JP2017200964A - Light control film, laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light ray control film whose transparency changes depending on temperature. A film for light control, comprising polyvinyl butyral, an ethylene-vinyl acetate copolymer, and a plasticizer. [Selection diagram] None

Description

  The present invention relates to a light control film and a laminate.

Conventionally, a material whose light transmittance changes with temperature is known.
For example, Patent Document 1 describes a heat-sensitive thermoplastic resin composition that contains an amorphous polyester resin and a vinyl cyanide-aromatic vinyl copolymer and is transparent at room temperature and opaque in a high temperature region. .

JP 2002-179928 A

On the other hand, the types of materials exhibiting the above characteristics are not yet sufficient, and further development has been desired.
An object of this invention is to provide the film for light control from which transparency changes with temperature.

  The configuration of the light control film of the present invention is as follows.

(1) A film for light control comprising polyvinyl butyral, an ethylene-vinyl acetate copolymer, and a plasticizer.
(2) The film for light control according to (1), wherein the difference between the refractive index of at least one of polyvinyl butyral and the ethylene-vinyl acetate copolymer and the refractive index of the plasticizer is 0.02 or more.
(3) The film for light control according to (1) or (2), wherein the plasticizer has an SP value of 8.0 to 9.5 (cal / cm ³ ) ^1/2 .
(4) The film for light control according to any one of (1) to (3), which is used for agriculture or building materials.
(5) A laminate including a substrate and the light control film according to any one of (1) to (4) disposed on the substrate.

  According to the present invention, it is possible to provide a light control film whose transparency changes with temperature.

The light control film of the present invention will be described in detail below.
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.
“Light control” in the present specification means controlling the amount of light transmission or transmittance.
The “refractive index” in this specification is a refractive index at a wavelength of 589 nm unless otherwise specified.

As a characteristic point of the film for light control of the present invention, there is a point that two predetermined kinds of resins and a plasticizer are used.
Usually, when two kinds of resins are mixed, a phase separation structure is formed in the mixture, and the mixture becomes opaque. On the other hand, polyvinyl butyral and ethylene-vinyl acetate copolymer show a relatively close refractive index. Therefore, a phase separation structure is formed in the mixture of both, but the mixture itself tends to be transparent.
Further, the plasticizer is mixed at a predetermined ratio with each of the polyvinyl butyral phase and the ethylene-vinyl acetate copolymer phase, and the mixing ratio varies depending on the temperature. Therefore, when heat treatment is applied to the light control film of the present invention that is transparent at room temperature, the compatibility of the plasticizer with each phase changes, and the plasticizer contained in one phase changes to the other. Move to the phase. Therefore, as a result, the difference in refractive index between the two phases increases, and the light control film becomes opaque.
That is, in the light control film of the present invention, the plasticizer moves between the phases as the temperature changes, and the transparency changes.

The film for light control contains polyvinyl butyral, an ethylene-vinyl acetate copolymer, and a plasticizer.
Hereinafter, each component will be described in detail.

<Polyvinyl butyral>
Polyvinyl butyral is a resin having at least vinyl butyral units. Usually, polyvinyl butyral is produced by reacting butyraldehyde with polyvinyl alcohol obtained by saponifying polyvinyl acetate, and often has a vinyl butyral unit, a vinyl alcohol unit, and a vinyl acetate unit.
The vinyl butyral unit, the vinyl alcohol unit, and the vinyl acetate unit correspond to units (repeating units) represented by the following formulas (1) to (3), respectively.

The content of the vinyl butyral unit in the polyvinyl butyral is not particularly limited, but is preferably 40 to 90% by mass and more preferably 60 to 85% by mass with respect to all the units in the polyvinyl butyral.
When the polyvinyl alcohol unit is contained in the polyvinyl butyral, the content of the vinyl alcohol unit is not particularly limited, but is preferably 5 to 50% by mass, and more preferably 10 to 30% by mass with respect to all units in the polyvinyl butyral.
When polyvinyl butyral contains vinyl acetate units, the content of vinyl acetate units is not particularly limited, but is preferably 0.1 to 10% by mass, and preferably 0.5 to 5% by mass with respect to all units in polyvinyl butyral. Is more preferable.

  The weight average molecular weight of polyvinyl butyral is not particularly limited, but is preferably 500 to 100,000 from the viewpoints of handleability and miscibility with an ethylene-vinyl acetate copolymer.

  The refractive index of polyvinyl butyral at room temperature (25 ° C.) is not particularly limited, but is preferably 1.43 to 1.53, and more preferably 1.45 to 1.51.

<Ethylene-vinyl acetate copolymer>
The ethylene-vinyl acetate copolymer is a copolymer mainly composed of ethylene units (repeating units derived from ethylene) and vinyl acetate units.
The ethylene-vinyl acetate copolymer may contain other units other than the ethylene unit and the vinyl acetate unit as long as the effects of the present invention are not impaired.

The total content of ethylene units and vinyl acetate units in the ethylene-vinyl acetate copolymer is preferably 90% by mass or more, and 95-100% by mass with respect to all units in the ethylene-vinyl acetate copolymer. More preferred.
The content of ethylene units in the ethylene-vinyl acetate copolymer is preferably from 50 to 90% by mass, more preferably from 65 to 85% by mass, based on all units in the ethylene-vinyl acetate copolymer.
The content of vinyl acetate units in the ethylene-vinyl acetate copolymer is preferably 10 to 50% by mass and more preferably 15 to 35% by mass with respect to all units in the ethylene-vinyl acetate copolymer.

  The weight average molecular weight of the ethylene-vinyl acetate copolymer is not particularly limited, but is preferably 500 to 100,000 from the viewpoints of handleability and miscibility with polyvinyl butyral.

  The refractive index at room temperature (25 ° C.) of the ethylene-vinyl acetate copolymer is not particularly limited, but is preferably 1.43 to 1.53, and more preferably 1.45 to 1.51.

<Plasticizer>
As described above, the plasticizer is present in the polyvinyl butyral phase and the ethylene-vinyl acetate copolymer phase in the light control film, and moves between the phases as the temperature changes. It is a compound to be produced.

  A known plasticizer can be used as the plasticizer. For example, aliphatic dibasic ester plasticizer, phthalate ester plasticizer, citrate ester plasticizer, trimellitic acid plasticizer, epoxidized vegetable oil, phosphate ester plasticizer, polyester plasticizer, chlorine Liquid paraffin and mixtures thereof can be used.

  Examples of the aliphatic dibasic acid ester plasticizer include an adipic acid ester plasticizer. Examples of the adipate ester plasticizer include di (2-ethylhexyl) adipate, diisodecyl adipate, and diisononyl adipate.

  Examples of the phthalate ester plasticizer include dibutyl phthalate (DBP), di-n-octyl phthalate (DOnP), dimethyl phthalate (DMP), diethyl phthalate (DEP), diheptyl phthalate (DHP), and di-2- Examples include ethylhexyl phthalate (DOP), diisodecyl phthalate (DIDP), butyl benzyl phthalate (BBP), and diisononyl phthalate (DINP).

  Examples of the phosphate plasticizer include aryl phosphate [TPP (triphenyl phosphate), tricresyl phosphate (TCP), trixylyl phosphate, diphenyl cresyl phosphate], alkyl phosphate [trimethyl phosphate, TEP (triethyl phosphate). , Tributyl phosphate, tri-2-ethylhexyl phosphate, trioctyl phosphate, trilauryl phosphate, triisodecyl phosphate], alkyl aryl phosphate [phenyl diethyl phosphate, phenyl dibutyl phosphate, phenyl dioctyl phosphate, diphenyl ethyl phosphate, diphenyl butyl phosphate, diphenyl octyl Phosphate]

Examples of the citrate ester plasticizer include acetyl tributyl citrate (ATBC).
Examples of trimellitic acid-based plasticizers include trimellitic acid n-octyl-n-decyl and trimellitic acid tri-2-ethylhexyl.
Examples of the epoxidized vegetable oil include epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, and epoxidized safflower oil.

The refractive index of the plasticizer at room temperature (25 ° C.) is not particularly limited, but is preferably 1.40 to 1.50, more preferably 1.43 to 1.47.
Among these, the difference between the refractive index of the plasticizer and the refractive index of at least one of polyvinyl butyral and ethylene-vinyl acetate copolymer is 0 in that the change in transparency due to temperature change of the light control film is larger. 0.02 or more is preferable. Among them, the difference between the refractive index of the plasticizer and the refractive index of polyvinyl butyral is 0.02 or more, and the difference between the refractive index of the plasticizer and the refractive index of the ethylene-vinyl acetate copolymer is 0.02 or more. It is more preferable that
Further, the difference in refractive index is more preferably 0.03 or more. The upper limit is not particularly limited, but is often 0.1 or less.
The difference between the refractive index of polyvinyl butyral and the refractive index of the ethylene-vinyl acetate copolymer is not particularly limited, but is preferably 0.01 or less, and preferably 0.005 or less, from the viewpoint of the transparency of the light control film. More preferred. Although a minimum in particular is not restrict | limited, 0 is mentioned.
In addition, the refractive index of each said component (Polyvinyl butyral, an ethylene-vinyl acetate copolymer, and a plasticizer) intends the refractive index of each component at room temperature (25 degreeC).

The range of the SP value of the plasticizer is not particularly limited, but is preferably 8.0 to 9.5 (cal / cm ³ ) ^{1/2 in} that the change in transparency due to the temperature change of the light control film is larger. It is more preferably 8.2 to 9.0 (cal / cm ³ ) ^1/2 .
“SP value” is a solubility parameter. The method described in “Polymer blend” by Saburo Akiyama et al., Pages 125 to (published by CMC, 1981), Journal of Applied Chemistry, Vol. 3, page 71 by Small. It is a value calculated by the well-known method described in (1953).

  The light control film may contain other components than the polyvinyl butyral, the ethylene-vinyl acetate copolymer, and the plasticizer, as long as the effects of the present invention are not impaired. Examples of other components include ultraviolet absorbers, adhesion improvers, plasticizers, light stabilizers, antioxidants, and heat stabilizers.

<Light control film>
The light control film contains the components described above. In the light control film, a phase separation structure is formed in which one of polyvinyl butyral and ethylene-vinyl acetate copolymer forms a continuous phase and the other forms a dispersed phase. The plasticizer may be contained in any of the polyvinyl butyral phase and the ethylene-vinyl acetate copolymer phase.
Note that which of polyvinyl butyral and ethylene-vinyl acetate copolymer forms a continuous phase depends on the amount of components in the light control film. For example, when the content of polyvinyl butyral is higher than the content of the ethylene-vinyl acetate copolymer, the polyvinyl butyral often forms a continuous phase.

The light control film has a high light transmittance at room temperature (25 ° C.) (for example, a light transmittance at a wavelength of 650 nm), and a light transmittance in a high temperature region is lower than a light transmittance near 25 ° C. In addition, although the specific temperature of a high temperature area | region changes with kinds of component to be used, it is usually 50 degreeC or more in many cases, and it is preferable that a high temperature area | region is the range of 50-80 degreeC from the point of handleability. .
The difference between the light transmittance at room temperature (25 ° C.) and the light transmittance in the high temperature region of the light control film is not particularly limited, but is preferably 50% or more in terms of greater transparency and opaqueness. 60% or more is more preferable. The light transmittance at room temperature and the light transmittance at high temperature are intended to be transmittance at a wavelength of 650 nm.

  As described in detail later, the light control film can be suitably used for agricultural applications (for example, for greenhouses) or for building materials (for example, for windows). For example, when the light control film of the present invention is used as a film constituting a greenhouse, the amount of transmitted light is large at room temperature, and the amount of transmitted light decreases as the temperature of the room and the film rises. The rise can be suppressed.

The content of polyvinyl butyral in the light control film is not particularly limited, but is 4 to 95 mass with respect to the total mass of the light control film in that the change in the transparency of the light control film with temperature change is larger. % Is preferable, and 7 to 85% by mass is more preferable.
The content of the ethylene-vinyl acetate copolymer in the light control film is not particularly limited, but it is based on the total mass of the light control film in that the change in transparency of the light control film with temperature change is larger. 4-95 mass% is preferable and 7-85 mass% is more preferable.
The content of the plasticizer in the light control film is not particularly limited, but is 0.1 to 0.1% of the total mass of the light control film in that the change in the transparency of the light control film with temperature change is larger. 20 mass% is preferable and 1-10 mass% is more preferable.

  The mass ratio of polyvinyl butyral and ethylene-vinyl acetate copolymer (mass of polyvinyl butyral / mass of ethylene-vinyl acetate copolymer) in the film for light control is not particularly limited, but for light control accompanying temperature change. 0.05-20 are preferable and 0.1-10 are more preferable at the point with the larger change of transparency of a film.

The average thickness of the light control film is not particularly limited, but is preferably 10 to 10,000 μm, more preferably 100 to 5000 μm, from the viewpoints of handleability and transparent and opaque switching.
The average thickness is obtained by measuring the thickness of any 10 points of the light control film and arithmetically averaging them.

<Application of light control film>
The light control film can be used for various applications. For example, agricultural use, building material use, vehicle use, equipment use, medical use, toy use, miscellaneous goods use, etc. are mentioned. More specifically, a greenhouse is mentioned as an agricultural use. Examples of the building material application include windows (for example, windows of buildings). A sunroof is mentioned as a vehicle use. A medical thermometer is mentioned as a medical use.

  The polyvinyl butyral and ethylene-vinyl acetate copolymer constituting the light control film also have a function as an adhesive resin. Therefore, the light control film can be disposed between the two members so that the light control film can function as an adhesive layer for bonding the two members.

<Method for producing light controlling film>
The production method of the light control film is not particularly limited, and a known method can be adopted.
For example, the following method is mentioned.
(1) Film constituent materials (polyvinyl butyral, ethylene-vinyl acetate copolymer, plasticizer, etc.) are melt-kneaded to form a resin mixture, which is cooled and solidified to obtain a solidified product having an appropriate shape such as a pellet. Get. Next, the obtained solidified product is heated and melted and formed into a film by a compression molding method or an extrusion molding method.
(2) The constituent materials of the film are melt-kneaded to form a resin mixture, and the resin mixture is formed into a film by a compression molding method or an extrusion molding method without cooling and solidifying.
(3) Dissolve the constituent materials of the film in a solvent, apply the obtained solution on a predetermined substrate, and perform a drying treatment as necessary to remove the solvent from the coating film to form a film .

Examples of the melt-kneading apparatus implemented in the above (1) and (2) include known kneading apparatuses such as a batch mixer, a kneader, and a twin-screw extruder capable of continuous kneading.
As kneading conditions such as the kneading time and kneading temperature for melt kneading, optimum conditions are appropriately selected depending on the type of material used.

As the solvent used in the above (3), a known solvent can be used, and examples thereof include water and an organic solvent.
The coating method performed in (3) is not particularly limited, and examples thereof include known coating methods such as bar coating, spin coating, and gravure coating.

<Laminated body>
A laminated body contains a base material and the said film for light control arrange | positioned on a base material.
The kind in particular of base material is not restrict | limited, A well-known base material can be used.
The shape of the substrate is not particularly limited, and examples thereof include a plate shape, a film shape, a sheet shape, a tube shape, a fiber shape, and a particle shape. The substrate surface may be a flat surface, a concave surface, or a convex surface.
As the substrate, a so-called transparent substrate is preferable. Specifically, the transparent substrate is a substrate having a light transmittance of 589 nm at a wavelength of 50% or more.
Examples of the material constituting the substrate include glass and resin. Examples of the resin include polyolefin resin, polycarbonate resin, polyester resin, polyamide resin, fluororesin, and silicone resin.
The thickness of the substrate is not particularly limited, but is often 1 to 20 mm.

  As a suitable aspect of a laminated body, the aspect which pinched | interposed the film for light control with two base materials is also mentioned. More specifically, a laminate including a first substrate, the light control film, and a second substrate can be used. In addition, a glass substrate is used suitably as a 1st base material and a 2nd base material.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited to these.

In this example, the refractive index of each component was a value measured at D line (wavelength 589 nm) using an Abbe refractometer (manufactured by Atago, NAR-1T) at 25 ° C. When contact liquid was required, 1-bromonaphthalene was used.
For the light transmittance of the film, a value measured with a 1 mm thick film using a spectrophotometer (manufactured by Perkin Elmer, Lamba25) capable of temperature control was applied. The measurement was performed at 15 ° C. and 60 ° C., and the value at a wavelength of 650 nm was used.

Example 1
Ethylene-vinyl acetate copolymer (EVA) (Mitsui / DuPont Fluorochemical, EV360, vinyl acetate unit content: 25 mass%, refractive index: 1.4866), polyvinyl butyral (PVB) (Denka, PVB4000- 4, refractive index: 1.4883), and di (2-ethylhexyl) adipate (DOA) (manufactured by Nippon Nippon Chemical Co., Ltd., refractive index: 1.4450, SP value: 8.6 (cal / cm ³ ) ^{1 / 2} ) was put into an internal mixer (labor plast mill, manufactured by Toyo Seiki Seisakusho, Ltd.) at a mass ratio of EVA: PVB: DOA = 50: 50: 10, and kneaded at 120 ° C. for 5 minutes at a blade rotation speed of 30 rpm. Then, the obtained kneaded material was shape | molded into the film of thickness 1mm with the compression molding machine. In addition, the heating temperature at the time of shaping | molding is 120 degreeC, and the cooling temperature is 25 degreeC.
When the light transmittance of the obtained film was measured, it was 64% at 15 ° C. and 3% at 60 ° C., and the difference between the light transmittance at 15 ° C. and the light transmittance at 60 ° C. was 61%. .
In addition, as a composition of each unit (each repeating unit) contained in PVB, the content of the vinyl butyral unit is 80% by mass, the content of the vinyl alcohol unit is 18% by mass, and the content of the vinyl acetate unit is 2% by mass. Met.

(Example 2)
A film was produced in the same manner as in Example 1 except that the mass ratio of EVA, PVB, and DOA was changed to EVA: PVB: DOA = 90: 10: 10.
When the light transmittance of the obtained film was measured, it was 82% at 15 ° C. and 20% at 60 ° C., and the difference between the light transmittance at 15 ° C. and the light transmittance at 60 ° C. was 62%. .

(Example 3)
A film was produced in the same manner as in Example 1 except that the mass ratio of EVA, PVB, and DOA was changed to EVA: PVB: DOA = 20: 80: 10.
When the light transmittance of the obtained film was measured, it was 74% at 15 ° C. and 6% at 60 ° C., and the difference between the light transmittance at 15 ° C. and the light transmittance at 60 ° C. was 68%. .

(Comparative Example 1)
A film was produced in the same manner as in Example 1 except that DOA was not added.
When the light transmittance of the obtained film was measured, it was 72% at 15 ° C and 38% at 60 ° C, and the difference between the light transmittance at 15 ° C and the light transmittance at 60 ° C did not exceed 60%. It was.

Claims (5)

  A film for light control, comprising polyvinyl butyral, an ethylene-vinyl acetate copolymer, and a plasticizer.   The film for light control according to claim 1, wherein a difference between a refractive index of at least one of the polyvinyl butyral and the ethylene-vinyl acetate copolymer and a refractive index of the plasticizer is 0.02 or more. The film for light control according to claim 1 or 2, wherein the plasticizer has an SP value of 8.0 to 9.5 (cal / cm ³ ) ^1/2 .   The film for light control according to any one of claims 1 to 3, which is used for agricultural use or building material use.   The laminated body containing the base material and the film for light control of any one of Claims 1-4 arrange | positioned on the said base material.