JP7279346B2 - Light control film, light control device - Google Patents

Description

The present invention relates to a light control film using liquid crystal.

The light control film has a liquid crystal layer between a pair of transparent electrodes, and changes the orientation direction of liquid crystal molecules in the liquid crystal layer by changing the voltage applied to the transparent electrodes. The transparency of the light control film changes by changing the orientation direction of the liquid crystal molecules. Types of light control films are broadly classified into a normal mode that does not have an alignment film and a reverse mode that has an alignment film. In the normal mode, the transmittance of the liquid crystal layer is increased by applying the driving voltage, and the transmittance of the liquid crystal layer is decreased by stopping the application of the driving voltage. In the reverse mode, the transmittance of the liquid crystal layer is decreased by applying the drive voltage, and the transmittance of the liquid crystal layer is increased by stopping the application of the drive voltage (see Patent Documents 1 and 2).

By fixing the light control film to a transparent base material such as glass, for example, it can be used for window glass, exhibition windows, partitions, and the like. For imparting mechanical strength, light management films are often used, especially in the form of laminated glass. The form of laminated glass is a form in which a light control film is sandwiched between a pair of glass plates and adhered to each other with an interlayer film.

WO2016/72498 Japanese Patent No. 4387931

A polyethylene terephthalate (PET) film is generally used as the base material of the light control film. In addition, PVB (polyvinyl butyral) resin is often used for the interlayer film of laminated glass. PVB has excellent adhesion to glass, but has a problem of low adhesion to resins such as PET.

An object of the present invention is to provide a light control film suitable for laminated glass using PVB as an interlayer.

A light control film according to the present invention for solving the above problems is a first transparent electrode having a first base film and a first transparent electrode formed on the first base film. a second transparent electrode film having a film, a second base film, and a second transparent electrode formed on the second base film; the first transparent electrode and the second transparent electrode; a liquid crystal layer sandwiched between the first transparent electrode film and the second transparent electrode film arranged to face two transparent electrodes, wherein the first base film and the The surface free energy of the second base film is 50 mN/m or more.

A PET film is used for the first base film and the second base film of the light control film.

A light control device may be formed by laminating and integrating a transparent plate having a higher rigidity and a larger thickness than the light control film on at least one side of the light control film via an intermediate film made of an adhesive resin.

In the light control device, the interface between the light control film and the intermediate film preferably has a tensile shear bond strength of 5 N/25 mm ² or more as defined in JIS K 6850 (1999).

Furthermore, it is preferable that the intermediate film is an intermediate film containing PVB resin.

ADVANTAGE OF THE INVENTION According to this invention, the light control film suitable for the laminated glass using PVB resin as an intermediate film can be provided.

The figure which shows the structure of the light control film of embodiment of this invention. FIG. 2 is a diagram showing the structure of a light control film having a hard coat layer formed thereon according to an embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited by the following description.

<Light control film>
As shown in FIG. 1 , the light control film 100 includes a pair of transparent electrode films 15 , 15 , a liquid crystal layer 13 , and a power supply section 110 . Each transparent electrode film 15 is a multilayer body comprising a film substrate 11 and a transparent electrode 12 in this order. A pair of transparent electrode films 15 and 15 sandwich the liquid crystal layer 13 with each transparent electrode 12 facing the liquid crystal layer 13 .

Film substrate 11 can be any substantially transparent flexible film substrate suitable for roll to roll manufacturing. In this embodiment, polyethylene terephthalate (PET) is used. Ultraviolet absorbers, stabilizers, and the like may be added to the PET film.

The film substrate 11 has a surface free energy of 50 mN/m or more on the surface opposite to the surface in contact with the liquid crystal layer 13 . In addition, the surface free energy of the surface of the film substrate 11 in contact with the liquid crystal layer 13 may be 50 mN/m or more. A film substrate having a surface with a surface free energy of 50 mN/m or more is produced, for example, by subjecting an untreated PET film to corona treatment or plasma treatment, or by forming a hydrophilic hard coat layer.

The transparent electrode 12 can be made of any conventionally known electrode material having transparency. and the like. The transparent electrode 12 can be formed by using a physical vapor deposition method (PVD method) such as a vacuum deposition method or a sputtering method, various chemical vapor deposition methods (CVD method), various coating methods, and the like. Moreover, when patterning of the transparent electrode 12 is required, patterning of the transparent electrode 12 can be performed by an arbitrary method such as an etching method, a lift-off method, a laser trimming method, or a method using various masks.

The liquid crystal layer 13 is, for example, a polymer network liquid crystal (PNLC), and includes liquid crystal molecules and a three-dimensional polymer network made of a resin. The liquid crystal molecules are held in the gaps of the polymer network. ing. The liquid crystal layer 13 may be of other structures, such as polymer dispersed liquid crystal (PDLC).

Conventionally known liquid crystal molecules such as nematic liquid crystals, smectic liquid crystals, and cholesteric liquid crystals can be used as the liquid crystal molecules. Among them, in consideration of driving at a low voltage and scattering characteristics, a material having a high anisotropy of dielectric constant and a large anisotropy of refractive index is preferable. The liquid crystal molecules may have functional groups such as ethylene groups that undergo polymerization reactions to form polymer networks.

The liquid crystal layer 13 may be in either normal mode or reverse mode. The liquid crystal layer 13 in the normal mode becomes a transmission state when a voltage is applied (ON), and becomes a scattering state when the voltage is removed (OFF). The liquid crystal layer 13 in the reverse mode becomes a transmission state when the voltage is removed (OFF), and becomes a scattering state when the voltage is applied (ON).

When the reverse mode liquid crystal layer 13 is used for the light control film 100 , the light control film 100 has an alignment film between each transparent electrode 12 and the liquid crystal layer 13 . The orientation film is selected according to the orientation method of the liquid crystal layer (TN method, VA method, IPS method, OCB method, etc.) to exhibit molecular orientation that exhibits a transparent state when the voltage is removed (OFF). Either an alignment film or a vertical alignment film is used.

In the production of a light control film having a liquid crystal layer 13 by reverse mode PNLC, a mixture of a liquid crystal and a photopolymerizable compound (monomer) is applied to a pair of transparent electrode films 15 (film substrate 11, transparent electrode 12, alignment layer). (not shown) are laminated). Next, by irradiating ultraviolet rays under certain conditions, the photopolymerizable compound in the liquid crystal is changed into a polymer by photopolymerization. Photopolymerization and cross-linking form a polymer network with countless fine domains (macromolecular voids) in the liquid crystal. On the other hand, in the production of the normal mode light control film, the transparent electrode 12 is laminated on the film substrate 11 instead of the transparent electrode film 15 in which the transparent electrode 12 and the orientation layer are laminated on the film substrate 11. A transparent electrode film 15 not laminated with an orientation layer is used, and the same procedure is followed.

Spacers may be introduced into the liquid crystal layer 13 . By introducing spacers, the thickness of the liquid crystal layer 13 can be kept uniform.

Although the spacer is not particularly limited, a granular resin spacer, a granular glass spacer, or the like can be preferably used.

Power feeding portion 110 is formed to feed power from the outside through a lead wire. Each power supply part 110 is formed by, for example, exposing the transparent electrode 12 by half-cutting, laminating a conductive paste and a conductive tape on the surface of the exposed transparent electrode 12, forming solder on the conductive tape, and connecting to a lead wire. be done.

When the liquid crystal layer 13 is in the first state (a state in which the liquid crystal molecules are aligned so that the light control film 100 exhibits opacity), the total light transmittance of the liquid crystal layer 13 is 10% or less, and the haze value is , is preferably 80% or more. When the liquid crystal layer 13 is in the second state (a state in which the liquid crystal molecules are aligned so that the light control film 100 exhibits transmission), the total light transmittance of the liquid crystal layer 13 is 80% or more, and the haze value is It is preferably 10% or less. The total light transmittance of each layer can be measured by a method conforming to JIS K 7361-1 (ISO 13468-1)). Also, the haze value of each layer can be measured by a method conforming to JIS K 7361 (ISO 14782).

A sealing portion 14 for protecting the liquid crystal layer 13 from moisture, acid, ultraviolet rays, etc. is provided at the periphery of the light control film 100 by coating.

As the material used for the sealing portion 14, for example, curable resins such as epoxy-based resins, urethane-based resins, acrylic-based resins, vinyl acetate-based resins, en-thiol-based resins, silicone-based resins, and modified polymers can be used. can. The curing type of the curable resin used for the sealing portion 14 may be any of a thermosetting type, a photo-curing type, a moisture-curing type, an anaerobic-curing type, and the like. The sealing portion 14 may be added with pigments, fillers, and the like. Considering weather resistance and the like, pigment-based dyes are desirable as the dyes to be added.

Preferably, the seal portion 14 further contains an ultraviolet absorber and has an ultraviolet shielding function. When the film thickness of the seal portion 14 is 150 μm, the transmittance of light (ultraviolet rays) having a wavelength of 380 nm is preferably in the range of 0 to 60%. This can prevent deterioration of the liquid crystal layer 13 due to ultraviolet rays incident from the periphery of the light control film 100 . The ultraviolet absorber can be arbitrarily selected from conventionally known ones and used. For example, inorganic UV absorbers such as titanium oxide, zinc oxide, and cerium oxide, and organic UV absorbers such as benzotriazole, triazine, and benzophenone may be appropriately selected and used alone or in combination of two or more. can be done.

The light control film 100 is used in a form integrated with a rigid transparent member and an adhesive or the like in many applications such as a partition. It is used in the form of laminated glass 200 in applications where resistance to impact is particularly required. The mode of the laminated glass 200 is a mode in which the light control film 100 is sandwiched between a pair of glass plates 150 , 150 and each glass plate 150 and the light control film 100 are adhered by an intermediate film 160 . Polyvinyl acetal resin such as polyvinyl butyral (PVB) resin can be used for the intermediate film 160 . The laminated glass 200 is obtained by laminating the glass plate 150, the intermediate film 160, the light control film 100, the intermediate film 160, and the glass plate 150 in this order. It is manufactured by a method of crimping.

A PET film having one surface subjected to corona treatment was prepared as a film substrate. The surface free energy of the corona-treated surface of the film substrate was 50.1 mN/m. A transparent electrode was formed on the surface of the film substrate opposite to the corona-treated surface, and this was used as a transparent electrode film. Using two sheets of this transparent electrode film, a laminate was produced in which a transparent electrode film, a liquid crystal layer, and a transparent electrode film were laminated in this order. At this time, each transparent electrode film was arranged so that the surface on which the transparent electrode was formed was in contact with the liquid crystal layer. This laminate was designated as Example 1.

Example 2 was a laminate having the same structure as that of Example 1, except that the PET film having one surface subjected to corona treatment was replaced with a PET film having one surface subjected to plasma treatment. The surface free energy of the plasma-treated surface of the PET film used in Example 2 was 59.3 mN/m.

Except that the PET film with corona treatment on one side was replaced with a PET film with a hydrophilic hard coat layer formed with "Hydrophilic anti-fogging hard coat agent LAF2700" (manufactured by Toyochem Co., Ltd.) on one side. A laminate having the same structure as that of Example 1 was used as Example 3. The surface free energy of the hard coat layer of the PET film used in Example 3 was 57.1 mN/m.

A laminate having the same structure as that of Example 1 was used as a comparative example, except that the PET film having one surface subjected to corona treatment was replaced with an untreated PET film having no processing treatment. The surface free energy of the PET film used in the comparative example was 43.8 mN/m.

The surface free energy was determined from the contact angles with respect to three solvents, water, diiodomethane, and hexadecane. The contact angle is measured using a contact angle meter (CA-X type, manufactured by Kyowa Interface Science Co., Ltd.).
Measured by a method conforming to ISR 3257.

Each of the laminates of Examples 1 to 3 and Comparative Example was sandwiched between two glass plates via an intermediate film containing a polyvinyl butyral resin, and processed into a laminated glass. For each laminated glass, the shear peel strength, which is an index of the adhesive strength at the adhesive interface with the PVB resin, was measured. The shear peel strength was measured by a method based on JIS K 6850 (1999) using a tensile tester (EZ-LX, manufactured by Shimadzu Corporation).

Comparative examples with a thickness of 5 N/25 mm or less had a shear peel strength (adhesive strength) of 5 N/25 mm or less at the interface between the PET substrate and the intermediate film. On the other hand, in Examples 1 to 3 in which the surface free energy of the PET substrate is 50 mN/m or more, the shear peel strength (adhesion strength) at the interface between the PET substrate and the interlayer film is 5 N/25 mm or more, and the light control It was shown that the adhesion between the film and the interlayer was high.

As described above, the light control film according to the present invention is suitable for the form of laminated glass.

REFERENCE SIGNS LIST 100 light control film 15 transparent electrode film 11 film substrate 12 transparent electrode 13 liquid crystal layer 14 sealing portion 110 power feeding portion 200 laminated glass 150 glass plate 160 intermediate film

Claims (5)

a first transparent electrode film having a first base film and a first transparent electrode formed on the first base film; a second base film; a second transparent electrode formed on a substrate film; and a second transparent electrode film having the first transparent electrode and the second transparent electrode facing each other. and a liquid crystal layer sandwiched between the transparent electrode film of and the second transparent electrode film,
Furthermore, a sealing portion using a curable resin provided along the peripheral edge portion of the first transparent electrode and the liquid crystal layer from the first base film,
A light control film, wherein the surfaces of the first base film and the second base film opposite to the liquid crystal layer have a surface free energy of 50 mN/m or more. 2. The light control film according to claim 1, wherein said first base film and said second base film are polyethylene terephthalate films. An intermediate film made of an adhesive resin and a transparent plate having a higher rigidity and a greater thickness than the light control film are provided in this order on at least one side of the light control film according to claim 1 or 2. A light control device comprising: 4. The light control device according to claim 3, wherein the interface between the light control film and the intermediate film has a tensile shear adhesive strength defined by JIS K 6850 (1999) of 5 N/25 mm ^<2> or more. 5. The light control device according to claim 3, wherein the intermediate film contains polyvinyl butyral resin.

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