JP2020170127A - Dimming sheet - Google Patents

Abstract

To propose a configuration of a peripheral seal part which is effective in improving the design property in addition to the improvement in waterproof function by a sealant.SOLUTION: Disclosed is a dimming sheet having a dimming layer consisting of a liquid crystal composition in which degradation due to contact with moisture, acid, ultraviolet rays, etc. is likely to occur at the edge of a sheet where the dimming layer is sandwiched. A seal part formed by applying a sealant is arranged so as to cover the exposed side surface of a laminated structure. The seal part is a thermosetting or radiation-curable resin and has a water vapor transmission rate of equal to or less than 100 g/m2-24h.SELECTED DRAWING: Figure 1

Description

The present invention relates to a dimming sheet including an optical element that controls a light transmission state by electrical control.

The light control sheet includes a light control layer containing a liquid crystal composition and a pair of transparent electrodes sandwiching the light control layer. The light transmittance of the light control sheet changes by changing the orientation state of the liquid crystal molecules according to the potential difference between the pair of transparent electrodes (see, for example, Patent Document 1). As a dimming layer that switches between the transmissive state (transparent state) and the scattered state (opaque state) of the liquid crystal, in the voids formed inside the polymer network made of resin formed in a three-dimensional network. A polymer network liquid crystal (PNLC) having a structure in which liquid crystal molecules are arranged, or a polymer dispersed liquid crystal (PDLC) having a structure in which liquid crystal molecules are dispersed in a polymer. The type of liquid crystal composition used is widespread, and in Patent Document 1, it is adopted as a dimming layer that changes the state of transparency-scattering.

When the light control sheet is placed at the boundary between two spaces with a large temperature difference, such as the boundary between the outdoor and indoor areas, moisture due to rainwater, dew condensation, etc. may adhere to the light control sheet. .. When moisture penetrates into the light control layer, the variable function of the light transmittance in the light control sheet is reduced.

Further, the dimming layer made of a liquid crystal material is liable to be deteriorated by acid, moisture, ultraviolet rays and the like. In particular, the sheet edge (peripheral portion) in which the dimming layer is sandwiched is highly likely to come into contact with moisture, acid, ultraviolet rays, etc., and the dimming layer is likely to deteriorate.

As a proposal relating to a seal structure of a peripheral portion in a liquid crystal panel in which a liquid crystal layer (PDLC) is coated on a front substrate and a back substrate is laminated therewith, in Patent Document 2, the front surface of the front substrate, the side surface of the back substrate, and A sealing structure for applying a sealing agent is disclosed on the side surface of the PDLC.

JP-A-2017-187775 JP-A-6-186574

The dimming sheet may be sealed at the end of the dimming sheet and bonded to glass or a partition by using a liquid or paste-like sealing agent at a construction site. At that time, depending on the skill of the operator, uneven coating or poor appearance may occur, and the design property may be easily impaired. An object of the present invention is to propose a dimming sheet that does not easily deteriorate and has excellent design.

The dimming sheet that solves the above problems is
A first transparent electrode film having a first base film and a first transparent electrode formed on the first base film.
A second transparent electrode film having a second base film and a second transparent electrode formed on the second base film.
Dimming containing a liquid crystal composition sandwiched between the first transparent electrode film and the second transparent electrode film arranged so that the first transparent electrode and the second transparent electrode face each other. With layers,
A dimming sheet having a sealing portion covering an exposed side surface of a laminated structure at least a part of a peripheral portion of the first transparent electrode film and the second transparent electrode film.
The sealing portion is made of a sealing agent containing a thermosetting type or radiation curable type resin.
Water vapor permeability of the seal portion is not more than 100g / m ² · 24h,
The content of the acid in the sealant is 104 ppm or less.

A configuration may be configured in which an alignment film is provided between each of the first and second transparent electrodes and the light control layer. The dimming sheet having the alignment film corresponds to the reverse type described later.

A dimming device having a configuration in which a sealing agent is formed so as to cover the peripheral portion of the transparent substrate and the dimming sheet at the peripheral edge of the dimming sheet having any of the above configurations installed on the transparent substrate may be used. As a transparent substrate, a dimming sheet having insufficient rigidity is attached to a glass plate, a partition, or the like for practical use.

It is preferable that the yellowness (YI value) of the sealant specified by JIS K 7373 is 5.0 or less, and the haze of the sealant specified by JIS K 7136 is 3% or less.

INDUSTRIAL APPLICABILITY The present invention provides a dimming sheet that is resistant to deterioration and has excellent design.

The cross-sectional view which shows an example of the dimming apparatus using the dimming sheet which concerns on embodiment of this invention. The cross-sectional view which shows an example of the light control sheet which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, components exhibiting similar or similar functions are designated by the same reference numerals, and duplicate description will be omitted. In addition, for convenience of explanation, the size may be exaggerated and shown in a size different from the actual scale.

FIG. 1 is a cross-sectional view showing an example of a dimming device according to an embodiment of the present invention. The light control sheet 10 includes a light control layer 13, a pair of transparent electrodes 12 and l2 sandwiching both surfaces thereof, and a flexible transparent film 11 sandwiching the light control layer 13 and a pair of transparent electrodes 12 and 12. The light control film 10 is provided with a sealing portion 14 on the peripheral portion thereof. The light control film 10 is installed on a rigid transparent substrate 20.

The material of the transparent substrate 20 is not particularly limited, and the transparent substrate 20 can be appropriately selected according to the intended use. For example, a glass plate, a sheet made of a resin material such as a polycarbonate resin or an acrylic resin may be used alone or as a composite material obtained by combining a plurality of materials, but the present invention is not limited thereto. Further, the transparent substrate 20 may be provided with various functional layers such as a barrier layer in addition to a reflective layer and an absorbing layer against ultraviolet rays, heat rays, electromagnetic waves and the like.

The transparent film 11 can be any substantially transparent flexible film substrate suitable for roll-to-roll production. Specifically, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate resins, acrylic resins, cellulose derivatives such as triacetyl cellulose (TAC), polyether sulfone (PES) resins, Examples of films made of polyimide resins and polyolefin resins such as polyethylene and polypropylene can be exemplified, but are not necessarily limited thereto.

An ultraviolet absorber, a stabilizer, or the like may be added to such a transparent film 11, and an ultraviolet absorbing layer, a heat ray reflecting layer, a barrier layer, or the like is provided on any surface of the transparent film. There is no problem even if there is.

Further, the transparent film may be appropriately subjected to an easy-adhesion treatment, an antistatic treatment, or the like, and there is no problem even if a reinforcing base material or the like is provided.

The transparent electrode 12 can be any conventionally known electrode material having transparency, and can be made of indium tin oxide (ITO) conductive film, tin oxide conductive film, zinc oxide conductive film, polymer conductive film, or the like. Can be exemplified, but is not necessarily limited to these.

Such a transparent electrode 12 is formed by using a physical vapor deposition method (PVD method) such as a vacuum vapor deposition method or a sputtering method, various chemical vapor deposition methods (CVD method), various coating methods, and the like. Can be done.

If it is necessary to pattern the transparent electrode 12 as desired, it can be performed by any method such as an etching method, a lift-off method, a laser trimming method, and a method using various masks.

In the present invention, any type of liquid crystal composition of PDLC or PNLC can be adopted as the dimming layer 13.

The dimming layer 13 made of a liquid crystal element may be in either a normal mode or a reverse mode depending on the mode of use thereof. The dimming layer 13 in the normal mode is in a transmissive state when a voltage is applied (ON), and is in a scattered state when the voltage is removed (OFF). Further, the dimming layer 13 in the reverse mode is put into a transmission state by removing the voltage (OFF) and is in a scattering state by applying a voltage (ON). In the reverse mode, an alignment film is required between each transparent electrode 12 and the light control layer 13. The alignment film is selected according to the alignment method of the dimming layer (TN method, VA method, IPS method, OCB method, etc.) and has a molecular orientation that exhibits a transmission state when the voltage is removed (OFF). Either an alignment film or a vertical alignment film is used.

In the light control layer by PNLC, there are almost no unreacted components in the phase separation, and the polymer network and the liquid crystal region show a behavior of being clearly separated with high purity.

In addition, it is possible to realize an ideal orientation state without performing pre-tilt orientation processing by rubbing the substrate (conductive film), and the liquid crystal molecules are oriented almost uniformly for each domain divided by the polymer network. It will be.

The drive voltage of the PNLC generally depends on the structural characteristics of the polymer network (domain size and shape, film thickness of the polymer network, etc.), and the structure of the polymer network and the obtained light transmittance or light scattering degree. The drive voltage is determined in relation to. In order to construct a PNLC that can obtain sufficient light transmittance or scattering degree in a voltage region of 100 V or less, each domain must have an appropriate size and be uniform, and the shape must be uniform. It is necessary to form a polymer network so as to. In the present invention, the domain size depending on the polymer network structure is controlled to be 3 μm or less, preferably 2 μm or less, and more preferably about 1 μm.

As the polymer material, any conventionally known material can be used, but an ultraviolet curable resin capable of inducing a polymerization reaction by ultraviolet irradiation and being cured is preferably used.

Specifically, various (meth) acrylate compounds such as urethane (meth) acrylate, epoxy (meth) acrylate, and isobonyl (meth) acrylate can be exemplified, but the present invention is not limited thereto.

A polymerization initiator, a sensitizer, various stabilizers, and the like may be added to such an ultraviolet curable resin.

As the liquid crystal material, any conventionally known liquid crystal material such as nematic liquid crystal, smectic liquid crystal, and cholesteric liquid crystal can be used. Among them, those having a high dielectric constant anisotropy and a large refractive index anisotropy are preferable in consideration of driving at a low voltage and scattering characteristics.

Such a liquid crystal material may have a functional group such as an ethylene group to be subjected to the polymerization reaction of the polymer material shown above, or has been introduced as a side chain in advance into the polymer material before the polymerization reaction. You may.

A spacer may be introduced in the dimming layer 13. By introducing the spacer, it is possible to keep the thickness of the dimming layer 13 uniform.

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

As a method for providing the dimming layer 13, a liquid crystal composition is applied onto the transparent film having the transparent electrode by using various coaters or the like, and then the transparent film having the other transparent electrode is laminated. Conventionally known construction methods such as a method and a so-called ODF (One-Drop-Fill) method in which a liquid crystal composition is dropped can be arbitrarily used.

A seal portion 14 for protecting the dimming layer 13 from moisture, acid, ultraviolet rays, etc. is provided on the peripheral edge of the dimming sheet 10 by coating.

As the material used for the sealing portion 14, for example, various resin systems such as epoxy resin, urethane resin, acrylic resin, vinyl acetate resin, en-thiol resin, silicone resin, and modified polymer are thermally cured. Various resin materials such as a mold, a photocurable type, a moisture curable type, and an anaerobic curable type can be used.

Seal portion 14, 100 [mu] m and to 40 ° C. The thickness, 100g / m ² · 24h or less of water vapor transmission rate, measured at 90% RH: having (WVTR water vapor transmission rate). If the seal portion 14 is excellent in blocking moisture and oxygen without requiring an excessive thickness, the non-display area (bezel) without causing a step in which the seal is thickened at the peripheral edge of the dimming sheet 10. Part) is narrowed and made compact. This improves the design.

It can be said that it is desirable that the sealing portion 14 for obtaining such characteristics is substantially transparent, but dyes, fillers and the like may be added as appropriate depending on the situation. When adding a dye, it is desirable to use a pigment-based dye in consideration of weather resistance and the like.

When coloring the seal portion 14, from the viewpoint of designability, the yellowness (YI value) of the sealant defined by JIS K 7373 is preferably 5.0 or less. In addition, JIS K 7
The haze of the sealant defined in 136 is preferably 3% or less.

Further, the sealing portion 14 preferably has a transmittance of light (ultraviolet rays) having a wavelength of 380 nm in the range of 0 to 60%. As a result, it is possible to prevent the light control layer 13 from being deteriorated due to the incident of ultraviolet rays from the peripheral edge of the light control film 10. In order to obtain the sealing portion 14 having such characteristics, it is desirable that an ultraviolet absorber is added to the sealing agent.

As the ultraviolet absorber, any conventionally known one can be arbitrarily used. Specifically, for example, inorganic UV absorbers such as titanium oxide, zinc oxide, and cerium oxide and organic UV absorbers such as benzotriazole, triazine, and benzophenone are appropriately selected, and are used alone or in combination of two or more. Can be used as a mixture of.

Regardless of the composition and formulation of the sealing agent constituting the sealing portion 14, the content of acid in the sealing agent is preferably 100 ppm or less.

By providing the sealing portion 14 as described above, it is possible to provide a highly reliable dimming sheet 10 and a dimming device having extremely high designability and suppressing problems such as deterioration.

FIG. 2 is an explanatory diagram relating to a mode in which the dimming sheet 10 is used alone without being attached to the transparent substrate 20.

As shown in the figure, the seal portion 14 is provided so as to cover the side surface where the laminated structure of the light control sheet 10 is exposed and the end portion of the surface of the transparent film 11 opposite to the surface in contact with the transparent electrode 12. Be done. When the light control sheet 10 is rectangular in a plan view, the seal portions 14 are formed on the two sides of the light control sheet 10 at both the left and right ends in the same figure (cross-sectional view), but the seal portion 14 has four rectangular sides. It may be formed in all.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples in which the water vapor permeability (WVTR) and the acid content in the sealant are variously changed for the seal portion 14.

Two flexible transparent films on which a transparent electrode made of ITO was formed were prepared, and a spacer of 25 μm was applied to one of them.

Then, the following liquid crystal composition was dropped onto the spacer-coated surface by the ODF method, and then bonded so that the ITO surfaces of the other transparent film with a transparent electrode faced each other, and the illuminance of 60 mW was cut to a wavelength of 350 nm or less. Using a metal halide lamp, ultraviolet irradiation was performed at 7 J / cm ^{2 in} terms of 365 nm to obtain a dimming sheet.

A transparent substrate with an adhesive material was laminated on the light control sheet, cut into a desired shape, and then a part of the end portion was cut in half to make it conductive with the electrode layers on both sides to form a feeding portion.

A dimming device (6 types of samples) having a structure in which a sealing portion is formed so as to cover the peripheral portion of the transparent substrate and the dimming sheet at the peripheral portion of the dimming sheet formed by forming the power feeding portion and laminating with the transparent substrate. ) Was obtained.

Three types of sealants, A, B and C, were used. The sealants A, B and C are all made of thermosetting or radiation curable acrylic resin or epoxy resin. The acid substance content of A is 32 ppm, the acid substance content of B is 104 ppm, and the acid substance content of C is 1028 ppm.

In Example 1, A was used as a sealing agent to form a sealing portion having a thickness of 130 μm. Water vapor permeability of the seal portion was 80g / m ² · 24h.

In Example 2, A was used as a sealing agent to form a sealing portion having a thickness of 100 μm. Water vapor permeability of the seal portion was 100g / m ² · 24h.

In Example 3, B was used as a sealing agent to form a sealing portion having a thickness of 50 μm. Water vapor permeability of the seal portion was 100g / m ² · 24h.

In Comparative Example 1, A was used as a sealing agent to form a sealing portion having a thickness of 70 μm. Water vapor permeability of the seal portion was 150g / m ² · 24h.

In Comparative Example 2, B was used as a sealing agent to form a sealing portion having a thickness of 30 μm. Water vapor permeability of the seal portion was 120g / m ² · 24h.

In Comparative Example 3, C was used as a sealing agent to form a sealing portion having a thickness of 60 μm. Water vapor permeability of the seal portion was 90g / m ² · 24h.

Table 1 shows the evaluation results of each sample based on the following evaluation means.
<Change in appearance at the end>
After manufacturing the dimming device, several reliability tests including an environmental resistance test under high temperature and high humidity conditions were performed, and after one week, the presence or absence of deterioration of the dimming layer near the peripheral edge of the dimming sheet was visually confirmed. ..

In Examples 1, 2 and 3, there was no deterioration in the appearance of the edges after the reliability test.

Deterioration of the appearance of the edges was confirmed in Comparative Examples 1 and ^{2 in} which the water vapor transmittance of the sealed portion exceeded 100 g / m 2.24 h.

Further, in Comparative Example 3 in which the acid substance content of the seal portion exceeds 100 ppm, the acid contained excessively in the dimming layer and the transparent electrode and the seal portion came into contact with each other at the edge of the dimming sheet covered by the seal portion. Deterioration of the appearance of the edges was confirmed.

10 ... Dimming sheet 11 ... Transparent film 12 ... Transparent electrode 13 ... Dimming layer 14 ... Sealing part 20 ... Transparent substrate

Claims (4)

A first transparent electrode film having a first base film and a first transparent electrode formed on the first base film.
A second transparent electrode film having a second base film and a second transparent electrode formed on the second base film.
Dimming containing a liquid crystal composition sandwiched between the first transparent electrode film and the second transparent electrode film arranged so that the first transparent electrode and the second transparent electrode face each other. With layers,
A dimming sheet having a sealing portion covering an exposed side surface of a laminated structure at least a part of a peripheral portion of the first transparent electrode film and the second transparent electrode film.
The sealing portion is made of a sealing agent containing a thermosetting type or radiation curing type resin.
Water vapor permeability of the seal portion is not more than 100g / m ² · 24h,
A light control sheet characterized in that the content of acid in the sealant is 104 ppm or less. The dimming sheet according to claim 1, further comprising an alignment film between the first and second transparent electrodes and the dimming layer. The peripheral portion of the dimming sheet according to claim 1 or 2 installed on the transparent substrate is configured such that the sealing portion is formed so as to cover the transparent substrate and the peripheral edge of the dimming sheet. A featured dimming device. According to claim 1 or 2, the yellowness (YI value) specified by JIS K 7373 of the sealant is 5.0 or less, and the haze specified by JIS K 7136 is 3% or less. The described dimming sheet.