JP2013076958A - Production method of electromagnetic wave reflection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave reflection film excellent in adhesiveness between a cholesteric layer and a substrate and excellent in orientation property of electromagnetic waves.SOLUTION: The electromagnetic wave reflection film is produced through: (a) a resin layer formation step of forming a resin layer 12 comprising an energy ray-curable resin on a substrate 11; (b) a temporary lamination step of temporarily laminating a biaxially oriented film 13 on the resin layer 12; (c) a resin layer curing step of curing the resin layer 12; (d) a peeling step of peeling the biaxially oriented film 13; and (e) a reflection layer formation step of directly forming a reflection layer 14 on the surface of the resin layer 12 after peeling, the reflection layer containing a cholesteric liquid crystal that reflects electromagnetic waves having a peak wavelength in an IR region. The biaxially oriented film is a film subjected to a rubbing treatment, and the rubbed surface is preferably brought into contact with the surface of the resin layer 12. Otherwise, the reflection layer can be formed after rubbing the surface of the resin layer 12 after the peeling step.

Description

  The present invention relates to a method for producing an electromagnetic wave reflection film.

  In recent years, electromagnetic wave reflection films that selectively reflect electromagnetic waves in a desired wavelength band are known. An electromagnetic wave reflection film reflects only electromagnetic waves in a desired wavelength band and transmits electromagnetic waves in other wavelength bands. Therefore, it is attached to a window of a car or a building and reflects only infrared rays, visible light or communication wavelength bands. It is expected to be used for applications that transmit electromagnetic waves.

  As an example of an electromagnetic wave reflection film, a film in which a reflection layer that selectively reflects an electromagnetic wave in a predetermined wavelength band is formed on a substrate is known. The reflection layer is composed of one or more layers formed by fixing a cholesteric liquid crystal phase, and reflects at least one of the right polarization component and the left polarization component.

  FIG. 3 is a cross section of the film when the film is observed with a transmission electron microscope (hereinafter referred to as “TEM”). The film cross section has regular striped irregularities, and the wavelength band of the electromagnetic wave selectively reflected is determined by the interval between the irregularities. The reflectance of electromagnetic waves is determined by the magnitude of the incident angle of electromagnetic waves on the cholesteric layer. Since this electromagnetic wave reflection film has regular irregularities, it has excellent electromagnetic wave orientation. However, there is a drawback that the adhesion between the cholesteric layer and the substrate is poor.

  In order to eliminate this drawback, it has been proposed to form a rubbing polyimide layer between the base material and the cholesteric layer (see Patent Document 1). FIG. 4 is a film cross section when this film is observed by TEM. The film cross section has a non-uniform helical axis. Since this electromagnetic wave reflecting film has irregular irregularities, it has excellent adhesion between the cholesteric layer and the substrate.

International Publication No. 99/34242

  However, in the electromagnetic wave reflection film described in Patent Document 1, the orientation of the electromagnetic wave is inferior compared to the case where the irregularities are regular.

  This invention is made | formed in view of the said situation, The place made into the objective provides the electromagnetic wave reflection film excellent in both the adhesiveness of a cholesteric layer and a base material, and the orientation of electromagnetic waves. That is.

  In order to solve the above-mentioned problems, the present inventor has conducted extensive research, and as a result, a resin layer forming step for forming a resin layer on a substrate and a temporary lamination of a biaxially stretched film on the resin layer. Laminating step, resin layer curing step of curing the resin layer by irradiating energy rays from the substrate side and / or the biaxially stretched film side, the peeling step of peeling the biaxially stretched film, and the resin layer after peeling Electromagnetic wave reflection that is excellent in both the adhesion between the reflective layer and the base material and the orientation of the electromagnetic wave by passing through a reflective layer forming step of directly forming a reflective layer containing cholesteric liquid crystal that reflects electromagnetic waves on the surface of The present inventors have found that a film can be provided and have completed the present invention. Specifically, the present invention provides the following.

  (1) The present invention provides a resin layer forming step for forming a resin layer made of energy ray-curable resin on a substrate, and a temporary laminating step for temporarily laminating a biaxially stretched film on the resin layer. A resin layer curing step of curing the resin layer by irradiating energy rays from the substrate side and / or the biaxially stretched film side, a peeling step of peeling the biaxially stretched film, and the resin layer after peeling And a reflective layer forming step of forming a reflective layer containing a cholesteric liquid crystal that reflects electromagnetic waves having a peak wavelength in the infrared region on the surface of the film.

  (2) Moreover, this invention is a manufacturing method of the electromagnetic wave reflection film as described in (1) whose said biaxially stretched film is a film by which the rubbing process was made | formed on the lamination surface.

  (3) Moreover, this invention performs the said reflection layer formation process, after performing the rubbing process on the surface of the said resin layer after the said peeling process, The electromagnetic wave reflection film as described in (1) or (2) It is a manufacturing method.

  (4) Moreover, this invention is a manufacturing method of the electromagnetic wave reflection film in any one of (1) to (3) whose said biaxially stretched film is a polyethylene terephthalate film.

  ADVANTAGE OF THE INVENTION According to this invention, the electromagnetic wave reflection film excellent in both the adhesiveness of a reflection layer and a base material and the orientation of electromagnetic waves can be provided.

It is a figure which shows the manufacturing method of the electromagnetic wave reflection film which concerns on this invention. It is a figure following FIG. It is a reference figure which shows a film cross section when the electromagnetic wave reflection film which formed the reflection layer which selectively reflects the electromagnetic wave of a predetermined wavelength band on the base material was observed with the transmission electron microscope. It is a reference figure which shows the film cross section when the electromagnetic wave reflection film which formed the rubbing polyimide layer between the base material and the reflection layer was observed with the transmission electron microscope.

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. can do.

<Method for Producing Electromagnetic Wave Reflecting Film 1>
The electromagnetic wave reflection film 1 of the present invention is manufactured through the steps shown in FIGS.

[Resin layer forming step]
First, as shown to (a) of FIG. 1, the resin layer forming composition which has energy-beam sclerosis | hardenability is applied on the base material 11, and the resin layer 12 is formed.

1. Base Material The base material of the present invention is not particularly limited as long as it can support the reflective layer and has predetermined transparency, and may be a flexible material having flexibility, or flexible. It may be a rigid material having no property. Examples of the base material include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, olefin resins such as polyethylene and polymethylpentene, acrylic resins, polyurethane resins, polyethersulfone and polycarbonate, polysulfone, polyether, and poly Examples thereof include those made of resins such as ether ketone, (meth) acrylonitrile, cycloolefin polymer, and cycloolefin copolymer. Among these, polyethylene terephthalate is preferable because of its high versatility and easy availability.

  The transmittance in the visible light region of the substrate is preferably 80% or more, and more preferably 90% or more. The transmittance of the substrate can be measured according to JIS K7361-1 (Testing method for total light transmittance of plastic transparent material).

  The thickness of the base material can be appropriately determined according to the use of the electromagnetic wave reflection film and the material constituting the base material, and is not particularly limited.

2. Resin Layer Forming Composition The resin layer may be any resin layer as long as it is made of a resin having energy ray curability, such as urethane (meth) acrylate, epoxy (meth) acrylate, polyester ( Polymerizable oligomers and monomers having (meth) acryloyl groups such as (meth) acrylate, polyether (meth) acrylate, melamine (meth) acrylate, and (meth) acrylic acid, (meth) acrylamide, (meth) acrylonitrile, styrene, etc. Polymeric oligomers having a polymerizable vinyl group, monomers and the like, or those added with additives such as sensitizers as necessary, and those obtained by adding a photopolymerization initiator can be mentioned. .

(1) (Meth) acrylic main agent The main agent is preferably (meth) acrylic from the viewpoint of good adhesion to the liquid crystal layer, high liquid crystal alignment ability, and high transparency. The main agent may be any material as long as it has energy ray curability, but is preferably a monomer because it is excellent in followability to a substrate. Examples of energy rays include rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, and infrared rays, electromagnetic waves such as X-rays and γ rays, electron beams, proton rays, and neutron rays. In view of the curing speed, the availability of the irradiation device, the price, etc., curing by ultraviolet irradiation is preferable.

  The number of ethylenic functional groups in one molecule of the monomer is not particularly limited, but when the acrylic monomer is polymerized, a crosslinked structure is expressed and the barrier property can be improved. It is preferable to have at least two functional groups, and it is more preferable to have three or four in terms of shortening the time until the desired degree of polymerization is achieved. When a (meth) acrylic monomer having 3 or 4 ethylenic functional groups is used, the reaction rate is 2 to 10 times higher than when a (meth) acrylic monomer having 2 ethylenic functional groups is used. become.

Examples of the (meth) acrylic monomer include pentaerythritol triacrylate (hereinafter, also referred to as “PET3A”) represented by the following formula (I), and pentaerythritol tetraacrylate (hereinafter, “PET3A”) represented by the following formula (II). Also referred to as “PET4A”) or a mixture thereof.

  It is preferable that the quantity of PET3A and PET4A is 20 mass parts or more with respect to 100 mass parts of (meth) acrylic-type monomers. By containing 20% by weight or more, the adhesion between the resin layer and the reflective layer can be improved and the barrier property can be maintained.

  It is preferable to include PET3A in a ratio of 2 or more with respect to PET4A on a weight basis. When the ratio of PET4A exceeds the above ratio, although the polymerization reaction rate of the (meth) acrylic monomer is improved, the reaction rate becomes excessively high, which is not preferable in terms of difficulty in controlling the reaction rate. Further, the increase in the mixing ratio of PET4A is not preferable in that the cured product becomes rigid and the electromagnetic wave reflection film becomes brittle with respect to bending stress.

  The resin (polymer) obtained by polymerizing and crosslinking a (meth) acrylic monomer preferably has a monomer reaction rate of 30 to 90%, more preferably 40 to 80%, and even more preferably 50 to 75%. . If the reaction rate is less than 30%, the fluidity of the resin layer is high, and it is difficult to form a reflective layer on the resin layer. On the other hand, when the reaction rate exceeds 90%, the surface free energy of the resin constituting the resin layer becomes less than 40 dyne / cm, the wettability of the resin surface is reduced, and uniform when the reflective layer is formed on the resin layer. It is not preferable in that there is a possibility that a thick film cannot be formed. In addition, since the unreacted functional group remains in the resin polymer by setting the reaction rate to 90% or less, when the cholesteric liquid crystal material is applied and cured on the resin layer, the cholesteric liquid crystal material and the resin are cross-linked. And it is also preferable in terms of enhancing the adhesion between the layers.

  The surface free energy of a resin obtained by polymerization crosslinking of a (meth) acrylic monomer is preferably 40 dyne / cm or more. By setting the surface free energy within this range, the affinity between the resin layer and the liquid crystal material constituting the reflective layer is improved, so that a uniform reflective layer can be formed.

By the way, for (meth) acrylic monomers such as PET3A and PET4A, the stretching vibration of the carbonyl group (C═O) is around 1730 cm ⁻¹ and the CH out-of-plane bending vibration of the terminal vinyl group is 810 cm ^−1. An infrared absorption peak is shown in the vicinity. Since the carbonyl group does not disappear even after polymerization, the peak intensity near 1730 cm ⁻¹ does not change before and after the polymerization, but the terminal vinyl group disappears by the polymerization reaction (from double bond to single bond), so 810 cm. The peak intensity near ⁻¹ decreases. Therefore, the degree of progress of the polymerization reaction, that is, the reaction rate, can be determined based on how much the reduced terminal vinyl group, that is, the peak intensity at 810 cm ⁻¹ is reduced compared to before the polymerization reaction. In this specification, the reduction rate of the peak intensity of 810 cm ⁻¹ before and after the polymerization reaction is defined as “reaction rate”.

That is, the reaction rate is obtained as follows. First, an infrared spectrum (hereinafter referred to as “IR”) of the resin layer is measured. The peak _{I C = O} derived from C = O stretching vibration of the carbonyl group, the point indicating the minimum absorbance between 2100～1900Cm ^-1, that absorbance between 1570～1540Cm ^-1 indicates the minimum value A line connecting the two points is used as a base line, and the height from the base line of the peak top showing the maximum value in the range of 1740 to 1710 cm ⁻¹ is obtained. The peak I _C-H derived from the C-H out-of-plane bending vibration of the terminal vinyl group is based on the baseline connecting the minimum value between 830 ± 10 cm ⁻¹ and the minimum value between 790 ± 10 cm ^−1. It is calculated | required by the height from the base line of the peak top which shows maximum value in the range of 810 +/- 5cm < ^-1 >. Then, determined for each of the front and rear polymerization ratio _{I C-H / I C =} O to the peak _{I C = O} derived from C = O stretching vibration peak _{I C-H} derived from out-of-plane deformation vibration of terminal vinyl groups The rate of decrease before and after the polymerization reaction is defined as “reaction rate”.

That is, assuming that the peak intensity ratio before polymerization is A ₀ and the peak intensity ratio after polymerization is A _x , the following formula:
Reaction rate (%) = (A ₀ −A _x ) / A ₀ × 100
Define the reaction rate.

  In addition, IR measurement can be measured by using a Fourier transform infrared spectrophotometer FT / IR-610 (manufactured by JASCO Corporation) according to the KBr tablet method with a sample concentration of 1-2% by weight of the KBr amount.

(2) Silane coupling agent In order to improve the crosslinking shrinkage rate of the resin layer and prevent deformation of the resin layer, the resin layer forming composition constituting the resin layer preferably contains a silane coupling agent.

  A conventionally known silane coupling agent may be used. For example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxy Silane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyldiethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltri Ethoxysilane, vinyltris (2-methoxyethoxy) silane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldie Xysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane, N- (2-amiethyl) 3-aminopropylmethyldiethoxysilane, 3 -Mercaptopropyltriethoxysilane, vinyltriethoxysilane, vinyltriethoxysilane, vinyltris (2-ethoxy) silane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane and the like.

  The content of the silane coupling agent is preferably 0.5 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic main agent. If it is less than 0.5 parts by mass, the effect of addition cannot be obtained, which is not preferable. If it exceeds 100 parts by mass, it tends to be a layer that disturbs the alignment of the liquid crystal, which is not preferable.

(Polymerization initiator)
Although not an essential component, the resin layer forming composition constituting the resin layer preferably contains a polymerization initiator in order to enhance the sensitivity of the acrylic main agent. The polymerization initiator is not particularly limited as long as it can accelerate the polymerization reaction of the liquid crystal material, and may be appropriately selected according to the type of energy to be irradiated. Examples of the polymerization initiator include a photopolymerization initiator and a thermal polymerization initiator. Moreover, when a polymerization initiator is contained in the composition for forming a reflective layer, the amount of the polymerization initiator is not particularly limited as long as a desired polymerization reaction occurs, and may be appropriately determined.

  The content of the polymerization initiator is not particularly limited as long as the radical chain reaction starts and proceeds. Generally, the polymerization initiator is blended in such an amount that the absorbance at the maximum absorption wavelength of the polymerization initiator measured using a commercially available spectrophotometer is within the range of 0.4 to 0.5.

(3) Other additives In addition, the resin layer forming composition may include a crosslinking agent, a tackifier, a metal chelating agent, a surfactant, an oxidation agent, as necessary, as long as the object of the present invention is not impaired. Various additives such as an inhibitor, an ultraviolet absorber, a pigment, a dye, a colorant, an antistatic agent, an antiseptic, an antifoaming agent, and a wettability adjusting agent can be blended.

3. Formation of Resin Layer The method for applying the resin layer forming composition on the substrate 11 is not particularly limited, and examples thereof include a bar coating method, a spin coating method, and a blade coating method. The thickness of the resin layer 12 is preferably in the range of 0.5 μm to 20 μm. When the thickness is less than 0.5 μm, orientation defects such as irregularities of the base film tend to be generated, which is not preferable. If the thickness exceeds 20 μm, curling due to the shrinkage of the resin layer tends to occur and it tends to be difficult to handle as a film.

[Temporary lamination process]
Next, as shown in FIG. 1B, the biaxially stretched film 13 is temporarily laminated on the resin layer 12.

  The film formed on the surface of the resin layer 12 needs to be a biaxially stretched film. If it is not a biaxially stretched film, the surface of the resin layer 12 after peeling off the biaxially stretched film 13 will have extremely irregular irregularities, and the electromagnetic wave orientation will be poor in the electromagnetic wave reflecting film formed thereafter. Therefore, it is not preferable. Further, the film formed on the surface of the resin layer 12 in order to enhance the orientation of the electromagnetic wave is a film that has been subjected to a rubbing treatment on at least one side. In the biaxially stretched film forming step, the rubbing treatment of the biaxially stretched film 13 is performed. It is preferable to form a surface on which the surface is made on the surface of the resin layer 12.

  Examples of commercially available biaxially stretched film 13 include polyethylene terephthalate film (hereinafter referred to as “PET film”) Lumirror (registered trademark) U35 (manufactured by Toray Industries, Inc.). The base material 11 and the biaxially stretched film 13 may be the same material or different materials.

  Lamination may be performed using a conventionally used laminator to prevent air from entering, but the lamination temperature is preferably 20 ° C. or higher and 120 ° C. or lower. If it is less than 20 degreeC, the base material 11 and the biaxially stretched film 13 may not be laminated appropriately, and it is not preferable. When the temperature exceeds 120 ° C., the base material 11 and the biaxially stretched film 13 are firmly adhered to each other, and thereafter, it is not preferable because the biaxially stretched film 13 may not be easily peeled off.

[Resin layer curing process]
Subsequently, as shown in FIG. 1C, the resin layer 12 is cured by irradiating energy rays from the substrate 11 side and / or the biaxially stretched film 13 side. The resin layer forming composition is cured by irradiating the resin layer forming composition with electromagnetic waves. The electromagnetic wave is preferably light having a wavelength range of 200 to 450 nm, and more preferably light having a wavelength range of 300 to 450 nm. The light source is not particularly limited, and for example, a high pressure mercury lamp, an ultra high pressure mercury lamp, a carbon arc lamp, a mercury vapor arc, a fluorescent lamp, an argon glow lamp, a halogen lamp, an incandescent lamp, a low pressure mercury lamp, a flash UV lamp, deep UV A lamp, a xenon lamp, a tungsten filament lamp, sunlight, etc. are mentioned. By using these light sources and irradiating light so that the integrated light quantity is 50 mJ / cm ² or more, preferably 200 mJ / cm ² or more, the resin layer forming composition can be cured.

[Peeling process]
Subsequently, as shown in FIG. 1D, the biaxially stretched film 13 is peeled off from the base material 11. Through these steps, the irregularities on the surface of the biaxially stretched film 13 are transferred to the surface of the resin layer 12. In addition, although not an essential process, when a biaxially stretched film that has been rubbed at least on one side is not used, a rubbing process is performed on the surface of the resin layer 12 after the peeling process in order to enhance the orientation of electromagnetic waves. Then, it is preferable to move to the next reflection layer forming step.

[Reflective layer forming step]
Subsequently, as shown in (e) of FIG. 2, the reflective layer forming composition is applied in layers on the resin layer 12.

1. Reflective layer forming composition The reflective layer forming composition contains a liquid crystal material having cholesteric regularity and a chiral agent. Moreover, you may contain a leveling agent, a polymerization initiator, an additive, etc. with respect to the composition for reflective layer formation.

(Liquid crystal material)
A cholesteric liquid crystal exhibiting cholesteric regularity can be used as the liquid crystal material. Such a material is not particularly limited as long as it is a liquid crystal material capable of forming a cholesteric liquid crystal structure, but is polymerizable at both ends of the molecule in that an optically stable reflective layer can be obtained after curing. A liquid crystal material having a functional group is preferred.

Examples of such a liquid crystal material include compounds represented by the following formulas (2-i) to (2-xi) in addition to the compounds represented by the following general formula (1). These compounds can be used alone or in combination.

In the general formula (1), R ¹ and R ² each represent hydrogen or a methyl group, but both R ¹ and R ² are preferably hydrogen because of the wide temperature range showing the liquid crystal phase. X may be hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group, but is preferably a chlorine or methyl group. Moreover, in the said General formula (1), a and b which show the chain length of the alkylene group which is a spacer of the (meth) acryloyloxy group and aromatic ring of both ends of a molecular chain are arbitrary in the range of 2-12, respectively. Although it can take an integer, it is preferably in the range of 4 to 10, and more preferably in the range of 6 to 9. If a = b = 0, the stability is poor, the compound is easily hydrolyzed, and the compound itself has high crystallinity, which is not preferable because the temperature range showing the liquid crystal phase is narrow. Further, when either a or b is 13 or more, the isotropic transition temperature (TI) is low, which is not preferable in that the temperature range showing the liquid crystal phase is narrow.

2. Chiral agent A chiral agent is a low molecular compound having an optically active site, and is mainly a compound having a molecular weight of 1500 or less. The chiral agent is mainly used for the purpose of inducing a helical structure in the positive uniaxial nematic regularity expressed by the polymerizable liquid crystal material exhibiting nematic regularity. As long as this purpose is achieved, it is compatible with a polymerizable liquid crystal material exhibiting nematic regularity in a solution state or a molten state, without impairing the liquid crystal property of the polymerizable liquid crystal material exhibiting nematic regularity, The kind of the low molecular compound as the chiral agent is not particularly limited as long as it can induce a desired helical structure.

  In addition, the chiral agent used for inducing a helical structure in the liquid crystal in this way needs to have at least some chirality in the molecule. Therefore, as the chiral agent used here, for example, a compound having one or two or more asymmetric carbons, a compound having an asymmetric point on a hetero atom such as a chiral amine or chiral sulfoxide, or cumulene And compounds having an optically active site having axial asymmetry such as binaphthol.

However, depending on the nature of the selected chiral agent, the nematic regularity formed by the polymerizable liquid crystal material exhibiting nematic regularity, the degradation of orientation, or the liquid crystal material when the chiral agent is non-polymerizable There is a risk of lowering the curability of the film and lowering the reliability of the cured film. Further, the use of a large amount of a chiral agent having an optically active site causes an increase in the cost of the liquid crystal material. Therefore, when forming a selective reflection layer having a cholesteric regularity with a short helical pitch length, a chiral agent having a large effect of inducing a helical structure is selected as a chiral agent having an optically active site to be contained in the liquid crystal material. Specifically, it is preferable to use a low molecular compound having axial asymmetry in the molecule as represented by the following general formula (3), (4) or (5).

In the general formula (3) or (4), R ⁴ represents hydrogen or a methyl group. Y is any one of formulas (i) to (xxiv) shown below, and among them, any one of formulas (i), (ii), (iii), (v) and (vii) Preferably there is. Moreover, although c and d which show the chain length of an alkylene group can each take arbitrary integers in the range of 2-12, it is preferable that it is the range of 4-10, and is the range of 6-9. Is more preferable. When the value of c or d is 0 or 1, since it lacks stability, is susceptible to hydrolysis, and has high crystallinity, compatibility with a polymerizable liquid crystal material exhibiting nematic regularity decreases, Depending on the concentration, phase separation is not preferable. On the other hand, when the value of c or d is 13 or more, the melting point (Tm) is low, so the compatibility with the polymerizable liquid crystal material exhibiting nematic regularity is lowered, and phase separation may occur depending on the concentration. This is not preferable.

  Such a chiral agent is not particularly required to have polymerizability. However, when the chiral agent has polymerizability, it is polymerized with a polymerizable liquid crystal material exhibiting nematic regularity, and the cholesteric regularity is stably fixed, which is preferable in terms of thermal stability and the like. In particular, it is preferable to have a polymerizable functional group at both ends of the molecule in order to obtain a selective reflection layer having good heat resistance.

  The wavelength band of the electromagnetic wave reflected by the reflective layer is determined by the amount of the chiral agent contained in the reflective layer forming composition. As an example, when the peak of the wavelength band of the electromagnetic wave reflected by the reflective layer is set to 780 nm, the ratio of the chiral agent that gives right-turning property is 2 parts by mass or more and 10 parts by mass with respect to 100 parts by mass of the reflective layer forming composition. The proportion of the chiral agent that gives left-turning property, and preferably 2 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the composition for forming a reflective layer.

3. Leveling agent The leveling agent is used to promote the formation of a cholesteric structure of the liquid crystal material. The leveling agent is not particularly limited as long as it can promote the cholesteric alignment of the liquid crystal material in the reflective layer, and examples thereof include a silicon compound, a fluorine compound, and an acrylic compound. As a commercially available leveling agent, BYK-361N manufactured by Big Chemie Japan, S-241 manufactured by AGC Seikagaku Co., etc. can be used. The leveling agent may be one kind or two or more kinds.

  The content of the leveling agent is not particularly limited as long as it is within a range in which the cholesteric structure of the liquid crystal material can be formed with a desired regularity, but is 0.01 mass with respect to 100 parts by mass of the reflective layer forming composition. Part or more and 5.0 parts by weight or less, more preferably 0.03 parts by weight or more and 10.0 parts by weight or less. If the amount is less than 0.01 parts by mass, liquid crystal molecules at the air interface are easily aligned vertically, and the film is difficult to be uniform. If it exceeds 10.0 parts by mass, it is not preferable because the case where the alignment of the liquid crystal may be inhibited is observed.

4). Polymerization initiator The polymerization initiator is used to crosslink a liquid crystal material in which a cholesteric structure is formed by the action of a chiral agent and a leveling agent while maintaining the cholesteric structure so that the cholesteric structure is not easily disturbed. The polymerization initiator is not particularly limited as long as it can accelerate the polymerization reaction of the liquid crystal material, and may be the same as that used in the resin layer or may be different.

5. Solvent In order to disperse the liquid crystal material, the chiral agent, the leveling agent, and the polymerization initiator, the reflective layer forming composition is usually dispersed in the solvent. A solvent will not be specifically limited if said component can be disperse | distributed, For example, a cyclohexanone etc. can be mentioned.

6). Formation of Reflective Layer Coating of the composition for forming a reflective layer may be the same method as the formation of the resin layer, and examples thereof include a bar coating method, a spin coating method, and a blade coating method. The thickness of the reflection layer is not particularly limited as long as it is within a range in which a function of selectively reflecting infrared light in a predetermined wavelength region can be realized, but it is within a range of 0.1 μm to 100 μm. Is preferable, more preferably in the range of 0.5 μm to 20 μm, still more preferably in the range of 1 μm to 10 μm. If the thickness is less than 0.1 μm, the desired reflectance cannot be obtained, which is not preferable. When the thickness exceeds 100 μm, the cholesteric orientation is likely to be disturbed, which is not preferable.

[Reflective layer drying process]
Subsequently, as shown in FIG. 2F, the reflective layer forming composition coated on the resin layer 12 is dried. The reflection layer forming composition is dried to remove the solvent. The drying temperature is preferably 50 ° C. or higher and 200 ° C. or lower. If it is less than 50 ° C., the solvent may not be removed properly, which is not preferable. If it is 200 ° C. or higher, heat wrinkles may be generated or deteriorated, which is not preferable.

[Reflective layer curing process]
Subsequently, as shown in FIG. 2G, the reflective layer-forming composition after drying is cured to form the reflective layer 14. Through these steps, the electromagnetic wave reflection film 1 of the present invention is formed.

  Curing of the composition for forming a reflective layer is performed by irradiating the composition for forming a reflective layer with an electromagnetic wave. The reason why the reflection layer forming composition is irradiated with electromagnetic waves is that a liquid crystal material having a cholesteric structure formed by the action of a chiral agent and a leveling agent is crosslinked while maintaining the cholesteric structure, so that the cholesteric structure is not easily disturbed. is there.

The light source may be the same as that used when forming the resin layer, and the accumulated light amount is 25 mJ / cm ^{2 to} 800 mJ / cm ² , preferably 25 mJ / cm ^{2 to} 400 mJ / cm ² , and more preferably. can by irradiation with light such that the range of ^{50mJ / cm 2 ~200mJ / cm 2} , curing the reflective layer forming composition. If the integrated light amount is less than 25 mJ / cm ² , the polymerization of the liquid crystal material becomes insufficient, and as a result, the cholesteric structure of the liquid crystal material can be disturbed. If it exceeds 800 mJ / cm ² , the leveling agent may appear on the surface of the reflective layer, which is not preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

<Example 1>
[Preparation of substrate]
A biaxially stretched film made of PET (trade name: Lumirror (registered trademark) U35, thickness: 125 μm, manufactured by Toray Industries, Inc.) was prepared.

[Formation of resin layer]
An ultraviolet curable resin (trade name: Unidic, manufactured by DIC) was applied onto the easy-adhesion layer of the PET film using a bar coater so as to be 5.4 g / m ² . Thereafter, the resin was heated and dried in an oven adjusted to 90 ° C. for 30 seconds.

[Transfer of orientation ability]
Apart from the substrate, the same film as the PET film was prepared. The retardation value of this film at a wavelength of 585 nm was 3710 nm. The retardation value was measured using an optical material inspection apparatus Rets-100 (manufactured by Otsuka Electronics Co., Ltd.). Hereinafter, unless otherwise noted, the retardation value at a wavelength of 585 nm is abbreviated as “Re value”.

The surface of the film that was not subjected to easy adhesion treatment was laminated so as to come into contact with the surface of the resin layer. Lamination was performed using a laminator to prevent air from entering. Subsequently, ultraviolet rays were irradiated from the laminated Lumirror U35 side using an ultraviolet irradiation device (H bulb manufactured by Fusion). At this time, the integrated light amount was 158 mJ / cm ² . Thereafter, the laminated PET film was peeled from the substrate. As a result, the orientation ability was transferred to the resin layer.
[Formation of reflective layer]
95.81 parts by weight of a liquid crystalline monomer molecule represented by the following formula having a polymerizable acrylate at both ends and a spacer between the mesogen and acrylate at the center, and a polymerizable acrylate at both ends 4.19 parts by weight of a chiral agent molecule (trade name: CNL715, manufactured by Adeka Co., Ltd.) was dissolved in a cyclohexanone solution. Then, 5.0 parts by weight of a photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF) was added to the liquid crystalline monomer molecule.

Next, the cyclohexanone solution was applied onto the resin layer with a bar coater. Next, the mixture was kept at 100 ° C. for 2 minutes to evaporate cyclohexanone in the cyclohexanone solution, thereby aligning the liquid crystalline monomer molecules. The coating film was irradiated with ultraviolet rays using an ultraviolet irradiation device (H bulb, manufactured by Fusion) so that the integrated light amount was 400 mJ / cm ² , and oriented by radicals generated from the photoinitiator in the coating film. A liquid crystal monomer molecule acrylate and a chiral agent molecule acrylate were three-dimensionally crosslinked to form a polymer, and a cholesteric structure was fixed to obtain a reflective layer (peak reflection wavelength: 880 nm). At this time, the thickness of the reflective layer was 6 μm.

  The electromagnetic wave reflection film of Example 1 was obtained through the above steps.

<Example 2>
An electromagnetic wave reflection film of Example 2 was obtained in the same manner as in Example 1 except that the transfer of orientation ability was performed in the following steps.

[Transfer of orientation ability]
Apart from the substrate, the same film as the PET film was prepared. The Re value of this film was 4196 nm. A rubbing treatment was performed twice on the surface of the film that was not subjected to the easy adhesion treatment. The rubbing treatment was performed using rayon (trade name: YA-18-R, manufactured by Yoshikawa Chemical). And the surface which carried out the rubbing process was temporarily laminated so that the surface of the said resin layer might be contacted. The temporary lamination was performed using a laminator and performed at 70 ° C. In addition, air was prevented from entering during temporary lamination. Subsequently, ultraviolet rays were irradiated from the laminated Lumirror U35 side using an ultraviolet irradiation device (H bulb manufactured by Fusion). At this time, the integrated light amount was 158 mJ / cm ² . Thereafter, the laminated PET film was peeled from the substrate. As a result, the orientation ability was transferred to the resin layer.

<Example 3>
An electromagnetic wave reflection film of Example 3 was obtained in the same manner as in Example 1 except that the Re value of the film used for transferring the orientation ability was 5718 nm.

<Example 4>
An electromagnetic wave reflection film of Example 3 was obtained in the same manner as in Example 1 except that the Re value of the film used for transferring the orientation ability was 6339 nm.

<Example 5>
The base material is a biaxially stretched film made of PET (trade name: Cosmo Shine (registered trademark) A4100, thickness: 125 μm, manufactured by Toyobo Co., Ltd.), and the Re value of the film used for transferring the orientation ability is An electromagnetic wave reflection film of Example 5 was obtained in the same manner as in Example 1 except that the thickness was 4196 nm.

<Example 6>
Except that the Re value of the film used for transferring the orientation ability was 3711 nm and that the surface of the resin layer was rubbed with the rayon after the orientation ability was transferred to the resin layer. The electromagnetic wave reflection film of Example 6 was obtained in the same manner as in Example 1.

<Comparative Example 1>
Comparative Example 1 was prepared in the same manner as in Example 1 except that the orientation ability was not transferred and the surface of the resin layer was rubbed with the rayon after the resin layer was formed. An electromagnetic wave reflection film was obtained.

<Comparative example 2>
The electromagnetic wave reflective film of Comparative Example 2 was obtained in the same manner as in Example 1 except that the resin layer was not formed and the reflective layer was directly formed on the surface of the substrate that was not subjected to easy adhesion treatment. It was.

<Comparative Example 3>
The electromagnetic wave reflective film of Comparative Example 3 was obtained in the same manner as in Example 1 except that the resin layer was not formed and the reflective layer was directly formed on the surface on which the base material was easily adhered. It was.

<Comparative example 4>
An electromagnetic wave reflection film of Comparative Example 4 was obtained in the same manner as in Example 1 except that the film used for transferring the orientation ability was an acrylic film (trade name: TECHNOLOGY S001, manufactured by Sumitomo Chemical Co., Ltd.). .

<Evaluation of orientation>
Evaluation of orientation was performed by measuring 5 ° regular reflectance at a wavelength of 880 nm using a spectrophotometer UV-3100PC (manufactured by Shimadzu Corporation). The results are shown in Table 2. 40% or more was designated as “、”, 20% or more as “◯”, 15% or more as “Δ”, and less than 15% as “x”.

<Evaluation of adhesion>
The evaluation of adhesion was performed by carrying out a crosscut according to the JIS K5400-8.5 method using a mending tape (manufactured by Sumitomo 3M). The results are shown in Table 2. The left shows the peak reflectivity, a peak reflectivity of 40% or more is “◎”, a peak reflectivity of less than 40% is 20% or more, and a peak reflectivity of less than 20% is 15% or more. ", And a peak reflectivity of less than 15% was taken as" x ". “X” indicates that a planar-aligned cholesteric liquid crystal is not obtained. On the right, the adhesiveness is shown, and 80% or more remaining is “◯”, and less than 80% is “X”.

  A resin layer forming step of forming a resin layer made of a resin having energy beam curability on the substrate, a temporary laminating step of temporarily laminating a biaxially stretched film on the resin layer, the substrate side and / or A resin layer curing step of curing the resin layer by irradiating energy rays from the biaxially stretched film side, a peeling step of peeling the biaxially stretched film, and a peak wavelength in the infrared region on the surface of the resin layer after peeling. The electromagnetic wave reflective film manufactured through the reflective layer forming step of directly forming the reflective layer containing the cholesteric liquid crystal that reflects the electromagnetic wave has both the adhesion between the reflective layer and the base material and the orientation of the electromagnetic wave. It was confirmed that it was excellent (Examples 1 to 6). In particular, it was confirmed that when the Re value of the biaxially stretched film formed on the surface of the resin layer exceeds 5000 nm, more suitable orientation is exhibited (Examples 3 and 4). And, as a biaxially stretched film to be formed on the surface of the resin layer, a film that has been rubbed on at least one surface is used (Example 2), or a rubbing treatment is performed after the peeling step, and then a reflective layer forming step (Example 6), it was confirmed that more suitable orientation was exhibited (Example 6).

  On the other hand, when the unevenness of the film was not transferred to the resin layer, it was confirmed that even when the rubbing treatment was performed on the resin layer, a suitable orientation could not be obtained (Comparative Example 1). . Moreover, it was confirmed that the adhesiveness between the reflective layer and the substrate may not be ensured without forming the resin layer (Comparative Examples 2 and 3). Moreover, even if the unevenness | corrugation of a film was transcribe | transferred to the resin layer, it was confirmed that suitable orientation cannot be acquired unless a film is a biaxially stretched film (comparative example 4).

DESCRIPTION OF SYMBOLS 1 Reflective film 11 Base material 12 Resin layer 13 Biaxially stretched film 14 Reflective layer

Claims (4)

On the substrate, a resin layer forming step of forming a resin layer made of a resin having energy ray curability,
A temporary laminating step of temporarily laminating a biaxially stretched film on the resin layer;
A resin layer curing step of curing the resin layer by irradiating energy rays from the substrate side and / or the biaxially stretched film side;
A peeling step of peeling the biaxially stretched film;
A method for producing an electromagnetic wave reflection film, comprising: forming a reflection layer including a cholesteric liquid crystal that reflects an electromagnetic wave having a peak wavelength in an infrared region on the surface of the resin layer after peeling.   The method for producing an electromagnetic wave reflecting film according to claim 1, wherein the biaxially stretched film is a film in which a laminated surface is rubbed.   The manufacturing method of the electromagnetic wave reflection film of Claim 1 or 2 which performs the said reflection layer formation process after performing the rubbing process on the surface of the said resin layer after the said peeling process.   The said biaxially stretched film is a manufacturing method of the electromagnetic wave reflective film in any one of Claim 1 to 3 which is a polyethylene terephthalate film.

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