KR20240035840A - Method for manufacturing laminates - Google Patents

Abstract

A method for manufacturing a laminate having a support and a translucent resin layer detachably disposed thereon, wherein a resin solution for forming a translucent resin layer is applied on the support to a thickness a (μm) and a thickness b of the support b (μm). A step of applying so that the ratio a/b is 0.5 to 5.8, a step of heating and drying the coating film of the resin solution, maintaining the temperature lower than the temperature at the time of heating, and curling the width direction end portion of the support having the coating film to 5 to 5.8. It includes a step of adjusting the thickness to 50 mm, and a step of heat-treating a support having a coating film whose curl amount has been adjusted.

Description

Method for manufacturing laminates

The present invention relates to a method for manufacturing a laminate.

Optical films with light transparency are used for various purposes. As an example, polarizing plate protective films used in various displays are known.

Additionally, in recent years, the development of foldable displays has been actively conducted. A foldable display has a thin cover glass (UTG) on the display surface, and an impact-resistant film is disposed on the front or back side (device main body side) of the cover glass to prevent the cover glass from breaking due to impact. .

Optical films such as these impact-resistant films and polarizing plate protective films are required to be further thinned, for example, from the viewpoint of improving bending resistance.

In contrast, a peelable laminated film having a base film (support) and a translucent film (translucent resin layer) is known (for example, patent document 1). The peelable laminated film is used by bonding the translucent film to the polarizer and peeling the base film to bond the thin translucent film to the polarizer.

Japanese Patent Publication No. 2018-41028

However, when a conventional thin translucent film as shown in Patent Document 1 is bonded to another member or exposed to high temperature and high humidity after bonding, there is a problem in that air entrainment is likely to occur. For example, when using a translucent film as an impact-resistant film of the foldable display, first, the translucent film and the release film on which the adhesive layer is formed are bonded roll to roll, and then the adhesive layer is transferred onto the translucent film, Attach the cover glass. When this light-transmitting film and the release film on which the adhesive layer is formed are bonded together, entrainment of air is likely to occur, or if exposed to high temperature and high humidity after bonding, entrainment of air is likely to occur. Due to such entrapment of air, the impact resistance performance of the cover glass unit after bonding sometimes deteriorated.

In this way, it is not limited to the case of use as an impact-resistant film, and it is desired to be able to suppress air entrainment when a thin translucent film is bonded to another member.

The present invention was made in consideration of the above circumstances, and aims to provide a method for manufacturing a laminate that can suppress entrainment of air during or after bonding and sufficiently exhibit the function of a translucent film (translucent resin layer). Do it as

The above problem can be solved by the following configuration.

The method for producing a laminate of the present invention is a method for producing a laminate having a support and a translucent resin layer peelably disposed thereon, wherein a resin solution for forming the translucent resin layer is applied on the support at a thickness of A step of applying so that the ratio a/b of a (μm) and 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, and maintaining a temperature lower than the temperature at the time of heating. Thus, it includes a step of adjusting the curl amount of the width direction end portion of the support having the coating film to 5 to 50 mm, and a step of heat treating the support having the coating film whose curl amount has been adjusted.

According to the present invention, it is possible to provide a method for manufacturing a laminate that suppresses air entrainment during bonding and can sufficiently exhibit the function of a translucent film.

1A to 1C are cross-sectional schematic diagrams showing the bonding method using the laminated body in this embodiment.
Fig. 2 is a cross-sectional schematic diagram showing the curl amount of the support having a coating film in this embodiment.
Fig. 3 is a schematic diagram of a manufacturing apparatus for a laminated body in this embodiment.
Fig. 4 is a cross-sectional schematic diagram showing the configuration of the display device in this embodiment.

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

1A to 1C are cross-sectional schematic diagrams showing a bonding method using the laminated body 100 according to this embodiment. Fig. 2 is a cross-sectional schematic diagram showing the amount of curl (H) of the support having a coating film in this embodiment. These drawings show a cross section in the width direction of the strip-shaped laminate 100.

As described above, before bonding the translucent resin layer 120 (of the laminate 100) and the cover glass (not shown) by roll-to-roll via the adhesive layer 220, the translucent resin layer 120 and the mold release The adhesive layer 220 formed on the film 210 is bonded (FIGS. 1A and 1B), and the adhesive layer 220 is transferred onto the translucent resin layer 120 (see FIG. 1C). The present inventors appropriately curled the laminate 100 at the time of bonding in advance so that both ends in the width direction bend upward toward the translucent resin layer 120, and further reduced the distribution of stress remaining in the translucent resin layer. (See FIG. 1A), it was found that lifting due to entrainment of air during and after bonding can be suppressed.

Although this mechanism is not clear, it is assumed as follows.

If it is not curled like a conventional laminate, or if the amount of curl is very small, the thin translucent resin layer has no elasticity, so wrinkles are likely to form when bonded to the adhesive layer 220, and air is likely to be drawn in. In addition, even if the laminate is appropriately curled, if local stress remains, air may be entrained in the laminate due to thermal deformation of the translucent resin layer 120 resulting from the local residual stress when exposed to a high temperature and high humidity environment after bonding. This is easy to happen.

In contrast, by curling the laminate 100 appropriately, the back surface of the central portion in the width direction of the laminate 100 is sufficiently supported by the roll surface, so that when bonding to the adhesive layer 220, the central portion in the width direction It is possible to easily adhere to the adhesive layer 220. As a result, air is easily pushed out from the central portion in the width direction toward both ends in the width direction during bonding, making it possible to prevent entrapment of air. Additionally, by making the residual stress distribution of the translucent resin layer uniform (removing local residual stress), entrainment of air when exposed to a high temperature and high humidity environment after bonding can also be suppressed.

Such a laminate 100 can be obtained by, after the drying process, maintaining the temperature at a relatively low temperature and going through a curl amount adjustment process of adjusting the curl amount to a predetermined range, and a process of heat treating the support having the coating film.

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, since the residual stress fixed in the curl amount adjustment step is not uniform in the width direction, lifting as is cannot be suppressed when exposed to high temperature and high humidity after bonding. In contrast, by additionally performing a heat treatment process, the distribution of residual stress in the width direction in the translucent resin layer can be made uniform. As a result, in the laminate obtained, the amount of curl is adjusted to an appropriate range, and the bias in residual stress is reduced, so that entrainment of air during bonding can be suppressed.

In addition, the curl amount of the laminate 100 substantially corresponds to the curl amount of the support having a coating film in the curl amount adjustment step; The curl amount of the support having the coating film in the curl amount adjustment step is the ratio a/b of the coating thickness a of the resin solution and the support thickness in the application step, the tensile elastic modulus of the coating film, the heating temperature T1 in the drying step, and the curl amount adjustment step. It can be adjusted by the ambient temperature T2, etc. In addition, the distribution of residual stress in the translucent resin layer can be adjusted by the heating temperature T3 in the heat treatment step (after the curl amount adjustment step), etc. Hereinafter, the configuration of the present invention will be described.

1. Manufacturing method of laminate

The manufacturing method of the laminate according to the present embodiment includes the following steps: 1) a process of applying a resin solution on a support (application process), 2) a process of heating and drying a coating film of the resin solution (drying process), 3) a coating film It includes a step of adjusting the curl amount of the support having the coating film (curl amount adjustment step), and 4) a step of heat treating the support having the coating film whose curl amount has been adjusted (heat treatment step).

1) Application process

On the support, a resin solution for forming a translucent resin layer is applied.

The support is not particularly limited as long as it can support the translucent resin layer, but can usually be a resin film. Examples of resin films include polyester films (e.g., polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), etc.), cycloolefin-based resin films (COP), acrylic resin films, and cellulose-based resin films (triacetylcellulose films (TAC), etc.). Among them, polyester films such as PET film are preferable from the viewpoint of versatility and sufficient strength.

The thickness of the support is not particularly limited, but for example, it is preferably 10 to 100 μm, and more preferably 25 to 50 μm.

The support preferably further includes a release layer on its surface. The release layer may contain a known release agent or release agent. Examples of release agents include silicone-based release agents and non-silicone-based release agents. The thickness of the release layer is not particularly limited as long as it exhibits the desired peelability, but is preferably, for example, 0.1 to 1.0 μm.

The resin solution preferably contains a thermoplastic resin and a solvent, and further contains rubber particles, etc. The composition of the resin solution is explained in detail later.

The application method of the resin solution is not particularly limited, and may be any known method such as, for example, a back roll coat method, a gravure coat method, a spin coat method, a wire bar coat method, or a roll coat method. Among them, the back coat method is preferable from the viewpoint of being able to form a thin and uniformly thick coating film.

The application thickness a (μm) of the resin solution is adjusted so that the ratio a/b with 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 more, it is easy to adjust the curl amount to a certain level or more, and if it is 5.8 or less, the curl amount does not become too large. Thereby, the curl amount of the width direction end part of the support body with a coating film can be adjusted to the range mentioned later. The ratio a/b can preferably be adjusted to the range of 0.8 to 4.8 from the same viewpoint. The application thickness a can be, for example, 30 to 250 μm.

2) Drying process (first heating process)

Next, the resin solution applied to the support is heated, the solvent is removed (dried), and a coating film is formed.

Heating conditions (e.g., heating temperature, heating time, etc.) are not particularly limited, but can be set so that the curl amount of the width direction end portion of the support having the coating film after the curl amount adjustment step can be adjusted to a range described later. The heating temperature T1 is preferably 60 to 140°C, and more preferably 80 to 120°C. If the heating temperature is within the above range, not only can the solvent be removed in a short time, but it is also easy to adjust the curl amount to the range described later, so it is easy to suppress bonding defects due to lifting. The heating temperature can be specified as the temperature of the heating atmosphere.

The tensile modulus of elasticity of the coating film at the heating temperature T1 is not particularly limited, but is preferably 1.6 GPa or less, and more preferably 1.0 GPa or less. If the tensile modulus of elasticity of the coating film is below the upper limit, the residual stress is likely to be alleviated because it has appropriate flexibility.

The tensile elastic modulus of the coating film can be measured by a tensile test based on JIS K 7127, which is the tensile elastic modulus of the coating film after peeling from the support. That is, the peeled coating film is cut into 1 cm (TD direction) x 10 cm (MD direction) to make a sample, and the humidity is controlled in an environment of 25°C and 60%RH for 24 hours. The obtained sample is subjected to a tensile test at a heating temperature T1 in the drying process to measure the tensile modulus of elasticity. The measurement is performed at a chuck-to-chuck distance of 50.0 mm and a tensile speed of 50 mm/min.

The tensile modulus of elasticity of the coating film can be adjusted by the composition of the coating film. For example, if the coating film contains rubber particles or the like, the tensile modulus of elasticity of the coating film is likely to be low.

3) Curl amount adjustment process

Next, the support with a coating film is maintained at a temperature T2 lower than the heating temperature T1 in the drying process, and the curl amount of the width direction end portion of the support with a coating film is adjusted. Specifically, the support with the coating film is conveyed for a certain period of time under a temperature T2 lower than the heating temperature T1, and the curl amount and residual stress at the width direction end portion of the support with the coating film are fixed.

The curl of the support having a coating film occurs when the solvent in the coating film is removed and shrinks during the drying process, so that both ends in the width direction are bent toward the coating film (see Fig. 2). The curl amount of the width direction end portion of the support having a coating film is in the range of 5 to 50 mm, and is preferably adjusted so as to be in the range of 15 to 35 mm. If the curl amount is 5 mm or more, entrainment of air during bonding can be suppressed, and if it is 50 mm or less, it is easy to suppress bonding defects or bending of the ends in the width direction due to the curl amount being too large.

The amount of curl at the ends in the width direction of the support having a coating film is the height H ( mm). The measurement is performed, for example, using an online measuring device Keyence LJX8200, specifically, Keyence LJ-X8200, at both ends in the width direction (lowest part) and the center part in the width direction (highest part) of the surface of the coating film on the support. ) The height of 100 points is measured in the longitudinal direction of the support, and the average value (height of both ends in the width direction - height of the center part in the width direction) at each point is taken as the “curl amount.”

As mentioned above, the amount of curl at the width direction end of the support having a coating film is determined by the ratio a/b of the coating thickness a and the thickness of the support in the application process, the tensile modulus of elasticity of the coating film, the heating temperature T1 in the drying process, and the curl amount adjustment process. It can be adjusted by the ambient temperature T2, etc.

From the viewpoint of adjusting the curl amount of the width direction end portion of the support having the coating film to the above range, the atmospheric temperature T2 in the curl amount adjustment step is 10 to 40°C, preferably 15 to 35°C. The difference (T1 - T2) between the temperature T2 in the curl amount adjustment process and the heating temperature T1 in the drying process can be, for example, 40 to 70°C. If (T1 - T2) is 70°C or lower, it is not easily cooled quickly, so the amount of curl does not become excessively large. The holding time at the ambient temperature T2 is sufficient as long as the amount of curl can be adjusted to a predetermined range, and can be longer than the heating time in the drying process, for example. For example, it can be done for 5 to 20 minutes.

In the coating film, solvents (for example, ketones or alcohols) derived from the resin solution may remain. The amount of residual solvent is preferably 3% or less relative to the coating film. The content of the residual solvent can be adjusted depending on the drying conditions of the resin solution.

The amount of residual solvent can be measured by headspace gas chromatography. In the headspace gas chromatography method, a sample is enclosed in a container, heated, the gas in the container is quickly injected into the gas chromatograph while the container is full of volatile components, and mass spectrometry is performed to identify the compound. Quantify volatile components.

4) Heat treatment process (second heating process)

Thereafter, the support having the coating film whose curl amount has been adjusted is further subjected to heat treatment. As a result, a laminate having a support and a translucent resin layer can be obtained, and the distribution of residual stress can be made uniform.

Specifically, it is preferable to heat the support having the coating film at a higher temperature than the step of adjusting the curl amount. That is, the heating temperature T3 is not particularly limited as long as it can uniformize the distribution of stress, but is preferably higher than the ambient temperature T2 in the curl amount adjustment step. For example, the heating temperature T3 is preferably 60 to 140°C, and more preferably 80 to 120°C. If the heating temperature T3 is more than the lower limit, it is easy to make the stress distribution uniform, and if it is less than the upper limit, conveyance stability is less likely to be impaired. Heating temperature T3 can be specified as the temperature of the heating atmosphere. The heating time may be sufficient to make the distribution of residual stress uniform, and may be equal to or longer than the holding time of the curl amount adjustment process, for example. For example, it can be done for 5 to 40 minutes.

Since the laminate according to the present embodiment is preferably in the shape of a strip, it is preferable to further perform the step of 5) winding the strip-shaped laminate into a roll to form a roll.

5) Winding process

The obtained strip-shaped laminate is wound into a roll in a direction perpendicular to the width direction to form a roll.

The length of the strip-shaped laminated body is not particularly limited, but may be, for example, about 100 to 10,000 m. Moreover, the width of the strip-shaped laminated body is preferably 1 m or more, and more preferably 1.3 to 4 m.

About resin solution:

The resin solution contains a thermoplastic resin and a solvent.

(thermoplastic resin)

The thermoplastic resin contained in the resin solution is not particularly limited, and includes (meth)acrylic resin, cycloolefin resin, and cellulose ester.

(Meth)acrylic resin is a polymer containing at least a structural unit 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; (meth)acrylic acid alkyl esters such as adamantyl acrylate; (meth)acrylic acid cycloalkyl esters such as 2-ethylhexyl acrylate, etc. are included.

Examples of (meth)acrylic resins include polymethyl methacrylate and copolymers of methyl methacrylate, phenylmaleimide, and alkyl acrylate.

The weight average molecular weight Mw of the (meth)acrylic resin is preferably 1 million or more, more preferably 1.5 million to 3 million. If the Mw of the (meth)acrylic resin is above a certain level, the mechanical strength of the translucent resin layer can be increased. Mw can be measured in polystyrene conversion by gel permeation chromatography (GPC).

The cycloolefin-based resin may be a (co)polymer of a norbornene-based monomer having a polar group. The norbornene-based monomer having a polar group is represented by the following formula (1).

[Formula 1]

At least one of R ¹ to R ⁴ in the formula (1) is preferably a polar group, and more preferably an alkoxycarbonyl group having 1 to 10 carbon atoms. A cycloolefin-based resin having a structural unit derived from a norbornene-based monomer having a polar group is not only easy to dissolve in a solvent, but can also increase the glass transition temperature of the resulting film.

The remainder among R ¹ to R ⁴ is preferably a hydrogen atom or a hydrocarbon group, respectively. The hydrocarbon group is a hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and examples thereof include an alkyl group and an aryl group.

For example, R ¹ in formula (1) may be a polar group, and R ² , R ³ and R ⁴ may each be a hydrogen atom or a hydrocarbon group; R ¹ and R ³ may each be a polar group, and R ² and R ⁴ may each be a hydrogen atom or a hydrocarbon group. p and m are each 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.

The cycloolefin-based resin may further contain a structural unit derived from another monomer that can be copolymerized with a norbornene-based monomer having a polar group. Examples of other copolymerizable monomers include norbornene-based monomers that do not have a polar group, and cycloolefin-based monomers that do not have norbornene skeletons, such as cyclobutene and cyclopentene.

The Mw of the cycloolefin resin is not particularly limited, but for example, it is preferably 100,000 to 300,000, and more preferably 120,000 to 200,000. Mw can be measured in the same way as above.

The cellulose ester is preferably triacetylcellulose (TAC).

Among these, the translucent resin layer of a thin film containing a (meth)acrylic resin or cycloolefin resin has no elasticity and is prone to entrainment of air during bonding, so the method for producing a laminate of the present invention is particularly effective. becomes valid.

The content of the resin is preferably 60% by mass or more, and more preferably 70% by mass or more, based on the solid content of the resin solution.

(other ingredients)

The resin solution may further contain components other than the above as needed. Examples of other components include rubber particles and matting agents (fine particles).

(rubber particles)

Rubber particles are particles containing a rubber-like polymer. The rubbery polymer is a soft crosslinked 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 crosslinked polymers include butadiene-based crosslinked polymers, (meth)acrylic-based crosslinked polymers, and organosiloxane-based crosslinked polymers. Among them, (meth)acrylic cross-linked polymers are preferable, and acrylic cross-linked polymers (acrylic rubber-like polymers) are more preferable from the viewpoint that the difference in refractive index with the (meth)acrylic resin is small and the transparency of the translucent resin layer is not easily impaired. .

The acrylic rubbery polymer (a) is a crosslinked polymer containing a structural unit derived from acrylic acid ester as a main component. The acrylic rubbery polymer (a) is polyfunctional, having structural units derived from acrylic acid ester, structural units derived from other monomers that can be copolymerized with it, and two or more radical polymerizable groups (non-conjugated reactive double bonds) in one molecule. It is preferable that it is a crosslinked polymer containing structural units derived from monomers.

The acrylic acid ester is preferably an acrylic acid alkyl ester having 1 to 12 carbon atoms of an alkyl group such as methyl acrylate, ethyl acrylate, n-propyl acrylate, or n-butyl acrylate. The content of the structural unit derived from acrylic acid ester is preferably 40 to 90% by mass, more preferably 50 to 80% by mass, based on the total structural units. If the content of acrylic acid ester is within the above range, it is easy to provide sufficient toughness to the protective film.

Other monomers that can be copolymerized are those other than polyfunctional monomers among monomers that can be copolymerized with acrylic acid ester. Examples of copolymerizable monomers include methacrylic acid esters such as methyl methacrylate; Styrenes such as styrene and methylstyrene are included. The content of structural units derived from other copolymerizable monomers is preferably 5 to 55% by mass, more preferably 10 to 45% by mass, based on the total structural units.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, diethylene glycol (meth)acrylate, and polyethylene glycol di(meth)acrylate. The content of the structural unit derived from the polyfunctional monomer is preferably 0.05 to 10% by mass, more preferably 0.1 to 5% by mass, based on all structural units. If the content of the polyfunctional monomer is 0.05% by mass or more, it is easy to increase the degree of crosslinking of the obtained acrylic rubber-like polymer (a), so the hardness and rigidity of the obtained light-transmitting resin layer are not excessively impaired, and if the content of the polyfunctional monomer is 10% by mass or less, the light-transmitting resin layer The toughness is not easily impaired.

The particles containing the acrylic rubber-like polymer (a) may be particles composed of the acrylic rubber-like polymer (a); Particles made of an acrylic graft copolymer obtained by polymerizing a mixture of monomers such as methacrylic acid ester in at least one stage in the presence of the acrylic rubbery polymer (a), that is, a core containing the acrylic rubbery polymer (a) Core-shell type particles having a portion and a shell portion covering the portion may be used.

The shell portion may contain a methacrylic polymer (b) containing as a main component a structural unit derived from methacrylic acid ester grafted to the acrylic rubber-like polymer (a). The methacrylic acid ester constituting the methacrylic polymer (b) is preferably an alkyl methacrylate ester having 1 to 12 carbon atoms of an alkyl group such as methyl methacrylate.

The average particle diameter of the rubber particles is preferably 100 to 400 nm, and more preferably 150 to 300 nm. If the average particle diameter of the rubber particles is within the above range, a stress relieving effect can be easily obtained without impairing the transparency of the translucent resin layer. The average particle diameter of the rubber particles can be specified as the dispersed particle size measured with a zeta potential/particle size measurement system (ELSZ-2000ZS, manufactured by Otsuka Electronics Co., Ltd.).

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

(made of mat)

A matting agent may be added from the viewpoint of providing sliding properties to the film. Examples of mat agents include inorganic fine particles such as silica particles.

(menstruum)

The solvent used in the resin solution is not particularly limited as long as it can well disperse the (meth)acrylic resin or 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, and glycol ethers (propylene glycol mono(C1 to C4) alkyl Hydrocarbons such as ether (specifically, propylene glycol monomethyl ether (PGME), etc.), propylene glycol monoalkyl ether ester (propylene glycol monomethyl ether acetate), toluene, benzene, cyclohexane, etc. Among them, the solvent is , from the viewpoint of easy dissolution of (meth)acrylic resin, relatively high affinity with rubber particles, low boiling point, and easy to increase drying speed and productivity, it is preferable to contain ketones and form a translucent resin layer with high planarity. From the viewpoint of ease of formation, it is preferable to further contain alcohol.

The resin concentration of the resin solution is preferably, for example, 1.0 to 20% by mass from the viewpoint of making it easy to adjust the viscosity to the range described later.

About manufacturing device:

The manufacturing method of the laminated body according to this embodiment can be carried out, for example, using the manufacturing apparatus shown in FIG. 3 .

FIG. 3 is a schematic diagram of a manufacturing apparatus 300 for carrying out the method for manufacturing a laminated body according to the present embodiment. The manufacturing apparatus 300 has a supply unit 310, an application unit 320, a drying unit 330, a curl amount adjustment unit 340, a heat treatment unit 350, and a winding unit 360. a and b represent conveyance rolls that convey the support body 110.

The supply unit 310 has a feeding device (not shown) that unwinds the roll body 301 of the strip-shaped support body 110 wound around the core.

The applicator 320 is an applicator for carrying out the above-mentioned application process, and applies the resin solution to the backup roll 321 holding the support 110 and the support 110 held by the backup roll 321. It has an application head 322, and a pressure reduction chamber 323 formed on the upstream side of the application head 322.

The decompression chamber 323 is a mechanism for stabilizing the beads (collection of the application liquid) formed between the resin solution from the application head 322 and the support 110 during application, and the degree of decompression can be adjusted. . The decompression chamber 323 is in a state where there is no air leakage, and the gap with the backup roll is narrowed, making it possible to form a stable bead of the coating liquid.

The drying unit 330 is a drying device for performing the drying process, and heats and dries the coating film applied to the support 110. For example, the drying unit 330 may be configured to apply hot air whose temperature is adjusted to the heating temperature T1, or may be a heating furnace whose ambient temperature is adjusted.

The curl amount adjustment unit 340 is a device for performing the curl amount adjustment process, and transports the support 110 with the coating film in an atmosphere adjusted to a temperature T2 lower than the heating temperature T1.

The heat treatment unit 350 is an apparatus for performing the heat treatment process, and heat-treats the support 110 having a coating film that has passed the curl amount adjustment unit 340.

The winding unit 360 is a winding device (not shown) for winding the support 110 (laminated body 100) on which the translucent resin layer 120 is formed to obtain the roll body 361.

2. Laminate

The laminated body obtained by the method for manufacturing a laminated body according to the present embodiment has a support and a translucent resin layer disposed on the surface so as to be peelable (see Fig. 1A).

The translucent resin layer is obtained from the above resin solution and is placed on a support. After being peeled from the support, the translucent resin layer is used as an optical film such as an impact-resistant film bonded to a cover glass or a protective film (including retardation film) bonded to a polarizer.

(Amount of curl at both ends in the width direction)

Due to the manufacturing process, the obtained laminate is also appropriately curled so that both ends in the width direction are bent upward towards the translucent resin layer. The curl amount may be in the same range as above.

(phase difference Ro and Rt)

From the viewpoint of using the translucent resin layer as, for example, a retardation film for IPS mode, the retardation Ro in the in-plane direction measured under a measurement wavelength of 550 nm and an environment of 23°C and 55%RH is preferably 0 to 10 nm, It is more preferable that it is 0-5 nm. The phase difference Rt in the thickness direction of the translucent resin layer is preferably -20 to 20 nm, and more preferably -10 to 10 nm.

Ro and Rt are each defined by the following formula.

Equation (2a): Ro = (nx - ny) × d

Equation (2b): Rt = ((nx + ny)/2 - nz) × d

(During the ceremony,

nx represents the refractive index of the translucent resin layer in the in-plane slow axis direction (the direction in which the refractive index is maximum),

ny represents the refractive index in the direction orthogonal to the in-plane slow axis of the translucent resin layer,

nz represents the refractive index in the thickness direction of the translucent resin layer,

d represents the thickness (nm) of the translucent resin layer.)

The in-plane slow axis of the translucent resin layer can be confirmed by an automatic birefringence meter, Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics).

Ro and Rt can be measured by the following method.

1) The translucent resin layer is humidified in an environment of 23°C and 55%RH for 24 hours. The average refractive index of this film is measured with an Abbe refractometer, and the thickness d is measured using a commercially available micrometer.

2) The phase difference Ro and Rt of the film after humidity control at a measurement wavelength of 550 nm were measured using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics) in an environment of 23°C and 55%RH. Measure.

(thickness)

The thickness of the translucent resin layer is not particularly limited, but from the viewpoint of realizing thinning of the polarizing plate, it is usually preferably thinner than the thickness of the support, specifically, for example, 0.1 to 35 μm, and 1 to 15 μm. It is more preferable to be

The laminate according to the present embodiment may further have another layer disposed between the support and the translucent resin layer as needed.

As described above, the laminate obtained by the method for manufacturing a laminate according to the present embodiment is appropriately curled so that both ends in the width direction are bent upward toward the translucent resin layer. As a result, it is possible to suppress entrainment of air when bonding with other members, which will be described later, and bonding defects such as lifting can be suppressed.

3. Display device

The display device according to this embodiment is a display device main body and includes a display element and a polarizing plate.

The display element may be an organic EL element or a liquid crystal element (liquid crystal cell). The polarizing plate is disposed at least on the viewing side of the display element.

The display device may additionally include other members depending on the purpose. When the display device is, for example, a foldable display, a cover glass may be disposed on the viewing side of the display device main body with an impact-resistant film interposed therebetween. The impact-resistant film may be a translucent resin layer of the laminate according to the present embodiment.

FIG. 4 is a cross-sectional schematic diagram showing the configuration of the display device 400 according to the present embodiment. In this embodiment, an example is shown where the display device 400 is an organic EL display device.

The display device 400 has a display device body 400A including an organic EL element 410 (display element) and a polarizing plate 420 (circularly polarizing plate), and a cover glass unit 500.

3-1. Display device body (400A)

(Organic EL device)

The organic EL element 410 includes a metal electrode 412, a light emitting layer 413, a transparent electrode (ITO, etc.) 414, and an encapsulation layer 415 on a transparent substrate 411 such as a glass plate or transparent film. They are in this order.

The metal electrode 412 can function as a cathode. In order to facilitate electron injection and increase luminous efficiency, it is desirable to use a material with a small work function for the metal electrode 412, and Mg-Ag or Al-Li are usually used.

The light emitting layer 413 is a laminate of organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, or a light emitting layer and a perylene derivative, etc. It may be a laminate of electron injection layers, a laminate of these hole injection layers, a light-emitting layer, and an electron injection layer.

The transparent electrode 414 can function as an anode. The transparent electrode 414 may typically be made of a transparent conductor such as indium tin oxide (ITO).

The encapsulation layer 415 may be a transparent substrate such as a glass plate or transparent film, or an encapsulation film such as an encapsulant.

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, and the energy generated by the recombination of these holes and electrons excites the fluorescent material, When the excited fluorescent material returns to its ground state, it emits light and emits light.

(Polarizer)

The polarizing plate 420 may be a circularly polarizing plate disposed on the viewing side surface of the organic EL element 410. Such a polarizing plate 420 has a polarizer 421, a protective film 422 disposed on its viewing side, and a protective film 423 disposed between the polarizer 421 and the organic EL element 410. .

The polarizer 421 may be, for example, a polyvinyl alcohol-based polarizing film. The protective film 423 is preferably a λ/4 film, and is bonded so 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°. It is done. The protective film 422 may be a known polarizing plate protective film. Such a circularly polarizing plate 420 can suppress reflection of external light incident from the outside of the display device 400 due to indoor lighting, etc.

3-2. Cover Glass Unit (500)

The cover glass unit 500 has a cover glass 510, an adhesive layer 220, and a translucent resin 120 as an impact-resistant film.

(cover glass)

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

(impact resistant film)

The impact-resistant film is disposed between the display device main body 400A and the cover glass 510. As an impact-resistant film, the translucent resin layer 120 of the above-described laminate 100 can be used.

3-3. Manufacturing method of display device

The display device 400 can be obtained through the following steps: 1) manufacturing the cover glass unit 500, and 2) bonding the display device main body 400A and the cover glass unit 500.

1) About the process

The cover glass unit 500 in this embodiment is a laminate ( It can be manufactured through a process of peeling off the support 110 of 100).

Specifically, the translucent resin layer 120 of the laminate 100 and the adhesive layer 220 formed on the release film 210 are bonded roll-to-roll to form an adhesive layer on the translucent resin layer 120. After transferring (220) (Figures 1a to 1c); It is preferable to further bond the cover glass 510 onto the adhesive layer 220 in a roll-to-roll manner.

At this time, since the laminated body 100 is appropriately curled, the laminated body 100 and the roll supporting it are in sufficient contact at the central portion in the width direction. Therefore, the translucent resin layer 120 and the adhesive layer 220 of the laminate 100 tend to come into close contact at the central portion in the width direction, making it difficult for air to enter during bonding. In addition, since the residual stress of the laminate 100 is uniform, even if exposed to high temperature and high humidity after bonding, entrainment of air due to thermal deformation of the translucent resin layer 120, etc., is unlikely to occur. Thereby, lifting due to poor bonding can be suppressed (see Fig. 1A).

2) About the process

The translucent resin layer 120 (impact-resistant film) of the obtained cover glass unit 500 is bonded to the display device main body 400A with an adhesive or the like to obtain the display device 400.

(variation example)

In addition, in the above embodiment, an example of using the translucent resin layer of the laminate as an impact-resistant film is shown, but it is not limited to this and may be used as a protective film of a polarizing plate.

In addition, in the above embodiment, an example of using the translucent resin layer of the laminate as an impact-resistant film for an organic EL display device is shown, but it is not limited to this and can be used as a protective film for a liquid crystal display device, a transparent substrate for a display element, etc. It may be possible.

Example

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these.

1. Laminate material

1-1. support

＜PET-1＞

Polyethylene terephthalate film (TN100 manufactured by Toyobo, with release layer (contains non-silicone release agent), thickness 50 ㎛)

＜PET-2＞

Polyethylene terephthalate film (TN100 manufactured by Toyobo, with release layer (contains non-silicone release agent), thickness 100 ㎛)

＜TAC＞

Triacetylcellulose film (4CT manufactured by Konica Minolta, no release layer, thickness 40 ㎛)

1-2. resin solution

(1) Preparation of materials

＜Resin＞

(meth)acrylic resin: methyl methacrylate (MMA)/phenylmaleimide (PMI)/methyl acrylate (MA) copolymer (85/10/5 mass ratio), Mw: 2 million, Tg: 122°C

COP: Cycloolefin resin G7810 (manufactured by JSR) (cycloolefin resin (COP) containing structural units derived from norbornene monomers represented by the formula below, Mw: 110,000, Tg: 170°C)

[Formula 2]

The glass transition temperature and weight average molecular weight of the resin were measured by the following methods.

(Glass transition temperature)

The glass transition temperature (Tg) of the resin was measured based on JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

(Weight average molecular weight)

The weight average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL series manufactured by Tosoh Corporation). 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 a column (temperature 40°C), the RI temperature of the detector was measured at 40°C, and the value converted to styrene was used.

＜Rubber particles＞

Rubber particles R1 prepared by the following method were used.

The following materials were injected into an 8 L polymerization apparatus equipped with a stirrer.

180 parts by mass of deionized water

Polyoxyethylene lauryl ether phosphoric acid 0.002 parts by mass

Boric acid 0.4725 parts by mass

Sodium carbonate 0.04725 parts by mass

Sodium hydroxide 0.0076 parts by mass

After sufficiently purging the polymerization reactor with nitrogen gas, the internal temperature was set to 80°C, and 0.021 part by mass of potassium persulfate was added as a 2% aqueous solution. Next, 21 parts by mass of a monomer mixture (c') 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 is added to 21 parts by mass of poly. A mixed solution containing 0.07 parts by mass of oxyethylene lauryl ether phosphoric acid was continuously added to the above solution over 63 minutes. Furthermore, the innermost hard polymer (c) was obtained by continuing the polymerization reaction for 60 minutes.

After that, 0.021 part by mass of sodium hydroxide was added as a 2 mass% aqueous solution, and 0.062 part by mass of potassium persulfate was added as a 2 mass% aqueous solution. Next, 0.25 parts by mass of polyoxyethylene lauryl ether phosphoric acid was added to 39 parts by mass of the 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, and the mixture was stirred for 117 minutes. It was added continuously. After the addition was completed, 0.012 parts by mass of potassium persulfate was added as a 2% by mass aqueous solution, and the polymerization reaction was continued for 120 minutes to obtain a soft layer (a layer made of 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.

After that, 0.04 parts by mass of potassium persulfate was added as a 2% by mass aqueous solution, and 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 was added continuously over 78 minutes. Furthermore, the polymerization reaction was continued for 30 minutes to obtain polymer (b).

The obtained polymer was put into a 3% by mass sodium sulfate hot water solution, salted out, and solidified. Next, dehydration and washing were repeated, and then dried to obtain acrylic graft copolymer particles (rubber particles R1) with a three-layer structure. The average particle diameter of the obtained rubber particles R1 was 200 nm.

The average particle diameter of the rubber particles was measured by the following method.

(average particle diameter)

The dispersed particle size of the rubber particles in the obtained dispersion was measured using a zeta potential/particle size measurement system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

(2) Preparation of resin solution

<Production of resin solution A>

The following components were mixed to obtain a solution for a translucent resin layer.

Methylene chloride: 900 parts by mass

COP (cycloolefin resin): 100 parts by mass

<Production of resin solutions B to F>

Resin solutions B to F were obtained in the same manner as resin solution A except that the composition was changed to that shown in Table 1.

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

2. Fabrication and evaluation of laminates

<Production of Laminate 1>

PET film (PET-1) was prepared as a support. On the release layer of this PET film, the resin solution A was applied using a slot die to an application thickness a (μm) shown in Table 2, and then dried by heating at 80°C for 4 minutes. Next, the support to which the resin solution A was applied was maintained at 25°C for 10 minutes while being transported (curl amount adjustment step), and then further heated at 80°C for 20 minutes (heat treatment step). As a result, a laminate 1 having a support and a translucent resin layer was obtained.

<Production of laminates 2 to 7>

Laminates 2 to 7 were obtained in the same manner as in Laminate 1 except that the combination of the support and the resin solution and the thickness ratio a/b were changed as shown in Table 2.

<Production of laminates 8 to 11>

Laminates 8 to 11 were obtained in the same manner as in Laminate 3, except that the conditions of the curl amount adjustment step were changed as shown in Table 2.

<Production of laminates 12 to 17>

Laminates 12 to 17 were obtained in the same manner as in Laminate 3, except that the content of the rubber particles in the resin solution or the heating temperature T1 in the drying process were changed as shown in Table 2.

<Production of laminate 18>

Laminate 18 was obtained in the same manner as Laminate 14, except that the curl amount adjustment step and the heat treatment step were not performed.

＜Evaluation＞

The amount of curl of the support having the coating film during production of the laminates 1 to 18, the tensile modulus of elasticity of the coating film, and the lifting and impact resistance of the samples using the laminates 1 to 18 were evaluated by the following methods.

(curl amount)

The amount of curl at the end portion in the width direction of the support having the coating film was measured online. Specifically, using Keyence LJ-X8200, the height of both ends (lowest part) in the width direction and the central part (highest part) in the width direction of the surface of the coating film on the support were measured at 100 points in the longitudinal direction of the support. , the average value of (height of both ends in the width direction - height of the center part in the width direction) at each point was taken as the “curl amount.”

(Tensile modulus of elasticity of the coating film)

(1) Immediately after the curl amount adjustment process

After completion of the curl amount adjustment process, the obtained coating film was peeled from the support, and the tensile modulus of elasticity was measured by a tensile test based on JIS K 7127.

That is, the peeled coating film was cut into 1 cm (TD direction) x 10 cm (MD direction) to make a sample, and the humidity was controlled in an environment of 25°C and 60%RH for 24 hours. The obtained sample was subjected to a tensile test by setting it in a tensilon tensile test device manufactured by Orientec, and the tensile modulus of elasticity was measured. The measurement was conducted at a distance between chucks of 50.0 mm, a tensile speed of 50 mm/min, and a heating temperature T1 in the drying process. In addition, the measurement was performed in both the MD direction and the TD direction, and the average value of the tensile elastic modulus in each direction was taken as the “tensile elastic modulus.”

(2) Immediately before the winding process

After the heat treatment process, the tensile modulus of elasticity of the coating film immediately before the winding process was measured in the same manner as above. The measurement temperature was set to the heating temperature T1 in the curl amount adjustment process.

(excited)

The translucent resin layer of the obtained laminate was bonded to a cover glass through an adhesive layer to obtain a sample of cover glass/adhesive layer/translucent resin layer. The resulting sample was visually observed to determine whether any lifting occurred when stored at 80°C and 90%RH for 500 hours.

◎: No lifting in all 10 samples

○: Lifting occurs in less than 2 samples out of 10.

△: Lifting occurs in more than 2 samples and less than 4 samples out of 10 samples.

×: 4 or more samples are not suitable for evaluation due to lifting or poor bonding due to entangled air bubbles.

If it was △ or higher, it was considered passing.

(impact resistance)

The samples prepared for evaluation of lifting were stored at 80°C and 90%RH for 500 hours and then subjected to the following impact resistance test.

On a stainless steel plate with a thickness of about 3 cm, the sample was placed so that the translucent resin layer was on the bottom, and the four corners were fixed with tape. After that, the state of the sample when an iron bead (weight: 500 g, diameter: 50 mm) was dropped onto the cover glass from a position 20 cm above the area was visually observed.

◎: When performed 10 times and the cover glass does not scatter (including cracks) even once.

○: When the cover glass scatters (including cracks) less than 2 times in 10 cases.

△: When performed 10 times and the scattering of the cover glass (including cracks) occurs more than 2 times but less than 4 times.

×: When performed 10 times and the cover glass scatters (including cracks) more than 4 times.

If it was △ or higher, it was considered passing.

The manufacturing conditions and evaluation results of the obtained laminates 1 to 18 are shown in Table 2.

As shown in Table 2, laminates 1 to 3, 5, 6, 9, 10 obtained through a curl amount adjustment process such that the thickness ratio a/b satisfies the range of 0.5 to 5.8 and the curl amount is 5 to 50 mm, and It can be seen that numbers 12 to 17 can suppress lifting during bonding and provide sufficient impact resistance.

On the other hand, in laminates 4 and 7 in which the thickness ratio a/b does not satisfy the range of 0.5 to 5.8, and in laminate 8 in which the temperature of the curl amount adjustment step exceeds 40° C., the curl amount is set to 5 to 50 in the curl amount adjustment step. It can be seen that it cannot be adjusted to mm and the lifting during bonding cannot be suppressed. In addition, it can be seen that in the laminate 18 without the curl amount adjustment step and the heat treatment step, lifting after bonding cannot be suppressed.

This application claims priority based on Japanese Patent Application 2021-146875, filed on September 9, 2021. All contents described in the application specification and drawings are incorporated into the present application specification and drawings.

According to the present invention, it is possible to provide a method for manufacturing a laminate that suppresses air entrainment during bonding and can sufficiently exhibit the function of a translucent film.

100: Laminate
110: support
120: Translucent resin layer (impact resistant film)
210: release film
220: Adhesive layer
300: manufacturing device
310: supply department
320: Applicator
330: drying unit
340: Curl amount adjustment unit
350: Heat treatment unit
360: winding unit
400: display device
400A: Display device body
410: Organic EL device
420: Polarizer
500: cover glass unit
510: cover glass

Claims (9)

A method for producing a laminate having a support and a translucent resin layer peelable thereon, comprising:
A step of applying a resin solution for forming the translucent resin layer on the support so that the ratio a/b of the application thickness a (μm) and the thickness b (μm) of the support is 0.5 to 5.8,
A process of drying the coating film of the resin solution by heating,
A step of maintaining the temperature lower than the temperature at the time of heating and adjusting the curl amount of the width direction end portion of the support having the coating film to 5 to 50 mm, and
A method for producing a laminate, comprising the step of heat-treating a support having the coating film whose curl amount has been adjusted. According to claim 1,
In the step of adjusting the curl amount, the support having the coating film is maintained at 10 to 40°C. The method of claim 1 or 2,
In the drying step, the tensile modulus of elasticity of the coating film at the heating temperature is 1.6 GPa or less. The method according to any one of claims 1 to 3,
A method for producing a laminate, wherein the heat treatment step is heated at a higher temperature than the curl amount adjustment step. The method according to any one of claims 1 to 4,
A method for producing a laminate, wherein the resin solution contains a cycloolefin-based resin or a (meth)acrylic-based resin. The method according to any one of claims 1 to 5,
The method of producing a laminate, wherein the resin solution further contains rubber particles. The method according to any one of claims 1 to 6,
A method for producing a laminate, wherein the thickness of the translucent resin layer is 0.1 to 35 μm. The method according to any one of claims 1 to 7,
A method of producing a laminate, wherein the support is a thermoplastic resin film. According to claim 8,
A method for producing a laminate, wherein the thermoplastic resin film is a polyester film.