JPH09226060A - Lid for heating container having fog resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lid for heating container having excellent fog resistance which prevents fog and attachment of water drops and has excellent visibility of foods to be displayed, by providing a surface layer which contains substantially transparent photocatalytic particles on at least an inside surface of a lid base material for a transparent heating container. SOLUTION: On at least an inside surface of a transparent lid base material, a surface layer which contains a substantially transparent photocatalyst is provided. Thus, the surface of the surface layer shows hydrophilic property in response to light excitation of the photocatalyst. To the surface layer, a silica and a solid acid or a silicone is added. The photocalyst means a substance wherein an excitation (light excitation) of electron in valence band is generated so as to generate conduction electron and electron hole when an energy which is larger than an energy gap between a conduction band of its crystal and the valence band, i.e., a light (excitation light) of short wavelength is applied. For example, an anatase-type titanium oxide, a rutile-type titanium oxide, a tin oxide, a zinc oxide, and a bismuth trioxide are suitably utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lid for a heating container for storing food such as oden sold in a warm state in a display state.

[0002]

2. Description of the Related Art Food such as oden is stored in a heating container in order to buy and sell it while keeping it warm. At that time, for example, a wooden lid is used for the purpose of suppressing evaporation of water.
But with a wooden lid, the food you buy and sell cannot be seen from the outside. Therefore, if the lid is made transparent, the food in the lid can be conveniently stored in a display state.

[0003]

However, if the lid is simply made transparent, the inside of the lid becomes cloudy due to vapor condensation, and it is difficult to visually recognize the displayed food from the outside. Even when the condensation of steam further progresses and even small condensed water droplets fuse with each other to grow into large water droplets, the perspective image is distorted by the refraction of light at the interface between the water droplet and the transparent lid and the interface between the water droplet and air. After all it is hard to see the food inside. An object of the present invention is to provide a lid for a heating container capable of preventing fogging and water droplet adhesion and having excellent anti-fogging property with excellent visibility of displayed food products.

[0004]

SUMMARY OF THE INVENTION The present invention is based on the discovery that, in a member having a surface layer containing a photocatalyst formed thereon, when the photocatalyst is photoexcited, the surface of the member is highly hydrophilized. This phenomenon is considered to proceed by the following mechanism. That is, when the photocatalyst is irradiated with light having an energy larger than the energy gap between the valence band upper end and the conduction band lower end of the photocatalyst, the electrons in the valence band of the photocatalyst are excited to generate conduction electrons and holes. The action of either or both of them probably imparts polarity to the surface and collects polar components such as water and hydroxyl groups. Then, one or both of conduction electrons and holes and the above-mentioned polar component cooperate with each other to cut off a chemical bond between the surface and the contaminant chemically adsorbed on the surface, and to cause a chemical adsorbed water on the surface. Is adsorbed, and a physically adsorbed water layer is formed thereon. Further, once the surface of the member is highly hydrophilized, the hydrophilicity of the surface is maintained for a certain period even if the member is kept in a dark place.

According to the present invention, there is provided a lid for a heating container having an antifogging property, which comprises a transparent lid base material and a surface layer containing a substantially transparent photocatalyst on at least an inner surface thereof. By providing the surface layer containing the photocatalyst, the surface of the surface layer exhibits hydrophilicity in response to photoexcitation of the photocatalyst. When the surface of the surface layer is hydrophilic, even if condensed water adheres to the inside of the lid due to condensation of steam, the condensed water of the adhered moisture spreads evenly on the surface of the layer, and the moisture is condensed. Water will prevent it from becoming cloudy.

In a preferred embodiment of the present invention, the surface layer further contains silica. By containing silica, the surface is likely to exhibit a high degree of hydrophilicity near a water wetting angle of 0 °, and the hydrophilicity retention when held in a dark place is improved. The reason seems to be related to the ability of silica to store water in its structure.

In a preferred embodiment of the present invention, the surface layer further contains a solid acid. When the solid acid is contained, the surface is likely to exhibit a high degree of hydrophilicity near a water wetting angle of 0 °, and the hydrophilicity retention when kept in a dark place is improved. The reason is that when a solid acid is contained in the surface layer, the polarity of the surface is large regardless of the presence or absence of light, so it is easier to selectively adsorb water molecules that are polar molecules than hydrophobic molecules. . Therefore, a stable physical adsorption water layer is easily formed, and even if it is kept in a dark place,
Surface hydrophilicity can be maintained at a high level for a fairly long time.

In a preferred embodiment of the present invention, the surface layer further contains silicone.
By containing silicone, by photoexcitation of the photocatalyst, at least a part of the organic group bonded to the silicon atom in the silicone is replaced with a hydroxyl group, and a physically adsorbed water layer is formed on the organic group, so that the surface is It exhibits a high degree of hydrophilicity close to a water wetting angle of 0 °, and improves the hydrophilicity maintaining ability when kept in a dark place.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a specific structure of the present invention will be described. As shown in FIG. 1 or 2, on the inner surface of the heating container lid base material of the present invention, a layer containing a photocatalyst is formed on the surface of the base material. By taking such a surface structure, the inner surface of the heating container lid is highly hydrophilized in response to photoexcitation of the photocatalyst. Thereby,
Even if condensed water adheres to the inside of the lid due to the condensation of steam, the condensed water of the adhered moisture spreads evenly on the surface of the layer and prevents the condensed water of the moisture from fogging. .

In FIG. 1, when the surface layer comprises only a photocatalyst, the photocatalyst is preferably an oxide.
By doing so, the oxide shows hydrophilicity in the state where the pollutants in the environment are not adsorbed, so that the pollutants are rejected by the photoexcitation action and the adsorbed water layer is formed, so that the oxides easily exhibit hydrophilicity. A uniform water film can be formed. In FIG. 2, M represents a metal element. Therefore, in the case of FIG. 2, the outermost surface is made of a general inorganic oxide. Again,
Since the oxide is hydrophilic when the pollutants in the environment are not adsorbed, the photocatalytic titanium oxide mixed into the surface layer other than the inorganic oxide removes the contaminants by the photoexciting action, and the adsorbed water layer Is formed, a uniform water film can be formed.

For the lid material for the heating container in the present invention, a transparent body such as glass, transparent plastic, or a transparent plastic substrate provided with a transparent hard coat can be preferably used.

A photocatalyst is a photocatalyst of an electron in the valence band when it is irradiated with light (excitation light) having an energy (that is, a short wavelength) larger than the energy gap between the conduction band and the valence band of the crystal. A substance that is excited (photoexcited) to generate conduction electrons and holes. For example, anatase-type titanium oxide, rutile-type titanium oxide, tin oxide, zinc oxide, dibismuth trioxide, tungsten trioxide, oxide trioxide. Diiron, strontium titanate and the like can be preferably used. Here, as the light source used for photoexcitation of the photocatalyst, sunlight, indoor lighting, dedicated lighting can be used, and types thereof include fluorescent lamps, incandescent lamps, indoor lighting, metal halide lamps, mercury lamps, xenon lamps, germicidal lamps, etc. It can be used suitably. In order to make the surface of the base material highly hydrophilic by photoexcitation of the photocatalyst, the illuminance of the excitation light is 0.001 mW / cm.
^The number is preferably ² or more, but is preferably 0.01 mW / cm ² or more, and more preferably 0.1 mW / cm ² or more.

The thickness of the surface layer containing the photocatalyst is 0.4
It is preferable that the thickness is less than or equal to μm. Then, white turbidity due to irregular reflection of light can be prevented, and the surface layer becomes substantially transparent. More preferably, the thickness of the surface layer containing the photocatalyst is 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.
The surface of the surface layer may be further provided with a wear-resistant or corrosion-resistant protective layer capable of being made hydrophilic and other functional films.

The surface layer preferably has a refractive index that is not so high as that of the substrate. Preferably, the refractive index of the surface layer is 2 or less. Then, light reflection at the interface between the substrate and the surface layer and the interface between the surface layer and air can be suppressed. In order to reduce the refractive index of the surface layer to 2 or less, a substance having a refractive index of 2 or less is used for the photocatalyst, or if the photocatalyst has a refractive index of 2 or more, another substance having a refractive index of 2 or less is used for the surface layer. To be added. As a photocatalyst having a refractive index of 2 or less, tin oxide (refractive index: 1.9) or the like can be used. 2
The photocatalyst having the above refractive index includes anatase type titanium oxide (refractive index 2.5 and rutile type titanium oxide (refractive index 2.
7), but in this case, another substance with a refractive index of 2 or less,
For example, calcium carbonate (refractive index 1.6), calcium hydroxide (refractive index 1.6), magnesium carbonate (refractive index 1.5), strontium carbonate (refractive index 1.5), dolomite (refractive index 1.7). ), Calcium fluoride (refractive index 1.4), magnesium fluoride (refractive index 1.4), silica (refractive index 1.5), alumina (refractive index 1.6), silica sand (refractive index 1.6). ), Montmorillonite (refractive index 1.
5), kaolin (refractive index 1.6), sericite (refractive index 1.6), zeolite (refractive index 1.5), tin oxide (refractive index 1.9) and the like may be added to the surface layer.

A metal such as Ag, Cu and 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.

The surface layer includes Pt, Pd, Ru, R
A platinum group metal such as h, Ir, Os can be added. The surface layer to which the metal is added can enhance the oxidation-reduction activity of the photocatalyst and improve the deodorizing and purifying action and the like. In addition, when a solid acid is added in addition to the photocatalyst, the acidity of the solid acid is improved by the addition of a platinum group metal, so that the hydrophilicity is also improved, and the formation of a water film on the attached water is further promoted. The hydrophilicity when the excitation light is not irradiated to the photocatalyst for a long period of time is also improved. Mo can be added to the surface layer. When a solid acid is added in addition to the photocatalyst, the addition of Mo increases the acidity of the solid acid, so that the hydrophilicity is also improved, and the formation of a water film on the attached water is further promoted. The hydrophilicity when light is not irradiated is also improved.

When the substrate is a glass containing alkali network modifying ions such as sodium (soda lime glass, parallel plate glass, etc.), an intermediate layer such as silica may be formed between the substrate and the surface layer. Good. Then, the diffusion of the alkali network modifying ions from the base material to the surface layer during the firing is prevented, and the photocatalytic function is more effectively exhibited.

The term "hydrophilic" refers to the property of being easily conformed when water is dropped on the surface, and generally refers to a state where the water wetting angle is less than 90 °. The term “high hydrophilicity” in the present invention refers to a property that is highly compatible when water is dropped on the surface, and more specifically, a state where the water wetting angle is about 10 ° or less. In particular, as disclosed in PCT / JP96 / 00734, the water wetting angle is preferably 10 ° or less, more preferably 5 ° or less, as disclosed in PCT / JP96 / 00734. The term “anti-fog” used herein broadly means not only the haze but also a technique for preventing optical obstacles due to the growth of condensed water droplets and the adhesion of water droplets.

The solid acid used in the present invention includes sulfuric acid-supported Al.
₂ O ₃ , sulfuric acid supported TiO ₂ , sulfuric acid supported ZrO ₂ , sulfuric acid supported S
nO ₂ , sulfuric acid supported Fe ₂ O ₃ , sulfuric acid supported SiO ₂ , sulfuric acid supported HfO ₂ , TiO ₂ / WO ₃ , WO ₃ / SnO ₂ , WO ₃ / Z
rO ₂ , WO ₃ / Fe ₂ O ₃ , SiO ₂ · Al ₂ O ₃ , TiO
₂ / SiO ₂ , TiO ₂ / Al ₂ O ₃ , TiO ² / ZrO _{2 and the} like can be preferably used.

Next, a method for forming the surface layer will be described. First, the production method in the case where the surface layer is composed only of the photocatalyst will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. In this case, there are roughly three methods. One method is a sol coating and firing method, the other method is an organic titanate method, and the other method is an electron beam evaporation method. (1) Sol-coating and firing method Anatase-type titanium oxide sol is applied to the surface of a substrate by a method such as spray coating, dip coating, flow coating, spin coating, or roll coating, and then fired. (2) Organic titanate method Titanium alkoxide (tetraethoxy titanium, tetramethoxy titanium, tetrapropoxy titanium, tetrabutoxy titanium, etc.), titanium acetate, titanium chelate, etc. are added with a hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.). , After diluting with a non-aqueous solvent such as alcohol (ethanol, propanol, butanol, etc.), while partially or completely proceeding the hydrolysis, the mixture is spray-coated, dip-coated, Apply by methods such as flow coating method, spin coating method, roll coating method,
dry. By drying, the hydrolysis of the organic titanate is completed to produce titanium hydroxide, and a layer of amorphous titanium oxide is formed on the surface of the base material by dehydration-condensation polymerization of the titanium hydroxide. Thereafter, the amorphous titanium oxide is calcined at a temperature equal to or higher than the crystallization temperature of anatase to cause a phase transition from the amorphous titanium oxide to the anatase titanium oxide. (3) Electron beam evaporation method An amorphous titanium oxide layer is formed on the surface of a substrate by irradiating a titanium oxide target with an electron beam. After that, firing at a temperature higher than the crystallization temperature of anatase,
Phase transition of amorphous titanium oxide to anatase titanium oxide.

Next, the case where the surface layer is composed of a photocatalyst and silica will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. In this case, for example, there are the following three methods. One method is the sol coating firing method, the other is the organic titanate method, the other is 4
This is a functional silane method. (1) Sol coating and baking method A mixture of anatase-type titanium oxide sol and silica sol is applied to the substrate surface by a method such as a spray coating method, a dip coating method, a flow coating method, a spin coating method, and a roll coating method, and then fired. I do. (2) Organic titanate method Titanium alkoxides (tetraethoxytitanium, tetramethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, etc.), titanium acetate, titanium chelate, and other organic titanates are added with a hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.) and silica sol. Add alcohol (ethanol,
After diluting with a non-aqueous solvent such as propanol, butanol, etc., and then allowing the hydrolysis to proceed partially or completely, the mixture is spray-coated, dip-coated, flow-coated,
It is applied by a method such as spin coating or roll coating and dried. By drying, the hydrolysis of the organic titanate is completed to produce titanium hydroxide, and a layer of amorphous titanium oxide is formed on the surface of the base material by dehydration-condensation polymerization of the titanium hydroxide. Thereafter, the amorphous titanium oxide is calcined at a temperature equal to or higher than the crystallization temperature of anatase to cause a phase transition from the amorphous titanium oxide to the anatase titanium oxide. (3) Tetrafunctional silane method A mixture of tetraalkoxysilane (tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetramethoxysilane, etc.) and anatase type titanium oxide sol is spray-coated or dip-coated on the surface of a substrate. , A flow coating method, a spin coating method, a roll coating method, or the like, and if necessary, hydrolyzing to form silanol, and then silanol is subjected to dehydration condensation polymerization by a method such as heating.

Next, the case where the surface layer is composed of a photocatalyst and a solid acid will be described by taking as an example the case where the photocatalyst is anatase type titanium oxide and the solid acid is TiO ₂ / WO ₃ . One method in this case is a method in which an ammonia solution of tungstic acid and an anatase type titanium oxide sol are mixed, and if necessary, a mixture diluted with a diluent (water, ethanol, etc.) is spray-coated on the surface of the base material, It is applied by a method such as a dip coating method, a flow coating method, a spin coating method or a roll coating method, and baked. Other methods include electron beam evaporation and hydrolysis and dehydration polycondensation of organic titanates such as titanium alkoxide, titanium acetate, and titanium chelate to form an amorphous titanium oxide film, and then tungstic acid is applied to the amorphous titanium oxide. Is crystallized and a heat treatment is performed at a temperature at which a TiO ₂ / WO ₃ composite oxide is formed.

Next, the case where the surface layer is composed of a photocatalyst and silicone will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. The method in this case is to mix a coating composed of uncured or partially cured silicone or a precursor of silicone and anatase type titanium oxide sol, and hydrolyze the precursor of silicone as needed, and then mix the mixture. Spray coating method on the surface of the substrate,
It is applied by a method such as a dip coating method, a flow coating method, a spin coating method, a roll coating method, etc., and a hydrolyzate of a silicone precursor is subjected to dehydration polycondensation by a method such as heating to obtain anatase type titanium oxide particles. A surface layer made of silicone is formed. The formed surface layer, by photoexcitation of anatase type titanium oxide by irradiation with light including ultraviolet rays, at least a part of the organic groups bonded to the silicon atom in the silicone molecule is substituted with a hydroxyl group, and further A physically adsorbed water layer is formed on the surface and exhibits a high degree of hydrophilicity. Here, the silicone precursor includes methyltrimethoxysilane, methyltriethoxysilane, methyltributoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltributoxysilane, ethyltripropoxysilane, and phenyl. Trimethoxysilane, phenyltriethoxysilane, phenyltributoxysilane, phenyltripropoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, dimethyldipropoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldibutoxy Silane, diethyldipropoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, phenylmethyldibutoxysilane, phenol Methylpropenylmethyl dipropoxy silane, .gamma.-glycidoxypropyltrimethoxysilane, and hydrolysates thereof, mixtures thereof can be suitably used.

In addition, the film coated with the above coating may be attached to the surface of the substrate with a transparent adhesive such as soapy water. Here, a plastic film such as polyethylene terephthalate, polyester, or polyethylene can be preferably used as the film substrate.

[0025]

【Example】

Example 1. A 10 cm square polycarbonate plate was coated with a primer coating (Shin-Etsu Silicone, PC-7A) by a flow coating method and then dried at 120 ° C. for 20 minutes,
The substrate was coated with a primer resin layer. Next, a silicone-based hard coating agent (Shin-Etsu Silicone, KP-8
After applying 5) by flow coating,
It was dried for 0 minutes to form a hard coat layer. Next, after the hard coat layer is subjected to corona discharge treatment, a titanium oxide-containing coating composition (anatase type titanium oxide sol (Nissan Chemical,
TA-15) 56 parts by weight and silica sol (Japan Synthetic Rubber,
(Grasca solution A) (33 parts by weight), diluted with ethanol, and further added with 11 parts by weight of trimethoxysilane (Nippon Synthetic Rubber, solution of Glasca solution B)) by a flow coating method, and then at 120 ° C. for 30 minutes. A sample was obtained by heat treatment and curing. After leaving this sample in the dark for several days,
UV light source (Sankyo Electric, Black Light Blue (BL
B) Using a fluorescent lamp), apply 0.5 mW / cm ² to the surface of the sample.
The sample was irradiated with ultraviolet rays at an ultraviolet illuminance of about 1 hour to obtain a # 1 sample. For comparison, a # 2 sample in which a 10 cm square polycarbonate plate was left in the dark for several days was also prepared. First, a water drop was dropped on the # 1 sample and the # 2 sample, and the state after the drop was observed and the contact angle with water was measured. Here, the contact angle with water is measured using a contact angle measuring device (Kyowa Interface Science, CA-X150).
Evaluation was made based on the contact angle with water 30 seconds after dropping. as a result#
When a water droplet was dropped from the microsyringe on one surface of one sample, it was observed that the water droplet spreads uniformly on the surface of the sample in the form of a water film. Further, the contact angle with water after 30 seconds was highly hydrophilized to about 0 °. On the other hand, in the case of the # 2 sample, when a water drop was dropped on the sample surface from the microsyringe, the water droplet adapted to the surface but did not reach a uniform water film state. The contact angle with water after 30 seconds is 6
It was 0 °. Next, the # 1 sample and the # 2 sample were blown to examine whether or not clouding occurred. As a result, fogging occurred in the # 2 sample, but no fogging occurred in the # 1 sample.
Further, the # 1 sample was left in the dark for 2 days thereafter,
A sample was obtained. Then, for the # 3 sample, the contact angle with water was similarly measured by a contact angle measuring device. As a result, when a water drop was dropped on the sample surface from the microsyringe on the # 3 sample, it was observed that the water droplet spread uniformly on the sample surface like a # 1 sample. The contact angle with water was maintained at about 3 °. Next, the presence or absence of fogging after spraying was observed for the # 3 sample. As a result, no fogging was observed.

Embodiment 2 FIG. 0.69 g of tetraethoxysilane (Wako Pure Chemical Industries), 1.07 g of anatase type titanium oxide sol (TA-15, average particle size 10 nm), 29.88 g of ethanol, and 0.36 g of pure water are mixed to form a coating liquid. Was prepared. This coating liquid was applied on a 10 cm square glass substrate by a flow coating method. By holding this glass plate at a temperature of about 150 ° C. for about 20 minutes, tetraethoxysilane is subjected to hydrolysis and dehydration polycondensation, and a coating in which anatase-type titanium oxide particles are bound with amorphous silica is applied to the glass plate. Formed on the surface. The weight ratio of titanium oxide and silica in this coating was 1. After leaving this glass plate in the dark for several days, 0.5 mW was applied to the surface of the sample by using an ultraviolet light source (Sankyo Denki, black light blue (BLB) fluorescent lamp).
Irradiate with UV light for about 1 hour at UV illuminance of / cm ² , and then # 4
A sample was obtained. For comparison, a # 5 sample in which a 10 cm square glass plate was left in the dark for several days was also prepared. First, a water drop was dropped on the # 4 sample and the # 5 sample, and the state after the drop was observed and the contact angle 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 # 4
When a water droplet was dropped on the sample surface from the microsyringe, it was observed that the water droplet spreads uniformly on the sample surface in the form of a water film. Further, the contact angle with water after 30 seconds was highly hydrophilized to about 0 °. On the other hand, in the # 5 sample, when a water droplet was dropped from the microsyringe on the surface of the sample, the water droplet adapted to the surface, but did not reach a uniform water film shape. The contact angle with water after 30 seconds is 30
Was ゜. Next, the # 4 sample and the # 5 sample were blown to examine whether or not clouding occurred. As a result, the # 5 sample showed haze, whereas the # 1 sample did not show haze. Further, the # 4 sample was left in the dark for 2 days thereafter to obtain a # 6 sample. Then, for the # 6 sample, the contact angle with water was similarly measured with a contact angle measuring device. As a result, when water droplets were dropped on the sample surface from the microsyringe to the # 6 sample, it was observed that the water droplets spread uniformly on the sample surface in the form of a water film, similarly to the # 4 sample. The contact angle with water was maintained at about 3 °. Next, with respect to the # 6 sample, it was observed whether or not clouding had occurred after the breathing. As a result, no fogging was observed.

Example 3 Amorphous titanium oxide was crystallized by depositing an amorphous titanium oxide film on the surface of a 10 cm square soda lime glass plate by an electron beam vapor deposition method and then firing it at a temperature of 500 ° C. Then, anatase type titanium oxide was produced. The film thickness of the anatase type titanium oxide film was 100 nm. Further, tungstic acid dissolved in 25% ammonia water was applied thereon to convert the weight of tungstic acid to 0.6 μg / cm 2, and then 500
Firing at a temperature of ° C. Next, after leaving this glass plate in the dark for several days, the surface of the sample was irradiated with ultraviolet rays at an ultraviolet illuminance of 0.5 mW / cm ² for about 1 hour using a BLB fluorescent lamp to obtain a # 7 sample. . For comparison, a # 5 sample of Example 2 in which a 10 cm square glass plate was left in the dark for several days was also prepared. First, water drops were dropped on the # 7 sample and the # 5 sample, and the state after the drop was observed and the contact angle with water was measured. Here, the contact angle with water is measured using a contact angle measuring instrument (Kyowa Interface Science, CA-
X150) was used and the contact angle with water was evaluated 30 seconds after the dropping. As a result, it was observed that when the # 7 sample was dropped from the microsyringe on the sample surface, the water droplet spreads uniformly on the sample surface in the form of a water film. Further, the contact angle with water after 30 seconds was highly hydrophilized to about 0 °. On the other hand, in the # 5 sample, when a water droplet was dropped from the microsyringe on the surface of the sample, the water droplet adapted to the surface, but did not reach a uniform water film shape. The contact angle with water after 30 seconds was 30 °. Next, # 7 sample and #
Five samples were blown to examine the occurrence of fogging. As a result, the # 5 sample showed haze, whereas the # 7 sample did not show haze. Further, the # 7 sample was left in a dark place for two days thereafter, to obtain a # 8 sample. Then, with respect to the # 8 sample, the contact angle with water was similarly measured with a contact angle measuring device. As a result, when water droplets were dropped on the sample surface from the microsyringe to the # 8 sample, it was observed that the water droplets spread uniformly on the sample surface in the form of a water film, similarly to the # 7 sample. The contact angle with water was maintained at about 1 °. Next, with respect to the # 8 sample, it was observed whether or not clouding occurred after the breathing. As a result, no fogging was observed.

Embodiment 4 FIG. First, a 10-cm-square polyethylene terephthalate (PET) film was subjected to corona discharge treatment, a primer (Shin-Etsu Silicone, PC-7A) was applied by a flow coating method, and heat-treated at 120 ° C. for 5 minutes to form a primer layer. . Next, after the primer layer was subjected to corona discharge treatment, a silicone-based hard coating agent (Shin-Etsu Silicone, KP-85) was applied by a flow coating method and heat-treated at 120 ° C. for 5 minutes to form a hard coat layer. Next, after the corona discharge treatment of the hard coat layer, a photocatalyst coating liquid (ST-K01 and ST-K03 of Ishihara Sangyo were mixed at 1: 1,
A coating solution containing a partial hydrolyzate of anatase type titanium oxide and tetraethoxysilane in a weight ratio of 13: 7 prepared by diluting with alcohol is applied by a flow coating method and dried at room temperature for 10 minutes to obtain a photocatalytic property. I got a film. Soap water was applied to the back side of this film and attached to a 10 cm square glass substrate. Next, after leaving this glass plate in the dark for several days, the surface of the sample was irradiated with ultraviolet rays for about 1 hour at a UV illuminance of 0.5 mW / cm ² using a BLB fluorescent lamp to obtain a # 9 sample. . For comparison,
Example 2 in which a 10 cm square glass plate was left in the dark for several days
# 5 sample was also prepared. First, water drops were dropped on the # 9 sample and the # 5 sample, and the state after the drop was observed and the contact angle 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, it was observed that when water droplets were dropped onto the sample surface of the # 9 sample from the microsyringe, the water droplets spread uniformly on the sample surface in the form of a water film. Further, the contact angle with water after 30 seconds was highly hydrophilized to about 0 °. On the other hand, in the # 5 sample, when a water droplet was dropped from the microsyringe on the surface of the sample, the water droplet adapted to the surface, but did not reach a uniform water film shape. The contact angle with water after 30 seconds was 30 °. Next, the # 9 sample and the # 5 sample were blown to examine whether or not clouding occurred. As a result, the # 5 sample showed haze, whereas the # 7 sample did not show haze. Further, the # 9 sample was left in a dark place for two days thereafter to obtain a # 10 sample.
Then, with respect to the # 10 sample, the contact angle with water was similarly measured by the contact angle measuring device. As a result, when water droplets were dropped onto the surface of the sample # 10 from the microsyringe, # 9
Similar to the sample, it was observed that the water droplets spread uniformly on the sample surface in the form of a water film. The contact angle with water was maintained at about 1 °. Next, with respect to the # 10 sample, it was observed whether or not clouding occurred after the breathing. As a result, no fogging was observed.

[0029]

According to the present invention, by providing a surface layer containing substantially transparent photocatalytic oxide particles on at least the inner surface of the lid for a transparent heating container, the surface is provided in response to photoexcitation of the photocatalyst. The surface of the layer exhibits hydrophilicity. As a result, the condensed water of the adhered moisture spreads evenly on the surface of the surface layer, so that the condensed water of the moisture can be prevented from becoming clouded.

[Brief description of drawings]

FIG. 1 is a view showing a surface structure inside a lid for a transparent heating container according to the present invention.

FIG. 2 is a view showing another surface structure inside the lid for the transparent heating container according to the present invention.

Claims (9)

[Claims] 1. A transparent base material for a lid for a heating container is provided with a surface layer containing substantially transparent photocatalyst particles on at least an inner surface thereof, and the surface of the layer becomes hydrophilic in response to photoexcitation of the photocatalyst. A lid for a heating container having an anti-fogging property, which is characterized by being presented. 2. The lid for a heating container having anti-fogging property according to claim 1, wherein the surface layer further contains silica. 3. The lid for a heating container having an antifogging property according to claim 1, wherein the surface layer further contains a solid acid. 4. The lid for a heating container having anti-fog property according to claim 1, wherein the surface layer further contains silicone. 5. The surface of the surface layer exhibits hydrophilicity of 10 ° or less in terms of contact angle with water in response to photoexcitation of the photocatalyst. Lid for heating container with anti-fog property. 6. The lid for a heating container having an antifogging property according to claim 1, wherein the film thickness of the surface layer is 0.4 μm or less. 7. The lid for a heating container having an antifogging property according to claim 1, wherein the film thickness of the surface layer is 0.2 μm or less. 8. A hydrophilic protective layer is further provided on the surface of the surface layer.
7. A lid for a heating container having the antifogging property according to 7. 9. The lid for a heating container having an antifogging property according to claim 1, wherein the surface layer has a refractive index of 2 or less.