Laminate for flexible display device, laminate for display device, and flexible display device

Abstract

To provide a laminate for a flexible display device excellent in abrasion resistance.SOLUTION: A laminate for a flexible display comprising a substrate layer and an antistatic layer, wherein a ratio of an angle of contact with water on a side of the antistatic layer to an initial angle of contact with water on the side of the antistatic layer after a steel-wool test in which the side of the antistatic layer of the laminate is rubbed back and forth 2500 times with #0000 steel-wool under a load of 9. 8N is 0.6 or more, and surface resistance on the side of the antistatic layer is 9 * 1013 Ω / square or less. Surface resistance on the side of the antistatic layer is 9 * 1013 Ω / square or less after a rubber eraser abrasion test in which the side of the antistatic layer is rubbed 2500 times back and forth with a 6mm rubber eraser under a load of 9. 8N.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a laminate for a flexible display, a laminate for a display, and a flexible display. [Background technology]

[0002] On the surface of the display device, a laminate including functional layers having various properties such as hard coating properties, scratch resistance, anti-reflection properties, anti-glare properties, anti-static properties, and anti-fouling properties is disposed.

[0003] For example, a glass substrate or a resin substrate is used as the substrate layer in such a laminate. However, because glass substrates and resin substrates have high insulating properties, they are easily charged, and contamination occurs due to the adhesion of dust and dirt. Furthermore, if static electricity is generated during the manufacturing process of a display device, the charged static electricity may be discharged, damaging the electronic components that make up the display device, resulting in so-called electrostatic breakdown. Furthermore, when attaching a device such as a battery to the display device, the display device may become charged. Therefore, it has been known to use a laminate having an antistatic layer to prevent such charging.

[0004] In recent years, touch functions have become available not only in smartphones and tablet terminals but also in display devices of notebook personal computers, etc. Display devices with touch functions are required to have abrasion resistance and slip resistance because they are operated by directly touching the surface with fingers or the like.

[0005] Furthermore, portable display devices such as smartphones and tablet terminals are often stored in, for example, clothing pockets or bags, and the surface of the display device may be rubbed by the fabric of the clothing or bag, other items stored in the clothing pocket or bag, etc. For this reason, portable display devices are required to have even greater abrasion resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-125063 [Patent Document 2] Patent No. 6140348 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, flexible displays such as foldable displays, rollable displays, and bendable displays have attracted attention, and active development of laminates to be placed on the surface of flexible displays has been underway. For example, the use of a resin substrate instead of a glass substrate has been considered, and Patent Document 1, for example, proposes a display device window film having a plastic substrate with high hardness and excellent optical properties and a hard coating layer placed on at least one surface of the plastic substrate.

[0008] Flexible displays are often used or stored in a bent state, and therefore the surfaces of the bent portions are easily abraded, so flexible displays are required to have excellent abrasion resistance at the bent portions.

[0009] It is generally known that wear resistance can be increased by, for example, increasing the surface hardness or decreasing the coefficient of friction.

[0010] However, in the case of a method for increasing the surface hardness, in the case of a laminate used in a flexible display, increasing the surface hardness may impair flexibility such as foldability, rollability, and bendability.

[0011] As a method for reducing the coefficient of friction, there are known techniques for imparting low friction, such as coating with a fluorine-based surface treatment agent or adding a fluorine-based additive. For example, Patent Document 2 discloses a surface treatment agent containing a fluorooxyalkylene group-containing polymer composition that can provide a coating excellent in water and oil repellency, scratch resistance, low dynamic friction, and abrasion resistance.

[0012] However, when the surface of the functional layer in the laminate is rubbed, the components contained in the functional layer may be rubbed off or the functional layer may be worn away, resulting in a decrease in the performance of the functional layer.As mentioned above, further improvement in abrasion resistance is desired in flexible displays.

[0013] The present disclosure has been made in view of the above-described circumstances, and a main object of the present disclosure is to provide a laminate for a flexible display device and a flexible display device that are excellent in abrasion resistance. [Means for solving the problem]

[0014] In order to solve the above problems, the inventors of the present disclosure focused on a steel wool test and an eraser test as abrasion tests and conducted extensive research on the abrasion resistance of laminates for flexible displays. As a result, they found that even if the steel wool resistance is good, the eraser resistance may be poor. Furthermore, through extensive research, the inventors of the present disclosure surprisingly discovered a new correlation between abrasion resistance and surface resistance. The present disclosure is based on this finding.

[0015] One embodiment of the present disclosure provides a laminate for a flexible display device, comprising a base layer and an antistatic layer, wherein a contact angle with water on a surface of the laminate for a flexible display device on the antistatic layer side is 100° or more, a ratio of a contact angle with water after a steel wool test in which the surface of the laminate for a flexible display device on the antistatic layer side is performed with #0000 steel wool and rubbed back and forth 2500 times under a load of 9.8 N to an initial contact angle with water on the surface of the laminate for a flexible display device on the antistatic layer side is 0.6 or more, and a surface resistance of the surface of the laminate for a flexible display device on the antistatic layer side is 9×10 13 Ω / □ or less, and after an eraser test is performed in which the surface of the laminate for a flexible display device on the antistatic layer side is rubbed back and forth 2500 times with an eraser having a diameter of 6 mm and a load of 9.8 N, the surface resistance of the surface of the laminate for a flexible display device on the antistatic layer side is 9×10 13 The present invention provides a laminate for a flexible display device having a resistance of Ω / □ or less.

[0016] In the laminate for a flexible display device according to the present disclosure, it is preferable that the ratio of the surface resistance after the eraser test to the initial surface resistance on the surface of the laminate for a flexible display device on the antistatic layer side is 20.0 or less.

[0017] In the laminate for a flexible display device according to the present disclosure, the antistatic layer preferably contains an antifouling agent.

[0018] The laminate for a flexible display device according to the present disclosure may further include an impact absorbing layer on the surface of the base layer opposite to the antistatic layer, or between the base layer and the antistatic layer.

[0019] The laminate for a flexible display device according to the present disclosure may also have an adhesive layer for attachment on the surface of the base layer opposite to the antistatic layer.

[0020] Another embodiment of the present disclosure is a laminate for a display device, comprising a base layer and an antistatic layer, wherein a contact angle with water on a surface of the laminate for a display device on the antistatic layer side is 100° or more, a ratio of a contact angle with water after a steel wool test in which the surface of the laminate for a display device on the antistatic layer side is performed, the surface being rubbed back and forth 2500 times with #0000 steel wool under a load of 9.8 N, to an initial contact angle with water on the surface of the laminate for a display device on the antistatic layer side, is 0.6 or more, and a surface resistance of the surface of the laminate for a display device on the antistatic layer side is 9×10 13 Ω / □ or less, and after an eraser test is performed in which the surface of the laminate for a display device on the side of the antistatic layer is rubbed back and forth 2500 times with an eraser having a diameter of 6 mm and a load of 9.8 N, the surface resistance of the surface of the laminate for a display device on the side of the antistatic layer is 9×10 13 The present invention provides a laminate for a display device having a resistance of Ω / □ or less.

[0021] Another embodiment of the present disclosure provides a flexible display device comprising a display panel and the above-described flexible display laminate disposed on a viewer side of the display panel. [Effects of the Invention]

[0022] The present disclosure has an effect of providing a laminate for a flexible display device, a laminate for a display device, and a flexible display device that are excellent in abrasion resistance. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic cross-sectional view illustrating a laminate for a flexible display device according to the present disclosure. [Figure 2] FIG. 1 is a schematic diagram illustrating a method for measuring frictional force against an eraser. [Figure 3] FIG. 1 is a schematic diagram illustrating a dynamic bending test. [Figure 4] 1 is a schematic cross-sectional view illustrating a laminate for a flexible display device according to the present disclosure. [Figure 5]1 is a schematic cross-sectional view illustrating a laminate for a flexible display device according to the present disclosure. [Figure 6] 1 is a schematic cross-sectional view illustrating a flexible display device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0024] Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be implemented in many different forms, and should not be construed as being limited to the description of the embodiments exemplified below. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual form, but these are merely examples and are not intended to limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings will be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0025] In this specification, when describing a mode in which another component is placed on a certain component, the terms "above" or "below" are used, unless otherwise specified, to include both a case in which another component is placed directly above or below a certain component so as to be in contact with the component, and a case in which another component is placed above or below a certain component with another component interposed therebetween. Also, in this specification, when describing a mode in which another component is placed on the surface of a certain component, the terms "on the surface side" or "on the surface" are used, unless otherwise specified, to include both a case in which another component is placed directly above or below a certain component so as to be in contact with the component, and a case in which another component is placed above or below a certain component with another component interposed therebetween.

[0026] The inventors of the present disclosure have focused on a steel wool test and an eraser test as abrasion tests and have conducted extensive research into the abrasion resistance of laminates for flexible display devices, and have come to the following findings.

[0027] The inventors of the present disclosure first focused on the contact angle of water on the surface of the laminate for a flexible display device. If the rate of change in the contact angle of water after the steel wool test relative to the initial contact angle of water is small, it can be said that the performance can be maintained even after the steel wool test, and that the abrasion resistance is high.

[0028] However, the inventors of the present disclosure have found that even if the rate of change in the water contact angle after the steel wool test relative to the initial water contact angle is small, the rate of change in the water contact angle after the eraser test relative to the initial water contact angle may be large in some cases. In other words, it has been found that even if the steel wool resistance is good, the eraser resistance may be poor in some cases.

[0029] Therefore, the inventors of the present disclosure conducted an eraser test on a laminate for a flexible display device and investigated the change in frictional force before and after the eraser test. Focusing on the eraser test and surface resistance, the inventors measured the frictional force and surface resistance before and after the eraser test and found that although both the frictional force and surface resistance tend to increase after the eraser test, when the surface resistance after the eraser test is relatively small, the change in frictional force before and after the eraser test tends to be relatively small, and when the surface resistance after the eraser test is relatively large, the change in frictional force before and after the eraser test tends to be relatively large. Furthermore, they found that when the initial surface resistance before the eraser test is small, the surface resistance after the eraser test tends to be small. That is, they found that there is a correlation between abrasion resistance and surface resistance after the eraser test. Furthermore, they found that abrasion resistance can be easily estimated from the initial surface resistance before the eraser test. That is, they newly found that there is a good correlation between abrasion resistance and surface resistance before and after the eraser test. Furthermore, upon detailed investigation of the relationship between abrasion resistance and surface resistance before and after the eraser test, it was found that in order to impart excellent abrasion resistance, it is important to keep the surface resistance before and after the eraser test at a predetermined value or less.

[0030] In the present disclosure, it is of great significance that a reduction in surface resistance after the eraser test has been found as an index for improving abrasion resistance.Furthermore, it is of great significance that the initial surface resistance before the eraser test has been found as an index for estimating abrasion resistance.

[0031] The reason why the abrasion test using steel wool was used here is that the steel wool test is generally used to evaluate abrasion resistance, and the steel wool test can evaluate the abrasion resistance against relatively hard objects such as items stored in clothing pockets or bags.

[0032] The reason for using an eraser for the abrasion test is that rubbing with an eraser is similar to rubbing with a touch pen, and the eraser test makes it possible to evaluate the abrasion resistance of relatively soft objects such as a touch pen, a finger, or the fabric of clothing or a bag.

[0033] The laminate for a flexible display device, the laminate for a display device, and the flexible display device according to the present disclosure will be described in detail below.

[0034] A. Laminates for flexible displays The laminate for a flexible display device according to the present disclosure is a laminate for a flexible display device having a base layer and an antistatic layer, wherein the surface of the laminate for a flexible display device on the antistatic layer side has a water contact angle of 100° or more, the ratio of the water contact angle after a steel wool test in which the surface of the laminate for a flexible display device on the antistatic layer side is rubbed back and forth 2500 times with #0000 steel wool under a load of 9.8 N to the initial water contact angle on the surface of the laminate for a flexible display device on the antistatic layer side is 0.6 or more, and the surface resistance of the surface of the laminate for a flexible display device on the antistatic layer side is 9×10 13Ω / □ or less, and after an eraser test is performed in which the surface of the laminate for a flexible display device on the antistatic layer side is rubbed back and forth 2500 times with an eraser having a diameter of 6 mm and a load of 9.8 N, the surface resistance of the surface of the laminate for a flexible display device on the antistatic layer side is 9×10 13 It is Ω / □ or less.

[0035] Fig. 1 is a schematic cross-sectional view showing an example of a laminate for a flexible display device according to the present disclosure. As shown in Fig. 1, the laminate for a flexible display device 1 has a base layer 2 and an antistatic layer 3. The contact angle with water on the surface of the laminate for a flexible display device 1 facing the antistatic layer 3 is equal to or greater than a predetermined value, and the ratio of the contact angle with water after a predetermined steel wool test to the initial contact angle with water on the surface of the laminate for a flexible display device 1 facing the antistatic layer 3 is equal to or greater than a predetermined value. Furthermore, the surface resistance of the surface of the laminate for a flexible display device 1 facing the antistatic layer 3 is equal to or less than a predetermined value, and the surface resistance of the surface of the laminate for a flexible display device 1 facing the antistatic layer 3 after a predetermined eraser test is also equal to or less than a predetermined value.

[0036] As described above, the present disclosure is based on the new finding that there is a correlation between the abrasion resistance and the surface resistance before and after the eraser test in a laminate for a flexible display device. In the present disclosure, excellent abrasion resistance can be obtained by having the initial water contact angle on the antistatic layer side of the laminate for a flexible display device be equal to or greater than a predetermined value, the ratio of the water contact angle after the steel wool test to the initial water contact angle be equal to or greater than a predetermined value, and further, the surface resistance before and after the eraser test be equal to or less than a predetermined value.

[0037] The reason for this is unclear, but is speculated as follows. That is, when an eraser test is performed on the surface of a flexible display laminate, the surface of the flexible display laminate becomes charged due to friction caused by the eraser. When discharge occurs, the layers constituting the flexible display laminate deteriorate, which may result in electrostatic breakdown. When such electrostatic breakdown occurs, it is thought that the surface condition of the flexible display laminate changes and the abrasion resistance may decrease. In contrast, in the present disclosure, since the surface resistance of the antistatic layer side of the flexible display laminate after the eraser test is below a predetermined value, it is possible to suppress charging of the antistatic layer side of the flexible display laminate due to the eraser test, and it is thought that the above-mentioned layer deterioration and electrostatic breakdown can be suppressed. As a result, it is speculated that excellent abrasion resistance can be obtained.

[0038] Furthermore, in the present disclosure, the initial contact angle with water on the antistatic layer side of the laminate for a flexible display device is equal to or greater than a predetermined value, and the ratio of the contact angle with water after a steel wool test to the initial contact angle with water is equal to or greater than a predetermined value, so that excellent abrasion resistance can be obtained against relatively hard objects such as items stored in clothing pockets or bags.

[0039] Furthermore, in the present disclosure, since the surface resistance on the antistatic layer side of the laminate for a flexible display device after the eraser test is equal to or less than a predetermined value, excellent abrasion resistance can be obtained against relatively soft objects such as touch pens, fingers, and the fabric of clothes and bags.

[0040] Furthermore, in the present disclosure, abrasion resistance can be easily estimated from the initial surface resistance before the eraser test, and therefore a laminate for a flexible display device can be easily designed to have the desired abrasion resistance.

[0041] Hereinafter, each component of the laminate for a flexible display device according to the present disclosure will be described.

[0042] 1. Properties of laminates for flexible displays In the present disclosure, the contact angle with water on the antistatic layer side of the laminate for a flexible display device is 100° or more. If the initial contact angle with water is within the above range, sufficient antifouling properties can be obtained, thereby preventing the adhesion of fingerprints and dirt, and even if fingerprints or dirt do adhere, they can be easily wiped off. Furthermore, the initial contact angle with water is preferably, for example, 150° or less.

[0043] Furthermore, in the present disclosure, after a steel wool test is conducted in which the antistatic layer side of the laminate for a flexible display device is rubbed back and forth 2500 times with #0000 steel wool under a load of 9.8 N, the contact angle with water on the antistatic layer side of the laminate for a flexible display device is preferably, for example, 100° or more. By having the contact angle with water after the steel wool test in the above range, excellent abrasion resistance can be obtained and excellent antifouling properties can be maintained. Furthermore, the contact angle with water after the steel wool test is preferably, for example, 150° or less.

[0044] Furthermore, the ratio of the water contact angle after the steel wool test to the initial water contact angle on the antistatic layer side of the laminate for flexible display devices can be 0.6 or more, preferably 0.8 or more, and more preferably 0.9 or more. When the water contact angle ratio is within the above range, abrasion resistance can be improved. Furthermore, since the water contact angle tends to decrease after the steel wool test, the water contact angle ratio can be, for example, 1.0 or less.

[0045] The ratio of the above contact angles with water is calculated by the following formula, where A is the contact angle with water on the surface of the antistatic layer side of the initial laminate for flexible display devices before the steel wool test, and B is the contact angle with water on the surface of the antistatic layer side of the laminate for flexible display devices after the steel wool test. Ratio of contact angle with water = B / A

[0046] The steel wool test can be performed using the following method. Specifically, using #0000 steel wool, the steel wool is fixed to a 2 cm x 2 cm jig and rubbed back and forth 2,500 times against the antistatic layer side of the flexible display laminate at a load of 9.8 N, a movement speed of 140 mm / sec, and a movement distance of 70 mm. Bonstar #0000 manufactured by Nippon Steel Wool Co., Ltd. can be used as the #0000 steel wool. Furthermore, the tester can be, for example, a Gakushin-type rubbing fastness tester AB-301 manufactured by Tester Sangyo Co., Ltd. The steel wool test is performed, for example, by fixing a 5 cm x 10 cm flexible display laminate to a glass plate with Nichiban Cellotape (registered trademark) to prevent folds or wrinkles.

[0047] The water contact angle can be measured by the sessile drop method in accordance with JIS R3257:1999. Specifically, 2 μL of water is dropped onto the antistatic layer side of the flexible display laminate, and the contact angle is measured immediately after the drop. The water contact angle is measured at 10 points on the antistatic layer side of the flexible display laminate, and the arithmetic mean value of the 10 measured values ​​is used. As a measuring device, for example, a contact angle meter, DropMaster 300 manufactured by Kyowa Interface Science Co., Ltd., can be used.

[0048] In the present disclosure, the surface resistance of the antistatic layer side of the laminate for a flexible display device is 9×10 13 Ω / □ or less, preferably 9×10 12 Ω / □ or less. If the initial surface resistance is within the above range, the surface resistance of the antistatic layer side of the laminate for flexible display devices after a predetermined eraser test tends to be within a predetermined range, and it can be assumed that excellent abrasion resistance can be obtained. Furthermore, if the initial surface resistance is within the above range, excellent antistatic properties can be obtained.

[0049] In addition, in the present disclosure, after an eraser test in which the surface of the antistatic layer side of the laminate for a flexible display device is rubbed back and forth 2500 times with an eraser having a diameter of 6 mm and a load of 9.8 N, the surface resistance of the surface of the antistatic layer side of the laminate for a flexible display device is 9×10 13 Ω / □ or less, preferably 5×10 13 Ω / □ or less, more preferably 9×10 12 When the surface resistance after the eraser test is in the above range, excellent abrasion resistance can be obtained and excellent antistatic properties can be maintained.

[0050] Furthermore, the ratio of the surface resistance after the eraser test to the initial surface resistance on the surface of the antistatic layer side of the flexible display laminate is, for example, preferably 20.0 or less, more preferably 10.0 or less, and even more preferably 5.0 or less. Having the surface resistance ratio within the above range can improve abrasion resistance. The reason for this is unclear, but it is speculated as follows. That is, the surface resistance ratio increases, for example, when the initial surface resistance is low and the surface resistance after the eraser test increases. On the other hand, the surface resistance ratio decreases, for example, when the initial surface resistance is low and the surface resistance after the eraser test also decreases. In the latter case, it is thought that the surface of the flexible display laminate is less likely to become charged due to friction caused by the eraser, making it less likely to cause electrostatic breakdown. Therefore, by having the surface resistance ratio as small as the above range, it is thought that charging of the surface of the antistatic layer side of the flexible display laminate in the eraser test can be more effectively suppressed, and electrostatic breakdown can be more effectively suppressed. As a result, it is speculated that abrasion resistance can be improved. Furthermore, since the surface resistance tends to increase after the eraser test, the surface resistance ratio can be set to, for example, 1.0 or more.

[0051] The above surface resistance ratio can be calculated by the following formula, where C is the surface resistance on the surface of the antistatic layer side of the initial laminate for a flexible display device before the eraser test, and D is the surface resistance on the surface of the antistatic layer side of the laminate for a flexible display device after the eraser test. Surface resistance ratio = D / C

[0052] The eraser test can be performed using the following method. Specifically, a 6 mm diameter eraser is inserted into a jig with a 6 mm diameter hole so that 4 mm of the eraser tip is exposed. The jig with the eraser attached is attached to a Gakushin-type friction tester, and the antistatic layer side of the flexible display laminate is rubbed back and forth 2,500 times with the eraser at a load of 9.8 N and a movement speed of 80 mm / sec. For example, a 6 mm diameter eraser manufactured by Minoan Corporation can be used as the 6 mm diameter eraser. Furthermore, for example, a Gakushin-type friction tester AB-301 manufactured by Tester Sangyo Co., Ltd. can be used as the Gakushin-type friction tester.

[0053] Surface resistance was measured using a Mitsubishi Chemical Analytech Hiresta UX MCP-HT resistivity meter, with the MCP-HTO14 URS probe used after the eraser test and the MCP-HTP11 UA probe used initially before the eraser test, at an applied voltage of 1000V. Surface resistance was measured at 10 locations on the antistatic layer side of the flexible display laminate, and the arithmetic mean of the 10 measurements was used. The flexible display laminate was left to stand for 1 hour at a temperature of 23±2°C and a humidity of 50±10% before the measurement.

[0054] In the present disclosure, the average value of the frictional force against an eraser on the surface of the antistatic layer side of the laminate for a flexible display device is, for example, preferably 0.98 N or more and 9.80 N or less, more preferably 1.96 N or more and 8.80 N or less, and even more preferably 2.45 N or more and 7.80 N or less. If the initial average value of the frictional force against an eraser is within the above range, the abrasion resistance can be increased.

[0055] Furthermore, in the present disclosure, after an eraser test is conducted in which the surface of the antistatic layer side of the laminate for a flexible display device is rubbed back and forth 2500 times with an eraser having a diameter of 6 mm under a load of 9.8 N, the maximum value of the friction force against the eraser on the surface of the antistatic layer side of the laminate for a flexible display device is, for example, preferably 0.98 N or more and 9.80 N or less, more preferably 1.96 N or more and 8.80 N or less, and even more preferably 2.45 N or more and 7.80 N or less. When the friction force against the eraser after the eraser test is within the above range, excellent abrasion resistance can be obtained and excellent antistatic properties can be maintained.

[0056] Furthermore, the ratio of the maximum frictional force against the eraser after the eraser test to the average initial frictional force against the eraser on the antistatic layer side of the laminate for flexible display devices is, for example, preferably 1.50 or less, more preferably 1.48 or less, and even more preferably 1.45 or less. By having the ratio of frictional force against the eraser in the above range, abrasion resistance can be improved. Furthermore, the ratio of frictional force against the eraser can be, for example, 1.00 or more.

[0057] The ratio of the frictional force against the eraser can be calculated using the following formula, where E is the average value of the frictional force against the eraser on the surface of the antistatic layer side of the initial laminate for a flexible display device before the eraser test, and F is the maximum amount of friction against the eraser on the surface of the antistatic layer side of the laminate for a flexible display device after the eraser test. Friction force ratio = F / E

[0058] Here, the frictional force against the eraser can be measured by inserting a 6 mm diameter eraser into a jig with a 6 mm diameter hole so that 4 mm of the eraser tip is exposed. The jig with the eraser attached is then attached to a friction tester and rubbed against the antistatic layer side of the flexible display laminate with the eraser at a load of 1.96 N and a movement speed of 840 mm / min. For example, a 6 mm diameter eraser manufactured by Minoan can be used as the 6 mm diameter eraser. Furthermore, for example, a TRIBOGEAR TYPE 18 manufactured by Shinto Scientific Co., Ltd. can be used as the friction tester. Specifically, as shown in Figure 2, the above-described eraser test is first performed on a portion of the antistatic layer side surface 30 of the flexible display laminate 1, forming a rectangular eraser test area 32. Next, the eraser is used to rub the antistatic layer side surface 30 of the flexible display laminate 1 in the order of eraser test untested area 31, eraser test area 32, and eraser test untested area 31, as indicated by the arrows, to measure the frictional force. At this time, the eraser is moved perpendicular to the longitudinal direction of the rectangular eraser test section 32, as shown by the arrow. The average value of the friction force against the eraser in the eraser test untested section can be taken as the average value of the friction force against the eraser at the initial stage, and the maximum value of the friction force against the eraser in the eraser test test section can be taken as the maximum value of the friction force against the eraser after the eraser test. Furthermore, as shown in Figure 2, the average value of the friction force against the eraser at the initial stage is taken as the average value of the friction force in the eraser test untested section 31 in the range of 4.2 mm to 9.8 mm, with the point (0 mm) at which the friction force against the eraser in the eraser test test section 32 is maximum.

[0059] The laminate for a flexible display device according to the present disclosure preferably has a total light transmittance of, for example, 85% or more, more preferably 88% or more, and even more preferably 90% or more. Such a high total light transmittance allows the laminate for a flexible display device to have good transparency.

[0060] Here, the total light transmittance of the laminate for a flexible display device can be measured in accordance with JIS K7361-1:1997, for example, using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

[0061] The haze of the laminate for a flexible display device according to the present disclosure is, for example, preferably 5% or less, more preferably 2% or less, and even more preferably 1% or less. Such a low haze allows the laminate for a flexible display device to have good transparency.

[0062] The haze of the laminate for a flexible display device can be measured in accordance with JIS K-7136:2000, for example, using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

[0063] The laminate for a flexible display device according to the present disclosure preferably has flex resistance. Specifically, it is preferable that the laminate for a flexible display device does not crack or break when subjected to a dynamic flex test described below 200,000 times, and it is even more preferable that the laminate for a flexible display device does not crack or break when subjected to a dynamic flex test 500,000 times.

[0064] In the dynamic bending test, the flexible display laminate may be folded so that the antistatic layer is on the outside, or the flexible display laminate may be folded so that the antistatic layer is on the inside, but in either case, it is preferable that the flexible display laminate does not crack or break.

[0065] The dynamic bending test is performed as follows. First, a laminate for a flexible display device measuring 20 mm × 100 mm is prepared. In the dynamic bending test, as shown in FIG. 3( a), a short side 1C of the laminate for a flexible display device 1 and a short side 1D opposite to the short side 1C are fixed by parallel fixing portions 51, respectively. As shown in FIG. 3( a), the fixing portions 51 are slidable horizontally. Next, as shown in FIG. 3( b), the fixing portions 51 are moved closer to each other to deform the laminate for a flexible display device 1 so as to fold it. Furthermore, as shown in FIG. 3( c), the fixing portions 51 are moved to a position where the distance d between the two opposing short side portions 1C and 1D fixed by the fixing portions 51 of the laminate for a flexible display device 1 is 30 mm. Then, the fixing portions 51 are moved in the opposite direction to eliminate the deformation of the laminate for a flexible display device 1. 3(a) to 3(c), the laminate 1 for a flexible display device can be folded 180° by moving the fixing portion 51. Furthermore, by performing a dynamic bending test so that the bending portion 1E of the laminate 1 for a flexible display device does not protrude from the lower end of the fixing portion 51 and controlling the distance when the fixing portions 51 are closest to each other, the distance d between the two opposing short side portions 1C, 1D of the laminate 1 for a flexible display device can be set to 30 mm. In this case, the outer diameter of the bending portion 1E is considered to be 30 mm.

[0066] It is preferable that the laminate for a flexible display device does not crack or break when a dynamic bending test is repeated 200,000 times in which the laminate for a flexible display device is folded 180° so that the distance d between the opposing short sides 1C and 1D of the laminate for a flexible display device is 30 mm.In particular, it is preferable that the laminate for a flexible display device does not crack or break when a dynamic bending test is repeated 200,000 times in which the laminate for a flexible display device is folded 180° so that the distance d between the opposing short sides 1C and 1D of the laminate for a flexible display device is 20 mm.It is particularly preferable that the laminate for a flexible display device does not crack or break when a dynamic bending test is repeated 200,000 times in which the laminate is folded 180° so that the distance d between the opposing short sides 1C and 1D of the laminate for a flexible display device is 10 mm.

[0067] 2.Antistatic layer The antistatic layer in the present disclosure is disposed on one surface of the base layer, and is a layer for imparting antistatic properties to the laminate for a flexible display device.

[0068] The antistatic layer is not particularly limited as long as it has antistatic properties, and may contain at least an antistatic agent. The antistatic layer may also contain, for example, an antistatic agent and a resin.

[0069] As the antistatic agent, for example, either a low molecular weight antistatic agent or a polymeric antistatic agent can be used. Further, as the antistatic agent, for example, an ion-conductive antistatic agent, an electron-conductive antistatic agent, etc. can be used. The antistatic agent may be used alone or in combination of two or more.

[0070] Examples of the ion-conducting antistatic agent include cationic antistatic agents such as quaternary ammonium salts and pyridium salts; anionic antistatic agents such as alkali metal salts of sulfonic acid, phosphoric acid, carboxylic acid, etc., such as lithium salts, sodium salts, and potassium salts; amphoteric antistatic agents such as amino acid-based and amino acid sulfate-based; nonionic antistatic agents such as amino alcohol-based, glycerin-based, and polyethylene glycol-based; ionic liquids, etc. Among these, quaternary ammonium salts and lithium salts are preferred because they exhibit excellent compatibility with resins.

[0071] Examples of the electron-conductive antistatic agent include conductive polymers such as polyacetylene and polythiophene; conductive particles and conductive fibers such as metal particles, metal oxide particles, and carbon nanotubes. Antistatic agents obtained by combining a dopant with a conductive polymer such as polyacetylene or polythiophene, or antistatic agents obtained by incorporating conductive particles into the conductive polymer, can also be used. Among these, conductive polymers are preferred from the viewpoint of maintaining antistatic properties.

[0072] Specific examples of the conductive polymer include polyacetylene, polyaniline, polythiophene, polypyrrole, polyphenylene sulfide, poly(1,6-heptadiyne), polybiphenylene (polyparaphenylene), polyparaphenylene sulfide, polyphenylacetylene, poly(2,5-thienylene), and derivatives thereof. Preferred examples include polythiophene-based conductive polymers such as 3,4-ethylenedioxythiophene (PEDOT). By using the conductive polymer as an antistatic agent, antistatic properties can be maintained for a long period of time.

[0073] Examples of metals constituting the metal fine particles include Au, Ag, Cu, Al, Fe, Ni, Pd, Pt, and the like, alone or alloys of these metals.

[0074] The metal oxide constituting the metal oxide particles is not particularly limited, and examples thereof include tin oxide, antimony oxide, antimony-doped tin oxide (ATO), tin-doped indium oxide (ITO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), and zinc oxide (ZnO). Among these, antimony-doped tin oxide (ATO) is preferred from the viewpoint of exhibiting excellent antistatic properties. Furthermore, among ATO, chain-like ATO in which multiple ATO particles are linked together is preferred.

[0075] Among the above antistatic agents, non-particulate antistatic agents are preferred. This is because non-particulate antistatic agents are more likely to maintain antistatic properties than particulate antistatic agents. In particular, polymeric antistatic agents are preferred. This is because polymeric antistatic agents can impart antistatic properties even in small amounts and can maintain optical properties and hardness.

[0076] The content of the antistatic agent is not particularly limited as long as it is an amount that can provide an antistatic layer that satisfies the above-mentioned surface resistance, and is appropriately selected depending on the material of the antistatic layer, etc. For example, when the antistatic layer contains an antistatic agent and a resin, the amount is preferably 0.1 to 100 parts by weight, more preferably 0.2 to 50 parts by weight, and even more preferably 0.3 to 20 parts by weight, per 100 parts by weight of the resin component. If the content of the antistatic agent is too low, the antistatic layer may not be able to have sufficient antistatic properties, or an antistatic layer that satisfies the above-mentioned surface resistance may not be obtained. On the other hand, if the content of the antistatic agent is too high, it may be difficult to form the antistatic layer, or the abrasion resistance may be reduced.

[0077] The resin can be appropriately selected depending on the performance to be imparted to the antistatic layer.

[0078] For example, when the antistatic layer does not need to have hard coat properties, the resin may be at least one selected from the group consisting of (meth)acrylic resins, cellulose resins, urethane resins, vinyl chloride resins, polyester resins, polyolefin resins, polycarbonate, nylon, polystyrene, and ABS resins. Among these, (meth)acrylic resins, polyester resins, etc. are preferred from the viewpoints of ease of processing and hardness.

[0079] Examples of the (meth)acrylic resin include polymethyl methacrylate. Examples of the cellulose resin include diacetyl cellulose, cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB), etc. Examples of the urethane resin include urethane resin. Examples of the vinyl chloride resin include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, etc. Examples of the polyester resin include polyethylene terephthalate, etc. Examples of the polyolefin resin include polyethylene, polypropylene, etc.

[0080] Furthermore, for example, when the antistatic layer has hard coating properties, the resin may specifically be a cured product of a polymerizable compound. The cured product of the polymerizable compound can be obtained by polymerizing the polymerizable compound by a known method, using a polymerization initiator as needed.

[0081] The polymerizable compound has at least one polymerizable functional group in the molecule, and may be, for example, at least one of a radical polymerizable compound and a cation polymerizable compound.

[0082] The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound is not particularly limited as long as it is a functional group capable of causing a radical polymerization reaction, and examples thereof include groups containing a carbon-carbon unsaturated double bond, and specific examples thereof include a vinyl group and a (meth)acryloyl group. When the radical polymerizable compound has two or more radical polymerizable groups, these radical polymerizable groups may be the same or different.

[0083] The number of radically polymerizable groups that the radically polymerizable compound has in one molecule is preferably two or more, and more preferably three or more, from the viewpoint of increasing the hardness of the antistatic layer and improving the steel wool resistance.

[0084] Among radically polymerizable compounds, compounds containing a (meth)acryloyl group are preferred due to their high reactivity. Examples of suitable compounds include polyfunctional (meth)acrylate monomers and oligomers with molecular weights ranging from 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. Polyfunctional (meth)acrylate polymers containing two or more (meth)acryloyl groups in the side chains of acrylate polymers are also suitable. Among these, polyfunctional (meth)acrylate monomers containing two or more (meth)acryloyl groups in one molecule are particularly preferred. By incorporating a cured product of a polyfunctional (meth)acrylate monomer into the antistatic layer, the hardness of the antistatic layer can be increased, steel wool resistance can be improved, and adhesion can also be improved. Also, polyfunctional (meth)acrylate oligomers or polymers having two or more (meth)acryloyl groups in one molecule can be preferably used. By including a cured product of a polyfunctional (meth)acrylate oligomer or polymer in the antistatic layer, the hardness of the antistatic layer can be increased, and the steel wool resistance can be improved. Furthermore, the bending resistance and adhesion can be improved.

[0085] In this specification, (meth)acryloyl refers to both acryloyl and methacryloyl, and (meth)acrylate refers to both acrylate and methacrylate.

[0086] Specific examples of polyfunctional (meth)acrylate monomers include those described in JP 2019-132930 A. Among them, those having 3 to 6 (meth)acryloyl groups per molecule are preferred because they have high reactivity, increase the hardness of the antistatic layer, and improve steel wool resistance. Examples of such polyfunctional (meth)acrylate monomers that can be preferably used include pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA), trimethylolpropane tri(meth)acrylate, tripentaerythritol octa(meth)acrylate, and tetrapentaerythritol deca(meth)acrylate. Particularly, at least one selected from pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexaacrylate is preferred.

[0087] Furthermore, when a radical polymerizable compound is used, the flexible groups in the molecular structure may reduce the steel wool resistance. Therefore, in order to prevent the reduction in steel wool resistance due to the flexible components (soft segments), it is preferable to use a radical polymerizable compound in which no flexible groups are introduced into the molecular structure. Specifically, it is preferable to use a radical polymerizable compound that is not EO- or PO-modified. The use of such a radical polymerizable compound can increase the number of crosslinking points and improve the steel wool resistance.

[0088] The antistatic layer may contain a monofunctional (meth)acrylate monomer as a radical polymerizable compound in order to adjust hardness and viscosity, improve adhesion, etc. Specific examples of the monofunctional (meth)acrylate monomer include those described in JP-A-2019-132930.

[0089] The cationically polymerizable compound is a compound having a cationically polymerizable group. The cationically polymerizable group of the cationically polymerizable compound is not particularly limited as long as it is a functional group capable of causing a cationic polymerization reaction, and examples thereof include an epoxy group, an oxetanyl group, and a vinyl ether group. When the cationically polymerizable compound has two or more cationically polymerizable groups, these cationically polymerizable groups may be the same or different.

[0090] The number of cationically polymerizable groups that the cationically polymerizable compound has in one molecule is preferably 2 or more, and more preferably 3 or more, from the viewpoint of increasing the hardness of the antistatic layer and improving the steel wool resistance.

[0091] Among the cationically polymerizable compounds, compounds having at least one of an epoxy group and an oxetanyl group as a cationically polymerizable group are preferred, and compounds having two or more of at least one of an epoxy group and an oxetanyl group per molecule are more preferred. Cyclic ether groups such as epoxy groups and oxetanyl groups are preferred because they cause minimal shrinkage during polymerization. Among cyclic ether groups, compounds having an epoxy group are readily available in a variety of structures, do not adversely affect the durability of the resulting antistatic layer, and are advantageous in that their compatibility with radically polymerizable compounds is easily controlled. Among cyclic ether groups, oxetanyl groups have a higher degree of polymerization and lower toxicity than epoxy groups. When the resulting antistatic layer is combined with a compound having an epoxy group, they accelerate the network formation rate from the cationically polymerizable compound in the coating film, forming an independent network without leaving unreacted monomers in the film, even in regions where the radically polymerizable compound coexists.

[0092] Examples of the cationically polymerizable compound having an epoxy group include alicyclic epoxy resins obtained by epoxidizing polyglycidyl ethers of polyhydric alcohols having an alicyclic ring or cyclohexene ring- or cyclopentene ring-containing compounds with a suitable oxidizing agent such as hydrogen peroxide or peracid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts, polyglycidyl esters of aliphatic long-chain polybasic acids, and glycidyl (meth)acrylate homopolymers and copolymers; and glycidyl ether-type epoxy resins derived from bisphenols, such as bisphenol A, bisphenol F, and hydrogenated bisphenol A, or derivatives thereof, such as alkylene oxide adducts or caprolactone adducts, and novolac epoxy resins.

[0093] Specific examples of alicyclic epoxy resins, glycidyl ether epoxy resins, and cationically polymerizable compounds having an oxetanyl group include those described in JP-A-2018-104682.

[0094] In particular, since the antistatic layer preferably has hard coating properties, the resin is preferably a cured product of a polymerizable compound. When the antistatic layer has hard coating properties, the surface of the laminate for a flexible display device on the side of the antistatic layer can be made to satisfy the contact angle with water after the steel wool test described above.

[0095] The antistatic layer may contain a polymerization initiator as needed. The polymerization initiator may be appropriately selected from radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, etc. These polymerization initiators are decomposed by at least one of light irradiation and heating to generate radicals or cations, thereby promoting radical polymerization and cationic polymerization. Note that in some cases, the polymerization initiator may be completely decomposed and not remain in the antistatic layer.

[0096] The antistatic layer preferably contains an antifouling agent, which can impart antifouling properties to the laminate for a flexible display device. When the antistatic layer contains an antifouling agent, the surface of the laminate for a flexible display device on the antistatic layer side can satisfy the above-mentioned contact angle with water.

[0097] The antifouling agent is not particularly limited, and examples thereof include silicone-based antifouling agents, fluorine-based antifouling agents, and silicone-based and fluorine-based antifouling agents. The antifouling agent may also be an acrylic-based antifouling agent. One type of antifouling agent may be used alone, or two or more types may be mixed and used.

[0098] An antistatic layer containing a silicone-based antifouling agent or a fluorine-based antifouling agent is less susceptible to fingerprints (less noticeable) and has good wiping properties. Furthermore, when a silicone-based antifouling agent or a fluorine-based antifouling agent is contained, the surface tension of the antistatic layer composition during application can be reduced, resulting in good leveling properties and a good appearance for the resulting antistatic layer.

[0099] Furthermore, the antistatic layer containing the silicone-based antifouling agent has good slipperiness and good scratch resistance. A flexible display device including a laminate for a flexible display device having an antistatic layer containing such a silicone-based antifouling agent has good slipperiness when touched with a finger, a touch pen, or the like, resulting in a good tactile feel.

[0100] As the antifouling agent, it is preferable to use an antifouling agent having a reactive functional group in order to improve the durability of antifouling performance.That is, it is preferable that the antistatic layer contains a cured product of a resin composition containing the above-mentioned polymerizable compound and an antifouling agent having a reactive functional group.By using an antifouling agent having a reactive functional group, it is possible to maintain antifouling performance even after steel wool test and eraser test, and it is possible to improve steel wool resistance and eraser resistance.

[0101] The number of reactive functional groups in the antifouling agent may be 1 or more, and preferably 2 or more. By using an antifouling agent having 2 or more reactive functional groups, it is possible to improve scratch resistance and abrasion resistance.

[0102] The content of the antifouling agent is not particularly limited as long as it is an amount that can obtain an antistatic layer that satisfies the above-mentioned contact angle with water, and is, for example, preferably 0.01 to 3.0 parts by mass per 100 parts by mass of the resin component. If the content of the antifouling agent is too low, the antistatic layer may not be able to be imparted with sufficient antifouling properties, and if the content of the antifouling agent is too high, the hardness of the antistatic layer may decrease, resulting in a decrease in abrasion resistance.

[0103] The antistatic layer may contain additives, such as inorganic particles, organic particles, ultraviolet absorbers, antioxidants, light stabilizers, antiglare agents, leveling agents, surfactants, lubricants, various sensitizers, flame retardants, adhesion promoters, polymerization inhibitors, and surface modifiers, as needed.

[0104] The thickness of the antistatic layer is not particularly limited as long as it is a thickness that can provide an antistatic layer that satisfies the above-mentioned surface resistance, and is, for example, preferably 0.5 μm to 50 μm, more preferably 1.0 μm to 40 μm, and even more preferably 1.5 μm to 30 μm. If the thickness of the antistatic layer is too thin, sufficient antistatic properties may not be obtained. Furthermore, if the thickness of the antistatic layer is too thick, flexibility may be impaired.

[0105] Here, the thickness of the antistatic layer can be the average value of thicknesses measured at any 10 points on a cross section in the thickness direction of the laminate for a flexible display device observed with a transmission electron microscope (TEM), a scanning electron microscope (SEM), or a scanning transmission electron microscope (STEM). The thicknesses of other layers in the laminate for a flexible display device can be measured in the same manner.

[0106] The antistatic layer may be disposed on one side of the base layer, but it is particularly preferred that the antistatic layer be disposed on the outermost surface of the laminate for a flexible display device, since this makes it easy to make the surface resistance of the surface of the laminate for a flexible display device on the antistatic layer side satisfy the above-mentioned surface resistance.

[0107] The antistatic layer can be formed, for example, by applying a composition for forming an antistatic layer onto a substrate layer.

[0108] 3.Base material layer The substrate layer in the present disclosure is a transparent member that supports the antistatic layer.

[0109] The substrate layer is not particularly limited as long as it has transparency, and examples thereof include a resin substrate and a glass substrate.

[0110] (1) Resin substrate The resin constituting the resin substrate is not particularly limited as long as it can provide a transparent resin substrate, and examples thereof include polyimide resins, polyamide resins, polyester resins, etc. Examples of polyimide resins include polyimide, polyamideimide, polyetherimide, polyesterimide, etc. Examples of polyester resins include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc. Among these, polyimide resins, polyamide resins, or mixtures thereof are preferred because they have flex resistance, excellent hardness, and transparency, and polyimide resins are more preferred.

[0111] The polyimide resin is not particularly limited as long as it can provide a resin substrate having transparency, but among the above, polyimide and polyamideimide are preferably used.

[0112] (a) Polyimide The polyimide is obtained by reacting a tetracarboxylic acid component with a diamine component. The polyimide is not particularly limited as long as it satisfies the above-mentioned average value of tensile storage modulus and has transparency, but for example, in terms of excellent transparency and excellent rigidity, it is preferable that the polyimide has at least one structure selected from the group consisting of structures represented by the following general formula (1) and the following general formula (3).

[0113] [ka]

[0114] In the above general formula (1), R 1 is a tetravalent group which is a tetracarboxylic acid residue, R 2 represents at least one divalent group selected from the group consisting of trans-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4'-diaminodiphenylsulfone residue, 3,4'-diaminodiphenylsulfone residue, and divalent groups represented by the following general formula (2): n represents the number of repeating units and is 1 or more.

[0115] [ka]

[0116] In the above general formula (2), R 3 and R 4 each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.

[0117] [ka]

[0118] In the above general formula (3), R 5represents at least one tetravalent group selected from the group consisting of a cyclohexanetetracarboxylic acid residue, a cyclopentanetetracarboxylic acid residue, a dicyclohexane-3,4,3',4'-tetracarboxylic acid residue, and a 4,4'-(hexafluoroisopropylidene)diphthalic acid residue; R 6 represents a divalent group that is a diamine residue, and n' represents the number of repeating units and is 1 or more.

[0119] The term "tetracarboxylic acid residue" refers to a residue obtained by removing four carboxyl groups from a tetracarboxylic acid, and has the same structure as a residue obtained by removing an acid dianhydride structure from a tetracarboxylic dianhydride. The term "diamine residue" refers to a residue obtained by removing two amino groups from a diamine.

[0120] In the above general formula (1), R 1 is a tetracarboxylic acid residue, and can be a residue obtained by removing the acid dianhydride structure from a tetracarboxylic acid dianhydride. Examples of tetracarboxylic acid dianhydrides include those described in WO 2018 / 070523. R in the above general formula (1) 1 Among these, from the viewpoint of improving transparency and rigidity, it is preferable that the dicarboxylic acid ester contains at least one selected from the group consisting of 4,4'-(hexafluoroisopropylidene)diphthalic acid residue, 3,3',4,4'-biphenyltetracarboxylic acid residue, pyromellitic acid residue, 2,3',3,4'-biphenyltetracarboxylic acid residue, 3,3',4,4'-benzophenonetetracarboxylic acid residue, 3,3',4,4'-diphenylsulfonetetracarboxylic acid residue, 4,4'-oxydiphthalic acid residue, cyclohexanetetracarboxylic acid residue, and cyclopentanetetracarboxylic acid residue, and it is further preferable that the dicarboxylic acid ester contains at least one selected from the group consisting of 4,4'-(hexafluoroisopropylidene)diphthalic acid residue, 4,4'-oxydiphthalic acid residue, and 3,3',4,4'-diphenylsulfonetetracarboxylic acid residue.

[0121] R 1In the formula (I), the total content of these suitable residues is preferably 50 mol % or more, more preferably 70 mol % or more, and even more preferably 90 mol % or more.

[0122] Also, R 1 It is also preferable to use a mixture of a group of tetracarboxylic acid residues (Group A) suitable for improving rigidity, such as at least one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic acid residues, 3,3',4,4'-benzophenonetetracarboxylic acid residues, and pyromellitic acid residues, and a group of tetracarboxylic acid residues (Group B) suitable for improving transparency, such as at least one selected from the group consisting of 4,4'-(hexafluoroisopropylidene)diphthalic acid residues, 2,3',3,4'-biphenyltetracarboxylic acid residues, 3,3',4,4'-diphenylsulfonetetracarboxylic acid residues, 4,4'-oxydiphthalic acid residues, cyclohexanetetracarboxylic acid residues, and cyclopentanetetracarboxylic acid residues.

[0123] In this case, the content ratio of the tetracarboxylic acid residue group (Group A) suitable for improving the rigidity to the tetracarboxylic acid residue group (Group B) suitable for improving the transparency is preferably 0.05 to 9 moles, more preferably 0.1 to 5 moles, and even more preferably 0.3 to 4 moles, of the tetracarboxylic acid residue group (Group A) suitable for improving the rigidity per mole of the tetracarboxylic acid residue group (Group B) suitable for improving the transparency.

[0124] R in the above general formula (1) 2 Among them, from the viewpoint of improving transparency and rigidity, it is preferable that the divalent group is at least one selected from the group consisting of a 4,4'-diaminodiphenyl sulfone residue, a 3,4'-diaminodiphenyl sulfone residue, and a divalent group represented by the above general formula (2), and further, it is preferable that the divalent group is at least one selected from the group consisting of a 4,4'-diaminodiphenyl sulfone residue, a 3,4'-diaminodiphenyl sulfone residue, and a divalent group represented by the above general formula (2). 3 and R4 is preferably at least one divalent group selected from the group consisting of divalent groups represented by the above general formula (2), which is a perfluoroalkyl group.

[0125] R in the above general formula (3) 5 Among these, those containing 4,4'-(hexafluoroisopropylidene)diphthalic acid residue, 3,3',4,4'-diphenylsulfonetetracarboxylic acid residue, and oxydiphthalic acid residue are preferred, as they improve transparency and rigidity.

[0126] R 5 In the above, these suitable residues are preferably contained in an amount of 50 mol % or more, more preferably 70 mol % or more, and even more preferably 90 mol % or more.

[0127] R in the above general formula (3) 6 is a diamine residue, and can be a residue obtained by removing two amino groups from a diamine. Examples of diamines include those described in WO 2018 / 070523. R in the above general formula (3) 6Among these, from the viewpoint of improving transparency and rigidity, 2,2'-bis(trifluoromethyl)benzidine residue, bis[4-(4-aminophenoxy)phenyl]sulfone residue, 4,4'-diaminodiphenyl sulfone residue, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane residue, bis[4-(3-aminophenoxy)phenyl]sulfone residue, 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether residue, 1,4-bis[4-amino-2-(trifluoromethyl)phenoxy]benzene residue, 2,2-bis[4-(4-amino-2-trifluoromethylphenyl) It is preferable that the alkyl group contains at least one divalent group selected from the group consisting of a 2,2'-bis(trifluoromethyl)benzidine residue, a bis[4-(4-aminophenoxy)phenyl]hexafluoropropane residue, a 4,4'-diamino-2-(trifluoromethyl)diphenyl ether residue, a 4,4'-diaminobenzanilide residue, an N,N'-bis(4-aminophenyl)terephthalamide residue, and a 9,9-bis(4-aminophenyl)fluorene residue, and it is further preferable that the alkyl group contains at least one divalent group selected from the group consisting of a 2,2'-bis(trifluoromethyl)benzidine residue, a bis[4-(4-aminophenoxy)phenyl]sulfone residue, and a 4,4'-diaminodiphenyl sulfone residue.

[0128] R 6 In the formula (I), the total content of these suitable residues is preferably 50 mol % or more, more preferably 70 mol % or more, and even more preferably 90 mol % or more.

[0129] Also, R 6and a diamine residue group (Group C) suitable for improving rigidity, such as at least one selected from the group consisting of bis[4-(4-aminophenoxy)phenyl]sulfone residue, 4,4'-diaminobenzanilide residue, N,N'-bis(4-aminophenyl)terephthalamide residue, paraphenylenediamine residue, metaphenylenediamine residue, and 4,4'-diaminodiphenylmethane residue; and a diamine residue group (Group C) suitable for improving rigidity, such as at least one selected from the group consisting of 2,2'-bis(trifluoromethyl)benzidine residue, 4,4'-diaminodiphenylsulfone residue, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane residue, bis[4-(3-aminophenoxy)phenyl]sulfone residue, It is also preferred to use a mixture of diamine residues (Group D) suitable for improving transparency, such as at least one selected from the group consisting of 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether residue, 1,4-bis[4-amino-2-(trifluoromethyl)phenoxy]phenyl]sulfone residue, 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether residue, 1,4-bis[4-amino-2-(trifluoromethyl)phenoxy]benzene residue, 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane residue, 4,4'-diamino-2-(trifluoromethyl)diphenyl ether residue, and 9,9-bis(4-aminophenyl)fluorene residue.

[0130] In this case, the content ratio of the diamine residue group suitable for improving rigidity (Group C) to the diamine residue group suitable for improving transparency (Group D) is preferably 0.05 to 9 moles, more preferably 0.1 to 5 moles, and even more preferably 0.3 to 4 moles, of the diamine residue group suitable for improving rigidity (Group C) per 1 mole of the diamine residue group suitable for improving transparency (Group D).

[0131] In the structures represented by the general formula (1) and the general formula (3), n and n' each independently represent the number of repeating units and are 1 or more. The number of repeating units n in the polyimide is not particularly limited and may be appropriately selected depending on the structure. The average number of repeating units can be, for example, 10 or more and 2000 or less, and preferably 15 or more and 1000 or less.

[0132] The polyimide may partially contain a polyamide structure, such as a polyamideimide structure containing a tricarboxylic acid residue such as trimellitic anhydride, or a polyamide structure containing a dicarboxylic acid residue such as terephthalic acid.

[0133] In order to improve transparency and surface hardness, R 1 or R 5 a tetravalent group which is a tetracarboxylic acid residue, and R 2 or R 6Preferably, at least one of the divalent groups, which are diamine residues, contains an aromatic ring and at least one selected from the group consisting of (i) a fluorine atom, (ii) an aliphatic ring, and (iii) a structure in which aromatic rings are linked together by a sulfonyl group or an alkylene group optionally substituted with fluorine. When a polyimide contains at least one selected from a tetracarboxylic acid residue having an aromatic ring and a diamine residue having an aromatic ring, the molecular skeleton becomes rigid, improving orientation and surface hardness. However, the rigid aromatic ring skeleton tends to extend the absorption wavelength toward longer wavelengths, resulting in reduced transmittance in the visible light region. On the other hand, when a polyimide contains (i) a fluorine atom, the electronic state within the polyimide skeleton is made less susceptible to charge transfer, thereby improving transparency. Furthermore, when a polyimide contains (ii) an aliphatic ring, the conjugation of π electrons within the polyimide skeleton is broken, thereby inhibiting charge transfer within the skeleton, thereby improving transparency. Furthermore, when the polyimide contains (iii) a structure in which aromatic rings are linked together by a sulfonyl group or an alkylene group which may be substituted with fluorine, the conjugation of π electrons in the polyimide skeleton can be broken, thereby inhibiting the movement of charges within the skeleton, thereby improving transparency.

[0134] Among them, R is the most popular because it improves transparency and surface hardness. 1 or R 5 a tetravalent group which is a tetracarboxylic acid residue, and R 2 or R 6 At least one of the divalent groups which are diamine residues preferably contains an aromatic ring and a fluorine atom, and R 2 or R 6 The divalent group which is the diamine residue preferably contains an aromatic ring and a fluorine atom.

[0135] Specific examples of such polyimides include those having a specific structure described in WO 2018 / 070523.

[0136] The polyimide can be synthesized by a known method. Alternatively, commercially available polyimides may be used. Examples of commercially available polyimides include Neoprim (registered trademark) manufactured by Mitsubishi Gas Chemical Company, Inc.

[0137] The weight-average molecular weight of the polyimide is, for example, preferably from 3,000 to 500,000, more preferably from 5,000 to 300,000, and even more preferably from 10,000 to 200,000. If the weight-average molecular weight is too small, sufficient strength may not be obtained, whereas if the weight-average molecular weight is too large, viscosity increases and solubility decreases, making it impossible to obtain a substrate layer with a smooth surface and uniform thickness.

[0138] The weight-average molecular weight of polyimide can be measured by gel permeation chromatography (GPC). Specifically, polyimide is dissolved in N-methylpyrrolidone (NMP) at a concentration of 0.1% by mass, and the developing solvent is a 30 mmol% LiBr-NMP solution with a water content of 500 ppm or less. Measurement is performed using a Tosoh GPC system (HLC-8120, column: SHODEX GPC LF-804) with a sample load of 50 μL, a solvent flow rate of 0.4 mL / min, and a temperature of 37°C. The weight-average molecular weight is determined based on a polystyrene standard sample of the same concentration as the sample.

[0139] (b) Polyamide-imide The polyamideimide is not particularly limited as long as it can produce a transparent resin substrate. For example, it may have a first block containing structural units derived from a dianhydride and structural units derived from a diamine, and a second block containing structural units derived from an aromatic dicarbonyl compound and structural units derived from an aromatic diamine. In the polyamideimide, the dianhydride may include, for example, biphenyltetracarboxylic dianhydride (BPDA) and 2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA). The diamine may include bistrifluoromethylbenzidine (TFDB). That is, the polyamideimide has a structure obtained by imidizing a polyamideimide precursor having a first block copolymerized with a monomer containing a dianhydride and a diamine, and a second block copolymerized with a monomer containing an aromatic dicarbonyl compound and an aromatic diamine. The polyamideimide has excellent optical properties as well as thermal and mechanical properties due to the first block containing an imide bond and a second block containing an amide bond. In particular, the use of bistrifluoromethylbenzidine (TFDB) as the diamine forming the first block can improve thermal stability and optical properties, while the use of 2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and biphenyltetracarboxylic dianhydride (BPDA) as the dianhydrides forming the first block can improve birefringence and ensure heat resistance.

[0140] The dianhydrides forming the first block include two types of dianhydrides, i.e., 6FDA and BPDA. The first block may contain a polymer bound to TFDB and 6FDA and a polymer bound to TFDB and BPDA, separated by separate repeating units, or may be arranged regularly or completely randomly within the same repeating unit.

[0141] Among the monomers forming the first block, it is preferable that BPDA and 6FDA are contained as dianhydrides in a molar ratio of 1:3 to 3:1, because this not only ensures optical properties but also prevents deterioration of mechanical properties and heat resistance, and allows for excellent birefringence.

[0142] The molar ratio of the first block to the second block is preferably 5:1 to 1:1. If the content of the second block is significantly low, the effect of the second block in improving thermal stability and mechanical properties may not be fully achieved. If the content of the second block is much higher than the content of the first block, although the thermal stability and mechanical properties may be improved, the optical properties may deteriorate, such as a decrease in yellowness and transmittance, and the birefringence properties may also increase. The first block and the second block may be a random copolymer or a block copolymer. The repeating unit of the block is not particularly limited.

[0143] Examples of the aromatic dicarbonyl compound forming the second block include one or more compounds selected from the group consisting of p-terephthaloyl chloride (TPC), terephthalic acid, isophthaloyl dichloride, and 4,4'-benzoyl chloride. Preferably, the aromatic dicarbonyl compound is one or more compounds selected from p-terephthaloyl chloride (TPC) and isophthaloyl dichloride.

[0144] Examples of diamines that form the second block include 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane (HFBAPP), bis(4-(4-aminophenoxy)phenyl)sulfone (BAPS), bis(4-(3-aminophenoxy)phenyl)sulfone (BAPSM), 4,4'-diaminodiphenylsulfone (4DDS), 3,3'-diaminodiphenylsulfone (3DDS), 2,2-bis(4-(4-aminophenoxy)phenylpropane (BAPP), 4,4'-diaminodiphenylpropane (6HDA), 1,3-bis(4-aminophenoxy)benzene (134APB), 1, Examples of diamines having one or more flexible groups include 3-bis(3-aminophenoxy)benzene (133APB), 1,4-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl (6FAPBP), 3,3-diamino-4,4-dihydroxydiphenyl sulfone (DABS), 2,2-bis(3-amino-4-hydroxyloxyphenyl)propane (BAP), 4,4'-diaminodiphenylmethane (DDM), 4,4'-oxydianiline (4-ODA), and 3,3'-oxydianiline (3-ODA).

[0145] Although aromatic dicarbonyl compounds can easily achieve high thermal stability and mechanical properties, they can also exhibit high birefringence due to the benzene rings in their molecular structure. Therefore, to prevent the birefringence from decreasing due to the second block, it is preferable to use diamines with flexible groups incorporated into their molecular structure. Specifically, the diamine is preferably one or more diamines selected from bis(4-(3-aminophenoxy)phenyl)sulfone (BAPSM), 4,4'-diaminodiphenylsulfone (4DDS), and 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane (HFBAPP). In particular, diamines with long flexible groups and meta-positioned substituents, such as BAPSM, can exhibit excellent birefringence.

[0146] A polyamideimide precursor having, in its molecular structure, a first block obtained by copolymerizing a dianhydride containing biphenyltetracarboxylic dianhydride (BPDA) and 2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) with a diamine containing bistrifluoromethylbenzidine (TFDB), and a second block obtained by copolymerizing an aromatic dicarbonyl compound with an aromatic diamine, preferably has a weight average molecular weight measured by GPC of, for example, 200,000 or more and 215,000 or less, and a viscosity of, for example, 2400 poise or more and 2600 poise or less.

[0147] Polyamideimide can be obtained by imidizing a polyamideimide precursor. Furthermore, a polyamideimide film can be obtained using the polyamideimide. For a method for imidizing a polyamideimide precursor and a method for producing a polyamideimide film, see, for example, JP-A-2018-506611.

[0148] (2) Glass substrate The glass constituting the glass substrate is not particularly limited as long as it has transparency, and examples thereof include silicate glass, silica glass, etc. Among them, borosilicate glass, aluminosilicate glass, and aluminoborosilicate glass are preferred, and alkali-free glass is more preferred. Examples of commercially available glass substrates include ultra-thin glass G-Leaf from Nippon Electric Glass Co., Ltd. and ultra-thin glass from Matsunami Glass Industry Co., Ltd.

[0149] The glass constituting the glass substrate is also preferably chemically strengthened glass. Chemically strengthened glass is preferable because it has excellent mechanical strength and can be made thinner accordingly. Chemically strengthened glass is typically glass whose mechanical properties have been strengthened by a chemical method by partially exchanging ion species, such as replacing sodium with potassium, near the surface of the glass, and has a compressive stress layer on the surface.

[0150] Examples of glasses that can be used to form chemically strengthened glass substrates include aluminosilicate glass, soda-lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborosilicate glass.

[0151] Examples of commercially available chemically strengthened glass substrates include Gorilla Glass from Corning and Dragontrail from AGC.

[0152] Among the above, the substrate layer is preferably a polyimide resin substrate containing a polyimide resin or a glass substrate, because it can provide a substrate layer having bending resistance, excellent hardness, and transparency.

[0153] (3) Structure of the base layer The thickness of the base material layer is not particularly limited as long as it is thick enough to provide flexibility, and may be appropriately selected depending on the type of base material layer, etc.

[0154] The thickness of the resin substrate is, for example, preferably 10 μm or more and 100 μm or less, and more preferably 25 μm or more and 80 μm or less. When the thickness of the resin substrate is within the above range, good flexibility can be obtained and sufficient hardness can be obtained. In addition, curling of the laminate for a flexible display device can be suppressed. Furthermore, it is preferable in terms of reducing the weight of the laminate for a flexible display device.

[0155] The thickness of the glass substrate is, for example, preferably 200 μm or less, more preferably 15 μm or more and 100 μm or less, even more preferably 20 μm or more and 90 μm or less, and particularly preferably 25 μm or more and 80 μm or less. When the thickness of the glass substrate is within the above range, good flexibility can be obtained and sufficient hardness can be obtained. Furthermore, curling of the laminate for a flexible display device can also be suppressed. Furthermore, this is preferable in terms of reducing the weight of the laminate for a flexible display device.

[0156] 4. Functional Layer The laminate for a flexible display device according to the present disclosure may have a functional layer on the surface of the antistatic layer of the base layer, such as a hard coat layer, an antireflection layer, an antiglare layer, a shatterproof layer, an antifouling layer, or a primer layer.

[0157] The functional layer may be a single layer or may have multiple layers, and may be a layer having a single function or may have multiple layers having different functions.

[0158] The arrangement of the functional layer is not particularly limited as long as the functional layer is arranged on the surface of the antistatic layer of the base layer. For example, the functional layer may be arranged between the base layer and the antistatic layer, or may be arranged on the surface of the antistatic layer opposite the base layer.

[0159] Hereinafter, a hard coat layer will be exemplified as a functional layer.

[0160] (1) Hard Coat Layer The laminate for a flexible display device according to the present disclosure may have a hard coat layer on the surface of the antistatic layer of the substrate layer. The hard coat layer is a component for increasing surface hardness. The provision of the hard coat layer can improve scratch resistance. In particular, when the substrate layer is a resin substrate, the provision of the hard coat layer can effectively improve scratch resistance. Furthermore, when the hard coat layer is provided, the surface of the laminate for a flexible display device on the antistatic layer side can satisfy the contact angle with water after the steel wool test described above.

[0161] The arrangement of the hard coat layer is not particularly limited as long as it is arranged on the antistatic layer side of the substrate layer. For example, although not shown, the hard coat layer may be arranged between the substrate layer and the antistatic layer, or as shown in FIG. 4, the hard coat layer 4 may be arranged on the surface of the antistatic layer 3 opposite to the substrate layer 2.

[0162] As the material for the hard coat layer, for example, an organic material, an inorganic material, an organic-inorganic composite material, or the like can be used.

[0163] In particular, the material of the hard coat layer is preferably an organic material. Specifically, the hard coat layer preferably contains a cured product of a resin composition containing a polymerizable compound. The cured product of the resin composition containing a polymerizable compound can be obtained by polymerizing the polymerizable compound using a polymerization initiator as needed by a known method.

[0164] The polymerizable compound can be the same as that described in the section on the antistatic layer, and therefore, a description thereof will be omitted here.

[0165] The hard coat layer may contain a polymerization initiator as needed. Note that the polymerization initiator may be the same as that described above in the section on the antistatic layer, and therefore, a description thereof will be omitted here.

[0166] The hard coat layer may further contain additives as necessary. The additives are appropriately selected depending on the function to be imparted to the hard coat layer and are not particularly limited, and examples thereof include inorganic particles, organic particles, ultraviolet absorbers, infrared absorbers, antifouling agents, antiglare agents, antistatic agents, leveling agents, surfactants, lubricants, various sensitizers, flame retardants, adhesion promoters, polymerization inhibitors, antioxidants, light stabilizers, and surface modifiers.

[0167] The thickness of the hard coat layer may be appropriately selected depending on the function of the hard coat layer and the application of the laminate for a flexible display device. The thickness of the hard coat layer is, for example, preferably 0.5 μm to 50 μm, more preferably 1.0 μm to 40 μm, even more preferably 1.5 μm to 30 μm, and particularly preferably 2 μm to 20 μm. If the thickness of the hard coat layer is within the above range, sufficient hardness as a hard coat layer can be obtained.

[0168] The hard coat layer can be formed, for example, by applying a composition for hard coat layer containing the polymerizable compound and the like onto the base layer or the antistatic layer, followed by curing.

[0169] 5. Shock absorbing layer The laminate for a flexible display device according to the present disclosure may have an impact absorbing layer on the surface of the substrate layer opposite the antistatic layer, or between the substrate layer and the antistatic layer. The impact absorbing layer can absorb impacts applied to the laminate for a flexible display device, improving impact resistance. Furthermore, when the substrate layer is a glass substrate, cracking of the glass substrate can be suppressed.

[0170] The material for the impact absorbing layer is not particularly limited as long as it can provide an impact absorbing layer having impact absorption properties and transparency, and examples thereof include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), urethane resin, epoxy resin, polyimide, polyamideimide, acrylic resin, triacetyl cellulose (TAC), silicone resin, etc. These materials may be used alone or in combination of two or more.

[0171] The impact absorbing layer may further contain additives as needed, such as inorganic particles, organic particles, ultraviolet absorbers, antioxidants, light stabilizers, surfactants, and adhesion improvers.

[0172] The thickness of the impact absorbing layer may be any thickness that is capable of absorbing impact, and may be, for example, preferably from 1 μm to 150 μm, more preferably from 10 μm to 120 μm, and even more preferably from 15 μm to 100 μm.

[0173] The impact absorbing layer may be, for example, a resin film. Alternatively, the impact absorbing layer may be formed by applying a composition for an impact absorbing layer onto the substrate layer.

[0174] 6. Adhesive layer for application 5, the laminate for a flexible display device according to the present disclosure can have an adhesive layer 6 for attachment on the surface of the base layer 2 opposite to the antistatic layer 3. The laminate for a flexible display device can be attached to, for example, a display panel via the adhesive layer for attachment.

[0175] The adhesive used in the attachment adhesive layer is not particularly limited as long as it is transparent and capable of adhering the flexible 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).

[0176] 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 selected appropriately depending on the material of the impact absorbing layer. Among these, acrylic adhesives are preferred because they are excellent in transparency, weather resistance, durability, and heat resistance, and are low in cost.

[0177] The thickness of the attachment adhesive layer is, for example, preferably 10 μm or more and 100 μm or less, more preferably 25 μm or more and 80 μm or less, and even more preferably 40 μm or more and 60 μm or less. If the attachment adhesive layer is too thin, it may not be possible to sufficiently bond the laminate for a flexible display device to a display panel or the like. Furthermore, if the attachment adhesive layer is a pressure-sensitive adhesive layer, if the attachment adhesive layer is too thin, it may not be possible to sufficiently achieve the effect of facilitating deformation of the shock-absorbing layer when an impact is applied to the laminate for a flexible display device. On the other hand, if the attachment adhesive layer is too thick, flexibility may be impaired.

[0178] The adhesive layer for application may be, for example, an adhesive film. Alternatively, the adhesive layer for application may be formed by applying an adhesive composition onto a support or a base layer.

[0179] 7.Interlayer adhesive layer In the laminate for a flexible display device according to the present disclosure, an interlayer adhesive layer may be disposed between each layer.

[0180] The adhesive used in the interlayer adhesive layer can be the same as the adhesive used in the attachment adhesive layer.

[0181] In particular, as described above, when an impact absorbing layer is arranged on the side of the base layer opposite the antistatic layer, an attachment adhesive layer is arranged on the side of the impact absorbing layer opposite the base layer, and an interlayer adhesive layer is arranged between the base layer and the impact absorbing layer, it is preferable that the attachment adhesive layer and the interlayer adhesive layer contain a pressure-sensitive adhesive, that is, they are preferably pressure-sensitive adhesive layers.

[0182] The pressure-sensitive adhesive layer may be the same as the pressure-sensitive adhesive layer used for the adhesive layer for attachment.

[0183] The thickness, formation method, etc. of the interlayer adhesive layer may be the same as the thickness, formation method, etc. of the adhesive layer for attachment.

[0184] 8. Uses of laminates for flexible displays The laminate for a flexible display device according to the present disclosure can be used as a front panel in a flexible display device that is disposed closer to the viewer than the display panel. Specifically, the laminate for a flexible display device according to the present disclosure can be used as a front panel in a flexible display device such as a foldable display, a rollable display, or a bendable display. In particular, the laminate for a flexible display device according to the present disclosure can improve abrasion resistance at a bending portion, and therefore can be suitably used as a front panel in a foldable display.

[0185] Furthermore, the laminate for a flexible display device according to the present disclosure can be used for the front panel of a display device such as a smartphone, a tablet terminal, a wearable terminal, a personal computer, a television, a digital signage, a public information display (PID), or an in-vehicle display.

[0186] B. Laminate for display device A laminate for a display device according to the present disclosure is a laminate for a display device having a base layer and an antistatic layer, wherein a contact angle with water on a surface of the laminate for a display device on the antistatic layer side is 100° or more, a ratio of a contact angle with water after a steel wool test in which the surface of the laminate for a display device on the antistatic layer side is conducted, the surface being rubbed back and forth 2500 times with #0000 steel wool under a load of 9.8 N, to an initial contact angle with water on the surface of the laminate for a display device on the antistatic layer side, is 0.6 or more, and a surface resistance of the surface of the laminate for a display device on the antistatic layer side is 9×10 13 Ω / □ or less, and after an eraser test is performed in which the surface of the laminate for a display device on the side of the antistatic layer is rubbed back and forth 2500 times with an eraser having a diameter of 6 mm and a load of 9.8 N, the surface resistance of the surface of the laminate for a display device on the side of the antistatic layer is 9×10 13 It is Ω / □ or less.

[0187] The details of the laminate for a display device according to the present disclosure can be the same as those of the laminate for a flexible display device described above, and therefore, description thereof will be omitted here.

[0188] C. Flexible Display Devices A flexible display device according to the present disclosure includes a display panel and the above-described laminate for a flexible display device, which is disposed on the viewer side of the display panel.

[0189] Fig. 6 is a schematic cross-sectional view showing an example of a flexible display device according to the present disclosure. As shown in Fig. 6, a flexible display device 20 includes a display panel 21 and a laminate 1 for a flexible display device arranged on the viewer side of the display panel 21. In the flexible display device 20, the laminate 1 for a flexible display device and the display panel 21 can be bonded together via, for example, an adhesive layer 6 for attachment of the laminate 1 for a flexible display device.

[0190] When the laminate for a flexible display device according to the present disclosure is disposed on the surface of a flexible display device, it is disposed so that the antistatic layer is on the outside and the base layer is on the inside.

[0191] The method for disposing the laminate for a flexible display device according to the present disclosure on the surface of the flexible display device is not particularly limited, but examples thereof include a method using an adhesive layer.

[0192] Examples of the display panel in the present disclosure include display panels used in flexible display devices such as organic EL display devices and liquid crystal display devices.

[0193] The flexible display device of the present disclosure may have a touch panel member between the display panel and the laminate for a flexible display device.

[0194] The flexible EL display device of the present disclosure is preferably foldable. That is, the flexible display device of the present disclosure is preferably a foldable display. The flexible display device of the present disclosure has excellent abrasion resistance at the bending portion and is suitable as a foldable display.

[0195] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0196] The present disclosure will be further described below with reference to examples and comparative examples.

[0197] [Example 1] First, the components were blended to obtain the composition shown below to obtain a composition 1 for antistatic layer.

[0198] (Composition of Antistatic Layer Composition 1) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (PEDOT-containing photocurable resin composition, product name "Beamset MT-2", manufactured by Arakawa Chemical Industries, Ltd.): 5 parts by mass (based on 100% solids) Methyl isobutyl ketone: 250 parts by weight

[0199] Next, a 50 μm thick polyimide resin substrate (product name "Neoprim", manufactured by Mitsubishi Gas Chemical Company, Inc.) was prepared as a substrate layer, and the antistatic layer composition 1 was applied to the substrate using a bar coater to form a coating film. The coating film was then heated at 70°C for 1 minute to evaporate the solvent in the coating film, and ultraviolet light was applied to the substrate using an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan, light source H bulb) at an oxygen concentration of 200 ppm or less with an integrated light intensity of 380 mJ / cm. 2 The coating was cured by irradiating the coating with light so that an antistatic layer having a thickness of 10 μm was formed. In this way, a laminate having a base layer and an antistatic layer was obtained.

[0200] [Example 2] A laminate was produced in the same manner as in Example 1, except that the following composition 2 for antistatic layer was used.

[0201] (Composition of Antistatic Layer Composition 2) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (lithium salt-containing photocurable resin composition, product name "Beamset 1604", manufactured by Arakawa Industries Co., Ltd.): 100 parts by mass (based on 100% solids) Methyl isobutyl ketone: 240 parts by weight

[0202] [Example 3] A laminate was produced in the same manner as in Example 1, except that the following composition 3 for antistatic layer was used.

[0203] (Composition of Antistatic Layer Composition 3) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (quaternary ammonium salt-containing polymeric antistatic agent, product name "1SX-1090", manufactured by Taisei Fine Chemical Co., Ltd.): 20 parts by weight (based on 100% solids) Methyl isobutyl ketone: 290 parts by weight

[0204] [Example 4] A laminate was produced in the same manner as in Example 1, except that the following composition 4 for antistatic layer was used.

[0205] (Composition of Antistatic Layer Composition 4) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (PEDOT-containing photocurable resin composition, product name "Beamset MT-2", manufactured by Arakawa Chemical Industries, Ltd.): 4 parts by mass (based on 100% solids) Methyl isobutyl ketone: 250 parts by weight

[0206] [Example 5] A laminate was produced in the same manner as in Example 1, except that the following composition 5 for antistatic layer was used.

[0207] (Composition of Antistatic Layer Composition 5) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (lithium salt-containing photocurable resin composition, product name "Beamset 1604", manufactured by Arakawa Industries Co., Ltd.): 75 parts by mass (based on 100% solids) Methyl isobutyl ketone: 240 parts by weight

[0208] [Example 6] A laminate was produced in the same manner as in Example 1, except that the following composition 6 for antistatic layer was used.

[0209] (Composition of Antistatic Layer Composition 6) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (quaternary ammonium salt-containing polymeric antistatic agent, product name "1SX-1090", manufactured by Taisei Fine Chemical Co., Ltd.): 10 parts by mass (based on 100% solids) Methyl isobutyl ketone: 290 parts by weight

[0210] [Example 7] A laminate was produced in the same manner as in Example 1, except that the following composition 7 for antistatic layer was used.

[0211] (Composition of Antistatic Layer Composition 7) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (quaternary ammonium salt-containing polymeric antistatic agent, product name "1SX-1090", manufactured by Taisei Fine Chemical Co., Ltd.): 25 parts by weight (based on 100% solids) Methyl isobutyl ketone: 290 parts by weight

[0212] [Example 8] A laminate was produced in the same manner as in Example 1, except that the following composition 8 for antistatic layer was used.

[0213] (Composition of Antistatic Layer Composition 8) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (ATO particle dispersion, product name "ELECOM V-3560", manufactured by JGC Catalysts and Chemicals Co., Ltd.): 15 parts by mass (based on 100% solids) Methyl isobutyl ketone: 280 parts by weight

[0214] [Comparative Example 1] A laminate was produced in the same manner as in Example 1, except that the following composition 9 for antistatic layer was used.

[0215] (Composition of Antistatic Layer Composition 9) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (PEDOT-containing photocurable resin composition, product name "Beamset MT-2", manufactured by Arakawa Chemical Industries, Ltd.): 2.5 parts by mass (based on 100% solids) Methyl isobutyl ketone: 250 parts by weight

[0216] Comparative Example 2 A laminate was produced in the same manner as in Example 1, except that the following composition 10 for antistatic layer was used.

[0217] (Composition of Antistatic Layer Composition 10) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (lithium salt-containing photocurable resin composition, product name "Beamset 1604", manufactured by Arakawa Industries Co., Ltd.): 30 parts by mass (based on 100% solids) Methyl isobutyl ketone: 240 parts by weight

[0218] Comparative Example 3 A laminate was produced in the same manner as in Example 1, except that the following composition 11 for antistatic layer was used.

[0219] (Composition of Antistatic Layer Composition 11) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (quaternary ammonium salt-containing polymeric antistatic agent, product name "1SX-1090", manufactured by Taisei Fine Chemical Co., Ltd.): 4 parts by mass (based on 100% solids) Methyl isobutyl ketone: 290 parts by weight

[0220] Comparative Example 4 A laminate was produced in the same manner as in Example 1, except that the following composition 12 for antistatic layer was used.

[0221] (Composition of Antistatic Layer Composition 12) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Antistatic agent (ATO particle dispersion, product name "ELECOM V-3560", manufactured by JGC Catalysts and Chemicals Co., Ltd.): 10 parts by mass (based on 100% solids) Methyl isobutyl ketone: 280 parts by weight

[0222] Comparative Example 5 A laminate was produced in the same manner as in Example 1, except that the following composition 13 for antistatic layer was used.

[0223] (Composition of Antistatic Layer Composition 13) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3510", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Methyl isobutyl ketone: 240 parts by weight

[0224] Comparative Example 6 A laminate was produced in the same manner as in Example 1, except that the following composition 14 for antistatic layer was used.

[0225] (Composition of Antistatic Layer Composition 14) Urethane acrylate (product name "UV-7650B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Methyl isobutyl ketone: 240 parts by weight

[0226] Comparative Example 7 A laminate was produced in the same manner as in Example 1, except that the following composition 15 for antistatic layer was used.

[0227] (Composition of Antistatic Layer Composition 15) Urethane acrylate (product name "UV-7600B", manufactured by Mitsubishi Chemical Corporation): 100 parts by weight (based on 100% solids) Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad184", manufactured by IGM Resins BV): 4 parts by mass Antifouling agent (product name "BYK-UV3500", manufactured by BYK Japan Co., Ltd.): 0.5 parts by mass (based on 100% solids) Methyl isobutyl ketone: 240 parts by weight

[0228] [evaluation] (1) Contact angle with water before and after steel wool test The contact angle (initial value) with water on the antistatic layer side of the laminates of Examples and Comparative Examples was measured. Specifically, according to the sessile drop method in accordance with JIS R3257:1999, 2 μL of water was dropped onto the antistatic layer side of the laminate at 25° C. using a microscope contact angle meter (DropMaster 300 manufactured by Kyowa Interface Science Co., Ltd.), and the contact angle was measured at 10 points immediately after the drop, and the arithmetic mean value was taken as the contact angle (initial value) with water on the antistatic layer side of the laminate.

[0229] The antistatic layer side of each of the laminates of the examples and comparative examples was subjected to the steel wool test described below, and the contact angle with water on the antistatic layer side of each of the laminates after the steel wool test was measured in the same manner as described above.

[0230] In the steel wool test, a 5 cm × 10 cm laminate was first prepared. The laminate was fixed to a glass plate with Nichiban Cellotape (registered trademark) to prevent folds or wrinkles, and then rubbed with #0000 steel wool (Bonstar #0000, manufactured by Nippon Steel Wool Co., Ltd.) attached to a 2 cm × 2 cm jig, at a speed of 140 mm / s and a distance of 70 mm, 2500 times with a load of 9.8 N.

[0231] The ratio of the water contact angle before and after the steel wool test was calculated using the following formula, where A is the contact angle (initial value) of the surface of the laminate facing the antistatic layer, and B is the contact angle of the surface of the laminate facing the antistatic layer after the steel wool test. Ratio of contact angle with water = B / A

[0232] (2) Slipperiness before and after steel wool test The antistatic layer side of the laminates of the Examples and Comparative Examples was subjected to the steel wool test, and the slipperiness of the antistatic layer side of the laminates before and after the steel wool test was evaluated. Specifically, the antistatic layer side of the laminates was rubbed with a fingertip at a moving speed of 10 cm / sec over the non-steel wool test area, the steel wool test area, and the non-steel wool test area in this order, and the slipperiness of the steel wool test area was evaluated according to the following criteria. A: More than 7 out of 10 people did not feel any discomfort. B: 5 or 6 out of 10 people did not feel any resistance C: 6 or 7 out of 10 people felt a sense of discomfort D: More than 8 out of 10 people felt a sense of discomfort.

[0233] (3) Surface resistance before and after the eraser test The following eraser test was carried out on the surface of the antistatic layer of each of the laminates of the Examples and Comparative Examples, and the surface resistance of the surface of the antistatic layer of each of the laminates was measured before and after the eraser test.

[0234] For the eraser test, a 15 cm × 10 cm laminate was prepared. The eraser test was then performed on the antistatic layer side of the laminate. Specifically, a 6 mm diameter Minoan eraser was inserted into a jig with a 6 mm diameter hole so that 4 mm of the eraser tip was exposed. This jig with the eraser attached was attached to a Gakushin-type friction and friction tester (product name "AB-301," manufactured by Tester Sangyo Co., Ltd.), and the antistatic layer side of the laminate was rubbed back and forth 2,500 times with the eraser at a load of 9.8 N, a movement speed of 80 mm / s, and a movement distance of 40 mm.

[0235] Next, the surface resistance was measured for the eraser test area and the non-eraser test area on the antistatic layer side of the laminate. The surface resistance was measured after leaving the laminate in an environment of 23±2°C temperature and 50±10% humidity for 1 hour. The surface resistance was measured using a resistivity meter (Mitsubishi Chemical Analytech Co., Ltd., Hiresta UX MCP-HT model), with an MCP-HTO14 URS probe on the eraser test area and an MCP-HTP11 UA probe on the non-eraser test area, at an applied voltage of 1000V. The surface resistance was measured at 10 points on the eraser test area and the non-eraser test area on the antistatic layer side of the laminate, and the arithmetic average of the 10 measurements was calculated.

[0236] In addition, the ratio of the surface resistance before and after the eraser test was calculated using the following formula, where the surface resistance of the area on the antistatic layer side of the laminate where the eraser test was not performed is C and the surface resistance of the area where the eraser test was performed is D. Surface resistance ratio = D / C

[0237] (5) Smoothness before and after the eraser test The surface of the antistatic layer side of the laminate of embodiment and comparative example is carried out above-mentioned eraser test, and the slipperiness of the surface of the antistatic layer side of the laminate before and after the eraser test is evaluated.Specifically, the surface of the antistatic layer side of the laminate is rubbed with fingertip in the order of not carrying out the eraser test, the eraser test carried out part and the eraser test not carried out part, with the moving speed of 10cm / second, and the slipperiness of the eraser test carried out part at this time is evaluated according to the following criteria: A: More than 7 out of 10 people did not feel any discomfort. B: 5 or 6 out of 10 people did not feel any resistance C: 6 or 7 out of 10 people felt a sense of discomfort D: More than 8 out of 10 people felt a sense of discomfort.

[0238] (6) Frictional force before and after the eraser test The above-mentioned eraser test was carried out on the antistatic layer side of the laminate of the examples and comparative examples, and the frictional force on the antistatic layer side of the laminate before and after the eraser test was measured. Specifically, a 6 mm diameter eraser made by Minoan was used, inserted into a jig with a 6 mm diameter hole so that 4 mm of the eraser tip was exposed, and this eraser-attached jig was attached to a continuous load scratch resistance tester (product name "TRIBOGEAR TYPE18", manufactured by Shinto Scientific Co., Ltd.), and the eraser was rubbed with a load of 1.96 N and a moving speed of 840 mm / min on the antistatic layer side of the laminate in the following order: the eraser test non-experimented area, the eraser test-experimented area, and the eraser test non-experimented area, to measure the frictional force. At this time, as shown in FIG. 2, the eraser was moved perpendicular to the longitudinal direction of the rectangular eraser test-experimented area 32, as indicated by the arrow. Then, the maximum frictional force was determined for the frictional force against the eraser in the eraser test-experimented area. Furthermore, with regard to the frictional force against the eraser in the area where the eraser test was not conducted, as shown in Figure 2, the point where the frictional force against the eraser in the eraser test conducted area 32 is maximum is set to 0 mm, and in the eraser test not conducted area 31, the average value of the frictional force was calculated in the range of 4.2 mm to 9.8 mm, with the above point (0 mm) as the base.

[0239] In addition, the ratio of the frictional force before and after the eraser test was calculated using the following formula, where E is the average value of the frictional force in the area on the antistatic layer side of the laminate where the eraser test was not performed, and F is the maximum value of the frictional force in the area where the eraser test was performed. Friction force ratio = F / E

[0240] [Table 1]

[0241] As shown in Table 1, the surface resistance before and after the eraser test was 9 × 10 13 All of the samples (Examples 1 to 8) with a surface resistance of 9×10 Ω / □ or less had good slip properties in the eraser test, but the surface resistance before and after the eraser test was 9×10 13 Those exceeding Ω / □ (Comparative Examples 1 to 7) were evaluated poorly for slipperiness in the eraser test. Furthermore, the eraser test slipperiness was slightly inferior in those samples (Example 8) in which the ratio of the surface resistance after the eraser test to the surface resistance before the eraser test (initial surface resistance) exceeded 20.0 compared to those samples in which the ratio was 20.0 or less. [Explanation of symbols]

[0242] 1 ... Laminate for flexible display devices 2...Base material layer 3...Antistatic layer 4...Hard coat layer 5... Shock absorbing layer 6... Adhesive layer for attachment 7 … Interlayer adhesive layer 20... Flexible display device 21... Display panel

Claims

[Claim 1] A laminate for a flexible display device having a base layer and an antistatic layer, the contact angle of water on the antistatic layer side of the laminate for a flexible display device is 100° or more; a ratio of the contact angle with water after a steel wool test in which the surface of the laminate for a flexible display device on the antistatic layer side is rubbed back and forth 2500 times with #0000 steel wool under a load of 9.8 N to the initial contact angle with water on the surface of the laminate for a flexible display device on the antistatic layer side is 0.6 or more; The surface resistance of the surface of the laminate for a flexible display device on the antistatic layer side is 9×10 １３ Ω / □ or less, After an eraser test was performed in which the surface of the antistatic layer side of the laminate for a flexible display device was rubbed back and forth 2500 times with an eraser having a diameter of 6 mm and a load of 9.8 N, the surface resistance of the surface of the antistatic layer side of the laminate for a flexible display device was 9×10 １３ A laminate for a flexible display device having a resistance of Ω / □ or less.

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