Light transmissive conductive film and light control film

Abstract

To provide a light transmissive conductive film and a light control film having good thermal stability and capable of reducing the variation in light control function.SOLUTION: There is provided a light transmissive conductive film 1 having a light transmissive base material 2 and a light transmissive conductive layer 3. The light transmissive conductive layer 3 has a crystalline region and an amorphous region. The maximum length of crystal grains in the light transmissive conductive layer 3 is 200 nm or less and when the light transmissive conductive layer 3 is heated under the conditions at 80°C for 240 hours in the atmosphere, the maximum length of crystal grains is 200 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a light-transmitting conductive film and a light control film including the same. [Background technology]

[0002] In recent years, the demand for light control devices, such as smart windows, has been increasing due to the need to reduce the cooling and heating load and to improve design. Light control devices are used for a variety of purposes, such as window glass in buildings and vehicles, partitions, and interior decoration.

[0003] As a film for use in a light control device, for example, Patent Document 1 proposes a light control film that includes two transparent conductive resin substrates and a light control layer sandwiched between the two transparent conductive resin substrates, in which the light control layer contains a resin matrix and a light control suspension, and the transparent conductive resin substrate has a thickness of 20 to 80 μm (see, for example, Patent Document 1).

[0004] The light control film of Patent Document 1 enables light control by adjusting the absorption and scattering of light passing through the light control layer by applying an electric field. The transparent conductive resin substrate of such a light control film is a film in which a transparent conductive layer made of indium tin oxide (ITO) is laminated on a supporting substrate such as a polyester film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2008 / 075773 Summary of the Invention [Problem to be solved by the invention]

[0006] By the way, transparent conductive materials such as ITO have a crystalline structure or an amorphous structure (amorphous) depending on the formation process. For example, when a transparent conductive layer (light-transmitting conductive layer) is formed on a supporting substrate by a dry method such as sputtering, an amorphous transparent conductive layer is formed. Then, the amorphous transparent conductive layer is converted into a crystalline transparent conductive layer by heat.

[0007] In general, crystalline transparent conductive layers are more likely to repel liquids (especially aqueous liquids) than amorphous transparent conductive layers. Therefore, when a light-control layer is disposed on the surface of a crystalline transparent conductive layer, the transparent conductive layer repels the liquid contained in the light-control layer. As a result, the thickness of the light-control layer becomes non-uniform, causing problems such as variations in the light-control function.

[0008] In addition, since the light-control film is exposed to the outside air or sunlight for a long period of time, it naturally converts to a crystalline state locally or entirely due to heat, causing a change in light transmittance. This causes a problem of uneven transparency within the light-control film surface. In other words, the thermal stability is poor.

[0009] The present invention provides a light-transmitting conductive film and a light-controlling film that have good thermal stability and can reduce variations in light-controlling function. [Means for solving the problem]

[0010] The present invention [1] provides a light-transmitting conductive film comprising a light-transmitting substrate and a light-transmitting conductive layer, the light-transmitting conductive layer having a crystalline region and an amorphous region, the maximum length of crystal grains in the light-transmitting conductive layer being 200 nm or less, and the maximum length of crystal grains when the light-transmitting conductive layer is heated in an air atmosphere at 80°C for 240 hours being 200 nm or less.

[0011] The present invention [2] includes the light-transmitting conductive film according to [1], in which the area ratio of the crystalline region in the light-transmitting conductive layer is 25% or less.

[0012] The present invention [3] includes the light-transmitting conductive film according to [1] or [2], in which the rate of change between the transmittance T0 of the light-transmitting conductive film and the transmittance T1 when the light-transmitting conductive film is heated in an air atmosphere at 80°C for 240 hours is 1.0% or less.

[0013] The present invention [4] includes the light-transmitting conductive film according to any one of [1] to [3], which is a light-control light-transmitting conductive film.

[0014] The present invention [5] includes a light-control film which comprises, in order, a first light-transmitting conductive film, a light-control function layer, and a second light-transmitting conductive film, and the first light-transmitting conductive film and / or the second light-transmitting conductive film is the light-transmitting conductive film according to any one of [1] to [4]. Effect of the Invention

[0015] According to the light-transmitting conductive film and the light-controlling film of the present invention, the light-controlling function layer can be uniformly arranged on the light-transmitting conductive layer, and the variation in the light-controlling function can be reduced. In addition, even if the film is stored in a heated state for a long period of time, the change in the light transmittance of the light-transmitting conductive layer can be suppressed, and therefore the film has good thermal stability. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 shows a cross-sectional view of one embodiment of the light-transmitting conductive film of the present invention. [Diagram 2] 2A-B show enlarged views of the light-transmitting conductive film shown in FIG. 1, with FIG. 2A showing a cross-sectional view and FIG. 2B showing a plan view. [Diagram 3] FIG. 3 shows a cross-sectional view of a light control film including the light-transmitting conductive film shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In Fig. 1, the up-down direction of the paper is the up-down direction (thickness direction, first direction), the upper side of the paper is the upper side (one side in the thickness direction, one side in the first direction), and the lower side of the paper is the lower side (the other side in the thickness direction, the other side in the first direction). The left-right direction and the depth direction of the paper are surface directions perpendicular to the up-down direction. Specifically, they follow the directional arrows in each figure.

[0018] 1. Light-transmitting conductive film The light-transmitting conductive film 1 according to one embodiment of the present invention is a film used in, for example, a light control device. As shown in FIG. 1, the light-transmitting conductive film 1 has a film shape (including a sheet shape) having a predetermined thickness, extends in a plane direction perpendicular to the up-down direction (thickness direction), and has a flat upper surface (one side in the thickness direction) and a flat lower surface (the other side in the thickness direction). The light-transmitting conductive film 1 is, for example, a part of a light control film 7 (described later, see FIG. 3) and a light control device (described later), that is, it is not the light control film 7 and the light control device. In other words, the light-transmitting conductive film 1 is a part for producing the light control film 7 and the light control device, does not include a light control functional layer 8, and is a device that is distributed as a part alone and is industrially applicable.

[0019] Specifically, the light-transmitting conductive film 1 includes a light-transmitting substrate 2 and a light-transmitting conductive layer 3 in the vertical direction. That is, the light-transmitting conductive film 1 includes the light-transmitting substrate 2 and the light-transmitting conductive layer 3 disposed on the upper side of the light-transmitting substrate 2. Preferably, the light-transmitting conductive film 1 includes only the light-transmitting substrate 2 and the light-transmitting conductive layer 3. Each layer will be described in detail below.

[0020] 2.Light transparent base material The light-transmitting base material 2 is the bottom layer of the light-transmitting conductive film 1 and is a supporting material that ensures the mechanical strength of the light-transmitting conductive film 1 .

[0021] The light-transmitting substrate 2 has a film shape (including a sheet shape).

[0022] The light-transmitting substrate 2 is made of, for example, an organic film or an inorganic plate (such as a glass plate). The light-transmitting substrate 2 is preferably made of an organic film, and more preferably made of a polymer film. Since the organic film contains water or an organic gas, it is possible to suppress the crystallinity of the light-transmitting conductive layer 3 caused by heating and to suppress the expansion of the crystalline region 4.

[0023] The polymer film has light transmittance and flexibility. Examples of materials for the polymer film include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate, (meth)acrylic resins (acrylic resins and / or methacrylic resins) such as polymethacrylate, olefin resins such as polyethylene, polypropylene, and cycloolefin polymers, and polycarbonate resins, polyethersulfone resins, polyarylate resins, melamine resins, polyamide resins, polyimide resins, cellulose resins, and polystyrene resins. These polymer films can be used alone or in combination of two or more.

[0024] From the viewpoints of light transparency, flexibility, mechanical strength, and the like, the light-transmitting substrate 2 is preferably a polyester-based film formed from a polyester resin, and more preferably a polyethylene terephthalate film.

[0025] The total light transmittance (JIS K 7375-2008) of the light-transmitting substrate 2 is, for example, 80% or more, or preferably 85% or more.

[0026] The thickness of the light-transmitting substrate 2 is, for example, 2 μm or more, preferably 20 μm or more, more preferably 40 μm or more, and is, for example, 300 μm or less, preferably 200 μm or less. The thickness of the light-transmitting substrate 2 can be measured, for example, using a film thickness meter.

[0027] The lower surface of the light-transmitting substrate 2 may be provided with a separator or the like.

[0028] 3.Light transparent conductive layer The light-transmitting conductive layer 3 is a conductive layer that can be patterned by etching in a later step, if necessary.

[0029] The light-transmitting conductive layer 3 has a film shape (including a sheet shape) and is disposed on the entire upper surface of the light-transmitting substrate 2 so as to be in contact with the upper surface of the light-transmitting substrate 2.

[0030] Examples of materials for the light-transmitting conductive layer 3 include metal oxides containing at least one metal selected from the group consisting of In, Sn, Zn, Ga, Sb, Ti, Si, Zr, Mg, Al, Au, Ag, Cu, Pd, and W. If necessary, the metal oxides may be doped with metal atoms shown in the above group.

[0031] The light-transmitting conductive layer 3 is preferably a conductive metal oxide, and specifically includes, for example, an indium-based conductive oxide such as indium tin oxide (ITO), and an antimony-based conductive oxide such as antimony tin oxide (ATO). From the viewpoint of reducing the surface resistance and ensuring excellent light transmittance, the light-transmitting conductive layer 3 contains an indium-based conductive oxide, and more preferably contains indium tin oxide (ITO). That is, the light-transmitting conductive layer 3 is preferably an indium-based conductive oxide layer, and more preferably an ITO layer.

[0032] When ITO is used as the material of the light-transmitting conductive layer 3, the tin oxide (SnO2) content is, for example, 0.5 mass% or more, preferably 3 mass% or more, more preferably 8 mass% or more, and for example, 25 mass% or less, preferably 15 mass% or less, more preferably 13 mass% or less, based on the total amount of tin oxide and indium oxide (In2O3). If the tin oxide content is equal to or more than the above lower limit, the light-transmitting conductive layer 3 can have a low resistance while more reliably suppressing conversion to crystalline. If the tin oxide content is equal to or less than the above upper limit, the light transmittance and the stability of the resistance can be improved.

[0033] In this specification, "ITO" refers to a composite oxide containing at least indium (In) and tin (Sn), and may contain additional components other than these. Examples of additional components include metal elements other than In and Sn, such as Zn, Ga, Sb, Ti, Si, Zr, Mg, Al, Au, Ag, Cu, Pd, W, Fe, Pb, Ni, Nb, Cr, and Ga.

[0034] The light-transmitting conductive layer 3 has a crystalline region 4 and an amorphous region 5. That is, the light-transmitting conductive layer 3 is semi-crystalline.

[0035] The crystalline region 4 is a region in plan view where the material (e.g., ITO) forming the light-transmitting conductive layer 3 is crystalline. That is, the crystalline region 4 contains crystal grains 6. In the crystalline region 4, it is sufficient that the crystal grains 6 are present in a portion of the vertical direction (part A in FIG. 2A ), and it is not necessary that the crystal grains 6 are present over the entire vertical direction (part B in FIG. 2A ).

[0036] The amorphous region 5 is a region other than the crystalline region 4, and is a region in a plan view in which the material (e.g., ITO) forming the light-transmitting conductive layer 3 is in an amorphous state. That is, in the amorphous region 5, no crystal grains 6 exist.

[0037] The light-transmitting conductive layer 3 has both the crystalline region 4 and the amorphous region 5, and thus can suppress defects (large fluctuations in light transmittance) that occur when the crystalline region 4 occurs from a completely amorphous state that has no crystalline region 4 at all. Furthermore, the light-transmitting conductive layer 3 has at least a flexible amorphous region 5 in at least a part (most of the layer in this embodiment) of the layer 3, and thus can suppress cracks caused by impacts during manufacturing or transportation. Furthermore, the occurrence of uneven light transmission and defects in the dimming function can be suppressed.

[0038] In the light-transmitting conductive layer 3 (before heating), the maximum length of the crystal grains 6 present in the crystalline region 4 is 200 nm or less, preferably 170 nm or less, more preferably 150 nm or less, even more preferably 120 nm or less, particularly preferably 80 nm or less, particularly preferably 60 nm or less, and most preferably 45 nm or less. The lower limit of the maximum length is, for example, 0.1 nm or more, preferably 1 nm or more. If the maximum length of the crystal grains is equal to or less than the above upper limit, the growth of the crystal grains 6 in the light-transmitting conductive layer 3 can be suppressed, the change in light transmittance after long-term heating storage can be suppressed to a low range, and durability is excellent.

[0039] The maximum length of the crystal grains 6 refers to the length of the crystal grain 6 (the maximum planar length that each crystal grain 6 can have) that is the longest among all the crystal grains 6 present in the crystalline region 4 (see Figure 2B).

[0040] In the light-transmitting conductive layer 3, the area occupied by the crystalline region 4 is, for example, 0.01% or more, preferably 0.1% or more, more preferably 0.5% or more, and even more preferably 1% or more, and, for example, 25% or less, preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. When the area of ​​the crystalline region is within the above range, the change in light transmittance after long-term heat storage can be further suppressed.

[0041] The area occupied by the amorphous region 5 is, for example, 75% or more, preferably 80% or more, more preferably 85% or more, even more preferably 90% or more, and particularly preferably 95% or more, and for example, 99.99% or less, preferably 99.9% or less, more preferably 99.5% or less, and even more preferably 99% or less.

[0042] The areas of the crystalline regions 4 and the amorphous regions 5, and the maximum length of the crystal grains 6 can be measured, for example, by observing the upper surface of the light-transmitting conductive layer 3 at a magnification of 100,000 times using a transmission electron microscope.

[0043] When the light-transmitting conductive layer 3 is subjected to high-temperature treatment, i.e., in the high-temperature-treated light-transmitting conductive layer, the maximum length of the crystal grains 6 is 200 nm or less, preferably 170 nm or less, more preferably 150 nm or less, even more preferably 120 nm or less, particularly preferably 100 nm or less, and most preferably 80 nm or less, and is, for example, 0.1 nm or more, preferably 1 nm or more.

[0044] In this case, the area occupied by the crystalline region 4 is, for example, 0.5% or more, preferably 1% or more, and, for example, 60% or less, preferably 50% or less, more preferably 40% or less, even more preferably 30% or less, particularly preferably 20% or less, especially preferably 15% or less, and most preferably 5% or less.

[0045] If the maximum length of the crystal grains 6 or the area of ​​the crystalline region 4 upon high temperature treatment is within the above range, the change in light transmittance after long-term heat storage can be suppressed to a very low range, and the thermal stability is excellent.

[0046] In the present invention, the high-temperature treatment refers to a treatment in which the light-transmitting conductive layer 3 (and thus the light-transmitting conductive film 1) is heated at 80° C. for 240 hours in an atmospheric environment. As an accelerated high-temperature treatment, a heating condition of 140° C. for 30 minutes in an atmospheric environment can also be adopted.

[0047] The light-transmitting conductive layer 3 preferably contains an impurity element. Examples of the impurity element include an element (e.g., Ar element) derived from the sputtering gas used when forming the light-transmitting conductive layer 3, and an element (e.g., H element, C element) derived from water or an organic gas contained in the light-transmitting substrate 2. By containing these elements, the area of ​​the crystalline region 4 of the light-transmitting conductive layer 3 can be further reduced.

[0048] The light-transmitting conductive layer 3 has a thickness of, for example, 10 nm or more, preferably 30 nm or more, more preferably 50 nm or more, and for example, 200 nm or less, preferably 150 nm or less, more preferably 80 nm or less.

[0049] The thickness of the light-transmitting conductive layer 3 can be measured, for example, by observing a cross section using a transmission electron microscope.

[0050] The resistivity of the light-transmitting conductive layer 3 is, for example, 6.5×10 -4 Ω cm or less, preferably 6.0×10 -4 Ω cm or less, more preferably 5.5×10 -4 Ω cm or less, more preferably 5.0×10 -4 Ω·cm or less, particularly preferably 4.6×10 -4 Ω cm or less, for example, 2.5×10 -4 Ω cm or more, preferably 3.0×10 -4 When the resistivity of the light-transmitting conductive layer 3 is equal to or lower than the upper limit, good electrical drive can be achieved even when the light-transmitting conductive layer 3 is used as a large-sized light control device. When the resistivity is equal to or higher than the lower limit, the amorphous nature of the light-transmitting conductive layer 3 can be more reliably maintained.

[0051] The specific resistance can be determined from the product of the surface resistance value and the thickness of the light-transmitting conductive layer 3, and the surface resistance value of the light-transmitting conductive layer 3 can be measured by a four-terminal method.

[0052] 4. Manufacturing method of light-transmitting conductive film Next, a method for producing the light-transmitting conductive film 1 will be described.

[0053] The light-transmitting conductive film 1 is obtained by preparing a light-transmitting substrate 2 and forming a light-transmitting conductive layer 3 on the upper surface of the light-transmitting substrate 2 .

[0054] For example, the light-transmitting conductive layer 3 is disposed (laminated) on the upper surface of the light-transmitting substrate 2 by a dry process.

[0055] Examples of the dry method include vacuum deposition, sputtering, and ion plating, with sputtering being preferred.

[0056] In the sputtering method, a target and an adherend (light-transmitting substrate 2) are placed facing each other in the chamber of a vacuum device, and gas is supplied while a voltage is applied to accelerate the gas ions, which are then irradiated onto the target, ejecting the target material from the target surface and depositing it on the surface of the adherend.

[0057] Examples of the sputtering method include a dipole sputtering method, an ECR (electron cyclotron resonance) sputtering method, a magnetron sputtering method, an ion beam sputtering method, etc. Preferably, the magnetron sputtering method is used.

[0058] The power source used in the sputtering method may be, for example, any of a direct current (DC) power source, an alternating current / medium frequency (AC / MF) power source, a radio frequency (RF) power source, and a radio frequency power source superimposed with a DC power source.

[0059] Examples of the target include the above-mentioned metal oxides constituting the light-transmitting conductive layer 3. For example, when ITO is used as the material of the light-transmitting conductive layer 3, a target made of ITO is used. The tin oxide (SnO2) content in the target is, for example, 0.5 mass% or more, preferably 5 mass% or more, more preferably more than 10 mass%, and for example, 25 mass% or less, preferably 15 mass% or less, based on the total amount of tin oxide and indium oxide (In2O3).

[0060] The voltage during sputtering is, for example, 200 V or more, preferably 300 V or more, more preferably 400 V or more, and for example, 800 V or less, preferably 600 V or less. If the voltage is set to a high voltage within the above range, an appropriate amount of impurities such as inert gas and water can be present inside the light-transmitting conductive layer 3, and as a result, the area of ​​the crystalline region 4 can be reduced and the grain size (particularly the maximum length) of the crystal grains 6 can be made smaller.

[0061] The temperature during sputtering (specifically, the temperature of the light-transmitting substrate 2) is, for example, 100° C. or less, preferably 50° C. or less, more preferably less than 0° C., and is, for example, −20° C. or more. When the film formation temperature is equal to or less than the above upper limit, the generation of the crystalline region 4 in the light-transmitting conductive layer 3 can be more reliably reduced.

[0062] The air pressure during sputtering is, for example, 1.0 Pa or less, preferably 0.5 Pa or less, and for example, 0.01 Pa or more.

[0063] The gas to be introduced may be, for example, an inert gas such as Ar. Also, preferably, a reactive gas such as oxygen gas is used in combination. The ratio of the flow rate of the reactive gas to the flow rate of the inert gas (flow rate of reactive gas (sccm) / flow rate of inert gas (sccm)) is, for example, 0.025 or more, preferably 0.03 or more, and, for example, 0.05 or less.

[0064] The water partial pressure ratio (water / total pressure) is, for example, 0.02 or more, preferably 0.05 or more, and for example, 0.10 or less.

[0065] When the flow rate ratio of the reactive gas or the partial pressure ratio of water is equal to or higher than the lower limit, an appropriate amount of impurities such as moisture can be present inside the light-transmitting conductive layer 3, and as a result, the area of ​​the crystalline region 4 can be reduced and the grain size (particularly the maximum length) of the crystal grains 6 can be made smaller.

[0066] In this way, a light-transmitting conductive film 1 including the light-transmitting substrate 2 and the light-transmitting conductive layer 3 is obtained.

[0067] The total thickness of the light-transmitting conductive film 1 is, for example, 2 μm or more, preferably 20 μm or more, and for example, 300 μm or less, preferably 200 μm or less.

[0068] The light transmittance T0 of the light transmissive conductive film 1 is, for example, 50% or more, or preferably 70% or more. The light transmittance T0 is the light transmittance of the light transmissive conductive film 1 before long-term heat storage described later.

[0069] When the light-transmitting conductive film 1 is stored under heat for a long period of time, that is, in the light-transmitting conductive film that has been heated for a long period of time, its light transmittance T1 is 50% or more, and preferably 70% or more.

[0070] The rate of change ΔT between the transmittance T0 and the transmittance T1 is, for example, 1.5% or less, preferably 1.0% or less, more preferably 0.8% or less, and even more preferably 0.5% or less. If the rate of change ΔT is within the above range, the change in light transmittance is reduced even when the light-transmitting conductive film 1 is used for a long period of time, and therefore unevenness in the light transmittance can be suppressed.

[0071] The rate of change ΔT can be calculated using the formula "{(T1-T0) / T0}×100%."

[0072] In the present invention, the long-term heat storage refers to a treatment in which the light-transmitting conductive film 1 is heated in an atmospheric environment at 80° C. for 240 hours.

[0073] In this light-transmitting conductive film 1, the light-transmitting conductive layer 3 has a crystalline region 4 and an amorphous region 5, and the maximum length of the crystal grains 6 in the light-transmitting conductive layer 3 is 200 nm or less.

[0074] Therefore, the light-adjusting function layer 8 can be applied uniformly to the surface of the light-transmitting conductive layer 3, and the formation of air bubbles on the surface of the transmissive conductive layer inside the light-adjusting function layer 8 can be suppressed. Therefore, the light-adjusting function layer 8 can be uniformly arranged, and the variation in the light-adjusting function can be reduced. This is presumably because the crystal grains 6 that easily repel liquid in the crystalline region 4 are smaller than a specific size, that is, the constituent units that repel liquid are subdivided, so that the area from which the solution that constitutes the light-adjusting function layer 8 is repelled is reduced.

[0075] Furthermore, the maximum length of the crystal grains when the light-transmitting conductive layer 3 is heated in an air atmosphere at 80° C. for 240 hours is 200 nm or less.

[0076] Therefore, even if the layer is heated for a long period of time, the change in the light transmittance of the light-transmitting conductive layer 3 can be suppressed, and the thermal stability of the light transmittance is good. This is presumably because, in the crystalline region 4, the crystal grains 6 have a size equal to or smaller than the specific size, so that the expansion and increase of the crystal grains 6 is suppressed, and the crystalline region 4 (a region having a light transmittance different from that of the amorphous region 5) is not significantly expanded.

[0077] In addition, since the light-transmitting conductive film 1 has a crystalline region 4 and an amorphous region 5, i.e., since it has a portion (most of the portion in this embodiment) of the amorphous region 5 which is more flexible than the crystalline region 4, it has excellent crack resistance, etc.

[0078] This light-transmitting conductive film 1 is an industrially applicable device.

[0079] If necessary, the light-transmitting conductive film 1 can be etched to pattern the light-transmitting conductive layer 3 into a predetermined shape. This allows the light-transmitting conductive layer 3 to be a transparent electrode, transparent wiring, etc. Such a light-transmitting conductive film 1 may be used as a transparent conductive film for a touch panel.

[0080] 5. Light control film Next, a method for producing a light control film 7 using the light-transmitting conductive film 1 will be described with reference to FIG.

[0081] The method for producing the light control film 7 includes, for example, a step of producing two light-transmitting conductive films 1, and then a step of sandwiching the light control function layer 8 between the two light-transmitting conductive films 1.

[0082] First, two of the above-described light-transmitting conductive films 1 are manufactured. Alternatively, two light-transmitting conductive films 1 can be prepared by cutting one light-transmitting conductive film 1.

[0083] The two light-transmitting conductive films 1 are a first light-transmitting conductive film 1A and a second light-transmitting conductive film 1B.

[0084] Next, the light-modulating layer 8 is formed on the upper surface (front surface) of the light-transmitting conductive layer 3 of the first light-transmitting conductive film 1A, for example, by a wet process.

[0085] For example, a liquid crystal composition or a solution thereof is applied to the upper surface of the light-transmitting conductive layer 3 of the first light-transmitting conductive film 1A to form a coating film. The liquid crystal composition is not limited as long as it can be used for light control applications, and known liquid crystal compositions can be used, for example, liquid crystal dispersion resins described in JP-A-8-194209.

[0086] Next, the second light-transmitting conductive film 1B is laminated on the upper surface of the coating film so that the light-transmitting conductive layer 3 of the second light-transmitting conductive film 1B contacts the coating film, thereby sandwiching the coating film between the two light-transmitting conductive films 1, i.e., the first light-transmitting conductive film 1A and the second light-transmitting conductive film 1B.

[0087] Thereafter, the coating film is subjected to appropriate treatment (e.g., heat drying treatment, photocuring treatment) as necessary to form the light-adjusting function layer 8. The light-adjusting function layer 8 is disposed between the light-transmitting conductive layer 3 of the first light-transmitting conductive film 1A and the light-transmitting conductive layer 3 of the second light-transmitting conductive film 1B.

[0088] In this way, the light control film 7 is obtained which includes the first light-transmitting conductive film 1A, the light control function layer 8, and the second light-transmitting conductive film 1B in this order.

[0089] The light control film 7 is used, for example, as an electric field-driven light control device (not shown) by attaching a power source (not shown) and a control device (not shown). In an electric field-driven light control device, a voltage is applied by the power source to the light transmissive conductive layer 3 in the first light transmissive conductive film 1A and the light transmissive conductive layer 3 in the second light transmissive conductive film 1B, thereby generating an electric field between them. Then, the electric field is controlled based on the control device, and the light control function layer 8 located between them becomes in an oriented state or an irregular state, thereby transmitting or blocking light.

[0090] Since the light control film 7 includes the light-transmitting conductive film 1, it can include a uniform light control function layer 8 and can reduce the variation in the light control function. In addition, even if the light control film 7 is stored in a heated state for a long period of time, the change in the light transmittance of the light-transmitting conductive layer 3 can be suppressed, and therefore the heat stability is good.

[0091] 6. Variations In the embodiment of FIG. 1, the light-transmitting conductive layer 3 is disposed directly on the upper surface of the light-transmitting substrate 2. However, for example, although not shown, a functional layer can be provided on the upper and / or lower surface of the light-transmitting substrate 2.

[0092] That is, for example, the light-transmitting conductive film 1 can include a light-transmitting substrate 2, a functional layer disposed on the upper surface of the light-transmitting substrate 2, and a light-transmitting conductive layer 3 disposed on the upper surface of the functional layer. Also, for example, the light-transmitting conductive film 1 can include a light-transmitting substrate 2, a light-transmitting conductive layer 3 disposed on the upper surface of the light-transmitting substrate 2, and a functional layer disposed on the lower surface of the light-transmitting substrate 2. Also, for example, the functional layer and the light-transmitting conductive layer 3 can be provided in this order on the upper and lower sides of the light-transmitting substrate 2.

[0093] Examples of the functional layer include an easy-adhesion layer, an undercoat layer, and a hard coat layer. The easy-adhesion layer is a layer provided to improve the adhesion between the light-transmitting substrate 2 and the light-transmitting conductive layer 3. The undercoat layer is a layer provided to adjust the reflectance and optical hue of the light-transmitting conductive film 1. The hard coat layer is a layer provided to improve the scratch resistance of the light-transmitting conductive film 1. These functional layers may be used alone or in combination of two or more kinds. EXAMPLES

[0094] The present invention will be described in detail below using examples. However, the present invention is not limited to the examples as long as it does not deviate from the gist of the present invention, and various modifications and changes are possible based on the technical concept of the present invention.

[0095] The present invention will be described in more detail below with reference to examples and comparative examples. The present invention is not limited to the examples and comparative examples. The specific numerical values ​​of the blending ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit (a numerical value defined as "not more than" or "less than") or lower limit (a numerical value defined as "not less than" or "exceeding") of the corresponding blending ratio (content ratio), physical property values, parameters, etc. described in the above "Form for carrying out the invention".

[0096] Example 1 A polyethylene terephthalate (PET) film having a thickness of 188 μm was prepared as a light-transmitting substrate.

[0097] The PET film was placed in a roll-to-roll sputtering apparatus and evacuated. After that, in a vacuum atmosphere (atmospheric pressure 0.2 Pa) containing Ar and O2, a light-transmitting conductive layer made of ITO with a thickness of 65 nm was formed by DC magnetron sputtering. This produced a light-transmitting conductive film.

[0098] The sputtering conditions were as follows. A sintered body of 13 mass% tin oxide and 87 mass% indium oxide was used as a target. The sputtering voltage was 400 V. The temperature of the light-transmitting substrate was cooled to -5°C. The ratio of the O2 flow rate to the Ar flow rate (O2 / Ar) was 0.03. The water pressure ratio of the vacuum atmosphere (H2O / total pressure) was 0.06.

[0099] Example 2 A light-transmitting conductive film was produced in the same manner as in Example 1, except that the sputtering conditions were changed to those shown in Table 1.

[0100] Comparative Example 1 A light-transmitting conductive film was produced in the same manner as in Example 1, except that the sputtering conditions were changed to those shown in Table 1. However, the thickness of the light-transmitting conductive layer was set to 25 nm.

[0101] (evaluation) (1) Thickness The thickness of the light-transmitting substrate was measured using a film thickness gauge (manufactured by Ozaki Manufacturing Co., Ltd., device name "Digital Dial Gauge DG-205"), and the thickness of the light-transmitting conductive layer was measured by cross-sectional observation using a transmission electron microscope (manufactured by Hitachi, Ltd., device name "HF-2000").

[0102] (2) Grains before heating In the light-transmitting conductive films of each Example and Comparative Example, the upper surface of the light-transmitting conductive layer was observed using a transmission electron microscope (Hitachi, "H-7650") to obtain a planar image at a magnification of 100,000 times. From this image, the area ratio of the crystalline region to the entire light-transmitting conductive layer and the maximum length of the crystal grains were measured. The results are shown in Table 1.

[0103] (3) Specific resistance The surface resistance of the upper surface of the optically transparent conductive layer of each optically transparent conductive film was measured by a four-terminal method, and the specific resistance was calculated from the product of the surface resistance and the thickness. The results are shown in Table 1.

[0104] (4) Observation of crystal grains after high-temperature treatment Each light-transmitting conductive film was heated at 80°C for 240 hours in an atmospheric environment. The area ratio of the crystalline region and the maximum length of the crystal grains of the high-temperature-treated light-transmitting conductive film were measured in the same manner as in the measurement in (2) above. The results are shown in Table 1.

[0105] (5) Thermal stability The total light transmittance of each light-transmitting conductive film was measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd., device name "HGM-2DP"), and the light transmittance before long-term heating storage was taken as T0.

[0106] Next, each light-transmitting conductive film was heated in an atmospheric environment at 80° C. for 240 hours. The total light transmittance of this light-transmitting conductive film was measured in the same manner as above, and was taken as the light transmittance T1 after long-term heating storage.

[0107] The rate of change ΔT before and after heating was calculated using the formula "{(T1-T0) / T0}×100%". When ΔT was 0.5% or less, it was evaluated as ◎, when ΔT was more than 0.5% and less than 1.0%, it was evaluated as ◯, when ΔT was more than 1.0% and less than 1.5%, it was evaluated as △, and when ΔT was more than 2.0%, it was evaluated as ×. The results are shown in Table 1.

[0108] (6) Uniformity of the light control layer As a liquid crystal composition for the dimming functional layer, an aqueous coating liquid was prepared by mixing nematic liquid crystal, resin, and water, and this aqueous coating liquid was uniformly applied to the upper surface of the light-transmitting conductive layer of the light-transmitting conductive film of each Example and Comparative Example to a thickness of 20 μm.

[0109] The case where the liquid crystal composition was uniformly arranged on the upper surface of the light-transmitting conductive layer was evaluated as "good." The case where the liquid crystal composition was not arranged on a part of the upper surface of the light-transmitting conductive layer, causing unevenness, was evaluated as "poor."

[0110] [Table 1]

[0111] The above invention is provided as an exemplary embodiment of the present invention, but this is merely an example and should not be interpreted as being limited. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the following claims. [Industrial Applicability]

[0112] The light-transmitting conductive film and light-control film of the present invention can be applied to various industrial products, such as window glass, partitions, and interior decorations in buildings and vehicles. [Explanation of symbols]

[0113] 1. Light-transmitting conductive film 2 Light-transparent base material 3 Light-transparent conductive layer 4 Crystalline region 5. Amorphous Region 6. Grain 7. Light-controlling film 8. Photochromic Layer

Claims

1. A light-transmissive conductive film comprising a light-transmissive substrate and a light-transmissive conductive layer, wherein the light-transmissive conductive layer has a crystalline region and an amorphous region, the area occupied by the crystalline region in the light-transmissive conductive layer is 0.5% or more and 25% or less, the maximum length of crystal grains in the light-transmissive conductive layer is 1 nm or more and 200 nm or less, and the maximum length of crystal grains when the light-transmissive conductive layer is heated in an air atmosphere at 80°C for 240 hours is 200 nm or less. A light-transmissive conductive film characterized by the above.

2. The light-transmissive conductive layer is an indium tin composite oxide layer, in the light-transmissive conductive layer, the content of tin oxide is 8% by mass or more based on the total amount of tin oxide and indium oxide, and the thickness of the light-transmissive conductive layer is 30 nm or more. The light-transmissive conductive film according to Claim 1, characterized by the above.

3. Transmittance T of the light-transmissive conductive film ０ and the transmittance T when the light-transmissive conductive film is heated under the conditions of 80°C for 240 hours in an air atmosphere １ The light-transmissive conductive film according to claim 1, characterized in that the change rate with respect to is 1.0% or less.

4. The light-transmissive conductive film according to Claim 1, which is a light-transmissive conductive film for light control.

5. A light control film comprising a first light-transmissive conductive film, a light control functional layer, and a second light-transmissive conductive film in this order, wherein the first light-transmissive conductive film and / or the second light-transmissive conductive film is the light-transmissive conductive film according to Claim 1.

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