Display device components, optical laminates, and display devices

Abstract

The present invention provides a display device component, an optical laminate, and a display device equipped therewith, which offer excellent impact resistance and flexibility, as well as improved safety. [Solution] This disclosure provides a display device component comprising a glass substrate with a thickness of 100 μm or less, and a resin layer disposed on one side of the glass substrate, having a composite elastic modulus of 5.7 GPa or more and a thickness of 5 μm or more and 60 μm or less.

Description

[Technical Field]

[0001] This disclosure relates to components for display devices, optical laminates, and display devices. [Background technology]

[0002] Traditionally, display devices have been fitted with glass or resin cover components to protect them. These cover components protect the display device from impacts and scratches, and therefore require strength, impact resistance, and scratch resistance. Glass cover components have features such as high surface hardness, scratch resistance, and high transparency, while resin cover components are lightweight and resistant to breakage. Generally, the thicker the cover component, the better the protection against impacts the display device has, and the material and thickness of the cover component are appropriately selected based on factors such as weight, cost, and the size of the display device.

[0003] In recent years, there has been a great deal of activity in the development of flexible displays such as foldable displays, rollable displays, and bendable displays, with particular emphasis on the development of foldable displays, or display devices that can be folded.

[0004] In bendable display devices, the cover member also needs to bend to follow the movement of the display device, and therefore, bendable cover members are used. In the case of resin cover members, polyimide and polyamide-imide films that have been made colorless and transparent by improving their chemical structure have been developed (see, for example, Patent Document 1). In the case of glass cover members, research is underway on cover members that can be bent by making the glass thin, such as ultra-thin glass (UTG) (see, for example, Patent Document 2). Among glass types, chemically strengthened glass has particularly high bending resistance. By imbuing the glass surface with expanding stress, it prevents minute scratches on the glass surface from becoming larger when bent, making the glass less likely to break. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-137864 [Patent Document 2] Japanese Patent Publication No. 2018-188335 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Glass has a higher modulus of elasticity than resin, so for the same thickness, it offers better protection for display devices than resin. Furthermore, glass has high optical transparency, making it possible to manufacture display devices with better visibility. On the other hand, as glass becomes thinner, it becomes more brittle, dramatically reducing its impact resistance. If the glass cover breaks due to an external impact, not only is its ability to protect the display device diminished, but the resulting fragments and sharp edges could injure the user's fingertips or other body parts.

[0007] This disclosure is made in view of the above circumstances, and its first objective is to provide a display device component, an optical laminate, and a display device equipped therewith that are excellent in impact resistance and flexibility and also have improved safety. The second objective of this disclosure is to provide a display device component, and a display device equipped therewith that are excellent in strength, impact resistance, scratch resistance and flexibility and also have improved safety. [Means for solving the problem]

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

[0009] The display device component in this disclosure may have a primer layer between the glass substrate and the resin layer.

[0010] Furthermore, the display device component in this disclosure may have a functional layer on the side of the resin layer opposite to the glass substrate. In this case, the functional layer may be a hard coat layer.

[0011] The display device component in this disclosure preferably has a total light transmittance of 80% or more. Furthermore, the display device component in this disclosure preferably has a haze of 2.0% or less.

[0012] Furthermore, in the display device component of this disclosure, the resin layer may contain polyimide or polyamideimide. In this case, it is preferable that the weight-average molecular weight of the polyimide is 100,000 or more. It is also preferable that the weight-average molecular weight of the polyamideimide is 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 composite 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 resins, polycycloolefin resins, acetylcellulose resins, polycarbonate resins, and polypropylene resins.

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

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

[0016] The optical laminate in this disclosure preferably has a total light transmittance of 80% or more. Furthermore, the optical laminate in this disclosure preferably has a haze of 2.0% or less.

[0017] Furthermore, in the optical laminate according to this disclosure, the first resin layer may contain polyimide or polyamideimide. In this case, it is preferable that the weight-average molecular weight of the polyimide is 100,000 or more. It is also preferable that the weight-average molecular weight of the polyamideimide is 50,000 or more.

[0018] Another embodiment of the present disclosure provides a display device comprising a display panel and the above-described display device component or optical laminate disposed on the observer side of the display panel.

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

[0020] This disclosure provides a display device component and optical laminate that are excellent in impact resistance and flexibility, and also have improved safety. Furthermore, this disclosure provides a display device component that is excellent in strength, impact resistance, scratch resistance, and flexibility, and also has improved safety. [Brief explanation of the drawing]

[0021] [Figure 1] This is a schematic cross-sectional view illustrating an example of a display device component in this disclosure. [Figure 2] This is a schematic cross-sectional view illustrating an example of a display device component in this disclosure. [Figure 3] This is a schematic cross-sectional view illustrating an example of a display device component in this disclosure. [Figure 4] This is a schematic cross-sectional view illustrating an example of a display device component in this disclosure. [Figure 5] This is a schematic diagram illustrating the dynamic flexion test. [Figure 6]This is a schematic diagram illustrating the static flexion test. [Figure 7] This is a schematic cross-sectional view illustrating an optical laminate in this disclosure. [Figure 8] This is a schematic cross-sectional view illustrating an optical laminate in this disclosure. [Figure 9] This is a schematic cross-sectional view illustrating an optical laminate in this disclosure. [Figure 10] This is a schematic cross-sectional view illustrating a display device in this disclosure. [Figure 11] This is a schematic cross-sectional view illustrating a display device in this disclosure. [Figure 12] This graph shows the relationship between the thickness of the resin layer and the evaluation of impact tests (pendrop tests) in resin components for display devices of the examples and comparative examples. [Modes for carrying out the invention]

[0022] Embodiments of this disclosure will be described below with reference to drawings and other figures. However, this disclosure can be implemented in many different ways and should not be interpreted as being limited to the embodiments described below. In addition, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual form, but these are merely examples and should not limit the interpretation of this disclosure. Furthermore, in this specification and each figure, elements similar to those described above with respect to previously shown figures will be denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0023] In this specification, when describing a configuration in which one component is placed on top of another component, unless otherwise specified, the terms "on top" or "below" include both cases: one where the other component is placed directly above or below the component in contact with it, and another where the other component is placed above or below the component via yet another component. Furthermore, when describing a configuration in this specification in which one component is placed on the surface of another component, unless otherwise specified, the terms "on the surface" or "on the surface" include both cases: one where the other component is placed directly above or below the component in contact with it, and another where the other component is placed above or below the component via yet another component.

[0024] Furthermore, in this specification, the term "film" also includes a component called a "sheet."

[0025] The following describes in detail the display device components, optical laminates, and display devices described herein.

[0026] A. Components for display devices To solve the above problems, the inventors of this disclosure conducted diligent research and found that by using a thin, flexible glass substrate and placing a resin layer on one side of the glass substrate, cracking of the glass substrate can be suppressed and impact resistance can be increased. Furthermore, by increasing the thickness of the resin layer, cracking of the glass substrate can be further suppressed and impact resistance can be further increased. However, when a display device component with a resin layer on one side of the glass substrate is placed on the observer side of the display panel of a display device, and the resin layer side of the display device component is placed on the observer side, it was found that if the thickness of the resin layer is thick, the hardness of the surface on the resin layer side of the display device component decreases, resulting in low scratch resistance. The inventors of this 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 thickness of the resin layer is relatively thin in order to increase surface hardness. In other words, it was found that a display device component with excellent strength, impact resistance, scratch resistance, and flexibility can be obtained. In addition, we have found that by using a resin layer with predetermined properties, even if the glass substrate is damaged, its fragments and sharp edges will not be exposed, enabling safer use. The display device component in this disclosure is based on this finding.

[0027] The display device component in this disclosure comprises a glass substrate with a thickness of 100 μm or less, and a resin layer disposed on one side of the glass substrate, 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] Figure 1 is a schematic cross-sectional view showing an example of a display device component in this disclosure. As shown in Figure 1, the display device component 1 comprises a glass substrate 2 and a resin layer 3 disposed on one side 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 modulus.

[0029] In this disclosure, the glass substrate is thin, with a thickness below a predetermined value, raising concerns about its fragility and low impact resistance. However, by arranging a resin layer on one side of the glass substrate, when an impact is applied to the display device component, the resin layer absorbs the impact, suppressing cracking of the glass substrate and improving impact resistance. Furthermore, even if the glass substrate does crack, the resin layer can suppress the scattering of glass fragments.

[0030] Increasing the thickness of the resin layer can further suppress cracking of the glass substrate and further improve impact resistance. However, if the resin layer is thick, the hardness of the surface on the resin layer side of the display device component decreases, resulting in lower scratch resistance. Therefore, in order to increase the hardness of the surface on the resin layer side of the display device component, the thickness of the resin layer needs to be relatively thin. According to this 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 relatively thin in order to increase surface hardness. Thus, both impact resistance and scratch resistance can be improved.

[0031] The composite elastic modulus of the resin layer is measured by the nanoindentation method (indentation test method), as described later. Furthermore, the pen drop test is one way to evaluate the impact resistance of thin glass substrates, and the impact resistance of display device components can be evaluated by the pen drop test, as described in the examples below. While there are various types of elastic moduli in addition to the composite elastic modulus, this disclosure uses the composite elastic modulus of the resin layer. This is because the indentation of the sample by the nanoindentation method (indentation test method) is similar to the impact and indentation of the sample by the tip of a pen in the pen drop test.

[0032] According to this disclosure, the impact resistance measured by the pendrop test can be improved by having the composite elastic modulus of the resin layer be greater than or equal to a predetermined value.

[0033] Furthermore, according to this disclosure, since the thickness of the glass substrate is below a predetermined value and is thin, and the thickness of the resin layer is within a predetermined range and is relatively thin, flexibility can be increased, cracking of the resin layer can be suppressed when the display device component is bent, and bending resistance can be maintained. Therefore, the display device component in this disclosure is bendable and can be used in a wide variety of display device components, for example, it can be used as a component for a foldable display.

[0034] Furthermore, according to this disclosure, by having a composite elastic modulus of the resin layer that is greater than a predetermined value, the restorative force when deformation is applied to the resin layer can be increased. The composite elastic modulus is an indicator of resistance to deformation; the greater the composite elastic modulus of the resin layer, the greater the restorative force when deformation is applied to the resin layer, while conversely, the smaller the composite elastic modulus of the resin layer, the smaller the restorative force when deformation is applied to the resin layer tends to be. Therefore, by having a composite elastic modulus of the resin layer that is greater than a predetermined value, the restorability of the display device component after being bent for a long period of time can be improved. In addition, the restorability of the display device component after repeated bending can also be improved.

[0035] Thus, this disclosure provides a display device component that is excellent in strength, impact resistance, scratch resistance, and flexibility. Furthermore, even if the glass substrate is damaged, the risk of injury to the human body can be reduced, making it a highly safe display device component.

[0036] Furthermore, while optical films having a resin substrate are also known as components to be placed on the surface of foldable displays, foldable displays using the above-mentioned optical film as the component have the drawback of being prone to folding marks, resulting in reduced image quality and an unsightly appearance. In contrast, according to this disclosure, a glass substrate is used, and a display device component having a glass substrate is less prone to folding marks, improves image quality, and enhances the appearance.

[0037] The configurations of the display device components in this disclosure will be described below.

[0038] 1. Resin layer The resin layer in this disclosure has a composite elastic modulus of 5.7 GPa or higher, a thickness of 5 μm to 60 μm, and is a component disposed on one side of the glass substrate. The resin layer is a shock-absorbing component and also functions as a component that suppresses the scattering of glass when the glass substrate breaks. The resin layer is light-transmitting, and when the display device component in this disclosure is placed on the observer side of the display panel of the display device, it is placed on the observer side of the glass substrate.

[0039] (1) Characteristics of the resin layer The composite modulus of the resin layer is 5.7 GPa or higher, preferably 6.0 GPa or higher, and more preferably 6.5 GPa or higher. Having the composite modulus of the resin layer within this range allows for suppression of cracking of the glass substrate due to impact, even when the thickness of the resin layer is relatively thin to increase surface hardness, thereby improving impact resistance and scratch resistance.

[0040] Furthermore, according to the composite modulus measurement method described later, the composite modulus of the glass substrate is approximately 40 GPa. Therefore, the composite modulus of the resin layer is preferably 40 GPa or less, and more preferably 20 GPa or less.

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

[0042] Indentation hardness (H ITThe measurement of shall be performed using a "TI950 TriboIndenter" manufactured by BRUKER for the measurement sample. Specifically, first, a block is prepared by embedding a member for a display device cut into 1 mm × 10 mm with an embedding resin. From this block, a uniform slice with a thickness of 50 nm or more and 100 nm or less without holes or the like is cut out by a general slicing method. For slicing, an "Ultra Microtome EM UC7" (manufactured by Leica Microsystems) or the like can be used. Then, the remaining block from which such a uniform slice without holes or the like has been cut out is used as the measurement sample. Next, on the cross-section obtained by cutting out the above slice in such a measurement sample, under the following measurement conditions, a Berkovich indenter (triangular pyramid, TI-0039 manufactured by BRUKER) as the above indenter is vertically pushed into the center of the cross-section of the resin layer up to a maximum pushing load of 25 μN over 10 seconds. Here, the Berkovich indenter is pushed into the portion of the resin layer that is 500 nm away from the interface between the glass substrate and the resin layer toward the center side of the resin layer and 500 nm away from the center side of the resin layer from both side ends of the resin layer in order to avoid the influence of the glass substrate and the influence of the side edge of the resin layer. In addition, when an arbitrary layer such as a hard coat layer exists on the surface of the resin layer opposite to the surface on the glass substrate side, it is pushed into the portion of the resin layer that is 500 nm away from the interface between the arbitrary layer and the resin layer toward the center side of the resin layer. Then, after maintaining it for a certain period to relax the residual stress, it is unloaded over 10 seconds, the maximum load after relaxation is measured, and the maximum load P max (μN) and the contact projected area A p (nm 2 ) are used, and P max / A p is used to calculate the indentation hardness (H IT ). The above contact projected area is the contact projected area corrected for the curvature of the indenter tip by the Oliver-Pharr method using fused quartz of a standard sample (5-0098 manufactured by BRUKER). The indentation hardness (H ITThe value (H) shall be the arithmetic mean of the values ​​obtained from 10 measurements. If any of the measurements deviate by more than ±20% from the arithmetic mean, those measurements shall be excluded and remeasured. Whether or not there are measurements that deviate by more than ±20% from the arithmetic mean shall be determined by checking whether the value (%) obtained by (AB) / B × 100, where A is the measured value and B is the arithmetic mean, is more than ±20%. Indentation hardness (H) IT This can be adjusted by the type of resin contained in the resin layer, as described later.

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

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

[0045]

number

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

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

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

[0049] Furthermore, the resin layer may be placed on only one surface of the glass substrate, or it may be placed to cover two or more surfaces of the glass substrate. In particular, when the resin layer is placed to cover the edge (side) of the glass substrate, it can mitigate impacts from the side of the glass substrate, suppress the occurrence of scratches, and thus suppress glass breakage.

[0050] (3) Materials of the resin layer (a) resin The resin included in the resin layer is not particularly limited as long as it satisfies the above-mentioned composite elastic modulus and has light transmittance, and examples include polyimide, polyamide-imide, acrylic resin, epoxy resin, urethane resin, triacetylcellulose (TAC), etc.

[0051] The following explanation will use polyimides and polyamideimides as examples.

[0052] (i) Polyimide Polyimides are obtained by reacting a tetracarboxylic acid component with a diamine component. It is preferable to obtain polyamic acid by polymerization of the tetracarboxylic acid component and the diamine component and then imidate it. Imidation may be carried out by chemical imidation, thermal imidation, or a combination of chemical and thermal imidation.

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

[0054] [ka]

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

[0056] Here, a tetracarboxylic acid residue refers to a residue obtained by removing four carboxyl groups from a tetracarboxylic acid, and represents the same structure as a residue obtained by removing the acidic dianhydride structure from a tetracarboxylic dianhydride. A 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 At least one of the following, as well as R 3 and R 4 At least one of the C1-C6 alkyl groups 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 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, more preferably an alkyl group having 1 to 2 carbon atoms, and more preferably a methyl group. In addition, from the viewpoint of solvent solubility, R 1 and R 2 , and R 3 and R 4 However, it is preferable to represent a methyl group.

[0058] In general formula (1), B represents a divalent group which 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 aromatic rings and diamines having aliphatic rings can be found in, for example, Japanese Patent Publication No. 2019-132930 and Japanese Patent Publication No. 2019-1989. These can be used individually or in combination of two or more types.

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

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

[0062] Specific examples of tetracarboxylic dianhydrides having aromatic rings and tetracarboxylic dianhydrides having aliphatic rings can be found in, for example, Japanese Patent Publication No. 2019-132930 and Japanese Patent Publication No. 2019-1989. These can be used individually or in combination of two or more types.

[0063] The polyimide preferably contains 10 mol% to 100 mol% of the constituent units represented by the above general formula (1). From the viewpoint of solubility in solvents, the polyimide is more preferably containing 15 mol% or more of the constituent units represented by the above general formula (1), even more preferably 25 mol% or more, and particularly preferably 50 mol% or more.

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

[0065] Furthermore, it is preferable that the polyimide contains (100-x) mol% of the constituent units represented by the above general formula (2) (where x is the mol% of the constituent units represented by the above general formula (1)). From the viewpoint of solubility in solvents, it is more preferable that the polyimide contains 85 mol% or less of the constituent units represented by the above general formula (2), even more preferable that it contains 75 mol% or less, and particularly preferable that it contains 50 mol% or less.

[0066] Furthermore, if the polyimide contains 100 mol% of the constituent units represented by the above general formula (1), then the constituent units represented by the above general formula (2) are 0 mol%, i.e., not included. The constituent units represented by the above general formula (2) may be 0 mol%, but they may also be included as copolymer components from the viewpoint of improving surface hardness and light transmittance, and the polyimide may contain 5 mol% or more, 10 mol% or more, or 20 mol% or more of the constituent units represented by the above general formula (2).

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

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

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

[0070] [ka]

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

[0072] Polyimides, in particular, are selected based on their light transmittance, flexibility, and surface hardness. Specifically, the tetracarboxylic acid residues having aromatic or aliphatic rings in A of the above general formula (2) are cyclohexanetetracarboxylic acid dianhydride residues, cyclopentanetetracarboxylic acid dianhydride residues, dicyclohexane-3,4,3',4'-tetracarboxylic acid dianhydride residues, cyclobutanetetracarboxylic acid dianhydride residues, pyromellitic acid dianhydride residues, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride residues, and 2,2',3,3 Preferably, it is at least one tetravalent group selected from the group consisting of '-biphenyltetracarboxylic dianhydride residue, 2,3,3',4'-biphenyltetracarboxylic dianhydride residue, 4,4'-(hexafluoroisopropylidene)diphthalic acid anhydride residue, 3,4'-(hexafluoroisopropylidene)diphthalic acid anhydride residue, 3,3'-(hexafluoroisopropylidene)diphthalic acid anhydride residue, 4,4'-oxydiphthalic acid anhydride residue, and 3,4'-oxydiphthalic acid anhydride residue.

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

[0074] In the above general formula (2), A preferably includes a group of tetracarboxylic acid residues (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 acid dianhydride residues, and 2,2',3,3'-biphenyltetracarboxylic acid dianhydride residues, from the viewpoint of improving surface hardness. Furthermore, as A in the above general formula (2), it is preferable that, from the viewpoint of improving light transmittance, A includes a group of tetracarboxylic acid residues (group B) suitable for improving light transmittance, such as cyclohexanetetracarboxylic acid dianhydride residue, cyclopentanetetracarboxylic acid dianhydride residue, dicyclohexane-3,4,3',4'-tetracarboxylic acid dianhydride residue, cyclobutanetetracarboxylic acid dianhydride residue, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride residue, 4,4'-(hexafluoroisopropylidene)diphthalic acid anhydride residue, 3,4'-(hexafluoroisopropylidene)diphthalic acid anhydride residue, 3,3'-(hexafluoroisopropylidene)diphthalic acid anhydride residue, 4,4'-oxydiphthalic acid anhydride residue, and 3,4'-oxydiphthalic acid anhydride residue. Group A and group B may be used in combination.

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

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

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

[0078] From the standpoint of good bending resistance, the weight-average molecular weight of the polyimide, calculated in terms of polystyrene in gel permeation chromatography, is preferably 100,000 or more. From the standpoint of bending 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, from the standpoint of being less prone to the occurrence of bubble defects, the weight-average molecular weight is preferably 270,000 or less. Furthermore, from the standpoint 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, the polyimide is used as a 0.1% by mass N-methylpyrrolidone (NMP) solution, and the developing solvent is a 30 mmol% LiBr-NMP solution with a water content of 500 ppm or less. The measurement is performed using a Tosoh GPC instrument (HLC-8120, column: SHODEX GPC LF-804) under the following conditions: sample input volume of 50 μL, solvent flow rate of 0.4 mL / min, and 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 polyamide-imide is not particularly limited as long as it satisfies the above-mentioned composite elastic modulus and has light transmittance, but it is preferable to include, for example, a polyimide constituent unit containing a constituent unit represented by the following formula (4) and a polyamide constituent unit containing a constituent unit represented by the following formula (5).

[0081] [ka]

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

[0083] By including polyimide units containing the structural unit represented by formula (4) and polyamide units containing the structural unit represented by formula (5), a resin layer with sufficient transparency, high composite modulus, and bending resistance can be obtained. In the above polyimide, a polyamide structural unit is introduced that further includes a dicarboxylic acid residue having an aromatic ring, promoting intermolecular interactions by hydrogen bonding, in addition to a polyimide structural unit having a specific structure of tetracarboxylic acid residues containing a parabiphenylene group with a dihedral angle twisted via an ester bond in the main chain and a specific diamine residue. It is presumed that by introducing an aromatic ring twist in the main chain structure of the polymer, intermolecular energy transitions occurring in π-conjugated polymers can be suppressed, and while achieving sufficient transparency, the introduction of amide bond sites and ester bond sites in the polyimide structural unit can enhance intermolecular forces due to hydrogen bond formation, thereby obtaining a resin layer with high composite modulus and bending resistance.

[0084] Furthermore, the above-mentioned polyamide-imide exhibits excellent bending resistance, especially in high-humidity environments. In the above-mentioned polyamide-imide, hydrogen bonding is formed between the amide bond sites and the ester bond sites in the polyimide constituent units, thereby suppressing hydrogen bonding with moisture even in high-humidity environments. This is presumed to suppress the deterioration of bending resistance in high-humidity environments, resulting in good bending resistance.

[0085] Furthermore, since the above polyamide-imide contains the constituent unit represented by formula (4), it exhibits good solubility in solvents even when containing the constituent unit represented by formula (4).

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

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

[0088] [ka]

[0089] The content of the component represented by formula (4) above may be 100 mol% of the total polyimide component units in the polyamide-imide. Furthermore, the polyimide component units may contain other polyimide component units different from those represented by formula (4). The content of the component represented by formula (4) above is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, preferably 100 mol% or less, and may also be 90 mol% or less. If the content of the component represented by formula (4) above is within the above range, it is possible to have sufficient transparency while also possessing high composite modulus and flexural resistance. Other polyimide component units different from those represented by formula (4) above may be included to improve the balance between transparency, composite modulus, and flexural resistance, or to add further properties.

[0090] The content of the tetracarboxylic dianhydride residue represented by formula (4-1) in polyamide-imide is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, preferably 100 mol% or less, and may also be 90 mol% or less, relative to the total amount of tetracarboxylic acid residues contained in the polyimide constituent units. If the content of the tetracarboxylic dianhydride residue represented by formula (4-1) is within the above range, it is possible to have sufficient transparency while also having high composite elastic modulus and bending resistance. To improve the balance between transparency, composite elastic modulus and bending resistance, or to add further properties, other tetracarboxylic dianhydride residues different from the tetracarboxylic dianhydride residue represented by formula (4-1) may be included.

[0091] Other polyimide constituent units that may be included in the polyimide constituent units include, for example, polyimide constituent units represented by the general formula (2) above that are different from the constituent units represented by formula (4) above. In the constituent units represented by the general formula (2) above, A and B may be the same or different in each constituent unit. That is, in the constituent units represented by the general formula (2) above, A and B may each be included independently as one type or as two or more types.

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

[0093] [ka]

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

[0095] Q aThe bonding position to each ring can be either ortho or meta relative to one of the two carboxyl groups bonded to each ring. a2 The bonding position to each ring is preferably independently at the meta or para position relative to the phenylene group, and more preferably at the para position.

[0096] In the constituent unit represented by the general formula (2) above, as A, among the tetravalent groups represented by formulas (a1) to (a7) above, in the case of structures containing aromatic rings as in formulas (a1) to (a3) ​​above, the tetravalent groups represented by formulas (a1) and (a2) above are preferred from the viewpoint of providing transparency and solubility in solvents. Furthermore, it is preferable to have a structure that can be bent between the aromatic rings, and Q in formula (a2) above is preferred. a Examples include -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -SO2-, and -Q a2 -Ph-Q a2 -(Q a2 Q represents -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -CO-, or -SO2-. It is preferable that it is Q. Furthermore, since transparency is improved when a fluorine atom is included, a For example, -C(CF3)2-, -Q a2 -Ph-Q a2 -(Q a2 -C(CF3)2-) is preferred, and from the viewpoint of the composite modulus, Q a Among these, -C(CF3)2- is more preferable.

[0097] Furthermore, in the constituent unit represented by the general formula (2) above, among the tetravalent groups represented by formulas (a1) to (a7) above, A is preferred when it includes an aliphatic ring as in formulas (a4) to (a7) above, because it has an aliphatic structure and therefore excellent transparency and solubility. In particular, tetravalent groups represented by structures (a4), (a5), or (a6) with few bending sites are preferred because they result in a good composite elastic modulus, and among these, the tetravalent group represented by (a4) is preferred.

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

[0099] [ka]

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

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

[0102] In the constituent unit represented by the general formula (2) above, B is preferably a molecular structure in which the π-conjugation between phenylene groups is cleaved while having a phenylene skeleton, from the viewpoint of transparency and maintenance of the composite elastic modulus, and it is even more preferable that it contains fluorine.

[0103] As a molecular structure in which the π-conjugation between phenylene groups is cleaved, in the divalent group represented by the above formula (b2), Q b However, it is preferable that the molecule is -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, or -SO2-, and more preferably -C(CF3)2- or -SO2-.

[0104] Furthermore, in the constituent unit represented by the general formula (2) above, B is preferably at least one divalent group selected from the group consisting of divalent groups represented by the general formula (3) above, from the viewpoint of transparency and maintenance of composite elastic modulus. As for the divalent group represented by the general formula (3) above, R is preferable from the viewpoint of transparency. 5 and R 6 It is more preferable that the group is a methyl group or a trifluoromethyl group, and even more preferable that it is a trifluoromethyl group from the viewpoint of transparency.

[0105] Furthermore, other polyimide constituent units, different from the constituent units represented by formula (4) above, may be the constituent units represented by the following formula (6).

[0106] [ka]

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

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

[0109] When polyimide constituent units include other polyimide constituent units, it is preferable to include the constituent unit represented by the following formula (7), the constituent unit represented by the following formula (8), or a combination thereof. Including the constituent unit represented by the following formula (7), the constituent unit represented by the following formula (8), or a combination thereof is preferable from the standpoint of improving transparency and increasing solubility in solvents. In particular, including the constituent unit represented by the following formula (7) is more preferable from the standpoint of improving transparency while maintaining a high composite modulus.

[0110] [ka]

[0111] The structural unit represented by formula (7) above can be obtained by reacting cyclobutanetetracarboxylic dianhydride with 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl. The structural unit represented by formula (8) above 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 constituent units, which are different from the constituent units represented by formula (4) above, relative to the total polyimide constituent units in the polyamide-imide may be 0 mol%, but if present, it is preferably 5 mol% or more, may be 10 mol% or more, 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 constituent units is within the above range, high transparency can be imparted and the composite elastic modulus will be good.

[0113] In particular, when the constituent unit represented by formula (7), the constituent unit represented by formula (8), or a combination thereof is included, the total content ratio of the constituent unit represented by formula (7) and the constituent unit represented by formula (8) relative to the total polyimide constituent units in the polyamide-imide is preferably 5 mol% or more, may be 10 mol% or more, preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less. If the total content ratio of the constituent unit represented by formula (7) and the constituent unit represented by formula (8) is within the above range, high transparency can be provided and the composite elastic modulus will be good.

[0114] (Polyamide constituent units) Polyamide structural units are structural units obtained by reacting a dicarboxylic acid component with a diamine component, and examples include structural units represented by the following general formula (9).

[0115] [ka]

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

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

[0118] The polyamide constituent units in polyamide-imide include the constituent unit represented by formula (5) above as an essential component. One or more of the constituent units represented by formula (5) above are included in the polyamide constituent units.

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

[0120] The constituent unit represented by formula (5) above preferably has at least one selected from the group consisting of structures represented by the following formulas (x1) to (x3) as X in formula (5). A resin layer with high composite elastic modulus can be obtained while having sufficient transparency. Furthermore, it may be a 1,3-phenylene group instead of the 1,4-phenylene group represented by the following formula (x1).

[0121] [ka]

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

[0123] In the above formula (5), among the structures represented by formulas (x1) to (x3), the structure represented by formula (x1) or formula (x2) is more preferable, and the structure represented by formula (x2) is even more preferable, in terms of X.

[0124] The content of the constituent unit represented by formula (5) above may be 100 mol% relative to the total polyamide constituent units in the polyamide-imide. In addition, the polyamide constituent units may further contain other polyamide constituent units different from the constituent unit represented by formula (5) above. The content of the constituent unit represented by formula (5) above is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, preferably 100 mol% or less, and may be 95 mol% or less, relative to the total polyamide constituent units in the polyamide-imide. If the content of the constituent unit represented by formula (5) above is within the above range, a good balance between transparency and composite elastic modulus is obtained.

[0125] From the viewpoint of balancing transparency and composite modulus, the total content of one or more types of X selected from the group consisting of structures represented by formulas (x1) to (x3) in the polyamide-imide may be 100 mol%, preferably 80 mol% or more and 100 mol%, more preferably 90 mol% or more and 100 mol%, and even more preferably 95 mol% or more and 100 mol%.

[0126] The polyamide constituent units may include other polyamide constituent units different from the constituent units represented by formula (5) above. For example, a polyamide constituent unit different from the constituent unit represented by general formula (9) above may be included. In the constituent units represented by general formula (9), X and B may be the same or different in each constituent unit. That is, in the constituent units represented by general formula (9), X and B may each be independently included in one or more types. In general formula (9), X may be the same as X in the constituent units represented by formula (5) above, and B may be the same as B in the constituent units represented by general formula (5) above.

[0127] Other polyamide structural units, different from the structural unit represented by formula (5) above, which may be included in the polyamide structural unit, include, from the viewpoint of transparency, in the general formula (9) above, X is selected from the group consisting of structures represented by formulas (x1) to (x3) above, and B is a divalent group represented by formula (b2) above, Q b However, R is either -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, or -SO2-, or in the divalent group represented by the general formula (3) above 5 and R 6 It is preferable that is a hydrogen atom or a methyl group, and in the divalent group represented by the above formula (b2), Q b However, in the case of a divalent group represented by the general formula (3) above, R 5 and R 6 It is more preferable that is a methyl group, and in the divalent group represented by the above formula (b2), Q b However, it is even more preferable that it be -C(CF3)2-.

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

[0129] The content of the dicarboxylic acid residue X having an aromatic ring in formula (5) above is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, even more preferably 50 mol% or more, preferably 80 mol% or less, even more preferably 70 mol% or less, and even more preferably 60 mol% or less, relative to the total of the tetracarboxylic acid residues and dicarboxylic acid residues in the polyamide-imide resin. If the content of the dicarboxylic acid residue X having an aromatic ring in formula (5) above is within the above range, the composite elastic modulus and bending resistance at room temperature of the resin layer tend to improve, and the solubility of the polyamide-imide in solvents and bending resistance under high temperature and high humidity conditions tend to improve.

[0130] Furthermore, polyamide-imide may have structures different from the above-mentioned polyimide constituent units and polyamide constituent units in part. Preferably, the total of polyimide constituent units containing the constituent unit represented by formula (4) and polyamide constituent units containing the constituent unit represented by formula (5) is 95% or more, more preferably 98% or more, and even more preferably 100% of the total constituent units of the polyamide-imide.

[0131] Examples of structures different from the above-mentioned polyimide and polyamide structural units include structural units in which the tetracarboxylic acid component is not completely imidized and has a polyamic acid structure in part, and polyamide-imide structural units containing tricarboxylic acid residues such as trimellitic anhydride.

[0132] The content percentage (mol%) of each constituent unit and each residue in polyamide-imide is: 1The structure can be measured using 1H-NMR, and can also be determined from the raw material ratio during polyamide-imide production. Furthermore, the structure of polyamide-imide can be determined using NMR, various mass spectrometers, etc. In addition, the structure and content of each residue in polyamide-imide can be determined, for example, by decomposing polyamide-imide with an alkaline aqueous solution or supercritical methanol, and then using high-performance liquid chromatography, gas chromatography-mass spectrometry, NMR, elemental analysis, XPS / ESCA, and TOF-SIMS on the decomposition products.

[0133] The weight-average molecular weight of the polyamide-imide is preferably 50,000 or more, more preferably 100,000 or more, even more preferably 150,000 or more, 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 polyamide-imide resin is within the above range, it is less likely to cause appearance defects such as cracks and whitening after firing, making it easier to obtain a resin layer with good transparency, and it is also easier to form a resin layer by suppressing viscosity increases during synthesis, varnish preparation, and resin layer formation.

[0134] The method for measuring the weight-average molecular weight of polyamide-imide can be the same as the method for measuring the weight-average molecular weight of polyamide-imide described above.

[0135] (b) UV absorbers The resin layer may contain an ultraviolet absorber. This can suppress the degradation of the resin layer due to ultraviolet light. In particular, if the resin layer contains polyimide, it can suppress the color change of the polyimide-containing resin layer over time. Furthermore, in a display device equipped with a display device component, it can suppress the degradation of components located on the display panel side of the display device component, such as polarizers, due to ultraviolet light.

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

[0137] Specific examples of triazine-based UV absorbers, benzophenone-based UV absorbers such as hydroxybenzophenone-based UV absorbers, and benzotriazole-based UV absorbers can be found, for example, in Japanese Patent Publication No. 2019-132930.

[0138] Among the ultraviolet absorbers, triazine-based ultraviolet absorbers, hydroxybenzophenone-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers are particularly preferred.

[0139] Furthermore, the ultraviolet absorber is preferably a polymer or oligomer. This is because it can suppress the bleed-out of the ultraviolet absorber 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 that the (meth)acrylate having a benzotriazole skeleton or a benzophenone skeleton is thermally copolymerized with methyl methacrylate (MMA) in any ratio.

[0140] The content of the UV 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 UV absorber is too low, the effect of the UV absorber may not be sufficiently obtained. On the other hand, if the content of the UV absorber is too high, the resin layer may become significantly discolored or the strength of the resin layer may decrease.

[0141] (c) Other additives The resin layer may contain additional additives as needed. Examples of additives include inorganic particles, silica fillers to facilitate winding, surfactants to improve film-forming and defoaming properties, and adhesion enhancers.

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

[0143] The following explanation will use the case where the resin layer contains polyimide or polyamide-imide as an example.

[0144] (i) Method for forming a resin layer containing polyimide Methods for forming a resin layer containing polyimide include, for example, applying a polyimide varnish containing polyimide and an organic solvent to a glass substrate and drying it, and 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. In the former method, the heating conditions of the film formation process can be relaxed. On the other hand, in the latter method, the constraints on the solubility of polyimide are removed, thus increasing the options for the chemical structure of the polyimide.

[0145] In particular, the following manufacturing method is preferred because it is less prone to the occurrence of air bubble defects and makes it easier to obtain a resin layer with good thickness uniformity.

[0146] A method for forming a resin layer containing polyimide preferably comprises a preparation step of preparing a polyimide varnish containing polyimide and an organic solvent, wherein the polyimide content is 6% by mass or more and 15% by mass or less in the polyimide varnish, and the viscosity at 25°C is 1,000 cps or more and 50,000 cps or less; a coating step of applying the polyimide varnish onto a glass substrate; a first drying step of drying the coating film at a temperature of 140°C or lower; and a second drying step of heating the dried coating film at a temperature of 200°C or higher.

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

[0148] According to the above method for forming the 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. As a result, a resin layer with good thickness uniformity and less prone to air bubble defects can be obtained.

[0149] The above organic solvent is not particularly limited as long as it can dissolve polyimide, and for example, aprotic polar solvents or water-soluble alcohol-based solvents can be used. In particular, it is preferable to use organic solvents containing nitrogen atoms such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone, or γ-butyrolactone. Furthermore, the above organic solvent can be used as one or a mixture of two or more solvents.

[0150] For a method of forming the resin layer containing the above-mentioned polyimide, refer to the methods described in, for example, Japanese Patent Publication No. 2019-1989 and Japanese Patent Publication No. 2019-182974.

[0151] (ii) Method for forming a resin layer containing polyamide-imide The method for forming a resin layer containing polyamide-imide is not particularly limited, and one example is to apply a polyamide-imide varnish containing polyamide-imide and an organic solvent to a glass substrate and then dry it.

[0152] The method for producing polyamideimide is not particularly limited, but for example, it can be produced by reacting one or more tetracarboxylic dianhydrides, including a tetracarboxylic dianhydride represented by formula (4-1) and optionally a tetracarboxylic dianhydride having an aromatic or aliphatic ring, with one or more diamines, including 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl and optionally a diamine having an aromatic or 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 polyamide-imide varnish can be the same as the organic solvent contained in the polyamide-imide varnish described above.

[0154] The method for applying the polyamide-imide varnish described above is not particularly limited as long as it can be applied to the desired thickness. Examples of common application methods include gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, and screen printing. Transfer methods can also be used to form the polyamide-imide varnish film.

[0155] After applying the polyamide-imide varnish, the solvent in the coating film is dried at a temperature of 150°C or lower, preferably between 30°C and 120°C, until the coating film becomes tack-free.

[0156] The drying time should be adjusted appropriately depending on the thickness of the coating film, the type of solvent, the drying temperature, etc. For example, it is preferable to have a drying time of 5 minutes or more and 60 minutes or less, preferably 10 minutes or more and 40 minutes or less. If the drying time is too long, the efficiency of resin layer formation may decrease. On the other hand, if the drying time is too short, the rapid drying of the solvent may affect the appearance of the resulting resin layer.

[0157] There are no particular restrictions on the method of drying the solvent, as long as it is possible to dry the solvent at the above temperature. For example, an oven, drying furnace, hot plate, infrared heating, etc., can be used.

[0158] The drying process may include a first drying step for drying the coating film and a second drying step for 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 flexibility, it is preferable to remove as much residual solvent as possible from the resin layer.

[0159] 2. Glass substrate The glass substrate in this 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 preferred. Chemically strengthened glass is preferable because it has excellent mechanical strength and can be made thinner. Chemically strengthened glass is typically glass whose mechanical properties have been strengthened by a chemical method, such as by partially exchanging ionic species near the glass surface, such as replacing sodium with potassium, and has a compressive stress layer on its surface.

[0161] Examples of glass materials that make up chemically strengthened glass substrates include aluminosilicate glass, soda-lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborsilicate glass.

[0162] Examples of commercially available chemically strengthened glass substrates include Corning's Gorilla Glass and AGC's Dragontrail. Alternatively, the chemically strengthened glass substrate described in Japanese Patent Publication No. 2019-194143 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. By making the glass substrate thin, as described above, good flexibility and sufficient hardness can be obtained. Furthermore, curling of the display device component can be suppressed. Moreover, it is preferable in terms of reducing the weight of the display device component.

[0164] 3. Functional Layer The display device component in this disclosure may further have a functional layer on the side of the resin layer opposite to the glass substrate. Examples of functional layers include a hard coat layer, a protective layer, an anti-reflective layer, an anti-glare layer, and the like.

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

[0166] (1) Hard coat layer In this disclosure, the display device component preferably further has a hard coat layer 4 on the side of the resin layer 3 opposite to the glass substrate 2, as shown in Figure 2, for example. The hard coat layer is a component for increasing surface hardness. The presence of the hard coat layer improves scratch resistance.

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

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

[0169] Here, pencil hardness is measured using 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 hard coat layer side of the display device component, and the highest pencil hardness that does not cause scratches is evaluated. Measurement conditions can be an angle of 45°, a load of 750g, a speed of 0.5mm / sec to 1mm / sec, and a temperature of 23±2℃. As a pencil hardness tester, for example, a pencil scratch coating hardness tester manufactured by Toyo Seiki Co., Ltd. can be used.

[0170] (b) composition of the hard coat layer The hard coat layer may be a single layer or may have a multilayer structure of two or more layers. When the hard coat layer has a multilayer structure, it is preferable that the hard coat layer has a layer to satisfy the pencil hardness requirement and a layer to satisfy the dynamic bending test requirement (a layer to satisfy the scratch resistance requirement) in order to improve surface hardness and to achieve a good balance between flexural resistance and elastic modulus.

[0171] (c) Material of the hard coat layer For the hard coat layer, materials such as organic materials, inorganic materials, and organic-inorganic composite materials can be used.

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

[0173] (i) Polymerizable compound A polymerizable compound is one that has at least one polymerizable functional group in its molecule. Examples of polymerizable compounds include at least one radical polymerizable compound and at least one cationic polymerizable compound.

[0174] A radical polymerizable compound is a compound that has a radical polymerizable group. The radical polymerizable group of a radical polymerizable compound can be any functional group capable of undergoing a radical polymerization reaction, and is not particularly limited, but examples include groups containing a carbon-carbon unsaturated double bond, and specifically, vinyl groups and (meth)acryloyl groups. If a radical polymerizable compound has two or more radical polymerizable groups, these radical polymerizable groups may be the same or different.

[0175] The number of radical polymerizable groups in a single molecule of a radical polymerizable compound is preferably two or more, and more preferably three or more, from the viewpoint of improving the hardness of the hard coat layer.

[0176] As radical polymerizable compounds, compounds having (meth)acryloyl groups are preferred due to their high reactivity. For example, polyfunctional (meth)acrylate monomers and oligomers with molecular weights of several hundred to several thousand and containing several (meth)acryloyl groups in the molecule, such as urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, and silicone (meth)acrylate, can be preferably used. Polyfunctional (meth)acrylate polymers having two or more (meth)acryloyl groups in the side chain of the acrylate polymer can also be preferably used. In particular, polyfunctional (meth)acrylate monomers having two or more (meth)acryloyl groups in one molecule can be preferably used. By including cured products of polyfunctional (meth)acrylate monomers in the hard coat layer, the hardness of the hard coat layer can be improved, and the adhesion can be further improved. Furthermore, polyfunctional (meth)acrylate oligomers or polymers having two or more (meth)acryloyl groups in one molecule can also be preferably used. By including a cured product of the polyfunctional (meth)acrylate oligomer or polymer in the hard coat layer, the hardness and flexural resistance of the hard coat layer can be improved, and the adhesion can be further improved.

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

[0178] Specific examples of polyfunctional (meth)acrylate monomers can be found in, for example, Japanese Patent Publication No. 2019-132930. In particular, those having 3 to 6 (meth)acryloyl groups per molecule are preferred due to their high reactivity, improved hardness of the hard coat layer, and adhesion. 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. are preferred, and at least one selected from pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexaacrylate, as well as those modified with PO, EO, or caprolactone, is preferred.

[0179] The resin composition may contain monofunctional (meth)acrylate monomers as radical polymerizable compounds for purposes such as adjusting hardness and viscosity, and improving adhesion. Specific examples of monofunctional (meth)acrylate monomers can be found in, for example, Japanese Patent Application Publication No. 2019-132930.

[0180] A cationic polymerizable compound is a compound having a cationic polymerizable group. The cationic polymerizable group of a cationic polymerizable compound can be any functional group capable of undergoing a cationic polymerization reaction, and is not particularly limited, but examples include epoxy groups, oxetanyl groups, and vinyl ether groups. If a cationic polymerizable compound has two or more cationic polymerizable groups, these cationic polymerizable groups may be the same or different.

[0181] The number of cationic polymerizable groups in one molecule of a cationic polymerizable compound is preferably two or more, and more preferably three or more, from the viewpoint of improving the hardness of the hard coat layer.

[0182] Furthermore, among cationic polymerizable compounds, compounds having at least one of epoxy and oxetanyl groups as cationic polymerizable groups are preferred, and compounds having two or more of at least one of epoxy and oxetanyl groups in one molecule are more preferred. Cyclic ether groups such as epoxy and oxetanyl groups are preferred because they exhibit less shrinkage during polymerization. In addition, compounds having epoxy groups among cyclic ether groups are readily available in a variety of structures, do not adversely affect the durability of the resulting hard coat layer, and have the advantage of being easy to control in terms of compatibility with radical polymerizable compounds. Moreover, among cyclic ether groups, oxetanyl groups have a higher degree of polymerization and lower toxicity compared to epoxy groups. When the resulting hard coat layer is combined with a compound having epoxy groups, it accelerates the network formation rate obtained from cationic polymerizable compounds in the coating film, and has the advantage of forming an independent network without leaving unreacted monomers in the film even in regions where it is mixed with radical polymerizable compounds.

[0183] Examples of cationic polymerizable compounds having epoxy groups include alicyclic epoxy resins obtained by epoxidizing polyglycidyl ethers of polyhydric alcohols having alicyclic rings, or compounds containing cyclohexene rings or cyclopentene rings, 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 homopolymers and copolymers of glycidyl (meth)acrylates; glycidyl ethers produced by the reaction of bisphenols such as bisphenol A, bisphenol F, and hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts and caprolactone adducts, with epichlorohydrin, and novolac epoxy resins, as well as glycidyl ether-type epoxy resins derived from bisphenols.

[0184] Specific examples of alicyclic epoxy resins, glycidyl ether type epoxy resins, and cationic polymerizable compounds having an oxetanyl group can be found, for example, in Japanese Patent Application Publication No. 2018-104682.

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

[0186] (ii) Polymerization initiator The resin composition may contain a polymerization initiator as needed. As the polymerization initiator, radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, etc., can be appropriately selected and used. These polymerization initiators decompose upon at least one of light irradiation and heating, generating radicals or cations to promote 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 can be found in, for example, Japanese Patent Publication No. 2018-104682.

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

[0189] Examples of inorganic particles include silica (SiO2), metal oxide particles such as 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, at least one selected from silica particles and aluminum oxide particles is more preferred, and silica particles are even more preferred because they provide excellent hardness.

[0190] Furthermore, it is preferable that the inorganic particles are reactive inorganic particles having photoreactive reactive functional groups on at least a portion of the particle surface that can crosslink with other inorganic particles or with at least one polymerizable compound to form covalent bonds. By crosslinking reactive inorganic particles with other reactive inorganic particles or with at least one radical polymerizable compound and a cationic polymerizable compound, the hardness of the hard coat layer can be further improved.

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

[0192] The reactive silica particles are not particularly limited and conventionally known particles can be used, for example, the reactive silica particles described in Japanese Patent Application Publication No. 2008-165040. Commercially available reactive silica particles include, for example, MIBK-SD, MIBK-SDMS, MIBK-SDL, MIBK-SDZL from Nissan Chemical Industries, Ltd., and V8802, V8803 from JGC Catalysts & Chemicals Co., Ltd.

[0193] Furthermore, the silica particles may be spherical silica particles, but irregularly shaped silica particles are preferred. Spherical silica particles and irregularly shaped silica particles may be mixed. In this specification, irregularly shaped silica particles refer to silica particles with a potato-like, randomly uneven surface. Since irregularly shaped silica particles have a larger surface area compared to spherical silica particles, including such irregularly shaped silica particles increases the contact area with the resin components, etc., thereby improving the hardness of the hard coat layer.

[0194] Furthermore, whether or not the particles are irregularly shaped silica particles can be confirmed by cross-sectional observation of the hard coat layer using an electron microscope.

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

[0196] Here, the average particle size of inorganic particles can be measured by cross-sectional observation of the hard coat layer using an electron microscope, and the average particle size is defined as the average of the particle sizes of 10 arbitrarily selected particles. The average particle size of irregularly shaped silica particles is the average value of the maximum (major axis) and minimum (minor axis) distances between two points on the outer circumference of the irregularly shaped silica particles observed by cross-sectional microscopy of the hard coat layer.

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

[0198] (iv) UV absorbers The hard coat layer may contain an ultraviolet absorber. This can suppress the degradation of the resin layer due to ultraviolet light. In particular, if the resin layer contains polyimide, it can suppress the color change of the polyimide-containing resin layer over time. Furthermore, in a display device equipped with a display device component, it can suppress the degradation of components located on the display panel side of the display device component, such as polarizers, due to ultraviolet light.

[0199] The UV absorber contained in the hard coat layer preferably has an absorption wavelength peak of 300 nm to 390 nm in absorbance measurements, more preferably 320 nm to 370 nm, and even more preferably 330 nm to 370 nm. This is because such a UV absorber can efficiently absorb UV light in the UVA region, and at the same time, by shifting its peak wavelength from the absorption wavelength of 250 nm of the initiator for curing the hard coat layer, it is possible to form a hard coat layer with UV absorption ability without inhibiting the curing of the hard coat layer.

[0200] Among UV absorbers, those with an absorption wavelength peak of 380 nm or less are preferable because they can suppress discoloration caused by the UV absorber.

[0201] The absorbance of the ultraviolet absorber can be measured using, for example, a UV-Vis-Near-Infrared spectrophotometer (e.g., JASCO Corporation V-7100).

[0202] The ultraviolet absorber can be the same as the ultraviolet absorber used in the resin layer described above.

[0203] In particular, from the viewpoint of suppressing degradation of the resin layer due to ultraviolet light, 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 can be found, for example, in Japanese Patent Publication No. 2019-132930.

[0205] Among the hydroxybenzophenone-based UV absorbers, 2-hydroxybenzophenone-based UV absorbers are preferred, and it is more preferable that one or more are selected from the group consisting of benzophenone-based UV absorbers having the following general formula (A). This can suppress the degradation of the resin layer due to ultraviolet light and improve its durability.

[0206] [ka]

[0207] (In general formula (A), X 1 and X 2 Each of these independently consists of a hydroxyl group and an -OR group. a , or represents a hydrocarbon group with 1 to 15 carbon atoms, R a (This represents a hydrocarbon group with 1 to 15 carbon atoms.)

[0208] In general formula (A), X 1 , X 2 and R a Examples of hydrocarbon groups having 1 to 15 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, dodecyl, allyl, and benzyl groups. Aliphatic hydrocarbon groups having 3 or more carbon atoms may be linear or branched. Hydrocarbon groups preferably have 1 to 12 carbon atoms, and more preferably 1 to 8. From the viewpoint of easily improving light transmittance, hydrocarbon groups are preferably aliphatic hydrocarbon groups, and among them, methyl and allyl groups are preferred.

[0209] Because it is easier to improve durability, X 1 and X 2 Each of these independently represents a hydroxyl group or -OR a It is preferable that this be the case.

[0210] As one or more selected from the group consisting of benzophenone-based ultraviolet absorbers having the general formula (A), among others, it 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 the benzotriazole-based ultraviolet absorber can include, for example, those described in JP-A-2019-132930.

[0212] As the benzotriazole-based ultraviolet absorber, among others, 2-(2-hydroxyphenyl)benzotriazoles are preferable, and more preferably one or more selected from the group consisting of benzotriazole-based ultraviolet absorbers having the following general formula (B). It can suppress the deterioration of the above resin layer by ultraviolet rays and improve the durability.

[0213] [Chemical formula]

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

[0215] In general formula (B), Y 1 , Y 2 , and Y 3 , and the hydrocarbon group having 1 to 15 carbon atoms in R b includes 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, and the like. 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, more preferably 1 to 8 carbon atoms. From the viewpoint of easy improvement of light transmittance, the hydrocarbon group is preferably an aliphatic hydrocarbon group, preferably a linear or branched alkyl group, and among them, a methyl group, a t-butyl group, a t-pentyl group, an n-octyl group, or a t-octyl group is preferable.

[0216] In general formula (B), the halogen atom in Y 4 includes a chlorine atom, a fluorine atom, a bromine atom, etc., and among them, a chlorine atom is preferable.

[0217] In general formula (B), among others, Y 1 , and Y 3 are hydrogen atoms, and Y 2 is a hydroxyl group or represents -OR b is preferably one or more selected from the group consisting of 2-(2-hydroxy-4-octyloxyphenyl)-2H-benzotriazole and 2-(2,4-dihydroxyphenyl)-2H-benzotriazole. Deterioration of the above resin layer due to ultraviolet rays can be suppressed and durability can be improved.

[0218] Regarding the content of the ultraviolet absorber in the hard coat layer, from the viewpoint of suppressing haze caused by mixing the ultraviolet absorber, for example, it is preferably 10% by mass or less, more preferably 7% by mass or less. Also, from the viewpoints of suppressing deterioration of the above 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 agents The hard coat layer may contain an antifouling agent. This can provide antifouling properties to the display device component.

[0220] The antifouling agent is not particularly limited and examples 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. The antifouling agent may be used individually or in combination of two or more types.

[0221] Hard coat layers containing silicone-based or fluorine-based antifouling agents are less prone to fingerprints (less noticeable) and have good wipeability. Furthermore, the inclusion of silicone-based or fluorine-based antifouling agents can lower the surface tension of the curable resin composition for the hard coat layer during application, resulting in good leveling properties and a superior appearance for the resulting hard coat layer.

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

[0223] It is preferable that the antifouling agent has reactive functional groups in order to enhance the durability of its antifouling performance. If the antifouling agent does not have reactive functional groups, regardless of whether the display device components are in the form of rolls or sheets, when the display device components are stacked, the antifouling agent may transfer to the side of the display device component opposite to the side with the hard coat layer. This may cause other layers to peel off when other layers are attached or coated to the side of the display device component opposite to the side with the hard coat layer, and furthermore, other layers may become more prone to peeling off when repeatedly bent. In contrast, if the antifouling agent has reactive functional groups, the durability of its antifouling performance is improved.

[0224] The number of reactive functional groups in the antifouling agent may be one or more, preferably two or more. By using an antifouling agent having two or more reactive functional groups, excellent scratch resistance can be imparted to the hard coat layer.

[0225] Furthermore, the antifouling agent preferably has a weight-average molecular weight of 5000 or less. 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 of additive and suppressing a decrease in the strength of the hard coat layer, it is preferable that it be unevenly distributed on the surface side of the hard coat layer.

[0227] Methods for distributing the antifouling agent unevenly on the surface side of the hard coat layer include, for example, a method in which, when forming the hard coat layer, the coating film of the curable resin composition for the hard coat layer is dried, and before curing, the coating film is heated to lower the viscosity of the resin components contained in the coating film, thereby increasing its fluidity and distributing the antifouling agent unevenly on the surface side of the hard coat layer; or a method in which an antifouling agent with low surface tension is used, the antifouling agent is allowed to float on the surface of the coating film without applying heat during drying, and then the coating film is cured, thereby distributing the antifouling agent unevenly on the surface side of the hard coat layer.

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

[0229] (vi) Other coatings The hard coat layer may further contain additives as needed. These additives are selected appropriately according to the function to be imparted to the hard coat layer and are not particularly limited, but examples include inorganic or organic particles for adjusting the refractive index, infrared absorbers, anti-glare agents, anti-fouling agents, antistatic agents, colorants such as blue or 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 can 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 component. For example, if 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. Also, if 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 component 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 determined depending on the material of the hard coat layer, and examples include applying a curable resin composition for hard coat layers containing the polymerizable compound onto the resin layer and curing it, as well as vapor deposition and sputtering methods.

[0232] The hard coat layer curable resin composition contains a polymerizable compound and may further contain polymerization initiators, particles, UV absorbers, solvents, additives, etc., as needed.

[0233] As a method of applying the curable resin composition for the hard coat layer onto the resin layer, there is no particular limitation as long as it is a method capable of applying with the target thickness. For example, general coating methods such as gravure coating method, gravure reverse coating method, gravure offset coating method, spin coating method, roll coating method, reverse roll coating method, blade coating method, dip coating method, screen printing method, etc. can be mentioned. Also, a transfer method can be used as a method for forming the coating film of the resin composition for the hard coat layer.

[0234] The coating film of the curable resin composition for the hard coat layer is dried as necessary to remove the solvent. As the drying method, for example, vacuum drying or heat drying, or a method combining these dryings can be mentioned. For example, it can be dried by heating at a temperature of 30°C or higher and 120°C or lower for 10 seconds or longer and 180 seconds or shorter.

[0235] As a method of curing the coating film of the curable resin composition for the hard coat layer, it is appropriately selected according to the polymerizable group of the polymerizable compound. For example, at least one of light irradiation and heating can be used.

[0236] For light irradiation, mainly ultraviolet rays, visible light, electron beams, ionizing radiation, etc. are used. In the case of ultraviolet curing, for example, ultraviolet rays emitted from light rays such as ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arcs, xenon arcs, metal halide lamps, etc. can be used. The irradiation amount of the energy ray source can be, for example, as the integrated exposure amount at an ultraviolet wavelength of 365 nm, 50 mJ / cm 2 or more and 5000 mJ / cm 2 or less.

[0237] When heating, for example, it can be processed at a temperature of 40°C or higher and 120°C or lower. Also, the reaction may be carried out by leaving it at room temperature (25°C) for 24 hours or longer.

[0238] (2) Protective layer The display device component in this disclosure may further have a protective layer on the side of the resin layer opposite to the glass substrate.

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

[0240] Here, 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 Technology Laboratory. The same method can be used to measure the total light transmittance of the other layers below.

[0241] The protective layer is not particularly limited as long as it is transparent, and may include, for example, a resin. The resin used for the protective layer is not particularly limited as long as it can produce a transparent protective layer, and any general-purpose resin can be used.

[0242] Methods for placing a protective layer on one side of a glass substrate include, for example, using a protective film as the protective layer and bonding the resin layer and the protective film via an adhesive layer, or forming a protective layer on top of the resin layer.

[0243] The adhesive layer described above is transparent. Specifically, the total light transmittance of the 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 OCA and photosensitive adhesives.

[0245] The thickness of the adhesive layer is preferably, for example, 1 μm to 100 μm. If the adhesive layer is too thick, the flexibility may be impaired. On the other hand, if the adhesive layer is too thin, the adhesion may not be guaranteed and it may peel off.

[0246] 4. Other configurations The display device component in this disclosure may have other layers in addition to the above-described layers, as necessary. Examples of other layers include a primer layer, a second resin layer, a decorative layer, and so on.

[0247] (1) Primer layer The display device component in this disclosure may have a primer layer 5 between the glass substrate 2 and the resin layer 3, for example, as shown in Figure 3. Alternatively, if the display device component in this disclosure has a second resin layer 6 on the side of the glass substrate 2 opposite to the resin layer 3, for example, as shown in Figure 4, a primer layer 7 may be provided 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 of the primer layer is not particularly limited as long as it can improve the adhesion between the glass substrate and the resin layer or the second resin layer, and resins can be used as examples. Examples of resins include (meth)acrylic resin, urethane resin, (meth)acrylic urethane copolymer, vinyl chloride-vinyl acetate copolymer resin, polyester, butyral resin, chlorinated polypropylene, chlorinated polyethylene, epoxy resin, silicone resin, etc. These resins may be used individually or in combination of two or more.

[0249] The thickness of the primer layer can be any thickness that is sufficient to improve the adhesion between the glass substrate and the resin layer or the second resin layer. For example, it can be 0.1 μm or more and 10 μm or less, and preferably 0.2 μm or more and 5 μm or less.

[0250] One method for forming the primer layer is to apply a primer layer composition onto a glass substrate. Examples of application methods include gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, and screen printing. Transfer methods can also be used to form the primer layer.

[0251] (2) Second resin layer The display device component in this disclosure may have a second resin layer 6 on the side of the glass substrate 2 opposite to the resin layer 3, as shown in Figure 4, for example. When an impact is applied to the display device component, the impact can be absorbed not only by the resin layer but also by the second resin layer, suppressing cracking of the glass substrate and improving impact resistance.

[0252] The resin included in the second resin layer is not particularly limited as long as it is a resin that can absorb impact, and examples include urethane resin, epoxy resin, polyimide, polyamide-imide, acrylic resin, triacetylcellulose (TAC), etc. These resins may be used individually 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 absorber can be the same as the one used in the above-mentioned resin layer.

[0254] The thickness of the second resin layer can be any thickness that is sufficient to absorb impact. For example, it is preferably 5 μm to 60 μm, more preferably 10 μm to 50 μm, and even more preferably 15 μm to 40 μm.

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

[0256] (3) Decorative layer The display device component in this disclosure may have a decorative layer between the glass substrate and the resin layer, or on the side of the glass substrate opposite to the resin layer.

[0257] The decorative layer includes a coloring agent and a binder resin. The binder resin included in the decorative layer is not particularly limited, and any resin commonly used in decorative layers can be used. Furthermore, the coloring agent included in the decorative layer is not particularly limited, and any known coloring agent commonly used in decorative layers can be used.

[0258] The decorative layer is typically placed on a portion of the glass substrate. The decorative layer may also have a patterned shape.

[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 components for display devices The display device component in this 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 for a display device component with good transparency.

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

[0262] The haze of the display device component in this disclosure is preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.0% or less. Such a low haze allows for a display device component with good transparency.

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

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

[0265] In the dynamic bending test, the display device component may be folded so that the glass substrate faces outward, or so that the glass substrate faces inward. In either case, it is preferable that no cracks or fractures occur in the display device component.

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

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

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

[0269] The static bending test is performed as follows. First, as shown in Figure 6(a), the short side portion 1C of the display device member 1 and the short side portion 1D opposite to the short side portion 1C are fixed with fixing portions 22 that are arranged parallel to each other so that the distance d between the short side portion 1C and the short side portion 1D is a predetermined value. Then, with the display device member 1 folded, a static bending test is performed by leaving it at 23°C for 240 hours. After that, as shown in Figure 6(b), the folding state is released by removing the fixing portion 22 from the short side portion 1D after the static bending test, 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 a larger opening angle θ indicates better resilience, with a maximum of 180°.

[0270] In the case of a display device component, when a static bending test is performed such that the distance d between opposing short sides 1C and 1D of the display device component 1 is 10 mm, it is preferable that the opening angle θ after the static bending test is 100° or more.

[0271] In the static bending test, the display device component may be folded so that the glass substrate faces inward, or so that the glass substrate faces outward. In either case, it is preferable that the opening angle θ is 100° or greater.

[0272] 6. Applications of components for display devices The display device component in this disclosure can be used in a display device as a component positioned on the observer side of the display panel. The display device component in this disclosure can be used in display devices such as smartphones, tablet terminals, wearable terminals, personal computers, televisions, digital signage, public information displays (PIDs), and in-vehicle displays. In particular, the display device component in this disclosure can be preferably used in flexible displays such as foldable displays, rollable displays, and bendable displays, and can be preferably used in foldable display components.

[0273] In the display device component described herein, it is preferable that the surface that becomes the outermost surface after the display device component is placed on the surface of the display device is the surface on the resin layer side.

[0274] The method for arranging the display device component on the surface of the display device in this disclosure is not particularly limited and includes, for example, a method using an adhesive layer. As the adhesive layer, a known adhesive layer used for bonding display device components can be used.

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

[0276] The optical laminate in this 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 resins, polycycloolefin resins, acetylcellulose resins, polycarbonate resins, and polypropylene resins.

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

[0278] In this disclosure, the glass substrate is thin, with a thickness below a predetermined value, raising concerns about its fragility and low impact resistance. However, by laminating a first resin layer having a predetermined composite elastic modulus, a second resin layer which is an adhesive layer, and a third resin layer which is a predetermined resin film on one side of the glass substrate in this order, when an impact is applied to the optical laminate, the first, second, and third resin layers absorb the impact, suppressing cracking of the glass substrate and improving impact resistance. The reason for this is not clear, but it is presumed to be as follows.

[0279] In other words, the first resin layer has a predetermined composite modulus, the second resin layer is an adhesive layer, and the third resin layer is a predetermined resin film. Therefore, the second resin layer is softer than the first and third resin layers, and the third resin layer is softer than the first resin layer. For example, the tensile modulus of the resins contained in the resin film constituting the third resin layer is 2.8-4 GPa for polyethylene terephthalate (PET), 2.1 GPa for polycycloolefin (COP), 1.4 GPa for triacetylcellulose (TAC), 2.4 GPa for polycarbonate (PC), and 2 GPa for polypropylene (PP). Thus, the third resin layer is softer than the first resin layer. Therefore, compared to the case where only the first resin layer is arranged on one side of the glass substrate, when the first, second, and third resin layers are laminated in this order on one side of the glass substrate, the second and third resin layers are more easily deformed than the first resin layer when an impact is applied to the optical laminate, so the impact is thought to be more easily dispersed.

[0280] Furthermore, because the second and third resin layers, which are softer than the first resin layer, are positioned on the side of the first resin layer opposite the glass substrate, it is thought 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 presumed that when the first, second, and third resin layers are laminated, the impact absorption will be higher compared to when only the first resin layer is present. Also, when only the second and third resin layers are laminated in this order on one side of the glass substrate, when an impact is applied to the optical laminate, the second and third resin layers are relatively soft and easily deformed, so there is a risk that the glass substrate may be damaged before the impact is fully absorbed. Therefore, it is presumed that when the first, second, and third resin layers are laminated, the impact resistance will be higher compared to when only the second and third resin layers are laminated.

[0281] As described in the section on display device components above, the reason for adopting the composite elastic modulus of the first resin layer in this disclosure is that the pressing of an indenter into the measurement sample in the nanoindentation method (indentation test method) is similar to the impact and pressing of the tip of a pen into the sample in the pen drop test.

[0282] According to this disclosure, the impact resistance measured by the pendrop test can be improved by having the composite elastic modulus of the first resin layer be greater than or equal to a predetermined value.

[0283] Furthermore, in this disclosure, even if the glass substrate breaks, the first resin layer, the second resin layer, and the third resin layer can suppress the scattering of glass fragments.

[0284] Furthermore, according to this disclosure, the glass substrate is thin, with a thickness of less than or equal to a predetermined value; the first resin layer, whose composite elastic modulus is greater than or equal to a predetermined value, is relatively thin, with a thickness within a predetermined range; the second resin layer is an adhesive layer and relatively soft; and the third resin layer is a predetermined resin film, thus increasing flexibility. Therefore, when the optical laminate is bent, cracking of the first, second, and third resin layers can be suppressed, and bending resistance can be maintained. Thus, the optical laminate in this disclosure is foldable and can be used in a wide variety of optical laminates, for example, as a component for foldable displays.

[0285] Furthermore, according to this disclosure, by having a composite elastic modulus of the first resin layer that is greater than or equal to a predetermined value, the restorative force when deformation is applied to the first resin layer can be increased. Therefore, by having a composite elastic modulus of the first resin layer that is greater than or equal to a predetermined value, the restorability of the optical laminate after being bent for a long period of time can be improved. In addition, the restorability of the optical laminate after repeated bending can also be improved.

[0286] Thus, this disclosure allows for the creation of an optical laminate with excellent impact resistance and flexibility. Furthermore, even if the glass substrate is damaged, the risk of injury to the human body can be reduced, resulting in a highly safe optical laminate.

[0287] The following describes the various components of the optical laminate in this disclosure.

[0288] 1.First resin layer The first resin layer in this disclosure has a composite elastic modulus of 5.7 GPa or more, a thickness of 5 μm or more and 60 μm or less, and is a component disposed on one side of the glass substrate. The first resin layer is a shock-absorbing component and also functions as a component that suppresses the scattering of glass when the glass substrate breaks. The first resin layer is transparent and, when the optical laminate in this disclosure is placed on the observer side of the display panel of a display device, it is placed on the observer 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 that of the resin layer in the display device component 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 display device component described above.

[0291] Furthermore, in order to avoid the influence of the glass substrate and the side edges of the first resin layer, the Berkovich indenter shall be pressed into the 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 both ends of the first resin layer toward the center of the first resin layer. In addition, it shall also be pressed into the portion of the first resin layer 500 nm away from the interface between the second resin layer and the first resin layer toward the center of the first resin layer.

[0292] (2) Composition 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 display device component described above.

[0293] Furthermore, the arrangement of the first resin layer with respect to the glass substrate can be the same as the arrangement of the resin layer with respect to the glass substrate in the display device component described above.

[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 of the display device component described above.

[0295] (b) UV absorbers The first resin layer may contain an ultraviolet absorber. The ultraviolet absorber can be the same as the ultraviolet absorber contained in the resin layer of the display device component described above.

[0296] (c) Other additives The first resin layer may further contain additives as needed. The additives may be the same as those contained in the resin layer of the display device component described above.

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

[0298] 2.Second resin layer In this disclosure, the second resin layer 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 shock-absorbing component. The second resin layer is transparent, and when the optical laminate in this disclosure is placed on the observer side of the display panel of a display device, it is placed on the observer side of the glass substrate.

[0299] The second resin layer is transparent, 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] Here, 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 Technology Research Institute. The same method can be used for measuring the total light transmittance of the other layers below.

[0301] The adhesive used in the second resin layer is not particularly limited as long as it can produce a transparent adhesive layer, and for example, OCA (Optical Clear Adhesive) can be used. Specifically, 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 to 100 μm. If the second resin layer is too thick, flexibility may be impaired. On the other hand, if the second resin layer is too thin, adhesion may not be ensured and it may peel off.

[0303] For example, an adhesive film can be used as the second resin layer. Alternatively, for example, an adhesive composition may be applied to the first or third resin layer to form the second resin layer.

[0304] 3.Third resin layer The third resin layer in this disclosure is a resin film containing a resin selected from the group consisting of polyester resins, polycycloolefin resins, acetylcellulose resins, polycarbonate resins, and polypropylene resins. The third resin layer is an impact-absorbing component and also functions as a component that suppresses the scattering of glass when the glass substrate breaks. The third resin layer is transparent and, when the optical laminate in this disclosure is placed on the observer side of the display panel of a display device, it is placed on the observer side of the glass substrate.

[0305] The third resin layer is transparent, 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 resins, polycycloolefin resins, acetylcellulose resins, polycarbonate resins, and polypropylene resins. The polyester resin is not particularly limited as long as it can produce a transparent resin film; examples include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT). The polycycloolefin resin is not particularly limited as long as it can produce a transparent resin film; examples include norbornene resins, monocyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and their hydrides. The acetylcellulose resin is not particularly limited as long as it can produce a transparent resin film; examples include triacetylcellulose (TAC). The polycarbonate resin is not particularly limited as long as it can produce a transparent resin film; examples include polycarbonate (PC). The polypropylene resin is not particularly limited as long as it can produce a transparent resin film; examples include polypropylene (PP).

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

[0308] The thickness of the third resin layer is preferably, for example, 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 thickness of the third resin layer is too thick, flexibility and bendability may be impaired. On the other hand, if the thickness of 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 bonded to the first resin layer via the second resin layer, which is an adhesive layer.

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

[0311] 5. Functional Layer The optical laminate in this disclosure may further have a functional layer on the side of the third resin layer opposite to the second resin layer. Examples of functional layers include a hard coat layer, an anti-reflective layer, an anti-glare layer, and the like.

[0312] Furthermore, the functional layer may be a single layer or may consist of multiple layers. Also, the functional layer may be a layer having a single function or may consist of multiple layers having different functions.

[0313] (1) Hard coat layer In this disclosure, the optical laminate preferably further has a hard coat layer 16 on the side of the third resin layer 15 opposite to the second resin layer 14, as shown in Figure 8, for example. The hard coat layer is a component for increasing surface hardness. The presence of the hard coat layer improves scratch resistance.

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

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

[0316] (1) Second hard coat layer The optical laminate in this disclosure may further have a second hard coat layer 17 between the first resin layer 13 and the second resin layer 14, as shown in Figure 9, for example. The second hard coat layer is a component for increasing surface hardness. The presence of the second hard coat layer improves impact resistance.

[0317] The second hard court layer can be the same as the hard court layer described above, so its explanation is omitted here.

[0318] (2) Fourth resin layer The optical laminate in this disclosure may have a fourth resin layer on the side of the glass substrate opposite to the first resin layer. When an impact is applied to the optical laminate, the impact is absorbed not only by the first, second, and third resin layers but also by the fourth resin layer, which can suppress cracking of the glass substrate and improve impact resistance.

[0319] The resin included in the fourth resin layer is not particularly limited as long as it is a resin that can absorb impact, and examples include urethane resin, epoxy resin, polyimide, polyamide-imide, acrylic resin, triacetylcellulose (TAC), etc. These resins may be used individually or in combination of two or more.

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

[0321] The thickness of the fourth resin layer can be any thickness that is sufficient to absorb impact, for example, preferably 5 μm to 60 μm, more preferably 10 μm to 50 μm, and even more preferably 15 μm to 40 μm.

[0322] The method for forming the fourth resin layer can be the same as the method for forming the first resin layer described above.

[0323] (3) Primer layer The optical laminate in this disclosure has a primer layer between the glass substrate and the first resin layer. It may also have the above first tree of the glass substrate. If the fourth resin layer is on the side opposite to the oil layer, a gap is formed between the glass substrate and the fourth resin layer. It may have a primer layer. The primer layer ensures that the glass substrate and the first resin layer are densely packed. This can improve adhesion and the bonding between the glass substrate and the fourth resin layer.

[0324] The primer layer can be the same as the primer layer in the display device component described above.

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

[0326] The decorative layer can be the same as the decorative layer in the display device component described above.

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

[0328] Furthermore, the resin layer located on the surface side of the first resin layer of the glass substrate refers to all layers containing resin that are located on the surface side of the first resin layer of the glass substrate. 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 in this disclosure can be the same as those of the display device component described above.

[0330] The optical laminate in this disclosure preferably has bending resistance. Specifically, it is preferable that no cracks or fractures occur in the optical laminate when the dynamic bending test described below is repeated 200,000 times.

[0331] In dynamic bending tests, the optical laminate may be folded so that the glass substrate faces outward, or so that the glass substrate faces inward. In either case, it is preferable that no cracks or fractures occur in the optical laminate.

[0332] The dynamic bending test can be conducted in the same manner as the dynamic bending test described in the section on display device components above.

[0333] In the case of an optical laminate, it is preferable that no cracks or fractures occur when a test is performed 200,000 times in which the optical laminate 1 is folded 180° so that the distance d between opposing short sides 1C and 1D is 10 mm. More preferably, no cracks or fractures occur when a test is performed 70,000 times in which the optical laminate 1 is folded 180° so that the distance d between opposing short sides 1C and 1D is 8 mm, even more preferably, no cracks or fractures occur when the test is performed 100,000 times, and particularly preferably, no cracks or fractures occur when the test is performed 200,000 times.

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

[0335] The static bending test can be performed in the same manner as the static bending test described in the section on display device components above.

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

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

[0338] The applications of the optical laminate in this disclosure can be the same as those of the display device components described above.

[0339] When the optical laminate in this disclosure is placed on the surface of a display device, the side facing the glass substrate is the front side. The display panel side and the third resin layer side are positioned so that they face outwards.

[0340] The method for arranging the optical laminate on the surface of the display device in this disclosure can be the same as that for the display device component described above.

[0341] B.Display device The display device in this disclosure comprises a display panel and the above-described display device component or the above-described optical laminate, which is positioned on the observer side of the display panel.

[0342] Figure 10 is a schematic cross-sectional view showing an example of a display device in this disclosure. As shown in Figure 10, the display device 30 comprises a display panel 31, a touch panel member 32, and a display device member 1 positioned on the observer 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 positioned on the surface of the display device 30, and an adhesive layer 34 is positioned between the display device member 1 and the touch panel member 32. An adhesive layer 33 is also positioned between the display panel 31 and the touch panel member 32.

[0343] Figure 11 is a schematic cross-sectional view showing another example of a display device in this disclosure. As shown in Figure 11, the display device 30 comprises a display panel 31 and an optical laminate 11 positioned on the observer side of the display panel 31. In the display device 30, the optical laminate 11 is used as a component positioned on the surface of the display device 30, and an adhesive layer 35 is positioned between the optical laminate 11 and the display panel 31.

[0344] The display device component in this disclosure may be the same as the display device component described above.

[0345] The optical laminate in this disclosure may be the same as the optical laminate described above.

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

[0347] The display device in this disclosure may have a touch panel member between the display panel and the display device component or optical laminate.

[0348] The display device in this disclosure is preferably a flexible display. In particular, the display device in this disclosure is preferably foldable. That is, the display device in this disclosure is more preferably a foldable display. Because the display device in this disclosure has the above-mentioned display device components, it has excellent bending resistance, or because it has the above-mentioned optical laminate, it has excellent impact resistance and flexibility, making it suitable as a flexible display and even more so as a foldable display.

[0349] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0350] The present disclosure will be further explained below with reference to examples and comparative examples.

[0351] [Example 1-1] (1) Formation of the primer layer A primer layer composition was prepared by blending each component to achieve the composition shown below. • Bisphenol A type solid epoxy resin (jER1256B40, manufactured by Mitsubishi Chemical Corporation) 28 parts by mass • Bisphenol A novolac type solid epoxy resin (jER157S65B80, manufactured by Mitsubishi Chemical Corporation) 5 parts by mass • 2-Ethyl-4-methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) 1 part by mass • Solvent (MEK) 11 parts by mass

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

[0353] (2) Formation of the resin layer Referring to Synthesis Example 1 in International Publication No. 2014 / 046180, a tetracarboxylic dianhydride represented by the following chemical formula was synthesized.

[0354] [ka]

[0355] In a 5 L separable flask, a solution containing dehydrated N,N-dimethylacetamide (DMAc) (1833.2 g) and 2,2'-bis(trifluoromethyl)benzidine (TFMB) (138.48 g) was added. The solution temperature was controlled to 30°C. Then, tetracarboxylic dianhydride (TMPBPTME) (176.70 g), represented by the above chemical formula, was gradually added so that the temperature rise would be less than 2°C, and the mixture was stirred with a mechanical stirrer for 30 minutes. Pyromellitic dianhydride (PMDA) (64.20 g) was then gradually added in several batches so that the temperature rise would be less than 2°C, synthesizing a polyimide precursor solution (solid content 18% by mass) in which the polyimide precursor was dissolved. The molar ratio (TMPBPTME:PMDA) of the tetracarboxylic dianhydrides TMPBPTME and 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, 2162g of the above polyimide precursor solution (at room temperature) was added to a 5L separable flask. Then, 432g of dehydrated N,N-dimethylacetamide was added and the mixture was stirred until homogeneous. Next, pyridine (6.622g) and acetic anhydride (213.67g), which serve as catalysts, were added and the mixture was stirred at room temperature for 24 hours to synthesize the polyimide solution.

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

[0358] A polyimide varnish (resin composition) containing 12% polyimide by mass was prepared by adding N,N-dimethylacetamide (DMAc) to polyimide so that the solid content concentration of polyimide was 12% by mass. The viscosity of the polyimide varnish (resin composition) (solid content concentration 12% by mass) at 25°C was 15,000 cps.

[0359] The above-mentioned polyimide varnish (resin composition) was applied to the above-mentioned 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 the hard coat layer A curable resin composition for a hard coat layer was prepared by blending each component to achieve the composition shown below. • Mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (M403, manufactured by Toagosei Co., Ltd.) 25 parts by mass • Dipentaerythritol EO-modified hexaacrylate (A-DPH-6E, manufactured by Shin-Nakamura Chemical Co., Ltd.) 25 parts by mass • Irregularly shaped silica microparticles (average particle size 25 nm, manufactured by JGC Catalysts & Chemicals Co., Ltd.) 50 parts by mass (solid equivalent) • Photopolymerization initiator (Irg184) 4 parts by mass • Fluorine-based leveling agent (F568, manufactured by DIC Corporation) 0.2 parts by mass (solids equivalent) • UV absorber 1 (DAINSORB P6, manufactured by Yamato Kasei) 3 parts by mass • Solvent (MIBK) 150 parts by mass

[0361] The above-mentioned curable resin composition for hard coat layer was applied to the above-mentioned 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] [Examples 1-2] A display device component was manufactured in the same manner as in Example 1-1, except that the resin layer was formed as shown below.

[0363] A 500 mL separable flask was purged with N2, and 293.29 g of dehydrated dimethylacetamide (DMAc) and 14.3 g (44.7 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) were dissolved in it. The solution was heated to a temperature of 30°C, and 24.8 g (40.1 mmol) of tetracarboxylic dianhydride (TMPBPTME), used in Example 1, was gradually added so that the temperature rise was less than 2°C. The mixture was stirred with a mechanical stirrer for 3 hours. Then, 0.91 g (4.5 mmol) of terephthalic acid dichloride (TPC) was added to the solution and stirred for another 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, which are catalysts, were added, and the mixture was stirred at 25°C for 30 minutes to confirm that the solution was homogeneous. The mixture was then heated to 70°C and stirred for 1 hour. Subsequently, 174.26 g of 2-propyl alcohol (IPA) was gradually added to the solution, which had been cooled to room temperature, to obtain a slightly turbid solution. 435.64 g of IPA was then added all at once to the turbid solution to obtain a white slurry. The slurry was filtered and washed five times with IPA, and then dried in an oven heated to 100°C under reduced pressure for 6 hours to obtain polyamide-imide powder (37.1 g). The weight-average molecular weight of the polyamide-imide, as measured by GPC, was 62,000.

[0364] A polyamide-imide varnish containing 19% by mass of polyamide-imide was prepared by adding DMAc to polyamide-imide so that the solid content concentration of polyamide-imide was 19% by mass. The viscosity of the polyamide-imide varnish (solid content concentration 19% by mass) at 25°C was 4000 mPa·s.

[0365] The above polyamide-imide 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.

[0366] [Examples 1-3] A display device component was manufactured in the same manner as in Example 1-1, except that the resin layer was formed as shown below.

[0367] In a 5 L separable flask, a solution containing dehydrated N,N-dimethylacetamide (DMAc) (1833.2 g) and 2,2'-bis(trifluoromethyl)benzidine (TFMB) (138.48 g) was added. The solution temperature was controlled to 30°C. Then, tetracarboxylic dianhydride (TMPBPTME) (256.026 g), represented by the above chemical formula, was gradually added, ensuring the temperature rise was 2°C or less. The mixture was stirred with a mechanical stirrer for 30 minutes. Pyromellitic dianhydride (PMDA) (4.7 g) was then gradually added in several batches, ensuring the temperature rise was 2°C or less, to synthesize a polyimide precursor solution (18% solid content) in which the polyimide precursor was dissolved. The molar ratio (TMPBPTME:PMDA) of the tetracarboxylic dianhydrides TMPBPTME and 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, 2162g of the above polyimide precursor solution (at room temperature) was added to a 5L separable flask. Then, 432g of dehydrated N,N-dimethylacetamide was added and the mixture was stirred until homogeneous. Next, pyridine (6.622g) and acetic anhydride (213.67g), which serve as catalysts, were added and the mixture was stirred at room temperature for 24 hours to synthesize the polyimide solution.

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

[0370] A polyimide varnish (resin composition) containing 12% polyimide by mass was prepared by adding N,N-dimethylacetamide (DMAc) to polyimide so that the solid content concentration of polyimide was 12% by mass. The viscosity of the polyimide varnish (resin composition) (solid content concentration 12% by mass) at 25°C was 15,000 cps.

[0371] The above 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.

[0372] [Comparative Example 1-1] A display device component was manufactured in the same manner as in Example 1-1, except that the resin layer was formed as shown below.

[0373] A composition containing a urethane-modified copolymer polyester resin (Byron 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 display device component was manufactured in the same manner as in Example 1-1, except that the resin layer was formed as shown below.

[0375] A composition containing epoxy resin (1256B40, manufactured by Mitsubishi Chemical Corporation) was applied to a predetermined thickness, 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 Examples 1-3] A display device component was manufactured in the same manner as in Example 1-1, except that the resin layer was formed as shown below.

[0377] 500g of dehydrated N,N-dimethylacetamide (boiling point: 165°C) was added to a container, and while flowing N2 into the container, the N,N-dimethylacetamide was heated to approximately 80°C while being stirred. The dissolved oxygen content of the N,N-dimethylacetamide was monitored continuously, and when the dissolved oxygen content 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 above-mentioned 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. Once the temperature of the solution containing the dissolved AprTMOS was controlled to 30°C, 1.23 g (3 mmol) of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was gradually added so that the temperature rise would be less than 2°C, and the mixture was stirred with a mechanical stirrer for 30 minutes. To this, 60.8 g (190 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) was added, and after confirming that it was completely dissolved, 91.6 g (206 mmol) of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was gradually added in several portions so that the temperature rise would not exceed 2°C, thereby synthesizing a polyimide precursor solution (25% solids by weight) in which the polyimide precursor was dissolved. The molar ratio of TFMB to AprTMOS used in the polyimide precursor was 95:5. The viscosity of the polyimide precursor solution (25% solids by weight) at 25°C was 48900 cps, and the weight-average molecular weight of the polyimide precursor, measured by GPC, was 156400.

[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 then added and stirred until homogeneous. Next, the catalyst pyridine and acetic anhydride were added and stirred at room temperature for 24 hours to synthesize the polyimide solution.

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

[0381] A polyimide varnish (resin composition) containing 12% by mass of polyimide was prepared by adding N,N-dimethylacetamide (DMAc) to polyimide so that the solid content concentration of polyimide was 12% by mass. The viscosity of the polyimide varnish (resin composition) (solid content concentration 12% by mass) at 25°C was 3000 cps.

[0382] The above-mentioned polyimide varnish (resin composition) was applied to the above-mentioned 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) Compound modulus The composite elastic modulus of the resin layer of the display device components in the examples and comparative examples was determined.

[0384] First, the indentation hardness of the resin layer was measured. Indentation hardness (H ITThe measurement of the ) was performed using a BRUKER "TI950 TriboIndenter" on the measurement sample. Specifically, first, a block was prepared by embedding a display device component cut to 1 mm x 10 mm in embedding resin, and from this block, uniform sections with a thickness of 50 nm to 100 nm, free of holes, etc., were cut using a general sectioning method. An "Ultramicrotome EM UC7" (Leica Microsystems) was used to prepare the sections. The remaining block from which these uniform sections free of holes, etc., had been cut was used as the measurement sample. Next, in the cross-section obtained by cutting the above section from the measurement sample, a Berkovich indenter (triangular pyramid, BRUKER TI-0039) was pressed vertically into the center of the resin layer cross-section for 10 seconds until a maximum indentation load of 25 μN was reached, under the following measurement conditions. In this process, 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 towards the center of the resin layer, 500 nm away from both ends of the resin layer towards the center of the resin layer, and also 500 nm away from the interface between the hard coat layer and the resin layer towards the center of the resin layer, in order to avoid the influence of the glass substrate and the side edges of the resin layer. After holding it for a certain period to allow residual stress to relax, the load was removed over 10 seconds, and the maximum load after relaxation was measured. max (μN) and contact projected area A p (nm 2 ) and P max / A p Therefore, indentation hardness (H IT The contact projected area was calculated using the Oliver-Pharr method with the indenter tip curvature corrected, using a standard sample of fused silica (BRUKER 5-0098). If any of the measured values ​​deviated by more than ±20% from the arithmetic mean, those values ​​were excluded and remeasured.

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

[0386] Next, the indentation hardness (H) of the obtained resin layer was measured. IT The above contact projected area A is required when measuring ) p The composite modulus was determined using the above formula (1). The composite modulus was calculated by measuring the indentation hardness at 10 locations, determining the composite modulus each time, and taking the arithmetic mean of the 10 obtained composite moduli.

[0387] (2) Impact test (pen drop test) Impact tests were conducted on the display device components of the examples and comparative examples. First, an optical adhesive (OCA) and PET were bonded in that order to the glass substrate surface of the display device component, and the display device component was placed on a 30 mm thick metal plate so that the PET side was in contact with the metal plate. Next, a pen was dropped onto the display device component from a test height with its tip facing downwards, and the highest test height at which no crack occurred in the glass substrate was evaluated. The results for the display device components of Examples 1-1 to 1-2 and Comparative Examples 1-1 to 1-3 are shown in Figure 12. The results when the resin layer thickness was 40 μm are shown in Table 1.

[0388] (3) Pencil hardness In the display device components of the examples and comparative examples, when the resin layer thickness was 20 μm, the pencil hardness on the hard coat layer side surface of the display device component was measured in accordance with JIS K5600-5-4 (1999). For the measurement of pencil hardness, a pencil hardness tester (product name "Pencil Scratch Coating Hardness Tester (Electric Type)", manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used, and the measurement conditions were: angle 45°, load 750g, speed 0.5 mm / sec to 1 mm / sec, and temperature 23±2℃.

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

[0390] (5) Flexural resistance In the display device components of the examples and comparative examples, when the resin layer thickness was 20 μm, dynamic bending tests and static bending tests were performed on the display device components to evaluate their bending resistance.

[0391] (5-1) Dynamic flexion test Dynamic bending tests were performed on the display device components of the examples and comparative examples to evaluate their bending resistance. Specifically, a 20mm x 100mm display device component was first fixed to a durability testing machine (product name "DLDMLH-FS", manufactured by Yuasa System Equipment Co., Ltd.) by fixing the short sides (20mm) of the display device component with fixing parts. As shown in Figure 5(c), the minimum distance d between the two opposing short sides was adjusted to 10mm, and a dynamic bending test was performed 200,000 times, folding the surface of the display device component 180°. In this test, the display device component was folded so that the hard coat layer side was on the inside and the glass substrate side was on the outside. Another display device component was then used to perform a dynamic bending test in the same manner as above, folding it so that the hard coat layer side was on the outside and the glass substrate side was on the inside. Then, 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 opens naturally, was measured. For the opening angle, the smaller angle was adopted between the case where the display device member is folded so that the hard coat layer side is inward and the case where the display device member is folded so that the hard coat layer side is outward.

[0392] (5-2) Static Flexion Test Static bending tests were performed on the display device components of the examples and comparative examples, and the opening angle after the static bending test was measured. Specifically, first, the short side (20 mm) of a 20 mm x 100 mm display device component was fixed to parallel fixing points such that the distance d between the opposing short sides of the display device component was 10 mm, and a static bending test was performed by leaving the display device component folded at 23°C for 240 hours. After the static bending test, the folding state was released by removing the fixing point from one of the short sides, and the opening angle (see Figure 6(b)), which is the angle at which the display device component naturally opens after 30 minutes at room temperature, was measured. For the opening angle, static bending tests were performed in both cases: when the display device component was folded so that the hard coat layer side was on the inside, and when the display device component was folded so that the hard coat layer side was on the outside, and the smaller angle was adopted.

[0393] [Table 1]

[0394] Table 1 and Figure 12 show that in Comparative Examples 1-1 to 1-3, the composite elastic modulus of the resin layer was below a predetermined value, so as the thickness of the resin layer increased, the surface hardness of the display device component decreased. In contrast, in Examples 1-1 to 1-3, the composite elastic modulus of the resin layer was above a predetermined value, so even when the thickness of the resin layer was 40 μm, for example, the surface hardness was high, indicating that it is possible to achieve both impact resistance and surface hardness. Furthermore, Table 1 and Figure 12 show that when the composite elastic modulus of the resin layer is above a predetermined value, the rate of increase in impact resistance with increasing thickness of the resin layer becomes larger. Also, in Table 1, a comparison between Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3 shows that when the composite elastic modulus of the resin layer is above a predetermined value, there is a tendency for bending resistance to improve. This is because the larger the composite elastic modulus of the resin layer, the greater the restorative 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 the primer layer A 1 μm thick primer layer was formed on the glass substrate in the same manner as in Example 1-1.

[0397] (2) Formation of the first resin layer A first resin layer with 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 with 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. This resulted in obtaining an optical laminate.

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

[0400] (2) Fabrication of optical stacks A chemically strengthened glass substrate with a thickness of 70 μm was prepared, and the glass substrate and the PET film side of the hard coat film were bonded together using a 50 μm thick acrylic adhesive film (manufactured by 3M, product name 8146-2). This resulted in obtaining an optical laminate.

[0401] [Examples 2-1 to 2-8] (1) Fabrication of glass resin laminate Except for setting the thickness of the first resin layer to 10 μm to 40 μm, a primer layer and a first resin layer were formed on a glass substrate in the same manner as in Comparative Example 2-1. This resulted in 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) Fabrication of optical stacks The first resin layer side of the glass-resin laminate and the PET film side of the hard coat film were bonded together using an acrylic adhesive film (3M, product name 8146-2) with a thickness of 10 μm to 50 μm. This created an optical laminate.

[0404] [Examples 2-9] (1) Fabrication of glass resin laminate Except for setting the thickness of the first resin layer to 23 μm, 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. This resulted in 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) Fabrication of optical stacks The side of the glass resin laminate facing the second hard coat layer and the side of the hard coat film facing the PET film were bonded together using a 50 μm thick acrylic adhesive film (manufactured by 3M, product name 8146-2). This created an optical laminate.

[0407] [Rating 2] (1) Compound modulus The composite elastic modulus of the first resin layer of the optical laminates in the examples and comparative examples was determined.

[0408] First, the indentation hardness of the first resin layer was measured. Indentation hardness (H IT The measurement of the optical laminate was performed using a BRUKER TI950 TriboIndenter on the measurement sample. Specifically, first, a block was prepared by embedding an optical laminate cut to 1 mm x 10 mm in embedding resin, and from this block, uniform sections with a thickness of 50 nm to 100 nm, free from holes, etc., were cut using a general sectioning method. An ultramicrotome EM UC7 (Leica Microsystems) was used to prepare the sections. The remaining block from which these uniform sections free from holes, etc., had been cut was used as the measurement sample. Next, in the cross-section obtained by cutting the above section from the measurement sample, a Berkovich indenter (triangular pyramid, BRUKER TI-0039) was pressed vertically into the center of the cross-section of the first resin layer for 10 seconds until a maximum indentation load of 25 μN was reached, under the following measurement conditions. In this process, 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 towards the center of the first resin layer, and 500 nm away from both ends of the first resin layer towards the center of the first resin layer, in order to avoid the influence of the glass substrate and the side edges of the first resin layer. After holding it in place for a certain period to allow residual stress to relax, the load was removed over 10 seconds, and the maximum load after relaxation was measured. max (μN) and contact projected area A p (nm 2 ) and P max / A p Therefore, indentation hardness (H IT The contact projected area was calculated using the Oliver-Pharr method with the indenter tip curvature corrected, using a standard sample of fused silica (BRUKER 5-0098). If any of the measured values ​​deviated by more than ±20% from the arithmetic mean, those values ​​were excluded and remeasured.

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

[0410] Next, the indentation hardness (H) of the obtained first resin layer was measured. IT The above contact projected area A is required when measuring ) p The composite modulus was determined using the above formula (1). The composite modulus was calculated by measuring the indentation hardness at 10 locations, determining the composite modulus each time, and taking the arithmetic mean of the 10 obtained composite moduli.

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

[0412] (3) Dynamic flexion test Dynamic bending tests were performed on the optical laminates of the examples and comparative examples to evaluate their bending resistance. Specifically, first, optical laminates measuring 20 mm x 100 mm were fixed to a durability testing machine (product name "DLDMLH-FS", manufactured by Yuasa System Equipment Co., Ltd.) by fixing the short sides (20 mm) of the optical laminates with fixing parts. As shown in Figure 5(c), the minimum distance d between the two opposing short sides was adjusted to 10 mm or 8 mm. A dynamic bending test was then performed 200,000 times or 70,000 times, in which the surface of the optical laminate was folded 180°. During this process, the optical laminate was folded so that the hard coat layer side was on the outside and the glass substrate side was on the inside. Then, under conditions of 25°C and 50% RH in a bright room at 2000 Lx, the laminates were visually inspected for cracks or fractures at the bends. The results of the dynamic bending tests were evaluated according to the following criteria. A: No cracks or fractures occurred in the bent section. B: Cracks or fractures were present in the bent section.

[0413] [Table 2]

[0414] In Comparative Example 2-1, the impact resistance was poor because the second and third resin layers were not present. Similarly, in Comparative Example 2-2, the impact resistance was poor because the first resin layer was not present. In contrast, in Examples 2-1 to 2-9, the predetermined first, second, and third resin layers were arranged in that order, resulting in excellent impact resistance. Furthermore, comparing Examples 2-1 to 2-7 with Example 2-8, when the total thickness of the resin layers was below a predetermined value, the bending resistance was also excellent. [Explanation of Symbols]

[0415] 1 ... Components for display devices 2… Glass substrate 3… Resin layer 4… Hard court layer 11 … Optical laminate 12… Glass substrate 13...First resin layer 14…Second resin layer 15...Third resin layer 16… Hard court layer

Claims

[Claim 1] A glass substrate with a thickness of 100 μm or less, A resin layer is disposed on one side of the glass substrate, having a composite elastic modulus of 5.7 GPa or more and a thickness of 5 μm or more and 60 μm or less. A component for a display device, having the following features.

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