JP2018169479A - Method for manufacturing retardation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a retardation film capable of uniformly aligning a liquid crystal compound.SOLUTION: A method for manufacturing a retardation film comprises the steps of: forming a first coating film 52 on a continuous film support body 51 to be conveyed by applying and drying an alignment layer forming material for forming an alignment layer having an alignment regulating force for a liquid crystal material; forming an alignment layer by imparting the alignment regulating force by irradiating the first coating film 52 with polarized light; forming a second coating film on the alignment layer by applying and drying a liquid crystal layer forming material containing the liquid crystal compound; and forming a liquid crystal layer by aligning the liquid crystal compound in the second coating film 52 and fixing the alignment. The method irradiates a conveying surface 50a of the continuous film support body 51 with unpolarized light having a peak wavelength at a peak wavelength ±30 nm of polarized light from a direction of a vertical direction S ±10 degree (θ) before irradiating polarized light.SELECTED DRAWING: Figure 3

Description

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

  As a retardation film or a viewing angle compensation film used for a liquid crystal display or the like, a film in which an alignment layer and a liquid crystal layer are provided on a support is 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 regulating force is given by performing an alignment treatment on the coating film containing the alignment material. The liquid crystal compounds in the liquid crystal layer formed on the alignment layer are regularly arranged according to the alignment of the alignment layer. Efficient alignment of liquid crystal compounds is important for improving the viewing angle and productivity of liquid crystal displays.

  For example, Patent Document 1 discloses an apparatus for irradiating a UV-cured layer that is continuously transported in order to efficiently align a liquid crystal compound in a biaxial retardation plate, and is arranged in front of the light source and the light source. There is disclosed an apparatus including an optical filter, the boundary of the optical filter being arranged so as to intersect with the conveyance direction of the support.

JP 2006-313239 A

  On the other hand, in the previous step of irradiating polarized light for imparting the alignment regulating force of the alignment layer, partial alignment unintentionally due to external factors such as the shearing force applied to the coating solution during formation of the alignment film, the wind during drying, etc. May occur. This partial alignment of the alignment film may remain after the polarization irradiation step, and as a result, the in-plane uniformity of the alignment of the upper liquid crystal compound may be deteriorated. In order to cancel the orientation due to such an external factor, it is necessary to increase the irradiation amount of polarized light. However, there is a problem that the production efficiency decreases when the irradiation amount is increased. The technique described in Patent Document 1 is a treatment performed at the time of curing the liquid crystal layer, and cannot cope with the partial alignment unintentionally generated in the alignment layer.

  The present invention has been made in view of the above circumstances, and is a method for producing a retardation film in which the orientation of a liquid crystal compound in a liquid crystal layer is controlled by a photo-alignment layer. It aims at providing the manufacturing method of the retardation film which can be suppressed.

The method for producing the retardation film of the present invention comprises:
A step of forming a first coating film by applying and drying an alignment layer forming material for forming an alignment layer having an alignment regulating force for a liquid crystal material on a continuous film support to be conveyed;
Irradiating the first coating film with polarized light that matches the absorption wavelength region of the alignment layer forming material to impart alignment regulating force to form an alignment layer, and forming a liquid crystal layer containing a liquid crystal compound on the alignment layer Applying and drying a material for forming a second coating film;
Aligning the liquid crystal compound in the second coating film, fixing the alignment and forming a liquid crystal layer;
A method for producing a retardation film comprising:
Before irradiating polarized light, it has the process of irradiating the non-polarized light which has a peak wavelength in the peak wavelength +/- 30nm of a polarized light from the direction of +/- 10 degree perpendicular | vertical with respect to the conveyance surface of a continuous film support body.
Here, the “peak wavelength” is defined as a wavelength having a maximum value up to the third position in the spectrum of the irradiated light.
Further, “polarized light that matches the absorption wavelength region of the alignment layer forming material” refers to polarized light whose peak wavelength is included in the half-value width range of the absorption spectrum of the alignment layer forming material.

  The peak wavelength of polarized light is preferably 200 nm or more and 400 nm or less.

  It is preferable to irradiate non-polarized light from a direction of ± 5 degrees perpendicular to the conveyance surface of the continuous film support.

  The first coating film is preferably heat-cured.

  The polarized light is preferably light emitted from a rod-like light source extending in a direction orthogonal to the transport direction and polarized by a wire grid polarizer.

  It is preferable that a louver composed of a plurality of parallel plates arranged in the longitudinal direction of the rod-shaped light source is provided between the rod-shaped light source and the wire grid polarizer.

  In the method for producing a retardation film of the present invention, polarized light may be irradiated on a backup roll.

The dose of non-polarized light is preferably ² mJ / cm ² or more.

  According to the method for producing a retardation film of the present invention, alignment disorder of a liquid crystal compound can be suppressed.

FIG. 1 is a processing flow of the method for producing a retardation film of the present invention. FIG. 2 is a schematic view showing a step of irradiating non-polarized light. FIG. 3 is a cross-sectional view showing an irradiation angle of non-polarized light. FIG. 4 is a schematic view showing a step of irradiating polarized light. FIG. 5 is a schematic view showing a case where polarized light is irradiated on a backup roll. FIG. 6 is a diagram showing the extinction degree and the measurement position of the alignment axis for the evaluation of the in-plane uniformity of the alignment axis.

  Hereinafter, the method for producing the retardation film of the present invention will be described with reference to the drawings.

[Method for producing retardation film]
The method for producing a retardation film of the present invention, as shown in FIG.
A step of forming a first coating film by applying and drying an alignment layer forming material for forming an alignment layer having an alignment regulating force for a liquid crystal material on a continuous film support to be conveyed (ST1),
A step of forming an alignment layer by applying an alignment regulating force by irradiating polarized light to the first coating film (ST3), and applying and drying a liquid crystal layer forming material containing a liquid crystal compound on the alignment layer Step (ST4) of forming the coating film of 2,
Aligning the liquid crystal compound in the second coating film, fixing the alignment and forming a liquid crystal layer (ST5);
A method for producing a retardation film comprising:
Before irradiating polarized light in the step of forming the alignment layer (ST3), non-polarized light having a peak wavelength of ± 30 nm from the direction perpendicular to the conveyance surface of the continuous film support ± 30 nm. The step of irradiating (ST2).

(ST2: Step of irradiating non-polarized light)
First, the step of irradiating non-polarized light (ST2), which is a characteristic step of the retardation film of the present invention, will be described with reference to FIG.
In the step of irradiating non-polarized light in the present invention (ST2), before the irradiation of polarized light in the step of forming the alignment layer (ST3), non-polarized light having a peak wavelength at a peak wavelength ± 30 nm of the polarized light is irradiated. .
As the step of irradiating non-polarized light (ST2), for example, as shown in FIG. 2, a rod-shaped light source 10 and a rod-shaped light source are applied to a film 50 having a first coating film 52 formed on a continuous film support 51. Emitted from an irradiating device composed of a concave reflecting mirror 11 that reflects the light in the direction of the film 50 and a louver 20 comprising a plurality of parallel plates 21 arranged in the longitudinal direction (X direction in the figure) of the rod-shaped light source. A mode of irradiating non-polarized light is exemplified.
An irradiation device that does not have the louver 20 may be used.

  As shown in FIG. 3, the non-polarized light is irradiated from a direction perpendicular to the transport surface 50a of the film 50 (S in the drawing) ± 10 degrees (θ in the drawing). The more preferable irradiation angle is ± 5 degrees in the vertical direction, and the most preferable irradiation angle is the vertical direction S.

Thus, by having the process (ST2) which irradiates a non-polarized light to a 1st coating film, a 1st coating film can be once made into a non-orientation state.
Here, the “non-aligned state” refers to a state in which liquid crystals are arranged randomly, and can be observed with an optical microscope or the like. In the present invention, the determination is made by qualitative evaluation performed in the following examples.
Thus, once the non-alignment state is formed, a uniform alignment layer can be formed with a small amount of irradiation in the subsequent polarized light irradiation. That is, the irradiation efficiency can be increased.

The dose of non-polarized light is preferably ² mJ / cm ² or more, and more preferably 5 J / cm ² or more. Moreover, it is preferable that it is 20 J / cm < ² > or less. By being ² mJ / cm ² or more, a non-oriented state can be formed sufficiently, and by being 20 J / cm ² or less, a non-oriented state can be formed without sacrificing productivity.

  The rod-shaped light source is a commonly used light source such as a tungsten lamp, a halogen lamp, a xenon lamp, a xenon flash lamp, a mercury lamp, a mercury xenon lamp, a carbon arc lamp, various lasers (eg, semiconductor laser, helium neon laser, Argon ion laser, helium cadmium laser, YAG (Yttrium Aluminum Garnet) laser), light emitting diode, cathode ray tube, and the like can be given.

(ST3: Step of forming alignment layer)
A step (ST3) of forming an alignment layer by irradiating polarized light, which is performed following the step (ST2) of irradiating non-polarized light, will be described.
The step of forming the alignment layer (ST3) is a step of forming the alignment layer by applying alignment regulation force by irradiating the first coating film with polarized light. The step of imparting alignment regulating force is an operation for causing a photoreaction in the alignment layer forming material.
As a step of forming an alignment layer by irradiating polarized light, for example, as shown in FIG. 4, a rod-shaped light source 10 and a rod-shaped light source are applied to a film 50 in which a first coating film 52 is formed on a continuous film support 51. The concave reflecting mirror 11 that reflects the light in the direction of the film 50, the louver 20 composed of a plurality of parallel plates 21 arranged in the longitudinal direction (X direction in the figure) of the rod-shaped light source, and the light collimated by the louver 20 Is performed by a photo-alignment apparatus composed of a wire grid polarizer 30 that linearly polarizes the light. The polarized light emitted from the wire grid polarizer 30 is applied to the first coating film 52. The peak wavelength of polarized ultraviolet light is preferably 200 nm to 400 nm.

  In the photo-alignment, the photo-alignment material is oriented by non-contact light irradiation as described above, and therefore, non-uniform physical uneven shapes such as rubbing are not easily generated. Therefore, in a liquid crystal display device using an optical film manufactured using an alignment layer to which an alignment regulating force is imparted by optical alignment, light leakage is reduced and high contrast can be realized.

  The polarized light irradiation may be performed by winding the film 50 around a backup roll 40 as shown in FIG. In particular, by performing it on a temperature-controllable backup roll, the orientation can be performed more uniformly and efficiently.

The backup roll is not particularly limited, and a known roll can be used. For example, a hard chrome plated surface can be preferably used. The thickness of the plating is preferably 40 μm to 60 μm from the viewpoint of ensuring conductivity and strength.
Further, the surface roughness of the backup roll is preferably 0.7 s or less from the viewpoint of preventing wrinkles and making the orientation uniform.
Further, the temperature adjustment of the backup roll may be performed by a temperature control means. For example, the surface temperature of the backup roll may be detected and the surface temperature of the backup roll may be maintained by the temperature control means based on the temperature. Examples of the heating method include induction heating, water heating, and oil heating.

  Hereinafter, steps other than the step of irradiating non-polarized light (ST2) and the step of forming the alignment layer (ST3) will be described in the order of steps.

(ST1: Step of forming the first coating film)
On the continuous film support conveyed in the conveyance direction Y, an alignment layer forming material for forming an alignment layer having an alignment regulating force for the liquid crystal compound is applied and dried.
Details of each component will be described below.

-Continuous film support-
As the continuous film support, a polymer film that can be wound around a backup roll is preferably used. Examples of polymer film materials used as the support include cellulose acylate films (for example, cellulose triacetate film (refractive index 1.48), cellulose diacetate film, cellulose acetate butyrate film, cellulose acetate propionate film). Polyolefin such as polyethylene and polypropylene, polyester resin film such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone film, polyacrylic resin film such as polymethylmethacrylate, polyurethane resin film, polycarbonate film, polysulfone film, polyether Film, polymethylpentene film, polyetherketone film, (meth) acrylonitrile film Polyolefin, polymer having an alicyclic structure (norbornene resin (trade name “Arton (registered trademark)”, manufactured by JSR Corporation, amorphous polyolefin (trade name “ZEONEX (registered trademark)”, manufactured by ZEON CORPORATION)), Of these, triacetyl cellulose, polyethylene terephthalate (PET), and polymers having an alicyclic structure are preferable, and triacetyl cellulose is particularly preferable.

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

-Material for alignment layer formation-
Examples of the alignment layer forming material used for the photo-alignment include, for example, JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, JP-A-2007-94071, and JP-A-2007. -121721, JP2007-140465, JP2007-156439, JP2007-133184, JP2009-109831, JP38883848, JP4151746 A compound, an aromatic ester compound described in JP-A No. 2002-229039, a maleimide and / or alkenyl-substituted nadiimide compound having a photo-alignment unit described in JP-A No. 2002-265541 and JP-A No. 2002-317013, Patent 4205195, Patent 42 Photocrosslinkable silane derivatives described in No. 5198, photocrosslinkable polyimides, polyamides, or esters described in Japanese Patent Publication No. 2003-520878, Japanese Patent Publication No. 2004-529220, and Japanese Patent No. 4162850, Japanese Patent Laid-Open No. 9-118717 JP-A-10-506420, JP-A-2003-505561, WO2010 / 150748, JP-A-2013-177561, JP-A-2014-12823, particularly cinnamate Examples thereof include compounds, chalcone compounds, and coumarin compounds. Particularly preferred examples include azo compounds, photocrosslinkable polyimides, polyamides, esters, cinnamate compounds, and chalcone compounds.

-Application method-
The methods for applying the alignment layer forming material 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, blade coating method, gravure. Well-known methods, such as a coating method and a wire bar method, are mentioned.

-Drying process-
Drying is preferably performed at 100 ° C. to 130 ° C. for about 2 minutes to 5 minutes using an oven, warm air, infrared rays, or the like.

  The first coating film is preferably heat-cured. Thermosetting may be performed either before or after the step of irradiating non-polarized light (ST2).

(ST4: Step of forming the second coating film)
A liquid crystal layer forming material containing a liquid crystal compound is applied and dried on the alignment layer to form a second coating film. The liquid crystal layer forming material can be applied and dried by the same method as the application and drying of the alignment layer forming material, and detailed description thereof will be omitted.

-Material for liquid crystal layer formation-
The liquid crystal layer-forming material contains a rod-like liquid crystal compound or a disk-like liquid crystal compound and at least a chiral agent, and may further contain other components such as an alignment controller, a polymerization initiator, and an alignment aid.

-Rod-shaped liquid crystal compound-
Examples of the rod-like liquid crystal compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. In addition to the above low-molecular liquid crystalline molecules, high-molecular liquid crystalline molecules can also be used.

  It is more preferable to fix the orientation of the rod-like liquid crystal compound by polymerization, and examples of the polymerizable rod-like liquid crystal compound include those described in Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. Nos. 4,683,327, 5,622,648 and 5,770,107, WO 95/22586, 95/24455. Publication No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, No. 6-16616, No. 7-110469, No. 11-80081 The compounds described in the gazette and Japanese Patent Application No. 2001-64627 can be used. Further, as the rod-like liquid crystal compound, for example, those described in JP-T-11-513019 and JP-A-2007-279688 can be preferably used.

-Discotic liquid crystal compound-
As the discotic liquid crystal compound, for example, those described in JP2007-108732A and JP2010-244038A can be preferably used.

(ST5: Step of forming a liquid crystal layer)
The liquid crystal compound in the second coating film is aligned and the alignment is fixed to form a liquid crystal layer.

-Orientation of liquid crystal compounds-
Prior to the orientation fixing (curing) of the liquid crystal layer forming material, the orientation treatment of the liquid crystal compound of the second coating film is performed. The alignment treatment can be performed by drying at room temperature or by heating. In the case of a thermotropic liquid crystal compound, the liquid crystal layer formed by the alignment 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 be transferred also by a composition ratio such as the amount of solvent.

  When the rod-like liquid crystal compound develops a smectic phase, the temperature region in which the nematic phase develops is usually higher than the temperature region in which the rod-like liquid crystal compound develops a smectic phase. Therefore, the rod-like liquid crystal compound is heated to a temperature range where the rod-like liquid crystal compound develops a nematic phase, and then the heating temperature is lowered to a temperature region where the rod-like liquid crystal compound develops a smectic phase, thereby bringing the rod-like liquid crystal compound into a nematic phase. To a smectic phase. By using such a method as a smectic phase, a liquid crystal layer in which liquid crystal compounds are aligned with a high degree of order can be provided.

In the temperature range where the rod-like liquid crystal compound develops a nematic phase, it is necessary to heat for a certain time until the rod-like 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 where the rod-like liquid crystal compound develops a smectic phase, it is necessary to heat for a certain time until the rod-like liquid crystal compound develops a 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.

-Fixed orientation-
A liquid crystal layer is formed by fixing the orientation of the liquid crystal compound in the second coating film.
The orientation can be fixed by thermal polymerization or polymerization by active energy rays, and can be performed 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 ultraviolet irradiation can be preferably used. When the irradiation amount of ultraviolet rays is small, unpolymerized polymerizable rod-like liquid crystal remains, which causes a change in temperature of optical characteristics and deterioration with time.
Therefore, it is preferable to determine the irradiation conditions such that the ratio of the remaining polymerizable rod-like liquid crystal is 5% or less, and the irradiation conditions depend on the prescription of the polymerizable composition and the thickness of the second coating film. 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 liquid crystal layer, descriptions in Japanese Patent Application Laid-Open Nos. 2008-225281 and 2008-026730 can be referred to.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[Example 1]
Below, each manufacturing process of the retardation film of Example 1 is demonstrated.

(ST1: Formation of the first coating film)
The support surface of the cellulose triacetate film TD80UL (manufactured by Fujifilm) was subjected to alkali saponification treatment. Specifically, after immersing the support in an aqueous 1.5N sodium hydroxide solution at 55 ° C for 2 minutes, the substrate was washed in a water bath at room temperature and neutralized using 0.1N sulfuric acid at 30 ° C. did. After neutralization, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C.
Next, an alignment layer forming material having the following composition was applied to the support surface with a wire bar. The first coating film was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds.

-Preparation of photo-alignment film forming material-
Photo-alignment material P-1 1.0 part by mass Butoxyethanol 33 parts by mass Propylene glycol monomethyl ether 33 parts by mass Water 33 parts by mass

(ST2: Step of irradiating non-polarized light)
Using the irradiation apparatus shown in FIG. 2, non-polarized light that matches the absorption wavelength region of the alignment layer forming material was irradiated on the first coating film with the irradiation angle as the vertical direction S to form a non-oriented state. .
The absorption wavelength of the alignment layer forming material was measured using a spectrophotometer V-750 manufactured by JASCO Corporation by preparing a 0.1 mass fraction chloroform solution.
The absorption wavelength of the alignment layer forming material has a range of UV-B.
Using a light source with a peak wavelength of 313 nm (trade name “H096-L41X”, manufactured by Eye Graphics, using an optical filter that selectively transmits UV-B), the irradiation angle is the vertical direction S, and the irradiation amount is UV ( 10 mJ / cm ² in the ultra-violet) -B region.

(ST3: Step of irradiating polarized light)

Next, using the photo-alignment apparatus shown in FIG. 4, linearly polarized light that matches the absorption wavelength region of the alignment layer-forming material is irradiated on the first coating film with the irradiation angle as the vertical direction S, and photo-alignment is performed. Processed.
At this time, a wire grid polarizer (manufactured by Moxtek, ProFlux UVT-300A) was exposed in parallel with the surface of the first coating film, and a photo-alignment treatment was performed. The light source used at this time is a light source with a peak wavelength of 313 nm (trade name “H096-L41X”, manufactured by Eye Graphics, using an optical filter that selectively transmits UV-B), and the amount of UV irradiation is UV−. It was set to 10 mJ / cm ² in the B region.

(ST4, ST5: Formation of second coating film, formation of liquid crystal layer)
Subsequently, the following liquid crystal layer forming material was prepared.

-Preparation of liquid crystal layer forming material-
Inverse wavelength dispersion liquid crystalline compound R-3 100 parts by mass Photopolymerization initiator 3.0 parts by mass (Irgacure 819, manufactured by BASF Corporation)
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 on the alignment layer using a bar coater. After aging for 60 seconds at a film surface temperature of 100 ° C. and cooling to 70 ° C., the sample was irradiated with 1000 mJ / cm ² of ultraviolet rays using an air-cooled metal halide lamp (produced by Eye Graphics Co., Ltd.) under air. A liquid crystal layer was formed by fixing the alignment state. In the formed liquid crystal layer, the slow axis direction was perpendicular to the polarized light irradiation direction (that is, perpendicular to the absorption axis of the polarizing plate) (the reverse wavelength dispersion liquid crystalline compound was aligned perpendicular to the polarized light irradiation direction. ) Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.), the light incident angle dependence of retardation Re and the tilt angle of the optical axis were measured. 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 reverse wavelength dispersion liquid crystalline compound is homogeneous. Orientation.

[Example 2]
A retardation film was produced in the same manner as in Example 1 except that the amount of non-polarized light was changed to 5 mJ / cm ² .

[Example 3]
A retardation film was produced in the same manner as in Example 1 except that the non-polarized light irradiation angle was 10 degrees.

[Comparative Example 1]
In the step of irradiating non-polarized light, except that a light source having a peak wavelength of 365 nm (trade name “H096-L41X”, manufactured by Eye Graphics, using an optical filter that selectively transmits UV-A) was used. A retardation film was produced in the same manner as in Example 1.

[Comparative Example 2]
A retardation film was produced in the same manner as in Example 1 except that the irradiation angle of non-polarized light was 20 degrees.

[Comparative Example 3]
A retardation film was produced in the same manner as in Example 1 except that the non-polarized light irradiation angle was 45 degrees.

[Comparative Example 4]
A retardation film was produced in the same manner as in Example 1 except that non-polarized light was not irradiated.

[Evaluation of in-plane uniformity of alignment axis]
The retardation films produced in the above examples and comparative examples were evaluated for in-plane uniformity of the orientation axis based on the following methods and evaluation criteria. The retardation film after forming the liquid crystal layer was cut into a 150 mm square, and the extinction degree and the orientation axis were measured at 5 points shown in FIG.

(Measurement of extinction degree)
The extinction degree means light leakage by the optical compensation film, and generally measured when the optical compensation film is arranged between the two polarizing plates arranged in crossed Nicols so that the transmittance is minimized. Is the transmittance. Specifically, one polarizing plate is fixed, the other polarizing plate and the retardation film are respectively rotated, and the minimum transmittance is measured.
For example, a polarizing plate is arranged in paranicol without installing an optical compensation film, the brightness is measured, and this is used as a denominator. Thereafter, an optical compensation film is placed between them, one polarizing plate is fixed, the darkest light is measured while rotating the optical compensation film and the other polarizing plate, and the ratio is calculated as a molecule. At this time, since the two sheets rotate independently, measurement is performed while shifting the optical compensation film and one polarizing plate by 0.25 ° for each rotation.
As described above, the extinction degree largely depends on the angle and the orientation state. Therefore, when the disturbance of the orientation state of the optical compensation film occurs, the quenching degree decreases. Utilizing this phenomenon, the state of alignment disorder was evaluated by the extinction degree.
In the examples, Win6OD (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the extinction degree. Moreover, 550 nm was used for the measurement wavelength of the transmittance, and the transmittance of the polarizing plate in the paranicol arrangement was set to 100%.

(Measurement of orientation axis)
The slow axis angle of the liquid crystal compound layer was measured with KOBRA-21DH (manufactured by Oji Scientific Instruments).

(Evaluation criteria)
For the measured value of the extinction degree, the value of 5 points is applied to {(maximum value) − (minimum value)} ÷ (average value) to calculate the variation, and for the orientation axis, the difference between the maximum value and the minimum value is calculated. Calculated. This was applied to Table 1, and the in-plane uniformity of the orientation axis was evaluated.

  Table 2 shows the non-polarized irradiation conditions, polarized irradiation conditions, and evaluations of the examples and comparative examples.

  As shown in Table 2, it can be seen that the retardation film of Example 1 is superior in in-plane uniformity of the orientation axis and the orientation disorder is well suppressed as compared with Comparative Example 4 in which non-polarized light is not irradiated. Moreover, the retardation film of an Example is excellent in the in-plane uniformity of an orientation axis compared with the comparative example 2 whose peak wavelength difference of non-polarized light and polarized light is 50 nm. Furthermore, the in-plane uniformity of the orientation axis is excellent as compared with Comparative Examples 2 and 3 in which the irradiation angle is irradiated from a direction perpendicular to the conveying surface of the continuous film support at 20 degrees or 45 degrees.

DESCRIPTION OF SYMBOLS 10 Bar light source 11 Concave reflector 20 Louver 21 Parallel plate 30 Wire grid polarizer 40 Backup roll 50 The support body in which the 1st coating film was formed 51 Support body 52 1st coating film 50a Conveyance surface S It is perpendicular | vertical to a conveyance surface Direction Y Transport direction X Longitudinal direction of the rod-shaped light source

Claims (8)

A step of forming a first coating film by applying and drying an alignment layer forming material for forming an alignment layer having an alignment regulating force for a liquid crystal material on a continuous film support to be conveyed;
Irradiating the first coating film with polarized light that matches the absorption wavelength region of the alignment layer forming material to impart the alignment regulating force to form the alignment layer; and the liquid crystal compound on the alignment layer. Applying and drying a liquid crystal layer-forming material containing a second coating film; and
Aligning the liquid crystal compound in the second coating film, fixing the alignment and forming a liquid crystal layer;
A method for producing a retardation film comprising:
Before irradiating the polarized light, a step of irradiating non-polarized light having a peak wavelength at a peak wavelength ± 30 nm of the polarized light from a direction of ± 10 degrees perpendicular to the transport surface of the continuous film support. A method for producing a phase difference film.   The method for producing a retardation film according to claim 1, wherein a peak wavelength of the polarized light is 200 nm or more and 400 nm or less.   3. The method for producing a retardation film according to claim 1, wherein the non-polarized light is irradiated from a direction of ± 5 degrees perpendicular to a conveyance surface of the continuous film support.   The method for producing a retardation film according to any one of claims 1 to 3, wherein the first coating film is thermally cured.   The method for producing a retardation film according to any one of claims 1 to 4, wherein light emitted from a rod-shaped light source in which the polarized light extends in a direction orthogonal to the transport direction is polarized by a wire grid polarizer.   The method for producing a retardation film according to claim 5, further comprising a louver composed of a plurality of parallel plates arranged in a longitudinal direction of the rod-shaped light source between the rod-shaped light source and the wire grid polarizer.   The method for producing a retardation film according to claim 1, wherein the polarized light is irradiated on a backup roll. The method for producing a retardation film according to any one of claims 1 to 7, wherein an irradiation amount of the non-polarized light is ² mJ / cm ² or more.