Method for manufacturing a laminate

Abstract

The present application relates to a manufacturing method of a laminate, which is a manufacturing method of a laminate having a support and a light-transmissive resin layer peelably arranged on the support, wherein the manufacturing method includes: a step of applying a resin solution for forming the light-transmissive resin layer on the support so that the ratio a / b of the application thickness a (μm) to the thickness b (μm) of the support is 0.5 to 5.8; a step of drying the coating film of the resin solution by heating; a step of adjusting the curling amount of the width direction end portion of the support having the coating film to 5 to 50 mm while maintaining the temperature lower than the temperature at the time of heating; and a step of performing a heating treatment on the support having the coating film whose curling amount has been adjusted.

Description

Technical Field

[0001] This invention relates to a method for manufacturing laminates. Background Technology

[0002] Optical films with light transmittance are used for a variety of applications. As an example, polarizing protective films for various displays are known.

[0003] In addition, foldable displays have been actively developed in recent years. Foldable displays have a UTG (Underglass Cover Glass) on the display surface. To prevent the UTG from breaking due to impact, an impact-resistant film is provided on the surface or back side (device body side) of the UTG.

[0004] These optical films, such as impact-resistant films and polarizer protective films, require further thinning, for example, from the perspective of improving bending resistance.

[0005] In contrast, a peelable laminated film having a substrate film (support) and a transparent film (transparent resin layer) is known (e.g., Patent Document 1). This peelable laminated film is used by attaching the transparent film to a polarizer and peeling off the substrate film to attach the transparent film of the thin film to the polarizer or the like.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2018-41028 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] However, when the conventional light-transmitting film, as shown in Patent Document 1, is laminated with other components, and then exposed to high temperature and humidity after lamination, air ingress is likely to occur. For example, when using the light-transmitting film as the impact-resistant film for the foldable display, the light-transmitting film is first laminated to a release film with an adhesive layer in a roll-to-roll manner, and after the adhesive layer is transferred onto the light-transmitting film, the cover glass is laminated. When this light-transmitting film is laminated to the release film with an adhesive layer, air ingress is likely to occur, or when exposed to high temperature and humidity after lamination, air ingress is likely to occur. Due to such air ingress, the impact resistance of the laminated cover glass unit is sometimes reduced.

[0011] Thus, not limited to use as an impact-resistant membrane, it is desirable to suppress air ingress when bonding a transparent membrane to other components.

[0012] The present invention was made in view of the above circumstances, and its object is to provide a method for manufacturing a laminate that can suppress the mixing of air during or after lamination and fully utilize the function of the light-transmitting film (light-transmitting resin layer).

[0013] means of solving technical problems

[0014] The aforementioned technical problem can be solved through the following solutions.

[0015] The manufacturing method of the laminate of the present invention is a method for manufacturing a laminate having a support and a light-transmitting resin layer peelably disposed on the support, wherein the manufacturing method includes: a step of coating the support with a resin solution for forming the light-transmitting resin layer, such that the ratio a / b of the coating thickness a (μm) to the thickness b (μm) of the support is 0.5 to 5.8; a step of heating the coating of the resin solution to dry it; a step of adjusting the curl of the width direction end of the support having the coating to 5 to 50 mm while maintaining it at a temperature lower than the temperature during heating; and a step of heat-treating the support having the coating after the curl has been adjusted.

[0016] Invention Effects

[0017] According to the present invention, a method for manufacturing a laminate that can suppress air ingress during bonding and fully utilize the function of the light-transmitting film can be provided. Attached Figure Description

[0018] Figure 1A ~C is a cross-sectional schematic diagram showing the bonding method of the laminated body using this embodiment.

[0019] Figure 2 This is a cross-sectional schematic diagram showing the amount of curling of the coated support in this embodiment.

[0020] Figure 3 This is a schematic diagram of the manufacturing apparatus for the laminate in this embodiment.

[0021] Figure 4 This is a cross-sectional schematic diagram showing the structure of the display device in this embodiment. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0023] Figure 1A ~C is a cross-sectional schematic diagram showing the bonding method of the laminate 100 using this embodiment. Figure 2 These are cross-sectional schematic diagrams showing the curling amount H of the coated support in this embodiment. These diagrams show cross-sections in the width direction of the strip-shaped laminate 100.

[0024] As described above, before bonding the light-transmitting resin layer 120 (of the laminate 100) to the cover glass (not shown) via the adhesive layer 220 in a roll-to-roll manner, the light-transmitting resin layer 120 is bonded to the adhesive layer 220 formed on the release film 210. Figure 1A and Figure 1B An adhesive layer 220 is transferred onto the translucent resin layer 120 (see reference). Figure 1C The inventors have discovered that by pre-curling the laminate 100 at both ends in the width direction toward the translucent resin layer 120 in a moderate manner during bonding, the distribution of stress remaining in the translucent resin layer is reduced (see reference). Figure 1A It can suppress the lifting caused by the mixing of air during and after bonding.

[0025] The mechanism is not yet clear, but the following is a speculation.

[0026] If the laminate is not curled or has very little curling, as is the case with conventional laminates, the transparent resin layer of the film lacks toughness, making it prone to wrinkling when bonded to the adhesive layer 220, and easily allowing air to get in. Furthermore, even if the laminate is moderately curled, if residual local stress remains, when exposed to a high temperature and humidity environment after bonding, the thermal deformation of the transparent resin layer 120 caused by this residual local stress can easily lead to air ingress.

[0027] In contrast, by pre-curling the laminate 100 to a moderate degree, the back side of the central portion of the laminate 100 in the width direction is sufficiently supported by the roller surface. Therefore, when it is bonded to the adhesive layer 220, it can easily adhere tightly to the adhesive layer 220 in the width direction at its central portion. As a result, air can be easily squeezed out from the central portion in the width direction toward both ends during bonding, and air ingress is less likely to occur. Furthermore, by uniformly distributing the residual stress of the light-transmitting resin layer (pre-eliminating local residual stress), air ingress when exposed to high temperature and high humidity environments after bonding can also be suppressed.

[0028] Such a laminate 100 can be obtained by a curl amount adjustment process after the drying process, in which the curl amount is adjusted to a given range by maintaining a relatively low temperature, and a process of heat-treating the support with the coating film.

[0029] That is, in the curl amount adjustment process, the residual stress of the laminate 100 generated in the drying process can be fixed. On the other hand, the residual stress fixed in the curl amount adjustment process is not uniform in the width direction, so if exposed to high temperature and high humidity after lamination, lifting cannot be suppressed. In contrast, by further performing a heat treatment process, the distribution of residual stress in the width direction of the translucent resin layer can be made uniform. As a result, the curl amount of the obtained laminate is adjusted to an appropriate range, and the deviation of residual stress is reduced, thus suppressing the mixing of air during lamination.

[0030] It should be noted that the curling amount of the laminate 100 roughly corresponds to the curling amount of the coated support in the curling amount adjustment process; the curling amount of the coated support in the curling amount adjustment process can be adjusted by the ratio of the coating thickness a of the resin solution to the support thickness a / b in the coating process, the tensile modulus of elasticity of the coating film, the heating temperature T1 in the drying process, and the air temperature T2 in the curling amount adjustment process, etc. Furthermore, the distribution of residual stress in the translucent resin layer can be adjusted by the heating temperature T3 in the heat treatment process (after the curling amount adjustment process), etc. The structure of the present invention will be described below.

[0031] 1. Manufacturing method of laminated body

[0032] The manufacturing method of the laminate in this embodiment includes: 1) a process of coating a resin solution onto a support (coating process); 2) a process of heating and drying the resin solution coating (drying process); 3) a process of adjusting the curl amount of the support with the coating (curl amount adjustment process); and 4) a process of heat-treating the support with the coating after the curl amount has been adjusted (heat treatment process).

[0033] 1) Coating process

[0034] A resin solution for forming a transparent resin layer is applied to the support.

[0035] Regarding the support, there are no particular limitations as long as it can support the light-transmitting resin layer; it can typically be a resin film. Examples of resin films include: polyester films (such as polyethylene terephthalate (PET), polypropylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), etc.), cyclic olefin resin films (COP), acrylic resin films, cellulose resin films (cellulose triacetate film (TAC), etc.), and other thermoplastic resin films. Among these, polyester films such as PET films are preferred from the viewpoint of versatility and sufficient strength.

[0036] There is no particular limitation on the thickness of the support, but it is preferably 10 μm to 100 μm, and more preferably 25 μm to 50 μm.

[0037] The support preferably further comprises a release layer on its surface. The release layer may contain a known release agent or mold release agent. Examples of release agents include polysiloxane-based release agents and non-polysiloxane-based release agents. The thickness of the release layer is not particularly limited as long as it exhibits the desired degree of peelability, and is preferably 0.1 to 1.0 μm.

[0038] The resin solution comprises a thermoplastic resin and a solvent, and preferably also contains rubber particles. The composition of the resin solution will be described in detail later.

[0039] There are no particular limitations on the coating method of the resin solution; for example, it can be a known method such as back coating, gravure coating, spin coating, wire rod coating, or roller coating. Among these methods, back coating is preferred from the viewpoint of forming a thin and uniform coating film.

[0040] The coating thickness a (μm) of the resin solution is adjusted such that the ratio a / b to the thickness b (μm) of the support is in the range of 0.5 to 5.8. If the ratio a / b is 0.5 or higher, it is easy to adjust the curl amount to a certain value or higher; if it is 5.8 or lower, the curl amount will not become too large. Therefore, the curl amount at the width-direction end of the support with the coating film can be adjusted to the range described later. From the same point of view, the ratio a / b can preferably be adjusted to the range of 0.8 to 4.8. The coating thickness a can be set, for example, to 30 μm to 250 μm.

[0041] 2) Drying process (first heating process)

[0042] Next, the resin solution coated on the support is heated to remove the solvent (to dry it) and form a coating film.

[0043] Heating conditions (e.g., heating temperature, heating time, etc.) are not particularly limited and can be set to adjust the curl amount at the width-direction end of the coated support after the curl amount adjustment process to the range described later. The heating temperature T1 is preferably 60–140°C, more preferably 80–120°C. When the heating temperature is within this range, not only can the solvent be removed in a short time, but the curl amount can also be easily adjusted to the range described later, thus easily suppressing poor adhesion caused by floating. The heating temperature can be determined as the temperature of the heating air.

[0044] There is no particular limitation on the tensile modulus of elasticity of the coating film at the heating temperature T1, but it is preferably 1.6 GPa or less, more preferably 1.0 GPa or less. If the tensile modulus of elasticity of the coating film is below the upper limit, it has moderate softness, thus easily mitigating residual stress.

[0045] The tensile modulus of elasticity of the coating film can be determined by tensile testing according to JIS K7127 after peeling from the support. Specifically, the peeled coating film is cut into 1cm (TD direction) × 10cm (MD direction) samples and conditioned at 25°C and 60% RH for 24 hours. For the obtained samples, a tensile test is performed at the heating temperature T1 during the drying process to determine the tensile modulus of elasticity. The test is conducted with a chuck distance of 50.0mm and a tensile speed of 50mm / min.

[0046] The tensile modulus of elasticity of a coating film can be adjusted by its composition. For example, when the coating film contains rubber particles, the tensile modulus of elasticity tends to be lower.

[0047] 3) Curling amount adjustment process

[0048] Next, the coated support is maintained at a temperature T2 lower than the heating temperature T1 in the drying process, and the amount of curling at the width-direction end of the coated support is adjusted. Specifically, the coated support is conveyed for a certain period of time at a temperature T2 lower than the heating temperature T1, and the amount of curling and residual stress at the width-direction end of the coated support are fixed.

[0049] The curling of the support with the coating film is caused by shrinkage due to the removal of solvent from the coating film during the drying process, and thus occurs in a manner where both ends curl upwards towards the coating film side in the width direction (see reference). Figure 2 The amount of curl at the width-direction end of the support with the coating is adjusted to a range of 5 to 50 mm, preferably 15 to 35 mm. When the curl amount is 5 mm or more, it can suppress the mixing of air during bonding, and when it is less than 50 mm, it is easy to suppress poor bonding and bending at the width-direction end caused by excessive curl amount.

[0050] The amount of curl at the width-direction ends of the support with the coating film can be considered as the lowest portion of both width-direction ends relative to the surface of the coating film when the support with the coating film is placed on a horizontal plane. Figure 2 The height H (mm) of the coating surface on the support (at the center in the width direction) is measured. For example, an online measuring device KEYENCE LJ-X8200 is used. Specifically, the height of the coating surface on the support at 100 points along the length of the support is measured at both ends (lowest part) and the center (highest part) in the width direction. The average value of (height at both ends in the width direction - height at the center in the width direction) at each point is taken as the "curl amount".

[0051] As described above, the amount of curl at the width end of the support with the coating film can be adjusted by the ratio of the coating thickness a to the thickness of the support film a / b in the coating process, the tensile elastic modulus of the coating film, the heating temperature T1 in the drying process, and the air temperature T2 in the curl amount adjustment process.

[0052] From the viewpoint of adjusting the curling amount at the width-direction end of the support with the coating film to the aforementioned range, the air temperature T2 in the curling amount adjustment process is 10–40°C, preferably 15–35°C. The difference between the temperature T2 in the curling amount adjustment process and the heating temperature T1 in the drying process (T1–T2) can be set, for example, to 40–70°C. When (T1–T2) is below 70°C, rapid cooling is less likely, thus preventing the curling amount from becoming excessive. The holding time at the air temperature T2 is only necessary to adjust the curling amount to the given range; for example, it can be longer than the heating time in the drying process. For example, it can be set to 5 to 20 minutes.

[0053] Solvents (e.g., ketones, alcohols) originating from the resin solution may remain in the coating film. The amount of residual solvent is preferably less than 3% relative to the coating film. The content of residual solvent can be adjusted by the drying conditions of the resin solution.

[0054] The amount of residual solvent can be determined by headspace gas chromatography. In headspace gas chromatography, the sample is sealed in a container and heated. While the container is filled with volatile components, the gas in the container is rapidly injected into the gas chromatograph for mass analysis, simultaneously identifying the compounds and quantifying the volatile components.

[0055] 4) Heat treatment process (second heating process)

[0056] Then, the coated support with adjusted curl is further heat-treated. This yields a laminate containing a support and a translucent resin layer, and also homogenizes the distribution of residual stress.

[0057] Specifically, it is preferable to heat the coated support at a higher temperature than in the curling amount adjustment process. That is, the heating temperature T3 is not particularly limited as long as it is sufficient to achieve uniform stress distribution, but it is preferably higher than the air temperature T2 in the curling amount adjustment process. For example, the heating temperature T3 is preferably 60–140°C, more preferably 80–120°C. When the heating temperature T3 is above the lower limit, it is easier to achieve uniform stress distribution; when it is below the upper limit, it is less likely to impair transport stability. The heating temperature T3 can be determined as the temperature of the heating air. The heating time is sufficient to achieve uniform distribution of residual stress, and for example, it can be equal to or longer than the holding time of the curling amount adjustment process. For example, it can be set to 5 to 40 minutes.

[0058] In this embodiment, the laminate is preferably in the form of a strip, and therefore it is preferable to further perform step 5) of winding the strip-shaped laminate into a roll to form a roll.

[0059] 5) Winding process

[0060] The obtained strip-shaped laminate is wound into a roll in a direction orthogonal to its width direction to form a roll.

[0061] There is no particular limitation on the length of the strip-shaped laminate, for example, it can be about 100 to 10,000 m. In addition, the width of the strip-shaped laminate is preferably more than 1 m, and more preferably 1.3 to 4 m.

[0062] Regarding the resin solution:

[0063] The resin solution contains thermoplastic resin and solvent.

[0064] (Thermoplastic resin)

[0065] There are no particular restrictions on the thermoplastic resins contained in the resin solution, including (meth)acrylic resins, cyclic olefin resins, and cellulose esters.

[0066] (Meth)acrylate resins are polymers that contain at least structural units derived from methyl methacrylate. The polymer may further contain structural units other than those derived from methyl methacrylate. Examples of other structural units include: maleimides such as phenylmaleimide; alkyl (meth)acrylates such as adamantyl acrylate; and cycloalkyl (meth)acrylates such as 2-ethylhexyl acrylate.

[0067] Examples of (meth)acrylic resins include: polymethyl methacrylate, copolymers of methyl methacrylate, phenylmaleimide, and alkyl acrylate, etc.

[0068] The weight-average molecular weight (Mw) of (meth)acrylic resins is preferably 1 million or more, more preferably 1.5 million to 3 million. When the Mw of (meth)acrylic resins is above a certain value, the mechanical strength of the transparent resin layer can be improved. Mw can be determined by gel permeation chromatography (GPC) using polystyrene conversion.

[0069] Cycloolefin resins can be (co)polymers of norbornon monomers with polar groups. Norbornon monomers with polar groups are represented by the following formula (1).

[0070] [Chemical Formula 1]

[0071]

[0072] R in equation (1) 1 ~R 4At least one of the components is preferably a polar group, more preferably an alkoxycarbonyl group having 1 to 10 carbon atoms. Cycloolefin resins having structural units derived from norbornene monomers with polar groups are not only readily soluble in solvents, but also improve the glass transition temperature of the resulting film.

[0073] Preferred R 1 ~R 4 The remaining atoms are either hydrogen atoms or hydrocarbon groups. The hydrocarbon group has 1 to 10 carbon atoms, preferably 1 to 4, more preferably 1 or 2, and examples include alkyl and aryl groups.

[0074] For example, it could be R in equation (1) 1 R is a polar group. 2 R 3 and R 4 They can be hydrogen atoms or hydrocarbon groups; they can be R 1 and R 3 These are polar groups, R 2 and R 4 Each of the atoms is either a hydrogen atom or a hydrocarbon group. p and m are integers from 0 to 3. m+p is preferably 0 to 4, more preferably 0 to 2, and even more preferably m=1 and p=0.

[0075] Cycloolefin resins may further comprise structural units derived from other monomers capable of copolymerizing with norbornene monomers having polar groups. Examples of other monomers capable of copolymerization include: norbornene monomers without polar groups, cyclobutene, cyclopentene, and other cycloolefin monomers that do not have a norbornene backbone.

[0076] The Mw of cyclic olefin resins is not particularly limited, but is preferably 100,000 to 300,000, more preferably 120,000 to 200,000. Mw can be determined by the same method described above.

[0077] The preferred cellulose ester is cellulose triacetate (TAC).

[0078] In particular, the transparent resin layer of the film containing (meth)acrylic resin or cycloolefin resin lacks toughness and is prone to air ingress during bonding. Therefore, the manufacturing method of the laminate of the present invention is particularly effective.

[0079] The resin content is preferably 60% by mass or more, more preferably 70% by mass or more, relative to the solid content of the resin solution.

[0080] (Other ingredients)

[0081] The resin solution may further contain other components besides those described, as needed. Examples of other components include rubber particles, matting agents (microparticles), etc.

[0082] (rubber particles)

[0083] Rubber particles are particles containing a rubber-like polymer. The rubber-like polymer is a soft, cross-linked polymer with a glass transition temperature of 20°C or lower, preferably 0°C or lower, and more preferably -10°C or lower. Examples of such cross-linked polymers include butadiene-based cross-linked polymers, (meth)acrylic acid-based cross-linked polymers, and organosiloxane-based cross-linked polymers. From the viewpoint of having a small refractive index difference with (meth)acrylic acid resins and being less likely to impair the transparency of the transparent resin layer, (meth)acrylic acid-based cross-linked polymers are preferred, and acrylic acid-based cross-linked polymers (acrylic rubber-like polymers) are more preferred.

[0084] Acrylic rubber-like polymer (a) is a crosslinked polymer containing structural units derived from acrylates as the main component. Acrylic rubber-like polymer (a) is preferably a crosslinked polymer containing structural units derived from acrylates, structural units derived from other monomers that can copolymerize with them, and structural units derived from polyfunctional monomers having two or more free radical polymerizable groups (non-conjugated reactive double bonds) in one molecule.

[0085] The acrylate is preferably an alkyl acrylate, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, or n-butyl acrylate, in which the alkyl group has 1 to 12 carbon atoms. The content of the structural unit derived from the acrylate is preferably 40% to 90% by mass, more preferably 50% to 80% by mass, relative to all structural units. If the content of the acrylate is within the above range, it is easy to impart sufficient toughness to the protective film.

[0086] Other monomers that can be copolymerized are monomers other than multifunctional monomers among those that can copolymerize with acrylates. Examples of monomers that can be copolymerized include methacrylates such as methyl methacrylate; and styrene-based monomers such as styrene and methylstyrene. The content of structural units derived from other copolymerizable monomers is preferably 5% to 55% by mass, more preferably 10% to 45% by mass, relative to all structural units.

[0087] Examples of multifunctional monomers include: ethylene glycol di(meth)acrylate, diethylene glycol (meth)acrylate, and polyethylene glycol di(meth)acrylate. The content of structural units derived from multifunctional monomers relative to all structural units is preferably 0.05 to 10% by mass, more preferably 0.1 to 5% by mass. If the content of multifunctional monomers is 0.05% by mass or more, the degree of crosslinking of the obtained acrylic rubber-like polymer (a) is easily increased, and therefore the hardness and rigidity of the resulting translucent resin layer are not excessively damaged. If it is 10% by mass or less, the toughness of the translucent resin layer is not easily damaged.

[0088] The particles containing the acrylic rubber polymer (a) can be particles formed from the acrylic rubber polymer (a); or they can be particles formed from acrylic graft copolymers obtained by polymerizing a mixture of monomers such as methacrylates in the presence of the acrylic rubber polymer (a) for at least one stage, i.e., core-shell type particles having a core containing the acrylic rubber polymer (a) and a shell covering it.

[0089] The shell may include: a methacrylate polymer (b) grafted and bonded to an acrylic rubber-like polymer (a), comprising structural units derived from methacrylates as the main component. The methacrylate constituting the methacrylate polymer (b) is preferably an alkyl methacrylate with 1 to 12 carbon atoms, such as methyl methacrylate.

[0090] The average particle size of the rubber particles is preferably 100–400 nm, more preferably 150–300 nm. When the average particle size of the rubber particles is within this range, stress relief can be easily achieved without compromising the transparency of the transparent resin layer. The average particle size of the rubber particles can be determined as the dispersed particle size measured using a Zeta potential particle size measurement system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

[0091] The content of rubber particles is not particularly limited, but is preferably 5 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 7 to 30% by mass, relative to the resin content in the resin solution.

[0092] (Matte agent)

[0093] From the perspective of imparting smoothness to the film, matting agents can be added. Examples of matting agents include inorganic particles such as silica particles.

[0094] (solvent)

[0095] The solvent used in the resin solution is not particularly limited as long as it can effectively disperse the (meth)acrylic resin and rubber particles. Examples of solvents include: alcohols such as methanol and ethanol; ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetone; esters such as ethyl acetate and methyl acetate; glycol ethers (propylene glycol mono(C1-C4)alkyl ethers (specifically propylene glycol monomethyl ether (PGME)), propylene glycol monoalkyl ether esters (propylene glycol monomethyl ether acetate); and hydrocarbons such as toluene, benzene, and cyclohexane. From the viewpoint of easily dissolving (meth)acrylic resins, having high affinity for rubber particles, low boiling points, and easily improving drying speed and productivity, the solvent preferably includes ketones; and from the viewpoint of easily forming a highly planar, transparent resin layer, it is further preferable to include alcohols.

[0096] From the viewpoint that the viscosity can be easily adjusted to the range described later, the resin concentration of the resin solution is preferably, for example, 1.0 to 20% by mass.

[0097] Manufacturing equipment:

[0098] The method for manufacturing the laminate in this embodiment can, for example, be achieved by... Figure 3 The manufacturing process is carried out using the apparatus shown.

[0099] Figure 3 This is a schematic diagram of a manufacturing apparatus 300 used for implementing the manufacturing method of the laminated body according to this embodiment. The manufacturing apparatus 300 includes a supply unit 310, a coating unit 320, a drying unit 330, a winding amount adjustment unit 340, a heat treatment unit 350, and a winding unit 360. a and b represent the conveying rollers of the conveying support 110.

[0100] The supply unit 310 has a release device (not shown) for releasing the roll 301 of the strip-shaped support 110 wound around the core.

[0101] The coating section 320 is a coating apparatus for performing the coating process, and includes a support roller 321 for holding the support body 110, a coating head 322 for applying a resin solution to the support body 110 held by the support roller 321, and a pressure reducing chamber 323 provided on the upstream side of the coating head 322.

[0102] The depressurization chamber 323 is a mechanism for stabilizing the droplets (accumulation of coating liquid) formed between the resin solution originating from the coating head 322 and the support 110 during coating, and can adjust the depressurization degree. The depressurization chamber 323 is in a state of no air leakage, and the gap with the support roller is also adjusted to be narrower, which enables the formation of stable coating liquid droplets.

[0103] The drying unit 330 is a drying apparatus used to perform the drying process, which heats the coating film applied to the support 110 to dry it. The drying unit 330 may be configured to blow hot air at a temperature adjusted to the heating temperature T1, or it may be a heating furnace with regulated air temperature.

[0104] The curl amount adjustment unit 340 is a device for performing the curl amount adjustment process, which transports the coated support 110 in air at a temperature T2 that is adjusted to be lower than the heating temperature T1.

[0105] The heat treatment unit 350 is an apparatus for performing the heat treatment process, which heats the coated support 110 that has passed through the curling amount adjustment unit 340.

[0106] The winding section 360 is a winding device (not shown) for winding a support 110 (laminated body 100) having a light-transmitting resin layer 120 formed thereon to obtain a roll 361.

[0107] 2. Laminated body

[0108] The laminate obtained by the manufacturing method of the laminate according to this embodiment has a support and a light-transmitting resin layer that can be peeled off and disposed on the surface of the support (see reference). Figure 1A ).

[0109] The light-transmitting resin layer is obtained from the resin solution and is disposed on the support. The light-transmitting resin layer is used as an optical film such as an impact-resistant film bonded to the cover glass after being peeled off from the support, or a protective film (including a phase retardation film) bonded to a polarizer.

[0110] (Curling amount at both ends in the width direction)

[0111] The resulting laminate is also moderately curled at both ends in the width direction towards the translucent resin layer due to the manufacturing process. The amount of curling can be within the same range as described above.

[0112] (Phase difference Ro and Rt)

[0113] From the viewpoint of using a phase retardation film for IPS mode, the in-plane phase difference Ro of the transparent resin layer, measured at a measurement wavelength of 550 nm, 23°C, and 55% RH, is preferably 0 to 10 nm, more preferably 0 to 5 nm. The phase difference Rt in the thickness direction of the transparent resin layer is preferably -20 to 20 nm, more preferably -10 to 10 nm.

[0114] Ro and Rt are defined by the following formulas respectively.

[0115] Equation (2a): Ro=(nx-ny)×d

[0116] Formula (2b): Rt=((nx+ny) / 2-nz)×d

[0117] (in the formula,

[0118] nx represents the refractive index along the slow axis (the direction of maximum refractive index) of the transparent resin layer.

[0119] ny represents the refractive index in the direction orthogonal to the in-plane slow axis of the translucent resin layer.

[0120] nz represents the refractive index in the thickness direction of the translucent resin layer.

[0121] d represents the thickness (nm) of the transparent resin layer.

[0122] The in-plane slow axis of the light-transmitting resin layer can be confirmed using an automatic birefringence meter, AxoScan (Axo Scan Mueller Matrix Polarimeter: manufactured by AXOMETRICS).

[0123] Ro and Rt can be determined by the following methods.

[0124] 1) Condition the transparent resin layer at 23°C and 55% RH for 24 hours. Measure the average refractive index of the film using an Abbe refractometer and the thickness d using a commercially available micrometer.

[0125] 2) The phase differences Ro and Rt of the conditioned film at a measurement wavelength of 550 nm were measured using an automatic birefringence meter AxoScan (Axo Scan Mueller Matrix Polarimeter: AXOMETRICS) at an environment of 23°C and 55%RH.

[0126] (thickness)

[0127] There is no particular limitation on the thickness of the light-transmitting resin layer. From the viewpoint of achieving a thinner polarizer, it is usually thinner than the thickness of the support. Specifically, for example, it is preferably 0.1 to 35 μm, and more preferably 1 to 15 μm.

[0128] The laminate of this embodiment may further have other layers disposed between the support and the light-transmitting resin layer as needed.

[0129] The laminate obtained by the manufacturing method of this embodiment is as described above, wherein both ends in the width direction are moderately curled towards the translucent resin layer. This suppresses air ingress during bonding with other components described later, and prevents poor bonding such as lifting caused by this.

[0130] 3. Display device

[0131] The display device of this embodiment includes a display element and a polarizer as the main body of the display device.

[0132] The display element can be an organic EL element, a liquid crystal element (liquid crystal cell), etc. A polarizer is disposed on at least the visible side of the display element.

[0133] The display device may also include other components depending on its application. In the case of a foldable display, for example, a cover glass may be disposed on the visible side of the display device body through an impact-resistant film. The impact-resistant film may be a light-transmitting resin layer of the laminated body of this embodiment.

[0134] Figure 4This is a cross-sectional schematic diagram showing the structure of the display device 400 according to this embodiment. In this embodiment, an example of an organic EL display device is shown for the display device 400.

[0135] The display device 400 includes a display device body 400A comprising an organic EL element 410 (display element) and a polarizer 420 (circular polarizer), and a cover glass unit 500.

[0136] 3-1. Display device main body 400A

[0137] (Organic EL element)

[0138] The organic EL element 410 has a metal electrode 412, a light-emitting layer 413, a transparent electrode (ITO, etc.) 414 and a sealing layer 415 sequentially on a transparent substrate 411 such as a glass plate or a transparent film.

[0139] The metal electrode 412 can be used as a cathode. To facilitate electron injection and improve luminescence efficiency, the metal electrode 412 is preferably made of a material with a low work function, typically Mg-Ag or Al-Li.

[0140] The light-emitting layer 413 is a stack of organic thin films, such as a stack of a hole injection layer composed of a triphenylamine derivative and a light-emitting layer composed of a fluorescent organic solid such as anthracene, a stack of such a light-emitting layer and an electron injection layer composed of a perylene derivative, or a stack of such hole injection layers, light-emitting layers, and electron injection layers.

[0141] The transparent electrode 414 can be used as an anode. The transparent electrode 414 is typically made of a transparent conductor such as indium tin oxide (ITO).

[0142] The sealing layer 415 can be a transparent substrate such as a glass plate or a transparent film, or a sealing film such as a sealant.

[0143] Then, by applying a voltage between the metal electrode 412 and the transparent electrode 414, holes and electrons are injected into the light-emitting layer 413. The energy generated by the recombination of these holes and electrons excites the fluorescent material, which emits light when it returns to the ground state.

[0144] (Polarizing filter)

[0145] The polarizer 420 may be a circular polarizer disposed on the visible side of the organic EL element 410. Such a polarizer 420 has a polarizer 421, a protective film 422 disposed on its visible side, and a protective film 423 disposed between the polarizer 421 and the organic EL element 410.

[0146] The polarizer 421 can be, for example, a polyvinyl alcohol polarizing film. The protective film 423 is preferably a λ / 4 film, bonded such that the angle between the transmission axis (or absorption axis) of the polarizer 421 and the in-plane slow axis of the protective film 423 is 45 ± 15°. The protective film 422 can be a known polarizer protective film. Such a circular polarizer 420 can suppress the reflection of external light incident from outside the display device 400 due to indoor lighting, etc.

[0147] 3-2. Cover glass unit 500

[0148] The cover glass unit 500 has a cover glass 510, an adhesive layer 220, and a light-transmitting resin 120 as an impact-resistant film.

[0149] (Cover with glass)

[0150] The cover glass 510 is disposed on the most visible side of the display device body 400A. The thickness of the cover glass 510 can be, for example, 30μm to 50μm.

[0151] (Impact-resistant membrane)

[0152] An impact-resistant film is disposed between the display device body 400A and the cover glass 510. As an impact-resistant film, the light-transmitting resin layer 120 of the laminate 100 can be used.

[0153] 3-3. Manufacturing method of display device

[0154] The display device 400 can be obtained by 1) manufacturing the cover glass unit 500 and 2) bonding the display device body 400A with the cover glass unit 500.

[0155] 1) process

[0156] The cover glass unit 500 in this embodiment can be manufactured by a process of bonding the light-transmitting resin layer 120 of the laminate 100 to the cover glass 510 via an adhesive layer 220 and peeling off the support 110 of the laminate 100.

[0157] Specifically, it is preferable to bond the translucent resin layer 120 of the laminate 100 to the adhesive layer 220 formed on the release film 210 in a roll-to-roll manner, and then transfer the adhesive layer 220 onto the translucent resin layer 120. Figure 1A ~C), the cover glass 510 is further bonded to the adhesive layer 220 in a roll-to-roll manner.

[0158] At this point, the laminate 100 is moderately curled, so that the laminate 100 and the roller supporting it are in full contact at the center in the width direction. Therefore, the translucent resin layer 120 and the adhesive layer 220 of the laminate 100 easily adhere at the center in the width direction, and air is not easily mixed in during bonding. In addition, since the residual stress of the laminate 100 is homogenized, even when exposed to high temperature and high humidity after bonding, air is not easily mixed in due to thermal deformation of the translucent resin layer 120. Thus, lifting caused by poor bonding can be suppressed (see reference). Figure 1A ).

[0159] 2) process

[0160] By using adhesives or the like to attach the light-transmitting resin layer 120 (impact-resistant film) of the obtained cover glass unit 500 to the display device body 400A, the display device 400 can be obtained.

[0161] (Modified Example)

[0162] It should be noted that, in the embodiments described, an example is shown of using the light-transmitting resin layer of the laminate as an impact-resistant film, but it is not limited to this and can also be used as a protective film for polarizers.

[0163] Furthermore, in the embodiments described, an example is shown of using the light-transmitting resin layer of the laminate as an impact-resistant film for an organic EL display device, but it is not limited thereto and can also be used as a protective film for a liquid crystal display device, a transparent substrate for a display element, etc.

[0164] Example

[0165] The present invention will be specifically described below through embodiments, but the present invention is not limited to these embodiments.

[0166] 1. Materials of laminated bodies

[0167] 1-1. Support

[0168] <pet-1>

[0169] Polyethylene terephthalate film (TN100 manufactured by Toyobo Co., Ltd., with a release layer (containing a non-polysiloxane release agent), 50μm thick)

[0170] <pet-2>

[0171] Polyethylene terephthalate film (TN100 manufactured by Toyobo Co., Ltd., with a release layer (containing a non-polysiloxane release agent), 100μm thick)

[0172] <tac>

[0173] Cellulose triacetate membrane (Konica Minolta 4CT, no release layer, 40μm thick)

[0174] 1-2. Resin solution

[0175] (1) Preparation of materials

[0176] <Resin>

[0177] (Meth)acrylic resin: methyl methacrylate (MMA) / phenylmaleimide (PMI) / methyl acrylate (MA) copolymer (85 / 10 / 5 mass ratio) Mw: 2 million, Tg: 122℃

[0178] COP: Cyclic olefin resin G7810 (manufactured by JSR Corporation) (a cyclic olefin resin (COP) containing structural units derived from norbornene monomers as shown in the following formula, Mw: 110,000, Tg: 170℃)

[0179] [Chemical Formula 2]

[0180]

[0181] The glass transition temperature and weight-average molecular weight of the resin were determined by the following method.

[0182] (Glass transition temperature)

[0183] The glass transition temperature (Tg) of the resin was determined using DSC (Differential Scanning Colorimetry) according to JIS K7121-2012.

[0184] (weight-average molecular weight)

[0185] The weight-average molecular weight (Mw) of the resin was determined using gel permeation chromatography (HLC8220GPC, Tosoh Corporation) with a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL, Tosoh Corporation, in tandem). 20 mg ± 0.5 mg of the sample was dissolved in 10 mL of tetrahydrofuran and filtered through a 0.45 mm filter. 100 mL of this solution was injected into the column (temperature 40 °C), and the measurement was performed at the detector RI temperature of 40 °C, using values ​​converted to styrene.

[0186] <Rubber Particles>

[0187] Use rubber particles R1 manufactured by the following method.

[0188] The following substances were loaded into an 8L polymerization apparatus equipped with a mixer.

[0189] 180 parts by weight of deionized water

[0190] 0.002 parts by weight of polyoxyethylene lauryl ether phosphate

[0191] 0.4725 parts by weight of boric acid

[0192] Sodium carbonate 0.04725 parts by weight

[0193] Sodium hydroxide 0.0076 parts by weight

[0194] After fully purging the polymer with nitrogen to a temperature of 80°C, 0.021 parts by mass of potassium persulfate as a 2% aqueous solution were added. Then, over 63 minutes, a mixture consisting of 84.6% by mass of methyl methacrylate, 5.9% by mass of butyl acrylate, 7.9% by mass of styrene, 0.5% by mass of allyl methacrylate, and 1.1% by mass of n-octyl mercaptan (c') and 0.07 parts by mass of polyoxyethylene lauryl ether phosphate were continuously added to the solution. The polymerization reaction was then continued for another 60 minutes, thereby obtaining the innermost rigid polymer (c).

[0195] Then, 0.021 parts by mass of sodium hydroxide as a 2% by mass aqueous solution and 0.062 parts by mass of potassium persulfate as a 2% by mass aqueous solution were added, respectively. Next, a mixture containing 0.25 parts by mass of polyoxyethylene lauryl ether phosphate was continuously added over 117 minutes to 39 parts by mass of a monomer mixture (a') consisting of 80.0% by mass of butyl acrylate, 18.5% by mass of styrene, and 1.5% by mass of allyl methacrylate. After the addition was complete, 0.012 parts by mass of potassium persulfate was added as a 2% by mass aqueous solution, and the polymerization reaction continued for 120 minutes to obtain a soft layer (a layer composed of an acrylic rubber-like polymer (a)). The glass transition temperature (Tg) of the soft layer was -30°C. The glass transition temperature of the soft layer was calculated by averaging the glass transition temperatures of the homopolymers of each monomer constituting the acrylic rubber-like polymer (a) according to the composition ratio.

[0196] Then, 0.04 parts by mass of potassium persulfate were added to a 2% by mass aqueous solution, followed by the continuous addition of 26.1 parts by mass of a monomer mixture (b') consisting of 97.5% by mass of methyl methacrylate and 2.5% by mass of butyl acrylate over 78 minutes. The polymerization reaction was then continued for another 30 minutes to obtain polymer (b).

[0197] The obtained polymer was placed in a 3% (w / w) warm aqueous solution of sodium sulfate to allow it to salt out and solidify. Then, after repeated dehydration and washing, it was dried to obtain three-layer acrylic graft copolymer particles (rubber particles R1). The average particle size of the obtained rubber particles R1 was 200 nm.

[0198] The average particle size of the rubber particles was determined by the following method.

[0199] (Average particle size)

[0200] The dispersed particle size of rubber particles in the dispersion was determined using a Zeta potential-particle size measurement system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

[0201] (2) Preparation of resin solution

[0202] <Preparation of Resin Solution A>

[0203] Mix the following components to obtain a solution for a transparent resin layer.

[0204] Dichloromethane: 900 parts by weight

[0205] COP (Cycloolefin resin): 100 parts by weight

[0206] <Preparation of Resin Solutions B-F>

[0207] Except for changing the composition to that shown in Table 1, resin solutions B to F are obtained in the same manner as resin solution A.

[0208] The compositions of the obtained resin solutions A to F are shown in Table 1.

[0209] [Table 1]

[0210]

[0211] *The rubber particle content is expressed as a percentage of mass relative to the dried coating (transparent resin layer).

[0212] 2. Fabrication and evaluation of laminated structures

[0213] <Manufacturing of Laminated Body 1>

[0214] A PET film (PET-1) is prepared as a support. Resin solution A is coated onto the release layer of this PET film using a slit mold to achieve a coating thickness a (μm) as shown in Table 2, and then dried by heating at 80°C for 4 minutes. Next, the support coated with resin solution A is conveyed at 25°C and held for 10 minutes (curling amount adjustment process), and then further heated at 80°C for 20 minutes (heat treatment process). Thus, a laminate 1 having a support and a translucent resin layer is obtained.

[0215] <Manufacturing of Laminated Structures 2-7>

[0216] As shown in Table 2, the combination of the support and the resin solution and the thickness ratio a / b are changed. Otherwise, laminates 2 to 7 are obtained in the same manner as laminate 1.

[0217] <Manufacturing of Laminated Structures 8-11>

[0218] Except for the conditions for changing the curling amount adjustment process as shown in Table 2, laminates 8 to 11 are obtained in the same manner as laminate 3.

[0219] <Manufacturing of Laminated Structures 12-17>

[0220] The content of rubber particles in the resin solution or the heating temperature T1 in the drying process is changed as shown in Table 2. Otherwise, laminates 12 to 17 are obtained in the same manner as laminate 3.

[0221] <Manufacturing of Laminated Body 18>

[0222] Except for omitting the curling amount adjustment process and the heat treatment process, the laminate 18 is obtained in the same way as the laminate 14.

[0223] <Evaluation>

[0224] The following methods were used to evaluate the curling amount of the coated support, the tensile modulus of the coating, and the buoyancy and impact resistance of samples using laminates 1 to 18 during the manufacturing process of laminates 1 to 18.

[0225] (Amount of curl)

[0226] The amount of curl at the width-direction ends of a coated support was measured online. Specifically, using a KEYENCELJ-X8200, the heights at both ends (lowest part) and the center (highest part) of the coating surface on the support were measured at 100 points along the length of the support. The average value of (height at both ends in the width direction - height at the center in the width direction) at each point was taken as the "curl amount".

[0227] (Tensile elastic modulus of the coating)

[0228] (1) Shortly after the curling amount adjustment process

[0229] After the curling amount adjustment process is completed, the resulting coating is peeled off from the support, and the tensile modulus of elasticity is determined by tensile test based on JIS K7 127.

[0230] That is, the peeled coating film is cut into a sample of 1 cm (TD direction) × 10 cm (MD direction), and conditioned for 24 hours in an environment of 25°C and 60% RH. The obtained sample is set in a Tensilon tensile testing device manufactured by ORI ENTEC for a tensile test to measure the tensile elastic modulus. The measurement is carried out at a chuck distance of 50.0 mm, a tensile speed of 50 mm / min, and at the heating temperature T1 in the drying step. In addition, the measurement is performed in both the MD direction and the TD direction, and the average value of the tensile elastic moduli in each direction is taken as the "tensile elastic modulus".

[0231] (2) Immediately before the winding step

[0232] After the heat treatment step, the tensile elastic modulus of the coating film immediately before the winding step is measured in the same manner as described above. The measurement temperature is the heating temperature T1 in the curl amount adjusting step.

[0233] (Lifting)

[0234] The light-transmitting resin layer of the obtained laminate is bonded to a cover glass via an adhesive layer to obtain a sample of cover glass / adhesive layer / light-transmitting resin layer. It is visually observed whether lifting occurs when the obtained sample is stored at 80°C and 90% RH for 500 hours.

[0235] ◎: No lifting occurs in all 10 samples

[0236] ○: Lifting occurs in less than 2 out of 10 samples

[0237] △: Lifting occurs in 2 or more and less than 4 out of 10 samples

[0238] ×: Lifting occurs in 4 or more samples, or poor bonding with air bubbles entrained, and there is no evaluation value

[0239] △ or higher is qualified.

[0240] (Impact resistance)

[0241] For the samples manufactured for evaluating lifting, after storing at 80°C and 90% RH for 500 hours, the following impact resistance test is performed.

[0242] Place said sample on a stainless steel plate with a thickness of about 3 cm, with the light-transmitting resin layer facing the lower surface, and fix the four corners with adhesive tape. Then, visually observe the state of the sample when an iron ball (weight: 500 g, diameter: 50 mm) is dropped from a position 20 cm above the cover glass region.

[0243] ◎: No scattering (including cracking) of the cover glass occurs even once after 10 implementations

[0244] ○: Cases where scattering (including cracking) of the back cover glass is less than 2 times after 10 implementations

[0245] △: Cases where scattering (including cracking) of the back cover glass is 2 times or more and less than 4 times after 10 implementations

[0246] ×: Cases where scattering (including cracking) of the back cover glass is 4 times or more after 10 implementations

[0247] △ or above is qualified.

[0248] The production conditions and evaluation results of the obtained laminates 1 to 18 are shown in Table 2.

[0249] [Table 2]

[0250]

[0251] As shown in Table 2, it can be seen that laminates 1 to 3, 5, 6, 9, 10, and 12 to 17 obtained through a curl amount adjusting step in which the thickness ratio a / b satisfies the range of 0.5 to 5.8 and the curl amount becomes 5 to 50 mm can suppress lifting during lamination and obtain sufficient impact resistance.

[0252] In contrast, it can be seen that in laminates 4 and 7 in which the thickness ratio a / b does not satisfy the range of 0.5 to 5.8, and laminate 8 in which the temperature of the curl amount adjusting step exceeds 40°C, the curl amount cannot be adjusted to 5 to 50 mm in the curl amount adjusting step, and lifting during lamination cannot be suppressed. Furthermore, it can be seen that in laminate 18 which does not have the curl amount adjusting step and the heating treatment step, lifting after lamination cannot be suppressed.

[0253] The present application claims priority based on Japanese Patent Application No. 2021-146875 filed on September 9, 2021. All the contents described in the specification and drawings of that application are incorporated by reference into the specification and drawings of the present application.

[0254] Industrial Applicability

[0255] According to the present invention, there can be provided a method for producing a laminate capable of suppressing air entrainment during lamination and fully exerting the function of a light-transmitting film.

[0256] Description of Symbols

[0257] 100 Laminate

[0258] 110 Support body

[0259] 120 Light-transmitting resin layer (impact-resistant film)

[0260] 210 Release film

[0261] 220 Adhesive layer

[0262] 300 Manufacturing Unit

[0263] 310 Supply Department

[0264] 320 Coating Section

[0265] 330 Drying Section

[0266] 340 Curling Amount Adjustment Section

[0267] 350 Heat Treatment Section

[0268] 360° winding section

[0269] 400 display device

[0270] 400A Display Device Main Body

[0271] 410 Organic EL Components

[0272] 420 polarizer

[0273] 500 glass units

[0274] 510 Cover Glass< / tac>

Claims

1. A method for manufacturing a laminate, comprising a method for manufacturing a laminate having a support and a light-transmitting resin layer peelably disposed on the support, wherein, The manufacturing method includes: The process of coating the support with a resin solution for forming the light-transmitting resin layer, such that the ratio of the coating thickness a μm to the thickness b μm of the support is a / b, is 0.5 to 5.

8. The process of heating and drying the coating film of the resin solution; The process of maintaining the support with the coating at 10~40°C and adjusting the amount of curling of the width end of the support with the coating toward the coating side to 5~50mm. as well as The process of heat-treating the support with the coating, whose curl amount has been adjusted. In the drying process, the tensile elastic modulus of the coating film at the heating temperature is below 1.6 GPa, and the heating temperature in the drying process is 60~140℃. The heating temperature in the heat treatment process following the curling amount adjustment process is 60~140℃.

2. The method for manufacturing a laminate according to claim 1, wherein, In the heat treatment process, heating is performed at a higher temperature than in the process of adjusting the amount of curling.

3. The method for manufacturing a laminate according to claim 1 or 2, wherein, The resin solution contains cyclic olefin resins or (meth)acrylic resins.

4. The method for manufacturing a laminate according to claim 1 or 2, wherein, The resin solution also contains rubber particles.

5. The method for manufacturing a laminate according to claim 1 or 2, wherein, The thickness of the light-transmitting resin layer is 0.1~35μm.

6. The method for manufacturing a laminate according to claim 1 or 2, wherein, The support is a thermoplastic resin film.

7. The method for manufacturing a laminate according to claim 6, wherein, The thermoplastic resin film is a polyester film.

Images