JPS6198581A - Thermal recording type releasing paper - Google Patents

Abstract

PURPOSE:To prevent the discoloration of print when bonded to food wraps by enhancing the reliability of pictures by using a releasing paper having a back coat consisting of the first back coat layer having good film-forming property and the second back coat layer having bad film-forming property. CONSTITUTION:The first back coat layer 2, the second back coat layer 3, and an adhesive layer 4 are laminated on the downside of a supporter 1. A silicone resin-processed releasing base paper 5 is bonded to the upside of the layer 4, and a thermal color-forming layer 6 and a protective layer 7 are laminated on the upside of the supporter. The first back coat layer is composed of PVA as main component, containing formalin, glyoxal, etc., as a water resistance improver, and the second layer 3 is composed primarily of a water-soluble high molecular resin other than PVA, containing a filler, a wax, etc., to improve the permeability of oxygen by lowering the film-forming property. The preferred amount of the second layer 3 to be formed is 3g/m<2> or more, whereas in the case of 3g/m<2> less, the oxygen permeability and discoloration preventing effect are decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording type release paper that utilizes a color-forming reaction between a leuco dye and a color developer.

[Prior art]

Conventionally, thermal recording paper has been known which contains a leuco dye and a color developer that develops color from the leuco dye when heated on the surface of a sheet-like support as a main component, and this thermal recording paper has been used as a thermal recording type packaging label. It is proposed to use. In the case of such a heat-sensitive recording type label, the printing method is based on a thermal head, and therefore, it has the advantage of being easier and more beautiful than the conventional printing method using ink or ink ribbon. however.

In the case of heat-sensitive recording paper, there is a problem that the color-forming area will fade if plasticizers or edible oils applied to plastic films such as dioctyl phthalate (OOP) or dioctyl adipate (DOA) penetrate into the heat-sensitive color-forming layer. However, it cannot be used as a label for plastic film packaging products.

For example, in bulk stores such as supermarkets, in order to sell fresh foods, fish, vegetables, meat, etc. are placed in plastic trays such as Styrofoam, and the entire tray is covered with plastic film such as polyvinyl chloride. In addition, a label with the weight value printed on it is pasted on the wrap, but in this case, if conventional thermal paper is used as the label, the label and the wrap may be separated by stacking the packaged items. When the wrap film is brought into close contact with the label, the plasticizer in the wrap film penetrates into the heat-sensitive coloring layer on the label surface, and after a certain period of time, the printing on the label surface disappears, causing a major hindrance to product sales. Put it away.

As a heat-sensitive recording material for such release paper.

A thermosensitive coloring layer containing a coloring agent made of a leuco dye and a color developer that develops color when heated from the leuco dye, such as an organic acid or a phenolic compound, is provided on the support. One is known that has a water-soluble polymer layer (hereinafter also referred to as an overcoat layer). However, when a label is attached to a plastic film for a long period of time, oil and plasticizer permeate from the back side of the label, causing a discoloration phenomenon, making the label unsatisfactory as a thermal label.

On the other hand, in order to prevent such undesirable effects due to penetration of oil and plasticizer from the back side, conventionally, a back coat layer mainly composed of resin such as polyvinyl alcohol or polyvinylidene dichloride has been provided. Ta. Providing such a back coat layer can prevent penetration of oils, plasticizers, etc., and prevent image fading, but if this label is attached to a product (meat) wrapped in food wrap, the area to which it is attached will be damaged. It has been found that new problems such as discoloration of the meat occur.6 This kind of discoloration of the meat does not occur unless a layer of coating is provided, but oil and other substances.

Penetration of the plasticizer could not be prevented, and it was not possible to obtain a product that satisfied both one-image reliability and discoloration of the meat.

〔the purpose〕

An object of the present invention is to provide a heat-sensitive recording type release paper which overcomes the above-mentioned drawbacks, has excellent image reliability against oils, plasticizers, etc., and does not cause discoloration of meat.

〔composition〕

That is, the present invention provides a support in which a heat-sensitive color forming layer containing a leuco dye and a color developer is provided on the surface of the support, and a release mount is provided on the back surface of the support with an adhesive layer interposed therebetween. A first back coat layer containing polyvinyl alcohol as a main component is provided between the back surface and the adhesive layer, and a layer containing a water-based polymer resin other than polyvinyl alcohol as a main component is provided on top of the first back coat layer. It is characterized by laminating a second back coat layer which has a poor film formation bottom.

As a result of extensive research into the cause of meat discoloration, the present inventors have discovered that this discoloration occurs due to the following phenomenon. In other words, the discoloration of meat is caused by myoglobin, a pigment protein.
Air oxidation of hemoglobin and its oxidation state (rate)
shows a maximum value at a certain oxygen partial pressure (1 to 20 mn+Hg), but it was found that when a backcoated label was attached to food wrap, the oxygen partial pressure value approached that value and discoloration occurred. Further investigation revealed that the degree of discoloration of meat differs depending on the type of back coating agent, and that polyvinyl alcohol, which has good film-forming properties, discolors regardless of the degree of saponification, degree of polymerization, etc.
It has been found that water-based polymer resins other than polyvinyl alcohol do not change color, but even if they change color, it is only slight. Therefore, it was found from this that discoloration of meat can be prevented by using a back coat layer with a poor film formation bottom (high oxygen permeability). Furthermore, when image reliability is similarly examined, image reliability is better when a back coat layer with a good film formation bottom where meat discoloration occurs is used, and the two have contradictory characteristics.

Conventional back coat layers have a one-layer structure, so there is no one that satisfies both meat discoloration and image reliability.
In the case of the present invention, the back coat layer has a two-layer structure, and the first
An undercoat layer mainly composed of polyvinyl alcohol improves image reliability.

The second undercoat layer improves the oxygen permeability of the food wrap contact surface to prevent meat from discoloring.

The undercoat layer used in the present invention consists of a first layer and a second layer, and the first undercoat layer is mainly composed of polyvinyl alcohol. It can be used together with a waterproofing agent. Examples of the waterproof agent include formalin, glyoxal, melamine-formalin, polyamide resin, polyamide-epichlorohydrin resin, and the like. It is also possible to use it in combination with other water-based polymer resins, and when using water-based polymer resins other than polyvinyl alcohol, the amount used is 0.6 or less, preferably 0.4 to 1 part polyvinyl alcohol in terms of weight ratio. The following is preferable. The second undercoat layer has an aqueous polymer resin other than polyvinyl alcohol as a main component, and two or more types of resins can be used in combination as necessary. Furthermore, fillers or waxes may be added to the second undercoat layer in order to worsen film formation dust and improve oxygen permeability.
The amount of adhesion of the undercoat layer should be 3 g/nf or more, preferably 5 g/m or more. If the amount of adhesion is small, the thickness of the second undercoat layer will be thinner, resulting in poor oxygen permeability and poor discoloration prevention effect. becomes smaller.

The water-soluble polymer used for the second backcoat layer is other than polyvinyl alcohol, and generally any polymer with inferior film-forming properties than polyvinyl alcohol may be used.For example, methoxycellulose, hydroxycellulose, In addition to materials made from cellulose derivatives such as carboxymethyl cellulose and carboxyethyl cellulose, starch and its derivatives, gelatin, and natural polymers such as sodium alginate, isobutylene/maleic anhydride copolymer alkali salts and styrene anhomaleic Synthetic polymers such as copolymer alkali salts and sodium polyacrylate can be used. In addition, even if the film-forming property is good, inorganic and organic fillers may be added to the back coat layer in order to worsen the film-forming dust of the obtained back coat layer. It is sufficient that the second back coat layer has a higher oxygen permeability than that of the first back coat layer, and has a higher oxygen permeability. It is thought that this occurs through the cut surface.

An explanatory cross-sectional view of the heat-sensitive recording type release paper of the present invention is shown in the drawing.

In this drawing, 1 is a support body, and on its lower surface,
First backcoat layer2. A second back coat layer 3 and an adhesive layer 4 are laminated, and a release mount 5 whose surface is treated with a silicone resin is adhered onto the adhesive layer 4. On the other hand, a thermosensitive coloring layer 6 and a protective layer 7 are laminated on the upper surface of the support.

In the present invention, the film formation dust of the second back coat layer 3 is worse than the film formation dust of the first back coat layer 2, and therefore the oxygen permeability in the second back coat layer is high. The gas passes through the second back coat layer from the outer circumferential cut surface, as indicated by arrows in the drawing, and then passes through the adhesive layer.

As the leuco dye used in the present invention, commonly used triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based leuco dyes are preferably used, such as 3-(N-(p-tolylamino))-7-aniline. Linofluorane, 3-(N-(p-tolyl)-N-methylamino)-7-anilinofluorane, 3-(N(p-tolyl)-N-dithylamino)-7-anilinofluorane , 3(N-(p-tolyl)-N-propylamino)-7
-anilinofluorane, 3(N-(p-tolyl)-N-
butylamino)-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-
Diethylamino-6-methyl-7-anilinofluorane, 3-dipropylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-pyrrolidino- 6-Methyl-7-anilinofur, oran, 3-piperidino-6-methyl-7
-anilinofluorane, 3-piperazino-6-methyl-
7-anilinofluorane, 3-N-(N'-methylpiperazino)-6-methyl-7-anilinofluorane, 3-
Morpholino-6-methyl-7-anilinofluorane, 3
-dibenzylamino-6-methyl-7-anilinofluorane and the like.

As the developer for the leuco dye, various electron-accepting substances such as phenolic substances, organic acids, inorganic acids or their salts, and activated clay, which have been commonly used in the past, can be used. It is shown below.

Phenolic substances; 3.5-xylenol, thymol, ρ-tert-butylphenol, 4-hydroxyphenoxide, methyl-
4-hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-naphthol, catechol, resorcinol, hydroquinone.

4-tert-octylcatechol, 4.4-se
a-Butylidenephenol, 2,2'-dihydroxydiphenyl, 2,2-methylenebis(4-methyl-6-
Lert-butylphenol), 2,2-bis(4-
hydroxyphenyl)propane, 4,4-isopropylidene-bis(2-tert-butylphenol), 4.
4-sec-butylidene diphenol, pyrogallol,
Phloroglucin, phloroglucin carboxylic acid, 4-te
rt-octylphenol, 4-phenylphenol,
2,2-bis(p-hydroxyphenyl)butane, 4.
4'-cyclohexylidene diphenol, 2,2-bis(2°5-dibromo-4-hydroxyphenyl)propane.

4.4'-isopropylidene bis(2-tert-butylphenol), 2,2'-methylenebis(4-chlorophenol), etc.

Acidic substances or their salts; benzoic acid, gallic acid, salicylic acid, zinc salicylate, ■
-Hydroxy-2-naphthoic acid, 0-hydroxybenzoic acid, m-hydroxybenzoic acid, benzyl p-hydroxybenzoate, 2-hydroxy-p-toluic acid, tartaric acid,
Oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-oxycyphthalic acid, boric acid, etc.

These color developers are preferably used in an amount of 1 to 5 parts by weight per 1 part by weight of the dye.

In addition to these leuco dyes and color developers, a binder is used to form the thermosensitive coloring layer. A wide variety of known binders can be used, but specific examples include polyvinyl alcohol, methoxycellulose, hydroxycellulose, carboxymethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, a! Examples include powder and gelatin.

In addition, in combination with these water-soluble binders, for example, styrene-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyacrylic acid ester, polymethacrylic acid ester such as polybutyl methacrylate, etc. latex can also be used.

Furthermore, the heat-sensitive coloring layer contains waxes such as shellac wax, montan wax, carnauba wax, and silica as auxiliary agents (sensitizer, head matching improvement).

Talc, calcium carbonate, urea-formalin resin, etc. may be added.

In the present invention, if necessary, an overcoat layer containing a water-soluble polymer can be provided on the thermosensitive coloring layer. Examples of the water-soluble polymer used in this case include polyvinyl alcohol, Examples include hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, starch and its derivatives, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide, and styrene-maleic acid copolymer.

This water-soluble polymer can be used together with a conventional water-resistant agent that can make it water-resistant. Examples of the water-resistant agent include formalin, glyoxazole, chromium-light melamine, melamine-formalin, polyamide resin, and polyamide-epichlorohydrin resin. etc.

〔effect〕

The heat-sensitive recording type release paper of the present invention has a two-layer backcoat layer consisting of a first backcoat layer with a high degree of film formation and a second backcoat layer with a poor degree of film formation. It has excellent reliability and is extremely effective in preventing discoloration of meat when attached to food wrap.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Note that all parts and percentages shown below are based on weight.

Example 1 [Liquid A] 3-n-ethyl-〇-dicyclohexyl-6-methyl-phanilinofluorane 10 parts HEC (hydroxyethyl cellulose, the same hereinafter) 10% aqueous solution
1o part water
30 parts of this composition was dispersed in a ball mill for 20 tlr to obtain liquid A.

[B liquid]

Bisphenol A 15 parts H
ECIO% aqueous solution 15 parts water
2
0 parts Disperse this composition in a ball mill for 10) 1r to obtain liquid B.

[Liquid C]

Calcium carbonate 15 parts Methyl cellulose (MC) 5% aqueous solution 15 parts Water
20
This composition was dispersed in a ball mill for 10 hours to obtain liquid C.

[D liquid]

N-octadecyl-carbamoyl-p-methoxycarbonylbenzene 10 parts MC5% aqueous solution
10 parts water
30 parts of this composition.
Disperse in a ball mill for 15 hours to obtain liquid B.

[Thermosensitive coloring liquid]

A M 10 parts B liquid
20 parts C liquid 15
Part D Liquid 20 parts PV
30 parts of A (polyvinyl alcohol) were uniformly mixed in each strip to prepare a heat-sensitive coloring solution.

[Overcoat liquid]

Carboxyl group-modified PVAl 0% aqueous solution 30 parts Thermosetting organic filler 1.2 parts Water resistance agent 10 parts Water
8.8 parts of each of the above components were dispersed in a ball mill for 5 hours to prepare an overcoat solution.

[First undercoat liquid] 20 parts of carboxyl group-modified PVAl 0% aqueous solution 5 parts of water resistant agent l aqueous solution This composition was mixed to prepare a first bank coat liquid.

Next, the heat-sensitive coloring liquid obtained above was added to a basis weight of 50 g/rr.
A heat-sensitive coloring layer is formed by coating and drying on the surface of the high-quality paper i to a dry weight of 6 g/rrr, and on top of that, the overcoat solution is coated and dried to a dry weight of 3.5 g/rr. to form an overcoat layer, and then apply 15g of the first backcoat liquid on the back side of the support in a dry amount.
/-, and then apply a second back coat liquid consisting of a 5% HEC aqueous solution to a coating weight of 4 g when dried.
/rrr was coated and dried to obtain heat-sensitive recording paper.

Example 2 [Second back coating liquid] Isobutylene/maleic anhydride copolymer ammonium salt 20% aqueous solution 20 parts Solution C
A second back coat solution was prepared by mixing one part of this composition.

Next, the heat-sensitive coloring liquid, overcoat liquid, and first backcoat liquid prepared in Example 1 were applied to the support in the same manner as in Example 1, and then the second bank coating liquid was applied to the support in a dry amount. A thermal recording paper was obtained by coating and drying at a concentration of 4.5 g/m.

Comparative Example 1 Thermal recording paper of Comparative Example 1 was prepared without performing the first and second back coat treatments of Example 1.

Comparative Example 2 A thermosensitive recording paper of Comparative Example 2 was prepared without performing the second back coat treatment of Example 1.

Comparative Example 3 Thermal recording paper of Comparative Example 3 was prepared by not performing the first back coat treatment of Example 1.

Next, after surface-treating each heat-sensitive recording paper obtained as described above using a super calender, a release paper coated with silicone resin on the back side and an adhesive layer provided on the silicone resin side of the release paper was bonded. The materials were bonded together via the agent layer, and then punched out to an appropriate size to obtain a heat-sensitive recording type release paper.

The heat-sensitive recording release paper obtained in this way was subjected to a color development test by being colored using a label printer with a built-in thermal head. tested for gender.

The results are shown in Table-1.

Table 1 The tests for the test items shown in Table 1 are as follows.

Color development: Printed with a label printer and measured the colored area (background) and non-colored area with a microphotometer. Oil resistance: Apply cottonseed oil to the back of the sample obtained in the color development test and dry at 50℃. After being left for 24 hours under these conditions, the concentration was measured using a microphotometer.

Plasticizer resistance: The back side of the sample obtained in the color development test was covered with food wrap containing a plasticizer, and the resistance was 100 g/chi? under dry conditions at 50°C. was measured with a microphotometer.

Water resistance: The sample obtained in the color development test was immersed in water at 20° C. for 10 hours, and the concentration was then measured using a microphotometer.

Discoloration of meat: Beef is covered with food wrap film,
Paste the sample obtained in the color development test on top of it and hold it at 5℃.
Visually judge the degree of discoloration of the meat after leaving it in the refrigerator for 15 hours. 0: No discoloration ×: Discoloration Table -
As is clear from the results shown in 1, the product of the present invention does not degrade basic qualities such as color development and background density (fogging) compared to the comparative example, and can easily absorb oils and plasticizers.

It maintains image stability due to water and has significantly improved chromaticity.

[Brief explanation of drawings]

The drawing shows a cross-sectional view of the heat-sensitive recording type release paper of the present invention. l... Support, 2... First back coat layer, 3...
...Second back coat layer, 4...Adhesive layer, 5...
- Peeling mount, 6...thermosensitive coloring layer, 7...protective layer.

Claims (1)

[Claims] (1) A heat-sensitive color forming layer containing a leuco dye and a color developer is provided on the surface of a support, and a release mount is provided on the back surface of the support via an adhesive layer, which adheres to the back surface of the support. A first backcoat layer containing polyvinyl alcohol as a main component is provided between the agent layer and the first backcoat layer containing a water-based polymer resin other than polyvinyl alcohol as a main component. 1. A heat-sensitive recording type release paper characterized by laminating a second back coat layer having a poor hardness.