Manufacturing method of laminates

Abstract

This laminate manufacturing method involves coating and forming a functional layer on a support body transported at a tension T (N) and a holding angle θ (°) by means of a roll having a plurality of grooves with the width W (μm) of expression 1 in the circumferential direction, wherein the coating and forming is performed such that a stress σ (N / mm) generated when the support body is pressed against the roll and a deformation amount δ (μm) of the support body in the depth direction of the grooves satisfy expressions 2 and 3.　Expression 1: 200<W<1000. Expression 2: 0.1<σ<0.75, σ=2×T×cos(θ / 2). Expression 3: 0.5≤δ<20.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a laminate. [Background technology]

[0002] As a method for applying a coating solution to a support, an extrusion coating method is known in which the support is supported and transported by a backup roll, while the coating solution is discharged from an extrusion die positioned opposite the backup roll.

[0003] The thickness of the coating obtained by the extrusion coating method is greatly influenced by factors such as the dimensional accuracy and smoothness of the components of the equipment, including the die coater and backup rolls, the rotational accuracy of the rolls, the transport condition of the support, and the accuracy of the spacing between the support and the die coater. Therefore, in order to form a uniform coating, it is necessary to improve the dimensional accuracy of the components of the die coater and backup rolls, and to improve the transport stability of the support by the backup rolls.

[0004] As a method to improve the transport stability of the support, a method is known in which grooves are provided in the transport rolls and backup rolls to allow the accompanying air on the back surface of the support to escape into the grooves, thereby stabilizing transport. For example, in order to suppress coating defects caused by the air layer trapped between the support and the backup roll, it has been proposed to use a back-wrap roll with multiple grooves 500 to 1000 μm wide (see, for example, Patent Document 1), and in order to suppress wrinkles, it has been proposed to use a backup roll with multiple inclined grooves 50 to 200 μm wide (see Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2000-225368 [Patent Document 2] Japanese Patent Publication No. 2015-221415 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In these coating methods, the support is pressed against the backup roll under transport tension, so if the groove width is large, as in Patent Document 1, the support is prone to deforming by becoming concave along the groove. This deformation is especially likely to occur when the support is thin or soft. As a result, in the width direction of the support, the distance between the tip of the coating die lip and the support (coating gap) differs between the convex and concave parts of the roll groove, which can cause coating unevenness (streaky coating unevenness) with the same pitch as the roll groove.

[0007] On the other hand, if the groove width is small, as in Patent Document 2, the support material tends to slip on the backup roll (it is difficult to grip), making the transport of the support material unstable. Also, if the coating thickness is too uniform, the enclosed air is difficult to escape during winding, which can cause winding misalignment and a decrease in winding shape. Furthermore, foreign matter adhering to the back surface of the support material can adhere to the roll, causing the support material to lift, which can lead to transfer failures corresponding to the rotation period of the roll.

[0008] Such uneven coating, scratches during transport, transfer failures, and defects due to deterioration of the winding shape can reduce the optical properties of optical films used in displays, for example, and therefore it is desirable to suppress them.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a laminate that can form a functional layer with suppressed defects such as uneven coating, without impairing transport stability, even with a thin support. [Means for solving the problem]

[0010] This invention relates to a method for manufacturing a laminate.

[0011] [1] A method for manufacturing a laminate, comprising coating and forming a functional layer on a support being conveyed by a roll having a plurality of grooves of width W (μm) of formula 1 in the circumferential direction with tension T (N) and gripping angle θ (°), wherein the coating and forming is performed such that the stress σ (N / mm) generated when the support is pressed against the roll and the amount of deformation δ (μm) of the support in the depth direction of the grooves satisfy formulas 2 and 3. formula 1:200 <W<1000 Formula 2: 0.1<σ<0.75, σ=2×T×cos(θ / 2) Formula 3: 0.5≦δ<20 [2] The method for manufacturing a laminate according to [1], wherein the thickness of the support is 50 μm or less. [3] The method for manufacturing a laminate according to [1] or [2], wherein the Young's modulus E of the support is greater than 3000 MPa and less than or equal to 5200 MPa. [4] The method for manufacturing a laminate according to any one of [1] to [3], wherein the support is a thermoplastic resin film. [5] The method for manufacturing a laminate according to [4], wherein the thermoplastic resin film is a polyester film. [6] The method for manufacturing a laminate according to any one of [1] to [5], wherein the functional layer is an optical functional layer formed peelably on the support. [7] The method for producing a laminate according to any one of [1] to [6], wherein the functional layer comprises a cycloolefin resin or a (meth)acrylic resin. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a method for manufacturing a laminate that can form a functional layer with suppressed defects such as uneven coating, even with a thin support, without impairing transport stability. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic cross-sectional view illustrating the coating method using a coating die. [Figure 2] Figure 2 is a schematic diagram showing the state of the support on the roll surface in Figure 1. [Figure 3] Figure 3 is a schematic diagram of a manufacturing apparatus for a laminate according to the present embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view showing the configuration of a laminate according to the present embodiment. [Figure 5] Figure 5 is a schematic cross-sectional view showing the configuration of a display device according to the present embodiment.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0015] 1. Method for Manufacturing a Laminate The method for manufacturing a laminate according to the present embodiment is a method for manufacturing a laminate having a support and a functional layer. The functional layer is preferably an optical functional layer and can be peeled off from the support and used as an optical film.

[0016] Such a method for manufacturing a laminate includes a step of applying and forming a functional layer on a support. For example, when the coating solution is a resin solution, the method for manufacturing a laminate includes 1) a step of applying a resin solution for forming a functional layer on a support (coating step), and a step of drying the coating film to form a functional layer (drying step).

[0017] 1) Coating Step A resin solution for forming a functional layer is applied onto the support.

[0018] The support can be any material capable of supporting the functional layer, such as a resin film. Examples of resin films include thermoplastic resin films such as polyester films (e.g., polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), etc.), cycloolefin resin films (COP), acrylic resin films, and cellulose resin films (e.g., triacetylcellulose film (TAC)). Among these, polyester films such as PET film, cycloolefin resin films, and acrylic resin films are preferred from the viewpoint of versatility and ease of satisfying the Young's modulus E described later, with polyester films such as PET film being more preferred.

[0019] The Young's modulus E of the resin film is not particularly limited, but is preferably between 3000 MPa and 5200 MPa, and more preferably between 4000 and 5000 MPa. This is to ensure that the amount of deformation δ of the support in the depth direction of the groove of the backup roll is within the range described later.

[0020] The Young's modulus E can be measured in accordance with JIS K7127:1999. For example, using the Tensilon RTC-1225A manufactured by Orientec Co., Ltd., with a chuck distance of 50 mm, it can be determined from the stress-strain curve until fracture while being pulled. The measurement can be performed under conditions of 23°C, 55% RH, and a tensile speed of 50 mm / min.

[0021] The Young's modulus E can be adjusted depending on the type of resin film and whether or not a cooling treatment is performed. From the viewpoint of satisfying the above Young's modulus E, it is preferable that no cooling treatment is performed.

[0022] The thickness t of the support is not particularly limited, but is, for example, 100 μm or less, preferably 50 μm or less. The present invention is particularly effective when the thickness t of the support is 50 μm or less, as it is easily deformed in the depth direction of the groove of the roll, as will be described later. In some cases, it may be less than 50 μm. The lower limit of the thickness t of the support is not particularly limited, but is, for example, 15 μm, preferably 20 μm.

[0023] The support preferably further includes a release layer on its surface. The release layer may contain known release agents or mold release agents. Examples of release agents include silicone-based release agents and non-silicone-based release agents. The thickness of the release layer should be sufficient to exhibit release properties, and is preferably, for example, 0.1 to 1.0 μm.

[0024] From the viewpoint of forming a thin and uniformly thick coating film, the method of applying the resin solution is preferably one using a coating die.

[0025] Figure 1 is a schematic cross-sectional diagram illustrating the coating method using a coating die. Figure 2 is a schematic diagram showing the state of the support on the roll surface in Figure 1.

[0026] As shown in Figure 1, in coating using a coating die, the support 110 is supported and conveyed by a roll 221 (backup roll), and the resin solution is dispensed from a coating die 222 positioned opposite the roll 221. Furthermore, a roll with multiple grooves in the circumferential direction is used to prevent foreign matter adhering to the back surface of the support 110 from protruding to the back surface by embedding it in the grooves.

[0027] Incidentally, from the viewpoint of preventing large foreign objects adhering to the back surface of the support 110 from protruding to the back surface of the support 110 by embedding them in the groove, it is preferable that the width W of the groove in the roll 221 be large (see Figure 2). However, since the support 110 is pressed against the roll 221 with a force corresponding to the tension T and the gripping angle θ (see the white arrow in Figure 2), if the width W of the groove in the roll 221 is large, the support 110 is likely to deform in a way that it is concave in the depth direction of the groove (see Figure 2). As a result, in the width direction of the support 110, the distance between the lip tip of the coating die 222 and the support 110 (coating gap) differs between the convex and concave parts of the groove in the roll 221, so the coating thickness is also likely to change, and uneven coating thickness (streaky coating unevenness) with the same pitch as the groove in the roll 221 is likely to occur. On the other hand, if no such deformation occurs at all, the support 110 is likely to slip on the surface of the roll 221, and conveyance is likely to become unstable. Furthermore, if the coating thickness is too uniform, the laminated layers will adhere too tightly to each other during winding, making it difficult for enclosed air to escape and increasing the likelihood of winding misalignment.

[0028] Therefore, in the present invention, it is preferable to suppress uneven coating in the form of streaks while suppressing instability and winding misalignment during transport; in order to do so, it is preferable to moderately reduce the deformation amount δ of the support and the stress σ generated when the support is pressed against the roll (hereinafter also simply referred to as "stress σ generated in the support" or "force received by the support when pressed against the roll").

[0029] In other words, in the present invention, when the width of the groove of the roll is W (μm), the tension per unit width of the support is T (N / mm), and the gripping angle is θ (°), it is preferable to perform the coating formation such that the stress σ (N / mm) generated when the support is pressed against the roll and the amount of deformation of the support in the depth direction of the groove δ (μm) satisfy equations 2 and 3, respectively. formula 1:200 <W<1000 Formula 2: 0.1<σ<0.75, σ=2×T×cos(θ / 2) Formula 3: 0.5≦δ<20

[0030] Regarding Equation 3: If the deformation amount δ of the support is less than 20 μm, the variation in the coating gap can be reduced, thereby suppressing streaky coating unevenness. On the other hand, if the deformation amount δ of the support is 0.5 μm or more, the support is gripped appropriately by the roll, so transport stability is not easily impaired. In addition, a thickness deviation that does not affect the optical properties can be given to the coating, so the laminates do not stick together too tightly during winding, and winding misalignment can be suppressed. From a similar viewpoint, the deformation amount δ of the support is more preferably satisfied with, for example, 0.7 ≤ δ ≤ 9.0, and even more preferably satisfied with 1.2 ≤ δ ≤ 6.0, although this also depends on the width of the groove. The deformation amount δ of the support can be measured with a laser displacement meter (for example, LJ-X8000 manufactured by Keyence Corporation). Specifically, from the measurement data obtained with the laser displacement meter, the distance between the highest and lowest points on the support surface in the depth direction of the groove of the roll can be determined for each groove, and the average value of these can be taken as the deformation amount δ of the support (see Figure 2).

[0031] The deformation δ of a support can be adjusted by the support's thickness t, Young's modulus E, stress σ, and tension T. In particular, the support's thickness t has a significant influence on the deformation δ (inversely proportional to the cube of the thickness t). Therefore, reducing the support's thickness t increases the deformation δ. Similarly, lowering the Young's modulus E also increases the deformation δ. On the other hand, reducing the stress σ and tension T decreases the deformation δ.

[0032] Regarding Equation 2: If the stress σ generated in the support is greater than 0.1 N / mm, the support is gripped appropriately by the roll, thereby improving transport stability. On the other hand, if the stress σ generated in the support is less than 0.75 N / mm, the coating gap between the convex and concave parts of the groove does not differ excessively, thus suppressing streaky coating unevenness. From a similar viewpoint, it is more preferable that the stress σ generated in the support satisfies 0.2 ≤ σ ≤ 0.7, and even more preferable that it satisfies 0.2 ≤ σ ≤ 0.6. The stress σ generated in the support can be calculated by applying the tension T and the wrapping angle θ to the above equation 2.

[0033] The stress σ generated in the support can be adjusted by the tension T and the gripping angle θ. For example, reducing the tension T and increasing the gripping angle θ will reduce the stress σ. In terms of adjusting σ to the above range, the tension T can be, for example, 0.1 to 0.7 N / mm, and the gripping angle θ can be, for example, 0 to 90°.

[0034] Regarding Equation 1: If the groove width W of the roll is greater than 200 μm, foreign matter adhering to the back surface of the support can be sufficiently embedded in the groove, making transfer failures less likely. If it is less than 1000 μm, the deformation amount δ of the support does not become too large, making streaky coating unevenness less likely. From a similar viewpoint, the groove width W is preferably, for example, 210 to 700 μm. The groove width W can be the distance (average value) between the highest point in the depth direction of the groove and the next highest point (see Figure 2).

[0035] The coating thickness (μm) of the resin solution is not particularly limited, but is preferably, for example, 30 to 200 μm. The coating gap G is usually about twice the coating thickness, so it is 60 to 400 μm. If the coating gap G is 60 μm or more, it is easier to further suppress transport stability and winding misalignment, and if it is 400 μm or less, it is easier to further suppress streaky coating unevenness.

[0036] 2)Drying process Next, the solvent is removed from the resin solution applied to the support (by drying it) to form a functional layer.

[0037] The drying method is not particularly limited and may be heat drying or non-heat drying. In the case of heat drying, the heating temperature is preferably 60 to 140°C, and more preferably 80 to 120°C. When the heating temperature is within the above range, the solvent can be removed in a short time. The heating temperature can be specified as the temperature of the heating atmosphere.

[0038] Since the laminate according to this embodiment is preferably in the shape of a strip, it is preferable to further carry out the step of winding the strip-shaped laminate into a roll to form a roll body.

[0039] 3) Winding process The resulting strip-shaped laminate is wound into a roll in a direction perpendicular to its width to form a roll body.

[0040] The length of the strip-shaped laminate is not particularly limited, but can be, for example, around 100 to 10,000 m. The width of the strip-shaped laminate is preferably 1 m or more, and more preferably 1.3 to 4 m.

[0041] In this embodiment, the functional layer is coated and formed in a manner that satisfies the above formulas 1 to 3. As a result, even with a thin support, streaky coating irregularities can be suppressed without causing a decrease in transport stability or winding misalignment. This makes it possible to obtain a thin film functional layer with desired optical properties.

[0042] Regarding resin solutions: The resin solution contains a thermoplastic resin and a solvent.

[0043] (thermoplastic resin) The thermoplastic resin contained in the resin solution is not particularly limited, but from the viewpoint of use as an optical film, a light-transmitting thermoplastic resin is preferred. Examples of such resins include (meth)acrylic resins, cycloolefin resins, and cellulose esters.

[0044] (Meth)acrylic resins are polymers containing at least structural units derived from methyl methacrylate. The polymer may further contain other 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.

[0045] Examples of (meth)acrylic resins include polymethyl methacrylate and copolymers of methyl methacrylate, phenylmaleimide, and alkyl acrylate.

[0046] The weight average molecular weight Mw of the (meth)acrylic resin is preferably 1,000,000 or more, more preferably 1,500,000 to 3,000,000. When the Mw of the (meth)acrylic resin is a certain value or more, the mechanical strength of the functional layer can be enhanced. Mw can be measured in terms of polystyrene conversion by gel permeation chromatography (GPC).

[0047] The cycloolefin resin can be a (co)polymer of a norbornene monomer having a polar group. The norbornene monomer having a polar group is represented by the following formula (1). [Chemical formula]

[0048] Of R in formula (1) 1 ~R 4 at least one is preferably a polar group, and more preferably an alkoxycarbonyl group having 1 to 10 carbon atoms. The cycloolefin resin having a structural unit derived from a norbornene monomer having a polar group is not only easily dissolved in a solvent but can also increase the glass transition temperature of the obtained film.

[0049] R 1 ~R 4 The rest are each preferably a hydrogen atom or a hydrocarbon group. 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.

[0050] For example, R in formula (1) 1 is 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 are each a polar group, and R 2 and R 4Each of these may be 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.

[0051] Cycloolefin resins may further contain structural units derived from other monomers copolymerizable with norbornene monomers having polar groups. Examples of other copolymerizable monomers include norbornene monomers without polar groups and cycloolefin monomers without a norbornene skeleton, such as cyclobutene and cyclopentene.

[0052] The Mw of the cycloolefin resin is not particularly limited, but is preferably between 100,000 and 300,000, and more preferably between 120,000 and 200,000. Mw can be measured by the same method as described above.

[0053] The cellulose ester is preferably cellulose triacetate (TAC).

[0054] Among these, the functional layer of a thin film containing (meth)acrylic resin or cycloolefin resin is particularly effective because it lacks rigidity and is prone to air trapping during lamination.

[0055] The resin content is preferably 60% by mass or more, and more preferably 70% by mass or more, relative to the solid content of the resin solution.

[0056] (Other ingredients) The resin solution may contain other components as needed. Examples of other components include rubber particles and matting agents (fine particles).

[0057] (rubber particles) The rubber particles are particles containing a rubbery 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 these, (meth)acrylic-based crosslinked polymers are preferred, and acrylic-based crosslinked polymers (acrylic rubbery polymers) are more preferred, from the viewpoint of having a small refractive index difference with (meth)acrylic resin and not impairing the transparency of the functional layer.

[0058] The acrylic rubber-like polymer (a) is a crosslinked polymer mainly composed of structural units derived from acrylic acid esters. Preferably, the acrylic rubber-like polymer (a) is a crosslinked polymer containing structural units derived from acrylic acid esters, structural units derived from other monomers copolymerizable thereto, and structural units derived from polyfunctional monomers having two or more radical polymerizable groups (non-conjugated reactive double bonds) in one molecule.

[0059] The acrylic acid ester is preferably an alkyl acrylate with 1 to 12 carbon atoms in the alkyl group, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, or n-butyl acrylate. The content of structural units derived from the acrylic acid ester is preferably 40 to 90% by mass, and more preferably 50 to 80% by mass, relative to the total structural units. When the acrylic acid ester content is within the above range, it is easier to impart sufficient toughness to the protective film.

[0060] Other copolymerizable monomers are monomers copolymerizable with acrylic acid esters, excluding polyfunctional monomers. Examples of copolymerizable monomers include methacrylate esters such as methyl methacrylate; and styrenes such as styrene and methylstyrene. The content of structural units derived from other copolymerizable monomers is preferably 5 to 55% by mass, and more preferably 10 to 45% by mass, relative to the total structural units.

[0061] Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, diethylene glycol (meth)acrylate, and polyethylene glycol di(meth)acrylate. The content of structural units derived from polyfunctional monomers is preferably 0.05 to 10% by mass, and more preferably 0.1 to 5% by mass, relative to the total structural units. If the content of polyfunctional monomers is 0.05% by mass or more, the degree of crosslinking of the resulting acrylic rubber-like polymer (a) is easily increased, so that the hardness and rigidity of the resulting functional layer are not excessively impaired. If the content is 10% by mass or less, the toughness of the functional layer is not easily impaired.

[0062] The particles containing the acrylic rubbery polymer (a) may be particles made of the acrylic rubbery polymer (a), or particles made of an acrylic graft copolymer obtained by polymerizing a mixture of monomers such as methacrylic acid esters in the presence of the acrylic rubbery polymer (a) in at least one step, i.e., core-shell type particles having a core portion containing the acrylic rubbery polymer (a) and a shell portion covering it.

[0063] The shell portion may contain a methacrylic polymer (b) grafted onto an acrylic rubber-like polymer (a), with structural units derived from methacrylate esters as the main component. The methacrylate ester constituting the methacrylic polymer (b) is preferably an alkyl methacrylate ester with 1 to 12 carbon atoms in the alkyl group, such as methyl methacrylate.

[0064] The average particle size of the rubber particles is preferably 100 to 400 nm, and more preferably 150 to 300 nm. When the average particle size of the rubber particles is within the above range, stress relaxation can be easily obtained without impairing the transparency of the functional layer. The average particle size of the rubber particles can be determined as the dispersed particle size measured by a zeta potential / particle size measurement system (ELSZ-2000ZS, manufactured by Otsuka Electronics Co., Ltd.).

[0065] The content of rubber particles is not particularly limited, but is preferably 5 to 50% by mass relative to the resin components in the resin solution, more preferably 5 to 40% by mass, and even more preferably 7 to 30% by mass.

[0066] (Mat agent) Matting agents can be added to films to impart slipperiness. Examples of matting agents include inorganic fine particles such as silica particles.

[0067] (solvent) The solvent used in the resin solution is not particularly limited, as long as it can dissolve the thermoplastic resin well. 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), etc.), propylene glycol monoalkyl ether esters (propylene glycol monomethyl ether acetate)), and hydrocarbons such as toluene, benzene, and cyclohexane. For example, when using (meth)acrylic resins, it is preferable to include ketones from the viewpoint of solubility and drying properties, and it is even preferable to include alcohols from the viewpoint of planarity.

[0068] The resin concentration of the resin solution is preferably, for example, 1.0 to 20% by mass, from the viewpoint of easily adjusting the viscosity to the range described later.

[0069] Regarding manufacturing equipment: The manufacturing method for the laminate according to this embodiment can be carried out, for example, by the manufacturing apparatus shown in Figure 3.

[0070] Figure 3 is a schematic diagram of a manufacturing apparatus 200 for carrying out the manufacturing method of a laminate according to this embodiment. The manufacturing apparatus 200 has a supply unit 210, a coating unit 220, a drying unit 230, and a winding unit 240. a and b indicate conveying rolls for conveying the support 110.

[0071] The supply unit 210 has a feeding device (not shown) that feeds out a roll body 301 of a strip-shaped support 110 wound around a core.

[0072] The coating unit 220 is a coating apparatus for performing the above coating process, and includes a roll 221 (backup roll) having multiple grooves in the circumferential direction, a coating die 222 positioned opposite the roll 221, and a reduced pressure chamber 223 positioned upstream of the coating die 222. The coating unit 220 is configured so that the groove width W, tension T, and gripping angle θ can be adjusted to satisfy the above equations 1 to 3. A control unit (not shown) controls the coating unit 220 so that the coating unit 220 discharges a resin solution from the coating die 222 onto the support 110 supported by the roll 221, thereby coating it, in a manner that satisfies the above equations 1 to 3.

[0073] The vacuum chamber 223 is a mechanism for stabilizing the bead (accumulation of coating liquid) formed between the resin solution from the coating die 222 and the support 110 during coating, and the degree of vacuum is adjustable. The vacuum chamber 223 is kept free of air leaks, and the gap with the backup roll is also narrowed, enabling the formation of a stable coating liquid bead.

[0074] The drying section 230 is a drying apparatus for performing the above drying process, and dries the coating applied to the support 110. The drying section 230 may be configured to apply hot air, for example, or it may be a heating furnace with an adjusted ambient temperature.

[0075] The winding section 240 winds up the support 110 (laminated body 100) on which the functional layer 120 is formed, to obtain a roll body 241.

[0076] 2. Laminate The laminate 100 obtained by the manufacturing method of the laminate according to this embodiment includes a support 110 and a functional layer 120 (see Figure 4).

[0077] As described above, the functional layer 120 is preferably an optical functional layer. After being peeled from the support, the optical functional layer can be used as an optical film. Examples of optical films include polarizer protective films (including phase difference films) that are bonded to a polarizer and impact-resistant films that are bonded to a cover glass.

[0078] (Phase difference Ro and Rt) When the functional layer is used, for example, as a phase difference film for IPS mode, the in-plane phase difference Ro measured at a measurement wavelength of 550 nm and under conditions of 23°C and 55% RH is preferably 0 to 10 nm, and more preferably 0 to 5 nm. The phase difference Rt in the thickness direction of the functional layer is preferably -20 to 20 nm, and more preferably -10 to 10 nm.

[0079] Ro and Rt are defined by the following formulas, respectively. Equation (2a): Ro = (nx - ny) × d Equation (2b): Rt = ((nx + ny) / 2 - nz) × d (In the formula, nx represents the refractive index in the in-plane slow axis direction of the functional layer (the direction in which the refractive index is maximum). ny represents the refractive index in the direction perpendicular to the in-plane slow axis of the functional layer. NZ represents the refractive index in the thickness direction of the functional layer. 'd' represents the thickness (nm) of the functional layer.

[0080] The in-plane lagging axis of the functional layer can be confirmed using an automated birefringent AxoScan Mueller Matrix Polarimeter (manufactured by Axometrics).

[0081] Ro and Rt can be measured by the following method. 1) The functional layer is conditioned for 24 hours in an environment of 23°C and 55% RH. The average refractive index of this film is measured using an Abbe refractometer, and the thickness d is measured using a commercially available micrometer. 2) The retardation Ro and Rt of the film after humidity control are measured at a measurement wavelength of 550 nm using an automated birefringent AxoScan Mueller Matrix Polarimeter (manufactured by Axometrics) in an environment of 23°C and 55% RH.

[0082] (Thickness) The thickness of the functional layer is not particularly limited, but from the viewpoint of achieving a thinner polarizing plate, it is usually thinner than the thickness of the support, for example, 0.1 to 35 μm, preferably 1 to 15 μm.

[0083] The laminate according to this embodiment may further have other layers disposed between the support and the functional layer, if necessary.

[0084] 3.Display device The display device according to this embodiment includes a display element and a polarizing plate.

[0085] The display element may be an organic EL element or a liquid crystal element (liquid crystal cell). The polarizing plate is placed at least on the viewing side of the display element. The display device may further include other components such as cover glass or impact-resistant film, as needed.

[0086] Furthermore, the functional layer (optical functional layer) obtained by the above manufacturing method can be used as a protective film or impact-resistant film for polarizing plates.

[0087] Figure 5 is a schematic cross-sectional view showing the configuration of the organic EL display device 300 according to this embodiment. The organic EL display device 300 includes an organic EL element 310 (display element), a polarizing plate 320 (circular polarizing plate), and a cover glass unit 330.

[0088] (Organic EL element) The organic EL element 310 has a metal electrode 312 (cathode), an emissive layer 313, a transparent electrode (anode such as ITO) 314, and a sealing layer 315 on a transparent substrate 311 such as a glass plate or transparent film, in this order. When a voltage is applied between the metal electrode 312 and the transparent electrode 314, holes and electrons are injected into the emissive layer 313. The energy generated by the recombination of these holes and electrons excites a fluorescent material, and when the excited fluorescent material returns to its ground state, it emits light, resulting in emission.

[0089] (Polarizing plate) The polarizing plate 320 may be a circular polarizing plate positioned on the viewing side of the organic EL element 310. Such a polarizing plate 320 includes a polarizer 321, a protective film 322 positioned on its viewing side, and a protective film 323 positioned between the polarizer 321 and the organic EL element 310.

[0090] The polarizer 321 may be, for example, a polyvinyl alcohol-based polarizing film. The protective film 323 is preferably a λ / 4 film, and is bonded so that the angle between the transmission axis (or absorption axis) of the polarizer 321 and the in-plane slow axis of the protective film 323 is 45 ± 15°. The protective film 322 may be a known polarizer protective film. Such a circular polarizer 320 can suppress reflection of ambient light incident from outside the organic EL display device 300, such as from indoor lighting.

[0091] (Cover glass unit) The cover glass unit 330 is positioned on the viewing side of the polarizing plate 320 and includes a cover glass 331, an adhesive layer 332, and an impact-resistant film 333.

[0092] The cover glass 331 is positioned on the most visible side of the organic EL display device 300. The thickness of the cover glass 331 can be, for example, 30 to 50 μm. The impact-resistant film 333 is positioned between the polarizing plate 320 and the cover glass 331.

[0093] The cover glass unit 330 can be obtained by bonding the functional layer 120 of the laminate 100 and the cover glass 331 via an adhesive layer 332, and then peeling off the support 110 of the laminate 100.

[0094] In this embodiment, one or more of the protective films 323, 322, and impact-resistant film 333 of the polarizing plate 320 can be used as the functional layer 120 obtained by the above manufacturing method. As described above, the functional layer 120 is free from failures due to unstable transport or winding misalignment, and streaky coating irregularities are suppressed. Therefore, by using the functional layer 120 as the protective film 323, it is possible to highly suppress the deterioration of display characteristics caused by such failures and streaky coating irregularities (for example, streaky phase difference irregularities on the screen of a display device, or light leakage due to external light reflection when displaying black).

[0095] (modified version) In the above embodiment, an example was shown in which the functional layer 120 of the laminate 100 is used as an optical film for an organic EL display device, but it may also be used as an optical film (protective film, etc.) for a liquid crystal display device. [Examples]

[0096] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0097] 1. Materials of the laminate 1-1.Support Supports 1 to 11 were prepared as described below. The Young's modulus E of the supports was measured by the following method. [Table 1]

[0098] (Young's modulus E) In accordance with JIS K7127:1999, a stress-strain curve was obtained using an Orientec Tensilon RTC-1225A with a chuck distance of 50 mm, while pulling until fracture. The stress-strain curve is represented with stress (MPa) on the vertical axis and tensile elongation at fracture (%) on the horizontal axis. The stress-strain curve was measured under conditions of 23°C, 55% RH, and a tensile speed of 50 mm / min.

[0099] 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℃ The glass transition temperature and weight-average molecular weight of the resin were measured by the following method.

[0100] (Glass transition temperature) The glass transition temperature (Tg) of the resin was measured using DSC (Differential Scanning Colorimetry) in accordance with JIS K 7121-2012.

[0101] (Weight average molecular weight) The weight-average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC, Tosoh Corporation) and columns (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL, Tosoh Corporation, in series). 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 (at 40°C), and the value was measured at a detector RI temperature of 40°C. The value converted to styrene equivalent was used.

[0102] (2) Preparation of resin solution The following components were mixed to obtain a resin solution. Methyl ethyl ketone: 900 parts by mass (Meth)acrylic resin (MMA / PMI / MA copolymer): 100 parts by mass

[0103] 2. Fabrication and evaluation of laminates <Exam 1-1 to 1-6> The support 4 (width 1350 mm, thickness 38 μm) was conveyed by a backup roll having multiple grooves with a width of 500 μm under tension T (N) and gripping angle θ (°). The prepared resin solution was then applied to the support using a slot die and dried at 80°C. As a result, a laminate with a functional layer of 14 μm thickness was obtained on the support. The stress σ was adjusted by the tension T and the gripping angle θ of the backup roll.

[0104] <Exams 2-1 to 2-11> A laminate was obtained in the same manner as in Test 1-4, except that the thickness t (μm) of the support and the width W (μm) of the groove of the backup roll were changed to alter the deformation amount δ of the support as shown in Table 2.

[0105] <Exams 3-1 to 3-7> A laminate was obtained in the same manner as in Test 1-4, except that the type of support and coating conditions (tension T, wrapping angle θ) were changed as shown in Table 2.

[0106] <Rating> The obtained laminates were evaluated for (1) streaky coating unevenness, (2) transport stability, (3) transfer failure, and (4) winding shape using the following methods.

[0107] (1) Streaky uneven coating The thickness distribution of the functional layer in the width direction of the laminate was measured using a laser displacement meter (Keyence LJ-X8000). The results were then evaluated according to the following criteria. ◎: No uneven application ○: Very slight streaky coating unevenness occurs along the grooves of the roll (thickness ratio of 3% to less than 5% compared to the normal area) or unevenness due to coating instability (unevenness due to coating instability as the support deforms), but this is at a level that does not pose a practical problem. △: Slight streaky coating unevenness along the grooves of the roll and unevenness due to the above coating instability occur, resulting in a slight decrease in yield, but it is at a level that does not pose a practical problem. ×: Streaky coating unevenness occurs along the grooves of the roll (thickness ratio of 5% or more compared to the normal area), or unevenness occurs due to the above coating instability, reaching a level that is problematic in practical use. A score of △ or higher was considered acceptable.

[0108] (2) Transport stability The presence or absence of displacement in the transport position of the support material before the application of the resin solution was measured using a Keyence LS-9000 ultra-high-speed, high-precision dimensional measuring instrument. The presence or absence of wrinkles was measured by visually observing the reflection state when a linear light source, such as a fluorescent lamp, was shone on the support material. These wrinkles represent tension-like wrinkles in the transport direction caused by excessive tension relative to the rigidity of the support material. The transport stability was then evaluated based on the following criteria. ◎: The transport position in the width direction is stable, and no wrinkles occur. ○: There may be very slight misalignment or wrinkles in the transport position in the width direction, but this does not affect the coating quality. △: Slight misalignment or wrinkling may occur in the width direction of the conveyed material, but this does not affect the coating quality. ×: Misalignment or wrinkling occurs in the transport position in the width direction, resulting in problems with coating quality. A score of △ or higher was considered acceptable.

[0109] (3) Transfer failure The coating film was visually inspected immediately after application, and the location of transfer failures was recorded. After the coating film was dried and wound up, the roll was unwound and sampled, and transfer failures were measured using the same measurement method as for the streaky coating irregularities described above. The transfer failures were then evaluated based on the following criteria. ◎: Even if foreign matter is present, no transfer failure will occur. ○: A transfer failure occurs in which the thickness of the functional layer periodically decreases to less than 5% in the longitudinal direction of the laminate, but there is no problem with the coating quality. ×: A transfer failure occurred in which the thickness of the functional layer periodically decreased by more than 5% in the longitudinal direction of the laminate, indicating a problem with the coating quality. ○ or higher was considered acceptable.

[0110] (4) Winding shape The surface irregularities (widthwise irregularities) of a rolled laminated material after winding it up to 4000m were measured using a laser displacement meter (LJ-X8000, manufactured by Keyence Corporation). Deformation was determined when the irregularities were 1mm or greater. ◎: No deformation of the winding shape when winding 1000m or more. ○: When winding more than 1000m, slight deformation of the winding shape occurs, but it is at an acceptable level. △: When winding less than 1000m, slight deformation of the winding shape occurs, but it is not a problem. ×: When winding less than 1000m, deformation of the winding shape occurs, making further winding impossible. A score of △ or higher was considered acceptable.

[0111] (5) Optical properties In tests 1-1, 1-2, and 1-3, λ / 4 films (phase difference films) 1, 2, and 3 were obtained by diagonally stretching the film at a 45° angle to the width direction (diagonal direction), respectively. Using the obtained phase difference films, a circular polarizer was fabricated in the same manner as in paragraphs 0253 to 0256 of Japanese Patent Application Publication No. 2018-180163, and an organic EL display was fabricated in the same manner as in paragraphs 0269 and 0270 of the same publication. The phase difference film was placed between the organic EL element and the circular polarizer (corresponding to the protective film 323 in Figure 5 of this specification). Then, light leakage due to ambient light reflection (phase difference unevenness caused by streaky coating irregularities, etc.) when the organic EL display was set to black was evaluated.

[0112] The manufacturing conditions and evaluation results for tests 1-1 to 1-6, 2-1 to 2-11, and 3-1 to 3-7 are shown in Table 2.

[0113] [Table 2]

[0114] As shown in Table 2, tests 1-2 to 1-5, 2-3, 2-6 to 2-10, and 3-1 to 3-5 (Examples), which satisfy all of Equations 1 to 3, show good results in terms of streaky coating unevenness, transportability, transfer failure, and winding shape.

[0115] Specifically, when the stress σ generated in the support is less than 0.1 N / mm or greater than 0.75 N / mm, the conveyance is unstable and streaky coating unevenness occurs (see Tests 1-1 and 1-6); however, when σ is in the range of 0.1 to 0.75 N / mm, the conveyance is stable and streaky coating unevenness can be suppressed (see Tests 1-2 to 1-5).

[0116] Furthermore, (even if σ is in the range of 0.1 to 0.75 N / mm) if the deformation amount δ of the support is less than 0.5 μm, air cannot escape during winding, causing bamboo shoot-shaped winding misalignment and a deterioration in winding shape (see Tests 2-1, 2-2, 3-6 and 3-7); however, if the deformation amount δ is 0.5 μm or more, air can escape appropriately, making bamboo shoot-shaped winding misalignment less likely and resulting in a good winding shape (see Tests 2-3 to 2-11). Furthermore, it was found that when the deformation amount δ of the support is greater than 20 μm, streaky coating unevenness occurs (see Test 2-10); however, when the deformation amount δ is 20 μm or less, streaky coating unevenness can be suppressed (see Tests 2-3 to 2-10).

[0117] Furthermore, even when σ is in the range of 0.1 to 0.75 N / mm, if the groove width W is 200 μm, the support lifts due to foreign matter adhering to the back surface, causing transfer failures. If the width W is 1050 μm, streaky coating unevenness occurs (Tests 2-4, 2-5, and 2-10). However, if the groove width W is greater than 200 μm but less than 1000 μm, transfer failures and streaky coating unevenness can be suppressed (see Tests 2-2, 2-3, 2-6 to 2-10).

[0118] Furthermore, it can be seen that when the Young's modulus E of the support exceeds 3000 MPa, streaky coating unevenness can be further suppressed, and when it is 5200 MPa or less, the decrease in transport stability and the deterioration of the winding shape due to winding misalignment can be further suppressed (see Tests 3-1 to 3-5). In particular, compared to Test 3-1, Tests 3-2 to 3-4 show that the tension is not too high relative to the Young's modulus E of the support, so wrinkles are less likely to occur and transport stability is further improved.

[0119] Furthermore, in the evaluation of display characteristics, no light leakage (phase difference unevenness) was observed in the display devices using phase difference films 2 and 3 (Examples), but light leakage was confirmed in the display device using the laminate obtained with phase difference film 1 (Comparative Example).

[0120] This application claims priority under Japanese Patent Application No. 2021-162940, filed on 1 October 2021. All provisions of the said application are incorporated herein by reference. [Industrial applicability]

[0121] According to the present invention, it is possible to provide a method for manufacturing a laminate that can form a functional layer with suppressed defects such as uneven coating, even with a thin support, without impairing transport stability. [Explanation of symbols]

[0122] 100-layer structure 110 Support 120 Functional Layers 200 Manufacturing equipment 210 Supply section 220 Coating area 230 Drying section 240 Winding section 300 Organic EL display device 310 Organic EL elements 320 Polarizing plate 330 Cover glass unit 331 Cover glass 332 Adhesive layer 333 Impact-resistant film

Claims

1. In a method for manufacturing a laminate, a functional layer is coated and formed on a support that is conveyed with tension T (N) and gripping angle θ (°) by a roll having multiple grooves of width W (μm) in the circumferential direction according to Equation 1, The coating process is carried out such that the stress σ (N / mm) generated when the support is pressed against the roll and the deformation amount δ (μm) of the support in the depth direction of the groove satisfy equations 2 and 3. A method for manufacturing laminates. Formula 1: 200<W<1000 Formula 2: 0.1<σ<0.75, σ=2×T×cos(θ / 2) Formula 3: 0.5≦δ<20

2. The thickness of the support is 50 μm or less. A method for manufacturing a laminate according to claim 1.

3. The Young's modulus E of the support is greater than 3000 MPa and less than or equal to 5200 MPa. A method for manufacturing a laminate according to claim 1 or 2.

4. The support is a thermoplastic resin film. A method for manufacturing a laminate according to claim 1.

5. The thermoplastic resin film is a polyester film. A method for manufacturing a laminate according to claim 4.

6. The functional layer is an optical functional layer formed in a peelable manner on the support. A method for manufacturing a laminate according to claim 1.

7. The functional layer comprises a cycloolefin resin or a (meth)acrylic resin. A method for manufacturing a laminate according to claim 1.

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