JPWO2020196659A1 - Manufacturing method of cholesteric liquid crystal film - Google Patents

Abstract

In one embodiment of the present invention, a coating film containing a solvent, a rod-shaped thermotropic liquid crystal compound, and a chiral agent is applied onto a substrate to form a coating film, and a residual solvent in the formed coating film. The spiral axes are aligned parallel to the film surface direction and perpendicular to the shearing direction, which comprises a step B of drying the ratio to 50% by mass or less and a step C of applying a shearing force to the surface of the coating film after drying. Provided is a method for manufacturing a shearlic liquid crystal film.

Description

The present disclosure relates to a method for producing a cholesteric liquid crystal film.

An optical film using a liquid crystal film having a large optical anisotropy is known.
In such an optical film, the liquid crystal film is manufactured, for example, by applying a coating liquid containing a liquid crystal compound on a member to be coated and drying it, and if necessary, performing alignment treatment of the liquid crystal compound, polymerization of the liquid crystal compound, and the like. NS.

According to Japanese Patent Application Laid-Open No. 2016-150286, in the method for producing an optical film, the coating film of the liquid crystal material applied on the film-forming surface of the base material is conveyed into the drying furnace together with the base material, and the solvent is removed. , It is described that a liquid crystal layer is formed. In addition to drying, it is described that liquid crystal molecules may be oriented, polymerization of liquid crystal monomers, and the like may be performed. In particular, in the lyotropic liquid crystal, the liquid crystal molecules are oriented in a predetermined orientation by applying a shearing force. It is disclosed that it can be oriented.

Further, Japanese Patent Application Laid-Open No. 2010-536782 discloses the application of mechanical shearing to the liquid crystal layer by applying a knife blade to the liquid crystal layer as one of the treatments of the liquid crystal layer for producing a desired liquid crystal phase. Has been done.

By the way, as the cholesteric liquid crystal film, the spiral axis of the cholesteric liquid crystal is parallel to the film surface direction and is arranged in a specific direction when viewed from above, thereby forming an optical film applied to an aerial imaging device or the like. Is expected to be applied.
In particular, there is an increasing demand for a cholesteric liquid crystal film having less variation in the film surface in which the spiral axes are arranged as described above.

Although the above-mentioned Japanese Patent Application Laid-Open No. 2016-150286 discloses that a shearing force is applied to a lyotropic liquid crystal, there is no description about a cholesteric liquid crystal film in which spiral axes are arranged parallel to the film surface direction. Not.
Further, although the above-mentioned Japanese Patent Publication No. 2010-536782 discloses the treatment performed on the liquid crystal layer in order to generate a desired liquid crystal phase, what is the dry state of the liquid crystal layer due to mechanical shearing? There is no description as to whether it is applied at the time of degree. Furthermore, Japanese Patent Application Laid-Open No. 2010-536782 only describes that the axis of the molecular helix extends laterally with respect to the layer, the axis of which is parallel to the film surface direction and the upper surface of the layer. There is no clear description about lining up in a specific direction when viewed. Therefore, in the liquid crystal layer described in JP-A-2010-536782, it is unlikely that there is little variation in the plane of the arrangement of the axes of the molecular helices.

Therefore, the problem to be solved by one embodiment of the present invention is that the spiral axes of the cholesteric liquid crystal are arranged parallel to the film surface direction and along a specific direction in a top view, and the arrangement within the film surface is uneven. The purpose is to provide a method for producing a small amount of cholesteric liquid crystal film.
Hereinafter, the fact that there is little variation in the membrane surface of the arrangement of the spiral axes is also referred to as “excellent in orientation accuracy”.

Specific means for solving the problem include the following aspects.

<1> A step A of applying a coating liquid containing a solvent, a rod-shaped thermotropic liquid crystal compound, and a chiral agent onto a substrate to form a coating film.
Step B of drying the residual solvent ratio in the formed coating film to 50% by mass or less,
Step C of applying shear force to the surface of the coating film after drying,
A method for producing a cholesteric liquid crystal film having spiral axes parallel to the film surface direction and aligned perpendicular to the shear direction.

<2> The method for producing a cholesteric liquid crystal film according to <1>, wherein step C is a step of applying a shearing force having a shear rate of 1000 seconds- ^{1 or more.}
<3> The method for producing a cholesteric liquid crystal film according to <1> or <2>, wherein the temperature of the coating film surface in step C is 50 ° C to 120 ° C.

<4> The method for producing a cholesteric liquid crystal film according to any one of <1> to <3>, wherein the shearing force in step C is applied by a blade.
<5> The method for producing a cholesteric liquid crystal film according to any one of <1> to <3>, wherein the shearing force in step C is applied by an air knife.

<6> The method for producing a cholesteric liquid crystal film according to any one of <1> to <5>, further comprising a step of curing the coating film after the step C.
<7> The method for producing a cholesteric liquid crystal film according to any one of <1> to <6>, wherein the thickness of the coating film when a shear force is applied in step C is 30 μm or less.
<8> The method for producing a cholesteric liquid crystal film according to any one of <1> to <7>, wherein the thickness of the coating film after the shearing force is applied in step C is 10 μm or less.

According to one embodiment of the present invention, the spiral axis of the cholesteric liquid crystal is parallel to the film surface direction and is arranged along a specific direction in a top view, and there is little variation in the arrangement within the film surface (that is,). A method for producing a cholesteric liquid crystal film (which is excellent in orientation accuracy) is provided.

FIG. 1 is a schematic diagram for explaining an example of the method for producing a cholesteric liquid crystal film of the present disclosure.

Hereinafter, the method for producing the cholesteric liquid crystal film of the present disclosure will be described in detail.
In the present disclosure, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes.

In the present disclosure, the numerical range indicated by using "~" indicates a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in another stepwise description. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.
When the reference numerals described in a plurality of drawings are the same, they refer to the same object.

The present inventors have found a novel liquid crystal orientation method using a step of applying a shearing force to a coating film, and the spiral axes of the cholesteric liquid crystal are arranged parallel to the film surface direction and along the shear direction. In addition, a shearlic liquid crystal film having little variation in the film surface of the arrangement (that is, excellent in orientation accuracy) has been obtained.
Specifically, a method of applying a shearing force to the surface of a coating film obtained by applying and drying a coating liquid containing a solvent, a rod-shaped thermotropic liquid crystal compound (hereinafter, also referred to as a specific liquid crystal compound), and a chiral agent. Is. In particular, by applying a shearing force to a coating film dried to a residual solvent ratio of 50% by mass or less, the spiral axes of the cholesteric liquid crystal are aligned parallel to the film surface direction and along the shearing direction, and further. , It has been found that a shearlic liquid crystal film having little variation in the film surface of the arrangement (that is, excellent in orientation accuracy) can be obtained.
In addition, since this new liquid crystal alignment method aligns the liquid crystal by a shearing force, it also has an effect that an alignment film (also referred to as an alignment layer) normally provided adjacent to the cholesteric liquid crystal film becomes unnecessary. ..

Here, in the present disclosure, the arrangement of the spiral axes of the cholesteric liquid crystal in parallel with the film surface direction is also referred to as "horizontal orientation", and the spiral axis of the cholesteric liquid crystal is horizontal (in other words, the film surface direction of the cholesteric liquid crystal film). , Vertical to the film thickness direction of the cholesteric liquid crystal film). However, it is not necessary that the spiral axis of the cholesteric liquid crystal is exactly horizontal with respect to the film surface direction of the cholesteric liquid crystal film, and the angle formed by the spiral axis of the cholesteric liquid crystal and the film surface direction of the cholesteric liquid crystal film is 45 °. If it is less than, it shall be included in the "horizontal orientation" in the present disclosure. The angle formed by the spiral axis of the cholesteric liquid crystal and the film surface direction of the cholesteric liquid crystal film is preferably in the range of 0 ° to 40 °.

Further, the fact that the spiral axes of the cholesteric liquid crystal are aligned perpendicular to the shearing direction means that the spiral axes of the cholesteric liquid crystal are aligned perpendicular to the direction in which the shearing force is applied at the time of manufacturing the cholesteric liquid crystal film. That is, when a shearing force is applied in the long direction when manufacturing a long cholesteric liquid crystal film, the spiral axis of the cholesteric liquid crystal is perpendicular to the long direction of the cholesteric liquid crystal film in the top view (in other words). For example, it means that they are lined up in the short direction of the shearlic liquid crystal film). However, it is not necessary that the spiral axis of the cholesteric liquid crystal is exactly perpendicular to the shear direction, and the angle formed by the spiral axis of the cholesteric liquid crystal and the shear direction is less than 90 ° ± 45 ° in the present disclosure. It shall be included in "perpendicular to the shear direction". The angle formed by the spiral axis of the cholesteric liquid crystal and the shearing direction is preferably in the range of 60 ° to 120 °.

The following method is used to confirm the arrangement of the spiral axes of the cholesteric liquid crystal in the cholesteric liquid crystal film.
First, the fact that the spiral axes of the cholesteric liquid crystal are aligned parallel to the film surface direction and perpendicular to the shear direction can be confirmed by using a cross-Nicol polarized light transmission photograph and a cross-sectional SEM photograph by a polarizing microscope.
The cholesteric liquid crystal has a laminated structure in which layers composed of molecular groups of a specific liquid crystal compound are stacked. The molecules of each specific liquid crystal compound are arranged in a certain direction in each layer, and the arrangement direction of the molecules of each layer is shifted so as to spirally swirl as it advances in the stacking direction.
Therefore, in the cross Nicol polarized light transmission photograph, the region corresponding to the layer in which the arrangement direction of the molecule of the specific liquid crystal compound is perpendicular to or close to the photographing direction is light, and the region other than the layer appears dark.
Therefore, in the cross Nicol polarized light transmission photograph on the upper surface of the cholesteric liquid crystal film, the regular striped pattern due to the above shading is confirmed, and the regular striped pattern is arranged parallel to the shearing direction, so that the spiral axis of the cholesteric liquid crystal is sheared. It can be confirmed that they are lined up vertically in the direction.
Of the regular striped patterns, select one line (uninterrupted) consisting of a light part in the center of the photo, and if the angle between this line and the shear direction is less than 45 °, the cholesteric liquid crystal The angle between the spiral axis and the shear direction is less than 90 ° ± 45 °.
In addition, the fact that the spiral axes of the cholesteric liquid crystal are lined up parallel to the film surface direction means that the cross section of the cholesteric liquid crystal film in the thickness direction is photographed at a magnification of 5000 times by a scanning electron microscope (SEM). It can be confirmed by (also called a cross-sectional SEM photograph). Here, the cross section in the thickness direction of the cholesteric liquid crystal film is a cross section cut along a direction orthogonal to the shear direction (for example, the transport direction of the coating film).
In the cross-sectional SEM photograph, if one uninterrupted cholesteric liquid crystal is selected and the angle between the spiral axis of the cholesteric liquid crystal and the film surface direction of the cholesteric liquid crystal film is less than 45 °, the spiral axis of the cholesteric liquid crystal is a film. It can be said that they are lined up parallel to the plane direction.

The following method is used to confirm that the orientation accuracy of the cholesteric liquid crystal film is excellent.
Cut out a 2 cm square test piece from the confirmation target. The test piece is placed on a black background, a photo of the same size is taken under a white light, and the obtained photo is binarized with image processing software (for example, Jtrim). Then, the number of white pixels is obtained from the binarized image, and this is used as the area of the "white area".
If there is a fine variation in the spiral axis of the cholesteric liquid crystal, scattering occurs in that region and appears as the above-mentioned "white region".
The smaller the ratio of the white area (that is, the area ratio of the white area) to the total area of the test piece in the photograph (that is, the total number of white and black pixels of the binarized image), the more the arrangement of the spiral axes of the cholesteric liquid crystal. It is shown that there is little variation in the film surface, and it can be judged that the alignment accuracy is excellent.
For example, one index is that the ratio of the white area to the total area of the test piece in the photograph is 10% or less.

The method for producing the cholesteric liquid crystal film of the present disclosure based on the above findings is as follows.
That is, the method for producing a cholesteric liquid crystal film of the present disclosure is a step A of applying a coating liquid containing a solvent, a rod-shaped thermotropic liquid crystal compound, and a chiral agent onto a substrate to form a coating film, and the formed coating. It has a step B of drying the residual solvent ratio in the film to 50% by mass or less, and a step C of applying a shearing force to the surface of the coating film after drying.
By having these steps A, B, and C, they are arranged parallel to the film surface direction (that is, horizontally oriented) and along the shear direction, and further, the arrangement is uneven in the film surface. A cholesteric liquid crystal film with less is obtained.

Hereinafter, each step of the method for producing a cholesteric liquid crystal film of the present disclosure will be described in detail with reference to the drawings.
An example of the method for producing a cholesteric liquid crystal film of the present disclosure shown in FIG. 1 is a method using a continuous process by a roll-to-roll method using a long substrate that is continuously conveyed. ..
The method for producing a cholesteric liquid crystal film of the present disclosure is not limited to a continuous process using a roll-to-roll method, and each step may be sequentially performed on a single-wafer substrate.

[Step A]
In step A, a coating liquid containing a solvent, a rod-shaped thermotropic liquid crystal compound, and a chiral agent (hereinafter, also referred to as a liquid crystal layer forming coating liquid) is applied onto the substrate to form a coating film.
The coating liquid for forming the liquid crystal layer in step A can be applied in a state where the substrate is stretched, and is applied to the substrate wound on the backup roll from the viewpoint of improving the coating accuracy. Is preferable.

An example of step A will be described with reference to FIG.
As shown in FIG. 1, when the tip of the rolled long base material F in a roll shape is sent out and transported via the transport roll 50, first, the coating means 10 is used to form a liquid crystal layer. The coating liquid is applied.
As shown in FIG. 1, it is preferable that the coating liquid for forming a liquid crystal layer is applied by the coating means 10 in a region where the base material F is wound on the backup roll 12.

(Base material)
The base material is not particularly limited, and may be a member that functions as a part of the optical film together with the cholesteric liquid crystal film, or is an object to be coated to which the coating liquid is applied and is peeled off from the cholesteric liquid crystal film. It may be a member to be used.
In particular, a polymer film is preferably used as the base material in consideration of applicability to the roll-to-roll method and ease of wrapping around the backup roll.

For optical film applications, the total light transmittance of the substrate is preferably 80% or more.
For optical film applications, when a polymer film is used as the substrate, it is preferable to use an optically isotropic polymer film.
Examples of the base material include a polyester-based base material (film or sheet such as polyethylene terephthalate and polyethylene naphthalate), a cellulose-based base material (film or sheet such as diacetyl cellulose and triacetyl cellulose (TAC)), and a polycarbonate-based base material. , Poly (meth) acrylic substrate (film or sheet such as polymethylmethacrylate), polystyrene-based substrate (film or sheet such as polystyrene, acrylonitrile-styrene copolymer), olefin-based substrate (polyethylene, polypropylene, cyclic or Polyethylene having a norbornene structure, film or sheet of ethylene-propylene copolymer, etc.), polyamide-based substrate (film or sheet of polyvinyl chloride, nylon, aromatic polyamide, etc.), polyimide-based substrate, polysulfone-based substrate, poly Ethersulfone-based base material, polyether ether ketone-based base material, polyphenylene sulfide-based base material, vinyl alcohol-based base material, polyvinylidene chloride-based base material, polyvinyl butyral-based base material, poly (meth) acrylate-based base material, polyoxy Examples thereof include a transparent base material such as a methylene-based base material and an epoxy resin-based base material, and a base material made of a blended polymer blended with the above polymer materials.

The thickness of the base material is preferably, for example, 30 μm to 150 μm, more preferably 40 μm to 100 μm, in consideration of manufacturing suitability, manufacturing cost, optical film use, and the like.

The base material may be one in which a layer is previously formed on the above-mentioned polymer film.
Examples of the layer formed in advance include an alignment layer having an orientation regulating force for a liquid crystal compound such as a rubbing alignment layer and a light alignment layer, and an adhesion layer.

(Coating liquid for forming a liquid crystal layer)
The liquid crystal layer forming coating liquid used in step A contains a solvent, a rod-shaped thermotropic liquid crystal compound, and a chiral agent. Further, the coating liquid for forming a liquid crystal layer may contain other components, if necessary.

-Solvent-
As the solvent, an organic solvent is preferably used.
Specific examples of the organic solvent include an amide solvent (for example, N, N-dimethylformamide), a sulfoxide solvent (for example, dimethyl sulfoxide), a heterocyclic compound (for example, pyridine), and a hydrocarbon solvent (for example, benzene, hexane, etc.). , Alkyl halide solvents (eg chloroform, dichloromethane), ester solvents (eg methyl acetate, butyl acetate, etc.), ketone solvents (eg acetone, methyl ethyl ketone, cyclohexanone, etc.), ether solvents (eg, tetrahydrofuran, 1,2- Dimethoxyethane, etc.). Among them, as the organic solvent, an alkyl halide solvent and a ketone solvent are preferable.
The organic solvent may be used alone or in combination of two or more.

-Bar-shaped thermotropic liquid crystal compound (specific liquid crystal compound)-
The rod-shaped thermotropic liquid crystal compound (that is, the specific liquid crystal compound) refers to a liquid crystal compound having a thermotropic property and a rod-shaped molecular structure.
In particular, the specific liquid crystal compound is preferably a compound having a polymerizable group. Examples of the polymerizable group of the specific liquid crystal compound include unsaturated polymerizable groups, epoxy groups, and aziridinyl groups, more preferably unsaturated polymerizable groups, and more preferably ethylenically unsaturated polymerizable groups. It is particularly preferable to have.
Specifically, as a specific liquid crystal compound, Makromol. Chem. , 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, 562,648, 5770107, International Publication 95/22586. No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, Japanese Patent Application Laid-Open No. 1-272551, No. 6-16616, No. 7-110469. Examples thereof include compounds described in Japanese Patent Application Laid-Open No. 11-80081, Japanese Patent Application Laid-Open No. 2001-328973, and the like.
Further, as the specific liquid crystal compound, for example, those described in JP-A No. 11-513019, JP-A-2007-279688, etc. can be preferably used, but the specific liquid crystal compounds are not limited thereto.

As the specific liquid crystal compound, for example, a compound represented by the following general formula (1) is preferably used as the liquid crystal compound having a forward wavelength dispersion characteristic.

In the general formula (1), Q ¹ and Q ² are independently polymerizable groups, and L ¹ , L ² , L ³ and L ⁴ are independently single-bonded or divalent linking groups, respectively. A ¹ and A ² each independently represent a divalent hydrocarbon group having 2 to 20 carbon atoms, and M represents a mesogen group.

The polymerizable group represented by Q ¹ and Q ^2, include a polymerizable group specific liquid crystal compound having the above-mentioned, and preferred examples are also the same.
The ^{linking groups represented by L 1} , L ² , L ³ and L ⁴ are -O-, -S-, -CO-, -NR-, -CO-O-, and -O-CO-O-. , -CO-NR-, -NR-CO-, -O-CO-, -O-CO-NR-, -NR-CO-O-, and NR-CO-NR- It is preferable that it is a linking group of. Here, R is an alkyl group or a hydrogen atom having 1 to 7 carbon atoms.
Further, ^{at least one of L 3} and L ⁴ is preferably —O—CO—O−.
In the general formula (1), Q ¹ − L ¹ − and Q ² − L ² − are CH ₂ = CH _{−CO−O−, CH 2} = C (CH ₃ ) −CO−O−, and CH ₂ =. C (Cl) -CO-O- is preferable, and CH ₂ = CH-CO-O- is most preferable.

As the ^{divalent hydrocarbon group having 2 to 20 carbon atoms represented by A 1} and A ² , an alkylene group, an alkenylene group, or an alkynylene group having 2 to 12 carbon atoms is preferable, and in particular, the number of carbon atoms is particular. 2-12 alkylene groups are preferred. The divalent hydrocarbon group is preferably chain-like and may contain non-adjacent oxygen or sulfur atoms. Further, the divalent hydrocarbon group may have a substituent, and examples of the substituent include a halogen atom (fluorine, chlorine, bromine), a cyano group, a methyl group, an ethyl group and the like.

The mesogen group represented by M is a group showing the main skeleton of the liquid crystal molecule that contributes to the formation of the liquid crystal.
The mesogen group represented by M is not particularly limited, and is described in, for example, "Flusgue Christalle in Tabellen II" (VEB Editorial Berg fur Grundstoff Industrie, Leipzig, 1984), pages 7 to 16 in particular. You can refer to the manual edition, LCD Handbook (Maruzen, 2000), especially the description in Chapter 3.
More specifically, the mesogen group represented by M has the structure described in paragraph 0086 of JP-A-2007-279688.
As the mesogen group, for example, a group containing at least one cyclic structure selected from the group consisting of an aromatic hydrocarbon group, a heterocyclic group, and an alicyclic group is preferable. Among them, the mesogen group is preferably a group containing an aromatic hydrocarbon group, more preferably a group containing 2 to 5 aromatic hydrocarbon groups, and more preferably 3 to 5 aromatic hydrocarbon groups. It is more preferable that the group contains a hydrogen group.
More preferably, the mesogen group is a group containing 3 to 5 phenylene groups and having phenylene groups linked with −CO—O—.
The cyclic structure contained in the mesogen group may further have an alkyl group having 1 to 10 carbon atoms such as a methyl group as a substituent.

Specific examples of the compound represented by the general formula (1) are shown below, but the present invention is not limited thereto. "Me" represents a methyl group.

Further, as the specific liquid crystal compound, a rod-shaped liquid crystal compound having a reverse wavelength dispersibility may be used.
Examples of the reverse wavelength dispersible rod-shaped liquid crystal compound include the liquid crystal compound represented by the general formula 1 of JP-A-2016-81035 and the general formula (I) or (II) of JP-A-2007-279688. Examples of the compound to be used. More specifically, examples of the specific liquid crystal compound having a reverse wavelength dispersibility include the following compounds, but the present disclosure is not limited to these.

The specific liquid crystal compound may be used alone or in combination of two or more.
The content of the specific liquid crystal compound in the coating liquid for forming a liquid crystal layer is preferably 70% by mass or more and less than 100% by mass, more preferably 90% by mass to 99% by mass, based on the mass of the total solid content.
The solid content refers to a component excluding the solvent.

-Chiral agent-
Chiral agents are various known chiral agents (for example, liquid crystal device handbook, Chapter 3, 4-3, TN, chiral auxiliary for STN, page 199, edited by Japan Society for the Promotion of Science, 42nd Committee, 1989). You can choose from.
The chiral agent generally contains an asymmetric carbon atom, but an axial asymmetric compound or a surface asymmetric compound that does not contain an asymmetric carbon atom can also be used as the chiral agent.
Examples of axial or asymmetric compounds include binaphthyl, helicene, paracyclophane, and derivatives thereof.

The chiral agent may have a polymerizable group.
When the chiral agent has a polymerizable group and the specific liquid crystal compound used in combination also has a polymerizable group, the specific liquid crystal compound is subjected to a polymerization reaction between the chiral agent having a polymerizable group and the specific liquid crystal compound having a polymerizable group. A polymer having a repeating unit derived from a chiral agent and a repeating unit derived from a chiral agent is obtained.
The polymerizable group of the chiral agent having a polymerizable group is preferably a group of the same type as the polymerizable group of the specific liquid crystal compound. The polymerizable group of the chiral agent is preferably an unsaturated polymerizable group, an epoxy group, or an aziridinyl group, more preferably an unsaturated polymerizable group, and preferably an ethylenically unsaturated polymerizable group. Especially preferable.

Moreover, the chiral agent may be a liquid crystal compound.
Examples of the chiral agent exhibiting a strong twisting force include JP-A-2010-181852, JP-A-2003-287623, JP-A-2002-80851, JP-A-2002-80478, and JP-A-2002-302487. Examples of the chiral agent described in the publications and the like can be preferably used in the coating liquid for forming a liquid crystal layer in the present disclosure.
Further, for the isosorbide compounds described in the above publications, isosorbide compounds having a corresponding structure can be used as a chiral agent, and for the isosorbide compounds described in the same publication, the corresponding structure can be used. Isosorbide compounds of the above can also be used as a chiral agent.

The content of the chiral agent in the coating liquid for forming a liquid crystal layer is preferably 0.5% by mass to 10.0% by mass, more preferably 1.0% by mass to 3.0% by mass, based on the mass of the total solid content. preferable.

-Other ingredients-
The liquid crystal layer forming coating liquid may contain other components such as an orientation control agent, a polymerization initiator, a leveling agent, and an orientation aid, if necessary.

-Orientation control agent As the orientation control agent, one that can reduce the tilt angle of the molecule of the specific liquid crystal compound at the air interface or make it substantially horizontal is preferable.
Examples of such an orientation control agent include the compounds described in paragraph numbers [0012] to [0030] of JP2012-2111306, and paragraph numbers [0037] to [0044] of JP2012-101999. The compound described in JP-A-2007-272185, the fluorine-containing (meth) acrylate polymer described in paragraph numbers [0018] to [0043] of JP-A-2007-272185, and the compound described in detail in JP-A-2005-09925 along with the synthesis method. And so on.
In addition, the polymer described in JP-A-2004-331812 which contains the polymerization unit of the fluoroaliphatic group-containing monomer in an amount of more than 50% by mass of the total polymerization unit may also be used as the orientation control agent.

An example of another orientation control agent is a vertical alignment agent. By blending a vertical alignment agent, the vertical orientation of the liquid crystal compound can be controlled. As an example of the vertical alignment agent, a boronic acid compound and / or an onium salt described in JP-A-2015-38598, an onium salt published in JP-A-2008-26730 and the like can be preferably used.

The content of the orientation control agent in the coating liquid for forming a liquid crystal layer is preferably 0% by mass to 5.0% by mass, more preferably 0.3% by mass to 2.0% by mass, based on the mass of the total solid content. ..

-Polymerization Initiator As the polymerization initiator, both a photopolymerization initiator and a thermal polymerization initiator are used, but from the viewpoint of suppressing deformation of the substrate due to heat, deterioration of the composition for forming a liquid crystal layer, etc., light Polymerization initiators are preferred.
Examples of the photopolymerization initiator include α-carbonyl compounds (for example, the compounds described in US Pat. Nos. 2,376,661 and 236,670), acidoin ethers (compounds described in US Pat. No. 2,448,828), and the like. α-hydrogen substituted aromatic acidoine compounds (eg, compounds described in US Pat. No. 2,225,512), polynuclear quinone compounds (eg, compounds described in US Pat. Nos. 3,46127 and 2951758), triaryl. A combination of an imidazole dimer and a p-aminophenyl ketone (eg, a compound described in US Pat. No. 3,549,67), an acridin and a phenazine compound (eg, JP-A-60-105667, US Pat. No. 4,239,850). , Oxadiazole compound (for example, the compound described in US Pat. No. 4,212,970), acylphosphine oxide compound (for example, Japanese Patent Application Laid-Open No. 63-40799, Japanese Patent Application Laid-Open No. 5-29234, JP-A-10). -95788, and the compounds described in JP-A No. 10-29997) and the like.

The content of the polymerization initiator in the coating liquid for forming a liquid crystal layer is preferably 0.5% by mass to 5.0% by mass, preferably 1.0% by mass to 4.0% by mass, based on the mass of the total solid content. More preferred.

The solid content of the liquid crystal layer forming coating liquid is preferably in the range of, for example, 25% by mass to 40% by mass, and 25% by mass to 35% by mass, based on the total mass of the liquid crystal layer forming coating liquid. The range is more preferred.

(Application)
As a coating means for applying the liquid crystal layer forming coating liquid (corresponding to the coating means 10 in FIG. 1), a known coating means is applied.
Specifically, as the coating means, the extrusion die coater method, the curtain coating method, the dip coating method, the spin coating method, the print coating method, the spray coating method, the slot coating method, the roll coating method, the slide coating method, the blade coating method, and the gravure Means using a coating method, a wire bar method, or the like can be mentioned.

(Backup role)
The backup roll (corresponding to the backup roll 12 in FIG. 1) preferably used in the step A is a member capable of winding the base material and continuously transporting the base material, and is rotationally driven at the same speed as the transport speed of the base material.
The backup roll used in the step A is not particularly limited, and a known backup roll can be used.
As the backup roll, for example, one having 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 0.1 μm or less in terms of the surface roughness Ra from the viewpoint of reducing the variation in the frictional force between the base material and the backup roll.

The backup roll used in the step A is added from the viewpoint of enhancing the drying promotion of the coating film and suppressing the brushing of the coating film (that is, the whitening of the coating film due to the formation of fine dew condensation) due to the decrease in the film surface temperature. It may be warmed.
The surface temperature of the backup roll may be determined according to the composition of the coating film, the curing performance of the coating film, the heat resistance of the base material, etc., for example, preferably 40 ° C to 120 ° C, more preferably 40 ° C to 100 ° C. preferable.

It is preferable that the backup roll used in the step A detects the surface temperature and the surface temperature of the backup roll is maintained by the temperature control means based on the temperature.
The temperature control means of the backup roll includes a heating means and a cooling means. As the heating means, induction heating, water heating, oil heating and the like are used, and as the cooling means, cooling with cooling water is used.

The diameter of the backup roll used in the step A is preferably 100 mm to 1000 mm, more preferably 100 mm to 800 mm, from the viewpoint of easy wrapping of the base material, easy coating by the coating means, and the manufacturing cost of the backup roll. It is preferable, and more preferably 200 mm to 700 mm.

The transport speed of the base material on the backup roll in the step A is preferably 10 m / min or more and 100 m / min or less from the viewpoint of ensuring productivity and coatability.

The lap angle of the base material with respect to the backup roll is preferably 60 ° or more, and more preferably 90 ° or more, from the viewpoint of stabilizing the transfer of the base material during coating and suppressing the occurrence of uneven thickness of the coating film. Further, the upper limit of the lap angle can be set to, for example, 180 °.
The lap angle refers to an angle including a transport direction of the base material when the base material comes into contact with the backup roll and a transport direction of the base material when the base material is separated from the backup roll.

[Step B]
In step B, the residual solvent ratio in the formed coating film is dried to 50% by mass or less.
The residual solvent ratio in the coating film in the step B is preferably 40% by mass or less, more preferably 30% by mass or less. The lower limit of the residual solvent ratio in the coating film in the step B is preferably 10% by mass from the viewpoint of easily suppressing deterioration of the coating surface condition.
The residual solvent ratio in the coating film may be 50% by mass or less immediately before the step C, for example, during transportation after drying by the drying means described later and before being subjected to the step C. In addition, the residual solvent ratio in the coating film may be 50% by mass or less.
In step B, in the process in which the residual solvent ratio becomes 50% by mass or less, the density of the specific liquid crystal compound in the coating film increases, and a cholesteric liquid crystal is obtained. In the cholesteric liquid crystal in step B, the spiral axis is often parallel to the film surface direction of the coating film. However, the coating film having a residual solvent ratio of 50% by mass or less in step B is in a state where the direction of the spiral axis of the cholesteric liquid crystal varies in the plane when viewed from above.

An example of step B will be described with reference to FIG.
In step B, after the coating liquid for forming the liquid crystal layer is applied by the coating means 10, the coating film is dried by the drying region of the drying means 20.
The dried coating film is conveyed to step C via the conveying roll 52. In step B, the residual solvent ratio in the coating film may be 50% by mass or less before the shearing force is applied to the surface of the coating film in step C.

(Dry)
As a drying means used for drying the coating film (corresponding to the drying means 20 in FIG. 1), a known drying means is applied.
Specific examples of the drying means include means using a method using an oven, a warm air blower, an infrared (IR) heater, or the like.
In the drying by a warm air blower, warm air may be blown from the surface opposite to the coating film forming surface of the base material, or a diffusion plate may be installed so that the coating film surface does not flow with warm air. ..
Further, the drying may be performed by inhalation. Drying by intake air is a method of reducing the residual solvent ratio in the coating film by inhaling the gas on the coating film using a decompression chamber or the like having an exhaust mechanism.
The drying conditions may be any conditions as long as the residual solvent ratio in the coating film is 50% by mass or less, and may be determined according to the composition, coating amount, transport speed and the like of the liquid crystal layer forming coating film.

Here, the residual solvent ratio of the coating film is measured by an absolute dry method.
Specifically, a part of the coating film is scraped off and dried at 60 ° C. (below the temperature at which the material constituting the coating film does not volatilize) for 24 hours, and the residual solvent ratio is obtained from the mass change before and after drying. This is performed 3 times, and the average value of the 3 times is taken as the residual solvent ratio.

[Process C]
In step C, a shearing force is applied to the surface of the coating film after drying.
As described above, the coating film after drying in step B is in a state where the orientation of the spiral axis of the cholesteric liquid crystal varies in the plane when viewed from above.
Therefore, in the method for producing a cholesteric liquid crystal film of the present disclosure, step C is performed after step B to reduce the variation in the direction of the spiral axis of the cholesteric liquid crystal when the coating film is viewed from above. Specifically, in step C, a shearing force is applied to the surface of the coating film after step B.
When a shearing force is applied to the surface of the coating film, the spiral axis of the cholesteric liquid crystal is regularly arranged perpendicular to the shearing direction triggered by this shearing force. As a result, by going through step C, the spiral axes of the cholesteric liquid crystal are aligned parallel to the film surface direction and perpendicular to the shear direction, and further, there is little variation in the arranged film surface (that is, alignment accuracy). Excellent) Cholesteric liquid crystal film can be obtained.
The cholesteric liquid crystal film having excellent orientation accuracy can be confirmed by the fact that there are few scattered regions (white regions described above) when the cholesteric liquid crystal film is viewed from above.
It is preferable that the shearing force is applied to the surface of the coating film in the step C on the base material wound on the backup roll from the viewpoint of enhancing the uniformity of the shearing force.

An example of step C will be described with reference to FIG.
In step C, the upper surface of the dried coating film in which the residual solvent ratio in the coating film is 50% by mass or less is scraped off by the blade 30 by the drying means 20 to apply a shearing force.
As a result, a shearing force is applied along the transport direction of the coating film (that is, the transport direction of the base material).
As shown in FIG. 1, it is preferable that the shearing force is applied by the blade 30 in the region where the base material F is wound on the backup roll 32.

In FIG. 1, the blade 30 is used to apply a shearing force to the surface of the coating film, but the present disclosure is not limited to this, and the spiral axes of the cholesteric liquid crystal can be arranged perpendicularly to the shearing direction. If possible, any method may be used. Examples of means for applying a shearing force other than the blade include an air knife, a bar, an applicator, and the like.

(Shear velocity)
When a shearing force is applied to the surface of the coating film after drying in step C, the higher the shearing rate, the easier it is to obtain a cholesteric liquid crystal film having excellent orientation accuracy. Specifically, the shear rate is ^{preferably 1000 seconds-1} (1 / sec) or more, more preferably 10,000 seconds- ¹ (1 / sec) or more, and 30,000 seconds- ¹ (1 / sec). ) And above are more preferable.
The upper limit of the shear rate is, for example, 1.0 × 10 ⁶ sec ^-1 (1 / sec) or less.
For example, as shown in FIG. 1, when a shearing force is applied to the surface of a coating film by the blade 30, the shear rate is such that the shortest distance between the blade 30 and the base material is "d" and the coating film in contact with the blade is in contact with the blade. When the transport speed (that is, the relative speed between the coating film and the blade) is "V", it is obtained by "V / d".
When a shear force is applied to the surface of the coating film with an air knife, the shear rate is set to "h" for the thickness of the coating film after the application of shear and the relative speed "V" between the surface of the coating film and the surface of the base material. Sometimes, it is obtained from "V / 2h".

(Giving shear force by blade)
As shown in FIG. 1, in the case of the method of applying a shearing force to the surface of the coating film by the blade 30, it is preferable to scrape the upper surface of the coating film.
That is, when the shearing force is applied by the blade, the film thickness of the coating film is regulated by the blade.
The film thickness of the coating film after the shearing force is applied by the blade may be 1/2 or less, or 1/3 or less, as compared with that before the shearing force is applied. However, as the lower limit of the thickness regulation, for example, it is preferable that the film thickness of the coating film after the shearing force is applied by the blade is 1/4 or more as compared with that before the shearing force is applied.

The shape, material, etc. of the blade used to apply the shearing force are not particularly limited.
The blade may be a metal plate-shaped member such as stainless steel, or a resin plate-shaped member such as Teflon (registered trademark) or PEEK (polyetheretherketone).
From the viewpoint of easily applying a constant shearing force to the coating film, it is preferable to use a metal plate-shaped member, and the thickness of the tip portion in contact with the coating film (that is, the thickness along the transport direction of the coating film). Is preferably a metal plate-like member having a size of 0.1 mm or more (preferably 1 mm or more). The upper limit of the thickness of the metal plate-shaped member is, for example, about 10 mm.

(Giving shear force with an air knife)
In the case of the method of applying a shearing force to the surface of the coating film by an air knife, the shearing force is applied by blowing compressed air by the air knife on the upper surface of the coating film.
The shear rate applied to the coating film can be adjusted by the speed at which compressed air is blown (that is, the flow velocity).
The direction in which the compressed air is blown by the air knife may be the same as or in the opposite direction to the transport direction of the coating film, but the coating film debris scraped off by the blown compressed air reappears on the coating film. From the viewpoint of preventing adhesion and the like, it is preferable that the direction is the same as the transport direction of the coating film.

(Temperature of coating film surface)
In step C, the temperature of the coating film surface to which the shearing force is applied depends on the phase transition temperature of the specific liquid crystal compound used, but is generally preferably 50 ° C to 120 ° C, preferably 60 ° C to 100 ° C. It is more preferable to have.
By setting the temperature of the coating film surface within the above range, it becomes easy to arrange the spiral axes of the cholesteric liquid crystal perpendicularly to the shearing direction by applying the shearing force, and it is possible to obtain a cholesteric liquid crystal film having high orientation accuracy.
Here, the temperature of the coating film surface is a value measured by using a radiation thermometer whose emissivity is calibrated by the temperature value measured by a non-contact thermometer. The measurement is performed in a state where there is no reflecting object within 10 cm from the surface on the opposite side (back side) of the measurement surface.

(Backup role)
The backup roll (corresponding to the backup roll 32 in FIG. 1) preferably used in the step C is a member capable of winding the base material and continuously transporting the base material, and is rotationally driven at the same speed as the transport speed of the base material.
The backup roll used in step C is the same as the backup roll used in step A, and the preferred embodiment is also the same.
In addition, step A and step C may be performed on one backup roll.

The backup roll used in the step C may be heated from the viewpoint of controlling the temperature of the coating film surface within the above range.
The surface temperature of the backup roll is, for example, preferably 50 ° C to 120 ° C, more preferably 60 ° C to 100 ° C.

It is preferable that the backup roll used in the step C detects the surface temperature and the surface temperature of the backup roll is maintained by the temperature control means based on the temperature.
The temperature control means of the backup roll is the same as that of the backup roll used in the step A.

The diameter of the backup roll used in step C is preferably 100 mm to 1000 mm, more preferably 100 mm to 800 mm, from the viewpoint of easy winding of the base material, easy application of shearing force, and the manufacturing cost of the backup roll. It is preferable, and more preferably 200 mm to 700 mm.

The transport speed of the base material on the backup roll in the step C is preferably 10 m / min or more and 100 m / min or less from the viewpoint of ensuring productivity and enhancing the uniformity of the shearing force.

The lap angle of the base material with respect to the backup roll in the step C is preferably 60 ° or more, and more preferably 90 ° or more, from the viewpoint of stabilizing the transfer of the base material at the time of coating and enhancing the uniformity of the shearing force. Further, the upper limit of the lap angle can be set to, for example, 180 °.

The thickness of the coating film when the shearing force is applied in the step C (that is, the thickness of the coating film dried in the step B) is 70 μm from the viewpoint of further improving the alignment accuracy of the spiral axis of the cholesteric liquid crystal due to the shearing force. It is preferably the following, more preferably 50 μm or less, and even more preferably 15 μm to 50 μm.

The thickness of the coating film after the shearing force is applied in the step C is preferably 10 μm or less from the viewpoint of further improving the alignment accuracy of the spiral axis of the cholesteric liquid crystal due to the shearing force.
Further, the thickness of the coating film obtained through the step C (that is, the coating film after the shearing force is applied in the step C) may be determined according to the intended use.
The thickness of the coating film obtained through the step C is preferably, for example, 5 μm or more.

[Step D]
In the method for producing a cholesteric liquid crystal film of the present disclosure, when a polymerizable compound (specifically, a specific liquid crystal compound having a polymerizable group, a chiral agent having a polymerizable group, etc.) is contained in the coating film, after step C, It is preferable to include the step D of curing the coating film.
In step D, it is preferable to apply heat to the coating film after the shearing force is applied, or to irradiate the coating film with active energy rays to cure the coating film.
Considering the manufacturing suitability and the like, it is preferable to use the curing by the active energy ray irradiated from the irradiation means 40 of the active energy ray as shown in FIG. 1 as the step D.

The means for irradiating the active energy rays is not particularly limited as long as it is a means for imparting energy capable of generating active species in the coating film to be irradiated.
Specific examples of the active energy ray include α-rays, γ-rays, X-rays, ultraviolet rays, infrared rays, visible rays, and electron beams. Of these, ultraviolet rays are preferably used as the active energy rays from the viewpoint of curing sensitivity and availability of the apparatus.

Examples of the light source of ultraviolet rays include tungsten lamps, halogen lamps, xenon lamps, xenon flash lamps, mercury lamps, mercury xenon lamps, carbon arc lamps and other lamps, and various lasers (eg, semiconductor lasers, helium neon lasers, argon ions). Examples include lasers, helium cadmium lasers, YAG (Yttrium Aluminum Garnet) lasers), light emitting diodes, cathode wire tubes, and the like.
The peak wavelength of ultraviolet rays emitted from the light source of ultraviolet rays is preferably 200 nm to 400 nm.
Further, as the amount of exposure energy of ultraviolet rays, for example, 100 mJ / cm ^{2 to} 500 mJ / cm ² is preferable.

As described above, the cholesteric liquid crystal film is manufactured on the base material.
The laminate of the base material and the cholesteric liquid crystal film may be used as an optical film.

[Other processes]
In the method for producing a cholesteric liquid crystal film of the present disclosure, other steps may be included in addition to the above steps A to D.
Examples of other steps include a step of forming an alignment layer on the substrate used in step A.
That is, the base material used in step A may be a base material having an alignment layer.

(Orientation layer)
The alignment layer is not particularly limited as long as it is a layer capable of imparting an orientation regulating force to the liquid crystal compound.
The oriented layer can be provided by means such as rubbing treatment of an organic compound (preferably a polymer), oblique vapor deposition of an inorganic compound, or formation of a layer having microgrooves.
Further, the alignment layer may be an alignment layer in which an alignment function is generated by applying an electric field, applying a magnetic field, or irradiating light.
When the base material is made of resin, depending on the resin type (for example, PET (polyethylene terephthalate) or the like), the support is directly oriented (for example, rubbing) without providing an alignment layer. The surface of the material can also function as an alignment layer.

In the method for producing a cholesteric liquid crystal film of the present disclosure, the alignment layer is not essential, and the spiral axes of the cholesteric liquid crystal can be arranged by applying a shearing force to the coating film in step C without using the alignment layer.

[Optical film]
In the method for producing a cholesteric liquid crystal film of the present disclosure, when an optically isotropic polymer film is used as a base material and a cholesteric liquid crystal film is formed on the polymer film, the obtained laminate can be used as an optical film. can.
Further, the cholesteric liquid crystal film itself may be used as an optical film.
The cholesteric liquid crystal film obtained by the method for producing a cholesteric liquid crystal film of the present disclosure can exhibit a function as a light reflecting layer. Therefore, it is also suitable as an optical film used in an aerial imaging device.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

[Example 1]
(Preparation of base material)
As a base material, a long triacetyl cellulose (TAC) film (Fujifilm Co., Ltd., refractive index 1.48) having a thickness of 80 μm and a width of 300 mm was prepared.

(Preparation of coating liquid 1 for forming a liquid crystal layer)
After mixing each of the components described below, the mixture was filtered through a polypropylene filter having a pore size of 0.2 μm to prepare a coating liquid 1 for forming a liquid crystal layer.

− Coating liquid for forming a liquid crystal layer 1-
• Rod-shaped thermotropic liquid crystal compound (compound (A) below): 100 parts by mass ・ Chiral agent (compound (B) below): 2.5 parts by mass ・ Photopolymerization initiator: 3 parts by mass (IRGACURE (registered trademark) 907, BASF)
-Orientation regulator (compound (C) below): 0.2 parts by mass-Vertical alignment agent (compound (D) below): 0.5 parts by mass-Solvent (methyl ethyl ketone): 215 parts by mass

(Step A and Step B)
The liquid crystal layer forming coating liquid 1 was applied onto the continuously conveyed substrate by the die coating method, and then passed through an oven at 70 ° C. for 60 seconds to dry the coating film.
Regarding step A, specifically, the base material is conveyed onto a backup roll having a surface temperature of 25 ° C. and an outer diameter of 300 mm, and as shown in FIG. 1, the base material wound on the backup roll is subjected to a die coating method. Was applied to the liquid crystal layer forming coating liquid 1.
The transfer speed of the base material in the steps A and B was 10 m / min.
The residual solvent ratio in the coating film after drying before step C was measured by the method described above and found to be 1.1% by mass.
The thickness of the coating film after drying was 50 μm, and the coating width was 250 mm.

(Process C)
A shear force was applied to the dried coating film with a stainless steel blade (thickness of the tip portion of 1 mm).
Specifically, regarding step C, first, the blade was installed so that the tip portion came to a position 20 μm away from the surface of the base material on the backup roll having a surface temperature of 70 ° C. and an outer diameter of 500 mm. The blade was kept warm at 70 ° C. The substrate having the coating film that had undergone step B was conveyed there onto the backup roll, the surface of the coating film was pressed against the blade, and the upper surface of the coating film was scraped off.
The shear rate applied by the blade was 10,000 seconds ^-1 .
The thickness of the coating film that had undergone step C was 10 μm.
The transport speed of the base material in step C was 12 m / min.

(Step D)
The coating film after the step C was irradiated with ultraviolet rays with an exposure energy amount of 500 mJ / cm ^{2 using a high-pressure mercury lamp to cure the coating film.}
As described above, a cholesteric liquid crystal film was produced on the substrate.

[Examples 2 and 3, Comparative Example 2]
A cholesteric liquid crystal film was produced on the substrate in the same manner as in Example 1 except that the drying conditions (specifically, the drying time) in step B were changed to change the solvent residual ratio in the coating film.

[Example 4]
A cholesteric liquid crystal film was produced on the substrate in the same manner as in Example 1 except that the transport speed of the coating film in step C was changed to 36 m / min.

[Example 5]
A cholesteric liquid crystal film was produced on the substrate in the same manner as in Example 1 except that the following alignment layer forming step was performed before the step A.

(Orientation layer formation step)
-Preparation of alignment layer composition A-
A mixture of 96 parts by mass of pure water and PVA-205 (Kuraray Co., Ltd., polyvinyl alcohol) was stirred and dissolved in a container kept at 80 ° C. to prepare an oriented layer composition.
The alignment layer composition is applied to the above-mentioned triacetyl cellulose (TAC) film to be continuously transported using a # 6 bar, and then dried in an oven at 100 ° C. for 10 minutes, and then the substrate is transported in the transport direction. The rubbing process was applied in the direction orthogonal to.

[Example 6]
(Step A and Step B)
The above-mentioned coating liquid 1 for forming a liquid crystal layer was applied onto a continuously conveyed substrate by a die coating method, and then passed through an oven at 70 ° C. for 60 seconds to dry the coating film.
Regarding step A, specifically, the base material is conveyed onto a backup roll having a surface temperature of 25 ° C. and an outer diameter of 300 mm, and as shown in FIG. 1, the base material wound on the backup roll is subjected to a die coating method. Was applied to the liquid crystal layer forming coating liquid 1.
The transfer speed of the base material in the steps A and B was 10 m / min.
The residual solvent ratio in the coating film after drying before step C was measured by the method described above and found to be 1.1% by mass.
The thickness of the coating film after drying was 50 μm, and the coating width was 250 mm.

(Process C)
A shearing force was applied to the dried coating film with an air knife.
Specifically, regarding step C, the substrate having the coating film that has undergone step B is conveyed to a backup roll having a surface temperature of 70 ° C. and an outer diameter of 500 mm, and compressed air is applied to the coating film surface on the backup roll with an air knife. I guessed. The blowing direction of the compressed air was the same as the transport direction of the coating film.
The shear rate applied by the air knife was 10,000 seconds ^-1 .
The thickness of the coating film that had undergone step C was 10 μm.
The transport speed of the base material in step C was 12 m / min.

(Step D)
The coating film after the step C was irradiated with ultraviolet rays with an exposure energy amount of 500 mJ / cm ^{2 using a high-pressure mercury lamp to cure the coating film.}
As described above, a cholesteric liquid crystal film was produced on the substrate.

[Examples 7 to 8]
A cholesteric liquid crystal film was produced on the substrate in the same manner as in Example 6 except that the drying conditions (specifically, the drying time) in step B were changed to change the solvent residual ratio in the coating film.

[Example 9]
A cholesteric liquid crystal film was produced on the substrate in the same manner as in Example 1 except that the transport speed of the coating film in step C was changed to 36 m / min.

[Example 10]
A cholesteric liquid crystal film was produced on the substrate in the same manner as in Example 6 except that the alignment layer forming step was performed in the same manner as in Example 5 before the step A.

[Comparative Example 1]
A cholesteric liquid crystal film was produced on the substrate in the same manner as in Example 3 except that step C was not performed.

〔evaluation〕
(Observation with a polarizing microscope)
A cross Nicol polarized light transmission photograph of the upper surface of the cholesteric liquid crystal film was taken using a polarizing microscope NV100LPOL manufactured by Nikon Corporation, and the state of striped patterns (that is, patterns generated at spiral pitch) and orientation defects was observed from the photographic images. ..

The spiral axis of the cholesteric liquid crystal was confirmed by the method described above based on the striped pattern appearing in the cross Nicol polarized light transmission photograph, and evaluated according to the following criteria.
By confirming that the striped patterns are aligned parallel to the transport direction of the coating film, it is possible to confirm that the spiral axes of the cholesteric liquid crystal are aligned perpendicularly to the transport direction (that is, the shear direction) of the coating film.
-Evaluation criteria-
A: The striped pattern is lined up parallel to the transport direction of the coating film and can be clearly seen, and there is no orientation defect in which a part of the striped pattern is interrupted.
B: The striped pattern is clearly visible in parallel with the transport direction of the coating film, but the orientation defect in which a part of the striped pattern is interrupted is slightly visible.
C: The striped pattern appears to be lined up parallel to the transport direction of the coating film, but there are many orientation defects in which a part of the striped pattern is interrupted.
D: I can't see the striped pattern.

(Observation by SEM)
The cross section of the cholesteric liquid crystal film was observed using SEM (SU3500 manufactured by Hitachi High-Technologies Corporation), and it was confirmed by the method described above whether the spiral axis of the cholesteric liquid crystal was parallel to the film surface direction.
-Evaluation criteria-
A: The spiral axis of the cholesteric liquid crystal is parallel to the film surface direction.
B: The spiral axis of the cholesteric liquid crystal is not parallel to the film surface direction.

(Evaluation of orientation accuracy)
The alignment accuracy of the cholesteric liquid crystal film was evaluated by confirming the scattering region (that is, the white region in the photograph) due to the spiral axis of the cholesteric liquid crystal and the fine variation by the method described above.

The measured scattering of the optical film was evaluated according to the following criteria. It was judged that the smaller the scattering region (that is, the white region in the photograph), the better the orientation accuracy, that is, the less the film surface variation.
-Evaluation criteria-
A: The ratio of the white area to the total area of the test piece (that is, the area ratio) is 0% (in other words, the white area is not seen in the photograph).
B: The ratio of the white area to the total area of the test piece (that is, the area ratio) is 10% or less.
The ratio of the white region (that is, the area ratio) to the total area of the test piece of C: is more than 10%.

As shown in Table 1, in each of the cholesteric liquid crystal films obtained in the examples, the spiral axis of the cholesteric liquid crystal is parallel to the film surface direction (the spiral axis of the cholesteric liquid crystal and the film surface direction of the cholesteric liquid crystal film). It can be seen that the angle is 50 ° to 90 °) and the lines are arranged along a specific direction in the top view, and there is little variation in the film surface of the arrangement (that is, the alignment accuracy is excellent).

The disclosure of Japanese Patent Application No. 2019-064853 filed on March 28, 2019 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated by reference herein.

Claims (8)

Step A of applying a coating liquid containing a solvent, a rod-shaped thermotropic liquid crystal compound, and a chiral agent onto the substrate to form a coating film.
Step B of drying the residual solvent ratio in the formed coating film to 50% by mass or less,
Step C of applying shear force to the surface of the coating film after drying,
A method for producing a cholesteric liquid crystal film having spiral axes parallel to the film surface direction and aligned perpendicular to the shear direction. The method for producing a cholesteric liquid crystal film according to claim 1, wherein the step C is a step of applying a shearing force having a shear rate of 1000 seconds- ^{1 or more.} The method for producing a cholesteric liquid crystal film according to claim 1 or 2, wherein the temperature of the coating film surface in step C is 50 ° C to 120 ° C. The method for producing a cholesteric liquid crystal film according to any one of claims 1 to 3, wherein the shearing force of step C is applied by a blade. The method for producing a cholesteric liquid crystal film according to any one of claims 1 to 3, wherein the shearing force of step C is applied by an air knife. The method for producing a cholesteric liquid crystal film according to any one of claims 1 to 5, further comprising a step of curing the coating film after the step C. The method for producing a cholesteric liquid crystal film according to any one of claims 1 to 6, wherein the thickness of the coating film when a shearing force is applied in step C is 30 μm or less. The method for producing a cholesteric liquid crystal film according to any one of claims 1 to 7, wherein the thickness of the coating film after the shearing force is applied in step C is 10 μm or less.

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