JPH1043013A - Heat insulating showcase with water droplet antisticking property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat insulating showcase with a transparent window panel and a heating device which hardly lets many water droplets splashed on the transparent window panel stick to it and thereby provides a good visibility of displayed foods. SOLUTION: A heat insulating showcase is provided with a transparent window panel 12 and a heating device. On an inner face of the transparent panel 12, a surface layer which has such a structure that sections with a hydrophilic property which are so exposed that photocatalytic oxide particles may be brought into contact with outside air and sections with a water repellent property which are so exposed that water repellent fluorine contained resin may be brought into contact with outside air may be microscopicly dispersed on the surface and which has a contact angle of 90 deg. or above between the surface and water and which is substantially transparent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulated showcase for displaying foods in an insulated state.

[0002]

2. Description of the Related Art A showcase for displaying food such as Chinese steamed bun which is desired to be kept warm is equipped with a heating device such as a steam generator so that the displayed food is kept warm. The heat-insulated showcase is provided with a transparent window panel made of glass, acrylic resin, or the like, so that the displayed food can be seen from the outside.

[0003]

On the inside of the transparent window panel of the heat-insulated showcase, condensed water is condensed due to condensation of steam. If the condensed condensed water thus generated grows in the form of water droplets and a large number of discrete water droplets adhere to the inside of the transparent window panel, it becomes difficult to clearly view the displayed food from the outside. In view of the above, an object of the present invention is to provide a heat insulating showcase provided with a transparent window panel to which a large number of discrete water droplets are unlikely to adhere.

[0004]

According to the present invention, in order to solve the above-mentioned problems, in a thermal insulation showcase provided with a transparent window panel and a heating device, photocatalytic oxide particles are coated on the inner surface of the transparent panel with the outside air. Has a structure in which both the hydrophilic part exposed to be in contact with and the water-repellent part exposed to the water-repellent fluororesin contact with the outside air are microscopically dispersed on the surface, and A heat-insulating showcase having a water droplet adhesion preventing property, wherein a substantially transparent surface layer having a contact angle with water of 90 ° or more is formed. A structure in which both a hydrophilic part exposed to contact the photocatalytic oxide particles with the outside air and a water-repellent part exposed to the water-repellent fluororesin contact with the outside are microscopically dispersed on the surface. In this case, since the hydrophilic surface and the water-repellent surface are adjacent to each other, the hydrophilic adherent that easily adapts to the hydrophilic surface does not adapt to the adjacent water-repellent portion. Conversely, hydrophobic deposits that are easily adapted to the water-repellent surface do not adapt to adjacent hydrophilic portions. Therefore, neither the hydrophilic deposit nor the hydrophobic deposit is fixed to the member surface, and the surface is maintained in a clean state. Furthermore, the presence of the photocatalyst causes the photocatalytic oxide particles to be exposed so as to be in contact with the outside air in response to the photoexcitation of the photocatalyst, so that the hydrophilic portion is permanently maintained. The structure in which both the water-repellent and water-repellent portions are microscopically dispersed on the surface is maintained. That is, if the contact angle with water on the surface is set to 90 ° or more during the production of the surface layer during the production of the surface layer, the state is maintained in accordance with the photoexcitation of the photocatalyst, and water droplets hardly adhere.

[0005]

FIG. 1 shows an embodiment of a heat-insulated showcase according to the present invention. Referring to FIG. 1, the heat-insulating showcase 10 includes, for example, four transparent window panels 12 made of glass, acrylic resin, or the like, and a shelf frame 14 on which food is placed. An internal illuminating lamp 16 such as a fluorescent lamp is arranged at an appropriate place of the showcase so as to illuminate the displayed food. Insulated showcase 1
A steam generator 18 is arranged at the lower part of 0 so as to steam the displayed food. On the inner side surface of the transparent window panel 12, both a portion exhibiting hydrophilicity where the photocatalytic oxide particles are exposed to contact with the outside air and a portion exhibiting water repellency where the water-repellent fluororesin is exposed to contact with the outside air are provided. A substantially transparent surface layer having a structure microscopically dispersed on the surface and having a contact angle of 90 ° or more with water on the surface is formed. When the photocatalyst in the surface layer is crystalline titanium oxide, the photocatalyst is photo-excited by the ultraviolet light contained in the light from the internal illumination lamp 16. A transparent intermediate layer may be provided between the transparent window panel base material and the surface layer for the purpose of improving adhesion to the base material and the like.

When the surface layer is manufactured, the contact angle of the surface with water is set to 90.
In order to achieve the above value, the mixing ratio of the water-repellent fluororesin to the total amount of the photocatalytic oxide and the water-repellent fluororesin in the surface layer is preferably 50% by weight or more, more preferably 60% by weight or more.

[0007] A photocatalyst emits light (excitation light) having an energy (ie, a shorter wavelength) larger than the energy gap between the conduction band and the valence band of the crystal, and emits electrons in the valence band. A substance capable of generating conduction electrons and holes by excitation (photoexcitation). Photocatalytic oxides include, for example, anatase-type titanium oxide, rutile-type titanium oxide, zinc oxide, tin oxide, and ferric oxide. And oxides such as bismuth trioxide, tungsten trioxide and strontium titanate. As a light source used for photoexcitation of the photocatalyst, indoor lighting may be used, and as ancillary equipment or portable equipment, a light source capable of irradiating excitation light may be used. As the light source to be used, for example, a fluorescent lamp, an incandescent lamp, a metal halide lamp, a mercury lamp, a xenon lamp, a germicidal lamp and the like can be suitably used. However, in a preferred embodiment, the insulated showcase is provided with an internal illuminator such as a fluorescent lamp that emits weak ultraviolet light together with visible light, and illuminates the displayed food with the illuminator and optically excites the photocatalyst. In order for the photocatalytic oxide particles on the surface of the base material to be exposed to the outside air and exhibit hydrophilicity in accordance with the photoexcitation of the photocatalyst, the illuminance of the excitation light is 0.001 mW / cm. More than ^two is fine,
It is preferably at least 0.01 mW / cm ² ,
cm ² or more is more preferable.

As the water-repellent fluororesin, polytetrafluoroethylene, polychlorotrifluoroethylene, polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymer and the like can be suitably used.

The thickness of the surface layer is preferably set to 0.4 μm or less. Then, cloudiness due to irregular reflection of light can be prevented, and the surface layer becomes substantially transparent. Further, it is more preferable that the thickness of the surface layer be 0.2 μm or less. Then, it is possible to prevent the surface layer from being colored by light interference. Also, the thinner the surface layer, the better its transparency. Further, when the film thickness is reduced, the wear resistance of the surface layer is improved.

A metal such as Ag, Cu, Zn can be added to the surface layer. The surface layer to which the metal is added can kill bacteria and fungi attached to the surface even in a dark place.

Pt, Pd, Ru, Rh, I
A platinum group metal such as r or Os can be added.
The surface layer to which the metal is added can enhance the redox activity of the photocatalyst, and can improve the decomposability of organic contaminants and the decomposability of harmful gases and odors.

The photocatalytic oxide particles are exposed to the outside air and exhibit a hydrophilic property, and the water-repellent fluororesin is exposed to the atmosphere and exhibit water repellency. Whether or not it has the structure described above can be confirmed by the following method. One such method is performed as follows. That is, first, a solution containing a metal having a large atomic number such as Ag, Pt, or Pd such as silver nitrate, silver lactate, chloroplatinic acid, or palladium chloride is applied to the substrate surface, and the substrate surface is irradiated with excitation light of a photocatalyst. Ag, P
A metal having a large atomic number, such as t or Pd, is deposited on the substrate surface. Since the deposition reaction of the metal is based on the reduction action of the metal by the photocatalyst, at this time, the metal adheres to the hydrophilic portion exposed by the photocatalytic oxide particles in contact with the outside air, but the water-repellent fluororesin Is hardly adhered to a portion exhibiting water repellency exposed so as to be in contact with the outside air.
Next, by observing the reflected electron image of the scanning electron microscope, if the density (contrast) is dispersed, the photocatalytic oxide particles are exposed so as to be in contact with the outside air and exhibit a hydrophilic property. It is concluded that both the water-repellent portions exposed so that the fluororesin comes into contact with the outside air have a structure microscopically dispersed on the surface. As another observation method, elemental analysis of the surface may be performed using an energy dispersive X-ray analyzer (EDX) or an electron probe microanalyzer (EPMA) instead of observing the density using a backscattered electron image. . As another observation method, if the metal is colored such as silver, the color may be observed by an optical microscope instead of observing the density by a reflected electron image.

Next, on the surface of the base material, both a portion exhibiting hydrophilicity in which the photocatalytic oxide particles are exposed to the outside air and a portion exhibiting water repellency in which the water-repellent fluororesin is exposed in contact with the outside air A method for producing an antifouling member having a surface layer having a structure in which is dispersed microscopically on the surface will be described. The manufacturing method in this case is basically based on applying the coating composition to the surface of the substrate and fixing the coating composition to the surface of the substrate.

Here, the coating composition comprises photocatalyst particles and a water-repellent fluororesin as essential components, and water,
A solvent such as ethanol or propanol, a cross-linking agent for a fluororesin, or a surfactant for improving the dispersibility of a coating solution may be added.

As a method for applying the above coating composition, methods such as spray coating, dip coating, flow coating, spin coating, roll coating, brush coating, and sponge coating can be suitably used. The coating composition is heat-treated at a temperature of 300 ° C. or higher at which the fluororesin melts, and when a crosslinking agent for the fluororesin is added, heat treatment at a temperature at which the fluororesin is cured by the crosslinking agent, pressure treatment, and heat treatment. It can be fixed by a method such as a combination of pressure treatment and the above heat treatment, or fixing by impact pressure. Further, before fixing by the above method, the surface of the substrate may be blasted or the like to provide irregularities. Then, the adhesion between the substrate and the surface layer can be improved.

[0016]

【Example】

Embodiment 1 FIG. Anatase type titanium oxide sol (Ishihara Sangyo, S
TS-11) and polytetrafluoroethylene (PTF
E) mixing the particles (Daikin Industries, D-1) and distilled water,
The coating liquid obtained by stirring for 30 minutes is applied on a 10 cm square soda lime glass substrate by a spray coating method, and heat-treated at 380 ° C. for 3 minutes to obtain 4 parts by weight of anatase type titanium oxide particles and polytetrafluorocarbon. A surface layer consisting of 6 parts by weight of ethylene particles was formed to obtain a # 1 sample. #
1 Observation of the surface of the sample shows that both the photocatalytic oxide particles exposed to be in contact with the outside air and exhibit a hydrophilic property and the water-repellent fluororesin exposed to be in contact with the outside have water repellency. It was confirmed that a surface layer having a structurally dispersed structure was formed. Next, the contact angle of the surface of the # 1 sample with water was measured. Here, the contact angle with water was evaluated using a contact angle measuring device (Kyowa Interface Science, CA-X150) based on the contact angle with water 30 seconds after dropping. As a result, the contact angle with water becomes 120 ° and a value of 90 ° or more,
When the # 1 sample was tilted, the water droplets fell while rolling. Next, an ultraviolet light source (Sankyo Electric Co., Ltd., black light blue (BLB) fluorescent lamp) was applied to the # 1 sample to form a 0.5
The sample was irradiated with ultraviolet rays at an ultraviolet illuminance of mW / cm ² for about 1 day to obtain a # 2 sample. The contact angle with water was measured for the # 2 sample. As a result, the contact angle with water became 110 ° and a value of 90 ° or more. When the # 2 sample was tilted, the water droplets fell while rolling.

[0017]

According to the present invention, in a heat insulation showcase having a transparent window panel and a heating device, a large number of discrete water droplets hardly adhere to the transparent window panel, thereby improving the visibility of displayed food. Can be done.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a heat retaining showcase of the present invention.

[Explanation of symbols]

 10: Insulated showcase 12: Transparent window panel

Claims (3)

[Claims] 1. A heat retaining showcase provided with a transparent window panel and a heating device, wherein a hydrophilic part exposed on the inner surface of the transparent panel so that the photocatalytic oxide particles are in contact with the outside air; Both of the water-repellent portions exposed so that the fluororesin comes into contact with the outside air have a structure in which both surfaces are microscopically dispersed, and the surface has a contact angle with water of 90.
温 A heat-insulated showcase having a water-drop adhesion-preventing property, wherein a substantially transparent surface layer of at least the above is formed. 2. The apparatus further comprises an internal illumination light, wherein the photocatalytic oxide is crystalline titania, the illumination light is of a type emitting light including both visible light and ultraviolet light, and the illumination light is The heat-insulated showcase according to claim 1, wherein the display article is illuminated and the photocatalyst is photo-excited. 3. The heat-insulated showcase according to claim 2, wherein the illuminating light optically excites the photocatalyst with an ultraviolet irradiance of 0.1 mW / cm 2 or more.