Window glass for combustion device, combustion device, and method for producing window glass for combustion device

Abstract

Provided are: a window glass for a combustion device, the window glass being easy to harmonize with the main body of a combustion device and capable of giving a highly aesthetic appearance to the combustion device; a combustion device including the window glass for a combustion device; and a method for producing the window glass for a combustion device.　A window glass (1) for use in combustion devices is characterized by comprising: a glass substrate (2) having a first main surface (2a), which is to lie on the outer side of the combustion device, and a second main surface (2b), which faces the first main surface (2a) and is to lie on the inner side of the combustion device; and a decorative layer (3) provided to a peripheral portion of the first main surface (2a) of the glass substrate (2).

Description

Window glass for combustion device, combustion device, and method for manufacturing window glass for combustion device

[0001] The present invention relates to a windowpane for a combustion apparatus used in a combustion apparatus such as a stove or a fireplace, a combustion apparatus using the windowpane for a combustion apparatus, and a method for manufacturing the windowpane for a combustion apparatus.

[0002] Conventionally, stoves and fireplaces that burn firewood, gas, coal, oil, etc. have been used as combustion devices for heating. Such combustion devices are equipped with window glass so that the state of the flame can be seen from the outside. Since window glass for combustion devices must be transparent to visible light and have high thermal shock resistance, low-expansion transparent crystallized glass plates are generally used.

[0003] Furthermore, windowpanes for combustion apparatuses are fixed to, for example, the metal frame of the combustion apparatus body via fixing members such as gaskets or adhesives. In this case, since the aesthetic appearance is impaired if the fixing members are visible from the outside, a light-shielding layer may be formed on the combustion apparatus side of the windowpane to conceal the fixing members. For example, Patent Document 1 discloses a windowpane for combustion apparatuses in which a light-shielding layer containing inorganic pigment powder and glass powder is formed by screen printing on the flame-side surface of a transparent crystallized glass plate. Furthermore, Patent Document 2 discloses a windowpane for combustion apparatuses in which the arithmetic mean roughness of the flame-side and indoor-side surfaces of the transparent crystallized glass plate is controlled.

[0004] JP 2013-148259 A JP 2022-90413 A

[0005] However, in the window glasses for combustion apparatuses disclosed in Patent Documents 1 and 2, when the combustion apparatus is observed from the indoor side, the color of the light-shielding layer is observed through the glass substrate, and therefore the sense of unity in color between the area where the light-shielding layer is provided and the main body of the combustion apparatus is still insufficient. In recent years, users have become increasingly interested in design, and there is a demand for a more harmonious appearance for the entire combustion apparatus.

[0006] An object of the present invention is to provide a window glass for a combustion apparatus that can easily be harmonized with the combustion apparatus body and can realize a combustion apparatus with a highly designed appearance, a combustion apparatus using the window glass for a combustion apparatus, and a method for manufacturing the window glass for a combustion apparatus.

[0007] A window glass for a combustion apparatus according to Aspect 1 of the present invention is a window glass used in a combustion apparatus, and is characterized by comprising: a glass substrate having a first main surface provided on the outside of the combustion apparatus and a second main surface facing the first main surface and provided on the inside of the combustion apparatus; and a decorative layer provided on the peripheral portion of the first main surface of the glass substrate.

[0008] In the combustion apparatus window glass according to Aspect 2 of the present invention, in Aspect 1, it is preferable that the 60° gloss value of the surface of the decorative layer is 60 or less.

[0009] In the combustion apparatus window glass according to Aspect 3 of the present invention, in Aspect 1 or 2, it is preferable that the arithmetic mean roughness Ra of the surface of the decorative layer is 0.57 μm or less.

[0010] In a combustion apparatus window glass according to Aspect 4 of the present invention, in any one of Aspects 1 to 3, it is preferable that the window glass further comprises a light-shielding layer provided on the peripheral portion of the second main surface of the glass substrate.

[0011] In a combustion apparatus window glass according to Aspect 5 of the present invention, in any one of Aspects 1 to 4, the decorative layer preferably contains a glass matrix and a pigment.

[0012] In a combustion apparatus window glass according to Aspect 6 of the present invention, in any one of Aspects 1 to 5, the decorative layer preferably contains inorganic beads.

[0013] A seventh aspect of the present invention provides a window glass for a combustion apparatus according to the sixth aspect, wherein the inorganic beads are glass beads.

[0014] In the combustion apparatus window glass according to Aspect 8 of the present invention, in Aspect 6, it is preferable that the inorganic beads are silica beads.

[0015] In a combustion apparatus window glass according to Aspect 9 of the present invention, in any one of Aspects 1 to 8, the glass substrate preferably has a curved shape.

[0016] A combustion device according to a tenth aspect of the present invention is characterized by including a window glass for a combustion device configured according to any one of the first to ninth aspects.

[0017] A method for manufacturing a window glass for a combustion apparatus according to aspect 11 of the present invention is a method for manufacturing a window glass for a combustion apparatus according to any one of aspects 1 to 10, characterized in that it includes a step of applying a decorative layer-forming paste to the peripheral portion of a first main surface of a glass substrate, the first main surface being provided on the outside of the combustion apparatus, and firing the glass substrate to form a decorative layer on the peripheral portion of the first main surface of the glass substrate.

[0018] In the method for manufacturing a window glass for a combustion apparatus according to Aspect 12 of the present invention, in Aspect 11, it is preferable to further include a step of applying a paste for forming a light-shielding layer to the peripheral edge of a second main surface of the glass substrate having a decorative layer formed on the peripheral edge of the first main surface of the glass substrate, and firing the glass substrate to form a light-shielding layer on the peripheral edge of the second main surface of the glass substrate.

[0019] According to the present invention, it is possible to provide a window glass for a combustion apparatus that can easily be harmonized with the combustion apparatus body and can realize an appearance of the combustion apparatus with high design quality, a combustion apparatus using the window glass for a combustion apparatus, and a method for manufacturing a window glass for a combustion apparatus.

[0020] Fig. 1 is a schematic perspective view showing a window glass for a combustion apparatus according to one embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of a portion of the window glass for a combustion apparatus according to one embodiment of the present invention taken along line A-A in Fig. 1. Fig. 3 is a schematic cross-sectional view illustrating the position of a fixing member such as an adhesive or a gasket in the window glass for a combustion apparatus. Fig. 4 is a schematic diagram showing a combustion apparatus according to one embodiment of the present invention. Fig. 5 is a schematic cross-sectional view illustrating the position of a light-shielding layer in the window glass for a combustion apparatus.

[0021] Preferred embodiments will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0022] (Window Glass for Combustion Apparatus) As shown in FIGS. 1 and 2 , the window glass 1 for a combustion apparatus includes a glass substrate 2 and a decorative layer 3. The glass substrate 2 has a first main surface 2a and a second main surface 2b that face each other. The first main surface 2a is the main surface that faces the outside (indoor side) of the combustion apparatus when attached to the combustion apparatus. The second main surface 2b faces the first main surface 2a and is the main surface that faces the inside (flame side) of the combustion apparatus when attached to the combustion apparatus. The decorative layer 3 is provided on the first main surface 2a of the glass substrate 2. More specifically, the decorative layer 3 is provided on the periphery of the first main surface 2a of the glass substrate 2. With this configuration, the window glass 1 for a combustion apparatus of the present invention easily blends in with the combustion apparatus body and can achieve a combustion apparatus with a highly designed appearance.

[0023] In this embodiment, the combustion apparatus window glass 1 has a flat shape and a rectangular plate shape in a plan view, but the shape of the combustion apparatus window glass 1 is not particularly limited in the present invention.

[0024] As shown in FIG. 3 , the decorative layer 3 is preferably provided in a region that at least partially overlaps, in plan view, with the region where the adhesive, gasket, or other fixing member 4 used to secure the combustion apparatus window glass 1 is disposed. For example, as shown in FIG. 4 , the decorative layer 3 preferably has a frame-like shape in plan view and is provided along the frame of the combustion apparatus main body 22. This configuration allows the decorative layer 3 to conceal the adhesive, gasket, or other fixing member 4. Furthermore, because the decorative layer 3 is provided on the first main surface 2 a (indoor side) of the glass substrate 2, the color of the decorative layer 3 can be observed without the glass substrate 2 when observing the combustion apparatus from the outside, making it easier to achieve color harmony between the decorative layer 3 and the combustion apparatus main body 22. As a result, the design of the entire combustion apparatus can be improved. In particular, from the perspective of enhancing concealment, the decorative layer 3 is preferably provided around the entire periphery along the frame of the combustion apparatus main body 22. However, the decorative layer 3 only needs to be provided on at least a portion of the periphery on the first main surface 2 a of the glass substrate 2, and may be provided, for example, on a portion along the frame of the combustion device main body 22. The decorative layer 3 may also be formed on the entire surface of the glass substrate 2. In this case, the decorative layer 3 may be formed thick in the portion that conceals the fixing members 4 such as the gasket or adhesive, and thin in the other portion (specifically, the portion inside the periphery of the first main surface 2 a) so that the internal flame can be adequately seen.

[0025] The window glass 1 for a combustion apparatus preferably has a 60° gloss value of 60 or less, more preferably 50 or less, and particularly preferably 45 or less, on the surface of the decorative layer 3. By setting the 60° gloss value on the surface of the decorative layer 3 at or below the above upper limit, the matte finish of the decorative layer 3 is easily enhanced. For combustion apparatuses installed indoors, matte designs that convey a warm and calm impression tend to be preferred over glossy designs. Therefore, by combining a matte-designed combustion apparatus body 22 with the window glass 1 for a combustion apparatus having the decorative layer 3, the design of the entire combustion apparatus can be further improved. Furthermore, since fingerprints and scratches are relatively less noticeable on matte designs, fingerprints and scratches on the surface of the decorative layer 3 can be made less noticeable when the combustion apparatus is observed from the outside. The lower limit of the 60° gloss value on the surface of the decorative layer 3 is not particularly limited, but may be, for example, 0 or more, particularly 10 or more.

[0026] In the window glass 1 for a combustion apparatus, the 20° gloss value on the surface of the decorative layer 3 is preferably 20 or less, more preferably 15 or less, and particularly preferably 10 or less. If it is equal to or less than the above upper limit, it becomes easier to further enhance the matte finish of the decorative layer 3. This makes it possible to further improve the design of the entire combustion apparatus, which has a matte finish design. The lower limit of the 20° gloss value on the surface of the decorative layer 3 is not particularly limited, but it may be, for example, 0 or more, particularly 1 or more.

[0027] In the window glass 1 for a combustion apparatus, the arithmetic mean roughness Ra of the surface of the decorative layer 3 is preferably 0.9 μm or less, more preferably 0.7 μm or less, even more preferably 0.57 μm or less, and particularly preferably 0.55 μm or less. The lower limit of the arithmetic mean roughness Ra is preferably 0.11 μm or more, more preferably 0.16 μm or more, even more preferably 0.2 μm or more, and particularly preferably 0.35 μm or more. Because the decorative layer 3 is provided on the first main surface 2 a of the glass substrate 2 (i.e., the outside of the combustion apparatus), dust, dirt, etc. may adhere to its surface. In particular, if the decorative layer 3 is black in color, the dust and dirt are noticeable, which can significantly degrade the design. While it is conceivable to wipe off such dust and dirt with a rag, if fibers remain on the surface of the decorative layer 3 after wiping, this may actually degrade the design. After extensive research, the inventors have found that the above problems can be solved by appropriately controlling the arithmetic mean roughness Ra of the surface of the decorative layer 3. Specifically, when the arithmetic mean roughness Ra of the surface of the decorative layer 3 is set to the upper limit or less, fibers from the rag or the like are less likely to remain on the surface of the decorative layer 3 after wiping with the rag or the like, thereby preventing a deterioration in the design. Furthermore, when the arithmetic mean roughness Ra of the surface of the decorative layer 3 is set to the lower limit or more, the gloss value tends to decrease, which tends to enhance the matte finish of the decorative layer 3, thereby further improving the design of the entire combustion device. The arithmetic mean roughness Ra can be measured using a method in accordance with JIS B0601:2001.

[0028] In the combustion apparatus window glass 1, the static friction coefficient between the surface of the decorative layer 3 and stainless steel (SUS304) is preferably 0.6 or less, more preferably 0.55 or less, and particularly preferably 0.2 or less. Setting the static friction coefficient below the upper limit reduces the likelihood of fibers from the rag or other material remaining on the surface of the decorative layer 3 after wiping it with the rag, thereby preventing a deterioration in design. The lower limit of the static friction coefficient on the surface of the decorative layer 3 is not particularly limited, but may be, for example, 0.01 or more, 0.05 or more, or particularly 0.1 or more. When the decorative layer 3 contains inorganic beads, the static friction coefficient on the surface of the decorative layer 3 can be easily reduced by polishing the surface of the decorative layer 3. The static friction coefficient on the surface of the decorative layer 3 can be determined by measuring the area where the decorative layer 3 is provided in a plan view from the first main surface 2a side using a tribometer.

[0029] The likelihood of fibers remaining when wiping the decorative layer 3 can be evaluated, for example, as follows: A cloth is fixed to the tip of a 600 g weight, and alcohol is applied to the cloth. The tip of the weight is brought into contact with the decorative layer 3 via the cloth, and the weight is slid back and forth across the decorative layer 3 at 50 mm / s over a distance of 100 mm, with only the weight itself exerting a load. The degree to which fibers from the cloth remain on the decorative layer 3 can then be evaluated according to the following index:

[0030] [Evaluation criteria] A: No fibers were found to be attached (no residual fibers were found). B: Fibers were found to be attached to the wiped edge of the sample, but this did not affect the appearance. C: Fibers were found to be attached to one end of the wiped area, slightly reducing the design. D: Fibers were found to be attached over the entire wiped area, reducing the design.

[0031] The window glass 1 for a combustion apparatus preferably has a light transmittance at a wavelength of 580 nm in the region where the decorative layer 3 is provided of 40% or less, more preferably 30% or less, and particularly preferably 20% or less. By setting the light transmittance at a wavelength of 580 nm to the above-mentioned upper limit or less, the concealing properties of the decorative layer 3 are easily improved, and it is possible to prevent a fixing member 4, such as an adhesive or a gasket, used to fix the window glass 1 for a combustion apparatus from being observed from the outside of the combustion apparatus, thereby reducing the design. The lower limit of the light transmittance at a wavelength of 580 nm is not particularly limited, but may be 0% or more, 1% or more. The light transmittance is measured by measuring the intensity of incident light (I) when light from a light source installed on the decorative layer 3 side is incident at an incident angle of 0° on a glass substrate 2 having a decorative layer 3 provided on its first main surface 2a (i.e., a glass substrate 2 having no layers provided on its second main surface 2b). ０ ) to the intensity (I) of the light emitted from the glass substrate 2 side (second main surface 2b side) (I １ / I ０ ) can be calculated.

[0032] For example, in the region where the decorative layer 3 is provided on the window glass 1 for a combustion apparatus, the L measured from the first main surface 2 a side of the glass substrate 2 ＊ a ＊ b ＊ L in color system ＊ The value is preferably 27 or less, and particularly preferably 26.7 or less. In this case, the fixing member 4 is more concealed, and the color harmony with the matte-toned combustion device main body 22 is easily achieved, thereby improving the design of the combustion device as a whole. ＊ The lower limit of the value is not particularly limited, but is, for example, 23 or more.

[0033] For example, in the region where the decorative layer 3 is provided on the window glass 1 for a combustion apparatus, the L measured from the first main surface 2 a side of the glass substrate 2 ＊ a ＊ b ＊ a in the color system ＊ The value is preferably +2.5 to −2.5, more preferably +1.5 to −1.5, and particularly preferably +0.7 to −0.7, in which case the effects of the present invention can be more effectively exhibited.

[0034] For example, in the region where the decorative layer 3 of the window glass 1 for a combustion apparatus is provided, L ＊ a ＊ b ＊ b in the color system ＊ The value is preferably +2 to -2, and particularly preferably +1.5 to -1.5, in which case the effects of the present invention can be more effectively exhibited.

[0035] In addition, the L of the window glass 1 for the combustion device ＊ Value, a ＊ value, b ＊ The value can be determined by placing the combustion apparatus window glass 1 on a black plate with the second principal surface 2b facing downward, and measuring the area where the decorative layer 3 is provided in a plan view from the first principal surface 2a side using a color difference meter.

[0036] As shown in FIG. 5 , the window glass 1 for a combustion apparatus preferably includes a light-shielding layer 5 on the second main surface 2b of the glass substrate 2. More specifically, the window glass 1 for a combustion apparatus preferably includes a light-shielding layer 5 provided on the peripheral portion of the second main surface 2b, and particularly preferably in an area that overlaps with the decorative layer 3 via the glass substrate 2 in a plan view. This makes it easier to conceal fixing members 4, such as adhesives and gaskets, used to fix the window glass 1 for a combustion apparatus, thereby further improving the design of the combustion apparatus. For example, the light-shielding layer 5 is preferably provided on at least a portion of the peripheral portion of the second main surface 2b of the glass substrate 2, and more preferably along the entire peripheral portion of the second main surface 2b. However, the light-shielding layer 5 only needs to be provided on at least a portion of the peripheral portion of the second main surface 2b of the glass substrate 2. For example, it may be provided on a portion along the frame of the combustion apparatus main body 22. However, the window glass 1 for a combustion apparatus does not necessarily have to include a light-shielding layer 5.

[0037] The light-shielding layer 5 may be formed over the entire second main surface 2b of the glass substrate 2. In this case, the light-shielding layer 5 may be formed thick in a portion that conceals the fixing member 4 such as a gasket or adhesive, and may be formed thin in other portions so that the internal flame can be moderately visible. In other words, the light-shielding layer 5 may be formed thick in the peripheral portion of the second main surface 2b of the glass substrate 2, and may be formed thin in other portions so that the internal flame can be moderately visible.

[0038] The components and layers constituting the combustion apparatus window glass 1 will be described in detail below.

[0039] (Glass Substrate) The glass substrate 2 is not particularly limited, but may be, for example, a transparent glass substrate. In this specification, the term "transparent" in relation to the glass substrate 2 means that the light transmittance in the visible wavelength range of 450 nm to 700 nm is 70% or more. The upper limit of the light transmittance of the glass substrate 2 in the wavelength range of 450 nm to 700 nm may be, for example, 95% or less, particularly 90% or less.

[0040] The window glass 1 for a combustion apparatus is repeatedly heated and cooled as the combustion apparatus is used. Therefore, it is preferable that the glass substrate 2 has high thermal shock resistance and a low thermal expansion coefficient. Specifically, the softening temperature of the glass substrate 2 is preferably 700°C or higher, and more preferably 750°C or higher. In addition, the average linear thermal expansion coefficient of the glass substrate 2 at 30°C to 750°C is -10×10 －７ / ℃~+60×10 －７ / °C, and is preferably within the range of -10 × 10 －７ / ℃~+50×10 －７ / °C, and more preferably within the range of -10 × 10 －７ / ℃~+40×10 －７ / °C. Therefore, the glass substrate 2 is preferably made of glass with a high glass transition temperature and low expansion, or glass-ceramic. For example, the glass substrate 2 is made of a borosilicate glass substrate or LAS (Li ２ O-Al ２ O ３ -SiO ２As the LAS-based crystallized glass substrate, for example, "N-0" manufactured by Nippon Electric Glass Co., Ltd. can be used.

[0041] The thickness of the glass substrate 2 is not particularly limited and can be set appropriately, for example, to about 2 mm to 6 mm.

[0042] (Decorative Layer) The decorative layer 3 preferably contains a glass matrix as a matrix component, and particularly preferably contains a glass matrix and a pigment.

[0043] The glass matrix is ​​made of, for example, glass frit. Examples of glass compositions of the glass matrix (glass frit) include borosilicate glass, aluminoborosilicate glass, silicate glass containing at least one of an alkali metal component and an alkaline earth metal component, and phosphate glass containing zinc and aluminum. Examples of the glass frit that can be used include "Frit NPF," "Frit NPF10," and "Fine Frit NPF" manufactured by Nippon Electric Glass Co., Ltd. Only one type of glass frit may be used, or two or more types may be used in combination.

[0044] The glass matrix content of the decorative layer 3 is preferably 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 55% by mass or more. If the content is above the lower limit, the arithmetic mean roughness Ra of the surface of the decorative layer 3 can be prevented from becoming too large, and when the surface of the decorative layer 3 is wiped with a cloth or the like, fibers derived from the cloth are less likely to remain. Furthermore, a decrease in the Mohs hardness of the decorative layer 3 can be easily prevented. The upper limit of the glass matrix content is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 75% by mass or less. If the content is below the upper limit, the arithmetic mean roughness Ra of the surface of the decorative layer 3 can be easily prevented from becoming too small. Furthermore, since the 60° gloss value of the surface of the decorative layer 3 can be easily reduced, the matte finish of the decorative layer 3 can be easily enhanced, further improving the overall design of the matte-finished combustion device.

[0045] The decorative layer 3 preferably contains a pigment. This makes it easier to harmonize the colors of the decorative layer 3 and the combustion device body 22. As a result, the design of the entire combustion device can be improved. As the pigment, it is preferable to use an inorganic pigment powder. For example, it is preferable to use a color pigment or an extender pigment.

[0046] The color pigment used in the decorative layer 3 is not particularly limited as long as it is a colored inorganic substance. For example, TiO ２ Powder, ZrO ２ Powder and ZrSiO ４ Examples of the color pigment include white pigment powders such as powders, blue inorganic pigment powders containing Co, green inorganic pigment powders containing Co, Ti—Sb—Cr and Ti—Ni based yellow inorganic pigment powders, Co—Si based red inorganic pigment powders, brown inorganic pigment powders containing Fe, and black inorganic pigment powders containing Cu. Only one type of the color pigments may be used, or two or more types may be used in combination.

[0047] Examples of blue inorganic pigment powders containing Co include Co-Al-based and Co-Al-Ti-based inorganic pigment powders. ２ O ４ Examples of Co-Al-Ti based inorganic pigment powders include CoAl ２ O ４ -TiO ２ -Li ２ O powder and the like.

[0048] Examples of green inorganic pigment powders containing Co include Co-Al-Cr and Co-Ni-Ti-Zn inorganic pigment powders. Examples of Co-Al-Cr inorganic pigment powders include Co(Al,Cr) ２ O ４ Examples of Co-Ni-Ti-Zn based inorganic pigment powders include (Co, Ni, Zn) ２ TiO ４ Examples include powder.

[0049] Examples of brown inorganic pigment powders containing Fe include Fe-Zn-based inorganic pigment powders. Examples of Fe-Zn-based inorganic pigment powders include (Zn, Fe)Fe ２ O４ Examples include powder.

[0050] Examples of black inorganic pigment powders containing Cu include Cu—Cr-based inorganic pigment powders and Cu—Fe-based inorganic pigment powders. Examples of Cu—Cr-based inorganic pigment powders include Cu(Cr,Mn) ２ O ４ Examples of Cu-Fe inorganic pigment powders include Cu-Fe-Mn powders and Cu-Cr-Mn powders.

[0051] Other color pigments include, for example, pearlescent pigments.

[0052] The pigment content of the decorative layer 3 is preferably more than 5% by mass, more preferably 10% by mass or more, particularly preferably 15% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, particularly preferably 50% by mass or less. If the content is equal to or greater than the lower limit, the adhesion and hiding power of the decorative layer 3 can be improved. On the other hand, if the content is equal to or less than the upper limit, the scratch resistance of the decorative layer 3 can be improved, and an increase in the static friction coefficient can be easily suppressed.

[0053] The extender pigment used in the decorative layer 3 may be an inorganic pigment powder different from the color pigment and inorganic beads. For example, the extender pigment may be a scaly, needle-like, or spherical inorganic pigment powder, and specific examples include potassium carbonate, potassium titanate, kaolin, talc, and mica. Only one type of extender pigment may be used, or two or more types may be used in combination.

[0054] The decorative layer 3 preferably further contains inorganic beads. This allows approximately spherical inorganic beads to be scattered throughout the decorative layer 3, and makes it easier to adjust the arithmetic mean roughness Ra of the surface of the decorative layer 3 to a desired level. As a result, light incident on the decorative layer 3 and light reflected from the surface of the decorative layer 3 are more easily scattered, making it easier to enhance the matte finish of the decorative layer 3. In addition, the decorative layer 3 more easily conceals the fixing member 4 used to fix the combustion apparatus window glass 1. Furthermore, when the surface of the decorative layer 3 is wiped with a cloth or the like, fibers from the cloth are less likely to remain.

[0055] The inorganic beads preferably include at least one selected from the group consisting of glass beads, alumina beads, silica beads, and zirconia beads, more preferably glass beads and / or silica beads, and particularly preferably glass beads and / or silica beads. This allows the effects of the present invention to be further enhanced. Only one type of inorganic beads may be used, or two or more types may be used in combination.

[0056] For example, the inorganic beads are preferably glass beads. By adjusting the composition of the glass beads, it is easy to adjust the average particle size and softening point, and therefore it is easy to control the surface shape to a desired level. Examples of the glass composition of the glass beads include borosilicate glass, aluminoborosilicate glass, silicate glass containing at least one of an alkali metal component and an alkaline earth metal component, and phosphate glass containing zinc and aluminum.

[0057] For example, the inorganic beads are preferably silica beads. Silica beads have a high softening point, which makes it easy to increase the difference between their softening points and that of the glass matrix, making it easy to scatter the inorganic beads in a substantially spherical state within the decorative layer 3. This improves the matte finish and hiding power of the decorative layer 3. Furthermore, when the surface of the decorative layer 3 is wiped with a cloth or the like, the cloth is less likely to get caught on the silica beads protruding from the surface of the decorative layer 3, and fibers from the cloth are less likely to remain.

[0058] The presence of inorganic beads in the decorative layer 3 can be confirmed using a scanning electron microscope or the like.

[0059] The softening points of the inorganic beads and the glass matrix are preferably different. More specifically, the softening point of the inorganic beads is preferably higher than that of the glass matrix. This allows for approximately spherical inorganic beads to be scattered throughout the decorative layer 3, and makes it easier to control the surface shape to the desired extent. This improves the matte finish and hiding power of the decorative layer 3. Furthermore, when the surface of the decorative layer 3 is wiped with a cloth or the like, fibers from the cloth are less likely to remain. Specifically, the difference in softening points between the inorganic beads and the glass matrix is ​​preferably 50°C or more, more preferably 80°C or more, and particularly preferably 100°C or more. If the difference in softening points between the inorganic beads and the glass matrix is ​​too small, both the glass matrix and the inorganic beads will soften and deform during the heating process during the formation of the decorative layer 3, making it difficult to control the surface shape of the inorganic beads to the desired extent. The upper limit of the softening point difference between the inorganic beads and the glass matrix is ​​not particularly limited, but may be, for example, 500°C or less.

[0060] The softening point of the inorganic beads is, for example, preferably 500°C or higher, more preferably 600°C or higher, and particularly preferably 800°C or higher. In this way, approximately spherical inorganic beads are scattered throughout the decorative layer 3, and the surface shape can be easily controlled to the desired degree. This improves the matte finish and hiding power of the decorative layer 3. Furthermore, when the surface of the decorative layer 3 is wiped with a cloth or the like, fibers from the cloth are less likely to remain. The upper limit of the softening point of the inorganic beads is not particularly limited, but may be, for example, 2000°C or lower, particularly 1800°C or lower.

[0061] The average particle size of the inorganic beads is preferably 0.1 μm to 9 μm. The upper limit of the average particle size of the inorganic beads is preferably 9 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, and particularly preferably 6 μm or less. The lower limit of the average particle size of the inorganic beads is preferably 0.1 μm or more, more preferably 0.3 μm or more, even more preferably 1 μm or more, and particularly preferably 2 μm or more. When the average particle size of the inorganic beads is equal to or less than the above upper limit and equal to or greater than the above lower limit, approximately spherical inorganic beads are scattered throughout the decorative layer 3, and the surface shape can be easily controlled to the desired degree. This improves the matte finish and hiding power of the decorative layer 3. Furthermore, when the surface of the decorative layer 3 is wiped with a cloth or the like, fibers derived from the cloth are less likely to remain. If the average particle size of the inorganic beads is too small, the Mohs hardness is likely to decrease. If the average particle size of the inorganic beads is too large, fibers derived from the cloth or the like are likely to remain when the surface of the decorative layer 3 is wiped with a cloth or the like. In the present invention, the average particle diameter is D ５０ (volume-based average particle size) and refers to a value measured by laser diffraction.

[0062] The inorganic beads are preferably substantially spherical in shape, which makes it difficult for fibers from a rag to remain when the surface of the decorative layer 3 is wiped with the rag.

[0063] When the decorative layer 3 contains inorganic beads, the content of the inorganic beads in the decorative layer 3 is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 11% by mass or more, and particularly preferably 15% by mass or more. The upper limit of the content of the inorganic beads is preferably less than 45% by mass, more preferably 40% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less. If the content of the inorganic beads is equal to or greater than the lower limit, the inorganic beads are easily dispersed in the decorative layer 3, and the surface shape can be easily controlled to the desired degree. Therefore, the matte finish and hiding power of the decorative layer 3 can be improved. If the content is equal to or less than the upper limit, the arithmetic mean roughness Ra of the surface of the decorative layer 3 can be prevented from becoming too large, and when the surface of the decorative layer 3 is wiped with a cloth or the like, fibers derived from the cloth are less likely to remain.

[0064] In the decorative layer 3, the upper limit of the mass ratio (inorganic beads / glass matrix) is preferably 0.8 or less, and particularly preferably 0.75 or less. When the mass ratio satisfies the above value, it becomes easier to improve the matte finish of the decorative layer 3 while improving the hiding power of the decorative layer 3, and fibers from rags and the like are less likely to remain. It also becomes easier to suppress an increase in the static friction coefficient. The lower limit of the mass ratio is not particularly limited and is 0 or more, but in order to improve the matte finish and hiding power of the decorative layer 3, it is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.1 or more. The "mass ratio (inorganic beads / glass matrix)" refers to the value obtained by dividing the content of inorganic beads by the content of glass matrix.

[0065] In the decorative layer 3, the mass ratio {(inorganic beads + pigment) / glass matrix} is preferably 2 or less, more preferably less than 1.5, and particularly preferably 1.4 or less. When the mass ratio satisfies the above value, the Mohs hardness of the decorative layer 3 is easily increased. Furthermore, the static friction coefficient of the decorative layer 3 is easily reduced. From the viewpoint of enhancing the matte finish, the lower limit of the mass ratio is preferably 0.01 or more, more preferably 0.05 or more, and particularly preferably 0.1 or more. Note that the "mass ratio {(inorganic beads + pigment) / glass matrix}" refers to the value obtained by dividing the total content of the inorganic beads and pigment by the content of the glass matrix.

[0066] In the decorative layer 3, the mass ratio {pigment / (inorganic beads + glass matrix)} is preferably 0.05 or more, more preferably 0.07 or more, even more preferably 0.1 or more, and particularly preferably 0.15 or more. When the mass ratio satisfies the above value, the L ＊This makes it easier to lower the mass ratio, which further conceals the fixing member 4 while harmonizing the color with the combustion device main body 22, thereby improving the design of the combustion device as a whole. From the viewpoint of suppressing the remaining fibers of rags and the like, the upper limit of this mass ratio is preferably 2 or less, more preferably 1.5 or less, even more preferably 1 or less, and particularly preferably 0.9 or less. Note that the "mass ratio {pigment / (inorganic beads + glass matrix)}" means the value obtained by dividing the pigment content by the combined content of the inorganic beads and the glass matrix.

[0067] The decorative layer 3 may further contain organic beads, such as phenyl polysiloxane, methyl polysiloxane, methyl phenyl polysiloxane, and organic functionalized polysiloxane.

[0068] The thickness of the decorative layer 3 is preferably 0.1 μm to 20 μm, more preferably 1 μm to 10 μm, even more preferably 2 μm to 5 μm, and particularly preferably 3 μm to 4 μm. When the thickness of the decorative layer 3 is within the above range, the effects of the present invention can be further exhibited.

[0069] The Mohs hardness of the decorative layer 3 is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and particularly preferably 5 or more. When the Mohs hardness of the decorative layer 3 is within the above range, the scratch resistance of the decorative layer 3 can be improved. If the Mohs hardness is too low, the scratch resistance of the decorative layer 3 decreases and the decorative layer 3 becomes more likely to peel off. There is no particular upper limit to the Mohs hardness, but it may be, for example, 7 or less, particularly 6 or less. The Mohs hardness can be measured using a known Mohs hardness tester, and for example, a Mohs hardness tester (MH-10R) manufactured by Narica Co., Ltd. can be used.

[0070] (Light-shielding layer) The light-shielding layer 5 preferably contains a glass matrix and a pigment. The glass frit and pigment that form the glass matrix may be the same as those used in the decorative layer 3.

[0071] The content of the glass matrix in the light-shielding layer 5 is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. The upper limit of the glass matrix content is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. If the content is equal to or greater than the lower limit, the scratch resistance of the light-shielding layer 5 can be improved. If the content is equal to or less than the upper limit, the adhesion and hiding power of the light-shielding layer 5 can be improved.

[0072] The pigment content of the light-shielding layer 5 is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. The upper limit of the pigment content is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. If the pigment content is equal to or greater than the lower limit, the adhesion and hiding power of the light-shielding layer 5 can be improved. If the pigment content is equal to or less than the upper limit, the scratch resistance of the light-shielding layer 5 can be improved.

[0073] In this embodiment, the combustion apparatus window glass 1 has been described as having a planar shape. However, from the viewpoints of design and practicality, the combustion apparatus window glass 1 may have a non-planar shape. For example, the combustion apparatus window glass 1 may have a curved shape. The combustion apparatus window glass 1 may also have a bent shape, etc. Furthermore, the combustion apparatus window glass 1 may have a shape other than a rectangular shape in a plan view, such as a circle or a polygon other than a rectangle. When the combustion apparatus window glass 1 has a curved shape, for example, either one of the long side or the short side may be curved, or both may be curved. The radius of curvature is not particularly limited, but is, for example, 30 mm or more and 7000 mm or less.

[0074] (Method for manufacturing window glass for combustion apparatus) The method for manufacturing a window glass for a combustion apparatus preferably includes a step of applying a decorative layer-forming paste to the peripheral edge of a first main surface of a glass substrate, the first main surface being provided on the outside of the combustion apparatus, and firing the paste to form a decorative layer on the peripheral edge of the first main surface of the glass substrate. For example, the window glass 1 for a combustion apparatus can be manufactured by the following manufacturing method.

[0075] First, a decorative layer-forming paste containing glass frit and a pigment is prepared. Next, the decorative layer-forming paste is applied to the surface that will become the first main surface 2a of the glass substrate 2, and then dried and fired to form the decorative layer 3 on the first main surface 2a of the glass substrate 2. More specifically, the decorative layer-forming paste is applied to the peripheral portion of the first main surface 2a of the glass substrate 2 and fired to form the decorative layer 3 on the peripheral portion of the first main surface 2a of the glass substrate 2.

[0076] The decorative layer forming paste can be applied using known application methods such as screen printing, inkjet printing, and spraying. The drying temperature of the decorative layer forming paste can be, for example, 50°C or higher and 150°C or lower. The drying time of the decorative layer forming paste can be, for example, 5 seconds or higher and 50 hours or lower. The firing temperature of the decorative layer forming paste can be, for example, 600°C or higher and 950°C or lower. The firing time of the decorative layer forming paste can be, for example, 10 minutes or higher and 2 hours or lower. When the firing temperature and firing time are equal to or higher than the above upper and lower limits, the approximately spherical inorganic beads are easily dispersed in the decorative layer 3, and the surface shape can be easily controlled to the desired degree. This improves the matte finish and hiding power of the decorative layer 3. Furthermore, when additional layers (e.g., an antifouling layer, a protective layer, etc.) are formed on the decorative layer 3, the layer forming pastes can be applied using known application methods such as screen printing, inkjet printing, and spraying.

[0077] After forming the decorative layer 3, the method may further include a step of polishing the surface of the decorative layer 3. Methods for polishing the surface of the coating layer 3 include physical polishing and chemical polishing. Physical polishing methods include a method of polishing with a polishing machine using an abrasive slurry or the like for a certain period of time, followed by cleaning; a method of polishing with a cloth or sponge using an abrasive paste or the like for a certain period of time, followed by cleaning; a method of applying an aqueous solution containing hydrogen fluoride or the like to the surface of the decorative layer 3 and leaving it for a certain period of time, followed by cleaning; a method of immersing the entire combustion device window glass 1 in an aqueous solution containing hydrogen fluoride or the like for a certain period of time, followed by removing and cleaning; and a method of spraying vapor of an aqueous solution containing hydrogen fluoride or the like onto the surface of the decorative layer 3, leaving it for a certain period of time, followed by cleaning.

[0078] The method for manufacturing a window glass for a combustion apparatus may further include a step of forming a light-shielding layer 5. For example, it is preferable to include a step of applying a light-shielding layer-forming paste to the peripheral edge of the second main surface 2b of the glass substrate 2, which has a decorative layer 3 formed on the peripheral edge of the first main surface 2a of the glass substrate 2, and firing the paste to form the light-shielding layer 5 on the peripheral edge of the second main surface 2b of the glass substrate 2. In this case, a light-shielding layer-forming paste containing glass frit and a pigment is first prepared. Next, the light-shielding layer-forming paste is applied to the surface that will become the second main surface 2b of the glass substrate 2, which has the decorative layer 3 formed on the first main surface 2a, and then dried and fired to form the light-shielding layer 5 on the second main surface 2b of the glass substrate 2. The light-shielding layer-forming paste can be applied by the same method as the method for applying the decorative layer-forming paste described above. The firing temperature and firing time can also be the same as those described above.

[0079] In the method for manufacturing a windowpane for a combustion apparatus, the decorative layer 3 and the light-shielding layer 5 may be formed first, or second. That is, the decorative layer-forming paste may be applied and fired, and then the light-shielding layer-forming paste may be applied and fired, or the light-shielding layer-forming paste may be applied and fired, and then the decorative layer-forming paste may be applied and fired. For example, the method for manufacturing a windowpane for a combustion apparatus may include a step of applying a light-shielding layer-forming paste to the peripheral portion of the second main surface 2 b of the glass substrate 2, which is provided inside the combustion apparatus, and firing the paste to form a light-shielding layer on the peripheral portion of the second main surface of the glass substrate 2, and a step of applying a decorative layer-forming paste to the peripheral portion of the first main surface 2 a of the glass substrate 2, on which the light-shielding layer 5 has been formed on the peripheral portion of the second main surface 2 b of the glass substrate 2, and firing the paste to form the decorative layer 3 on the peripheral portion of the first main surface 2 a of the glass substrate 2.

[0080] It is preferable to apply either the decorative layer-forming paste or the light-shielding layer-forming paste after firing the other layer-forming paste, for example, it is preferable to apply the decorative layer-forming paste, fire it, and then apply the light-shielding layer-forming paste and fire it. For example, if the light-shielding layer-forming paste is formed after the decorative layer-forming paste is applied and before firing, there is a possibility that the layer of the decorative layer-forming paste will peel off during the step of printing the light-shielding layer-forming paste.

[0081] In this manner, the window glass 1 for a combustion apparatus can be manufactured.

[0082] (Combustion Device) As shown in Fig. 4, a combustion device 21 includes the above-described combustion device window glass 1. The combustion device window glass 1 is fixed to the frame of the combustion device main body 22 by a fixing member 4 (see Fig. 5), such as an adhesive or a gasket. The decorative layer 3 is provided on the first main surface 2a of the glass substrate 2 and is arranged along the frame of the combustion device main body 22. With the above-described configuration, it becomes easier to achieve color harmony between the decorative layer 3 and the combustion device main body 22. As a result, the design of the entire combustion device can be improved.

[0083] The present invention will be described in more detail below with reference to specific examples. The present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the present invention.

[0084] The following glass substrates were prepared:

[0085] Transparent crystallized glass plate (manufactured by Nippon Electric Glass Co., Ltd., product number "N-0", average thermal expansion coefficient at 30°C to 750°C: 0.5 × 10 －７ / ℃, thickness: 4mm)

[0086] The following materials were prepared for the decorative layer and the light-shielding layer.

[0087] <Glass matrix> Glass frit: "Frit NPF" manufactured by Nippon Electric Glass Co., Ltd. (average particle size 3.5 μm, softening point 660°C, borosilicate glass) <Inorganic beads> Glass beads: "UBS-0010E" manufactured by Unitika Ltd. (average particle size 6.1 μm, softening point 850°C, aluminoborosilicate glass) Silica beads: "SS-10" manufactured by Tokuyama Corporation (average particle size 1.0 μm, melting point >1600°C), "SP-03P" manufactured by Tokuyama Corporation (average particle size 0.3 μm, melting point >1600°C) <Pigment> Color pigment: "Daipyroxide Black #9510" manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd. (black inorganic pigment powder), "42-129A" ​​manufactured by TOMATEC Corporation (brown inorganic pigment powder)

[0088] Example 1: A paste for forming a decorative layer was prepared by mixing glass frit ("Frit NPF" manufactured by Nippon Electric Glass Co., Ltd.), a color pigment, and a resin binder (cellulose resin binder) in a mass ratio (glass frit:color pigment:resin binder) of 5:5:7.7. The paste for forming a decorative layer was then screen-printed onto the first main surface of a transparent crystallized glass plate ("N-0" manufactured by Nippon Electric Glass Co., Ltd.) so that the thickness after firing would be 5.7 μm. The paste was then heated and dried at 80°C for 1 minute, and then fired at 800°C for 30 minutes to form a decorative layer, thereby obtaining a sample of Example 1. The resin binder was completely volatilized by the heat drying and firing. Tables 1 and 2 show the content of each component in the decorative layer after drying and firing.

[0089] Examples 2 to 16: A decorative layer was formed in the same manner as in Example 1, except that the ratio of each component in the decorative layer after firing was changed to the ratios shown in Tables 1 and 2 below. A paste for forming a light-shielding layer was prepared by mixing glass frit, color pigment, and resin binder in a mass ratio (glass frit:color pigment:resin binder) of 5:5:7.7. The paste for forming a light-shielding layer was then screen-printed onto the second main surface of a transparent crystallized glass plate ("N-0" manufactured by Nippon Electric Glass Co., Ltd.) so that the thickness after firing would be 3 to 7 μm. The light-shielding layer was positioned so that it overlapped the decorative layer via the glass substrate in a planar view. The samples were then heated and dried at 80°C for 1 minute, followed by firing at 800°C for 30 minutes to form a light-shielding layer, thereby obtaining samples of Examples 2 to 16.

[0090] The following evaluations (1) to (8) were carried out on the samples of Examples 1 to 16. Note that evaluation (3) used samples of Examples 2 to 6 on which only the decorative layer was formed (i.e., samples before the light-shielding layer was formed). The results are shown in Tables 1 and 2.

[0091] (1) 60° Gloss Value and 20° Gloss Value on the Surface of the Decorative Layer The 60° gloss value and 20° gloss value on the surface of the decorative layer were evaluated in accordance with JIS K5600-5-4 (1999) using a HORIBA IG-331 manufactured by Horiba, Ltd.

[0092] (2) Concealment The obtained sample was placed on a concealment test paper having a white background portion and a black background portion with the second main surface facing downwards, and the visibility of the concealment test paper from the decorative layer side (first main surface side) was evaluated according to the following index. [Evaluation criteria] A: Neither the white background portion nor the black background portion of the concealment test paper was visible at all. B: The boundary between the white background portion and the black background portion of the concealment test paper was visible, and the white background portion and the black background portion appeared to be different shades of gray. C: The boundary between the white background portion and the black background portion of the concealment test paper was clearly visible, and the white background portion appeared to be almost white, and the black background portion appeared to be almost black.

[0093] (3) Light transmittance at a wavelength of 580 nm The light transmittance of the obtained sample at a wavelength of 580 nm was measured using a spectrophotometer ("V-770" manufactured by JASCO Corporation). The measurement was performed from the decorative layer side (first main surface side) of the sample.

[0094] (4) L ＊ Value, a ＊ value, b ＊ The obtained sample was placed on a black plate with the second main surface facing downward, and ＊ a ＊ b ＊ L in color system ＊ Value, a ＊ value, b ＊ The measurement was performed using a color difference meter (Konica Minolta "CM-600D") from the decorative layer side (first main surface side) of the sample.

[0095] (5) Mohs Hardness The Mohs hardness of the surface of the decorative layer of the obtained sample was measured using a Mohs hardness tester ("MH-10R" manufactured by Narika Co., Ltd.).

[0096] (6) Arithmetic mean roughness Ra The arithmetic mean roughness Ra of the surface of the decorative layer of the obtained sample was measured using a Mitutoyo "SURFTEST SJ-210" in accordance with JIS B0601:2001 under the following conditions: Measurement speed: 0.5 mm / s Cutoff values ​​λc: 2.5 mm, λs: 8 mm Number of sections: 5 Gaussian filter

[0097] (7) Static Friction Coefficient The static friction coefficient of the obtained sample (the static friction coefficient between the surface of the decorative layer and the stainless steel (SUS304)) was measured from the first main surface side of the area where the decorative layer was provided in a plan view using a "Portable Friction Meter Muse 94i-II" manufactured by Shinto Scientific Co., Ltd.

[0098] (8) Tendency of Fiber Remaining After Wiping the Decorative Layer A cloth (Hard Wipe A300) folded eight times was fixed to the tip of a 600 g weight, and alcohol ("Neoethanol P-7" manufactured by Taishin Chemical Co., Ltd.) was applied to the cloth. The tip of the weight was brought into contact with the decorative layer (glass substrate) via the cloth, and the weight was slid across the decorative layer at 50 mm / s for 10 reciprocating strokes of 100 mm, with only the weight itself exerting a load. The degree to which fibers from the cloth remained on the decorative layer was then evaluated according to the following criteria. [Evaluation Criteria] A: No fibers were found to be attached (no residual fibers were generated). B: Fibers were found to be attached to the wiped edge of the sample, but this did not affect the appearance. C: Fibers were found to be attached to one end of the wiped area, slightly reducing the design. D: Fibers were found to be attached over the entire wiped area, reducing the design.

[0099] Furthermore, the surfaces of the decorative layers of the samples of Examples 1 to 16 were buffed, and the samples after surface polishing were also subjected to the above evaluations (6) to (8). The results are shown in Tables 1 and 2.

[0100]

[0101]

[0102] As shown in Tables 1 and 2, in Examples 1 to 16, the 60° gloss value of the surface of the decorative layer was 60 or less. In addition, in Examples 2 to 16, the arithmetic mean roughness Ra of the surface of the decorative layer was 0.57 μm or less, and the evaluation of the likelihood of fibers remaining after wiping the decorative layer was C or higher. In this way, when installed in the frame of the combustion device main body, it was confirmed that the colors of the combustion device main body and the decorative layer were harmonized, and the design of the entire combustion device could be improved.

[0103] DESCRIPTION OF SYMBOLS 1 Window glass for combustion device 2 Glass substrate 2a First main surface 2b Second main surface 3 Decorative layer 4 Fixing member 5 Light-shielding layer 21 Combustion device 22 Combustion device body

Claims

1. A window glass for use in a combustion device, comprising: a glass substrate having a first main surface provided on the outside of the combustion device and a second main surface facing the first main surface and provided on the inside of the combustion device; and a decorative layer provided on the peripheral edge of the first main surface of the glass substrate.

2. A window glass for a combustion apparatus according to claim 1, characterized in that the 60° gloss value of the surface of the decorative layer is 60 or less.

3. A window glass for a combustion apparatus according to claim 1 or 2, characterized in that the arithmetic mean roughness Ra of the surface of the decorative layer is 0.57 μm or less.

4. A window glass for a combustion apparatus according to claim 1 or 2, further comprising a light-shielding layer provided on the peripheral edge of the second main surface of the glass substrate.

5. A window glass for a combustion device according to claim 1 or 2, characterized in that the decorative layer contains a glass matrix and a pigment.

6. A window glass for a combustion apparatus according to claim 1 or 2, characterized in that the decorative layer contains inorganic beads.

7. A window glass for a combustion apparatus according to claim 6, characterized in that the inorganic beads are glass beads.

8. A window glass for a combustion apparatus according to claim 6, characterized in that the inorganic beads are silica beads.

9. A window glass for a combustion apparatus according to claim 1 or 2, characterized in that the glass substrate has a curved shape.

10. A combustion device comprising the window glass for a combustion device according to claim 1 or 2.

11. A method for manufacturing a window glass for a combustion device as set forth in claim 1 or 2, characterized in that it comprises a step of applying a decorative layer forming paste to the peripheral edge of a first main surface of a glass substrate, the first main surface being provided on the outside of the combustion device, and firing the glass substrate, thereby forming a decorative layer on the peripheral edge of the first main surface of the glass substrate.

12. A method for manufacturing a window glass for a combustion apparatus as set forth in claim 11, characterized in that it includes a step of applying a paste for forming a light-shielding layer to the peripheral edge of the second main surface of the glass substrate having the decorative layer formed on the peripheral edge of the first main surface of the glass substrate, and firing the glass substrate to form a light-shielding layer on the peripheral edge of the second main surface of the glass substrate.

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