Folding display device and optical adhesive

Abstract

The application discloses a kind of folding display device and optical glue, wherein, folding display device includes the display component of laminated arrangement, first adhesive layer and first cover plate;Display component includes organic light emitting layer and drive backplate layer, drive backplate layer is located the side of organic light emitting layer deviating from first adhesive layer;Folding display device has first bending area, the storage modulus of first adhesive layer in first bending area is greater than the storage modulus of first adhesive layer in other areas of folding display device, the neutral layer of display component is located in the range of drive backplate layer, so as to avoid drive backplate layer damage, avoid the crack or fracture phenomenon in display component inside, improve the protection performance and stability of folding display device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of display technology, and in particular to a folding display device and optical adhesive. BACKGROUND

[0002] The folding display device includes a plurality of film layer structures, and the film layers can be bonded by optical adhesive. When the display device is folded, each film layer needs to withstand complex stress. There are regions in the plurality of film layers where the stresses cancel each other out, which are referred to as neutral layers.

[0003] The thinner the folding display device, the easier it is to bend the screen. As the product demand for folding display devices tends to be thinner, the integration is higher and higher. However, the display device becomes thinner, which causes a problem of insufficient rigidity. If impacted during use, the display assembly, especially the driving backboard layer with low rigidity, is prone to cracks and other phenomena. The performance of resisting external force and scratch resistance is reduced. To balance the relationship between the folding performance and the protection performance of the folding display device, the position of the neutral layer in the folding display device needs to be adjusted. SUMMARY

[0004] The present application provides a folding display device and optical adhesive. The folding display device can have good folding performance and good protection performance.

[0005] In one aspect, the present application provides a folding display device, comprising a display assembly, a first adhesive layer and a first cover plate arranged in layers; the display assembly comprises an organic light-emitting layer and a driving backboard layer, the driving backboard layer is located on the side of the organic light-emitting layer away from the first adhesive layer.

[0006] The folding display device has a first bending area, the storage modulus of the first adhesive layer in the first bending area is greater than the storage modulus of the first adhesive layer in other areas of the folding display device, and the neutral layer of the display assembly is located within the range of the driving backboard layer.

[0007] In some embodiments of the present application, a flat area is further included, and the storage modulus of the first adhesive layer in the flat area is less than the storage modulus of the first adhesive layer in the first bending area.

[0008] In some embodiments of the present application, a second bending area is further included, and the bending direction of the second bending area is opposite to that of the first bending area.

[0009] The storage modulus of the first adhesive layer in the second bending area is less than the storage modulus of the first adhesive layer in the first bending area.

[0010] In some embodiments of the present application, the storage modulus of the first adhesive layer in the second bending area is equal to the storage modulus of the first adhesive layer in the flat area.

[0011] In some embodiments of the present application, in the first bending area, the material of the first adhesive layer is isooctadecyl acrylate, n-hexyl acrylate, butyl acrylate, hydroxybutyl acrylate and azobisisobutyronitrile.

[0012] In some embodiments of the present application, the proportion of isooctadecyl acrylate is 30% to 50%; the proportion of n-hexyl acrylate is 1% to 30%; the proportion of butyl acrylate is 20% to 50%; the proportion of hydroxybutyl acrylate is 1% to 10%; and the proportion of azobisisobutyronitrile is 0.01% to 5%.

[0013] In some embodiments of the present application, in the first bending area, the storage modulus of the first adhesive layer at a first temperature is 80kPa to 100kPa, and the storage modulus of the first adhesive layer at a second temperature is 200kPa to 500kPa, the second temperature being lower than the first temperature.

[0014] In some embodiments of the present application, the adhesion of the first adhesive layer is greater than 1500gf / 25mm, and the recovery of the first adhesive layer is greater than 90%.

[0015] In some embodiments of the present application, the material of the first cover plate is any one of ultra-thin glass, polyimide or polyethylene terephthalate.

[0016] In some embodiments of the present application, the display assembly further comprises:

[0017] A second adhesive layer is located on the side of the first cover plate away from the first adhesive layer.

[0018] A second cover plate is located on the side of the second adhesive layer away from the first cover plate, and the material of the second cover plate is polyimide or polyethylene terephthalate.

[0019] A support assembly is located on the side of the display assembly away from the first adhesive layer.

[0020] In some embodiments of the present application, the display assembly further comprises:

[0021] A polarizing film is located between the organic light-emitting layer and the first adhesive layer.

[0022] A back film is located on the side of the driving back plate layer away from the organic light-emitting layer, and the back film has a supporting effect.

[0023] Another aspect of the present application provides an optical adhesive, comprising a heavy release film, an optical adhesive body and a light release film; the optical adhesive body is located between the heavy release film and the light release film;

[0024] The material adopted by the optical adhesive body is isooctadecyl acrylate, n-hexyl acrylate, butyl acrylate, hydroxybutyl acrylate and azobisisobutyronitrile; wherein the proportion of isooctadecyl acrylate is 30%-50%; the proportion of n-hexyl acrylate is 1%-30%; the proportion of butyl acrylate is 20%-50%; the proportion of hydroxybutyl acrylate is 1%-10%; and the proportion of azobisisobutyronitrile is 0.01%-5%.

[0025] The present application has the following advantages:

[0026] The present application provides a folding display device and an optical adhesive, wherein the folding display device comprises a display assembly, a first adhesive layer and a first cover plate which are arranged in layers; the display assembly comprises an organic light-emitting layer and a driving backplate layer, the driving backplate layer is located on the side of the organic light-emitting layer away from the first adhesive layer; the folding display device has a first bending area, the storage modulus of the first adhesive layer in the first bending area is greater than the storage modulus of the first adhesive layer in other areas of the folding display device, and the neutral layer of the display assembly is located within the range of the driving backplate layer, so as to avoid damage to the driving backplate layer, avoid the occurrence of cracking or breaking phenomenon in the display assembly, and improve the protection performance and stability of the folding display device. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. Obviously, the drawings introduced below are only some embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0028] Figure 1 A cross-sectional view of the folding display device provided by the embodiments of the present application;

[0029] Figure 2 One of the structure schematic diagrams of the folding display device provided by the embodiments of the present application;

[0030] Figure 3 A structure schematic diagram of the display assembly provided by the embodiments of the present application;

[0031] Figure 4 A relationship schematic diagram of the storage modulus and the strain percentage of the adhesive material provided by the embodiments of the present application;

[0032] Figure 5 The second structure schematic diagram of the folding display device provided by the embodiments of the present application;

[0033] Figure 6 A process diagram of the optical adhesive provided by the embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the above objectives, characteristics and advantages of the present application more apparent, comprehensible and easier to understand, the present application will be further described below in conjunction with the accompanying drawings and embodiments. However, the example embodiments can be implemented in various forms, and should not be understood as being limited to the embodiments set forth herein; on the contrary, these embodiments are provided so as to make the present application more comprehensive and complete, and to fully convey the concept of the example embodiments to those skilled in the art. The same reference numerals in the drawings represent the same or similar structures, and thus repeated description thereof will be omitted. The expressions of position and direction described in the present application are described with reference to the drawings, but can be changed as needed, and the changes made are included in the scope of protection of the present application. The drawings of the present application are only used to illustrate the relative positional relationship and do not represent the true proportions.

[0035] The multi-layer structure having the functions of supporting, displaying and protecting in the folding display device needs to bear complex stress when the display device is folded. Under the action of the stress, each film layer of the folding display device tends to displace, and the optical adhesive needs to be used to bond each film layer into a whole to avoid the above phenomenon. At this time, there is an area in which the stresses are mutually offset in the display device, which is a neutral layer. The probability of damage of the film layer in the neutral layer area during the folding process can be greatly reduced.

[0036] For the folding display device, its folding performance, thinness and resistance to external force impact are problems that need to be concerned. The thinner the folding display device is, the easier it is to achieve bending, and the better its folding performance is. However, the thinning of the display device will cause the problem of insufficient rigidity, resulting in the reduction of the resistance to external force impact of the display device. Therefore, it is necessary to balance the relationship between the folding performance and the protection performance of the folding display device, and the position of the neutral layer of the folding display device can be reasonably set to achieve this. In view of this, the embodiment of the present application provides a folding display device.

[0037] Figure 1 A cross-sectional view of the folding display device provided by the embodiment of the present application is shown.

[0038] Figure 1 A cross-sectional structure of the folding display device in an unfolded state is shown. As shown in Figure 1 The folding display device includes a multi-layer structure, which specifically can include a display assembly 100, a first adhesive layer 200 and a first cover plate 300 arranged in layers, and the first adhesive layer 200 is used to bond the first cover plate 300 and the display assembly 100.

[0039] Wherein, in order to realize the folding function, the display assembly 100 can adopt an organic light-emitting diode (Organic Light-Emitting Diode, OLED for short) display assembly, the first adhesive layer 200 can adopt optical adhesive, and the material of the first cover plate 300 can adopt one of ultra-thin glass (Ultra Thin Glass, UTG for short), ultra-flexible glass (Ultra Flexible Glass, UFG for short) or a polymer material such as colorless polyimide (Colorless Polyimide, CPI for short), polyethylene terephthalate (Polyethylene Terephthalate, PET for short) and the like.

[0040] Figure 2 A structural schematic diagram of a folding display device provided by an embodiment of the present application.

[0041] Figure 2 The structure of the folding display device in the folded state is shown, as shown in Figure 2 The folding display device has a first bending area S1, in the first bending area S1, the folding display device can be folded outward, and the folding display device is shown in Figure 1 For ease of description, the direction in which the display assembly 100 points to the first cover plate 300 when the first bending area S1 is in the bending state shown in Figure 2 is marked as the first direction X, and in the first direction X, the bending degree of each film layer increases in turn.

[0042] In the first bending area S1, the display assembly 100 is more prone to cracking or breaking during folding or when subjected to impact than other film layers, and controlling the neutral layer within the area where the display assembly 100 is located can effectively avoid this problem, and the position of the neutral layer will be further described below.

[0043] Figure 3 A structural schematic diagram of a display assembly provided by an embodiment of the present application.

[0044] As shown in Figure 3 The display assembly 100 can include a back film 101, a driving back plate layer 102 and an organic light-emitting layer 103, a polarizing film 104 and the like.

[0045] The back film 101 has a protective effect and can be made of an organic material, and the back film 101 can be arranged on the surface at the bottom of the driving back plate layer 102, and in some embodiments, a polyimide (Polyimide, PI for short) film can also be arranged between the back film 101 and the driving back plate layer 102.

[0046] The driving backboard layer 102 includes a substrate and a driving circuit disposed on the substrate. In some embodiments, the substrate can be made of glass materials such as soda lime glass, quartz glass, sapphire glass, or metal materials such as stainless steel, aluminum, and nickel. In some embodiments, the substrate can be made of one or a combination of polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyvinyl phenol (PVP), polyether sulfone (PES), polyimide (PI), polyamide, polyacetal, polycarbonate (PC), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN).

[0047] The organic light-emitting layer 103 is located on the side of the driving backboard layer 102 away from the back film 101. The organic light-emitting layer 103 includes a plurality of organic light-emitting devices such as OLEDs or OLED chips, which can emit light under the driving of the driving backboard layer 102. An encapsulation layer can be disposed on the plurality of organic light-emitting devices to prevent water vapor from entering the inside of the organic light-emitting layer 103 and adversely affecting the performance of the light-emitting devices.

[0048] The polarizing film 104 is located on the side of the organic light-emitting layer 103 away from the driving backboard layer 102 and is bonded to the first adhesive layer 200. The polarizing film 104 can be formed on the uppermost layer of the display assembly 100 by evaporation or other methods, so that the polarizing film 104 is integrated inside the display assembly 100 and does not need to be bonded with optical adhesive, which is conducive to reducing the thickness of the display assembly 100.

[0049] In specific implementations, the display assembly 100 can further include other functional film layers such as a color film layer and a brightness enhancement film layer. The embodiments of the present application only illustrate the main functional film layers of the display assembly 100 by way of example of the above structure, and the internal structure of the display assembly 100 can be adjusted according to specific needs, which is not limited herein.

[0050] In the related art, the neutral layer is usually located in the range of the back film 101 of the display assembly 100 or between the back film 101 and the driving back plate layer 102. In comparison with the back film 101 and the organic light-emitting layer 103 made of organic materials, the driving back plate layer 102 is more likely to be damaged and cracked or broken when the display device is folded or impacted. In the embodiment of the present application, the position of the neutral layer in the first bending area S1 of the folding display device is adjusted to the range of the driving back plate layer 102 of the display assembly 100, so as to avoid damage to the display assembly 100 during use. This can be achieved by adjusting the properties of the first adhesive layer 200 adjacent to the display assembly 100.

[0051] Figure 4 The schematic diagram of the relationship between the storage modulus and the strain percentage of the adhesive material provided in the embodiment of the present application is shown in the following figure.

[0052] Figure 4 In the figure, the abscissa represents the storage modulus of the adhesive material at room temperature (25℃), and the unit is kPa. The ordinate represents the strain percentage of the adhesive material. It can be seen from the figure that Figure 4 When the adhesive layer is bent, the higher the storage modulus of the adhesive material, the smaller the strain percentage of the adhesive layer formed, the better the rigidity and the greater the hardness of the adhesive layer.

[0053] In the embodiment of the present application, the storage modulus of the first adhesive layer 200 in the first bending area S1 is greater than the storage modulus of the first adhesive layer 200 in other areas of the folding display device, so that the first adhesive layer 200 is less likely to deform in the first bending area S1, and has greater rigidity and hardness. Thus, the first adhesive layer 200 can balance the stress relationship in the first bending area S1, so that the neutral layer is controlled in the range of the driving back plate layer 102 of the display assembly 100, the driving back plate layer 102 is prevented from being damaged, and the protection performance and stability of the folding display device are improved.

[0054] The storage modulus of the adhesive layer is related to the material and the material ratio used. In the first adhesive layer 200 in the first bending area S1 of the embodiment of the present application, Isooctadecyl Acrylate (ISTA) is introduced, so that the first adhesive layer 200 has high storage modulus and high recovery. Specifically, the material used in the first adhesive layer 200 in the first bending area S1 is Isooctadecyl Acrylate (ISTA), Hexyl Acrylate (HA), Butyl Acrylate (BA), 4HBA and Azobisisobutyronitrile (AIBN). The following table shows the test results of the characteristic parameters of the above-mentioned materials at different ratios:

[0055]

[0056] G' represents the storage modulus, Tg represents the critical temperature point of the glass material vitrification, and Recovery represents the recovery of the glass material.

[0057] The table shows the peel strength of the glass material to the CPI interface and the UTG interface, the storage modulus of the glass material at the first temperature (normal temperature 25℃), the second temperature (low temperature -20℃) and the third temperature (high temperature 60℃), the critical temperature of the glass material vitrification, the recovery of the glass material, and the state of the display device under the conditions of dynamic bending of the display device 200,000 times at normal temperature and bending state for 240 hours at low temperature, OK represents that the display device is normal, and NG represents that the interface delamination phenomenon occurs in the display device, and bending failure.

[0058] From the above table, in a feasible embodiment, the proportion of ISTA is 40%, the proportion of HA is 15%, the proportion of BA is 40%, the proportion of 4HBA is 4.95%, and the proportion of AIBN is 0.05%. Based on the above ratio, the adhesion of the glass material to CPI is greater than 1532 gf / 25mm, and the adhesion to UTG is greater than 1618 gf / 25mm; the storage modulus of the glass material at the first temperature (normal temperature 25℃) is 80kPa, the storage modulus at the second temperature (low temperature -20℃) is 210kPa, and the storage modulus at the third temperature (high temperature 60℃) is 46kPa; the Tg point of the glass material is -25℃; and the recovery of the glass material is 92%.

[0059] In a feasible embodiment, the proportion of ISTA is 45%, the proportion of HA is 10%, the proportion of BA is 40%, the proportion of 4HBA is 4.95%, and the proportion of AIBN is 0.05%. Based on the above ratio, the adhesion of the glass material to CPI is greater than 1640 gf / 25mm, and the adhesion to UTG is greater than 1750 gf / 25mm; the storage modulus of the glass material at the first temperature (normal temperature 25℃) is 90kPa, the storage modulus at the second temperature (low temperature -20℃) is 320kPa, and the storage modulus at the third temperature (high temperature 60℃) is 53kPa; the Tg point of the glass material is -20℃; and the recovery of the glass material is 95%.

[0060] In an implementable embodiment, the proportion of ISTA is 50%, the proportion of HA is 5%, the proportion of BA is 40%, the proportion of 4HBA is 4.95%, and the proportion of AIBN is 0.05%. Based on the above proportions, the adhesive force of the adhesive material to CPI is greater than 1710 gf / 25 mm, and the adhesive force to UTG is greater than 1750 gf / 25 mm; the storage modulus of the adhesive material at a first temperature (normal temperature 25℃) is 100 kPa, the storage modulus at a second temperature (low temperature-20℃) is 450 kPa, and the storage modulus at a third temperature (high temperature 60℃) is 68 kPa; the Tg point of the adhesive material is-15℃; and the recovery of the adhesive material is 97.5%.

[0061] Based on the experimental and test results, the embodiment of the present application can give the proportioning range of each material in the first adhesive layer 200 in the first bending region S1, which is as follows: the proportion of isostearic acid acrylate (ISTA) is 30%-50%, optionally, the proportion of ISTA can be 30%, 40%, 45%, or 50%; the proportion of n-hexyl acrylate (HA) is 1%-30%, optionally, the proportion of HA can be 1%, 5%, 10%, 15%, or 30%; the proportion of butyl acrylate (BA) is 20%-50%, optionally, the proportion of BA can be 20%, 40%, or 50%; the proportion of hydroxybutyl acrylate (4HBA) is 1%-10%, optionally, the proportion of 4HBA can be 1%, 4.95%, or 10%; and the proportion of azobis isobutyronitrile (AIBN) is 0.01%-5%, optionally, the proportion of AIBN can be 0.01%, 0.05%, or 5%.

[0062] Figure 5 The structure schematic diagram two of the folding display device provided by the embodiment of the present application is shown.

[0063] Figure 5 The structure of the folding display device in a folded state is shown, as shown in Figure 5 The folding display device can further include a second bending region S2, the bending direction of the second bending region S2 is opposite to that of the first bending region S1, that is, the folding display device can be folded inward in the second bending region S2, and the display device can simultaneously include two forms of outward folding and inward folding, to realize more diverse folding effects. The following table is the test results of various performance parameters of the outward folding region and the inward folding region of the display device:

[0064] Inner folding area Inner folding area Outer folding area Outer folding area Outer folding area Outer folding area Outer folding area OCA room temperature modulus / Kpa 25℃ 45 80 45 62 80 90 112 OCA low temperature modulus / Kpa -20℃ 89 210 89 402 210 320 820 Adhesion / @UTG (gf / 25mm) 1700 1618 1700 1500 1618 1750 1300 Room temperature dynamic bending / 10w times OK NG NG NG OK OK OK Low temperature dynamic bending / 10w times OK NG OK Crack OK OK Crack

[0065] Among them, Crack represents the phenomenon of crack or fracture in the display device. The test conditions of the storage modulus are frequency 1 Hz, normal force 0.5 N, and temperature range-50℃-120℃.

[0066] From the above table, when the display device includes areas with different folding directions, if the same storage modulus adhesive material is used in the first adhesive layer, the bending characteristics of the inner folding area and the outer folding area cannot be satisfied at the same time. For example, when the low-temperature storage modulus is too high, the display assembly may be broken. When the normal-temperature storage modulus is too low, the bending failure problem may occur.

[0067] In the embodiment of the present application, the storage modulus of the first adhesive layer 200 in the second bending area S2 is less than the storage modulus of the first adhesive layer 200 in the first bending area S1. In the first bending area S1, the storage modulus of the first adhesive layer 200 at the first temperature is 80 kPa to 100 kPa. Optionally, the storage modulus of the first adhesive layer 200 at the first temperature can be 80 kPa, 90 kPa, or 100 kPa. In the first bending area S1, the storage modulus of the first adhesive layer 200 at the second temperature is 200 kPa to 500 kPa. Optionally, the storage modulus of the first adhesive layer 200 at the second temperature can be 200 kPa, 210 kPa, 320 kPa, or 500 kPa. The second temperature is lower than the first temperature. The first temperature can be normal temperature 25℃, and the second temperature can be low temperature -20℃. At the same time, the adhesion of the first adhesive layer 200 to the UTG interface is greater than 1500 gf / 25 mm. Optionally, the adhesion of the first adhesive layer 200 to the UTG interface can be 1500 gf / 25 mm, 1618 gf / 25 mm, or 1750 gf / 25 mm. The recovery of the first adhesive layer 200 is greater than 90%, so that the display device can meet various folding requirements while avoiding problems such as interface delamination, bending failure, and display assembly breakage.

[0068] In some embodiments, in the first bending area S1, the storage modulus of the first adhesive layer 200 at the first temperature (normal temperature 25℃) can be 80 kPa, the storage modulus at the second temperature (low temperature -20℃) can be 210 kPa, and the adhesion of the first adhesive layer 200 can be 1618 gf / 25 mm.

[0069] In some embodiments, in the first bending area S1, the storage modulus of the first adhesive layer 200 at the first temperature (normal temperature 25℃) can be 90 kPa, the storage modulus at the second temperature (low temperature -20℃) can be 320 kPa, and the adhesion of the first adhesive layer 200 can be 1750 gf / 25 mm.

[0070] In some embodiments, in the second bending area S2, the storage modulus of the first adhesive layer 200 at the first temperature (normal temperature 25℃) can be 45 kPa, the storage modulus at the second temperature (low temperature -20℃) can be 89 kPa, and the adhesion of the first adhesive layer 200 can be 1700 gf / 25 mm.

[0071] In specific implementation, other folding regions for outer folding or inner folding can also be included in the display device, for example, two inner folding regions can be included in the display device, and the folding degree of one of the inner folding regions is greater than that of the other inner folding region. The number of folding regions and the folding direction thereof in the display device are not limited in the embodiments of the present application. In the folding region for outer folding, a glue material with a relatively high storage modulus can be used to achieve the purpose of controlling the neutral layer to be located within the driving backboard layer of the display assembly, thereby avoiding the cracking and breaking of the display assembly.

[0072] As shown in Figure 2 and Figure 5 , the folding display device also includes a flat region S3, i.e., a region without folding. The storage modulus of the first glue layer 200 in the flat region S3 is less than that of the first glue layer 200 in the first folding region S1, so as to ensure the bonding performance and the displacement performance of the first glue layer 200 and to ensure that the folding stress in the display device can be effectively released, thereby improving the folding ability and the service life of the folding display device.

[0073] In some embodiments of the present application, the storage modulus of the first glue layer 200 in the second folding region S2 can be equal to that of the first glue layer 200 in the flat region S3, so that the first glue layer 200 in the second folding region S2 and the flat region S3 can be formed at the same time without being made in sections, thereby simplifying the process flow.

[0074] As shown in Figure 1 , the folding display device can also include a second glue layer 400, a second cover plate 500 and a support assembly 600.

[0075] The second glue layer 400 is located on the side of the first cover plate 300 away from the first glue layer 200. The second glue layer 400 adopts optical glue, and the material and material ratio thereof can be the same as or different from those of the first glue layer 200. The storage modulus of the second glue layer 400 in the folding region and the storage modulus thereof in the flat region can be the same or different. The glue material adopted by the second glue layer 400 is not limited in the embodiments of the present application.

[0076] The second cover plate 500 is located on the side of the second glue layer 400 away from the first cover plate 300. The material of the second cover plate 500 can be colorless polyimide (CPI) or polyethylene terephthalate (PET). The second cover plate 500 has a relatively large hardness and can protect the folding display device from being scratched.

[0077] The support assembly 600 is located on the side of the display assembly 100 away from the first adhesive layer 200, can include at least one support component, and the support component farther away from the side of the display assembly 100 in the support assembly 600 can have higher hardness. For example, the support assembly 600 can include a first support layer 601 and a second support layer 602, wherein the second support layer 602 is located on the side of the first support layer 601 away from the display assembly 100, the first support layer 601 can be made of PET or PI, and the second support layer 602 can be made of carbon, metal or alloy.

[0078] The support assembly 600 can be used to support the multi-layer structure arranged above in the folding display device, while having a protective effect. In specific implementation, the specific shape of the support assembly 600, the number of support components included therein and the material used thereby can be designed according to requirements, which are not limited herein by the embodiments of the present application.

[0079] Based on the same inventive concept, the embodiments of the present application also provide an optical adhesive, which includes a heavy release film, an optical adhesive body and a light release film, the optical adhesive body is located between the heavy release film and the light release film, and the release films on both sides of the optical adhesive body need to be removed before the optical adhesive is applied to the display device.

[0080] The material used by the optical adhesive body is isostearic acid acrylate (ISTA), n-hexyl acrylate (HA), butyl acrylate (BA), hydroxybutyl acrylate (4HBA) and azobis isobutyronitrile (AIBN), wherein the proportion of isostearic acid acrylate (ISTA) is 30%-50%; the proportion of n-hexyl acrylate (HA) is 1%-30%; the proportion of butyl acrylate (BA) is 20%-50%; the proportion of hydroxybutyl acrylate (4HBA) is 1%-10%; and the proportion of azobis isobutyronitrile (AIBN) is 0.01%-5%.

[0081] Based on the above ratio, the optical adhesive can have good adhesion, good bending ability, high hardness and good recovery performance at the same time, and can improve the folding ability and protection performance of the folding display device when applied to the folding display.

[0082] Based on the same inventive concept, the embodiments of the present application also provide a manufacturing method of an optical adhesive. In the embodiments of the present application, the optical adhesive can be made by using a coating process or an ink jet printer (IJP) process, and the curing method thereof can include thermal curing or ultraviolet (UV) curing. When the adhesive layer of the optical adhesive needs to have different storage moduli in different regions, it can be made in sections.

[0083] Figure 6 The process diagram of the optical adhesive provided by the embodiments of the present application is shown in the following figure.

[0084] Figure 6 A process chart for making optical adhesive by using inkjet printing process is shown. The adhesive material is inkjet printed onto a heavy release film and then cured to form an adhesive layer (i.e. the main body of the optical adhesive), and then a light release film is overlaid on the adhesive layer to form the optical adhesive. A specific manufacturing method is given below as an example:

[0085] Mix 40g of ISTA, 15g of HA, 40g of BA, 4.95g of 4HBA and 0.05g of D1173 photoinitiator in a transparent glass jar; purge the jar with nitrogen for 5-8 minutes until the air in the jar is exhausted; irradiate the mixed solution with UV light until the viscosity of the mixed solution is 30-50 cP, at this time the UV light can be selected as 420nm LED lamp low intensity UV; turn off the UV lamp and stop the air blowing to stop the polymerization; add 0.05g of AIBN to the mixed solution, and then print the mixed solution onto the surface of the heavy release film using inkjet printing; irradiate the mixed solution printed on the surface of the heavy release film with UV light at this time, which can be irradiated with UV light of 2000mJ / cm 2 to make the mixed solution polymerize and solidify to form the main body of the optical adhesive; overlay a light release film on the main body of the optical adhesive, and roll up to complete the preparation process.

[0086] Although preferred embodiments of the application have been described, those skilled in the art will be able to make additional changes and modifications without departing from the spirit and scope of the application. Therefore, the appended claims are intended to cover all such changes and modifications that fall within the scope of the application.

[0087] Obviously, various modifications and changes can be made to the present application by those skilled in the art without departing from the spirit and scope of the present application. Thus, it is intended that the present application cover the modifications and changes as long as they come within the scope of the claims and their equivalents.

Claims

1. A foldable display device, characterized by, The display assembly includes a display assembly, a first adhesive layer and a first cover plate; the display assembly includes an organic light-emitting layer and a driving backplate layer, and the driving backplate layer is located on the side of the organic light-emitting layer away from the first adhesive layer; The folding display device has a first bending area, the storage modulus of the first adhesive layer in the first bending area is greater than the storage modulus of the first adhesive layer in other areas of the folding display device, and the neutral layer of the display assembly is located in the range of the driving backplate layer; The folding display device further includes a flat area, and the storage modulus of the first adhesive layer in the flat area is less than the storage modulus of the first adhesive layer in the first bending area; The folding display device further includes a second bending area, and the bending direction of the second bending area is opposite to that of the first bending area; The storage modulus of the first adhesive layer in the second bending area is less than the storage modulus of the first adhesive layer in the first bending area.

2. The folded display device of claim 1, wherein, The storage modulus of the first adhesive layer in the second bending area is equal to the storage modulus of the first adhesive layer in the flat area.

3. The folded display device of claim 1, wherein, In the first bending area, the material used by the first adhesive layer is isooctadecyl acrylate, n-hexyl acrylate, butyl acrylate, hydroxybutyl acrylate and azobisisobutyronitrile; Among them, the proportion of isooctadecyl acrylate is 30%-50%; the proportion of n-hexyl acrylate is 1%-30%; the proportion of butyl acrylate is 20%-50%; the proportion of hydroxybutyl acrylate is 1%-10%; the proportion of azobisisobutyronitrile is 0.01%-5%.

4. The folded display device of claim 3, wherein, In the first bending area, the storage modulus of the first adhesive layer at a first temperature is 80kPa-100kPa, and the storage modulus of the first adhesive layer at a second temperature is 200kPa-500kPa, and the second temperature is lower than the first temperature.

5. The folded display device of claim 3, wherein, The adhesion of the first adhesive layer is greater than 1500gf / 25mm; the recovery of the first adhesive layer is greater than 90%.

6. The folded display device according to any one of claims 1 to 5, wherein The material of the first cover plate uses any one of ultra-thin glass, polyimide or polyethylene terephthalate.

7. The folded display device of any one of claims 1-5, wherein Further comprising: A second adhesive layer located on the side of the first cover plate away from the first adhesive layer; A second cover plate located on the side of the second adhesive layer away from the first cover plate; The material of the second cover plate is polyimide or polyethylene terephthalate; A support assembly located on the side of the display assembly away from the first adhesive layer.

8. The folded display device of any one of claims 1-5, wherein, The display assembly further comprises: A polarizing film located between the organic light-emitting layer and the first adhesive layer; A back film located on the side of the driving backplate layer away from the organic light-emitting layer, the back film having a protective effect.

9. An optical adhesive, characterized by, The display assembly further comprises: A heavy release film, an optical adhesive body and a light release film; the optical adhesive body is located between the heavy release film and the light release film; The material of the optical glue body is isooctadecyl acrylate, n-hexyl acrylate, butyl acrylate, hydroxybutyl acrylate and azobisisobutyronitrile; wherein, the proportion of isooctadecyl acrylate is 30%-50%; the proportion of n-hexyl acrylate is 1%-30%; the proportion of butyl acrylate is 20%-50%; the proportion of hydroxybutyl acrylate is 1%-10%; and the proportion of azobisisobutyronitrile is 0.01%-5%.

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