Light control film and transparent conductive film

Abstract

The purpose of the present invention is to provide a light control film that has excellent appearance quality by suppressing cissing defects and foreign matter defects, and a transparent conductive film. A light control film according to the present embodiment is characterized by comprising: a pair of transparent conductive films; and a light control layer located between the transparent conductive films, wherein the surface tension of a surface, which is in contact with the light control layer, of each transparent conductive film is 51 to 70 dyn / cm inclusive. A light control film according to the present embodiment is characterized in that a transparent conductive film is applied to the light control film, and the surface tension of a surface thereof that is in contact with a light control layer of the light control film is 51 to 70 dyn / cm inclusive.

Description

Light control film and transparent conductive film

[0001] The present invention relates to a light control film and a transparent conductive film.

[0002] Patent Document 1 discloses that the surface tension of the transparent conductive layer of the transparent conductive film used in the light control film is 28 dyn / cm or more and 50 dyn / cm or less, and that this can prevent uneven bonding between the transparent conductive film and the light control layer and can also improve adhesion between the transparent conductive layer and the light control layer.

[0003] International Publication No. 2018 / 180172

[0004] Since the light-controlling layer is formed directly on the surface of the transparent conductive film, it is strongly influenced by the surface of the transparent conductive film. It has been found that, depending on the magnitude of the surface tension, cissing defects and foreign matter defects are observed in the light-controlling layer, resulting in problems such as poor appearance and deterioration of characteristics.

[0005] The present invention has been made in view of the above points, and has an object to provide a light control film and a transparent conductive film that suppress cissing defects and foreign matter defects and have excellent appearance quality.

[0006] The light-controlling film of this embodiment has a pair of transparent conductive films and a light-controlling layer located between the transparent conductive films, and is characterized in that the surface tension of the transparent conductive film surface in contact with the light-controlling layer is 51 dyn / cm or more and 70 dyn / cm or less.

[0007] The transparent conductive film of this embodiment is a transparent conductive film that is applied to a light-controlling film, and is characterized in that the surface tension of the surface that contacts the light-controlling layer of the light-controlling film is 51 dyn / cm or more and 70 dyn / cm or less.

[0008] According to the present invention, it is possible to provide a light control film that can reduce the occurrence of cissing defects and foreign matter defects and has good appearance quality, and a transparent conductive film used therefor.

[0009] 1 is a cross-sectional schematic diagram of a light-control film according to a first embodiment; FIG. 2 is an enlarged schematic diagram showing a state in which a cissing defect has occurred in the light-control layer; (a) is a photograph of a cissing defect, and (b) is its schematic diagram; FIG. 3 is an enlarged schematic diagram showing a state in which a foreign matter defect has occurred in the light-control layer; (a) is a photograph of a foreign matter defect, and (b) is its schematic diagram; FIG. 4 is an explanatory diagram showing a method for measuring defect size; FIG. 5 is a cross-sectional schematic diagram of a light-control film according to a second embodiment; FIG. 6 is a cross-sectional schematic diagram of a light-control film according to a third embodiment; FIG. 7 is a cross-sectional schematic diagram of a light-control film according to a fourth embodiment; FIG. 8 is a graph showing the relationship between the surface tension of a transparent conductive film and the number of cissing defects and the number of foreign matter defects.

[0010] The following describes in detail an embodiment of the present invention, but the following description is an example (representative example) of the embodiment of the present description, and the present invention is not limited to these contents as long as it does not go beyond the gist of the present invention.

[0011] <Configuration of light control film 10 in first embodiment> Figure 1 is a cross-sectional schematic diagram of light control film 10 in the first embodiment. As shown in Figure 1, light control film 10 is configured to have a pair of transparent conductive films 1, 1 and a light control layer 2 located between the transparent conductive films 1, 1. The light control layer 2 is in direct contact with the transparent conductive film surfaces 1a, 1a.

[0012] (Transparent conductive film 1) The transparent conductive film 1 is composed of a transparent substrate 3 and a transparent conductive layer 4 formed on the surface of the transparent substrate 3. Here, "film" refers to a planar shape in which the planar width and length are much greater than the thickness, but it can also be read as "sheet." In this embodiment, "film" and "sheet" are not distinguished by the thickness specified in the JIS standard. The surface of the transparent conductive layer 4 facing the photochromic layer 2 constitutes the transparent conductive film surface 1a that is in direct contact with the photochromic layer 2.

[0013] The material of the transparent substrate 3 is not limited, but for example, a PET (Polyethylene Terephthalate) film is preferably used.

[0014] The transparent conductive layer 4 is a transparent layer having conductivity, and the material is not limited, but examples thereof include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide, zinc oxide, carbon nanotubes (CNT), polymers containing poly(3,4-ethylenedioxythiophene) (PEDOT), and multilayer films containing Ag alloy thin films. Of these, it is preferable to use ITO or an Ag alloy for the transparent conductive layer 4.

[0015] Although there are no limitations on the film thickness, the transparent substrate 3 has a thickness of about 50 μm to 200 μm, and the transparent conductive layer 4 has a thickness of about 10 nm to 100 nm.

[0016] (Light-modulating layer 2) The light-modulating layer 2 is composed of, for example, a polymer network liquid crystal (PNLC: Polymer Network Liquid Crystal), a polymer dispersed liquid crystal (PDLC: Polymer Dispersed Liquid Crystal), or a nematic curvilinear aligned phase (NCAP) liquid crystal. For example, a polymer network liquid crystal has a three-dimensional mesh-like polymer network and holds liquid crystal molecules in the voids of the polymer network. The liquid crystal molecules contained in the light-modulating layer 2 have, for example, a positive dielectric anisotropy, and the dielectric constant in the long axis direction of the liquid crystal molecules is larger than the dielectric constant in the short axis direction of the liquid crystal molecules. The liquid crystal molecules are, for example, Schiff base-based, azo-based, azoxy-based, biphenyl-based, terphenyl-based, benzoate-based, tolan-based, pyrimidine-based, cyclohexanecarboxylic acid ester-based, phenylcyclohexane-based, or dioxane-based liquid crystal molecules.

[0017] The light-controlling layer 2 in this embodiment preferably contains liquid crystal molecules, a photocurable resin, and spacers.

[0018] <How the light-control film 10 of the present embodiment was developed> Figure 2 is an enlarged schematic diagram showing a state in which a cissing defect 13 has occurred in a conventional light-control layer 12. As shown in Figure 2, a cissing defect 13 was observed near the boundary between a pair of transparent conductive films 11 and the light-control layer 12 located between the transparent conductive films 11, resulting in poor appearance. Figure 3(a) is a photograph of the cissing defect, and Figure 3(b) is a schematic diagram thereof.

[0019] Fig. 4 is an enlarged schematic diagram showing a state in which a foreign matter defect 14 has occurred in a conventional light-controlling layer 12. As shown in Fig. 4, a foreign matter 14a has been mixed into the light-controlling layer 12 located between a pair of transparent conductive films 11, and a foreign matter defect 14 including the foreign matter 14a and its surroundings has been observed, resulting in a poor appearance. Defects such as the formation of a void or irregular alignment of liquid crystal molecules have occurred around the foreign matter 14a. Fig. 5(a) is a photograph of the foreign matter defect, and Fig. 5(b) is a schematic diagram thereof.

[0020] In this way, the light-controlling layer 12 is formed in direct contact with the transparent conductive film 11. For this reason, it has been found that the appearance and characteristics are affected by the transparent conductive film surface 11a, and the above-mentioned cissing defects 13 and foreign matter defects 14 occur.

[0021] Therefore, as a result of intensive research, the inventors have invented a light control film 10 that has good appearance quality and can reduce the occurrence of cissing defects and foreign matter defects by adjusting the surface tension of the transparent conductive film surface 1a.

[0022] <Characteristics of the light-controlling film 10 of this embodiment> This embodiment is characterized in that the surface tension of the transparent conductive film surface 1a in contact with the light-controlling layer 2 is 51 dyn / cm or more and 70 dyn / cm or less. The surface tension is evaluated in accordance with JIS K 6768.

[0023] By adjusting the surface tension within the above range, the occurrence of cissing defects 13 shown in FIG. 2 and foreign matter defects 14 shown in FIG. 4 can be suppressed. In this embodiment, the defect sizes of cissing defects and foreign matter defects are set to a diameter of 2.0 mm or more. For circular or elliptical defects as shown in FIG. 6( a) or irregular shapes as shown in FIG. 6( b), the diameter φ can be calculated by measuring the width dimension a and the length dimension b, respectively, and then calculating the formula (width dimension a + length dimension b) / 2. The width dimension a and the length dimension b are orthogonal to each other. While circular, elliptical, and irregularly shaped defects are exemplified here, the diameter φ can be calculated in the same manner for defects of other shapes.

[0024] As shown in Fig. 2, cissing defects 13 occur near the interface between the photochromic layer 12 and the transparent conductive film 11, but by setting the surface tension of the transparent conductive film surface to 51 dyn / cm or more, the wettability at the interface is improved, and the occurrence of cissing can be suppressed when the photochromic material is applied. On the other hand, if the surface tension of the transparent conductive film surface is too high, foreign matter 14a is likely to become mixed into the photochromic layer 12 during the coating process of the photochromic material, as shown in Fig. 4, so by setting the surface tension to 70 dyn / cm or less, it is possible to suppress the intrusion of foreign matter 14a during the coating of the photochromic layer.

[0025] In this embodiment, the surface tension is preferably 54 dyn / cm or more, more preferably 56 dyn / cm or more, and is preferably 66 dyn / cm or less, more preferably 64 dyn / cm or less, and even more preferably 62 dyn / cm or less.

[0026] In this embodiment, the total number of defects including cissing defects and foreign matter defects is set to 0.69 / m ２ The number of particles can be reduced to 0.5 particles / m or less, preferably 0.5 particles / m ２ More preferably, it can be 0.45 pieces / m or less. ２ You can do the following:

[0027] As the surface modification treatment for adjusting the surface tension, corona treatment or atmospheric pressure plasma treatment can be carried out, but the treatment is not limited to these.

[0028] <Configuration of light-controlling film in other embodiments> In Figure 7, the transparent conductive film 5 is a laminated film of a transparent substrate 3 / transparent conductive layer 4 / protective layer 6, and the transparent conductive film surface 5a in contact with the light-controlling layer 2 is the protective layer 6.

[0029] In FIG. 8, the transparent conductive film 7 is a laminated film of a transparent substrate 3 / a transparent conductive layer 4 / an alignment layer 8 , and the surface 7 a of the transparent conductive film in contact with the light-controlling layer 2 is the alignment layer 8 .

[0030] In FIG. 9, the transparent conductive film 9 is a laminated film of a transparent substrate 3 / a transparent conductive layer 4 / a protective layer 6 / an alignment layer 8 , and the transparent conductive film surface 9 a in contact with the light-controlling layer 2 is the alignment layer 8 .

[0031] As described above, the surface of the transparent conductive film in contact with the light-controlling layer 2 is not limited to the transparent conductive layer 4 as shown in Fig. 1, but may be a protective layer 6 as shown in Fig. 7 or an alignment layer 8 as shown in Figs. 8 and 9. In any case, the surface tension of the transparent conductive film surfaces 6a, 7a, and 8a is adjusted to 51 dyn / cm or more and 70 dyn / cm or less.

[0032] The configuration in which an orientation layer 8 is provided in the layer structure of the light control film as shown in FIGS. 8 and 9 is applied to a reverse-type light control film.

[0033] (Alignment layer 8) The alignment layer 8 is a layer that controls the alignment of the liquid crystal molecules contained in the light control layer 2. The light control film 10 of this embodiment shown in Figures 8 and 9 is a reverse-type light control film, which is transparent when no driving voltage is applied, with the liquid crystal molecules oriented along the normal direction of the alignment layer 8 (vertical alignment), and becomes opaque when a driving voltage is applied.

[0034] There is no limitation on the material that constitutes the alignment layer 8, but examples thereof include polyamide, polyimide, polycarbonate, polystyrene, polysiloxane, polyesters such as polyethylene terephthalate and polyethylene naphthalate, and polyacrylates such as polymethyl methacrylate. Of these, it is preferable to use a polyimide-based resin.

[0035] Although there are no limitations on the film thickness of the alignment layer 8, it is about 50 nm to 250 nm, and preferably about 100 nm to 200 nm, which allows for excellent alignment regulation of the liquid crystal molecules.

[0036] In the reverse type, the appearance quality in the transparent state with the power off is important. Therefore, it is desirable to adjust the surface tension of the surface of the alignment layer 8 to minimize the occurrence of cissing defects and foreign matter defects between the alignment layer 8 and the light-controlling layer 2, thereby obtaining excellent appearance quality.

[0037] 7 and 9 is not particularly limited and may be, for example, a primer layer. In addition, the transparent conductive film may include at least one functional layer, such as a hard coat layer, an antiblocking layer, a primer layer, or an index matching layer. When the functional layer corresponds to the transparent conductive film surface in contact with the switchable layer 2, the surface tension of the functional layer surface is adjusted to 51 dyn / cm or more and 70 dyn / cm or less.

[0038] The present invention will be described in detail below with reference to examples carried out to clarify the effects of the present invention, but the present invention is not limited to the following examples.

[0039] <Surface Modification Method> The surface of the transparent conductive layer of the transparent conductive film was subjected to a modification treatment. Although the modification treatment method is not limited, in this experiment, atmospheric pressure plasma treatment was performed. In the experiment, the electrode output was controlled at 0% to 90% of 30 kV.

[0040] <Method for Evaluating Surface Tension> The surface tension of the transparent conductive layer surface was determined in accordance with JIS K 6768 (Plastics - Films and Sheets - Wetting Tension Test Method).

[0041] <Preparation of Light Control Film> Using a plurality of transparent conductive films with different surface tensions subjected to the above surface modification treatment, light control films shown in FIG. 1 were prepared.

[0042] <Defect Evaluation Method> Defects were evaluated using an optical inspection machine. A high-intensity LED was used for illumination, and the detection method was a scattering transmission type.

[0043] In determining whether a defect is a cissing defect or a foreign matter defect, defects with a diameter of 2 mm or more are considered to be defects. The defect size is determined using the method shown in Figure 6. The experimental results are shown in Table 1 and Figure 10.

[0044]

[0045] The total number of defects, including cissing and foreign matter, is 0.69 / m ２ If it is more than this, the judgment is marked as ×, and the number is 0.69 / m ２ If the result was below the above, the result was judged as ◯.

[0046] According to experiments, when the surface tension is 50 dyn / cm or less, many cissing defects occur, and the total number of defects is 0.69 / m. ２ When the surface tension is 71 dyn / cm or more, many foreign matter defects occur, and the total number of defects reaches 0.69 / m ２ That's all.

[0047] Therefore, the surface tension is set to 51 dyn / cm or more and 70 dyn / cm or less, and preferably 54 dyn / cm or more, or 56 dyn / cm or more and 66 dyn / cm or less, or 64 dyn / cm or less.

[0048] This application is based on Japanese Patent Application No. 2024-086017, filed May 28, 2024, the contents of which are incorporated herein in their entirety.

Claims

1. A light-controlling film comprising a pair of transparent conductive films and a light-controlling layer positioned between the transparent conductive films, wherein the surface tension of the transparent conductive film surface in contact with the light-controlling layer is 51 dyn / cm or more and 70 dyn / cm or less.

2. The light control film according to claim 1, wherein the light control layer contains liquid crystal molecules, a photocurable resin, and spacers.

3. A transparent conductive film to be used in a light control film, characterized in that the surface tension of the surface in contact with the light control layer of the light control film is 51 dyn / cm or more and 70 dyn / cm or less.

4. The light control film or transparent conductive film according to claim 1 or 3, characterized in that the surface tension is 56 dyn / cm or more.

5. The light control film or transparent conductive film according to claim 1 or 3, characterized in that the outermost layer in contact with the light control layer is one of a transparent conductive layer, a protective layer, or an alignment layer.

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