WO2024071391A1

WO2024071391A1 - Laminate for display device, display device, and display device equipped with support plate

Info

Publication number: WO2024071391A1
Application number: PCT/JP2023/035677
Authority: WO
Inventors: 篤弘小林; 清弘高地; 和滋堀; 治渡邉
Original assignee: 大日本印刷株式会社
Priority date: 2022-09-29
Filing date: 2023-09-29
Publication date: 2024-04-04

Abstract

Provided is a laminate for a display device, the laminate having a resin substrate, a hard coat layer disposed on one surface of the resin substrate, and a resin layer disposed on the surface of the resin substrate on the reverse side thereof from the hard coat layer, the amount of cross-sectional indentation by an indenter in the resin layer being 200-3000 nm, the amount of cross-sectional indentation by an indenter in the resin substrate being smaller than the amount of cross-sectional indentation by an indenter in the resin layer, the thickness of the resin layer being 5-45 µm, and the total thickness of the resin substrate and the resin layer being 50-130 µm.

Description

Laminate for display device, display device, and display device with support plate

This disclosure relates to a laminate for a display device, a display device, and a display device with a support plate.

On the surface of the display device, a laminate for the display device having various properties such as hard coat properties, abrasion resistance, anti-reflection properties, anti-glare properties, anti-static properties, and anti-fouling properties is arranged as a front panel.

For example, Patent Document 1 discloses such a laminate for a display device, which has an impact absorbing layer, a support, and a functional layer, the thickness of the impact absorbing layer being 1 μm or more, and the maximum value of the ratio (tan δ) of the loss modulus to the storage modulus in the frequency range of 10 to 105 Hz at 25°C is 2.0 or less.

On the other hand, flexible display devices such as foldable displays, rollable displays, bendable displays, and slidable displays have been attracting attention in recent years, and laminates for display devices to be placed on the surface of flexible display devices have been actively developed. Among them, slidable displays, which allow the screen size to be expanded by sliding the display, have been attracting particular attention in recent years.

JP 2021-14014 A

　Laminates for display devices that are placed on the surface of flexible display devices are required to be scratch-resistant. For this reason, it is considered to use laminates for display devices that have a hard coat layer. Among flexible display devices, foldable displays are required to be able to display images without defects even when repeatedly bent, and laminates for display devices that are placed on the surface of flexible display devices are required to have bending resistance that prevents peeling or cracking when repeatedly bent.

In contrast, when a laminate for a display device having a hard coat layer is used in a slidable display or rollable display, the following problems may occur that are different from those in a foldable display.

FIG. 2(a) is a schematic front view of a smartphone with a slidable display, and FIGS. 2(b) and 2(c) are schematic cross-sectional views taken along line A-A of FIG. 2(a). The smartphone 20 shown in FIG. 2 has a caterpillar structure X for sliding the slidable display 21 stored inside the device and sending it out to the observer when the screen is expanded, and for sliding the slidable display 21 and storing it inside the device when the screen is reduced.

Figure 3 shows a partial enlarged view of the caterpillar structure X. Specifically, the slidable display 21 is arranged on a support plate S (e.g., made of SUS) and is capable of sliding. The support plate S has a linear through pattern P in the bending area with the longitudinal direction perpendicular to the screen expansion direction so that it can be easily bent. In the caterpillar structure X, the slidable display 21 is generally bent so that the display device laminate, which is the surface material, faces outward. In addition, because the support plate S has the through pattern P, there are locally high curvature steps. These step steps in the support plate affect the display device laminate, which is the surface material of the display device.

Therefore, when a display laminate having a hard coat layer is used as a surface material for a slidable display or rollable display, for example, as shown in Figures 4 and 5, cracks may occur in the hard coat layer at the bends (hereinafter sometimes referred to as slide bends or slide bends) in the caterpillar structure X of the display laminate, or lifting may occur in the adhesive layer between the display panel on which the display laminate is disposed and the support plate.

This disclosure was made in consideration of the above-mentioned circumstances, and its main objective is to provide a laminate for a display device that has excellent scratch resistance and suppresses defects in the sliding bending portion.

One embodiment of the present disclosure provides a laminate for a display device, comprising a resin substrate, a hard coat layer disposed on one side of the resin substrate, and a resin layer disposed on the side of the resin substrate opposite the hard coat layer, the resin layer having a cross-sectional indenter indentation amount of 200 nm or more and 3000 nm or less, the cross-sectional indenter indentation amount of the resin substrate being smaller than the cross-sectional indenter indentation amount of the resin layer, the resin layer having a thickness of 5 μm or more and 45 μm or less, and the total thickness of the resin substrate and the resin layer being 50 μm or more and 130 μm or less.

Another embodiment of the present disclosure provides a display device comprising a display panel and the above-described laminate for a display device arranged on the viewer side of the display panel, the laminate for a display device being arranged so that the hard coat layer side faces the viewer side.

Another embodiment of the present disclosure provides a display device with a support plate, comprising the above-mentioned display device and a support plate arranged on the surface of the display device facing the display panel, the display device being a flexible display, and the support plate having a through pattern penetrating in the thickness direction.

The present disclosure has the effect of providing a laminate for a display device that has excellent scratch resistance and suppresses defects in the slide bending portion.

1 is a schematic cross-sectional view illustrating a laminate for a display device according to the present disclosure. FIG. 2(a) is a schematic front view of a smartphone having a slidable display, and FIG. 2(b) and FIG. 2(c) are schematic cross-sectional views taken along line AA of FIG. 2(a). FIG. 2 is a partially enlarged view of the caterpillar structure. FIG. 1 is a schematic cross-sectional view showing an example of a conventional laminate for a display device. FIG. 1 is a schematic cross-sectional view showing an example of a conventional laminate for a display device. FIG. 1 is a schematic diagram for explaining a slide bending test. FIG. 2 is a schematic top view of a support plate used in a slide bending test. 1 is a schematic cross-sectional view illustrating a display device according to the present disclosure. 1 is a schematic cross-sectional view illustrating a display device according to the present disclosure. 1 is a schematic cross-sectional view illustrating an example of a support plate-attached display device according to the present disclosure.

Below, an embodiment of the present disclosure will be described with reference to the drawings. However, the present disclosure can be implemented in many different forms, and should not be interpreted as being limited to the description of the embodiment exemplified below. Furthermore, in order to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part in a schematic manner compared to the actual form, but these are merely examples and do not limit the interpretation of the present disclosure. Furthermore, in this specification and each figure, elements similar to those described above with reference to the previous figures are given the same reference numerals, and detailed explanations may be omitted as appropriate.

In this specification, when describing a mode in which another component is placed on a certain component, the term "above" or "below" is intended to include both cases in which another component is placed directly above or below a certain component so as to be in contact with the component, and cases in which another component is placed above or below a certain component with another component in between, unless otherwise specified. Also, in this specification, when describing a mode in which another component is placed on the surface of a certain component, the term "on the surface side" or "on the surface" is intended to include both cases in which another component is placed directly above or below a certain component so as to be in contact with the component, and cases in which another component is placed above or below a certain component with another component in between, unless otherwise specified.

The laminate for a display device and the display device in this disclosure are described in detail below.

A. Display laminate FIG. 1 is a schematic cross-sectional view showing an example of a display laminate in the present disclosure. The display laminate 10 shown in FIG. 1 has a resin substrate 1, a hard coat layer 2 arranged on one side of the resin substrate 1, and a resin layer 3 arranged on the side of the resin substrate 1 opposite to the hard coat layer 2. The cross-sectional indenter indentation amount of the resin layer 3 is 200 nm or more and 3000 nm or less, and the cross-sectional indenter indentation amount of the resin substrate 1 is smaller than the cross-sectional indenter indentation amount of the resin layer 3. Furthermore, the thickness of the resin layer 3 is 5 μm or more and 45 μm or less, and the total thickness of the resin substrate 1 and the resin layer 3 is 50 μm or more and 130 μm or less.

FIG. 4(a) is a schematic cross-sectional view showing an example of a conventional display laminate. The display laminate 50 shown in FIG. 4(a) has a resin substrate 51 and a hard coat layer 52. FIG. 4(b) is an explanatory diagram of a slide bending test performed on a test piece in which the display laminate 50 is bonded to a support plate S via an adhesive layer 53, simulating slide bending during use of a slidable display. As shown in FIG. 4(b), in this slide bending test, a problem occurs in which the adhesive layer 53 floats off the support plate S. This is presumably because the resin substrate 51 is too hard to follow the high curvature that exists locally on the support plate S. This problem also occurs during use of an actual slidable display, and the adhesive layer between the display panel and the support plate peels off from the display panel, etc.

FIG. 5(a) is a schematic cross-sectional view showing another example of a conventional laminate for a display device. The laminate for a display device 60 shown in FIG. 5(a) has a resin layer 61 and a hard coat layer 62. FIG. 5(b) is an explanatory diagram of a slide bending test simulating slide bending during use of a slidable display, performed on a test piece in which the laminate for a display device 60 is bonded to a support plate S via an adhesive layer 63. As shown in FIG. 5(b), cracks occur in the hard coat layer 62 during this slide bending test. It is presumed that this is because, although the resin layer 61 follows the steps of the support plate S, the hard coat layer 62 cannot follow the high curvature that exists locally on the support plate S, causing cracks. This problem also occurs during actual use of a slidable display, causing cracks in the hard coat layer.

In contrast, the laminate for a display device according to the present disclosure has a resin layer disposed on one side of the resin substrate that has a thickness equal to or greater than a predetermined value and also has a cross-sectional indenter depression amount equal to or greater than a predetermined value, and therefore functions as a step absorption layer. Therefore, the laminate for a display device can follow the steps of the support plate when slidably bent. As a result, when the laminate for a display device according to the present disclosure is disposed on the observer side of a display panel and used as a display device, peeling of the adhesive layer between the display panel disposed via an adhesive layer on the surface of the support plate that constitutes a caterpillar structure and the support plate can be suppressed in a screen expansion area such as a slidable display.

In addition, because a resin substrate harder than the resin layer is disposed, and the combined thickness of the resin substrate and the resin layer is equal to or greater than a predetermined value, it is possible to reduce the curvature of areas with locally high curvature caused by the support plates that make up the caterpillar structure when the screen is expanded, and it is possible to prevent locally high curvature from being applied to the hard coat layer. This makes it possible to suppress the occurrence of cracks in the hard coat layer.

Furthermore, the laminate for a display device of the present disclosure has a hard coat layer, the thickness of the resin layer is equal to or less than a predetermined value, and a resin substrate that is harder than the resin layer is present, so that the laminate has excellent scratch resistance.

The property of suppressing defects in the slide bending portion as described above is sometimes referred to as slide bending resistance.

The laminate for a display device of the present disclosure has a resin substrate, a hard coat layer disposed on one surface of the resin substrate, and a resin layer disposed on the surface of the resin substrate opposite to the hard coat layer. That is, the laminate for a display device of the present disclosure has the resin layer, the resin substrate, and the hard coat layer in this order in the stacking direction.
The display device laminate of the present disclosure will be described in detail below.

I. Resin Layer The resin layer used in the display device laminate of the present disclosure can absorb steps caused by the support plate constituting the caterpillar structure used in the screen expansion region of a slidable display, etc. This can suppress peeling between the support plate constituting the caterpillar structure and the display panel arranged on the surface of the support plate via an adhesive layer in the screen expansion region of a slidable display, etc.

1. Cross-sectional indenter indentation amount The cross-sectional indenter indentation amount of the resin layer in the present disclosure is 200 nm or more, preferably 250 nm or more, and more preferably 280 nm or more. By having the cross-sectional indenter indentation amount of the resin layer in the above range, step absorption performance can be obtained and lifting of the adhesive layer between the display panel and the support plate can be suppressed.

On the other hand, the cross-sectional indenter indentation amount of the resin layer is 3000 nm or less, preferably 2800 nm or less, and more preferably 2000 nm or less. By having the cross-sectional indenter indentation amount of the resin layer in the above range, it is possible to maintain the hardness of the hard coat surface, and high scratch resistance is obtained.

In the present disclosure, the cross-sectional indenter indentation amount of the resin layer is obtained by performing an indentation test in which a Berkovich indenter is pressed into the resin layer with a constant load, and measuring the displacement d at that time. Specifically, first, a block is produced by embedding a laminate for a display device cut to 1 mm x 10 mm in embedding resin, and then a uniform slice with a thickness of 70 nm to 100 nm without holes is cut out from this block using a general slice production method. An ultramicrotome EM UC7 from Leica Microsystems Inc. is used to produce the slices. The remaining block from which the uniform slice without holes is cut out is used as the measurement sample. Next, in the cross section obtained by cutting out the above-mentioned slice from such a measurement sample, a nanoindenter (TI950 TriboIndenter manufactured by Bruker) is used to vertically indent the center of the cross section of the resin layer with a maximum load of 200 μN for 40 seconds under the following measurement conditions using a Berkovich indenter (triangular pyramid, TI-0039 manufactured by Bruker), and the displacement (indentation depth) d at that time is measured. Here, in order to avoid the influence of the side edges of the resin layer, the Berkovich indenter is pressed into a portion 500 nm or more away from each of the two ends of the resin layer toward the center of the resin layer. The displacement d was the arithmetic average value of the values obtained by measuring at 10 points. Note that if the measured values include any that deviate from the arithmetic average value by ±20% or more, the measured values are excluded and remeasured. Whether or not there are any measured values that deviate from the arithmetic mean by ±20% or more is determined by whether the value (%) calculated by (A-B)/B x 100, where A is the measured value and B is the arithmetic mean, is ±20% or more.

(Measurement condition)
Control method: Load control (maximum load 200 μN)
Lift amount: 0 nm
Preload: 0.5 μN
Loading speed: 5 μN/sec. Maximum load holding time: 10 sec. Unloading speed: 5 μN/sec. Temperature: 23° C.
Relative humidity: 50%

2. Total Light Transmittance The resin layer used in the present disclosure preferably has a total light transmittance of, for example, 80% or more, more preferably 85% or more, and even more preferably 88% or more. Such a high total light transmittance allows a laminate for a display device to have good transparency.

The total light transmittance of the resin layer can be measured in accordance with JIS K7361-1, for example, using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

3. Thickness The thickness of the resin layer in the present disclosure is 5 μm or more, and preferably 10 μm or more. By having the thickness in the above range, a step absorption performance can be obtained.

On the other hand, from the viewpoint of the ease of storage within a display device such as a slidable display or rollable display, it is preferable that the thickness of the resin layer is thin. Specifically, it is 45 μm or less, and may be 35 μm or less, 30 μm or less, or 25 μm or less. By having a thickness within the above range, good storage within the display device can be obtained, and the hardness of the hard coat layer surface can be maintained, so that scratch resistance can be maintained.

4. Material of the resin layer The material of the resin layer in the present disclosure is not particularly limited as long as the cross-sectional indenter pressing amount of the resin layer falls within the above-mentioned range and is transparent, and examples thereof include urethane-based resins, acrylic gels, silicone gels, etc. In the present disclosure, urethane-based resins are preferred, and ionizing radiation curable urethane-based resins and thermoplastic polyurethanes (TPUs) are particularly preferred. The urethane-based resin is a resin having a urethane bond.

Thermoplastic polyurethane is a polyurethane that exhibits plasticity when heated, and generally refers to a polyurethane that has a linear structure with a certain degree of high molecular weight. Thermoplastic polyurethane can be obtained, for example, by copolymerization of polyisocyanate, polymeric polyol, and chain extender. The polyisocyanate is, for example, an aliphatic, alicyclic, or aromatic diisocyanate, with aromatic diisocyanate being preferred.

The polymer polyol is preferably a polyether polyol or polyester polyol having a molecular weight of 500 or more and 8000 or less, more preferably 600 or more and 4000 or less. Examples of polyether polyols include polyoxyethylene glycol, polyoxypropylene glycol, polyoxyethyleneoxypropylene glycol, polyoxytetramethylene glycol, and polyoxyhexamethylene glycol. Among these, polyoxytetramethylene glycol is preferred. The polyester polyol is preferably an aliphatic polyester polyol derived from an aliphatic dicarboxylic acid and an aliphatic diol.

The ionizing radiation curable urethane resin is a cured product of an ionizing radiation curable urethane resin composition, and preferably a cured product of an ultraviolet ray curable urethane resin composition. The ionizing radiation curable urethane resin composition contains a urethane (meth)acrylate. The urethane (meth)acrylate may be any of a monomer, an oligomer, and a prepolymer. The number of (meth)acryloyl groups (functionality) in the urethane (meth)acrylate is preferably 2 or more and 4 or less. The term "(meth)acryloyl group" includes both "acryloyl group" and "methacryloyl group". The weight average molecular weight of the urethane (meth)acrylate is preferably 1500 or more and 20000 or less. The ionizing radiation curable urethane resin composition may contain a (meth)acrylate compound. Examples of the (meth)acrylate compound include a monofunctional (meth)acrylate compound and a polyfunctional (meth)acrylate compound. The ionizing radiation curable urethane resin composition may contain, for example, one or both of a monofunctional (meth)acrylate compound and a polyfunctional (meth)acrylate compound. By adjusting the type and amount of the (meth)acrylate compound, particularly the polyfunctional (meth)acrylate compound, it is possible to adjust the cross-sectional indenter pressing depth of the resin layer.

A variety of acrylic gels can be used as long as they are polymers made by polymerizing monomers containing acrylic esters, which are used in adhesives, etc. Specifically, examples of acrylic gels that can be used include those obtained by polymerizing or copolymerizing acrylic monomers such as ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, n-amyl (meth)acrylate, i-amyl (meth)acrylate, octyl (meth)acrylate, i-octyl (meth)acrylate, i-myristyl (meth)acrylate, lauryl (meth)acrylate, nonyl (meth)acrylate, i-nonyl (meth)acrylate, i-decyl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, and i-stearyl (meth)acrylate. In this specification, "(meth)acrylate" means both "acrylate" and "methacrylate". The acrylic acid ester used in the (co)polymerization may be used alone or in combination of two or more kinds.

　Silicone gel means a solid state obtained by gelling silicone oil. Two-liquid addition reaction type silicone gel is preferably used, especially from the viewpoint of not generating reaction by-products (outgassing). Two-liquid addition reaction type silicone gel is obtained by hydrosilylation reaction of a silicone polymer (base) having a vinyl group with a silicone polymer (curing agent) having a hydroxyl group in the presence of a platinum catalyst. As the raw material of two-liquid addition reaction type silicone, various conventionally known silicon compounds can be appropriately selected and used, and silicon compounds commercially available as various silicone materials may also be used. In addition, the substituent of the silicon atom is not particularly limited, and examples thereof include alkyl groups having 1 to 10 carbon atoms such as methyl groups, ethyl groups, and propyl groups, cycloalkyl groups having 5 to 10 carbon atoms such as cyclopentyl groups and cyclohexyl groups, alkenyl groups having 2 to 10 carbon atoms such as vinyl groups and allyl groups, aryl groups having 5 to 20 carbon atoms such as phenyl groups and tolyl groups, and those in which some of the hydrogen atoms of these substituents have been replaced with other atoms or substituents.

Specific examples of two-liquid reaction heat addition silicone gels include CF-5106 (product name: manufactured by Dow Corning Toray Co., Ltd.), KE-1012A/B (product name: manufactured by Shin-Etsu Silicones Co., Ltd.), and XE14-685(A)/(B) (product name: manufactured by Momentive Corporation). These silicone gels are made from silicone resin, which is the raw material, separated into liquid A and liquid B, and can be used by mixing the two liquids in a specified ratio.

The resin layer may contain ultraviolet absorbers, spectral transmittance adjusters, antifouling agents, inorganic particles and/or organic particles, etc., as long as the cross-sectional indenter pressing amount of the resin layer falls within the above-mentioned range and a transparent resin layer can be obtained.

5. Method for forming a resin layer In the present disclosure, the method for forming a resin layer may be, for example, a method for applying a resin composition to one side of a resin substrate, optionally via a primer layer. The application method is not particularly limited as long as it can be applied to a desired thickness, and may be, for example, a general application method such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, or screen printing.

The resin layer can be formed by a transfer method in which a resin layer is transferred to one side of a resin substrate, or by a method in which a film-like resin layer is attached to one side of a resin substrate via a primer layer.

II. Resin substrate The resin substrate in the present disclosure is disposed between the resin layer and the hard coat layer, has a predetermined film thickness together with the resin layer, and is formed of a material harder than the resin layer. Therefore, it is possible to reduce the curvature of the area with high curvature locally caused by the support plate constituting the caterpillar structure used in the screen expansion area of a slideable display, etc., and to prevent the hard coat layer from being locally subjected to high curvature. This makes it possible to suppress the occurrence of cracks in the hard coat layer.

1. Cross-sectional indenter indentation amount The cross-sectional indenter indentation amount of the resin substrate in the present disclosure is smaller than the cross-sectional indenter indentation amount of the resin layer described above. By making the cross-sectional indenter indentation amount of the resin substrate smaller than the cross-sectional indenter indentation amount of the upper resin layer, it is possible to suppress the occurrence of cracks in the hard coat layer. The cross-sectional indenter indentation amount of the resin substrate is, for example, less than 200 nm, preferably 180 nm or less. The method for measuring the cross-sectional indenter indentation amount of the resin substrate is the same as the method described in "I. Resin layer" above.

2. Young's modulus The Young's modulus of the resin substrate in the present disclosure is preferably 2 GPa or more, more preferably 4 GPa or more, particularly preferably 5 GPa or more. This is because it is possible to reduce the curvature of the area with high curvature locally, and prevent the hard coat layer from being locally subjected to high curvature. Note that the resin substrate used is one with a Young's modulus of 12 GPa or less.

In this disclosure, the Young's modulus of the resin substrate is measured by the following tensile test method. In the tensile test, a sample is obtained by first cutting out a single-layered resin substrate layer measuring 0.5 cm x 7 cm from the resin substrate. Then, both ends of the cut sample are fixed to a chucking jig attached to a Tensilon universal testing machine (product name "RTC-1310A", manufactured by Orientec Co., Ltd.) so that the longitudinal direction of the cut sample is the tensile direction. Then, a tensile test is performed by pulling the sample at 25°C and a tensile speed of 10 mm/min using the Tensilon universal testing machine. In the stress-strain curve obtained from the tensile test of the resin substrate layer, the Young's modulus is calculated by determining the slope of the line connecting the stress when the strain is 0.05% and the stress when the strain is 0.25% in accordance with JIS K7161-4. The Young's modulus is the arithmetic average value obtained from three measurements.

3. Thickness of Resin Substrate The thickness of the resin substrate is not particularly limited as long as the total thickness of the resin substrate and the resin layer falls within the range described below, but may be, for example, 20 μm or more, 30 μm or more, or 65 μm or more. On the other hand, it may be, for example, 125 μm or less, 100 μm or less, or 80 μm or less.

4. Materials for Resin Substrate The resin constituting the resin substrate used in the present disclosure is not particularly limited as long as the cross-sectional indenter indentation amount of the resin substrate is the above-mentioned cross-sectional indenter indentation amount and a resin substrate having transparency can be obtained, and examples thereof include polyester-based resins, polyimide-based resins, cellulose-based resins, etc.

In this disclosure, polyimide resin refers to a polymer having an imide bond in the main chain. Examples of polyimide resins include polyimide, polyamideimide, polyesterimide, polyetherimide, etc. Examples of polyester resins include polyethylene terephthalate (PET), polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PEN), etc. Examples of cellulose resins include triacetyl cellulose (TAC), etc. Among these, polyester resins are preferred. These resins may be used alone or in combination of two or more. Among these, polyimide resins, PET, TAC, etc. are preferably used in this disclosure.

The resin substrate may further contain additives as necessary. Examples of additives include ultraviolet absorbers, light stabilizers, antioxidants, inorganic particles, silica fillers for smooth winding, surfactants for improving film-forming and defoaming properties, and adhesion improvers.

III. Hard Coat Layer The laminate for a display device in the present disclosure has a hard coat layer on the surface of the resin substrate opposite to the resin layer. The hard coat layer is a member for increasing the surface hardness. By disposing the hard coat layer, it is possible to improve scratch resistance.

The hard coat layer in this disclosure may be a single layer or may have a multi-layer structure of two or more layers.

1. Pencil Hardness Here, the term "hard coat layer" refers to a member for increasing surface hardness, and specifically refers to a layer having a hard coat layer in a configuration in which the laminate for a display device in the present disclosure has a hard coat layer, and exhibits a hardness of "H" or more when a pencil hardness test specified in JIS K 5600-5-4 (1999) is carried out.

The pencil hardness of the surface of the hard coat layer side of the laminate for a display device according to the present disclosure is preferably H or more, more preferably 2H or more, and even more preferably 3H or more.

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

2. Thickness The thickness of the hard coat layer may be appropriately selected according to the material of the hard coat layer, the function of the hard coat layer, and the use of the laminate for display device. For example, when the material of the hard coat layer is an organic material, the thickness of the hard coat layer is preferably 5 μm or more, and may be 10 μm or more. If the thickness of the hard coat layer is the above value or more, scratch resistance can be reliably obtained. On the other hand, the thickness of the hard coat layer is, for example, 20 μm or less.

In addition, for example, 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 nm.

3. Materials for the Hard Coat Layer As the material for the hard coat layer, for example, an organic material, an inorganic material, or an organic-inorganic composite material can be used.

Among these, the material of the hard coat layer is preferably an organic material. Specifically, the hard coat layer preferably contains a cured product of a resin composition containing a polymerizable compound. The cured product of a resin composition containing a polymerizable compound can be obtained by subjecting the polymerizable compound to a polymerization reaction by a known method, using a polymerization initiator as necessary.

(1) Polymerizable Compound The polymerizable compound has at least one polymerizable functional group in the molecule. As the polymerizable compound, for example, at least one of a radical polymerizable compound and a cationic polymerizable compound can be used.

A radically polymerizable compound is a compound that has a radically polymerizable group. The radically polymerizable group of a radically polymerizable compound is not particularly limited as long as it is a functional group that can cause a radical polymerization reaction, but examples include groups that contain a carbon-carbon unsaturated double bond, and specific examples include a vinyl group and a (meth)acryloyl group. Note that when a radically polymerizable compound has two or more radically polymerizable groups, these radically polymerizable groups may be the same or different.

The number of radically polymerizable groups that the radically polymerizable compound has in one molecule is preferably 2 or more, and more preferably 3 or more, in order to improve the hardness of the hard coat layer.

As the radical polymerizable compound, from the viewpoint of high reactivity, a compound having a (meth)acryloyl group is preferable. For example, polyfunctional (meth)acrylate monomers and oligomers having several (meth)acryloyl groups in the molecule and a molecular weight of several hundred to several thousand, such as urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, silicone (meth)acrylate, etc., can be preferably used. In addition, polyfunctional (meth)acrylate polymers having two or more (meth)acryloyl groups in the side chain of the acrylate polymer can also be preferably used. Among them, polyfunctional (meth)acrylate monomers having two or more (meth)acryloyl groups in one molecule can be preferably used. By including a cured product of a polyfunctional (meth)acrylate monomer in the hard coat layer, the hardness of the hard coat layer can be improved and the adhesion can be further improved. Also preferably used are polyfunctional (meth)acrylate oligomers or polymers having two or more (meth)acryloyl groups in one molecule. By including a cured product of a polyfunctional (meth)acrylate oligomer or polymer in the hard coat layer, the hardness and bending resistance of the hard coat layer can be improved, and the adhesion can be further improved.

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

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

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

A cationic polymerizable compound is a compound that has a cationic polymerizable group. The cationic polymerizable group of a cationic polymerizable compound is not particularly limited as long as it is a functional group that can cause a cationic polymerization reaction, and examples of the cationic polymerizable group include an epoxy group, an oxetanyl group, and a vinyl ether group. When a cationic polymerizable compound has two or more cationic polymerizable groups, these cationic polymerizable groups may be the same or different.

The number of cationic polymerizable groups that the cationic polymerizable compound has in one molecule is preferably 2 or more, and more preferably 3 or more, in order to improve the hardness of the hard coat layer.

Among the cationic polymerizable compounds, compounds having at least one of epoxy and oxetanyl groups as cationic polymerizable groups are preferred, and compounds having at least two of epoxy and oxetanyl groups in one molecule are more preferred. Cyclic ether groups such as epoxy and oxetanyl groups are preferred because they cause little shrinkage during polymerization. Among cyclic ether groups, compounds having epoxy groups have the advantages of being readily available in a variety of structures, not adversely affecting the durability of the resulting hard coat layer, and being easy to control compatibility with radically polymerizable compounds. Among cyclic ether groups, oxetanyl groups have the advantages of having a higher degree of polymerization and lower toxicity than epoxy groups, and of accelerating the network formation rate obtained from the cationic polymerizable compound in the coating film when the resulting hard coat layer is combined with a compound having an epoxy group, and forming an independent network without leaving unreacted monomers in the film even in areas where the radically polymerizable compound is mixed.

Cationically polymerizable compounds having epoxy groups include, for example, 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)acrylate; glycidyl ethers produced by reacting bisphenols such as bisphenol A, bisphenol F, and hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts or caprolactone adducts, with epichlorohydrin, and novolac epoxy resins, etc., which are glycidyl ether-type epoxy resins derived from bisphenols.

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

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

(2) Polymerization initiator The resin composition may contain a polymerization initiator as necessary. As the polymerization initiator, a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, etc. may be appropriately selected and used. These polymerization initiators are decomposed by at least one of light irradiation and heating to generate radicals or cations, and cause radical polymerization and cationic polymerization to proceed. Note that there are cases where the polymerization initiator is completely decomposed and does not remain in the hard coat layer.

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

(3) Particles The hard coat layer preferably contains inorganic or organic particles, and more preferably inorganic fine particles. When the hard coat layer contains particles, the hardness can be improved.

Examples of inorganic particles include metal oxide particles such as silica (SiO ₂ ), aluminum oxide, zirconia, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide, metal fluoride particles such as magnesium fluoride and sodium fluoride, metal particles, metal sulfide particles, and metal nitride particles. Among these, metal oxide particles are preferred, and at least one selected from silica particles and aluminum oxide particles is more preferred, with silica particles being even more preferred, because excellent hardness can be obtained.

The inorganic particles are preferably reactive inorganic particles having photoreactive reactive functional groups on at least a portion of the particle surface that undergo a crosslinking reaction between the inorganic particles themselves or between the inorganic particles and at least one type of polymerizable compound to form a covalent bond. The hardness of the hard coat layer can be further improved by crosslinking between the reactive inorganic particles themselves or between the reactive inorganic particles and at least one type of radically polymerizable compound and cationic polymerizable compound.

Reactive inorganic particles have at least a portion of their surface coated with an organic component, and have reactive functional groups on the surface introduced by the organic component. As the reactive functional group, for example, a polymerizable unsaturated group is preferably used, and a photocurable unsaturated group is more preferably used. As the reactive functional group, for example, ethylenically unsaturated bonds such as (meth)acryloyl groups, vinyl groups, and allyl groups, and epoxy groups can be mentioned.

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

The silica particles may be spherical silica particles, but are preferably irregular silica particles. Spherical silica particles and irregular silica particles may be mixed. In this specification, irregular silica particles refer to silica particles having random potato-like irregularities on the surface. Since irregular silica particles have a larger surface area than spherical silica particles, the inclusion of such irregular silica particles increases the contact area with the resin components, etc., and the hardness of the hard coat layer can be improved.

Whether or not the particles are atypical silica particles can be confirmed by observing the cross section of the hard coat layer using an electron microscope.

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

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

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

(4) Additives The hard coat layer used in the present disclosure may contain an ultraviolet absorbing agent. It is possible to suppress the deterioration of the resin layer due to ultraviolet rays. In particular, when the resin layer contains polyimide, it is possible to suppress the color change over time of the resin layer containing polyimide. In addition, in a display device including the laminate for a display device, it is possible to suppress the deterioration of a member arranged on the display panel side of the laminate for a display device, such as a polarizer, due to ultraviolet rays.

The hard coat layer in this disclosure may also contain an antifouling agent. This can impart antifouling properties to the laminate for display devices.

Furthermore, the hard coat layer in the present disclosure may further contain different additives as necessary. The additives are appropriately selected depending on the function to be imparted to the hard coat layer, and are not particularly limited. Examples of the additives include inorganic or organic particles for adjusting the refractive index, infrared absorbing agents, anti-glare agents, antifouling agents, antistatic agents, colorants such as blue and purple dyes, leveling agents, surfactants, lubricants, various sensitizers, flame retardants, adhesion promoters, polymerization inhibitors, antioxidants, light stabilizers, surface modifiers, spectral transmittance adjusters, etc.

4. Method for forming a hard coat layer The method for forming a hard coat layer is appropriately selected depending on the material of the hard coat layer, and examples thereof include a method of applying a curable resin composition for a hard coat layer containing the polymerizable compound on the resin substrate and curing the composition, a vapor deposition method, a sputtering method, and the like.

The method for applying the curable resin composition for the hard coat layer onto the resin substrate is not particularly limited as long as it is a method that allows application to the desired thickness, and 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. A transfer method can also be used to form a coating film of the resin composition for the hard coat layer.

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

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

For light irradiation, ultraviolet light, visible light, electron beams, ionizing radiation, etc. are mainly used. In the case of ultraviolet curing, for example, ultraviolet light emitted from light rays of an ultra-high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a xenon arc, a metal halide lamp, etc. can be used. The irradiation amount of the energy ray source can be, for example, about 50 mJ/ ^cm2 or more and 5000 mJ/ ^cm2 or less as an integrated exposure amount at an ultraviolet wavelength of 365 nm.

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

IV. Other Layers The laminate for a display device of the present disclosure essentially comprises the above-mentioned resin layer, resin substrate, and hard coat layer, but may also have other layers described below.

1. Adhesive layer for attachment The laminate for a display device of the present disclosure may have an adhesive layer for attachment on the surface of the resin layer opposite to the resin substrate. The laminate for a display device may be attached to, for example, a display panel or the like via the adhesive layer for attachment.

The adhesive used in the attachment adhesive layer is not particularly limited as long as it is transparent and capable of adhering the display device laminate to a display panel or the like, and examples thereof include heat-curing adhesives, ultraviolet-curing adhesives, two-component curing adhesives, hot-melt adhesives, and pressure-sensitive adhesives (so-called pressure-sensitive adhesives). Of these, it is preferable that the attachment adhesive layer contains a pressure-sensitive adhesive, that is, it is preferable that the attachment adhesive layer is a pressure-sensitive adhesive layer. Examples of pressure-sensitive adhesives used in the pressure-sensitive adhesive layer include acrylic adhesives, silicone adhesives, rubber adhesives, and urethane adhesives, and can be appropriately selected depending on the material of the impact absorbing layer. Of these, acrylic adhesives are preferable because they have excellent transparency, weather resistance, durability, and heat resistance, and are low cost.

The thickness of the attachment adhesive layer is, for example, preferably 10 μm to 100 μm, more preferably 15 μm to 60 μm, and even more preferably 25 μm to 50 μm. If the attachment adhesive layer is too thin, it may not be possible to sufficiently bond the display device laminate to the display panel, etc. Furthermore, if the attachment adhesive layer is too thick, flexibility may be impaired.

As the attachment adhesive layer, for example, an adhesive film may be used. Also, for example, an adhesive composition may be applied onto a support or a polyimide substrate to form the attachment adhesive layer. The laminate for a display device of the present disclosure may have a peelable separator layer on the surface opposite to the resin layer of the attachment adhesive layer.

2. Antifouling layer The laminate for a display device of the present disclosure may have an antifouling layer on the side of the hard coat layer opposite to the resin substrate. By disposing the antifouling layer, it is possible to impart antifouling properties to the laminate for a display device. As the material for the antifouling layer, a general material for an antifouling layer may be applied.

The thickness of the antifouling layer is, for example, preferably 1 nm or more and 30 nm or less, more preferably 2 nm or more and 20 nm or less, and even more preferably 3 nm or more and 10 nm or less. If the thickness of the antifouling layer is within the above range, it is possible to improve the antifouling properties and durability.

The method for forming the antifouling layer is appropriately selected depending on the material of the antifouling layer, and examples include a method in which a resin composition for the antifouling layer is applied onto the hard coat layer and cured, a vacuum deposition method, a sputtering method, etc.

3. Primer layer The display laminate of the present disclosure may have a primer layer between the resin substrate and the resin layer. The primer layer can improve the adhesion between the resin substrate and the resin layer. For the same reason, a primer layer may be provided between the resin substrate and the hard coat layer.

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

The thickness of the primer layer may be any thickness that can increase the adhesion between the resin substrate and the resin layer or between the resin substrate and the hard coat layer, and may be, for example, from 0.1 μm to 10 μm, and preferably from 0.2 μm to 5 μm.

The method of forming the primer layer can be, for example, a method of applying a primer layer composition onto a resin substrate. Examples of the application method include general application methods such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, and screen printing. A transfer method can also be used to form the primer layer.

4. Antireflection Layer The laminate for a display device of the present disclosure may have an antireflection layer on the side of the hard coat layer opposite to the resin substrate. By disposing the antireflection layer, it is possible to suppress reflection of external light and improve visibility.

The material constituting the anti-reflection layer preferably has a certain degree of light transparency and a certain degree of flexibility. Specific examples include materials that can be used for general anti-reflection layers, so a description of these will be omitted here.

V. Others The laminate for a display device of the present disclosure further has the following characteristics.

1. Total thickness of resin substrate and resin layer The laminate for a display device of the present disclosure has a total thickness of the resin substrate and resin layer of 50 μm or more, preferably 70 μm or more. By having the total thickness in the above range, it is possible to prevent the hard coat layer from having a high curvature locally at the sliding bending portion, and therefore it is possible to suppress the occurrence of cracks in the hard coat layer.
On the other hand, the total thickness is 130 μm or less, preferably 120 μm or less. By having the total thickness in the above range, the repulsive force in the bending direction can be suppressed, the step of the support plate can be followed, and the lifting of the adhesive layer can be suppressed. In addition, the stretching of the hard coat layer arranged on the outermost periphery can be suppressed in the sliding bending part, and the occurrence of cracks can be reliably suppressed.

2. Slide bending resistance The laminate for a display device of the present disclosure preferably has the slide bending resistance as described above. Specifically, the slide bending resistance of the laminate for a display device can be evaluated by carrying out a slide bending test described below. The slide bending test is carried out as follows.

[Slide bending test]
FIG. 6 is a schematic diagram for explaining the slide bending test. First, a display laminate having a size of 20 mm×100 mm is prepared. As shown in FIG. 6(a), the prepared display laminate 10 is attached to a test support plate 31 via a test adhesive layer 32 to obtain a test piece 30. Here, a schematic top view of the test support plate 31 is shown in FIG. 7(a). As shown in FIG. 7, the test support plate is a SUS304 plate having a thickness of 150 μm, on which a through pattern is formed by etching. The numerical values in FIG. 7 indicate the length (mm). FIG. 7(b) is a partial enlarged view of one block in FIG. 7(a), and FIG. 7(c) is a partial enlarged view of FIG. 7(b). The test adhesive layer 32 is specifically 3M Adhesive 8146-1 (the thickness of the adhesive layer after peeling off the separator is 25 μm).

Next, as shown in FIG. 6(b), the test piece 30 is bent so that the test support plate 31 faces inward, and one end of the test piece 30 is opposed to the other end in the longitudinal direction. In this state, the test piece 30 is set in a slide tester (Yuasa Corp. DMLHB-FU). Next, with the one end fixed, the other end is slid with a slide length (stroke length) of 35 mm, a slide speed of 30 rpm, and a slide diameter d of 8.0 mm (radius 4.0 mm), and is repeatedly moved back and forth.

The laminate disclosed herein preferably does not experience lifting of the adhesive layer or cracks in the hard coat layer when subjected to 200,000 reciprocating motions in the above-mentioned slide bending test.

Furthermore, when the slide diameter d is changed to 7 mm (radius 3.5 mm) in the above-mentioned slide bending test and the slide is repeatedly moved back and forth 200,000 times, it is more preferable that no lifting of the adhesive layer or cracks occur in the hard coat layer.

In particular, when the slide diameter d is changed to 6 mm (radius 3.0 mm) in the above-mentioned slide bending test and the slide is repeatedly moved back and forth 200,000 times, it is preferable that no lifting of the adhesive layer or cracks occur in the hard coat layer.

3. Thickness The thickness of the laminate for a display device of the present disclosure is, for example, preferably 55 μm or more and 150 μm or less, more preferably 70 μm or more and 140 μm or less, and even more preferably 85 μm or more and 130 μm or less. If the thickness of the laminate for a display device is in the above range, flexibility can be increased, and further, it becomes easy to accommodate it in a display device such as a slideable display.

4. Total Light Transmittance and Haze The laminate for a display device according to the present disclosure preferably has a total light transmittance of, for example, 80% or more, more preferably 85% or more, and even more preferably 88% or more. Such a high total light transmittance allows the laminate for a display device to have good transparency.

The total light transmittance of the laminate for display devices can be measured in accordance with JIS K7361-1, for example, using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

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

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

VI. Uses The laminate for a display device according to the present disclosure is a member disposed on the viewer side of the display panel in a display device.
When the laminate for a display device according to the present disclosure is disposed on the surface of a display device, it is preferably disposed so that the surface on the resin layer side is on the display panel side and the surface on the hard coat layer side is on the outside.

The method for disposing the display device laminate of the present disclosure on the surface of the display device is not particularly limited, and examples include a method using an adhesive layer. An example of the adhesive layer is an adhesive layer for attaching the display device laminate.

The laminate for display devices in the present disclosure can be used in display devices used in electronic devices such as smartphones, tablet terminals, wearable terminals, personal computers, televisions, digital signage, public information displays (PIDs), and in-vehicle displays. In particular, the laminate for display devices in the present disclosure can be used in flexible displays, and is preferably used in slidable displays and rollable displays, and is more preferably used in slidable displays.

B. Display Device A display device in the present disclosure includes a display panel and the above-described laminate for a display device, which is disposed on the viewer's side of the display panel.

FIG. 8 is a schematic cross-sectional view showing an example of a display device according to the present disclosure. As shown in FIG. 8, the display device 40 includes a display panel 41 and a laminate 10 for a display device arranged on the viewer's side of the display panel 41. In the display device 40, the laminate 10 for a display device and the display panel 41 can be bonded together, for example, via an attachment adhesive layer 42. In the display device 40, the surface of the hard coat layer 2 of the laminate 10 for a display device constitutes the surface 40A of the display device 40.

Although not shown here, as explained in the section "A. Laminate for display device", the display panel 41 is adhered by an adhesive layer to a support plate having a linear through pattern with its longitudinal direction perpendicular to the screen expansion direction in the area that will become the bent portion.

FIG. 9 is a schematic cross-sectional view showing another example of a display device according to the present disclosure. As shown in FIG. 9, a display device 40 has, in this order, a housing 43 housing a battery and the like, a protective film 44, a display panel 41, a touch panel member 45, and a display device laminate 10. An attachment adhesive layer 42 is disposed between the display panel 41 and the touch panel member 45, and between the touch panel member 45 and the display device laminate 10, and these members are fixed to each other by the attachment adhesive layer 42. Similarly in this example, the display panel 41 is adhered to the support plate (not shown) by an adhesive layer.

The laminate for a display device in this disclosure is similar to "A. Laminate for a display device" described above, so a description thereof will be omitted here.

Display panels in this disclosure include, for example, display panels used in display devices such as liquid crystal display devices, organic EL display devices, and LED display devices.

The display device of the present disclosure can have a touch panel member between the display panel and the display device laminate.

The display device in the present disclosure is preferably a flexible display. Examples of flexible displays include slidable displays, rollable displays, and foldable displays. In particular, the display device in the present disclosure is preferably a display that is bent so that the laminate for a display device faces outward and that bends while sliding. In other words, the display device in the present disclosure is more preferably a slidable display and a rollable display. Since the display device in the present disclosure has the above-mentioned laminate for a display device, it has excellent abrasion resistance and sliver bending resistance, and is suitable as a flexible display, as well as a slidable display and a rollable display.

C. Display device with support plate The display device with support plate in the present disclosure includes a display device and a support plate arranged on a surface of the display device on the display panel side, the display device being a flexible display, and the support plate having a through pattern penetrating in the thickness direction.

10 is a schematic cross-sectional view showing an example of a display device with a support plate according to the present disclosure. As shown in FIG. 10, the display device with a support plate 70 has the above-mentioned display device 40 and a support plate S arranged on the surface 40B of the display panel 41 side of the display device 40. The "surface 40B of the display device 40 on the display panel 41 side" refers to the surface of the display device 40 located on the display panel 41 side when the display device laminate 10 is used as a reference. The display device 40 is a flexible display. The support plate S has a through pattern (through hole) penetrating in the thickness direction. Since the support plate S has a through pattern, it is easy to bend together with the display device. On the other hand, since the support plate has a through pattern, there is a step with a high curvature locally, and the above-mentioned defects are likely to occur. On the other hand, since the display device with a support plate according to the present disclosure has the above-mentioned display device laminate, defects in the bending portion (particularly the sliding bending portion) can be suppressed for the above-mentioned reasons.

The display device in the present disclosure is a flexible display. Examples of flexible displays include slidable displays, rollable displays, and foldable displays. Of these, a display that bends while sliding while placed on a support plate S is preferred. In other words, it is more preferred that the display device in the present disclosure is a slidable display or a rollable display.

Other features of the display device are the same as those described above in "B. Display device," so a description of them will be omitted here.

The support plate is preferably made of metal (e.g., SUS). The through pattern in the support plate is preferably a linear through pattern, and in particular, is preferably a linear through pattern with the longitudinal direction perpendicular to the sliding direction (screen expansion direction) (the direction into the paper in FIG. 10). The support plate preferably has a plurality of through patterns. For example, as in the test support plate shown in FIG. 7, the support plate preferably has a plurality of blocks along the sliding direction, each block consisting of a group of a plurality of closely spaced through patterns (through holes). The width of each through pattern in the sliding direction (symbol W in FIG. 10) is, for example, 0.1 mm or more, and may be 0.2 mm or more. Alternatively, it may be, for example, 1 mm or less, and may be 0.5 mm or less. The thickness of the support plate is, for example, 100 μm or more, and may be 150 μm or more. Alternatively, it is, for example, 300 μm or less.

As shown in FIG. 10, it is preferable that an adhesive layer 71 is disposed between the support plate S and the display panel 41. The adhesive layer disposed between the support plate and the display panel may be the same as the attachment adhesive layer described above.

Note that this disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical ideas described in the claims of this disclosure and provides similar effects is included within the technical scope of this disclosure.

The following examples and comparative examples will further explain this disclosure.

(Example 1, Examples 3 to 6, Examples 8 to 11, Comparative Examples 1 to 5)
First, a PET film having a thickness shown in Table 2 was prepared as a resin substrate. A hard coat layer was formed on one surface of the resin substrate using the following composition for hard coat layer.

The compositions for hard coat layers and the methods for forming hard coat layers used in the examples and comparative examples are as follows.
<Preparation of hard coat layer composition>
First, the components were mixed so as to obtain the composition shown below to obtain a composition for a hard coat layer.
(Hard Coat Layer Composition)
Urethane acrylate (product name "UX5000", manufactured by Nippon Kayaku Co., Ltd.): 30 parts by mass Mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (product name "M403", manufactured by Toa Gosei Co., Ltd.): 35 parts by mass Multifunctional acrylate polymer (product name "Acrylit 8KX-012C", manufactured by Taisei Fine Chemical Co., Ltd.): 35 parts by mass (based on 100% solids)
Fluorine-based leveling agent (product name "F568", manufactured by DIC Corporation): 0.2 parts by mass (based on 100% solids)
Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad 184", manufactured by IGM Resins B.V.): 3 parts by mass Methyl isobutyl ketone (MIBK): 150 parts by mass Note that "value converted to 100% solid content" refers to a value when the solid content in the solvent-diluted product is taken as 100%.

<Formation of hard coat layer>
A hard coat layer composition was applied to one side of the resin substrate with a bar coater to form a coating film. The formed coating film was heated at 70°C for 1 minute to evaporate the solvent in the coating film. Next, using an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan, light source H bulb), ultraviolet light was irradiated to an integrated light amount of 300 mJ/ ^cm2 under conditions of an oxygen concentration of 200 ppm or less, and the coating film was completely cured (fully cured). As a result, a hard coat layer with a film thickness of 5 μm was formed.

Next, a resin layer was formed on the surface of the resin substrate opposite the hard coat layer using a resin layer composition. This resulted in a laminate for a display device.

The resin layer compositions and resin layer forming methods used in the examples and comparative examples are as follows.
<Preparation of Resin Layer Composition>
The components were mixed so as to obtain the compositions shown in Table 1, thereby obtaining resin layer compositions 1 to 6.
Urethane acrylate 1: Urethane acrylate (product name "UV3310B", manufactured by Nippon Synthetic Chemical Industry Co., Ltd., bifunctional)
Urethane acrylate 2: Urethane acrylate (product name "UV2000B", manufactured by Nippon Synthetic Chemical Industry Co., Ltd., bifunctional)
Acrylate compound 1: a mixture of tripentaerythritol acrylate, mono- and dipentaerythritol acrylate, and polypentaerythritol acrylate (product name: Viscoat #802, manufactured by Osaka Organic Chemical Industry Co., Ltd.)
Acrylate compound 2: ethoxylated pentaerythritol tetraacrylate (product name "ATM-35E", manufactured by Shin-Nakamura Chemical Co., Ltd.)
Acrylate compound 3: phenoxyethyl acrylate (product name "Viscoat #192", manufactured by Osaka Organic Chemical Industry Ltd.)
Polymerization initiator: 1-hydroxycyclohexyl phenyl ketone (product name "Omnirad 184", manufactured by IGM Resins B.V.)
・Anti-fouling agent: Product name "BYK-302", manufactured by BYK-Chemie ・Solvent: Methyl isobutyl ketone (MIBK)

<Formation of Resin Layer>
The resin layer composition shown in Table 2 was applied to the surface of the resin substrate opposite to the hard coat layer with a bar coater to form a coating film. The formed coating film was heated at 70°C for 2 minutes to evaporate the solvent in the coating film. Next, using an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan, light source H bulb), ultraviolet light was irradiated to an integrated light amount of 300 mJ/ ^cm2 under conditions of an oxygen concentration of 200 ppm or less, and the coating film was completely cured (fully cured). As a result, a resin layer having a thickness shown in Table 2 was formed. The total thickness of the resin substrate and the resin layer is shown in Table 2.

(Examples 2, 7 and 12)
A laminate for a display device was obtained in the same manner as in Example 1, except that instead of forming a resin layer using a resin layer composition, a resin film made of 100 μm thermoplastic urethane (product name "DUS270-CER", manufactured by Seedham) was sliced to the film thickness shown in Table 2 (Example 2: 35 μm, Example 7: 20 μm, Example 12: 5 μm) and attached to a resin substrate to form a resin layer.

[Indenter push-in measurement]
For the laminates for displays obtained in Examples 1 to 12 and Comparative Examples 1 to 5, the cross-sectional indenter indentation depths of the resin substrate and the resin layer were measured in the same manner as described in "A. Laminates for displays I. Resin layer" above. The results are shown in Table 2.

[evaluation]
(Steel wool test (scratch resistance test))
First, a protective film having an adhesive layer on one side of a PET substrate (PET substrate thickness: 100 μm to 125 μm, adhesive layer thickness: 10 μm to 25 μm) was attached to the resin layer side of a laminate having a size of 4 cm x 10 cm so as not to cause curling, and then the end of the laminate was fixed with cellophane tape to the test stand of a Gakushin-type friction fastness tester AB-301 manufactured by Tester Sangyo Co., Ltd. Next, using #0000 steel wool (Bonstar #0000 manufactured by Nippon Steel Wool Co., Ltd.), the steel wool was fixed to a jig of 2 cm x 2 cm, and the hard coat layer side of the laminate for display device was rubbed back and forth 1000 times under the conditions of temperature 23 ± 5 ° C., humidity 40 ± 10% RH, load: 500 g, reciprocating speed: 40 rpm, reciprocating distance: 40 mm, and steel wool installation area: 4 cm ^2. Then, the presence or absence of scratches was confirmed by transmission and reflection. The results are shown in Table 3.

(Slide bending test)
The obtained laminate was subjected to a slide bending test to evaluate the bending resistance. First, a laminate for a display device having a size of 20 mm x 100 mm was prepared. As shown in FIG. 6(a), the prepared laminate for a display device 10 was attached to a test support plate 31 via a test adhesive layer 32 so as not to cause curling, to obtain a test piece 30. The test support plate 31 was a SUS304 plate having a thickness of 150 μm and a through pattern as shown in FIG. 7. The test adhesive layer 32 was 3M Adhesive 8146-1 (adhesive layer thickness after peeling off separator is 25 μm).

Next, as shown in FIG. 6(b), the support plate 31 is bent so that it faces inward, and one end side and the other end side in the longitudinal direction are opposed to each other, and in this state, it is set in a slide tester (product name "DMLHB-FU" manufactured by Yuasa Systems Machinery Co., Ltd.). Next, with the one end side fixed, the other end side is slid with a slide length (stroke length) of 35 mm, a slide speed of 30 rpm, and a slide diameter d of 7.0 mm (radius 3.5 mm), and the slide is reciprocated 200,000 times (condition 1). In addition, under the same conditions except that the slide diameter d was changed to 6 mm (radius 3.0 mm), the slide bending test was repeated 200,000 times (condition 2). The slide diameter d is the distance between one end side and the other end side in the longitudinal direction of the display laminate. The results of the slide bending test were evaluated according to the following criteria.

Crack evaluation A: Even under condition 2, no cracks were generated in the hard coat layer (HC layer) of the laminate.
B: Under condition 2, cracks occurred in the hard coat layer (HC layer) of the laminate, but under condition 1, no cracks occurred.
C: Under

conditions

2 and 1, cracks occurred in the hard coat layer (HC layer) of the laminate.

Lifting evaluation A: Even under condition 2, the adhesive layer did not lift off from the support plate.
B: Under condition 2, the adhesive layer peeled off from the support plate, but under condition 1, no peeling of the adhesive layer occurred.
C: Under

conditions

2 and 1, the adhesive layer peeled off from the support plate.

As shown in Table 3, it was confirmed that Comparative Example 1 had low scratch resistance because the resin layer was too thick. In Comparative Example 2, the indenter pressing amount of the resin layer was too large and too soft, so the scratch resistance was low. In Comparative Example 3, the indenter pressing amount of the resin layer was too small and too hard, so the adhesive layer lifted. In Comparative Example 4, the total thickness of the resin substrate and the resin layer was too thin, so sufficient step absorption performance could not be obtained, and cracks occurred in the hard coat layer. In Comparative Example 5, the total thickness of the resin substrate and the resin layer was too thick, so the adhesive layer lifted. Examples 1 to 12 had excellent scratch resistance and good results in the slide bending test. In Example 12, the resin layer was thinner than the other examples, and slight lifting occurred in the adhesive layer under condition 1, but it was not a problem in practical use (B ^* ).

In other words, this disclosure provides the following inventions:

[1]
1. A laminate for a display device comprising: a resin substrate; a hard coat layer disposed on one side of the resin substrate; and a resin layer disposed on a side of the resin substrate opposite the hard coat layer, wherein a cross-sectional indenter indentation amount of the resin layer is 200 nm or more and 3000 nm or less, a cross-sectional indenter indentation amount of the resin substrate is smaller than a cross-sectional indenter indentation amount of the resin layer, a thickness of the resin layer is 5 μm or more and 45 μm or less, and a total thickness of the resin substrate and the resin layer is 50 μm or more and 130 μm or less.

[2]
The laminate for a display device according to [1], wherein a cross-sectional indenter indentation depth of the resin substrate is less than 200 nm.

[3]
The laminate for a display device according to [1] or [2], wherein the resin substrate contains at least one of polyethylene terephthalate, triacetyl cellulose, and polyimide.

[4]
The laminate for a display device according to any one of [1] to [3], wherein the hard coat layer has a thickness of 5 μm or more and 20 μm or less.

[5]
A laminate for a display device according to any one of [1] to [4], wherein when a test piece prepared by bonding the laminate for a display device to a test support plate via a test adhesive layer is subjected to the following slide bending test with a slide diameter of 7.0 mm and the slide is moved back and forth 200,000 times, peeling of the test adhesive layer and cracks do not occur in the hard coat layer.
[Slide bending test]
A display laminate measuring 20 mm x 100 mm is prepared, and a test specimen is obtained by bonding the laminate to a 150 μm thick SUS304 test support plate having a through pattern via a test adhesive layer. The test specimen is bent so that the test support plate is on the inside, and one end side and the other end side in the longitudinal direction are opposed to each other, and in this state, the test specimen is set in a slide tester (Yuasa Corporation DMLHB-FU). Next, with the one end side fixed, the other end side is slid with a slide length (stroke length) of 35 mm and a slide speed of 30 rpm, and repeatedly reciprocated.

[6]
The laminate for a display device according to any one of [1] to [5], further comprising an adhesive layer for attachment on a surface of the resin layer opposite to the resin substrate.

[7]
A display device comprising: a display panel; and a laminate for a display device according to any one of [1] to [6], which is arranged on a viewer side of the display panel, and the laminate for a display device is arranged so that the hard coat layer side faces the viewer side.

[8]
A display device with a support plate, comprising: the display device described in [7]; and a support plate arranged on a surface of the display device facing the display panel, wherein the display device is a flexible display, and the support plate has a through pattern penetrating in the thickness direction.

[9]
The display device with a support plate according to [8], wherein the display device is a display that is bent while sliding in a state where it is disposed on the support plate.

[10]
The display device with a support plate according to [9], wherein the through pattern is a linear through pattern whose longitudinal direction is perpendicular to the sliding direction.

[11]
The support plate-attached display device according to any one of [8] to [10], further comprising an adhesive layer between the display device and the support plate.

REFERENCE SIGNS LIST 1: resin substrate 2: hard coat layer 3: resin layer 10: laminate for display device 40: display device 41: display panel 42: light-transmitting adhesive layer 43: housing 44: protective film 45: touch panel member

Claims

A resin substrate;
a hard coat layer disposed on one surface of the resin substrate;
a resin layer disposed on a surface of the resin substrate opposite to the hard coat layer,
The cross-sectional indentation depth of the resin layer is 200 nm or more and 3000 nm or less,
The cross-sectional indenter indentation amount of the resin substrate is smaller than the cross-sectional indenter indentation amount of the resin layer,
The thickness of the resin layer is 5 μm or more and 45 μm or less,
The laminate for a display device, wherein the total thickness of the resin substrate and the resin layer is 50 μm or more and 130 μm or less.
The laminate for a display device according to claim 1, wherein the cross-sectional indenter indentation amount of the resin substrate is less than 200 nm.
The laminate for a display device according to claim 1, wherein the resin substrate contains one or more of polyethylene terephthalate, triacetyl cellulose, and polyimide.
The laminate for a display device according to claim 1, wherein the thickness of the hard coat layer is 5 μm or more and 20 μm or less.
2. The laminate for a display device according to claim 1, wherein when a test piece prepared by bonding the laminate for a display device to a test support plate via a test adhesive layer is subjected to the following slide bending test with a slide diameter of 7.0 mm and the slide is repeatedly moved back and forth 200,000 times, peeling of the test adhesive layer and cracks do not occur in the hard coat layer.
[Slide bending test]
A display laminate measuring 20 mm x 100 mm is prepared, and a test specimen is obtained by bonding the laminate to a 150 μm thick SUS304 test support plate having a through pattern via a test adhesive layer. The test specimen is bent so that the test support plate is on the inside, and one end side and the other end side in the longitudinal direction are opposed to each other, and in this state, the test specimen is set in a slide tester (Yuasa Corporation DMLHB-FU). Next, with the one end side fixed, the other end side is slid with a slide length (stroke length) of 35 mm and a slide speed of 30 rpm, and is repeatedly reciprocated.
The laminate for a display device according to claim 1, which has an adhesive layer for attachment on the surface of the resin layer opposite the resin substrate.
A display device comprising a display panel and a laminate for a display device according to any one of claims 1 to 6, which is arranged on the viewer side of the display panel, and the laminate for a display device is arranged so that the hard coat layer side faces the viewer side.
A display device with a support plate, comprising the display device according to claim 7 and a support plate arranged on the display panel side of the display device, the display device being a flexible display, and the support plate having a through pattern penetrating in the thickness direction.
The display device with support plate according to claim 8, wherein the display device is a display that bends while sliding while being placed on the support plate.
The display device with a support plate according to claim 9, wherein the through pattern is a linear through pattern with a longitudinal direction perpendicular to the sliding direction.
The display device with support plate according to claim 8, having an adhesive layer between the display device and the support plate.