JP6789164B2 - Manufacturing method of retardation film - Google Patents

Description

The present invention relates to a method for producing a retardation film.

As a retardation film and a viewing angle compensating film used for a liquid crystal display or the like, those in which an alignment layer and a liquid crystal layer are provided on a support are known. The alignment layer is a film for arranging the liquid crystal compounds of the liquid crystal layer in a certain direction, and an alignment treatment is performed on a coating film containing an orientation factor to give an orientation regulating force. Then, the liquid crystal compounds in the liquid crystal layer formed on the alignment layer are in a state of being regularly arranged according to the orientation of the alignment layer.

As the orientation treatment, a rubbing method has been widely used in which a roller wrapped with a cloth such as nylon is rotated while being pushed into a substrate at a constant pressure. However, there is a problem that fine dust and static electricity are generated due to friction of the substrate, and in recent years, a photo-alignment method of irradiating polarized light to give an orientation-regulating force has been used.

For example, in Patent Document 1, a photoaligning device including a light guide portion formed of a substantially rectangular plate having a non-reflective film on the surface, which is provided between a rod-shaped lamp and a substrate at regular intervals in the longitudinal direction of the rod-shaped lamp, is provided. It is disclosed. Further, Patent Document 2 discloses a polarization irradiating device for photo-alignment including a rod-shaped lamp and a wire grid polarizer. Further, Patent Document 3 includes a light irradiation unit including a linear light source and a wire grid polarizing element, and is provided with a mechanism for rotating the light irradiation unit around an axis orthogonal to the alignment film. The device is disclosed.

JP-A-2014-26133 Japanese Unexamined Patent Publication No. 2004-144884 Japanese Unexamined Patent Publication No. 2006-133498

The irradiation method described in the above patent document is to transport a support on which a coating film for an alignment layer is formed to irradiate polarized light on a flat plate, or between a delivery roll and a take-up roll without a flat plate. Irradiation is performed with the support hung on the surface. In either case, the transport tension is applied, wrinkles may occur on the support on the flat plate, and the support flutters up and down when the support is hung between the rolls (so-called). There is fluttering). In such a case, there is a problem that the irradiation of polarized light is not uniformly performed and the light orientation is not uniformly performed.

Therefore, the present inventors can irradiate polarized light without wrinkles or fluttering by wrapping a support around the backup roll and irradiating the backup roll, and can improve the axial variation of the liquid crystal compound. I thought. When the transmission axis direction of the wire grid polarizer is perpendicular or parallel to the longitudinal direction of the backup roll, the change in the incident angle of polarized light does not change even if light from an angle or light from directly in front is applied and projected onto the backup roll. No. However, for the purpose of imparting a pretilt angle (rising angle of the liquid crystal) of the liquid crystal compound, there is a case where polarized light is irradiated from an oblique angle with an incident angle on the alignment layer. In such a case, if the transmission axis has an angle with respect to the longitudinal direction of the backup roll, the projected angle of the light directly in front is the same as the transmission axis angle, but the light from an angle is the transmission axis angle. Is projected at a different angle. Then, there is a problem that the orientation angle of the liquid crystal compound changes and an axial misalignment distribution of the liquid crystal compound occurs.

The present invention has been made in view of the above circumstances, and is a retardation film for suppressing the occurrence of axial misalignment distribution of a liquid crystal compound in a retardation film in which an alignment layer and a liquid crystal layer are provided on a support. It is an object of the present invention to provide a manufacturing method.

The method for producing a retardation film of the present invention is
A step of applying and drying an alignment layer forming material for forming an alignment layer having an orientation regulating force on a liquid crystal compound on a continuous film support to be conveyed to form a first coating film.
A step of forming an alignment layer by irradiating the first coating film with polarized ultraviolet light to apply an orientation regulating force, and a second coating and drying of a liquid crystal layer forming material containing a liquid crystal compound on the alignment layer. And the process of forming the coating film
A step of orienting the liquid crystal compound in the second coating film and fixing the orientation to form a liquid crystal layer,
It is a manufacturing method of a retardation film provided with
The step of forming the alignment layer is to wrap the continuous film support on which the first coating film is formed around a temperature-adjustable backup roll and irradiate it with polarized ultraviolet light.
Polarized ultraviolet light is the light emitted from a rod-shaped light source polarized by a wire grid polarizer.
The wire grids of the wire grid polarizers are arranged at an angle θ that is perpendicular to or not parallel to the longitudinal direction of the backup roll, and the light emitted from the rod-shaped light source is transferred to the wire grid polarizer between the rod-shaped light source and the wire grid polarizer. A louver composed of a plurality of parallel plates arranged in the longitudinal direction of the backup roll for guiding light is installed.

Here, the “angle θ that is not perpendicular or parallel to the longitudinal direction of the backup roll” means an angle that is neither perpendicular to nor parallel to the longitudinal direction X of the backup roll in FIG. In addition, "vertical" and "parallel" here are defined in consideration of the design accuracy and installation accuracy of the mechanical device.

The diameter of the backup roll is preferably 2000 mm or less.

It is preferable that the angle θ of the wire grid and the pitch L (mm) of the louver satisfy the relationship of the following equation.
L × (sin θ + 1) <40, where 0 <θ <90 °

In the method for producing a retardation film of the present invention,
In a plane perpendicular to the axis center of the backup roll
The line passing through the axis center of the backup roll and perpendicular to the substrate surface of the wire grid polarizer is used as the reference line.
Let θ1 be the angle formed by the reference line and the line connecting the axis center of the backup roll and the upstream end of the irradiation region of polarized ultraviolet light on the continuous film support in the transport direction.
When the angle formed by the reference line and the line connecting the axis center of the backup roll and the downstream end of the irradiation region of polarized ultraviolet light on the continuous film support in the transport direction is θ2, the relationship of the following equation can be satisfied. preferable.
| Θ1-θ2 | <5 °

According to the method for producing a retardation film of the present invention, it is possible to suppress the occurrence of an axial misalignment distribution of a liquid crystal compound.

FIG. 1 is a processing flow of the method for producing a retardation film of the present invention. FIG. 2 is a schematic configuration diagram showing a process of forming an alignment layer. FIG. 3 is a top view showing the louver. FIG. 4 is a plan view showing the arrangement of the wire grid of the wire grid polarizer. FIG. 5 is a schematic view showing the angle adjusting mechanism of the wire grid polarizer. FIG. 6 is a schematic view showing an example of arrangement of polarizing elements in a wire grid polarizer. FIG. 7 is a schematic view showing another example of the arrangement of the polarizing elements in the wire grid polarizer. FIG. 8 is a diagram illustrating an irradiation angle. FIG. 9 is a schematic view showing a case where the transmission axis of the wire grid polarizer is parallel to the longitudinal direction X of the backup roll. FIG. 10 is a schematic view showing a case where the transmission axis of the wire grid polarizer is perpendicular to the longitudinal direction X of the backup roll.

Hereinafter, an embodiment of the method for producing a retardation film of the present invention will be described with reference to the drawings. FIG. 1 shows a processing flow of the method for producing a retardation film of the present invention. FIG. 2 shows a schematic configuration diagram showing a process of forming an alignment layer in the retardation film of the present invention.

[Manufacturing method of retardation film]
In the method for producing a retardation film of the present invention, as shown in FIG. 1, a material for forming an alignment layer for forming an alignment layer having an orientation regulating force for a liquid crystal compound is applied onto a continuous film support to be conveyed. And the step of drying to form the first coating,
A step of forming an alignment layer by irradiating the first coating film with polarized ultraviolet light to apply an orientation regulating force, and a second coating and drying of a liquid crystal layer forming material containing a liquid crystal compound on the alignment layer. And the process of forming the coating film
A step of orienting the liquid crystal compound in the second coating film and fixing the orientation to form a liquid crystal layer,
This is a method for producing a retardation film.

The method for producing a retardation film of the present invention has the following features in the step of forming an alignment layer. This will be described with reference to FIG.

That is, in the step of forming the alignment layer, the continuous film support 50 on which the first coating film is formed is wound around a temperature-adjustable backup roll 40 and irradiated with polarized ultraviolet light.
The polarized ultraviolet light is obtained by polarized the ultraviolet light emitted from the rod-shaped light source 10 with the wire grid polarizer 30, and the wire grid 34 of the wire grid polarizer 30 is perpendicular to the longitudinal direction X of the backup roll 40 or A louver 20 composed of a plurality of parallel plates 21 arranged at a non-parallel angle θ and arranged in the longitudinal direction X of the backup roll 40 is installed between the rod-shaped light source 10 and the wire grid polarizing element 30. At this time, the first coating film is arranged on the rod-shaped light source 10 side.

When the transmission axis of the wire grid polarizing element 30 is tilted on a curved surface such as a backup roll, light from an angle enters in a region deviated from the front of the backup roll. Then, the light from an angle is projected at an angle deviated from the transmission axis. According to the present invention, by installing the louver 20 between the rod-shaped light source 10 and the wire grid polarizer 30, the wire grid 34 of the wire grid polarizer 30 is not perpendicular to or parallel to the longitudinal direction X of the backup roll 40. Even if they are arranged at an angle θ, light incident on the support from an angle can be suppressed. That is, it is possible to irradiate the backup roll with light from the front.

A concave reflector 11 that covers a part of the rod-shaped light source 10 is provided above the rod-shaped light source 10. As a result, the light emitted from the rod-shaped light source 10 can be efficiently reflected to the wire grid polarizer 30 side in the vertical direction.
Examples of the rod-shaped light source 10 include a high-pressure mercury lamp and a metal halide lamp. Further, a plurality of lamps or light emitting diodes may be arranged in a straight line to form a rod shape.
The diameter of the backup roll is preferably 2000 mm or less. When the thickness is 2000 mm or less, it is possible to suppress the support from floating on the backup roll and suppress the deformation of the support, so that the variation in the orientation axis can be suppressed. On the other hand, the lower limit of the diameter of the backup roll is not particularly limited as long as it is thick enough to convey the film.

(louver)
As shown in FIG. 3, the louvers 20 have parallel plates 21 arranged in the longitudinal direction X of the backup roll 40 at a pitch L (mm), and are arranged between the rod-shaped light source 10 and the wire grid polarizer 30. To. By installing the louver 20, the light from the rod-shaped light source 10 can be parallelized, the spread of the light incident on the wire grid polarizer 30 can be suppressed, and the light can be made directly in front of the backup roll. Further, in FIG. 3, the parallel plates 21 are arranged at an angle orthogonal to the longitudinal direction X of the backup roll, but the parallel plates 21 may be arranged not only orthogonally but also in parallel in an oblique direction. The pitch and angle of the parallel plate 21 can be adjusted by an interlocking mechanism (not shown).
Although FIG. 3 shows a case where the louver 20 is composed of parallel plates arranged in the longitudinal direction of the backup roll 40, the configuration of the louver 20 is not limited to this. It may be composed of a plurality of tubular portions having a polygonal or circular cross section, and the central axis of the cylinder may be arranged in a direction perpendicular to the central axis of the backup roll, and the surface constituting the cylinder has a non-reflective film. You may.
Further, it is preferable to install the louver as close as possible to the lamp so that light does not leak from the louver. In order to suppress light leakage, the louver and the lamp may be brought into contact with each other, or the gap may be shielded by another member. The same applies to the gap between the louver and the wire grid polarizer.

The material of the louver can be a heat-resistant material such as stainless steel or aluminum. The surface of the louver can be smoothed to improve the reflectance in order to improve the efficiency of the irradiation light. Further, it is also possible to impart surface irregularities in order to improve the straightness of the irradiation light, or to cover with a non-reflective film to reduce the reflectance. When reducing the reflectance, it is preferable that a light absorbing member is provided on the surface of the parallel plate 21 of the louver 20.

(Wire grid polarizer)
As shown in FIG. 4, the wire grid polarizing element 30 includes a plurality of wire grid polarizing elements 32 held in a frame 31. Each wire grid polarizing element 32 is formed by arranging a wire grid 34 composed of a plurality of linear electric conductors on a substrate 33 at an angle θ that is not perpendicular to or parallel to the longitudinal direction X of the backup roll 40. The wire grid polarizing element 32 reflects the polarized (polarized) component parallel to the longitudinal direction of the wire grid 34, and passes the polarized (polarized) component orthogonal to the wire grid 34. The direction of passing through the orthogonal polarization components is called the transmission axis.
Examples of the electric conductor include metal wires such as chromium and aluminum.

In the wire grid polarizing element 32 of the present invention, the wire grid 34 is arranged at an angle θ that is perpendicular to or not parallel to the longitudinal direction of the backup roll, as shown in FIG.

(Relationship between wire grid angle θ and louver pitch L)
In the present invention, it is preferable that the angle θ of the wire grid 34 and the pitch L (mm) of the louver satisfy the relationship of the following equation.
L × (sin θ + 1) <40, where 0 <θ <90 °.

By setting L × (sinθ + 1) <40, the orientation of the alignment layer can be made uniform, and the axial deviation of the liquid crystal compound formed thereafter can be reduced.
L × (sin θ + 1) is more preferably 20 or less.
When the louver pitches are not even, it is preferable that the maximum pitch satisfies the relationship of the above formula.

As shown in FIGS. 9 and 10, when the transmission axis T of the wire grid polarizer 30 is parallel to the longitudinal direction of the backup roll, it is projected onto the backup roll by irradiating light from an angle or light from directly in front of the backup roll. However, if the wire grid has an angle θ with respect to the longitudinal direction of the backup roll, the light from an angle is projected at an angle different from the angle θ. That is, the liquid crystal light distribution angle changes to generate an axial distribution. However, by satisfying the above equation, it is possible to suppress light from an angle.

-How to adjust the angle of the wire grid-
Here, a method of adjusting the angle of the wire grid 34 of the wire grid polarizing element in the present invention will be described with reference to FIG.
As shown in FIG. 5, the angle adjusting mechanism 60 includes a light source 61, a reference wire grid polarizing element 63, and a polarized light receiving unit 65. The polarized light receiving unit 65 includes a light receiving element 66 that detects the polarized light 67. A polarizing element unit 64 whose angle of the wire grid is to be adjusted is installed between the reference wire grid polarizing element 63 and the polarizing light receiving unit 65, and the angle of the wire grid is adjusted.

The light 62 from the light source 61 passes through the reference wire grid polarizing element 63, is polarized, and is incident on the polarizer unit 64. At this time, the polarizing light receiving unit 65 receives the light that has passed through the reference wire grid polarizing element 63 as the detection light by the light receiving element 66. The positions of the reference wire grid polarizing element 63 and the polarizer unit 64 may be reversed.

As the light source 61, a UV (ultraviolet) lamp, a laser, a light emitting diode, a HID (high-intensity discharge) lamp, or the like can be used.
Further, as the light receiving element 66, an illuminometer, a photodiode, a photomultiplier tube, a phototube, or the like can be used.

As the reference wire grid polarizing element 63, any polarizing element can be used as long as it is a linear polarizing element. The shape of the reference wire grid polarizing element 63 may be a rectangular parallelepiped, a parallelogram, or a circle.

Further, the polarizer unit 64 is configured to be rotatable over a detection and measurement range of 180 ° or more with its normal direction S as a rotation axis. The rotation of the polarizer unit 64 is determined by the rotation angle θs from the preset detection position P0.

When the rotation angle θs of the polarizer unit 64 is an angle at which the direction of the transmission axis T1 of the reference wire grid polarizing element 63 and the direction of the transmission axis T2 of the polarizer unit 64 coincide with each other, the light received by the light receiving element 66 The illuminance is maximum. Further, when the rotation angle θs of the polarizer unit 64 is an angle at which the transmission axis T2 is orthogonal to the transmission axis T1, the illuminance of the light received by the light receiving element 66 is minimized.

That is, the illuminance of the light received by the light receiving element 66 periodically fluctuates according to the rotation angle of the polarizer unit 64. Therefore, the polarization axis angle of the polarized light 67 can be measured by monitoring the illuminance of the light received by the light receiving element 66 while rotating the polarizing element unit 64. As a result, by installing the wire grid of the reference wire grid polarizing element 63 in the 90 ° direction of the target wire grid angle θ (see FIG. 4), the detection light of the light receiving portion when the polarizer unit 64 is rotated The wire grid 34 can be installed at a desired angle by minimizing.

-How to install the wire grid polarizing element-
Next, the arrangement of the wire grid polarizing element 32 of the wire grid polarizer 30 will be described.
As the wire grid polarizing elements, those arranged in series on the same plane and installed in the frame are widely used. However, in this installation method, there is a case where a slight gap is generated between the wire grid polarizing elements, unbiased light is emitted, and the orientation is not uniform.

Therefore, in the present invention, a more preferable installation method in which unbiased light is not generated is used. An example of how to install the wire grid polarizing element will be described with reference to FIG. FIG. 6 shows a top view of the wire grid polarizing element in the upper part and a cross-sectional view taken along the line AA'in the lower part in order to make it easy to understand the arrangement state of the wire grid polarizing element.
As shown in FIG. 6, the wire grid polarizing element 30 of an example is composed of a rectangular frame 31 and a wire grid polarizing element 32 held by the frame 31. The wire grid polarizing element 32 is formed on a rectangular substrate 33 at an angle θ in which the wire grid 34 is not perpendicular to or parallel to the X direction. The plurality of wire grid polarizing elements 32 are arranged in the X direction (longitudinal direction of the rod-shaped light source) by overlapping the end portions 36 of the wire grid polarizing elements 32 with the back surfaces 35 of the substrate 33 aligned.

In the installation method of one example, the wire grid polarizing elements 32 are partially superposed and installed so that unbiased light is not emitted. In that case, if the processed surfaces of the wire grid 34 are brought into contact with each other, the deflection performance of the wire grid polarizer 30 deteriorates, so that the back surface 35 of the substrate is aligned.

Further, another example of the method of installing the wire grid polarizing element will be described with reference to FIG. 7. FIG. 7 also shows a top view of the wire grid polarizing element in the upper part and a cross-sectional view taken along the line AA'in the lower part in order to make it easier to understand the arrangement of the wire grid polarizing elements.
Since the wire grid polarizing element 32 itself is the same as that shown in FIG. 6, the same reference numerals are given and the description thereof will be omitted. In the wire grid polarizing element 30 in another example, as shown in FIG. 7, a plurality of wire grid polarizing elements 32 are all arranged in the frame 31 toward the upper part of the paper surface. Then, the wire grid 34 of one wire grid polarizing element 32 is separated so as not to come into contact with the back surface 35 of the substrate 33 of the adjacent wire grid polarizing element 32, and the end portions 36 are overlapped with each other in the X direction (rod shape). They are arranged in the longitudinal direction of the light source).

By arranging the wire grid polarizing element 32 in the arrangement shown in FIGS. 6 and 7, there is no gap 37 between the wire grid polarizing element 32 and the wire grid polarizing element 32, so that the non-deflection light is wire grid polarized light. It is not emitted from the child 30.
Therefore, poor orientation does not occur, and the occurrence of axial misalignment distribution of the liquid crystal compound in the liquid crystal layer can be suppressed.

(Irradiation angle)
Next, the irradiation angle on the backup roll will be described with reference to FIG.

As shown in FIG. 8, in the plane perpendicular to the axis center O of the backup roll 40,
The line passing through the axis center O of the backup roll 40 and perpendicular to the substrate surface 38 of the wire grid polarizer 30 is set as the reference line L1.
Let θ1 be the angle formed by the reference line L1 and the line L2 connecting the axis center O of the backup roll 40 and the upstream end M of the irradiation region A of the polarized ultraviolet light irradiation region A on the continuous film support 50 in the transport direction.
When the angle formed by the reference line L1 and the line L3 connecting the axis center O of the backup roll 40 and the downstream end N of the irradiation region A of the polarized ultraviolet light irradiation region A on the continuous film support 50 in the transport direction is θ2, the following It is preferable to satisfy the relation of the formula.
| Θ1-θ2 | <10 °
More preferably, | θ1-θ2 | <7 °, and most preferably | θ1-θ2 | = 0 °.

By setting the relationship of θ1 and θ2 as described above, polarized ultraviolet light can be irradiated from directly in front of the irradiation phase of the backup roll 40, and the occurrence of axial deviation distribution of the liquid crystal compound can be suppressed.

The backup roll has a temperature control function. By warming the entire backup roll, the alignment element can be easily oriented, and it is possible to prevent the liquid crystal compound from having an axial distribution.

Next, configurations other than the above of the method for producing a retardation film of the present invention will be described in order of steps.

(Step of forming the first coating film)
On the continuous film support to be conveyed, a material for forming an alignment layer for forming an alignment layer having an orientation regulating force for a liquid crystal compound is applied and dried.

(Support)
As the support, it is preferable to use a polymer film that can be wrapped around a backup roll. Examples of materials for polymer films used as supports include cellulose acylate films (eg, cellulose triacetate film (refractive index 1.48), cellulose diacetate film, cellulose acetate butyrate film, cellulose acetate propionate film). , Polyethylene such as polyethylene and polypropylene, polyester resin film such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone film, polyacrylic resin film such as polymethylmethacrylate, polyurethane resin film, polycarbonate film, polysulfone film, polyether Film, polymethylpentene film, polyether ketone film, (meth) acrylic nitrile film, polyolefin, polymer with alicyclic structure (norbornen resin (trade name "Arton (registered trademark)", manufactured by JSR, amorphous Examples thereof include polyolefin (trade name "Zeonex (registered trademark)", manufactured by Nippon Zeon Co., Ltd.). Of these, triacetyl cellulose, polyethylene terephthalate (PET), and polymers having an alicyclic structure are preferable, and triacetyl cellulose is particularly preferable. Is preferable.

The film thickness of the support may be about 5 μm to 1000 μm, preferably 10 μm to 250 μm, and more preferably 15 μm to 90 μm.
To.

-Material for forming an orientation layer-
Examples of the photo-alignment material used for the alignment film include JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, JP-A-2007-94071, and JP-A-2007-121721. Azo compounds described in JP-A-2007-140465, JP-A-2007-156439, JP-A-2007-133184, JP-A-2009-109831, Patent No. 3883848, and Patent No. 4151746. Aromatic ester compounds described in JP-A-2002-229039, maleimide and / or alkenyl-substituted nadiimide compounds having photoorientation units described in JP-A-2002-265541, JP-A-2002-317013, Patent No. 4205195, Photocrossable silane derivative described in Japanese Patent No. 4205198, Photocrossable polyimide, polyamide, or ester described in Japanese Patent Application Laid-Open No. 2003-520878, Japanese Patent Application Laid-Open No. 2004-522220, Japanese Patent No. 4162850, Can be photodiquantized as described in Kaihei 9-118717, JP-A-10-506420, JP-A-2003-505561, WO2010 / 150748, JP-A-2013-177561, and JP-A-2014-12823. Compounds, particularly cinnamate compounds, chalcone compounds, and coumarin compounds. Particularly preferred examples include azo compounds, photocrosslinkable polyimides, polyamides, esters, synnamate compounds, and chalcone compounds.

-Applying method-
The methods for applying the liquid crystal layer forming material to the surface of the alignment film include curtain coating method, dip coating method, spin coating method, print coating method, spray coating method, slot coating method, roll coating method, slide coating method, and blade. Known methods such as a coating method, a gravure coating method, and a wire bar method can be mentioned.

-Drying process-
Drying is preferably carried out at 50 ° C. to 130 ° C. for about 10 seconds to 10 minutes using an oven, warm air, an IR (infrared) heater or the like.

(Step of forming an orientation layer)
This is a step of forming an alignment layer by imparting an orientation regulating force by irradiating the first coating film with polarized ultraviolet light. The step of applying the orientation regulating force is an operation for causing a photoreaction in the alignment layer forming material. The peak wavelength of polarized ultraviolet light is preferably 200 nm to 400 nm.

Light sources used for light irradiation include commonly used light sources such as tungsten lamps, halogen lamps, xenon lamps, xenon flash lamps, mercury lamps, mercury xenon lamps, carbon arc lamps, and various lasers (eg, semiconductor lasers, helium). Examples include neon lasers, argon ion lasers, helium cadmium lasers, YAG (Yttrium Aluminum Garnet) lasers), light emitting diodes, and cathode wire tubes.

In photo-alignment, since the photo-alignment material is oriented by non-contact light irradiation as described above, non-uniform physical uneven shape such as rubbing is unlikely to occur. Therefore, in a liquid crystal display device using an optical film produced by using an alignment layer to which an orientation regulating force is applied by photo-alignment, light leakage is reduced and high contrast can be realized.

(Step of forming the second coating film)
A liquid crystal layer forming material containing a liquid crystal compound is applied onto the alignment layer and dried to form a second coating film. For the application and drying of the liquid crystal layer forming material, the same method as the application and drying of the alignment layer forming material can be used, and detailed description thereof will be omitted.

-Material for forming a liquid crystal layer-
The liquid crystal layer forming material contains a rod-shaped liquid crystal compound or a disk-shaped liquid crystal compound and at least a chiral agent, and may further contain other components such as an orientation control agent, a polymerization initiator and an orientation auxiliary.

--Stick liquid crystal compound ---
Examples of the rod-shaped liquid crystal compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, and the like. Phenyldioxans, trans and alkenylcyclohexylbenzonitriles are preferably used. Not only low molecular weight liquid crystal molecules as described above, but also high molecular weight liquid crystal molecules can be used.

It is more preferable to fix the orientation of the rod-shaped liquid crystal compound by polymerization, and examples of the polymerizable rod-shaped liquid crystal compound include Makromol. Chem. , 190, 2255 (1989), Advanced Materials 5, 107 (1993), U.S. Pat. Nos. 4,683,327, 562,648, 5770107, WO95 / 22586, 95/24455. No. 97/00600, No. 98/23580, No. 98/52905, No. 1-272551, No. 6-16616, No. 7-110469, No. 11-8801. The compounds described in Japanese Patent Application Laid-Open No. 2001-64627 and the like can be used. Further, as the rod-shaped liquid crystal compound, for example, those described in JP-A No. 11-513019 and JP-A-2007-279688 can also be preferably used.

--Disc-shaped liquid crystal compound ---
As the disk-shaped liquid crystal compound, for example, those described in JP-A-2007-108732 and JP-A-2010-244038 can be preferably used.

(Step of forming a liquid crystal layer)
The liquid crystal compound in the second coating film is oriented and the orientation is fixed to form a liquid crystal layer.

-Orientation of liquid crystal compounds-
Prior to curing the liquid crystal layer forming material, the liquid crystal compound of the second coating film is oriented. The orientation treatment can be performed by drying at room temperature or the like or by heating. In the case of a thermotropic liquid crystal compound, the liquid crystal layer formed by the orientation treatment can generally be transferred by a change in temperature or pressure. In the case of a liquid crystal compound having lyotropic properties, it can also be transferred by a composition ratio such as the amount of solvent.

When the rod-shaped liquid crystal compound expresses the smectic phase, the temperature range in which the nematic phase is expressed is usually higher than the temperature range in which the rod-shaped liquid crystal compound expresses the smectic phase. Therefore, the rod-shaped liquid crystal compound is heated to the temperature range in which the rod-shaped liquid crystal compound expresses the nematic phase, and then the heating temperature is lowered to the temperature range in which the rod-shaped liquid crystal compound expresses the smectic phase, whereby the rod-shaped liquid crystal compound is brought into the nematic phase. Can be transferred to the smectic phase. By using such a method as the smectic phase, it is possible to provide a liquid crystal layer in which the liquid crystal compounds are oriented with high order.

In the temperature range where the rod-shaped liquid crystal compound expresses the nematic phase, it is necessary to heat for a certain period of time until the rod-shaped liquid crystal compound forms a monodomain. The heating time is preferably 10 seconds to 5 minutes, more preferably 10 seconds to 3 minutes, and most preferably 10 seconds to 2 minutes.
In the temperature range in which the rod-shaped liquid crystal compound expresses the smectic phase, it is necessary to heat for a certain period of time until the rod-shaped liquid crystal compound expresses the smectic phase. The heating time is preferably 10 seconds to 5 minutes, more preferably 10 seconds to 3 minutes, and most preferably 10 seconds to 2 minutes.

-Fixing of orientation-
The liquid crystal compound in the second coating film is oriented and the orientation is fixed to form a liquid crystal layer.
The orientation can be fixed by thermal polymerization or polymerization by an active energy ray, and can be carried out by appropriately selecting a polymerizable group or a polymerization initiator suitable for the polymerization. In consideration of production suitability and the like, a polymerization reaction by irradiation with ultraviolet rays can be preferably used. When the irradiation amount of ultraviolet rays is small, unpolymerized polymerizable rod-shaped liquid crystal remains, which causes temperature changes in optical characteristics and deterioration over time.
Therefore, it is preferable to determine the irradiation conditions so that the ratio of the remaining polymerizable rod-shaped liquid crystal is 5% or less, and the irradiation conditions depend on the formulation of the polymerizable composition and the thickness of the second coating film, but as a guide. UV irradiation dose as is preferably 50~1000mJ / cm ^2, and more preferably 100 to 500 mJ / cm ^2.
In addition, for details of the method for producing the liquid crystal layer, the description of JP-A-2008-225281 and JP-A-2008-026730 can be referred to.

Hereinafter, the present invention will be described in more detail with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[Example 1]
Each layer constituting the retardation film of Example 1 will be described below. The orientation treatment was performed by the method shown in FIG.

(Formation of first coating film, formation of alignment layer)
The surface of the support of the cellulose triacetate film TD80UL (manufactured by Fujifilm) was subjected to alkali saponification treatment. Specifically, the support is immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes, washed in a water washing bath at room temperature, and neutralized with 0.1N sulfuric acid at 30 ° C. did. After neutralization, it was washed in a water washing bath at room temperature, and further dried with warm air at 100 ° C.
On the support, a material for forming an orientation layer having the following composition was applied with a wire bar. It was dried with warm air at 60 ° C. for 60 seconds and further with warm air at 100 ° C. for 120 seconds to form a photoalignment layer.

-Preparation of materials for forming an orientation layer-
Material for photoalignment P-1 1.0 part by mass Butoxyethanol 33 part by mass Propylene glycol monomethyl ether 33 part by mass Water 33 part by mass

Wrap the prepared support on which the alignment layer is formed around a backup roll (diameter 1000 mm, made of stainless steel) (see Fig. 2), and use an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) in the atmosphere to obtain ultraviolet rays. Was irradiated. At this time, the transmission axis of the wire grid polarizer (ProFlux PPL02 manufactured by Moxtek Co., Ltd.) and the absorption axis of the alignment layer were set to be 60 degrees for exposure, and photoalignment treatment was performed. At this time, the illuminance of the ultraviolet rays used was 100 mW / cm ^{2 in} the UV (ultra-violet) -A region (integration of wavelengths of 380 nm to 320 nm), and the irradiation amount was 1000 mJ / cm ² in the UV-A region.

(Formation of second coating film, formation of liquid crystal)
Subsequently, the following materials for forming a liquid crystal layer were prepared.

-Preparation of coating liquid for forming liquid crystal layer-
Reverse wavelength dispersion liquid crystal compound R-3 100 parts by mass Photopolymerization initiator 3.0 parts by mass (Irgacure 819, manufactured by BASF Ltd.)
Fluorine-containing compound A 0.8 parts by mass Crosslinkable polymer O-2 0.3 parts by mass Chloroform 588 parts by mass

A liquid crystal layer forming material was applied onto the alignment layer using a bar coater. After aging by heating at a film surface temperature of 100 ° C. for 60 seconds and cooling to 70 ° C., an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) is used to irradiate the film with ultraviolet rays of 1000 mJ / cm ^2. The positive A plate A-0 was formed by immobilizing the orientation state. The formed liquid crystal layer was orthogonal to the polarization irradiation direction in the slow phase axis direction (that is, also orthogonal to the absorption axis of the polarizing plate) (the inverse wavelength dispersed liquid crystal compound was oriented orthogonally to the polarization irradiation direction). Was). When the light incident angle dependence of the retardation Re and the tilt angle of the optical axis were measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Measuring Instruments Co., Ltd.), Re was 130 nm at a wavelength of 550 nm, and retardation. Rth is 65 nm, Re (450) / Re (550) is 0.83, Re (650) / Re (550) is 1.05, the tilt angle of the optical axis is 0 °, and the inverse wavelength dispersion liquid crystal compound is homogeneous. It was an orientation.

(Louvre and irradiation angle)
The pitch L of the louver was 10 mm, and the relationship L × (sin θ + 1) between the angle of the wire grid and L was 15.
Regarding polarized light irradiation, as shown in FIG. 8, irradiation was performed from a position where θ1 and θ2 were θ1 / θ2 = 10 ° / 10 °. That is, the backup roll was irradiated from the front.

[Example 2]
A retardation film was produced in the same manner as in Example 1 except that the pitch L of the louver was 27 mm and L × (sinθ + 1) was 41.

[Example 3]
A retardation film was produced in the same manner as in Example 1 except that θ1 / θ2 = 5 ° / 11 °.

[Comparative Example 1]
A retardation film was produced in the same manner as in Example 1 except that the louver was not provided.

[Evaluation of axis deviation distribution in the width direction]
With respect to the retardation films produced in the above Examples and Comparative Examples, the axial deviation distribution in the width direction (X direction in FIG. 2) was evaluated based on the following method and evaluation criteria.

The obtained retardation film (500 mm) was cut out by 1 m, and 10 small piece samples were cut out at equal intervals in the width direction. Using Axoscan (manufactured by Axometrics), 10 points were measured for each of the cut small piece samples, and the axial angle of each small piece sample was obtained. Next, the axial misalignment distribution of the obtained retardation film was calculated using the following formula 1.
Axis deviation distribution = maximum axis angle-minimum axis angle ... (Equation 1)

The axis deviation distribution obtained above was judged based on the following evaluation criteria.
(Evaluation criteria)
A: Axis deviation distribution <0.5 °
B: 0.5 ° ≤ axis deviation distribution <1.0 °
C: 1.0 ° ≤ axis deviation distribution

Table 1 shows the production conditions and evaluation results of Examples and Comparative Examples.

As shown in Table 1, the retardation film produced by the method for producing a retardation film of the present invention has an axial deviation distribution of 0.7 or less in the width direction, and has an axis as compared with a comparative example in which no louver is provided. The deviation distribution could be suppressed.
In particular, Example 1 in which L × (sin θ + 1) is less than 40 was able to further suppress the axial deviation distribution as compared with Example 2 in which L × (sin θ + 1) was 40 or more.
Further, Examples 1 and 2 (θ1 / θ2 = 10 ° / 10 °) in which the backup roll was irradiated from the front were compared with Example 3 (θ1 / θ2 = 5 ° / 11 °) which was deviated from the front. , The axis deviation distribution could be further suppressed.

10 Rod-shaped light source 11 Reflector 20 Louver 21 Parallel plate 30 Wire grid polarizing element 31 Frame 32 Wire grid polarizing element 33 Substrate 34 Wire grid 35 Back side 36 End part 37 Between wire grid polarizing element and wire grid polarizing element 38 Board surface 40 Backup Roll 50 Support on which the first coating film is formed 60 Optical alignment mechanism 61 Light source 62 Light 63 Reference wire grid Polarizing element 64 Polarizer unit 65 Polarized light receiving unit 66 Light receiving element 67 Polarized X X Backup roll longitudinal direction Y Conveying direction T1 , T2 transmission axis S normal direction P0 detection position θs rotation angle L1 reference line A irradiation area M upstream end of irradiation area N downstream end of irradiation area O axis center of backup roll L2 axis center and upstream end of irradiation area Connected line Line θ1, θ2 angle connecting the center of the L3 axis and the downstream end of the irradiation area

Claims (6)

A step of applying and drying an alignment layer forming material for forming an alignment layer having an orientation regulating force on a liquid crystal compound on a continuous film support to be conveyed to form a first coating film.
A step of imparting the orientation restricting force by irradiating the first coating film with polarized ultraviolet light to form the alignment layer, and applying a liquid crystal layer forming material containing the liquid crystal compound on the alignment layer. The process of drying to form a second coating and
A step of orienting the liquid crystal compound in the second coating film and fixing the orientation to form a liquid crystal layer.
It is a manufacturing method of a retardation film provided with
In the step of forming the alignment layer, the continuous film support on which the first coating film is formed is wound on a temperature-adjustable backup roll, and the irradiation of the continuous film support wrapped around the backup roll. The region is irradiated with the polarized ultraviolet light,
The polarized ultraviolet light is the light emitted from a rod-shaped light source polarized by a wire grid polarizer.
The irradiation region is defined as a reference line in a plane perpendicular to the axis center of the backup roll, passing through the axis center of the backup roll and perpendicular to the substrate surface of the wire grid polarizer, and the reference line and the backup. The angle formed by the axis center of the roll and the line connecting the upstream end of the irradiation region in the transport direction on the continuous film support is θ1, and the reference line, the axis center of the backup roll, and the continuous film support When the angle formed by the line connecting the downstream end of the irradiation region in the transport direction is θ2,
| Θ1-θ2 | <10 °
The filling,
The wire grids of the wire grid polarizers are arranged at an angle θ that is perpendicular to or not parallel to the longitudinal direction of the backup roll, and the light emitted from the rod-shaped light source is emitted between the rod-shaped light source and the wire grid polarizer. A method for manufacturing a retardation film, which is a louver that guides light to the wire grid polarizer, and in which a louver composed of parallel plates arranged in the longitudinal direction of the backup roll is installed. The method for producing a retardation film according to claim 1, wherein the backup roll has a diameter of 2000 mm or less. The method for producing a retardation film according to claim 1 or 2, wherein the angle θ of the wire grid and the pitch L (mm) of the louver satisfy the relationship of the following formula.
L × (sin θ + 1) <40, where 0 <θ <90 ° The method for producing a retardation film according to any one of claims 1 to 3, which satisfies the relationship of the following formula.
| Θ1-θ2 | <5 ° The θ1 and the θ2 is 11 ° or less, method for producing a retardation film according to any one of claims 1 4. The wire grid polarizing element includes a rectangular frame and a plurality of wire grid polarizing elements held in the frame, and the plurality of wire grid polarizing elements overlap ends of adjacent wire grid polarizing elements. The method for producing a retardation film according to any one of claims 1 to 5, which is arranged in the longitudinal direction of the rod-shaped light source.