Decorative sheet for high-temperature and high-humidity environment

Abstract

To provide a decorative sheet that shows high durability even under a high-temperature and high-humidity environment.SOLUTION: A decorative sheet for a high-temperature and high-humidity environment 1 includes a substrate layer 11, a pattern layer 12 disposed on the substrate layer, an adhesive layer 13 disposed on the pattern layer, and a transparent resin layer 14 disposed on the adhesive layer. The transparent resin layer 14 is composed mainly of polyethylene or polypropylene. The adhesive layer 13 contains a polyester resin and a bisphenol A type epoxy resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a decorative sheet, and more particularly to a decorative sheet that can be suitably used in a hot and humid environment. [Background technology]

[0002] BACKGROUND ART It has been known to improve the appearance of buildings such as houses by covering the surfaces of building materials, such as interior materials, exterior walls, fixtures, and fittings, with decorative sheets.

[0003] The range of applications for decorative sheets is expanding, and they are now being used to improve the surface designs of kitchen doors, bathroom interiors, etc. A decorative sheet applicable to such uses is disclosed in Patent Document 1. This decorative sheet has a configuration in which a biaxially oriented polyethylene terephthalate (PET) sheet is laminated to the outermost surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-076222 Summary of the Invention [Problem to be solved by the invention]

[0005] Kitchen doors and bathroom interiors, for example, are more humid and prone to high temperatures than typical environments where decorative sheets are used, so greater durability is required. Taking this into consideration, the inventors have conducted extensive research into the configuration of a decorative sheet suitable for such applications, and have completed the present invention.

[0006] An object of the present invention is to provide a decorative sheet for use in hot and humid environments that exhibits high durability even in hot and humid environments. [Means for solving the problem]

[0007] The present invention is a decorative sheet for use in hot and humid environments, comprising a base layer, a pattern layer provided on the base layer, an adhesive layer provided on the pattern layer, and a transparent resin layer provided on the adhesive layer, wherein the transparent resin layer is primarily composed of polyethylene or polypropylene, and the adhesive layer contains polyester resin and bisphenol A type epoxy resin. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a decorative sheet for use in hot and humid environments that exhibits high durability even in hot and humid environments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing a decorative sheet according to one embodiment of the present invention. [Figure 2] FIG. 10 is a schematic cross-sectional view showing a decorative sheet according to a modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described with reference to FIGS. 1 is a plan view of a decorative sheet for use in hot and humid environments according to this embodiment (hereinafter simply referred to as "decorative sheet") 1. The decorative sheet 1 has a structure in which a design layer 12, an adhesive layer 13, a transparent resin layer 14, and a protective layer 15 are sequentially formed on a base layer 11.

[0011] The base layer 11 is formed of a synthetic resin film. Examples of materials include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN), and examples of methods for producing the film include calendaring, inflation, and T-die extrusion. The base layer 11 may be a single layer or may have multiple layers, and a layer may contain two or more types of synthetic resins. The base layer 11 may be colored, and the color in this case will constitute the background color of the decorative sheet 1. Instead of coloring the base layer 11 itself, a colored layer that will become the background color may be provided on the base layer.

[0012] The pattern layer 12 imparts design characteristics with a desired pattern to the base layer 11. The type of pattern can be various, such as wood grain, stone grain, sand grain, tiled pattern, brickwork pattern, fabric pattern, leather-grained pattern, geometric figures, letters, symbols, abstract patterns, etc., depending on the type of colored layer including the background color.

[0013] The transparent resin layer 14 is a layer whose main component (the component with the highest mass ratio) is a synthetic resin, and has lower water vapor permeability than PET and PBT. Examples of the main component of the transparent resin layer include PE and PP. PE has a density of 0.910 to 0.925 g / cm. 3 Low density polyethylene (LDPE) is more preferred. When the surface of the decorative sheet 1 is to be matte, the transparent resin layer 14 can be formed by extrusion lamination, and after formation, embossing may be further carried out.

[0014] The protective layer 15 is formed of a resin harder than the transparent resin layer 14, and covers the surface of the transparent resin layer 14 to impart durability and protect the uneven surface to maintain a matte or other appearance. Therefore, providing the protective layer 15 is not essential and may be omitted. Furthermore, the protective layer 15 can be provided whether the surface of the decorative sheet 1 is mirror-finished or matte. Examples of materials for the protective layer 15 include thermosetting urethane resin and ultraviolet-curing resin.

[0015] The adhesive layer 13 is a layer made of synthetic resin and has the function of bonding the base layer 11 and the pattern layer 12 to the transparent resin layer 14 and the protective layer 15 .

[0016] The inventors noticed that delamination between the base layer 11 and the pattern layer 12 and the transparent resin layer 14 and the protective layer 15 is likely to occur in high-temperature, high-humidity environments such as kitchen doors and bathrooms, and conducted various studies to prevent this. As a result, they found that the main reason for this is that water vapor that has permeated the transparent resin layer 14 and the protective layer 15 reaches the adhesive layer 13 and reduces the adhesive ability.

[0017] Based on this knowledge, the inventors discovered that by forming the transparent resin layer 14 from a resin with lower water vapor permeability than PET and PBT, and further selecting the material of the adhesive layer 13, it is possible to significantly reduce the above-mentioned interlayer delamination even in environments prone to high temperatures and humidity.

[0018] Specifically, the adhesive layer 13 according to this embodiment contains a polyester resin and a bisphenol A epoxy resin. The polyester resin contains phthalic acid, a linear dicarboxylic acid, and an alkylene diol as components. The polyester resin can be produced by a known technique (for example, a polycondensation reaction of a dicarboxylic acid and a diol).

[0019] The adhesive layer 13 of this embodiment is made by blending the bisphenol A type epoxy resin with the polyester resin described above, thereby enabling the decorative sheet to exhibit sufficient moist heat resistance for practical use. The bisphenol A epoxy resin can be appropriately selected from various grades of commonly available bisphenol A epoxy resins with different molecular weights and epoxy equivalents. From the viewpoint of achieving both moist heat resistance and adhesiveness, the molecular weight (mass average molecular weight MW) of the bisphenol A epoxy resin is preferably in the range of 1,000 to 4,000, and particularly preferably in the range of 1,000 to 2,000.

[0020] From the viewpoint of achieving both moist heat resistance and adhesiveness, the blending amount of bisphenol A type epoxy resin is preferably in the range of (polyester resin / bisphenol A type epoxy resin) = 50 / 50 to 90 / 10 in mass ratio. If the blending ratio of bisphenol A type epoxy resin is too low, moist heat resistance may be insufficient, while if it is too high, adhesiveness may be insufficient. Phthalic acid (which in this embodiment refers collectively to orthophthalic acid and terephthalic acid), a component of polyester resin, is used to enhance the moist heat resistance of the adhesive layer. The phthalic acid content is preferably in the range of (phthalic acid / linear dicarboxylic acid) = 45 / 55 to 85 / 15 in terms of substance ratio. If the phthalic acid content is too high, the adhesive layer may become hard and brittle, which may adversely affect the adhesive properties. If the phthalic acid content is too low, the adhesive layer may lack cohesive strength, resulting in insufficient adhesive strength.

[0021] The linear dicarboxylic acid, which is a constituent element of the polyester resin, is not particularly limited and may be appropriately selected from, for example, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and the like. The alkylene diol, which is a component of the polyester resin, can be, for example, (poly)ethylene glycol, (poly)propylene glycol, (poly)tetramethylene glycol, or (poly)hexamethylene glycol, but it is preferable to use neopentyl glycol in combination with the alkylene diol in terms of resistance to moist heat.

[0022] The content of the alkylene diol is preferably within a range of the ratio of the amount of substance of {alkylene diol / (phthalic acid + linear dicarboxylic acid)} = 40 / 60 to 60 / 40. Polyester resins outside this range have a small molecular weight, and may therefore lack adhesiveness and heat resistance. The adhesive layer 13 can be formed by a common coating method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating.

[0023] The transparent resin layer 14 according to this embodiment has lower water vapor permeability than PET and PBT. As a result, the water vapor permeability of the decorative sheet 1 according to this embodiment is 5.0 g / m 2 The low transmittance is achieved by the transparent resin layer 14. Furthermore, the adhesive layer 13 configured as described above has high hydrolysis resistance, so that it does not easily deteriorate even when it comes into contact with moisture that has permeated through the transparent resin layer 14 or the base material layer 11.

[0024] As a result, even when the decorative sheet 1 is attached to a wall surface in an environment prone to high temperature and humidity, such as a kitchen door or a bathroom, delamination between the base layer 11 and the pattern layer 12 and the transparent resin layer 14 and the protective layer 15 is extremely unlikely to occur, and durability in such an environment is significantly improved. Furthermore, because the transparent resin layer made of PE or PP can be easily produced by co-extrusion, it is also suitable for creating a matte surface, which is a major advantage in that it can easily meet the recent growing demand for matte decorative sheets used on kitchen doors, bathrooms, etc.

[0025] The decorative sheet according to this embodiment will be described in more detail using examples. The technical scope of the present invention is not limited solely by the specific content of each example.

[0026] Example 1 A 75 μm thick polyester sheet was used as the substrate layer, and a background color printing layer and a design layer (both about several μm thick) were formed by gravure printing using urethane ink. An adhesive composition for forming the adhesive layer 13 was prepared by the following procedure. Polyester diol (polyester resin) P was synthesized using isophthalic acid (IP) and adipic acid (AD) as dicarboxylic acids and ethylene glycol and hexanediol as diols (IP / AD = 90 / 10 (molar ratio), number average molecular weight: 1 × 10). 4 , solid content hydroxyl value: 10 mg KOH / g). A polyester diol (polyester resin) P was mixed with a bisphenol A-type epoxy resin EP (jER1004AF, Mitsubishi Chemical Corporation) at a solid mass ratio of P / EP = 70 / 30, and an isocyanate curing agent and a diluting solvent were further added to obtain an adhesive composition. The adhesive composition was applied to the design layer (to a thickness of about several μm), and then extrusion lamination was performed on top of it using a transparent resin layer-forming material mainly composed of PP, thereby forming a 60 μm-thick transparent resin layer mainly composed of PP. Furthermore, a thermosetting urethane resin was applied onto the transparent resin layer and dried to form a protective layer (thickness: about several μm). In this manner, a decorative sheet with a matte surface according to Example 1 was produced.

[0027] Example 2 A decorative sheet with a matte surface according to Example 2 was produced using the same procedure as in Example 1, except that a mixture of thermosetting urethane resin and ionizing radiation curable resin was applied onto the transparent resin layer to form a protective layer.

[0028] (Comparative Example 1) A decorative sheet having a matte surface according to Comparative Example 1 was produced in the same manner as in Experimental Example 1, except that the adhesive layer 13 was formed using only the polyester diol (polyester resin) P described above. (Comparative Example 2) A polyester adhesive was applied to the pattern layer (to a thickness of about several μm), and a 60 μm thick transparent PBT film was attached by dry lamination to form a transparent resin layer. A decorative sheet according to Comparative Example 2 was produced using the same procedures as in Example 1 in other respects.

[0029] The decorative sheets according to the examples were evaluated as follows. (Water Vapor Transmission Rate (WVTR)) Measurements were made in accordance with JIS Z 0208. The unit is "g / m 2 -24 hours. (Transparent resin layer peeling test) (Peel test 1: Peel strength measurement of decorative sheet alone) The decorative sheet for each example was tested in accordance with JIS K6854-3:1999 (n=5). The measurements were taken at two different times: immediately after production and after 250 hours of storage in an environment of 85°C and 85% RH (relative humidity) (accelerated test).The base layer 11 and the pattern layer 12, and the transparent resin layer 14 and the protective layer 15 were each chucked and measured. (Peeling test 2: Measurement in installed state) The decorative sheet according to each example was attached to a steel plate using a polyester adhesive, and the steel plate was held upright in an environment of 85°C and 85% RH (relative humidity) for 2000 hours. After that, the steel plate was removed and the presence or absence of peeling of the transparent resin layer was evaluated using the following two-point scale. ◯ (Good): No peeling between the transparent resin layer and the pattern layer was observed. × (Bad): Even slight peeling between the transparent resin layer and the pattern layer is observed. (Pencil hardness test) The decorative sheet according to each example was attached to a steel plate, and then testing was carried out in accordance with JIS K5600 under a load of 1000 g. Pencil hardness of HB or higher was rated as ◯ (Good), and pencil hardness of H or higher was rated as ⊚ (Excellent). The results are shown in Table 1.

[0030] [Table 1]

[0031] In Example 1, the transparent resin layer and adhesive layer were formed from predetermined materials, so that the decorative sheet as a whole had a weight of 5.0 g / m 2 A WVTR of 24 hours or less was achieved. Furthermore, sufficient peel strength was maintained in peel test 1 (accelerated test). As a result, peeling of the transparent resin layer was sufficiently suppressed even in peel test 2, which was conducted in a high-temperature, high-humidity environment simulating the actual application environment. In Comparative Example 1, the result of Peel Test 2 was good, but a significant decrease in peel strength was observed in Peel Test 1 (accelerated test). This was thought to be because in Peel Test 2, the intrusion of moisture from the base layer side was suppressed because the film was attached to a steel plate, whereas in Peel Test 1 (accelerated test), more moisture intrusion occurred from the base layer side, and because the adhesive layer 13 did not contain bisphenol A-type epoxy resin, the hydrolysis resistance was inferior to that of Example 1. From these results, it was thought that the decorative sheet according to Example 1 could be expected to stably maintain interlayer adhesion even when stored for a long period of time before application. In Comparative Example 2, the WVTR of the entire decorative sheet was 5.0 g / m due to the use of a transparent resin layer similar to that of the conventional one. 2 - It took more than 24 hours, and peeling of the transparent resin layer could not be suppressed in peeling test 2.

[0032] The results of Example 1 showed that the protective layer provided on the transparent resin layer can be suitably formed by using a thermosetting resin. Furthermore, the results of Example 2 showed that adding an ionizing radiation curable resin to this layer can improve the surface hardness without adversely affecting the WVTR or peel strength.

[0033] The present invention has been described above using embodiments and examples, but the specific configuration is not limited to these embodiments, and configuration changes and combinations within the scope that do not deviate from the gist of the present invention are also included.

[0034] In the decorative sheet according to the present invention, the transparent resin layer 14 may have a barrier layer 21, as in the modified decorative sheet 1A shown in Figure 2. This can further reduce the WVTR and improve durability.

[0035] Examples of the barrier layer 21 include a layer made of an inorganic oxide such as silicon oxide or aluminum oxide, and a structure in which this is further covered with a layer containing a water-soluble polymer such as polyvinyl alcohol or a metal alkoxide. The barrier layer 21 may be located on either the adhesive layer 13 side or the protective layer 15 side, but when the surface of the transparent resin layer 14 is embossed or the like, cracks may occur in the barrier layer 21, which may reduce the barrier properties, so it is preferable to locate the barrier layer 21 on the adhesive layer 13 side. [Explanation of symbols]

[0036] 1. 1A Decorative sheet for high temperature and humidity environments 11 Base material layer 12 Picture layer 13 Adhesive layer 14 Transparent resin layer 15 Protective layer

Claims

1. a substrate layer; A pattern layer provided on the base layer; an adhesive layer provided on the design layer; a transparent resin layer provided on the adhesive layer; Equipped with the transparent resin layer contains polyethylene or polypropylene as a main component, The adhesive layer contains a polyester resin and a bisphenol A type epoxy resin. Decorative sheet for high temperature and humidity environments.

2. The transparent resin layer has a matte appearance due to its surface irregularities. The decorative sheet for use in hot and humid environments according to claim 1.

3. Further comprising a protective layer provided on the transparent resin layer. The decorative sheet for use in hot and humid environments according to claim 1.

4. the protective layer contains a thermosetting resin and an ionizing radiation curable resin, The decorative sheet for use in hot and humid environments according to claim 3.

5. The water vapor permeability of the entire sheet is 5.0 g / m ２ - 24 hours or less, The decorative sheet for use in hot and humid environments according to claim 1.

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