JPWO2020196658A1 - Manufacturing method of cholesteric liquid crystal film - Google Patents

Abstract

In one embodiment of the present invention, a coating liquid containing a solvent, a rod-shaped liquid crystal compound, and a chiral agent is applied onto a substrate to form a coating film, and the formed coating film is conveyed and conveyed. Provided is a method for producing a cholesteric liquid crystal film, which comprises a step B of raising or lowering the film surface temperature of the coating film at 0.1 ° C./mm or more in the transport direction.

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, a liquid crystal film is produced, 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.

Japanese Patent Application Laid-Open No. 2006-284862 describes a polymerizable liquid crystal exhibiting cholesteric regularity in a method for producing an anisotropic optical element having an anisotropic optical property with respect to the normal direction of the element plane. A liquid crystal having a first phase transition temperature, which is a transition point from the cholesteric phase to the isotropic phase on the high temperature side, and a second phase transition temperature, which is a transition point from the cholesteric phase to the low temperature side, is used as a base material. The step of coating the coating film in a planar shape on the substrate, the step of raising the coating film formed on the substrate to a temperature equal to or higher than the first phase transition temperature, and the step of raising the temperature to a temperature equal to or higher than the first phase transition temperature. By lowering the temperature of the coating film to a temperature equal to or lower than the first phase transition temperature while the gas is sprayed onto the coating film from a predetermined direction, the liquid crystal in the coating film is transitioned from the isotropic phase to the cholesteric phase and coated. An orientation step in which the average of the anisotropy directions of the liquid crystal domains in the film is inclined with respect to the normal direction of the membrane plane, and coating in a state where the liquid crystal in the coating film retains the cholesteric phase. A method for manufacturing an anisotropic optical element including a polymerization step of polymerizing a liquid crystal in a film is disclosed.

Further, Japanese Patent Application Laid-Open No. 2016-19469 describes a coating step of applying a polymerizable liquid crystal composition containing a polymerizable liquid crystal compound, a photopolymerization initiator, a surfactant, and a solvent onto a supporting substrate. the coating film obtained in the coating step is heated at a temperature T _H, a heating step to evaporate the solvent, and a cooling step of cooling to room temperature T _R of the coating film obtained in the heating step under certain conditions, in the cooling step A method for producing an optical compensation film, which comprises a polymerization step of polymerizing the obtained coating film by irradiation with light, is disclosed.

Further, Japanese Patent Application Laid-Open No. 2001-133784 describes a method for aligning a liquid crystal polymer by heating while sandwiching a liquid crystal polymer layer between the surfaces of a base material having a surface having an orientation ability. Is disclosed.

By the way, as a cholesteric liquid crystal film, an optical film applied to an aerial imaging device or the like can be obtained by arranging the spiral axes of the cholesteric liquid crystal in a specific direction when viewed from above and parallel to the film surface direction. 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 shafts are arranged as described above.

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 the top view, and the variation in the arrangement within the film surface is generated. 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 liquid crystal compound, and a chiral agent onto a base material to form a coating film.
Step B of transporting the formed coating film and raising or lowering the film surface temperature of the transported coating film at 0.1 ° C./mm or more in the transport direction.
A method for producing a cholesteric liquid crystal film.
<2> By setting the temperature difference between the coating liquid and the surface of the substrate in step A to 30 ° C. or higher, the film surface temperature of the coating film in step B is raised or lowered at 0.1 ° C./mm or higher. , <1>. The method for producing a cholesteric liquid crystal film.
<3> In step A, the temperature of the coating liquid is 40 ° C. to 80 ° C., the temperature of the base material surface is 10 ° C. to 30 ° C., and the temperature difference between the coating liquid and the base material surface is 30 ° C. or more. <2 > The method for producing a cholesteric liquid crystal film.
<4> In step A, the temperature of the coating liquid is 10 ° C. to 40 ° C., the temperature of the base material surface is 40 ° C. to 120 ° C., and the temperature difference between the coating liquid and the base material surface is 30 ° C. or more. <2 > The method for producing a cholesteric liquid crystal film.
<5> The coating amount of the coating liquid in the step A is ^{1mL / m 2 ~100mL / m 2} , <1> ~ <4> method for producing a cholesteric liquid crystal film according to any one of the.
<6> The method for producing a cholesteric liquid crystal film according to any one of <1> to <5>, wherein the transport speed of the coating film in step B is 0.1 m / min to 50 m / min.
<7> The method for producing a cholesteric liquid crystal film according to any one of <1> to <6>, further comprising a step C of curing the coating film after the step B.
<8> The method for producing a cholesteric liquid crystal film according to any one of <1> to <7>, which is carried out by a roll-to-roll method using a long substrate that is continuously conveyed.

<9> A step of moving the coating portion or moving the coating portion and the base material to each other to apply a coating liquid containing a solvent, a rod-shaped liquid crystal compound, and a chiral agent onto the base material to form a coating film. a and
Step b in which the film surface temperature of the coating film is raised or lowered at 0.1 ° C./mm or more in the moving direction of the coating portion.
A method for producing a cholesteric liquid crystal film.
<10> By setting the temperature difference between the coating liquid and the surface of the base material in step a to 30 ° C. or higher, the film surface temperature of the coating film in step b is set to 0.1 ° C./ The method for producing a cholesteric liquid crystal film according to <9>, wherein the temperature is raised or lowered by mm or more.
<11> In step a, the temperature of the coating liquid is 40 ° C. to 80 ° C., the temperature of the base material surface is 10 ° C. to 30 ° C., and the temperature difference between the coating liquid and the base material surface is 30 ° C. or more. > The method for producing a cholesteric liquid crystal film.
<12> In step a, the temperature of the coating liquid is 10 ° C. to 40 ° C., the temperature of the base material surface is 40 ° C. to 120 ° C., and the temperature difference between the coating liquid and the base material surface is 30 ° C. or more. > The method for producing a cholesteric liquid crystal film.
<13> The coating amount of the coating liquid in step a is ^{1mL / m 2 ~100mL / m 2} , <9> ~ method of manufacturing a cholesteric liquid crystal film according to any one of <12>.
<14> The method for producing a cholesteric liquid crystal film according to any one of <9> to <13>, wherein the moving speed of the coated portion in step a is 0.1 m / min to 50 m / min.
<15> The method for producing a cholesteric liquid crystal film according to any one of <9> to <14>, further comprising a step c of curing the coating film after the step b.

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

FIG. 1 is a schematic view for explaining an example of a method for producing a cholesteric liquid crystal film according to the first aspect of the present disclosure. FIG. 2 is an enlarged view of a main part for explaining step A and step B in FIG.

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 the term not only in an independent process but also in the case where 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 a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. 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 focusing on the film surface temperature of the coating film, and the spiral axis of the cholesteric liquid crystal is aligned along the direction parallel to the film surface direction and perpendicular to the coating film transport direction. In addition, a cholesteric liquid crystal film having little variation in the film surface of the arrangement (that is, excellent in orientation accuracy) has been obtained.
Specifically, it is a method of applying a coating liquid containing a solvent, a rod-shaped liquid crystal compound, and a chiral agent, and then changing the film surface temperature of the formed coating film with a specific gradient.
More specifically, by raising or lowering the film surface temperature of the coating film to be transported at 0.1 ° C./mm or more in the transport direction, this rapid temperature gradient becomes a trigger for the cholesteric liquid crystal. A cholesteric liquid crystal film is obtained in which the spiral axis is parallel to the film surface direction and is aligned along the direction perpendicular to the coating film transport direction, and there is little variation in the film surface (that is, excellent alignment accuracy). I found that it was possible.
In addition to the mode of transporting the coating film, there is also a mode of using a method of moving the coating portion, which is a supply site of the coating liquid to the base material, on the base material. Specifically, the coating liquid is applied onto the substrate by moving the coating portion, and the film surface temperature of the formed coating film is raised at 0.1 ° C./mm or more in the moving direction of the coating device. Or it is a method of lowering. Also in this method, triggered by this rapid temperature gradient, the spiral axis of the cholesteric liquid crystal is aligned in the direction parallel to the film surface direction and perpendicular to the moving direction of the coating film, and further, in the film surface of the arrangement. It has been found that a cholesteric liquid crystal film having little variation (that is, excellent orientation accuracy) can be obtained.
In these novel liquid crystal alignment methods, the rod-shaped liquid crystal compound is oriented by the temperature change of the film surface temperature of the coating film, so that the alignment film (alignment layer) usually provided adjacent to the cholesteric liquid crystal film is usually provided. It also has the effect of eliminating the need for (also called).

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 axes of the cholesteric liquid crystal are horizontal (in other words, in other words) with respect to 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 parallel to the film surface direction of the cholesteric liquid crystal film, and the inclination 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 inclination angle formed by the spiral axis of the cholesteric liquid crystal and the film surface direction of the cholesteric liquid crystal film is preferably 0 ° to 40 °.

Further, when the spiral axis of the cholesteric liquid crystal is lined up along the direction perpendicular to the transport direction of the coating film or the moving direction of the coating film, the spiral axis of the cholesteric liquid crystal is the cholesteric liquid crystal film when the cholesteric liquid crystal film is viewed from above. It refers to arranging in a direction perpendicular to the transport direction of the coating film at the time of manufacture or the movement direction of the coating film. For example, when manufacturing a long cholesteric liquid crystal film, the coating film is conveyed in the long direction, so that 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, parallel to the short direction of the cholesteric liquid crystal film). Further, for example, when producing a single-wafered cholesteric liquid crystal film, the coating portion in the coating apparatus may be moved on the substrate for coating. In this case, the spiral axes of the cholesteric liquid crystal indicate that they are aligned in a direction perpendicular to the moving direction of the coating portion (in other words, the coating direction of the coating liquid) when the cholesteric liquid crystal film is manufactured in the top view. However, it is not necessary that the spiral axis of the cholesteric liquid crystal is exactly perpendicular to the transport direction of the coating film or the moving direction of the coating film, and when the cholesteric liquid crystal film is viewed from above, the spiral axis of the cholesteric liquid crystal and the coating film When the inclination angle formed by the transport direction or the moving direction of the coating portion is less than 90 ° ± 45 °, it is included in “perpendicular to the transport direction of the coating film” in the present disclosure. The inclination angle formed by the spiral axis of the cholesteric liquid crystal and the transport direction of the coating film or the moving direction of the coating film is preferably 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 axis of the cholesteric liquid crystal is parallel to the film surface direction and perpendicular to the transport direction of the coating film or the movement direction of the coating portion means that the cross-Nicol polarized light transmission photograph and the cross-section SEM photograph by the polarizing microscope are obtained. It can be confirmed by using.
The cholesteric liquid crystal has a laminated structure in which layers composed of molecular groups of rod-shaped liquid crystal compounds are stacked. In each layer, the molecules of each rod-shaped liquid crystal compound are arranged in a certain direction, 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 molecules of the rod-shaped 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 transport direction of the coating film or the moving direction of the coating portion. Therefore, it can be confirmed that the spiral axes of the cholesteric liquid crystal are aligned perpendicular to the transport direction of the coating film or the moving direction of the coating portion.
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 formed by 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 a cross-sectional SEM photograph). Here, the cross section of the cholesteric liquid crystal film in the thickness direction is a cross section cut along a direction orthogonal to the transport direction of the coating film or the moving direction of the coating film.
In the cross-sectional SEM photograph, if one uninterrupted cholesteric liquid crystal is selected 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 less than 45 °, the spiral axis of the cholesteric liquid crystal is a film. It can be said that they are lined up along a direction 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 photograph of the same size is taken under a white light, and the obtained photograph 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 spiral axis of the cholesteric liquid crystal is arranged. 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 region to the total area of the test piece in the photograph is 10% or less.

Based on the above findings, the method for producing the cholesteric liquid crystal film of the present disclosure is as follows.
That is, the method for producing a cholesteric liquid crystal film according to the first aspect of the present disclosure is formed in step A of applying a coating liquid containing a solvent, a rod-shaped liquid crystal compound, and a chiral agent on a substrate to form a coating film. The present invention includes a step B of transporting the coated coating film and raising or lowering the film surface temperature of the transported coating film at 0.1 ° C./mm or more in the transport direction.
By having these steps A and B, the spiral axis of the cholesteric liquid crystal is aligned parallel to the film surface direction (that is, horizontally oriented) and along the direction perpendicular to the transport direction of the coating film, and further, the alignment is further present. A cholesteric liquid crystal film with little variation in the film surface can be obtained.
Further, in the method for producing a cholesteric liquid crystal film according to the second aspect of the present disclosure, a solvent, a rod-shaped liquid crystal compound, and a chiral agent are placed on the base material by moving the coating portion or moving the coating portion and the base material to each other. A step a of applying a coating liquid containing the above to form a coating film, and a step b of raising or lowering the film surface temperature of the coating film at 0.1 ° C./mm or more in the moving direction of the coating portion. Have.
By having these steps a and b, the spiral axis of the cholesteric liquid crystal is aligned parallel to the film surface direction (that is, horizontally oriented) and along the direction perpendicular to the moving direction of the coating portion, and further, the alignment is further present. A cholesteric liquid crystal film with little variation in the film surface can be obtained.
Hereinafter, the method for producing a cholesteric liquid crystal film of the first aspect is referred to as "method for producing a cholesteric liquid crystal film (1)", and the method for producing a cholesteric liquid crystal film of the second aspect is referred to as "method for producing a cholesteric liquid crystal film (2)". Each will be explained.

Japanese Patent Application Laid-Open No. 2006-284862, Japanese Patent Application Laid-Open No. 2016-194693, and Japanese Patent Application Laid-Open No. 2001-133784 described above describe a method for changing the film surface temperature of a coating film with a specific gradient. In addition, the orientation of the rod-shaped liquid crystal compound triggered by the temperature gradient has not been investigated at all.

<Manufacturing method of cholesteric liquid crystal film (1)>
Hereinafter, each step of the cholesteric liquid crystal film manufacturing method (1) of the present disclosure will be described in detail with reference to the drawings.
FIG. 1 is a schematic view for explaining an example of the method (1) for producing a cholesteric liquid crystal film of the present disclosure. FIG. 1 shows an embodiment in which step A and step B are performed by a roll-to-roll method using a long base material that is continuously conveyed. Further, FIG. 2 is an enlarged view of a main part for explaining the process A and the process B in FIG.
The method (1) for producing a cholesteric liquid crystal film of the present disclosure is not limited to the continuous process of the 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 liquid crystal compound, and a chiral agent (hereinafter, also referred to as a coating liquid for forming a liquid crystal layer) is applied onto the base material to form a coating film.
The coating liquid for forming the liquid crystal layer in the step A can be applied in a state where the base material is stretched, and is applied to the base material 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 roll-shaped wound long base material F 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 FIGS. 1 and 2, it is preferable that the coating liquid for forming the liquid crystal layer is applied by the coating means 10 in the 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, considering the applicability to the roll-to-roll method and the ease of wrapping around the backup roll, a polymer film is preferably used as the base material.

For optical film applications, the total light transmittance of the base material is preferably 80% or more.
For optical film applications, when a polymer film is used as the base material, 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 base material (film or sheet such as polymethylmethacrylate), polystyrene base material (film or sheet such as polystyrene, acrylonitrile styrene copolymer), olefin base material (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 application, and the like.

The base material may be one in which a layer is formed in advance on the above 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 photoalignment layer, and an adhesion layer.

(Coating liquid for forming liquid crystal layer)
The liquid crystal layer forming coating liquid used in step A contains a solvent, a rod-shaped 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.
Specifically, as the organic solvent, an amide solvent (for example, N, N-dimethylformamide), a sulfoxide solvent (for example, dimethyl sulfoxide), a heterocyclic compound (for example, pyridine), 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.

− Rod-shaped liquid crystal compound −
The rod-shaped liquid crystal compound refers to a liquid crystal compound having a rod-shaped molecular structure.
In particular, the rod-shaped liquid crystal compound is preferably a compound having a polymerizable group. Examples of the polymerizable group contained in the rod-shaped liquid crystal compound include unsaturated polymerizable groups, cyclic ether groups, and nitrogen-containing heterocyclic groups capable of causing a ring-opening reaction, which are unsaturated polymerizable groups. Is more preferable.

The unsaturated polymerizable group is more preferably a group having an ethylenically unsaturated double bond, for example, an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group, a vinyl group, a vinylphenyl group, an allyl group and the like. Can be mentioned.
Examples of the cyclic ether group include an epoxy group and an oxetanyl group.
Examples of the nitrogen-containing heterocyclic group capable of causing a ring-opening reaction include an aziridinyl group.
Among them, the polymerizable group is more preferably at least one group selected from the group consisting of an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group, more preferably than the group consisting of an acryloyloxy group and a methacryloyloxy group. It is particularly preferred that it is at least one group of choice.

Specifically, as a rod-shaped liquid crystal compound, Makromol. Chem. , 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, 5,622,648, 5,770,107, 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. 11-8801, Japanese Patent Application Laid-Open No. 2001-328973, and the like.
Further, as the rod-shaped liquid crystal compound, for example, those described in JP-A No. 11-513019, JP-A-2007-279688, etc. can be preferably used, but the rod-shaped liquid crystal compounds are not limited thereto.

As the rod-shaped liquid crystal compound, for example, a compound represented by the following general formula (1) is preferably used as a 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 rod-like liquid crystal compound to the aforementioned has, 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 more preferable.

The ^{divalent hydrocarbon group having 2 to 20 carbon atoms represented by A 1} and A ² includes an alkylene group having 2 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, or 2 carbon atoms. Alquinylene groups of ~ 12 are preferable, and alkylene groups having 2 to 12 carbon atoms are particularly preferable. 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. 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 a liquid crystal molecule that contributes to liquid crystal formation.
The mesogen group represented by M is not particularly limited, and for example, "Flusige Kristalle in Tabellen II" (VEB Deutsche Verlag fur Grundstoff Industrie, Leipzig, 1984), in particular, pages 7 to 16 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 0083 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 3 to 5 aromatic hydrocarbons. 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. In addition, "Me" represents methyl.

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

The rod-shaped liquid crystal compound may be used alone or in combination of two or more.
The content of the rod-shaped 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 asymmetric compounds or surface 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 rod-shaped liquid crystal compound used in combination also has a polymerizable group, the rod-shaped liquid crystal compound is separated from the rod-shaped liquid crystal compound by a polymerization reaction between the chiral agent having a polymerizable group and the rod-shaped 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 rod-shaped liquid crystal compound. The polymerizable group contained in 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, with respect to the isosorbide compounds described in the above-mentioned publications, isosorbide compounds having a corresponding structure can also be used as a chiral agent. Further, with respect to the isosorbide compounds described in the same publication, isosorbide compounds having a corresponding structure 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, those capable of reducing the tilt angle of the molecules of the rod-shaped liquid crystal compound at the air interface or making them substantially horizontal are preferable.
Examples of such an orientation control agent include the compounds described in paragraph numbers [0012] to [0030] of JP2012-2011306A, 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-2005-099258 together with the synthesis method. And so on.
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 the 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 0.15% by mass to 2.0% by mass, based on the mass of the total solid content. ..

-Polymerization initiator Both a photopolymerization initiator and a thermal polymerization initiator are used as the polymerization initiator, but from the viewpoint of suppressing deformation of the base material 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. 2,348,828), and the like. α-hydrogen-substituted aromatic acidoine compounds (eg, compounds described in US Pat. No. 2,725,512), polynuclear quinone compounds (eg, compounds described in US Pat. Nos. 3,043127 and 2951758), triaryls. Combination of imidazole dimer and p-aminophenyl ketone (for example, the compound described in US Pat. No. 3,549,637), aclysine and phenazine compounds (eg, JP-A-60-105667, US Pat. No. 4,239,850). , Oxaziazole 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-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 is 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 Examples include means using a coating method, a wire bar method, and the like.

(Backup role)
The backup roll preferably used in the step A (corresponding to the backup roll 12 in FIG. 1) 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.
The surface roughness of the backup roll is preferably 0.1 μm or less in terms of 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 preferably adjusted in temperature from the viewpoint of adjusting the temperature of the surface of the base material.
The surface temperature of the backup roll may be determined according to the temperature of the target substrate surface, for example, preferably 10 ° C to 120 ° C, more preferably 10 ° C to 30 ° C or 40 ° C to 120 ° C, 20 ° C. to 120 ° C. ° C to 30 ° C is more 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. Induction heating, water heating, oil heating and the like are used as the heating means, and cooling with cooling water is used as the cooling means.

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 stabilizes the transport of the base material during coating, suppresses the occurrence of uneven thickness of the coating film, regulates the temperature of the base material surface, and also the film surface temperature of the coating film. From the viewpoint of temperature control, 60 ° or more is preferable, and 90 ° or more is more preferable. 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 separates from the backup roll.

(Application conditions)
The coating condition in the step A is to raise or lower the film surface temperature of the coating film formed in the next step, step B, at 0.1 ° C./mm or more in the transport direction of the coating film. It is preferable to adopt the following condition I.
That is, the condition I is a condition that the temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material in the step A is 20 ° C. or more. The temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material refers to the absolute value of the difference between the liquid crystal layer forming coating liquid and the surface of the base material.
By satisfying this condition I, from the temperature difference between the two, the film surface temperature of the coating film formed by coating is directed toward the transport direction of the coating film (for example, in FIG. 2, the base material F indicated by the arrow). It becomes easy to raise or lower the temperature at 0.1 ° C./mm or higher (in the transport direction).
The temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material is more preferably 30 ° C. or higher, further preferably 40 ° C. or higher. The upper limit of the temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material is, for example, 100 ° C.

Here, the temperature of the liquid crystal layer forming coating liquid refers to the temperature of the liquid crystal layer forming coating liquid immediately before coating, and the liquid crystal layer forming coating liquid existing in the coating portion (for example, the discharge portion) in the device means. It becomes the temperature of. For example, when the coating means is a die coater, it is the temperature of the coating liquid for forming a liquid crystal layer at the discharge portion of the die.
The temperature of the coating liquid for forming a liquid crystal layer can be measured by a conventional method using a thermometer or the like capable of measuring the liquid temperature.
The temperature of the surface of the base material refers to the temperature of the surface of the base material immediately before the liquid crystal layer forming coating liquid is applied. When the base material is wound on the backup roll, it is the temperature of the base material surface in the region in contact with the backup roll. The temperature of the surface of the base material is a value measured using a contact thermometer (for example, a thermocouple).

In particular, in order to satisfy the above condition I, it is preferable to use the following aspect I-1 or aspect I-2.
That is, in step A, the temperature of the coating liquid for forming the liquid crystal layer is 35 ° C. to 80 ° C. (preferably 40 ° C. to 80 ° C., more preferably 50 ° C. to 70 ° C.) and the temperature of the substrate surface is 5 ° C. to 30 ° C. (Preferably 10 ° C to 30 ° C, more preferably 20 ° C to 30 ° C), and the temperature difference between the liquid crystal layer forming coating liquid and the surface of the substrate is 20 ° C or more (preferably 30 ° C or more). 1 is preferable.
By setting this aspect I-1, the film surface temperature of the coating film formed by coating is set from the temperature difference between the two toward the transport direction of the coating film (for example, in FIG. 2, the base material indicated by the arrow). It becomes easy to lower the temperature with a temperature gradient of 0.1 ° C./mm or more (in the transport direction of F).

Further, in step A, the temperature of the coating liquid for forming the liquid crystal layer is 10 ° C. to 40 ° C. (preferably 20 ° C. to 30 ° C.) and the temperature of the substrate surface is 40 ° C. to 120 ° C. (preferably 40 ° C. to 80 ° C.). Aspect I-2 in which the temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material is 20 ° C. or higher (preferably 30 ° C. or higher) is also preferable.
By setting this aspect I-2, the film surface temperature of the coating film formed by coating is set from the temperature difference between the two toward the transport direction of the coating film (for example, in FIG. 2, the base material indicated by the arrow). It becomes easy to raise the temperature with a temperature gradient of 0.1 ° C./mm or more (in the transport direction of F).

From the viewpoint of producing a cholesteric liquid crystal film having high orientation accuracy, the former aspect I-1 is preferable among the above aspects I-1 and I-2.

As the coating conditions in the step A, from the viewpoint of producing a cholesteric liquid crystal film having high orientation accuracy, it is preferable that the coating amount of the liquid crystal layer forming coating liquid satisfies the following condition II.
That is, the condition II is, the coating amount of the liquid crystal layer forming coating solution in step A is a condition which is ^{1mL / m 2 ~100mL / m 2} .
The coating amount of the liquid crystal layer forming coating solution in the step ^{A, 10mL / m 2 ~50mL / m} 2 is more preferable.

[Step B]
In step B, the coating film formed in step A is transported, and the film surface temperature of the transported coating film is raised or lowered at 0.1 ° C./mm or more in the transport direction.
That is, in step B, the film surface temperature of the coating film is raised or lowered with the above-mentioned temperature gradient per unit distance toward the transport direction of the coating film.
The temperature of the film surface of the coating film is raised or lowered in the process of removing the solvent in the coating film and increasing the content of the rod-shaped liquid crystal compound in the coating film. In particular, raising or lowering the film surface temperature of the coating film is a situation in which the content of the rod-shaped liquid crystal compound in the coating film tends to increase, and for example, the temperature difference between the coating liquid and the surface of the substrate. From the viewpoint of easy control, it is preferable to perform the step A immediately after the liquid crystal layer forming coating liquid is applied onto the substrate.

Further, in step B, the solid content concentration of the coating film for raising or lowering the film surface temperature at 0.1 ° C./mm or more is preferably 30% by mass to 90% by mass, preferably 40% by mass to 90% by mass. More preferably, it is 80% by mass.
When the solid content concentration in the coating film is within the above range, raising or lowering the film surface temperature facilitates the production of a cholesteric liquid crystal film having high orientation accuracy.

The means used to change the film surface temperature of the coating film in step B is not particularly limited, and as shown in the above-mentioned condition I, the coating conditions in step A may be adjusted, or the coating film may be adjusted. May be heated or cooled, or these may be combined.
In addition, in order to change the film surface temperature of the coating film, as shown in the above-mentioned condition I, when the coating conditions in the step A are adjusted, the coating film (that is, the coating film is simply provided in the step B). The base material) may be transported.
The transport speed of the coating film in step B is preferably 0.1 m / min to 50 m / min, and more preferably 1 m / min to 30 m / min.

An example of step B will be described with reference to FIGS. 1 and 2.
In step B, after the coating liquid for forming the liquid crystal layer is applied by the coating means 10, the film surface temperature of the coating film L is changed, for example, in the region 20.
In the region 20, a predetermined distance toward the conveying direction from the coating position _{P 1} (e.g., during 10Mm～3000mm, preferably 200 mm) up to a position _{P 2} spaced, the surface temperature of the coating film L, 0.1 It is preferable to raise or lower the temperature at ° C./mm or higher.
Here, the coating position P ₁ shown in FIG. 2, on the substrate F, refers to a position where the base material F and the liquid crystal layer forming coating solution S in contact.
Here, "film surface temperature of the coating film L" in the coating position P ₁ is the temperature of the coating solution S for liquid crystal layer formation described above. Further, "film surface temperature of the coating film L" in position P ₂ is a value measured using a contact thermometer (for example, a thermocouple).

(Heating or cooling of coating film)
In step B, the coating film may be heated or cooled in order to change the film surface temperature of the coating film.
As the means for heating the coating film, the same means as the drying means for drying the coating film by indirectly or directly applying heat are used. Specific examples thereof include means using a method using an oven, a hot air blower, an infrared (IR) heater, a heating roll, or the like.
Further, as a means for cooling the coating film, a means using a cooling action by the heat of vaporization at the time of volatilization of a solvent such as a cooling roll or an intake air can be mentioned.

(Dry)
After changing the film surface temperature of the coating film as described above, it is preferable to dry the coating film.
As a drying means used for drying the coating film (corresponding to the drying means 30 in FIG. 1), a known drying means is applied.
Specific examples of the drying means include means using a method using an oven, a hot air blower, an infrared (IR) heater, or the like.
In drying with a warm air blower, warm air may be blown from the surface of the base material opposite to the coating film forming surface, 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 removing the solvent in the coating film by sucking the gas on the coating film using a decompression chamber or the like having an exhaust mechanism.

[Step C]
In the method (1) for producing a cholesteric liquid crystal film of the present disclosure, when a polymerizable compound (specifically, a rod-shaped liquid crystal compound having a polymerizable group, a chiral agent having a polymerizable group, etc.) is contained in the coating film, the step After B, it is preferable to include a step C of curing the coating film.
In the step C, it is preferable that the coating film after the step B is cured, for example, by applying heat or irradiating the coating film with active energy rays.
In consideration of manufacturing suitability and the like, it is preferable to use curing by the active energy ray irradiated from the activation energy ray irradiation means 40 as shown in FIG. 1 as the step C.
More specifically, in step C, the coating film on the base material F transported via the transport rolls 52 and 54 is irradiated with active energy rays by the activation energy ray irradiating means 40.

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 rays 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 equipment.

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, and cathode wire tubes.
The peak wavelength of ultraviolet rays emitted from the light source of ultraviolet rays is preferably 200 nm to 400 nm.
As the exposure energy amount of ultraviolet rays, for ^{example, 100mJ / cm 2 ~500mJ / cm} 2 is preferred.

By the above method (1) for producing a cholesteric liquid crystal film, a cholesteric liquid crystal film is produced on a base material.
The laminate of the base material and the cholesteric liquid crystal film obtained by the method for producing the cholesteric liquid crystal film (1) may be used as it is as an optical film.

<Manufacturing method of cholesteric liquid crystal film (2)>
Each step of the method (2) for producing a cholesteric liquid crystal film of the present disclosure will be described in detail.
Since the method (2) for producing a cholesteric liquid crystal film of the present disclosure is an embodiment in which the coating portion is moved, it is applied to a method of producing a cholesteric liquid crystal film on a single-wafer-shaped base material. Is preferable.

[Step a]
In step a, the coating portion is moved or the coating portion and the base material are moved to each other, and a coating liquid containing a solvent, a rod-shaped liquid crystal compound, and a chiral agent is applied onto the base material to form a coating film. ..
The coating portion used in the step a is a portion for supplying the coating liquid for forming a liquid crystal layer to the base material, and the coating portion may be moved by the coating apparatus itself having the coating portion or in the coating apparatus. Only the coating part may move.
Examples of a coating device or a coating device having a coating portion include a coating device and a coating blade configured to move a downward applicator nozzle along a straight guide rail arranged on a support member such as a glass plate. , A coating device configured to move along a straight guide rail arranged on a support member such as a glass plate.
In step a, the coating portion and the base material may be moved to each other along a certain coating direction on the base material. That is, in the step a, both the coating portion and the base material may be moved to apply the coating liquid on the base material.

The coating liquid containing the solvent, the rod-shaped liquid crystal compound, and the chiral agent, which is coated on the substrate by the coating portion in the step a, is the same as the coating liquid for forming the liquid crystal layer in the method (1) for producing a cholesteric liquid crystal film. Yes, and the preferred embodiment is the same. Hereinafter, the coating liquid used in the step a is also referred to as a coating liquid for forming a liquid crystal layer.
Further, as the base material used in the step a, the same base material as that in the method (1) for producing the cholesteric liquid crystal film is used, and the preferred embodiment is also the same.

(Application conditions)
As a coating condition in the step a, in order to raise or lower the film surface temperature of the coating film formed in the next step, step b, at 0.1 ° C./mm or more in the moving direction of the coating portion. It is preferable to adopt the following condition i.
That is, the condition i is a condition in which the temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material in the step A is 20 ° C. or more. The temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material refers to the absolute value of the difference between the liquid crystal layer forming coating liquid and the surface of the base material.
By satisfying this condition i, the film surface temperature of the coating film formed by the movement of the coating portion is raised at 0.1 ° C./mm or more in the moving direction of the coating portion due to the temperature difference between the two. It becomes easy to lower the temperature.
The temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material is more preferably 30 ° C. or higher, further preferably 40 ° C. or higher. The upper limit of the temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material is, for example, 100 ° C.

In particular, in order to satisfy the above condition i, it is preferable to use the following aspect i-1 or aspect i-2.
That is, in step a, the temperature of the coating liquid for forming the liquid crystal layer is 35 ° C. to 80 ° C. (preferably 40 ° C. to 80 ° C., more preferably 50 ° C. to 70 ° C.) and the temperature of the substrate surface is 5 ° C. to 30 ° C. (Preferably 10 ° C to 30 ° C, more preferably 20 ° C to 30 ° C), and the temperature difference between the liquid crystal layer forming coating liquid and the surface of the substrate is 20 ° C or more (preferably 30 ° C or more). 1 is preferable.
By setting this aspect i-1, the coating film temperature becomes higher as it is closer to the coating portion due to the temperature difference between the two, and the film surface temperature of the coating film formed by the movement of the coating portion is set to the moving direction of the coating portion. It becomes easy to raise the temperature with a temperature gradient of 0.1 ° C./mm or more toward.

Further, in the step a, the temperature of the coating liquid for forming the liquid crystal layer is 10 ° C. to 40 ° C. (preferably 20 ° C. to 30 ° C.) and the temperature of the substrate surface is 40 ° C. to 120 ° C. (preferably 40 ° C. to 80 ° C.). Aspect i-2 in which the temperature difference between the liquid crystal layer forming coating liquid and the surface of the base material is 20 ° C. or higher (preferably 30 ° C. or higher) is also preferable.
By setting this aspect i-2, the coating film temperature becomes lower as it is closer to the coating portion due to the temperature difference between the two, and the film surface temperature of the coating film formed by the movement of the coating portion is set to the moving direction of the coating portion. It becomes easy to lower the temperature with a temperature gradient of 0.1 ° C./mm or more toward.

From the viewpoint of producing a cholesteric liquid crystal film having high orientation accuracy, the former aspect i-1 is preferable among the above aspects i-1 and i-2.

As the coating conditions in the step a, it is preferable that the coating amount of the liquid crystal layer forming coating liquid satisfies the following condition ii from the viewpoint of producing a cholesteric liquid crystal film having high orientation accuracy.
That is, condition ii a coating amount of the liquid crystal layer forming coating solution in step a is a condition which is ^{1mL / m 2 ~100mL / m 2} .
The coating amount of the liquid crystal layer forming coating solution in step ^{a, 10mL / m 2 ~50mL / m} 2 is more preferable.

[Step b]
In step b, the film surface temperature of the coating film is raised or lowered at 0.1 ° C./mm or more in the moving direction of the coating portion.
That is, in step b, the film surface temperature of the coating film is raised or lowered with the above-mentioned temperature gradient per unit distance toward the moving direction of the coating portion.
The temperature of the film surface of the coating film is raised or lowered in the process of removing the solvent in the coating film and increasing the content of the rod-shaped liquid crystal compound in the coating film. In particular, raising or lowering the film surface temperature of the coating film is a situation in which the content of the rod-shaped liquid crystal compound in the coating film tends to increase, and for example, the temperature difference between the coating liquid and the surface of the substrate. From the viewpoint of easy control, it is preferable to perform the step a immediately after the liquid crystal layer forming coating liquid is applied onto the substrate.

Further, in step b, the solid content concentration of the coating film for raising or lowering the film surface temperature at 0.1 ° C./mm or more is preferably 30% by mass to 90% by mass, preferably 40% by mass to 90% by mass. More preferably, it is 80% by mass.
When the solid content concentration in the coating film is within the above range, raising or lowering the film surface temperature facilitates the production of a cholesteric liquid crystal film having high orientation accuracy.

The means used to change the film surface temperature of the coating film in step b is not particularly limited, and as shown in the above-mentioned condition i, the coating conditions in step b may be adjusted, or the coating film may be adjusted. May be heated or cooled, or these may be combined.
As shown in the above-mentioned condition i, when adjusting the coating conditions in the step a, a part or all of the step b is coated with the liquid crystal layer forming coating liquid by moving the coating portion in the step a. It should be done by doing. That is, a part or all of the step b may be performed in the step a.
In this case, the moving speed of the coated portion in the step a is preferably 0.1 m / min to 50 m / min, and more preferably 1 m / min to 30 m / min.

In step b, or coating start position _{P 3} on the substrate, a distance coated portion from the coating start position _{P 3} is being coated with a liquid crystal layer forming coating solution (e.g., during 10Mm～3000mm, preferably 200mm ) between the spaced locations P _4, the surface temperature of the coating film it is preferable to warm or cooling at 0.1 ° C. / mm or higher.
"Film surface temperature of the coating film" in the coating start position P ₃ is a value measured using a contact thermometer (for example, a thermocouple). Further, "film surface temperature of the coating film" in the position P ₄ is the temperature of the liquid crystal layer forming coating solution applied onto the coating section.

(Heating or cooling of coating film)
In step b, the coating film may be heated or cooled in order to change the film surface temperature of the coating film.
The means for heating the coating film is the same as the means for heating the coating film in step B of the method for producing the cholesteric liquid crystal film (1), and the means for cooling the coating film is also the means for producing the cholesteric liquid crystal film (the method for producing the cholesteric liquid crystal film). This is the same as the means for cooling the coating film in step B of 1).

(Dry)
After changing the film surface temperature of the coating film as described above, it is preferable to dry the coating film.
The drying means used for drying the coating film is the same as the drying means in step B of the cholesteric liquid crystal film manufacturing method (1).

[Step c]
In the method (2) for producing a cholesteric liquid crystal film of the present disclosure, when a polymerizable compound (specifically, a rod-shaped liquid crystal compound having a polymerizable group, a chiral agent having a polymerizable group, etc.) is contained in the coating film, the step After b, it is preferable to include a step c of curing the coating film.
The step c is the same as the step C of the method (1) for producing a cholesteric liquid crystal film, and the preferred embodiment is also the same.

By the above method (2) for producing a cholesteric liquid crystal film, a cholesteric liquid crystal film is produced on a base material.
The laminate of the base material and the cholesteric liquid crystal film obtained by the method for producing the cholesteric liquid crystal film (2) may be used as it is as an optical film.

[Other processes]
In the method (1) for producing a cholesteric liquid crystal film of the present disclosure, other steps may be included in addition to the above steps A to C.
Similarly, the method (2) for producing a cholesteric liquid crystal film of the present disclosure may also have other steps in addition to the above steps a to c.
Examples of other steps include a step of forming an orientation layer on the base material used in step A or step a.
That is, the base material used in step A or 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)), 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 methods (1) and (2) for producing a cholesteric liquid crystal film of the present disclosure, the alignment layer is not essential, and the film surface temperature of the coating film is adjusted to a specific gradient in step B or step b without using the alignment layer. By changing it, the spiral axes of the cholesteric liquid crystal can be arranged.

[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.
Moreover, you may use the cholesteric liquid crystal film itself 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 having a thickness of 80 μm and a width of 300 mm (FUJIFILM Corporation, refractive index 1.48) 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-
-Stick 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® 907, BASF) )
-Orientation control agent (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 15 ° 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. The coating liquid 1 for forming a liquid crystal layer was applied at a coating amount of 35 mL / m ^2. The temperature of the coating liquid 1 for forming the liquid crystal layer at the time of coating was 35 ° C., and the temperature of the surface of the base material at the time of coating was 15 ° C. The solid content concentration of the coating film was 32.4% by mass.
Surface temperature of the coating film of the coating position P ₁ is 35 ° C., the surface temperature of the coating film from the coating position P ₁ at 200mm spaced locations P ₂ was 15 ° C.. From this, it can be seen that the film surface temperature of the coating film changed at 0.1 ° C./mm in the transport direction.

(Step C)
The coating film after step B 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, the cholesteric liquid crystal film of Example 1 was produced.

[Examples 2 to 11, Comparative Examples 1 to 2]
In step A and step B, as shown in Table 1, the temperature of the liquid crystal layer forming coating liquid 1 (denoted as “coating liquid temperature A” in Table 1) and the surface temperature of the backup roll (“BUR” in Table 1). (Indicated as "Temperature of the substrate") was appropriately changed to control the temperature of the surface of the substrate at the time of coating (indicated as "Temperature surface B of the substrate" in Table 1). Cholesteric liquid crystal films of Examples 2 to 10 and Comparative Examples 1 and 2 were prepared.
The film surface temperature of the coating film at the coating position P _{1 (denoted as "coating film temperature at P 1} " in Table 1) and the film surface temperature of the coating film at the _{position P 2} 200 mm away from the _{coating position P 1 (} referred to as "coating film temperature at P 1" in Table 1). in Table 1 denoted as "coating temperature over P _2") are shown in Table 1.
In Example 10, the coating film after coating was brought into contact with the base material side by a backup roller having a temperature control function, and the base material with the coating film was conveyed to perform heating.
Further, in Example 11, the coating film after coating was cooled by bringing the substrate side into contact with a backup roller having a temperature control function and transporting the substrate with the coating film.

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

Specifically, 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 lined up parallel to the transport direction of the coating film, it is possible to confirm that the spiral axes of the cholesteric liquid crystal are lined up perpendicularly to the transport direction of the coating film or the moving direction of the coating film.
-Evaluation criteria-
A: The striped pattern is clearly visible in parallel with the transport direction of the coating film or the moving direction of the coating film, 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 or the moving direction of the coating film, but a slight orientation defect in which a part of the striped pattern is interrupted is visible.
C: The striped pattern appears to be lined up in parallel with the transport direction of the coating film or the moving 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 or not 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 orientation 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 in the film surface and the fine variation by the method described above.

Specifically, the scattering of the measured 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 (the less the in-plane variation of the spiral axis of the cholesteric liquid crystal).
-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.
C: The ratio of the white area to the total area of the test piece (that is, the area ratio) exceeds 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 and in a specific direction in top view (that is, in the coating film transport direction). It can be seen that they are lined up along the vertical direction) and that the orientation accuracy is excellent.

The disclosure of Japanese Patent Application No. 2019-064852 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 herein by reference.

Claims (15)

Step A of applying a coating liquid containing a solvent, a rod-shaped liquid crystal compound, and a chiral agent onto the base material to form a coating film,
Step B of transporting the formed coating film and raising or lowering the film surface temperature of the transported coating film at 0.1 ° C./mm or more in the transport direction.
A method for producing a cholesteric liquid crystal film. By setting the temperature difference between the coating liquid and the surface of the substrate in step A to 30 ° C. or higher, the film surface temperature of the coating film in step B can be raised at 0.1 ° C./mm or higher in the transport direction. The method for producing a cholesteric liquid crystal film according to claim 1, wherein the temperature is lowered. The second aspect of the present invention, wherein in the step A, the temperature of the coating liquid is 40 ° C. to 80 ° C., the temperature of the base material surface is 10 ° C. to 30 ° C., and the temperature difference between the coating liquid and the base material surface is 30 ° C. or more. How to manufacture a cholesteric liquid crystal film. The second aspect of the present invention, wherein in the step A, the temperature of the coating liquid is 10 ° C. to 40 ° C., the temperature of the base material surface is 40 ° C. to 120 ° C., and the temperature difference between the coating liquid and the base material surface is 30 ° C. or more. How to manufacture a cholesteric liquid crystal film. The coating amount of the coating liquid in the step A is ^{1mL / m 2 ~100mL / m 2} , a manufacturing method of a cholesteric liquid crystal film according to any one of claims 1 to 4. The method for producing a cholesteric liquid crystal film according to any one of claims 1 to 5, wherein the transport speed of the coating film in step B is 0.1 m / min to 50 m / min. The method for producing a cholesteric liquid crystal film according to any one of claims 1 to 6, further comprising a step C of curing the coating film after the step B. The method for producing a cholesteric liquid crystal film according to any one of claims 1 to 7, which is performed by a roll-to-roll method using a long base material that is continuously conveyed. Step a of forming a coating film by applying a coating liquid containing a solvent, a rod-shaped liquid crystal compound, and a chiral agent onto the substrate by moving the coating portion or moving the coating portion and the base material to each other.
Step b in which the film surface temperature of the coating film is raised or lowered at 0.1 ° C./mm or more in the moving direction of the coating portion.
A method for producing a cholesteric liquid crystal film. By setting the temperature difference between the coating liquid and the surface of the substrate in step a to 30 ° C. or higher, the film surface temperature of the coating film in step b is 0.1 ° C./mm or higher in the moving direction of the coating portion. The method for producing a cholesteric liquid crystal film according to claim 9, wherein the temperature is raised or lowered. The tenth aspect of the present invention, wherein in the step a, the temperature of the coating liquid is 40 ° C. to 80 ° C., the temperature of the substrate surface is 10 ° C. to 30 ° C. How to manufacture a cholesteric liquid crystal film. The tenth aspect of the present invention, wherein in the step a, the temperature of the coating liquid is 10 ° C. to 40 ° C., the temperature of the substrate surface is 40 ° C. to 120 ° C. How to manufacture a cholesteric liquid crystal film. The coating amount of the coating liquid in step a is ^{1mL / m 2 ~100mL / m 2} , a manufacturing method of a cholesteric liquid crystal film according to any one of claims 9 to 12. The method for producing a cholesteric liquid crystal film according to any one of claims 9 to 13, wherein the moving speed of the coated portion in the step a is 0.1 m / min to 50 m / min. The method for producing a cholesteric liquid crystal film according to any one of claims 9 to 14, further comprising a step c of curing the coating film after the step b.

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