Display device member, optical laminate and display device

Abstract

To provide a member for a display device which has excellent impact resistance and flexibility and has improved safety.SOLUTION: A member for a display device includes a glass substrate having a thickness of 100 μm or less, and a resin layer which is disposed on one surface of the glass substrate and has a composite elastic modulus of 5.7 GPa or more and a thickness of 5-60 μm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a member for a display device, an optical laminate, and a display device. [Background technology]

[0002] Conventionally, display devices have used glass or resin cover members to protect the display device. These cover members protect the display device from impacts and scratches, and are required to have strength, impact resistance, scratch resistance, and the like. Glass cover members are characterized by high surface hardness, scratch resistance, and high transparency, while resin cover members are characterized by light weight and shatter resistance. In addition, the thicker the cover member, the better its ability to protect the display device from impacts, and the material and thickness of the cover member are appropriately selected based on the weight, cost, size of the display device, and the like.

[0003] BACKGROUND ART In recent years, flexible displays such as foldable displays, rollable displays, and bendable displays have been actively developed, and among these, development of foldable displays, i.e., display devices that can be bent, has been progressing.

[0004] In bendable display devices, the cover member must also bend in accordance with the movement of the display device, and therefore a bendable cover member is used. In the case of resin cover members, polyimide or polyamide-imide films that have been made colorless and transparent through ingenuity in their chemical structure have been developed (see, for example, Patent Document 1). In the case of glass cover members, studies are underway to develop bendable cover members made by thinning the glass, such as ultra-thin glass (UTG) (see, for example, Patent Document 2). Among glass types, chemically strengthened glass has particularly high bending resistance. By incorporating expansion stress into the glass surface, minute scratches on the glass surface do not become larger when bent, making the glass less likely to break. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-137864 [Patent Document 2] Japanese Patent Application Publication No. 2018-188335 Summary of the Invention [Problem to be solved by the invention]

[0006] Glass has a higher elastic modulus than resin, so it has a better ability to protect a display device than resin at the same thickness. Glass also has high optical transparency, making it possible to manufacture display devices with better visibility. However, as glass becomes thinner, it becomes more fragile, dramatically reducing its impact resistance. If the glass cover member breaks due to an external impact, not only does it reduce its ability to protect the display device, but the resulting fragments and sharp edges may injure the user's fingertips, etc.

[0007] The present disclosure has been made in view of the above circumstances, and has a first object to provide a display device member, an optical laminate, and a display device including the same, which are excellent in impact resistance and flexibility and have improved safety. The present disclosure also has a second object to provide a display device member, which is excellent in strength, impact resistance, scratch resistance, and flexibility and has improved safety, and a display device including the same. [Means for solving the problem]

[0008] One embodiment of the present disclosure provides a member for a display device, comprising: a glass substrate having a thickness of 100 μm or less; and a resin layer disposed on one side of the glass substrate, the resin layer having a composite elastic modulus of 5.7 GPa or more and a thickness of 5 μm or more and 60 μm or less.

[0009] The member for a display device according to the present disclosure may have a primer layer between the glass substrate and the resin layer.

[0010] The display device member according to the present disclosure may further include a functional layer on the resin layer on the side opposite to the glass substrate, in which case the functional layer may be a hard coat layer.

[0011] The member for a display device according to the present disclosure preferably has a total light transmittance of 80% or more, and a haze of 2.0% or less.

[0012] In the display device member according to the present disclosure, the resin layer may contain polyimide or polyamideimide. In this case, the weight-average molecular weight of the polyimide is preferably 100,000 or more. The weight-average molecular weight of the polyamideimide is preferably 50,000 or more.

[0013] Another embodiment of the present disclosure provides an optical laminate having a glass substrate, a first resin layer, a second resin layer, and a third resin layer in this order, wherein the thickness of the glass substrate is 100 μm or less, the first resin layer has a composite elastic modulus of 5.7 GPa or more, the first resin layer has a thickness of 5 μm or more and 60 μm or less, the second resin layer is an adhesive layer, and the third resin layer is a resin film containing a resin selected from the group consisting of polyester-based resins, polycycloolefin-based resins, acetyl cellulose-based resins, polycarbonate-based resins, and polypropylene-based resins.

[0014] In the optical laminate according to the present disclosure, it is preferable that the total thickness of the resin layers disposed on the surface of the first resin layer of the glass substrate is 143 μm or less.

[0015] The optical laminate according to the present disclosure may have a functional layer on the side of the third resin layer opposite to the second resin layer, in which case the functional layer may be a hard coat layer.

[0016] The optical layered body according to the present disclosure preferably has a total light transmittance of 80% or more, and a haze of 2.0% or less.

[0017] In the optical laminate according to the present disclosure, the first resin layer may contain polyimide or polyamideimide. In this case, the weight-average molecular weight of the polyimide is preferably 100,000 or more. The weight-average molecular weight of the polyamideimide is preferably 50,000 or more.

[0018] Another embodiment of the present disclosure provides a display device including a display panel and the above-described member for a display device or the above-described optical laminate arranged on a viewer side of the display panel.

[0019] The display device of the present disclosure is preferably foldable. [Effects of the Invention]

[0020] The present disclosure has the effect of providing a display device member and an optical laminate that are excellent in impact resistance and flexibility and have improved safety. The present disclosure also has the effect of providing a display device member that is excellent in strength, impact resistance, scratch resistance, and flexibility and has improved safety. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic cross-sectional view illustrating a member for a display device according to the present disclosure. [Figure 2] 1 is a schematic cross-sectional view illustrating a member for a display device according to the present disclosure. [Figure 3] 1 is a schematic cross-sectional view illustrating a member for a display device according to the present disclosure. [Figure 4] 1 is a schematic cross-sectional view illustrating a member for a display device according to the present disclosure. [Figure 5] FIG. 1 is a schematic diagram for explaining a dynamic bending test. [Figure 6]FIG. 1 is a schematic diagram for explaining a static bending test. [Figure 7] 1 is a schematic cross-sectional view illustrating an example of an optical laminate according to the present disclosure. [Figure 8] 1 is a schematic cross-sectional view illustrating an example of an optical laminate according to the present disclosure. [Figure 9] 1 is a schematic cross-sectional view illustrating an example of an optical laminate according to the present disclosure. [Figure 10] 1 is a schematic cross-sectional view illustrating a display device according to the present disclosure. [Figure 11] 1 is a schematic cross-sectional view illustrating a display device according to the present disclosure. [Figure 12] 1 is a graph showing the relationship between the thickness of the resin layer and the evaluation of an impact test (pen drop test) in the resin members for a display device of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0022] Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be implemented in many different forms, and should not be construed as being limited to the description of the embodiments exemplified below. Furthermore, to clarify the explanation, the drawings may schematically depict the width, thickness, shape, etc. of each part compared to the actual form, but these are merely examples and are not intended to limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those previously described with reference to the previous drawings will be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0023] In this specification, when describing a mode in which another component is placed on a certain component, the terms "above" or "below" are used, unless otherwise specified, to include both a case in which another component is placed directly above or below a certain component so as to be in contact with the component, and a case in which another component is placed above or below a certain component with another component interposed therebetween. Also, in this specification, when describing a mode in which another component is placed on the surface of a certain component, the terms "on the surface side" or "on the surface" are used, unless otherwise specified, to include both a case in which another component is placed directly above or below a certain component so as to be in contact with the component, and a case in which another component is placed above or below a certain component with another component interposed therebetween.

[0024] In this specification, the term "film" also includes a member called a "sheet."

[0025] Hereinafter, the member for a display device, the optical laminate, and the display device according to the present disclosure will be described in detail.

[0026] A. Display device components To solve the above problems, the inventors of the present disclosure conducted extensive research and found that by using a thin, flexible glass substrate and disposing a resin layer on one side of the glass substrate, cracking of the glass substrate can be suppressed and impact resistance can be improved. Furthermore, by increasing the thickness of the resin layer, cracking of the glass substrate can be further suppressed and impact resistance can be further improved. However, when a display device component having a resin layer disposed on one side of the glass substrate is placed on the viewer side of the display panel of a display device, and the surface of the display device component facing the resin layer faces the viewer, the inventors found that a thick resin layer reduces the hardness of the surface of the display device component facing the resin layer, resulting in poor scratch resistance. The inventors of the present disclosure then conducted further research and found that by setting the composite elastic modulus of the resin layer within a predetermined range, cracking of the glass substrate can be suppressed even when the resin layer thickness is relatively thin to increase surface hardness. In other words, they found that a display device component excellent in all of strength, impact resistance, scratch resistance, and flexibility can be obtained. In addition, it has been found that by using a resin layer having predetermined properties, even if the glass substrate is broken, fragments or sharp edges are not exposed, allowing for safer use. The display device member of the present disclosure is based on this finding.

[0027] The display device member according to the present disclosure includes a glass substrate having a thickness of 100 μm or less, and a resin layer disposed on one side of the glass substrate, the resin layer having a composite elastic modulus of 5.7 GPa or more and a thickness of 5 μm or more and 60 μm or less.

[0028] Fig. 1 is a schematic cross-sectional view showing an example of a member for a display device according to the present disclosure. As shown in Fig. 1, the member for a display device 1 includes a glass substrate 2 and a resin layer 3 disposed on one surface of the glass substrate 2. The glass substrate 2 has a predetermined thickness, and the resin layer 3 has a predetermined thickness and a predetermined composite elastic modulus.

[0029] In the present disclosure, the glass substrate has a thickness of a predetermined value or less, which is a concern as it is thin and therefore prone to breakage and has low impact resistance, but by disposing a resin layer on one side of the glass substrate, when an impact is applied to the display device member, the resin layer absorbs the impact and can suppress breakage of the glass substrate, thereby improving impact resistance. Furthermore, even if the glass substrate is broken, the resin layer can suppress glass from scattering.

[0030] Here, increasing the thickness of the resin layer can further suppress cracking of the glass substrate and further improve impact resistance. However, if the thickness of the resin layer is too thick, the hardness of the surface of the display device member on the resin layer side decreases, resulting in poor scratch resistance. Therefore, in order to increase the hardness of the surface of the display device member on the resin layer side, it is necessary to make the thickness of the resin layer relatively thin. According to the present disclosure, since the composite elastic modulus of the resin layer is within a predetermined range, cracking of the glass substrate can be suppressed even when the thickness of the resin layer is made relatively thin to increase the surface hardness. Therefore, both impact resistance and scratch resistance can be improved.

[0031] The composite elastic modulus of the resin layer is measured by a nanoindentation method (indentation test method) as described below. A pen drop test is one way to evaluate the impact resistance of a thin glass substrate, and the impact resistance of a display device component can be evaluated by the pen drop test as described in the Examples below. There are various types of elastic modulus in addition to the composite elastic modulus, but the composite elastic modulus of the resin layer is used in the present disclosure. This is because, in measuring the composite elastic modulus of the resin layer by the nanoindentation method (indentation test method), the indenter is pressed into the measurement sample, which is similar to the pen tip colliding with and pressing into the sample in the pen drop test.

[0032] According to the present disclosure, the composite elastic modulus of the resin layer is equal to or greater than a predetermined value, thereby making it possible to improve impact resistance in a pen drop test.

[0033] Furthermore, according to the present disclosure, since the thickness of the glass substrate is thin, being equal to or less than a predetermined value, and the thickness of the resin layer is relatively thin, being within a predetermined range, flexibility can be increased, cracking of the resin layer can be suppressed when the display device member is bent, and bending resistance can be maintained. Therefore, the display device member of the present disclosure can be bent and can be used for a wide variety of display device members, for example, as a foldable display member.

[0034] Furthermore, according to the present disclosure, by having the composite elastic modulus of the resin layer equal to or greater than a predetermined value, the restoring force when the resin layer is deformed can be increased. Note that the composite elastic modulus is an index that indicates the resistance to deformation. The greater the composite elastic modulus of the resin layer, the greater the restoring force when the resin layer is deformed. Conversely, the smaller the composite elastic modulus of the resin layer, the smaller the restoring force when the resin layer is deformed. Therefore, by having the composite elastic modulus of the resin layer equal to or greater than a predetermined value, the restoring force of the display device member after being continuously bent for a long period of time can be improved. Furthermore, the restoring force of the display device member after repeated bending can also be improved.

[0035] In this manner, the present disclosure provides a display device member that is excellent in strength, impact resistance, scratch resistance, and flexibility. Furthermore, even if the glass substrate is broken, the risk of injury to the human body can be reduced, resulting in a highly safe display device member.

[0036] In addition, optical films having a resin substrate have also been known as components to be placed on the surface of foldable displays, but foldable displays using such optical films as the components have the disadvantage that they are prone to leaving folding marks, reducing image quality and impairing the appearance.In contrast, according to the present disclosure, a display device component using a glass substrate is used, and the component has a glass substrate, which is less likely to leave folding marks, improving image quality and improving the appearance.

[0037] Hereinafter, each configuration of the member for a display device according to the present disclosure will be described.

[0038] 1. Resin layer The resin layer in the present disclosure is a member having a composite elastic modulus of 5.7 GPa or more and a thickness of 5 μm or more and 60 μm or less, and is disposed on one side of a glass substrate. The resin layer is a member having impact absorption properties and also functions as a member for suppressing glass shattering when the glass substrate is broken. The resin layer is optically transparent, and when the display device member in the present disclosure is disposed on the viewer side of the display panel of the display device, the resin layer is disposed on the viewer side of the glass substrate.

[0039] (1) Resin layer characteristics The composite elastic modulus of the resin layer can be 5.7 GPa or more, preferably 6.0 GPa or more, and more preferably 6.5 GPa or more. When the composite elastic modulus of the resin layer is in the above range, even if the thickness of the resin layer is made relatively thin to increase the surface hardness, cracking of the glass substrate due to impact can be suppressed, and impact resistance and scratch resistance can be improved.

[0040] Furthermore, according to the method for measuring the composite elastic modulus described below, the composite elastic modulus of the glass substrate is approximately 40 GPa, so the composite elastic modulus of the resin layer is preferably, for example, 40 GPa or less, and more preferably 20 GPa or less.

[0041] Here, the composite elastic modulus of the resin layer is the indentation hardness (H IT ) when measuring the contact projection area A p "Indentation hardness" is a value determined from the load-displacement curve from loading to unloading of the indenter obtained by hardness measurement using the nanoindentation method. The composite elastic modulus of the resin layer is an elastic modulus that includes the elastic deformation of the resin layer and the elastic deformation of the indenter.

[0042] Indentation hardness (H ITThe measurement of the dimensional indentation (DIN) is performed on the measurement sample using a BRUKER TI950 TriboIndenter. Specifically, a 1 mm x 10 mm piece of a display device component is first embedded in an embedding resin to prepare a block. A uniform, hole-free section with a thickness of 50 nm to 100 nm is then cut from this block using a standard sectioning method. An Ultramicrotome EM UC7 (Leica Microsystems) or similar instrument can be used to prepare the section. The remaining block from which the uniform, hole-free section is cut serves as the measurement sample. Next, a Berkovich indenter (triangular pyramid, BRUKER TI-0039) is pressed vertically into the center of the cross section of the resin layer for 10 seconds to a maximum indentation load of 25 μN under the following measurement conditions: Here, in order to avoid the influence of the glass substrate and the side edges of the resin layer, the Berkovich indenter is pressed into a portion of the resin layer 500 nm away from the interface between the glass substrate and the resin layer toward the center of the resin layer, and 500 nm away from each of the two ends of the resin layer toward the center of the resin layer. If an optional layer such as a hard coat layer is present on the surface of the resin layer opposite to the surface facing the glass substrate, the Berkovich indenter is pressed into a portion of the resin layer 500 nm away from the interface between the optional layer and the resin layer toward the center of the resin layer. After that, the residual stress is relaxed by holding the pressure constant, and then the pressure is released over 10 seconds, and the maximum load after relaxation is measured, and the maximum load P max (μN) and contact projection area A p (nm 2 ) and P max / A p The indentation hardness (H IT The above contact projected area is the contact projected area corrected for the indenter tip curvature by the Oliver-Pharr method using a standard sample of fused quartz (5-0098 manufactured by BRUKER). Indentation hardness (H IT) is the arithmetic mean value of the values ​​obtained by measuring at 10 points. If the measured values ​​include values ​​that deviate from the arithmetic mean value by more than ±20%, those values ​​shall be excluded and remeasured. Whether or not there are any measured values ​​that deviate from the arithmetic mean value by more than ±20% shall be judged by whether the value (%) calculated by (AB) / B x 100 is more than ±20%, where A is the measured value and B is the arithmetic mean value. Indentation hardness (H IT ) can be adjusted by the type of resin contained in the resin layer, which will be described later.

[0043] (Measurement conditions) ·Loading speed: 2.5μN / sec ·Holding time: 5 seconds ·Loading and unloading speed: 2.5μN / sec ·Measurement temperature: 25℃

[0044] Composite elastic modulus of resin layer E r is the contact projected area A obtained during the indentation hardness measurement using the following formula (1). p The composite elastic modulus is determined by measuring the indentation hardness at 10 locations, calculating the composite elastic modulus each time, and using the arithmetic mean value of the composite elastic moduli obtained at the 10 locations.

[0045]

number

[0046] (In the above formula (1), A p is the contact projected area, and E r is the composite elastic modulus of the resin layer, and S is the contact stiffness.)

[0047] (2) Resin layer structure The thickness of the resin layer can be 5 μm to 60 μm, preferably 10 μm to 50 μm, and more preferably 15 μm to 40 μm. When the thickness of the resin layer is relatively thin within the above range, flexibility can be increased, cracking of the resin layer can be suppressed when the display device member is bent, and bending resistance can be maintained.

[0048] Here, the thickness of the resin layer can be the average value of thicknesses at any 10 locations obtained by measuring a cross section of a member for a display device in the thickness direction observed with a transmission electron microscope (TEM), a scanning electron microscope (SEM), or a scanning transmission electron microscope (STEM). The same method can be used to measure the thicknesses of other layers in the member for a display device.

[0049] The resin layer may be disposed on only one surface of the glass substrate, or may be disposed so as to cover two or more surfaces of the glass substrate. In particular, by disposing the resin layer so as to cover the end surfaces (side surfaces) of the glass substrate, it is possible to reduce impacts from the side surfaces of the glass substrate and suppress the occurrence of scratches, thereby suppressing breakage of the glass.

[0050] (3) Resin layer material (a) Resin The resin contained in the resin layer is not particularly limited as long as it satisfies the above-mentioned composite elastic modulus and has optical transparency, and examples thereof include polyimide, polyamideimide, acrylic resin, epoxy resin, urethane resin, triacetyl cellulose (TAC), etc.

[0051] Hereinafter, polyimide and polyamideimide will be used as examples for explanation.

[0052] (i) Polyimide Polyimide is obtained by reacting a tetracarboxylic acid component with a diamine component. It is preferable to obtain a polyamic acid by polymerization of the tetracarboxylic acid component and the diamine component, and then imidize the polyamic acid. The imidization may be performed by chemical imidization, thermal imidization, or a combination of chemical imidization and thermal imidization.

[0053] The polyimide is not particularly limited as long as it satisfies the above-mentioned composite elastic modulus and has optical transparency, but for example, it is preferable that the polyimide contains 10 mol % to 100 mol % of structural units represented by the following general formula (1) and (100-x) mol % (where x is the mol % of the structural units represented by the general formula (1)) of structural units represented by the following general formula (2), and has a weight-average molecular weight of 100,000 or more. This is because the polyimide has tetracarboxylic acid residues of a specific structure containing a parabiphenylene group with a twisted dihedral angle via an ester bond in the main chain, and diamine residues having an aromatic ring or an aliphatic ring, and has a specific weight-average molecular weight, which makes it easy to achieve a good balance between the composite elastic modulus and flexural resistance.

[0054] [ka]

[0055] (In general formulas (1) and (2), R 1 ~R 4 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; R 1 and R 2 and at least one of R 3 and R 4 At least one of A represents an alkyl group having 1 to 6 carbon atoms, A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.

[0056] Here, the term "tetracarboxylic acid residue" refers to a residue obtained by removing four carboxyl groups from a tetracarboxylic acid, and has the same structure as a residue obtained by removing an acid dianhydride structure from a tetracarboxylic dianhydride, and the term "diamine residue" refers to a residue obtained by removing two amino groups from a diamine.

[0057] In general formula (1), R 1 and R 2 and at least one of R 3 and R 4 At least one of R represents an alkyl group having 1 to 6 carbon atoms. The alkyl group having 1 to 6 carbon atoms may be a linear or branched alkyl group, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, an n-pentyl group, and an n-hexyl group. From the viewpoint of solvent solubility, an alkyl group having 1 to 4 carbon atoms is preferred, an alkyl group having 1 to 2 carbon atoms is more preferred, and a methyl group is even more preferred. Furthermore, from the viewpoint of solvent solubility, among these, R 1 and R 2 , and R 3 and R 4 preferably represents a methyl group.

[0058] In general formula (1), B represents a divalent group that is a diamine residue having an aromatic ring or an aliphatic ring. The diamine residue having an aromatic ring or an aliphatic ring can be a residue obtained by removing two amino groups from a diamine having an aromatic ring or a diamine having an aliphatic ring.

[0059] Specific examples of diamines having an aromatic ring and diamines having an aliphatic ring include those described in, for example, JP-A-2019-132930 and JP-A-2019-1989. These can be used alone or in combination of two or more.

[0060] In the general formula (2), A represents a tetravalent group that is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group that is a diamine residue having an aromatic ring or an aliphatic ring. B in the general formula (2) may be the same as B in the general formula (1), and therefore, a description thereof will be omitted here. B in the general formula (1) and B in the general formula (2) may be the same or different.

[0061] The tetracarboxylic acid residue in A of the general formula (2) can be a residue obtained by removing an acid dianhydride structure from a tetracarboxylic acid dianhydride having an aromatic ring, or a residue obtained by removing an acid dianhydride structure from a tetracarboxylic acid dianhydride having an aliphatic ring.

[0062] Specific examples of tetracarboxylic acid dianhydrides having an aromatic ring and tetracarboxylic acid dianhydrides having an aliphatic ring include those described in, for example, JP-A-2019-132930 and JP-A-2019-1989. These may be used alone or in combination of two or more.

[0063] The polyimide preferably contains 10 mol % or more and 100 mol % or less of the structural unit represented by the general formula (1). From the viewpoint of solubility in a solvent, the polyimide more preferably contains 15 mol % or more of the structural unit represented by the general formula (1), even more preferably 25 mol % or more, and particularly preferably 50 mol % or more.

[0064] On the other hand, in order to improve surface hardness and light transmittance, a copolymer component may be contained, and the polyimide may contain 95 mol % or less, 90 mol % or less, or 80 mol % or less of the structural unit represented by the above general formula (1).

[0065] Furthermore, the polyimide preferably contains (100-x) mol % (where x is the mol % of the structural unit represented by the general formula (1)) of the structural unit represented by the general formula (2). From the viewpoint of solubility in a solvent, the polyimide more preferably contains 85 mol % or less, even more preferably 75 mol % or less, and particularly preferably 50 mol % or less of the structural unit represented by the general formula (2).

[0066] When the polyimide contains 100 mol % of the structural unit represented by the general formula (1), the structural unit represented by the general formula (2) is 0 mol %, i.e., not contained. The structural unit represented by the general formula (2) may be 0 mol %, but may be contained as a copolymerization component from the viewpoint of improving surface hardness and light transmittance. The polyimide may contain 5 mol % or more, 10 mol % or more, or 20 mol % or more of the structural unit represented by the general formula (2).

[0067] In order to improve light transmittance and surface hardness, it is preferable that at least one of the tetravalent group of the tetracarboxylic acid residue of A and the divalent group of the diamine residue of B contains an aromatic ring and at least one selected from the group consisting of (i) a fluorine atom, (ii) an aliphatic ring, and (iii) a structure in which aromatic rings are linked together by a sulfonyl group or an alkylene group optionally substituted with fluorine. When the polyimide contains at least one selected from a tetracarboxylic acid residue having an aromatic ring and a diamine residue having an aromatic ring, the molecular skeleton becomes rigid, improving orientation and surface hardness. However, the rigid aromatic ring skeleton tends to extend the absorption wavelength to longer wavelengths, reducing transmittance in the visible light region. On the other hand, when the polyimide contains (i) a fluorine atom, the electronic state within the polyimide skeleton becomes less susceptible to charge transfer, thereby improving light transmittance. Furthermore, when the polyimide contains (ii) an aliphatic ring, the conjugation of π electrons in the polyimide skeleton can be broken, thereby inhibiting charge transfer within the skeleton, and thus light transmittance is improved. Furthermore, when the polyimide contains (iii) a structure in which aromatic rings are linked together by a sulfonyl group or an alkylene group which may be substituted with fluorine, the conjugation of π electrons in the polyimide skeleton can be broken, thereby inhibiting charge transfer within the skeleton, and thus light transmittance is improved.

[0068] In particular, from the viewpoint of improving light transmittance and surface hardness, it is preferable that at least one of the tetravalent group that is the tetracarboxylic acid residue of A and the divalent group that is the diamine residue of B contains an aromatic ring and a fluorine atom, and it is preferable that the divalent group that is the diamine residue of B contains an aromatic ring and a fluorine atom.

[0069] In terms of light transmittance, bending resistance and surface hardness, the polyimide is preferably selected from the group consisting of a diamine residue having an aromatic ring or an aliphatic ring in B in the general formulas (1) and (2), a trans-cyclohexanediamine residue, a trans-1,4-bismethylenecyclohexanediamine residue, a 4,4'-diaminodiphenylsulfone residue, a 3,4'-diaminodiphenylsulfone residue, a 2,2-bis(4-aminophenyl)propane residue, a 3,3'-bis(trifluoromethyl)-4,4'-[ Preferably, the divalent group is at least one selected from the group consisting of a (1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(4,1-phenyleneoxy)]dianiline residue, a 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, a 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, and a divalent group represented by the following general formula (3): In particular, from the viewpoint of achieving both optical transparency and surface hardness, the divalent group is preferably at least one selected from the group consisting of a 4,4'-diaminodiphenylsulfone residue, a 3,4'-diaminodiphenylsulfone residue, a 2,2-bis(4-aminophenyl)propane residue, and a divalent group represented by the following general formula (3), and more preferably a divalent group represented by the following general formula (3): The divalent group represented by the following general formula (3) is R 5 and R 6 is more preferably a perfluoroalkyl group, and among these, a perfluoroalkyl group having 1 to 3 carbon atoms is preferred, and a trifluoromethyl group or a perfluoroethyl group is more preferred. 5 and R 6 The alkyl group in is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group.

[0070] [ka]

[0071] (In the general formula (3), R5 and R 6 each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.

[0072] In particular, from the viewpoints of light transmittance, bending resistance, and surface hardness, the polyimide is preferably one in which the tetracarboxylic acid residue having an aromatic ring or an aliphatic ring in A in the general formula (2) is a cyclohexanetetracarboxylic acid dianhydride residue, a cyclopentanetetracarboxylic acid dianhydride residue, a dicyclohexane-3,4,3',4'-tetracarboxylic acid dianhydride residue, a cyclobutanetetracarboxylic acid dianhydride residue, a pyromellitic acid dianhydride residue, a 3,3',4,4'-biphenyltetracarboxylic acid dianhydride residue, a 2,2',3 ... and at least one tetravalent group selected from the group consisting of 2,3,3',4'-biphenyltetracarboxylic dianhydride residue, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene)diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride residue, and 3,4'-oxydiphthalic anhydride residue.

[0073] A in the above general formula (2) preferably contains 50 mol % or more of these suitable residues in total, more preferably 70 mol % or more, and even more preferably 90 mol % or more.

[0074] In terms of improving surface hardness, A in the above general formula (2) preferably contains a tetracarboxylic acid residue group (Group A) suitable for improving rigidity, such as at least one selected from the group consisting of pyromellitic dianhydride residues, 3,3',4,4'-biphenyltetracarboxylic dianhydride residues, and 2,2',3,3'-biphenyltetracarboxylic dianhydride residues. Furthermore, in terms of improving light transmittance, A in the above general formula (2) preferably includes at least one tetracarboxylic acid residue group (Group B) suitable for improving light transmittance, such as at least one selected from the group consisting of cyclohexanetetracarboxylic dianhydride residue, cyclopentanetetracarboxylic dianhydride residue, dicyclohexane-3,4,3',4'-tetracarboxylic dianhydride residue, cyclobutanetetracarboxylic dianhydride residue, 2,3,3',4'-biphenyltetracarboxylic dianhydride residue, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene)diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride residue, and 3,4'-oxydiphthalic anhydride residue. Group A and Group B may also be used in combination.

[0075] When Group A and Group B are mixed, the content ratio of the tetracarboxylic acid residue group (Group A) suitable for improving the rigidity to the tetracarboxylic acid residue group (Group B) suitable for improving light transmittance is preferably 0.05 mol to 9 mol, more preferably 0.1 mol to 5 mol, and even more preferably 0.3 mol to 4 mol, of the tetracarboxylic acid residue group (Group A) suitable for improving the rigidity per 1 mol of the tetracarboxylic acid residue group (Group B) suitable for improving light transmittance.

[0076] Among these, from the viewpoint of improving surface hardness and light transmittance, it is preferable to use at least one of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride residues and 3,4'-(hexafluoroisopropylidene)diphthalic anhydride residues, each containing a fluorine atom, as Group B.

[0077] The content (mol %) of each repeating unit, tetracarboxylic acid residue, and diamine residue in the polyimide can be determined from the molecular weight of the polyimide during production. The content (mol %) of each tetracarboxylic acid residue and diamine residue in the polyimide can also be determined by high-performance liquid chromatography, gas chromatography mass spectrometry, NMR, elemental analysis, XPS / ESCA, and TOF-SIMS on decomposition products of the polyimide obtained in the same manner as above.

[0078] In view of good flex resistance, the polyimide preferably has a weight-average molecular weight of 100,000 or more as measured by gel permeation chromatography in terms of polystyrene. In view of flex resistance, the weight-average molecular weight may be 120,000 or more, 140,000 or more, or 160,000 or more. On the other hand, in view of the reduced risk of bubble defects, the weight-average molecular weight is preferably 270,000 or less. Furthermore, in view of solubility, the weight-average molecular weight may be 250,000 or less, 230,000 or less, or 210,000 or less.

[0079] The weight-average molecular weight of polyimide can be measured by gel permeation chromatography (GPC). Specifically, polyimide is dissolved in N-methylpyrrolidone (NMP) at a concentration of 0.1% by mass, and the developing solvent is a 30 mmol% LiBr-NMP solution with a water content of 500 ppm or less. Measurements are performed using a Tosoh GPC system (HLC-8120, column: SHODEX GPC LF-804) with a sample load of 50 μL, a solvent flow rate of 0.4 mL / min, and a temperature of 37°C. The weight-average molecular weight is determined based on a polystyrene standard sample of the same concentration as the sample.

[0080] (ii) Polyamide-imide The polyamideimide is not particularly limited as long as it satisfies the above-mentioned composite elastic modulus and has optical transparency. For example, it is preferable that the polyamideimide contains a polyimide structural unit including a structural unit represented by the following formula (4) and a polyamide structural unit including a structural unit represented by the following formula (5).

[0081] [ka]

[0082] (In formula (5), X represents a divalent group that is a dicarboxylic acid residue having an aromatic ring.)

[0083] The polyamideimide contains a polyimide structural unit containing a structural unit represented by formula (4) and a polyamide structural unit containing a structural unit represented by formula (5), thereby enabling the production of a resin layer with sufficient transparency and a high composite modulus and flexural durability. The polyamideimide contains a polyimide structural unit having a specific structure containing a parabiphenylene group with a twisted dihedral angle via an ester bond in the main chain, and a specific diamine residue, and further contains a polyamide structural unit containing a dicarboxylic acid residue having an aromatic ring, which promotes intermolecular interactions through hydrogen bonding. By imparting a twisted aromatic ring to the main chain structure of the polymer, the intermolecular energy transition that occurs in π-conjugated polymers can be suppressed, achieving sufficient transparency. Furthermore, by introducing an amide bond site and an ester bond site into the polyimide structural unit, the intermolecular force due to hydrogen bonding can be increased, resulting in a resin layer with a high composite modulus and flexural durability.

[0084] Furthermore, the polyamideimide has good flex resistance, particularly in high-humidity environments. In the polyamideimide, hydrogen bonds are formed between the amide bond sites and the ester bond sites in the polyimide structural units, which prevents hydrogen bonding with moisture even in high-humidity environments. This is thought to prevent deterioration of flex resistance in high-humidity environments, resulting in good flex resistance.

[0085] Furthermore, since the polyamideimide contains the constitutional unit represented by the formula (4), it has good solubility in solvents even though it contains the constitutional unit represented by the formula (4).

[0086] (Polyimide structural unit) The polyimide structural unit is a structural unit obtained by reacting a tetracarboxylic acid component with a diamine component, and examples thereof include the structural unit represented by the general formula (2) described above in the section on polyimides.

[0087] The constitutional unit represented by the above formula (4) can be obtained by reacting a tetracarboxylic dianhydride represented by the following formula (4-1) with 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl.

[0088] [ka]

[0089] The content of the structural unit represented by the formula (4) relative to the total polyimide structural units in the polyamideimide may be 100 mol %. Furthermore, the polyimide structural units may contain other polyimide structural units different from the structural unit represented by the formula (4). The content of the structural unit represented by the formula (4) relative to the total polyimide structural units in the polyamideimide is preferably 50 mol % or more, more preferably 60 mol % or more, even more preferably 70 mol % or more, and is preferably 100 mol % or less, and may be 90 mol % or less. When the content of the structural unit represented by the formula (4) is within the above range, the polyamideimide can have a high composite modulus and flexural durability while maintaining sufficient transparency. To improve the balance between transparency, composite modulus, and flexural durability, or to add additional properties, the polyamideimide may contain other polyimide structural units different from the structural unit represented by the formula (4).

[0090] The content of the tetracarboxylic acid dianhydride residues represented by the above formula (4-1) relative to the total tetracarboxylic acid residues contained in the polyimide structural units in the polyamideimide is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and preferably 100 mol% or less, and may be 90 mol% or less. When the content of the tetracarboxylic acid dianhydride residues represented by the above formula (4-1) is within the above range, the polyamideimide can have a high composite modulus and flexural durability while maintaining sufficient transparency. To improve the balance between transparency, composite modulus, and flexural durability, or to add additional properties, the polyamideimide may contain a tetracarboxylic acid dianhydride residue other than the tetracarboxylic acid dianhydride residue represented by the above formula (4-1).

[0091] Examples of other polyimide structural units that may be contained in the polyimide structural unit include, among the structural units represented by the general formula (2) above, polyimide structural units that are different from the structural unit represented by the formula (4) above. In the structural units represented by the general formula (2) above, A and B may be the same or different in each structural unit. That is, in the structural unit represented by the general formula (2) above, A and B may each independently be one type or two or more types.

[0092] In the structural unit represented by the general formula (2) above, A represents a tetravalent group that is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring. Examples of A include tetravalent groups represented by the following formulae (a1) to (a7) and tetravalent groups in which some or all of the hydrogen atoms in the tetravalent groups represented by these formulae have been substituted with one or more substituents selected from the group consisting of fluoro groups, methyl groups, methoxy groups, trifluoromethyl groups, and trifluoromethoxy groups.

[0093] [ka]

[0094] (In formulas (a1) to (a7), * represents a bond, and Q a represents a single bond, -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -CO-, -SO2-, -Ph-, -Ph-Q a2 -Ph-, -Q a2 -Ph-Q a2 -, -Q a2 -Ph-Ph-Q a2 -, -Q a2 -Ph-Q a2 -Ph-Q a2 - or a fluorene group. Ph represents a phenylene group, and Q a2 represents -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -CO-, or -SO2-.

[0095] Q aThe bonding positions of each of the rings may be independently ortho or meta to one of the two carboxy groups bonded to each ring. a2 The bonding positions of the groups to each ring are preferably, independently, meta or para to the phenylene group, and more preferably para.

[0096] In the constitutional unit represented by the general formula (2), among the tetravalent groups represented by the formulae (a1) to (a7), in the case of a structure containing an aromatic ring as in the formulae (a1) to (a3), the tetravalent groups represented by the formulae (a1) and (a2) are preferred from the viewpoint of imparting transparency and solubility in solvents. Furthermore, those having a flexible structure between the aromatic rings are preferred, and Q in the formula (a2) is a Examples include -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -SO2-, and -Q a2 -Ph-Q a2 -(Q a2 represents -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -CO-, or -SO2-.) Furthermore, since the transparency is improved when a fluorine atom is contained, Q a Examples include -C(CF3)2- and -Q a2 -Ph-Q a2 -(Q a2 is preferably -C(CF3)2-), and from the viewpoint of the composite elastic modulus, Q a Among these, -C(CF3)2- is more preferable.

[0097] Furthermore, in the structural unit represented by the general formula (2), A is preferably a tetravalent group represented by the formulae (a1) to (a7) above, containing an aliphatic ring as in the formulae (a4) to (a7) above, because the aliphatic structure provides excellent transparency and solubility. Among these, tetravalent groups represented by structures (a4), (a5), or (a6), which have fewer bending sites, are preferred, and of these, a tetravalent group represented by (a4) is preferred, because they provide a good composite modulus.

[0098] In the structural unit represented by the general formula (2) above, B represents a divalent group that is a diamine residue having an aromatic ring or an aliphatic ring. Examples of B include divalent groups represented by the following formulae (b1) to (b6) and divalent groups in which some or all of the hydrogen atoms in the divalent groups represented by these formulae have been substituted with one or more substituents selected from the group consisting of a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, and a trifluoromethoxy group.

[0099] [ka]

[0100] (In formulas (b1) to (b6), * represents a bond, and Q b represents a single bond, -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -CO-, -SO2-, -Ph-, -Ph-Q b2 -Ph-, -Q b2 -Ph-Q b2 -, -Q b2 -Ph-Ph-Q b2 -, -Q b2 -Ph-Q b2 -Ph-Q b2 - or a fluorene group. Ph represents a phenylene group, and Q b2 represents -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -CO-, or -SO2-.

[0101] Q b The bonding position of each of the rings is preferably the meta or para position relative to the amino group bonded to each ring, and more preferably the para position. b2 The bonding positions of the groups to each ring are preferably, independently, meta or para to the phenylene group, and more preferably para.

[0102] In the structural unit represented by the general formula (2) above, from the viewpoint of maintaining transparency and complex modulus, B is preferably a divalent group represented by the formulae (b1) to (b6) that has a phenylene skeleton and a molecular structure in which the π-conjugation between phenylene groups is broken, and more preferably further contains fluorine.

[0103] In the divalent group represented by the above formula (b2), Q b is preferably -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2- or -SO2-, and more preferably -C(CF3)2- or -SO2-.

[0104] In the structural unit represented by the general formula (2), B is preferably at least one divalent group selected from the group consisting of divalent groups represented by the general formula (3) in terms of transparency and maintaining the composite elastic modulus. As the divalent group represented by the general formula (3), R 5 and R 6 is more preferably a methyl group or a trifluoromethyl group, and even more preferably a trifluoromethyl group from the viewpoint of transparency.

[0105] Furthermore, the polyimide structural unit other than the structural unit represented by the above formula (4) may be a structural unit represented by the following formula (6).

[0106] [ka]

[0107] (In formula (6), B' represents a divalent group that is a diamine residue having an aromatic ring or an aliphatic ring, and is different from a 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl residue.)

[0108] In the above formula (6), B' represents a diamine residue having an aromatic ring or an aliphatic ring, which is different from a 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl residue, and may be the same as B in the above general formula (5).

[0109] When the polyimide structural unit contains other polyimide structural units, it is preferable to contain a structural unit represented by the following formula (7), a structural unit represented by the following formula (8), or a combination thereof. When the polyimide structural unit contains a structural unit represented by the following formula (7), a structural unit represented by the following formula (8), or a combination thereof, it is preferable from the viewpoint of improving transparency and increasing solubility in solvents. When the polyimide structural unit contains a structural unit represented by the following formula (7), it is more preferable from the viewpoint of improving transparency while maintaining a high composite elastic modulus.

[0110] [ka]

[0111] The structural unit represented by the above formula (7) can be obtained by reacting cyclobutanetetracarboxylic dianhydride with 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl. The structural unit represented by the above formula (8) can be obtained by reacting 4,4'-(hexafluoroisopropylidene)diphthalic anhydride with 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl.

[0112] The total content of other polyimide structural units different from the structural unit represented by formula (4) relative to the total polyimide structural units in the polyamideimide may be 0 mol%, but when contained, it is preferably 5 mol% or more, and may be 10 mol% or more, and is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less. If the total content of the other polyimide structural units is within the above range, high transparency can be imparted and the composite elastic modulus will be good.

[0113] In particular, when the polyamideimide contains a structural unit represented by the formula (7), a structural unit represented by the formula (8), or a combination thereof, the total content of the structural unit represented by the formula (7) and the structural unit represented by the formula (8) relative to the total polyimide structural units in the polyamideimide is preferably 5 mol% or more, and may be 10 mol% or more, and is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less. If the total content of the structural unit represented by the formula (7) and the structural unit represented by the formula (8) is within the above range, high transparency can be imparted and the composite elastic modulus can be improved.

[0114] (Polyamide structural unit) The polyamide structural unit is a structural unit obtained by reacting a dicarboxylic acid component with a diamine component, and examples thereof include a structural unit represented by the following general formula (9).

[0115] [ka]

[0116] (In general formula (9), X represents a divalent group which is a dicarboxylic acid residue having an aromatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.)

[0117] Here, the dicarboxylic acid residue refers to a residue obtained by removing two carboxyl groups from a dicarboxylic acid, and has the same structure as a residue obtained by removing two carboxylic acid chloride groups from a dicarboxylic acid chloride, and the diamine residue refers to a residue obtained by removing two amino groups from a diamine.

[0118] The polyamide structural unit in the polyamideimide contains, as an essential component, a structural unit represented by the above formula (5). One or more types of structural units represented by the above formula (5) are contained in the polyamide structural unit.

[0119] The structural unit represented by the above formula (5) can be obtained by reacting a dicarboxylic acid component having an aromatic ring with 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl. Examples of the dicarboxylic acid component include dicarboxylic acids and dicarboxylic acid chlorides, but it is preferable to use dicarboxylic acid chlorides from the viewpoint of reactivity.

[0120] In the constitutional unit represented by the formula (5), X in the formula (5) is preferably at least one selected from the group consisting of structures represented by the following formulae (x1) to (x3). A resin layer having sufficient transparency and a high composite elastic modulus can be obtained. In addition to the 1,4-phenylene group represented by the following formula (x1), a 1,3-phenylene group may also be used.

[0121] [ka]

[0122] (In formula (x3), L represents -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, or -CO-, and * represents a bond.)

[0123] In X in the above formula (5), among the structures represented by the above formulas (x1) to (x3), the structure represented by the above formula (x1) or formula (x2) is more preferred, and the structure represented by the above formula (x2) is even more preferred, in terms of improving the high composite elastic modulus and flexural resistance.

[0124] The content of the structural unit represented by the formula (5) relative to the total polyamide structural units in the polyamideimide may be 100 mol%. Furthermore, the polyamide structural units may further contain other polyamide structural units different from the structural unit represented by the formula (5). The content of the structural unit represented by the formula (5) relative to the total polyamide structural units in the polyamideimide is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, and is preferably 100 mol% or less, and may be 95 mol% or less. When the content of the structural unit represented by the formula (5) is within the above range, a good balance between transparency and composite modulus of elasticity is achieved.

[0125] From the viewpoint of the balance between transparency and composite modulus, the total content of X in the above formula (5), which is one or more types selected from the group consisting of structures represented by the above formulas (x1) to (x3), relative to the total number of structural units represented by the above formula (5) in the polyamideimide, may be 100 mol%, preferably 80 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, and even more preferably 95 mol% to 100 mol%.

[0126] The polyamide structural unit may contain other polyamide structural units different from the structural unit represented by the above formula (5), for example, among the structural units represented by the above general formula (9), polyamide structural units different from the structural unit represented by the above formula (5) may be mentioned. In the structural unit represented by the above general formula (9), X and B may be the same or different in each structural unit. That is, in the structural unit represented by the above general formula (9), X and B may each independently contain one type or two or more types. In the above general formula (9), X may be the same as X in the structural unit represented by the above formula (5), and B may be the same as B in the structural unit represented by the above general formula (5).

[0127] The polyamide structural unit other than the structural unit represented by the formula (5) may be contained in the polyamide structural unit, and from the viewpoint of transparency, may be a structural unit represented by the general formula (9) above, in which X is at least one selected from the group consisting of the structures represented by the formulas (x1) to (x3) above, and B is a divalent group represented by the formula (b2) above, in which Q b is -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, or -SO2-, or in the divalent group represented by the general formula (3), R 5 and R 6 is preferably a hydrogen atom or a methyl group, and in the divalent group represented by the above formula (b2), Q b is —C(CF3)2— or —SO2—, or in the divalent group represented by the general formula (3), R 5 and R 6 is more preferably a methyl group, and in the divalent group represented by the above formula (b2), Q b is even more preferably —C(CF 3 ) 2 —.

[0128] (Polyamide-imide) The content of the polyamide structural unit containing the structural unit represented by the formula (5) is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, still more preferably 50 mol% or more, and preferably 80 mol% or less, even more preferably 70 mol% or less, and still more preferably 60 mol% or less, relative to the total of the polyimide structural unit containing the structural unit represented by the formula (4) and the polyamide structural unit containing the structural unit represented by the formula (5). If the content of the polyamide structural unit containing the structural unit represented by the formula (5) is within the above range, the composite elastic modulus and flex resistance at room temperature of the resin layer are likely to be improved, and the solubility of the polyamideimide in solvents and the flex resistance at high temperatures and high humidity are likely to be improved.

[0129] The content of the dicarboxylic acid residue X having an aromatic ring in the above formula (5) is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, still more preferably 50 mol% or more, and preferably 80 mol% or less, even more preferably 70 mol% or less, and still more preferably 60 mol% or less, based on the total of the tetracarboxylic acid residues and dicarboxylic acid residues in the polyamideimide resin. If the content of the dicarboxylic acid residue X having an aromatic ring in the above formula (5) is within the above range, the composite elastic modulus of the resin layer and the flex resistance at room temperature are likely to be improved, and the solubility of the polyamideimide in solvents and the flex resistance at high temperatures and high humidity are likely to be improved.

[0130] Furthermore, the polyamideimide may partially have a structure different from the above polyimide structural units and the above polyamide structural units. In the polyamideimide, the sum of the polyimide structural units containing the structural units represented by the above formula (4) and the polyamide structural units containing the structural units represented by the above formula (5) preferably accounts for 95% or more, more preferably 98% or more, and even more preferably 100% of all structural units of the polyamideimide.

[0131] Examples of structures different from the polyimide constituent unit and the polyamide constituent unit include a constituent unit in which the tetracarboxylic acid component is not completely imidized and has a polyamic acid structure in part, and a polyamideimide constituent unit containing a tricarboxylic acid residue such as trimellitic anhydride.

[0132] The content (mol %) of each structural unit and each residue in the polyamideimide is: 1The polyamideimide can be measured using H-NMR, and can also be determined from the ratio of raw materials used during polyamideimide production. The structure of the polyamideimide can be determined using NMR, various mass spectrometry, etc. The structure and content ratio of each residue in the polyamideimide can be determined, for example, by decomposing the polyamideimide with an alkaline aqueous solution or supercritical methanol, and then using high-performance liquid chromatography, gas chromatograph mass spectrometry, NMR, elemental analysis, XPS / ESCA, and TOF-SIMS on the resulting decomposition product.

[0133] The weight-average molecular weight of the polyamideimide is preferably 50,000 or more, more preferably 100,000 or more, even more preferably 150,000 or more, and preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 300,000 or less. If the weight-average molecular weight of the polyamideimide resin is within the above range, poor appearance such as cracking or whitening is unlikely to occur after baking, a resin layer with good transparency is easily obtained, and an increase in viscosity during synthesis, varnish preparation, and resin layer formation is suppressed, making it easier to form a resin layer.

[0134] The method for measuring the weight average molecular weight of polyamideimide can be the same as the method for measuring the weight average molecular weight of polyimide described above.

[0135] (b) UV absorber The resin layer may contain an ultraviolet absorber. This can suppress deterioration of the resin layer due to ultraviolet rays. In particular, when the resin layer contains polyimide, it can suppress color change over time in the resin layer containing polyimide. Furthermore, in a display device including a display device member, it can suppress deterioration due to ultraviolet rays of components arranged on the display panel side of the display device member, such as a polarizer.

[0136] Examples of the ultraviolet absorber contained in the resin layer include triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers such as hydroxybenzophenone-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers.

[0137] Specific examples of triazine-based UV absorbers, benzophenone-based UV absorbers such as hydroxybenzophenone-based UV absorbers, and benzotriazole-based UV absorbers include those described in JP-A-2019-132930.

[0138] Among them, triazine-based ultraviolet absorbers, hydroxybenzophenone-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers are preferably used as the ultraviolet absorber.

[0139] Furthermore, the ultraviolet absorber is preferably a polymer or oligomer, because this can prevent the ultraviolet absorber from bleeding out when the display device member is repeatedly bent. Examples of such ultraviolet absorbers include polymers or oligomers having a triazine skeleton, a benzophenone skeleton, or a benzotriazole skeleton. Specifically, it is preferable to use a polymer or oligomer obtained by thermally copolymerizing a (meth)acrylate having a benzotriazole skeleton or a benzophenone skeleton with methyl methacrylate (MMA) in any ratio.

[0140] The content of the ultraviolet absorber in the resin layer is not particularly limited, but is preferably 1% by mass or more and 6% by mass or less, and more preferably 2% by mass or more and 5% by mass or less. If the content of the ultraviolet absorber is too low, the effect of the ultraviolet absorber may not be fully obtained. On the other hand, if the content of the ultraviolet absorber is too high, the resin layer may be significantly colored or the strength of the resin layer may be reduced.

[0141] (c) Other additives The resin layer may further contain additives as needed, such as inorganic particles, silica fillers for facilitating winding, surfactants for improving film-forming properties and defoaming properties, and adhesion improvers.

[0142] (4) Method for forming resin layer Examples of methods for forming the resin layer include a method of applying a resin composition onto a glass substrate. The application method is not particularly limited as long as it is a method that can apply the resin composition to a desired thickness, and examples thereof include common application methods such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, and screen printing. A transfer method can also be used to form the resin layer.

[0143] Hereinafter, an example in which the resin layer contains polyimide or polyamideimide will be described.

[0144] (i) Method for forming a resin layer containing polyimide Examples of methods for forming a polyimide-containing resin layer include a method of applying a polyimide varnish containing polyimide and an organic solvent to a glass substrate and drying the varnish, and a method of applying a polyimide precursor composition containing a polyimide precursor (polyamic acid) and an organic solvent to a glass substrate and then imidizing the polyimide precursor by heat treatment or chemical treatment. The former method can ease the heating conditions in the film formation process. On the other hand, the latter method eliminates restrictions on the solubility of the polyimide, thereby increasing the options for the chemical structure of the polyimide.

[0145] Among these, the following manufacturing method is preferred because it is less likely to cause bubble defects and makes it easier to obtain a resin layer with good thickness uniformity.

[0146] The method for forming a polyimide-containing resin layer preferably includes the following steps: a preparation step of preparing a polyimide varnish containing polyimide and an organic solvent, wherein the polyimide content in the polyimide varnish is 6% by mass or more and 15% by mass or less and the polyimide has a viscosity at 25°C of 1,000 cps or more and 50,000 cps or less; a coating step of applying the polyimide varnish to a glass substrate; a first drying step of drying the coating at a temperature of 140°C or less; and a second drying step of heating the coating at a temperature of 200°C or more after drying.

[0147] When polyimide dissolves well in organic solvents, the heating conditions in the film-forming process can be alleviated, so it is preferable to form a resin layer using a polyimide varnish obtained by dissolving polyimide in an organic solvent. When polyimide has a specific amount or more of structural units containing tetracarboxylic acid residues of a specific structure containing a parabiphenylene group with a twisted dihedral angle via an ester bond in the main chain, it is easily soluble in organic solvents. When polyimide has a solvent solubility such that it dissolves in an organic solvent at 25°C in an amount of 6% by mass or more, the above-mentioned resin layer formation method can be suitably used.

[0148] According to the above-mentioned method for forming a resin layer, the polyimide content in the varnish can be increased to a sufficient concentration, and the varnish can be adjusted to a desired viscosity range, so that a resin layer with good thickness uniformity and with less bubble defects can be obtained.

[0149] The organic solvent is not particularly limited as long as it can dissolve polyimide, and for example, an aprotic polar solvent or a water-soluble alcohol solvent can be used. Among them, organic solvents containing nitrogen atoms such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, and 1,3-dimethyl-2-imidazolidinone; γ-butyrolactone, etc. are preferred. The organic solvents can be used alone or in combination of two or more.

[0150] For the method of forming the resin layer containing the polyimide, reference can be made to the methods described in, for example, JP-A-2019-1989 and JP-A-2019-182974.

[0151] (ii) Method for forming a resin layer containing polyamideimide The method for forming the resin layer containing polyamideimide is not particularly limited, and examples thereof include a method in which a polyamideimide varnish containing polyamideimide and an organic solvent is applied to a glass substrate and then dried.

[0152] The method for producing polyamideimide is not particularly limited. For example, polyamideimide can be produced through the steps of: reacting one or more tetracarboxylic dianhydrides, including the tetracarboxylic dianhydride represented by the above formula (4-1) and, if necessary, a tetracarboxylic dianhydride having an aromatic ring or an aliphatic ring, with one or more diamines, including 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl and, if necessary, a diamine having an aromatic ring or an aliphatic ring, to obtain a polyimide precursor (polyamic acid); reacting the obtained polyimide precursor (polyamic acid) with a dicarboxylic acid component having an aromatic ring to obtain a polyamide-polyimide precursor (polyamic acid) copolymer; and imidizing the obtained polyamide-polyimide precursor (polyamic acid) copolymer.

[0153] The organic solvent contained in the polyamideimide varnish may be the same as the organic solvent contained in the polyimide varnish described above.

[0154] The method for applying the polyamideimide varnish is not particularly limited as long as it can be applied to the desired thickness, and examples thereof include common application methods such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, screen printing, etc. A transfer method can also be used to form a coating film of the polyamideimide varnish.

[0155] After the polyamideimide varnish is applied, the solvent in the coating film is dried at a temperature of 150° C. or less, preferably at a temperature of 30° C. or more and 120° C. or less, until the coating film becomes tack-free, for example.

[0156] The drying time may be adjusted appropriately depending on the thickness of the coating film, the type of solvent, the drying temperature, etc., and is preferably set to, for example, 5 minutes or more and 60 minutes or less, and preferably 10 minutes or more and 40 minutes or less. If the drying time is too long, the efficiency of forming the resin layer may decrease. On the other hand, if the drying time is too short, the solvent may dry out too quickly, which may affect the appearance of the resulting resin layer.

[0157] The method for drying the solvent is not particularly limited as long as it is possible to dry the solvent at the above temperature, and for example, an oven, a drying furnace, a hot plate, infrared heating, etc. can be used.

[0158] The drying step may include a first drying step of drying the coating film and a second drying step of heating the dried coating film at a high temperature. The heating temperature in the second drying step is preferably, for example, 150°C or higher. From the viewpoint of flex resistance, it is preferable to remove as much residual solvent as possible from the resin layer.

[0159] 2. Glass substrate The glass substrate in the present disclosure has a thickness of 100 μm or less and is a member that supports the resin layer.

[0160] The glass constituting the glass substrate is not particularly limited, but chemically strengthened glass is preferable. Chemically strengthened glass is preferable because it has excellent mechanical strength and can be made thinner accordingly. Chemically strengthened glass is typically glass whose mechanical properties have been strengthened by a chemical method by partially exchanging ion species near the surface of the glass, such as by replacing sodium with potassium, and has a compressive stress layer on the surface.

[0161] Examples of glasses that can be used to form chemically strengthened glass substrates include aluminosilicate glass, soda-lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborosilicate glass.

[0162] Commercially available chemically strengthened glass substrates include, for example, Gorilla Glass from Corning and Dragontrail from AGC Inc. In addition, as the chemically strengthened glass substrate, for example, the one described in JP 2019-194143 A can also be used.

[0163] The thickness of the glass substrate is 100 μm or less, preferably 15 μm or more and 100 μm or less, more preferably 20 μm or more and 90 μm or less, and even more preferably 25 μm or more and 80 μm or less. A glass substrate having a thin thickness within the above range can provide good flexibility and sufficient hardness. It can also suppress curling of the display device member. Furthermore, this is preferable in terms of reducing the weight of the display device member.

[0164] 3. Functional Layer The display device member according to the present disclosure may further include a functional layer on the surface of the resin layer opposite to the glass substrate, such as a hard coat layer, a protective layer, an anti-reflection layer, or an anti-glare layer.

[0165] The functional layer may be a single layer or may have multiple layers. The functional layer may be a layer having a single function or may have multiple layers having different functions. For example, the display device member of the present disclosure may have, as the functional layer, a hard coat layer and a protective layer in this order from the resin layer side.

[0166] (1) Hard Coat Layer As shown in Fig. 2, the display device member according to the present disclosure preferably further includes a hard coat layer 4 on the surface of the resin layer 3 opposite to the glass substrate 2. The hard coat layer is a member for increasing surface hardness. The presence of the hard coat layer can improve scratch resistance.

[0167] (a) Characteristics of the hard coat layer Here, the "hard coat layer" refers to a member for increasing surface hardness, and specifically refers to a member for a display device according to the present disclosure that has a hard coat layer and exhibits a hardness of "H" or higher when subjected to a pencil hardness test specified in JIS K 5600-5-4 (1999).

[0168] When the display device member in the present disclosure has a hard coat layer on the side of the resin layer opposite to the glass substrate, the pencil hardness of the surface of the display device member on the hard coat layer side is preferably H or more, more preferably 2H or more, and even more preferably 3H or more.

[0169] Here, pencil hardness is measured by the pencil hardness test specified in JIS K5600-5-4 (1999). Specifically, using a test pencil specified in JIS-S-6006, the pencil hardness test specified in JIS K5600-5-4 (1999) is performed on the surface of the hard coat layer side of the display device member, and the highest pencil hardness that does not cause scratches is evaluated. Measurement conditions can be an angle of 45°, a load of 750 g, a speed of 0.5 mm / s to 1 mm / s, and a temperature of 23±2°C. For example, a pencil scratch coating hardness tester manufactured by Toyo Seiki Co., Ltd. can be used as the pencil hardness tester.

[0170] (b) Hard Coat Layer Structure The hard coat layer may be a single layer or may have a multi-layer structure of two or more layers. When the hard coat layer has a multi-layer structure, in order to improve the surface hardness and to achieve a good balance between the flex resistance and the elastic modulus, the hard coat layer preferably has a layer for satisfying the pencil hardness and a layer for satisfying the dynamic flex test (a layer for satisfying the abrasion resistance).

[0171] (c) Hard Coat Layer Material As the material for the hard coat layer, for example, an organic material, an inorganic material, an organic-inorganic composite material, or the like can be used.

[0172] In particular, the material of the hard coat layer is preferably an organic material. Specifically, the hard coat layer preferably contains a cured product of a resin composition containing a polymerizable compound. The cured product of the resin composition containing a polymerizable compound can be obtained by polymerizing the polymerizable compound using a polymerization initiator as needed by a known method.

[0173] (i) Polymerizable compound The polymerizable compound has at least one polymerizable functional group in the molecule, and may be, for example, at least one of a radical polymerizable compound and a cation polymerizable compound.

[0174] The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound is not particularly limited as long as it is a functional group capable of causing a radical polymerization reaction, and examples thereof include groups containing a carbon-carbon unsaturated double bond, and specific examples thereof include a vinyl group and a (meth)acryloyl group. When the radical polymerizable compound has two or more radical polymerizable groups, these radical polymerizable groups may be the same or different.

[0175] The number of radically polymerizable groups that the radically polymerizable compound has in one molecule is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.

[0176] Among radical polymerizable compounds, compounds having a (meth)acryloyl group are preferred in terms of high reactivity. For example, polyfunctional (meth)acrylate monomers and oligomers having several (meth)acryloyl groups in the molecule and molecular weights of several hundred to several thousand, such as urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, and silicone (meth)acrylate, are preferably used. Polyfunctional (meth)acrylate polymers having two or more (meth)acryloyl groups in the side chains of the acrylate polymer are also preferably used. Among these, polyfunctional (meth)acrylate monomers having two or more (meth)acryloyl groups in one molecule are preferably used. By including a cured product of a polyfunctional (meth)acrylate monomer in the hard coat layer, the hardness of the hard coat layer can be improved, and adhesion can also be improved. Also, polyfunctional (meth)acrylate oligomers or polymers having two or more (meth)acryloyl groups in one molecule can be preferably used. When the hard coat layer contains a cured product of the polyfunctional (meth)acrylate oligomer or polymer, the hardness and flex resistance of the hard coat layer can be improved, and further, the adhesion can be improved.

[0177] In this specification, (meth)acryloyl refers to both acryloyl and methacryloyl, and (meth)acrylate refers to both acrylate and methacrylate.

[0178] Specific examples of polyfunctional (meth)acrylate monomers include those described in JP-A-2019-132930. Among these, from the viewpoints of high reactivity, improved hardness of the hard coat layer, and adhesion, those having 3 to 6 (meth)acryloyl groups in one molecule are preferred. For example, pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA), trimethylolpropane tri(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, etc. can be preferably used, and in particular, at least one selected from pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexaacrylate, and those modified with PO, EO, or caprolactone is preferred.

[0179] The resin composition may contain a monofunctional (meth)acrylate monomer as a radical polymerizable compound to adjust hardness and viscosity, improve adhesion, etc. Specific examples of the monofunctional (meth)acrylate monomer include those described in JP 2019-132930 A.

[0180] The cationically polymerizable compound is a compound having a cationically polymerizable group. The cationically polymerizable group of the cationically polymerizable compound is not particularly limited as long as it is a functional group capable of causing a cationic polymerization reaction, and examples thereof include an epoxy group, an oxetanyl group, and a vinyl ether group. When the cationically polymerizable compound has two or more cationically polymerizable groups, these cationically polymerizable groups may be the same or different.

[0181] The number of cationically polymerizable groups that the cationically polymerizable compound has in one molecule is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.

[0182] Among the cationically polymerizable compounds, compounds having at least one of an epoxy group and an oxetanyl group as the cationically polymerizable group are preferred, and compounds having two or more of at least one of an epoxy group and an oxetanyl group per molecule are more preferred. Cyclic ether groups such as epoxy groups and oxetanyl groups are preferred because they cause minimal shrinkage during polymerization. Among cyclic ether groups, compounds having an epoxy group are readily available in a variety of structures, do not adversely affect the durability of the resulting hard coat layer, and are advantageous in that their compatibility with radically polymerizable compounds is easily controlled. Among cyclic ether groups, oxetanyl groups have a higher degree of polymerization and lower toxicity than epoxy groups. When the resulting hard coat layer is combined with a compound having an epoxy group, they accelerate the network formation rate from the cationically polymerizable compound in the coating film, forming an independent network without leaving unreacted monomers in the film, even in regions where the radically polymerizable compound coexists.

[0183] Examples of the cationically polymerizable compound having an epoxy group include alicyclic epoxy resins obtained by epoxidizing polyglycidyl ethers of polyhydric alcohols having an alicyclic ring or cyclohexene ring- or cyclopentene ring-containing compounds with a suitable oxidizing agent such as hydrogen peroxide or peracid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts, polyglycidyl esters of aliphatic long-chain polybasic acids, and glycidyl (meth)acrylate homopolymers and copolymers; and glycidyl ether-type epoxy resins derived from bisphenols, such as bisphenol A, bisphenol F, and hydrogenated bisphenol A, or derivatives thereof, such as alkylene oxide adducts or caprolactone adducts, and novolac epoxy resins.

[0184] Specific examples of alicyclic epoxy resins, glycidyl ether epoxy resins, and cationically polymerizable compounds having an oxetanyl group include those described in JP-A-2018-104682.

[0185] The cured product of the resin composition containing the polymerizable compound contained in the hard coat layer can be analyzed using a Fourier transform infrared spectrophotometer (FTIR), a pyrolysis gas chromatograph (GC-MS), or the decomposition product of the polymer can be analyzed using a combination of high performance liquid chromatography, a gas chromatograph mass spectrometer, NMR, elemental analysis, XPS / ESCA, and TOF-SIMS.

[0186] (ii) Polymerization initiator The resin composition may contain a polymerization initiator as needed. The polymerization initiator may be appropriately selected from radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, etc. These polymerization initiators are decomposed by at least one of light irradiation and heating to generate radicals or cations, thereby promoting radical polymerization and cationic polymerization. Note that in some cases, the polymerization initiator may be completely decomposed and not remain in the hard coat layer.

[0187] Specific examples of radical polymerization initiators and cationic polymerization initiators include those described in JP-A-2018-104682.

[0188] (iii) particles The hard coat layer preferably contains inorganic or organic particles, more preferably inorganic fine particles, which can improve the hardness of the hard coat layer.

[0189] Examples of inorganic particles include metal oxide particles such as silica (SiO), aluminum oxide, zirconia, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide; metal fluoride particles such as magnesium fluoride and sodium fluoride; metal particles; metal sulfide particles; and metal nitride particles. Among these, metal oxide particles are preferred, and at least one selected from silica particles and aluminum oxide particles is more preferred, with silica particles being even more preferred because excellent hardness can be obtained.

[0190] The inorganic particles are preferably reactive inorganic particles having, at least on a part of their surface, photoreactive reactive functional groups capable of forming covalent bonds by crosslinking with each other or with at least one polymerizable compound. The hardness of the hard coat layer can be further improved by crosslinking with each other or with at least one of a radical polymerizable compound and a cation polymerizable compound.

[0191] The reactive inorganic particles have at least a portion of their surface coated with an organic component and have reactive functional groups on their surface introduced by the organic component. Examples of the reactive functional groups include polymerizable unsaturated groups, and more preferably photocurable unsaturated groups. Examples of the reactive functional groups include ethylenically unsaturated bonds such as (meth)acryloyl groups, vinyl groups, and allyl groups, and epoxy groups.

[0192] The reactive silica particles are not particularly limited, and conventionally known ones can be used, such as the reactive silica particles described in JP 2008-165040 A. Commercially available reactive silica particles include MIBK-SD, MIBK-SDMS, MIBK-SDL, and MIBK-SDZL manufactured by Nissan Chemical Industries, Ltd., and V8802 and V8803 manufactured by JGC Catalysts and Chemicals, Ltd.

[0193] In addition, silica particles may be spherical silica particles, but preferably irregular silica particles.Spherical silica particles and irregular silica particles may be mixed.In this specification, irregular silica particles refer to silica particles with a shape that has random potato-like irregularities on the surface.Since irregular silica particles have a larger surface area than spherical silica particles, by including such irregular silica particles, the contact area with the resin component etc. is increased, and the hardness of the hard coat layer can be improved.

[0194] Whether or not the silica particles are irregular shaped can be confirmed by observing the cross section of the hard coat layer with an electron microscope.

[0195] The average particle size of the inorganic particles is preferably 5 nm or more, more preferably 10 nm or more, from the viewpoint of improving hardness. If the average particle size of the inorganic particles is too small, it may be difficult to produce the particles and the particles may be prone to agglomeration. Furthermore, from the viewpoint of transparency, the average particle size of the inorganic particles is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. If the average particle size of the inorganic particles is too large, there is a risk that large irregularities may be formed in the hard coat layer or that haze may increase.

[0196] Here, the average particle size of the inorganic particles can be measured by observing the cross section of the hard coat layer with an electron microscope, and the average particle size is the average of the particle sizes of 10 arbitrarily selected particles. The average particle size of the irregular silica particles is the average of the maximum (longer diameter) and minimum (minor diameter) distances between two points on the periphery of the irregular silica particles that appear in the cross section of the hard coat layer with a microscope.

[0197] The hardness of the hard coat layer can be controlled by adjusting the size and content of the inorganic particles. For example, the content of silica particles is preferably 25 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the polymerizable compound.

[0198] (iv) ultraviolet absorber The hard coat layer may contain an ultraviolet absorber. This can suppress deterioration of the resin layer due to ultraviolet rays. In particular, when the resin layer contains polyimide, it can suppress color change over time in the resin layer containing polyimide. Furthermore, in a display device including a display device member, it can suppress deterioration due to ultraviolet rays of components arranged on the display panel side of the display device member, such as polarizers.

[0199] The ultraviolet absorber contained in the hard coat layer preferably has an absorption wavelength peak in absorbance measurement of 300 nm to 390 nm, more preferably 320 nm to 370 nm, and even more preferably 330 nm to 370 nm. This is because such an ultraviolet absorber can efficiently absorb ultraviolet rays in the UVA region, and can form a hard coat layer having ultraviolet absorbing ability without causing curing inhibition of the hard coat layer by shifting the peak wavelength from the absorption wavelength of 250 nm of the initiator for curing the hard coat layer.

[0200] Among them, it is preferable that the ultraviolet absorber has an absorption wavelength peak of 380 nm or less, since coloring caused by the ultraviolet absorber can be suppressed.

[0201] The absorbance of the ultraviolet absorber can be measured using, for example, an ultraviolet-visible-near infrared spectrophotometer (for example, V-7100 manufactured by JASCO Corporation).

[0202] The ultraviolet absorber may be the same as the ultraviolet absorber used in the resin layer.

[0203] Among these, from the viewpoint of suppressing deterioration of the resin layer due to ultraviolet rays, one or more ultraviolet absorbers selected from the group consisting of hydroxybenzophenone-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers are preferred, and one or more ultraviolet absorbers selected from the group consisting of hydroxybenzophenone-based ultraviolet absorbers are more preferred.

[0204] Specific examples of hydroxybenzophenone-based ultraviolet absorbers include those described in JP-A-2019-132930.

[0205] Among the hydroxybenzophenone-based ultraviolet absorbers, 2-hydroxybenzophenone-based ultraviolet absorbers are preferred, and one or more selected from the group consisting of benzophenone-based ultraviolet absorbers having the following general formula (A) are more preferred. These can suppress deterioration of the resin layer due to ultraviolet rays and improve durability.

[0206] [ka]

[0207] (In the general formula (A), X 1 and X 2 are each independently a hydroxyl group, -OR a or a hydrocarbon group having 1 to 15 carbon atoms, R a represents a hydrocarbon group having 1 to 15 carbon atoms.

[0208] In general formula (A), X 1 , X 2 and R a Examples of the hydrocarbon group having 1 to 15 carbon atoms in the formula (I) include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a dodecyl group, an allyl group, and a benzyl group. Each of the aliphatic hydrocarbon groups having 3 or more carbon atoms may be linear or branched. The hydrocarbon group preferably has 1 to 12 carbon atoms, and more preferably has 1 to 8 carbon atoms. In terms of facilitating improved light transmittance, the hydrocarbon group is preferably an aliphatic hydrocarbon group, and of these, a methyl group and an allyl group are preferred.

[0209] X is a material that is easy to improve durability. 1 and X 2 are each independently a hydroxyl group or -OR a It is preferable that:

[0210] The one or more selected from the group consisting of benzophenone-based ultraviolet absorbers having general formula (A) is preferably one or more selected from the group consisting of 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and 2,2'-dihydroxy-4,4'-diallyloxybenzophenone, and more preferably one or more selected from the group consisting of 2,2',4,4'-tetrahydroxybenzophenone and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone.

[0211] Specific examples of benzotriazole-based ultraviolet absorbers include those described in JP-A-2019-132930.

[0212] Among the benzotriazole-based UV absorbers, 2-(2-hydroxyphenyl)benzotriazoles are preferred, and one or more selected from the group consisting of benzotriazole-based UV absorbers having the following general formula (B) are more preferred, which can suppress deterioration of the resin layer due to UV rays and improve durability.

[0213] [ka]

[0214] (In the general formula (B), Y 1 , Y 2 , and Y 3 are each independently a hydrogen atom, a hydroxyl group, or -OR b or a hydrocarbon group having 1 to 15 carbon atoms, R b represents a hydrocarbon group having 1 to 15 carbon atoms, and Y 1 , Y 2 , and Y 3 At least one of the groups is a hydroxyl group, -OR b or a hydrocarbon group having 1 to 15 carbon atoms. 4 represents a hydrogen atom or a halogen atom.

[0215] In general formula (B), Y 1 , Y 2 , and Y 3 , and R b In the formula (I), examples of the hydrocarbon group having 1 to 15 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a dodecyl group. Each of the aliphatic hydrocarbon groups having 3 or more carbon atoms may be linear or branched. The hydrocarbon group preferably has 1 to 12 carbon atoms, and more preferably has 1 to 8 carbon atoms. In terms of facilitating improved light transmittance, the hydrocarbon group is preferably an aliphatic hydrocarbon group, and is preferably a linear or branched alkyl group, and among these, a methyl group, a t-butyl group, a t-pentyl group, an n-octyl group, or a t-octyl group is preferred.

[0216] In general formula (B), Y 4 Examples of the halogen atom in include a chlorine atom, a fluorine atom, and a bromine atom, and among these, a chlorine atom is preferred.

[0217] In general formula (B), Y 1 , and Y 3 is a hydrogen atom, and Y 2 is a hydroxyl group or -OR b and more preferably one or more selected from the group consisting of 2-(2-hydroxy-4-octyloxyphenyl)-2H-benzotriazole and 2-(2,4-dihydroxyphenyl)-2H-benzotriazole. This can suppress deterioration of the resin layer due to ultraviolet light and improve durability.

[0218] The content of the ultraviolet absorber in the hard coat layer is, for example, preferably 10% by mass or less, more preferably 7% by mass or less, from the viewpoint of suppressing haze caused by mixing the ultraviolet absorber. Also, from the viewpoint of suppressing deterioration of the resin layer due to ultraviolet rays and improving durability, the content of the ultraviolet absorber in the hard coat layer is preferably 1% by mass or more and 6% by mass or less, more preferably 2% by mass or more and 5% by mass or less.

[0219] (v) antifouling agent The hard coat layer may contain an antifouling agent, which can impart antifouling properties to the member for a display device.

[0220] The antifouling agent is not particularly limited, and examples thereof include silicone-based antifouling agents, fluorine-based antifouling agents, and silicone-based and fluorine-based antifouling agents. The antifouling agent may also be an acrylic-based antifouling agent. One type of antifouling agent may be used alone, or two or more types may be mixed and used.

[0221] A hard coat layer containing a silicone-based antifouling agent or a fluorine-based antifouling agent is less susceptible to fingerprints (less noticeable) and has good wiping properties. Furthermore, when a silicone-based antifouling agent or a fluorine-based antifouling agent is contained, the surface tension of the curable resin composition for a hard coat layer can be reduced during application, resulting in good leveling properties and a good appearance of the resulting hard coat layer.

[0222] Furthermore, a hard coat layer containing a silicone-based antifouling agent has good slipperiness and good scratch resistance, and a display device including a display device member having a hard coat layer containing such a silicone-based antifouling agent has good slipperiness when touched with a finger, a pen, or the like, resulting in a good tactile feel.

[0223] The antifouling agent preferably has a reactive functional group in order to improve the durability of the antifouling performance. If the antifouling agent does not have a reactive functional group, regardless of whether the display device member is in the form of a roll or a sheet, when the display device member is stacked, the antifouling agent will be transferred to the surface opposite to the hard coat layer side of the display device member, and when another layer is attached or applied to the surface opposite to the hard coat layer side of the display device member, the other layer may peel off, and further, the other layer may be easily peeled off when repeatedly bent. In contrast, when the antifouling agent has a reactive functional group, the antifouling performance will be more durable.

[0224] The number of reactive functional groups in the antifouling agent may be at least 1, and preferably at least 2. By using an antifouling agent having two or more reactive functional groups, it is possible to impart excellent scratch resistance to the hard coat layer.

[0225] The antifouling agent preferably has a weight-average molecular weight of not more than 5000. The weight-average molecular weight of the antifouling agent can be measured by gel permeation chromatography (GPC).

[0226] The antifouling agent may be uniformly dispersed in the hard coat layer, but from the viewpoint of obtaining sufficient antifouling properties with a small amount added and suppressing a decrease in the strength of the hard coat layer, it is preferable that the antifouling agent be unevenly distributed on the surface side of the hard coat layer.

[0227] Examples of methods for unevenly distributing the antifouling agent on the surface side of the hard coat layer include a method in which, when forming the hard coat layer, a coating film of a curable resin composition for a hard coat layer is dried and heated before being cured to reduce the viscosity of the resin component contained in the coating film, thereby increasing the fluidity and thereby unevenly distributing the antifouling agent on the surface side of the hard coat layer; and a method in which an antifouling agent with low surface tension is used, and the antifouling agent is floated on the surface of the coating film without applying heat when drying the coating film, and then the coating film is cured, thereby unevenly distributing the antifouling agent on the surface side of the hard coat layer.

[0228] The content of the antifouling agent is preferably, for example, 0.01 to 3.0 parts by mass per 100 parts by mass of the resin component. If the content of the antifouling agent is too low, sufficient antifouling properties may not be imparted to the hard coat layer, whereas if the content of the antifouling agent is too high, the hardness of the hard coat layer may decrease.

[0229] (vi) Other additives The hard coat layer may further contain additives as necessary. The additives are appropriately selected depending on the function to be imparted to the hard coat layer, and are not particularly limited, and examples thereof include inorganic or organic particles for adjusting the refractive index, infrared absorbers, antiglare agents, antifouling agents, antistatic agents, colorants such as blue pigments and purple pigments, leveling agents, surfactants, lubricants, various sensitizers, flame retardants, adhesion promoters, polymerization inhibitors, antioxidants, light stabilizers, and surface modifiers.

[0230] (d) Thickness of the hard coat layer The thickness of the hard coat layer may be appropriately selected depending on the material of the hard coat layer, the function of the hard coat layer, and the application of the display device member. For example, when the material of the hard coat layer is an organic material, the thickness of the hard coat layer is preferably 2 μm to 50 μm, more preferably 3 μm to 30 μm, even more preferably 5 μm to 20 μm, and particularly preferably 6 μm to 10 μm. Furthermore, when the material of the hard coat layer is an inorganic material, the thickness of the hard coat layer can be about several tens of nanometers. If the thickness of the hard coat layer is within the above range, sufficient hardness as a hard coat layer can be obtained, and a display device member with good bending resistance can be obtained.

[0231] (e) Method for forming a hard coat layer The method for forming the hard coat layer is appropriately selected depending on the material of the hard coat layer, etc., and examples thereof include a method of applying a curable resin composition for the hard coat layer containing the polymerizable compound or the like onto the resin layer and curing the composition, a vapor deposition method, a sputtering method, etc.

[0232] The curable resin composition for a hard coat layer contains a polymerizable compound, and may further contain a polymerization initiator, particles, an ultraviolet absorber, a solvent, an additive, and the like, as necessary.

[0233] The method for applying the curable resin composition for a hard coat layer onto the resin layer is not particularly limited as long as it is a method that allows application to a desired thickness, and examples thereof include common application methods such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, screen printing, etc. Furthermore, a transfer method can also be used as a method for forming a coating film of the resin composition for a hard coat layer.

[0234] The coating film of the curable resin composition for the hard coat layer is dried as needed to remove the solvent. Examples of drying methods include vacuum drying, heat drying, and a combination of these drying methods. For example, the coating film can be dried by heating at a temperature of 30°C to 120°C for 10 to 180 seconds.

[0235] The method for curing the coating film of the curable resin composition for the hard coat layer is appropriately selected depending on the polymerizable group of the polymerizable compound, and for example, at least one of light irradiation and heating can be used.

[0236] For light irradiation, ultraviolet rays, visible light, electron beams, ionizing radiation, etc. are mainly used. In the case of ultraviolet curing, for example, ultraviolet rays emitted from the light beam of an ultra-high pressure mercury lamp, high pressure mercury lamp, low pressure mercury lamp, carbon arc, xenon arc, metal halide lamp, etc. can be used. The irradiation dose of the energy ray source is, for example, 50 mJ / cm as the cumulative exposure dose at an ultraviolet wavelength of 365 nm. 2 More than 5000mJ / cm 2 It can be set to the following extent.

[0237] When heating is performed, the treatment can be performed at a temperature of, for example, 40° C. or higher and 120° C. or lower. Alternatively, the reaction may be carried out by leaving the mixture at room temperature (25° C.) for 24 hours or more.

[0238] (2) Protective layer The member for a display device according to the present disclosure may further include a protective layer on the surface of the resin layer opposite to the glass substrate.

[0239] The protective layer has transparency. Specifically, the total light transmittance of the protective layer is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more.

[0240] The total light transmittance of the protective layer can be measured in accordance with JIS K7361-1, for example, using a haze meter HM150 manufactured by Murakami Color Research Laboratory Co., Ltd. The same method can be used to measure the total light transmittance of other layers.

[0241] The protective layer is not particularly limited as long as it has transparency, and may contain, for example, a resin. The resin used for the protective layer is not particularly limited as long as it is a resin that can provide a transparent protective layer, and a general resin can be used.

[0242] Examples of methods for disposing a protective layer on one surface of a glass substrate include a method in which a protective film is used as the protective layer and the resin layer and the protective film are bonded together via an adhesive layer, and a method in which a protective layer is formed on a resin layer.

[0243] The pressure-sensitive adhesive layer has transparency. Specifically, the total light transmittance of the pressure-sensitive adhesive layer is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more.

[0244] Examples of adhesives used in the adhesive layer include adhesives such as OCA and photosensitive adhesives.

[0245] The thickness of the adhesive layer is preferably, for example, 1 μm or more and 100 μm or less. If the adhesive layer is too thick, flexibility may be impaired. On the other hand, if the adhesive layer is too thin, adhesion may not be ensured and peeling may occur.

[0246] 4. Other configurations In addition to the above-described layers, the display device member according to the present disclosure may also include other layers as needed, such as a primer layer, a second resin layer, and a decorative layer.

[0247] (1) Primer layer The display device member according to the present disclosure may have a primer layer 5 between the glass substrate 2 and the resin layer 3, as shown in Fig. 3, for example. When the display device member according to the present disclosure has a second resin layer 6 on the surface of the glass substrate 2 opposite to the resin layer 3, as shown in Fig. 4, for example, the display device member according to the present disclosure may have a primer layer 7 between the glass substrate 2 and the second resin layer 6. The primer layer can improve the adhesion between the glass substrate and the resin layer and the second resin layer.

[0248] The material for the primer layer is not particularly limited as long as it can enhance the adhesion between the glass substrate and the resin layer or the second resin layer, and examples thereof include resins. Examples of resins include (meth)acrylic resins, urethane resins, (meth)acrylic urethane copolymers, vinyl chloride-vinyl acetate copolymer resins, polyesters, butyral resins, chlorinated polypropylene, chlorinated polyethylene, epoxy resins, and silicone resins. These resins may be used alone or in combination of two or more.

[0249] The thickness of the primer layer may be any thickness that can increase the adhesion between the glass substrate and the resin layer or the second resin layer, and may be, for example, 0.1 μm or more and 10 μm or less, and preferably 0.2 μm or more and 5 μm or less.

[0250] The method for forming the primer layer may include, for example, a method of applying a primer layer composition onto a glass substrate. Examples of the application method include general application methods such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, and screen printing. Alternatively, a transfer method may be used to form the primer layer.

[0251] (2) Second resin layer 4, the display device member according to the present disclosure may have a second resin layer 6 on the surface of the glass substrate 2 opposite to the resin layer 3. When an impact is applied to the display device member, not only the resin layer but also the second resin layer absorbs the impact, which can suppress cracking of the glass substrate and improve impact resistance.

[0252] The resin contained in the second resin layer is not particularly limited as long as it is a resin that can absorb impact, and examples thereof include urethane resin, epoxy resin, polyimide, polyamideimide, acrylic resin, triacetyl cellulose (TAC), etc. These resins may be used alone or in combination of two or more.

[0253] The second resin layer may further contain additives as needed. Examples of additives include ultraviolet absorbers. The ultraviolet absorbers may be the same as those used in the resin layer.

[0254] The thickness of the second resin layer may be any thickness that can absorb impact, and is preferably, for example, 5 μm or more and 60 μm or less, more preferably 10 μm or more and 50 μm or less, and even more preferably 15 μm or more and 40 μm or less.

[0255] The second resin layer can be formed by the same method as the method for forming the resin layer described above.

[0256] (3) Decorative layer The display device member according to the present disclosure may have a decorative layer between the glass substrate and the resin layer, or on the surface of the glass substrate opposite to the resin layer.

[0257] The decorative layer includes a colorant and a binder resin. The binder resin included in the decorative layer is not particularly limited, and a resin used in a general decorative layer can be used. The colorant included in the decorative layer is not particularly limited, and a known colorant used in a general decorative layer can be used.

[0258] The decorative layer is usually disposed on a part of the glass substrate, and may have a pattern.

[0259] The thickness of the decorative layer is not particularly limited, but can be, for example, 5 μm or more and 40 μm or less.

[0260] 5. Characteristics of display device components The display device member according to the present disclosure preferably has a total light transmittance of, for example, 80% or more, more preferably 85% or more, and even more preferably 88% or more. Such a high total light transmittance allows the display device member to have good transparency.

[0261] Here, the total light transmittance of the member for a display device can be measured in accordance with JIS K7361-1, for example, by using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

[0262] The haze of the display device member in the present disclosure is, for example, preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.0% or less. Such a low haze allows the display device member to have good transparency.

[0263] The haze of the display member can be measured in accordance with JIS K-7136, for example, using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

[0264] The member for a display device in the present disclosure preferably has flexural resistance. Specifically, it is preferable that the member for a display device does not crack or break when subjected to a dynamic flexural test described below 200,000 times, and it is even more preferable that the member for a display device does not crack or break when subjected to a dynamic flexural test 1,000,000 times.

[0265] In the dynamic bending test, the display device component may be folded so that the glass substrate is on the outside, or the display device component may be folded so that the glass substrate is on the inside, but in either case, it is preferable that the display device component does not crack or break.

[0266] The dynamic bending test is performed as follows. As shown in FIG. 5(a), in the dynamic bending test, first, a short side 1C of a display device member 1 measuring 20 mm × 100 mm and a short side 1D opposite the short side 1C are fixed by parallel fixing portions 21. Also, as shown in FIG. 5(a), the fixing portions 21 are slidable horizontally. Next, as shown in FIG. 5(b), the fixing portions 21 are moved closer to each other to deform the display device member 1 so as to fold it. Furthermore, as shown in FIG. 5(c), the fixing portions 21 are moved to a position where the distance d between the two opposing short side portions 1C and 1D fixed by the fixing portions 21 of the display device member 1 becomes a predetermined value. Then, the fixing portions 21 are moved in the opposite direction to eliminate the deformation of the display device member 1. By moving the fixing portions 21 as shown in FIGS. 5(a) to 5(c), the display device member 1 can be folded 180°. Furthermore, by conducting a dynamic bending test so that the bent portion 1E of the display device member 1 does not protrude from the lower end of the fixing portion 21 and controlling the distance d when the fixing portion 21 is closest, it is possible to set the distance d between the two opposing short side portions 1C, 1D of the display device member 1 to a predetermined value. For example, if the distance d between the two opposing short side portions 1C, 1D is 10 mm, the outer diameter of the bent portion 1E is considered to be 10 mm.

[0267] It is preferable that no cracks or breaks occur in a display device member when a test in which the display device member 1 is folded 180° so that the distance d between the opposing short sides 1C, 1D of the display device member is 10 mm is repeated 200,000 times, but it is even more preferable that no cracks or breaks occur when a dynamic bending test in which the display device member is folded 180° so that the distance d between the opposing short sides of the display device member is 10 mm, 8 mm, 6 mm, 5 mm, 4 mm, 3 mm, 2.5 mm, or 2 mm is repeated 200,000 times.

[0268] Furthermore, when a static bending test described below is carried out on a member for a display device, it is preferable that the opening angle θ of the member for a display device after the static bending test is 100° or more.

[0269] The static bending test is performed as follows. First, as shown in FIG. 6(a), the short side 1C of the display device member 1 and the short side 1D opposite to the short side 1C are fixed by fixing parts 22 arranged parallel to each other so that the distance d between the short side 1C and the short side 1D is a predetermined value. Then, a static bending test is performed in which the display device member 1 is left in a folded state at 23°C for 240 hours. After the static bending test, as shown in FIG. 6(b), the fixing parts 22 are removed from the short side 1D to unfold the display device member 1, and the opening angle θ, which is the angle at which the display device member 1 naturally opens after 30 minutes at room temperature, is measured. Note that the larger the opening angle θ, the better the restorability, and the maximum opening angle is 180°.

[0270] In a member for a display device, when a static bending test is conducted so that the distance d between the opposing short sides 1C, 1D of the member for a display device 1 is 10 mm, the opening angle θ after the static bending test is preferably 100° or more.

[0271] In the static bending test, the display device component may be folded so that the glass substrate is on the inside, or the display device component may be folded so that the glass substrate is on the outside, but in either case, it is preferable that the opening angle θ is 100° or more.

[0272] 6. Uses for display device components The display device member according to the present disclosure can be used as a member arranged on the viewer's side of the display panel in a display device. The display device member according to the present disclosure can be used as a display device member for, for example, smartphones, tablet terminals, wearable terminals, personal computers, televisions, digital signage, public information displays (PIDs), in-vehicle displays, and the like. In particular, the display device member according to the present disclosure can be preferably used for flexible displays such as foldable displays, rollable displays, and bendable displays, and can be suitably used as a foldable display member.

[0273] In the member for a display device according to the present disclosure, the surface that becomes the outermost surface after the member for a display device is placed on the surface of a display device is preferably the surface on the resin layer side.

[0274] The method for disposing the display device member of the present disclosure on the surface of the display device is not particularly limited, and examples thereof include a method using an adhesive layer, etc. As the adhesive layer, a known adhesive layer used for adhering display device members can be used.

[0275] B. Optical laminate To solve the above problems, the inventors of the present disclosure conducted extensive research and found that by using a thin, flexible glass substrate and disposing a resin layer on one side of the glass substrate, cracking of the glass substrate can be suppressed and impact resistance can be improved. Furthermore, by setting the composite modulus of the resin layer within a predetermined range, cracking of the glass substrate can be suppressed and impact resistance can be improved, even when the thickness of the resin layer is relatively thin for flexibility. The inventors of the present disclosure then conducted further research and found that by laminating a first resin layer having a predetermined composite modulus, a second resin layer that is an adhesive layer, and a third resin layer that is a predetermined resin film, cracking of the glass substrate can be further suppressed and impact resistance can be further improved compared to when only a resin layer having a predetermined composite modulus is used. In addition, by laminating a specific first resin layer, second resin layer, and third resin layer, even if the glass substrate is broken, fragments and sharp edges are not exposed, allowing for safer use. The optical laminate of the present disclosure is based on these findings.

[0276] The optical laminate in the present disclosure is an optical laminate having a glass substrate, a first resin layer, a second resin layer, and a third resin layer in this order, wherein the thickness of the glass substrate is 100 μm or less, the composite elastic modulus of the first resin layer is 5.7 GPa or more, the thickness of the first resin layer is 5 μm or more and 60 μm or less, the second resin layer is an adhesive layer, and the third resin layer is a resin film containing a resin selected from the group consisting of polyester-based resins, polycycloolefin-based resins, acetyl cellulose-based resins, polycarbonate-based resins, and polypropylene-based resins.

[0277] Fig. 7 is a schematic cross-sectional view showing an example of an optical laminate according to the present disclosure. As shown in Fig. 7, optical laminate 11 includes, in this order, a glass substrate 12, a first resin layer 13, a second resin layer 14, and a third resin layer 15. Glass substrate 12 has a predetermined thickness, first resin layer 13 has a predetermined thickness and a predetermined composite elastic modulus, second resin layer 14 is an adhesive layer, and third resin layer 15 is a resin film containing a predetermined resin.

[0278] In the present disclosure, the glass substrate is thin, having a thickness of less than a predetermined value, and therefore is prone to breakage and has low impact resistance. However, by laminating a first resin layer having a predetermined composite elastic modulus, a second resin layer as an adhesive layer, and a third resin layer as a predetermined resin film in this order on one side of the glass substrate, when an impact is applied to the optical laminate, the first resin layer, the second resin layer, and the third resin layer absorb the impact, preventing the glass substrate from breaking and improving impact resistance. The reason for this is not clear, but is presumed to be as follows.

[0279] That is, since the first resin layer has a predetermined composite elastic modulus, the second resin layer is an adhesive layer, and the third resin layer is a predetermined resin film, the second resin layer is a layer softer than the first and third resin layers, and the third resin layer is a layer softer than the first resin layer. For example, the tensile elastic modulus of the resin contained in the resin film constituting the third resin layer is 2.8 to 4 GPa for polyethylene terephthalate (PET), 2.1 GPa for polycycloolefin (COP), 1.4 GPa for triacetyl cellulose (TAC), 2.4 GPa for polycarbonate (PC), and 2 GPa for polypropylene (PP), and it can be said that the third resin layer is a layer softer than the first resin layer. Therefore, compared to when only the first resin layer is arranged on one side of the glass substrate, when the first resin layer, second resin layer, and third resin layer are stacked in this order on one side of the glass substrate, when an impact is applied to the optical laminate, the second resin layer and the third resin layer are more likely to deform than the first resin layer, and therefore it is thought that the impact is more easily dispersed.

[0280] Furthermore, since the second and third resin layers, which are softer than the first resin layer, are disposed on the side of the first resin layer opposite the glass substrate, it is believed that when an impact is applied to the optical laminate, the impact is less likely to be transmitted to the glass substrate. Therefore, it is believed that when the first, second, and third resin layers are laminated, the impact absorption is higher than when only the first resin layer is laminated. Furthermore, when only the second and third resin layers are laminated in this order on one side of the glass substrate, the second and third resin layers are relatively soft and easily deformed when an impact is applied to the optical laminate, which may damage the glass substrate before the impact is fully absorbed. Therefore, it is believed that when the first, second, and third resin layers are laminated, the impact resistance is higher than when only the second and third resin layers are laminated.

[0281] As described above in the section on display device components, the composite elastic modulus of the first resin layer is adopted in the present disclosure because, when measuring the composite elastic modulus of the first resin layer using the nanoindentation method (indentation test method), the indenter is pressed into the measurement sample, which is similar to the tip of a pen colliding with and pressing into the sample in a pen drop test.

[0282] According to the present disclosure, the composite elastic modulus of the first resin layer is equal to or greater than a predetermined value, thereby making it possible to improve impact resistance in a pen drop test.

[0283] Furthermore, in the present disclosure, even if the glass substrate is broken, the first resin layer, the second resin layer, and the third resin layer can prevent the glass from scattering.

[0284] Furthermore, according to the present disclosure, the thickness of the glass substrate is thin, being equal to or less than a predetermined value, the thickness of the first resin layer having a composite elastic modulus equal to or greater than a predetermined value is relatively thin within a predetermined range, the second resin layer is a relatively soft adhesive layer, and the third resin layer is a predetermined resin film, thereby improving flexibility. Therefore, when the optical laminate is bent, cracking of the first resin layer, the second resin layer, and the third resin layer can be suppressed, and bending resistance can be maintained. Therefore, the optical laminate of the present disclosure can be bent and can be used in a wide variety of optical laminates, for example, as a component for a foldable display.

[0285] Furthermore, according to the present disclosure, by having the composite elastic modulus of the first resin layer be equal to or greater than a predetermined value, it is possible to increase the restoring force when the first resin layer is deformed. Therefore, by having the composite elastic modulus of the first resin layer be equal to or greater than a predetermined value, it is possible to improve the restoring property of the optical laminate after it has been bent for a long period of time. It is also possible to improve the restoring property of the optical laminate after it has been repeatedly bent.

[0286] In this manner, the present disclosure provides an optical laminate having excellent impact resistance and flexibility. Furthermore, even if the glass substrate is broken, the risk of injury to the human body can be reduced, resulting in a highly safe optical laminate.

[0287] Hereinafter, each configuration of the optical laminate according to the present disclosure will be described.

[0288] 1.First resin layer The first resin layer in the present disclosure is a member having a composite elastic modulus of 5.7 GPa or more and a thickness of 5 μm or more and 60 μm or less, and is disposed on one side of a glass substrate. The first resin layer is a member having impact absorption properties and also functions as a member for suppressing glass shattering when the glass substrate is broken. The first resin layer is transparent, and when the optical laminate in the present disclosure is disposed on the viewer side of a display panel of a display device, the first resin layer is disposed on the viewer side of the glass substrate.

[0289] (1) Characteristics of the first resin layer The composite elastic modulus of the first resin layer can be the same as the composite elastic modulus of the resin layer in the member for a display device described above.

[0290] Here, the method for measuring the composite elastic modulus of the first resin layer can be the same as the method for measuring the composite elastic modulus of the resin layer in the member for a display device described above.

[0291] In order to avoid the influence of the glass substrate and the side edges of the first resin layer, the Berkovich indenter is pressed into a portion of the first resin layer that is 500 nm from the interface between the glass substrate and the first resin layer toward the center of the first resin layer, 500 nm from each of the two side edges of the first resin layer toward the center of the first resin layer, and 500 nm from the interface between the second resin layer and the first resin layer toward the center of the first resin layer.

[0292] (2) Structure of the first resin layer The thickness of the first resin layer can be the same as the thickness of the resin layer in the member for a display device described above.

[0293] The first resin layer may be disposed on the glass substrate in the same manner as the resin layer in the member for a display device described above is disposed on the glass substrate.

[0294] (3) Material of the first resin layer (a) Resin The resin contained in the first resin layer can be the same as the resin contained in the resin layer in the member for a display device described above.

[0295] (b) UV absorber The first resin layer may contain an ultraviolet absorber, which may be the same as the ultraviolet absorber contained in the resin layer in the member for a display device described above.

[0296] (c) Other additives The first resin layer may further contain additives as needed, which may be the same as the additives contained in the resin layer in the member for a display device described above.

[0297] (4) Method for forming the first resin layer The first resin layer can be formed by the same method as the method for forming the resin layer in the member for a display device described above.

[0298] 2.Second resin layer The second resin layer in the present disclosure is an adhesive layer. The first resin layer and the third resin layer, which is a predetermined resin film, can be bonded together via the second resin layer, which is an adhesive layer. The second resin layer is a member having impact absorption properties. The second resin layer is transparent, and when the optical laminate in the present disclosure is placed on the viewer side of the display panel of a display device, it is placed on the viewer side of the glass substrate.

[0299] The second resin layer has transparency, and specifically, the total light transmittance of the second resin layer is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more.

[0300] The total light transmittance of the second resin layer can be measured in accordance with JIS K7361-1, for example, using a haze meter HM150 manufactured by Murakami Color Research Laboratory Co., Ltd. The same method can be used to measure the total light transmittance of the other layers.

[0301] The adhesive used in the second resin layer is not particularly limited as long as it is an adhesive that can provide a transparent adhesive layer, and for example, OCA (Optical Clear Adhesive) can be used.Specific examples include acrylic adhesives, silicone adhesives, urethane adhesives, rubber adhesives, polyvinyl ether adhesives, polyvinyl acetate adhesives, etc.

[0302] The thickness of the second resin layer is preferably, for example, 1 μm or more and 100 μm or less. If the thickness of the second resin layer is too thick, flexibility may be impaired. On the other hand, if the thickness of the second resin layer is too thin, adhesion may not be ensured and peeling may occur.

[0303] The second resin layer may be, for example, an adhesive film. Alternatively, the second resin layer may be formed by applying an adhesive composition onto the first resin layer or the third resin layer.

[0304] 3.Third resin layer The third resin layer in the present disclosure is a resin film containing a resin selected from the group consisting of polyester-based resins, polycycloolefin-based resins, acetyl cellulose-based resins, polycarbonate-based resins, and polypropylene-based resins. The third resin layer is a member having impact absorption properties and also functions as a member for suppressing glass shattering when the glass substrate is broken. The third resin layer is transparent, and when the optical laminate in the present disclosure is disposed on the viewer side of the display panel of a display device, the third resin layer is disposed on the viewer side of the glass substrate.

[0305] The third resin layer has transparency, and specifically, the total light transmittance of the third resin layer is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more.

[0306] The resin contained in the resin film constituting the third resin layer is a resin selected from the group consisting of polyester-based resins, polycycloolefin-based resins, acetyl cellulose-based resins, polycarbonate-based resins, and polypropylene-based resins. The polyester-based resin is not particularly limited as long as it can provide a transparent resin film, and examples thereof include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT). The polycycloolefin-based resin is not particularly limited as long as it can provide a transparent resin film, and examples thereof include norbornene-based resins, monocyclic olefin-based resins, cyclic conjugated diene-based resins, vinyl alicyclic hydrocarbon-based resins, and hydrogenated versions thereof. The acetyl cellulose-based resin is not particularly limited as long as it can provide a transparent resin film, and examples thereof include triacetyl cellulose (TAC). The polycarbonate-based resin is not particularly limited as long as it can provide a transparent resin film, and examples thereof include polycarbonate (PC). The polypropylene-based resin is not particularly limited as long as it can provide a transparent resin film, and examples thereof include polypropylene (PP).

[0307] The third resin layer may contain additives such as fillers, ultraviolet absorbers, stabilizers, antioxidants, antistatic agents, flame retardants, and lubricants, as needed.

[0308] The thickness of the third resin layer is, for example, preferably 0.5 μm to 30 μm, more preferably 1.0 μm to 25 μm, and even more preferably 1.5 μm to 20 μm. If the third resin layer is too thick, flexibility and bendability may be impaired. On the other hand, if the third resin layer is too thin, sufficient impact resistance may not be obtained.

[0309] The third resin layer, which is a resin film, can be attached to the first resin layer via the second resin layer, which is an adhesive layer.

[0310] 4. Glass substrate The glass substrate in the present disclosure has a thickness of 100 μm or less and is a member that supports the first resin layer. The glass substrate may be the same as the glass substrate in the above-mentioned member for a display device.

[0311] 5. Functional Layer The optical laminate according to the present disclosure may further include a functional layer on the surface of the third resin layer opposite to the second resin layer, such as a hard coat layer, an anti-reflection layer, or an anti-glare layer.

[0312] The functional layer may be a single layer or may have multiple layers, and may be a layer having a single function or may have multiple layers having different functions.

[0313] (1) Hard Coat Layer As shown in Fig. 8, the optical laminate according to the present disclosure preferably further includes a hard coat layer 16 on the surface of the third resin layer 15 opposite the second resin layer 14. The hard coat layer is a member for increasing surface hardness. The presence of the hard coat layer can improve scratch resistance.

[0314] The hard coat layer can be the same as the hard coat layer in the member for a display device described above.

[0315] 6. Other configurations The optical laminate of the present disclosure may have other layers in addition to the above-described layers, as needed.

[0316] (1) Second hard coat layer The optical laminate according to the present disclosure may further include a second hard coat layer 17 between the first resin layer 13 and the second resin layer 14, as shown in Fig. 9. The second hard coat layer is a component for increasing surface hardness. The presence of the second hard coat layer can improve impact resistance.

[0317] The second hard coat layer can be the same as the hard coat layer described above, and therefore, a description thereof will be omitted here.

[0318] (2) Fourth resin layer The optical laminate according to the present disclosure may have a fourth resin layer on the surface of the glass substrate opposite to the first resin layer. When an impact is applied to the optical laminate, the fourth resin layer as well as the first, second, and third resin layers can absorb the impact, thereby suppressing cracking of the glass substrate and improving impact resistance.

[0319] The resin contained in the fourth resin layer is not particularly limited as long as it is a resin that can absorb impact, and examples thereof include urethane resin, epoxy resin, polyimide, polyamideimide, acrylic resin, triacetyl cellulose (TAC), etc. These resins may be used alone or in combination of two or more.

[0320] The fourth resin layer may further contain additives as needed, such as fillers, ultraviolet absorbers, stabilizers, antioxidants, antistatic agents, flame retardants, and lubricants.

[0321] The thickness of the fourth resin layer may be any thickness that is capable of absorbing impact, and may be, for example, preferably 5 μm or more and 60 μm or less, more preferably 10 μm or more and 50 μm or less, and even more preferably 15 μm or more and 40 μm or less.

[0322] The fourth resin layer can be formed by the same method as the first resin layer.

[0323] (3) Primer layer The optical laminate according to the present disclosure includes a primer layer between the glass substrate and the first resin layer. In addition, the optical laminate according to the present disclosure may have the first resin of the glass substrate. When the fourth resin layer is provided on the side opposite to the oil layer, a protrusion is provided between the glass substrate and the fourth resin layer. The glass substrate and the first resin layer may have a primer layer. The primer layer improves the adhesion between the glass substrate and the first resin layer. This can improve adhesion between the glass substrate and the fourth resin layer.

[0324] The primer layer may be the same as the primer layer in the member for a display device described above.

[0325] (4) Decorative layer The optical laminate of the present disclosure is a laminate formed between the glass substrate and the first resin layer, or The glass substrate may have a decorative layer on the surface opposite to the first resin layer.

[0326] The decorative layer may be the same as the decorative layer in the member for a display device described above.

[0327] 7.Optical laminate In the optical laminate of the present disclosure, the total thickness of the resin layers disposed on the surface of the first resin layer of the glass substrate is not particularly limited as long as it is a thickness that provides impact resistance and flexibility, but is, for example, preferably 143 μm or less, more preferably 135 μm or less. By having the total thickness of the resin layers in the above range, the flexibility of the optical laminate can be improved.

[0328] The resin layer disposed on the side of the glass substrate facing the first resin layer refers to all layers containing resin among the layers disposed on the side of the glass substrate facing the first resin layer. The resin layer includes at least the first resin layer, the second resin layer, and the third resin layer, and may further include the functional layer, the second hard coat layer, the primer layer, and the decorative layer.

[0329] The total light transmittance and haze of the optical laminate of the present disclosure can be the same as those of the above-mentioned member for a display device.

[0330] The optical laminate of the present disclosure preferably has flex resistance. Specifically, it is preferable that the optical laminate does not crack or break when subjected to the dynamic flex test described below 200,000 times.

[0331] In the dynamic bending test, the optical laminate may be folded so that the glass substrate is on the outside, or the optical laminate may be folded so that the glass substrate is on the inside, but in either case, it is preferable that no cracks or breaks occur in the optical laminate.

[0332] The dynamic bending test can be the same as the dynamic bending test described in the section on members for display devices above.

[0333] It is preferable that the optical laminate does not crack or break when a test in which the optical laminate 1 is folded 180° so that the distance d between the opposing short side portions 1C and 1D of the optical laminate 1 is 10 mm is repeated 200,000 times. In particular, it is more preferable that no crack or break occurs when a test in which the optical laminate 1 is folded 180° so that the distance d between the opposing short side portions 1C and 1D of the optical laminate 1 is 8 mm is repeated 70,000 times, even more preferable that no crack or break occurs when repeated 100,000 times, and particularly preferable that no crack or break occurs when repeated 200,000 times.

[0334] Furthermore, when the optical laminate is subjected to a static bending test described below, it is preferable that the opening angle θ of the optical laminate after the static bending test is 100° or more.

[0335] The static bending test can be the same as the static bending test described above in the section on members for display devices.

[0336] In the optical laminate, when a static bending test is conducted so that the distance d between the opposing short sides 1C, 1D of the optical laminate 1 is 10 mm, the opening angle θ after the static bending test is preferably 100° or more.

[0337] In the static bending test, the optical laminate may be folded so that the glass substrate is on the inside, or the optical laminate may be folded so that the glass substrate is on the outside, but in either case, the opening angle θ is preferably 100° or more, and more preferably 130° or more.

[0338] The uses of the optical laminate of the present disclosure can be the same as the uses of the above-mentioned members for display devices.

[0339] When the optical laminate of the present disclosure is disposed on the surface of a display device, the surface on the glass substrate side is the surface. The display panel side and the third resin layer side are arranged to face outward.

[0340] The method for disposing the optical laminate of the present disclosure on the surface of a display device can be the same as that for the above-mentioned member for a display device.

[0341] B.Display device A display device according to the present disclosure includes a display panel and the above-described member for a display device or the above-described optical laminate, which is disposed on the viewer side of the display panel.

[0342] Fig. 10 is a schematic cross-sectional view showing an example of a display device according to the present disclosure. As shown in Fig. 10, a display device 30 includes a display panel 31, a touch panel member 32, and a display device member 1 disposed on the viewer side of the display panel 31 and the touch panel member 32. In the display device 30, the display device member 1 is used as a member disposed on the surface of the display device 30, and an adhesive layer 34 is disposed between the display device member 1 and the touch panel member 32. An adhesive layer 33 is also disposed between the display panel 31 and the touch panel member 32.

[0343] Fig. 11 is a schematic cross-sectional view showing another example of a display device according to the present disclosure. As shown in Fig. 11, a display device 30 includes a display panel 31 and an optical laminate 11 disposed on the viewer side of the display panel 31. In the display device 30, the optical laminate 11 is used as a member disposed on the surface of the display device 30, and an adhesive layer 35 is disposed between the optical laminate 11 and the display panel 31.

[0344] The member for a display device in the present disclosure can be similar to the member for a display device described above.

[0345] The optical laminate in the present disclosure can be the same as the optical laminate described above.

[0346] Examples of the display panel in the present disclosure include display panels used in display devices such as liquid crystal display devices, organic EL display devices, and LED display devices.

[0347] The display device according to the present disclosure may have a touch panel member between the display panel and the display device member or the optical laminate.

[0348] The display device according to the present disclosure is preferably a flexible display. In particular, the display device according to the present disclosure is preferably foldable. That is, the display device according to the present disclosure is more preferably a foldable display. The display device according to the present disclosure has excellent bending resistance because it includes the above-described member for a display device, or has excellent impact resistance and flexibility because it includes the above-described optical laminate, and is therefore suitable as a flexible display, and further as a foldable display.

[0349] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0350] Hereinafter, the present disclosure will be further described with reference to examples and comparative examples.

[0351] [Example 1-1] (1) Formation of primer layer The components were blended to obtain the composition shown below to prepare a primer layer composition. Bisphenol A solid epoxy resin (jER1256B40, manufactured by Mitsubishi Chemical) 28 parts by weight Bisphenol A novolac solid epoxy resin (jER157S65B80, manufactured by Mitsubishi Chemical) 5 parts by weight 2-Ethyl-4-methylimidazole (Tokyo Chemical Industry Co., Ltd.) 1 part by mass Solvent (MEK) 11 parts by mass

[0352] A chemically strengthened glass substrate having a thickness of 70 μm was prepared, and the above primer layer composition was applied to the glass substrate to a predetermined thickness, and dried at 80°C for 3 minutes and at 150°C for 60 minutes to form a primer layer having a thickness of 1 μm.

[0353] (2) Formation of resin layer A tetracarboxylic dianhydride represented by the following chemical formula was synthesized with reference to Synthesis Example 1 of WO 2014 / 046180.

[0354] [ka]

[0355] A 5 L separable flask was charged with a solution of dehydrated N,N-dimethylacetamide (DMAc) (1833.2 g) and 2,2'-bis(trifluoromethyl)benzidine (TFMB) (138.48 g). The temperature was controlled at 30 °C. Tetracarboxylic dianhydride (TMPBPTME) (176.70 g) represented by the above formula was gradually added so that the temperature did not rise more than 2 °C, and the mixture was stirred with a mechanical stirrer for 30 minutes. Pyromellitic dianhydride (PMDA) (64.20 g) was gradually added in several portions so that the temperature did not rise more than 2 °C, synthesizing a polyimide precursor solution (solids content 18% by mass). The molar ratio of TMPBPTME to PMDA (TMPBPTME:PMDA) used in the polyimide precursor was 90:10. The weight average molecular weight of the polyimide precursor was 75,000.

[0356] Under a nitrogen atmosphere, the above polyimide precursor solution (2162 g) was added to a 5 L separable flask, cooled to room temperature. Dehydrated N,N-dimethylacetamide (432 g) was added and stirred until homogenous. Next, catalysts pyridine (6.622 g) and acetic anhydride (213.67 g) were added and stirred at room temperature for 24 hours to synthesize a polyimide solution.

[0357] N,N-dimethylacetamide (DMAc) (2000 g) was added to the resulting polyimide solution and stirred until homogeneous. The polyimide solution was then divided into three equal parts and transferred to 5 L beakers. Isopropyl alcohol (3500 g) was slowly added to each beaker to obtain a white slurry. The slurry was transferred to a Buchner funnel and filtered. It was then washed with isopropyl alcohol (9000 g in total), followed by filtration. This process was repeated three times, and the polyimide was dried at 110 °C in a vacuum dryer to obtain polyimide (polyimide powder). The weight-average molecular weight of the polyimide measured by GPC was 100,000.

[0358] N,N-dimethylacetamide (DMAc) was added to the polyimide to prepare a polyimide varnish (resin composition) containing 12% by weight of polyimide in the varnish. The viscosity of the polyimide varnish (resin composition) (solid content concentration 12% by weight) at 25°C was 15,000 cps.

[0359] The polyimide varnish (resin composition) was applied to the primer layer to a predetermined thickness, and dried at 100°C for 10 minutes, 150°C for 10 minutes, and 230°C for 30 minutes to form a resin layer with a thickness of 5 μm to 60 μm.

[0360] (3) Formation of hard coat layer The components were blended to obtain the composition shown below to prepare a curable resin composition for a hard coat layer. 25 parts by weight of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (M403, manufactured by Toagosei Co., Ltd.) Dipentaerythritol EO-modified hexaacrylate (A-DPH-6E, manufactured by Shin-Nakamura Chemical Co., Ltd.) 25 parts by mass 50 parts by weight (solid equivalent) of irregular silica particles (average particle size 25 nm, manufactured by JGC Catalysts and Chemicals) Photopolymerization initiator (Irg184) 4 parts by mass Fluorine-based leveling agent (F568, manufactured by DIC Corporation) 0.2 parts by mass (solid equivalent) Ultraviolet absorber 1 (DAINSORB P6, manufactured by Daiwa Kasei) 3 parts by weight Solvent (MIBK) 150 parts by weight

[0361] The curable resin composition for hard coat layer was applied to the resin layer to a predetermined thickness, dried at 80°C for 3 minutes, and then cured by ultraviolet irradiation to form a hard coat layer with a thickness of 10 µm.

[0362] [Example 1-2] A member for a display device was produced in the same manner as in Example 1-1, except that a resin layer was formed as follows.

[0363] A 500 mL separable flask was purged with N2 and a solution containing 293.29 g of dehydrated dimethylacetamide (DMAc) and 14.3 g (44.7 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) was dissolved. The temperature was controlled to 30°C. 24.8 g (40.1 mmol) of the tetracarboxylic dianhydride (TMPBPTME) used in Example 1 above was gradually added so that the temperature did not rise more than 2°C. The solution was stirred with a mechanical stirrer for 3 hours. 0.91 g (4.5 mmol) of terephthalic acid dichloride (TPC) was then added and stirred for an additional 3 hours to obtain a polyamic acid solution. Next, 6.66 g (84.2 mmol) of pyridine and 8.60 g (84.2 mmol) of acetic anhydride catalyst were added. The solution was stirred at 25°C for 30 minutes to confirm homogeneity, and then heated to 70°C and stirred for 1 hour. After cooling to room temperature, 174.26 g of 2-propyl alcohol (IPA) was gradually added to the solution, resulting in a slightly cloudy solution. 435.64 g of IPA was added to the cloudy solution all at once, resulting in a white slurry. The slurry was filtered and washed five times with IPA, then dried in an oven heated to 100°C under reduced pressure for six hours to obtain a polyamideimide powder (37.1 g). The weight-average molecular weight of the polyamideimide measured by GPC was 62,000.

[0364] DMAc was added to polyamideimide to prepare a polyamideimide varnish with a polyamideimide content of 19% by mass. The viscosity of the polyamideimide varnish (solid content of 19% by mass) at 25°C was 4000 mPa·s.

[0365] The above polyamideimide varnish (resin composition) was applied to a predetermined thickness on the primer layer and dried at 100°C for 10 minutes, 150°C for 10 minutes, and 230°C for 30 minutes to form a resin layer with a thickness of 5 μm to 60 μm.

[0366] [Examples 1-3] A member for a display device was produced in the same manner as in Example 1-1, except that a resin layer was formed as follows.

[0367] A 5 L separable flask was charged with a solution of dehydrated N,N-dimethylacetamide (DMAc) (1833.2 g) and 2,2'-bis(trifluoromethyl)benzidine (TFMB) (138.48 g). The temperature was controlled at 30 °C. Tetracarboxylic dianhydride (TMPBPTME) (256.026 g) represented by the above formula was gradually added so that the temperature did not rise more than 2 °C, and the mixture was stirred with a mechanical stirrer for 30 minutes. Pyromellitic dianhydride (PMDA) (4.7 g) was gradually added in several portions so that the temperature did not rise more than 2 °C, synthesizing a polyimide precursor solution (solids content 18% by mass) containing the polyimide precursor. The molar ratio of TMPBPTME to PMDA (TMPBPTME:PMDA) used in the polyimide precursor was 95:5. The weight-average molecular weight of the polyimide precursor was 75,000.

[0368] Under a nitrogen atmosphere, the above polyimide precursor solution (2162 g) was added to a 5 L separable flask, cooled to room temperature. Dehydrated N,N-dimethylacetamide (432 g) was added and stirred until homogenous. Next, catalysts pyridine (6.622 g) and acetic anhydride (213.67 g) were added and stirred at room temperature for 24 hours to synthesize a polyimide solution.

[0369] N,N-dimethylacetamide (DMAc) (2000 g) was added to the resulting polyimide solution and stirred until homogeneous. The polyimide solution was then divided into three equal parts and transferred to 5 L beakers. Isopropyl alcohol (3500 g) was slowly added to each beaker to obtain a white slurry. The slurry was transferred to a Buchner funnel and filtered. It was then washed with isopropyl alcohol (9000 g in total), followed by filtration. This process was repeated three times, and the polyimide was dried at 110 °C in a vacuum dryer to obtain polyimide (polyimide powder). The weight-average molecular weight of the polyimide measured by GPC was 100,000.

[0370] N,N-dimethylacetamide (DMAc) was added to the polyimide to prepare a polyimide varnish (resin composition) containing 12% by weight of polyimide in the varnish. The viscosity of the polyimide varnish (resin composition) (solid content concentration 12% by weight) at 25°C was 15,000 cps.

[0371] The above polyimide varnish (resin composition) was applied to a predetermined thickness on the primer layer and dried at 100°C for 10 minutes, 150°C for 10 minutes, and 230°C for 30 minutes to form a resin layer with a thickness of 5 μm to 60 μm.

[0372] [Comparative Example 1-1] A member for a display device was produced in the same manner as in Example 1-1, except that a resin layer was formed as follows.

[0373] A composition containing a urethane-modified copolymer polyester resin (Vylon UR4800, manufactured by Toyobo) was applied to a predetermined thickness and dried at 100° C. for 5 minutes to form a resin layer with a thickness of 5 μm to 60 μm.

[0374] [Comparative Example 1-2] A member for a display device was produced in the same manner as in Example 1-1, except that a resin layer was formed as follows.

[0375] A composition containing an epoxy resin (1256B40, manufactured by Mitsubishi Chemical) was applied to a predetermined thickness and dried at 80°C for 5 minutes and then at 150°C for 60 minutes to form a resin layer with a thickness of 5 μm to 60 μm.

[0376] [Comparative Example 1-3] A member for a display device was produced in the same manner as in Example 1-1, except that a resin layer was formed as follows.

[0377] 500 g of dehydrated N,N-dimethylacetamide (boiling point: 165°C) was added to a vessel, and while N2 was flowing through the vessel, the N,N-dimethylacetamide was heated to approximately 80°C while stirring. The amount of dissolved oxygen in the N,N-dimethylacetamide was monitored at every step, and when the amount of dissolved oxygen in the N,N-dimethylacetamide fell below the detection limit of the dissolved oxygen meter (less than 0.005 mg / L), heating was stopped, and the N,N-dimethylacetamide was cooled to room temperature before being subjected to the next step.

[0378] The following steps were carried out under a nitrogen atmosphere. 466.1 g of the N,N-dimethylacetamide and 2.46 g (10 mmol) of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS) were placed in a 500 mL separable flask, and the temperature of the solution containing dissolved AprTMOS was controlled at 30°C. 1.23 g (3 mmol) of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was then gradually added so that the temperature did not rise by more than 2°C, and the mixture was stirred with a mechanical stirrer for 30 minutes. To this mixture, 60.8 g (190 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) was added. After confirming complete dissolution, 91.6 g (206 mmol) of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was gradually added in several portions so that the temperature did not rise more than 2°C. This resulted in the synthesis of a polyimide precursor solution (25 wt% solids content) containing the dissolved polyimide precursor. The molar ratio of TFMB to AprTMOS used in the polyimide precursor was 95:5. The viscosity of the polyimide precursor solution (25 wt% solids content) at 25°C was 48,900 cps, and the weight-average molecular weight of the polyimide precursor measured by GPC was 156,400.

[0379] Under a nitrogen atmosphere, the above polyimide precursor solution, cooled to room temperature, was added to a 5 L separable flask. Dehydrated N,N-dimethylacetamide was added and stirred until homogenous. Next, pyridine and acetic anhydride, which act as catalysts, were added and stirred at room temperature for 24 hours to synthesize a polyimide solution.

[0380] N,N-dimethylacetamide (DMAc) was added to the resulting polyimide solution and stirred until homogeneous. The polyimide solution was then divided into three equal parts and transferred to 5 L beakers. Isopropyl alcohol was slowly added to each beaker to obtain a white slurry. The slurry was then transferred to a Buchner funnel, filtered, washed with isopropyl alcohol, and filtered three times. This process was repeated three times, and the resulting solution was dried at 110°C in a vacuum dryer to obtain the polyimide (polyimide powder).

[0381] N,N-dimethylacetamide (DMAc) was added to the polyimide to prepare a polyimide varnish (resin composition) containing 12% by weight of polyimide in the varnish. The viscosity of the polyimide varnish (resin composition) (solid content concentration 12% by weight) at 25°C was 3000 cps.

[0382] The polyimide varnish (resin composition) was applied to the primer layer to a predetermined thickness, and dried at 100°C for 10 minutes, 150°C for 10 minutes, and 230°C for 30 minutes to form a resin layer with a thickness of 5 μm to 60 μm.

[0383] [Rating 1] (1) Composite modulus The composite elastic modulus of the resin layer of the members for a display device of the examples and comparative examples was determined.

[0384] First, the indentation hardness of the resin layer was measured. ITMeasurements of the σ were performed on the measurement sample using a BRUKER TI950 TriboIndenter. Specifically, a display device component cut to a size of 1 mm x 10 mm was embedded in an embedding resin to prepare a block. From this block, uniform, hole-free sections with a thickness of 50 nm to 100 nm were cut using a standard sectioning method. An Ultramicrotome EM UC7 (Leica Microsystems) was used to prepare the sections. The remaining block from which the uniform, hole-free sections were cut served as the measurement sample. Next, a Berkovich indenter (triangular pyramid, BRUKER TI-0039) was pressed vertically into the center of the cross section of the resin layer over 10 seconds until a maximum indentation load of 25 μN was reached, under the following measurement conditions: At this time, in order to avoid the influence of the glass substrate and the side edges of the resin layer, the Berkovich indenter was pressed into a portion of the resin layer 500 nm away from the interface between the glass substrate and the resin layer toward the center of the resin layer, 500 nm away from each of the two ends of the resin layer toward the center of the resin layer, and also 500 nm away from the interface between the hard coat layer and the resin layer toward the center of the resin layer. After that, the residual stress was relaxed by holding it constant, and then the load was removed over 10 seconds, and the maximum load after relaxation was measured, and this maximum load P max (μN) and contact projection area A p (nm 2 ) and P max / A p The indentation hardness (H IT ) was calculated. The above projected contact area was determined by correcting the indenter tip curvature using the Oliver-Pharr method using a standard sample of fused quartz (5-0098 manufactured by BRUKER). If any of the measured values ​​deviated from the arithmetic mean value by ±20% or more, that measured value was excluded and remeasured.

[0385] (Measurement conditions) ·Loading speed: 2.5μN / sec ·Holding time: 5 seconds ·Loading and unloading speed: 2.5μN / sec ·Measurement temperature: 25℃

[0386] Next, the indentation hardness (H IT ) the above contact projection area A p The composite elastic modulus was calculated from the above formula (1) using the above formula. The indentation hardness was measured at 10 points, the composite elastic modulus was calculated each time, and the arithmetic mean value of the composite elastic moduli obtained at the 10 points was used.

[0387] (2) Impact test (pen drop test) Impact tests were conducted on the display device members of Examples and Comparative Examples. First, an optical pressure-sensitive adhesive (OCA) and PET were attached in this order to the surface of the glass substrate of the display device member, and the display device member was placed on a metal plate with a thickness of 30 mm so that the PET side was in contact with the metal plate. Next, a pen was dropped from the test height onto the display device member with its tip facing downward, and the highest test height at which the glass substrate did not crack was evaluated. The results for the display device members of Examples 1-1 to 1-2 and Comparative Examples 1-1 to 1-3 are shown in Figure 12. Table 1 also shows the results when the resin layer thickness was 40 μm.

[0388] (3) Pencil hardness In the display device members of the Examples and Comparative Examples, when the resin layer was 20 μm thick, the pencil hardness of the surface of the hard coat layer side of the display device member was measured in accordance with JIS K5600-5-4 (1999). The pencil hardness was measured using a pencil hardness tester (product name: "Pencil Scratch Coating Hardness Tester (Electric)", manufactured by Toyo Seiki Seisakusho Co., Ltd.) under the following measurement conditions: angle 45°, load 750 g, speed 0.5 mm / sec to 1 mm / sec, and temperature 23±2°C.

[0389] (4) Total light transmittance and haze In the display device members of Examples and Comparative Examples, when the resin layer had a thickness of 20 μm, the total light transmittance and haze of the display device members were measured. The total light transmittance of the display device members was measured using a haze meter (HM150 manufactured by Murakami Color Research Laboratory) in accordance with JIS K7361-1. The haze of the display device members was measured using a haze meter (HM150 manufactured by Murakami Color Research Laboratory) in accordance with JIS K-7136.

[0390] (5) Bending resistance In the members for a display device of the Examples and Comparative Examples, when the thickness of the resin layer was 20 μm, a dynamic bending test and a static bending test were carried out on the members for a display device to evaluate bending resistance.

[0391] (5-1) Dynamic bending test Dynamic bending tests were performed on the display device members of the examples and comparative examples to evaluate their bending resistance. Specifically, first, a display device member measuring 20 mm × 100 mm was fixed to a durability testing machine (product name "DLDMLH-FS", manufactured by Yuasa System Co., Ltd.) with the short sides (20 mm) of the display device member secured by fixing parts. The minimum distance d between the two opposing short sides was adjusted to 10 mm as shown in FIG. 5(c). A dynamic bending test was performed 200,000 times, folding the surface of the display device member by 180°. The display device member was folded so that the surface of the hard coat layer was facing inward and the surface of the glass substrate was facing outward. A dynamic bending test was also performed using another display device member, folding it so that the surface of the hard coat layer was facing outward and the surface of the glass substrate was facing inward, in the same manner as above. After the dynamic bending test, the fixing part was removed from one of the short sides to release the folded state, and the opening angle (see Figure 6(b)), which is the angle at which the display device member naturally opens, was measured. The opening angle was determined by the smaller angle between when the display device member was folded so that the surface on the hard coat layer side was on the inside, and when the display device member was folded so that the surface on the hard coat layer side was on the outside.

[0392] (5-2) Static bending test A static bending test was performed on the display device members of the examples and comparative examples, and the opening angle after the static bending test was measured. Specifically, first, the short sides (20 mm) of a display device member measuring 20 mm × 100 mm were fixed to fixing parts arranged parallel to each other so that the distance d between the opposing short sides of the display device member was 10 mm. The display device member was then folded and left to stand at 23 °C for 240 hours in a static bending test. After the static bending test, the fixing part was removed from one of the short sides to unfold the member. The opening angle (see Figure 6(b)), which is the angle at which the display device member naturally opened after 30 minutes at room temperature, was measured. The static bending test was performed both when the display device member was folded so that the surface on the hard coat layer side was facing inward and when the display device member was folded so that the surface on the hard coat layer side was facing outward, and the smaller angle was used.

[0393] [Table 1]

[0394] Table 1 and FIG. 12 show that in Comparative Examples 1-1 to 1-3, the composite elastic modulus of the resin layer was less than a predetermined value, and therefore, as the thickness of the resin layer increased, the surface hardness of the display device member decreased. In contrast, in Examples 1-1 to 1-3, the composite elastic modulus of the resin layer was equal to or greater than a predetermined value, and therefore, even when the resin layer was 40 μm thick, the surface hardness was high, demonstrating that both impact resistance and surface hardness could be achieved. Furthermore, Table 1 and FIG. 12 confirm that when the composite elastic modulus of the resin layer was equal to or greater than a predetermined value, the rate of increase in impact resistance with increasing resin layer thickness increased. Furthermore, a comparison of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3 in Table 1 shows that when the composite elastic modulus of the resin layer was equal to or greater than a predetermined value, bending resistance tended to improve. This is because the greater the composite elastic modulus of the resin layer, the greater the restoration force when deformation is applied to the resin layer.

[0395] Hereinafter, in Comparative Examples 2-1 to 2-2 and Examples 2-1 to 2-9, the hard coat layer formed on the third resin layer will be referred to as the first hard coat layer, and the hard coat layer formed on the first resin layer will be referred to as the second hard coat layer.

[0396] [Comparative Example 2-1] (1) Formation of primer layer A primer layer having a thickness of 1 μm was formed on the glass substrate in the same manner as in the formation of the primer layer in Example 1-1.

[0397] (2) Formation of the first resin layer A first resin layer having a thickness of 20 μm was formed on the primer layer in the same manner as in the formation of the resin layer in Example 1-1.

[0398] (3) Formation of the second hard coat layer A second hard coat layer having a thickness of 10 μm was formed on the first resin layer in the same manner as in the formation of the hard coat layer in Example 1-1, thereby obtaining an optical laminate.

[0399] [Comparative Example 2-2] (1) Preparation of hard coat film A 50 μm thick PET film (manufactured by Toyobo Co., Ltd., product name A4100) was prepared as the third resin layer, and the same hard coat layer curable resin composition as in Example 1-1 was applied to the PET film using a bar coater to complete a coating film. The formed coating film was then dried at 100° C. for 3 minutes and then cured by irradiating with 200 mJ of ultraviolet light to form a 10 μm thick first hard coat layer. This resulted in a hard coat film.

[0400] (2) Preparation of optical laminate A 70 μm thick chemically strengthened glass substrate was prepared, and the glass substrate was bonded to the PET film side of the hard coat film using a 50 μm thick acrylic adhesive film (manufactured by 3M, product name 8146-2), thereby obtaining an optical laminate.

[0401] [Examples 2-1 to 2-8] (1) Preparation of glass-resin laminate A primer layer and a first resin layer were formed on a glass substrate in the same manner as in Comparative Example 2-1, except that the thickness of the first resin layer was set to 10 μm to 40 μm, thereby obtaining a glass resin laminate.

[0402] (2) Preparation of hard coat film A hard coat film was prepared in the same manner as in Comparative Example 2-2.

[0403] (3) Preparation of optical laminate The surface of the glass resin laminate on the first resin layer side and the surface of the hard coat film on the PET film side were bonded together using an acrylic pressure-sensitive adhesive film (manufactured by 3M, product name 8146-2) having a thickness of 10 μm to 50 μm, thereby producing an optical laminate.

[0404] [Example 2-9] (1) Preparation of glass-resin laminate A primer layer, a first resin layer, and a second hard coat layer were formed on a glass substrate in the same manner as in Comparative Example 2-1, except that the thickness of the first resin layer was 23 μm, thereby obtaining a glass resin laminate.

[0405] (2) Preparation of hard coat film A hard coat film was prepared in the same manner as in Comparative Example 2-2.

[0406] (3) Preparation of optical laminate The surface of the glass resin laminate on the side of the second hard coat layer and the surface of the hard coat film on the side of the PET film were bonded together using a 50 μm thick acrylic adhesive film (manufactured by 3M, product name 8146-2), thereby producing an optical laminate.

[0407] [Rating 2] (1) Composite modulus The composite elastic modulus of the first resin layer of the optical laminate of the example and comparative example was determined.

[0408] First, the indentation hardness of the first resin layer was measured. IT The measurement of the dimensional relationship (D) was performed on the measurement sample using a BRUKER TI950 TriboIndenter. Specifically, a 1 mm x 10 mm cut-out optical laminate was embedded in an embedding resin to prepare a block. A uniform, hole-free section with a thickness of 50 nm to 100 nm was then cut from this block using a standard sectioning method. An Ultramicrotome EM UC7 (Leica Microsystems) was used to prepare the section. The remaining block from which the uniform, hole-free section was cut served as the measurement sample. Next, a Berkovich indenter (triangular pyramid, BRUKER TI-0039) was pressed vertically into the center of the cross section of the first resin layer over 10 seconds until a maximum indentation load of 25 μN was reached, under the following measurement conditions: At this time, in order to avoid the influence of the glass substrate and the side edges of the first resin layer, the Berkovich indenter was pressed into a portion of the first resin layer 500 nm away from the interface between the glass substrate and the first resin layer toward the center of the first resin layer, and 500 nm away from each of the two side edges of the first resin layer toward the center of the first resin layer. After that, the pressure was held constant to allow the residual stress to relax, and then the pressure was released over 10 seconds, and the maximum load after relaxation was measured, and this maximum load P max (μN) and contact projection area A p (nm 2 ) and P max / A p The indentation hardness (H IT ) was calculated. The above projected contact area was determined by correcting the indenter tip curvature using the Oliver-Pharr method using a standard sample of fused quartz (5-0098 manufactured by BRUKER). If any of the measured values ​​deviated from the arithmetic mean value by ±20% or more, that measured value was excluded and remeasured.

[0409] (Measurement conditions) ·Loading speed: 2.5μN / sec ·Holding time: 5 seconds ·Loading and unloading speed: 2.5μN / sec ·Measurement temperature: 25℃

[0410] Next, the indentation hardness (H IT ) the above contact projection area A p The composite elastic modulus was calculated from the above formula (1) using the above formula. The indentation hardness was measured at 10 points, the composite elastic modulus was calculated each time, and the arithmetic mean value of the composite elastic moduli obtained at the 10 points was used.

[0411] (2) Impact test (pen drop test) Impact tests were conducted on the optical laminates of the examples and comparative examples. First, a 50 μm-thick optical adhesive film (OCA) and a 100 μm-thick PET film were attached in this order to the glass substrate side of the optical laminate to prepare a test laminate. The test laminate was placed on a 30 mm-thick metal plate so that the PET film side of the test laminate was in contact with the metal plate. Next, a pen was dropped from the test height onto the test laminate with its tip facing downwards. A Zebra Blen 0.5BAS88-BK pen (weight 12 g, pen tip 0.5 mmφ) was used. Table 1 shows the highest test height at which no cracks occurred in the glass substrate and the lowest test height at which cracks occurred in the glass substrate.

[0412] (3) Dynamic bending test Dynamic bending tests were performed on the optical laminates of the examples and comparative examples to evaluate their bending resistance. Specifically, first, an optical laminate measuring 20 mm × 100 mm was fixed to a durability tester (product name "DLDMLH-FS," manufactured by Yuasa System Co., Ltd.) with the short sides (20 mm) of the optical laminate fixed to each other. The minimum distance d between the two opposing short sides was adjusted to 10 mm or 8 mm as shown in FIG. 5(c). A dynamic bending test was then performed in which the surface of the optical laminate was folded 180° 200,000 times or 70,000 times. The optical laminate was folded so that the surface on the hard coat layer side was facing outward and the surface on the glass substrate side was facing inward. The bending portion was then visually inspected for cracks or fractures in a bright room at 2000 Lx under an environment of 25°C and 50% RH. The results of the dynamic bending test were evaluated according to the following criteria. A: No cracks or breaks occurred in the bent portion. B: Cracks or breaks occurred at the bent portion.

[0413] [Table 2]

[0414] In Comparative Example 2-1, the second resin layer and the third resin layer were not arranged, and therefore the impact resistance was poor. Also, in Comparative Example 2-2, the first resin layer was not arranged, and therefore the impact resistance was poor. In contrast, in Examples 2-1 to 2-9, the predetermined first resin layer, second resin layer, and third resin layer were arranged in this order, and therefore the impact resistance was excellent. Furthermore, when Examples 2-1 to 2-7 were compared with Example 2-8, when the total thickness of the resin layers was equal to or less than a predetermined value, the bending resistance was also excellent. [Explanation of symbols]

[0415] 1. Display device components 2...Glass substrate 3...resin layer 4...Hard coat layer 11 … Optical laminate 12...Glass substrate 13...First resin layer 14…Second resin layer 15...Third resin layer 16...Hard coat layer

Claims

1. An optical laminate having a glass substrate, a first resin layer, a second resin layer, and a third resin layer in this order, The thickness of the glass substrate is 100 μm or less, the first resin layer has a composite elastic modulus of 5.7 GPa or more, and a thickness of 5 μm or more and 60 μm or less; the second resin layer is an adhesive layer, An optical laminate, wherein the third resin layer is a resin film containing a resin selected from the group consisting of polyester-based resins, polycycloolefin-based resins, acetyl cellulose-based resins, polycarbonate-based resins, and polypropylene-based resins.

2. The optical laminate according to claim 1 , wherein the total thickness of the resin layers disposed on the side of the glass substrate facing the first resin layer is 143 μm or less.

3. The optical laminate according to claim 1 or 2, further comprising a functional layer on the side of the third resin layer opposite to the second resin layer.

4. The optical laminate according to claim 3 , wherein the functional layer is a hard coat layer.

5. The optical laminate according to any one of claims 1 to 4, which has a total light transmittance of 80% or more.

6. The optical laminate according to any one of claims 1 to 5, having a haze of 2.0% or less.

7. The optical laminate according to claim 1 , wherein the first resin layer contains polyimide or polyamideimide.

8. The optical laminate according to claim 7 , wherein the weight average molecular weight of the polyimide is 100,000 or more and 270,000 or less.

9. 8. The optical laminate according to claim 7, wherein the weight average molecular weight of the polyamideimide is 50,000 or more and 1,000,000 or less.

10. A display panel; The optical laminate according to any one of claims 1 to 9, which is disposed on the viewer side of the display panel; A display device comprising:

11. The display device of claim 10, which is foldable.

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