Method for manufacturing joint structure

Abstract

Provided is a method for manufacturing a joint structure capable of achieving moldability of the joint structure as well as prevention of peeling of a layer. A method for manufacturing a joint structure of an embodiment is characterized by coating a liquid reaction-type adhesive on a joining surface of a first base material, curing the reaction-type adhesive coated on the first base material to form a cured resin layer on the first base material, activating the surface of the cured resin layer formed on the first base material to form a first modified layer, in which said surface has been activated, on the surface of the cured resin layer, activating a joining surface of a second base material to form a second modified layer, in which said surface has been activated, on the surface of the second base layer, setting the first modified layer and the second modified layer opposite each other, and pressure-bonding the first base material and the second base material.

Description

Method for manufacturing a bonded structure

[0001] The present invention relates to a method for manufacturing a bonded structure.

[0002] Display panels such as liquid crystal displays are installed inside automobiles and other transportation vehicles. These display panels are used as display devices for navigation systems and various meters. Display panels may be equipped with touch sensors. For example, there are known types of touch sensors, such as in-cell and on-cell types, in which the touch sensor is built into the display panel, and out-cell types, in which the touch sensor is externally attached.

[0003] A cover lens made of a transparent substrate is attached to the display panel or the out-cell touch sensor. In general, the display panel or the like and the cover lens are bonded together to form a bonded structure.

[0004] If an air gap exists between the bonded structure of a display panel or the like and a cover lens, incident light is reflected at the interface between them. This causes deterioration of the visibility of the display panel or the like. Therefore, the air gap in the bonded structure, which is a laminated structure, is filled with a transparent resin having a refractive index close to that of the cover lens or the display panel. Specifically, a resin layer (adhesive layer) is formed between the display panel or the cover lens.

[0005] Resins capable of forming a resin layer having a predetermined refractive index and filling a laminated structure are called optical bonding agents. Optical bonding agents have the function of improving the optical performance of the laminated structure by reducing or eliminating light reflection caused by differences in the refractive index of each of the substrates that make up the laminated structure. Known forms of optical bonding agents include double-sided tape-type OCA (Optical Clear Adhesive) and adhesive-type OCR (Optical Clear Resin).

[0006] A bonded structure using an OCA can be easily manufactured by bonding it between a display panel or the like and a cover lens. However, because the OCA is formed in a sheet, it is difficult to adjust and ensure the shape and thickness between the display panel or the cover lens. This can cause peeling of the layers in the bonded structure due to differences in linear expansion coefficients.

[0007] The manufacturing of a bonded structure using OCR allows for a high degree of freedom in the thickness and shape between the display panel and the cover lens, etc. However, because OCR is generally liquid, it is difficult to mold it into a resin layer with a predetermined shape and thickness.

[0008] JP 2015-5049 A International Publication No. 2019 / 009026 JP 2017-196823 A

[0009] As described above, the conventional manufacturing method of the joint structure has problems in that it is difficult to form the resin layer that fills the air gap in the joint structure, and there is a possibility that the layers of the joint structure may peel off. The present invention has been made to solve these problems, and an object of the present invention is to provide a manufacturing method of the joint structure that can achieve both the formability of the joint structure and the prevention of peeling off of the layers.

[0010] A manufacturing method of a bonded structure according to an embodiment is a manufacturing method of a bonded structure in which a first substrate and a second substrate are bonded. The manufacturing method of the bonded structure according to the embodiment includes applying a liquid reactive adhesive to a bonding surface of the first substrate, curing the reactive adhesive applied to the first substrate to form a cured resin layer on the first substrate, activating the surface of the cured resin layer formed on the first substrate to form a first modified layer with the activated surface on the surface of the cured resin layer, activating the bonding surface of the second substrate to form a second modified layer with the activated surface on the surface of the second substrate, and pressing the first substrate and the second substrate together with the first modified layer and the second modified layer facing each other.

[0011] 1 is a cross-sectional view showing a cross section of a bonded structure produced by the method for manufacturing a bonded structure according to the first embodiment; FIG. 2 is a cross-sectional view showing an adhesive application step in the method for manufacturing a bonded structure according to the first embodiment; FIG. 3 is a cross-sectional view showing an adhesive curing step in the method for manufacturing a bonded structure according to the first embodiment; FIG. 4 is a cross-sectional view showing a cured resin layer modification step in the method for manufacturing a bonded structure according to the first embodiment; FIG. 5 is a cross-sectional view showing a display panel modification step in the method for manufacturing a bonded structure according to the first embodiment; FIG. 6 is a cross-sectional view showing a substrate inversion step in the method for manufacturing a bonded structure according to the first embodiment; FIG. 7 is a cross-sectional view showing a pressure bonding step in the method for manufacturing a bonded structure according to the first embodiment; FIG. 8 is a flowchart showing a method for manufacturing a bonded structure according to the first embodiment; FIG. 9 is a diagram comparing the method for manufacturing a bonded structure according to the first embodiment with a comparative example; FIG. 10 is a diagram showing deformation of the adhesive in the method for manufacturing a bonded structure according to the comparative example; FIG. 11 is a diagram showing misalignment after lamination in the method for manufacturing a bonded structure according to the comparative example; FIG. 12 is a diagram showing overflow of the adhesive in the method for manufacturing a bonded structure according to the comparative example; FIG. 13 is a cross-sectional view showing a cross section of a bonded structure produced by the method for manufacturing a bonded structure according to the second embodiment; FIG. 14 is a cross-sectional view showing an adhesive application step in the method for manufacturing a bonded structure according to the second embodiment; FIG. 15 is a cross-sectional view showing an adhesive curing step in the method for manufacturing a bonded structure according to the second embodiment; FIG. 16 is a cross-sectional view showing a cured resin layer modification step in the method for manufacturing a bonded structure according to the second embodiment; 10 is a cross-sectional view showing a pressure bonding step in the method for manufacturing a bonded structure according to a second embodiment; FIG. 11 is a flowchart showing a method for manufacturing a bonded structure according to a second embodiment; FIG. 12 is a cross-sectional view showing a cross section of a bonded structure produced by a method for manufacturing a bonded structure according to a third embodiment; FIG. 13 is a cross-sectional view showing an adhesive application step in the method for manufacturing a bonded structure according to the third embodiment; FIG. 14 is a cross-sectional view showing an adhesive curing step in the method for manufacturing a bonded structure according to the third embodiment; FIG. 15 is a cross-sectional view showing a cured resin layer modification step in the method for manufacturing a bonded structure according to the third embodiment; FIG. 16 is a cross-sectional view showing a cover lens modification step in the method for manufacturing a bonded structure according to the third embodiment.10 is a cross-sectional view showing a pressure bonding step in a method for manufacturing a joint structure according to a third embodiment; and FIG.

[0012] (First Embodiment) Hereinafter, an embodiment will be described in detail with reference to the drawings. In this embodiment, a manufacturing method is used to laminate and bond a cover lens to a display panel using an adhesive. FIG. 1 is a cross-sectional view showing a cross section of a bonded structure produced by the manufacturing method for a bonded structure according to the first embodiment. In the example shown in FIG. 1, a bonded structure 1 produced by the manufacturing method according to the embodiment constitutes a display device having a display panel 10, a cover lens 20, and a cured resin layer 30.

[0013] The display panel 10 (second substrate) is, for example, a flat electronic component equipped with a liquid crystal display element. The liquid crystal display element of the display panel 10 may display characters or the like by reflecting incident light from the outside, or may display characters or the like by incorporating light-emitting elements. The display panel 10 is generally formed by molding the liquid crystal display element with resin or the like.

[0014] The cover lens 20 (first substrate) is a transparent substrate that reduces reflection of external light and protects the display panel 10 from external impact. Examples of materials for the cover lens 20 include glass, acrylic resin, and polycarbonate resin. The cover lens 20 is not necessarily limited to a lens having a light-refracting lens function. The cover lens 20 is not limited to a resin or glass having a flat plate shape, and may also have a curved shape or be bendable. The cover lens 20 is not necessarily limited to a transparent substrate, and may also be an opaque substrate.

[0015] The cured resin layer 30 is an intermediate layer that bonds the display panel 10 and the cover lens 20 in the bonded structure 1. The cured resin layer 30 also functions as an optical bonding agent for the display panel 10 and the cover lens 20. Examples of the cured resin layer 30 include optically transparent resins such as acrylic resin, urethane resin, and silicone resin.

[0016] The cured resin layer 30 needs to have an adhesive function, an optical function as an optical bonding agent, and a mechanical function to absorb stress caused by the difference in the linear expansion coefficients of the display panel 10 and the cover lens 20. In order to absorb stress, it is desirable that the cured resin layer 30 be a resin layer having a predetermined thickness. Therefore, the cured resin layer 30 is formed by curing an adhesive.

[0017] Examples of the manner in which the adhesive forming the cured resin layer 30 is cured include a heat curing type, an ultraviolet curing type, and an ultraviolet delayed curing type. Heat curing is a type in which the adhesive is cured by heating to a predetermined temperature. Ultraviolet curing is a type in which the adhesive is cured by irradiating ultraviolet light of a predetermined wavelength. Ultraviolet delayed curing is a type of ultraviolet curing in which the curing time can be controlled.

[0018] The cured resin layer 30 preferably has a hardness of, for example, a penetration of 200 or more as defined by JIS K2220 (JIS: Japanese Industrial Standards K2220) at 25° C. This is because a material with a penetration of less than 200 cannot maintain the shape and thickness of the cured resin layer 30.

[0019] The adhesive that forms the cured resin layer 30 is generally in a liquid state. The viscosity of the adhesive that forms the cured resin layer 30 is desirably 0.001 to 100,000 mPa·s, for example, in terms of formability. The adhesive that forms the cured resin layer 30 may be thixotropic.

[0020] When forming the cured resin layer 30 between the display panel 10 and the cover lens 20, it is difficult to simultaneously bond the display panel 10 and the cover lens 20 and form the resin layer. However, the cured resin layer 30 obtained by curing the adhesive often has reduced adhesive function compared to before curing. Therefore, in the manufacturing method of the embodiment, the surface of the cured resin layer 30 is activated (modified) to restore the reduced adhesive function.

[0021] Therefore, the adhesive that forms the cured resin layer 30 must be capable of activating its surface after curing. Surface activation is achieved by introducing polar functional groups such as hydroxyl groups or carbonyl groups to the terminals using active oxygen species. For example, a modified layer having OH groups is generated on the surface of the cured resin layer 30 by exposure to a plasma environment. The surface of the cured resin layer 30, on which OH groups have been generated by modification, can retain adhesive properties even after curing.

[0022] The method of modification is not limited to exposure to a plasma environment, and other methods such as flame treatment and corona treatment may be used as long as they can activate the surface of the resin layer where the adhesive has been cured.

[0023] The adhesive forming the cured resin layer 30 may be a reactive resin adhesive. Examples of the adhesive forming the cured resin layer 30 include at least one of polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyolefin resins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer, acrylic resins such as norbornene resin, polyacrylate, and polymethyl methacrylate, urethane resin, vinyl chloride resin, fluororesin, polycarbonate resin, polyvinyl butyral resin, polyvinyl alcohol resin, polyimide resin, polyamide-imide resin, epoxy resin, silicone resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, and polyarylene ether phosphine oxide resin. That is, the adhesive forming the cured resin layer 30 may be one of these resins used alone, or two or more of them may be used in combination.

[0024] (Manufacturing Method of First Embodiment) Next, a manufacturing method of a bonded structure of the first embodiment will be described with reference to FIGS. 2 to 8. FIG. 2 is a cross-sectional view showing an adhesive application step in the manufacturing method of a bonded structure of the first embodiment. FIG. 3 is a cross-sectional view showing an adhesive curing step in the manufacturing method of a bonded structure of the first embodiment. FIG. 4 is a cross-sectional view showing a cured resin layer modification step in the manufacturing method of a bonded structure of the first embodiment. FIG. 5 is a cross-sectional view showing a display panel modification step in the manufacturing method of a bonded structure of the first embodiment. FIG. 6 is a cross-sectional view showing a substrate reversal step in the manufacturing method of a bonded structure of the first embodiment. FIG. 7 is a cross-sectional view showing a pressure bonding step in the manufacturing method of a bonded structure of the first embodiment. FIG. 8 is a flowchart showing a manufacturing method of a bonded structure of the first embodiment.

[0025] [Adhesive Application Process] As shown in Figure 2, the cover lens 20 having a flat plate shape is placed on a horizontal table (not shown). Next, a slit die 40 and a pump (not shown) or the like are prepared. The slit die 40 is a device capable of forming a coating film on a planar member. The slit die 40 has the function of supplying liquid adhesive 31 supplied by a pump (not shown) or the like to the cover lens 20. In the example shown in Figure 2, the cover lens 20 is coated using a slit die, but the display panel may also be placed on a horizontal table (not shown) and coated.

[0026] The adhesive 31 is applied to the surface (bonding surface) of the cover lens 20 while the slit die 40 is moved along the surface of the cover lens 20 (S100). A film of the adhesive 31 is formed on the surface of the cover lens 20.

[0027] 2, the adhesive 31 is applied while the slit die 40 is moved along the surface of the fixed cover lens 20, but this is not limiting. The slit die 40 may be fixed and apply the adhesive 31 while the cover lens 20 is moved in the horizontal direction.

[0028] [Adhesive Curing Process] Next, as shown in Figure 3, an ultraviolet (UV) irradiation device 50 is used to irradiate the adhesive 31 on the cover lens 20 with ultraviolet light 51 of a predetermined wavelength for a predetermined period of time (S110). Irradiating the adhesive 31 with ultraviolet light acts to harden the adhesive 31. This prevents the adhesive 31 from flowing over the cover lens 20 and changing its shape or thickness. The adhesive 31 hardens to become a cured resin layer 30. The wavelength of the ultraviolet light irradiated onto the adhesive 31 is, for example, 365 nm.

[0029] The ultraviolet irradiation device 50 may be of any type as long as it can generate ultraviolet light of a wavelength that hardens the adhesive 31. The ultraviolet irradiation device 50 may be configured integrally with the slit die 40. For example, by providing the ultraviolet irradiation device 50 on the downstream side of the movement direction of the slit die 40, it becomes possible to irradiate ultraviolet light immediately after the slit die 40 applies the adhesive 31 to the cover lens 20. This makes it possible to harden the adhesive 31 before it flows over and deforms the cover lens 20. When the slit die 40 is fixed and the cover lens 20 is moved horizontally, it is possible to similarly apply ultraviolet light irradiating the adhesive 31 downstream of the application position of the adhesive 31 on the slit die 40.

[0030] 4, a plasma generator 60 is used to irradiate the cured resin layer 30 cured on the cover lens 20 with plasma 61 for a predetermined time (S120). The surface of the cured resin layer 30 exposed to the plasma 61 is activated (modified). As a result, a modified layer 32 (first modified layer) having OH groups is formed on the surface of the cured resin layer 30.

[0031] 5, a plasma generator 60 is used to irradiate the display panel 10 with plasma 61 for a predetermined time (S120). The surface of the display panel 10 exposed to the plasma 61 is activated (modified). As a result, a modified layer 12 (second modified layer) having OH groups is formed on the surface (bonding surface) of the display panel 10.

[0032] The adhesive function of the adhesive 31 is reduced when it hardens to form the cured resin layer 30. On the other hand, the adhesive function of the modified layer 32 is restored by the OH groups. Similarly, the adhesive function of the modified layer 12 on the display panel 10 is imparted by the OH groups.

[0033] [Substrate Reversal Step] Subsequently, the cover lens 20 is reversed (S130) as shown in Fig. 6. This step may be omitted.

[0034] 7, the cover lens 20 and the display panel 10 are housed in a chamber 70 and pressed together in a substantially vacuum (S140). The cover lens 20 is pressed onto the surface (bonding surface) of the display panel 10 with the modified layer 32 facing the surface.

[0035] In the step of bonding the display panel 10 and the cover lens 20 together, the cover lens 20 may be placed face down and the display panel 10 may be bonded from above. The bonding does not have to be performed inside the chamber 70. In other words, the bonding does not have to be performed in a vacuum. The display panel 10 and the cover lens 20 may be bonded together using a roller or the like.

[0036] As a result of the pressure bonding, the bonded structure 1 shown in Fig. 1 is completed. According to the manufacturing method described above, the cured resin layer 30 is formed between the display panel 10 and the cover lens 20 while maintaining a predetermined shape. Before laminating the display panel 10 and the cover lens 20, the cured resin layer 30 is formed on the cover lens 20 by curing the adhesive 31, so that the adhesive 31 can be formed into and maintained in a predetermined shape before lamination.

[0037] Furthermore, according to the manufacturing method described above, the surface of the cured resin layer 30 obtained by curing the adhesive 31 is activated to generate OH groups, so that the cured resin layer 30 can be adhered to the display panel 10 without changing its shape.

[0038] In the above-described manufacturing method, the adhesive 31 is assumed to be an ultraviolet-curing type and is cured using ultraviolet light, but this is not limiting. If the adhesive 31 is a heat-curing type, the adhesive 31 may be cured by heating it at a predetermined temperature for a predetermined time using a heater. Furthermore, if the adhesive 31 is an ultraviolet delayed-curing type, the adhesive 31 may be cured by appropriately adjusting the ultraviolet irradiation time using the ultraviolet irradiation device 50.

[0039] In the above-described manufacturing method, the surface of the cured resin layer 30 obtained by curing the adhesive 31 and the surface of the display panel 10 are activated (modified) by plasma irradiation, but this is not limiting. Other methods may be used as long as they can activate the surface of the cured resin layer 30 and the surface of the display panel 10 and generate OH groups. For example, ultraviolet irradiation at a predetermined wavelength may be used.

[0040] Comparative Example Next, a comparative example based on a method different from the manufacturing method of the embodiment will be described with reference to Fig. 9. Fig. 9 is a diagram showing a comparison between the manufacturing method of the joined structure according to the first embodiment and the comparative example.

[0041] Figure 9 compares the bonded structure manufacturing methods using OCA, OCR, and the method of the first embodiment. In Figure 9, "deformation of adhesive after application" means that the shape and thickness of the adhesive 31 cannot be maintained after the adhesive 31 is applied to the cover lens 20. Figure 10 shows the state in which the adhesive 31 has flowed down the surface of the cover lens 20 after being applied to the cover lens 20. Even if the cover lens 20 is laminated on the display panel 10 in the state shown in Figure 10, the thickness of the adhesive 31 between the display panel 10 and the cover lens 20 becomes uneven, and the gap between them cannot be filled.

[0042] 9, "misalignment after lamination" means that the display panel 10 and the cover lens 20 are displaced from their predetermined positions after the bonded structure is formed by laminating the display panel 10 and the cover lens 20. Fig. 11 shows the cover lens 20 displaced from its predetermined position after the bonded structure is formed.

[0043] In Fig. 9, "adhesive overflow during lamination" means that the adhesive overflows from a predetermined position when laminating the display panel 10 and the cover lens 20. Fig. 12 shows the adhesive 31a overflowing from between the display panel 10 and the cover lens 20 when forming the bonded structure.

[0044] In Fig. 9, "cure shrinkage after lamination" means that when adhesive 31 is cured to form cured resin layer 30, it shrinks and changes in shape and size. In Fig. 9, "release liner" means whether or not a release liner is required when handling adhesive 31. In Fig. 9, "thickening" means forming cured resin layer 30 to a predetermined thickness. In Fig. 9, "cost" means the cost required to manufacture the bonded structure.

[0045] As shown in Figure 9, the manufacturing of a bonded structure using OCA has the following characteristics: there is no deformation of the adhesive after application, no misalignment after lamination, no overflow of the adhesive during lamination, and little shrinkage after curing. On the other hand, the manufacturing of a bonded structure using OCA requires a process for removing the release liner because it has a so-called double-sided tape structure. Furthermore, it is difficult to process the cured resin layer to a large thickness when manufacturing a bonded structure using OCA. These factors result in increased costs.

[0046] In the manufacturing of bonded structures using OCR, the adhesive is liquid, so there is no need for a release liner, thick films can be produced, and costs are low. On the other hand, in the manufacturing of bonded structures using OCR, the adhesive may deform after application, which may cause misalignment of the cover lens or display panel after lamination. Furthermore, in the manufacturing of bonded structures using OCR, there is a risk of adhesive overflow during lamination, and there is a risk of the cured resin layer shrinking after lamination.

[0047] In the manufacturing of the bonded structure of the embodiment, an adhesive curing process is performed after applying the adhesive to the cover lens. This prevents deformation of the adhesive after application, even when using a liquid adhesive such as OCR, and allows a resin layer of a predetermined thickness to be obtained. Furthermore, because the adhesive functions to the cover lens and the adhesive function of the modified cured resin layer surface are used to bond the display panel, misalignment of the cover lens and display panel after lamination can be suppressed. Furthermore, the adhesive curing process can also prevent adhesive overflow during lamination.

[0048] Furthermore, since OCR is bonded when viscosity increase has not yet begun or is relatively low in order to develop sufficient adhesive strength, curing shrinkage occurs after bonding, and internal stress due to curing shrinkage occurs between the cover or display panel and the cured resin layer. However, in the manufacturing of the bonded structure of the embodiment, after the adhesive on the cover lens is cured to form a cured resin layer, the surface of the cured resin layer is modified, so that curing shrinkage of the cured resin layer after lamination can also be suppressed. In other words, this contributes to preventing peeling of the bonded structure.

[0049] In this way, according to the manufacturing method of the joined structure of the embodiment, it is possible to achieve both formability of the joined structure and prevention of peeling of layers.

[0050] Second Embodiment A second embodiment will be described in detail below with reference to the drawings. In the manufacturing method of this embodiment, the display panel 10 and cover lens 20 having a planar shape in the manufacturing method of the first embodiment are changed to a display panel and cover lens having a curved shape. In the following description, elements common to the first embodiment are denoted by the same reference numerals, and duplicated description will be omitted. Figure 13 is a cross-sectional view showing a cross section of a bonded structure produced by the manufacturing method of a bonded structure according to the second embodiment.

[0051] 13, the bonded structure 2 produced by the manufacturing method of the embodiment constitutes a display device having a display panel 15, a cover lens 25, and a cured resin layer 35. As shown in Fig. 13, in this embodiment, the display panel 15, the cover lens 25, and the cured resin layer 35 have curved shapes.

[0052] The display panel 15 is the same as the display panel 10 of the first embodiment except for its shape. The cover lens 25 is the same as the cover lens 20 of the first embodiment except for its shape. The cured resin layer 35 is the same as the cured resin layer 30 of the first embodiment except for its shape.

[0053] (Manufacturing method of second embodiment) Next, a manufacturing method of a bonded structure of the second embodiment will be described with reference to Figs. 14 to 19. Fig. 14 is a cross-sectional view showing an adhesive application step in the manufacturing method of a bonded structure of the second embodiment. Fig. 15 is a cross-sectional view showing an adhesive curing step in the manufacturing method of a bonded structure of the second embodiment. Fig. 16 is a cross-sectional view showing a cured resin layer modification step in the manufacturing method of a bonded structure of the second embodiment. Fig. 17 is a cross-sectional view showing a display panel modification step in the manufacturing method of a bonded structure of the second embodiment. Fig. 18 is a cross-sectional view showing a pressure bonding step in the manufacturing method of a bonded structure of the second embodiment. Fig. 19 is a flowchart showing the manufacturing method of a bonded structure of the second embodiment.

[0054] [Adhesive Application Process] As shown in Figure 14, a cover lens 25 having a curved shape is placed on a curved table (not shown). Next, a slit die 41 and a pump (not shown) or the like are prepared. The slit die 41 is a device capable of forming a coating film on a curved member. The slit die 41 has a function of supplying liquid adhesive 31 supplied by a pump (not shown) or the like to the cover lens 25. The item placed on the curved table (not shown) may be a display panel, and the adhesive 31 may be applied thereto using the slit die.

[0055] The adhesive 31 is applied to the convex surface (bonding surface) of the cover lens 25 while the slit die 41 is moved along the surface of the cover lens 25 (S200). A film of the adhesive 31 is formed on the convex surface of the cover lens 25. The convex surface is, for example, a surface whose central portion protrudes more than the peripheral portion (convex surface).

[0056] 14, the adhesive 31 is applied while the slit die 41 is moved along the convex surface of the fixed cover lens 25, but this is not limiting. The slit die 41 may be fixed and apply the adhesive 31 while the cover lens 25 is moved along the convex surface.

[0057] [Adhesive Curing Process] Next, as shown in Figure 15, an ultraviolet (UV) irradiation device 50 is used to irradiate the adhesive 31 on the cover lens 25 with ultraviolet light 51 of a predetermined wavelength for a predetermined period of time (S210). Irradiating the adhesive 31 with ultraviolet light acts to harden the adhesive 31. This prevents the adhesive 31 from flowing over the cover lens 25 and changing its shape or thickness. When hardened, the adhesive 31 becomes a cured resin layer 35 having a curved shape. The wavelength of the ultraviolet light irradiated on the adhesive 31 is, for example, 365 nm.

[0058] The ultraviolet irradiation device 50 may be of any type as long as it can generate ultraviolet light of a wavelength that hardens the adhesive 31. The ultraviolet irradiation device 50 may be configured integrally with the slit die 41. For example, by providing the ultraviolet irradiation device 50 on the downstream side of the movement direction of the slit die 41, it becomes possible for the slit die 41 to apply ultraviolet light at the same time as the adhesive 31 is applied to the cover lens 25. This makes it possible to harden the adhesive 31 before it flows over the convex surface of the cover lens 25. If the slit die 41 is fixed and the cover lens 25 is moved along the convex surface, it is possible to similarly apply ultraviolet light by irradiating the adhesive 31 downstream of the application position of the adhesive 31 on the slit die 41.

[0059] 16 , a plasma generator 60 is used to irradiate the cured resin layer 35 cured on the cover lens 25 with plasma 61 for a predetermined time (S220). The surface of the cured resin layer 35 exposed to the plasma 61 is activated (modified). As a result, a modified layer 36 having OH groups is formed on the surface of the cured resin layer 35.

[0060] 17, a plasma generator 60 is used to irradiate plasma 61 onto the concave surface of the display panel 15 for a predetermined time (S220). The concave surface of the display panel 15 exposed to the plasma 61 is activated (modified). As a result, a modified layer 16 having OH groups is formed on the concave surface of the display panel 15. The concave surface is, for example, a surface whose center is recessed more than its peripheral edge (concave surface).

[0061] The adhesive function of the adhesive 31 is reduced when it hardens to form the cured resin layer 35. The adhesive function of the modified layer 36 is restored by the OH groups. Similarly, the adhesive function of the modified layer 16 on the display panel 15 is imparted by the OH groups.

[0062] 18 , the cover lens 25 and the display panel 15 are housed in a chamber 70 and pressed together in a substantially vacuum (S230). The display panel 15 is pressed against the convex surface of the cover lens 25 with its concave surface (bonding surface) on which the modified layer 16 is formed facing the convex surface of the cover lens 25 on which the modified layer 36 is formed.

[0063] The step of bonding the display panel 15 and the cover lens 25 may be performed by placing the display panel 15 face down and bonding the cover lens 25 from above. The bonding does not have to be performed inside the chamber 70. That is, the bonding does not have to be performed in a vacuum. The display panel 15 and the cover lens 25 may be bonded together using a roller or the like.

[0064] As a result of the pressure bonding, the bonded structure 2 shown in Fig. 13 is completed. According to the manufacturing method described above, the cured resin layer 35 is formed between the display panel 15 and the cover lens 25 while maintaining a predetermined shape. Before laminating the display panel 15 and the cover lens 25, the cured resin layer 35 is formed on the cover lens 25 by curing the adhesive 31, so that the adhesive 31 can be formed into and maintained in a predetermined shape before lamination.

[0065] Furthermore, according to the manufacturing method described above, the surface of the cured resin layer 35 obtained by curing the adhesive 31 is modified to generate OH groups, so that the cured resin layer 35 can be adhered to the display panel 15 without changing its shape.

[0066] In the above-described manufacturing method, the adhesive 31 is assumed to be an ultraviolet-curing type and is cured using ultraviolet light, but this is not limiting. If the adhesive 31 is a heat-curing type, the adhesive 31 may be cured by heating it at a predetermined temperature for a predetermined time using a heater. Furthermore, if the adhesive 31 is an ultraviolet delayed-curing type, the ultraviolet irradiation time by the ultraviolet irradiation device 50 may be appropriately adjusted.

[0067] In the above-described manufacturing method, the surface of the cured resin layer 35 obtained by curing the adhesive 31 and the surface of the display panel 15 are activated (modified) by plasma irradiation, but this is not limiting. Other methods may be used as long as they can activate the surface of the cured resin layer 35 and the surface of the display panel 15 and generate OH groups. For example, ultraviolet irradiation at a predetermined wavelength may be used.

[0068] In the manufacturing method of the joined structure of this embodiment, it is possible to achieve both formability of the joined structure and prevention of peeling of layers.

[0069] (Third Embodiment) Hereinafter, a third embodiment will be described in detail with reference to the drawings. In the manufacturing method of this embodiment, the display panel 10 and cover lens 20 having a planar shape in the manufacturing method of the first embodiment are changed to a display panel and cover lens having a curved shape. In the following description, elements common to the first embodiment will be denoted by the same reference numerals, and duplicated description will be omitted. Figure 20 is a cross-sectional view showing a cross section of a bonded structure produced by the manufacturing method of a bonded structure according to the third embodiment.

[0070] 20, the bonded structure 3 produced by the manufacturing method of the embodiment constitutes a display device having a display panel 17, a cover lens 27, and a cured resin layer 37. As shown in Fig. 20, in this embodiment, the display panel 17, the cover lens 27, and the cured resin layer 37 have curved shapes.

[0071] The display panel 17 is the same as the display panel 10 of the first embodiment except for the fact that it has a property that allows it to be bent in a direction perpendicular to its surface. The cover lens 27 is the same as the cover lens 20 of the first embodiment except for its shape. The cured resin layer 37 is the same as the cured resin layer 30 of the first embodiment except for the fact that it has a property that allows it to be bent in a direction perpendicular to its surface after the adhesive has hardened.

[0072] (Manufacturing Method of Third Embodiment) Next, a method for manufacturing a bonded structure of the third embodiment will be described with reference to Figs. 21 to 26. Fig. 21 is a cross-sectional view showing an adhesive application step in the method for manufacturing a bonded structure of the third embodiment. Fig. 22 is a cross-sectional view showing an adhesive curing step in the method for manufacturing a bonded structure of the third embodiment. Fig. 23 is a cross-sectional view showing a cured resin layer modification step in the method for manufacturing a bonded structure of the third embodiment. Fig. 24 is a cross-sectional view showing a cover lens modification step in the method for manufacturing a bonded structure of the third embodiment. Fig. 25 is a cross-sectional view showing a pressure bonding step in the method for manufacturing a bonded structure of the third embodiment. Fig. 26 is a flowchart showing the method for manufacturing a bonded structure of the third embodiment.

[0073] 21, a display panel 17 that can be bent in the vertical direction of its surface is placed on a horizontal table (not shown). Next, a slit die 40 and a pump (not shown) are prepared. The slit die 40 is a device that can form a coating film on a member.

[0074] The adhesive 38 is applied to the surface (joining surface) of the display panel 17 while the slit die 40 is moved along the surface of the display panel 17 (S300). A film of the adhesive 38 is formed on the surface of the display panel 17.

[0075] 21, the adhesive 38 is applied while the slit die 40 is moved along the surface of the display panel 17 placed on a horizontal table, but the present invention is not limited to this. The slit die 40 may be fixed and apply the adhesive 38 while the display panel 17 is moved in the horizontal direction.

[0076] 22, an ultraviolet (UV) irradiation device 50 is used to irradiate the adhesive 38 on the display panel 17 with ultraviolet light 51 of a predetermined wavelength for a predetermined time (S310). Irradiating the adhesive 38 with ultraviolet light acts to harden the adhesive 38. This prevents the adhesive 38 from flowing on the display panel 17 and changing its shape or thickness. The adhesive 38 hardens to form a cured resin layer 37. The wavelength of the ultraviolet light irradiated on the adhesive 38 is, for example, 365 nm.

[0077] The adhesive 38 preferably has a property that, when cured to form the cured resin layer 37, enables the cured resin layer 37 to bend in a direction perpendicular to its surface. This property may be realized by adjusting the irradiation time of the ultraviolet light 51.

[0078] The ultraviolet irradiation device 50 may be of any type as long as it can generate ultraviolet light of a wavelength sufficient to harden the adhesive 38. The ultraviolet irradiation device 50 may be configured integrally with the slit die 40. For example, by providing the ultraviolet irradiation device 50 downstream of the slit die 40 in the direction of movement, it becomes possible for the slit die 40 to apply the adhesive 38 to the display panel 17 and simultaneously irradiate ultraviolet light. This makes it possible to harden the adhesive 38 before it flows over the surface of the display panel 17. In the case where the slit die 40 is fixed and the display panel 17 is moved along the surface, it is possible to similarly apply ultraviolet light irradiating the adhesive 38 downstream of the application position of the adhesive 38 on the slit die 40.

[0079] 23 , a plasma generator 60 is used to irradiate plasma 61 onto the cured resin layer 37 on the display panel 17 for a predetermined time (S320). The surface of the cured resin layer 37 exposed to the plasma 61 is activated (modified). As a result, a modified layer 39 having OH groups is formed on the surface of the cured resin layer 37.

[0080] 24 , plasma 61 is irradiated onto the convex surface of cover lens 27 for a predetermined time using plasma generator 60 (S320). The convex surface of cover lens 27 exposed to plasma 61 is activated (modified). As a result, modified layer 28 having OH groups is formed on the convex surface of cover lens 27.

[0081] The adhesive function of the adhesive 38 decreases when it hardens to form the cured resin layer 37. The adhesive function of the modified layer 39 is restored by the OH groups. Similarly, the adhesive function of the modified layer 28 on the cover lens 27 is imparted by the OH groups.

[0082] 25 , the display panel 17 and the cover lens 27 are housed in a chamber 70 and pressed together in a substantially vacuum (S330). The display panel 17 is pressed against the convex surface of the cover lens 27 with the surface on which the modified layer 39 is formed (the bonding surface) facing the convex surface of the cover lens 27 on which the modified layer 28 is formed.

[0083] In the step of bonding the display panel 17 and the cover lens 27 together, the display panel 17 may be placed face down and the cover lens 27 may be attached from above. The bonding does not have to be performed inside the chamber 70. In other words, the bonding does not have to be performed in a vacuum. The display panel 17 and the cover lens 27 may be bonded together using a roller or the like.

[0084] As a result of the pressure bonding, the bonded structure 3 shown in Fig. 20 is completed. According to the manufacturing method described above, the cured resin layer 37 is formed between the display panel 17 and the cover lens 27 while maintaining a predetermined shape. Because the cured resin layer 37 is formed on the display panel 17 by curing the adhesive 38 before laminating the display panel 17 and the cover lens 27, the adhesive 38 can be formed into and maintained in a predetermined shape before lamination.

[0085] In this embodiment, the cured resin layer 37 is formed on the display panel 17 having a bendable characteristic, and is then pressure-bonded to the cover lens 27 having a curved surface, but this is not limiting. A cured resin layer may also be formed on a cover lens having a bendable characteristic, and then the cover lens may be pressure-bonded to the display panel having a curved surface.

[0086] Furthermore, according to the manufacturing method described above, the surface of the cured resin layer 37 obtained by curing the adhesive 38 is modified to generate OH groups, so that the cured resin layer 37 can be adhered to the cover lens 27 without changing its shape.

[0087] In the above-described manufacturing method, the adhesive 38 is assumed to be ultraviolet-curable and is cured using ultraviolet light, but this is not limiting. If the adhesive 38 is a heat-curable type, the adhesive 38 may be cured by heating it at a predetermined temperature for a predetermined time using a heater. Furthermore, if the adhesive 38 is an ultraviolet delayed-curable type, the ultraviolet irradiation time by the ultraviolet irradiation device 50 may be appropriately adjusted.

[0088] In the manufacturing method described above, the surface of the cured resin layer 37 obtained by curing the adhesive 38 and the surface of the cover lens 27 are activated (modified) by plasma irradiation, but this is not limiting. Other methods may be used as long as they can activate the surface of the cured resin layer 37 and generate OH groups. For example, ultraviolet irradiation at a predetermined wavelength may be used.

[0089] In the manufacturing method of the joined structure of this embodiment, it is possible to achieve both formability of the joined structure and prevention of peeling of layers.

[0090] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0091] DESCRIPTION OF SYMBOLS 1 to 3... Bonded structure 10, 15, 17... Display panel 12, 16, 28... Modified layer 20, 25, 27... Cover lens 30, 35, 37... Cured resin layer 31, 31a, 38... Adhesive 32, 36, 39... Modified layer 40, 41... Slit die 50... Ultraviolet irradiation device 60... Plasma generation device

Claims

1. A method for manufacturing a bonded structure in which a first substrate and a second substrate are bonded, comprising the steps of: applying a liquid reactive adhesive to a bonding surface of the first substrate; curing the reactive adhesive applied to the first substrate to form a cured resin layer on the first substrate; activating a surface of the cured resin layer formed on the first substrate to form a first modified layer with an activated surface on the surface of the cured resin layer; activating a bonding surface of the second substrate to form a second modified layer with an activated surface on the surface of the second substrate; and crimping the first substrate and the second substrate together with the first modified layer facing each other.

2. The manufacturing method according to claim 1, wherein the curing of the reactive adhesive includes curing by heating to a predetermined temperature or by irradiating ultraviolet light of a predetermined wavelength.

3. The manufacturing method according to claim 1, characterized in that the activation of the surface of the cured resin layer and the activation of the bonding surface of the second substrate are achieved by introducing polar functional groups such as hydroxyl groups and carbonyl groups to the ends using active oxygen species.

4. The manufacturing method according to claim 1, wherein the cured resin layer has a hardness of at least 200 in terms of penetration at 25° C. as defined by JIS K2220.

5. The manufacturing method according to claim 1, wherein the reactive adhesive has a viscosity of 0.001 to 100,000 mPa·s.

6. The manufacturing method according to claim 1, characterized in that the reactive adhesive is one or a mixture of two or more of polyester resin, polyolefin resin, norbornene resin, acrylic resin, urethane resin, polyvinyl chloride resin, fluororesin, polycarbonate resin, polyvinyl butyral resin, polyvinyl alcohol resin, polyimide resin, polyamideimide resin, epoxy resin, silicone resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, and polyarylene ether phosphine oxide resin.

7. The manufacturing method according to claim 6, characterized in that the polyester resin includes at least one of polyethylene terephthalate and polybutylene terephthalate, the polyolefin resin includes at least one of polyethylene, polypropylene and ethylene-vinyl acetate copolymer, and the acrylic resin includes at least one of polyacrylate and polymethyl methacrylate.

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