JP7492190B2 - Manufacturing method of laminate - Google Patents

Description

The present invention relates to a method for manufacturing a laminate in which a glass plate and a resin plate are bonded together via an intermediate layer.

As is well known, glass plates have excellent weather resistance, chemical resistance, and scratch resistance, but they have the disadvantage of being easily damaged by physical and thermal shock. To overcome this drawback of glass plates, a laminate has been proposed in which a glass plate and a resin plate are integrated via an intermediate layer (adhesive layer) (see Patent Document 1).

Although resin plates are inferior to glass plates in terms of weather resistance, chemical resistance, and scratch resistance, they have the advantage of having a lower specific gravity than glass plates and being more resistant to physical impacts. Therefore, in the above laminate, the disadvantages of the glass plate and the resin plate can be compensated for by the advantages of each. Furthermore, in the above laminate, it is possible to achieve a significant weight reduction compared to a glass plate having the same thickness as the laminate.

When producing the above laminate, for example, a thermoplastic or thermosetting intermediate layer can be used as the intermediate layer. When a thermoplastic intermediate layer is used, the laminate is produced, for example, through the following process.

First, at room temperature, as shown in FIG. 2(a), a glass plate 300 is superimposed on each of the front and back sides of a resin plate 100 via an intermediate layer 200 to produce a provisional laminate 400x that is the basis of the laminate 400. Next, the provisional laminate 400x is subjected to heat treatment. Specifically, the provisional laminate 400x is heated while being pressurized using an autoclave, and the temperature is raised to a temperature exceeding the softening point of the intermediate layer 200, and then the provisional laminate 400x is cooled. The intermediate layer 200 solidifies near the softening point during the cooling process, and the resin plate 100 and the glass plate 300 are bonded and integrated via the intermediate layer 200. In this way, a laminate 400 as shown in FIG. 2(b) is obtained.

JP 2012-254625 A

However, the above-mentioned manufacturing method for laminates had the following problems that needed to be solved:

That is, in the above manufacturing method, the dimensions of the resin plate 100 included in the temporary laminate 400x expand as the temperature of the temporary laminate 400x is heated. In contrast, when the temperature of the integrated resin plate 100 and the glass plate 300 is lowered, the dimensions of the resin plate 100 shrink, in contrast to when the temperature is raised. However, the dimensions of the resin plate 100 after the temperature is lowered do not return to the same dimensions as before the temperature is raised, but become larger than before the temperature is raised. This is because the resin plate 100 at the time of temperature rise is in a state before it is bonded to the glass plate 300, whereas the resin plate 100 at the time of temperature drop (more specifically, below the softening point of the intermediate layer 200) is already in a state after it has been bonded to the glass plate 300. That is, while the resin plate 100 can expand freely during heating, the resin plate 100 during cooling (below the softening point of the intermediate layer 200) is significantly hindered from shrinking in size by the glass plate 300, which has a significantly smaller coefficient of thermal expansion than the resin plate 100. In this way, in the above manufacturing method, the dimensions of the resin plate 100 change before and after the heat treatment, and after the heat treatment, the dimensions of the resin plate 100 are expanded (expanded by ΔL) compared to before the heat treatment.

Here, the resin plate 100 prepared for the production of the provisional laminate 400x has a dimension La (dimension before heat treatment) that is the same as the design dimension Lb (only the dimension is shown) of the resin plate 100 constituting the laminate 400. However, in this case, the dimension Lc (=dimension La + elongation ΔL) of the resin plate 100 after heat treatment becomes larger than the dimension La before heat treatment, which causes a problem that the dimension Lc of the resin plate 100 after heat treatment becomes excessive relative to the design dimension Lb. Therefore, after obtaining the laminate 400, in order to finish it as a product, it was necessary to process the outer peripheral end of the resin plate 100 to correct the excessive dimension Lc of the resin plate 100 to the design dimension Lb. This caused a problem of rising manufacturing costs.

In view of the above circumstances, the present invention aims to reduce manufacturing costs when manufacturing a laminate in which a glass plate and a resin plate are bonded together using an intermediate layer.

The present invention, which aims to solve the above problems, is a method for manufacturing a laminate, which includes a lamination process in which a glass plate, a resin plate, and an intermediate layer to be interposed between the two plates are laminated to produce a provisional laminate, and a heat treatment process in which the provisional laminate is heated to obtain a laminate in which the glass plate and the resin plate are bonded together via the intermediate layer, and is characterized in that the dimensions of the resin plate prepared in the lamination process are smaller than the design dimensions of the resin plate that constitutes the laminate.

In this manufacturing method, the dimensions of the resin plates prepared in the lamination process are smaller than the design dimensions of the resin plates that make up the laminate. This makes it possible to prevent the dimensions of the resin plates after the heat treatment process, which are larger than before the heat treatment process, from becoming excessively larger than the design dimensions. Therefore, after obtaining a laminate through the heat treatment process, in order to finish it as a product, it is possible to eliminate or significantly reduce the work of machining the outer peripheral edge to correct the dimensions of the resin plates to the design dimensions. As a result, manufacturing costs can be reduced.

In the above manufacturing method, it is preferable to determine the dimensions of the resin plates prepared in the lamination process based on the design dimensions of the resin plates, the difference between room temperature and the temperature at which the resin plates are bonded together in the heat treatment process, and the thermal expansion coefficient of the resin plates.

The expansion of the resin plate during the heat treatment process varies mainly depending on the design dimensions of the resin plate, the difference between room temperature and the temperature at which the resin plate is bonded together during the heat treatment process, and the thermal expansion coefficient of the resin plate. Therefore, if the dimensions of the resin plate prepared in the lamination process are determined based on the design dimensions of the resin plate, the difference between room temperature and the temperature at which the resin plate is bonded together during the heat treatment process, and the thermal expansion coefficient of the resin plate, it is possible to accurately eliminate or significantly reduce the work of processing the outer peripheral end of the resin plate described above.

ここで、Ｌ２は樹脂板の設計寸法、ΔＴは熱処理工程で樹脂板が接着一体化する温度と常温との差、αは樹脂板の熱膨張率である。 In the above manufacturing method, it is preferable to determine the dimension L1 of the resin plate prepared in the lamination step based on the following formula (1).

Here, L2 is the design dimension of the resin plate, ΔT is the difference between the temperature at which the resin plate is bonded and integrated in the heat treatment process and room temperature, and α is the thermal expansion coefficient of the resin plate.

In this way, the work of processing the outer peripheral end of the resin plate can be eliminated, and the manufacturing cost can be further reduced. This is for the following reason. That is, when a resin plate with a dimension L1 is prepared in the lamination process, the inventor has found through intensive research that in the subsequent heat treatment process, the elongation of the resin plate after the heat treatment process relative to the elongation before the heat treatment process is approximately L1 x α x ΔT. For this reason, L1 is determined based on the formula [1] so that the sum of L1, which is the dimension of the resin plate before the heat treatment process, and L1 x α x ΔT, which is the elongation of the resin plate accompanying the heat treatment process, is equal to L2, which is the design dimension of the resin plate. This makes it possible to almost reliably prevent the dimension of the resin plate after the heat treatment process from becoming larger than the design dimension. Furthermore, even if the dimension of the resin plate after the heat treatment process becomes larger than the design dimension, the difference from the design dimension can be kept within the allowable error range (dimensional tolerance). As a result, it is possible to eliminate the above-mentioned work, and the manufacturing cost can be further reduced.

In the above manufacturing method, in the lamination step, it is preferable to prepare a provisional laminate by laminating a glass plate on both the front and back sides of the resin plate via an intermediate layer.

In this way, a laminate can be manufactured in which the front and back sides are symmetrical with respect to the resin plate. This makes it possible to eliminate as much as possible the risk of warping occurring in the laminate.

According to the present invention, it is possible to reduce manufacturing costs when manufacturing a laminate in which a glass plate and a resin plate are bonded together using an intermediate layer.

1A is a cross-sectional view showing a provisional laminate produced by a lamination step, and FIG. 1B is a cross-sectional view showing a laminate obtained by a heat treatment step. 1A and 1B are cross-sectional views for explaining problems with the conventional technology.

The manufacturing method of the laminate according to the embodiment of the present invention will be described below with reference to the attached drawings.

The method for manufacturing a laminate according to this embodiment includes a lamination process shown in FIG. 1(a) and a heat treatment process carried out after the lamination process. The lamination process is a process for producing a provisional laminate 1x. The heat treatment process is a process for obtaining the laminate 1 shown in FIG. 1(b) by subjecting the provisional laminate 1x to a heat treatment. In this embodiment, the laminate 1 obtained in the heat treatment process becomes the product as is.

In the lamination process, first, the glass plate 2, resin plate 3, and intermediate layer 4 that form the provisional laminate 1x are prepared. Then, at room temperature, the glass plate 2 is laminated on both the front and back sides of the resin plate 3 via the intermediate layer 4 to produce the provisional laminate 1x.

In this embodiment, the intermediate layer 4 interposed between the glass plate 2 and the resin plate 3 is a thermoplastic intermediate layer 4 that softens when heated and solidifies when cooled to exert adhesive strength. The temporary laminate 1x is a state before heat is applied to the intermediate layer 4. Therefore, in the temporary laminate 1x, the glass plate 2 and the resin plate 3 are not bonded by the intermediate layer 4 and are simply stacked.

The glass plate 2 and resin plate 3 prepared in the lamination process are both rectangular. The resin plate 3 is prepared to have a surface area slightly larger than that of the glass plate 2. This causes the entire outer periphery of the outer edge of the resin plate 3 to protrude beyond the glass plate 2 in the temporary laminate 1x. The shape and size of the intermediate layer 4 may be any as long as it has a surface area larger than that of the glass plate 2. Various intermediate layers other than those shown in the illustration may be used, since unnecessary portions (such as portions protruding from the glass plate 2 or resin plate 3) can be easily cut and removed after the heat treatment process.

The dimension L1 of the resin plate 3 prepared in the lamination process is smaller than the design dimension L2 (only the dimension is shown) of the resin plate 3 constituting the laminate 1. Here, the "dimension L1 of the resin plate 3" in this embodiment is the dimension representing the length of one side of the rectangle formed by the resin plate 3 at the time of performing the lamination process (before integration). Also, the "design dimension L2 of the resin plate 3 constituting the laminate 1" is the dimension representing the design length of the above-mentioned one side of the laminate 1 (product) integrated through the lamination process and the heat treatment process. As described above, the design dimension L2 is merely a dimension representing the design length, so the dimension L3 of the resin plate 3 in the laminate 1 actually manufactured may differ in size from the design dimension L2. Also, the design dimension L2 is a reference dimension, and an allowable error range (dimensional tolerance) is set for this reference dimension. And, as described above, the dimension L1 is made smaller than the design dimension L2 in consideration of the fact that the resin plate 3 will elongate by the amount of elongation ΔL accompanying the heat treatment process performed later. Specifically, it is ideal for the dimension L3 of the resin plate 3 after the heat treatment process to be equal to the design dimension L2, so the purpose is to subtract in advance from the design dimension L2 the length of the expected elongation ΔL due to the heat treatment process.

The dimension L1 of the resin plate 3 prepared in the lamination process may be determined as follows. That is, when the difference (T1-T2) between the temperature T1 at which the resin plate 3 is bonded and integrated in the heat treatment process executed later and room temperature T2 is ΔT and the thermal expansion coefficient of the resin plate 3 is α, the dimension L1 is determined based on L1=L2/(1+αΔT). When a thermoplastic intermediate layer 4 is used as in this embodiment, the temperature at which the resin plate 3 is bonded and integrated at ΔT can be the softening point of the intermediate layer 4. The reason for this is as follows.

In the heat treatment process to be performed later, the dimension L3 of the resin plate 3 after the heat treatment process is elongated by the elongation ΔL compared to the dimension L1 of the resin plate 3 before the heat treatment process (at the time of lamination process). When a thermoplastic intermediate layer 4 is used as in this embodiment, the resin plate 3 is bonded and integrated with the glass plate 2 near the softening point during the cooling process of the heat treatment process, and the thermal contraction of the resin plate 3 is inhibited below the softening point. For this reason, the magnitude of the elongation ΔL is approximately L1 × α × ΔT, that is, approximately equal to the amount of thermal expansion when the temperature is raised from room temperature to the softening point. Based on this, the dimension L1 is determined based on the above L1 = L2 / (1 + αΔT) so that the sum of the dimension L1 of the resin plate 3 before the heat treatment process and the elongation L1 × α × ΔT (= ΔL) of the resin plate 3 accompanying the heat treatment process, i.e., the value of L1 (1 + αΔT), is equal to the design dimension L2 of the resin plate 3. By determining the dimension L1 in this manner, it is possible to almost certainly prevent the dimension L3 of the resin plate 3 after the heat treatment process from becoming larger than the design dimension L2. Even if the dimension L3 becomes larger than the design dimension L2, the dimension L3 falls within the range of allowable error (dimensional tolerance) for the design dimension L2. Therefore, it is possible to eliminate the need to process the outer peripheral end of the resin plate 3 in order to correct the dimension L3 of the resin plate 3 to the design dimension L2 after the heat treatment process.

Here, the glass plate 2 is not particularly limited, but it is preferable to use a glass plate 2 made of alkali-free glass or chemically strengthened glass. The composition of chemically strengthened glass is preferably aluminosilicate glass. Here, "alkali-free glass" refers to glass that does not substantially contain alkali components (alkali metal oxides), and more specifically, glass with a weight ratio of alkali components of 1000 ppm or less. The weight ratio of alkali components is preferably 500 ppm or less, and more preferably 300 ppm or less.

The thickness of the glass plate 2 is preferably 700 μm or less, more preferably 100 μm to 500 μm, and even more preferably 200 μm to 500 μm. With such a thickness, it becomes easier to reduce the proportion of the thickness of the glass plate 2 in the thickness of the laminate 1, making it easier to reduce the weight of the laminate 1. On the other hand, if the thickness is less than 100 μm, the strength of the glass plate 2 is likely to be insufficient, and there is a risk that the glass plate 2 will be damaged if a flying object strikes the laminate 1.

The resin constituting the resin plate 3 can be polycarbonate (PC), acrylic (PMMA), polyethylene terephthalate (PET), polyether ether ketone (PEEK), polyamide (PA), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyethylene naphthalate (PEN), etc. The resin plate 3 can be transparent or opaque depending on the application of the laminate 1 (product).

The thickness of the resin plate 3 is about 0.01 mm to 20 mm. If the laminate 1 is a protective cover for a touch panel mounted on a portable electronic device, the thickness of the resin plate 3 is preferably 0.1 mm to 3 mm, and more preferably 0.1 mm to 2 mm. The thickness of the resin plate 3 is preferably greater than the thickness of the glass plate 2.

As the intermediate layer 4, it is possible to use an ethylene vinyl acetate adhesive, a polyurethane adhesive, a cycloolefin adhesive, an epoxy adhesive, a melamine adhesive, a phenol adhesive, or the like. A functional film may be provided in the intermediate layer 4. Examples of functional films include a heat shielding film, a sound insulating film, a decorative film, and an ultraviolet shielding film.

The thickness of the intermediate layer 4 is approximately 100 μm to 1000 μm.

After the lamination process is performed to produce the provisional laminate 1x by stacking the glass plate 2, the resin plate 3, and the intermediate layer 4 as described above, the heat treatment process is then performed.

In the heat treatment process, first, the temporary laminate 1x is heated while being pressurized using an autoclave to raise the temperature of the temporary laminate 1x from room temperature to the heat treatment temperature, and then the intermediate layer 4 is softened by holding it at the heat treatment temperature for a predetermined time, and then the temporary laminate 1x is cooled to room temperature. Near the softening point during the cooling process, the intermediate layer 4 solidifies, and the resin plate 3 and the glass plates 2 on both the front and back sides are bonded and integrated via the intermediate layer 4. With the above, the heat treatment process is completed and the laminate 1 is obtained.

The resin plate 3 in the laminate 1 is in a state of being elongated by the elongation ΔL compared to before the heat treatment process. In the embodiment illustrated in FIG. 1(b), the resin plate 3 is evenly elongated by ΔL/2 at one end and the other end, but the elongation at both ends may be uneven. Due to the elongation ΔL, the dimension L3 of the resin plate 3 in the laminate 1 is equal to the sum of the dimension L1 before the heat treatment process and the elongation ΔL. Since the magnitude of the elongation ΔL is approximately L1×α×ΔT as described above, the dimension L3 (= dimension L1 + elongation ΔL) is equal to the design dimension L2 or falls within the range of allowable error (dimensional tolerance) for the design dimension L2. Therefore, there is no need to process the outer peripheral end of the resin plate 3, and the laminate 1 can be used as a product as it is. As a result, it is possible to reduce manufacturing costs.

As mentioned above, the resin plate 3 is bonded and integrated with the glass plate 2 near the softening point during the cooling process of the heat treatment step, and thermal contraction of the resin plate 3 is inhibited below the softening point. As a result, compressive stress is generated in the glass plate 2, so that the glass plate 2 of the obtained laminate 1 is in a state in which compressive stress is applied. This compressive stress enables the laminate 1 to reduce breakage of the glass plate 2. Furthermore, even when the laminate 1 is used outdoors or in a high-temperature environment below the softening point, no tensile stress is generated in the glass plate 2, so breakage of the glass plate 2 can be reduced.

Below is a specific example of a method for manufacturing a laminate according to this embodiment.

In a specific example, an alkali-free glass (product name: OA-10G) manufactured by Nippon Electric Glass Co., Ltd. is used as the glass plate 2. The thermal expansion coefficient of the glass plate 2 is 38×10 ⁻⁷ /°C. Meanwhile, a polycarbonate plate is used as the resin plate 3. The thermal expansion coefficient α of the resin plate 3 is 600×10 ⁻⁷ /°C. The design dimension L2 of the resin plate 3 is 1000 mm. An ethylene vinyl acetate adhesive is used as the intermediate layer 4, and its softening point is 60°C. The conditions of the heat treatment process are that the temperature of the provisional laminate 1x is raised from 20°C to 100°C, and then maintained at 100°C for 30 minutes. In other words, the above ΔT is 40°C.

Applying the above conditions to the above dimensional conditions gives L1 = 1000/(1 + 600 × 10 ^-7 × 40), which gives L1 = 997.60.... Based on this, a resin plate 3 with a dimension L1 of 998 mm was prepared when carrying out the lamination process.

When the laminate 1 was manufactured under the above conditions, the resin plate 3 was elongated by 2.4 mm as ΔL before and after the heat treatment process, and the dimension L3 of the resin plate 3 became 1000.4 mm. The value of ΔL of 2.4 mm is approximately equal to the value calculated from L1×α×ΔT (998×600×10 ⁻⁷ ×40). The value of the dimension L3 of 1000.4 mm is 0.4 mm larger than the design dimension L2 of 1000 mm, but the value of 0.4 mm was within the allowable error range (dimensional tolerance) for the design dimension L2. Therefore, the manufactured laminate 1 could be used as a product as it is.

The method for manufacturing a laminate according to the present invention is not limited to the aspects described in the above embodiment. For example, in the above embodiment, a laminate 1 is manufactured in which a glass plate 2 is laminated on both the front and back sides of a resin plate 3, but a laminate 1 in which a glass plate 2 is laminated on only one side, either the front or back, may be manufactured.

In the above embodiment, a thermoplastic intermediate layer 4 is used, but a thermosetting intermediate layer 4 may also be used. Even when a thermosetting intermediate layer 4 is used, in the heat treatment process, the provisional laminate 1x is heated from room temperature to the heat treatment temperature while being pressurized, and then held at the heat treatment temperature for a predetermined time, and then the provisional laminate 1x is cooled to room temperature. When a thermoplastic intermediate layer 4 is used, the resin plate 3 is bonded and integrated with the glass plate 2 near the softening point during the cooling process, but when a thermosetting intermediate layer 4 is used, the intermediate layer 4 hardens during the process of holding for a predetermined time, and the resin plate 3 is bonded and integrated with the glass plate 2. Therefore, when a thermosetting intermediate layer 4 is used, the temperature at which the resin plate 3 is bonded and integrated in the heat treatment process can be the heat treatment temperature.

REFERENCE SIGNS LIST 1 Laminate 1x Temporary laminate 2 Glass plate 3 Resin plate 4 Intermediate layer L1 Dimension L2 Design dimension L3 Dimension

Claims (4)

a lamination step of laminating a glass plate, a resin plate, and a thermoplastic intermediate layer to be interposed between the two plates in a state where they are not bonded to each other, to produce a temporary laminate;
A method for producing a laminate, comprising: a heat treatment step of heating the provisional laminate to obtain a laminate in which the glass plate and the resin plate are bonded and integrated via the intermediate layer,
The heat treatment process includes a step of raising the temperature of the temporary laminate from room temperature to a heat treatment temperature exceeding the softening point of the intermediate layer, a step of holding the heated temporary laminate at the heat treatment temperature for a predetermined time to soften the intermediate layer, and a step of cooling the temporary laminate held at the heat treatment temperature for the predetermined time to room temperature to solidify the intermediate layer and obtain the laminate,
the resin plate is made of polycarbonate, acrylic, polyethylene terephthalate, polyether ether ketone, polyamide, polyvinyl chloride, polyethylene, polypropylene, or polyethylene naphthalate;
The dimensions of the resin plates prepared in the lamination step are made smaller than the design dimensions of the resin plates constituting the laminate;
A method for manufacturing a laminate, comprising determining a dimension L1 of the resin plate prepared in the lamination step based on the following formula [Mathematical Formula 1].
Here, L2 is the design dimension of the resin plate, ΔT is the difference between the softening point of the intermediate layer and room temperature, and α is the thermal expansion coefficient of the resin plate. The method for manufacturing a laminate according to claim 1, characterized in that in the lamination process, the provisional laminate is produced by laminating the glass plate on both the front and back sides of the resin plate via the intermediate layer. 3. The method for producing a laminate according to claim 1, wherein the glass plate is made of alkali-free glass or chemically strengthened glass. The method for producing a laminate according to any one of claims 1 to 3, wherein the intermediate layer is made of an ethylene vinyl acetate adhesive, a polyurethane adhesive, a cycloolefin adhesive, an epoxy adhesive, a melamine adhesive, or a phenol adhesive.

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