Light control film and transparent conductive film

Abstract

To provide a reverse-type light control film and transparent conductive film, which offer reduced white spots and superior appearance quality.SOLUTION: A light control film according to an embodiment comprises a pair of transparent base materials, alignment layers provided on inner sides of the transparent base materials, and a light control layer with liquid crystal molecules provided on the inner sides of the alignment layers, where surfaces of transparent electrode layers facing the alignment layers have an arithmetic average roughness Sa of 2.5 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a display device having a pair of substrates, a pair of electrodes formed on opposing surfaces of the pair of substrates, and an electrolyte layer sandwiched between the pair of electrodes and containing an electrochromic material containing silver and a mediator. One of the pair of electrodes is a transparent electrode with irregularities, and the difference between the maximum height and the minimum height is preferably 50 nm or more and 400 nm or less. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6256881 Summary of the Invention [Problem to be solved by the invention]

[0004] Reverse-type light-control films have a problem in which white spots appear due to the disordered alignment of liquid crystal molecules.

[0005] However, the display device of Patent Document 1 uses a light control method that enables multicolor display by providing relatively large irregularities on the electrode surface, and is different in both configuration and purpose from the reverse-type light control film.

[0006] The present invention has been made in view of the above points, and aims to provide a reverse-type light control film and a transparent conductive film that reduce the occurrence of white spots and have excellent appearance quality. [Means for solving the problem]

[0007] The light control film of this embodiment comprises a pair of transparent substrates, a transparent electrode layer disposed inside the transparent substrates, an alignment layer disposed inside the transparent electrode layer, and a light control layer disposed inside the alignment layer and containing liquid crystal molecules, and is characterized in that the arithmetic mean roughness Sa value of the surface of the transparent electrode layer facing the alignment layer is 2.5 nm or less.

[0008] Alternatively, the light control film of this embodiment has a pair of transparent substrates, a transparent electrode layer arranged inside the transparent substrates, an alignment layer arranged inside the transparent electrode layer, and a light control layer arranged inside the alignment layer and containing liquid crystal molecules, and is characterized in that the height of the protrusions formed on the surface of the transparent electrode layer facing the alignment layer is smaller than the film thickness of the alignment layer.

[0009] Furthermore, the transparent conductive film of this embodiment is a transparent conductive film applicable to a reverse-type light-control film in which a transparent electrode layer is formed on the surface of a transparent substrate, and is characterized in that the arithmetic mean roughness Sa value of the surface of the transparent electrode layer is 2.5 nm or less. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a reverse light control film that can reduce the occurrence of white spots and has good appearance quality, and a transparent conductive film used therefor. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional schematic diagram of a light control film according to an embodiment of the present invention. [Figure 2] FIG. 10 is a partially enlarged schematic diagram for explaining the cause of white spots. [Figure 3] (a) is a photograph of a vitiligo, and (b) is a schematic diagram. [Figure 4] FIG. 2 is a partially enlarged schematic diagram for explaining a characteristic configuration of the light control film in the present embodiment. [Figure 5] 1 is a graph showing the relationship between the arithmetic mean roughness Sa value of the surface of the transparent electrode layer and the number of white spots. [Figure 6] 1 is a graph showing the relationship between the PEEK value and the number of white spots on the surface of a transparent electrode layer. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes in detail an embodiment of the present invention, but the following description is an example (typical example) of the embodiment of the present description, and the present invention is not limited to these details as long as it does not deviate from the gist of the present invention. In addition, the expression "to" includes both a lower limit and an upper limit.

[0013] <Configuration of light control film 10> Fig. 1 is a cross-sectional schematic diagram of a light control film 10 according to a first embodiment. As shown in Fig. 1, the light control film 10 has a laminated structure including a pair of transparent substrates 1, transparent electrode layers 2 formed on the inside of each transparent substrate 1, alignment layers 3 formed on the inside of each transparent electrode layer 2, and light control layers 4 formed on the inside of each alignment layer. The "inside" refers to the opposing side.

[0014] In other words, the light-controlling film 10 is laminated in the following order from the bottom: transparent substrate 1 (first transparent substrate), transparent electrode layer 2 (first transparent electrode layer), alignment layer 3 (first alignment layer), light-controlling layer 4, alignment layer 3 (second alignment layer), transparent electrode layer 2 (second transparent electrode layer), and transparent substrate (second transparent substrate).

[0015] (Transparent conductive film 5) The transparent substrate 1 and transparent electrode layer 2 shown in Fig. 1 constitute a transparent conductive film 5. Here, "film" refers to a planar shape whose planar width and length are much greater than its thickness, but it can also be read as "sheet." Note that in this embodiment, "film" and "sheet" are not distinguished by the thickness defined in the JIS standard.

[0016] Although there is no limitation on the material of the transparent substrate 1, a PET (Polyethylene Terephthalate) film is preferably used.

[0017] The transparent electrode layer 2 is a transparent layer having electrical 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 Ag alloy for the transparent electrode layer 2. Although there are no limitations on the film thickness, the transparent substrate 1 has a thickness of about 50 μm to 200 μm, and the transparent electrode layer 2 has a thickness of about 10 μm to 100 μm.

[0018] The transparent conductive film 5 may also have a functional layer provided between the transparent substrate 1 and the transparent electrode layer 2 or on at least one of the outer surfaces 1a (surfaces opposite to the transparent electrode layer 2) of the transparent substrate 1. The functional layer preferably includes at least one of a hard coat layer, an anti-blocking layer, a primer layer, a protective layer, and an index matching layer, for example.

[0019] (Alignment layer 3) The alignment layer 3 is a layer that controls the alignment of the liquid crystal molecules contained in the light control layer 4. The light control film 10 of this embodiment 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 3 (vertical alignment), and becomes opaque when a driving voltage is applied.

[0020] There is no limitation on the material constituting the alignment layer 3, but examples thereof include polyamide, polyimide, polycarbonate, polystyrene, polysiloxane, polyesters such as polyethylene terephthalate and polyethylene naphthalate, and polyacrylates such as polymethyl methacrylate. Among these, it is preferable to use a polyimide-based resin.

[0021] Although there are no limitations on the film thickness of the alignment layer 3, it is about 50 μm to 250 μm, preferably about 70 μm to 220 μm, and more preferably about 100 μm to 200 μm, which allows for excellent alignment control power for liquid crystal molecules.

[0022] (Photochromic layer 4) The light-controlling layer 4 contains liquid crystal molecules. The liquid crystal molecules have, for example, a positive dielectric anisotropy, and the dielectric constant in the long axis direction of the liquid crystal molecules is greater than the dielectric constant in the short axis direction of the liquid crystal molecules. The liquid crystal molecules are not limited to, but examples include Schiff base, azo, azoxy, biphenyl, terphenyl, benzoate, tolan, pyrimidine, cyclohexane carboxylic acid ester, phenylcyclohexane, and dioxane liquid crystal molecules.

[0023] The light control layer 4 is preferably made of polymer network liquid crystal (PNLC). The polymer network liquid crystal has a three-dimensional mesh-like polymer network, and holds liquid crystal molecules in the voids of the polymer network.

[0024] The PNLC layer in this embodiment preferably contains liquid crystal molecules, a photocurable resin, and spacers.

[0025] <Background to the development of the light control film 10 of this embodiment> Figure 2 is a partially enlarged schematic diagram illustrating the problem of white spots occurring in the conventional light control film. Figure 2 shows only the layers below the light control layer 4 of the light control film 10 shown in Figure 1. Note that, in the conventional light control film, the same problem occurs in the layers above the light control layer 4, but since this is the same as the lower layer, its description will be omitted. In Figure 2, the transparent substrate is designated by the symbol 11, the transparent electrode layer by the symbol 12, the alignment layer by the symbol 13, and the light control layer by the symbol 14.

[0026] As shown in Figure 2, the surface 12a of the transparent electrode layer 12 is not flat but has protrusions 12b. In other words, the surface 12a is uneven. As shown in Figure 2, large protrusions 12b are present and vary widely. As a result, the flatness of the surface 13a of the alignment layer 13 formed on the surface 12a of the transparent electrode layer 12 is reduced, disrupting the vertical alignment of the crystalline molecules 15. As a result, white spots appear even when the device is turned off and is otherwise transparent. Figure 3(a) is a photograph of the white spots, and (b) is a schematic diagram. The whitish circular area in the center of Figure 3 is a white spot, and the diameter of the white spot is 1 mm or more. This makes it visible, resulting in a decrease in appearance quality.

[0027] In particular, as shown in Figure 2, in areas where the height t1 of the protrusions 12b formed on the surface 12a of the transparent electrode layer 12 is greater than the film thickness t2 of the alignment layer 13, the unevenness of the surface 13a of the alignment layer 13 becomes more pronounced, making the vertical alignment of the crystalline molecules 15 more likely to be disturbed.

[0028] Therefore, the inventors have conducted extensive research and have come up with the invention of a reverse-type light control film 10 that can adjust the surface roughness of the transparent electrode layer, smooth the surface of the alignment layer, and reduce the occurrence of white spots.

[0029] <Features of the light control film 10 of this embodiment> This embodiment is characterized in that the arithmetic mean roughness Sa of the surface of the transparent electrode layer 2 facing the alignment layer 3 is 2.5 nm or less.

[0030] The arithmetic mean roughness Sa (international standard for three-dimensional surface texture, ISO25178) is a parameter that extends the arithmetic mean roughness Ra of a line to a surface, and indicates the average of the absolute values ​​of the height differences at multiple points on the measurement surface. The "measurement surface" is defined as, for example, the area of ​​a unit (1 m 2 ), but is not limited to this size, and for example, measurements can be made on a measurement surface with one side greater than 0.5 mm and equal to or less than 5 mm. The Sa value can be measured together with the PEEK value (described later) using a VertScan R3300G Lite from Ryoka Systems Co., Ltd.

[0031] In this embodiment, it is preferable that the maximum height PEEK value of adjacent valleys (which can also be called depressions) and peaks (which can also be called protrusions or convex portions) on the surface of the transparent electrode layer 2 facing the alignment layer 3 is 140 nm or less.

[0032] In this embodiment, by adjusting the arithmetic mean roughness Sa value, and preferably adjusting the PEEK value together with the arithmetic mean roughness Sa value, the flatness of the surface 3a of the alignment layer 3 can be improved compared to conventional methods, as shown in Figure 4, thereby suppressing disturbance in the vertical alignment of the liquid crystal molecules 6 contained in the dimming layer 4 and reducing the occurrence of white spots.

[0033] As shown in Figure 4, the protrusions 2b formed on the surface 2a of the transparent electrode layer 2 are smaller than those shown in Figure 2, and the height t3 of the protrusions 2b is smaller than the film thickness t4 of the alignment layer 3. Here, the height t3 of the protrusions 2b is the dimension from the flat surface 2a (the bottom surface of the recess) of the transparent electrode layer 2, and the film thickness t4 of the alignment layer 3 is represented by the dimension from the surface 2a of the transparent electrode layer 2 to the surface 3a of the alignment layer 3. In this way, when a liquid alignment material is applied to the surface 2a of the transparent electrode layer 2 and cured so that the relationship of height t3 of the protrusions 2b < film thickness t4 of the alignment layer 3 is satisfied, the surface 3a of the alignment layer 3 is made flat, and the number and size of the protrusions formed on the surface 3a of the alignment layer 3 can be reduced.

[0034] Therefore, the alignment layer 3 can exert an excellent alignment control force on the liquid crystal molecules 6, and can properly align the liquid crystal molecules 6 vertically when the power is off. As a result, it is possible to reduce white spots and provide a reverse-type light-control film with good appearance quality. Specifically, 2 The number of white spots with a diameter of 1 mm or more can be reduced to 1 or less, preferably 0.7 or less.

[0035] In this embodiment, the arithmetic mean roughness Sa of the surface 2a of the transparent electrode layer 2 is more preferably 2.0 nm or less, and even more preferably 1.5 nm or less. The PEEK value of the surface 2a of the transparent electrode layer 2 is more preferably 100 nm or less, more preferably 70 nm or less, and even more preferably 50 nm or less. 2 The number of white spots with a diameter of 1 mm or more can be reduced to 0.6 or less, preferably 0.5 or less. [Example]

[0036] 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.

[0037] <Surface roughness measurement> Using multiple samples with different surface roughness of the transparent electrode layer of the conductive film, the Sa value and PEEK value were measured as ISO25178 surface properties (surface roughness measurement) for each sample using a VertScan R3300G Lite from Ryoka Systems Co., Ltd.

[0038] The Sa value indicates the three-dimensional arithmetic mean roughness, and the PEEK value indicates the maximum height of adjacent valleys and peaks.

[0039] <Preparation of reverse-type light-control film and measurement of the number of white spots> Using each conductive film, a reverse-type light-control film was manufactured. At this time, the film thickness of the alignment layer was set to about 100 nm to 200 nm. 2 The number of white spots with a diameter of 1 mm or more was calculated. The experimental results are shown in Table 1 below.

[0040] [Table 1]

[0041] FIG. 5 is a graph showing the relationship between the arithmetic mean roughness Sa value of the surface of the transparent electrode layer and the number of white spots, and FIG. 6 is a graph showing the relationship between the PEEK value of the surface of the transparent electrode layer and the number of white spots.

[0042] As shown in Table 1 and Figure 5, when the Sa value is 2.5 nm or less, 2 It was found that the number of white spots with a diameter of 1 mm or more can be kept within one. In particular, if the Sa value is 2.0 nm or less, the number of white spots with a diameter of 1 mm or more can be kept within one. 2 It was found that the number of white spots with a diameter of 1 mm or more could be reduced to 0.5 or less.

[0043] In addition, as shown in Table 1 and Figure 6, by making the PEEK value 140 nm or less, 2 It was found that the number of white spots with a diameter of 1 mm or more can be kept to one or less. It is preferable to keep the PEEK value to 100 nm or less, and in particular, by making it 50 nm or less, it is possible to keep the number of white spots with a diameter of 1 mm or more within 1 mm. 2 It was found that the number of white spots with a diameter of 1 mm or more could be reduced to 0.5 or less. [Explanation of symbols]

[0044] 1: Transparent base material 2, 12: Transparent electrode layer 2a, 3a, 12a, 13a: Surface 2b, 12b: Protrusion 3, 13: Alignment layer 4: Light control layer 5: Transparent conductive film 6: Liquid crystal molecules 10: Light control film 15: Crystalline molecules

Claims

1. a pair of transparent substrates, a transparent electrode layer disposed inside the transparent substrates, an alignment layer disposed inside the transparent electrode layer, and a light control layer disposed inside the alignment layer and containing liquid crystal molecules; A light-controlling film, characterized in that the arithmetic mean roughness Sa value of the surface of the transparent electrode layer on the side facing the alignment layer is 2.5 nm or less.

2. 2. The light-control film according to claim 1, wherein the maximum height (PEEK value) of adjacent valleys and peaks on the surface of the transparent electrode layer is 140 nm or less.

3. a pair of transparent substrates, a transparent electrode layer disposed inside the transparent substrates, an alignment layer disposed inside the transparent electrode layer, and a light control layer disposed inside the alignment layer and containing liquid crystal molecules; A light-controlling film, characterized in that the height of the protrusions formed on the surface of the transparent electrode layer facing the alignment layer is smaller than the film thickness of the alignment layer.

4. 4. The light control film according to claim 1, wherein the transparent electrode layer is made of ITO or an Ag alloy.

5. The light control film according to claim 1 or 3, wherein the alignment layer is formed from a polyimide resin.

6. The light control film according to claim 1 or 3, wherein the transparent substrate is a PET substrate.

7. 4. The light-controlling film according to claim 1, wherein a functional layer is provided between the transparent substrate and the transparent electrode layer, and on at least one of the outer surfaces of the transparent substrate opposite the side facing the transparent electrode layer.

8. The light control film according to claim 7, wherein the functional layer includes at least one of a hard coat layer, an anti-blocking layer, a primer layer, a protective layer, and an index matching layer.

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

10. A transparent conductive film applied to a reverse-type light control film, in which a transparent electrode layer is formed on the surface of a transparent substrate, A transparent conductive film, wherein the arithmetic mean roughness Sa of the surface of the transparent electrode layer is 2.5 nm or less.

11. 11. The transparent conductive film according to claim 10, wherein the maximum height (PEEK value) of adjacent peaks and valleys on the surface of the transparent electrode layer is 140 nm or less.

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