JP2025001987A - Glass laminate and manufacturing method of glass laminate - Google Patents

Abstract

To secure excellent flex resistance of a glass laminate under a high temperature environment.SOLUTION: A glass laminate comprises a glass film having a first principal plane and a second principal plane, and a resin film adhered at least to the first principal plane. When a measurement sample of the rectangular glass laminate whose product of the long side and the short side is 8000 mm2 or more, and whose ratio of the long side/the short side is 2.5 or less is heated at 100°C for 30 minutes, both of a curl height Ci of the initial glass laminate before heating, and a curl height Ch of the glass laminate after heating are 10 mm or less.SELECTED DRAWING: Figure 1

Description

This disclosure relates to a glass laminate and a method for manufacturing a glass laminate.

Patent Document 1 proposes an optical laminate comprising a glass plate, an adhesive layer, and a film in that order toward one side in the thickness direction, the glass plate having a thickness of less than 40 μm, an average tan δ of the film at -100°C to -50°C determined by a dynamic viscoelasticity test in a tensile mode with a frequency of 10 Hz and a heating rate of 2°C/min is 0.04 or more, and an average tensile storage modulus E' of the film at -100°C to -50°C determined by the dynamic viscoelasticity test is 3 GPa or more and 6 GPa or less. In addition to Patent Document 1, several optical laminates comprising glass plates have been proposed (Patent Documents 2 to 4, etc.).

JP 2022-83323 A JP 2022-83324 A JP 2022-83325 A JP 2022-83326 A

Thin glass or glass film is used in the process of manufacturing products in the form of a glass laminate with a resin film in order to prevent scratches and ensure a certain degree of ease of handling. However, even if the glass laminate does not curl at room temperature, it may curl when exposed to high temperatures. When the glass laminate curls, its bending resistance decreases. Curling refers to the phenomenon in which the glass laminate warps and bends.

A first aspect of the present disclosure relates to a glass laminate including a glass film having a first principal surface and a second principal surface, and a resin film bonded to the first principal surface, wherein when a measurement sample of the rectangular glass laminate having a product of long sides and short sides of 8,000 ^mm2 or more and a long side/short side ratio of 2.5 or less is heated at 100°C and 55% RH for 30 minutes, an initial curl height _Ci of the glass laminate before heating and a curl height _Ch of the glass laminate after heating are both 10 mm or less.

A second aspect of the present disclosure relates to a method for manufacturing a glass laminate including a glass film having a first main surface and a second main surface and a resin film bonded to the first main surface, the method including a first step of preparing a precursor film for the resin film, a second step of annealing the precursor film to obtain the resin film, and a third step of bonding the resin film to the first main surface of the glass film to obtain the glass laminate.

This ensures excellent bending resistance of the glass laminate in high temperature environments.

FIG. 1 is a schematic vertical cross-sectional view of a glass laminate according to an embodiment of the present disclosure.

A laminate of a glass film, such as thin glass, and a resin film (hereinafter referred to as a "glass laminate") has a certain degree of flexibility and may be used in applications where it needs to be folded or bent. Even if the glass laminate does not curl at room temperature, it may curl when exposed to high temperatures. This is because the glass film and the resin film expand or contract to different degrees when heated.

Conventionally, glass films that have shown excellent results in continuous bending tests at room temperature are considered to have sufficient performance, and are also used in applications where folding and bending are repeated. On the other hand, even in products using glass laminates or glass films that are considered to have sufficient performance, unexpected cracks in the glass film may occur. As a result of investigation into the cause, it was found that even in glass laminates in which the glass film does not crack when repeatedly bent at room temperature, cracks may occur when repeatedly bent at high temperatures (e.g., 80°C). In addition, it was found that in glass laminates that curl significantly when exposed to high temperatures, the glass film does not crack even when repeatedly bent at room temperature, but cracks may occur when repeatedly bent at high temperatures (e.g., 80°C). In such glass laminates, cracks may become noticeable when repeatedly bent in a high-temperature and high-humidity environment (e.g., an environment of 60°C and 90% RH (relative humidity)). In this specification, room temperature refers to a temperature of 20°C or higher and 35°C or lower.

In view of the above, (1) a glass laminate according to a first aspect of the present disclosure includes a glass film having a first main surface and a second main surface, and a resin film bonded to the first main surface. When a measurement sample of a rectangular glass laminate having a product of long side and short side of 8000 mm ² or more and a long side/short side ratio of 2.5 or less is heated at 100° C. and 55% RH for 30 minutes, the curl height C _i of the initial glass laminate before heating and the curl height C _h of the glass laminate after heating are both 10 mm or less. In a measurement sample having a product of long side and short side of about 8000 mm ² to 10000 mm ² , which is the lower limit, when the curl height C _i and curl height C _h are both 10 mm or less, the curl height C _i and curl height C _h of a glass laminate of a size larger than this will also be 10 mm or less in principle. The product of the long side and short side may be, for example, 8000 mm ² or more and 10000 mm ² or less.

Thus, the glass laminate of the present disclosure exhibits a small degree of curl even when heated at 100°C and 55% RH for 30 minutes. A glass laminate that exhibits a small degree of curl after heating suppresses cracking of the glass film even when repeatedly bent in a high-temperature environment. In other words, the glass laminate exhibits excellent bending resistance even in a high-temperature environment.

In addition, when a glass laminate is repeatedly bent in a high-temperature, high-humidity environment, cracking of the glass film usually tends to become even more pronounced. However, a glass laminate that shows a small degree of curl after heating can suppress cracking of the glass film and achieve flex resistance even when repeatedly bent in a high-temperature, high-humidity environment.

As described above, the glass laminate of the present disclosure has excellent bending resistance and high reliability in high temperature environments or high temperature and high humidity environments.

The curl height C _i and height C _h of the glass laminate are determined by the following procedure for a rectangular glass laminate (hereinafter referred to as sample A) having a product of long and short sides of 8000 mm ² or more (e.g., 8000 mm ² or more and 10000 mm ² or less) and a long side/short side ratio before heating of 2.5 or less. Sample A may be, for example, a sample having a long side/short side ratio of 1.0 (long side = short side). The glass laminate is placed on a flat table so that the curl is on the upper side, and the heights of the four corners (the lower surfaces of the four corners) from the upper surface of the flat table are measured and averaged. This average value corresponds to the curl height C _i or C _h .

The curl height C _h is measured after the glass laminate is heated at 100° C. for 30 minutes in an environment of 55% RH and cooled to 25° C. The curl height C _i is measured at 25° C. in an environment of 55% RH for the glass laminate in an initial state before the glass laminate is subjected to any treatment such as heating.

(2) In the above (1), the thickness of the glass film may be 50 μm or less. In this case, the glass laminate is generally prone to curling when heated, and the bending resistance is likely to be reduced in a high temperature environment and a high temperature and high humidity environment. Since the glass laminate according to the present disclosure has a small curl C _h , even when the thickness of the glass film is relatively small, 50 μm or less, it can obtain high bending resistance in a high temperature environment and a high temperature and high humidity environment.

The thickness of the glass laminate is also calculated as the average thickness measured at multiple locations (e.g., five locations) at 25°C in an environment of 55% RH for the glass laminate in its initial state.

(3) In the above (1) or (2), the resin film may have a thermal shrinkage or thermal expansion rate of 0.10% or less in the MD and TD directions when heated at 100°C and 55% RH for 30 minutes. In this case, the curl C _h of the glass laminate tends to be small. Therefore, the glass laminate can have even higher bending resistance in high temperature environments and high temperature and high humidity environments.

The thermal shrinkage (or thermal expansion) of the resin film is measured for the resin film after the glass film is peeled off from the glass laminate or the resin film before being bonded to the glass film (resin film after annealing treatment described later). In this specification, the thermal shrinkage (or thermal expansion) corresponds to the ratio (%) of the absolute value of the difference between the length ( ^mm ) of the long side before heating and the length (mm) of the long side after heating of a rectangular resin film (hereinafter referred to as sample B) having a product of the long side and the short side of 8000 mm2 or more and a long side/short side ratio of 2.5 or less in an environment of 55% RH at 100 ° C. for 30 minutes. When sample B is rectangular, it is prepared by cutting the resin film so that the MD direction is parallel to the long side and the TD direction is parallel to the short side.

(4) In any one of (1) to (3) above, when a continuous bending test of multiple (e.g., three or more) glass laminates is performed under condition (a) at 25°C and 55% RH and condition (b) at 80°C and 55% RH, it is preferable that the crack occurrence rate, which corresponds to the number ratio of samples in which cracks occur in the glass film, is 5% or less under condition (a) and 35% or less under condition (b). In other words, excellent bending resistance in high-temperature environments of the glass laminate is ensured.

(5) In any one of (1) to (4) above, when a continuous bending test of multiple (e.g., three or more) glass laminates is performed under condition (a) at 25°C and 55% RH and condition (c) at 60°C and 90% RH, it is preferable that the crack occurrence rate, which corresponds to the number ratio of samples in which cracks occur in the glass film, is 5% or less under condition (a) and 35% or less under condition (c). In other words, excellent bending resistance of the glass laminate in a high-temperature, high-humidity environment is ensured.

When a continuous bending test of the glass laminate of the present disclosure is performed under the following conditions for multiple samples of the glass laminate under condition (a), 95% or more of the samples show no cracks in the glass film (i.e., the crack occurrence rate is 5% or less). When a continuous bending test of the glass laminate is performed under condition (b) or condition (c) similar to the case of condition (a), 65% or more of the samples show no cracks in the glass film (i.e., the crack occurrence rate is 35% or less). For the continuous bending test, a rectangular glass laminate sample (sample C) with a long side of 152 mm and a short side of 65 mm is used. The long side of sample C may be parallel to the MD direction of the resin film, parallel to the TD direction, or oblique to both.

(6) In any one of the above (1) to (5), when the long side of the glass laminate for measuring the curl height is L1, the ratio of the curl height C _h to the long side L1: C _h /L1 may be 0.1 or less. In this case, the unit of both the long side L1 and the curl height C _h is mm. When the _{C h} /L1 ratio is in such a range, higher bending resistance in a high temperature environment and a high temperature and high humidity environment is likely to be obtained.

(7) The present disclosure also includes a method for manufacturing a glass laminate including a glass film having a first main surface and a second main surface, and a resin film bonded to at least the first main surface. The manufacturing method includes a first step of preparing a precursor film of the resin film, a second step of annealing the precursor film to obtain a resin film, and a third step of bonding the resin film to the first main surface of the glass film to obtain a glass laminate. Prior to the formation of the glass laminate, the resin film constituting the glass laminate is formed by annealing the precursor film, thereby making it possible to reduce the curl height C _h when the glass laminate is heated, and to improve the bending resistance of the glass laminate in a high-temperature environment and a high-temperature and high-humidity environment. The precursor film is a film in a state before the annealing treatment of the resin film.

(8) In the above (7), in the second step, the annealing treatment may be performed at a temperature of 90°C or higher and 200°C or lower. In this case, the thermal shrinkage rate or thermal expansion rate of the resin film obtained by the annealing treatment is easily reduced. Therefore, the curl height C _h of the glass laminate can be further reduced, and the bending resistance in a high temperature environment and a high temperature and high humidity environment can be further improved. The environment for the annealing treatment may be, for example, 50% to 60% RH.

The glass laminate and the method for manufacturing the glass laminate of the present invention, including the above (1) to (8), are described in more detail below. At least one of the above (1) to (8) may be combined with at least one of the elements described below, provided that there is no technical contradiction.

When referring to the drawings, the shape or dimensions of each component in each drawing are not shown to the same scale as in reality. In order to clarify the characteristics of each component, the relative relationship of these dimensions is shown diagrammatically and exaggerated.

[Glass laminate]
The glass laminate includes a glass film having a first principal surface and a second principal surface, and a resin film adhered to at least the first principal surface.

In a glass laminate according to one aspect of the present disclosure, when a measurement sample (sample A) of a rectangular glass laminate having a product of long sides and short sides of 8000 ^mm2 or more and a long side/short side ratio of 2.5 or less is heated at 55% RH and 100°C for 30 minutes, the initial curl height C _i of sample A before heating and the curl height C _h of sample A after heating are both 10 mm or less. Thus, in the present disclosure, the curl height C _h of the glass laminate after heating is small. This ensures high bending resistance of the glass laminate in high temperature environments and high temperature and high humidity environments.

The initial curl height C _i is 10 mm or less, may be 5 mm or less, or may be 1 mm or less. The initial curl height C _i may be 0 mm. The curl height C _i is usually smaller than the curl height C _h .

The curl height C _h is 10 mm or less, and may be 5 mm or less. When the curl height C _h is so small, it can be said that the thermal shrinkage rate or thermal expansion rate of the resin film included in the glass laminate is low. As a result, even when the glass laminate is exposed to a high temperature environment or a high temperature and high humidity environment, the expansion and contraction of the resin film is suppressed, and even when the glass laminate is repeatedly bent under such an environment, cracking of the glass film and peeling between the glass film and the resin film are suppressed, and high bending resistance is obtained.

The difference between the curl height C _h and the curl height C _i (=C _h -C _i ) may be 10 mm or less, 5 mm or less, or 3 mm or less. When the difference (C _h -C _i ) is in such a range, higher bending resistance in a high temperature environment or a high temperature and high humidity environment is obtained. The difference (C _h -C _i ) may be 0 mm.

The glass laminate of the present disclosure includes a resin film (sometimes referred to as a first resin film) adhered to a first main surface of a glass film. If necessary, the glass laminate may include a first resin film adhered to the first main surface and a second resin film adhered to the second main surface.

In a glass laminate, the resin film is adhered to the main surface of the glass film via an adhesive layer.

(Glass film)
The glass film is generally also referred to as thin glass. It is preferable that the glass film has a uniform thickness.

The composition of the glass constituting the glass film is not particularly limited. Examples of the glass include soda-lime glass, borate glass, aluminosilicate glass, and quartz glass. The glass may be non-alkali glass or low-alkali glass. The total content of alkali metal components (e.g., Na ₂ O, K ₂ O, Li ₂ O) in the glass may be 15 mass% or less, or 10 mass% or less.

The thickness of the glass film may be 100 μm or less. The thickness of the glass film may be 50 μm or less, 35 μm or less, or 30 μm or less. When the thickness of the glass film is in such a range, the bending resistance in a high temperature environment and a high temperature and high humidity environment tends to be low. However, since the curl C _h is small in the present disclosure, even when the thickness of the glass film is in such a range, high bending resistance in a high temperature environment and a high temperature and high humidity environment can be obtained. The thickness of the glass film may be 10 μm or more.

In this specification, the thickness of each component of the glass laminate is the average value of thicknesses measured at multiple arbitrary locations (e.g., five locations) of the cross-sectional image, unless otherwise specified. The initial glass laminate is used as the cross-sectional sample for measurement.

The glass film is manufactured by any suitable method. Typically, the glass film is produced by melting a mixture containing ceramics (silica, alumina, etc.) as the main raw material, an antifoaming agent (mirabilite, antimony oxide, etc.), and a reducing agent (carbon, etc.) at a temperature of 1400°C to 1600°C, forming it into a film, and then cooling it. Examples of methods for forming the glass film include the slot downdraw method, the fusion method, and the float method. The glass film obtained by these methods may be chemically polished with a solvent such as hydrofluoric acid, if necessary, to further thin the glass film or to improve the smoothness of the surface and edges.

The surface of the glass film may be surface-treated to improve adhesion with the adhesive layer that comes into contact with the glass film. Examples of surface treatments include, but are not limited to, corona treatment, plasma treatment, and coupling treatment.

(Resin film)
In the glass laminate, the resin film (first resin film) is adhered to a first main surface of the glass film. When the glass laminate has a second resin film, the second resin film is adhered to a second main surface of the glass film.

The resin constituting each resin film may be a thermoplastic resin or a thermosetting resin. Examples of thermoplastic resins are polyethersulfone-based resins, polycarbonate-based resins, acrylic-based resins, polyester-based resins, polyolefin-based resins, cycloolefin-based resins, polyimide-based resins, polyamide-based resins, polyimideamide-based resins, polyarylate-based resins, polysulfone-based resins, and polyetherimide-based resins. An example of a polyester-based resin is an aromatic polyester-based resin (such as a polyalkylene arylate resin). Examples of polyalkylene arylate resins are polyethylene terephthalate (PET) resins, polybutylene terephthalate resins, and polyethylene naphthalate resins. An example of a cycloolefin-based resin is a norbornene-based resin. Examples of thermosetting resins are epoxy-based resins, urethane-based resins, and silicone-based resins. However, these resins are merely examples, and the resins constituting the resin film are not limited to these. The resin film may contain one type of resin, or may contain a combination of two or more types of resins. Each resin film may be a single layer or a multilayer. Each layer constituting a multilayer resin film may contain one type of resin or a combination of two or more types of resin. In consideration of the handleability and strength of the glass laminate, a film made of PET resin is preferable.

In the present disclosure, the resin film in the glass laminate (or the resin film before being adhered to the glass film) shrinks or expands little when heated. This reduces curling of the glass laminate when heated, making it easier to obtain high bending resistance of the glass laminate in high temperature environments and high temperature/high humidity environments.

Each resin film may have a thermal shrinkage or thermal expansion rate of 0.10% or less when heated at 55% RH and 100°C for 30 minutes. When the thermal shrinkage or thermal expansion rate is in such a range, the glass laminate can have even higher bending resistance in high temperature and high humidity environments. The thermal shrinkage or thermal expansion rate is measured by the above-mentioned procedure using sample B of the resin film. In the direction parallel to the long side of sample B (MD direction), the thermal shrinkage or thermal expansion rate may be 0.10% or less, or may be 0.09% or less. In the direction parallel to the short side of sample B (TD direction), the thermal shrinkage or thermal expansion rate may be 0.10% or less, or may be 0.05% or less. The thermal shrinkage or thermal expansion rate may be 0.00%.

The thickness of the resin film may be 10 μm or more, or may be 30 μm or more. When the thickness of the resin film is 50 μm or more, the curl height C _h is likely to be large due to thermal contraction or thermal expansion of the resin film. In the present disclosure, even if the thickness of the resin film is in such a range, the curl height C _h can be reduced, and high bending resistance can be ensured in a high temperature environment or a high temperature and high humidity environment. The thickness of the resin film may be 100 μm or less, 80 μm or less, or 75 μm or less.

(Adhesive Layer)
The glass film and the first resin film are bonded via an adhesive layer. The adhesive layer is formed by applying an adhesive to at least one of the first main surface of the glass film and the main surface of the resin film facing the first main surface of the glass film, stacking the glass film and the resin film so as to sandwich the adhesive, and then pressing and bonding them. More specifically, the adhesive is sandwiched between the glass film and the resin film, and the adhesive is cured while being pressed in the thickness direction. When the glass laminate has a second resin film, the second resin film may be bonded to the second main surface of the glass film via an adhesive layer, similar to the case of the first resin film.

In this way, the adhesive layer is formed by curing the coating of the adhesive. Therefore, the adhesive layer does not have substantial fluidity. On the other hand, the adhesive layer, which is made of an adhesive, is non-curable and has fluidity. The storage modulus of the adhesive layer at 25°C is greater than 10 MPa and may be 100 MPa or more, and is usually about 1 GPa. In contrast, the storage modulus of the adhesive layer at 25°C is, for example, 10 MPa or less, and is usually 1 MPa or less. In this way, the adhesive layer and the adhesive layer are also distinguished by their storage modulus.

The storage modulus of the adhesive layer can be measured as the tensile storage modulus in accordance with JIS K 7244-1:1998. Specifically, the adhesive is first formed into a film and cured to produce a cured film with a thickness of approximately 20 μm. This film is then cut to a specified size to produce a test piece. The viscoelasticity of this test piece is measured under the following conditions using a dynamic viscoelasticity measuring device (for example, the multifunction dynamic viscoelasticity measuring device "DMS6100" manufactured by Hitachi High-Tech Science Corporation), and the tensile storage modulus at 25°C is determined. The measurement may be performed five or more times to obtain the average value.

Measurement conditions Temperature range: -100℃ to +200℃
Heating rate: 2°C/min
Mode: Tensile Sample width: 10 mm
Distance between chucks: 20mm
Frequency: 10Hz
Strain amplitude: 10 μm
Atmosphere: Air (250ml/min)
Data acquisition interval: 0.5 min (every 1°C)

The adhesive is not particularly limited, and any suitable adhesive may be used. Examples of adhesives include adhesives containing a resin having a cyclic ether group (such as an epoxy group, a glycidyl group, or an oxetanyl group), adhesives containing an acrylic resin, and adhesives containing a silicone resin. The adhesive may be a thermosetting type or a photosetting type (such as an ultraviolet-curing type).

The thickness of the adhesive layer may be 0.5 μm or more and 20 μm or less, 1 μm or more and 20 μm or less, or 1 μm or more and 5 μm or less.

(Crack occurrence rate)
When the continuous bending test of the glass laminate is performed under condition (a) 25°C and 55% RH, the cracking rate may be 5% or less, 1% or less, or 0%. The glass laminate of the present disclosure has a low cracking rate even under high temperature and high temperature and high humidity environments. More specifically, when the continuous bending test of the glass laminate is performed under condition (b) 80°C and 55% RH, the cracking rate is preferably 35% or less, more preferably 30% or less or 10% or less. When the continuous bending test is performed under condition (c) 60°C and 90% RH, the cracking rate is preferably 35% or less, more preferably 30% or less or 10% or less. The cracking rate is the ratio (%) of the number of samples in which cracks have occurred to the total number of samples subjected to the test when the continuous bending test is performed. In addition, in the present disclosure, the cracking rate is also low when the continuous bending test of the glass laminate is performed at a low temperature. For example, when the continuous bending test is performed under condition (d) at −20° C., the crack occurrence rate may be 30% or less, 10% or less, 5% or less, 1% or less, or 0%. The continuous bending test is performed according to the following procedure.

(Continuous bending test)
A plurality of samples C of the glass laminate (e.g., three samples) are prepared. The shape of the sample C may be, for example, a rectangular shape with a long side of 152 mm and a short side of 65 mm. The sample C is set in a testing machine ("CL09-typeD01-FMC90" manufactured by Yuasa System Equipment Co., Ltd.) so that the glass film is on the inside of the bend. In this state, a continuous bending test is performed under the following conditions. The state of the bent portion of the sample C after the test is visually observed, and the number ratio (%) of samples in which cracks are observed is calculated as the peeling rate.

Environmental conditions: Condition (a) 25°C, 55% RH
Condition (b) 80°C, 55%RH
Condition (c) 60°C, 90%RH
Condition (d): -20°C
Test speed: 60 rpm
Bending radius: R1.5mm
Number of flexes: 200,000

(others)
When the long side of the glass laminate sample A for measuring the curl height is L1 (unit: mm), the ratio of the curl height C _h (unit: mm) to the long side L1: C _h /L1 may be 0.1 or less, or even 0.05 or less. When the C _h /L1 ratio is in such a range, higher bending resistance is likely to be obtained in high temperature environments and high temperature and high humidity environments.

The glass laminate may further include other layers as required. For example, a surface coating layer having various functions may be provided on at least a portion of the main surface of the glass film as required. Examples of surface coating layers include an anti-fingerprint coating layer, a hard coating layer, an anti-reflection layer, an anti-glare layer, an anti-soiling layer, an anti-sticking layer, a hue adjustment layer, an antistatic layer, an easy-adhesion layer, a layer preventing component deposition, an impact absorbing layer, and an anti-shattering layer. In addition, such a surface coating layer may be provided on the main surface of the resin film opposite the glass film as required.

An optical film or a multilayer film including an optical film may be disposed on the main surface of the resin film opposite the glass film via a pressure-sensitive adhesive layer or adhesive layer. Such a multilayer film may be a multilayer film including an optical film and a base film (such as the above-mentioned resin film), a multilayer film including two or more layers of optical film, or a multilayer film including one or more layers of optical film and a separator. Each film constituting the multilayer film may be directly bonded, or may be bonded via a pressure-sensitive adhesive layer or adhesive layer.

The optical film is not particularly limited, but may be, for example, a polarizing plate, a retardation plate, or an isotropic film. Examples of materials constituting the optical film include polyvinyl alcohol resins, polyolefin resins, cyclic olefin resins, polycarbonate resins, cellulose resins, polyester resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, (meth)acrylic resins, (meth)acrylic urethane resins, polysulfone resins, acetate resins, epoxy resins, and silicone resins. The optical film may be a metal oxide film (metal film, ITO film, etc.), or a laminate film of a metal film and a resin film.

[Method of manufacturing glass laminate]
An example of a method for producing a glass laminate according to the present disclosure will be described below. For components of the glass laminate, the above description of the glass laminate can be referred to.

The glass laminate is manufactured by a manufacturing method including, for example, a first step of preparing a precursor film for the resin film, a second step of annealing the precursor film to obtain a resin film, and a third step of bonding the resin film to a first main surface of the glass film to obtain a glass laminate.

(First step)
In the first step, a precursor film is prepared. Examples of the precursor film include films formed from the resin materials exemplified for the resin film. The precursor film may be prepared by film formation, or a commercially available product may be used.

The size of the precursor film is determined taking into account, for example, thermal contraction or thermal expansion due to annealing treatment.

(Second step)
In the second step, the precursor film is annealed to obtain a resin film. The annealing treatment suppresses the thermal contraction or expansion of the resin film when the glass laminate is exposed to high temperatures, so that the curl height C _h can be reduced compared to when the annealing treatment is not performed. As a result, the glass laminate can have high bending resistance in high temperature environments and high temperature and high humidity environments.

In the annealing treatment, the precursor film is heated. The temperature of the annealing treatment may be 90° C. or higher and 200° C. or lower, or 100° C. or higher and 160° C. or lower. When the temperature of the annealing treatment is in such a range, the precursor film is easily brought into a sufficiently thermally shrunk or thermally expanded state, which is advantageous in reducing the curl height C _h of the glass laminate.

The annealing time may be from 1 minute to 60 minutes, from 5 minutes to 40 minutes, or from 10 minutes to 30 minutes. When the annealing time is within such a range, the precursor film is easily brought into a sufficiently thermally shrunk or thermally expanded state, which is advantageous in reducing the curl height C _h of the glass laminate.

The temperature and time of the annealing treatment are not limited to the above ranges, and may be determined so that the thermal shrinkage or thermal expansion rate of the resin film when heated at 100°C for 30 minutes falls within the above ranges.

The annealing process may be performed in air or in an inert gas atmosphere. Examples of inert gas include nitrogen gas, helium gas, and argon gas.

(Third process)
In the third step, a resin film (first resin film) is bonded to the first main surface of the glass film to obtain a glass laminate. More specifically, an adhesive is applied to at least one of the first main surface of the glass film and the main surface of the resin film facing the first main surface, and the glass film and the resin film are pressed together with the adhesive sandwiched between them. At this time, the adhesive is cured to form an adhesive layer. In this manner, a glass laminate in which the glass film and the resin film are bonded together by the adhesive layer is obtained. The adhesive may be cured by heating or by light irradiation depending on the type of adhesive. When the second resin film is bonded to the second main surface of the glass film, a glass laminate is obtained in the same manner as when the first resin film is bonded.

FIG. 1 is a schematic vertical cross-sectional view showing an embodiment of a glass laminate according to the present disclosure.
1 includes a glass film 1, a resin film 2, and an adhesive layer 3 interposed therebetween. The glass film 1 has a first principal surface and a second principal surface, and the resin film 2 is adhered to the first principal surface by the adhesive layer 3.

[Example]
The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

Examples 1 to 3 and Comparative Examples 1 to 2
A glass laminate having the layer structure shown in FIG. 3 was produced by the following procedure.
(1) Preparation of Materials Constituting Each Layer The following materials were prepared.
(precursor film)
A biaxially stretched PET film having a thickness of 25 μm (Diafoil T600E25 (registered trademark) manufactured by Mitsubishi Chemical Corporation) was prepared. The PET film was cut so that the long side was parallel to the MD direction and the short side was parallel to the TD direction, to prepare a rectangular precursor film having a long side of 200 mm and a short side of 100 mm.

(Glass film)
As the glass film, an ultra-thin glass sheet having a thickness of 30 μm ("G-leaf (registered trademark)" manufactured by Nippon Electric Glass Co., Ltd.) was prepared. The glass film had a rectangular shape in a plan view and a size of 152 mm long side x 65 mm short side.

(Adhesive for adhesive layer)
An epoxy adhesive was prepared by blending 70 parts by mass of an aliphatic alicyclic epoxy resin (Celloxide 2021P, epoxy equivalent 128 to 133 g/eq., manufactured by Daicel Corporation), 5 parts by mass of a trifunctional aliphatic epoxy resin (EHPE3150, epoxy equivalent 170 to 190 g/eq., manufactured by Daicel Corporation), 19 parts by mass of an oxetane resin (Aron Oxetane (registered trademark), manufactured by Toa Gosei Co., Ltd.), 4 parts by mass of a silane coupling agent (KBM-403, 3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.), and 2 parts by mass of a photoacid generator (CPI101A, triarylsulfonium salt, manufactured by San-Apro Ltd.).

(2) Annealing Treatment The precursor film prepared in (1) above was annealed by heating at a temperature shown in Table 1, at 50% to 60% RH, for a time shown in Table 1 to obtain a resin film (PET film). In Comparative Example 1, the annealing treatment was not performed, and the precursor film was used as the resin film.

(3) Formation of glass laminate An adhesive was applied to both one main surface of the resin film obtained in (2) above and the first main surface of the glass film to form a coating film, and then the two were bonded together. The obtained laminate was pressed in the thickness direction, and UV irradiation was performed to cure the adhesive, thereby forming an adhesive layer. In this way, a glass laminate was formed.

(4) Evaluation The following evaluations were carried out using the resin film or the glass laminate.

(4-1) Thermal Shrinkage of Resin Film Sample B was prepared by cutting the resin film to a size of 100 mm x 100 mm. The initial dimensions of sample B were measured using a Mitutoyo image measuring instrument "QVA606-PRO_AE10". Next, sample B was heated at 55% RH and 100°C for 30 minutes in the same manner as described above, and the dimensions were measured again. The thermal shrinkage (%) was calculated from the following formula. The dimensions were measured in both the MD and TD directions.

Heat shrinkage rate (%) = {(initial dimension - dimension after heating) / (initial dimension)} x 100

(4-2) Curl heights C _i and C _h
A glass laminate having a long side (MD direction) of 152 mm and a short side (TD direction) of 65 mm was produced as Sample A. Using Sample A, curl heights C _i and C _h were determined by the above-mentioned procedure.

(4-3) Continuous bending test A glass laminate having a size of 152 mm long side (MD direction) × 65 mm short side (TD direction) was prepared as sample C. Using sample C, a continuous bending test was performed under each of the conditions (a) to (d) according to the procedure described above, and the peeling rate was determined.

The results of the examples and comparative examples are shown in Table 1. In Table 1, A1 to A3 correspond to examples 1 to 3, and B1 and B2 correspond to comparative examples 1 and 2.

As shown in Table 1, in the Examples in which the curl height C _h is 10 mm or less and the Comparative Examples in which the curl height C h exceeds 10 mm, the crack occurrence rate in the continuous bending test is low, 0%, under condition (a) or condition (d). However, under a high temperature environment (condition (b)) or a high temperature and high humidity environment (condition (c)), the crack occurrence rate in the continuous bending test is significantly higher in the Comparative Examples. In contrast, in the Examples, the crack occurrence rate is low and excellent bending resistance is obtained under both a high temperature environment and a high temperature and high humidity environment.

The glass laminate of the present disclosure has excellent bending resistance in high-temperature environments and is therefore highly reliable. Therefore, the glass laminate is suitable for applications requiring a glass film with excellent appearance and high bending properties (such as applications for cover windows of foldable or flexible devices). However, the applications of the glass laminate are not limited to these.

1 Glass film 2 Resin film 3 Adhesive layer 11 Glass laminate

Claims (8)

A glass laminate comprising a glass film having a first main surface and a second main surface, and a resin film adhered to the first main surface,
a measurement sample of the glass laminate having a rectangular shape with a product of long sides and short sides of 8,000 ^mm2 or more and a long side/short side ratio of 2.5 or less, is heated at 100°C and 55% RH for 30 minutes, and an initial curl height Ci of the glass laminate before heating and a curl height Ch of the glass laminate after heating are both 10 mm or less. The glass laminate according to claim 1, wherein the thickness of the glass film is 50 μm or less. The glass laminate according to claim 1 or 2, wherein the resin film has a thermal shrinkage or thermal expansion rate of 0.10% or less when heated at 100°C and 55% RH for 30 minutes. When a continuous bending test of the glass laminate is performed under condition (a) of 25° C. and 55% RH and condition (b) of 80° C. and 55% RH, a crack occurrence rate corresponding to the number ratio of samples in which cracks occur in the glass film is:
In the condition (a), it is 5% or less,
The glass laminate according to claim 1 or 2, wherein the ratio under condition (b) is 35% or less. When a continuous bending test of the glass laminate is performed under condition (a) of 25° C. and 55% RH and condition (c) of 60° C. and 90% RH, a crack occurrence rate corresponding to the number ratio of samples in which cracks occur in the glass film is:
In the condition (a), it is 5% or less,
The glass laminate according to claim 1 or 2, wherein the thickness under condition (c) is 35% or less. When the long side is L1, a ratio of the curl height C _h to the long side L1: C _h /L1 is 0.1 or less,
The glass laminate according to claim 1 or 2, wherein the long side L1 and the curl height C _h are both measured in mm. A method for producing a glass laminate including a glass film having a first main surface and a second main surface, and a resin film bonded to the first main surface, comprising:
A first step of preparing a precursor film of the resin film;
A second step of annealing the precursor film to obtain the resin film;
and a third step of bonding the resin film to the first main surface of the glass film to obtain the glass laminate. The method for manufacturing a glass laminate according to claim 7, wherein in the second step, the annealing treatment is carried out at a temperature of 90°C or higher and 200°C or lower.

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