JP6842848B2 - Metal cap - Google Patents

Description

The present invention relates to a metal cap having a temperature indicating ink region and a protective layer, and more particularly to a metal cap having a temperature indicating ink region and a protective layer containing an iron oxide pigment.

Beverages such as fruit juice drinks, sake, and coffee have a temperature at which they can be drunk. Therefore, the surface of a container such as a can or a bottle containing a beverage contains a temperature-indicating material that discolors at a predetermined temperature so that consumers can know whether or not the beverage is at the temperature at which it is ready to drink. Characters and the like may be printed using ink.

However, the temperature indicating ink has a drawback that it gradually loses its discoloring function when exposed to ultraviolet rays. Loss of discoloration function is also caused by weak ultraviolet rays emitted from fluorescent lamps in stores and indoors after purchase. Therefore, it is required to establish a means for avoiding the loss of discoloration function of the temperature indicating ink.

As a means for avoiding the loss of the discoloration function of the temperature indicating ink, for example, it is conceivable to impart weather resistance to the temperature indicating ink itself, but such a means narrows the degree of freedom in selecting the material of the temperature indicating ink.

As a means for avoiding the loss of discoloration function of the temperature-indicating ink without impairing the degree of freedom of the material of the temperature-indicating ink, there is a means of covering the temperature-indicating ink region where characters, patterns, etc. are formed by the temperature-indicating ink with a protective layer. As such a protective layer, for example, a protective layer in which an inorganic pigment that reflects ultraviolet rays is dispersed can be considered. However, since the protective layer is white or silver, the temperature indicating ink region under the protective layer is shielded and the temperature is indicated. It is not practical because the characters and patterns made of ink are difficult to see and the design is impaired.

Further, Patent Document 1 discloses a temperature indicating material printing can provided with a printing layer containing a temperature indicating material and a protective coating film layer containing an ultraviolet absorber such as titanium dioxide or zinc oxide on the outer surface of the can. .. In the temperature-indicating material printing can of Patent Document 1, since ultraviolet rays are absorbed by titanium dioxide or the like, the amount of ultraviolet rays reaching the printing layer containing the temperature-indicating material is reduced, and the printed layer is not shielded.

By the way, until now, printing using temperature-indicating ink has generally been applied to containers such as bottles and cans. However, when the beverage container is a bottle, the letters and patterns on the cap are more likely to be seen by consumers than the letters and patterns on the body of the bottle when opened. Therefore, recently, there is an increasing demand for printing on caps with temperature-indicating ink.

JP-A-2004-115905

However, capped bottles containing beverages are usually arranged in an upright state on a display shelf or the like, and the cap is easily exposed to light from a fluorescent lamp. Therefore, it is necessary to impart particularly excellent weather resistance to the cap having a pattern or the like using the temperature indicating ink.

In addition, since the printable area of the cap is smaller than that of the bottle, it may be necessary to print characters and patterns in a small and fine manner. Therefore, high visibility is also required so that the consumer can clearly recognize the pattern or the like by the temperature indicating ink on the surface of the cap.

The ultraviolet absorber such as titanium dioxide used in Patent Document 1 has insufficient ultraviolet absorbing ability, and cannot impart sufficient weather resistance to the cap, or impart sufficient weather resistance. Had to be used in large quantities. Large amounts of UV absorbers lead to opacity of the protective layer.

Therefore, an object of the present invention is to provide a metal cap which has a temperature indicating ink region containing a temperature indicating ink and is excellent in both weather resistance and visibility.

According to the present invention, it is a metal cap having a metal base material, a temperature indicating ink region containing a temperature indicating ink, and a protective layer, and the metal cap has a top surface and a skirt portion hanging from the top surface. A screw cap having a screw portion formed on the skirt portion and fixed to the container mouth portion, the temperature indicating ink region is formed on the top surface, is not formed on the skirt portion, and the protective layer is formed. The paint composition comprises a red iron oxide pigment in the paint, and the content of the red iron oxide pigment is 5 to 10 parts by mass per 100 parts by mass of the paint, and the average particle size of the red iron oxide pigment is Provided is a metal cap having a color difference of 20 to 70 nm and a color difference ΔE larger than 25 when a fluorescent lamp having an illuminance of 1530 lux is used and the temperature is changed at a position 30 cm below the fluorescent lamp. Will be done.

In the metal cap of the present invention
(1) before Symbol protective layer, the transmittance of ultraviolet light at a wavelength of 200~380nm is 17-42%,
( 2 ) The color difference ΔE when the temperature is changed from 23 ° C to 5 ° C is larger than 25 .
Is preferable.

Further, according to the present invention, a metal cap having a metal base material, a base layer, a temperature-indicating ink region containing a temperature-indicating ink, and a protective layer, wherein the metal cap is a top surface and a skirt hanging from the top surface. It is a screw cap having a portion and a screw portion formed on the skirt portion and fixed to the container mouth portion, and the temperature indicating ink region is formed on the top surface and not formed on the skirt portion. the protective layer is made of a coating composition a red iron oxide pigment is contained in the paint, the content of the red iron oxide pigments are paints 5-10 parts by weight per 100 parts by weight, the red iron oxide Provided are metal caps characterized in that the average particle size of the pigment is 20-70 nm and the transmission of light at a wavelength of 200-380 nm is 17-42%.

In the present invention, the color difference is defined by ΔE of ^{the CIE1976L *} a ^* b ^{* color system. The CIE1976L *} a ^* b ^* color system is the color space recommended by the CIE (Commission Internationale de l'Eclairage) in 1976, and is defined in JIS Z 8781-4: 2013 in the Japanese Industrial Standards. The color difference is the distance in the color space of two colors, ^{and the color difference in the CIE1976L *} a ^* b ^* color system is the difference between the two colors L ^* , the difference between a ^{* and} the difference between b ^* , respectively. It can be calculated by adding the square and taking the square root. Then, in the present invention, the case where "the color difference ΔE is larger than 25" is regarded as the color being different before and after the temperature change, in other words, the color change is considered to have occurred, and the case where the color difference ΔE is 25 or less is the color. Are the same, in other words, no discoloration has occurred.

In the metal cap of the present invention, the discoloration function of the temperature indicating ink can be maintained for a long period of time, that is, the weather resistance is enhanced. Moreover, the consumer can clearly recognize the characters and patterns in the temperature indicating ink area, and high visibility is also realized.

The reason why both weather resistance and visibility can be realized at the same time in the present invention is that the protective layer has a specific composition. That is, in the cap of the present invention, a protective layer covers the temperature indicating ink region, and this protective layer has a coating composition in which iron oxide pigments such as red iron oxide pigment and yellow iron oxide pigment are contained in a specific amount. It consists of things. Specifically, when a red iron oxide pigment is selected as the iron oxide pigment, a coating composition containing 5 to 10 parts by mass of iron oxide pigment per 100 parts by mass of the paint is used, and a yellow iron oxide pigment or a yellow iron oxide pigment is used. When a mixture of iron oxide pigment and red iron oxide pigment is used, a coating composition containing 10 to 15 parts by mass of iron oxide pigment per 100 parts by mass of the coating material is used. As a result, the transmittance of ultraviolet rays (wavelength 200 to 380 nm) of the protective layer is suppressed to 17 to 42%, so that even if the cap is left indoors for a long period of time, the color difference ΔE when the temperature of the cap is changed Can be maintained to be greater than 25, that is, the discoloration function can be maintained. Moreover, when the iron oxide pigment is used in an amount in the above numerical range, the protective layer is not colored, and the characters and patterns in the temperature indicating ink region under the protective layer can be clearly recognized.

In fact, referring to the experimental example described later, in Experimental Example 1 in which the red iron oxide pigment was used as the ultraviolet absorber, the protective layer was not colored due to the red iron oxide pigment, and after 30 days had passed indoors. The color difference ΔE was as high as 25.9, and the discoloration function was maintained. However, in Experimental Example 11 in which a protective layer containing titanium dioxide as an ultraviolet absorber was formed as in Patent Document 1, the color difference ΔE after 30 days was only 10.1, and the discoloration function was lost. Whether or not titanium dioxide can exhibit UV absorption capacity depends on the combination with the materials used together, but titanium dioxide could hardly exhibit UV absorption capacity due to the laminated structure of the metal cap and the composition of each layer. It is presumed to be.

Further, in Experimental Example 3 in which a small amount of the red iron oxide pigment was used, coloring of the protective layer was avoided, but the color difference ΔE after 30 days was 18.7, and conversely, the red iron oxide pigment was excessively used. In Experimental Example 4, the protective layer was colored, making it difficult to see the characters and patterns in the temperature-indicating ink region.

As described above, in the cap of the present invention, the iron oxide pigment is used as the ultraviolet absorber, and the amount of the iron oxide pigment used is adjusted to a specific numerical range to improve the weather resistance without impairing the visibility.

The metal cap of the present invention (hereinafter, may be abbreviated as the cap of the present invention) comprises a top surface and a skirt portion hanging from the top surface. Then, it has a temperature-indicating ink region on which characters and patterns are drawn by the temperature-indicating ink on a metal base material, and further has a protective layer covering the temperature-indicating ink region.

The metal base material is obtained by molding a metal plate conventionally used for a metal cap. Examples of such a metal plate include a surface-treated steel plate such as tin-free steel and tin plate, and a light metal plate such as aluminum and an aluminum alloy, and an aluminum plate and an aluminum alloy plate are preferable.

The thickness of the metal plate is generally preferably 0.18 to 0.25 mm, and in the case of an aluminum plate, 0.22 to 0.25 mm is particularly preferable.

A known base varnish such as a thermosetting resin paint or a thermoplastic resin paint such as a saturated polyester resin is applied to the surface of the metal base material to form a base layer in order to improve the adhesion of the temperature indicating ink region described later. From the viewpoint of further improving visibility, it is particularly preferable to apply a known base varnish mixed with a white pigment to form a base layer. The coating amount is generally preferably ^{20 to 65 mg / cm 2.} If the coating amount is excessively small, the thickness of the base layer may be uneven, and if it is excessively large, curing failure or the like may occur.

In the present invention, a temperature-indicating ink region in which characters, patterns, etc. are formed by the temperature-indicating ink is formed on the metal base material (in the case where the base layer is provided, the base layer).

The temperature-indicating ink is a heat-discoloring material dispersed in a medium (a known binder, an organic solvent, or the like). As the heat-discoloring material, a known material that causes reversible or irreversible discoloration due to temperature change may be used, but if it is used for the purpose of indicating the drinking time of a cold beverage such as juice, it is 10 ° C. or less. A heat-discoloring material that reaches a discoloration peak at a low temperature is preferable. As such thermal discoloration materials, for example, the following are known.
Essential components are (1) (a) an electron-donating color-forming organic compound, (b) a compound having a phenolic hydroxyl group, and (c) a chain-type aliphatic monohydric alcohol having no polar substituent. Reversible thermal discoloration material.
(2) (a) electron-donating color-forming organic compound, (b) compound having a phenolic hydroxyl group, (c) chain-type aliphatic monohydric alcohol having no polar substituent, and polar substituent. A reversible thermal discoloration material containing an ester having no polar substituent and an essential component obtained from an aliphatic monocarboxylic acid having no alcohol.
(3) A microcapsule containing the reversible thermochromic material of (1) or (2) above.
(4) The reversible thermochromic material of (1) or (2) above is dissolved or dispersed in a vehicle.

The temperature indicating ink region may be provided on the entire surface or a part of the cap, but from the viewpoint of peeling resistance, it is preferable that the temperature indicating ink region is provided on the top surface and not on the skirt portion. More specifically, according to the research of the present inventor, it has been newly found that if the temperature indicating ink region exists in the skirt portion of the cap, the temperature indicating ink region may be peeled off. The reason is not clear, but the present inventor speculates as follows. That is, in general, the metal cap is wound around the bottle after filling with the contents by a roller or the like, and then sterilization treatment such as heat sterilization with warm water is performed. Then, at the time of winding, strong stress is applied to the skirt portion of the metal cap from the roller, which slightly impairs the adhesion between the temperature indicating ink and the metal base material (base layer). Next, when the sterilization treatment is performed, it is considered that hot water or water vapor invades between the temperature indicating ink and the metal base material (base layer), and the temperature indicating ink starts to peel off from the portion where the adhesion is impaired. Therefore, it is preferable not to provide the temperature indicating ink region on the skirt portion.

In the present invention, ordinary ink may be used in addition to the temperature indicating ink, that is, both a temperature indicating ink region containing the temperature indicating ink and a non-temperature indicating ink region including characters and patterns made of the ordinary ink may be formed.

A protective layer is provided above the temperature indicating ink region. The protective layer comprises a coating composition containing a specific amount of iron oxide pigment in the coating.

As the paint, a paint that has been conventionally used for the outer paint of a metal cap can be used. Examples of such paints include epoxy-phenol paints, epoxy-amino paints, polyester paints, urethane paints and the like. A polyester-based paint can be preferably used from the viewpoint of being excellent in properties that should be possessed as an outer coating film of a metal cap, such as adhesion, processability, corrosion resistance (barrier property), and hygiene.

As the polyester-based paint, a solvent-based paint in which a polyester resin is the main component and a thermosetting resin such as an amino resin, a phenol resin, an isocyanate-based resin, or a thermosetting acrylic resin is blended therein, or a polyester resin is acrylic-modified. A polyester water-based paint or the like can be preferably used.

More preferably, the polyester resin as the main component generally has a number average molecular weight of 1,000 to 50,000, a glass transition point of 20 to 80 ° C., and a reducing viscosity of 0.25 to 0.70 dl / g. Is preferable.

The polyester-based paint preferably contains a polyester resin and a thermosetting resin in a ratio of 95: 5 to 60:40. Further, it is preferable that the coating material contains a solvent in an amount of 150 to 500 parts by mass per 100 parts by mass of the resin component. As the solvent, a solvent known per se as long as it can dissolve the above-mentioned resin component can be used, and examples thereof include isopropyl alcohol, isobutyl acetate, n-butanol, and sorbesso 110.

In the present invention, the protective layer comprises a coating composition containing an iron oxide pigment as an ultraviolet absorber in the above coating. Iron oxide has the property of transmitting visible light and absorbing ultraviolet rays (wavelength 200 to 380 nm), is non-toxic, and is excellent in safety, so that it can be suitably applied to the lid of a beverage bottle.

Iron oxide pigments include red iron oxide pigments and yellow iron oxide pigments. The red iron oxide pigment is _{mainly composed of α-Fe 2} O ₃ , and reflects light having a wavelength near 650 nm by surface treatment, hue adjustment, particle size adjustment, etc., and the tint is adjusted to red. The yellow iron oxide pigment is mainly composed of α-FeOOH, and is adjusted to have a yellow tint by reflecting light having a wavelength near 600 nm by surface treatment, hue adjustment, particle size adjustment, and the like.

In the present invention, when a red iron oxide pigment is selected as the iron oxide pigment, it is important that the content of the iron oxide pigment in the coating composition for forming the protective layer is 5 to 10 parts by mass per 100 parts by mass of the coating material. is there. When selecting a yellow iron oxide pigment or selecting a mixture of a yellow iron oxide pigment and a red iron oxide pigment, the content of the iron oxide pigment in the coating composition for forming a protective layer is set to 10 per 100 parts by mass of the coating material. It is important to have ~ 15 parts by mass. As described above, in the present invention, by adjusting the amount of the iron oxide pigment to a specific numerical range, the ultraviolet (wavelength 200 to 380 nm) transmittance of the protective layer can be significantly suppressed to 17 to 42%, and moreover, protection is achieved. No coloring occurs in the layers.

As a result of significantly suppressing the ultraviolet (wavelength 200 to 380 nm) transmittance of the protective layer to 17 to 42%, the cap of the present invention fully exerts the discoloration function of the temperature indicating ink, and the fluorescent lamp having an illuminance of 1530 lux. At the lower 30 cm position, the color difference ΔE becomes larger than 25 when the temperature of the cap is changed according to the discoloration temperature of the temperature indicating ink to be used. In particular, when using a temperature-indicating ink made of a heat-discoloring material that reaches a discoloration peak at a low temperature of 10 ° C. or lower, the temperature was changed from 23 ° C. to 5 ° C. at a position 30 cm below a fluorescent lamp having an illuminance of 1530 lux. The color difference ΔE at that time becomes larger than 25. The color change function in which the color difference ΔE before and after the temperature change is larger than 25 is not only immediately after the production of the cap, but also a number that maintains the brightness sufficient for general indoor environment, for example, office work. It is exhibited even after aging for 30 days or more in a work place equipped with a fluorescent lamp.

As the iron oxide pigment, it is preferable to select a red iron oxide pigment. This is because the red iron oxide pigment has a more remarkable effect of improving weather resistance. The average particle size of the iron oxide pigment is preferably 20 to 70 nm from the viewpoint of the balance between handleability and dispersibility in the paint. The average particle size is represented by a volume-based average particle size measured by a laser diffraction / scattering method.

Further, the average thickness of the protective layer is based on the condition that the ultraviolet transmittance of the protective layer is within the above numerical range and the color difference ΔE is larger than 25 even after aging for 30 days or more in a general indoor environment. Any thickness may be selected as long as it is satisfied, but it is generally 3 to 6 μm. In order to form a protective layer having such a thickness, it is preferable to apply the ^{coating composition with a dry film in an amount of 20 to 60 mg / dm 2.}

From the viewpoint of uniformly dispersing the iron oxide pigment and stably exerting the ultraviolet absorbing effect, it is preferable to add a known dispersant such as a vinyl salt vinegar resin to the coating composition for forming the protective layer. The blending amount may be appropriately determined according to the type of paint and the like.

Further, as long as the effect of the present invention is not impaired, the composition for paint may be filled with other ultraviolet absorbers such as zinc oxide or known compounding agents for paint such as plasticizers, lubricants, pigments and fillings, if necessary. Agents, stabilizers and the like may be further added.

The cap of the present invention can be manufactured by a known method. For example, a temperature indicating ink region is provided on an unpainted metal plate or a metal plate having a base layer by offset printing or the like, and further, dip coating, roller coating, etc. The coating composition is applied by a conventionally known method such as spray coating or electrodeposition coating. Next, the paint is baked to obtain a painted metal plate. The baking conditions may be set to a heating temperature according to the coating material in the coating composition. For example, when a polyester amino-based coating material is used, the maximum curing temperature is set as the peak temperature and heated to reach the maximum curing temperature. After that, the heating is finished. It should be noted that the curing is not completed when the maximum curing temperature is reached, and the curing further progresses due to the residual heat.

The obtained coated metal plate is formed into a cap shape by conventionally known drawing molding or the like. The cap of the present invention can take various forms as long as it has the above-mentioned temperature indicating ink region and the protective layer on at least one surface, but from the viewpoint of maximizing the effect of the present invention. , It is preferable that the cap is of a type that can be opened by swirling, particularly a cap that is screwed and fixed to the container mouth. The metal cap is drawn and molded so that the surface on which the temperature indicating ink region and the protective layer are formed of the coated metal plate is on the outer surface side, then a screw portion is formed, and if necessary, a tamper evidence band or the like is formed. After forming the cap shell, the liner material is formed on the inner surface of the top plate of the cap shell.

The present invention will be described with reference to the following experimental examples. The test conditions and various measurement conditions in each experimental example are shown below.

<Ultraviolet transmittance>
The red iron oxide pigment used in each experimental example was blended with a PET resin having a thickness of 1 mm in an amount of 0.1 wt% to obtain a test piece. For the obtained test piece, the ultraviolet transmittance of each experimental example was measured based on the value obtained by measuring the ultraviolet transmittance in the wavelength range of 200 to 380 nm using a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Corporation). I got a rate.

<Weather resistance>
A 1 cm × 3 cm test piece was cut out from the coated plate obtained in each experimental example. The test piece was installed in a room with a depth of 40 cm, a width of 70 cm, and a height of 70 cm. Under a desk lamp with two fluorescent lamps with a total luminous flux of 1343 lumens {TWINBIRD (model LK-H377) manufactured by Twinbird Corporation}. It was allowed to stand at a position of 30 cm and stored for 30 days under the condition of an illuminance of 1530 lux. ^{The test pieces after storage were measured for brightness L *} and color coordinates a ^* and b ^* when the temperature was 23 ° C. and 5 ° C. using a color difference meter (CR-221 manufactured by Minolta Co., Ltd.). Based on the colorimetric value when the temperature was 23 ° C., the color difference ΔE before and after the temperature change was calculated by the following formula.
ΔE = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2
Weather resistance was evaluated based on the following criteria.
◯: Color difference ΔE is larger than 25 (color change function was maintained)
X: Color difference ΔE is 25 or less (discoloration function was lost)

<Coloring of protective layer>
A 1 cm × 3 cm test piece was cut out from the coated plate obtained in each experimental example. ^{The test piece was measured for brightness L *} and color coordinates a ^* and b ^* at a temperature of 23 ° C. using a color difference meter (CR-221 manufactured by Minolta Co., Ltd.). Based on the colorimetric value of the test piece (without UV absorber) obtained in Experimental Example 10, the color difference ΔE with and without the UV absorber was calculated based on the above formula.
The coloring of the protective layer by the UV absorber was evaluated based on the following criteria.
◯: Color difference ΔE is 25 or less (coloring derived from an ultraviolet absorber has not occurred)
X: Color difference ΔE is larger than 25 (coloring derived from an ultraviolet absorber has occurred)

<Scratch resistance>
A 1 cm × 3 cm test piece was cut out from the coated plate obtained in each experimental example. From the surface of the test piece, select the part where the temperature indicating ink region exists and the part where the temperature indicating ink region does not exist, and for each part, the pencil hardness defined by the scratch hardness test method (JIS K 5600-5-4). The test was conducted. Scratch resistance was evaluated based on the following criteria.
◯: Has a hardness of 2H or more.
X: There is no hardness of 2H or more.

<Peeling resistance>
The metal cap after molding was boiled for 30 minutes, and the presence or absence of peeling was visually confirmed and evaluated according to the following criteria.
◯: Peeling is seen.
X: No peeling is seen.

<Experimental example 1>
Prepare a coated aluminum plate with a thickness of 0.23 mm, which is coated on both sides with a 10 μm-thick polyester-based white coating film (base layer), and at a position corresponding to the top surface of one of the coating film surfaces, the temperature indicating ink { A prototype of offset printing ink manufactured by DIC Graphics Co., Ltd., a pattern was printed at 18 ° C. start of discoloration (colorless) and 3 ° C. completion of discoloration (blue)}. Next, 100 parts by mass of polyester paint (finishing varnish manufactured by Toyochem), 5 parts by mass of red iron oxide pigment (transparent iron oxide pigment manufactured by Toda Kogyo Co., Ltd., average particle size 20 to 70 nm) as an ultraviolet absorber, and chloride as a dispersant. A vinyl-vinyl acetate copolymer was mixed to prepare a coating composition. The coating composition was uniformly roll-coated by a wet-on-wet method so as to have a dry film of 45 mg / dm ^2, and baked at 180 ° C. for 5 minutes to form a protective layer to obtain a coated plate. A test piece was cut out from the obtained coated plate, and the weather resistance, the coloring of the protective layer, and the scratch resistance were measured and evaluated.

A cap having an outer diameter of 30 mm and a height of 16 mm was formed from the obtained coated plate so that the protective layer was on the outside of the cap, and the peel resistance was measured and evaluated. In addition, the ultraviolet transmittance of the protective layer was also measured and evaluated using the coating composition for forming the protective layer.

<Experimental example 2>
A metal cap was formed in the same manner as in Experimental Example 1 except that the amount of red iron oxide was 10 parts by mass. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 1.

<Experimental example 3>
A metal cap was formed in the same manner as in Experimental Example 1 except that the amount of red iron oxide was 1 part by mass. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 1.

<Experimental Example 4>
A metal cap was formed in the same manner as in Experimental Example 1 except that the amount of red iron oxide was 14 parts by mass. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 1.

<Experimental Example 5>
A metal cap was molded in the same manner as in Experimental Example 1 except that a dispersant was not used. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 1.

<Experimental example 6>
A metal cap was molded in the same manner as in Experimental Example 2 except that a dispersant was not used. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 1.

<Experimental Example 7>
A metal similar to Experimental Example 1 except that yellow iron oxide (transparent iron oxide pigment manufactured by Toda Kogyo Co., Ltd., average particle size 20 to 70 nm) was used instead of red iron oxide and no dispersant was used. The cap was molded. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 1.

<Experimental Example 8>
A metal cap was formed in the same manner as in Experimental Example 7 except that the amount of yellow iron oxide was 10 parts by mass. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 7.

<Experimental Example 9>
A metal cap was formed in the same manner as in Experimental Example 7 except that the amount of yellow iron oxide was 1 part by mass. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 7.

<Experimental Example 10>
A metal cap was molded in the same manner as in Experimental Example 1 except that no ultraviolet absorber was used and no dispersant was used. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 1.

<Experimental Example 11>
A metal cap was molded in the same manner as in Experimental Example 1 except that titanium dioxide powder was used instead of the red iron oxide pigment. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 1.

<Experimental Example 12>
A metal cap was molded in the same manner as in Experimental Example 11 except that the amount of titanium dioxide was 10 parts by mass. Various measurements and evaluations were also carried out in the same manner as in Experimental Example 9.

Table 1 below shows the layer structure of the metal cap molded in each experimental example and the results of various measurements and evaluations.

Claims (4)

A metal cap having a metal base material, a temperature indicating ink region containing a temperature indicating ink, and a protective layer.
The metal cap is a screw cap having a top surface and a skirt portion hanging from the top surface, and a screw portion is formed on the skirt portion and fixed to the container mouth portion, and the temperature indicating ink region is the ceiling portion. It is formed on the surface, not on the skirt,
The protective layer comprises a coating composition containing a red iron oxide pigment in the coating material.
The content of the red iron oxide pigment is 5 to 10 parts by mass per 100 parts by mass of the paint, and the average particle size of the red iron oxide pigment is 20 to 70 nm.
A metal cap characterized in that a color difference ΔE when a fluorescent lamp having an illuminance of 1530 lux is used and the temperature is changed at a position 30 cm below the fluorescent lamp is larger than 25. The metal cap according to claim 1, wherein the protective layer has a transmittance of ultraviolet rays having a wavelength of 200 to 380 nm of 17 to 42%. The metal cap according to any one of claims 1 to 2 , wherein the color difference ΔE when the temperature is changed from 23 ° C. to 5 ° C. is larger than 25. A metal cap having a metal base material, a base layer, a temperature indicating ink region containing a temperature indicating ink, and a protective layer.
The metal cap is a screw cap having a top surface and a skirt portion hanging from the top surface, and a screw portion is formed on the skirt portion and fixed to the container mouth portion, and the temperature indicating ink region is the ceiling portion. It is formed on the surface, not on the skirt,
The protective layer comprises a coating composition containing a red iron oxide pigment in the coating material.
The content of the red iron oxide pigment is 5 to 10 parts by mass per 100 parts by mass of the paint, and the average particle size of the red iron oxide pigment is 20 to 70 nm.
A metal cap characterized in that the transmittance of light having a wavelength of 200 to 380 nm is 17 to 42%.