JP7501192B2 - Method for manufacturing a rigid laminate - Google Patents

Description

The present invention relates to a method for manufacturing a rigid laminate by bonding flexible substrates together.

Laminates made by stacking multiple base materials have been used in various fields. For example, in the field of radio frequency identification (RFID) technology, laminates made by stacking multiple resin substrates and incorporating IC tags between the resin substrates are used as information recording media for contactless IC cards such as ID cards, credit cards, transportation cards, and electronic money (see Patent Document 1).

In recent years, depending on the application, there is a demand for a laminate to be thin and have high rigidity. One possible method for increasing the rigidity of a laminate is to increase the rigidity of each substrate that constitutes the laminate. However, this method tends to increase the thickness of each substrate in order to provide rigidity, making it difficult to make the laminate thinner. As a result, another method has been considered in which a substrate having flexibility (hereinafter, sometimes referred to as a flexible substrate) such as a film substrate is bonded with a curable adhesive, and the rigidity of the adhesive after curing is used to provide rigidity to the entire laminate. For example, in the case of a non-contact IC card, a method of laminating a flexible substrate such as a design film to both sides of a flexible printed circuit board (FPC) via a photocurable adhesive, and then photocuring the photocurable adhesive, for example, can be used.

Japanese Patent Application Laid-Open No. 10-147087

However, in the method using a photocurable adhesive, the photocurable adhesive completes the curing reaction and solidifies in a short time after irradiation with light, so it is difficult to, for example, irradiate the photocurable adhesive with light first and then bond the flexible substrate. Therefore, in general, it is necessary to apply a photocurable adhesive to one of a pair of flexible substrates to be bonded to provide an adhesive layer, and then irradiate light through the flexible substrate to cause a photocuring reaction of the adhesive layer while the other flexible substrate is placed on the adhesive layer. However, in this method, when a flexible substrate with low light transmittance or no light transmittance is used, it is not possible to irradiate light to the adhesive layer through the flexible substrate, which is a problem in that the flexible substrates that can be used are limited. In addition, if a sufficient amount of light does not reach the adhesive layer due to the flexible substrate blocking the transmission of light, it becomes necessary to extend the light irradiation time, which may increase the manufacturing time of the laminate.

In addition, as a method of using a curable adhesive, there is also a method of using a thermosetting adhesive instead of a photocurable adhesive, which can be applied to flexible substrates that do not have optical transparency. However, when using a thermosetting adhesive, the adhesive must be applied to one flexible substrate to provide an adhesive layer, and the other flexible substrate must be placed on the adhesive layer and heated to cause a thermosetting reaction of the adhesive layer. Therefore, a long period of heating is required to cure the adhesive layer, and depending on the heat resistance of the flexible substrate, heat deterioration occurs due to high temperature heating, so there is a problem that the flexible substrates that can be used are limited. In addition, compared to when a photocurable adhesive is used, a laminate using a thermosetting adhesive tends to take longer to complete the curing reaction, which may increase the manufacturing time of the laminate, and there is also a problem that it is difficult to obtain high rigidity compared to when a photocurable adhesive is used.

As a method that does not use a curable adhesive, there is also a method that uses an adhesive sheet having a pressure-sensitive adhesive layer (adhesive layer), and with this method, lamination is possible without being restricted by the light transmittance or heat resistance of the flexible substrate. However, with this method, it is difficult to obtain sufficient bonding strength compared to when an adhesive is used, and there is a problem that the flexibility of the adhesive sheet makes it difficult to obtain sufficient rigidity for the laminate. Furthermore, when an attempt is made to increase the bonding strength or rigidity by using an adhesive sheet, the thickness of the adhesive sheet tends to increase, making it difficult to achieve a thin structure.

The present invention was made in consideration of the above-mentioned circumstances, and provides a method for producing a rigid laminate that can produce a thin, highly rigid laminate in a short time by bonding flexible substrates together, without being restricted by the light transmittance or heat resistance of the flexible substrates.

The present invention provides a method for producing a rigid laminate, which comprises at least a step [1] of attaching a first adhesive sheet having an adhesive layer containing at least a photocurable resin having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator to one side of a first substrate having flexibility to obtain a first substrate having an adhesive sheet, a step [2] of irradiating the adhesive layer of the first substrate having an adhesive sheet with active energy rays, and a step [3] of pressing the adhesive layer of the first substrate having an adhesive sheet and a second substrate having flexibility after the step [2], wherein the gel fraction of the adhesive layer of the first substrate having an adhesive sheet is within a range of 35% to 90% 5 minutes after the step [2] is performed, the time from the step [2] to the step [3] is less than 10 minutes, and the pressing temperature in the step [3] is 100°C or less.

The method for producing a rigid laminate of the present invention can produce a thin, highly rigid laminate in a short time by bonding flexible substrates together without being restricted by the light transmittance or heat resistance of the flexible substrate, and is particularly suitable for in-line production.

1 is a process diagram showing an example of a method for producing a rigid laminate of the present invention. 1 is a process diagram showing an example of a method for producing a rigid laminate of the present invention. FIG. 2 is a schematic diagram illustrating a stiffness test method.

The method for producing a rigid laminate of the present invention (hereinafter sometimes abbreviated as the production method of the present invention) comprises at least a step [1] of attaching a first adhesive sheet having an adhesive layer containing at least a photocurable resin having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator to one side of a first substrate having flexibility to obtain a first substrate having an adhesive sheet, a step [2] of irradiating the adhesive layer of the first substrate having an adhesive sheet with active energy rays, and, after the step [2], a step [3] of pressing the adhesive layer of the first substrate having an adhesive sheet to a second substrate having flexibility. In addition, in the method for producing a rigid laminate of the present invention, the gel fraction of the adhesive layer of the first adhesive sheet-attached substrate is within the range of 35% to 90% 5 minutes after carrying out the step [2], the time from carrying out the step [2] to carrying out the step [3] is less than 10 minutes, and the pressure bonding temperature in the step [3] is 100°C or less.

Figure 1 is a process diagram showing an example of the method for producing a rigid laminate of the present invention, showing steps [1] to [3]. First, in step [1] shown in Figure 1 (a), a first adhesive sheet 2 having an adhesive layer 2A containing at least a photocurable resin having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator is attached to one side of a first substrate 1 having flexibility to obtain a first adhesive sheet-attached substrate 10. In the example shown in Figure 1, the first adhesive sheet 2 is a substrate-less adhesive sheet having only the adhesive layer 2A, but the method for producing a rigid laminate of the present invention is not limited to this. Next, in step [2] shown in Figure 1 (b), the adhesive layer 2A of the first adhesive sheet-attached substrate 10 is irradiated with active energy rays X1. As a result, the adhesive layer 2A becomes an adhesive layer 2A' in which a curing reaction has started. Next, in step [3] shown in FIG. 1(c) after step [2], the adhesive layer 2A' of the first adhesive sheet-attached substrate 10 and the second substrate 3 having flexibility are pressure-bonded. Step [3] shown in FIG. 1(c) shows an embodiment in which the first adhesive sheet-attached substrate 10 and the second substrate 3 are pressure-bonded to each other, and shows an example in which the first adhesive sheet-attached substrate 10 and the second substrate 3 are pressed against rollers Y1 and Y2, respectively, in in-line production by roll-to-roll. Thereafter, the curing reaction of the adhesive layer 2A' progresses and is completed, and a rigid laminate 100 is obtained in which the first substrate 1 is bonded to one side of the rigid cured adhesive layer (cured adhesive layer) 2A" and the second substrate 3 is bonded to the other side of the cured adhesive layer (cured adhesive layer) 2A" and the first substrate 1 and the second substrate 3 are firmly bonded via the cured adhesive layer 2A".

In this specification, "rigidity" refers to the fact that the laminate is not easily deformed even when subjected to bending or folding forces, and specifically refers to the fact that the distance L measured by the stiffness test method described below is less than 45 mm. In particular, it is preferable that the stiff laminate of the present invention has the above-mentioned distance L of 25 mm or less, since this allows for higher stiffness. On the other hand, in this specification, "flexibility" refers to the fact that the laminate can be repeatedly bent or folded, and specifically refers to the fact that the distance L measured by the stiffness test method described below is 45 mm or more.

As shown in FIG. 3, the stiffness test method is as follows: first, an evaluation sample S is cut out from a measurement object (laminate, substrate, adhesive layer, cured adhesive layer, etc.) with a rectangular surface having a length of 100 mm in the longitudinal direction X and a length of 20 mm in the transverse direction Y as its main surface. Of a pair of ends A and B located in the longitudinal direction X of the evaluation sample S, an area of 10 mm in the longitudinal direction from one end A is fixed, and the position of the other end B of the evaluation sample S before the load is applied is set as the reference O. A load W of 5 g is applied to the end B of the evaluation sample S, and the end B of the evaluation sample S is left to stand for 5 seconds. The position of the end B of the evaluation sample S in the vertical direction (load direction) Z after the load is applied is set as the position P, and the distance L from the reference O before the load to the position P of the end B of the evaluation sample after the load is measured.

The method for producing a rigid laminate of the present invention makes it possible to produce a thin, highly rigid laminate in a short time by bonding flexible substrates together, without being restricted by the optical transparency or heat resistance of the flexible substrate.

In detail, in the manufacturing method of the rigid laminate of the present invention, in step [1], since the adhesive layer in the first adhesive sheet has a predetermined composition, it can exhibit pressure-sensitive adhesion (tackiness) before irradiation with active energy rays, and it is possible to bond the adhesive layer in the first adhesive sheet and the first substrate by pressure-sensitive adhesion. Next, when the adhesive layer is irradiated with active energy rays in step [2], the polymerizable functional groups of the photocurable resin (A) and the thermoplastic resin (B) are activated, and curing begins in a state of enhanced reactivity. At this time, since the polymerizable functional groups of the photocurable resin (A) and the thermoplastic resin (B) are polymerizable functional groups other than polymerizable unsaturated double bonds, a rapid curing reaction after irradiation with active energy rays is suppressed, and it is possible to gradually proceed with the curing reaction. In other words, the adhesive layer in the present invention is a delayed-curing type adhesive layer. Therefore, the adhesive layer can retain flexibility and pressure-sensitive adhesiveness (tackiness) for a certain period of time even after being irradiated with active energy rays in step [2], and by carrying out step [3] after step [2], it becomes possible to bond a second substrate to the adhesive layer of the first substrate with adhesive sheet.

Here, since the gel fraction of the adhesive layer of the first adhesive sheet-attached substrate 5 minutes after the step [2] is performed is within a predetermined range, the adhesive sheet maintains a flexible state when the step [3] is performed, and the adhesive sheet and the second substrate can be sufficiently adhered by applying pressure. In addition, the desired rigidity can be easily imparted to the laminate after the step [3] is performed in a short time. In addition, by setting the time from the step [2] to the step [3] to be less than 10 minutes, the adhesive sheet can easily maintain a flexible state, and the adhesive sheet and the second substrate can be sufficiently adhered by applying pressure. Furthermore, by setting the pressure bonding temperature in the step [3] to 100°C or less, even flexible substrates that are easily thermally damaged or thermally deformed can be laminated, and thermal deterioration of the first substrate and the second substrate can be suppressed.

In step [3], after the first substrate with adhesive sheet is laminated to the second substrate after irradiation with active energy rays, the curing reaction of the adhesive layer is completed, and the cured adhesive layer, i.e., the cured adhesive layer, can firmly bond the first substrate to the second substrate. Furthermore, the cured adhesive layer allows the obtained laminate to have the desired hardness. This makes it possible to obtain a thin and highly rigid laminate in which flexible substrates are bonded together via the cured adhesive layer.

Here, when a photocurable adhesive layer is used instead of the adhesive layer in the present invention, the reaction proceeds immediately when the adhesive layer is irradiated with light, and the curing is completed, making it difficult to attach the second substrate after a certain time. For this reason, the photocurable adhesive layer must be placed between the first substrate and the second substrate and then irradiated with active energy rays, and at least one of the first substrate and the second substrate must be light-transmitting. In addition, if a sufficient amount of light does not reach the adhesive layer due to the substrate blocking the transmission of light, it becomes necessary to extend the light irradiation time, which may result in a longer manufacturing time for the laminate.

Similarly, when a thermosetting adhesive layer is used instead of the adhesive layer in the present invention, the reaction proceeds immediately when the adhesive layer is heated, and the curing is completed, making it difficult to wait a while before laminating the second substrate. For this reason, the first substrate and the second substrate must be heated with the thermosetting adhesive layer disposed between them, and the first substrate and the second substrate must have high heat resistance. In addition, the thermosetting adhesive layer tends to take time to complete the curing reaction, which may lengthen the manufacturing time of the laminate.

In contrast, according to the present invention, since the adhesive layer is formed of a delayed-curing adhesive as described above, it is not necessary to irradiate the adhesive layer with active energy rays or heat it in step [2] to cause a curing reaction of the adhesive layer while the adhesive layer is disposed between the first substrate and the second substrate. In addition, in step [2], the adhesive layer can be cured by irradiating the first adhesive sheet-attached substrate with active energy rays from the first adhesive sheet side, so the first substrate and the second substrate do not need to have high light transmittance, and even substrates with low light transmittance or substrates with no light transmittance are applicable. Furthermore, since the start of the curing reaction of the adhesive layer in the present invention is not triggered by heat, the first substrate and the second substrate do not need to have high heat resistance, and even substrates with low heat resistance are applicable. In addition, in step [3], the gel fraction is adjusted after a certain time has elapsed since the implementation of step [1] so that the second substrate can be attached and the resulting laminate has the desired rigidity. In step [2], the adhesive layer is irradiated with active energy rays to cause a curing reaction, thereby shortening the manufacturing time, which is particularly effective in in-line manufacturing as it simplifies the manufacturing process.

In this specification, the terms "face", "surface" and "principal surface" of a substrate or adhesive layer refer to the surface of the substrate or adhesive layer that is in a planar direction when viewed as a whole.

Below, we will explain each step in the manufacturing method of the rigid laminate of the present invention.

A. Step [1]
The step [1] in the method for producing a rigid laminate of the present invention is a step of preparing a photocurable resin having a polymerizable functional group other than a polymerizable unsaturated double bond, A first adhesive sheet having an adhesive layer containing at least a thermoplastic resin having a thermoplastic resin composition and a photopolymerization initiator is attached to one surface of a first base material having flexibility, thereby forming a first adhesive sheet. This is the step of obtaining a substrate.

(1) First Substrate The first substrate is a substrate having flexibility.

The first substrate may have a thickness that allows it to exhibit the desired flexibility, preferably in the range of 20 μm to 1000 μm, more preferably in the range of 30 μm to 700 μm, and even more preferably in the range of 100 μm to 500 μm. By setting the thickness of the first substrate within the above range, it is possible to exhibit the desired flexibility, and in particular to enable in-line lamination and bonding in a roll-to-roll process.

The first substrate may be colorless or colored. The first substrate may or may not have optical transparency. In the present invention, even if the optical transparency of one or both of the first substrate and the second substrate described later is low, it is possible to cure the adhesive layer. When the optical transparency of the first substrate is low or non-transparent, specifically, when the transmittance of light having a wavelength of 200 nm to 780 nm of the first substrate is 80% or less, particularly 50% or less, further 40% or less, and particularly 30% or less, it is difficult to irradiate the adhesive layer with active energy rays through the first substrate. In steps [2] and [3] described later, active energy rays can be irradiated from the adhesive layer side of the first adhesive sheet to cause a curing reaction, and the second substrate can be bonded. Therefore, the manufacturing method of the present invention can be preferably used.

The first substrate may have high or low heat resistance. In the present invention, even if the heat resistance of one or both of the first substrate and the second substrate described later is low, high temperature heating is not required for the curing reaction of the adhesive layer, so that the adhesive layer can be cured without thermally deteriorating the substrate. The first substrate having low heat resistance refers to, for example, a substrate having a melting point of 80°C or more and 200°C or less, and a substrate having a melting point of 90°C or more and 180°C or less can be preferably used. As described later, when the first substrate is a composite film of a resin film and an inorganic film, it is preferable that the melting point of the resin film alone is in the above range. Also, as described later, when other members are provided on one or both surfaces of the first substrate, it is preferable that the melting point of the first substrate, excluding the other members placed on the surface, is in the above range.

The melting point of the substrate is the temperature at which the maximum exothermic peak (exothermic peak top) is observed when the substrate is heated from 20°C to 150°C at a heating rate of 10°C/min using differential scanning calorimetry (DSC), held for 1 minute, cooled to -10°C at a cooling rate of 10°C/min, held for 10 minutes, and then measured again at a heating rate of 10°C/min.

The first substrate may be a single layer or a multi-layer structure as long as it has the desired flexibility. When the first substrate has a multi-layer structure, it is sufficient that the entire first substrate exhibits flexibility. Examples of the first substrate include a paper substrate, a resin film, an inorganic film, and a composite film of a resin film and an inorganic film.

Examples of paper substrates include fine paper, art paper, coated paper, cast coated paper, glassine paper, Japanese paper, synthetic paper, synthetic resin or emulsion impregnated paper, cellulose fiber paper, etc.

Examples of resin films include resin films made of resins such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl chloride, polyimide (PI), polyester, polycarbonate, polystyrene, polylactic acid, cycloolefin polymer (COP), cycloolefin copolymer (COC), polyvinyl alcohol, triacetyl cellulose, and acrylonitrile-butadiene-styrene (ABS).

The resin film may contain additives such as organic pigments, inorganic pigments, and stabilizers, and may contain components that reduce the UV transmittance, such as UV absorbers and plasticizers. The surface of the resin film may also be subjected to various treatments, such as antistatic treatment and easy adhesion treatment.

Examples of inorganic films include flexible glass and metal foil.

Other members may be provided on one or both surfaces of the first substrate. When the other members are provided, it is sufficient that the entire first substrate on which the other members are provided can exhibit the desired flexibility. Examples of other members include wiring members, semiconductor layers, receiving or transmitting antenna coils, IC chips, batteries, polarizing layers, colored layers, printed layers, hologram layers, etc.

Specific examples of items that can be used as the first substrate include color filters, polarizing films, protective films, decorative films, wiring films, flexible batteries, transparent conductive films, etc.

(2) First Adhesive Sheet The first adhesive sheet has an adhesive layer containing at least a photocurable resin having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator.

(a) Adhesive layer The adhesive layer in the first adhesive sheet contains at least a photocurable resin (A) having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin (B) having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator (C). The adhesive layer in the first adhesive sheet contains the above-mentioned composition, so that it can exhibit pressure-sensitive adhesiveness (tackiness), can be attached to the first substrate, and can be reattached if a defect occurs during attachment such as misalignment. In addition, the adhesive layer exhibits flexibility and pressure-sensitive adhesiveness for a desired time even after irradiation with active energy rays, so that it can be attached to the second substrate within a desired time, and can be reattached if a defect occurs during attachment such as misalignment.

Furthermore, since the adhesive layer contains the above-mentioned composition, it has excellent conforming and adhesive properties, so even if the surface of the substrate has steps due to the components being placed on it, it can conform and adhere firmly to the substrate surface including the components. In particular, when each process is performed in-line, the bonding time tends to be short, but the adhesive layer makes it possible to conform and adhere to steps on the substrate surface even with a short bonding time.

In the following description, the substrate to be bonded to the adhesive layer of the present invention may be referred to simply as the adherend. Also, the surface (main surface) of the substrate that is in contact with the adhesive layer may be referred to simply as the adherend surface.

The total amount of the adhesive layer refers to the total amount of solids in the adhesive composition that constitutes the adhesive layer, and the content in the adhesive layer refers to the content in the total amount of solids in the adhesive composition that constitutes the adhesive layer.

<Photocurable resin (A)>
The photocurable resin (A) has a polymerizable functional group other than a polymerizable unsaturated double bond. By including the photocurable resin (A), the adhesive layer in the present invention initiates polymerization by irradiation with active energy rays due to the polymerizable functional group of the photocurable resin (A), and the polymerization proceeds even in a dark reaction or at a low temperature, so that the first substrate and the second substrate can be bonded without being limited by the light transmittance or heat resistance of the first substrate and the second substrate.

Examples of the photocurable resin (A) include photopolymerizable compounds such as photoradical polymerizable compounds, photocationic polymerizable compounds, and photoanionic polymerizable compounds. Among them, photocationic polymerizable compounds and/or photoanionic polymerizable compounds are preferred. In other words, it is preferred that the photocurable resin (A) has a photocationic polymerizable functional group and/or a photoanionic polymerizable functional group as a polymerizable functional group other than the polymerizable unsaturated double bond. By including a polymerizable compound having these functional groups in the adhesive layer, the adhesive layer is less susceptible to inhibition by oxygen during curing, and the reaction is more likely to proceed continuously even after irradiation with active energy rays, so that bonding is possible without being limited by the light transmittance or heat resistance of the adherend. In particular, photocationic polymerizable compounds are more preferred because they have excellent reactivity after irradiation with active energy rays and are easy to obtain high bonding properties after curing. The above photopolymerizable compounds may be used alone or in combination.

The photocationically polymerizable compound is not particularly limited as long as it has one or more photocationically polymerizable functional groups in one molecule. It is preferable that the photocationically polymerizable compound has one or more photocationically polymerizable functional groups in one molecule, such as an epoxy group, an oxetanyl group, a hydroxyl group, a vinyl ether group, an episulfide group, an ethyleneimine group, or an oxazoline group. In particular, in order to obtain high curability and bondability after curing, it is more preferable that the photocationically polymerizable compound has an epoxy group or an oxetanyl group.

As the photocationically polymerizable compound having an epoxy group, a compound having one or more epoxy groups in one molecule can be used. Specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, tetramethylbiphenyl type epoxy resin, polyhydroxynaphthalene type epoxy resin, isocyanate-modified epoxy resin, 10-(2,5-dihydroxyphenyl)-9,10-dihydro 9-oxa-10-phosphaphenanthrene-10-oxide modified epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, hexanediol type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, dicyclopentadiene-phenol addition reaction type epoxy resin, phenol aralkyl type epoxy resin, naphthol novolac type epoxy resin, naphthol aralkyl type epoxy resin, naphthol-phenol co-condensed novolac type epoxy resin, naphthol-cresol co-condensed novolac type epoxy resin, aromatic hydrocarbon formaldehyde resin modified phenol resin type epoxy resin, biphenyl modified novolac type epoxy resin, trimethylolpropane type epoxy resin, alicyclic epoxy resin, acrylic resin having epoxy group, polyurethane resin having epoxy group, polyester resin having epoxy group, flexible epoxy resin, etc. can be used.

Among them, it is preferable to use at least one of alicyclic epoxy resins and polyfunctional aliphatic epoxy resins, and it is more preferable to use alicyclic epoxy resins. These have excellent photocationic polymerization properties, and therefore form an adhesive layer with excellent curing properties. Furthermore, after bonding, the adhesive layer has high rigidity while also having suitable elasticity that can suppress deformation over time.

Furthermore, the epoxy resin may be modified. By blending or adding other resin components to the epoxy resin, it is possible to increase the flexibility of the adhesive layer and improve the adhesive strength and bending strength. Examples of such modified resins include CTBN (carboxyl-terminated butadiene-acrylonitrile rubber) modified epoxy resins; epoxy resins in which various rubbers such as acrylic rubber, NBR, SBR, butyl rubber, or isoprene rubber are dispersed in the resin; epoxy resins modified with liquid rubbers such as those mentioned above; epoxy resins to which various resins such as acrylic, urethane, urea, polyester, and styrene have been added; chelate-modified epoxy resins; and polyol-modified epoxy resins.

On the other hand, examples of photocationically polymerizable compounds having the oxetanyl group include oxetane compounds such as 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 1,4-bis[(3-methyl-3-oxetanylmethoxy)methyl]benzene, 3-methyl-3-glycidyloxetane, 3-ethyl-3-glycidyloxetane, 3-methyl-3-hydroxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, and di{1-ethyl(3-oxetanyl)}methyl ether.

The adhesive layer preferably uses a photocurable resin (a1) having a temperature (Tg-tan δ) at which the loss tangent after curing is at a maximum value of 100°C or more as the photocurable resin (A). This is because the heat cycle resistance of the cured adhesive layer (cured adhesive layer) is improved, and the rigid laminate obtained is able to suppress shape change and exhibit high dimensional stability. In particular, the photocurable resin (a1) preferably has a temperature at which the loss tangent after curing is at a maximum value of 105°C or more, 110°C or more, or 115°C or more, and the temperature is preferably 250°C or less, and more preferably 230°C or less, or 200°C or less. The temperature (Tg-tan δ) at which the loss tangent after curing of the photocurable resin (a1) is at a maximum value is a value measured at a frequency of 1.0 Hz using a dynamic viscoelasticity measuring device (manufactured by Rheometrics, product name: RSA-II) for a cured product obtained by curing an epoxy resin alone.

Examples of photocurable resins (a1) whose temperature (Tg-tan δ) at which the loss tangent after curing is at its maximum value is 100°C or higher include epoxy resins that are solid at room temperature (hereinafter referred to as room temperature solid epoxy resins). Room temperature refers to 25°C ± 5°C.

Specific examples of room temperature solid epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, biphenyl type epoxy resins, tetramethylbiphenyl type epoxy resins, polyhydroxynaphthalene type epoxy resins, isocyanate modified epoxy resins, 10-(2,5-dihydroxyphenyl)-9,10-dihydro 9-oxa-10-phosphaphenanthrene-10-oxide modified epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, hexanediol type epoxy resins, triphenylmethane type epoxy resins, tetraphenylethane type epoxy resins, dicyclopentadiene-phenol addition reaction type epoxy resins, phenol aralkyl type epoxy resins, naphthol novolac type epoxy resins, naphthol aralkyl type epoxy resins, naphthol-phenol co-condensed novolac type epoxy resins, naphthol-cresol co-condensed novolac type epoxy resins, aromatic hydrocarbon formaldehyde resin modified phenol resin type epoxy resins, biphenyl modified novolac type epoxy resins, etc.

The adhesive layer preferably contains at least one or more types of epoxy resins that are solid at room temperature as the photocurable resin (A), and more preferably contains one or more types of epoxy resins that are solid at room temperature and one or more types of epoxy resins that are liquid at room temperature (hereinafter referred to as room temperature liquid epoxy resins). By containing both a room temperature solid epoxy resin and a room temperature liquid epoxy resin as the photocurable resin (A), the adhesive layer is more likely to exhibit appropriate adhesion for a certain period of time before and after irradiation with active energy rays, and can be easily attached to an adherend. In particular, the adhesive layer can be sufficiently bonded to the first substrate even during in-line production, in which the time for step [1] is short.

Specific examples of room temperature liquid epoxy resins include trimethylolpropane type epoxy resins, alicyclic epoxy resins, acrylic resins having epoxy groups, polyurethane resins having epoxy groups, and polyester resins having epoxy groups.

When the photocurable resin (A) is an epoxy resin, the proportion of the epoxy resin that is solid at room temperature in the total amount of epoxy resin is preferably in the range of 20% by mass to 80% by mass, more preferably in the range of 30% by mass to 70% by mass, even more preferably in the range of 35% by mass to 65% by mass, and even more preferably in the range of 40% by mass to 65% by mass. This is because the heat resistance of the adhesive layer after curing can be increased and the curing reaction can be completed in a relatively short time. The proportion of the epoxy resin that is solid at room temperature in the total amount of epoxy resin can be calculated using the following formula.

Proportion of epoxy resin that is solid at room temperature in the total amount of epoxy resin = {Content of epoxy resin that is solid at room temperature [parts by mass] / (Content of epoxy resin that is solid at room temperature [parts by mass] + Epoxy resin that is liquid at room temperature [parts by mass])} x 100 [% by mass]

The content of the photocurable resin (A) in the adhesive layer is preferably in the range of 10% to 84% by mass, preferably in the range of 20% to 70% by mass, preferably in the range of 25% to 65% by mass, preferably in the range of 30% to 60% by mass, and preferably in the range of 30% to 50% by mass, based on the total amount of the adhesive layer, in other words, the total amount of solids in the adhesive composition. By setting the content of the photocurable resin (A) in the adhesive layer within the above range, the adhesion to the adherend can be improved. If the content of the photocurable resin (A) is more than the above range, it may be difficult to maintain the shape of the adhesive layer, and if it is less than the above range, the heat resistance of the adhesive layer after curing may decrease.

The photocurable resin (A) preferably has a weight average molecular weight in the range of 100 to 5000, more preferably in the range of 150 to 3000, and even more preferably in the range of 200 to 2500. By setting the weight average molecular weight of the photocurable resin (A) within the above range, the shape of the adhesive sheet becomes more stable, the handleability is improved, and the follow-up adhesion to the adherend surface can be increased. If the weight average molecular weight of the photocurable resin (A) is too small, the adhesive layer may have insufficient cohesive force, and the adhesive layer may bleed over time, which may lead to poor handleability. On the other hand, if the weight average molecular weight of the photocurable resin (A) is too large, the compatibility with the thermoplastic resin (B) may decrease, making it difficult for the reaction to proceed. The weight average molecular weight of the photocurable resin (A) can be measured using a method similar to the method for measuring the weight average molecular weight of the thermoplastic resin (B) described above.

<Thermoplastic resin (B)>
The adhesive layer contains the thermoplastic resin (B). The content of the thermoplastic resin (B) is preferably in the range of 15% by mass to 50% by mass in the total amount of the adhesive layer, in other words, in the total amount of solids of the adhesive composition, and more preferably in the range of 25% by mass to 50% by mass, more preferably in the range of 25% by mass to 45% by mass, more preferably in the range of 30% by mass to 45% by mass, and particularly preferably in the range of 34% by mass to 45% by mass. If the content of the thermoplastic resin (B) is more than the above range, the adhesive layer may be deformed and elongated due to temperature, or the heat resistance of the adhesive layer after curing may be reduced. On the other hand, if the content is less than the above range, the adhesive followability to the adherend may be reduced, or the proportion of high molecular weight components in the entire adhesive layer may be reduced, making it difficult to maintain the shape as an adhesive sheet.

In addition, the ratio of the content of thermoplastic resin (B) to the total content of photocurable resin (A) and thermoplastic resin (B) in the adhesive layer is preferably within the range of 25% to 68% by mass, more preferably within the range of 25% to 60% by mass, 30% to 60% by mass, 30% to 55% by mass, 30% to 50% by mass, or 35% to 50% by mass. By setting the ratio of the content of thermoplastic resin (B) to the total content of photocurable resin (A) and thermoplastic resin (B) in the adhesive layer within the above range, the adhesive layer after irradiation with active energy rays can be easily attached to the adherend.

The ratio of the content of thermoplastic resin (B) to the total content of photocurable resin (A) and thermoplastic resin (B) can be calculated using the following formula.

The proportion of the thermoplastic resin (B) content in the total of the photocurable resin (A) content and the thermoplastic resin (B) content = {Thermoplastic resin (B) content in the adhesive layer [parts by mass] / (Thermoplastic resin (A) content in the adhesive layer [parts by mass] + Thermoplastic resin (B) content in the adhesive layer [parts by mass])} x 100 [% by mass]

The thermoplastic resin (B) has a polymerizable functional group other than a polymerizable unsaturated double bond. By including the thermoplastic resin (B), the adhesive layer can react with the photocurable resin (A), suppressing a rapid curing reaction after irradiation with active energy rays and allowing the curing reaction to proceed gradually.

The thermoplastic resin (B) preferably has at least one polymerizable functional group selected from the group consisting of an isocyanate group, a hydroxyl group, an oxetanyl group, and an epoxy group as a polymerizable functional group other than the polymerizable unsaturated double bond. By using a thermoplastic resin (B) having at least one selected from the group consisting of an isocyanate group, a hydroxyl group, an oxetanyl group, and an epoxy group, it becomes possible to react with the photocurable resin (A), and it is possible to suppress a rapid curing reaction after irradiation with active energy rays and to gradually progress the curing reaction.

Examples of the thermoplastic resin (B) include polyester resins, polyurethane resins, acrylic resins, polyvinyl acetal resins, and epoxy resins (thermoplastic epoxy resins), each of which has a polymerizable functional group other than a polymerizable unsaturated double bond. These thermoplastic resins may be homopolymers or copolymers. These thermoplastic resins may be used alone or in combination of two or more.

In particular, the adhesive layer in the present invention preferably contains, as the thermoplastic resin (B), one or more resins selected from the group consisting of polyurethane resins, acrylic resins, and epoxy resins, each having a polymerizable functional group other than a polymerizable unsaturated double bond, and more preferably contains at least one or more polyurethane resins having a polymerizable functional group other than a polymerizable unsaturated double bond. By using a polyurethane resin having a polymerizable functional group other than a polymerizable unsaturated double bond as the thermoplastic resin (B), it is possible to suppress a rapid curing reaction after irradiation with active energy rays and to allow the curing reaction to proceed gradually, making it possible to bond to the second substrate in step [3].

In addition, the polyurethane resin having a polymerizable functional group other than a polymerizable unsaturated double bond is preferably crystalline. By including a crystalline polyurethane resin having a polymerizable functional group other than a polymerizable unsaturated double bond in the adhesive layer of the present invention, the adhesive layer is easily maintained in a sheet shape, and the adhesive sheet is excellent in shape retention during the manufacturing process of the adhesive sheet having the adhesive layer, the manufacturing process of the rigid laminate using the adhesive sheet, and even during storage of the adhesive sheet.

The polyurethane resin having a polymerizable functional group other than a polymerizable unsaturated double bond is preferably a polyurethane resin (B') having at least one selected from the group consisting of an isocyanate group, a hydroxyl group, an oxetanyl group, and an epoxy group, and among these, a polyurethane resin (B') having a hydroxyl group is preferred.

As the polyurethane resin (B') having an isocyanate group, for example, a polyurethane resin (B'1) having an isocyanate group obtained by reacting a polyol (b'1) with a polyisocyanate (b'2) can be used. As the polyurethane resin (B') having a hydroxyl group, for example, a polyurethane resin (B'2) having a hydroxyl group obtained by reacting a polyol (b'1) with a polyisocyanate (b'2) can be used.

The polyol (b'1) preferably has a number average molecular weight in the range of 500 to 5000, and more preferably has a number average molecular weight in the range of 1000 to 3000 in order to obtain an adhesive layer that is excellent in shape retention, coating workability, initial cohesive strength, etc. The above number average molecular weight is a value measured under the following conditions.

The number average molecular weight described in this specification is a value measured by gel permeation chromatography (GPC) using polystyrene standards under the following conditions.
(conditions)
Resin sample solution: 0.4% by mass tetrahydrofuran (THF) solution Measurement device model: HLC-8220GPC (manufactured by Tosoh Corporation)
Column: TSKgel (manufactured by Tosoh Corporation)
Eluent: Tetrahydrofuran (THF)

As such polyol (b'1), for example, one or more selected from the group consisting of polyester polyols, polycarbonate polyols, and polyether polyols can be suitably used.

In particular, in the present invention, it is preferable to use one or more polyols selected from the group consisting of polyester polyols and polycarbonate polyols as the polyol (b'1), it is preferable to use at least one or more polyester polyols, and it is preferable to use one or more polyester polyols and one or more polycarbonate polyols. This is because the shape stability of the adhesive layer before curing is increased, the handling is improved, and the conforming adhesion to the adherend surface is improved.

The total amount of polyols selected from the group consisting of the polycarbonate polyols and the polyester polyols used as polyol (b'1) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and more preferably 50 parts by mass or more, per 100 parts by mass of polyol (b'1). This is because the adhesive layer containing polyurethane resin (B') can maintain a level of adhesion that allows application at room temperature, and can further improve the conforming and adhesive properties to the adherend surface.

When the polycarbonate polyol and the polyester polyol are used in combination as the polyol (b'1), the mass ratio of the polycarbonate polyol and the polyester polyol (polycarbonate polyol/polyester polyol) is preferably in the range of 0.4 to 7.0, and more preferably in the range of 1.0 to 2.0. This is because a polyurethane resin having a loss tangent value within the desired range can be obtained, the adhesive layer before curing becomes easy to handle, and the adhesiveness to the adherend surface is high.

As the polyester polyol, for example, one obtained by an esterification reaction between polyol (b'1a) and a polycarboxylic acid, a polyester obtained by a ring-opening polymerization reaction of a cyclic ester compound such as ε-caprolactone, a copolymer polyester of these, etc. can be used.

Examples of polyols (b'1a) that can be used to prepare the polyester polyols include low molecular weight polyols, specifically aliphatic alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, and 1,3-butanediol, which have a molecular weight of about 50 to 300, and cyclohexanedimethanol.

In addition, examples of polyols (b'1a) that can be used to prepare the polyester polyol include aromatic polyols. By using aromatic polyols, the rigidity of the polyurethane resin (B') can be improved, and it is possible to suppress the adhesive layer (cured adhesive layer) from slipping or deforming over time after curing. Specific examples of aromatic polyols include hydroquinone, resorcinol, dihydroxyphenyl, naphthalenediol, dihydroxydiphenyl ether, bisphenol F, bisphenol A, adducts of bisphenol A with alkylene oxides such as ethylene oxide and propylene oxide (diethoxylated bisphenol A, etc.), p-xylylene glycol, m-xylylene glycol, o-xylylene glycol, 4,4'-bishydroxymethylbiphenyl, 4,2'-bishydroxymethylbiphenyl, 2,2'-bishydroxymethylbiphenyl, 4,3'-bishydroxymethylbiphenyl, 3,3'-bishydroxymethylbiphenyl, 3,2'-bishydroxymethylbiphenyl, phenol novolac, cresol novolac, 1,4-benzenedimethanol, 1,3-benzenedimethanol, 1,2-benzenedimethanol, 4,4'-naphthalenedimethanol, 3,4'-naphthalenedimethanol, and modified compounds thereof.

The polycarboxylic acids that can be used to prepare the polyester polyols include, for example, aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid, and their anhydrides or esters.

The polyester polyol is preferably one or more selected from the group consisting of aromatic polyester polyols and aliphatic polyester polyols, and preferably contains both aromatic polyester polyols and aliphatic polyester polyols.

Among aliphatic polyester polyols, linear aliphatic polyester polyols are preferred in that they can produce polyurethane resin (B') with a loss tangent value within the desired range, and can form an adhesive layer that is easy to handle before curing and has high conformability and adhesion to the adherend surface. The linear aliphatic polyester polyol refers to a polyester polyol that does not have an alkyl group in the side chain.

The above-mentioned aliphatic polyester polyols include those obtained by reacting the above-mentioned aliphatic alkylene glycols with aliphatic dicarboxylic acids. For example, it is preferable to use an aliphatic polyester polyol obtained by an esterification reaction of 1,6-hexanediol with adipic acid, or an aliphatic polyester polyol obtained by reacting 1,6-hexanediol with dodecanedioic acid.

In addition, it is preferable to use the aromatic polyester polyol as the polyester polyol, since it is possible to improve the rigidity of the polyurethane resin (B') and suppress the adhesive layer (cured adhesive layer) from slipping or deforming over time after curing. Examples of the aromatic polyester polyol include those obtained by reacting the aromatic polyol with an aliphatic or aromatic dicarboxylic acid, and for example, an aromatic polyester polyol obtained by reacting an ethylene oxide adduct of bisphenol A with phthalic acid and adipic acid is preferably used.

The polyester polyol preferably has a number average molecular weight in the range of 1,000 to 5,000. This is because a polyurethane resin (B') having a loss tangent value within the desired range can be obtained, the adhesive layer before curing becomes easy to handle, and the adhesiveness to the adherend surface is improved.

In particular, when using a polyester polyol obtained by reacting an aliphatic diol such as 1,2-ethanediol or 1,4-butanediol with adipic acid as the polyester polyol, it is preferable to use one having a number average molecular weight in the range of 1100 to 2900, when using a polyester polyol obtained by reacting 1,6-hexanediol with adipic acid, it is preferable to use one having a number average molecular weight in the range of 1100 to 5000, and when using a polyester polyol obtained by reacting 1,6-hexanediol with sebacic acid, it is preferable to use one having a number average molecular weight in the range of 1000 to 5000.

The polyester polyol is preferably used in the range of 10% by mass to 50% by mass, and more preferably 20% by mass to 40% by mass, based on the total amount of the polyol (b'1). This is because the adhesive layer containing the polyurethane resin (B') can maintain a level of adhesion that allows application at room temperature, and the conformability and adhesion to the adherend surface is further improved.

As the polycarbonate polyol, for example, one obtained by reacting a carbonate ester and/or phosgene with a low molecular weight polyol can be used. As the carbonate ester, for example, methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, diphenyl carbonate, etc. can be used.

Examples of low molecular weight polyols that can react with the above carbonate esters and phosgene include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 1,7-heptanediol, 1,8-hexanediol, 1,9-hexanediol, 2,10-hexanediol, 2,20-hexanediol, 2,30-hexanediol, 2,40-hexanediol, 2,50-hexanediol, 2,60-hexanediol, 2,70-hexanediol, 2,80-hexanediol, 2,90-hexanediol, 2,100-hexanediol, 2,100-hexanediol, 2,20-hexanediol, 2,30-hexanediol, 2,40-hexanediol, 2,50-hexanediol, 2,60-hexanediol, 2,70-hexanediol, 2,80-hexanediol, 2,100-hexanediol, 2,20-hexanediol, 2,30-hexanediol, 2,40-hexanediol, 2,5 ... Can be used with 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanedimethanol, hydroquinone, resorcinol, bisphenol A, bisphenol F, 4,4'-biphenol, etc.

It is also preferable to use an aliphatic polycarbonate polyol or an alicyclic polycarbonate polyol as the polycarbonate polyol.

As the aliphatic polycarbonate polyol, it is preferable to use one obtained by reacting a dialkyl carbonate with one or more polyols selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol. This is because the adhesive layer containing the polyurethane resin (B') can have adhesion that allows application at room temperature.

As the alicyclic polycarbonate polyol, it is preferable to use one obtained by reacting, for example, a dialkyl carbonate with a polyol containing one or more selected from the group consisting of cyclohexanedimethanol and its derivatives. This is because the adhesive layer containing the polyurethane resin (B') can have adhesion that allows application at room temperature and excellent initial cohesion.

The polycarbonate polyol preferably has a number average molecular weight in the range of 500 to 5,000, and more preferably in the range of 800 to 3,000. This is because a polyurethane resin (B') having a loss tangent value within the desired range can be obtained, the adhesive layer before curing becomes easy to handle, and the adhesiveness to the adherend surface becomes higher.

The polycarbonate polyol is preferably used in the range of 20% by mass to 80% by mass, more preferably 30% by mass to 70% by mass, and more preferably 40% by mass to 50% by mass, relative to the total amount of the polyol (b'1). This is because the adhesive layer containing the polyurethane resin (B') can exhibit adhesion that allows application at room temperature, and the conformability and adhesion to the adherend surface is further improved.

Examples of polyether polyols include those obtained by addition polymerization of alkylene oxides using one or more compounds having two or more active hydrogen atoms as an initiator.

Examples of the initiator that can be used include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, bisphenol A, glycerin, trimethylolethane, and trimethylolpropane.

As the alkylene oxide, for example, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, etc. can be used.

As the polyether polyol, it is preferable to use an aliphatic polyether polyol or a polyether polyol having an alicyclic structure.

As the polyether polyol, polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran, polytetramethylene glycol derivative obtained by reacting tetrahydrofuran with alkyl-substituted tetrahydrofuran, polytetramethylene glycol derivative obtained by copolymerizing neopentyl glycol with tetrahydrofuran, etc. can be used. Among them, it is preferable to use polytetramethylene glycol (PTMG) and polytetramethylene glycol derivative (PTXG) as the polyether polyol. This is because the adhesive layer exhibits adhesion at room temperature and can further increase physical properties such as flexibility and durability.

In addition to the above, other polyols can be used as the polyol (b'1). Examples of the other polyols include acrylic polyols.

As the polyisocyanate (b'2) to be reacted with the polyol (b'1), an alicyclic polyisocyanate, an aliphatic polyisocyanate, an aromatic polyisocyanate, etc. can be used, and it is preferable to use an alicyclic polyisocyanate.

As the alicyclic polyisocyanate, for example, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, 2,4- and/or 2,6-methylcyclohexane diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexylene-1,2-dicarboxylate, 2,5- and/or 2,6-norbornane diisocyanate, dimer acid diisocyanate, bicycloheptane triisocyanate, etc. can be used alone or in combination of two or more kinds.

Among the above-mentioned alicyclic polyisocyanates, it is preferable to use 4,4'-dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), and 1,3-bis(isocyanatomethyl)cyclohexane (BICH) in order to obtain an adhesive sheet that has good reactivity with the above-mentioned polyol (b'1) and is excellent in heat resistance, light transmittance, etc.

As a method for preparing polyurethane resin (B') by reacting polyol (b'1) with polyisocyanate (b'2), for example, the polyol (b'1) charged in a reaction vessel is heated under normal or reduced pressure conditions to remove moisture, and then polyisocyanate (b'2) is supplied all at once or in portions to react.

The reaction of the polyol (b'1) with the polyisocyanate (b'2) is preferably carried out in such a manner that the equivalent ratio of the isocyanate groups of the polyisocyanate (b'2) to the hydroxyl groups of the polyol (b'1) (hereinafter referred to as the "NCO/OH equivalent ratio") is in the range of 1.1 to 20.0, more preferably in the range of 1.1 to 13.0, even more preferably in the range of 1.1 to 5.0, and particularly preferably in the range of 1.5 to 3.0.

The reaction conditions (temperature, time, etc.) between the polyol (b'1) and the polyisocyanate (b'2) may be appropriately set in consideration of various conditions such as safety, quality, and cost, and are not particularly limited. For example, the reaction temperature is preferably in the range of 70 to 120°C, and the reaction time is preferably in the range of 30 minutes to 5 hours.

When reacting the polyol (b'1) with the polyisocyanate (b'2), a catalyst such as a tertiary amine catalyst or an organometallic catalyst can be used as needed.

The reaction may be carried out in a solvent-free environment or in the presence of an organic solvent. Examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl butyl ketone, and cyclohexanone; ether ester solvents such as methyl cellosolve acetate and butyl cellosolve acetate; aromatic hydrocarbon solvents such as toluene and xylene; and amide solvents such as dimethylformamide and dimethylacetamide. These solvents may be used alone or in combination. The organic solvent may be removed during or after the production of the polyurethane resin (B') by an appropriate method such as heating under reduced pressure or drying at normal pressure.

The polyurethane resin (B') having an oxetanyl group or an epoxy group may be, for example, a polyurethane resin (B'1) having an isocyanate group,
2) a monomer (B") having a functional group (b"1) capable of reacting with an isocyanate group, an oxetanyl group or an epoxy group, and one or more polymerizable functional groups (b"2) other than a polymerizable unsaturated double bond;
It is possible to use a polyurethane resin (B'3) obtained by reacting

As the functional group (b"1) capable of reacting with the isocyanate group, for example, a hydroxyl group, an amino group, a carboxyl group, a mercapto group, etc. can be used, and among these, it is preferable to use a hydroxyl group or an amino group.

The polymerizable functional group (b"2) other than the above-mentioned polymerizable unsaturated double bond refers to a functional group other than the so-called radically polymerizable functional group, such as a functional group having cationic polymerizability or an anionic polymerizability, for example, an epoxy group, an oxetanyl group, an ethylene sulfide group, etc.

The monomer (B") is not particularly limited as long as it has a functional group (b"1) and a polymerizable functional group (b"2), and examples thereof include 3-ethyl-3-(4-hydroxybutyl)oxymethyl-oxetane, 3-hydroxymethyl-3-ethyloxetane, 2-hydroxymethyloxetane, and 3-hydroxyoxetane.

The monomer (B") is preferably used in an amount of 5 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the polyurethane resin (B'1).

More specifically, the monomer (B") can be used in an amount capable of supplying functional groups reactive with the isocyanate groups, preferably more than 50 mol% to 100 mol%, more preferably 60 mol% to 100 mol%, and even more preferably 80 mol% to 100 mol%, of the molar number of isocyanate groups in the polyurethane resin (B'1). This makes it possible to obtain a polyurethane resin that has appropriate flexibility before curing, and excellent shape retention, mechanical strength, durability (particularly hydrolysis resistance), and conformability and adhesion to the adherend surface.

When reacting the polyurethane resin (B'1) with the monomer (B"), a urethanization catalyst can be used as necessary. The urethanization catalyst can be added as appropriate at any stage of the urethanization reaction. The urethanization reaction is preferably carried out until the isocyanate group content (%) becomes substantially constant. Examples of the urethanization catalyst that can be used include nitrogen-containing compounds such as triethylamine, triethylenediamine, and N-methylmorpholine, organic metal salts such as potassium acetate, zinc stearate, and stannous octoate, and organic metal compounds such as dibutyltin dilaurate.

In addition, as the thermoplastic epoxy resin having a polymerizable functional group other than a polymerizable unsaturated double bond, a polymer or copolymer of epoxy compounds having a linear structure, or a copolymer of an epoxy compound and a monomer polymerizable with this epoxy compound having a linear structure may be used. Specific examples include bisphenol A type epoxy resin, bisphenol fluorene type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, cyclic aliphatic type epoxy resin, long chain aliphatic type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, etc., among which bisphenol A type epoxy resin and bisphenol fluorene type epoxy resin are preferred.

The adhesive layer preferably contains, as the thermoplastic resin (B), a polyester urethane resin having hydroxyl groups, which is a reaction product of a polyol including polyester polyol and a polyisocyanate. This is because delayed curing properties can be exhibited. In addition, it is preferable that the polyester urethane resin having hydroxyl groups is a crystalline polyester urethane resin having hydroxyl groups, since it has excellent delayed curing properties, the adhesive layer is easily maintained in a sheet shape, and the adhesive sheet has excellent shape retention during the manufacturing process of the adhesive sheet having the adhesive layer, the manufacturing process of the rigid laminate using the adhesive sheet, and during storage of the adhesive sheet.

The fact that the polyurethane or polyester urethane contained in the adhesive layer as the thermoplastic resin (B) is crystalline can be confirmed by detecting the melting point as a peak in DSC measurement (differential scanning calorimetry).

The thermoplastic resin (B) preferably has a loss tangent (tan δ ₄₀ ) of 3 or less at a frequency of 1.0 Hz and a temperature of 40° C. before curing, more preferably 0.001 to 2.0, even more preferably 0.001 to 1.0, and even more preferably 0.001 to 0.9. By setting the loss tangent of the thermoplastic resin (B) at a frequency of 1.0 Hz and a temperature of 40° C. within the above range, it is possible to suppress changes in the thickness and shape of the adhesive layer.

The thermoplastic resin (B) preferably has a loss tangent (tan δ ₆₀ ) at a frequency of 1.0 Hz and a temperature of 60° C. before curing of 1 or more, more preferably 1.2 to 20, further preferably 1.3 to 15, and even more preferably 1.5 to 15. This is because, by setting the loss tangent at a frequency of 1.0 Hz and a temperature of 60° C. of the thermoplastic resin (B) within the above range, the conformability to the adherend is excellent.

The loss tangent of thermoplastic resin (B) at each temperature (40°C, 60°C) at a frequency of 1.0 Hz is obtained by molding thermoplastic resin (B) before curing to a thickness of 1 mm, molding and cutting it into a circle with a diameter of 8 mm to prepare a test piece, and using a dynamic viscoelasticity tester (manufactured by Rheometrics, product name: Ares 2K STD), sandwiching the test piece between the parallel disks that are the measuring section of the tester, and measuring the storage modulus (G') and loss modulus (G") at each temperature at a frequency of 1.0 Hz (G"/G').

When a urethane resin is used as the thermoplastic resin (B), the loss tangent (tan δ) at each temperature of the thermoplastic resin (B) can be adjusted by appropriately selecting the composition of the polyol and polyisocyanate that constitute the urethane resin, the number average molecular weight, etc.

The melting point of the thermoplastic resin (B) is preferably in the range of 30°C to 120°C, more preferably in the range of 35°C to 100°C, and even more preferably in the range of 40°C to 80°C. By using a thermoplastic resin (B) having a melting point within the above range, the shape of the adhesive layer before curing becomes more stable, improving handleability, and also improving the conformability and adhesion to the adherend surface.

The melting point of thermoplastic resin (B) is the temperature at which the maximum exothermic peak (exothermic peak top) is observed when the material is heated from 20°C to 150°C at a heating rate of 10°C/min using differential scanning calorimetry (DSC), held for 1 minute, cooled to -10°C at a cooling rate of 10°C/min, held for 10 minutes, and then measured again at a heating rate of 10°C/min.

The weight average molecular weight of the thermoplastic resin (B) is preferably in the range of 5,500 to 2,000,000, more preferably in the range of 5,500 to 1,000,000, and even more preferably in the range of 5,500 to 800,000. By setting the weight average molecular weight of the thermoplastic resin (B) within the above range, the shape of the adhesive layer before curing becomes more stable, improving handleability, and the adhesiveness to the adherend surface can be increased. If the weight average molecular weight of the thermoplastic resin (B) is too small, the adhesive layer may have insufficient cohesive force, and the adhesive layer may bleed over time, making it easier to handle. On the other hand, if the weight average molecular weight of the thermoplastic resin (B) is too large, the compatibility with the photocurable resin (A) may decrease, making it difficult for the reaction to proceed.

The weight average molecular weight described in this specification is a value measured by gel permeation chromatography (GPC) in terms of polystyrene under the following conditions.
(conditions)
Resin sample solution: 0.4% by mass tetrahydrofuran (THF) solution Measurement device model: HLC-8220GPC (manufactured by Tosoh Corporation)
Column: TSKgel (manufactured by Tosoh Corporation)
Eluent: Tetrahydrofuran (THF)

<Photopolymerization initiator (C)>
The adhesive layer contains one or more photopolymerization initiators (C), which promotes reactivity after irradiation with active energy rays in step [2]. In addition, the adhesive layer can improve the adhesiveness after curing. In addition, the adhesive layer contains a photopolymerization initiator (C) that is activated by light and reacts, so that the reaction continues even after the irradiation with active energy rays is stopped, and the reaction proceeds even in a dark place or at a low temperature, and a good curing reaction can be obtained.

The photopolymerization initiator (C) is not particularly limited as long as it is activated by light. Examples of the photopolymerization initiator (C) include a photoradical polymerization initiator, a photocationic polymerization initiator, and a photoanionic polymerization initiator. Among them, at least one of a photocationic polymerization initiator and a photoanionic polymerization initiator is preferred, and a photocationic polymerization initiator is more preferred because it can suitably adjust the polymerization reaction.

The photocationic polymerization initiator is not particularly limited as long as it can induce a ring-opening reaction of a cationic polymerizable functional group by light of the wavelength used. Among them, a compound that induces a ring-opening reaction of a cationic polymerizable functional group by light of a wavelength of 300 nm to 370 nm and is inactive in the wavelength region exceeding 370 nm is preferably used. Examples of such photocationic polymerization initiators include onium salts such as aromatic diazonium salts, aromatic iodonium salts, and aromatic sulfonium salts.

Specific examples of onium salts include OPTOMER SP-150, OPTOMER SP-170, OPTOMER SP-171 (all manufactured by ADEKA Corporation), UVE-1014 (manufactured by General Electronics Corporation), OMNICAT250, OMNICAT270 (all manufactured by IGM Resin Corporation), IRGACURE290 (manufactured by BASF Corporation), SAN-AID SI-60L, SAN-AID SI-80L, SAN-AID SI-100L (all manufactured by Sanshin Chemical Industry Co., Ltd.), CPI-100P, CPI-101A, CPI-200K (all manufactured by San-Apro Ltd.), etc.

The cationic photopolymerization initiator may be used alone or in combination of two or more. Furthermore, the adhesive layer may be cured in two stages by using multiple cationic photopolymerization initiators with different effective active wavelengths.

The above photocationic polymerization initiators may be used in combination with sensitizers such as anthracene-based and thioxanthone-based sensitizers, if necessary.

The photopolymerization initiator (C) is preferably contained in the adhesive layer, in other words, in the total solid content of the adhesive composition constituting the adhesive layer, in a range of 0.001% by mass to 30% by mass, more preferably in a range of 0.01% by mass to 20% by mass, and even more preferably in a range of 0.1% by mass to 10% by mass. By setting the amount of photopolymerization initiator (C) in the adhesive layer in the above range, the curing reaction of the adhesive layer after irradiation with active energy rays proceeds slowly, and sufficient bonding properties and rigidity can be exhibited after curing.

<Other Components (D)>
The adhesive layer may contain, in addition to the above-mentioned photocurable resin (A), thermoplastic resin (B), and photopolymerization initiator (C), other components (D) as necessary.

By including a pressure-sensitive adhesive resin as the other component (D), the adhesive layer can exhibit good room temperature lamination properties and can also improve the conformability and adhesion to the adherend surface.

The weight average molecular weight of the adhesive resin is preferably in the range of 2,000 to 2,000,000, more preferably in the range of 5,000 to 1,000,000, and even more preferably in the range of 5,000 to 800,000. The weight average molecular weight of the adhesive resin can be measured by the same method as that for the weight average molecular weight of the thermoplastic resin (B) described above.

Examples of the adhesive resin include polyester, polyurethane, poly(meth)acrylate, polyvinyl acetal, and the like. These adhesive resins may be homopolymers or copolymers. These adhesive resins may be used alone or in combination of two or more kinds.

The adhesive resin preferably has a glass transition temperature in the range of -30°C to 20°C, and more preferably in the range of -25°C to 10°C. By including an adhesive resin having a glass transition temperature within the above range, the adhesive layer can exhibit good adhesion and elasticity at room temperature, and can exhibit good adhesion and high bonding strength to the adherend.

The glass transition temperature can be calculated, for example, by using a dynamic viscoelasticity tester (manufactured by Rheometrics, product name: Ares 2KSTD) to sandwich a test piece of adhesive resin between parallel disks, which are the measuring section of the tester, and measuring the storage modulus (G') and loss modulus (G") at a frequency of 1.0 Hz. The glass transition temperature can be calculated as the temperature at which the loss tangent (tan δ), which can be calculated by dividing the loss modulus (G") by the storage modulus (G'), (G"/G'), is maximum.

The adhesive resin may have a functional group introduced therein that can react with a crosslinking agent or with the functional groups contained in the photocurable resin (A) or thermoplastic resin (B). This is because the adhesive resin can be crosslinked. Examples of the functional group include a hydroxyl group, a carboxyl group, an epoxy group, and an amino group. It is preferable to select the functional group appropriately within a range that does not inhibit the polymerization reaction of the photocurable resin (A) and the thermoplastic resin (B).

The adhesive resin is preferably contained in the range of 0.1 to 100 parts by mass, more preferably 1 to 50 parts by mass, and even more preferably 5 to 30 parts by mass relative to the total amount (100 parts by mass) of the adhesive layer, in other words the adhesive composition that forms the adhesive layer. By making the adhesive resin blend ratio within the above range, it is possible to prevent a decrease in the adhesion at room temperature and the bonding property of the adhesive layer after curing.

The adhesive layer may contain inorganic fillers such as metal particles or silica particles, organic fillers, thermally expandable particles, silane coupling agents, phosphoric acid additives, acrylate additives, etc. as other components (D). When the substrate contains a glass component or when a member containing a glass component is placed on the substrate surface, the adhesive layer may contain a silane coupling agent that is highly reactive with the glass component to further enhance adhesion to the adherend. The adhesive layer may also contain a photocurable silane coupling agent that can react with the photocurable resin (A) or the thermoplastic resin (B).

The adhesive layer may also contain other components (D), such as softeners, stabilizers, adhesion promoters, leveling agents, defoamers, plasticizers, tackifying resins, fibers, antioxidants, hydrolysis inhibitors, thickeners, colorants such as pigments, fillers, tackifying resins, etc.

<Physical properties of adhesive layer>
The thickness of the adhesive layer is preferably 20 μm to 5000 μm, more preferably 20 μm to 1000 μm, more preferably 30 μm to 300 μm, and particularly preferably 50 μm to 250 μm. By setting the thickness of the adhesive layer within the above range, the total thickness of the rigid laminate can be thinned, and the adhesive layer after curing can impart sufficient rigidity to the entire rigid laminate. In addition, the shape stability and handleability of the adhesive layer before curing are improved, and sufficient adhesion to the adherend and high follow-up adhesion to the adherend surface can be exhibited. Furthermore, when the adhesive layer is irradiated with active energy rays from one direction, the active energy rays reach deep into the adhesive layer, preventing the occurrence of curing unevenness in the thickness direction.

The adhesive layer preferably has a melting point of 25°C or higher, preferably 30°C or higher, preferably 35°C or higher, and preferably 40°C or higher. The melting point is preferably 120°C or lower, preferably 90°C or lower, preferably 85°C or lower, and preferably 60°C or lower. More specifically, the melting point of the adhesive layer can be preferably in the range of 30°C to 120°C, 30°C to 90°C, or 40°C to 85°C. By setting the melting point of the adhesive layer within the above range, the adhesive layer has excellent shape stability and handleability before curing, and the adhesiveness to the adherend is further improved. In other words, the melting point of the adhesive layer is the same as the melting point of the adhesive composition that constitutes the adhesive layer.

The melting point of the adhesive layer is the temperature at which the maximum exothermic peak (exothermic peak top) is observed when the adhesive layer is heated from 20°C to 150°C at a heating rate of 10°C/min using differential scanning calorimetry (DSC), held for 1 minute, cooled to -10°C at a cooling rate of 10°C/min, held for 10 minutes, and then measured again at a heating rate of 10°C/min.

The adhesive layer preferably has a loss tangent (tan δ ₂₃ ) at 23° C. of less than 3.0, more preferably 1.5 or less, even more preferably 1.0 or less, and particularly preferably 0.8 or less. The loss tangent (tan δ ₂₃ ) at 23° C. can be 0.01 or more, preferably 0.1 or more. When the loss tangent of the adhesive layer before being irradiated with active energy rays is within the above-mentioned range, the thickness of the adhesive layer can be kept constant, and the adhesive layer has excellent handleability when being attached to a flexible substrate.

The loss tangent of the adhesive layer before being irradiated with active energy rays can be adjusted by appropriately selecting the composition and number average molecular weight of the photocurable resin, thermoplastic resin, and other components contained in the adhesive layer, in addition to the conditions during the manufacture of the adhesive layer.

The loss tangent (tan δ ₂₃ ) of the adhesive layer at 23° C. was measured using a dynamic viscoelasticity tester (manufactured by Rheometrics, product name: Ares 2KSTD) by sandwiching a test piece between parallel disks, which are the measuring part of the tester, and measuring the storage modulus (G') and loss modulus (G") at temperatures of 0 to 150° C. and a frequency of 1 Hz. The loss modulus (G") at 23° C. was divided by the storage modulus (G') at 23° C., and the value (G"/G') was taken as the loss tangent (tan δ) at 23° C. The test piece used in the measurement was the adhesive layer cut into a circle with a thickness of 1 mm and a diameter of 8 mm before irradiation with active energy rays.

(b) Optional Configuration The first adhesive sheet may have the adhesive layer described above. The configuration of the first adhesive sheet may be an adhesive layer only, or an adhesive layer containing the desired composition may be provided on each of both sides of the supporting substrate.

When the first adhesive sheet is an embodiment in which adhesive layers are provided on both sides of the supporting substrate, the supporting substrate in the above embodiment preferably exhibits a transmittance of 80% or more, and preferably 90% or more, for light having a wavelength of 200 nm to 780 nm. This is because, in step [2] described below, even if active energy rays are irradiated only from one adhesive layer side of the first adhesive sheet in which adhesive layers are provided on both sides of the supporting substrate, the adhesive layer on the opposite side can also be activated through the supporting substrate, causing a polymerization reaction.

Examples of light-transmitting support substrates include thermoplastic resin films and resin foams. Specific examples of light-transmitting thermoplastic resin films include polyester resins such as polyethylene terephthalate resin, polyvinyl chloride resins, acrylonitrile-butadiene-styrene copolymers, polycarbonate resins, polyacrylic acid ester resins, polymethacrylic acid ester resins, styrene-methyl methacrylate copolymers, polylactic acid resins, and polyolefin resins. Specific examples of light-transmitting resin foams include polyolefin resin foams, polyurethane resin foams, polychloroprene resin foams, rubber-based resin foams, and acrylic resin foams.

The first adhesive sheet may have a release liner on one or both sides. When the first adhesive sheet has a release liner, the release liner is removed to expose the surface of the adhesive layer when the sheet is attached to the first substrate and to the second substrate in step [3] described below.

Examples of the release liner that can be used include paper such as kraft paper, glassine paper, and wood-free paper; resin films such as polyethylene, polypropylene (OPP, CPP), and polyethylene terephthalate; laminated paper in which the above-mentioned paper and resin film are laminated together; and paper that has been sealed with clay, polyvinyl alcohol, or the like and then treated with a release agent such as silicone resin on one or both sides.

(3) Step [1]
In step [1], the adhesive layer of the first adhesive sheet is bonded to one side of the first substrate. When the first adhesive sheet has a structure in which the adhesive layer and the release liner are laminated in this order, the side of the adhesive layer opposite the release liner is bonded to one side of the first substrate. When the first adhesive sheet has a structure in which the first adhesive layer, the support substrate, the second adhesive layer, and the release liner are laminated in this order, the side of the first adhesive layer opposite the support substrate is bonded to one side of the first substrate.

The adhesive layer of the first adhesive sheet before irradiation with active energy rays exhibits pressure-sensitive adhesion. Therefore, the adhesive layer of the first adhesive sheet and the first substrate can be bonded by pressure bonding. Furthermore, before irradiation with active energy rays in step [2], the first adhesive sheet can be easily re-attached after being bonded to the first substrate.

In step [1], the gel fraction of the adhesive layer of the first adhesive sheet-attached substrate when the first substrate is pressure-bonded is preferably within the range of 0.1% to 30%, more preferably within the range of 0.1% to 20%, and even more preferably within the range of 0.1% to 10%. By keeping the gel fraction of the adhesive layer within a predetermined range when the first substrate is pressure-bonded in step [1], the adhesive layer is in a very flexible state while maintaining the shape of the adhesive sheet, and can therefore be sufficiently adhered to the first substrate.

The gel fraction of the adhesive layer of the first adhesive sheet-attached substrate when the first substrate is pressure-bonded is calculated based on the following formula: a sample is prepared by forming an adhesive layer on one side of a release liner, and is immersed in toluene adjusted to 23°C for 24 hours. The mass of the adhesive layer remaining in the solvent after drying and the mass of the adhesive layer before immersion in toluene are then calculated. The mass of the adhesive layer is the mass of the sample minus the mass of the release liner.

Gel fraction (mass%) = {(mass of adhesive layer remaining undissolved in toluene) / (mass of adhesive layer before immersion in toluene)} x 100

In step [1], the adhesive layer of the first adhesive sheet and the first substrate are preferably bonded together at a pressure in the range of 0.1 kPa to 3000 KPa, more preferably at a pressure in the range of 0.5 kPa to 1000 kPa, and even more preferably at a pressure in the range of 1.0 kPa to 500 kPa.

The bonding time is preferably in the range of 0.1 seconds to 10 minutes, more preferably in the range of 0.3 seconds to 5 minutes, and even more preferably in the range of 0.5 seconds to 3 minutes. By setting the bonding force and bonding time in the above ranges, sufficient pressure can be applied to the adhesive sheet and the first substrate without damaging the first substrate, and the first substrate and the first adhesive sheet can be sufficiently adhered to each other to obtain high bonding strength. It is also possible to improve adhesion to the substrate and improve production efficiency, especially in online manufacturing.

The adhesive layer of the first adhesive sheet and the first substrate can be bonded at room temperature, but may be bonded while being heated. In step [1], the adhesive layer of the first adhesive sheet and the first substrate are preferably bonded at a temperature in the range of 5°C to 100°C, more preferably at a temperature in the range of 10°C to 70°C, and even more preferably at a temperature in the range of 20°C to 40°C. By setting the bonding temperature in the above range, it is possible to prevent thermal deterioration of the first substrate, sufficiently adhere the first substrate and the first adhesive sheet, and obtain high bonding strength.

B. Step [2]
Step [2] in the method for producing a rigid laminate of the present invention is a step of irradiating the adhesive layer of the first adhesive sheet-attached substrate with active energy rays.

In step [2], active energy rays are irradiated from the adhesive layer side of the first adhesive sheet-attached substrate, thereby initiating the curing reaction of the adhesive layer, regardless of the presence or absence of light transmittance or heat resistance of the first substrate. In addition, when the first substrate has light transmittance, active energy rays may be irradiated from the first substrate side of the first adhesive sheet-attached substrate.

The active energy rays used in step [2] are not particularly limited, but it is preferable to use ultraviolet rays. In order to efficiently carry out the curing reaction of the adhesive layer, ultraviolet rays may be irradiated in an inert gas atmosphere such as nitrogen gas, or in an air atmosphere.

When ultraviolet light is used as the active energy ray, examples of the light source include low-pressure mercury lamps, high-pressure mercury lamps, extra-high-pressure mercury lamps, metal halide lamps, electrodeless lamps (fusion lamps), chemical lamps, black light lamps, mercury-xenon lamps, short arc lamps, helium-cadmium lasers, argon lasers, sunlight, LEDs, etc. Among these, LEDs are preferred because they generate less heat during irradiation and can suppress thermal degradation of the first substrate.

As the irradiation device for the active energy rays, in addition to those mentioned above, germicidal lamps, carbon arcs, xenon lamps, metal halide lamps, scanning type, curtain type electron beam accelerators, etc. can be used.

The irradiation conditions of the active energy rays can be set so that the gel fraction of the adhesive layer of the first adhesive sheet-attached substrate 5 minutes after carrying out this step is within a predetermined range. The irradiation intensity of the active energy rays is preferably within the range of 10 mW/cm ² to 1000 mW/cm ² , more preferably within the range of 10 mW/cm ² to 800 mW/cm ² , and even more preferably within the range of 50 mW/cm ² to 400 mW/cm ^2. By adjusting the irradiation intensity within the above range, the heat generated when irradiated with active energy rays can be reduced, so that the thermal deterioration of the first substrate can be suppressed, and the curing rate of the adhesive layer after irradiation with active energy rays can be adjusted.

The irradiation time of the active energy rays is preferably within the range of 1 to 60 seconds, more preferably within the range of 5 to 50 seconds, and even more preferably within the range of 10 to 40 seconds. By adjusting the irradiation time within the above range, the heat generated upon irradiation with active energy rays can be reduced, so that thermal deterioration of the first substrate can be suppressed, and the curing rate of the adhesive layer after irradiation with active energy rays can be adjusted.

The active energy rays may be irradiated all at once or in separate doses. In the case of separate doses, the heat generated when the active energy rays are irradiated can be reduced, so that thermal deterioration of the first substrate can be suppressed, and the curing rate of the adhesive layer after irradiation with the active energy rays can be more easily adjusted. When the active energy rays are irradiated in separate doses, for example, one minute of irradiation may be divided into two doses, and two doses of 30 seconds may be irradiated. In the case of separate doses of irradiation with the active energy rays, "five minutes after step [2] is performed" refers to five minutes after the last active energy ray irradiation is performed.

Step [2] is preferably carried out in a room temperature environment (e.g., an atmosphere of 23°C). In addition, if the first substrate of the first adhesive sheet-attached substrate is heat resistant, the curing reaction may be accelerated by heating after irradiation with active energy rays.

Five minutes after the step [2] is performed, the gel fraction of the adhesive layer of the first adhesive sheet-attached substrate may be within the range of 35% to 90%, preferably within the range of 40% to 90%, more preferably within the range of 45% to 90%, and even more preferably within the range of 50% to 85%. This is because, between the time when the step [2] is performed and the step [3] is performed, that is, when the first adhesive sheet-attached substrate and the second substrate are pressure-bonded, the adhesive layer of the first adhesive sheet-attached substrate can maintain the flexibility required for bonding with the second substrate, and at the same time, it is easy to impart the desired rigidity to the laminate after the step [3] is performed. Even if the time between the step [2] and the step [3] is shorter than five minutes, the above-mentioned effect can be achieved as long as the adhesive layer is capable of exhibiting a gel fraction within the above-mentioned range five minutes after the step [2] is performed. The gel fraction of the adhesive layer of the first adhesive sheet-attached substrate five minutes after the step [2] is performed can be adjusted by adjusting the composition of the adhesive layer and the irradiation conditions of the active energy ray. Note that 5 minutes after carrying out step [2], or 5 minutes after carrying out step [2], refers to the time from when the adhesive layer of the first adhesive sheet-attached substrate is irradiated with active energy rays until measurement is carried out; in other words, when 5 minutes have passed since carrying out step [2], the adhesive layer of the first adhesive sheet-attached substrate has the above-mentioned gel fraction.

The gel fraction of the adhesive layer of the first adhesive sheet-attached substrate 5 minutes after carrying out step [2] was determined by preparing a sample in which an adhesive layer was formed on one side of a release liner, carrying out step [2] on the sample, and immersing the sample 5 minutes after carrying out step [2] in toluene adjusted to 23°C for 24 hours. The gel fraction was calculated based on the following formula from the dried mass of the adhesive layer remaining in the solvent and the mass of the adhesive layer before immersion in toluene. The mass of the adhesive layer is the mass of the sample minus the mass of the release liner.

Gel fraction (mass%) = {(mass of adhesive layer remaining undissolved in toluene) / (mass of adhesive layer before immersion in toluene)} x 100

C. Step [3]
In the process for producing a rigid laminate of the present invention, the step [3] includes, after the step [2], bonding the adhesive layer of the first adhesive sheet-attached substrate and a flexible second substrate. This is the crimping process.

(1) Second Base Material The second base material is a base material having flexibility. The second base material has a thickness that allows it to exhibit the desired flexibility, and for example, is preferably in the range of 20 μm to 1000 μm, more preferably in the range of 30 μm to 700 μm, and even more preferably in the range of 100 μm to 500 μm.

Details of the second substrate, such as its optical transparency, structure, and specific material, are the same as those of the first substrate described above in "A. Step [1] (1) First substrate."

Other members may be provided on one or both surfaces of the second substrate. When other members are provided on the second substrate, the entire second substrate provided with the other members exhibits the desired flexibility. Specific articles that can be used as the other members and the second substrate are the same as the examples of specific articles that can be used as the other members and the first substrate described above in "A. Step [1] (1) First Substrate". The first substrate and the second substrate may be the same or different.

(2) Step [3]
Step [3] is carried out within a predetermined time after step [2]. Specifically, the time from carrying out step [2] to carrying out step [3] may be less than 10 minutes, and is preferably within the range of 1 second to 8 minutes, more preferably within the range of 2 seconds to 6 minutes, and even more preferably within the range of 2 seconds to 5 minutes. By pressing the first adhesive sheet-attached substrate and the second substrate within a predetermined time after carrying out step [2], the second substrate and the adhesive layer of the first adhesive sheet-attached substrate can be sufficiently adhered to each other, and the usable time from carrying out step [2] to moving to step [3] can also be secured.

The pressure bonding temperature in the above step [3] may be 100°C or less, and is preferably in the range of 20°C to 100°C, more preferably in the range of 40°C to 90°C, and even more preferably in the range of 50°C to 85°C. By bonding the adhesive layer of the first adhesive sheet-attached substrate and the second substrate at the above pressure bonding temperature in step [3], thermal damage to the first substrate and the second substrate can be suppressed, and the adhesive layer of the first adhesive sheet-attached substrate and the second substrate can be sufficiently adhered to each other.

In step [3], the adhesive layer of the first adhesive sheet-attached substrate and the second substrate are preferably bonded together at a pressure in the range of 0.1 KPa to 3000 KPa, more preferably at a pressure in the range of 0.5 KPa to 1000 KPa, and even more preferably at a pressure in the range of 1.0 KPa to 500 KPa.

A longer compression time is preferable to ensure sufficient adhesion to the flexible second substrate, while a shorter compression time is preferable from the viewpoint of production efficiency in the lamination process. From the viewpoint of satisfying both requirements, the compression time is preferably in the range of 0.1 seconds to 10 minutes, more preferably in the range of 0.3 seconds to 5 minutes, and even more preferably in the range of 0.5 seconds to 3 minutes. By setting the compression force and compression time in step [3] within the above ranges, the adhesive layer of the first adhesive sheet-attached substrate and the second substrate can be sufficiently adhered without damaging the first substrate and the second substrate, and high bonding strength can be obtained.

In step [3], the adhesive strength of the adhesive layer of the first adhesive sheet-attached substrate when the second substrate is pressure-bonded is preferably within the range of 2N/20mm to 100N/20mm, more preferably within the range of 4N/20mm to 100N/20mm, and even more preferably within the range of 5N/20mm to 100N/20mm. By setting the adhesive strength of the adhesive layer of the first adhesive sheet-attached substrate when the second substrate is pressure-bonded within the above range, the second substrate is less likely to peel off from the first adhesive sheet-attached substrate.

The adhesive strength of the adhesive layer of the first adhesive sheet-attached substrate when the second substrate is pressed in step [3] is the adhesive strength when the first substrate and the second substrate are fixed to a jig and one substrate is peeled off in the vertical direction at a pulling speed of 5 mm/min for the laminate 5 minutes after step [3] is performed.

In the present invention, the storage modulus E' _25°C of the adhesive layer 5 minutes after carrying out the step [3], as measured by a dynamic viscoelasticity measuring device, is preferably 1.0 x ¹⁰⁸ Pa or more, more preferably 5.0 x ¹⁰⁸ Pa or more, and particularly preferably 1.0 x ¹⁰⁹ Pa or more. When the storage modulus E' _25°C of the adhesive layer 5 minutes after carrying out the step [3] is in the above range, sufficient rigidity can be imparted to the laminate. The higher the upper limit of the storage modulus E' _25°C of the adhesive layer 5 minutes after carrying out the step [3], the more desirable it is, and it can be, for example, 1.0 x ¹⁰¹² Pa, preferably 1.0 x ¹⁰¹¹ Pa, and more preferably 1.0 x ¹⁰¹⁰ Pa or less. "Five minutes after carrying out step [3]" or "five minutes after carrying out step [3]" refers to the time from laminating the second substrate to the adhesive layer of the first substrate with adhesive sheet until measurement is carried out; in other words, five minutes after carrying out step [3], the adhesive layer of the first substrate with adhesive sheet has the above-mentioned storage modulus E' _25°C .

The storage modulus _E'25°C of the adhesive layer 5 minutes after carrying out the step [3] is a value measured using a dynamic viscoelasticity measuring device at a frequency of 1.0 Hz and a temperature of 25°C, and can be measured by the following measurement method.
<Measurement method>
A laminate is prepared by carrying out steps [1] to [3] using release liners instead of the first substrate and the second substrate, and 5 minutes after carrying out step [3], a dumbbell cutter is used to punch out the laminate into the shape of a type 5 test piece according to JIS K 7127, and the release liners are removed to prepare a test piece of the cured adhesive layer (cured adhesive layer). The dynamic viscoelasticity of the test piece is measured using a dynamic viscoelasticity measuring device (manufactured by Rheometrics, Inc., product name: RSA-II), and the value measured at a frequency of 1.0 Hz and a temperature of 25°C is taken as the storage modulus E' _25°C .

The above step [3] is preferably carried out in a room temperature environment (for example, an atmosphere of 23°C). In addition, in the above step [3], after the adhesive layer of the first adhesive sheet-attached substrate and the flexible second substrate are pressure-bonded, the laminate in which the first adhesive sheet-attached substrate and the second substrate are laminated is preferably exposed to an environmental temperature in the range of 20°C to 80°C, more preferably to an environmental temperature in the range of 20°C to 60°C, and more preferably to an environmental temperature in the range of 20°C to 40°C. By exposing to the above-mentioned environmental temperature, the adhesive layer can be sufficiently cured while suppressing damage to the first substrate and the second substrate, and the first substrate and the second substrate can be firmly bonded via the cured adhesive layer (cured adhesive layer). In addition, when exposed to an environmental temperature higher than room temperature, the time until the curing reaction is completed can be further shortened.

The laminate in which the second substrate is bonded to the first substrate with adhesive sheet is preferably exposed to the above-mentioned environmental temperature for 60 minutes to 1 week, more preferably for 120 minutes to 3 days, and even more preferably for 180 minutes to 2 days. By exposing the laminate in which the second substrate is bonded to the first substrate with adhesive sheet for the desired time, the curing of the adhesive layer can be sufficiently completed, and the first substrate and the second substrate can be firmly bonded via the cured adhesive layer (cured adhesive layer).

The laminate after the above step [3] is able to have rigidity throughout the entire laminate due to the curing of the adhesive layer. In particular, it is preferable that the degree of curing (gel fraction) of the adhesive layer 5 minutes after the above step [3] is performed is within the range of the degree of curing (gel fraction) of the cured adhesive layer described in the section "F. Rigid Laminate" described below. In addition, it is preferable that the distance L measured when the above-mentioned rigidity test is performed on the laminate 5 minutes after the above step [3] is less than 45 mm, and more preferably 25 mm or less. By providing the laminate with the above-mentioned physical properties within 5 minutes after the step [3] is performed, sufficient rigidity is imparted to the obtained laminate within 5 minutes after the step [3] is performed, and therefore the manufacturing time of the rigid laminate can be shortened.

Furthermore, it is preferred that the storage modulus (E' ₂₅ ) at 25° C., measured at a frequency of 1.0 Hz, of the adhesive layer in the laminate 5 minutes after carrying out the above step [3] is within the range of the storage modulus (E' ₂₅ ) at 25° C., measured at a frequency of 1.0 Hz, of the cured adhesive layer described below in the section "F. Rigid Laminate". By providing the laminate with the above-mentioned physical properties within 5 minutes after carrying out step [3], sufficient rigidity is imparted to the obtained laminate within 5 minutes after carrying out step [3], and therefore the production time of the rigid laminate can be shortened.

Here, 5 minutes after carrying out step [3], or 5 minutes after carrying out step [3], refers to the time from bonding the second substrate to the first adhesive sheet-attached substrate to measurement; in other words, it is preferable that the adhesive layer of the first adhesive sheet-attached substrate and the laminate have the above-mentioned gel fraction and distance L 5 minutes after carrying out step [3], and it is also preferable that the adhesive layer have the above-mentioned storage modulus ( _E'25 ) 5 minutes after carrying out step [3].

D. Steps [4] to [6]
The method for producing the rigid laminate of the present invention includes at least the above-mentioned steps [1] to [3], and further includes the following steps [4] to [6]. By the manufacturing method including steps [1] to [6], it is possible to obtain a multi-layered rigid laminate including three or more layers of flexible substrates.

2 is a process diagram showing an example of the method for producing a rigid laminate of the present invention, showing steps [4] to [5]. First, in step [4] shown in FIG. 2(a), a second adhesive sheet 5 having an adhesive layer 5A containing at least a photocurable resin having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator is attached to one surface of a third substrate 4 having flexibility to obtain a second adhesive sheet-attached substrate 20. The second adhesive sheet 5 exemplified in FIG. 2 is a substrate-less adhesive sheet having only the adhesive layer 5A, but is not limited to this in the method for producing a rigid laminate of the present invention. Next, in step [5] shown in FIG. 2(b), the adhesive layer 5A of the second adhesive sheet-attached substrate 20 is irradiated with active energy rays X2. As a result, the adhesive layer 5A becomes an adhesive layer 5A' in which a curing reaction has started. Subsequently, in step [6] shown in FIG. 2(c) after step [5], the surface of the first substrate 2 of the first adhesive sheet-attached substrate 10, or the surface of the second substrate 3 opposite to the surface in contact with the first adhesive sheet-attached substrate 10, is pressure-attached to the adhesive layer 5A' of the second adhesive sheet-attached substrate 20. FIG. 2(c) shows an example in which the surface of the first substrate 2 of the first adhesive sheet-attached substrate 10 and the adhesive layer 5A' of the second adhesive sheet-attached substrate 20 are pressure-attached. FIG. 2(c) shows an example in which steps [3] and [6] are simultaneously performed by in-rolling, but steps [3] and [6] may be performed separately. Pressure-attaching is performed, for example, by pressing rollers Y1 and Y2 against the first adhesive sheet-attached substrate 10 or the second substrate 3, or the second adhesive sheet-attached substrate 20, respectively. Then, the curing reaction of the adhesive layer 5A' progresses and is completed, and the third substrate 4 is bonded to one side of the rigid cured adhesive layer (cured adhesive layer) 5A'', and the second substrate 3 and the second adhesive sheet-attached substrate 20 are bonded to the other side in no particular order, resulting in a rigid laminate 100 in which the first substrate, the second substrate 3, and the third substrate 4 are firmly bonded via the cured adhesive layers 2A'', 5A''. The rigid laminate 100 obtained by the process illustrated in Figures 2(a) to (c) has a layer structure in which the third substrate 4, the cured adhesive layer 5A'', the first substrate 1, the cured adhesive layer 2A'', and the second substrate 3 are laminated in this order.

(1) Step [4]
Step [4] is a step of attaching a second adhesive sheet having an adhesive layer containing at least a photocurable resin having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator to one surface of a flexible third substrate, to obtain a substrate with a second adhesive sheet.

Details regarding the second adhesive sheet and the third substrate in step [4] can be the same as those described for the first adhesive sheet and the first substrate in step [1].

The third substrate may be the same as or different from the first substrate. Also, the second adhesive sheet may be the same as or different from the first adhesive sheet.

(2) Step [5]
The step [5] is a step of irradiating the adhesive layer of the second adhesive sheet-attached substrate with active energy rays.

The details of step [5] can be the same as those of step [2].

Five minutes after carrying out the step [5], the gel fraction of the adhesive layer of the second adhesive sheet-attached substrate may be within the range of 35% to 95%, preferably within the range of 40% to 95%, more preferably within the range of 45% to 90%, and even more preferably within the range of 50% to 90%. This is because, during the period from carrying out the step [5] until carrying out the step [6], that is, in the step [6], when the adhesive layer of the second adhesive sheet-attached substrate and the first substrate or the second substrate of the first adhesive sheet-attached substrate are pressure-bonded to each other, the adhesive layer of the second adhesive sheet-attached substrate can retain flexibility that allows bonding to the substrate, while easily imparting the desired rigidity to the laminate after carrying out the step [6]. The gel fraction of the adhesive layer of the second adhesive sheet-attached substrate can be measured by the same method as the method for measuring the gel fraction of the adhesive layer of the first adhesive sheet-attached substrate described above.

(3) Step [6]
Step [6] is a step, which is performed after step [5], of pressing the adhesive layer of the second adhesive sheet-attached substrate onto a surface of the first substrate of the first adhesive sheet-attached substrate, or onto a surface of the second substrate opposite to a surface in contact with the first adhesive sheet-attached substrate.

In step [6], the adhesive layer of the second adhesive sheet-attached substrate and the surface of the first substrate of the first adhesive sheet-attached substrate (the surface of the first substrate opposite the surface that contacts the adhesive layer of the first adhesive sheet-attached substrate) may be bonded by pressure, or the adhesive layer of the second adhesive sheet-attached substrate and the surface of the second substrate opposite the surface that contacts the first adhesive sheet-attached substrate may be bonded by pressure.

The time between carrying out step [5] and carrying out step [6] may be less than 10 minutes, and is preferably within the range of 1 second to 8 minutes, more preferably within the range of 2 seconds to 6 minutes, and even more preferably within the range of 2 seconds to 5 minutes. By carrying out step [6] within the above time after carrying out step [5], the first substrate or the second substrate in the first substrate with adhesive sheet can be sufficiently adhered to the second substrate with adhesive sheet, and the usable time from carrying out step [5] to moving to step [6] can also be secured.

The bonding temperature in step [6] may be 100°C or less, and is preferably in the range of 20°C to 100°C, more preferably in the range of 40°C to 90°C, and even more preferably in the range of 50°C to 85°C. By setting the bonding temperature in step [6] within the above range, thermal damage to the first substrate, second substrate, and third substrate can be suppressed, and the adhesive layer of the second substrate with adhesive sheet can be sufficiently adhered to the second substrate or the first substrate.

The pressure and time required for compression in step [6], as well as the conditions for curing after compression, are the same as those described in "C. Step [3] (2) Step [3]".

The timing of performing step [6] is not particularly limited as long as it can be performed within a predetermined time from step [5], and it may be performed simultaneously with step [3] or after step [3]. In particular, it is preferable to perform step [3] and step [6] simultaneously. By performing step [3] and step [6] simultaneously, the manufacturing time can be shortened, and the first substrate, the second substrate, and the third substrate can be bonded more closely via the adhesive layer by pressing from above and below.

After carrying out the above step [6], the laminate can have rigidity throughout the entire laminate due to the progress of curing of the adhesive layer of the first adhesive sheet-attached substrate and the adhesive layer of the second adhesive sheet-attached substrate. In particular, it is preferable that the adhesive layer of the second adhesive sheet-attached substrate 5 minutes after carrying out the above step [6] is within the range of the degree of curing (gel fraction) of the cured adhesive layer described in the section "F. Rigid laminate" below.

In addition, the distance L measured when the above-mentioned stiffness test is performed on the laminate 5 minutes after the execution of the step [6] is preferably less than 45 mm, and more preferably 25 mm or less. Since sufficient stiffness is imparted to the laminate within 5 minutes after the execution of the step [6], the manufacturing time of the rigid laminate can be shortened.

Furthermore, it is preferable that the storage modulus ( _E'25 ) at 25°C of the adhesive layer in the laminate 5 minutes after carrying out the above step [6], measured at a frequency of 1.0 Hz, is within the range of the storage modulus ( _E'25 ) at 25°C of the cured adhesive layer, measured at a frequency of 1.0 Hz, described below in the section "F. Rigid Laminate".

E. Others The method for producing a rigid laminate of the present invention includes at least the above-mentioned steps [1] to [3]. The above steps [1] to [3] may be carried out independently, or may be carried out continuously in-line. In particular, it is preferable to carry out steps [1] to [3] continuously in-line. By carrying out a series of steps continuously in-line, it becomes possible to efficiently bond the first substrate and the second substrate via the adhesive layer, and the method for producing a rigid laminate of the present invention has excellent workability and productivity.

The method for producing a rigid laminate of the present invention can further include steps [4] to [6] in addition to the above-mentioned steps [1] to [3]. The above steps [4] to [6] may be carried out independently, or may be carried out continuously in-line. In particular, it is preferable to carry out steps [4] to [6] continuously in-line, and it is more preferable to carry out steps [1] to [6] continuously in-line. By carrying out a series of steps continuously in-line, it becomes possible to efficiently bond the first to third substrates via the adhesive layer, and the method for producing a rigid laminate of the present invention has excellent workability and productivity.

When each process is carried out continuously in-line, the conveying speed (line speed) of the first substrate, the first adhesive sheet, the substrate with the first adhesive sheet, and the second substrate is preferably 0.1 m/min or more and 100 m/min or less, more preferably 0.3 m/min or more and 50 m/min or less, and even more preferably 0.5 m/min or more and 20 m/min or less.

In addition to the above-mentioned steps [1] to [6], the method for producing the rigid laminate of the present invention may include the steps of: attaching the adhesive sheet described in the above section "A. Step [1] (1) Adhesive Sheet" to one side of a flexible substrate to obtain a substrate with an adhesive sheet; irradiating the adhesive layer of the substrate with the adhesive sheet with active energy rays; and, within less than 10 minutes after the irradiation of the active energy rays, pressing the adhesive layer of the substrate with an adhesive sheet having a gel fraction in the range of 50% to 90% at a pressing temperature of 100°C or less to the laminate obtained by steps [1] to [6]. A rigid laminate in which four or more substrates are bonded with a cured adhesive layer may be obtained.

The method for producing a rigid laminate of the present invention can be widely applied to the production of laminates that require thinness and rigidity, regardless of the type of laminate. In particular, the method for producing a rigid laminate of the present invention can be suitably used as a method for producing information recording media, more specifically, as a method for producing cards such as non-contact IC cards, and as a method for producing lightweight substrates.

F. Rigid Laminate The rigid laminate obtained by the manufacturing method of the present invention has at least a cured adhesive layer which is an adhesive layer after curing, the first substrate bonded to one side of the cured adhesive layer, and the second substrate bonded to the other side of the cured adhesive layer.

In addition, by carrying out the above-mentioned steps [1] to [6], the rigid laminate obtained by the manufacturing method of the present invention can have a configuration in which the first substrate, the second substrate, and the third substrate are bonded together via a cured adhesive layer, and can have a layer configuration in which, for example, the first substrate, the first cured adhesive layer, the second substrate, the second cured adhesive layer, and the third substrate are laminated in this order, or the second substrate, the first cured adhesive layer, the first substrate, the second cured adhesive layer, and the third substrate are laminated in this order.

The total thickness of the rigid laminate obtained by the manufacturing method of the present invention can be 60 μm or more, and preferably the total thickness is in the range of 60 μm to 10 mm, more preferably in the range of 100 μm to 10 mm, even more preferably in the range of 100 μm to 5 mm, and particularly preferably in the range of 200 μm to 1 mm. By keeping the total thickness of the rigid laminate within the above range, the desired rigidity can be achieved.

In the rigid laminate obtained by the manufacturing method of the present invention, the cured adhesive layer contains the cured product of the adhesive composition described in the above section "A. Step [1] (2) First adhesive sheet (a) Adhesive layer". The cured adhesive layer preferably has a curing rate of 70% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, and even more preferably 85% by mass or more and 100% by mass or less. When the cured adhesive layer has a curing rate within the above range, it is possible to firmly bond multiple flexible substrates together, and since the cured adhesive layer itself has the desired rigidity, the entire rigid laminate can also have the desired rigidity.

The curing rate of the cured adhesive layer can be expressed as the gel fraction, and is calculated based on the following formula from the mass of the cured adhesive layer remaining in toluene adjusted to 23°C after immersing the cured adhesive layer of the rigid laminate in the solvent for 24 hours and the mass of the adhesive layer before immersion in toluene.

Cure rate (gel fraction) (mass%) = {(mass of cured adhesive layer remaining undissolved in toluene) / (mass of cured adhesive layer before immersion in toluene)} x 100

The cured adhesive layer preferably has a storage modulus ( _E'25 ) at 25°C measured at a frequency of 1.0 Hz of 1.0 x ¹⁰⁹ Pa to 1.0 x ¹⁰¹² Pa, more preferably 1.0 x ¹⁰⁹ Pa to 1.0 x ¹⁰¹¹ Pa, and even more preferably 1.0 x ¹⁰⁹ Pa to 5.0 x ¹⁰¹⁰ Pa. This is because, when the storage modulus of the cured adhesive layer is within the above range, sufficient rigidity can be imparted to the laminate in which a flexible substrate is bonded via the cured adhesive layer.

The storage modulus of the cured adhesive layer was measured using a dynamic viscoelasticity measuring device (manufactured by Rheometrics, product name: RSA-II) at a frequency of 1 Hz and a temperature of 25°C. For the above measurement, a cured adhesive layer with a thickness of 100 μm was prepared and punched out using a dumbbell cutter into the shape of a test piece type 5 according to JIS K 7127.

The rigid laminate obtained by the manufacturing method of the present invention can be used in applications that require a thin and rigid body, such as cards such as contactless IC cards, and lightweight substrates that replace glass epoxy substrates.

This disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical ideas described in the claims of this disclosure and provides similar effects is included within the technical scope of this disclosure.

The present invention will be explained in more detail below with reference to examples and comparative examples.

<Preparation of Thermoplastic Resin (X-1)>
A reaction vessel was charged with 51 parts by mass of an aromatic polyester polyol having a number average molecular weight of 1,300 obtained by reacting an ethylene oxide 2-mol adduct of bisphenol A, phthalic acid, and adipic acid, 32 parts by mass of an aliphatic polyester polyol having a number average molecular weight of 3,500 obtained by reacting 1,6-hexanediol and dodecanedioic acid, 7 parts by mass of polypropylene glycol having a number average molecular weight of 1,000, and 2 parts by mass of an ethylene oxide 2-mol adduct of bisphenol A, and the mixture was dehydrated until the moisture content became 0.05% by mass by heating to 100° C. under reduced pressure conditions to obtain a mixture.

Next, the mixture was cooled to 70°C and mixed with 8.0 parts by mass of 4,4'-diphenylmethane diisocyanate, then the temperature was raised to 100°C and reacted for 3 hours until the hydroxyl group content became constant, to obtain a crystalline polyester polyurethane as a thermoplastic resin (X-1). The crystalline polyester polyurethane has a hydroxyl group as a polymerizable functional group.

<Preparation of Thermoplastic Resin (X-2)>
A reaction vessel was charged with 51 parts by mass of an aromatic polyester polyol having a number average molecular weight of 1,300 obtained by reacting an ethylene oxide 2-mol adduct of bisphenol A, phthalic acid, and adipic acid, 32 parts by mass of an aliphatic polyester polyol having a number average molecular weight of 3,500 obtained by reacting 1,6-hexanediol and dodecanedioic acid, 7 parts by mass of polypropylene glycol having a number average molecular weight of 1,000, and 2 parts by mass of an ethylene oxide 2-mol adduct of bisphenol A, and the mixture was dehydrated until the moisture content became 0.05% by mass by heating to 100° C. under reduced pressure conditions to obtain a mixture.

Next, the mixture was cooled to 70°C and mixed with 8.0 parts by mass of 4,4'-diphenylmethane diisocyanate, then the temperature was raised to 100°C and reacted for 3 hours until the hydroxyl group content became constant, to obtain a crystalline polyester polyurethane as a thermoplastic resin (X-2). The crystalline polyester polyurethane has a hydroxyl group as a polymerizable functional group.

<Preparation of Adhesive Sheet (Y-1)>
An adhesive solution containing an adhesive composition was obtained by mixing and stirring 40 parts by mass of a thermoplastic resin (X-1), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 2.5 parts by mass of a sulfonium salt-based cationic photopolymerization initiator (manufactured by San-Apro Ltd., "CPI-100P", solids concentration 50%), and 10.0 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd., "Sylohorbic 603", average particle size 6.7 μm), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass.

Next, an adhesive solution containing the above adhesive composition was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side treated for release with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm. The film was then placed in a dryer at 85° C. for 5 minutes to dry, after which the exposed surface of the adhesive layer was bonded to the release-treated surface of release liner B (a 38 μm-thick polyethylene terephthalate film with one side treated for release with a silicone compound) using a hand roller, to obtain adhesive sheet (Y-1).

<Preparation of Adhesive Sheet (Y-2)>
An adhesive solution containing an adhesive composition was obtained by mixing and stirring 43 parts by mass of a thermoplastic resin (X-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 2.5 parts by mass of a sulfonium salt-based cationic photopolymerization initiator (manufactured by San-Apro Ltd., "CPI-100P", solids concentration 50%), and 10.0 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Corporation, "Sylohorbic 603", average particle size 6.7 μm), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass.

Next, an adhesive solution containing the above adhesive composition was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side treated for release with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm. The film was then placed in a dryer at 85° C. for 5 minutes to dry, after which the exposed surface of the adhesive layer was bonded to the release-treated surface of release liner B (a 38 μm-thick polyethylene terephthalate film with one side treated for release with a silicone compound) using a hand roller, to obtain adhesive sheet (Y-2).

<Preparation of Adhesive Sheet (Y-3)>
A thermosetting resin composition (X-3) was prepared by mixing 167 parts by mass of a methyl ethyl ketone solution (solid content 30% by mass) of a bisphenol A type epoxy resin (JER-1256 manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 8,000 g/eq.), 20 parts by mass of a bisphenol A type epoxy resin (850-S manufactured by DIC Corporation, epoxy equivalent 188 g/eq.), 30 parts by mass of a bisphenol A type epoxy resin (1055 manufactured by DIC Corporation, epoxy equivalent 475 g/eq.), 2.0 parts by mass of dicyandiamide (DICY-7 manufactured by Mitsubishi Chemical Corporation), and 1 part by mass of 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct (2MA-OK manufactured by Shikoku Chemical Industry Co., Ltd.).

The above thermosetting resin composition (X-3) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side treated for release with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm.

Next, the coated product was placed in a dryer at 85°C for 5 minutes to dry, after which the exposed surface of the adhesive layer was bonded to the release-treated surface of release liner B (a 38 μm-thick polyethylene terephthalate film with one side release-treated with a silicone compound) using a hand roller to obtain an adhesive sheet (Y-3) with a thickness of 150 μm.

<Preparation of Adhesive Sheet (Y-4)>
In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen gas inlet, 44.9 parts by mass of butyl acrylate, 50 parts by mass of 2-ethylhexyl acrylate, 2 parts by mass of acrylic acid, 3 parts by mass of vinyl acetate, 0.1 parts by mass of 4-hydroxybutyl acrylate, and 0.1 parts by mass of 2,2'-azobisisobutylnitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate, and polymerized at 70°C for 10 hours, thereby obtaining an acrylic copolymer solution having a weight average molecular weight of 800,000.

Next, 40 parts by mass of polymerized rosin ester tackifier resin (Pensel D-160, manufactured by Arakawa Chemical Industries, Ltd., softening point 150-160°C) was added to 100 parts by mass of the acrylic copolymer, ethyl acetate was added and mixed, and then 1.1 parts by mass of an isocyanate crosslinking agent (Coronate L-45, manufactured by Nippon Polyurethane Industry Co., Ltd., solid content 45% by mass) was added and stirred for 15 minutes to obtain a pressure-sensitive adhesive solution (X-4).

Next, the pressure-sensitive adhesive solution (X-4) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side treated for release with a silicone compound) using a rod-shaped metal applicator so that the dried thickness would be 150 μm. The film was then placed in a dryer at 85°C for 15 minutes to dry, after which the exposed surface of the adhesive layer was bonded to the release-treated surface of release liner B (a 38 μm-thick polyethylene terephthalate film with one side treated for release with a silicone compound) using a hand roller, and the film was left in a 40°C environment for 2 days to obtain adhesive sheet (Y-4).

Example 1
Step [1]: The adhesive sheet (Y-1) was cut to a size of 20 mm wide x 100 mm long to prepare a test sample. The release liner B of the test sample was removed to expose the surface of the adhesive layer in the adhesive sheet (Y-1), and a 100 μm thick polyethylene terephthalate film (melting point 255° C.) cut to a size of 20 mm wide x 100 mm long was pressed together as a first substrate at a pressure of 0.05 MPa for 5 seconds in a temperature environment of 23° C. to obtain a first substrate with adhesive sheet.

Step [2]: Next, the surface of the first adhesive sheet-attached substrate having the release liner A facing up was irradiated with ultraviolet light having an intensity of about 100 mW/ ^cm2 for 10 seconds using an electrodeless lamp (Fusion Lamp H bulb).

Step [3]: After the above-mentioned UV irradiation, the first adhesive sheet-attached substrate was left in a temperature environment of 23°C for 2 minutes, and then the release liner A of the first adhesive sheet-attached substrate was removed to expose the surface of the adhesive layer of the first adhesive sheet-attached substrate, and a 100 μm-thick polyethylene terephthalate film cut to a size of 20 mm wide x 100 mm long was pressed and bonded to the second substrate with a pressure of 0.5 MPa for 2 seconds using a heat press machine heated to 80°C, and the two were left in a temperature environment of 23°C for 5 minutes and cooled to obtain an evaluation sample of the laminate (Z-1).

Example 2
Except for the fact that the temperature of the hot press in the above step [3] was heated to 90°C, steps [1], [2] and [3] were carried out in the same manner as in Example 1, to obtain an evaluation sample (Z-2) of the laminate.

Example 3
Except for using the adhesive sheet (Y-2) instead of the adhesive sheet (Y-1), steps [1], [2] and [3] were carried out in the same manner as in Example 1, to obtain a laminate evaluation sample (Z-3).

Example 4
After carrying out the above step [2], steps [1], [2] and [3] were carried out in the same manner as in Example 1, except that the first adhesive sheet-attached substrate after ultraviolet irradiation was left in a temperature environment of 23°C for 9 minutes, thereby obtaining an evaluation sample (Z-4) of the laminate.

(Comparative Example 1)
Steps [1], [2] and [3] were carried out in the same manner as in Example 1, except that ultraviolet light was not irradiated in the above step [2], to obtain an evaluation sample (Z-5) of the laminate.

(Comparative Example 2)
Steps [1], [2], and [3] were carried out in the same manner as in Example 1, except that the time from carrying out the step [2] to carrying out the step [3] was 120 minutes, to obtain an evaluation sample (Z-6) of the laminate.

(Comparative Example 3)
Steps [1], [2], and [3] were carried out in the same manner as in Example 1, except that the temperature of the hot press in the above step [3] was heated to 150° C., to obtain an evaluation sample (Z-7) of the laminate.

(Comparative Example 4)
Steps [1], [2], and [3] were carried out in the same manner as in Example 1, except that the adhesive sheet (Y-3) was used instead of the adhesive sheet (Y-1), to obtain a laminate evaluation sample (Z-8).

(Comparative Example 5)
Except for using the adhesive sheet (Y-3) instead of the adhesive sheet (Y-1) and heating the temperature of the hot press in the step [3] to 150° C., steps [1], [2] and [3] were carried out in the same manner as in Example 1, to obtain an evaluation sample (Z-9) of the laminate.

(Comparative Example 6)
Steps [1], [2], and [3] were carried out in the same manner as in Example 1, except that the adhesive sheet (Y-4) was used instead of the adhesive sheet (Y-1), to obtain an evaluation sample (Z-10) of a laminate.

<Evaluation 1> Storage modulus E' of adhesive layer 5 minutes after carrying out step [3] _{at 25°C}
Instead of the first substrate and the second substrate (both 100 μm thick polyethylene terephthalate films) used in the examples and comparative examples, a release liner C (a 100 μm thick polyethylene terephthalate film with one side subjected to release treatment with a silicone compound) was used to prepare an evaluation sample of the laminate in the same manner as in each of the examples and comparative examples. Five minutes after the step [3] was performed, the specimen was punched out into the shape of a test piece type 5 of JIS K 7127 using a dumbbell cutter, and the release liner C was removed to obtain a test piece of the cured adhesive layer (cured adhesive layer). The dynamic viscoelasticity of the test piece was measured using a dynamic viscoelasticity measuring device (manufactured by Rheometrics, product name: RSA-II), and the storage modulus (E') at a frequency of 1.0 Hz and a temperature of 25°C was measured. The storage modulus E' _25°C measured using the test piece was taken as the storage modulus E' _25°C of the adhesive layer 5 minutes after the step [3] was performed in each of the examples and comparative examples.

<Evaluation 2> Gel fraction of adhesive layer 5 minutes after carrying out step [2] Instead of the first substrate and the second substrate (both 100 μm thick polyethylene terephthalate films) used in the examples and comparative examples, a release liner C (a 100 μm thick polyethylene terephthalate film with one side treated for release with a silicone compound) was used, and steps [1] and [2] were carried out in the same manner as in each example and comparative example. Five minutes after carrying out step [2], the release liner C was peeled off to remove the adhesive layer, and the adhesive layer was immersed in toluene adjusted to 23° C. for 24 hours. The gel fraction was calculated based on the following formula from the mass of the adhesive layer remaining in the solvent after drying and the mass of the adhesive layer before immersion in toluene.

Gel fraction (mass%) = {(mass of adhesive layer remaining undissolved in toluene) / (mass of adhesive layer before immersion in toluene)} x 100

<Evaluation 3> Temporary fixation (adhesiveness) after step [1]
After carrying out step [1] in the Examples and Comparative Examples and before carrying out step [2], the temporary fixation property was evaluated based on the degree of adhesion of the adhesive sheet to the polyethylene terephthalate film, which is the first substrate, when the release liner A was removed from the first adhesive sheet-attached substrate, according to the following criteria.

◯: The release liner can be removed without the adhesive sheet peeling off from the first substrate (polyethylene terephthalate film).
Δ: The adhesive sheet is partially peeled off from the first substrate (polyethylene terephthalate film), but the release liner can be removed.
x: The adhesive sheet peeled off from the first substrate (polyethylene terephthalate film), and the release liner could not be removed.

<Evaluation 4> Adhesion to substrate after step [3] For the laminates produced in the Examples and Comparative Examples, 5 minutes after step [3] was performed, the laminates were curved so as to fit around a metal cylinder having a diameter of 100 mm and held for 10 seconds, and then the evaluation samples were observed and evaluated according to the following criteria.

A: No change in appearance. The adhesive sheet was not peeled off from either the polyethylene terephthalate film of the first substrate or the polyethylene terephthalate film of the second substrate.
x: Peeling of the adhesive sheet was observed from the polyethylene terephthalate film of at least one of the first and second substrates.

<Evaluation 5> Rigidity of the laminate after step [3] For the evaluation sample S of the laminate prepared in the examples and comparative examples, 5 minutes after step [3] was performed, as shown in FIG. 3, an area of 10 mm from one end A in the longitudinal direction X of the evaluation sample S (length in the longitudinal direction X: 100 mm, length in the transverse direction Y: 20 mm) was fixed, and the position of the other end B of the evaluation sample S before the load was applied was set as a reference O. Next, a load W of 5 g was applied to the fixed end B of the evaluation sample S, and the end B was left for 5 seconds, after which the position P of the end B of the evaluation sample S in the vertical (load) direction Z was measured. The distance L from the position (reference O) of the end B of the evaluation sample S before the load W was applied to the position P of the end B of the evaluation sample S when the load W was applied was calculated, and the rigidity was evaluated according to the following criteria.

◯: 25mm or less △: 25mm or more but less than 45mm ×: 45mm or more

When the first and second substrates (both 100 μm thick polyethylene terephthalate films) used in the examples and comparative examples were measured using the same test method, the distance L exceeded 45 mm, indicating flexibility.

<Evaluation 6> Appearance of Evaluation Samples after Step [3] The evaluation samples of the laminates prepared in the Examples and Comparative Examples were visually observed after step [3], and the appearance was evaluated according to the following criteria.

Good: No warping was observed in the evaluation sample, and no deformation such as wrinkles was observed in either the polyethylene terephthalate film of the first substrate or the second substrate.
x: The evaluation sample is warped or curved, or at least one of the polyethylene terephthalate films of the first substrate and the second substrate is deformed and wrinkles are observed.

The results of the examples and comparative examples are shown in the table below.

Although not shown in the table, in Comparative Example 7, an adhesive sheet with a general-purpose photocurable adhesive layer was used instead of the adhesive sheet (Y-1) used in Example 1. The adhesive layer of the adhesive sheet was completely cured immediately after step [2] was performed, and when the temperature during compression in step [3] was 100°C or lower, the adhesive did not adhere to the polyethylene terephthalate film, which was the second substrate, and a rigid laminate was not obtained.

REFERENCE SIGNS LIST 1...First substrate having flexibility 2...First adhesive sheet 2A...Adhesive layer 2A'...Adhesive layer of first adhesive sheet in which curing reaction has started 2A''...Adhesive layer of first adhesive sheet after curing (cured adhesive layer)
3: Second substrate having flexibility 4: Third substrate having flexibility 5: Second adhesive sheet 5A: Adhesive layer of second adhesive sheet 5A': Adhesive layer of second adhesive sheet in which curing reaction has started 5A'': Adhesive layer of second adhesive sheet after curing (cured adhesive layer)
10...first adhesive sheet-attached substrate 20...second adhesive sheet-attached substrate 100...rigid laminate X1, X2...active energy rays

Claims (10)

A step [1] of attaching a first adhesive sheet having an adhesive layer containing at least a photocurable resin having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator to one side of a first substrate having flexibility to obtain a substrate with a first adhesive sheet;
A step [2] of irradiating the adhesive layer of the first adhesive sheet-attached substrate with active energy rays;
After the step [2], a step [3] of pressure-bonding the adhesive layer of the first adhesive sheet-attached substrate to a flexible second substrate;
At least
5 minutes after carrying out the step [2], the gel fraction of the adhesive layer of the first adhesive sheet-attached substrate is within the range of 35% to 90%,
the time from carrying out the step [2] to carrying out the step [3] is less than 10 minutes;
The compression temperature in the step [3] is 100° C. or less,
A method for producing a rigid laminate, wherein the adhesive layer has a storage modulus E'25°C of 1.0 x ¹⁰⁹ Pa or more 5 minutes after carrying out the step [3], as measured by a dynamic viscoelasticity measuring device . The method for producing a rigid laminate according to claim 1, wherein the thickness of the adhesive layer is within the range of 20 μm to 5000 μm. The method for producing a rigid laminate according to claim 1 or 2 , wherein the thickness of the first substrate and the second substrate is in the range of 20 μm to 1000 μm. The method for producing a rigid laminate according to any one of claims 1 to 3 , wherein at least one of the first substrate and the second substrate has a transmittance of 80% or less for light having a wavelength of 200 nm to 780 nm. The method for producing a rigid laminate according to any one of claims 1 to 4 , wherein at least the steps [1] to [3] are carried out continuously in-line. a step [4] of attaching a second adhesive sheet having an adhesive layer containing at least a photocurable resin having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator to one surface of a flexible third substrate to obtain a substrate with a second adhesive sheet;
A step [5] of irradiating the adhesive layer of the second adhesive sheet-attached substrate with active energy rays;
After the step [5], a step [6] of pressure-bonding the adhesive layer of the second adhesive sheet-attached substrate to a surface of the first substrate of the first adhesive sheet-attached substrate or to a surface of the second substrate opposite to a surface in contact with the first adhesive sheet-attached substrate;
having
5 minutes after carrying out the step [5], the gel fraction of the adhesive layer of the second adhesive sheet-attached substrate is within the range of 35 to 90%,
the time from carrying out the step [5] to carrying out the step [6] is less than 10 minutes;
The method for producing a rigid laminate according to any one of claims 1 to 5 , wherein the pressure bonding temperature in the step [6] is 100°C or less. The method of claim 6 , wherein the thickness of the adhesive layer of the second adhesive sheet is in the range of 20 μm to 5000 μm. The method for producing a rigid laminate according to claim 6 or 7 , wherein steps [4] to [6] are carried out continuously in-line. The method for producing a rigid laminate according to any one of claims 6 to 8 , wherein the steps [3] and [6] are carried out simultaneously. The method for producing a rigid laminate according to any one of claims 1 to 9, wherein the rigid laminate has at least a cured adhesive layer, the first substrate bonded to one side of the cured adhesive layer, and the second substrate bonded to the other side of the cured adhesive layer, and has a total thickness in the range of 60 μm to 10 mm.

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