JP7628568B2 - Light-transmitting conductive layer and light-transmitting conductive sheet - Google Patents

Description

The present invention relates to a light-transmitting conductive layer and a light-transmitting conductive sheet.

Conventionally, a light-transmitting conductive sheet is known that has a transparent substrate and a transparent conductive layer in that order in the thickness direction. The light-transmitting conductive layer made of indium tin oxide (ITO) is used as a conductive film for patterning transparent electrodes in various devices such as liquid crystal displays, touch panels, and optical sensors.

On the other hand, from the viewpoint of improving the response speed of touch panels, there is an increasing demand for light-transmitting conductive sheets that have a low-resistance light-transmitting conductive layer (ITO layer). Therefore, it has been proposed to increase the average crystal grain size of the crystal grains contained in the light-transmitting conductive layer to reduce resistance (for example, see Patent Document 1 below).

JP 2013-152827 A

On the other hand, in recent years, transparent conductive films are required to have low resistance and excellent flexibility.

However, the light-transmitting conductive layer of Patent Document 1 contains crystal grains with a large average crystal grain size, so when the light-transmitting conductive layer is bent, a large stress is applied to the bent portion, causing cracks, i.e., the layer has poor flexibility.

The present invention aims to provide a light-transmitting conductive layer and a light-transmitting conductive sheet that have low resistance and excellent flexibility.

The present invention [1] includes a light-transmitting conductive layer having a first main surface and a second main surface opposed to the first main surface in the thickness direction, the thickness of the light-transmitting conductive layer being greater than 50 nm, the light-transmitting conductive layer having crystal grains, and the average crystal grain size of the crystal grains being 105 nm or less.

The present invention [2] includes the light-transmitting conductive layer described in [1] above, in which the crystal grains include crystal grains having a maximum crystal grain size of 110 nm or more.

The present invention [3] includes the light-transmitting conductive layer described in [1] or [2] above, in which the content of crystal grains having a crystal grain size of 100 nm or more relative to the total number of the crystal grains is 70% or less.

The present invention [4] includes a light-transmitting conductive sheet comprising the light-transmitting conductive layer according to any one of [1] to [3] above, and a base layer on the side of the first main surface and/or the second main surface of the light-transmitting conductive layer.

The present invention provides a light-transmitting conductive layer having a first main surface and a second main surface opposed to the first main surface in the thickness direction, the thickness of the light-transmitting conductive layer being greater than 50 nm, the light-transmitting conductive layer having crystal grains, the average crystal grain size of which is 105 nm or less. Therefore, the light-transmitting conductive layer has low resistance and excellent flexibility.

The light-transmitting conductive sheet of the present invention comprises the light-transmitting conductive layer of the present invention. Therefore, it has low resistance and excellent flexibility.

FIG. 1 shows a cross-sectional view of one embodiment of the light-transmitting conductive sheet of the present invention. Fig. 2 is a schematic diagram showing one embodiment of the light-transmitting conductive layer and the method for producing the light-transmitting conductive sheet of the present invention. Fig. 2A shows a step of preparing a transparent substrate in the first step. Fig. 2B shows a step of forming an optical adjustment layer on one surface in the thickness direction of the transparent substrate in the first step. Fig. 2C shows a step of forming a hard coat layer on the other surface in the thickness direction of the transparent substrate in the first step. Fig. 2D shows a second step of arranging a light-transmitting conductive layer on one surface in the thickness direction of the substrate layer. Fig. 2E shows a third step of heating the light-transmitting conductive layer.

With reference to Figure 1, one embodiment of the light-transmitting conductive layer and light-transmitting conductive sheet of the present invention will be described.

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

<Light-transmitting conductive sheet>
As shown in Fig. 1, the light-transmitting conductive sheet 1 has a sheet shape (including a film shape) having a predetermined thickness, extends in a predetermined direction (front-rear and left-right directions, i.e., surface 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 sheet 1 is, for example, a part of a touch panel and a light control panel provided in an optical device, that is, it is not an optical device. In other words, the light-transmitting conductive sheet 1 is a part for producing an optical device, etc., does not include an image display element such as an LCD module or a light source such as an LED, is distributed as a part alone, and is an industrially applicable device.

The light-transmitting conductive sheet 1 also includes a light-transmitting conductive layer 2 and a base layer 3. The light-transmitting conductive layer 2 includes a first main surface 21 and a second main surface 22 that faces the first main surface 21 in the thickness direction. That is, the light-transmitting conductive sheet 1 includes a light-transmitting conductive layer 2 and a base layer 3 on the side of the first main surface 21 and/or the second main surface 22 of the light-transmitting conductive layer 2. Specifically, the light-transmitting conductive sheet 1 includes a light-transmitting conductive layer 2 and a base layer 3 on the side of the second main surface 22 of the light-transmitting conductive layer 2 (the other side in the thickness direction).

The thickness of the light-transmitting conductive sheet 1 is, for example, 300 μm or less, preferably 200 μm or less, more preferably 150 μm or less, and, for example, 20 μm or more, preferably 40 μm or more, more preferably 60 μm or more, and even more preferably 80 μm or more.

<Base layer>
The substrate layer 3 is a transparent substrate that ensures the mechanical strength of the light-transmitting conductive sheet 1 .

The substrate layer 3 has a sheet shape (including a film shape).

The substrate layer 3 is disposed on the side of the first main surface 21 and/or the second main surface 22 of the light-transmitting conductive layer 2. Preferably, the substrate layer 3 is disposed on the side of the second main surface 22 of the light-transmitting conductive layer 2 (the other side in the thickness direction). Specifically, the substrate layer 3 is disposed on the entire surface of the second main surface 22 of the light-transmitting conductive layer 2 so as to contact the second main surface 22 of the light-transmitting conductive layer 2.

The substrate layer 3 includes, for example, a transparent substrate 31 and, if necessary, a functional layer 32. Preferably, the substrate layer 3 includes a transparent substrate 31 and a functional layer 32 on one thickness-wise surface and/or the other thickness-wise surface of the transparent substrate 31, and more preferably, the substrate layer 3 includes a transparent substrate 31 and a functional layer 32 on one thickness-wise surface and the other thickness-wise surface of the transparent substrate 31.

The thickness of the base layer 3 is, for example, 300 μm or less, preferably 200 μm or less, more preferably 150 μm or less, and, for example, 20 μm or more, preferably 40 μm or more, more preferably 60 μm or more, and even more preferably 80 μm or more.

[Transparent substrate]
The transparent substrate 31 has flexibility and supports the light-transmitting conductive layer 2 .

The transparent substrate 31 has a sheet shape (including a film shape).

The transparent substrate 31 is made of, for example, a polymer film. Therefore, it has excellent flexibility. Furthermore, if the transparent substrate 31 is made of a polymer film, the light-transmitting conductive sheet 1 has excellent manufacturing efficiency.

In addition, when the transparent substrate 31 is made of a polymer film, the light-transmitting conductive sheet 1 (crystalline light-transmitting conductive layer 2) may be reheated from the standpoint of imparting dimensional stability to the light-transmitting conductive sheet 1, but this light-transmitting conductive sheet 1 has excellent heat stability.

Examples of materials for the polymer film include polyester resin, (meth)acrylic resin, olefin resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, melamine resin, polyamide resin, polyimide resin, cellulose resin, polystyrene resin, and norbornene resin. From the standpoint of flexibility, heat resistance, mechanical strength, etc., the transparent substrate 4 is preferably a polymer film made of polyester resin.

Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate, with polyethylene terephthalate being preferred.

An example of a (meth)acrylic resin is polymethacrylate.

Examples of olefin resins include polyethylene, polypropylene, and cycloolefin polymer.

The polymer films can be used alone or in combination of two or more types.

The total light transmittance (JIS K 7375-2008) of the transparent substrate 31 is, for example, 60% or more, preferably 80% or more, and more preferably 85% or more.

If the total light transmittance of the transparent substrate 31 is equal to or greater than the lower limit, the transparent substrate 31 has excellent transparency.

The thickness of the transparent substrate 31 is, for example, 1 μm or more, preferably 10 μm or more, more preferably 50 μm or more, even more preferably 80 μm or more, and particularly preferably 100 μm or more, and is, for example, 300 μm or less, preferably 200 μm or less, and more preferably 150 μm or less.

If the thickness of the transparent substrate 31 is within the above range, the light-transmitting conductive sheet 1 can be made thin and has excellent mechanical strength.

The thickness of the transparent substrate 31 can be measured, for example, using a film thickness gauge.

[Functional layer]
The functional layer 32 is disposed on one surface and/or the other surface in the thickness direction of the transparent substrate 31. Preferably, the functional layer 32 is disposed on one surface and the other surface in the thickness direction of the transparent substrate 31.

The functional layer 32 has a sheet shape (including a film shape).

Examples of the functional layer 32 include an anti-blocking layer, an optical adjustment layer, and a hard coat layer, and preferably an optical adjustment layer and a hard coat layer.

When the functional layer 32 is an optical adjustment layer and a hard coat layer, the substrate layer 3 includes, for example, a transparent substrate 31, a hard coat layer 33 on the other thickness-wise surface of the transparent substrate 31, and an optical adjustment layer on one thickness-wise surface of the transparent substrate 31. In other words, the substrate layer 3 includes the hard coat layer 33, the transparent substrate 31, and the optical adjustment layer 34, in that order toward one thickness-wise side.

{Hard coat layer}
The hard coat layer 33 is an abrasion protection layer for making the light-transmitting conductive sheet 1 less susceptible to abrasions.

The hard coat layer 33 is disposed on the other surface in the thickness direction of the transparent substrate 31. Specifically, the hard coat layer 33 is disposed on the entire lower surface (other surface in the thickness direction) of the transparent substrate 31 so as to contact the other surface in the thickness direction of the transparent substrate 31. The hard coat layer 33 is the bottom layer of the light-transmitting conductive sheet.

In FIG. 1, the hard coat layer 33 is disposed on the other surface in the thickness direction of the transparent substrate 31, but this is not limited thereto. In other words, the hard coat layer 33 may be disposed on one side in the thickness direction of the transparent substrate 31, or may be disposed in multiple layers. In addition, when the substrate layer 3 includes the hard coat layer 33 and the optical adjustment layer 34 described later in the same direction, either on one side or on the other side in the thickness direction of the transparent substrate 31, the order of stacking is not particularly limited.

The hard coat layer 33 is formed, for example, from a hard coat composition.

The hard coat composition contains, for example, a resin and, if necessary, particles. In other words, the hard coat layer 33 contains, for example, a resin and, if necessary, particles.

Examples of resins include thermoplastic resins and curable resins.

An example of a thermoplastic resin is polyolefin resin.

Examples of curable resins include acrylic resins, urethane resins, amide resins, silicone resins, epoxy resins, melamine resins, alkyd resins, siloxane-based polymers, and organic silane condensates, with acrylic resins being preferred.

Curable resins include, for example, active energy ray curable resins that are cured by irradiation with active energy rays (e.g., ultraviolet rays and electron beams) and thermosetting resins that are cured by heating.

Resins can be used alone or in combination of two or more types.

Examples of particles include metal oxide microparticles and organic microparticles.

Examples of materials for metal oxide particles include silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide.

Materials for organic microparticles include polymethyl methacrylate, silicone, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate.

The particles can be used alone or in combination of two or more types.

The hard coat composition contains, for example, a resin, preferably a curable resin, and more preferably an active energy ray curable resin. Specifically, the hard coat composition contains an acrylic resin.

The hard coat composition may also contain, for example, a thixotropy-imparting agent, a photopolymerization initiator, a filler (e.g., organic clay), and a leveling agent in appropriate proportions. Furthermore, the hard coat composition may be diluted with a known solvent.

To form the hard coat layer 33, a diluted solution of the hard coat composition is applied to the other surface in the thickness direction of the transparent substrate 31, and dried as necessary, as described in detail below. After drying, the hard coat composition is cured, for example, by irradiation with active energy rays.

This forms the hard coat layer 33.

The thickness of the hard coat layer 33 is, for example, 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, and, for example, 10 μm or less, preferably 5 μm or less, more preferably 3 μm or less.

The thickness of the hard coat layer 33 can be determined, for example, by observing a cross section of the hard coat layer 33 with a scanning electron microscope (SEM).

{Optical Adjustment Layer}
The optical adjustment layer 34 is a layer that adjusts the optical properties (e.g., refractive index) of the light-transmitting conductive sheet 1 in order to suppress the visibility of the pattern of the light-transmitting conductive layer 2 and further suppress reflection at the interfaces within the light-transmitting conductive sheet 1 while ensuring excellent transparency of the light-transmitting conductive sheet 1.

The optical adjustment layer 34 is disposed on one surface in the thickness direction of the transparent substrate 31. Specifically, the optical adjustment layer 34 is disposed on the entire upper surface (one surface in the thickness direction) of the transparent substrate 31 so as to contact the one surface in the thickness direction of the transparent substrate 31. The optical adjustment layer 34 contacts the second main surface 22 of the light-transmitting conductive layer 2.

In FIG. 1, the optical adjustment layer 34 is disposed on one surface in the thickness direction of the transparent substrate 31, but this is not limited thereto. In other words, the optical adjustment layer 34 may be disposed on the other side in the thickness direction of the transparent substrate 31, and may further be disposed in multiple layers. Furthermore, when the substrate layer 3 includes the hard coat layer 33 and the optical adjustment layer 34 in the same direction, either on one side or on the other side in the thickness direction of the transparent substrate 31, the order of stacking is not particularly limited.

The optical adjustment layer 34 is formed, for example, from an optical adjustment composition.

The optical adjustment composition contains, for example, a resin, and optionally contains particles. That is, the optical adjustment layer 34 contains, for example, a resin, and optionally contains particles.

Examples of resins include those listed in the hard coat composition above, and preferred examples include melamine resins, alkyd resins, and organic silane condensates.

Examples of particles include the particles listed above for the hard coat composition.

The optical adjustment composition includes, for example, a resin, preferably a curable resin, and more preferably a thermosetting resin. Specifically, the optical adjustment composition includes a melamine resin, an alkyd resin, and an organic silane condensate.

The optical adjustment composition may also contain, for example, a thixotropy-imparting agent, a photopolymerization initiator, a filler (e.g., organic clay), and a leveling agent in appropriate proportions. Furthermore, the optical adjustment composition may be diluted with a known solvent.

To form the optical adjustment layer 34, a diluted solution of the optical adjustment composition is applied to one surface in the thickness direction of the transparent substrate 31, and dried as necessary, as described in detail below. After drying, the optical adjustment composition is cured, for example, by heating.

This forms the optical adjustment layer 34.

The thickness of the optical adjustment layer 34 is, for example, 1 nm or more, preferably 5 nm or more, more preferably 10 nm or more, even more preferably 20 nm or more, particularly preferably 30 nm or more, and, for example, 1000 nm or less, preferably 500 nm or less, more preferably 100 nm or less, even more preferably 50 nm or less.

The thickness of the optical adjustment layer 34 can be calculated, for example, based on the wavelength of the interference spectrum observed using an instantaneous multi-photometer system. The thickness can also be determined by observing a cross-section of the optical adjustment layer 34 with a field emission transmission electron microscope (FE-TEM).

<Light-transmitting conductive layer>
The light-transmitting conductive layer 2 is a transparent layer having excellent electrical conductivity.

The light-transmitting conductive layer 2 has a first main surface 21 and a second main surface 22 facing the first main surface 21 in the thickness direction. In addition, a base layer 3 is arranged on the first main surface 21 and/or the second main surface 22 side of the light-transmitting conductive layer 2. Preferably, the base layer 3 is arranged on the second main surface 22 side (the other side in the thickness direction) of the light-transmitting conductive layer 2. Specifically, the light-transmitting conductive layer 2 has an optical adjustment layer 34, a transparent base material 31, and a hard coat layer 33 in this order on the second main surface 22 side (the other side in the thickness direction). In other words, the light-transmitting conductive layer 2 is arranged on the entire upper surface (one side in the thickness direction) of the optical adjustment layer 34 so as to contact one side in the thickness direction of the optical adjustment layer 34. The light-transmitting conductive layer 2 is the uppermost layer of the light-transmitting conductive sheet.

The first main surface 21 is exposed to one side in the thickness direction. The first main surface 21 is a flat surface.

The second main surface 22 is disposed opposite the first main surface 21 at a distance from the first main surface 21 on the other side in the thickness direction. The second main surface 22 is a flat surface parallel to the first main surface 21. In this embodiment, the light-transmitting conductive layer 2 is provided with an optical adjustment layer 34, a transparent substrate 31, and a hard coat layer 33, in that order, on the side of the second main surface 22 (the other side in the thickness direction).

Note that a flat surface does not necessarily mean that the first main surface 21 and the second main surface 22 are substantially parallel planes. For example, minute irregularities and waviness that are not observable are permitted.

Examples of materials for the light-transmitting conductive layer 2 include metal oxides containing at least one metal and/or semimetal 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.

Specific examples of the light-transmitting conductive layer 2 include indium-containing oxides such as indium tin oxide (ITO), indium gallium oxide (IGO), indium zinc oxide (IZO), and indium gallium zinc oxide (IGZO), and antimony-containing oxides such as antimony tin oxide (ATO), and preferably indium-containing oxides, and more preferably indium tin oxide (ITO).

When the light-transmitting conductive layer 2 contains an indium tin composite oxide, it is possible to reduce the resistance.

When ITO is used as the material for the light-transmitting conductive layer 2, the content of tin oxide is, for example, 0.5% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 8% by mass or more, and for example, 20% by mass or less, preferably 15% by mass or less, more preferably 12% by mass or less, based on the total amount of tin oxide and indium oxide.

If the content of tin oxide is equal to or greater than the lower limit, the resistance is reduced. If the content of tin oxide is equal to or less than the upper limit, the light-transmitting conductive layer 2 has excellent heat stability.

The tin oxide concentration in the light-transmitting conductive layer 2 is measured by X-ray photoelectron spectroscopy, and the tin oxide content can be calculated. The tin oxide content can also be estimated from the components (known) of the target used when forming the light-transmitting conductive layer 2 by sputtering.

The light-transmitting conductive layer 2 has crystal grains, and preferably has a plurality of crystal grains. The crystal grains are sometimes called grains.

In addition, the light-transmitting conductive layer 2 has multiple crystal grains and therefore has grain boundaries. Note that the grain boundaries refer to the boundaries between multiple adjacent crystal grains.

Note that the grain sizes of the crystal grains described below are equivalent circle diameters.

The average crystal grain size of the crystal grains is 105 nm or less, preferably 100 nm or less, more preferably 95 nm or less, and for example, 20 nm or more, preferably 40 nm or more, more preferably 60 nm or more, and even more preferably 80 nm or more.

If the average crystal grain size is equal to or less than the upper limit, the crystal grains are small, resulting in excellent flexibility. If the average crystal grain size is equal to or more than the lower limit, low resistance is possible.

The average grain size of the crystal grains can be determined by photographing the crystal grains using a field emission transmission electron microscope (FE-TEM) and subjecting the photographed images to image analysis processing. Details are given by the method described in the examples below.

The crystal grains include crystal grains having a maximum crystal grain size of, for example, 100 nm or more, preferably 110 nm or more, more preferably 130 nm or more, even more preferably 150 nm or more, and particularly preferably 170 nm or more.

If the maximum crystal grain size includes crystal grains that are equal to or larger than the lower limit above, low resistance is possible.

The maximum crystal grain size of the crystal grains is, for example, 300 nm or less, preferably 250 nm or less, and more preferably 220 nm or less.

If the maximum crystal grain size is below the upper limit, there will be no excessively coarse crystal grains and the flexibility will be excellent.

The maximum grain size of the crystal grains can be determined by photographing the crystal grains using a field emission transmission electron microscope (FE-TEM) and subjecting the photographed image to image analysis processing. Details are given by the method described in the examples below.

In the light-transmitting conductive layer 2, the content of crystal grains with a crystal grain size of 100 nm or more relative to the total number of crystal grains is, for example, 80% or less, preferably 70% or less, more preferably 60% or less, even more preferably 50% or less, particularly preferably 40% or less, and, for example, more than 0%, preferably 5% or more, more preferably 10% or more, even more preferably 20% or more, particularly preferably 30% or more.

If the ratio of the content of crystal grains with a grain size of 100 nm or more to the total number of crystal grains is equal to or less than the upper limit, the flexibility is excellent. Also, if the ratio of the content of crystal grains with a grain size of 100 nm or more to the total number of crystal grains is equal to or greater than the lower limit, the resistance can be reduced.

In the light-transmitting conductive layer 2, the content of crystal grains with a crystal grain size of 150 nm or more relative to the total number of crystal grains is, for example, 50% or less, preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, and particularly preferably 5% or less.

If the ratio of crystal grains with a grain size of 150 nm or more to the total number of crystal grains is equal to or less than the above upper limit, the flexibility is excellent.

The percentage of crystal grains with a specific grain size or larger relative to the total number of crystal grains can be determined by photographing the crystal grains using a field emission transmission electron microscope (FE-TEM) and subjecting the photographed images to image analysis processing. Details are given by the method described in the examples below.

The light-transmitting conductive layer 2 is crystalline because it has crystal grains. In other words, it is preferable that the light-transmitting conductive layer 2 does not include amorphous regions in the surface direction, and includes only crystalline regions. Note that a transparent conductive layer that includes amorphous regions can be identified, for example, by observing the crystal grains in the surface direction of the transparent conductive layer with a transmission electron microscope (TEM).

When the light-transmitting conductive layer 2 is crystalline, for example, the light-transmitting conductive layer 2 is immersed in a 5% by weight aqueous hydrochloric acid solution for 15 minutes, then washed with water and dried, and the resistance between two terminals is measured over a distance of about 15 mm on the first main surface 21, and the resistance between two terminals is 10 kΩ or less. On the other hand, if the resistance between two terminals exceeds 10 kΩ, the light-transmitting conductive layer 2 is amorphous.

The total light transmittance (JIS K 7375-2008) of the light-transmitting conductive layer 2 is, for example, 60% or more, preferably 80% or more, and more preferably 85% or more.

If the total light transmittance of the light-transmitting conductive layer 2 is equal to or greater than the lower limit, the light-transmitting conductive layer 2 has excellent transparency.

The thickness of the light-transmitting conductive layer 2 is more than 50 nm, preferably 55 nm or more, more preferably 60 nm or more, even more preferably 80 nm or more, particularly preferably 100 nm or more, most preferably 120 nm or more, and for example, 1000 nm or less, preferably 300 nm or less, more preferably 250 nm or less, even more preferably 200 nm or less, particularly preferably 150 nm or less, most preferably 130 nm or less.

If the thickness of the light-transmitting conductive layer 2 is equal to or greater than the lower limit, the resistance can be reduced. If the thickness of the light-transmitting conductive layer 2 is equal to or less than the upper limit, the flexibility is excellent.

The thickness of the light-transmitting conductive layer 2 can be measured, for example, by observing a cross section of the light-transmitting conductive sheet 10 using a field emission transmission electron microscope (FE-TEM).

The resistivity of the light-transmitting conductive layer 2 is, for example, 5.0×10 ⁻⁴ Ω·cm or less, preferably 3.0×10 ⁻⁴ Ω·cm or less, more preferably 2.8×10 ⁻⁴ Ω·cm or less, even more preferably 2.6×10 ⁻⁴ Ω·cm or less, and for example, 0.1×10 ⁻⁴ Ω·cm or more, preferably 0.5×10 ⁻⁴ Ω·cm or more, more preferably 1.0×10 ⁻⁴ Ω·cm or more.

The resistivity can be measured using the four-terminal method in accordance with JIS K7194.

The surface resistance of the light-transmitting conductive layer 2 is, for example, 200 Ω/□ or less, preferably 80 Ω/□ or less, more preferably 50 Ω/□ or less, even more preferably 40 Ω/□ or less, particularly preferably 30 Ω/□ or less, most preferably 25 Ω/□ or less, and usually more than 0 Ω/□ or 1 Ω/□ or more.

The surface resistance can be measured using the four-terminal method in accordance with JIS K7194.

The number of light-transmitting conductive layers 2 in the light-transmitting conductive sheet 10 is not particularly limited, and may be, for example, one layer. Specifically, the number of light-transmitting conductive layers 2 for one base layer 3 is, for example, one layer.

<Method for producing light-transmitting conductive sheet>
A method for producing the light-transmitting conductive sheet 1 will be described with reference to FIG.

The manufacturing method of the light-transmitting conductive sheet 1 includes a first step of preparing the base layer 3, a second step of stacking (arranging) the light-transmitting conductive layer 2 on one surface in the thickness direction of the base layer 3, and a third step of heating and crystallizing the light-transmitting conductive layer 2. In this manufacturing method, each layer is arranged in order, for example, by a roll-to-roll method.

[First step]
In the first step, the base layer 3 is prepared.

To fabricate the substrate layer 3, first prepare a transparent substrate 31 as shown in FIG. 2A.

Next, as shown in FIG. 2B, a diluted solution of the optical adjustment composition is applied to one surface in the thickness direction of the transparent substrate 31, and after drying, the optical adjustment composition is cured by ultraviolet irradiation or heating. This forms an optical adjustment layer 34 on one surface in the thickness direction of the transparent substrate 31.

Furthermore, as shown in FIG. 2C, a diluted solution of the hard coat composition is applied to the other surface in the thickness direction of the transparent substrate 31, and after drying, the hard coat composition is cured by ultraviolet light irradiation or heating. This forms a hard coat layer 33 on the other surface in the thickness direction of the transparent substrate 31. This produces the substrate layer 3.

[Second step]
In the second step, as shown in FIG. 2D, the light-transmitting conductive layer 2 is laminated (placed) on one surface in the thickness direction of the base layer 3 (optical adjustment layer 34).

Methods for laminating the light-transmitting conductive layer 2 include, for example, vacuum deposition, sputtering, and ion plating. Sputtering is preferred.

In the sputtering method, one surface in the thickness direction of the adherend (substrate layer 3) is placed facing a target made of the material of the light-transmitting conductive layer 2 in a chamber of a vacuum device, and gas is supplied and a voltage is applied to accelerate the gas ions and irradiate the target, ejecting the target material from the target surface and layering the target material on the surface of the adherend. The substrate layer 3 is also in close contact with the circumferential direction of the film-forming roll.

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. Of these, the magnetron sputtering method is preferable.

The power source used in the sputtering method may be, for example, a direct current (DC) power source, an alternating current medium frequency (AC/MF) power source, a radio frequency (RF) power source, or a radio frequency power source superimposed on a DC power source, and preferably a DC power source.

In other words, in the second step, a DC magnetron sputtering device is preferably used.

Examples of targets include the above-mentioned metal oxides that constitute the light-transmitting conductive layer 2. Specifically, when ITO is used as the material for the light-transmitting conductive layer 2, a target made of ITO is used.

The horizontal magnetic field strength on the target is, for example, 10 mT or more, preferably 60 mT or more, and, for example, 300 mT or less.

By setting the horizontal magnetic field strength above the target within the above range, it is possible to reduce the resistance of the light-transmitting conductive layer 2.

The film formation temperature during sputtering (specifically, the temperature of the substrate layer 3) is, for example, 100°C or less, preferably 50°C or less, more preferably 0°C or less, even more preferably -5°C or less, and for example, -20°C or more.

If the deposition temperature during sputtering is within the above range, the base layer 3 can be cooled sufficiently, and crystal growth during deposition of the light-transmitting conductive layer 2 (particularly crystal growth in the thickness direction of the light-transmitting conductive layer 2) can be suppressed, making it easier to obtain crystal grains in the light-transmitting conductive layer 2 after the third step described below.

The air pressure inside the sputtering deposition apparatus is, for example, 1.0 Pa or less, preferably 0.5 Pa or less, and, for example, 0.01 Pa or more, preferably 0.1 Pa or more.

The gas introduced (sputtering gas) may be, for example, an inert gas, preferably argon gas. A reactive gas (for example, oxygen) may also be used in combination.

The ratio of the amount of reactive gas introduced to the total amount of sputtering gas and reactive gas introduced is, for example, 0.1 flow% or more, preferably 1.0 flow% or more, more preferably 2.0 flow% or more, and for example, 10.0 flow% or less, preferably 8.0 flow% or less, more preferably 5.0 flow% or less.

By adjusting the ratio of the amount of reactive gas introduced to the total amount of sputtering gas and reactive gas introduced, the grain size of the crystal grains 6 in the light-transmitting conductive layer 2 can be adjusted.

This results in an amorphous light-transmitting conductive sheet 1 comprising an amorphous light-transmitting conductive layer 2 and a base layer 3.

<Third step>
In the third step, the amorphous light-transmitting conductive layer 2 is heated. For example, the amorphous light-transmitting conductive layer 2 is heated by a heating device (for example, an infrared heater and a hot air oven).

The heating temperature is, for example, 80°C or higher, preferably 110°C or higher, and, for example, less than 200°C, preferably 180°C or lower. The heating time is, for example, 1 minute or more, preferably 10 minutes or more, more preferably 20 minutes or more, and, for example, 24 hours or less, preferably 4 hours or less, more preferably 1 hour or less.

As a result, the amorphous light-transmitting conductive layer 2 is crystallized to form a crystalline light-transmitting conductive layer 2, as shown in FIG. 2E.

This results in a light-transmitting conductive layer 2, and a light-transmitting conductive sheet 1 comprising the light-transmitting conductive layer 2 and the base layer 3.

The light-transmitting conductive layer 2 can then be patterned. The patterning can be performed, for example, by etching.

<Action and effect>
The present invention provides a light-transmitting conductive layer having a first main surface and a second main surface opposed to the first main surface in a thickness direction, the light-transmitting conductive layer having a thickness of more than 50 nm and having crystal grains with an average crystal grain size of 105 nm or less, and therefore having low resistance and excellent flexibility.

Specifically, the light-transmitting conductive layer has a thickness of more than 50 nm, so it has low resistance, and furthermore, it has crystal grains with an average crystal grain size of 105 nm or less, so it has excellent flexibility.

In addition, the light-transmitting conductive sheet having the light-transmitting conductive layer of the present invention has low resistance and excellent flexibility.

The present invention will be described in more detail below with reference to examples and comparative examples. Note that the present invention is in no way limited to the examples and comparative examples. Furthermore, 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 "equal to or less than") or lower limit (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding blending ratio (content ratio), physical property value, parameter, etc. described in the above "Form for carrying out the invention."

Example 1
<Production of Light-Transmitting Conductive Sheet>
[First step]
A roll of polyethylene terephthalate (PET) film (thickness 100 μm, manufactured by Mitsubishi Chemical Corporation) was prepared as a long transparent substrate, and a thermosetting resin composition C1 was applied to one surface in the thickness direction of the PET film to form a coating film. The coating film of the resin composition C1 was heated at 185 ° C. for 1 minute to be cured. This formed an optical adjustment layer with a thickness of 35 nm. The resin composition C1 is a resin composition containing 100 parts by mass of melamine resin, 100 parts by mass of alkyd resin, and 50 parts by mass of an organic silane condensate. Next, a UV-curable resin composition C2 was applied to the other surface in the thickness direction of the PET film to form a coating film. The coating film of the resin composition C2 was cured by UV irradiation. This formed a hard coat layer with a thickness of 2 μm. The resin composition C2 is a resin composition containing an acrylic resin.

This produced a substrate layer (having a hard coat layer, a transparent substrate, and an optical adjustment layer in that order toward one side in the thickness direction).

[Second step]
An amorphous light-transmitting conductive layer having a thickness of 125 nm was laminated (disposed) on one surface of the substrate layer (optical adjustment layer) in the thickness direction by a reactive sputtering method. In the reactive sputtering method, a sputtering film formation device (DC magnetron sputtering device) capable of performing a film formation process by a roll-to-roll method was used.

In detail, a sintered body of indium oxide and tin oxide (tin oxide concentration: 10% by mass) was used as the target. A DC power supply was used as the power supply for applying voltage to the target. The horizontal magnetic field strength above the target was 90 mT. The transport speed of the substrate layer was 2.0 m/min. The film formation temperature (temperature of the substrate layer) was -8°C.

The sputtering deposition apparatus was evacuated until the ultimate vacuum in the deposition chamber of the sputtering deposition apparatus reached 0.8×10 ⁻⁴ Pa, after which argon was introduced as a sputtering gas and oxygen as a reactive gas into the sputtering deposition apparatus, and the pressure in the sputtering deposition apparatus was set to 0.4 Pa. The ratio of the amount of oxygen introduced to the total amount of argon and oxygen introduced into the sputtering deposition apparatus was approximately 3.4 flow %.

This resulted in a light-transmitting conductive sheet with an amorphous light-transmitting conductive layer 125 nm thick.

[Third step]
The light-transmitting conductive sheet having the amorphous light-transmitting conductive layer was heated in a hot air oven at 155° C. for 30 minutes to crystallize the light-transmitting conductive layer.

This resulted in the production of the light-transmitting conductive sheet of Example 1, which includes a light-transmitting conductive layer and a base layer on the second main surface side of the light-transmitting conductive layer (the other side in the thickness direction).

Comparative Example 1
A light-transmitting conductive sheet was obtained in the same manner as in Example 1, except that in the second step, krypton was used as the sputtering gas.

Comparative Example 2
A light-transmitting conductive sheet was obtained in the same manner as in Example 1, except that in the third step, the light-transmitting conductive sheet was not heated and the amorphous light-transmitting conductive layer was not crystallized.

<Evaluation>
[Thickness of Light-Transmitting Conductive Layer]
The thickness of the light-transmitting conductive layer of Example 1 and each Comparative Example was measured by field emission transmission electron microscope (FE-TEM) observation (cross-sectional observation). Specifically, first, a cross-sectional observation sample of the light-transmitting conductive layer of Example 1 and each Comparative Example was prepared by a focused ion beam (FIB) microsampling method. In the FIB microsampling method, an FIB device (trade name "FB2200", manufactured by Hitachi) was used, and the acceleration voltage was set to 10 kV. Next, the thickness of the light-transmitting conductive layer in the cross-sectional observation sample was measured by FE-TEM observation. In the FE-TEM observation, an FE-TEM device (trade name "JEM-2800", manufactured by JEOL) was used, and the acceleration voltage was set to 200 kV. The results are shown in Table 1.

[Resistance value]
The resistance values (R0) of the light-transmitting conductive sheets of Example 1 and Comparative Example were measured by a four-terminal method. The resistance values were evaluated according to the following criteria. The results are shown in Table 1.

{standard}
〇: Below 40Ω/□ ×: Over 40Ω/□

[Crystal grain size (planar view)]
The light-transmitting conductive sheets of Example 1 and Comparative Example 1 were cut out and fixed to a sample holder of an ultramicrotome. Next, a microtome knife was placed at an extremely acute angle to the light-transmitting conductive layer surface, and the cut surface was cut so as to be approximately parallel to the light-transmitting conductive layer to obtain an observation sample. This observation sample was photographed using an FE-TEM device (trade name "JEM-2800", manufactured by JEOL) with an acceleration voltage of 200 kV to photograph the crystal grains in a planar view of the light-transmitting conductive layer (direct magnification: 100,000 times). The photographed range was about 1400 nm x 1400 nm. Next, the photographed image was subjected to image analysis processing to determine the area of each crystal grain boundary region from the number of pixels present in the region defined by the crystal grain boundaries (each crystal grain boundary region), and the diameter of a circle having the same area as the area was calculated as the crystal grain size (circle equivalent diameter), and the average crystal grain size and the maximum crystal grain size were obtained. Furthermore, the number of crystal grains with a crystal grain size of 100 nm or more among the crystal grains observed (photographed) by FE-TEM was determined, and the content ratio of crystal grains with a crystal grain size of 100 nm or more to the total number of crystal grains observed was determined. Similarly, the content ratio of crystal grains with a crystal grain size of 150 nm or more was determined. The results are shown in Table 1. Note that the light-transmitting conductive sheet of Comparative Example 2 is amorphous and therefore does not have crystal grains.

[Flexibility]
The light-transmitting conductive sheets of Example 1 and each of the comparative examples were cut to a width of 10 mm and a length of 150 mm. The cut light-transmitting conductive sheets were placed on the mandrel so that the light-transmitting conductive layer was on the outside and the other surface in the thickness direction of the base layer (hard coat layer) was in contact with the mandrel. Then, both ends of the light-transmitting conductive sheet in the length direction were clipped, and a weight of 1000 g was attached to the center of the clip. That is, a load of 100 g/mm was applied downward with respect to the width of the light-transmitting conductive sheet to fold the light-transmitting conductive sheet. This folded state was maintained for 10 seconds. In the folded state, the bent portion was painted with a marker, and the folded state was released, and the painted portion was observed with a microscope. The diameter of the mandrel was changed from a large diameter to a small diameter every 1 mm, and the smallest diameter at which no cracks were observed in the observation of the painted portion is shown in Table 1. The smaller the diameter at which no cracks were observed, the better the bending resistance. Each time the diameter of the mandrel was changed, a new light-transmitting conductive sheet was used.

Reference Signs List 1: Light-transmitting transparent conductive sheet 2: Light-transmitting conductive layer 3: Base layer 21: First main surface 22: Second main surface

Claims (6)

A light-transmitting conductive layer having a first main surface and a second main surface opposed to the first main surface in a thickness direction,
The thickness of the light-transmitting conductive layer is greater than 50 nm;
the light-transmitting conductive layer has crystal grains,
The average crystal grain size of the crystal grains is 105 nm or less,
The content ratio of crystal grains having a crystal grain size of 100 nm or more to the total number of the crystal grains is 5% or more and 80% or less,
The optically transparent conductive layer has a specific resistance of 3.0×10 ⁻⁴ Ω·cm or less . The optically transparent conductive layer according to claim 1, wherein the crystal grains include crystal grains having a maximum crystal grain size of 110 nm or more. The light-transmitting conductive layer according to claim 1, wherein the content of crystal grains having a crystal grain size of 100 nm or more relative to the total number of crystal grains is 70% or less. A light-transmitting conductive layer having a first main surface and a second main surface opposed to the first main surface in a thickness direction,
The thickness of the light-transmitting conductive layer is greater than 50 nm;
the light-transmitting conductive layer is made of an indium tin composite oxide;
the light-transmitting conductive layer has crystal grains,
The crystal grains include crystal grains having a maximum crystal grain size of 110 nm or more,
The average crystal grain size of the crystal grains is 105 nm or less,
The optically transparent conductive layer has a specific resistance of 3.0×10 ⁻⁴ Ω·cm or less . The light-transmitting conductive layer according to claim 4, wherein the content of crystal grains having a crystal grain size of 100 nm or more relative to the total number of crystal grains is 70% or less. The light-transmitting conductive layer according to any one of claims 1 to 5,
A light-transmitting conductive sheet comprising a base material layer on the side of the first main surface and/or the second main surface of the light-transmitting conductive layer.