Manufacturing method for a structure having a foamed resin layer, manufacturing method for an interior body, and manufacturing method for an electronic device

Abstract

To provide a method for manufacturing a structure having a foamed resin layer that can form a foamed resin layer in a short time, a method for manufacturing an interior component, and a method for manufacturing an electronic device. [Solution] A substrate 5 coated with mixture 10 is placed inside the cavity 4 of mold 1. The mixture 10 contains an ultraviolet-curable adhesive and heat-expandable microcapsules. When mold 1 is closed and ultraviolet light is irradiated onto the mixture 10, the adhesive resin component contained in the adhesive polymerizes, and the heat generated by the polymerization reaction heats the microcapsules. As the heated microcapsules expand, a foamed resin layer 11 is produced that is bonded to the substrate 5.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a structure having a foamed resin layer that has good adhesion to a substrate and can generate air bubbles inside in a short time, a method for manufacturing an interior component using the method for manufacturing the structure, and a method for manufacturing an electronic device using the method for manufacturing the structure. [Background technology]

[0002] Patent documents 1 and 2 describe inventions relating to methods for manufacturing articles. The invention described in Patent Document 1 involves placing a foamed adhesive sheet between a first member and a second member. The foamed adhesive sheet contains an adhesive composition containing a thermosetting resin and a foaming agent. The foaming agent is a thermally expandable microcapsule, in which a thermally expandable agent such as a hydrocarbon is encapsulated inside a resin shell. The foamed adhesive sheet is heated to advance the curing reaction of the thermosetting resin and improve the adhesive strength, thereby joining the two members with the foamed adhesive sheet. At the same time, the shells of the thermally expandable microcapsules are softened, and the thermally expandable agent inside the shells is expanded, forming a foamed layer on the foamed adhesive sheet.

[0003] The method for manufacturing an article described in Patent Document 2 also includes an adhesive member between a first member and a second member. The adhesive member has at least a curable adhesive layer, and the curable adhesive layer is a foam layer having a foamed cured product containing a curable adhesive and a foaming agent. Examples of foaming agents include thermally expandable microcapsules. Examples of curable adhesives include thermosetting adhesives and photocurable adhesives. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7280986 [Patent Document 2] Japanese Patent Publication No. 2023-137382 [Overview of the project] [Problems that the invention aims to solve]

[0005] The methods for manufacturing articles described in Patent Documents 1 and 2 both involve heating an adhesive layer provided between a first member and a second member from the outside to soften the shells of the thermally expandable microcapsules contained in the adhesive member, thereby expanding the thermally expandable agent inside the shells. However, this manufacturing method requires a long time to expand the thermally expandable microcapsules. This is thought to be because the heat applied to the adhesive layer from the outside is absorbed by the adhesive composition, making it difficult to transfer heat to the expandable microcapsules dispersed inside the adhesive layer, and thus requiring a long time to reach the temperature at which the expandable microcapsules expand.

[0006] Because the heat-expandable microcapsules require a long heating time to fully expand, the adhesive composition may be subjected to excessive heat, potentially leading to degradation of the adhesive composition and a decrease in adhesive strength.

[0007] The present invention aims to solve the above-mentioned conventional problems and to provide a method for manufacturing a structure having a foamed resin layer, which can form a foamed resin layer in a short time by polymerizing the adhesive resin in the adhesive by ultraviolet irradiation and expanding the thermally expandable microcapsules with the heat generated by the polymerization reaction, as well as a method for manufacturing an interior body and a method for manufacturing an electronic device using the method for manufacturing the structure. [Means for solving the problem]

[0008] The present invention relates to a method for manufacturing a structure having a base material and a foamed resin layer bonded to the base material, (A) A step of applying a mixture of a photopolymerization initiator and an adhesive resin component, and a heat-expandable microcapsule, to the substrate. (B) A step of irradiating the mixture with ultraviolet light to polymerize the adhesive resin component and expanding the microcapsules due to the heat generated by the polymerization reaction to produce the foamed resin layer, Includes, A method for manufacturing a structure having a foamed resin layer, characterized in that the foamed resin layer is bonded to the substrate by the adhesive strength of the adhesive resin component.

[0009] The method for manufacturing a structure having a foamed resin layer of the present invention is as follows: In step (A) above, it is preferable to apply the mixture to the substrate to a thickness dimension less than or equal to the curing depth when the cumulative amount of ultraviolet energy recommended for the adhesive is applied.

[0010] The method for manufacturing a structure having a foamed resin layer of the present invention is as follows: Preferably, the curing depth is greater than 5 mm, and more preferably, the curing depth is 5.1 mm or more and 10.5 mm or less.

[0011] The method for manufacturing a structure having a foamed resin layer of the present invention is as follows: The mixture preferably contains 50 parts by mass or less of the microcapsules per 100 parts of the adhesive, and more preferably contains 0.1 parts by mass or more and 50 parts by mass or less of the microcapsules per 100 parts of the adhesive.

[0012] The method for manufacturing a structure having a foamed resin layer of the present invention is as follows: Using a mold having a cavity whose internal height dimension is greater than the total thickness dimension of the substrate and the mixture used in step (A) above, the substrate and the mixture are placed in the cavity. The process in (B) above can be carried out by irradiating the mixture with ultraviolet light, which is transmitted through the mold.

[0013] The present invention relates to a method for manufacturing an interior lining, characterized by forming a cushion layer with the foamed resin layer using the method for manufacturing a structure having the foamed resin layer.

[0014] Further, in the method for manufacturing an electronic device of the present invention, the base material is a printed circuit board on which electronic components are mounted, and a cover layer that covers the electronic components with the foamed resin layer is formed by using the method for manufacturing the structure having the foamed resin layer.

Advantages of the Invention

[0015] In the method for manufacturing a structure having a foamed resin layer of the present invention, ultraviolet rays are irradiated onto a mixture of an ultraviolet-curable adhesive and thermally expandable microcapsules to polymerize the adhesive resin component contained in the adhesive. With the heat generated from the inside of the mixture accompanying this polymerization reaction, the microcapsules are expanded to form a foamed resin layer. By utilizing the heat generation from the inside of the mixture, the thermally expandable microcapsules can be expanded in a short time. Further, since it is not necessary to heat the mixture with high-temperature heat from the outside, the adhesive resin component is not deteriorated, and it becomes possible to exhibit a strong adhesive force to the base material.

[0016] In the manufacturing method of the present invention, the volume expansion rate of the adhesive can be adjusted by adjusting the mixing amount of the microcapsules with respect to the adhesive. By setting the volume expansion rate higher, a cushion layer for an interior body such as an automobile can be manufactured. By setting the volume expansion rate lower, it is also possible to manufacture a cover layer that covers electronic components with a foamed resin layer.

Brief Description of the Drawings

[0017] <m [Figure 1] (A)(B)(C)(D) are explanatory diagrams showing embodiments of the method for manufacturing a structure having a foamed resin layer of the present invention. [Figure 2] A perspective view showing an interior body used in an automobile or the like manufactured by the manufacturing method of the present invention. [Figure 3] A cross-sectional view showing an electronic device manufactured by the manufacturing method of the present invention. [Figure 4] A diagram explaining the bonding strength between the foamed resin layer and the base material manufactured by the manufacturing method of the present invention. [Figure 5] An explanatory diagram showing the method for measuring the bonding strength shown in FIG. 4. [Modes for carrying out the invention]

[0018] Figure 1 shows an embodiment of a method for manufacturing a structure having a foamed resin layer according to the present invention.

[0019] The mold 1 for molding the foamed resin layer has a lower mold 2 and an upper mold 3. At least the upper mold 3 is made of a material that transmits ultraviolet light. The wavelength of ultraviolet light that the upper mold 3 can transmit is, for example, 300 nm or more and 430 nm or less. As shown in Figure 1(B), when the lower mold 2 and the upper mold 3 are joined together, a cavity 4 is formed in which the recess 2a of the lower mold 2 and the recess 3a of the upper mold 3 are continuous. The upper mold 3 is made of a transparent resin material that has poor affinity for ultraviolet-curable adhesives, for example, an olefin resin such as polypropylene or polyethylene. Alternatively, a fluororesin film may be formed on the inner surface of the recess 3a of the upper mold 3. Furthermore, it is preferable that the inner surface of the recess 2a of the lower mold 2 also has a structure that has poor affinity for ultraviolet-curable adhesives.

[0020] As shown in Figure 1(A), when mold 1 is open, the base material 5 and the mixture 10 containing adhesive are placed in the recess 2a of the lower mold 2. The mixture 10 is a liquid mixture with the adhesive still uncured. The base material 5 is placed in the recess 2a with the mixture 10 already applied to it. Alternatively, the base material 5 may be placed at the bottom of the recess 2a first, and then the mixture 10 containing adhesive may be applied to the base material 5. The base material 5 is selected according to the intended use of the manufactured structure. If the manufactured structure is the interior body 21 of an automobile shown in Figure 2, the base material 5 is a metal such as iron. If the manufactured structure is the electronic device 22 shown in Figure 3, the base material 5 is a printed circuit board on which electronic components are mounted.

[0021] As shown in Figure 1(B), with mold 1 closed, the internal height dimension H1 of cavity 4 is sufficiently larger than the thickness dimension T which includes both the base material 5 and the mixture 10, and a molding space with height dimension H2 is formed inside cavity 4 above the surface (liquid surface) of the mixture 10. The height dimension H2 is 0.1 mm or more, preferably 0.2 mm or more. The upper limit of the height dimension H2 varies depending on the product being manufactured, but is for example 50 mm, preferably about 25 mm.

[0022] The mixture (mixture) 10 contains an ultraviolet-curable adhesive and thermally expandable microcapsules as a foaming agent. The microcapsules are granular, and numerous microcapsules are dispersed within the adhesive. The ultraviolet-curable adhesive contains a photopolymerization initiator, an adhesive resin component, and various additives. As the adhesive resin component, acrylic-based materials (various acrylate monomers) that cure by radical polymerization and epoxy-based materials that cure by cationic polymerization can be used. The thermal expansion of the microcapsules utilizes internal heat generation due to the polymerization reaction of the adhesive resin component. However, the amount of heat generated by the polymerization reaction is affected by the reactivity of the monomers, the type of photoradical polymerization initiator, and the respective mixing ratios. Therefore, it is preferable to select these factors optimally to construct the adhesive.

[0023] Thermally expandable microcapsules consist of a thermoplastic polymer shell containing an expander such as a liquid hydrocarbon. For example, "Matsumoto Microspheres®" manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd. are used. These microcapsules have a particle size of approximately 5 μm to 50 μm. When heated, the shell softens, the liquid hydrocarbon inside turns into a gas, the internal pressure of the shell increases, and the shell expands. The expansion of a single microcapsule alone can increase its volume by 50 to 100 times.

[0024] In the mold clamping state shown in Figure 1(B), ultraviolet (UV) light is irradiated into the cavity through the upper mold 3. A UV LED is used as the light source for UV irradiation, with a wavelength of, for example, 365-405 nm. When UV light is irradiated onto the mixture 10, the adhesive resin component of the UV-curable adhesive contained in the mixture 10 polymerizes and begins to harden. At the same time, the mixture 10 is heated from the inside due to the heat generated by the polymerization reaction of the adhesive resin component, and the thermally expandable microcapsules expand with this internal heat, causing the mixture 10 to become a foamed resin layer. If the adhesive resin component is acrylic, UV irradiation decomposes the photopolymerization initiator and generates radicals, which act on the acrylate, which is a monomer or oligomer, and polymerization begins. Due to the internal heat generated by this radical polymerization, the shells of the microcapsules soften, and the liquid hydrocarbons inside the shells expand and vaporize, causing the mixture 10 to transform into a foamed resin layer 11, as shown in Figure 1(C).

[0025] At the time the mixture 10 is applied to the substrate 5, the UV-curable adhesive has affinity for the substrate 5, such as metal. As soon as the mixture 10 is applied to the substrate 5, it adheres to the surface of the substrate 5, so even after the adhesive resin component polymerizes and the microcapsules expand, the adhesive strength between the foamed resin layer 11 and the substrate 5 is maintained. On the other hand, during the foaming process, the mixture 10 comes into contact with the inner surface of the recess 2a of the lower mold 2 that is not covered by the substrate 5 and the inner surface of the recess 3a of the upper mold 3, but the mixture 10 during the foaming process does not exhibit strong adhesion to the inner surfaces of the recesses 2a and 3a that it subsequently comes into contact with. In addition, since the lower mold 2 and the upper mold 3 are made of materials that have poor affinity for the adhesive resin component, such as olefin resin, as shown in Figure 1(D), when the mold 1 is opened, the upper mold 3 easily separates from the foamed resin layer 11, and the foamed resin layer 11 can maintain its outer shape at the time of molding.

[0026] Figure 2 shows an example of an automobile interior 21 having a foamed resin layer manufactured by the above manufacturing method. In this interior 21, the base material 5 is a metal plate. The volume expansion rate when the mixture 10 containing the UV-curable adhesive is transformed into the foamed resin layer 11 is 500% or more, preferably 900% or more, so that the foamed resin layer 11 can function as a cushioning layer. The foamed resin layer 11 takes on a three-dimensional shape with a smooth curved surface on its surface, depending on the shape of the cavity of the mold 1. Figure 3 shows an electronic device 22 as an example of an electronic device having a foamed resin layer manufactured by the above manufacturing method. The base material 5 of this electronic device 22 is a printed circuit board 5a on which a plurality of electronic components 5b constituting an electronic circuit are mounted. The foamed resin layer 11 is a cover layer that covers the plurality of electronic components 5b. The volume expansion rate when the mixture 10 containing the UV-curable adhesive is transformed into the foamed resin layer 11 which becomes the cover layer is preferably 105% or more and about 130% or less, for example, 110%. By setting a lower coefficient of volumetric expansion, the cover layer can exhibit sufficient strength while also possessing elasticity, thus reducing the stress acting on each electronic component 5b from the cover layer.

[0027] The volume expansion rate when the mixture 10 transforms into the foamed resin layer 11 can be controlled by changing the amount of microcapsules added to the UV-curable adhesive in the mixture 10. To achieve a volume expansion rate of 500% or more, as in the foamed resin layer 11 which forms the cushion layer of the interior body 21 shown in Figure 2, it is preferable to add 15 parts by mass or more, or 20 parts by mass or more, of microcapsules per 100 parts of UV-curable adhesive. To achieve a volume expansion rate of 900% or more for the foamed resin layer 11 of the interior body 21, it is preferable to add 25 parts by mass or more of microcapsules per 100 parts of UV-curable adhesive. To achieve a volume expansion rate of approximately 105% or more and 130% or less for the foamed resin layer 11, as in the cover layer used in the electronic device 22 shown in Figure 3, it is preferable to add 0.05 parts by mass or more and 0.5 parts by mass or less of microcapsules per 100 parts of UV-curable adhesive. However, if the amount of microcapsules added exceeds 50 parts by mass per 100 parts of UV-curable adhesive, it is undesirable because the adhesive strength of the foamed resin layer 11 to the substrate 5 decreases. Regarding the formation of the mixture 10, it is preferable that the amount of microcapsules is 0.05 parts by mass or more and 50 parts by mass or less per 100 parts of adhesive, and it is even more preferable that the amount of microcapsules is 0.1 parts by mass or more and 50 parts by mass or less per 100 parts of adhesive.

[0028] The UV-curable adhesive contained in mixture 10, when irradiated with UV light at the recommended cumulative light intensity, undergoes polymerization of its adhesive resin components due to the energy of the UV light, causing the adhesive to harden to a predetermined depth from the liquid surface. In this specification, the depth to which polymerization proceeds and hardening occurs when irradiated with UV light at the recommended cumulative light intensity is referred to as "hardening depth," and standards for adhesives with different hardening depths are referred to as "deep hardening properties." For example, UV-curable adhesive A2, exemplified in Table 1 in the Examples section later, undergoes polymerization at the recommended cumulative light intensity of 3,000 mJ / cm². 2 The depth of curing, i.e., curing depth, is 5.5 mm when irradiated with ultraviolet light at 4,500 mJ / cm². Furthermore, the ultraviolet-curable adhesive B1 exemplified in Table 2 has a recommended cumulative light intensity of 4,500 mJ / cm². 2The depth of curing, or curing depth, when irradiated with ultraviolet light is 1.7 mm. This difference in depth of curing can be attributed to differences in the properties and content of the photopolymerization initiator contained in the adhesive, as well as differences in the properties of the monomers and oligomers that make up the adhesive resin components.

[0029] Next, we will consider the relationship between the difference in curing depth and the thermal expansion of microcapsules. When using mixture 10 containing a UV-curable adhesive with a large (deep) curing depth, as listed in Table 1 in the Examples section below, when irradiated with the recommended cumulative amount of UV light, the thermally expandable microcapsules expand in an extremely short time of 3 to 10 seconds, forming a foamed resin layer. In contrast, when using mixture 10 containing a UV-curable adhesive with a small (shallow) curing depth, as listed in Table 2, even when irradiated with the recommended cumulative amount of UV light, the thermally expandable microcapsules do not expand, or if they do expand, the time required for expansion is long. The reason for this is that adhesives with a large (deep) curing depth, such as adhesive A2, generate a large amount of heat inside the adhesive due to the polymerization reaction of the adhesive resin components, and as a result, the polymerization reaction proceeds quickly from the liquid surface of the adhesive to a deep position. It is thought that adhesives with a large (deep) curing depth can expand microcapsules in a short time because of the large amount of heat generated. On the other hand, adhesives with a small (shallow) curing depth, such as adhesive B1, require an integrated light intensity of 4,500 mJ / cm². 2 Despite the high value of ultraviolet energy delivered to the adhesive, the amount of heat generated inside the adhesive due to the polymerization reaction of the adhesive resin component is small. As a result, it can be inferred that the polymerization reaction only proceeds to a shallow depth from the liquid surface of the adhesive. This adhesive is thought to be unable to provide sufficient heat for the expansion of the microcapsules.

[0030] In this invention, it is preferable to use an ultraviolet-curable adhesive that has a curing depth of more than 5 mm when irradiated with the recommended cumulative amount of ultraviolet light. Furthermore, it is preferable to use an ultraviolet-curable adhesive that has a curing depth of 5.1 mm or more and 10.5 mm or less. In addition, the amount of ultraviolet light required to reach the recommended cumulative amount is 500 mW / cm². 2 Preferably, it is 1,000 mW / cm² or higher. 2 It is even more preferable that the above conditions are met. Furthermore, even when using an ultraviolet-curable adhesive with a curing depth of 5 mm or less at the recommended cumulative light intensity, the ultraviolet light intensity (unit: mW / cm²) is also important. 2 ) to increase and / or integrated light quantity (unit is mJ / cm 2 It is possible to promote heat generation inside the adhesive by changing the ultraviolet irradiation conditions, such as by increasing the size of the UV irradiator, thereby expanding the microcapsules inside the mixture and generating a foamed resin layer. Furthermore, the present invention includes a method in which the mixture 10 is auxiliaryly heated from the outside, and the microcapsules are expanded by utilizing the internal heat generation of the adhesive due to polymerization of the adhesive resin component and the auxiliary external heating. [Examples]

[0031] The foaming function of mixtures containing UV-curable adhesives and heat-expandable microcapsules is described below. UV-curable adhesives A1, A2, A3, and A4 shown in Table 1 have a curing depth of 5.1 mm or more and 10.5 mm or less. UV-curable adhesives B1, B2, and B3 shown in Table 2 have a curing depth of 1.7 mm or more and 5.0 mm or less.

[0032] [Table 1]

[0033] Adhesive A1 is model number "5343" from the 5300 series of Kyōritsu Chemical Industry Co., Ltd., and its main component is modified acrylate monomer. Adhesives A2, A3, and A4 are all UV adhesives manufactured by Chemitech Co., Ltd., and their model numbers are "U2193C", "U2202", and "U2193B". The main component of adhesives A2, A3, and A4 is modified acrylate monomer.

[0034] [Table 2]

[0035] Adhesive B1 is model number "XVL-14L" from the XVL series of Kyōritsu Chemical Industry Co., Ltd., adhesive B2 is the UV adhesive "LOCTITE AA 8671 PSA AD" from Henkel Japan Ltd., and adhesive B3 is "AU589V" from Bostik Nitta Corporation. The main component of adhesives B1, B2, and B3 is modified acrylate monomer.

[0036] Table 3 shows Examples 1, 2, 3, and 4, which are mixtures of adhesives A1, A2, A3, and A4 with added thermally expandable microcapsules. Each example's mixture has a strength of 1,000 mW / cm 2 Table 1 shows the results of irradiating with ultraviolet light to achieve the cumulative light intensity shown. In Examples 1, 2, 3, and 4, the coating thickness of the mixture was set to 5.0 mm, which is smaller than the respective curing depth values. For the thermally expandable microcapsules, Matsumoto Microsphere F-35 from Matsumoto Oil & Fat Pharmaceutical Co., Ltd. was used.

[0037] [Table 3]

[0038] Each of the examples shown in Table 3 is mainly composed of a modified acrylate monomer, and for 100 parts of an ultraviolet curable adhesive with a curing depth of 5.1 mm to 10.5 mm, a mixture in which 0.1 to 50 parts by mass of thermally expandable microcapsules are added is used, and irradiated with ultraviolet rays of 1,000 (mW / cm 2 ). As a result, in Example 1, a foamed resin layer with a volume expansion rate of 110% could be obtained with an ultraviolet irradiation time of 5 seconds. In Example 2, a foamed resin layer with a volume expansion rate of 900% could be obtained with an ultraviolet irradiation time of 3 seconds. In Example 3, a foamed resin layer with a volume expansion rate of 1100% could be obtained with an ultraviolet irradiation time of 10 seconds. In Example 4, a foamed resin layer with a volume expansion rate of 1200% could be obtained with an ultraviolet irradiation time of 7 seconds. In all cases, a foamed resin layer could be obtained in a short time of 10 seconds or less of ultraviolet irradiation without requiring external heating. The foamed resin layer which is the result of Example 1 is suitable for use as a cover layer covering the electronic component 5b in the electronic device 22 shown in FIG. 3. The foamed resin layers which are the results of Example 2, Example 3 and Example 4 are suitable for use as cushion layers in the interior body 21 shown in FIG. 2.

[0039] Table 4 shows the results of irradiating Comparative Example 1, Comparative Example 2, and Comparative Example 3, which are mixtures obtained by adding thermally expandable microcapsules to adhesives B1, B2, and B3, with ultraviolet rays having an intensity of 1,000 (mW / cm 2 ) so as to obtain the integrated light quantity shown in Table 2. The mixture was not externally heated. In Comparative Example 1, Comparative Example 2, and Comparative Example 3, the coating thickness dimension of the mixture was 5.0 mm.

[0040]

Table 4

[0041] Table 5 shows the mixtures using the same adhesives B1, B2, and B3 as in Comparative Examples 1, 2, and 3, with the same parts by mass of microcapsules added as in Table 4. Comparative Example 4 uses the same mixture as Comparative Example 1, Comparative Example 5 uses the same mixture as Comparative Example 2, and Comparative Example 6 uses the same mixture as Comparative Example 3. However, in Comparative Examples 4, 5, and 6, the strength is 1,000 mW / cm². 2 The mixture was irradiated with ultraviolet light for the same amount of time as in Comparative Examples 1, 2, and 3, and then heated from the outside at a temperature of 100 degrees Celsius for 10 minutes.

[0042] [Table 5]

[0043] According to Comparative Examples 1, 2, and 3 shown in Table 4, when using UV-curable adhesives with a curing depth of 1.7 mm to 5.0 mm, even with irradiation of the recommended cumulative amount of UV light, the amount of heat generated inside the adhesive is insufficient, and the microcapsules hardly expand. According to Comparative Examples 4, 5, and 6 shown in Table 5, even when using UV-curable adhesives with a curing depth of 1.7 mm to 5.0 mm, the microcapsules can be expanded by heating from the outside to about 100 degrees Celsius in addition to UV irradiation.

[0044] In the present invention, as shown in Examples 1, 2, 3, and 4 of Table 3, if an UV-curable adhesive mainly composed of acrylic resin with a curing depth of 5.1 mm to 10.5 mm is used, a foamed resin layer can be formed in a short time of 10 seconds or less by UV irradiation alone, which is the most preferred embodiment. However, as shown in Comparative Examples 4, 5, and 6 of Table 5, even when a UV-curable adhesive with a curing depth of 1.7 mm to 5.0 mm is used, the microcapsules can be expanded by heating from the outside to about 100 degrees Celsius in addition to UV irradiation, although this takes about 10 minutes. Therefore, embodiments that involve heating in addition to UV irradiation, as shown in Comparative Examples 4, 5, and 6, are also included in the present invention.

[0045] Figures 4 and 5 show the evaluation of the adhesive strength between a mixture containing UV-curable adhesive and microcapsules and a substrate. In the adhesive strength measurement test shown in Figure 5, in (A), the mixture 10 is applied to the opposing surfaces of two polycarbonate resin plates 31 and 32, and in (B), the two resin plates 31 and 32 are joined together. The mixture is the same as in Example 1 of Table 3, and was applied to a width of 2 mm, a thickness of 0.2 mm, and a length of 25 mm in the transverse direction. In the diagram in Figure 4, the horizontal axis shows the displacement (mm) when the resin plates 31 and 32 are pulled in the planar direction, and the vertical axis shows the shear stress (MPa) acting on the mixture 10 at each displacement. In the diagram in Figure 4, (i) is the bonded state shown in Figure 5(B), where the mixture 10 is first heated at 100 degrees Celsius for 10 minutes, and then subjected to 1,000 mW / cm². 2 The figure shows the change in shear stress when the resin plates 31 and 32 are pulled in the planar direction after being irradiated with ultraviolet light of 1,000 mW / cm² for 5 seconds, causing the microcapsules to expand. Figure 4(ii) shows the bonded state shown in Figure 5(B), with 1,000 mW / cm² first applied. 2 The image shows the change in shear stress when the resin plates 31 and 32 are pulled in the planar direction after being irradiated with ultraviolet light for 5 seconds and then heated at 100 degrees Celsius for 10 minutes to expand the microcapsules.

[0046] As shown in Figure 4(ii), when the mixture is applied to the substrate 5 and then irradiated with ultraviolet light to form a foamed resin layer, the maximum shear stress (shear fracture strength) is large, indicating that the foamed resin layer has sufficient adhesive strength to the substrate 5. As shown in Figure 4(i), when the mixture 10 is foamed by external heating before ultraviolet irradiation, the maximum shear stress (shear fracture strength) decreases. From Figures 4 and 5, it can be seen that when the adhesive resin component contained in the mixture 10 is cured with ultraviolet light, the adhesive strength between the foamed resin layer and the substrate is maintained at a high level. Therefore, when heating is used as an auxiliary measure in addition to ultraviolet irradiation, the adhesive strength to the substrate can be maintained by irradiating with ultraviolet light first and then heating. [Explanation of symbols]

[0047] Type 1 2 Lower mold 3 Upper mold 4 Cavities 5 Base material 10 mixture 11 Foamed resin layer

Claims

1. In a method for manufacturing a structure having a base material and a foamed resin layer bonded to the base material, (A) A step of applying a mixture of a photopolymerization initiator, an ultraviolet-curable adhesive having an adhesive resin component, and a heat-expandable microcapsule to the substrate, (B) A step of irradiating the mixture with ultraviolet light to polymerize the adhesive resin component and to expand the microcapsules with the heat generated by the polymerization reaction to produce the foamed resin layer, Includes, A method for manufacturing a structure having a foamed resin layer, characterized by bonding the foamed resin layer to the substrate by the adhesive strength of the adhesive resin component.

2. A method for manufacturing a structure having a foamed resin layer according to claim 1, wherein in step (A) above, the mixture is applied to the substrate to a thickness dimension less than or equal to the curing depth when the ultraviolet energy of the cumulative amount of light recommended for the adhesive is applied.

3. A method for manufacturing a structure having a foamed resin layer according to claim 2, wherein the curing depth is greater than 5 mm.

4. A method for manufacturing a structure having a foamed resin layer according to claim 3, wherein the curing depth is 5.1 mm or more and 10.5 mm or less.

5. The method for producing a structure having a foamed resin layer according to claim 1, wherein the mixture comprises 50 parts by mass or less of the microcapsules per 100 parts of the adhesive.

6. A method for manufacturing a structure having a foamed resin layer according to claim 5, comprising 0.1 parts by mass or more and 50 parts by mass or less of the microcapsules with respect to 100 parts of the adhesive.

7. Using a mold having a cavity whose internal height dimension is greater than the total thickness dimension of the substrate and the mixture used in step (A) above, the substrate and the mixture are placed in the cavity. A method for manufacturing a structure having a foamed resin layer according to any one of claims 1 to 6, wherein in step (B) above, ultraviolet light is irradiated onto the mixture through the mold.

8. A method for manufacturing an interior lining, characterized by forming a cushion layer with the foamed resin layer using a method for manufacturing a structure having a foamed resin layer as described in claim 7.

9. A method for manufacturing an electronic device, characterized in that the substrate is a printed circuit board on which electronic components are mounted, and a cover layer is formed by covering the electronic components with the foamed resin layer using the method for manufacturing a structure having a foamed resin layer as described in claim 7.

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