JP7780905B2 - Laminate, laminate manufacturing method, optical member, optical device, optical member manufacturing method, and optical device manufacturing method - Google Patents

Description

The present invention relates to a laminate, a method for manufacturing a laminate, an optical member, an optical device, a method for manufacturing an optical member, and a method for manufacturing an optical device.

In optical devices, for example, an air layer with a low refractive index is used as a total reflection layer. Specifically, for example, in a liquid crystal device, each optical film component (e.g., a light guide plate and a reflector) is laminated with an air layer between them. However, when each component is separated by an air layer, problems such as component deflection may occur, especially when the components are large. Furthermore, with the trend toward thinner devices, there is a demand for integrating each component. For this reason, each component is integrated with an adhesive without an air layer (e.g., Patent Document 1). However, if the air layer that performs the role of total reflection is lost, there is a risk of light leakage and other degradation of optical properties.

As a result, it has been proposed to use a low refractive index layer instead of an air layer. For example, Patent Document 2 describes a structure in which a layer with a lower refractive index than the light guide plate is inserted between the light guide plate and the reflector. As the low refractive index layer, for example, an air gap layer with voids is used to achieve a refractive index as low as possible that is close to that of air.

Furthermore, a structure incorporating an adhesive layer into a device has also been proposed (Patent Document 3).

JP 2012-156082 A Japanese Patent Application Publication No. 10-62626 JP 2014-46518 A

The void layer is used by laminating it with another layer, for example, via an adhesive layer. However, when the void layer and the adhesive layer are laminated together, the adhesive or pressure-sensitive adhesive that constitutes the adhesive layer may penetrate into the voids of the void layer and fill the voids, which may reduce the porosity of the void layer and increase the refractive index. The higher the porosity of the void layer, the easier it is for the adhesive or pressure-sensitive adhesive to penetrate. Furthermore, in high-temperature environments, the molecular motion of the adhesive or pressure-sensitive adhesive (reduced elastic modulus) makes it easier for the adhesive or pressure-sensitive adhesive to penetrate into the voids. In high-humidity environments, the adhesive or pressure-sensitive adhesive absorbs water, making it easier for the adhesive or pressure-sensitive adhesive to penetrate into the voids.

In order to suppress or prevent the pressure-sensitive adhesive or adhesive from penetrating into the voids, it is best to use a pressure-sensitive adhesive or adhesive with as high a modulus of elasticity (hardness) as possible. However, if the pressure-sensitive adhesive or adhesive has a high modulus of elasticity (hardness), there is a risk that the adhesive strength or bonding force will be reduced. Conversely, if the pressure-sensitive adhesive or adhesive has a low modulus of elasticity (softness), high adhesive strength or bonding force will be easily obtained, but there is a risk that the pressure-sensitive adhesive or adhesive will be more likely to penetrate into the voids.

The present invention therefore aims to provide a laminate, a method for manufacturing a laminate, an optical element, an optical device, a method for manufacturing an optical element, and a method for manufacturing an optical device that combines adhesive strength or bonding strength with resistance to penetration of the adhesive or bonding agent into voids.

To achieve the above object, the laminate of the present invention is characterized in that a void layer, an intermediate layer, and an adhesive layer are laminated in the above order, and the intermediate layer is a layer containing a polymer having a glass transition temperature (Tg) of 30°C or higher.

The method for producing the laminate of the present invention includes the steps of:
an intermediate layer forming step of coating an intermediate layer coating liquid containing the polymer on one surface of the void layer and the adhesive layer to form the intermediate layer;
an intermediate layer attaching step of attaching the intermediate layer to the other of the porous layer and the adhesive layer;
The method for producing a laminate of the present invention is characterized by comprising:

The optical member of the present invention is characterized by including the laminate of the present invention.

The optical device of the present invention is characterized by including the optical element of the present invention.

The method for producing an optical member of the present invention is characterized by including a step of producing the laminate of the present invention by the method for producing a laminate of the present invention.

The method for manufacturing an optical device of the present invention is characterized by including a step of manufacturing the optical element of the present invention by the method for manufacturing an optical element of the present invention.

The present invention provides a laminate, a method for manufacturing a laminate, an optical element, an optical device, a method for manufacturing an optical element, and a method for manufacturing an optical device that combines adhesive strength or bonding strength with resistance to penetration of the adhesive or bonding agent into voids.

1(a) and 1(b) are cross-sectional views illustrating the structure of the laminate of the present invention.

Next, the present invention will be explained in more detail using examples. However, the present invention is not limited in any way by the following explanation.

In the laminate of the present invention, for example, the polymer in the intermediate layer may be a polymer having an amino group.

In the laminate of the present invention, the intermediate layer may be, for example, a layer formed by applying an intermediate layer coating liquid containing the polymer.

In the laminate of the present invention, for example, the intermediate layer coating liquid may further contain a crosslinking agent.

In the laminate of the present invention, the thickness of the intermediate layer may be, for example, 5 to 150 nm. The thickness of the intermediate layer may be, for example, 10 nm or more, 15 nm or more, 20 nm or more, nm or more, or may be, for example, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, or 100 nm or less. From the viewpoint of suppressing penetration of the adhesive or bonding agent into the voids, it is preferable that the thickness of the intermediate layer is not too small. Furthermore, from the viewpoint of suppressing peeling of the void layer from the intermediate layer and the adhesive layer, it is preferable that the thickness of the intermediate layer is not too large.

The laminate of the present invention may have a residual void ratio of the porous layer exceeding 50% by volume after a heat durability test in which the laminate is maintained at a temperature of 95°C for 1,000 hours, for example.

The method for producing the laminate of the present invention includes, for example,
In the intermediate layer forming step, an intermediate layer coating liquid containing the polymer is applied onto a surface of the adhesive layer to form the intermediate layer,
In the intermediate layer attaching step, the intermediate layer may be attached to the air gap layer.

The method for manufacturing a laminate of the present invention may further include, for example, a heating step of heating the void layer, the intermediate layer, and the adhesive layer after the intermediate layer attachment step.

The laminate of the present invention may be, for example, a laminate produced by the method for producing a laminate of the present invention.

In the laminate of the present invention, for example, the adhesive layer may be formed from an adhesive containing a (meth)acrylic polymer.

In the laminate of the present invention, for example, the (meth)acrylic polymer may contain 1 to 30% by weight of a nitrogen-containing monomer as a monomer unit.

In the laminate of the present invention, the nitrogen-containing monomer may be, for example, a heterocycle-containing acrylic monomer.

In the laminate of the present invention, the (meth)acrylic polymer may have a weight average molecular weight (Mw) of 1.5 million to 4 million, for example.

In the present invention, a "tacky-adhesive layer" refers to a layer formed from at least one of a pressure-sensitive adhesive and an adhesive. Furthermore, in the present invention, pressure-sensitive adhesives and adhesives may be collectively referred to as "tacky-adhesive." Generally, a distinction is made between an agent with relatively weak adhesive or bonding strength (for example, an agent that allows the adherend to be removably attached) and an agent with relatively strong adhesive or bonding strength (for example, an agent that makes it impossible or extremely difficult to removably attach the adherend) and is referred to as an "adhesive." In the present invention, there is no clear distinction between a pressure-sensitive adhesive and an adhesive. Furthermore, in the present invention, there is no clear distinction between "adhesive strength" and "adhesive strength."

In addition, in the present invention, "on" or "on the surface" can refer to a state of being in direct contact with the surface or a state of being interposed between another layer, etc.

In the laminate of the present invention, for example, the (meth)acrylic polymer may be a (meth)acrylic polymer having a weight-average molecular weight of 1.5 million to 4 million obtained by polymerizing 1 to 30% by weight of a nitrogen-containing acrylic monomer, 0.5 to 5% by weight of (meth)acrylic acid, 0.05 to 2% by weight of a hydroxyalkyl (meth)acrylate, and 83 to 96.45% by weight of an alkyl (meth)acrylate as monomer components.

In the adhesive layer of the laminate of the present invention, for example, the nitrogen-containing monomer may be a monomer having one or two reactive double bonds per molecule. The monomer having one or two reactive double bonds per molecule may be, for example, a heterocycle-containing acrylic monomer (heterocycle-containing acrylate).

In the laminate of the present invention, the gel fraction of the adhesive forming the adhesive layer may be, for example, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 100% by weight or less, 99% by weight or less, 98% by weight or less, or 97% by weight or less.

In the laminate of the present invention, for example, the refractive index of the void layer may be 1.25 or less.

The laminate of the present invention may have a refractive index of the void layer of 1.25 or less after a heat durability test in which the laminate is held at a temperature of 95°C for 1,000 hours, for example.

The laminate of the present invention may, for example, have a porosity of the void layer of 35% by volume or more.

In the laminate of the present invention, for example, the void layer may be a porous body in which microporous particles are chemically bonded to each other.

In the laminate of the present invention, the adhesive layer may be a layer formed by a method including, for example, an adhesive coating liquid preparation step of preparing an adhesive coating liquid containing a (meth)acrylic polymer, an adhesive coating liquid application step of applying the adhesive coating liquid to a substrate, and a heat drying step of heating and drying the substrate coated with the adhesive coating liquid. In the laminate of the present invention, for example, the adhesive layer may be formed from an adhesive coating liquid having a specific composition and integrated with the void layer. This can suppress significant penetration of the adhesive layer into the void layer, especially during long-term heat durability tests. The adhesive coating liquid may further include, for example, a crosslinking agent, or may include other components as described below.

In the laminate of the present invention, by disposing the intermediate layer, which is a layer containing a polymer having a glass transition temperature (Tg) of 30°C or higher, between the void layer and the adhesive layer, it is possible to suppress or prevent penetration of the adhesive layer into the voids in the void layer. As a result, the laminate of the present invention can achieve both adhesive strength or bond strength and resistance to penetration of the adhesive or adhesive into the voids. In the laminate of the present invention, the intermediate layer acts as a stopper, even under conditions such as the heat durability test, and can suppress a decrease in porosity caused by the voids in the void layer being filled with the adhesive. Furthermore, even under conditions such as the heat durability test, the intermediate layer does not expand excessively.

The laminate of the present invention may or may not include other components in addition to the void layer, the intermediate layer, and the adhesive layer. The other components are not particularly limited, and may be, for example, a substrate (e.g., a resin film, etc.) or an optically functional layer, as described below. The optically functional layer is also not particularly limited, and may be, for example, an optically functional layer used in general optical films, such as a microlens film, prism film, diffusion film, polarized reflection film, polarizing film, retardation film, or high refractive index layer. Furthermore, other components may or may not be present between the void layer and the intermediate layer. That is, the void layer and the intermediate layer may be laminated so as to be in direct contact with each other, or may be laminated via another component. Other components may or may not be present between the intermediate layer and the adhesive layer. That is, the intermediate layer and the adhesive layer may be laminated so as to be in direct contact with each other, or may be laminated via another component.

In the adhesive coating liquid for forming the adhesive layer in the laminate of the present invention, the nitrogen-containing monomer preferably has a small number of functional groups (the number of reactive double bonds per molecule) in order to efficiently crosslink main chains in the graft reaction; for example, the number of reactive double bonds per molecule is preferably one or two.

Even if a monomer having one or two reactive double bonds is mixed during the production of a (meth)acrylic polymer, it is difficult to reduce the amount of the aforementioned semi-high molecular weight polymer (which has a small molecular weight and easily penetrates into the voids of the void layer). However, according to the present invention, by using an adhesive coating liquid in which a monomer having one or two reactive double bonds is later mixed into a (meth)acrylic polymer and then subjected to a crosslinking reaction, for example, a graft reaction such as that described above occurs, making it possible to reduce the amount of the semi-high molecular weight polymer.

In the present invention, "(meth)acrylic" means at least one of acrylic and methacrylic. For example, "(meth)acrylic acid" means at least one of acrylic acid and methacrylic acid. "(meth)acrylic acid ester" means at least one of acrylic acid ester and methacrylic acid ester. "Methyl (meth)acrylate" means at least one of methyl acrylate and methyl methacrylate.

In the present invention, "(meth)acrylic polymer" refers to a polymer having a structure obtained by polymerizing a component containing at least one selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, monomers having an acryloyl group, and monomers having a methacryloyl group. The component may or may not contain a substance other than at least one selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, monomers having an acryloyl group, and monomers having a methacryloyl group, as appropriate.

In the present invention, "acrylic monomer" refers to a monomer containing at least one selected from the group consisting of, for example, acrylic acid, acrylic acid esters, and monomers having an acryloyl group.

In the present invention, "isocyanate-based crosslinking agent" refers to, for example, a crosslinking agent having an isocyanate group (isocyanato group) in the molecule. In the present invention, the number of isocyanate groups (isocyanato groups) in one molecule of the isocyanate-based crosslinking agent is not particularly limited, but is preferably 2 or more, and may be, for example, 2, 3, or 4. The upper limit is not particularly limited, but is, for example, 10 or less.

[1. Laminate, optical member, and optical device]
As described above, the laminate of the present invention is characterized in that a void layer, an intermediate layer, and an adhesive layer are laminated in the above order, and the intermediate layer is a layer containing a polymer having a glass transition temperature (Tg) of 30° C. or higher. The intermediate layer and the adhesive layer may be laminated on only one side of the void layer, or on both sides of the void layer, for example.

The cross-sectional view of Figure 1(a) shows an example of the configuration of a laminate of the present invention. As shown, this laminate 10 has a void layer 11, an intermediate layer 12, and an adhesive layer 13 laminated in the above order. The intermediate layer 12 is a layer containing a polymer with a glass transition temperature (Tg) of 30°C or higher.

The cross-sectional view of Figure 1(b) shows an example of the configuration of a laminate of the present invention. As shown, this laminate 10a is the same as the laminate 10 of Figure 1(a), except that a substrate 14 is provided in direct contact with the surface of the void layer 11 opposite the intermediate layer 12, and with the surface of the adhesive layer 13 opposite the intermediate layer 12. The substrate 14 is not particularly limited, and may be, for example, a film (e.g., a resin film), a glass plate, etc., as described below.

The configuration of the laminate of the present invention is not limited to the configurations shown in Figures 1(a) and 1(b). For example, the intermediate layer 12 and the adhesive layer 13 are laminated on only one side of the void layer 11 in Figures 1(a) and 1(b), but as described above, they may be laminated on both sides of the void layer 11. Also, in Figure 1(b), a substrate 14 is provided on both sides of the laminate. However, the present invention is not limited to this. For example, the substrate 14 may be provided on only one side. Also, in Figure 1(b), the substrate 14 is provided so as to be in direct contact with the void layer 11 or the adhesive layer 13. However, the present invention is not limited to this. For example, other components may be present between the substrate 14 and the void layer 11 or the adhesive layer 13. Furthermore, in Figures 1(a) and 1(b), the void layer 11 is laminated so that it is in direct contact with the intermediate layer 12, and the intermediate layer 12 is laminated so that it is in direct contact with the adhesive layer 13. However, other components may be present between the void layer 11 and the intermediate layer 12, or between the intermediate layer 12 and the adhesive layer 13. The other components are not particularly limited, and may be, for example, an optically functional layer. The optically functional layer is also not particularly limited, and may be, for example, an optically functional layer used in a general optical film, such as a microlens film, prism film, diffusion film, polarized reflection film, polarizing film, retardation film, or high refractive index layer.

As described above, after a heat durability test in which the laminate of the present invention is maintained at a temperature of 95°C for 1,000 hours, the residual void ratio of the porous layer may be, for example, greater than 50% by volume, as described above, and may be, for example, 55% by volume or more, 60% by volume or more, 65% by volume or more, or 70% by volume or more. While the upper limit is not particularly limited, it is ideally 100% by volume, and may be, for example, 98% by volume or less, 95% by volume or less, 92% by volume or less, or 90% by volume or less.

Furthermore, in the laminate of the present invention, the void remaining rate of the void layer after the heat durability test may be, for example, 50% or more, 55% or more, 60% or more, 70% or more, 80% or more, 85% or more, or 88% or more of the void remaining rate when only the void layer is subjected to the heat durability test. The upper limit is not particularly limited, but is ideally 100% by volume, and may be, for example, 99% or less, 98% or less, or 97% or less.

The laminate of the present invention may have a light transmittance of 80% or more for the laminate of the adhesive layer and the void layer, or for the laminate of the adhesive layer, the intermediate layer, and the void layer. Furthermore, the haze of the laminate may be 3% or less. The light transmittance may be, for example, 82% or more, 84% or more, 86% or more, or 88% or more. The upper limit is not particularly limited, but is ideally 100%, and may be, for example, 95% or less, 92% or less, 91% or less, or 90% or less. The haze of the laminate may be measured, for example, by the same method as used to measure the haze of the void layer, which will be described later. The light transmittance is the transmittance of light with a wavelength of 550 nm, and can be measured, for example, by the following measurement method.

(Method for measuring light transmittance)
The laminate is used as a sample to be measured using a spectrophotometer U-4100 (trade name of Hitachi, Ltd.). The total light transmittance (light transmittance) of the sample is measured when the total light transmittance of air is taken as 100%. The total light transmittance (light transmittance) value is the value measured at a wavelength of 550 nm.

In the laminate of the present invention, the adhesive strength or bond strength of the adhesive layer may be, for example, 0.7 N/25 mm or more, 0.8 N/25 mm or more, 1.0 N/25 mm or more, or 1.5 N/25 mm or more, or 50 N/25 mm or less, 30 N/25 mm or less, 10 N/25 mm or less, 5 N/25 mm or less, or 3 N/25 mm or less. From the viewpoint of the risk of peeling during handling when the laminate is attached to another layer, it is preferable that the adhesive strength or bond strength of the adhesive layer is not too low. Furthermore, from the viewpoint of rework when reattaching, it is preferable that the adhesive strength or bond strength of the adhesive layer is not too high. The adhesive strength or bond strength of the adhesive layer can be measured, for example, as follows.

(Method for measuring adhesive strength or adhesion)
The laminate film of the present invention (a resin film substrate on which the laminate of the present invention is formed) is sampled in the form of a 50 mm x 140 mm strip, and the sample is fixed to a stainless steel plate with double-sided tape. An acrylic adhesive layer (20 μm thick) is attached to a PET film (T100: manufactured by Mitsubishi Plastics Film Co., Ltd.), and a piece of adhesive tape cut to 25 mm x 100 mm is attached to the side of the laminate film of the present invention opposite the resin film, thereby laminating the PET film. The sample is then chucked in an autograph tensile tester (manufactured by Shimadzu Corporation: AG-Xplus) with a chuck distance of 100 mm, and a tensile test is performed at a tensile speed of 0.3 m/min. The average test force after a 50 mm peel test is taken as the adhesive peel strength, i.e., adhesive strength. Adhesion strength can also be measured using the same measurement method. In the present invention, there is no clear distinction between "adhesive strength" and "adhesive strength."

The laminate of the present invention may be formed on a substrate such as a film. The film may be, for example, a resin film. Generally, a relatively thin material is called a "film" and a relatively thick material is called a "sheet," but in the present invention, no particular distinction is made between "film" and "sheet."

The substrate is not particularly limited, and examples of suitable substrates include, but are not limited to, substrates made of thermoplastic resins, glass substrates, inorganic substrates such as silicon, plastics molded from thermosetting resins, semiconductor elements, and carbon fiber materials such as carbon nanotubes. Examples of the substrate form include films and plates. Examples of thermoplastic resins include polyethylene terephthalate (PET), acrylic, cellulose acetate propionate (CAP), cycloolefin polymer (COP), triacetyl cellulose (TAC), polyethylene naphthalate (PEN), polyethylene (PE), and polypropylene (PP).

The optical component of the present invention is not particularly limited, but may be, for example, an optical film containing the laminate of the present invention.

The optical device of the present invention is not particularly limited, and may be, for example, an image display device or a lighting device. Examples of image display devices include liquid crystal displays, organic electroluminescence (EL) displays, and micro LED (light-emitting diode) displays. Examples of lighting devices include organic EL lighting.

[2. void layer]
The void layer in the laminate of the present invention (hereinafter sometimes referred to as the "void layer of the present invention") will be described below with examples, although the void layer of the present invention is not limited thereto.

The porous layer of the present invention may have, for example, a porosity of 35% by volume or more and a peak pore diameter of 50 nm or less. However, this is merely an example, and the porous layer of the present invention is not limited to this.

The porosity may be, for example, 35% by volume or more, 38% by volume or more, or 40% by volume or more, or 90% by volume or less, 80% by volume or less, or 75% by volume or less. The porous layer of the present invention may be, for example, a highly porous layer with a porosity of 60% by volume or more.

The porosity can be measured, for example, by the following measurement method.

(Method for measuring void ratio)
If the layer to be measured for porosity is a single layer containing only voids, the ratio (volume ratio) of the constituent material of the layer to air can be calculated by a standard method (for example, measuring the weight and volume to calculate the density), and the porosity (volume %) can be calculated from this. In addition, since there is a correlation between the refractive index and the porosity, the porosity can also be calculated from the refractive index value of the layer, for example. Specifically, the porosity is calculated from the refractive index value measured with an ellipsometer using the Lorentz-Lorenz formula.

The porous layer of the present invention can be produced, for example, by chemically bonding pulverized gel particles (microporous particles), as described below. In this case, the pores in the porous layer can be conveniently divided into the following three types (1) to (3).

(1) Voids in the raw gel itself (inside the particles) (2) Voids in the gel pulverized material units (3) Voids between the pulverized gel particles generated by the accumulation of the pulverized gel particles

The voids (2) are voids formed during grinding, separate from the voids (1) that can be formed within each block when each particle group produced by grinding the gel is considered to be a single block, regardless of the size, dimensions, etc., of the ground gel (microporous particles). The voids (3) are voids that arise during grinding (e.g., medialess grinding) because the size, dimensions, etc., of the ground gel (microporous particles) become uneven. The porous layer of the present invention has an appropriate porosity and peak pore diameter, for example, by having the voids (1) to (3) above.

The peak pore diameter may be, for example, 5 nm or more, 10 nm or more, or 20 nm or more, or 50 nm or less, 40 nm or less, or 30 nm or less. If the peak pore diameter is too large when the porosity of the porous layer is high, light will be scattered and the layer will become opaque. In the present invention, there is no particular limit on the lower limit of the peak pore diameter of the porous layer. However, if the peak pore diameter is too small, it will be difficult to increase the porosity, so it is preferable that the peak pore diameter is not too small. In the present invention, the peak pore diameter can be measured, for example, by the following method.

(Method for measuring peak pore diameter)
The peak pore diameter is calculated from the results of BJH plots and BET plots and isothermal adsorption curves calculated by nitrogen adsorption using a pore distribution/specific surface area measuring device (BELLSORP MINI, trade name of Microtrack Bell).

Furthermore, the thickness of the void layer of the present invention is not particularly limited, but may be, for example, 100 nm or more, 200 nm or more, or 300 nm or more, or 10,000 nm or less, 5,000 nm or less, or 2,000 nm or less.

As described below, the porous layer of the present invention is formed by, for example, using pulverized porous gel, destroying the three-dimensional structure of the porous gel and forming a new three-dimensional structure different from the porous gel. In this way, the porous layer of the present invention is a layer with a new pore structure (new void structure) that cannot be obtained in a layer formed from the porous gel, thereby enabling the formation of a nanoscale void layer with high porosity. Furthermore, when the porous layer of the present invention is a silicone porous body, the pulverized materials are chemically bonded together while adjusting the number of siloxane bond functional groups in the silicon compound gel. Here, "porous silicone body" refers to a polymeric porous body containing siloxane bonds, including, for example, a porous body containing silsesquioxane as a structural unit. Furthermore, after a new three-dimensional structure is formed as a precursor to the porous layer, chemical bonding (e.g., cross-linking) is performed in a bonding process. Therefore, when the porous layer of the present invention is a functional porous body, the porous layer has a voided structure but maintains sufficient strength and flexibility. Therefore, according to the present invention, a porous layer can be easily and simply applied to a variety of objects.

The porous layer of the present invention contains, for example, pulverized porous gel, with the pulverized particles chemically bonded together, as described below. In the porous layer of the present invention, the form of chemical bonding (chemical bonding) between the pulverized particles is not particularly limited, and specific examples of chemical bonding include cross-linking. Note that the method for chemically bonding the pulverized particles together is, for example, as described in detail in the porous layer manufacturing method described above.

The crosslinked bond is, for example, a siloxane bond. Examples of siloxane bonds include the T2 bond, T3 bond, and T4 bond shown below. When the silicone porous body of the present invention has siloxane bonds, it may have, for example, any one type of bond, any two types of bonds, or all three types of bonds. The higher the ratio of T2 and T3 among the siloxane bonds, the greater the flexibility and the more the gel's inherent properties can be expected, but the weaker the film strength. On the other hand, if the ratio of T4 among the siloxane bonds is high, the film strength is more likely to be achieved, but the pore size becomes smaller and the flexibility becomes weaker. For this reason, it is preferable to change the ratios of T2, T3, and T4 depending on the application, for example.

When the porous layer of the present invention has the siloxane bond, the ratio of T2, T3, and T4, relative to T2 being "1," is, for example, T2:T3:T4 = 1:[1-100]:[0-50], 1:[1-80]:[1-40], or 1:[5-60]:[1-30].

Furthermore, in the porous layer of the present invention, it is preferable that the silicon atoms contained therein are siloxane-bonded. Specific examples include the proportion of unbonded silicon atoms (i.e., residual silanols) among all silicon atoms contained in the silicone porous body being, for example, less than 50%, 30% or less, or 15% or less.

The void layer of the present invention has, for example, a pore structure. In the present invention, the void size of the pores refers to the diameter of the long axis of the void (pore), out of the diameter of the long axis and the diameter of the short axis. The pore size is, for example, 5 nm to 50 nm. The void size has a lower limit of, for example, 5 nm or more, 10 nm or more, or 20 nm or more, and an upper limit of, for example, 50 nm or less, 40 nm or less, or 30 nm or less, and the range is, for example, 5 nm to 50 nm or 10 nm to 40 nm. The preferred void size is determined depending on the application of the void structure, so it is necessary to adjust the void size to the desired size depending on the purpose, for example. The void size can be evaluated, for example, by the following method.

(SEM observation of cross section of void layer)
In the present invention, the morphology of the void layer can be observed and analyzed using a scanning electron microscope (SEM). Specifically, for example, the void layer is subjected to FIB processing (acceleration voltage: 30 kV) under cooling, and a cross-sectional sample obtained is subjected to an FIB-SEM (manufactured by FEI: product name Helios NanoLab 600, acceleration voltage: 1 kV) to obtain a cross-sectional electron image at an observation magnification of 100,000 times.

(Evaluation of void size)
In the present invention, the pore size can be quantified by the BET test method. Specifically, 0.1 g of a sample (the porous layer of the present invention) is placed in the capillary of a pore distribution/specific surface area measuring device (BELLSORP MINI, a product name of Microtrack Bell), and then dried under reduced pressure at room temperature for 24 hours to remove gas from the pore structure. Nitrogen gas is then adsorbed onto the sample, and a BET plot, a BJH plot, and an adsorption isotherm are plotted to determine the pore distribution. This allows the pore size to be evaluated.

The void layer of the present invention may have, for example, a pore structure (porous structure) as described above, and may be, for example, an open-cell structure in which the pore structure is continuous. The open-cell structure means, for example, that the pore structure in the void layer is connected three-dimensionally, and the internal voids of the pore structure are continuous. When a porous material has an open-cell structure, it is possible to increase the porosity in the bulk, but an open-cell structure cannot be formed when closed-cell particles such as hollow silica are used. In contrast, the void layer of the present invention has a three-dimensional dendritic structure in which the sol particles (pulverized porous gel forming the sol) have a three-dimensional dendritic structure, and the dendritic particles settle and deposit in the coating film (coated film of the sol containing the pulverized porous gel). Furthermore, it is more preferable that the void layer of the present invention form a monolithic structure in which the open-cell structure has a distribution of multiple pores. The monolithic structure refers to, for example, a structure in which nano-sized voids exist and a hierarchical structure in which the nano-voids exist as an open-cell structure. When forming the monolithic structure, for example, it is possible to achieve both membrane strength through fine pores and high porosity through coarse open-cell pores. To form such a monolithic structure, it is important to first control the pore distribution of the resulting pore structure in the porous gel prior to pulverization into the pulverized material. Furthermore, for example, when pulverizing the porous gel, the particle size distribution of the pulverized material can be controlled to the desired size, thereby forming the monolithic structure.

In the porous layer of the present invention, the haze that indicates transparency is not particularly limited, and the lower limit is, for example, 0.1% or more, 0.2% or more, or 0.3% or more, and the upper limit is, for example, 10% or less, 5% or less, or 3% or less, and the range is, for example, 0.1 to 10%, 0.2 to 5%, or 0.3 to 3%.

The haze can be measured, for example, by the following method.

(Hayes's assessment)
The porous layer (porous layer of the present invention) is cut to a size of 50 mm x 50 mm, and is set in a haze meter (HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd.) to measure the haze. The haze value is calculated using the following formula.
Haze (%) = [Diffuse transmittance (%) / Total light transmittance (%)] × 100 (%)

The refractive index of a medium is generally defined as the ratio of the propagation velocity of the wavefront of light in a vacuum to the propagation velocity within that medium. The refractive index of the air gap layer of the present invention is not particularly limited, and its upper limit is, for example, 1.3 or less, less than 1.3, 1.25 or less, 1.2 or less, or 1.15 or less, and its lower limit is, for example, 1.05 or more, 1.06 or more, or 1.07 or more, and its range is, for example, 1.05 or more but less than 1.3, 1.05 or more but less than 1.3, 1.05 or more but less than 1.25, 1.06 or more but less than 1.2, or 1.07 or more but less than 1.15.

In the present invention, unless otherwise specified, the refractive index refers to the refractive index measured at a wavelength of 550 nm. Furthermore, there are no particular limitations on the method for measuring the refractive index, and it can be measured, for example, by the following method.

(Evaluation of refractive index)
After forming a void layer (void layer of the present invention) on an acrylic film, cut it to a size of 50 mm x 50 mm and attach it to the surface of a glass plate (thickness: 3 mm) with an adhesive layer. The center of the back surface of the glass plate (diameter: approximately 20 mm) is painted with black ink to prepare a sample that does not reflect light from the back surface of the glass plate. The sample is placed in an ellipsometer (manufactured by J.A. Woollam Japan: VASE) and the refractive index is measured at a wavelength of 550 nm and an incident angle of 50 to 80 degrees, and the average value is taken as the refractive index.

The thickness of the void layer of the present invention is not particularly limited, and the lower limit is, for example, 0.05 μm or more, 0.1 μm or more, and the upper limit is, for example, 1000 μm or less, 100 μm or less, and the range is, for example, 0.05 to 1000 μm, 0.1 to 100 μm.

The shape of the void layer of the present invention is not particularly limited and may be, for example, a film shape or a block shape.

The method for producing the porous layer of the present invention is not particularly limited, but it can be produced, for example, by the methods described in WO 2019/065999 and WO 2019/065803. The disclosures of these publications are incorporated herein by reference.

[3. Adhesive Coating Liquid]
In the laminate of the present invention, the adhesive layer can be formed, for example, using an adhesive coating liquid, as described above. In the present invention, the terms "pressure-sensitive adhesive" and "adhesive" are not necessarily clearly distinguishable, as will be described later. In the present invention, the term "adhesive" includes both "pressure-sensitive adhesive" and "adhesive" unless otherwise specified. The adhesive coating liquid may be, for example, an adhesive coating liquid containing the (meth)acrylic polymer. The adhesive coating liquid may be, for example, an adhesive coating liquid further containing a crosslinking agent (e.g., an isocyanate-based crosslinking agent), and may further contain, for example, a monomer having one or two reactive double bonds per molecule and an organic peroxide. The adhesive coating liquid is not particularly limited, but examples are as shown below.

In the adhesive layer of the laminate of the present invention, the (meth)acrylic polymer may contain, for example, 1 to 30% by weight of a nitrogen-containing monomer as a monomer unit. Furthermore, the (meth)acrylic polymer may have, for example, a polydispersity (weight average molecular weight (Mw)/number average molecular weight (Mn)) of 3.0 or less. The adhesive coating liquid may be, for example, an adhesive coating liquid containing the (meth)acrylic polymer.

The adhesive coating liquid may be, for example, a (meth)acrylic polymer containing, as monomer components, 3 to 10% by weight of a heterocycle-containing acrylic monomer, a polymerizable functional group, 0.5 to 5% by weight of (meth)acrylic acid, 0.05 to 2% by weight of a hydroxyalkyl (meth)acrylate, and 83 to 96.45% by weight of an alkyl (meth)acrylate, and this (meth)acrylic polymer may be used as the base polymer.

Heterocycle-containing acrylic monomers can be used without particular limitation, for example, those having a polymerizable functional group and a heterocycle. Examples of polymerizable functional groups include (meth)acryloyl groups and vinyl ether groups. Of these, (meth)acryloyl groups are preferred. Examples of heterocycles include morpholine rings, piperidine rings, pyrrolidine rings, and piperazine rings. Examples of heterocycle-containing acrylic monomers include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine. Of these, N-acryloylmorpholine is preferred. Heterocycle-containing acrylic monomers can improve both heat resistance and moisture resistance when the pressure-sensitive adhesive layer is made thinner. Hereinafter, N-acryloylmorpholine will sometimes be referred to as "ACMO."

Heterocycle-containing acrylic monomers are also preferred because they can improve the adhesive strength of the pressure-sensitive adhesive layer to the optical film. They are particularly preferred because they improve the adhesive strength to cyclic polyolefins such as norbornene-based resins, and are suitable when cyclic polyolefins are used as the optical film.

The heterocycle-containing acrylic monomer is used, for example, in a proportion of 3 to 20% by weight based on the total amount of monomer components forming the (meth)acrylic polymer. The proportion of the heterocycle-containing acrylic monomer may be, for example, 4 to 19% by weight or 6 to 18% by weight. From the viewpoint of heat resistance and moisture resistance when the pressure-sensitive adhesive layer is thinned, it is preferable that the proportion of the heterocycle-containing acrylic monomer is not less than the above-mentioned range. From the viewpoint of moisture resistance when the pressure-sensitive adhesive layer is thinned, it is preferable that the proportion of the heterocycle-containing acrylic monomer is not more than the above-mentioned range. From the viewpoint of improving the adhesion of the pressure-sensitive adhesive layer, it is preferable that the proportion of the heterocycle-containing acrylic monomer is not more than the above-mentioned range. From the viewpoint of adhesive strength, it is preferable that the proportion of the heterocycle-containing acrylic monomer is not more than the above-mentioned range.

Acrylic acid is particularly preferred as the (meth)acrylic acid.

(Meth)acrylic acid is used, for example, in a proportion of 0.5 to 5% by weight relative to the total amount of monomer components forming the (meth)acrylic polymer. The proportion of (meth)acrylic acid may be, for example, 1 to 4.5% by weight or 1.5 to 4% by weight. From the viewpoint of heat resistance when the pressure-sensitive adhesive layer (adhesive layer) is thinned, it is preferable that the proportion of (meth)acrylic acid is not less than the above range. Furthermore, from the viewpoint of heat resistance and moisture resistance when the pressure-sensitive adhesive layer (adhesive layer) is thinned, it is preferable that the proportion of (meth)acrylic acid is not more than the above range. Furthermore, from the viewpoint of adhesive strength, it is preferable that the proportion of (meth)acrylic acid is not more than the above range.

Hydroxyalkyl (meth)acrylates that have a polymerizable functional group and a hydroxyl group can be used without particular restrictions. Suitable hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate.

The hydroxyalkyl (meth)acrylate is used, for example, in a proportion of 0.05 to 2 wt % relative to the total amount of monomer components forming the (meth)acrylic polymer. The proportion of hydroxyalkyl (meth)acrylate may be, for example, 0.075 to 1.5 wt % or 0.1 to 1 wt %. From the viewpoint of heat resistance when the pressure-sensitive adhesive layer (adhesive layer) is thinned, it is preferable that the proportion of hydroxyalkyl (meth)acrylate is not less than the above range. Furthermore, from the viewpoint of heat resistance and moisture resistance when the pressure-sensitive adhesive layer (adhesive layer) is thinned, it is preferable that the proportion of hydroxyalkyl (meth)acrylate is not more than the above range. Furthermore, from the viewpoint of adhesive strength, it is preferable that the proportion of hydroxyalkyl (meth)acrylate is not more than the above range.

The alkyl (meth)acrylate may have an average of 1 to 12 carbon atoms in the alkyl group. (Meth)acrylate refers to acrylate and/or methacrylate, and (meth) in the present invention has the same meaning. Specific examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, and lauryl (meth)acrylate, which can be used alone or in combination. Among these, alkyl (meth)acrylates in which the alkyl group has 1 to 9 carbon atoms are preferred.

The alkyl (meth)acrylate is used, for example, in a proportion of 83 to 96.45% by weight based on the total amount of monomer components that form the (meth)acrylic polymer. The alkyl (meth)acrylate is usually the remainder other than the heterocycle-containing acrylic monomer, (meth)acrylic acid, and hydroxyalkyl (meth)acrylate.

As the monomer components that form the (meth)acrylic polymer, in addition to the above-mentioned monomers, any other monomers can be used in an amount of 10% or less of the total amount of monomers, as long as the objectives of the present invention are not impaired.

Examples of the optional monomer include acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate. Examples include nitrogen-containing vinyl monomers. For example, maleimide, N-cyclohexylmaleimide, N-phenylmaleimide; (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, and other (N-substituted) amide monomers; aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, N,N (meth)acrylic acid Examples include alkylaminoalkyl (meth)acrylate monomers such as 3-(3-pyridyl)propyl (meth)acrylate, t-butylaminoethyl (meth)acrylate, and 3-(3-pyridyl)propyl (meth)acrylate; alkoxyalkyl (meth)acrylate monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; and succinimide monomers such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyoctamethylene succinimide.

Furthermore, vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxylic acid amides, styrene, α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; and acrylic ester monomers such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl acrylate can also be used.

Furthermore, copolymerizable monomers other than those mentioned above include silane-based monomers containing silicon atoms. Examples of silane-based monomers include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

As described above, the (meth)acrylic polymer used in the adhesive layer of the laminate of the present invention may have a weight-average molecular weight (Mw) of, for example, 1.5 million to 4 million. The weight-average molecular weight may be, for example, 1.5 million to 3.8 million, or 2 million to 3.8 million or 2.2 million to 3.5 million. From the viewpoint of heat resistance and moisture resistance when the adhesive layer is thinned, it is preferable that the weight-average molecular weight is not smaller than the above range. Furthermore, from the viewpoint of durability, lamination ability, and adhesive strength when the adhesive layer is thinned, it is preferable that the weight-average molecular weight is not larger than the above range. In the present invention, the weight-average molecular weight refers to a value measured, for example, by GPC (gel permeation chromatography) and calculated in polystyrene equivalent terms.

The method for producing such a (meth)acrylic polymer is not particularly limited, and any known production method can be appropriately selected, such as solution polymerization, bulk polymerization, emulsion polymerization, or various radical polymerizations. Furthermore, the resulting (meth)acrylic polymer may be any of a random copolymer, block copolymer, graft copolymer, etc.

In solution polymerization, for example, ethyl acetate or toluene is used as the polymerization solvent. In a specific example of solution polymerization, the reaction is carried out under a stream of inert gas such as nitrogen, with the addition of a polymerization initiator, at a temperature of approximately 50 to 70°C, for approximately 1 to 30 hours.

The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization are not particularly limited and can be selected appropriately. The weight-average molecular weight of the (meth)acrylic polymer can be controlled by the amount of polymerization initiator and chain transfer agent used and the reaction conditions, and the amounts used are adjusted appropriately depending on the type of these.

Examples of polymerization initiators include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (VA-057, manufactured by Wako Pure Chemical Industries, Ltd.), persulfates such as potassium persulfate and ammonium persulfate, di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, and di-sec-butylperoxydicarbonate. Examples of initiators include, but are not limited to, peroxide initiators such as dicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide, as well as redox initiators that combine peroxides and reducing agents, such as combinations of persulfates and sodium hydrogen sulfite, and combinations of peroxides and sodium ascorbate.

The polymerization initiators may be used alone or in combination of two or more. The total content of the polymerization initiators may be, for example, approximately 0.005 to 1 part by weight, or approximately 0.02 to 0.5 parts by weight, per 100 parts by weight of the monomer.

When producing a (meth)acrylic polymer having the above weight-average molecular weight using, for example, 2,2'-azobisisobutyronitrile as a polymerization initiator, the amount of polymerization initiator used may be, for example, approximately 0.06 to 0.2 parts by weight or approximately 0.08 to 0.175 parts by weight per 100 parts by weight of the total amount of monomer components.

Examples of chain transfer agents include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. Chain transfer agents may be used alone or in combination of two or more. The total amount of the chain transfer agents is, for example, approximately 0.1 parts by weight or less per 100 parts by weight of the total amount of monomer components.

Emulsifiers used in emulsion polymerization include, for example, anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene alkyl ether ammonium sulfate, and polyoxyethylene alkyl phenyl ether sodium sulfate; and nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, and polyoxyethylene-polyoxypropylene block polymers. These emulsifiers may be used alone or in combination of two or more.

Furthermore, reactive emulsifiers incorporating radically polymerizable functional groups such as propenyl groups and allyl ether groups include, for example, Aqualon HS-10, HS-20, KH-10, BC-05, BC-10, and BC-20 (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and Adeka Reasoap SE10N (manufactured by Asahi Denka Kogyo Co., Ltd.). Reactive emulsifiers are preferred because they are incorporated into the polymer chain after polymerization, improving water resistance. The amount of emulsifier used is 0.3 to 5 parts by weight per 100 parts by weight of the total amount of monomer components, with 0.5 to 1 part by weight being more preferred from the perspective of polymerization stability and mechanical stability.

The content of the (meth)acrylic polymer in the adhesive coating liquid is not particularly limited, but may be, for example, 3% by mass or more, or 5% by mass or more, or may be, for example, 30% by mass or less, 20% by mass or less, or 10% by mass or less, relative to the total mass of the adhesive coating liquid.

The adhesive coating liquid may or may not contain, for example, a monomer having one or two reactive double bonds in one molecule. The monomer having one or two reactive double bonds in one molecule is not particularly limited, but from the viewpoint of the reaction rate of the grafting reaction, acrylic monomers, vinyl monomers, methacrylic monomers, and allyl monomers are preferred, and acrylic monomers are more preferred. The acrylic monomer is not particularly limited, but may be, for example, the same as the monomers exemplified as the monomer components of the acrylic polymer. The side chain structure of the monomer having one or two reactive double bonds in one molecule is not particularly limited, but heterocycle-containing monomers are preferred because they can simultaneously achieve a high elastic modulus within an appropriate range and a reduced amount of semi-high molecular weight polymer.

When the adhesive coating liquid contains a monomer having one or two reactive double bonds per molecule, the content thereof is not particularly limited, and may be, for example, 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more, relative to the total mass of the (meth)acrylic polymer in the adhesive coating liquid, and may be, for example, 30% by mass or less, 20% by mass or less, or 10% by mass or less.

The adhesive coating liquid may or may not contain a crosslinking agent, as described above. The crosslinking agent is not particularly limited, but examples thereof include isocyanate-based crosslinking agents. The isocyanate-based crosslinking agent is not particularly limited, but examples thereof include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate.

More specifically, examples of the isocyanate-based crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate, aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and polymethylene polyphenyl isocyanate, and trimethylolpropane/tolylene diisocyanate trimer adducts (Japanese Examples include isocyanate adducts such as a trimethylolpropane/hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate L), a trimethylolpropane/hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate HL), and an isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate HX), polyether polyisocyanates, polyester polyisocyanates, and adducts of these with various polyols, and polyisocyanates multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc.

The crosslinking agent (e.g., an isocyanate-based crosslinking agent) may be used alone or in a mixture of two or more types. The total content of the crosslinking agent may be, for example, 0.02 to 2 parts by mass, 0.04 to 1.5 parts by mass, or 0.05 to 1 part by mass per 100 parts by mass of the (meth)acrylic polymer. From the viewpoint of cohesive strength, the content of the isocyanate-based crosslinking agent is preferably 0.02 parts by mass or more. On the other hand, from the viewpoint of suppressing or preventing a decrease in adhesive strength due to excessive crosslinking, 2 parts by mass or less is preferred.

In the adhesive coating liquid, the crosslinking agent may consist solely of an isocyanate-based crosslinking agent, or may or may not further contain other crosslinking agents besides the isocyanate-based crosslinking agent. Examples of the other crosslinking agents include organic crosslinking agents and polyfunctional metal chelates. Examples of organic crosslinking agents include epoxy-based crosslinking agents and imine-based crosslinking agents. Preferred organic crosslinking agents are isocyanate-based crosslinking agents. Polyfunctional metal chelates are those in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. Examples of atoms in the organic compound that form covalent or coordinate bonds include oxygen atoms, and examples of organic compounds include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds.

The adhesive coating liquid may or may not contain, for example, an organic peroxide. The organic peroxide is not particularly limited, but examples include di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, and t-butyl hydroperoxide. A single type may be used, or multiple types may be used in combination.

When the adhesive coating liquid contains the organic peroxide, its content is not particularly limited, and may be, for example, 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, or 2.5% by mass or more relative to the total mass of the (meth)acrylic polymer in the adhesive coating liquid, or may be, for example, 20% by mass or less, 10% by mass or less, 8% by mass or less, or 6% by mass or less.

The adhesive coating liquid may further contain a solvent or the like. The solvent is not particularly limited, but for example, the polymerization solvent used in the solution polymerization in producing the (meth)acrylic polymer may be used as is.

Furthermore, the adhesive coating liquid may contain various additives, such as tackifiers, plasticizers, fillers made of glass fibers, glass beads, metal powders, and other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, and silane coupling agents, as needed, as long as they do not deviate from the objectives of the present invention. The adhesive layer may also contain fine particles to exhibit light diffusing properties.

[4. Intermediate layer coating liquid]
The intermediate layer in the laminate of the present invention can be formed, for example, by applying the intermediate layer coating liquid as described above.

The intermediate layer coating liquid may contain, for example, as described above, the polymer that is the material for forming the intermediate layer and has a glass transition temperature (Tg) of 30°C or higher. The polymer having a glass transition temperature (Tg) of 30°C or higher may be, for example, a polymer having an amino group, as described above. The polymer having a glass transition temperature (Tg) of 30°C or higher may be, for example, an acrylic polymer. In the present invention, "acrylic polymer" refers to, for example, a polymer represented by the following chemical formula (1):

In the chemical formula (1),
^R1 is a hydrogen atom or a substituent, and may be one or more types of substituents, and the substituent is, for example, an alkyl group or an alkoxy group, and may be further substituted with an amino group or an amido group;
^R2 is a hydrogen atom or a substituent, and may be one or more types of substituents, and the substituent is, for example, an alkyl group, a poly(aminoalkyl) group, or an alkoxy group, and may be further substituted with an amino group or an amido group;
n is the degree of polymerization.
In ^R1 and ^R2 , the alkyl group may be linear or branched, and the number of carbon atoms in the alkyl group is not particularly limited, but may be, for example, 1 to 24, 1 to 18, 1 to 12, or 1 to 6, etc.

The polymer having a glass transition temperature (Tg) of 30°C or higher may be, for example, an aminoethylated acrylic polymer.

For the polymer having a glass transition temperature (Tg) of 30°C or higher, the glass transition temperature (Tg) may be, for example, 35°C or higher, 40°C or higher, 45°C or higher, or 50°C or higher, or may be, for example, 150°C or lower, 140°C or lower, 130°C or lower, or 120°C or lower.

The glass transition temperature (Tg) can be measured, for example, by differential scanning calorimetry (DSC).

The intermediate layer coating liquid may further contain a solvent. The solvent is not particularly limited, but may be, for example, at least one of water and an organic solvent. When the solvent contains an organic solvent, the organic solvent may be, but is not particularly limited, an alcohol such as IPA (isopropanol) or IBA (isobutyl alcohol), an ether such as PM (propylene glycol monomethyl ether), a ketone such as MIBK (methyl isobutyl ketone) or MEK (methyl ethyl ketone), a hydrocarbon such as toluene, or an ester such as ethyl acetate. A single organic solvent may be used, or multiple organic solvents may be used in combination. The concentration of the polymer having a glass transition temperature (Tg) of 30°C or higher in the solvent is not particularly limited, but may be, for example, 0.01 mol/L or higher, 0.05 mol/L or higher, 0.1 mol/L or higher, 0.5 mol/L or higher, or 1 mol/L or higher, or, for example, 20 mol/L or lower, 15 mol/L or lower, 10 mol/L or lower, 5 mol/L or lower, or 3 mol/L or lower.

The intermediate layer coating fluid may be, for example, a commercially available solution in which a polymer with a glass transition temperature (Tg) of 30°C or higher is dissolved in a solvent, and used as is, or may be used with the addition of optional components, as described below. Examples of such solutions include Polyment NK-380 and NK-350 (both trade names of Nippon Shokubai Co., Ltd.), which are solutions of aminoethylated acrylic polymers. According to Nippon Shokubai Co., Ltd.'s website (https://www.shokubai.co.jp/ja/products/detail/polyment.html, search date: September 24, 2021), the "Polyment" series is a solution of aminoethylated acrylic polymer having a structure similar to the following chemical formula (2):

The intermediate layer coating liquid may contain, for example, optional components other than the polymer having a glass transition temperature (Tg) of 30°C or higher and the solvent. The optional components include, but are not limited to, the crosslinking agent described above, as well as tackifier resins. The tackifier resin includes, but is not limited to, terpene resins. The terpene resin is also not limited to, but is exemplified by "Tackifier," a trade name of Yasuhara Chemical Co., Ltd. The crosslinking agent is also not limited to, but is exemplified by, for example, epoxy crosslinking agents, isocyanate crosslinking agents, imine crosslinking agents, and polyfunctional metal chelates. These crosslinking agents may be used alone or in combination. Examples of the epoxy crosslinking agent include "TETRAD-C," a trade name of Mitsubishi Gas Chemical Company, Inc. The isocyanate crosslinking agent is not limited to, but is exemplified by the isocyanate crosslinking agents exemplified for the adhesive layer coating liquid. The concentration of the crosslinking agent in the solvent is not particularly limited, and may be, for example, 0.001 mol/L or more, 0.01 mol/L or more, 0.05 mol/L or more, 0.1 mol/L or more, or mol/L or more, or may be, for example, 5 mol/L or less, 3 mol/L or less, or 1 mol/L or less.

[5. Manufacturing method of laminate]
The method for producing the laminate of the present invention is not particularly limited, and can be produced, for example, by the method for producing the laminate of the present invention described above. The method for producing the laminate of the present invention can be carried out, for example, as described below. However, the following description is an example and does not limit the present invention in any way. The void layer of the present invention is not particularly limited, but is, for example, as described above. Furthermore, as described above, the method for producing the void layer of the present invention is also not particularly limited, and can be produced, for example, by the methods described in WO 2019/065999 and WO 2019/065803.

As described above, the method for producing a laminate of the present invention is characterized by comprising an intermediate layer forming step of applying an intermediate layer coating liquid containing the polymer to one surface of the void layer and the adhesive layer to form the intermediate layer, and an intermediate layer attaching step of attaching the intermediate layer to the other surface of the void layer and the adhesive layer.

In the method for producing the laminate of the present invention, for example, as described above, the intermediate layer forming step may involve applying an intermediate layer coating liquid containing the polymer onto the surface of the adhesive layer to form the intermediate layer, and then applying the intermediate layer to the void layer in the intermediate layer applying step. For example, the intermediate layer forming step may involve applying an intermediate layer coating liquid containing the polymer onto the surface of the adhesive layer of an adhesive tape or the like having the adhesive layer of the present invention laminated on a substrate to form the intermediate layer, and then applying the intermediate layer to the void layer in the intermediate layer applying step. In this case, the substrate of the adhesive tape or the like may be left attached as is, or may be peeled from the adhesive layer. In particular, peeling the substrate to form a void layer-containing adhesive sheet that does not have a substrate (substrate-less) can significantly reduce the thickness, thereby suppressing an increase in the thickness of a device or the like. In the present invention, the terms "adhesive" and "adhesive layer" refer to, for example, an agent or layer intended to be removably attached to an adherend. In the present invention, "adhesive" and "adhesive layer" refer to, for example, an agent or layer that is not intended to be removably attached to an adherend. However, in the present invention, a "pressure-sensitive adhesive" and an "adhesive" cannot necessarily be clearly distinguished, and a "pressure-sensitive adhesive layer" and an "adhesive layer" cannot necessarily be clearly distinguished. In the present invention, the pressure-sensitive adhesive layer can be produced, for example, using the pressure-sensitive adhesive coating liquid described above.

The adhesive layer production step can be performed, for example, as follows. First, the adhesive coating liquid is produced by a mixing step in which all components of the adhesive coating liquid are mixed. As described above, the adhesive coating liquid may contain, for example, the (meth)acrylic polymer and may further contain a crosslinking agent (e.g., an isocyanate-based crosslinking agent). The adhesive coating liquid may contain, for example, the (meth)acrylic polymer, a monomer having one or two reactive double bonds per molecule, and an organic peroxide. In this case, if the adhesive coating liquid contains other components, the other components may also be mixed together. For example, the polymerization solvent used in producing the (meth)acrylic polymer may be mixed directly as a component of the adhesive coating liquid without removing it. Furthermore, the production method of the adhesive coating liquid may, but need not, include other steps in addition to the mixing step. It is also possible to simply mix all components of the adhesive coating liquid in the mixing step.

Next, the adhesive coating liquid is applied to a substrate (adhesive coating liquid application step). The substrate is not particularly limited and may be, for example, a film or other substrate. Suitable substrates include, but are not limited to, thermoplastic resin substrates, glass substrates, inorganic substrates such as silicon, plastics molded from thermosetting resins, semiconductor elements, and carbon fiber materials such as carbon nanotubes. Examples of the substrate form include, but are not limited to, films and plates. Examples of thermoplastic resins include polyethylene terephthalate (PET), acrylic, cellulose acetate propionate (CAP), cycloolefin polymer (COP), triacetyl cellulose (TAC), polyethylene naphthalate (PEN), polyethylene (PE), and polypropylene (PP). In the adhesive coating liquid application step, the thickness of the adhesive coating liquid is not particularly limited and may be adjusted as needed to achieve a desired thickness for the adhesive layer after drying. The thickness of the adhesive layer after drying is also not particularly limited and may be as described below.

Next, the substrate coated with the adhesive coating liquid is heated and dried (heat drying step). In this heat drying step, the heat drying temperature is not particularly limited, but may be, for example, 50°C or higher, 80°C or higher, 100°C or higher, or 155°C or higher, and may be, for example, 200°C or lower, 180°C or lower, or 160°C or lower. The heat drying time is not particularly limited, but may be, for example, 1 minute or higher, 2 minutes or higher, or 3 minutes or higher, and may be, for example, 60 minutes or lower, 30 minutes or lower, 20 minutes or lower, or 10 minutes or lower. In this heat drying step, for example, a crosslinking reaction and graft polymerization occur between the (meth)acrylic polymer and the crosslinking agent. This reduces the amount of semi-high molecular weight polymer present in the adhesive coating liquid, as described above, making it difficult for the adhesive layer to penetrate into the voids of the void layer. In this manner, the adhesive layer used in the laminate of the present invention can be produced.

Next, an intermediate layer coating liquid containing the polymer is applied onto the surface of the adhesive layer to form the intermediate layer (intermediate layer forming step). The amount of the intermediate layer coating liquid to be applied is not particularly limited, and can be adjusted as appropriate so that the thickness of the intermediate layer is appropriate. In the intermediate layer forming step, for example, after the intermediate layer coating liquid is applied, the coating may be allowed to stand or heated to dry, thereby forming the intermediate layer. The drying temperature is not particularly limited, and may be, for example, 30°C or higher, 50°C or higher, 70°C or higher, or 90°C or higher, or may be, for example, 160°C or lower, 140°C or lower, 120°C or lower, or 100°C or lower. The drying time is not particularly limited, and may be, for example, 10 seconds or higher, 30 seconds or higher, or 1 minute or higher, or may be, for example, 30 minutes or lower, 10 minutes or lower, or 5 minutes or lower.

Furthermore, after the intermediate layer forming step, the intermediate layer is attached to the void layer (intermediate layer attaching step). At this time, the layers may simply be attached, but, for example, as described above, a heating step may be performed after the intermediate layer attaching step to heat the void layer, the intermediate layer, and the adhesive layer. By performing this heating step, the adhesion between the void layer, the intermediate layer, and the adhesive layer that are in contact with each other can be improved. The heating temperature in the heating step is not particularly limited, but may be, for example, 30°C or higher, 40°C or higher, 10°C or higher, or 50°C or higher, and may be, for example, 100°C or lower, 90°C or lower, or 80°C or lower. The heating time in the heating step is not particularly limited, but may be, for example, 1 hour or higher, 10 hours or higher, 20 hours or higher, or 30 hours or higher, and may be, for example, 120 hours or lower, 100 hours or lower, or 80 hours or lower. Hereinafter, this heating step may be referred to as the "aging step."

The laminate of the present invention can be manufactured in this manner. As described above, the intermediate layer of the laminate of the present invention acts as a stopper, preventing the voids in the porous layer from being filled with adhesive, thereby preventing a decrease in porosity.

In the laminate of the present invention, for example, the adhesive layer and the intermediate layer can protect the void layer from physical damage (particularly scratches). Furthermore, the adhesive layer preferably has excellent pressure resistance so that the void layer does not collapse even in a void layer-containing adhesive sheet that does not have a substrate (substrate-less), but this is not particularly limited. The thickness of the adhesive layer is also not particularly limited, but is, for example, 0.1 to 100 μm, 5 to 50 μm, 10 to 30 μm, or 12 to 25 μm.

The laminate of the present invention obtained in this manner may be further laminated with another film (layer), for example, as described above, to form a laminate structure including the void layer (porous structure). In this case, each component of the laminate structure may be laminated via, for example, the adhesive layer (pressure-sensitive adhesive or adhesive).

The lamination of each of the above components may be carried out efficiently by continuous processing using a long film (such as roll-to-roll processing), or if the substrate is a molded product, element, etc., batch processing may be carried out and then laminated.

The following describes a method for forming the laminate of the present invention on a substrate (resin film) using a continuous processing process, taking laminate 10a in Figure 1(b) as an example. Note that the film-forming method described below is merely an example and is not limited to this.

The substrate may be the resin film described above. In this case, the void layer of the present invention can be obtained by forming the void layer on the substrate. Alternatively, the void layer of the present invention can be obtained by forming the void layer on the substrate and then laminating the void layer on the resin film described above in the description of the void layer of the present invention.

In a method for manufacturing the laminate 10a shown in FIG. 1(b), for example, first, a tacky adhesive layer 13 is formed on a substrate 14. Alternatively, for example, a commercially available adhesive tape having a tacky adhesive layer 13 formed on a substrate 14 may be used. Next, an intermediate layer coating liquid is applied to the surface of the tacky adhesive layer 13 opposite the substrate 14 to form an intermediate layer 12 (intermediate layer forming step). Meanwhile, a void layer 11 is formed on one surface of another substrate 14. Then, the intermediate layer 12 is attached to the void layer 11 (intermediate layer attaching step), thereby manufacturing the laminate 10a shown in FIG. 1(b). As described above, the heating step (aging step) may be further performed after the intermediate layer attaching step to enhance the adhesion of each layer. The intermediate layer forming step, intermediate layer attaching step, and aging step may be performed, for example, as described above.

The substrate 14 may be used while still attached to the porous layer 11 or the adhesive layer 13, respectively, or may be peeled off and used, for example, as shown in Figure 1(a).

More specifically, the process of forming the void layer 11 on the substrate 14 may include, for example, a coating step (1) of applying a sol particle liquid of a pulverized gel compound to the substrate (resin film) 14 to form a coating film; a drying step (2) of drying the sol particle liquid to form a dried coating film; and a chemical treatment step (3) of chemically treating the coating film (e.g., crosslinking) to form the void layer 11. The method for producing the sol particle liquid of the pulverized gel compound is not particularly limited. Specifically, the sol particle liquid can be produced by the methods described in, for example, WO 2019/065999 or WO 2019/065803. The sol particle liquid can also be produced by the method described in "Reference Example 1" of the Examples of the present application, which will be described later. Although not shown, the method for producing a laminate of the present invention also includes, as described above, an adhesive layer production step of producing the adhesive layer by the adhesive layer production method of the present invention, and a lamination step of laminating the adhesive layer to the void layer. As described above, the method for producing an adhesive layer of the present invention also includes an adhesive coating liquid application step of applying the adhesive coating liquid to a substrate, and a heat drying step of heat drying the substrate coated with the adhesive coating liquid. The chemical treatment step (crosslinking step) (3) corresponds to a "void layer formation step" of forming a void layer in the laminate of the present invention.

The aging process may also serve as a process for improving the strength of the void layer 11 (a cross-linking reaction process for causing a cross-linking reaction within the void layer 11), in which case the void layer 11 changes to a void layer 11 with further improved strength after the aging process. However, the present invention is not limited to this, and for example, the void layer 11 may not change after the aging process. Furthermore, the manufacturing method of the laminate of the present invention may or may not include steps other than those described above, as appropriate. Furthermore, while the laminate film (laminate) 10a in Figure 1(b) has the intermediate layer 12 and adhesive layer 13 provided on only one side of the void layer 11, the intermediate layer 12 and adhesive layer 13 may be provided on both sides of the void layer 11, for example.

In the coating step (1), the method for coating the sol particle liquid is not particularly limited, and any common coating method can be used. Examples of coating methods include the slot die method, reverse gravure coating, microgravure coating, dip coating, spin coating, brush coating, roll coating, flexographic printing, wire bar coating, spray coating, extrusion coating, curtain coating, and reverse coating. Among these, extrusion coating, curtain coating, roll coating, and microgravure coating are preferred from the standpoints of productivity and the smoothness of the coating film. The amount of the sol particle liquid to be coated is not particularly limited, and can be appropriately set, for example, so as to achieve an appropriate thickness for the void layer 11. The thickness of the void layer 11 is not particularly limited, and may be, for example, as described above.

In the drying step (2), the sol particle liquid is dried (i.e., the dispersion medium contained in the sol particle liquid is removed) to form the dried coating film (precursor of the void layer). The conditions for the drying process are not particularly limited and are as described above.

Furthermore, in the chemical treatment step (3), the dried coating film (containing the catalyst or catalyst generator (e.g., a photoactive catalyst, photocatalyst generator, thermally active catalyst, or thermal catalyst generator) added before coating is irradiated with light or heated to chemically bond (e.g., crosslink) the pulverized materials in the dried coating film (together) to form a void layer 11. The light irradiation or heating conditions in the chemical treatment step (3) are not particularly limited and are as described above.

Meanwhile, although not shown, the adhesive layer of the present invention is separately produced by the adhesive layer production step. The adhesive layer production step (the method for producing the adhesive layer of the present invention) is, for example, as described above.

Next, examples of the present invention will be described. However, the present invention is not limited to the following examples.

In the following Reference Examples, Examples, and Comparative Examples, the number of parts (relative amount used) of each substance is in parts by mass (parts by weight) unless otherwise specified.

In the following Reference Examples, Examples, and Comparative Examples, the glass transition temperature (Tg) of the polymer was determined by referring to the value listed in the product catalog. The thickness of each layer was measured by observing cross-sectional photographs taken with a SEM (scanning electron microscope). The porosity and refractive index were measured using the following methods.

<Method for measuring refractive index of laminate>
The prism of the device was attached to the substrate side of a laminate with an adhesive bonded to the air gap layer of a prism coupler (manufactured by Metricon), and the critical angle of total reflection was measured using a laser.The refractive index at a wavelength of 550 nm was calculated from the critical angle value.

<Method for measuring void ratio>
The refractive index was calculated from the refractive index measured as described above using the Lorentz-Lorenz's formula.

In the adhesive layers in the following reference examples, examples, and comparative examples, it is assumed that the polymer (acrylic polymer) is crosslinked by the crosslinking agent when the applied adhesive is heated and dried, forming a crosslinked structure, but the crosslinked structure has not been confirmed.

[Reference Example 1: Production of coating liquid for forming porous layer]
First, a gel having a porous structure (porous silicone body) was produced by gelling the silicon compound (step (1) below) and aging (step (2) below). The following steps (3) morphology control, (4) solvent substitution, and (5) gel crushing were then carried out to obtain a coating liquid for forming a void layer (liquid containing crushed gel). In this reference example, the following step (3) morphology control was carried out as a separate step from the following step (1), as described below. However, the present invention is not limited to this, and for example, the following step (3) morphology control may be carried out during the following step (1).

(1) Gelation of silicon compound 9.5 kg of MTMS, a precursor of the silicon compound, was dissolved in 22 kg of DMSO. 5 kg of 0.01 mol/L oxalic acid solution was added to the mixture, and the mixture was stirred at room temperature for 120 minutes to hydrolyze MTMS and produce tris(hydroxy)methylsilane.

3.8 kg of 28% aqueous ammonia and 2 kg of pure water were added to 55 kg of DMSO, and the hydrolyzed mixture was then added and stirred at room temperature for 60 minutes. After stirring for 60 minutes, the liquid was poured into a stainless steel container measuring 30 cm long x 30 cm wide x 5 cm high and allowed to stand at room temperature to gel the tris(hydroxy)methylsilane and obtain a gel-like silicon compound.

(2) Aging process: The gel-like silicon compound obtained by the gelation treatment was incubated at 40°C for 20 hours to perform an aging treatment, thereby obtaining the rectangular shaped mass of gel. Since the amount of DMSO (a high-boiling solvent with a boiling point of 130°C or higher) used in the raw material was approximately 83% by weight of the total raw material, it was clear that this gel contained 50% by weight or more of a high-boiling solvent with a boiling point of 130°C or higher. Furthermore, since the amount of MTMS (a monomer that is a constituent unit of the gel) used in the raw material was approximately 8% by weight of the total raw material, it was clear that the content of a solvent (methanol in this case) with a boiling point of less than 130°C generated by hydrolysis of the monomer (MTMS), a constituent unit of the gel, was 20% by weight or less.

(3) Morphology control step: Water, a substitution solvent, was poured onto the gel synthesized in the 30 cm × 30 cm × 5 cm stainless steel vessel by steps (1) and (2). Next, the cutting blade of a cutting tool was slowly inserted into the gel from above in the stainless steel vessel, and the gel was cut into a rectangular parallelepiped with a size of 1.5 cm × 2 cm × 5 cm.

(4) Solvent Substitution Step Next, the solvent substitution step was carried out as follows (4-1) to (4-3).

(4-1)
After the "(3) morphology control step", the gel silicon compound was immersed in water with a weight 8 times that of the gel silicon compound, and slowly stirred for 1 hour so that only the water was circulating. After 1 hour, the water was replaced with the same amount of water, and the mixture was further stirred for 3 hours. After that, the water was replaced again, and the mixture was heated at 60°C for 3 hours with slow stirring.

(4-2)
After (4-1), the water was replaced with isopropyl alcohol in an amount four times the weight of the gel silicon compound, and the mixture was heated at 60° C. for 6 hours while stirring.

(4-3)
After (4-2), the isopropyl alcohol was replaced with the same weight of isobutyl alcohol, and the mixture was heated at 60°C for 6 hours to replace the solvent contained in the gel silicon compound with isobutyl alcohol. In this way, the gel for producing a void layer of the present invention was produced.

(5) Gel Crushing Step The gel (gel silicon compound) after the (4) solvent replacement step was subjected to two stages of continuous emulsification dispersion (manufactured by Pacific Machinery Co., Ltd., Milder MDN304 type) in the first crushing stage, and high-pressure medialess crushing (manufactured by Sugino Machine Co., Ltd., Starburst HJP-25005 type) in the second crushing stage. In this crushing process, 26.6 kg of isobutyl alcohol was added to 43.4 kg of gel containing the solvent-substituted gel silicon compound, and then weighed. The first crushing stage was circulated for 20 minutes, and the second crushing stage was crushed at a crushing pressure of 100 MPa. In this way, an isobutyl alcohol dispersion (gel crushed product-containing liquid) in which nanometer-sized particles (crushed product of the gel) were dispersed was obtained. Furthermore, 224 g of a 1.5% solution of WPBG-266 (trade name, manufactured by Wako) in methyl isobutyl ketone was added to 3 kg of the gel powder-containing liquid, and then 67.2 g of a 5% solution of bis(trimethoxysilyl)ethane (manufactured by TCI) in methyl isobutyl ketone was added, and then 31.8 g of N,N-dimethylformamide was added and mixed to obtain a coating liquid.

In this manner, the void layer-forming coating liquid (liquid containing pulverized gel) of this Reference Example (Reference Example 1) was produced. Furthermore, the peak pore diameter of the pulverized gel (microporous particles) in the void layer-forming coating liquid (liquid containing pulverized gel) was measured using the method described above and was found to be 12 nm.

[Reference Example 2: Formation of adhesive layer]
The adhesive layer of this Reference Example (Reference Example 2) was formed by the following procedures (1) to (3).

(1) (Preparation of (meth)acrylic polymer (A1))
A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with a monomer mixture containing 91.5 parts of butyl acrylate, 5 parts of N-acryloylmorpholine, 3 parts of acrylic acid, and 0.5 parts of 4-hydroxybutyl acrylate. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts of ethyl acetate were charged to 100 parts of the monomer mixture. Nitrogen gas was introduced to replace the atmosphere with nitrogen while gently stirring, and the temperature in the flask was maintained at around 55°C, allowing the polymerization reaction to proceed for 6 hours to prepare a solution of a (meth)acrylic polymer (A1) having a weight-average molecular weight of 1.

(2) (Preparation of Pressure-Sensitive Adhesive Composition)
0.2 parts of an isocyanate crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd., an adduct of trimethylolpropane and tolylene diisocyanate) and 0.2 parts of benzoyl peroxide (trade name "Niper BMT" manufactured by Nippon Oil & Fats Corporation) were blended with 100 parts of the solid content of the obtained solution of the (meth)acrylic polymer (A1) to prepare a solution of an acrylic pressure-sensitive adhesive composition.

(3) (Formation of adhesive layer)
Next, the solution of the acrylic pressure-sensitive adhesive composition was applied to one surface of a polyethylene terephthalate film (separator film: MRF38, manufactured by Mitsubishi Chemical Polyester Film Corporation) that had been treated with a silicone-based release agent, so that the thickness of the pressure-sensitive adhesive layer after drying would be 10 μm, and the applied film was dried at 155° C. for 1 minute, thereby forming a pressure-sensitive adhesive layer (adhesive layer) on the surface of the separator film.

[Reference Example 3: Formation of intermediate layer]
A solution of an aminoethylated acrylic polymer (manufactured by Nippon Shokubai Co., Ltd., trade name "Polyment NK-380") was applied (coated) onto the 10 μm-thick adhesive layer obtained in Reference Example 2 so as to have a thickness of 70 nm after drying, and dried at 60°C for 1 minute to form an intermediate layer (intermediate layer forming step).

[Reference Example 4: Formation of intermediate layer]
A solution of an aminoethylated acrylic polymer (manufactured by Nippon Shokubai Co., Ltd., trade name "Polyment NK-350") was applied (coated) onto the 10 μm-thick adhesive layer obtained in Reference Example 2 so as to have a thickness of 70 nm after drying, and dried at 60°C for 1 minute to form an intermediate layer (intermediate layer forming step).

[Reference Example 5: Formation of intermediate layer]
A solution obtained by blending 100 parts of an aminoethylated acrylic polymer solution (manufactured by Nippon Shokubai Co., Ltd., trade name "Polyment NK-380") with 0.1 parts of an epoxy crosslinker (manufactured by Mitsubishi Gas Chemical Company, Ltd., "TETRAD-C") was applied (coated) onto the 10 μm-thick adhesive layer obtained in Reference Example 2 so as to give a thickness of 70 nm after drying, and the coating was dried at 60° C. for 1 minute to form an intermediate layer (intermediate layer forming step).

[Reference Example 6: Formation of intermediate layer]
An aminoethylated acrylic polymer (manufactured by Nippon Shokubai Co., Ltd., trade name "Polyment NK-200PM") was applied onto the 10 μm thick adhesive layer obtained in Reference Example 2 so as to have a thickness of 70 nm after drying, and the applied layer was dried at 60°C for 1 minute to form an intermediate layer.

[Example 1]
(Production of laminate)
The high-porosity layer-forming coating solution prepared in Reference Example 1 was applied to an acrylic substrate and dried at 100 ° C for 2 minutes to form a void layer with a thickness of approximately 850 nm (void ratio 59% by volume). Next, UV irradiation (300 mJ) was performed from the void layer surface. Thereafter, the intermediate layer obtained in Reference Example 3 was attached to the void layer surface (intermediate layer attachment step), and aging was performed at 60 ° C for 20 hours (aging step), producing the laminate of this example.

[Example 2]
The laminate of this example was produced in the same manner as in Example 1, except that the intermediate layer in Reference Example 3 was formed so that the thickness (after drying) of the intermediate layer was 30 nm.

[Example 3]
A laminate of this example was produced in the same manner as in Example 1, except that the intermediate layer of Reference Example 4 was used instead of the intermediate layer of Reference Example 3.

[Example 4]
A laminate of this example was produced in the same manner as in Example 1, except that the intermediate layer of Reference Example 5 was used instead of the intermediate layer of Reference Example 3.

[Example 5]
The laminate of this example was produced in the same manner as in Example 1, except that the intermediate layer in Reference Example 3 was formed so that the thickness (after drying) of the intermediate layer was 180 nm.

[Comparative Example 1]
A laminate of this comparative example was produced in the same manner as in Example 1, except that the intermediate layer of Reference Example 6 was used instead of the intermediate layer of Reference Example 3.

Furthermore, the laminates of the present example and comparative example manufactured as described above were placed in an oven at a temperature of 95°C and subjected to a heat durability test for 1000 hours. The remaining porosity in the void layer after the heat durability test was calculated using the Lorentz-Lorenz formula. Peeling between the intermediate layer and the void layer after the heat durability test was also visually confirmed. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 5, in which the glass transition temperature (Tg) of the intermediate layer-forming polymer was 30°C or higher, the residual void ratio of the void layer exceeded 50% by volume after a heat durability test in which the polymer was maintained at 95°C for 1,000 hours. In other words, the laminates of Examples 1 to 5 were able to prevent the pressure-sensitive adhesive or adhesive from penetrating into the voids. In particular, Example 4, in which a crosslinking agent was used in the intermediate layer formation process, had a particularly high residual void ratio in the void layer after the heat durability test. Furthermore, in Example 5, in which the intermediate layer was thick at 180 nm, peeling between the intermediate layer and the void layer was confirmed after the heat durability test, confirming that the adhesion between the intermediate layer and the void layer was slightly inferior to that of the other Examples. Furthermore, it was confirmed that all Examples 1 to 5 had good adhesive strength (adhesion). In contrast, in Comparative Example 1, in which the glass transition temperature (Tg) of the polymer for forming the intermediate layer was less than 30°C, the residual void rate of the void layer was 50% by volume or less, and the adhesive or adhesive was not able to penetrate the voids with ease.

As explained above, the present invention can provide a laminate of a void layer and a pressure-sensitive adhesive layer, an optical element, and an optical device that combines adhesive strength or adhesion with resistance to penetration of the pressure-sensitive adhesive or adhesive into the voids. The applications of the present invention are not particularly limited. For example, the optical device of the present invention is not particularly limited, and examples thereof include image display devices and lighting devices. Examples of image display devices include liquid crystal displays, organic EL displays, and micro LED displays. Examples of lighting devices include organic EL lighting. The laminate of the present invention is particularly suitable for use under high-durability conditions, such as in-vehicle installations, because the pressure-sensitive adhesive or adhesive is less likely to penetrate into the voids in the void layer, even under high temperatures or high humidity. Furthermore, the applications of the laminate of the present invention are not limited to the optical element and optical device of the present invention, and are optional, and the laminate can be used in a wide range of applications.

10, 10a laminate 11 void layer 12 intermediate layer 13 adhesive layer 14 base material

Claims (12)

The void layer, the intermediate layer, and the adhesive layer are laminated in the above order,
the intermediate layer is a layer containing a polymer having a glass transition temperature (Tg) of 30°C or higher ,
A laminate characterized in that the thickness of the intermediate layer is 5 to 150 nm . The laminate according to claim 1, wherein the polymer in the intermediate layer is a polymer having an amino group. The laminate according to claim 1 or 2, wherein the intermediate layer is a layer formed by applying an intermediate layer coating liquid containing the polymer. The laminate according to claim 3, wherein the intermediate layer coating liquid further contains a crosslinking agent. The laminate according to claim 1 , wherein the residual void ratio of the porous layer exceeds 50% by volume after a heat durability test in which the laminate is maintained at a temperature of 95° C. for 1000 hours. an intermediate layer forming step of coating an intermediate layer coating liquid containing the polymer on one surface of the void layer and the adhesive layer to form the intermediate layer;
an intermediate layer attaching step of attaching the intermediate layer to the other of the porous layer and the adhesive layer;
The method for producing the laminate according to any one of claims 1 to 5 , comprising: In the intermediate layer forming step, an intermediate layer coating liquid containing the polymer is applied onto a surface of the adhesive layer to form the intermediate layer,
The manufacturing method according to claim 6 , wherein the intermediate layer is attached to the air gap layer in the intermediate layer attaching step. The manufacturing method according to claim 6 or 7 , further comprising a heating step of heating the porous layer, the intermediate layer and the adhesive layer after the intermediate layer attaching step. An optical member comprising the laminate according to claim 1 . An optical device comprising the optical member according to claim 9 . The method for producing an optical member according to claim 9 , comprising the step of producing the laminate according to any one of claims 1 to 5 by the method according to any one of claims 6 to 8 . 11. The method for manufacturing an optical device according to claim 10 , further comprising the step of manufacturing the optical member according to claim 9 by the manufacturing method according to claim 11 .