Patent Application
20160309955
The present invention relates to bakeware made of glass for use in heating and cooking of various kinds of foods such as gratin, pizza, cheese cake, custard pudding and quiche by use of a cooking appliance such as a microwave oven.
Conventionally, dishes and bowls made of ceramic have been mainly used as bakeware for use in heating and cooking of foods. However, ceramic is opaque, and thus involves the disadvantage that the contents in ceramic bakeware cannot be seen. Therefore, transparent glass bakeware has also been proposed recently.
Borosilicate glass having excellent heat resistance and thermal shock resistance is used as a material for glass bakeware. Such glass bakeware advantageously has a transparent and beautiful appearance, cleanliness and easiness to see the contents thereof,
However, glass bakeware lacks non-sticking property, and thus has the disadvantages that foods easily burn, and that the burned foods are hard to be peeled. Further, there was the disadvantage that soils cannot be easily removed from glass bakeware. These disadvantages are unignorable to users, and have prevented the spread of glass bakeware.
JP 2010-202437 A discloses an antimicrobial heat-resistant glass container usable in a microwave oven, of which the inner surface has silver ions diffused therein. However, this aims at attaining antimicrobial property, and is not a technique of improving the non-sticking property of glass bakeware. There cannot be found any prior art document which discloses a means for effectively solving such disadvantages of glass bakeware.
Patent Document 1: JP 2010-202437 A
An object of the present invention is to provide glass bakeware which solves the above-described conventional problems, and which has excellent non-sticking property, is hard to burn foods and allows for easy removal of soils.
In order to solve the above-described problems, a ceramic coating layer which prevents burning of a food is formed on an inner surface of a transparent glass container, in the present invention. The phrase “ceramic coating layer” used herein means a coating layer containing metal oxide particles (ceramic particles) of silica, alumina, magnesia, zirconia or the like.
In a preferred embodiment, the ceramic coating layer contains ceramic particles dispersed in a matrix. Also, the ceramic particles are silica particles. The ceramic coating layer can further contain mica particles. Further, the ceramic coating layer is a transparent layer including heat-resistant silicone as the matrix.
The bakeware of the present invention is made of glass, but, nevertheless, can prevent burning of foods also when heated in a microwave oven or the like, because its ceramic coating layer has non-sticking property. The bakeware is made of glass that is hard to be soiled and transparent, and thus can be used as dishware as it is, and can impart cleanliness and freshness to tables. The ceramic coating layer, when containing mica particles, can provide a sparkling appearance which is peculiar to mica.
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
The ceramic coating layer 2 is preferably formed on the entire inner surface of the glass container 1 as shown in
As shown in
The matrix of the ceramic coating layer 2 is silicone in this embodiment. This can be formed by curing polymethylsiloxane. Silicone has heat resistance, and can withstand use temperatures around 300° C. However, the component of the matrix of the ceramic coating layer 2 is not necessarily limited to silicone, and other materials may also be used so long as the materials are heat resistant and have the function of reliably holding the ceramic particle 3.
In addition to the ceramic particles 3, mica particles 4 can be dispersed in the ceramic coating layer 2. The mica particles 4 shed luster, as is used in metallic coating materials, can impart a sparkling appearance to the ceramic coating layer 2, and can improve the design of the entire bakeware.
Additionally, an antimicrobial metal 5 can also be incorporated into the ceramic coating layer 2. Silver is preferably used from the viewpoint of safety and antimicrobial property, but zinc can also be used. The antimicrobial metal 5 may be incorporated in the form of particles, but can also be carried on the ceramic particles 3 or mica particles 4.
In order to form the ceramic coating layer 2 on the inner surface of the glass container 1, ceramic particles 3 and the like are firstly dispersed in water and an organic solvent. The mixing ratio is preferably as follows: 10% to 35% (by mass) of ceramic particles 3 (for example, silica particles), 1% to 10% of mica particles on which an antimicrobial metal 5 is carried, 2% to 25% of an organic solvent (for example, isopropyl alcohol), and 30% to 45% of water. There can be employed a method comprising mixing this with polymethylsiloxane, spraying the solution mixture over the inner surface of the glass container 1 having an uneven layer 6 formed by sand blasting in advance, and then heating and drying it at 200° C. to 230° C. As a result, a ceramic coating layer 2 comprising ceramic particles 3 as the main component is formed based on principles similar to those of the sol-gel method. The ceramic coating layer 2 can also be formed by an immersion (dipping) method in addition to the above-described spraying method.
The thus-configured bakeware according to the present invention is used to heat and cook various kinds of foods such as gratin, pizza, cheese cake, custard pudding and quiche by use of a cooking appliance such as a microwave oven, and has resistance to heat around 300° C., and thus is not likely to be destroyed unless a sudden thermal impact is applied. Also, the ceramic coating layer 2 is a semitransparent layer, and especially improves its aesthetic appearance when mica particles 4 are added thereto. The ceramic coating layer 2 contains a large amount of ceramic particles 3, and thus is excellent in non-sticking property, and is hard to burn foods during heating and cooking and allows for easy removal of soils, as will be illustrated in an Example.
When the bakeware according to the present invention is heated to a high temperature above 300° C. due to some cause, silicone or the like which constitutes the matrix of the ceramic coating layer 2 is likely to be decomposed. In that case, however, the ceramic particles 3 of silica or the like, which are the main component of the ceramic coating layer 2, form a network on the surface of the glass container 1, and thus can maintain non-sticking property.
30% (by mass) of silica particles, 20% of isopropyl alcohol, 43% of water and 7% of mica particles on which silver was carried were uniformly mixed, and the mixture was further mixed with an equal amount of polymethylsiloxane to yield a solution mixture. This solution mixture was sprayed over the inner surface of a glass container made of borosilicate glass by means of a spray nozzle, and heated and dried at 230° C. In meantime, the inner surface of the glass container was sand-blasted in advance. As a result, bakeware having a transparent or semitransparent ceramic coating layer 2 formed on the inner surface of the transparent glass container was obtained.
Eight monitors were requested to use this bakeware for cooking, and evaluated its non-sticking property, easiness of soil removal and mold releasability of foods. The results are shown in Table 1.
Also, this bakeware (inventive product) and conventional bakeware having no ceramic coating layer (blank) were evaluated in terms of antimicrobial property in conformity to JTS Z 2801 2010. The target bacteria are E. coli and Staphylococcus aureus. The results are shown in Table 2. The antimicrobial activity value is defined by the following formula, and the above-described JTS stipulates that a substance having an antimicrobial activity value of 2.0 or more has an antimicrobial effect.
Antimicrobial activity value=log [(viable cell count after 24-hour culture of blank)/(viable cell count after 24-hour culture of inventive product)]
Staphylococ-
E. coli
cus aureus
From the data on this Example, it could be confirmed that the bakeware of the present invention is superior to the conventional one in the respective items: non-sticking property, easiness of soil removal, mold releasability of foods and antimicrobial property.
