WO2016052404A1 - Optical film having cholesteric liquid crystal layer and production method for optical film having cholesteric liquid crystal layer - Google Patents

Optical film having cholesteric liquid crystal layer and production method for optical film having cholesteric liquid crystal layer Download PDF

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Publication number
WO2016052404A1
WO2016052404A1 PCT/JP2015/077326 JP2015077326W WO2016052404A1 WO 2016052404 A1 WO2016052404 A1 WO 2016052404A1 JP 2015077326 W JP2015077326 W JP 2015077326W WO 2016052404 A1 WO2016052404 A1 WO 2016052404A1
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liquid crystal
optical film
cholesteric liquid
chiral agent
layer
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PCT/JP2015/077326
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French (fr)
Japanese (ja)
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渉 星野
克行 養父
武田　淳
由紀 松田
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富士フイルム株式会社
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Publication of WO2016052404A1 publication Critical patent/WO2016052404A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/26—Reflecting filters
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors

Definitions

  • the present invention relates to an optical film including a cholesteric liquid crystal layer. More specifically, the present invention relates to an optical film including a cholesteric liquid crystal layer exhibiting selective reflection in a wide wavelength band. The present invention also relates to a method for producing an optical film including a cholesteric liquid crystal layer.
  • the cholesteric liquid crystal phase exhibits selective reflection having a reflection center wavelength correlated with the helical pitch.
  • a layer in which a cholesteric liquid crystal phase is fixed hereinafter sometimes referred to as “cholesteric liquid crystal layer” in this specification
  • a layer in which the helical pitch is changed in the thickness direction of the layer also referred to as a pitch gradient layer or a PG layer
  • a broadband reflection film that expands the range of the selective reflection wavelength band more than the layer in which the cholesteric liquid crystal phase having a uniform helical pitch is fixed, and exhibits selective reflection in a wide wavelength range.
  • a method for obtaining a pitch gradient layer a method of including a weak ultraviolet irradiation step when forming a cholesteric liquid crystal layer by curing a coating film of a polymerizable liquid crystal composition containing a liquid crystal compound and a chiral agent, for example, Patent Document Known as seen in 1-4.
  • the present inventors have made various studies on the liquid crystal composition used for forming the cholesteric liquid crystal layer, and found that the curing process of the liquid crystal composition can be controlled by selecting the liquid crystal compound and the chiral agent. Based on the above, further studies were made to complete the present invention.
  • An optical film including a cholesteric liquid crystal layer is a layer obtained by curing a polymerizable liquid crystal composition containing a polyfunctional liquid crystal compound and a chiral agent,
  • the polyfunctional liquid crystal compound has two or more polymerizable groups and an average molar extinction coefficient at 300 to 400 nm of 5000 or more,
  • the above chiral agent has no polymerizable group or only one,
  • the chiral agent has a concentration distribution in a film thickness direction.
  • a method for producing an optical film including a cholesteric liquid crystal layer Forming the cholesteric liquid crystal layer by curing a coating film of a polymerizable liquid crystal composition containing a polyfunctional liquid crystal compound and a chiral agent, wherein the curing has an illuminance of 0.1 mW / cm 2 to 100 mW / cm 2 .
  • a production method comprising a temporary curing step of irradiating ultraviolet rays for 30 seconds or less.
  • the present invention provides an optical film including a cholesteric liquid crystal layer exhibiting selective reflection in a wide wavelength band.
  • the optical film of the present invention can be produced by a highly productive method.
  • a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
  • the “half width” of a peak means the width of the peak at a peak height of 1/2.
  • the reflection center wavelength and half width of the light reflection layer can be obtained as follows. When the transmission spectrum of the light reflection layer is measured using AxoScan of Axometrix, a wavelength band in which the transmittance decreases can be seen. Of the two wavelengths having a transmittance of 1/2 the maximum peak height, the wavelength value on the short wave side is ⁇ 1 (nm) and the wavelength value on the long wave side is ⁇ 2 (nm).
  • Re ( ⁇ ) represents in-plane retardation at wavelength ⁇ .
  • the unit is nm.
  • Re ( ⁇ ) is measured with KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments) by allowing light of wavelength ⁇ nm to be incident in the normal direction of the film.
  • the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.
  • visible light means light having a wavelength of 380 nm to 780 nm.
  • a measurement wavelength is 550 nm.
  • the angle for example, an angle such as “90 °”
  • the relationship for example, “orthogonal”, “parallel”, “crossing at 45 °”, etc.
  • the range of allowable error is included. For example, it means that the angle is within the range of strict angle ⁇ 10 °, and the error from the strict angle is preferably 5 ° or less, and more preferably 3 ° or less.
  • the shape of the optical film of the present invention is not particularly limited, it may be usually a sheet shape, a film shape, a plate shape, or the like.
  • the optical film may be long and may have a size according to the application.
  • the optical film may be cut into a size according to the application.
  • “cutting” includes “punching” and “cutting out”.
  • the use of the optical film is not particularly limited as long as it is used for various reflective films, reflective polarizers, brightness enhancement films, and the like. As will be described later, since the optical film of the present invention exhibits selective reflection in a wide wavelength band, it can be used in applications where reflection in a wide wavelength band is preferred or required.
  • the optical film of the present invention is particularly preferably used for a brightness enhancement film.
  • the brightness enhancement film can be configured to include an arbitrary ⁇ / 4 plate, and a cholesteric liquid crystal layer, which will be described later, may be formed on the surface of the ⁇ / 4 plate.
  • a ⁇ / 4 plate may be formed by applying a coating solution for liquid, or the optical film of the present invention may be bonded to a separately prepared ⁇ / 4 plate.
  • the optical film of the present invention includes a cholesteric liquid crystal layer.
  • a cholesteric liquid crystal layer means a layer in which a cholesteric liquid crystal phase formed in a polymerizable liquid crystal composition containing a liquid crystal compound is fixed.
  • the layer in which the cholesteric liquid crystal phase is fixed is a layer in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained.
  • the cholesteric liquid crystal layer may be a layer in which a layer having no fluidity is formed by curing of the polymerizable liquid crystal composition, and at the same time, the layer is changed to a state in which the alignment form is not changed by an external field or an external force.
  • the liquid crystal compound in the layer may no longer exhibit liquid crystallinity.
  • the liquid crystal compound may have a high molecular weight due to a curing reaction and may no longer have liquid crystallinity.
  • the cholesteric liquid crystal layer exhibits selective reflection having a reflection center wavelength ⁇ based on the helical period of the cholesteric liquid crystal phase.
  • the light reflection layer formed by fixing the cholesteric liquid crystal phase selectively reflects either the right circularly polarized light or the left circularly polarized light and transmits the other circularly polarized light in the wavelength region exhibiting selective reflection.
  • “Introduction to Liquid Crystal Chemistry Experiment” edited by the Japanese Liquid Crystal Society, Sigma Publishing 2007, page 46, and “Liquid Crystal Handbook” Kai Maruzen The method described on page 196 can be used.
  • a cholesteric liquid crystal layer having a pitch or spiral direction suitable for the application may be used alone or in combination.
  • the width of the selective reflection band can also be controlled by adjusting ⁇ n.
  • ⁇ n can be adjusted by adjusting the type of liquid crystal compound and its mixing ratio, or by controlling the temperature at the time of fixing the alignment.
  • the upper limit of ⁇ n of liquid crystals currently industrialized is about 0.5
  • the half-value width ⁇ of selective reflection is usually about 50 nm to 150 nm for one kind of material, and the wavelength band of selective reflection is adjusted by adjusting ⁇ n. There is a limit to the width control.
  • the optical film of the present invention selective reflection is exhibited in a wide wavelength band (for example, about 200 nm at half width) by changing the pitch P in the film thickness direction (pitch gradient) in one cholesteric liquid crystal layer.
  • a cholesteric liquid crystal layer is used.
  • the pitch gradient layer by using the pitch gradient layer, a wide wavelength band that cannot be achieved within the range studied from the upper limit of ⁇ n of the liquid crystal can be obtained.
  • c is the concentration of the chiral agent
  • ⁇ is an index of the force with which the chiral agent twists the liquid crystal
  • HTP Helical Twisting Power
  • the chiral agent has a concentration distribution in the film thickness direction. Therefore, the pitch changes in the film thickness direction in the cholesteric liquid crystal layer, and therefore the reflection center wavelength changes, and a cholesteric liquid crystal layer showing selective reflection in a wide wavelength band can be obtained.
  • a method of giving a concentration distribution in the film thickness direction to the chiral agent in the cholesteric liquid crystal layer will be described later.
  • the polymerizable liquid crystal composition for forming a cholesteric liquid crystal layer contains a liquid crystal compound and a chiral agent.
  • the polymerizable liquid crystal composition may contain other components such as an alignment controller, a polymerization initiator, and an alignment aid.
  • the cholesteric liquid crystal layer can be obtained by applying the polymerizable liquid crystal composition to another layer such as a support, an alignment layer, or another cholesteric liquid crystal layer, and then curing the coating film.
  • liquid crystal compound examples include a rod-like liquid crystal compound and a disk-like liquid crystal compound.
  • the liquid crystal compound is preferably a rod-like liquid crystal compound.
  • There is no limitation in particular as a polymeric group Although a (meth) acryloyl group, an epoxy group, oxetanyl group, a vinyl ether group etc. are mentioned, A (meth) acryloyl group is preferable.
  • the polymerizable liquid crystal composition for forming the cholesteric liquid crystal layer of the optical film of the present invention contains a polyfunctional liquid crystal compound having two or more polymerizable groups as the liquid crystal compound.
  • the polymerizable liquid crystal composition may include a liquid crystal compound having one polymerizable group or not having a polymerizable group as a liquid crystal compound, but a polyfunctional liquid crystal compound having two or more polymerizable groups is , Preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, substantially with respect to the total mass of the liquid crystal compound in the polymerizable liquid crystal composition. It is particularly preferable that the amount is 100% by mass.
  • the term “liquid crystal compound” simply means “polyfunctional liquid crystal compound”.
  • the polyfunctional liquid crystal compound having two or more polymerizable groups used in the present invention has an average molar extinction coefficient of 5000 or more at 300 to 400 nm.
  • the average molar extinction coefficient is preferably 7000 or more.
  • the average molar extinction coefficient at 300 nm to 400 nm of the liquid crystal compound is determined by measuring a solution prepared at an appropriate concentration in a range of 250 to 500 nm every 1 nm using a spectrophotometer UV3150 (Shimadzu Corporation). It means a value obtained by calculating an extinction coefficient and calculating an average value in a range of 300 to 400 nm.
  • the liquid crystal compound having an average molar extinction coefficient at 300 to 400 nm of 5000 or more include a liquid crystal compound having a tolan (diphenylacetylene) structure, an azomethine structure, an azine structure, or a cinnamoyl structure in the molecule.
  • Examples of the liquid crystal compound having a tolan structure include, for example, Japanese Patent No. 4836335, Japanese Patent No. 4947676, Japanese Patent No. 3999400, Japanese Patent No. 3963035, Japanese Patent No. 4053782, Japanese Patent No. 4268058, Japanese Patent No. 4461692, Japanese Patent No. 5082538. And compounds described in JP2013-112163A and JP2013-534646A.
  • Examples of the liquid crystal compound having an azomethine structure include compounds described in JP 2012-006996 A, JP 2012-006997 A, JP 2012-006843 A, and JP 2012-006996 A. Can do.
  • liquid crystal compound having an azine structure examples include compounds described in JP2011-207940A, JP2011-207941A, JP2011-207940A, and JP5510321A.
  • liquid crystal compound having a cinnamoyl structure examples include compounds described in JP2011-207942.
  • a compound having an average molar extinction coefficient of 300 to 400 nm of 5000 or more can be arbitrarily used.
  • liquid crystal compounds with a tolan structure, azomethine structure, azine structure or cinnamoyl structure in the molecule have a high molecular extinction coefficient and a molecular aspect ratio (the length of the molecule in the direction perpendicular to it). The ratio of length) is high, which is advantageous for the expression of liquid crystallinity.
  • the birefringence ⁇ n is increased, and the film thickness of the cholesteric liquid crystal layer having the same bandwidth can be reduced, which is advantageous from the viewpoint of defect suppression and cost.
  • ⁇ n of the liquid crystal compound used in the present invention, particularly the polyfunctional liquid crystal compound is preferably 0.16 or more, more preferably 0.2 or more.
  • the thickness of the cholesteric liquid crystal layer is preferably 6 ⁇ m or more, and more preferably 8 ⁇ m or more. More preferably, it is more preferably 10 ⁇ m or more.
  • the film thickness may be 30 ⁇ m or less, and preferably 20 ⁇ m or less.
  • the film thickness is preferably 2 ⁇ m or more, more preferably 3 ⁇ m or more, further preferably 4 ⁇ m or more, and 5 ⁇ m or more. Is particularly preferred.
  • the film thickness is preferably 15 ⁇ m or less, more preferably 10 ⁇ m or less, preferably 8 ⁇ m or less, and particularly preferably 5.5 ⁇ m or less.
  • ⁇ n of the liquid crystal compound is the p. It can be measured according to the method described in 202.
  • the chiral agent used in the present invention is a chiral agent having no polymerizable group or only one. Specifically, it is preferably 90% by mass or more, more preferably 95% by mass or more, further preferably 99% by mass or more, and particularly preferably substantially 100% by mass with respect to the total mass of the chiral agent in the polymerizable liquid crystal composition. % May be a chiral agent having no polymerizable group or only one.
  • the chiral agent When the chiral agent has no polymerizable group or only one, the difference in the degree of polymerization from the above polyfunctional liquid crystal compound having two or more polymerizable groups increases, and the film thickness direction It is presumed that the concentration distribution of the chiral agent is easy to be attached to the film, and the wavelength band of selective reflection of the cholesteric liquid crystal layer can be expanded by ultraviolet irradiation in a short time.
  • Examples of the chiral agent are not particularly limited as long as the chiral agent has no polymerizable group or only one, and various known chiral agents (for example, liquid crystal device handbook, Chapter 3). 4-3, chiral agent for TN and STN, page 199, edited by Japan Society for the Promotion of Science, 42nd Committee, 1989).
  • the chiral agent generally contains an asymmetric carbon atom, but an axially asymmetric compound or a planar asymmetric compound containing no asymmetric carbon atom can also be used as the chiral agent.
  • Examples of the axial asymmetric compound or the planar asymmetric compound include binaphthyl, helicene, paracyclophane, and derivatives thereof.
  • the chiral agent may have a polymerizable group.
  • the chiral agent has a polymerizable group and the rod-shaped liquid crystal compound used in combination also has a polymerizable group, it is derived from the rod-shaped liquid crystal compound by a polymerization reaction between the chiral agent having a polymerizable group and the polymerizable rod-shaped liquid crystal compound.
  • a polymer having a repeating unit derived from a chiral agent can be formed.
  • the polymerizable group possessed by the chiral agent having a polymerizable group is preferably the same group as the polymerizable group possessed by the polymerizable rod-like liquid crystal compound.
  • the polymerizable group of the chiral agent is preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and still more preferably an ethylenically unsaturated polymerizable group.
  • (meth) acryloyl groups are particularly preferred.
  • the above chiral agent may be a liquid crystal compound.
  • the chiral agent exhibiting a strong twisting force include, for example, JP 2010-181852 A, JP 2003-287623 A, JP 2002-80851 A, JP 2002-80478 A, and JP 2002-80478 A.
  • Examples include chiral agents described in JP-A No. 2002-302487, which can be preferably used in the present invention.
  • isosorbide compounds having a corresponding structure can be used for the isosorbide compounds described in these publications, and isosorbide compounds having a corresponding structure can be used for the isomannide compounds described in these publications. It can also be used.
  • the addition amount of the chiral agent is preferably added so that the central wavelength of the reflection band of the cholesteric liquid crystal layer formed from the polymerizable liquid crystal composition containing the chiral agent is in the visible region of 380 nm to 780 nm. Since the twisting force varies depending on the liquid crystal compound and the chiral agent, the addition amount is appropriately adjusted depending on the combination of the liquid crystal compound and the chiral agent. As can be seen from the above HTP equation, if the HTP provided by the chiral agent is large, the amount of chiral agent added required for selective reflection at the same wavelength becomes small. When the amount of the chiral agent added is small, the HTP distribution obtained with the same concentration distribution of the chiral agent in the film thickness direction becomes large.
  • the amount of chiral agent added is 0.1 to 8% by mass with respect to the total amount of liquid crystal compounds in the polymerizable liquid crystal composition. Is preferable, 0.1 to 7% by mass is more preferable, and 0.1 to 5% by mass is particularly preferable.
  • the amount of the chiral agent added is also preferable from the viewpoint of preventing alignment defects in the cholesteric liquid crystal layer.
  • ⁇ Polymerization initiator> Although there is no restriction
  • Various photopolymerization initiators can be used without particular limitation. Examples of photopolymerization initiators include ⁇ -carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), ⁇ -hydrocarbon substituted aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos.
  • the addition amount of the photopolymerization initiator is preferably 0.01 to 20 parts by mass, and preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the liquid crystal compound.
  • the polymerization of the polyfunctional liquid crystal compound can be appropriately advanced, and by setting the initiator to 20 parts by mass or less, the polymerizable liquid crystal composition has a concentration distribution of the chiral agent. Curing can proceed.
  • the polymerizable liquid crystal composition may contain an alignment controller (may be a surfactant).
  • orientation control agent examples include compounds exemplified in [0092] and [0093] of JP-A-2005-99248, and [0076] to [0078] and [0082] of JP-A-2002-129162.
  • the compounds exemplified in JP-A-2005-99248, [0094] and [0095], and JP-A-2005-99248, [0096]. Can be mentioned.
  • alignment control agent compounds described in [0082] to [0090] of JP-A No. 2014-119605 may be used as the fluorine-based alignment control agent.
  • orientation control agent a copolymer containing a repeating unit having a fluoroaliphatic group may be used as the orientation control agent. Examples of the copolymer containing a repeating unit having a fluoroaliphatic group are disclosed in JP-A-2008-257205.
  • a copolymer comprising a structural unit derived from a fluoroaliphatic group-containing monomer described in [0051] to [0052] of the gazette and a structural unit derived from a monomer described in [0055] to [0056]; Compounds described in [0028] to [0056] of JP-A-2008-257205, JP-A-2008-111110, JP-A-2007-27218, JP-A-2007-217656, JP-A-2001-330725 And compounds described in JP-A-2005-179636, [0100] to [0118].
  • the addition amount of the alignment control agent is preferably 0.005 to 3.0 parts by mass, more preferably 0.008 to 2.0 parts by mass with respect to 100 parts by mass of the liquid crystal compound.
  • a polymerizable non-liquid crystal monomer may be added to the liquid crystal composition of the present invention.
  • the non-liquid crystalline polymerizable monomer that can be used in the present invention is not particularly limited as long as the alignment of the liquid crystal composition is not significantly inhibited.
  • compounds having a polymerization active ethylenically unsaturated group such as vinyl group, vinyloxy group, oxetanyl group, acryloyl group and methacryloyl group are preferably used.
  • the addition amount of the non-liquid crystalline polymerizable monomer is preferably in the range of 0.5 to 30 parts by mass, more preferably in the range of 1 to 20 parts by mass with respect to the liquid crystal compound.
  • the polymerizable liquid crystal composition may contain a solvent.
  • a solvent of the composition for forming each light reflection layer an organic solvent is preferably used.
  • organic solvents include amides (eg N, N-dimethylformamide), sulfoxides (eg dimethyl sulfoxide), heterocyclic compounds (eg pyridine), hydrocarbons (eg benzene, hexane), alkyl halides (eg , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone, cyclohexanone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.
  • the application of the polymerizable liquid crystal composition is carried out by using a suitable liquid crystal composition such as a roll coating method, a gravure printing method, a spin coating method, etc. It can be performed by a method of developing by a method. Furthermore, it can be performed by various methods such as a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method.
  • a coating film can be formed by discharging a polymerizable liquid crystal composition from a nozzle using an ink jet apparatus.
  • the coating film may be dried by a known method after the application of the polymerizable liquid crystal composition and before the polymerization reaction for curing. For example, it may be dried by standing or may be dried by heating.
  • the liquid crystal compound molecules in the polymerizable liquid crystal composition only need to be aligned in the steps of applying and drying the polymerizable liquid crystal composition.
  • the coating film may be dried and the solvent may be removed to obtain a cholesteric liquid crystal phase. Further, heating at a transition temperature to the cholesteric liquid crystal phase may be performed.
  • the cholesteric liquid crystal phase can be stably formed by heating to the temperature of the isotropic phase and then cooling to the cholesteric liquid crystal phase transition temperature.
  • the liquid crystal phase transition temperature of the aforementioned polymerizable liquid crystal composition is preferably in the range of 10 to 250 ° C., more preferably in the range of 10 to 150 ° C., from the viewpoint of production suitability and the like. It is preferable that the temperature is not less than the above lower limit value because a cooling step or the like is not required in order to lower the temperature to a temperature range exhibiting a liquid crystal phase.
  • Curing may be performed by ultraviolet irradiation.
  • the irradiation energy is preferably 20mJ / cm 2 ⁇ 50J / cm 2, more preferably 100mJ / cm 2 ⁇ 1,500mJ / cm 2, 100mJ / cm 2 ⁇ 800mJ / cm 2 is more preferred. It is preferable to irradiate with a light source including light emission at an irradiation ultraviolet wavelength of 200 nm to 430 nm. In order to accelerate the curing reaction, ultraviolet irradiation may be performed under heating conditions.
  • the temperature at the time of ultraviolet irradiation in the temperature range which exhibits a cholesteric liquid crystal phase so that a cholesteric liquid crystal phase may not be disturbed.
  • the oxygen concentration in the atmosphere is related to the degree of cure, if the desired degree of polymerization is not reached in the air and the film strength is insufficient, the oxygen concentration in the atmosphere is reduced by a method such as nitrogen substitution. It is preferable.
  • the oxygen concentration is preferably 10% or less, more preferably 7% or less, and most preferably 3% or less.
  • a method of increasing the irradiation amount of ultraviolet rays to be irradiated and polymerization under a nitrogen atmosphere or heating conditions are effective.
  • the cholesteric liquid crystal layer of the optical film of the present invention is a pitch gradient layer in which the helical pitch of the cholesteric liquid crystal layer is changed in the film thickness direction.
  • Various methods for forming a pitch gradient layer have been conventionally studied, and methods for changing the HTP by isomerizing a chiral agent by light irradiation during curing for forming a cholesteric liquid crystal layer have been studied.
  • the pitch gradient layer is obtained by providing the concentration distribution of the chiral agent in the film thickness direction as described above.
  • the polymerizable liquid crystal composition containing a liquid crystal compound and a chiral agent as described above before the normal curing process ⁇ illuminance 0.1 mW / cm 2 or more 100 mW / cm 2 It is preferable to perform temporary curing with the weak ultraviolet rays.
  • the illuminance means a value measured at a wavelength of 300 to 390 nm.
  • the chiral agent having no monofunctional or functional group is less likely to participate in curing, and therefore moves to the uncured side of the coating film where the curing is slow, resulting in chiral It is thought that the concentration distribution of the agent occurs.
  • UV intensity during pre-curing is preferably 0.1mW / cm 2 ⁇ 100mW / cm 2, more preferably 1mW / cm 2 ⁇ 70mW / cm 2, more preferably 5mW / cm 2 ⁇ 50mW / cm 2, 5mW / Particularly preferred is cm 2 to 30 mW / cm 2 .
  • the chiral agent in the case of the concentration distribution of the chiral agent includes a partial structure derived from the chiral agent in a product produced by reaction with a polymerizable group moiety. Further, the concentration distribution of the chiral agent may be continuous or discontinuous in the film thickness direction, but is preferably continuous.
  • the concentration of the chiral agent is preferably continuously decreased (or continuously increased) from one side of the cholesteric liquid crystal layer to the other side.
  • the conditions for ultraviolet irradiation at the time of temporary curing are not particularly limited as long as the illuminance is 0.1 mW / cm 2 or more to 100 mW / cm 2 .
  • the ultraviolet irradiation may be performed in an air atmosphere or a nitrogen atmosphere.
  • ultraviolet latitude irradiation may be performed from any side of the coating film. For example, it may be performed from the support side or from the opposite side.
  • the ultraviolet irradiation at the time of temporary curing may be 30 seconds or less.
  • the ultraviolet irradiation time at the time of temporary hardening may be short, it is not necessary to reduce line speed in a manufacturing line, and it is preferable.
  • the ultraviolet irradiation during temporary curing is preferably longer than 1 second and shorter than 25 seconds, and more preferably 2 seconds to 22 seconds.
  • ultraviolet irradiation may be performed while heating.
  • the heating temperature can be adjusted according to the phase transition point of the polymerizable liquid crystal composition, and the concentration distribution of the chiral agent can be controlled by the heating temperature.
  • the heating temperature is preferably from room temperature to 200 ° C, more preferably from room temperature to 150 ° C.
  • ultraviolet rays may be irradiated through a wavelength cut filter that cuts a specific wavelength at the time of ultraviolet irradiation.
  • a wavelength cut filter that cuts a specific wavelength at the time of ultraviolet irradiation.
  • the wavelength cut filter to be used can be appropriately selected according to the absorption wavelength and extinction coefficient of the liquid crystal compound and the initiator and the amount of the initiator added.
  • the concentration distribution of the chiral agent can be adjusted by selectively irradiating ultraviolet light having a wavelength that the polyfunctional liquid crystal compound absorbs with a wavelength cut filter to adjust the progress of curing in the coating film.
  • the main curing may be performed with a higher illuminance than in the temporary curing. For example, 30 mW / cm 2 greater than 300 mW / cm 2 or less, 40 mW / cm 2 greater than 200 mW / cm 2 or less, may be performed in such large 100 mW / cm 2 or less than 50 mW / cm 2.
  • the ultraviolet irradiation conditions in the main curing are not particularly limited as long as the irradiation is performed with a higher dose than in the temporary curing and the cholesteric liquid crystal phase can be fixed.
  • the ultraviolet irradiation may be performed in an air atmosphere or a nitrogen atmosphere.
  • ultraviolet latitude irradiation may be performed from any side of the coating film.
  • it may be performed from the support side or from the opposite side.
  • the ultraviolet irradiation time for the main curing is not particularly limited, but may be about 0.5 seconds to 3 minutes, and preferably about 1 second to 1 minute.
  • ultraviolet rays may be irradiated through a filter that cuts a specific wavelength.
  • the temporary curing there is a difference in the degree of curing of the liquid crystal compound in the coating film. That is, it is considered that it is a semi-hardened state when viewed in the whole film thickness direction. A film in such a state is concerned with durability and winding ability in continuous roll production. In consideration of these, it is desired to sufficiently cure by adding a large amount of an initiator. However, if the curing rate is too high, it is disadvantageous for obtaining a broadband cholesteric liquid crystal film as described above.
  • a wavelength cut filter is used so that the curing speed does not become too fast.
  • the fixing step main curing step
  • the main curing may be performed by heating.
  • the main curing is performed by the ultraviolet irradiation, it is preferable not to include a heating step between the temporary curing and the main curing. This is because by using the polymerizable liquid crystal composition having the above composition, a pitch gradient layer can be produced by performing ultraviolet irradiation for 30 seconds or less and without including a heating step.
  • the heating step here may be heating to a temperature higher than room temperature, preferably heating to 50 ° C. or higher, and particularly preferably heating to 70 ° C. or higher.
  • the optical film of the present invention may include an alignment layer.
  • the alignment layer is used to align the molecules of the liquid crystal compound in the polymerizable liquid crystal composition when forming the cholesteric liquid crystal layer.
  • the alignment layer only needs to be used in the formation of the cholesteric liquid crystal layer, and the alignment layer may or may not be included in the optical film.
  • the alignment layer examples include a rubbing-treated alignment layer of an organic compound (preferably a polymer), an oblique deposition alignment layer of an inorganic compound such as SiO, and an alignment layer obtained by forming a layer having microgrooves. Furthermore, a photo-alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. Depending on the material of the lower layer such as a support, the support can be directly functioned as an alignment layer by performing an alignment treatment (for example, rubbing treatment) without providing an alignment layer.
  • An example of such a lower layer support is PET.
  • the lower light reflecting layer may behave as an alignment layer, and the liquid crystal compound for producing the upper light reflecting layer may be aligned.
  • the upper liquid crystal compound can be aligned without providing an alignment layer or without performing a special alignment process (for example, rubbing process).
  • Examples of the polymer that can be used for the rubbing treatment oriented layer include, for example, a methacrylate copolymer, a styrene copolymer, a polyolefin, polyvinyl alcohol, and the like described in paragraph No. [0022] of JP-A-8-338913.
  • Examples include modified polyvinyl alcohol, poly (N-methylolacrylamide), polyester, polyimide, vinyl acetate copolymer, carboxymethylcellulose, and polycarbonate.
  • Silane coupling agents can be used as the polymer.
  • Poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol, polyester and polyimide are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol, polyester and polyimide are most preferred. preferable.
  • the aforementioned composition is applied to the rubbing-treated surface of the alignment layer to align the molecules of the liquid crystal compound. After that, if necessary, the alignment layer polymer and the polyfunctional monomer contained in the optically anisotropic layer are reacted, or the alignment layer polymer is crosslinked using a crosslinking agent, thereby the optical anisotropy described above.
  • a layer can be formed.
  • the film thickness of the alignment layer is preferably in the range of 0.1 to 10 ⁇ m.
  • the surface of the lower layer such as the support or the alignment layer coated with the polymerizable liquid crystal composition may be rubbed as necessary.
  • the rubbing treatment can be generally performed by rubbing the surface of a film containing a polymer as a main component with paper or cloth in a certain direction.
  • a general method of rubbing is described in, for example, “Liquid Crystal Handbook” (issued by Maruzen, October 30, 2000).
  • the rubbing density (L) is quantified by the following formula (A).
  • Formula (A) L Nl (1 + 2 ⁇ rn / 60v)
  • N is the number of rubbing
  • l is the contact length of the rubbing roller
  • r is the radius of the roller
  • n is the number of rotations (rpm) of the roller
  • v is the stage moving speed (second speed).
  • the rubbing frequency should be increased, the contact length of the rubbing roller should be increased, the radius of the roller should be increased, the rotation speed of the roller should be increased, and the stage moving speed should be decreased, while the rubbing density should be decreased. To do this, you can reverse this.
  • the description in Japanese Patent No. 4052558 can also be referred to as conditions for the rubbing process.
  • the optical film of the present invention may include a support.
  • a support body can function as a layer which supports the layer formed from the composition containing a liquid crystal compound.
  • the optical film of the present invention may not include a support for forming a cholesteric liquid crystal layer.
  • glass or a transparent film is used as a support for forming a cholesteric liquid crystal layer. After forming the film, only the cholesteric liquid crystal layer may be peeled off from the support during film formation to form the optical film of the present invention.
  • polymer film materials used as the support include cellulose acylate films (for example, cellulose triacetate film (refractive index 1.48), cellulose diacetate film, cellulose acetate butyrate film, cellulose acetate propionate film).
  • Polyolefins such as polyethylene and polypropylene, polyester resin films such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyether sulfone films, polyacrylic resin films such as polymethyl methacrylate, polyurethane resin films, polyester films, polycarbonate films , Polysulfone film, polyether film, polymethylpentene film, polyetherketone film (Meth) acrylonitrile film, polyolefin, polymer having an alicyclic structure (norbornene resin (Arton: trade name, manufactured by JSR Corporation, amorphous polyolefin (ZEONEX: trade name, manufactured by ZEON Corporation)), etc. Of these, triacetyl cellulose, polyethylene tere
  • the thickness of the transparent support may be about 5 ⁇ m to 150 ⁇ m, preferably 5 ⁇ m to 80 ⁇ m, and more preferably 20 ⁇ m to 60 ⁇ m.
  • the transparent support may be composed of a plurality of laminated layers. A thinner one is preferable for suppressing external light reflection, but if it is thinner than 5 ⁇ m, the strength of the film tends to be low, which tends to be undesirable.
  • the transparent support may be subjected to surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment). .
  • An adhesive layer undercoat layer may be provided on the support.
  • the long support is provided with inorganic particles having an average particle size of about 10 to 100 nm in order to provide slippage in the transport process and to prevent sticking between the back surface and the surface after winding. It is preferable to use a polymer layer in which 5% to 40% of the solid content is mixed and formed on one side of the support by coating or co-casting with the support.
  • Example 1 The following coating liquid was prepared as a composition for forming a cholesteric liquid crystal layer.
  • Cholesteric liquid crystal layer forming composition ⁇ The following liquid crystal compound (LC1) 100 parts by mass The following chiral agent (C1) 2.5 parts by mass Photopolymerization initiator (Irgacure 819; manufactured by BASF) 0.75 parts by mass The following surfactant (W1) 0.05 Part by weight The following surfactant (W2) 0.01 part by weight Methyl ethyl ketone 250 parts by weight Cyclohexanone 50 parts by weight ⁇ ⁇
  • LC1 liquid crystal compound 100 parts by mass
  • C1 2.5 parts by mass
  • Photopolymerization initiator (Irgacure 819; manufactured by BASF) 0.75 parts by mass
  • the following surfactant (W1) 0.05 Part by weight
  • the following surfactant (W2) 0.01 part by weight Methyl ethyl ketone 250 parts by weight Cyclohexanone 50 parts by weight ⁇
  • the surface of PET (Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) having a film thickness of 75 ⁇ m was rubbed using a rubbing apparatus. At this time, the longitudinal direction of the long film and the transport direction were parallel, and the rotation axis of the rubbing roller was 45 ° clockwise relative to the longitudinal direction of the film.
  • the coating liquid was applied to a PET rubbing surface using a wire bar so as to have a film thickness of 3 ⁇ m to form a film made of a polymerizable liquid crystal composition. Next, this film was heated at 70 ° C. for 1 minute to perform cholesteric alignment treatment. Thereafter, the coating film cooled to 25 ° C.
  • UV irradiation apparatus EXECURE 3000-W manufactured by HOYA
  • UVR-T1 UVR-T36; manufactured by TOPCON
  • a transmission spectrum was measured in the range of 400 nm to 800 nm before and after UV irradiation using an AxoScan from Axometrix. Two wavelengths at which the transmittance was 0.7 were read, and the difference was calculated as a reflection band (half width).
  • the chiral agent had a concentration distribution in the film thickness direction.
  • the optical film was cut obliquely at an angle of 1 ° with respect to the coated surface, and the cross section and surface of the produced film were measured with a time-of-flight secondary ion mass spectrometer (TOF-SIMS).
  • the above liquid crystal compound (LC1) 0.5 mg was dissolved in 50 ml of acetolitol.
  • the obtained solution was transferred to a quartz glass container (optical path length 1 cm), and absorbance was measured every 1 nm in the wavelength range of 250 to 500 nm using a spectrophotometer UV3150 (Shimadzu Corporation).
  • the molar extinction coefficient at each wavelength was calculated from the measured values, and the average value of the values of 300 to 400 nm was calculated.
  • Examples 2 to 6 Comparative Examples 1 to 3>
  • the liquid crystal compound, chiral agent, photopolymerization initiator, surfactant, film thickness, provisional curing conditions at the time of forming the cholesteric liquid crystal layer, and the substrate on which the polymerizable liquid crystal composition is applied are changed as shown in Table 1.
  • optical films of Examples 2 to 6 and Comparative Examples 1 to 3 were produced.
  • the average molar extinction coefficient of the liquid crystal compound used was also measured in the same manner.
  • the obtained optical film was evaluated for the reflection band and the concentration distribution of the chiral agent in the same manner as in Example 1.
  • the evaluation results of the reflection band are shown in Table 1.
  • the results are shown in Table 1.
  • the photopolymerization initiators in Table 1 are as follows. Irg819 (Irgacure 819; manufactured by BASF) Irg907 (Irgacure 907; manufactured by BASF) OXE02 (Irgacure OXE02; manufactured by BASF)
  • TAC alignment film and “ ⁇ / 4 plate” in Table 1 were prepared as follows.
  • the side surface of the alignment layer was used for the TAC alignment film, and the side surface of the optical anisotropic layer was used for the ⁇ / 4 plate after being rubbed in the same manner as the above PET surface.
  • TAC alignment film Cellulose acylate film T1 (“TD40UL” (manufactured by FUJIFILM Corporation) is passed through a dielectric heating roll at a temperature of 60 ° C., and the film surface temperature is raised to 40 ° C., and then the composition shown below on one side of the film was applied at a coating amount of 14 ml / m 2 using a bar coater and heated to 110 ° C. It was transported for 10 seconds under a steam far-infrared heater manufactured by Noritake Company Limited. Using a bar coater, pure water was applied at a rate of 3 ml / m 2. Next, washing with a fountain coater and draining with an air knife were repeated three times, followed by transporting to a drying zone at 70 ° C. for 10 seconds to dry, An alkali saponified cellulose acylate film was prepared.
  • alignment film coating solution having the following composition was continuously applied with a # 14 wire bar. Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds.
  • Composition of alignment film coating solution ⁇ Denatured polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde 0.5 parts by weight Photopolymerization initiator (Irgacure 2959, manufactured by BASF) 0.3 parts by weight ⁇ ⁇
  • the coating liquid was heated with warm air of 130 ° C. for 90 seconds. Subsequently, UV irradiation was performed at 80 ° C. to fix the orientation of the liquid crystal compound, and an optically anisotropic layer that was a ⁇ / 4 plate was formed. Thereafter, UV irradiation was performed at 50 mW for 6 seconds in a nitrogen atmosphere (UV irradiation amount was 300 mJ / cm ⁇ 1 ).

Abstract

The present invention provides an optical film having a cholesteric liquid crystal layer, wherein the cholesteric liquid crystal layer is a layer obtained by curing a polymerizable liquid crystal composition containing a polyfunctional liquid crystal compound and a chiral agent, the polyfunctional liquid crystal compound has two or more polymerizable groups and has an average molar absorption coefficient, at 300-400 nm, of 5000 or higher, the chiral agent has no or only one polymerizable group, and, in the cholesteric liquid crystal layer, the chiral agent has a concentration distribution in the film thickness direction. The present invention also provides a production method for an optical film having a cholesteric liquid crystal layer, wherein the production method comprises forming the cholesteric liquid crystal layer by curing a coating film of a polymerizable liquid crystal composition containing a polyfunctional liquid crystal compound and a chiral agent, and the curing comprises a precuring step including irradiation with ultraviolet rays having an illuminance of 0.1-100 mW/cm2 for 30 seconds or less. According to the present invention, an optical film having a cholesteric liquid crystal layer that shows selective reflection in a broad wavelength band can be produced at a high productivity.

Description

コレステリック液晶層を含む光学フィルム、およびコレステリック液晶層を含む光学フィルムの製造方法Optical film including cholesteric liquid crystal layer and method for producing optical film including cholesteric liquid crystal layer
　本発明は、コレステリック液晶層を含む光学フィルムに関する。より詳しくは、本発明は、広い波長帯域で選択反射を示すコレステリック液晶層を含む光学フィルムに関する。また、本発明はコレステリック液晶層を含む光学フィルムの製造方法に関する。 The present invention relates to an optical film including a cholesteric liquid crystal layer. More specifically, the present invention relates to an optical film including a cholesteric liquid crystal layer exhibiting selective reflection in a wide wavelength band. The present invention also relates to a method for producing an optical film including a cholesteric liquid crystal layer.
　コレステリック液晶相はその螺旋ピッチと相関する反射中心波長を有する選択反射を示すことが知られている。コレステリック液晶相を固定した層（以下、本明細書において、「コレステリック液晶層」ということがある。）において、螺旋ピッチを層の厚み方向で変化させた層（ピッチグラジエント層またはＰＧ層とも言う）により、均一な螺旋ピッチを有するコレステリック液晶相を固定した層よりも選択反射の波長帯域の範囲を広げ、広範な波長領域で選択反射を示す広帯域反射フィルムを得ることができる。 It is known that the cholesteric liquid crystal phase exhibits selective reflection having a reflection center wavelength correlated with the helical pitch. In a layer in which a cholesteric liquid crystal phase is fixed (hereinafter sometimes referred to as “cholesteric liquid crystal layer” in this specification), a layer in which the helical pitch is changed in the thickness direction of the layer (also referred to as a pitch gradient layer or a PG layer) Thus, it is possible to obtain a broadband reflection film that expands the range of the selective reflection wavelength band more than the layer in which the cholesteric liquid crystal phase having a uniform helical pitch is fixed, and exhibits selective reflection in a wide wavelength range.
　ピッチグラジエント層を得る方法としては、コレステリック液晶層を液晶化合物およびカイラル剤を含む重合性液晶組成物の塗布膜の硬化により形成する際に、微弱な紫外線照射工程を含ませる方法が、例えば特許文献１～４で見られるように、知られている。 As a method for obtaining a pitch gradient layer, a method of including a weak ultraviolet irradiation step when forming a cholesteric liquid crystal layer by curing a coating film of a polymerizable liquid crystal composition containing a liquid crystal compound and a chiral agent, for example, Patent Document Known as seen in 1-4.
ＵＳ２０１０／０２０８１９１Ａ１US2010 / 0208191A1 特開２００９－４２７６４号公報JP 2009-42764 A 特許第５１５１２２８号Japanese Patent No. 5151228 特開２００３－３０６４９０号公報JP 2003-306490 A
　しかしながら、特許文献１～４に記載のピッチグラジエントコレステリック液晶層の製造方法では、微弱な紫外線照射のための時間が長く、または、微弱な紫外線照射の後に加熱が必要であった。コレステリック液晶層を含むフィルムの連続生産時に紫外線照射のために必要な時間が長いとラインスピードを落とす必要が生じ、また、加熱が必要であると微弱な紫外線照射ゾーンの後に加熱ゾーンを設置する必要がある。このような観点から、特許文献１～４に記載のピッチグラジエントコレステリック液晶層、またはその製造方法には、生産性の観点でまだ改善の余地がある。 However, in the method for producing a pitch gradient cholesteric liquid crystal layer described in Patent Documents 1 to 4, it takes a long time for weak ultraviolet irradiation, or heating is necessary after weak ultraviolet irradiation. If the time required for UV irradiation is long during continuous production of a film containing a cholesteric liquid crystal layer, it will be necessary to reduce the line speed, and if heating is required, it will be necessary to install a heating zone after the weak UV irradiation zone There is. From such a viewpoint, the pitch gradient cholesteric liquid crystal layer described in Patent Documents 1 to 4 or the manufacturing method thereof still has room for improvement from the viewpoint of productivity.
　本発明は、広い波長帯域で選択反射を示すコレステリック液晶層を含む光学フィルムの提供を課題とする。本発明はまた、広い波長帯域で選択反射を示すコレステリック液晶層を含む光学フィルムを生産性高く製造する方法を提供することを課題とする。 An object of the present invention is to provide an optical film including a cholesteric liquid crystal layer exhibiting selective reflection in a wide wavelength band. Another object of the present invention is to provide a method for producing an optical film including a cholesteric liquid crystal layer exhibiting selective reflection in a wide wavelength band with high productivity.
　本発明者らはコレステリック液晶層の形成に用いられる液晶組成物について様々に検討を行い、液晶化合物およびカイラル剤の選択によって、液晶組成物の硬化過程のコントロールが可能であることを見出し、この知見に基づいて、さらに検討を行って本発明を完成させた。 The present inventors have made various studies on the liquid crystal composition used for forming the cholesteric liquid crystal layer, and found that the curing process of the liquid crystal composition can be controlled by selecting the liquid crystal compound and the chiral agent. Based on the above, further studies were made to complete the present invention.
　すなわち、本発明は以下［１］～［１４］を提供するものである。
［１］コレステリック液晶層を含む光学フィルムであって、
上記コレステリック液晶層は多官能液晶化合物およびカイラル剤を含む重合性液晶組成物を硬化した層であり、
上記多官能液晶化合物は、重合性基を２つ以上有し、かつ
３００ｎｍ～４００ｎｍにおける平均モル吸光係数が５０００以上であり、
上記カイラル剤は、重合性基を有していないかまたは１つのみ有しており、
上記コレステリック液晶層において、上記カイラル剤は膜厚方向に濃度分布を有する光学フィルム。
［２］上記多官能液晶化合物が、上記重合性液晶組成物に含まれる液晶化合物の総量の９０質量％以上である［１］に記載の光学フィルム。
［３］上記重合性液晶組成物において、上記カイラル剤の総量が液晶化合物の総量に対して８質量％以下である［１］または［２］に記載の光学フィルム。
［４］上記重合性液晶組成物において、上記カイラル剤の総量が液晶化合物の総量に対して０．１～５質量％である［１］または［２］に記載の光学フィルム。 That is, the present invention provides the following [1] to [14].
[1] An optical film including a cholesteric liquid crystal layer,
The cholesteric liquid crystal layer is a layer obtained by curing a polymerizable liquid crystal composition containing a polyfunctional liquid crystal compound and a chiral agent,
The polyfunctional liquid crystal compound has two or more polymerizable groups and an average molar extinction coefficient at 300 to 400 nm of 5000 or more,
The above chiral agent has no polymerizable group or only one,
In the cholesteric liquid crystal layer, the chiral agent has a concentration distribution in a film thickness direction.
[2] The optical film according to [1], wherein the polyfunctional liquid crystal compound is 90% by mass or more of the total amount of liquid crystal compounds contained in the polymerizable liquid crystal composition.
[3] The optical film as described in [1] or [2], wherein in the polymerizable liquid crystal composition, the total amount of the chiral agent is 8% by mass or less based on the total amount of the liquid crystal compound.
[4] The optical film as described in [1] or [2], wherein in the polymerizable liquid crystal composition, the total amount of the chiral agent is 0.1 to 5% by mass based on the total amount of the liquid crystal compound.
［５］コレステリック液晶層の選択反射の中心波長が４００～８００ｎｍの波長領域内にある［１］～［４］のいずれか一項に記載の光学フィルム。
［６］上記多官能液晶化合物が棒状液晶化合物である［１］～［５］のいずれか一項に記載の光学フィルム。
［７］上記多官能液晶化合物が分子内に、トラン構造、アゾメチン構造、アジン構造またはシンナモイル構造を有する［６］に記載の光学フィルム。
［８］上記多官能液晶化合物が以下の化合物のいずれかである［６］に記載の光学フィルム。 [5] The optical film according to any one of [1] to [4], wherein the central wavelength of selective reflection of the cholesteric liquid crystal layer is in a wavelength region of 400 to 800 nm.
[6] The optical film according to any one of [1] to [5], wherein the polyfunctional liquid crystal compound is a rod-like liquid crystal compound.
[7] The optical film according to [6], wherein the polyfunctional liquid crystal compound has a tolan structure, an azomethine structure, an azine structure, or a cinnamoyl structure in the molecule.
[8] The optical film as described in [6], wherein the polyfunctional liquid crystal compound is one of the following compounds.
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000002
［９］上記コレステリック液晶層の膜厚が３μm以上である［７］または［８］に記載の光学フィルム。
［１０］コレステリック液晶層を含む光学フィルムの製造方法であって、
上記コレステリック液晶層を多官能液晶化合物およびカイラル剤を含む重合性液晶組成物の塗布膜を硬化することにより形成することを含み、上記硬化が、照度０．１ｍＷ／ｃｍ2～１００ｍＷ／ｃｍ2の紫外線を３０秒以下照射する仮硬化工程を含む、製造方法。
［１１］上記仮硬化の紫外線照射を加熱しながら行う［１０］に記載の製造方法。 [9] The optical film as described in [7] or [8], wherein the cholesteric liquid crystal layer has a thickness of 3 μm or more.
[10] A method for producing an optical film including a cholesteric liquid crystal layer,
Forming the cholesteric liquid crystal layer by curing a coating film of a polymerizable liquid crystal composition containing a polyfunctional liquid crystal compound and a chiral agent, wherein the curing has an illuminance of 0.1 mW / cm 2 to 100 mW / cm 2 . A production method comprising a temporary curing step of irradiating ultraviolet rays for 30 seconds or less.
[11] The production method according to [10], wherein the pre-curing ultraviolet irradiation is performed while heating.
［１２］上記仮硬化工程の後に、紫外線を上記仮硬化の際よりも強い照度で照射する本硬化工程を含む［１０］または［１１］に記載の製造方法。
［１３］上記仮硬化工程と上記本硬化工程との間に、５０℃以上に加熱する加熱工程を含まない［１２］に記載の製造方法。
［１４］上記仮硬化工程で波長カットフィルターを用いる［１０］～［１３］のいずれか一項に記載の製造方法。 [12] The production method according to [10] or [11], including a main curing step of irradiating ultraviolet rays with an illuminance stronger than that during the temporary curing after the temporary curing step.
[13] The manufacturing method according to [12], which does not include a heating step of heating to 50 ° C. or higher between the temporary curing step and the main curing step.
[14] The production method according to any one of [10] to [13], wherein a wavelength cut filter is used in the temporary curing step.
　本発明により、広い波長帯域で選択反射を示すコレステリック液晶層を含む光学フィルムが提供される。本発明の光学フィルムは生産性の高い方法で製造することができる。 The present invention provides an optical film including a cholesteric liquid crystal layer exhibiting selective reflection in a wide wavelength band. The optical film of the present invention can be produced by a highly productive method.
　以下、本発明を詳細に説明する。
　以下に記載する構成要件の説明は、本発明の代表的な実施態様に基づいてなされることがあるが、本発明はそのような実施態様に限定されるものではない。なお、本明細書において「～」を用いて表される数値範囲は、「～」の前後に記載される数値を下限値および上限値として含む範囲を意味する。 Hereinafter, the present invention will be described in detail.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
　本明細書中、ピークの「半値幅」とは、ピーク高さ１／２でのピークの幅のことを言う。光反射層の反射中心波長と半値幅は下記のように求めることができる。
　Ａｘｏｍｅｔｒｉｘ社のＡｘｏＳｃａｎを用いて、光反射層の透過スペクトルを測定すると、透過率が低下する波長帯域が見られる。この最も大きいピーク高さの１／２の高さの透過率となる２つの波長のうち、短波側の波長の値をλ１（ｎｍ）、長波側の波長の値をλ２（ｎｍ）とすると、反射中心波長と半値幅は下記式で表すことができる。
反射中心波長＝（λ１＋λ２）／２
半値幅＝（λ２－λ１） In the present specification, the “half width” of a peak means the width of the peak at a peak height of 1/2. The reflection center wavelength and half width of the light reflection layer can be obtained as follows.
When the transmission spectrum of the light reflection layer is measured using AxoScan of Axometrix, a wavelength band in which the transmittance decreases can be seen. Of the two wavelengths having a transmittance of 1/2 the maximum peak height, the wavelength value on the short wave side is λ1 (nm) and the wavelength value on the long wave side is λ2 (nm). The reflection center wavelength and the half width can be expressed by the following formula.
Reflection center wavelength = (λ1 + λ2) / 2
Half width = (λ2-λ1)
　本明細書において、Ｒｅ（λ）は、波長λにおける面内のレターデーションを表す。単位はいずれもｎｍである。Ｒｅ（λ）はＫＯＢＲＡ　２１ＡＤＨ、またはＷＲ（王子計測機器（株）製）において、波長λｎｍの光をフィルム法線方向に入射させて測定される。測定波長λｎｍの選択にあたっては、波長選択フィルターをマニュアルで交換するか、または測定値をプログラム等で変換して測定することができる。 In this specification, Re (λ) represents in-plane retardation at wavelength λ. The unit is nm. Re (λ) is measured with KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments) by allowing light of wavelength λ nm to be incident in the normal direction of the film. In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.
　本明細書では、「可視光」とは、波長３８０ｎｍ～７８０ｎｍの光をいう。また、本明細書では、測定波長について特に付記がない場合は、測定波長は５５０ｎｍである。
　また、本明細書において、角度（例えば「９０°」等の角度）、及びその関係（例えば「直交」、「平行」、及び「４５°で交差」等）については、本発明が属する技術分野において許容される誤差の範囲を含むものとする。例えば、厳密な角度±１０°未満の範囲内であることなどを意味し、厳密な角度との誤差は、５°以下であることが好ましく、３°以下であることがより好ましい。
　また、本明細書において、コレステリック液晶層等の各部材の光学特性を示す数値、数値範囲、及び定性的な表現（例えば、「同等」、「等しい」等の表現）については、液晶表示装置やそれに用いられる部材について一般的に許容される誤差を含む数値、数値範囲及び性質を示していると解釈されるものとする。 In this specification, “visible light” means light having a wavelength of 380 nm to 780 nm. Moreover, in this specification, when there is no special mention about a measurement wavelength, a measurement wavelength is 550 nm.
Further, in the present specification, regarding the angle (for example, an angle such as “90 °”) and the relationship (for example, “orthogonal”, “parallel”, “crossing at 45 °”, etc.), the technical field to which the present invention belongs. The range of allowable error is included. For example, it means that the angle is within the range of strict angle ± 10 °, and the error from the strict angle is preferably 5 ° or less, and more preferably 3 ° or less.
Further, in this specification, numerical values, numerical ranges, and qualitative expressions (for example, expressions such as “equivalent” and “equal”) indicating optical characteristics of each member such as a cholesteric liquid crystal layer, It shall be construed to indicate numerical values, numerical ranges and properties including generally acceptable errors for the members used therein.
＜光学フィルム＞
　本発明の光学フィルムの形状は特に限定されないが、通常、シート状、フィルム状、板状などであればよい。光学フィルムは、長尺状のものであってもよく、用途に応じた大きさとなっていてもよい。例えば、光学フィルムは、用途に応じた大きさに裁断されていてもよい。なお、ここでいう「裁断」には「打ち抜き」および「切り出し」等も含むものとする。光学フィルムの用途は、特に限定されず、各種反射フィルム、反射偏光子、輝度向上フィルムなどに用いられるものであればよい。後述のように本発明の光学フィルムは広い波長帯域で選択反射を示すため、広い波長帯域での反射が好ましいまたは必要とされる用途で用いることができる。本発明の光学フィルムは、特に輝度向上フィルムに用いられることが好ましい。輝度向上フィルムは任意のλ／４板を含んで構成することができ、後述のコレステリック液晶層の形成をλ／４板表面で行ってもよく、本発明の光学フィルム表面にλ／４板形成用塗布液を塗布してλ／４板を形成してもよく、本発明の光学フィルムを別途用意されたλ／４板と貼り合わせてもよい。 <Optical film>
Although the shape of the optical film of the present invention is not particularly limited, it may be usually a sheet shape, a film shape, a plate shape, or the like. The optical film may be long and may have a size according to the application. For example, the optical film may be cut into a size according to the application. Here, “cutting” includes “punching” and “cutting out”. The use of the optical film is not particularly limited as long as it is used for various reflective films, reflective polarizers, brightness enhancement films, and the like. As will be described later, since the optical film of the present invention exhibits selective reflection in a wide wavelength band, it can be used in applications where reflection in a wide wavelength band is preferred or required. The optical film of the present invention is particularly preferably used for a brightness enhancement film. The brightness enhancement film can be configured to include an arbitrary λ / 4 plate, and a cholesteric liquid crystal layer, which will be described later, may be formed on the surface of the λ / 4 plate. A λ / 4 plate may be formed by applying a coating solution for liquid, or the optical film of the present invention may be bonded to a separately prepared λ / 4 plate.
［コレステリック液晶層］
　本発明の光学フィルムはコレステリック液晶層を含む。本明細書においてコレステリック液晶層は液晶化合物を含む重合性液晶組成物において形成されるコレステリック液晶相を固定化した層を意味する。コレステリック液晶相を固定した層は、コレステリック液晶相となっている液晶化合物の配向が保持されている層である。コレステリック液晶層は、重合性液晶組成物の硬化により、流動性が無い層が形成され、同時に、また外場や外力によって配向形態に変化を生じさせることない状態に変化した層であればよい。なお、コレステリック液晶層においては、コレステリック液晶相の光学的性質が層中において保持されていれば十分であり、層中の液晶化合物はもはや液晶性を示していなくてもよい。例えば、液晶化合物は、硬化反応により高分子量化して、もはや液晶性を失っていてもよい。 [Cholesteric liquid crystal layer]
The optical film of the present invention includes a cholesteric liquid crystal layer. In this specification, a cholesteric liquid crystal layer means a layer in which a cholesteric liquid crystal phase formed in a polymerizable liquid crystal composition containing a liquid crystal compound is fixed. The layer in which the cholesteric liquid crystal phase is fixed is a layer in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. The cholesteric liquid crystal layer may be a layer in which a layer having no fluidity is formed by curing of the polymerizable liquid crystal composition, and at the same time, the layer is changed to a state in which the alignment form is not changed by an external field or an external force. In the cholesteric liquid crystal layer, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained in the layer, and the liquid crystal compound in the layer may no longer exhibit liquid crystallinity. For example, the liquid crystal compound may have a high molecular weight due to a curing reaction and may no longer have liquid crystallinity.
　コレステリック液晶層はコレステリック液晶相の螺旋周期に基づく反射中心波長λを有する選択反射を示す。コレステリック液晶相を固定してなる光反射層は選択反射を示す波長域において、右円偏光または左円偏光のいずれか一方を選択的に反射させ、他方の円偏光を透過させる。なお、螺旋が右であるか左である下かの測定やピッチの測定法については「液晶化学実験入門」日本液晶学会編　シグマ出版２００７年出版、４６頁、および「液晶便覧」液晶便覧編集委員会　丸善　１９６頁に記載の方法を用いることができる。光学フィルムの用途に応じて、用途に適したピッチまたは螺旋の方向を有するコレステリック液晶層を単独、または複数組み合わせて用いればよい。 The cholesteric liquid crystal layer exhibits selective reflection having a reflection center wavelength λ based on the helical period of the cholesteric liquid crystal phase. The light reflection layer formed by fixing the cholesteric liquid crystal phase selectively reflects either the right circularly polarized light or the left circularly polarized light and transmits the other circularly polarized light in the wavelength region exhibiting selective reflection. As for the measurement of whether the spiral is right or left and the method of pitch measurement, “Introduction to Liquid Crystal Chemistry Experiment” edited by the Japanese Liquid Crystal Society, Sigma Publishing 2007, page 46, and “Liquid Crystal Handbook” Kai Maruzen The method described on page 196 can be used. Depending on the application of the optical film, a cholesteric liquid crystal layer having a pitch or spiral direction suitable for the application may be used alone or in combination.
　コレステリック液晶層の反射中心波長λは、コレステリック液晶相における螺旋構造のピッチＰ（螺旋の周期）に依存し、コレステリック液晶層の平均屈折率ｎとλ＝ｎ×Ｐの関係に従う。
　コレステリック液晶においては、液晶本来の常光屈折率ｎｏと異常光屈折率ｎｅを用いると、面内の平均屈折率ｎは
（ｎｘ＋ｎｙ）／２＝（ｎｏ＋ｎｅ）／２
で表される。 The reflection center wavelength λ of the cholesteric liquid crystal layer depends on the pitch P (helical period) of the helical structure in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P.
In the cholesteric liquid crystal, when the normal ordinary refractive index no and the extraordinary refractive index ne of the liquid crystal are used, the in-plane average refractive index n is (nx + ny) / 2 = (no + ne) / 2.
It is represented by
　選択反射の半値幅ΔλはΔλが液晶化合物の複屈折Δｎと上記ピッチＰに依存し、Δλ＝Δｎ×Ｐの関係に従う。上記式からわかるように、選択反射帯の幅の制御は、Δｎを調整しても行うことができる。Δｎの調整は液晶化合物の種類やその混合比率を調整したり、配向固定時の温度を制御したりすることで行うことができる。但し、現在工業化されている液晶のΔｎの上限は０．５程度であり、選択反射の半値幅Δλは、通常１種の材料では５０ｎｍ～１５０ｎｍ程度でありΔｎの調製により選択反射の波長帯域の幅の制御を行うことには限度がある。 The half-value width Δλ of selective reflection depends on the relationship of Δλ = Δn × P, where Δλ depends on the birefringence Δn of the liquid crystal compound and the pitch P. As can be seen from the above equation, the width of the selective reflection band can also be controlled by adjusting Δn. Δn can be adjusted by adjusting the type of liquid crystal compound and its mixing ratio, or by controlling the temperature at the time of fixing the alignment. However, the upper limit of Δn of liquid crystals currently industrialized is about 0.5, and the half-value width Δλ of selective reflection is usually about 50 nm to 150 nm for one kind of material, and the wavelength band of selective reflection is adjusted by adjusting Δn. There is a limit to the width control.
　本発明の光学フィルムにおいては、１つのコレステリック液晶層内において、ピッチＰを膜厚方向に対して変化させる（ピッチグラジエント）ことで広い波長帯域（例えば、半値幅で２００ｎｍ程度）で選択反射を示すコレステリック液晶層が用いられている。本発明の光学フィルムにおいては、ピッチグラジエント層を用いることで液晶のΔｎの上限から検討した範囲では達成できない広い波長帯域を得ることができる。 In the optical film of the present invention, selective reflection is exhibited in a wide wavelength band (for example, about 200 nm at half width) by changing the pitch P in the film thickness direction (pitch gradient) in one cholesteric liquid crystal layer. A cholesteric liquid crystal layer is used. In the optical film of the present invention, by using the pitch gradient layer, a wide wavelength band that cannot be achieved within the range studied from the upper limit of Δn of the liquid crystal can be obtained.
　コレステリック液晶相のピッチは液晶化合物とともに用いるカイラル剤の種類、またはその添加濃度に依存し、Ｐ＝１／（β・ｃ）で表すことができる。ここで、ｃはカイラル剤の濃度、βはカイラル剤が液晶をねじる力の指標であり、Helical Twisting Power (ＨＴＰ)と呼ばれる指標である。ＨＴＰは、カイラル剤と液晶化合物とを含む重合性液晶組成物から形成されたコレステリック液晶層の、選択反射波長λと、平均屈折率ｎ、および加えたカイラル剤濃度ｃ（質量％）から、式ＨＴＰ＝ｎ／（λ×０．０１×ｃ）を用いて算出することができる。 The pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used together with the liquid crystal compound or the concentration of the chiral agent, and can be expressed as P = 1 / (β · c). Here, c is the concentration of the chiral agent, β is an index of the force with which the chiral agent twists the liquid crystal, and is an index called Helical Twisting Power (HTP). HTP is calculated from a selective reflection wavelength λ, an average refractive index n, and an added chiral agent concentration c (mass%) of a cholesteric liquid crystal layer formed from a polymerizable liquid crystal composition containing a chiral agent and a liquid crystal compound. It can be calculated using HTP = n / (λ × 0.01 × c).
　本発明の光学フィルム中のコレステリック液晶層においてカイラル剤は膜厚方向に濃度分布を有する。そのため、コレステリック液晶層内の膜厚方向でピッチが変化し、故に、反射中心波長が変化し、広い波長帯域で選択反射を示すコレステリック液晶層を得ることができる。コレステリック液晶層において、カイラル剤に膜厚方向に濃度分布を与える方法については後述する。 In the cholesteric liquid crystal layer in the optical film of the present invention, the chiral agent has a concentration distribution in the film thickness direction. Therefore, the pitch changes in the film thickness direction in the cholesteric liquid crystal layer, and therefore the reflection center wavelength changes, and a cholesteric liquid crystal layer showing selective reflection in a wide wavelength band can be obtained. A method of giving a concentration distribution in the film thickness direction to the chiral agent in the cholesteric liquid crystal layer will be described later.
（重合性液晶組成物）
　コレステリック液晶層を形成するための重合性液晶組成物は、液晶化合物およびカイラル剤を含む。重合性液晶組成物は、配向制御剤、重合開始剤、配向助剤などのその他の成分を含有していてもよい。
　コレステリック液晶層は、重合性液晶組成物を、支持体、配向層、他のコレステリック液晶層などの他の層に塗布後、塗布膜を硬化して得ることができる。 (Polymerizable liquid crystal composition)
The polymerizable liquid crystal composition for forming a cholesteric liquid crystal layer contains a liquid crystal compound and a chiral agent. The polymerizable liquid crystal composition may contain other components such as an alignment controller, a polymerization initiator, and an alignment aid.
The cholesteric liquid crystal layer can be obtained by applying the polymerizable liquid crystal composition to another layer such as a support, an alignment layer, or another cholesteric liquid crystal layer, and then curing the coating film.
　（液晶化合物）
　液晶化合物としては、棒状液晶化合物および円盤状液晶化合物が挙げられる。液晶化合物は棒状液晶化合物であることが好ましい。
　重合性基としては特に限定はなく、（メタ）アクリロイル基、エポキシ基、オキセタニル基、ビニルエーテル基などが挙げられるが、（メタ）アクリロイル基が好ましい。
　本発明の光学フィルムのコレステリック液晶層を形成するための重合性液晶組成物は液晶化合物として、重合性基を２つ以上有する多官能液晶化合物を含む。重合性液晶組成物は液晶化合物として、重合性基が１つであるか、または重合性基を有しない液晶化合物を含んでいてもよいが、重合性基を２つ以上有する多官能液晶化合物は、重合性液晶組成物中の液晶化合物の総質量に対し、９０質量％以上であることが好ましく、９５質量％以上であることがより好ましく、９９質量％以上であることがさらに好ましく、実質的に１００質量％であることが特に好ましい。重合性基を２つ以上有することで、短時間の紫外線照射で液晶化合物の硬化が進みやすく、カイラル剤の濃度分布をもたせるために好適である。なお、本明細書において、単に「液晶化合物」というときは、「多官能液晶化合物」も含む意味である。 (Liquid crystal compound)
Examples of the liquid crystal compound include a rod-like liquid crystal compound and a disk-like liquid crystal compound. The liquid crystal compound is preferably a rod-like liquid crystal compound.
There is no limitation in particular as a polymeric group, Although a (meth) acryloyl group, an epoxy group, oxetanyl group, a vinyl ether group etc. are mentioned, A (meth) acryloyl group is preferable.
The polymerizable liquid crystal composition for forming the cholesteric liquid crystal layer of the optical film of the present invention contains a polyfunctional liquid crystal compound having two or more polymerizable groups as the liquid crystal compound. The polymerizable liquid crystal composition may include a liquid crystal compound having one polymerizable group or not having a polymerizable group as a liquid crystal compound, but a polyfunctional liquid crystal compound having two or more polymerizable groups is , Preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, substantially with respect to the total mass of the liquid crystal compound in the polymerizable liquid crystal composition. It is particularly preferable that the amount is 100% by mass. By having two or more polymerizable groups, curing of the liquid crystal compound is facilitated by irradiation with ultraviolet rays for a short time, which is suitable for providing a chiral agent concentration distribution. In this specification, the term “liquid crystal compound” simply means “polyfunctional liquid crystal compound”.
　本発明で用いられる重合性基を２つ以上有する多官能液晶化合物は、３００ｎｍ～４００ｎｍにおける平均モル吸光係数が５０００以上である。上記平均モル吸光係数は７０００以上であることが好ましい。このような光吸収特性を有する多官能液晶化合物を用いることにより、コレステリック液晶層の作製時、塗布膜の膜厚方向で硬化のために必要な紫外線の透過率に差をつけ、膜厚方向での液晶化合物の硬化に差をつけることが容易になる。本明細書において、液晶化合物の３００ｎｍ～４００ｎｍにおける平均モル吸光係数は、適切な濃度に調製した溶液を、分光光度計ＵＶ３１５０（島津製作所）を用いて２５０～５００ｎｍの範囲を１ｎｍ毎に測定、モル吸光係数を算出し、３００～４００ｎｍの範囲での平均値を計算して得られた値を意味するものとする。
　３００ｎｍ～４００ｎｍにおける平均モル吸光係数が５０００以上である液晶化合物としては、分子内に、トラン（ジフェニルアセチレン）構造、アゾメチン構造、アジン構造またはシンナモイル構造を有する液晶化合物が挙げられる。 The polyfunctional liquid crystal compound having two or more polymerizable groups used in the present invention has an average molar extinction coefficient of 5000 or more at 300 to 400 nm. The average molar extinction coefficient is preferably 7000 or more. By using a polyfunctional liquid crystal compound having such light absorption characteristics, when producing a cholesteric liquid crystal layer, a difference is made in the transmittance of ultraviolet rays necessary for curing in the film thickness direction of the coating film, and in the film thickness direction. It becomes easy to make a difference in the curing of the liquid crystal compound. In this specification, the average molar extinction coefficient at 300 nm to 400 nm of the liquid crystal compound is determined by measuring a solution prepared at an appropriate concentration in a range of 250 to 500 nm every 1 nm using a spectrophotometer UV3150 (Shimadzu Corporation). It means a value obtained by calculating an extinction coefficient and calculating an average value in a range of 300 to 400 nm.
Examples of the liquid crystal compound having an average molar extinction coefficient at 300 to 400 nm of 5000 or more include a liquid crystal compound having a tolan (diphenylacetylene) structure, an azomethine structure, an azine structure, or a cinnamoyl structure in the molecule.
　トラン構造を有する液晶化合物としては、例えば、特許第４８３６３３５号、特許第４９４７６７６号、特許第３９９９４００号、特許第３９６３０３５号、特許第４０５３７８２号、特許第４２６８０５８号、特許第４４６１６９２号、特許第５０８２５３８号、特開２０１３－１１２６３１号公報、特開２０１３－５３４６４６号公報に記載された化合物を挙げることができる。アゾメチン構造を有する液晶化合物としては、例えば、特開２０１２－００６９９６号公報、特開２０１２－００６９９７号公報、特開２０１２－００６８４３号公報、特開２０１２－００６９９６号公報に記載された化合物を挙げることができる。アジン構造を有する液晶化合物としては、例えば、特開２０１１－２０７９４０号公報、特開２０１１－２０７９４１号公報、特開２０１１－２０７９４０号公報、特許第５５１０３２１号に記載された化合物を挙げることができる。シンナモイル構造を有する液晶化合物としては、例えば特開２０１１－２０７９４２号公報に記載された化合物を挙げることができる。液晶化合物としてはこれらの液晶化合物以外でも、３００ｎｍ～４００ｎｍにおける平均モル吸光係数が５０００以上である化合物を任意に用いることができる。 Examples of the liquid crystal compound having a tolan structure include, for example, Japanese Patent No. 4836335, Japanese Patent No. 4947676, Japanese Patent No. 3999400, Japanese Patent No. 3963035, Japanese Patent No. 4053782, Japanese Patent No. 4268058, Japanese Patent No. 4461692, Japanese Patent No. 5082538. And compounds described in JP2013-112163A and JP2013-534646A. Examples of the liquid crystal compound having an azomethine structure include compounds described in JP 2012-006996 A, JP 2012-006997 A, JP 2012-006843 A, and JP 2012-006996 A. Can do. Examples of the liquid crystal compound having an azine structure include compounds described in JP2011-207940A, JP2011-207941A, JP2011-207940A, and JP5510321A. Examples of the liquid crystal compound having a cinnamoyl structure include compounds described in JP2011-207942. As the liquid crystal compound, other than these liquid crystal compounds, a compound having an average molar extinction coefficient of 300 to 400 nm of 5000 or more can be arbitrarily used.
　分子内に、トラン構造、アゾメチン構造、アジン構造またはシンナモイル構造を持つ液晶化合物は、モル吸光係数が高いことに加えて、分子のアスペクト比（分子の長軸方向長さとそれに垂直な方向の分子の長さの比）が高く、液晶性の発現に有利である。また、複屈折Δｎが高くなり同じ帯域幅のコレステリック液晶層の膜厚を薄くすることができ、欠陥の抑制やコストの観点から有利である。
　なお、本発明で用いられる液晶化合物、特に多官能液晶化合物のΔｎは、好ましくは０．１６以上、より好ましくは０．２以上であればよい。 In addition to having a high molar extinction coefficient, liquid crystal compounds with a tolan structure, azomethine structure, azine structure or cinnamoyl structure in the molecule have a high molecular extinction coefficient and a molecular aspect ratio (the length of the molecule in the direction perpendicular to it). The ratio of length) is high, which is advantageous for the expression of liquid crystallinity. Further, the birefringence Δn is increased, and the film thickness of the cholesteric liquid crystal layer having the same bandwidth can be reduced, which is advantageous from the viewpoint of defect suppression and cost.
Note that Δn of the liquid crystal compound used in the present invention, particularly the polyfunctional liquid crystal compound, is preferably 0.16 or more, more preferably 0.2 or more.
　例として、Δｎが０．１５６である液晶化合物を用いる場合であって、選択波長帯域（半値幅）４００～６００ｎｍを少なくとも有する場合は、コレステリック液晶層の膜厚は６μｍ以上が好ましく、８μｍ以上がより好ましく、１０μｍ以上が更に好ましい。また、上記膜厚は、３０μｍ以下であればよく、２０μｍ以下であることが好ましい。Δｎが０．３である液晶化合物を用いる場合であって、ピッチグラジエント帯域４００～６００ｎｍを少なくとも有する場合は、膜厚は２μｍ以上が好ましく、３μｍ以上がより好ましく、４μｍ以上が更に好ましく、５μｍ以上が特に好ましい。また、このとき、上記膜厚は、１５μｍ以下であることが好ましく、１０μｍ以下であることがより好ましく、８μｍ以下であることが好ましく、５．５μｍ以下であることが特に好ましい。
　なお、液晶化合物のΔｎは、液晶便覧（液晶便覧編集委員会）のｐ．２０２に記載の方法に従って測定することができる。 As an example, when a liquid crystal compound having Δn of 0.156 is used and has a selective wavelength band (half-value width) of 400 to 600 nm, the thickness of the cholesteric liquid crystal layer is preferably 6 μm or more, and more preferably 8 μm or more. More preferably, it is more preferably 10 μm or more. The film thickness may be 30 μm or less, and preferably 20 μm or less. In the case of using a liquid crystal compound having Δn of 0.3 and having at least a pitch gradient band of 400 to 600 nm, the film thickness is preferably 2 μm or more, more preferably 3 μm or more, further preferably 4 μm or more, and 5 μm or more. Is particularly preferred. At this time, the film thickness is preferably 15 μm or less, more preferably 10 μm or less, preferably 8 μm or less, and particularly preferably 5.5 μm or less.
In addition, Δn of the liquid crystal compound is the p. It can be measured according to the method described in 202.
（カイラル剤）
　本発明で用いられるカイラル剤は、重合性基を有していないかまたは１つのみ有しているカイラル剤である。具体的には重合性液晶組成物中のカイラル剤の総質量に対し、好ましくは９０質量％以上、より好ましくは９５質量％以上、さらに好ましくは９９質量％以上、特に好ましくは実質的に１００質量％が重合性基を有していないかまたは１つのみ有しているカイラル剤であればよい。カイラル剤が重合性基を有していないかまたは１つのみ有していることで、重合性基を２つ以上有する上記の多官能液晶化合物との重合度の差が大きくなり、膜厚方向でのカイラル剤の濃度分布がつきやすく、短時間での紫外線照射でコレステリック液晶層の選択反射の波長帯域を広げることができると推定している。 (Chiral agent)
The chiral agent used in the present invention is a chiral agent having no polymerizable group or only one. Specifically, it is preferably 90% by mass or more, more preferably 95% by mass or more, further preferably 99% by mass or more, and particularly preferably substantially 100% by mass with respect to the total mass of the chiral agent in the polymerizable liquid crystal composition. % May be a chiral agent having no polymerizable group or only one. When the chiral agent has no polymerizable group or only one, the difference in the degree of polymerization from the above polyfunctional liquid crystal compound having two or more polymerizable groups increases, and the film thickness direction It is presumed that the concentration distribution of the chiral agent is easy to be attached to the film, and the wavelength band of selective reflection of the cholesteric liquid crystal layer can be expanded by ultraviolet irradiation in a short time.
　カイラル剤の例としては、重合性基を有していないかまたは１つのみ有しているカイラル剤であれば特に制限はなく、公知の種々のカイラル剤（例えば、液晶デバイスハンドブック、第３章４－３項、ＴＮ、ＳＴＮ用カイラル剤、１９９頁、日本学術振興会第一４２委員会編、１９８９に記載）を用いることができる。カイラル剤は、一般に不斉炭素原子を含むが、不斉炭素原子を含まない軸性不斉化合物あるいは面性不斉化合物もカイラル剤として用いることができる。軸性不斉化合物または面性不斉化合物の例には、ビナフチル、ヘリセン、パラシクロファンおよびこれらの誘導体が含まれる。カイラル剤は、重合性基を有していてもよい。カイラル剤が重合性基を有するとともに、併用する棒状液晶化合物も重合性基を有する場合は、重合性基を有するカイラル剤と重合性棒状液晶合物との重合反応により、棒状液晶化合物から誘導される繰り返し単位と、カイラル剤から誘導される繰り返し単位とを有するポリマーを形成することができる。この態様では、重合性基を有するカイラル剤が有する重合性基は、重合性棒状液晶化合物が有する重合性基と、同種の基であることが好ましい。カイラル剤の重合性基は、不飽和重合性基、エポキシ基またはアジリジニル基であることが好ましく、不飽和重合性基であることがより好ましく、エチレン性不飽和重合性基であることがさらに好ましく、（メタ）アクリロイル基であることが特に好ましい。 Examples of the chiral agent are not particularly limited as long as the chiral agent has no polymerizable group or only one, and various known chiral agents (for example, liquid crystal device handbook, Chapter 3). 4-3, chiral agent for TN and STN, page 199, edited by Japan Society for the Promotion of Science, 42nd Committee, 1989). The chiral agent generally contains an asymmetric carbon atom, but an axially asymmetric compound or a planar asymmetric compound containing no asymmetric carbon atom can also be used as the chiral agent. Examples of the axial asymmetric compound or the planar asymmetric compound 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, it is derived from the rod-shaped liquid crystal compound by a polymerization reaction between the chiral agent having a polymerizable group and the polymerizable rod-shaped liquid crystal compound. And a polymer having a repeating unit derived from a chiral agent can be formed. In this embodiment, the polymerizable group possessed by the chiral agent having a polymerizable group is preferably the same group as the polymerizable group possessed by the polymerizable rod-like liquid crystal compound. The polymerizable group of the chiral agent is preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and still more preferably an ethylenically unsaturated polymerizable group. And (meth) acryloyl groups are particularly preferred.
　また、上述のカイラル剤は、液晶化合物であってもよい。
　強い捩れ力（高いＨＴＰ）を示すカイラル剤としては、例えば、特開２０１０－１８１８５２号公報、特開２００３－２８７６２３号公報、特開２００２－８０８５１号公報、特開２００２－８０４７８号公報、特開２００２－３０２４８７号公報に記載のカイラル剤などが挙げられ、本発明に好ましく用いることができる。さらに、これらの公開公報に記載されているイソソルビド化合物類については対応する構造のイソマンニド化合物類を用いることもでき、これらの公報に記載されているイソマンニド化合物類については対応する構造のイソソルビド化合物類を用いることもできる。そのほか、特開２０１０－１８１８５２号、特開２００３－２８７６２３号、特開２００２－８０８５１号、特開２００２－８０４７８号、特開２００２－１７９６８１号、特開２００２－１７９６８２号、特開２００２－３３８５７５号、特開２００３－３０６４９０号、特開２００３－３１３１８８号、特開２００２－３０２４８７号、特開２００７－２７１８０８号、特開２００２－１８００５１号、特開２００３－０７３６６９号、特開２００３－０５５３１５号、特開２００２－１７９６６８号、特開２００２－１７９６６９号、特開２００２－１７９６７０号、特許第５２９５９４６号、特表２００９－５１４７９９号、特開２００４－２５０３９７号、特開２００４－２５０３４１号、特開２０１３－２２７３０８号、特開２０１３－１３６７４０号、特許第４２３４９３９号、特許第５３９０３０号、特許第４８０２４７９号、特許第５０７６４１４号、特許第５４９３６２９号、特開２００２－１７９６３３号、および特開２０３－０７３３８１号の各公報、ならびにＵＳ６５１４５７８、ＷＯ２００７／０３９１０４、ＵＳ２０１０／０２０８１９１、ＵＳ２０１４／１１７２８４、およびＵＳ８７０９２８１に記載のカイラル剤を用いることもできる。 Further, the above chiral agent may be a liquid crystal compound.
Examples of the chiral agent exhibiting a strong twisting force (high HTP) include, for example, JP 2010-181852 A, JP 2003-287623 A, JP 2002-80851 A, JP 2002-80478 A, and JP 2002-80478 A. Examples include chiral agents described in JP-A No. 2002-302487, which can be preferably used in the present invention. Furthermore, isosorbide compounds having a corresponding structure can be used for the isosorbide compounds described in these publications, and isosorbide compounds having a corresponding structure can be used for the isomannide compounds described in these publications. It can also be used. In addition, JP 2010-181852, JP 2003-287623, JP 2002-80851, JP 2002-80478, JP 2002-179681, JP 2002-179682, JP 2002-338575. JP, 2003-306490, JP, 2003-313188, JP, 2002-302487, JP, 2007-271808, JP, 2002-180051, JP, 2003-073669, JP, 2003-055315, JP 2002-179668, JP 2002-179669, JP 2002-179670, JP 5295946, JP 2009-514799, JP 2004-250397, JP 2004-250341, JP 2013 -227308, JP-A-2 13-136740, Japanese Patent No. 4234939, Japanese Patent No. 539030, Japanese Patent No. 4802479, Japanese Patent No. 5076414, Japanese Patent No. 5493629, Japanese Patent Application Laid-Open No. 2002-179633, and Japanese Patent Application Laid-Open No. 203-073381, and US Pat. No. 6,514,578. , WO2007 / 039104, US2010 / 0208191, US2014 / 117284, and US8709291 can also be used.
　カイラル剤の添加量は、そのカイラル剤を含む重合性液晶組成物から形成されるコレステリック液晶層の反射帯域の中心波長が可視領域である３８０ｎｍ～７８０ｎｍになるように添加されていることが好ましい。液晶化合物及びカイラル剤によって捩れ力が異なるため、液晶化合物とカイラル剤の組み合わせにより添加量は適宜調整される。
　上記のＨＴＰの式から分かるように、カイラル剤が与えるＨＴＰが大きいと同じ波長での選択反射に必要な、カイラル剤添加量が少量となる。そして、カイラル剤添加量が少量で済む場合、膜厚方向でのカイラル剤の同じ濃度分布で得られるＨＴＰ分布が大きくなる。したがって、十分に広い選択波長帯域を有するコレステリック液晶層が得られやすい。そして、より大きなカイラル剤の濃度分布をつけるための長い紫外線照射時間や紫外線照射後の加熱が必要ないので、生産性の観点から有利である。３０秒以内での仮硬化の紫外線照射で広帯域コレステリック液晶フィルムを得るためには、カイラル剤の添加量は、重合性液晶組成物中の液晶化合物の総量に対して、０．１～８質量％が好ましく、０．１～７質量％がより好ましく、０．１～５質量％が特に好ましい。上記のカイラル剤添加量は、コレステリック液晶層の配向欠陥を防止する観点からも好ましい。 The addition amount of the chiral agent is preferably added so that the central wavelength of the reflection band of the cholesteric liquid crystal layer formed from the polymerizable liquid crystal composition containing the chiral agent is in the visible region of 380 nm to 780 nm. Since the twisting force varies depending on the liquid crystal compound and the chiral agent, the addition amount is appropriately adjusted depending on the combination of the liquid crystal compound and the chiral agent.
As can be seen from the above HTP equation, if the HTP provided by the chiral agent is large, the amount of chiral agent added required for selective reflection at the same wavelength becomes small. When the amount of the chiral agent added is small, the HTP distribution obtained with the same concentration distribution of the chiral agent in the film thickness direction becomes large. Therefore, it is easy to obtain a cholesteric liquid crystal layer having a sufficiently wide selection wavelength band. Further, it is advantageous from the viewpoint of productivity because it does not require a long ultraviolet irradiation time or a heating after the ultraviolet irradiation for providing a larger concentration distribution of the chiral agent. In order to obtain a broadband cholesteric liquid crystal film by UV irradiation of pre-curing within 30 seconds, the amount of chiral agent added is 0.1 to 8% by mass with respect to the total amount of liquid crystal compounds in the polymerizable liquid crystal composition. Is preferable, 0.1 to 7% by mass is more preferable, and 0.1 to 5% by mass is particularly preferable. The amount of the chiral agent added is also preferable from the viewpoint of preventing alignment defects in the cholesteric liquid crystal layer.
＜重合開始剤＞
　本発明に用いることができる重合開始剤としては特に制限はないが、光重合開始剤であることが好ましい。光重合開始剤としては各種のものを特に制限なく使用できる。光重合開始剤の例には、α－カルボニル化合物（米国特許第２３６７６６１号、同２３６７６７０号の各明細書記載）、アシロインエーテル（米国特許第２４４８８２８号明細書記載）、α－炭化水素置換芳香族アシロイン化合物（米国特許第２７２２５１２号明細書記載）、多核キノン化合物（米国特許第３０４６１２７号、同２９５１７５８号の各明細書記載）、トリアリールイミダゾールダイマーとｐ－アミノフェニルケトンとの組み合わせ（米国特許第３５４９３６７号明細書記載）、アクリジンおよびフェナジン化合物（特開昭６０－１０５６６７号公報、米国特許第４２３９８５０号明細書記載）およびオキサジアゾール化合物（米国特許第４２１２９７０号明細書記載）、アシルフォスフィンオキシド化合物（特公昭６３－４０７９９号公報、特公平５－２９２３４号公報、特開平１０－９５７８８号公報、特開平１０－２９９９７号公報記載）等が挙げられる。例えば、ＢＡＳＦ製のイルガキュア１８４、イルガキュア９０７、イルガキュア３６９、イルガキュア６５１等があげられる。 <Polymerization initiator>
Although there is no restriction | limiting in particular as a polymerization initiator which can be used for this invention, It is preferable that it is a photoinitiator. Various photopolymerization initiators can be used without particular limitation. Examples of photopolymerization initiators include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US patent) No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,221,970), acylphosphine Oxide compounds (Japanese Patent Publication No. 63-40) No. 799, JP-B-5-29234, JP-A-10-95788, JP-A-10-29997) and the like. For example, BASF made Irgacure 184, Irgacure 907, Irgacure 369, Irgacure 651, and the like.
　光重合開始剤の添加量は、液晶化合物１００質量部に対し、０．０１～２０質量部が好ましく、０．１～１０質量部が好ましい。開始剤が０．０１質量部以上とすることより、多官能液晶化合物の重合を適切に進めることができ２０質量部以下とすることにより、カイラル剤の濃度分布をつけつつ重合性液晶組成物が硬化を進めることができる。 The addition amount of the photopolymerization initiator is preferably 0.01 to 20 parts by mass, and preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the liquid crystal compound. By setting the initiator to 0.01 parts by mass or more, the polymerization of the polyfunctional liquid crystal compound can be appropriately advanced, and by setting the initiator to 20 parts by mass or less, the polymerizable liquid crystal composition has a concentration distribution of the chiral agent. Curing can proceed.
（配向制御剤）
　重合性液晶組成物は、配向制御剤（界面活性剤であってもよい）を含んでいてもよい。
　配向制御剤の例としては、特開２００５－９９２４８号公報の［００９２］及び［００９３］中に例示されている化合物、特開２００２－１２９１６２号公報の［００７６］～［００７８］及び［００８２］～［００８５］中に例示されている化合物、特開２００５－９９２４８号公報の［００９４］及び［００９５］中に例示されている化合物、特開２００５－９９２４８号公報の［００９６］中に例示されている化合物を挙げることができる。 (Orientation control agent)
The polymerizable liquid crystal composition may contain an alignment controller (may be a surfactant).
Examples of the orientation control agent include compounds exemplified in [0092] and [0093] of JP-A-2005-99248, and [0076] to [0078] and [0082] of JP-A-2002-129162. To [0085], the compounds exemplified in JP-A-2005-99248, [0094] and [0095], and JP-A-2005-99248, [0096]. Can be mentioned.
　配向制御剤としては、フッ素系配向制御剤として、特開２０１４－１１９６０５号公報の［００８２］～［００９０］に記載の化合物を用いてもよい。さらに、配向制御剤としては、フルオロ脂肪族基を有する繰り返し単位を含む共重合体を用いてもよく、フルオロ脂肪族基を有する繰り返し単位を含む共重合体の例としては特開２００８－２５７２０５号公報の［００５１］～［００５２］に記載のフルオロ脂肪族基含有モノマーより誘導される構成単位と［００５５］～［００５６］に記載のモノマーより誘導される構成単位とからなる共重合体、特開２００８－２５７２０５号公報、特開２００８－１１１１１０号公報、特開２００７－２７２１８号号公報、特開２００７－２１７６５６号公報、特開２００１－３３０７２５号公報の［００２８］～［００５６］記載の化合物、特開２００５－１７９６３６号公報の［０１００］～［０１１８］に記載の化合物が挙げられる。
　配向制御剤の添加量は、液晶化合物１００質量部に対し、０．００５～３．０質量部が好ましく、０．００８～２．０質量部がより好ましい。 As the alignment control agent, compounds described in [0082] to [0090] of JP-A No. 2014-119605 may be used as the fluorine-based alignment control agent. Further, as the orientation control agent, a copolymer containing a repeating unit having a fluoroaliphatic group may be used. Examples of the copolymer containing a repeating unit having a fluoroaliphatic group are disclosed in JP-A-2008-257205. A copolymer comprising a structural unit derived from a fluoroaliphatic group-containing monomer described in [0051] to [0052] of the gazette and a structural unit derived from a monomer described in [0055] to [0056]; Compounds described in [0028] to [0056] of JP-A-2008-257205, JP-A-2008-111110, JP-A-2007-27218, JP-A-2007-217656, JP-A-2001-330725 And compounds described in JP-A-2005-179636, [0100] to [0118].
The addition amount of the alignment control agent is preferably 0.005 to 3.0 parts by mass, more preferably 0.008 to 2.0 parts by mass with respect to 100 parts by mass of the liquid crystal compound.
（その他モノマー）
　本発明の液晶組成物には、重合性の非液晶性モノマーを添加してもよい。本発明で使用できる非液晶性重合性モノマーとしては、液晶組成物の配向阻害を著しく引き起こさない限り、特に限定はない。これらの中では重合活性なエチレン性不飽和基、例えばビニル基、ビニルオキシ基、オキセタニル基、アクリロイル基およびメタクリロイル基などを有する化合物が好ましく用いられる。上記非液晶性重合性モノマーの添加量は、液晶化合物に対して０．５～３０質量部の範囲にあることが好ましく、１～２０質量部の範囲にあることがより好ましい。 (Other monomers)
A polymerizable non-liquid crystal monomer may be added to the liquid crystal composition of the present invention. The non-liquid crystalline polymerizable monomer that can be used in the present invention is not particularly limited as long as the alignment of the liquid crystal composition is not significantly inhibited. Of these, compounds having a polymerization active ethylenically unsaturated group such as vinyl group, vinyloxy group, oxetanyl group, acryloyl group and methacryloyl group are preferably used. The addition amount of the non-liquid crystalline polymerizable monomer is preferably in the range of 0.5 to 30 parts by mass, more preferably in the range of 1 to 20 parts by mass with respect to the liquid crystal compound.
（溶媒）
　重合性液晶組成物は、溶媒を含んでいてもよい。各光反射層を形成するための組成物の溶媒としては、有機溶媒が好ましく用いられる。有機溶媒の例には、アミド（例、Ｎ、Ｎ－ジメチルホルムアミド）、スルホキシド（例、ジメチルスルホキシド）、ヘテロ環化合物（例、ピリジン）、炭化水素（例、ベンゼン、ヘキサン）、アルキルハライド（例、クロロホルム、ジクロロメタン）、エステル（例、酢酸メチル、酢酸ブチル）、ケトン（例、アセトン、メチルエチルケトン、シクロヘキサノン）、エーテル（例、テトラヒドロフラン、１、２－ジメトキシエタン）が含まれる。アルキルハライドおよびケトンが好ましい。二種類以上の有機溶媒を併用してもよい。 (solvent)
The polymerizable liquid crystal composition may contain a solvent. As a solvent of the composition for forming each light reflection layer, an organic solvent is preferably used. Examples of organic solvents include amides (eg N, N-dimethylformamide), sulfoxides (eg dimethyl sulfoxide), heterocyclic compounds (eg pyridine), hydrocarbons (eg benzene, hexane), alkyl halides (eg , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone, cyclohexanone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.
＜重合性液晶組成物の塗布＞
　重合性液晶組成物の塗布は、重合性液晶組成物を溶媒により溶液状態としたり、加熱による溶融液等の液状物としたものを、ロールコーティング方式やグラビア印刷方式、スピンコート方式などの適宜な方式で展開したりする方法などにより行うことができる。さらにワイヤーバーコーティング法、押し出しコーティング法、ダイレクトグラビアコーティング法、リバースグラビアコーティング法、ダイコーティング法、等の種々の方法によって行うことができる。また、インクジェット装置を用いて、重合性液晶組成物をノズルから吐出して、塗布膜を形成することもできる。 <Application of polymerizable liquid crystal composition>
The application of the polymerizable liquid crystal composition is carried out by using a suitable liquid crystal composition such as a roll coating method, a gravure printing method, a spin coating method, etc. It can be performed by a method of developing by a method. Furthermore, it can be performed by various methods such as a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method. In addition, a coating film can be formed by discharging a polymerizable liquid crystal composition from a nozzle using an ink jet apparatus.
＜重合性液晶組成物の乾燥、加熱＞
　重合性液晶組成物の塗布後であって、硬化のための重合反応前に、塗布膜は、公知の方法で乾燥してもよい。例えば放置によって乾燥してもよく、加熱によって乾燥してもよい。
　重合性液晶組成物の塗布および乾燥の工程で、重合性液晶組成物中の液晶化合物分子が配向していればよい。
　例えば、重合性液晶組成物が、溶媒を含む塗布液として調製されている態様では、塗布膜を乾燥し、溶媒を除去することで、コレステリック液晶相の状態にすることができる場合がある。また、コレステリック液晶相への転移温度での加熱を行ってもよい。例えば、一旦等方性相の温度まで加熱し、その後、コレステリック液晶相転移温度まで冷却する等によって、安定的にコレステリック液晶相の状態にすることができる。前述の重合性液晶組成物の液晶相転移温度は、製造適性等の面から１０～２５０℃の範囲内であることが好ましく、１０～１５０℃の範囲内であることがより好ましい。前述の下限値以上であると液晶相を呈する温度範囲にまで温度を下げるために冷却工程等が必要とならず、好ましい。また前述の上限値以下であると、一旦液晶相を呈する温度範囲よりもさらに高温の等方性液体状態にするために高温を要さず、熱エネルギーの浪費、基板の変形、変質等から好ましい。 <Drying and heating of polymerizable liquid crystal composition>
The coating film may be dried by a known method after the application of the polymerizable liquid crystal composition and before the polymerization reaction for curing. For example, it may be dried by standing or may be dried by heating.
The liquid crystal compound molecules in the polymerizable liquid crystal composition only need to be aligned in the steps of applying and drying the polymerizable liquid crystal composition.
For example, in an embodiment in which the polymerizable liquid crystal composition is prepared as a coating solution containing a solvent, the coating film may be dried and the solvent may be removed to obtain a cholesteric liquid crystal phase. Further, heating at a transition temperature to the cholesteric liquid crystal phase may be performed. For example, the cholesteric liquid crystal phase can be stably formed by heating to the temperature of the isotropic phase and then cooling to the cholesteric liquid crystal phase transition temperature. The liquid crystal phase transition temperature of the aforementioned polymerizable liquid crystal composition is preferably in the range of 10 to 250 ° C., more preferably in the range of 10 to 150 ° C., from the viewpoint of production suitability and the like. It is preferable that the temperature is not less than the above lower limit value because a cooling step or the like is not required in order to lower the temperature to a temperature range exhibiting a liquid crystal phase. Further, if it is not more than the above upper limit value, it is preferable from the viewpoint of wasting heat energy, deformation of the substrate, alteration, etc., because it does not require a high temperature in order to make the isotropic liquid state higher than the temperature range once exhibiting the liquid crystal phase. .
（重合性液晶組成物の硬化）
　硬化は、紫外線照射により行えばよい。照射エネルギーは、２０ｍＪ／ｃｍ2～５０Ｊ／ｃｍ2が好ましく、１００ｍＪ／ｃｍ2～１，５００ｍＪ／ｃｍ2がより好ましく、１００ｍＪ／ｃｍ2～８００ｍＪ／ｃｍ2がさらに好ましい。照射紫外線波長は２００ｎｍ～４３０ｎｍに発光を含む光源により照射することが好ましい。
　硬化反応を促進するため、加熱条件下で紫外線照射を実施してもよい。また、紫外線照射時の温度は、コレステリック液晶相が乱れないように、コレステリック液晶相を呈する温度範囲に維持することが好ましい。また、雰囲気の酸素濃度は硬化度に関与するため、空気中で所望の重合度に達せず、膜強度が不十分の場合には、窒素置換等の方法により、雰囲気中の酸素濃度を低下させることが好ましい。酸素濃度としては、１０％以下が好ましく、７％以下がさらに好ましく、３％以下が最も好ましい。硬化度を向上させるためには照射する紫外線の照射量を増大する方法や窒素雰囲気下あるいは加熱条件下での重合が効果的である。 (Curing of the polymerizable liquid crystal composition)
Curing may be performed by ultraviolet irradiation. The irradiation energy is preferably 20mJ / cm 2 ~ 50J / cm 2, more preferably 100mJ / cm 2 ~ 1,500mJ / cm 2, 100mJ / cm 2 ~ 800mJ / cm 2 is more preferred. It is preferable to irradiate with a light source including light emission at an irradiation ultraviolet wavelength of 200 nm to 430 nm.
In order to accelerate the curing reaction, ultraviolet irradiation may be performed under heating conditions. Moreover, it is preferable to maintain the temperature at the time of ultraviolet irradiation in the temperature range which exhibits a cholesteric liquid crystal phase so that a cholesteric liquid crystal phase may not be disturbed. In addition, since the oxygen concentration in the atmosphere is related to the degree of cure, if the desired degree of polymerization is not reached in the air and the film strength is insufficient, the oxygen concentration in the atmosphere is reduced by a method such as nitrogen substitution. It is preferable. The oxygen concentration is preferably 10% or less, more preferably 7% or less, and most preferably 3% or less. In order to improve the curing degree, a method of increasing the irradiation amount of ultraviolet rays to be irradiated and polymerization under a nitrogen atmosphere or heating conditions are effective.
（仮硬化）
　本発明の光学フィルムのコレステリック液晶層は、コレステリック液晶層の螺旋ピッチを膜厚方向で変化させたピッチグラジエント層である。ピッチグラジエント層の形成方法は従来から種々検討されており、コレステリック液晶層形成のための硬化の際の光照射でキラル剤を異性化してＨＴＰを変化させることによる方法なども従来検討されている。本発明では、従来の方法とは異なり、上述のように膜厚方向でのカイラル剤の濃度分布をつけることによってピッチグラジエント層を得ている。
　カイラル剤の濃度分布をつけるためには、上記したような液晶化合物とカイラル剤とを含む重合性液晶組成物を通常の硬化工程の前に、照度０．１ｍＷ／ｃｍ2以上～１００ｍＷ／ｃｍ2の微弱な紫外線による仮硬化を行うことが好ましい。なお、本明細書において、照度は、波長３００～３９０ｎｍで測定した値を意味する。微弱な紫外線による仮硬化により塗布膜において硬化の早い部分と遅い部分が生じる。重合性液晶組成物中で多官能液晶化合物と比較して、１官能または官能基の無いカイラル剤は、硬化に関与しにくいため、塗布膜中の硬化の遅い未硬化の側に移動し、カイラル剤の濃度分布が生じると考えられる。 (Temporary curing)
The cholesteric liquid crystal layer of the optical film of the present invention is a pitch gradient layer in which the helical pitch of the cholesteric liquid crystal layer is changed in the film thickness direction. Various methods for forming a pitch gradient layer have been conventionally studied, and methods for changing the HTP by isomerizing a chiral agent by light irradiation during curing for forming a cholesteric liquid crystal layer have been studied. In the present invention, unlike the conventional method, the pitch gradient layer is obtained by providing the concentration distribution of the chiral agent in the film thickness direction as described above.
To give a concentration distribution of the chiral agent, the polymerizable liquid crystal composition containing a liquid crystal compound and a chiral agent as described above before the normal curing process, ~ illuminance 0.1 mW / cm 2 or more 100 mW / cm 2 It is preferable to perform temporary curing with the weak ultraviolet rays. In this specification, the illuminance means a value measured at a wavelength of 300 to 390 nm. By the temporary curing with weak ultraviolet rays, a fast curing portion and a slow curing portion are generated in the coating film. Compared with the polyfunctional liquid crystal compound in the polymerizable liquid crystal composition, the chiral agent having no monofunctional or functional group is less likely to participate in curing, and therefore moves to the uncured side of the coating film where the curing is slow, resulting in chiral It is thought that the concentration distribution of the agent occurs.
　仮硬化の際の紫外線照度は０．１ｍＷ／ｃｍ2～１００ｍＷ／ｃｍ2が好ましく、１ｍＷ／ｃｍ2～７０ｍＷ／ｃｍ2がより好ましく、５ｍＷ／ｃｍ2～５０ｍＷ／ｃｍ2がさらに好ましく、５ｍＷ／ｃｍ2～３０ｍＷ／ｃｍ2が特に好ましい。
　なお、本明細書において、カイラル剤の濃度分布というときのカイラル剤としては、重合性基部分で反応して生じる生成物中のカイラル剤由来の部分構造を含むものとする。また、カイラル剤の濃度分布は膜厚方向で連続的であっても非連続的であってもよいが、連続的であることが好ましい。すなわち、カイラル剤の濃度はコレステリック液晶層の片面から他方の面に向かって、連続的に減少（または連続的に増加）していることが好ましい。
　仮硬化の際の、紫外線照射条件としては、照度０．１ｍＷ／ｃｍ2以上～１００ｍＷ／ｃｍ2であるかぎり特に限定されない。例えば紫外線照射は大気雰囲気下であっても窒素雰囲気下であってもよい。また、紫外緯線照射は塗布膜のいずれの面側から行ってもよい。例えば支持体側から行ってもよく、その反対側から行ってもよい。
　仮硬化の際の紫外線照射は３０秒以下であればよい。本発明の光学フィルムの製造方法においては、仮硬化の際の紫外線照射時間が短くてよいため、製造ラインにおいて、ラインスピードを落とす必要がなく、好ましい。仮硬化の際の紫外線照射は１秒より長く２５秒より短いことが好ましく、２秒～２２秒であることがより好ましい。 UV intensity during pre-curing is preferably 0.1mW / cm 2 ~ 100mW / cm 2, more preferably 1mW / cm 2 ~ 70mW / cm 2, more preferably 5mW / cm 2 ~ 50mW / cm 2, 5mW / Particularly preferred is cm 2 to 30 mW / cm 2 .
In the present specification, the chiral agent in the case of the concentration distribution of the chiral agent includes a partial structure derived from the chiral agent in a product produced by reaction with a polymerizable group moiety. Further, the concentration distribution of the chiral agent may be continuous or discontinuous in the film thickness direction, but is preferably continuous. That is, the concentration of the chiral agent is preferably continuously decreased (or continuously increased) from one side of the cholesteric liquid crystal layer to the other side.
The conditions for ultraviolet irradiation at the time of temporary curing are not particularly limited as long as the illuminance is 0.1 mW / cm 2 or more to 100 mW / cm 2 . For example, the ultraviolet irradiation may be performed in an air atmosphere or a nitrogen atmosphere. Further, ultraviolet latitude irradiation may be performed from any side of the coating film. For example, it may be performed from the support side or from the opposite side.
The ultraviolet irradiation at the time of temporary curing may be 30 seconds or less. In the manufacturing method of the optical film of this invention, since the ultraviolet irradiation time at the time of temporary hardening may be short, it is not necessary to reduce line speed in a manufacturing line, and it is preferable. The ultraviolet irradiation during temporary curing is preferably longer than 1 second and shorter than 25 seconds, and more preferably 2 seconds to 22 seconds.
　さらに、加熱しながら紫外線照射をしてもよい。加熱温度は、重合性液晶組成物の相転移点に応じて調整することができ、加熱温度によってカイラル剤の濃度分布を制御することができる。加熱温度は室温～２００℃が好ましく、室温～１５０℃がさらに好ましい。重合性液晶組成物の相転移点に応じた温度に加熱しながら仮硬化のための紫外線を照射することで、多官能液晶化合物の重合を効率良く進め、硬化の早い部分を早く形成することができ、カイラル剤の濃度分布も得やすくなる。
　カイラル剤の濃度分布を得るための仮硬化の工程において、紫外線照射時に特定の波長をカットする波長カットフィルターを介して紫外線を照射してもよい。このように波長カットフィルターを用いることで、後述するように、多量の開始剤を用いた場合であっても広帯域コレステリック液晶フィルムを得ることが可能になる。用いる波長カットフィルターは、液晶化合物と開始剤の吸収波長や吸光係数、開始剤の添加量に応じて適宜選択することができる。例えば波長カットフィルターにより多官能液晶化合物が吸収を示す波長の紫外線を選択的に照射して、塗布膜内での硬化の進行を調節することによりカイラル剤の濃度分布を調節することができる。 Further, ultraviolet irradiation may be performed while heating. The heating temperature can be adjusted according to the phase transition point of the polymerizable liquid crystal composition, and the concentration distribution of the chiral agent can be controlled by the heating temperature. The heating temperature is preferably from room temperature to 200 ° C, more preferably from room temperature to 150 ° C. By irradiating ultraviolet rays for temporary curing while heating to a temperature corresponding to the phase transition point of the polymerizable liquid crystal composition, the polymerization of the polyfunctional liquid crystal compound can be efficiently advanced, and the fast-curing part can be formed quickly. The concentration distribution of the chiral agent can be easily obtained.
In the temporary curing step for obtaining the concentration distribution of the chiral agent, ultraviolet rays may be irradiated through a wavelength cut filter that cuts a specific wavelength at the time of ultraviolet irradiation. By using the wavelength cut filter as described above, a broadband cholesteric liquid crystal film can be obtained even when a large amount of initiator is used, as will be described later. The wavelength cut filter to be used can be appropriately selected according to the absorption wavelength and extinction coefficient of the liquid crystal compound and the initiator and the amount of the initiator added. For example, the concentration distribution of the chiral agent can be adjusted by selectively irradiating ultraviolet light having a wavelength that the polyfunctional liquid crystal compound absorbs with a wavelength cut filter to adjust the progress of curing in the coating film.
（本硬化）
　上記の仮硬化の後には、本硬化を行うことが好ましい。本硬化は仮硬化の際よりも高い照度で行えばよい。例えば、３０ｍＷ／ｃｍ2より大きく３００ｍＷ／ｃｍ2以下、４０ｍＷ／ｃｍ2より大きく２００ｍＷ／ｃｍ2以下、５０ｍＷ／ｃｍ2より大きく１００ｍＷ／ｃｍ2以下などで行えばよい。
　本硬化の際の、紫外線照射条件としては、仮硬化の際よりも高い照射量で行い、コレステリック液晶相の固定化が可能であるかぎり、特に限定されない。例えば紫外線照射は大気雰囲気下であっても窒素雰囲気下であってもよい。また、紫外緯線照射は塗布膜のいずれの面側から行ってもよい。例えば支持体側から行ってもよく、その反対側から行ってもよい。
　本硬化のための紫外線照射時間は特に限定されないが、０．５秒～３分程度であればよく、１秒～１分程度が好ましい。 (Full cure)
It is preferable to perform the main curing after the temporary curing. The main curing may be performed with a higher illuminance than in the temporary curing. For example, 30 mW / cm 2 greater than 300 mW / cm 2 or less, 40 mW / cm 2 greater than 200 mW / cm 2 or less, may be performed in such large 100 mW / cm 2 or less than 50 mW / cm 2.
The ultraviolet irradiation conditions in the main curing are not particularly limited as long as the irradiation is performed with a higher dose than in the temporary curing and the cholesteric liquid crystal phase can be fixed. For example, the ultraviolet irradiation may be performed in an air atmosphere or a nitrogen atmosphere. Further, ultraviolet latitude irradiation may be performed from any side of the coating film. For example, it may be performed from the support side or from the opposite side.
The ultraviolet irradiation time for the main curing is not particularly limited, but may be about 0.5 seconds to 3 minutes, and preferably about 1 second to 1 minute.
　また、本硬化においても、特定の波長をカットするフィルターを介して紫外線を照射してもよい。
　仮硬化においては、塗布膜中で液晶化合物の硬化度に差がついている。すなわち膜厚方向全体で見ると半硬化状態であると考えられる。このような状態のフィルムは耐久性や連続ロール生産での巻き適性に懸念がある。これらを考慮すると、開始剤を多く添加し十分に硬化を進めたいが、硬化速度が速すぎると前述のように広帯域コレステリック液晶フィルムを得るのに不利になる。そこで開始剤を多く添加した場合であっても、コレステリック液晶フィルムの反射帯域を広げる上記の工程（仮硬化工程）では、硬化速度が速くなりすぎないように波長カットフィルターを用い、コレステリック液晶フィルムを固定化する工程（本硬化工程）では、波長カットフィルターを用いないか或いはコレステリック液晶フィルムの反射帯域を広げる工程とは異なる波長カットフィルターを用いてコレステリック液晶相を固定化することが可能である。 Also in the main curing, ultraviolet rays may be irradiated through a filter that cuts a specific wavelength.
In the temporary curing, there is a difference in the degree of curing of the liquid crystal compound in the coating film. That is, it is considered that it is a semi-hardened state when viewed in the whole film thickness direction. A film in such a state is concerned with durability and winding ability in continuous roll production. In consideration of these, it is desired to sufficiently cure by adding a large amount of an initiator. However, if the curing rate is too high, it is disadvantageous for obtaining a broadband cholesteric liquid crystal film as described above. Therefore, even when a large amount of initiator is added, in the above process (temporary curing process) that widens the reflection band of the cholesteric liquid crystal film, a wavelength cut filter is used so that the curing speed does not become too fast. In the fixing step (main curing step), it is possible to fix the cholesteric liquid crystal phase without using the wavelength cut filter or using a wavelength cut filter different from the step of expanding the reflection band of the cholesteric liquid crystal film.
　本硬化は、加熱により行ってもよい。ただし、本硬化を上記紫外線照射により行う場合は、上記仮硬化と本硬化との間に加熱工程を含まないことが好ましい。上記組成の重合性液晶組成物を用いることにより、紫外線照射を３０秒以下行うのみで、加熱工程を含まなくてもピッチグラジエント層を作製することができるからである。ここでいう加熱工程は、室温より高い温度への加熱であればよく、５０℃以上への加熱であることが好ましく、７０℃以上への加熱であることが特に好ましい。 The main curing may be performed by heating. However, when the main curing is performed by the ultraviolet irradiation, it is preferable not to include a heating step between the temporary curing and the main curing. This is because by using the polymerizable liquid crystal composition having the above composition, a pitch gradient layer can be produced by performing ultraviolet irradiation for 30 seconds or less and without including a heating step. The heating step here may be heating to a temperature higher than room temperature, preferably heating to 50 ° C. or higher, and particularly preferably heating to 70 ° C. or higher.
＜配向層＞
　本発明の光学フィルムは配向層を含んでいてもよい。配向層はコレステリック液晶層の形成の際、重合性液晶組成物中の液晶化合物の分子を配向させるために用いられる。
　配向層はコレステリック液晶層の形成の際に用いられていればよく、光学フィルムにおいては、配向層が含まれていてもいなくてもよい。 <Alignment layer>
The optical film of the present invention may include an alignment layer. The alignment layer is used to align the molecules of the liquid crystal compound in the polymerizable liquid crystal composition when forming the cholesteric liquid crystal layer.
The alignment layer only needs to be used in the formation of the cholesteric liquid crystal layer, and the alignment layer may or may not be included in the optical film.
　配向層の例としては、有機化合物（好ましくはポリマー）のラビング処理配向層、ＳｉＯなどの無機化合物の斜方蒸着配向層、マイクログルーブを有する層の形成により得られる配向層などが挙げられる。さらには、電場の付与、磁場の付与、或いは光照射により配向機能が生じる光配向層も知られている。
　支持体などの下層の材料によっては、配向層を設けなくても、支持体を直接配向処理（例えば、ラビング処理）することで、配向層として機能させることもできる。そのような下層となる支持体の一例としては、ＰＥＴを挙げることができる。
　また、光反射層の上に直接光反射層を積層する場合、下層の光反射層が配向層として振舞い上層の光反射層の作製のための液晶化合物を配向させることができる場合もある。このような場合、配向層を設けなくても、また、特別な配向処理（例えば、ラビング処理）を実施しなくても上層の液晶化合物を配向することができる。 Examples of the alignment layer include a rubbing-treated alignment layer of an organic compound (preferably a polymer), an oblique deposition alignment layer of an inorganic compound such as SiO, and an alignment layer obtained by forming a layer having microgrooves. Furthermore, a photo-alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.
Depending on the material of the lower layer such as a support, the support can be directly functioned as an alignment layer by performing an alignment treatment (for example, rubbing treatment) without providing an alignment layer. An example of such a lower layer support is PET.
Further, when the light reflecting layer is laminated directly on the light reflecting layer, the lower light reflecting layer may behave as an alignment layer, and the liquid crystal compound for producing the upper light reflecting layer may be aligned. In such a case, the upper liquid crystal compound can be aligned without providing an alignment layer or without performing a special alignment process (for example, rubbing process).
（ラビング処理配向層）
　ラビング処理配向層に用いることができるポリマーの例には、例えば特開平８－３３８９１３号公報明細書中段落番号［００２２］記載のメタクリレート系共重合体、スチレン系共重合体、ポリオレフィン、ポリビニルアルコール及び変性ポリビニルアルコール、ポリ（Ｎ－メチロールアクリルアミド）、ポリエステル、ポリイミド、酢酸ビニル共重合体、カルボキシメチルセルロース、ポリカーボネート等が含まれる。シランカップリング剤をポリマーとして用いることができる。ポリ（Ｎ－メチロールアクリルアミド）、カルボキシメチルセルロース、ゼラチン、ポリビニルアルコール、変性ポリビニルアルコール、ポリエステル、ポリイミドが好ましく、ゼラチン、ポリビニルアルコール及び変性ポリビニルアルコールが更に好ましく、ポリビニルアルコール及び変性ポリビニルアルコール、ポリエステル、ポリイミドが最も好ましい。 (Rubbing alignment layer)
Examples of the polymer that can be used for the rubbing treatment oriented layer include, for example, a methacrylate copolymer, a styrene copolymer, a polyolefin, polyvinyl alcohol, and the like described in paragraph No. [0022] of JP-A-8-338913. Examples include modified polyvinyl alcohol, poly (N-methylolacrylamide), polyester, polyimide, vinyl acetate copolymer, carboxymethylcellulose, and polycarbonate. Silane coupling agents can be used as the polymer. Poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol, polyester and polyimide are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol, polyester and polyimide are most preferred. preferable.
　配向層のラビング処理面に前述の組成物を塗布して、液晶化合物の分子を配向させる。その後、必要に応じて、配向層ポリマーと光学異方性層に含まれる多官能モノマーとを反応させるか、あるいは、架橋剤を用いて配向層ポリマーを架橋させることで、前述の光学異方性層を形成することができる。
　配向層の膜厚は、０．１～１０μｍの範囲にあることが好ましい。 The aforementioned composition is applied to the rubbing-treated surface of the alignment layer to align the molecules of the liquid crystal compound. After that, if necessary, the alignment layer polymer and the polyfunctional monomer contained in the optically anisotropic layer are reacted, or the alignment layer polymer is crosslinked using a crosslinking agent, thereby the optical anisotropy described above. A layer can be formed.
The film thickness of the alignment layer is preferably in the range of 0.1 to 10 μm.
－ラビング処理－
　重合性液晶組成物が塗布され支持体、配向層などの下層の表面は、必要に応じてラビング処理をしてもよい。ラビング処理は、一般にはポリマーを主成分とする膜の表面を、紙や布で一定方向に擦ることにより実施することができる。ラビング処理の一般的な方法については、例えば、「液晶便覧」（丸善社発行、平成１２年１０月３０日）に記載されている。 -Rubbing treatment-
The surface of the lower layer such as the support or the alignment layer coated with the polymerizable liquid crystal composition may be rubbed as necessary. The rubbing treatment can be generally performed by rubbing the surface of a film containing a polymer as a main component with paper or cloth in a certain direction. A general method of rubbing is described in, for example, “Liquid Crystal Handbook” (issued by Maruzen, October 30, 2000).
　ラビング密度を変える方法としては、「液晶便覧」（丸善社発行）に記載されている方法を用いることができる。ラビング密度（Ｌ）は、下記式（Ａ）で定量化されている。
式（Ａ）　Ｌ＝Ｎｌ（１＋２πｒｎ／６０ｖ）
式（Ａ）中、Ｎはラビング回数、ｌはラビングローラーの接触長、ｒはローラーの半径、ｎはローラーの回転数（ｒｐｍ）、ｖはステージ移動速度（秒速）である。 As a method for changing the rubbing density, a method described in “Liquid Crystal Handbook” (published by Maruzen) can be used. The rubbing density (L) is quantified by the following formula (A).
Formula (A) L = Nl (1 + 2πrn / 60v)
In the formula (A), N is the number of rubbing, l is the contact length of the rubbing roller, r is the radius of the roller, n is the number of rotations (rpm) of the roller, and v is the stage moving speed (second speed).
　ラビング密度を高くするためには、ラビング回数を増やす、ラビングローラーの接触長を長く、ローラーの半径を大きく、ローラーの回転数を大きく、ステージ移動速度を遅くすればよく、一方、ラビング密度を低くするためには、この逆にすればよい。また、ラビング処理の際の条件としては、特許４０５２５５８号の記載を参照することもできる。 In order to increase the rubbing density, the rubbing frequency should be increased, the contact length of the rubbing roller should be increased, the radius of the roller should be increased, the rotation speed of the roller should be increased, and the stage moving speed should be decreased, while the rubbing density should be decreased. To do this, you can reverse this. In addition, the description in Japanese Patent No. 4052558 can also be referred to as conditions for the rubbing process.
＜支持体＞
　本発明の光学フィルムは、支持体を含んでいてもよい。支持体は液晶化合物を含有する組成物から形成された層を支持する層として機能できる。
　本発明の光学フィルムは、コレステリック液晶層を製膜する際の支持体を含んでいなくてもよく、例えばガラスや透明フィルムをコレステリック液晶層を製膜する際の支持体として用いてコレステリック液晶層を形成した後、コレステリック液晶層のみを製膜時の支持体から剥離して本発明の光学フィルムとしてもよい。 <Support>
The optical film of the present invention may include a support. A support body can function as a layer which supports the layer formed from the composition containing a liquid crystal compound.
The optical film of the present invention may not include a support for forming a cholesteric liquid crystal layer. For example, glass or a transparent film is used as a support for forming a cholesteric liquid crystal layer. After forming the film, only the cholesteric liquid crystal layer may be peeled off from the support during film formation to form the optical film of the present invention.
　支持体として用いられるポリマーフィルムの材料の例には、セルロースアシレートフィルム（例えば、セルローストリアセテートフィルム（屈折率１．４８）、セルロースジアセテートフィルム、セルロースアセテートブチレートフィルム、セルロースアセテートプロピオネートフィルム）、ポリエチレン、ポリプロピレン等のポリオレフィン、ポリエチレンテレフタレート（ＰＥＴ）やポリエチレンナフタレート等のポリエステル系樹脂フィルム、ポリエーテルスルホンフィルム、ポリメチルメタクリレート等のポリアクリル系樹脂フィルム、ポリウレタン系樹脂フィルム、ポリエステルフィルム、ポリカーボネートフィルム、ポリスルホンフィルム、ポリエーテルフィルム、ポリメチルペンテンフィルム、ポリエーテルケトンフィルム、（メタ）アクリルニトリルフィルム、ポリオレフィン、脂環式構造を有するポリマー（ノルボルネン系樹脂（アートン：商品名、ＪＳＲ社製、非晶質ポリオレフィン（ゼオネックス：商品名、日本ゼオン社製））、などが挙げられる。このうちトリアセチルセルロース、ポリエチレンテレフタレート、脂環式構造を有するポリマーが好ましく、特にトリアセチルセルロースが好ましい。 Examples of polymer film materials used as the support include cellulose acylate films (for example, cellulose triacetate film (refractive index 1.48), cellulose diacetate film, cellulose acetate butyrate film, cellulose acetate propionate film). Polyolefins such as polyethylene and polypropylene, polyester resin films such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyether sulfone films, polyacrylic resin films such as polymethyl methacrylate, polyurethane resin films, polyester films, polycarbonate films , Polysulfone film, polyether film, polymethylpentene film, polyetherketone film (Meth) acrylonitrile film, polyolefin, polymer having an alicyclic structure (norbornene resin (Arton: trade name, manufactured by JSR Corporation, amorphous polyolefin (ZEONEX: trade name, manufactured by ZEON Corporation)), etc. Of these, triacetyl cellulose, polyethylene terephthalate, and polymers having an alicyclic structure are preferable, and triacetyl cellulose is particularly preferable.
　透明支持体の厚さは５μｍ～１５０μｍ程度のものを用いることができるが、好ましくは５μｍ～８０μｍであり、２０μｍ～６０μｍであることがより好ましい。また、透明支持体は複数枚の積層からなっていてもよい。外光反射の抑制には薄い方が好ましいが、５μｍより薄いと、フィルムの強度が弱くなり、好ましくない傾向がある。透明支持体とその上に設けられる層との接着を改善するため、透明支持体に表面処理（例、グロー放電処理、コロナ放電処理、紫外線（ＵＶ）処理、火炎処理）を実施してもよい。支持体の上に、接着層（下塗り層）を設けてもよい。また、長尺の支持体には、搬送工程でのすべり性を付与したり、巻き取った後の裏面と表面の貼り付きを防止するために、平均粒径が１０～１００ｎｍ程度の無機粒子を固形分質量比で５％～４０％混合したポリマー層を支持体の片側に塗布や支持体との共流延によって形成したものを用いることが好ましい。 The thickness of the transparent support may be about 5 μm to 150 μm, preferably 5 μm to 80 μm, and more preferably 20 μm to 60 μm. The transparent support may be composed of a plurality of laminated layers. A thinner one is preferable for suppressing external light reflection, but if it is thinner than 5 μm, the strength of the film tends to be low, which tends to be undesirable. In order to improve adhesion between the transparent support and the layer provided thereon, the transparent support may be subjected to surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment). . An adhesive layer (undercoat layer) may be provided on the support. In addition, the long support is provided with inorganic particles having an average particle size of about 10 to 100 nm in order to provide slippage in the transport process and to prevent sticking between the back surface and the surface after winding. It is preferable to use a polymer layer in which 5% to 40% of the solid content is mixed and formed on one side of the support by coating or co-casting with the support.
　以下に実施例と比較例を挙げて本発明の特徴をさらに具体的に説明する。以下の実施例に示す材料、使用量、割合、処理内容、処理手順等は、本発明の趣旨を逸脱しない限り適宜変更することができる。したがって、本発明の範囲は以下に示す具体例により限定的に解釈されるべきものではない。 Hereinafter, the features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
＜実施例１＞
　コレステリック液晶層形成用組成物として以下の塗布液を調製した。
――――――――――――――――――――――――――――――――――
コレステリック液晶層形成用組成物
――――――――――――――――――――――――――――――――――
下記の液晶化合物　　（LC１）　　　　　　　　　　　　　　１００質量部
下記のカイラル剤　　　　　（C1）　　　　　　　　　　　　２．５質量部
光重合開始剤（イルガキュア８１９；BASF社製）　　 　　 ０．７５質量部
下記の界面活性剤　　　　（W1）　　　　　　　　　　　　０．０５質量部
下記の界面活性剤　　　　（W2）　　　　　　　　　　　　０．０１質量部
メチルエチルケトン　　　　　　　　　　　　　　　　　　　２５０質量部
シクロヘキサノン　　　　　　　　　　　　　　　　　　　　　５０質量部
―――――――――――――――――――――――――――――――――― <Example 1>
The following coating liquid was prepared as a composition for forming a cholesteric liquid crystal layer.
――――――――――――――――――――――――――――――――――
Cholesteric liquid crystal layer forming composition ――――――――――――――――――――――――――――――――――
The following liquid crystal compound (LC1) 100 parts by mass The following chiral agent (C1) 2.5 parts by mass Photopolymerization initiator (Irgacure 819; manufactured by BASF) 0.75 parts by mass The following surfactant (W1) 0.05 Part by weight The following surfactant (W2) 0.01 part by weight Methyl ethyl ketone 250 parts by weight Cyclohexanone 50 parts by weight ――――――――――――――――――――――――――― ―――――――
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
　膜厚７５μｍのＰＥＴ（コスモシャインＡ４１００、東洋紡株式会社製）の表面にラビング装置を用いてラビング処理を施した。このとき、長尺状のフィルムの長手方向と搬送方向は平行であり、フィルム長手方向に対して、ラビングローラーの回転軸は時計回りに４５°の方向とした。
　ＰＥＴのラビング処理面に、上記塗布液を膜厚３μｍになるようにワイヤーバーを用いて塗布し、重合性液晶組成物からなる膜を形成した。次いでこの膜を７０℃で１分間加熱し、コレステリック配向処理を施した。
　その後、２５℃に冷却した塗布膜を、高圧水銀灯を有する紫外線照射装置ＥＸＥＣＵＲＥ３０００－Ｗ（ＨＯＹＡ社製）を用いて大気雰囲気下で１０ｍＷ／ｃｍ2で１０秒間紫外線を塗布表面側から照射して仮硬化を行った。なお、上記照度は、ＵＶＲ－Ｔ１（ＵＤ－Ｔ３６；ＴＯＰＣＯＮ社製）を用いて３００～３９０ｎｍの範囲で測定した照度である。
その後、窒素雰囲気下５０ｍＷ／ｃｍ2で３０秒間紫外線を塗布表面側から照射して、膜を本硬化させ、コレステリック液晶層を有する光学フィルムを得た。 The surface of PET (Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) having a film thickness of 75 μm was rubbed using a rubbing apparatus. At this time, the longitudinal direction of the long film and the transport direction were parallel, and the rotation axis of the rubbing roller was 45 ° clockwise relative to the longitudinal direction of the film.
The coating liquid was applied to a PET rubbing surface using a wire bar so as to have a film thickness of 3 μm to form a film made of a polymerizable liquid crystal composition. Next, this film was heated at 70 ° C. for 1 minute to perform cholesteric alignment treatment.
Thereafter, the coating film cooled to 25 ° C. is irradiated with ultraviolet rays from the coating surface side for 10 seconds at 10 mW / cm 2 in the air atmosphere using an ultraviolet irradiation apparatus EXECURE 3000-W (manufactured by HOYA) having a high-pressure mercury lamp. Curing was performed. The illuminance is the illuminance measured in the range of 300 to 390 nm using UVR-T1 (UD-T36; manufactured by TOPCON).
Thereafter, ultraviolet rays were irradiated from the coated surface side at 50 mW / cm 2 in a nitrogen atmosphere for 30 seconds to fully cure the film, thereby obtaining an optical film having a cholesteric liquid crystal layer.
　Ａｘｏｍｅｔｒｉｘ社のＡｘｏＳｃａｎを用いて、紫外線照射前後での４００ｎｍ～８００ｎｍの範囲で透過スペクトルを測定した。透過率が０．７となる２点の波長を読み取り、その差を反射帯域（半値幅）として算出した。
　上記光学フィルムにおいて、カイラル剤が膜厚方向で濃度分布を持っていることは、以下の方法で確認した。
　上記光学フィルムを塗布面に対して１°の角度で斜めに切削し、生成したフィルムの断面及び表面を飛行時間型二次イオン質量分析計（ＴＯＦ－ＳＩＭＳ）で測定した。カイラル剤に由来するフェニル基のフラグメントイオンの膜厚方向の変化を見ると、塗布表面に近いほど強いピーク強度を示した。この結果、膜厚方向でカイラル剤の濃度分布が生成していることを確認した。 A transmission spectrum was measured in the range of 400 nm to 800 nm before and after UV irradiation using an AxoScan from Axometrix. Two wavelengths at which the transmittance was 0.7 were read, and the difference was calculated as a reflection band (half width).
In the optical film, it was confirmed by the following method that the chiral agent had a concentration distribution in the film thickness direction.
The optical film was cut obliquely at an angle of 1 ° with respect to the coated surface, and the cross section and surface of the produced film were measured with a time-of-flight secondary ion mass spectrometer (TOF-SIMS). Looking at the change in the film thickness direction of the fragment ions of the phenyl group derived from the chiral agent, the closer to the coating surface, the stronger the peak intensity. As a result, it was confirmed that a concentration distribution of the chiral agent was generated in the film thickness direction.
　上記液晶化合物（ＬＣ１）０．５ｍｇをアセトリトリル５０ｍｌに溶解させた。得られた溶液を石英ガラス製の容器（光路長１ｃｍ）に移し、分光光度計ＵＶ３１５０（島津製作所）を用いて、波長２５０～５００ｎｍの範囲で１ｎｍ毎に吸光度を測定した。測定値から各波長におけるモル吸光係数を算出し、３００～４００ｎｍの値の平均値を算出した。 The above liquid crystal compound (LC1) 0.5 mg was dissolved in 50 ml of acetolitol. The obtained solution was transferred to a quartz glass container (optical path length 1 cm), and absorbance was measured every 1 nm in the wavelength range of 250 to 500 nm using a spectrophotometer UV3150 (Shimadzu Corporation). The molar extinction coefficient at each wavelength was calculated from the measured values, and the average value of the values of 300 to 400 nm was calculated.
＜実施例２～６、比較例１～３＞
　液晶化合物、カイラル剤、光重合開始剤、界面活性剤、膜厚と、コレステリック液晶層形成時の仮硬化条件、重合性液晶組成物を塗布する基材を表１に示すように変更し、実施例と同様にして、実施例２～６、比較例１～３の光学フィルムをそれぞれ作製した。また、用いた液晶化合物の平均モル吸光係数も同様にして測定した。
　得られた光学フィルムについて実施例１と同様に反射帯域の評価とカイラル剤の濃度分布について評価を行った。反射帯域の評価結果を表１に示す。実施例２～６の光学フィルムについては膜厚方向でカイラル剤の濃度分布が生成していることを確認できたが、比較例１～３については、そのような濃度分布は確認できなかった。結果を表１に示す。 <Examples 2 to 6, Comparative Examples 1 to 3>
The liquid crystal compound, chiral agent, photopolymerization initiator, surfactant, film thickness, provisional curing conditions at the time of forming the cholesteric liquid crystal layer, and the substrate on which the polymerizable liquid crystal composition is applied are changed as shown in Table 1. In the same manner as the examples, optical films of Examples 2 to 6 and Comparative Examples 1 to 3 were produced. The average molar extinction coefficient of the liquid crystal compound used was also measured in the same manner.
The obtained optical film was evaluated for the reflection band and the concentration distribution of the chiral agent in the same manner as in Example 1. The evaluation results of the reflection band are shown in Table 1. For the optical films of Examples 2 to 6, it was confirmed that a chiral agent concentration distribution was generated in the film thickness direction, but for Comparative Examples 1 to 3, such a concentration distribution could not be confirmed. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-C000005
Figure JPOXMLDOC01-appb-C000005
Figure JPOXMLDOC01-appb-C000006
Figure JPOXMLDOC01-appb-C000006
　表１中の光重合開始剤は以下の通りである。
Irg819　　(イルガキュア８１９；BASF社製)
Irg907　　(イルガキュア９０７；BASF社製)
OXE02     (イルガキュアOXE０２；BASF社製) The photopolymerization initiators in Table 1 are as follows.
Irg819 (Irgacure 819; manufactured by BASF)
Irg907 (Irgacure 907; manufactured by BASF)
OXE02 (Irgacure OXE02; manufactured by BASF)
　表１中の「ＴＡＣ配向膜」「λ／４板」は以下のように作製した。光学フィルム作製時は、ＴＡＣ配向膜については配向層側面、λ／４板については光学異方性層側面を上記のＰＥＴ表面と同様にラビング処理して使用した。 “TAC alignment film” and “λ / 4 plate” in Table 1 were prepared as follows. When the optical film was prepared, the side surface of the alignment layer was used for the TAC alignment film, and the side surface of the optical anisotropic layer was used for the λ / 4 plate after being rubbed in the same manner as the above PET surface.
（ＴＡＣ配向膜）
　セルロースアシレートフィルムＴ１（「ＴＤ４０ＵＬ」（富士フイルム株式会社製）を、温度６０℃の誘電式加熱ロールを通過させ、フィルム表面温度を４０℃に昇温した後に、フィルムの片面に下記に示す組成のアルカリ溶液を、バーコーターを用いて塗布量１４ｍｌ／ｍ2で塗布し、１１０℃に加熱した。（株）ノリタケカンパニーリミテド製のスチーム式遠赤外ヒーターの下に、１０秒間搬送した。続いて、同じくバーコーターを用いて、純水を３ｍｌ／ｍ2塗布した。次いで、ファウンテンコーターによる水洗とエアナイフによる水切りを３回繰り返した後に、７０℃の乾燥ゾーンに１０秒間搬送して乾燥し、アルカリ鹸化処理したセルロースアシレートフィルムを作製した。 (TAC alignment film)
Cellulose acylate film T1 (“TD40UL” (manufactured by FUJIFILM Corporation) is passed through a dielectric heating roll at a temperature of 60 ° C., and the film surface temperature is raised to 40 ° C., and then the composition shown below on one side of the film Was applied at a coating amount of 14 ml / m 2 using a bar coater and heated to 110 ° C. It was transported for 10 seconds under a steam far-infrared heater manufactured by Noritake Company Limited. Using a bar coater, pure water was applied at a rate of 3 ml / m 2. Next, washing with a fountain coater and draining with an air knife were repeated three times, followed by transporting to a drying zone at 70 ° C. for 10 seconds to dry, An alkali saponified cellulose acylate film was prepared.
──────────────────────────────────
アルカリ溶液組成
──────────────────────────────────
　水酸化カリウム　　　　　　　　　　　　　　　　　　　　４．７質量部
　水　　　　　　　　　　　　　　　　　　　　　　　　　１５．８質量部
　イソプロパノール　　　　　　　　　　　　　　　　　　６３．７質量部
　界面活性剤ＳＦ－１：Ｃ14Ｈ29Ｏ（ＣＨ2ＣＨ2Ｏ）20Ｈ　　 　１．０質量部
　プロピレングリコール　　　　　　　　　　　　　　　　１４．８質量部
────────────────────────────────── ──────────────────────────────────
Alkaline solution composition ──────────────────────────────────
Potassium hydroxide 4.7 parts by weight Water 15.8 parts by weight Isopropanol 63.7 parts by weight Surfactant SF-1: C 14 H 29 O (CH 2 CH 2 O) 20 H 1.0 part by weight Propylene glycol 14. 8 parts by mass ──────────────────────────────────
（配向膜の形成）
　上記のように鹸化処理した長尺状のセルロースアセテートフィルムに、下記の組成の配向膜塗布液を＃１４のワイヤーバーで連続的に塗布した。６０℃の温風で６０秒、更に１００℃の温風で１２０秒乾燥した。
──────────────────────────────────
配向膜塗布液の組成
──────────────────────────────────
下記変性ポリビニルアルコール　　　　　　　　　　　　　　　１０質量部
水　　　　　　　　　　　　　　　　　　　　　　　　　　　３７１質量部
メタノール　　　　　　　　　　　　　　　　　　　　　　　１１９質量部
グルタルアルデヒド　　　　　　　　　　　　　　　　　　　０．５質量部
光重合開始剤（イルガキュア２９５９、ＢＡＳＦ社製）　　　０．３質量部
────────────────────────────────── (Formation of alignment film)
On the long cellulose acetate film saponified as described above, an alignment film coating solution having the following composition was continuously applied with a # 14 wire bar. Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds.
──────────────────────────────────
Composition of alignment film coating solution ──────────────────────────────────
Denatured polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde 0.5 parts by weight Photopolymerization initiator (Irgacure 2959, manufactured by BASF) 0.3 parts by weight ────────── ───────────────────────
Figure JPOXMLDOC01-appb-C000007
Figure JPOXMLDOC01-appb-C000007
（λ／４板）
　ＴＡＣ配向膜表面に光学異方性層を形成して形成した。
　ＴＡＣ配向膜の配向層表面にラビング装置を用いてラビング処理を施した。このとき、長尺状のフィルムの長手方向と搬送方向は平行であり、フィルム長手方向に対して、ラビングローラーの回転軸は時計回りに４５°の方向とした。ＴＡＣ配向膜の配向層のラビングした面に、下記組成のλ／４板形成用塗布液を＃３．６のワイヤーバーで連続的に塗布し、λ／４板を作製した。λ／４板の搬送速度（Ｖ）は２０ｍ／ｍｉｎとした。塗布液の溶媒の乾燥及びディスコティック液晶化合物の配向熟成のために、１３０℃の温風で９０秒間加熱した。続いて、８０℃にてＵＶ照射を行い、液晶化合物の配向を固定化し、λ／４板である光学異方性層を形成した。その後、窒素雰囲気下で、ＵＶ照度を５０ｍＷで６秒間照射した（ＵＶ照射量は３００ｍＪ／ｃｍ-1）。 (Λ / 4 plate)
An optically anisotropic layer was formed on the surface of the TAC alignment film.
The surface of the alignment layer of the TAC alignment film was rubbed using a rubbing apparatus. At this time, the longitudinal direction of the long film and the transport direction were parallel, and the rotation axis of the rubbing roller was 45 ° clockwise relative to the longitudinal direction of the film. A λ / 4 plate-forming coating solution having the following composition was continuously applied to the rubbed surface of the alignment layer of the TAC alignment film with a # 3.6 wire bar to prepare a λ / 4 plate. The conveyance speed (V) of the λ / 4 plate was 20 m / min. In order to dry the solvent of the coating solution and to mature the orientation of the discotic liquid crystal compound, the coating liquid was heated with warm air of 130 ° C. for 90 seconds. Subsequently, UV irradiation was performed at 80 ° C. to fix the orientation of the liquid crystal compound, and an optically anisotropic layer that was a λ / 4 plate was formed. Thereafter, UV irradiation was performed at 50 mW for 6 seconds in a nitrogen atmosphere (UV irradiation amount was 300 mJ / cm −1 ).
――――――――――――――――――――――――――――――――――
λ／４板形成用塗布液
――――――――――――――――――――――――――――――――――
ディスコティック液晶化合物（以下に記載の化合物１０１）　　８０質量部
ディスコティック液晶化合物（以下に記載の化合物１０２）　　２０質量部
配向助剤１（以下に記載の構造）　　　　　　　　　　　　　０．９質量部
配向助剤２（以下に記載の構造）　　　　　　　　　　　　　０．１質量部
ＤＩＣ社製メガファックＦ４４４　　　　　　　　　　　　０．１５質量部
重合開始剤１（以下に記載の構造）　　　　　　　　　　　　　　３質量部
メチルエチルケトン　　　　　　　　　　　　　　　　　　　１７０質量部
ｔ－ブタノール　　　　　　　　　　　　　　　　　　　　　　３０質量部
シクロヘキサノン　　　　　　　　　　　　　　　　　　　　　３０質量部
―――――――――――――――――――――――――――――――――― ――――――――――――――――――――――――――――――――――
Coating solution for forming λ / 4 plate ――――――――――――――――――――――――――――――――――
Discotic liquid crystal compound (compound 101 described below) 80 parts by mass Discotic liquid crystal compound (compound 102 described below) 20 parts by mass alignment aid 1 (structure described below) 0.9 parts by mass alignment aid 2 (Structure described below) 0.1 part by mass Megafac F444 manufactured by DIC 0.15 part by mass Polymerization initiator 1 (structure described below) 3 parts by mass methyl ethyl ketone 170 parts by mass t-butanol 30 parts by mass cyclohexanone 30 parts by mass Department ――――――――――――――――――――――――――――――――――
Figure JPOXMLDOC01-appb-C000008
Figure JPOXMLDOC01-appb-C000008

Claims (14)

  1. コレステリック液晶層を含む光学フィルムであって、
    前記コレステリック液晶層は多官能液晶化合物およびカイラル剤を含む重合性液晶組成物を硬化した層であり、
    前記多官能液晶化合物は、重合性基を２つ以上有し、かつ
    ３００ｎｍ～４００ｎｍにおける平均モル吸光係数が５０００以上であり、
    前記カイラル剤は、重合性基を有していないかまたは１つのみ有しており、
    前記コレステリック液晶層において、前記カイラル剤は膜厚方向に濃度分布を有する光学フィルム。     An optical film including a cholesteric liquid crystal layer,
    The cholesteric liquid crystal layer is a layer obtained by curing a polymerizable liquid crystal composition containing a polyfunctional liquid crystal compound and a chiral agent,
    The polyfunctional liquid crystal compound has two or more polymerizable groups and an average molar extinction coefficient at 300 to 400 nm of 5000 or more,
    The chiral agent has no polymerizable group or only one,
    In the cholesteric liquid crystal layer, the chiral agent is an optical film having a concentration distribution in a film thickness direction.
  2. 前記多官能液晶化合物が、前記重合性液晶組成物に含まれる液晶化合物の総量の９０質量％以上である請求項１に記載の光学フィルム。 The optical film according to claim 1, wherein the polyfunctional liquid crystal compound is 90% by mass or more of the total amount of liquid crystal compounds contained in the polymerizable liquid crystal composition.
  3. 前記重合性液晶組成物において、前記カイラル剤の総量が液晶化合物の総量に対して８質量％以下である請求項１または２に記載の光学フィルム。 The optical film according to claim 1, wherein in the polymerizable liquid crystal composition, the total amount of the chiral agent is 8% by mass or less based on the total amount of the liquid crystal compound.
  4. 前記重合性液晶組成物において、前記カイラル剤の総量が液晶化合物の総量に対して０．１～５質量％である請求項１または２に記載の光学フィルム。 3. The optical film according to claim 1, wherein in the polymerizable liquid crystal composition, the total amount of the chiral agent is 0.1 to 5% by mass with respect to the total amount of the liquid crystal compound.
  5. 前記コレステリック液晶層の選択反射の中心波長が４００～８００ｎｍの波長領域内にある請求項１～４のいずれか一項に記載の光学フィルム。 The optical film according to any one of claims 1 to 4, wherein a central wavelength of selective reflection of the cholesteric liquid crystal layer is in a wavelength region of 400 to 800 nm.
  6. 前記多官能液晶化合物が棒状液晶化合物である請求項１～５のいずれか一項に記載の光学フィルム。 The optical film according to any one of claims 1 to 5, wherein the polyfunctional liquid crystal compound is a rod-like liquid crystal compound.
  7. 前記多官能液晶化合物が分子内に、トラン構造、アゾメチン構造、アジン構造またはシンナモイル構造を有する請求項６に記載の光学フィルム。 The optical film according to claim 6, wherein the polyfunctional liquid crystal compound has a tolan structure, an azomethine structure, an azine structure, or a cinnamoyl structure in a molecule.
  8. 前記多官能液晶化合物が以下の化合物のいずれかである請求項６に記載の光学フィルム。
    Figure JPOXMLDOC01-appb-C000001
         The optical film according to claim 6, wherein the polyfunctional liquid crystal compound is one of the following compounds.
    Figure JPOXMLDOC01-appb-C000001
  9. 前記コレステリック液晶層の膜厚が３μm以上である請求項７または８に記載の光学フィルム。 The optical film according to claim 7 or 8, wherein a film thickness of the cholesteric liquid crystal layer is 3 µm or more.
  10. コレステリック液晶層を含む光学フィルムの製造方法であって、
    前記コレステリック液晶層を多官能液晶化合物およびカイラル剤を含む重合性液晶組成物の塗布膜を硬化することにより形成することを含み、前記硬化が、照度０．１ｍＷ／ｃｍ2～１００ｍＷ／ｃｍ2の紫外線を３０秒以下照射する仮硬化工程を含む、製造方法。     A method for producing an optical film including a cholesteric liquid crystal layer,
    Forming the cholesteric liquid crystal layer by curing a coating film of a polymerizable liquid crystal composition containing a polyfunctional liquid crystal compound and a chiral agent, wherein the curing has an illuminance of 0.1 mW / cm 2 to 100 mW / cm 2 . A production method comprising a temporary curing step of irradiating ultraviolet rays for 30 seconds or less.
  11. 前記仮硬化の紫外線照射を加熱しながら行う請求項１０に記載の製造方法。 The manufacturing method according to claim 10, wherein the pre-curing ultraviolet irradiation is performed while heating.
  12. 前記仮硬化工程の後に、紫外線を前記仮硬化の際よりも強い照度で照射する本硬化工程を含む請求項１０または１１に記載の製造方法。 The manufacturing method according to claim 10 or 11, further comprising a main curing step of irradiating ultraviolet rays with an illuminance stronger than that during the temporary curing after the temporary curing step.
  13. 前記仮硬化工程と前記本硬化工程との間に、５０℃以上に加熱する加熱工程を含まない請求項１２に記載の製造方法。 The manufacturing method of Claim 12 which does not include the heating process heated to 50 degreeC or more between the said temporary curing process and the said main curing process.
  14. 前記仮硬化工程で波長カットフィルターを用いる請求項１０～１３のいずれか一項に記載の製造方法。 The production method according to any one of claims 10 to 13, wherein a wavelength cut filter is used in the temporary curing step.
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