TW201529813A - Two-band-cholesteric liquid-crystal film and process for producing same - Google Patents

Abstract

This cholesteric liquid-crystal film is a cured object obtained from a liquid-crystal composition which comprises a polymerizable mesogenic compound and a chiral reagent that is a cyclic compound which is changed in twisting power by an intramolecular dimerization reaction. In a transmission spectrum examination, this film shows a transmission spectrum which has a first selective-reflection wavelength band, a second selective-reflection wavelength band located on the longer-wavelength side of the first selective-reflection wavelength band, and a transmission band that lies between the first selective-reflection wavelength band and the second selective-reflection wavelength band.

Description

Dual-band cholesteric liquid crystal film and manufacturing method thereof

The present invention relates to a dual-band cholesteric liquid crystal film and a method of manufacturing the same.

The cholesteric liquid crystal film is a film obtained by forming a helical structure by adding a chiral agent to a non-twisted nematic liquid crystal, and has a circularly polarized light corresponding to a period of the spiral (spiral pitch) by reflection (selective reflection). Wavelength band.

As a cholesteric liquid crystal film having a plurality of selective reflection wavelength bands, for example, a cholesteric liquid crystal film is known which is characterized in that a liquid crystal mixture containing a polymerizable liquid crystal cell compound and a polymerizable chiral agent is applied to an alignment group. The material is obtained by irradiating ultraviolet rays, and the cholesteric liquid crystal film is composed of one layer and has at least two independent selective reflection wavelength bands (Patent Document 1).

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-333671

According to Patent Document 1, in order to make the cholesteric liquid crystal film have at least two independent selective reflection wavelength bands, it is necessary to move the remaining polymerizable liquid crystal cell compound while performing polymerization, so that the polymerizable liquid crystal cell compound in the latter half of the polymerization is: The mixing ratio of the polymerizable chiral agent changes in the film thickness direction.

However, the movement (diffusion) of a polymerizable liquid crystal cell compound takes time, patent document The production efficiency of the cholesteric liquid crystal film described in 1 is not sufficient.

Therefore, the inventors of the present invention conducted research on a chiral agent, and found that a cholesteric liquid crystal film can be efficiently produced by using a chiral agent which is a cyclic compound whose torsion is changed by intramolecular dimerization reaction. In the present specification, sometimes referred to as a "dual-band cholesteric liquid crystal film", the cholesteric liquid crystal film exhibits a first selective reflection wavelength band and a longer wavelength in the first selective reflection wavelength band in the transmission spectrum measurement. a second selected reflection wavelength band of the side, and a transmission spectrum of the transmission band between the first selected reflection wavelength band and the second selected reflection wavelength band.

It is an object of the present invention to provide a novel dual-band cholesteric liquid crystal film and a method for producing the same.

The present invention provides a cholesteric liquid crystal film which is a cured product of a liquid crystal composition containing a polymerizable liquid crystal cell compound and a cyclic compound chiral agent whose torsional force is changed by intramolecular dimerization reaction, and is in a transmission spectrum. In the measurement, the second selective reflection wavelength band having the first selective reflection wavelength band, the longer wavelength side of the first selective reflection wavelength band, and the first selective reflection wavelength band and the second selective reflection wavelength are displayed. The transmission spectrum of the transmitted band between the bands.

Here, "Helical Twisting Power" (HTP) in the present invention means a force by which a chiral agent induces a twist on a molecular arrangement of liquid crystal molecules.

When the spiral structure of the cholesteric liquid crystal film is right-twisted (when the twist direction is right), the cholesteric liquid crystal film reflects right-handed circularly polarized light, and the spiral structure of the cholesteric liquid crystal film is left-turned (the twisting direction is left). In case, the cholesteric liquid crystal film reflects left-handed circularly polarized light. That is, for example, when natural light is incident on the right-twisted cholesteric liquid crystal film, right-handed circularly polarized light corresponding to the selected reflection wavelength band is reflected, and left-handed circularly polarized light is transmitted. The circularly polarized light of the wavelength other than the reflected wavelength band is selected and transmitted directly without being reflected. Moreover, when the right-handed circularly polarized light is incident on the right-twisted cholesteric liquid crystal film, it is reflected and Select the right-handed circularly polarized light corresponding to the reflected wavelength band. On the other hand, since there is no left-handed circularly polarized light transmitted, the transmittance (%) is theoretically 0%. Right-handed circularly polarized light having a wavelength other than the reflected wavelength band is selected and transmitted directly without being reflected.

In the present invention, the "selective reflection wavelength band" means "a wavelength region (range) in which the transmittance is 30% or less for circularly polarized light corresponding to the twist direction of the cholesteric liquid crystal film", and "transmission band" means "for The refractive index of the cholesteric liquid crystal film corresponds to the circularly polarized light, the transmittance is greater than 30% of the wavelength region (range), and the "transmittance" is "the ratio of the intensity of the light that transmits the substance to the intensity of the incident light is expressed as a percentage. By". That is, the transmittance T (%) is T = I / I ₀ × 100

(where I is the intensity of the transmitted light and I ₀ is the intensity of the incident light)

Said. Here, the transmittance of the first selective reflection wavelength band and the second selective reflection wavelength band is the transmittance of light incident from the front (normal) direction.

The first selected reflected wavelength band may comprise a selected reflected wavelength band for light having a wavelength of the visible region. Further, the upper selective reflection wavelength band may include a selected reflection wavelength band for light having a wavelength of a visible light region or an infrared region.

As an aspect of the present invention, there is a method in which a first selected reflection wavelength band includes a selected reflection wavelength band for light having a wavelength of a visible light region and a second selected reflection wavelength band includes a wavelength for a visible region or an infrared region. In the dual-band cholesteric liquid crystal film of the present invention in which the reflection wavelength band is selected, if the observation direction is changed from the front to the oblique direction, the color (selective reflection color) is changed from the color corresponding to the short-wavelength light to The color corresponding to the long wavelength light (red shift).

Moreover, the present invention provides a method for producing a cholesteric liquid crystal film, comprising: step (A) (first step), which comprises a polymerizable liquid crystal cell compound, and a torsional force is changed by intramolecular dimerization reaction a liquid crystal composition of a cyclic compound chiral agent applied to a substrate to form a coating film; and a step (B) (second step) of the coating film and the base When the surface on the opposite side of the plate is in contact with the gas containing oxygen, the polymerizable liquid crystal cell compound is polymerized in preference to intramolecular dimerization of the above chiral agent to obtain a cured product as the liquid crystal composition. a cholesteric liquid crystal film; and the cholesteric liquid crystal film exhibits a second selective reflection wavelength band having a first selective reflection wavelength band, a longer wavelength side of the first selective reflection wavelength band, and the above-mentioned A transmission spectrum of a transmission band between the reflected wavelength band and the second selected reflection wavelength band is selected.

According to the method for producing a dual-band cholesteric liquid crystal film of the present invention, a dual-band cholesteric liquid crystal film can be efficiently produced.

Further, the method for producing a cholesteric liquid crystal film of the present invention may comprise the step of forming a cholesterol alignment of the above polymerizable liquid crystal cell compound between the step (A) (first step) and the step (B) (second step).

The inventors have estimated that when a cyclic compound chiral agent whose torsional force changes due to intramolecular dimerization reaction is used, the case where the cured product of the liquid crystal composition becomes a dual-band cholesteric liquid crystal film is based on the following principle.

When a liquid crystal composition is applied onto a substrate to form a coating film, and the surface of the coating film opposite to the substrate (that is, the surface of the coating film) is in contact with a gas containing oxygen, priority is given to the chiral agent. When the intramolecular dimerization is carried out to polymerize the polymerizable liquid crystal cell compound, polymerization of the polymerizable liquid crystal cell compound is preferentially dimerized in the molecule of the chiral agent on the substrate side. On the other hand, the polymerization of the polymerizable liquid crystal cell compound is slowed down by oxygen on the opposite side (surface side) of the substrate, but the intramolecular dimerization of the chiral agent is also on the surface side as in the case of the substrate side. After that, the polymerizable liquid crystal cell compound is polymerized in a state where the intramolecular dimerization reaction of the chiral agent is carried out as compared with the substrate side.

Here, when the spiral pitch is P, the chiral agent concentration is c, and the torsional force is β, the relationship of P=(c‧β) ^-1 is established, and the center wavelength of the reflection is selected. =n‧P (n is the refractive index and P is the helical pitch). Therefore, if the torsional force (β) of the chiral agent changes due to intramolecular dimerization, the wavelength of the selective reflection also changes.

Therefore, the cured product of the liquid crystal composition becomes a dual-band cholesteric liquid crystal film having different reflection wavelength bands on the substrate side and the surface side.

According to the present invention, a novel dual-band cholesteric liquid crystal film and a method for producing the same are provided.

Fig. 1 is a view showing a transmission spectrum of light incident from a front direction of the dual-band cholesteric liquid crystal film of Example 1.

Fig. 2 is a view showing a transmission spectrum of light incident from a front direction of the dual-band cholesteric liquid crystal film of Example 2.

Fig. 3 is a view showing a transmission spectrum of light incident from a front direction of the dual-band cholesteric liquid crystal film of Example 3.

Fig. 4 is a view showing a transmission spectrum of light incident from a front direction of the dual-band cholesteric liquid crystal film of Example 4.

5 is a view showing a transmission spectrum of light incident from a front direction of the dual-band cholesteric liquid crystal film of Example 5 and a direction of incidence of 20 degrees from the front direction (that is, 20 degrees with respect to the normal direction).

Hereinafter, embodiments of the present invention will be described in detail.

[Double-band cholesteric liquid crystal film]

Since the dual-band cholesteric liquid crystal film of the present invention contains a polymerizable liquid crystal cell compound and a cured product of a liquid crystal composition of a cyclic compound chiral agent whose torsional force changes due to intramolecular dimerization reaction, firstly, liquid crystal is used. The composition is described.

The cyclic compound chiral agent which changes the torsional force contained in the liquid crystal composition by the intramolecular dimerization reaction, and is capable of aligning the polymerizable liquid crystal element compound Any suitable chiral agent for the desired cholesterol structure. The chiral agent may be polymerizable or non-polymerizable, and may be liquid crystal or non-liquid crystal. By using such a chiral agent, the cured product of the liquid crystal composition can be made into a dual-band cholesteric liquid crystal film. The chiral agent may be used alone or in combination of two or more.

As the intramolecular dimerization reaction, for example, a photoreaction such as an ultraviolet reaction can be mentioned. The intramolecular dimerization reaction involves a reversible reaction and an irreversible reaction such as a cyclization reaction. From the viewpoint of suppressing color reduction, color unevenness, fading, and the like to obtain a dual-band cholesteric liquid crystal film having good stability, an irreversible reaction such as a cyclization reaction is preferred.

As described above, the "torsional force" means a force by which a chiral agent induces a twist on a molecular arrangement of liquid crystal molecules. The torsional strength of the chiral agent before the intramolecular dimerization reaction is not particularly limited, but is preferably 10 μm ^-1 or more, and more preferably 20 μm ^-1 or more. When the twisting force is large, the addition amount of the chiral agent can be reduced, and the performance of the polymerizable nematic liquid crystal (liquid crystal phase temperature range, birefringence, etc.) and the phase separation at the time of hardening of the liquid crystal composition can be suppressed, which is preferable.

The amount of change in the torsional force of the chiral agent caused by the intramolecular dimerization reaction also depends on the torsional force before the reaction, and therefore cannot be generalized. Further, although not particularly limited, in order to have a dual-band cholesteric liquid crystal film desired The first selective reflection wavelength band and the second selective reflection wavelength band have a larger variation in the torsional force. When the torsional force is increased, the torsional force after the reaction is preferably 3/2 times or more, more preferably 2 times or more, and still more preferably 3 times or more, based on the torsional force before the reaction. Further, when the torsional force is reduced, the torsional force after the reaction is preferably 2/3 or less, more preferably 1/2 or less, and further preferably 1/3 times, based on the torsional force before the reaction. the following.

For example, when the selected reflection color corresponding to the first selective reflection wavelength band is blue and the selected reflection color corresponding to the second selected reflection wavelength band is red, it is necessary to select the amount of the reflected color to change from at least blue to red. The amount of change in torsional force (about 2 times or 1/2 times).

The cyclic compound whose torsional force changes due to the intramolecular dimerization reaction preferably has a cinnamic acid moiety as a reaction site. By introducing the cinnamic acid moiety into the molecule of the cyclic compound, the cyclization reaction of the cyclic compound is likely to occur, and the cyclization reaction can be carried out at a high reaction rate for a short period of time. Further, the cyclic compound having two cinnamic acid sites causes an intramolecular dimerization reaction of the two cinnamic acid sites to form a cyclobutane ring by ultraviolet irradiation, and the torsional force is reduced.

Further, the cyclic compound whose torsional force is changed by the intramolecular dimerization reaction has a structure (having a polymer group or exhibiting a rotaxane structure, etc.) which does not diffuse into the liquid crystal composition when the liquid crystal composition is cured. Further, it is less likely to cause alignment defects of the cured product of the liquid crystal composition or whitening caused by phase separation. Further, when the cyclic compound has a structure that absorbs light (such as a benzene ring), the reaction rate is increased and the production time is shortened.

When the cyclic compound whose torsional force is changed by the intramolecular dimerization reaction exhibits liquid crystallinity, it is excellent in compatibility with the polymerizable liquid crystal cell compound, and does not easily damage the liquid crystal of the polymerizable liquid crystal cell compound during mixing. Sex. Further, since the addition amount of the chiral agent can be increased at the time of mixing, the preferred range of the torsional force of the cyclic compound is not limited to the above, and may be a lower torsional force. Further, by the cyclic compound, the alignment defect of the cured product of the liquid crystal composition or the clouding caused by the phase separation is also suppressed.

Specific examples of the cyclic compound chiral agent in which the torsional force is changed by the intramolecular dimerization reaction include a cyclic compound represented by the following formula (1a), (2a) or (3a).

[In the formulae (1a) to (3a), R independently represents hydrogen or a monovalent substituent, X and Y represent a divalent group, and either X or Y includes a chiral moiety (also referred to as a "palm region"). "). ]

The cyclic compounds represented by the above formulas (1a) to (3a) can form a cyclobutane ring by intramolecular dimerization reaction according to the following reaction schemes (I), (II) or (III), respectively. Compound.

[R, X, and Y in the formulas (1b) to (3b) respectively represent the same definitions as R, X, and Y in the formulas (1a) to (3b)]

The palmar part of the chiral agent is either spacer or directly introduced into any of X, Y in the formula. The structure of the palm portion is not particularly limited, and preferred examples thereof include the following.

Preferred examples of the cyclic compound represented by the formulae (1a) to (3a) include the following.

In the formulae (1c) to (3c), R ¹ to R ⁶ each independently represent hydrogen, fluorine, chlorine, iodine, bromine or an alkyl group. When R ¹ to R ⁶ are an alkyl group, the alkyl group is preferably a linear or branched alkyl group having 1 to 8 carbon atoms.

In the formulae (1c) to (3c), X ¹ and X ² each independently represent a divalent group having any of the following structures. In the following three structural formulas, n and m represent integers of 0 or more, and in the two structural formulas on the left and right sides, the sum of n and m is preferably 4 to 16. Further, in the central structural formula, n is preferably 4 to 16. Further, in the case of the structural formula on the right side (that is, in the case where palmitic carbon is present), it is preferable to introduce the palmar portion at a position close to the aromatic ring in the formulas (1c) to (3c), and thus in this case, Preferably, either n or m is 0 to 1.

In the formulae (1c) to (3c), Y ¹ to Y ⁴ each independently represent a divalent group having any of the following structures.

(R ⁷ represents an alkylene group; as the alkylene group, a straight or branched alkyl group having 1 to 8 carbon atoms; R ⁸ represents fluorine, chlorine, iodine, bromine or an alkyl group; , preferably a linear or branched alkyl group having a carbon number of 1 to 8)

Preferred examples of the cyclic compound represented by the formulae (1c) to (3c) include the following.

(Here, n and m in the above X ¹ and X ² are respectively set to n ¹ and m ¹ and n ² and m ² )

The content ratio of the chiral agent in the liquid crystal composition is preferably from 1 to 20% by mass, more preferably from 1.5 to 15% by mass, even more preferably from 2 to 10% by mass, based on the total amount of the liquid crystal composition. When the content ratio of the chiral agent is 1% by mass or more, the formation of the cholesterol and the formation of the helical pitch can be more sufficiently and surely performed, and if the content is 20% by mass or less, the temperature range in which the liquid crystal state is exhibited can be surely suppressed. Narrow phenomenon.

In the case where the chiral agent is a liquid crystal, since the liquid crystallinity of the polymerizable liquid crystal cell compound is not impaired, the content ratio thereof is not limited to the above, and may be increased.

The liquid crystal composition contains a polymerizable liquid crystal cell compound in addition to a chiral agent which is a cyclic compound whose torsional force changes due to intramolecular dimerization reaction. As the polymerizable liquid crystal cell compound, any appropriate polymerizable liquid crystal cell compound can be used. For example, a polymerizable liquid crystal cell compound described in JP-A-2002-533742 (WO 00/37585), EP 358208 (US Pat. No. 5,211, 877), EP 66 137 (US Pat. No. 4,438, 453), WO 93/22397, EP 0 261 172, DE 19 504 224, DE 4 408 171, and GB 2280445 can be used. Specific examples of such a polymerizable liquid crystal cell compound include commercially available products such as LC242 (manufactured by BASF Corporation), E7 (manufactured by Merck Co., Ltd.), and LC-Sillicon-CC3767 (manufactured by Wacker-Chem Co., Ltd.).

Further, as the polymerizable liquid crystal cell compound, for example, a liquid crystal monomer described in JP-A-2003-287623 (paragraphs 0035 to 0047) can be suitably used. The polymerizable liquid crystal cell compound may be used alone or in combination of two or more.

The compound which exhibits a nematic phase or a cholesterol phase exhibits a temperature of the liquid crystal phase, and is not limited, but a heating device is not required, and room temperature is preferred.

The content ratio of the polymerizable liquid crystal cell compound in the liquid crystal composition is preferably from 75 to 97.5% by mass, more preferably from 80 to 97.5% by mass, even more preferably from 85 to 97.5% by mass, based on the total amount of the liquid crystal composition. When the content ratio of the polymerizable liquid crystal cell compound is 75% by mass or more, the liquid crystal state exhibited by the liquid crystal composition is further improved, and the cholesterol alignment can be more reliably formed. Further, if the content ratio of the polymerizable liquid crystal cell compound is 97.5 When the amount is less than or equal to a certain amount, the content of the chiral agent can be sufficiently ensured, and the formation of the helical pitch and the cholesterol alignment can be performed more reliably.

In the case where the chiral agent is a liquid crystal, the amount of the chiral agent added can be increased without impairing the liquid crystallinity of the polymerizable liquid crystal cell compound. Therefore, the content ratio of the polymerizable liquid crystal cell compound is not limited to the above, and may be further cut back.

The liquid crystal composition may further comprise a polymerization initiator, preferably a photopolymerization initiator. As the photopolymerization initiator, any photopolymerization initiator can be employed. The photopolymerization initiator is not particularly limited, and is preferably a photopolymerization initiator which can be polymerized by visible light or ultraviolet light to initiate polymerization, for example, IRGACURE 651, IRGACURE 184, DAROCUR 1173, Commercial products such as IRGACURE 2959, IRGACURE 127, IRGACURE 907, IRGACURE 369, and IRGACURE TPO (all manufactured by BASF Corporation).

The content ratio of the polymerization initiator in the liquid crystal composition is preferably 0.01 to 10% by mass, and more preferably 0.05 to 5% by mass based on the total amount of the liquid crystal composition. When the content ratio of the polymerization initiator is more than 10% by mass, the temperature range in which the liquid crystal composition exhibits a liquid crystal state is narrowed, and white turbidity occurs. Therefore, it is preferably within the above range.

Further, in the liquid crystal composition, a photosensitizer may be added to the extent that the effects of the present invention are not impaired. Examples of the photosensitizer include benzophenones such as anthraquinones and rice ketones. The content ratio of the photosensitizer in the liquid crystal composition is preferably from 0.1 to 7% by mass, and more preferably from 1 to 4% by mass based on the total amount of the liquid crystal composition.

Further, a crosslinking agent may be added to the liquid crystal composition. When a crosslinking agent is added to the liquid crystal composition, the cured double-band cholesteric liquid crystal film becomes a three-dimensional crosslinked person, and is excellent in heat resistance reliability and physical strength.

The crosslinking agent is not particularly limited, and examples thereof include a polyfunctional vinyl compound having two or more polymerizable functional groups such as an acryloyl group or a methacryl group, or an organometallic compound or an aldehyde compound. A polyfunctional vinyl compound is preferred.

Examples of the polyfunctional vinyl compound include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and the like. Further, the polyfunctional vinyl compound preferably contains a liquid crystal forming site.

In addition, the amount of the crosslinking agent to be used is, for example, preferably 1 to 20 parts by mass, more preferably 100 parts by mass, based on 100 parts by mass of the total of the three components of the polymerizable liquid crystal cell compound, the chiral agent and the polymerization initiator. It is 2 to 10 parts by mass.

In order to improve the film surface smoothness and appearance of the dual-band cholesteric liquid crystal film, a surface conditioner may be added to the liquid crystal composition. As the surface conditioning agent, a lanthanoid surface conditioner, a fluorine-based surface conditioner, an acrylic surface conditioner, or the like can be used. Among these, it is preferably Fluorad. 171 (manufactured by 3M Company), Zonyl FSN (manufactured by Dupont Co., Ltd.), and BYK361 (manufactured by BYK-Chemie Japan Co., Ltd.).

The content ratio of the surface conditioner in the liquid crystal composition is 0.01 to 1% by mass, preferably 0.02 to 0.5% by mass, and more preferably 0.03 to 0.2% by mass based on the total amount of the liquid crystal composition.

Examples of other additives include an anti-aging agent, a modifier, a surfactant, a dye, a pigment, an anti-tarnishing agent, an ultraviolet absorber, a polymerization inhibitor, and the like. These additives may be used alone or in combination of two or more. More specifically, examples of the anti-aging agent include a phenol compound, an amine compound, an organic sulfur compound, and a phosphine compound. Examples of the modifier include glycols, polyoxins, and alcohols. class. Examples of the surfactant include polyfluorene-based, acrylic-based, and fluorine-based surfactants. Further, an additive for adjusting the phase transition temperature or the birefringence may also be used.

Next, a dual-band cholesteric liquid crystal film which is a cured product of the above liquid crystal composition will be described. The dual-band cholesteric liquid crystal film is characterized by having a first selective reflection wavelength band, a second selective reflection wavelength band located on a longer wavelength side of the first selected reflection wavelength band, and the first selective reflection in the transmission spectrum measurement. a cholesteric liquid crystal film having a transmission spectrum of a transmission band between the wavelength band and the second selected reflection wavelength band.

"Selecting the reflection wavelength band" means "the wavelength range (range) in which the transmittance is 30% or less for circularly polarized light corresponding to the twist direction of the cholesteric liquid crystal film", and "transmission band" means "for twisting with the cholesteric liquid crystal film" The direction corresponds to the circularly polarized light, the transmittance is greater than 30% of the wavelength region (range), and the "transmittance" is "the ratio of the intensity of the transmitted light to the intensity of the incident light is expressed as a percentage". That is, the transmittance T (%) is T = I / I ₀ × 100

(where I is the intensity of the transmitted light and I ₀ is the intensity of the incident light)

Said. Here, the transmittance of the first selective reflection wavelength band and the second selective reflection wavelength band is the transmittance of light incident from the front (normal) direction.

The wavelength of light incident from the front (normal) direction may be in the ultraviolet region (200 to 380 nm), the visible region (380 to 780 nm), and the infrared region (780 nm to 1 mm). This case is not limited to, and may not be limited to the regions. It is in any wavelength region.

The first selected reflected wavelength band and the second selected reflected wavelength band may comprise a selected reflected wavelength band for light having an arbitrary wavelength. For example, the first selected reflected wavelength band can include a selected reflected wavelength band for light having a wavelength of the visible region. Also, the second selectively reflected wavelength band may comprise a selected reflected wavelength band for light having a wavelength in the visible or infrared region.

Furthermore, light having a certain wavelength is not limited to light of one wavelength. The first selected reflected wavelength band or the second selected reflected wavelength band may also include a selected reflected wavelength band for two or more types of light having different wavelengths.

The first selective reflection wavelength band and the second selective reflection wavelength band may be any wavelength region. It may be in an ultraviolet region, a visible region or an infrared region, or may be a wavelength region spanning the regions.

The first selective reflection wavelength band is preferably in the wavelength region of 400 to 700 nm, and more preferably in the wavelength region of 400 to 650 nm.

Moreover, the second selective reflection wavelength band is preferably in a wavelength region of 550 to 900 nm. The domain is particularly preferably in the wavelength range of 550 to 800.

In particular, as a dual-band cholesteric liquid crystal film, it is appropriate that the first selective reflection wavelength band is in a wavelength region of 500 to 650 nm and the second selective reflection wavelength band is in a wavelength region of 700 to 800 nm, or the first selective reflection wavelength band is at 400. The wavelength region of ~500 nm and the second selective reflection wavelength band are in the wavelength region of 550-650 nm.

Specifically, as the dual-band cholesteric liquid crystal film, the first selective reflection wavelength band is 550 to 610 nm and the second selective reflection wavelength band is 710 to 780 nm; the first selective reflection wavelength band is 530 to 580 nm and the second Selecting the reflection wavelength band at 710~760nm; the first selective reflection wavelength band is at 530~580nm and the second selective reflection wavelength band is at 710~740nm; the first selective reflection wavelength band is at 440~500nm and the second selective reflection wavelength band is At 560~640nm.

Furthermore, the dual-band cholesteric liquid crystal film may also have a selective reflection wavelength band other than the first selective reflection wavelength band and the second selective reflection wavelength band.

The dual-band cholesteric liquid crystal film has a first spiral pitch corresponding to the first selective reflection wavelength band and a second spiral pitch corresponding to the second selective reflection wavelength band. The selected reflection wavelength bands corresponding to the first spiral pitch and the second spiral pitch may respectively exist in plural, and the first selective reflection wavelength band and the second selective reflection wavelength band are only selective reflections of light incident from the front direction thereof. Wavelength band.

Therefore, the dual-band cholesteric liquid crystal film may further have a selective reflection wavelength band (third selective reflection wavelength band) of light incident from a direction other than the front side (inclination direction) corresponding to the first spiral pitch, and a second spiral section The selected reflection wavelength band (fourth selected reflection wavelength band) of the light incident from the corresponding oblique direction. Here, the third selective reflection wavelength band and the fourth selective reflection wavelength band may be any wavelength region, but the third selective reflection wavelength band is a wavelength region on a shorter wavelength side of the first selective reflection wavelength band, and the fourth selective reflection The wavelength band is a wavelength region on the shorter wavelength side of the second selected reflection wavelength band. The reason for this is that it will be reflected in the selective reflection of incident light from the front (normal) direction. When the center wavelength of the light is λ(0) and the center wavelength of the selective reflection of light incident at an angle θ with respect to the normal direction is λ(θ), λ(θ)=λ(0)‧cosθ

The relationship is established, and the center wavelength λ(θ) of the selective reflection becomes smaller as the incident angle of light becomes larger, that is, shifts to the short wavelength side (blue shift).

Therefore, according to the wavelength range of the first selective reflection wavelength band to the fourth selective reflection wavelength band of the dual-band cholesteric liquid crystal film, the selected reflection color is recognized when viewed from the front and when viewed from the oblique direction ( Also includes colorless).

For example, the first selected reflection wavelength band includes a selected reflection wavelength band for light having a wavelength of a visible light region, and the second selected reflection wavelength band includes a selected reflection wavelength band for light having a wavelength of the infrared region, and the third selected reflection wavelength The frequency band includes a selected reflection wavelength band for light having a wavelength of the ultraviolet region, and the fourth selected reflection wavelength band includes a dual-band cholesteric liquid crystal film for a selective reflection wavelength band of light having a wavelength of the visible region, when viewed from the front, The selected reflection color corresponding to the first selected reflection wavelength band is visually recognized, and when viewed from the oblique direction, the selected reflection color corresponding to the fourth selected reflection wavelength band is recognized. In fact, although the third selective reflection wavelength band of the dual-band cholesteric liquid crystal film is the wavelength region on the shorter wavelength side of the first selective reflection wavelength band, the fourth selective reflection wavelength band is the shorter wavelength side of the second selective reflection wavelength band. The wavelength region, but when the direction of observation is changed from the front to the oblique direction, it is like feeling that the color of the dual-band cholesteric liquid crystal film changes from the short-wavelength light to the selected reflection color of the long-wavelength light (red shift) ). That is, a color change different from that of a normal cholesteric liquid crystal film having only one selected reflection wavelength band (which produces a blue shift) can be produced.

Specific examples of such a dual-band cholesteric liquid crystal film include a yellow-green color when viewed from the front, a red color when viewed from an oblique direction, a green color when viewed from the front, and a visual view when viewed from an oblique direction. Red, when viewing from the front, seeing blue-green and recognizing red when observing from oblique direction, recognizing blue when viewed from the front and observing from oblique direction When the red person is recognized, the blue color is recognized from the front, and the golden color is recognized when viewed from the oblique direction.

Further, the first selective reflection wavelength band and the second selective reflection wavelength band include a selective reflection wavelength band for light having a wavelength of a visible light region, and the third selected reflection wavelength band includes a selective reflection wavelength for light having a wavelength of the ultraviolet region a frequency band, and the fourth selected reflection wavelength band includes a dual-band cholesteric liquid crystal film for a selective reflection wavelength band of light having a wavelength of a visible light region, when viewed from the front, visually recognizing the first selected reflection wavelength band and the second selective reflection The selected reflection color corresponding to the wavelength band, when viewed from the oblique direction, visually recognizes the selected reflection color corresponding to the fourth selected reflection wavelength band.

Specific examples of such a dual-band cholesteric liquid crystal film include a dark red color when viewed from the front and a blue color when viewed from an oblique direction, and an orange (copper yellow) and self-slanting when viewed from the front. Observe the yellow-green color when observing.

Next, the use of the dual-band cholesteric liquid crystal film will be described. The dual-band cholesteric liquid crystal film can be suitably used for color materials, IR (infrared ray) filters, band pass filters, UV (ultraviolet) reflective films, brightness enhancement films, dimming films, phase difference plates, traps Wave filter (notch filter), etc. In particular, it is useful as a reflective film that reflects light having a wavelength in a first selective reflection wavelength band and a second selective reflection wavelength band.

Further, a dual-band cholesteric liquid crystal film, particularly in the case of viewing from the front and the case of observing from the oblique direction, may be used as a safety medium. For example, if an article to which the dual-band cholesteric liquid crystal film is applied is used as a genuine product and an unapplied article is set as a non-genuine product, whether or not the target article is genuine can be easily recognized based on whether or not the selected reflection color is recognized as a reference. In particular, a dual-band cholesteric liquid crystal film which appears to be red-shifted may have a characteristic of exhibiting a color change different from that of a normal cholesteric liquid crystal film which produces a blue shift.

Further, the intramolecular dimerization reaction of the cyclic compound represented by any one of the above formulas (1a) to (3a) as a chiral agent is an irreversible reaction, and thus the dual-band cholesteric liquid crystal film can be used. A cyclobutane ring (that is, a cyclic compound represented by the formula (1b) to (3b)) is formed by an intramolecular dimerization reaction thereof. Further, the dual-band cholesteric liquid crystal film may also contain an unreacted chiral agent.

[Method of manufacturing dual-band cholesteric liquid crystal film]

Next, a method of producing a dual-band cholesteric liquid crystal film will be described. In the production of the dual-band cholesteric liquid crystal film, first, the liquid crystal composition is applied onto a substrate to form a coating film (step (A), first step).

The liquid crystal composition can be directly coated on a substrate, or can be dissolved or dispersed in a solvent and then coated on a substrate. Examples of the solvent include chloroform, dichloro methane, carbon tetrachloride, dichloroethane, tetrachloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, and chlorobenzene. Halogenated hydrocarbons such as o-dichlorobenzene; phenols such as phenol, p-chlorophenol, o-chlorophenol, m-cresol, o-cresol, p-cresol; benzene, toluene, xylene, methoxybenzene, 1, 2 Aromatic hydrocarbons such as dimethoxybenzene; acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2 a ketone solvent such as pyrrolidone; an ester solvent such as ethyl acetate or butyl acetate; a third butanol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, and diethylene glycol An alcohol solvent such as ether, propylene glycol, dipropylene glycol or 2-methyl-2,4-pentanediol; a guanamine solvent such as dimethylformamide or dimethylacetamide; and a nitrile such as acetonitrile or butyronitrile. Solvent; diethyl ether, dibutyl ether, tetrahydrofuran, two An ether solvent such as an alkane; carbon disulfide, ethyl siroli, butyl siroli, and the like. These solvents may be used alone or in combination of two or more.

Examples of the coating method include a spin coating method, a casting method, a roll coating method, a flow coating method, a die coating method, a printing method, a dip coating method, a casting film forming method, and a bar coating method. Law, gravure printing method, etc.

The material, shape, structure, thickness and the like of the substrate are not particularly limited, and an optimum substrate can be selected from the viewpoints of dimensional stability, uniformity of thickness, strength, heat resistance, chemical resistance, water resistance, and the like. Moreover, the substrate can also be appropriately selected from known substrates. Choose.

The resin which is a material of the substrate is a polymer obtained by polymerizing one or two or more kinds of polymerizable monomers, or a mixture thereof. In the case where the polymer is a copolymer obtained by polymerizing two or more kinds of polymerizable monomers, the copolymer may be any copolymer comprising a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer. Things. The resin substrate may be a composite substrate such as a substrate in which two or more kinds of resins are laminated.

In particular, as the substrate, it is preferred to use various plastic films from the viewpoint of causing the liquid crystal to undergo cholesterol alignment. Examples of the plastics include cellulose resins such as triacetin cellulose (TAC); polyolefins such as polyethylene, polypropylene, poly(4-methylpentene-1), and cycloolefin polymer; Amine, polyamidamine, polyether oximine, polyamidamine, polyether ether ketone, polyether ketone, polyketone sulfide, polyether oxime, polyfluorene, polyphenylene sulfide, polyphenylene ether, poly Ethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, epoxy resin, phenol Resin, etc. The plastic film can be obtained, for example, by extending the plastic.

Further, the material of the substrate may be glass, for example, normal soda glass or the like. It can also be a substrate in which a resin and a glass are combined.

Further, a plastic film or a sheet as described above may be disposed on a surface of a metal substrate such as aluminum, copper or iron, a ceramic substrate or a glass substrate.

A film such as an SiO ₂ oblique vapor deposition film may be formed on the surface of the substrate on the side where the liquid crystal composition is applied.

The thickness of the substrate is preferably 5 to 500 μm, more preferably 10 to 200 μm, still more preferably 15 to 150 μm. If it has such a thickness, it will have sufficient strength as a board|substrate, and it can prevent that it can generate|occur|

The thickness of the coating film of the liquid crystal composition is not particularly limited, but is preferably 3 to 50 μm, more preferably 3 to 25 μm, still more preferably 4 to 20 μm. When the thickness is thicker than 3 μm, a sufficient spiral pitch is easily formed, and if the thickness is thinner than 50 μm, the alignment restricting force is sufficiently exerted. Used, so it is not easy to produce poor alignment. Further, in terms of cost, it is preferably 50 μm or less.

In the present embodiment, the formation of the cholesterol alignment of the polymerizable liquid crystal cell compound is preferably carried out after the step (A) (first step) and before the step (B) (second step) described below.

Thereafter, in the state where the surface of the formed coating film opposite to the substrate (that is, the surface of the coating film) is in contact with the gas containing oxygen, the polymerization is made in preference to intramolecular dimerization of the chiral agent. Polymerization of the liquid crystal cell compound (step (B), second step).

Thus, on the substrate side, polymerization of the polymerizable liquid crystal cell compound takes precedence over intramolecular dimerization of the chiral agent. On the other hand, on the opposite side (surface side) of the substrate, the polymerization of the polymerizable liquid crystal cell compound is inhibited by oxygen and becomes slow, but the intramolecular dimerization of the chiral agent on the surface side is also performed in the same manner as the substrate side. Therefore, the polymerizable liquid crystal cell compound is polymerized in a state in which the intramolecular dimerization reaction of the chiral agent is carried out as compared with the substrate side.

The gas containing oxygen is not limited, and the oxygen concentration may be appropriately set according to the characteristics of the desired dual-band cholesteric liquid crystal film, etc., and is at least 0.5% by volume or more, preferably 10% by volume based on the total amount of the gas. the above. The gas containing oxygen may also be atmospheric (oxygen concentration: about 21% by volume). The use of a special device in the atmosphere is also preferred in terms of cost.

Further, the gas containing oxygen may contain any suitable inert gas. Examples of the inert gas include nitrogen gas, argon gas, helium gas, neon gas, xenon gas, and helium gas. Among these, nitrogen is preferred because it has the highest versatility and low cost.

The intramolecular dimerization of the chiral agent and the polymerization of the polymerizable liquid crystal cell compound can be carried out by irradiating light such as visible light or ultraviolet light, and by increasing the intensity of light such as visible light or ultraviolet light (exposure illuminance), The latter takes precedence over the former.

For example, the intensity of light is preferably from 15 to 100 mW/cm ² , more preferably from 20 to 90 mW/cm ² , still more preferably from 20 to 80 mW/cm ² . However, by increasing the content ratio of the photopolymerization initiator or the photosensitizer in the liquid crystal composition, the intensity of light can be made smaller. For example, when the content ratio of the photosensitizer in the liquid crystal composition is 2% by mass, the light intensity can be 3 mW/cm ² or more, and preferably 4 to 60 mW/cm ² .

The wavelength of light is preferably from 160 to 500 nm, more preferably from 220 to 450 nm, still more preferably from 280 to 420 nm.

The irradiation time of the light varies depending on the intensity of the light to be irradiated. For example, if the intensity of the light is 50 mW/cm ² , it is preferably 1 to 600 seconds, more preferably 5 to 500 seconds, and further preferably 10 to 10 seconds. 400 seconds. However, by increasing the content ratio of the photopolymerization initiator or the photosensitizer in the liquid crystal composition, the irradiation time of light can be shortened. In this case, the irradiation time is preferably from 1 to 60 seconds, more preferably from 3 seconds to 50 seconds.

The temperature at which the liquid crystal composition is irradiated with light such as visible light or ultraviolet light also depends on the polymerizable liquid crystal element compound to be used, and therefore cannot be generalized, and is preferably 10 to 150 ° C, more preferably 20 to 120 ° C, and further preferably 25~90 °C. Further, when the heating temperature is low, the viscosity of the liquid crystal composition becomes high, and there is a problem that the cured product is caused to have an alignment defect. Further, when the heating temperature is high, the liquid crystal composition is phase-transferred into an isotropic phase, and the cured product is not subjected to selective reflection.

Further, the polymerization of the polymerizable liquid crystal cell compound can be made more preferentially than the intramolecular dimerization of the chiral agent, that is, the wavelength of light is set to a wavelength other than the intramolecular dimerization wavelength of the chiral agent. The polymerizable liquid crystal cell compound is polymerized, and then the wavelength of light is set to the intramolecular dimerization wavelength of the chiral agent to carry out intramolecular dimerization of the chiral agent, and thereafter, the wavelength of light is set as the case The polymerizable liquid crystal cell compound is polymerized by intramolecular dimerization of the chiral agent. Here, the wavelength other than the intramolecular dimerization wavelength is preferably the cleavage wavelength of the photopolymerization initiator.

For example, since the cracking wavelength of the long-wavelength side absorption end of the photopolymerization initiator IRGACURE TPO is 420 nm, the intramolecular dimerization wavelength of the above cyclic compound is 315 nm, and thus the wavelength of one of the bright lines of the high-pressure mercury lamp is initially irradiated. Only 405nm The light is then irradiated with light having a wavelength of 315 nm, and light having a wavelength of 405 nm is irradiated in the subsequent case, whereby the polymerization of the polymerizable liquid crystal cell compound can be made to preferentially dimerize in the molecule of the chiral agent.

Further, after the curing of the liquid crystal composition is completed, the substrate may be peeled off or peeled off.

[Examples]

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the examples.

Unless otherwise stated, the "parts" and "%" in the examples are the quality standards. Further, the structures and physical properties of all the compounds used in the examples are shown in Table 1.

<Evaluation method>

(Measurement of transmission spectrum)

A two-band cholesteric liquid crystal film formed on a aligning substrate is used as a sample for measurement, and a spectroscope USB4000 (manufactured by Ocean Optics Co., Ltd.) equipped with a polarizing microscope eclipse lv100 POL (manufactured by Nikon Co., Ltd.) equipped with an optical fiber BIS600-VIS-NIR is used. ) Perform the measurement. The light incident on the dual-band cholesteric liquid crystal film is from the front (normal) direction. The transmittance when the substrate on which the liquid crystal composition was not applied was incident from the normal direction to the right-handed circularly polarized light was used as a reference (transmittance: 100%). In the case where the right circularly polarized light is incident at a tilt angle of 20 degrees from the normal direction and the transmittance is measured, the right-hand circularly polarized light is incident on the substrate on which the liquid crystal composition is not applied from the normal direction. Transmittance is used as a reference (100% transmittance). In addition, the setting of the analysis software Spectra Suite used for measuring the transmittance is set to a cumulative time of about 400 milliseconds and a sample bin width (boxcar width).

In the measurement of the transmission spectrum, a wavelength region (range) having a transmittance of 30% or less is set as a selective reflection wavelength band.

(adjustment of irradiation intensity)

Ultraviolet irradiation was performed using SPOT9-250UB (manufactured by Ushio Electric Co., Ltd.) as a UV irradiation device having a variable intensity.

(Measurement of thickness)

The thickness of the dual-band cholesteric liquid crystal film (after ultraviolet irradiation) was measured using Alpha-Step IQ (manufactured by Yamato Scientific Co., Ltd.) as a step measuring device.

(visuality)

The color of the dual-band cholesteric liquid crystal film observed from the front and the color of the dual-band cholesteric liquid crystal film observed from the direction of 45 degrees from the front side.

[Synthesis Example 1: Synthesis of Compound 1]

Compound 1 shown in Table 1 was synthesized according to the following synthetic scheme.

(Step 1) Synthesis of 4-(4-pentenyloxy)cinnamic acid (compound (a))

One equivalent of trans-4-hydroxycinnamic acid was placed in an eggplant flask and dissolved in ethanol. To the solution, a catalyst amount of potassium iodide (KI) dissolved in water, 3 equivalents of potassium hydroxide (KOH), and 1.2 equivalents of 5-bromo-1-pentene dissolved in ethanol were added at 70 ° C. Stir for 24 hours. Thereafter, after returning to room temperature, the unnecessary ethanol was removed by an evaporator and water was added, and in order to precipitate the ionized product, dilute hydrochloric acid was added to acidify it. The obtained precipitate was filtered and washed with water to obtain the objective compound (a).

(Step 2): Synthesis of Compound (b)

2.2 equivalents of the compound (a) and 1 equivalent of (R)-(+)-2-methyl-1,4-butanediol were dissolved in dehydrated dichloromethane in an eggplant flask. To the solution, 2.4 equivalent of DCC (dicyclohexylcarbodiimide) and a catalytic amount of DMAP (4-dimethylaminopyridine) were added, and the mixture was stirred at room temperature for 24 hours. Thereafter, DCC urea solids formed by the reaction were separated by filtration from the reaction liquid, and the filtrate was concentrated under reduced pressure. The target compound (b) is obtained by purification by ruthenium oxide column chromatography using chloroform as a developing solvent.

(Step 3): Synthesis of Compound 1

To a 1 L three-necked flask, 500 mg of the compound (b) and 1 L of dehydrated dichloromethane were added, and the mixture was purged with nitrogen. The sample was stirred at room temperature for 2 hours in order to dissolve the sample uniformly. Thereafter, it was dissolved in dehydrated dichloromethane by using a syringe for three times at intervals of several hours. The first generation of Grubbs catalyst was 0.2 equivalent and stirred at room temperature for 24 hours. The obtained reaction solution was concentrated under reduced pressure, and purified by dichloromethane column chromatography and ruthenium oxide column chromatography using dichloromethane as a developing solvent, and then recrystallized by ethyl acetate-hexane. Compound 1 was obtained. Further refining is carried out by recycling GPC as needed.

[Example 1]

With respect to 90 parts by weight of LC242 (manufactured by BASF Corporation) as a polymerizable liquid crystal cell compound, 8 parts by weight of a compound 1 as a chiral agent, and 2 parts by weight of Irg907 as a photopolymerization initiator (BASF Corporation) To a mixture of 1 part by weight of the mixture, 100 parts by weight of chloroform was added to prepare a chloroform solution.

The solution was cast on an alignment substrate obtained by rubbing a glass substrate coated with polyimide, and irradiated with ultraviolet rays having an ultraviolet irradiation intensity of 23 mW/cm ² at 70 ° C in the atmosphere (oxygen concentration: 21% by volume). 300 seconds to obtain a dual-band cholesteric liquid crystal film.

[Embodiment 2]

A two-band cholesteric liquid crystal film was obtained in the same manner as in Example 1 except that the ultraviolet irradiation intensity was changed to 48 mW/cm ² .

[Example 3]

A two-band cholesteric liquid crystal film was obtained in the same manner as in Example 1 except that the ultraviolet irradiation intensity was changed to 73 mW/cm ² .

[Example 4]

The polymerizable liquid crystal cell compound was 86 parts by weight, the chiral agent was made up to 10 parts by weight, the rice ketone as a photosensitizer was 2 parts by weight, and the ultraviolet irradiation intensity was set to 4.4 mW/cm. ² , a double-band cholesteric liquid crystal film was obtained in the same manner as in Example 1 except that the ultraviolet irradiation time was 30 seconds.

[Example 5]

The amount of the polymerizable liquid crystal cell compound was 89 parts by weight, the chiral agent was 9 parts by weight, the ultraviolet light intensity was 73 mW/cm ² , and the ultraviolet irradiation time was 120 seconds. In the same manner as in Example 1, a dual-band cholesteric liquid crystal film was obtained.

Table 2 summarizes Examples 1 to 5. Further, the transmission spectra of the light incident from the front (normal) direction of the dual-band cholesteric liquid crystal films of Examples 1 to 5 are shown in Figs. 1 to 5, respectively. Fig. 5 also shows the transmission spectrum of light incident on the double-band cholesteric liquid crystal film of Example 5 from a direction inclined by 20 degrees with respect to the front (normal) direction. In FIG. 5, the transmission spectrum on the long wavelength side is the transmission spectrum of light incident from the front (normal) direction, and the transmission spectrum on the short wavelength side is incident from the direction inclined by 20 degrees with respect to the front (normal) direction. The transmission spectrum of light. Further, the vertical axis of FIGS. 1 to 5 is the transmittance (%), and the horizontal axis is the wavelength (nm).

[Industrial availability]

The dual-band cholesteric liquid crystal film of the present invention can be suitably used for a color material, an IR filter, a band pass filter, a UV reflection film, a brightness enhancement film, a light adjustment film, a phase difference plate, a notch filter, and the like. In particular, it is useful as a reflective film that reflects light having a wavelength in a first selective reflection wavelength band and a second selective reflection wavelength band.

Further, a dual-band cholesteric liquid crystal film, particularly in the case of viewing from the front and the case of observing from the oblique direction, may be used as a safety medium.

Claims (6)

A cholesteric liquid crystal film comprising a polymerizable liquid crystal cell compound and a cured product of a liquid crystal composition of a cyclic compound chiral agent whose torsional force is changed by intramolecular dimerization reaction, and in transmission spectrum measurement, Displaying a transmission spectrum having a wavelength band of: a first selected reflection wavelength band, a second selected reflection wavelength band located on a longer wavelength side of the first selected reflection wavelength band, and a first selected reflection wavelength band and the foregoing Second, select the transmission band between the reflected wavelength bands. The cholesteric liquid crystal film of claim 1, wherein the first selective reflection wavelength band comprises a selective reflection wavelength band for light having a wavelength of the visible light region. A cholesteric liquid crystal film according to claim 1 or 2, wherein said second selective reflection wavelength band comprises a selective reflection wavelength band for light having a wavelength of the infrared region. A cholesteric liquid crystal film according to claim 1 or 2, wherein said second selective reflection wavelength band comprises a selective reflection wavelength band for light having a wavelength of a visible light region. A method for producing a cholesteric liquid crystal film, comprising: a first step of a liquid crystal composition comprising a polymerizable liquid crystal cell compound and a cyclic compound chiral agent whose torsional force is changed by intramolecular dimerization reaction Coating a substrate to form a coating film; and a second step of contacting the surface of the coating film opposite to the substrate in contact with a gas containing oxygen, in preference to the intramolecular component of the chiral agent Polymerization of the above polymerizable liquid crystal cell compound to obtain a cholesteric liquid crystal film as a cured product of the above liquid crystal composition; and the above cholesteric liquid crystal film exhibits the following band in transmission spectrum measurement Transmission spectrum: a first selective reflection wavelength band, a second selective reflection wavelength band located on a longer wavelength side of the first selected reflection wavelength band, and a first selected reflection wavelength band and the second selected reflection wavelength band Through the frequency band. The method for producing a cholesteric liquid crystal film according to claim 5, wherein the step of forming the cholesterol alignment of the polymerizable liquid crystal cell compound is included between the first step and the second step.