JPH0393590A - Thermal recording sheet and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a thermal recording sheet excellent in dot reproducibility by successively providing an adhesive layer, an ionomer layer and a thermal recording layer on a sheet like base material based on cellulose. CONSTITUTION:A biaxially stretched polypropylene film being a film like base material made of a synthetic resin is subjected to surface roughening treatment and an ionomer resin is extruded to be laminated to the treated film or dissolved in or emulsified with a solvent to be applied and laminated thereto. When the biaxially stretched polypropylene film is used as the film like base material made of the synthetic resin, the ionomer resin and a propylene resin are integrated by co-extrusion to be formed into a film or the ionomer resin is extruded and laminated before the completion of the stretching of the propylene resin or an ionomer laminated film may be formed by applying the solvent or emulsion type ionomer resin before the completion of stretching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat-sensitive recording sheet, and particularly to a heat-sensitive recording sheet with excellent dot reproducibility, that is, high thermal responsiveness.

[Conventional technology]

Thermal recording method does not require a developing and fixing process and has easy hardware maintenance, so it has recently become popular.
It is widely used for recording various printers, facsimiles, measuring instruments, recording television images, etc.

The required characteristics of the recording medium used for these recordings vary depending on the use, but dot reproducibility of the recording medium is particularly required for halftone recording.

Conventionally, in order to improve dot reproducibility, a method of using a composite resin film or synthetic paper, a method of providing an undercoat layer, etc. have been adopted.

However, the former method of using synthetic resin film or synthetic paper has problems such as insufficient adhesion with a water-based heat-sensitive recording layer or coating liquid, or problems with static electricity generation and paper feeding. There is. In addition, the latter method of providing an undercoat layer is inferior to composite resin films and synthetic paper in terms of dot reproducibility, and the surface strength is weakened, causing problems such as paper dust in a part of the cutter. , it was still not sufficient.

[Problem to be solved by the invention]

Therefore, it is an object of the present invention to solve the above-mentioned drawbacks that have been a problem in the past, to provide a heat-sensitive recording sheet with excellent dot reproducibility, and to provide an efficient manufacturing method for the heat-sensitive recording sheet. .

[Means to solve the problem]

The present invention proposes that when a heat-sensitive recording layer is provided on a sheet-like base material mainly made of cellulose such as paper, the above problems can be efficiently solved by providing an adhesive layer and an ionomer resin layer therebetween. This is done based on knowledge. In addition, the present invention provides that an ionomer resin layer is previously provided on a release base material to form a layer, and a heat-sensitive recording layer is provided on the surface from which the release base material has been peeled off, whereby a uniform thickness can be obtained.
This was done based on the knowledge that heat-sensitive recording sheets could be obtained extremely efficiently.

That is, the present invention provides a heat-sensitive recording sheet in which an adhesive layer, an adhesive layer, and a heat-sensitive recording layer are sequentially provided on a sheet-like base material containing cellulose as a main component.

The present invention also provides an ionomer resin layer on a composite resin film base material, and the following. Then, a sheet-like base material mainly made of cellulose and having an adhesive layer on one side is stacked and integrated so that the adhesive layer and the ionomer resin layer are bonded together, and then a film-like base material is formed. Provided is a method for producing a heat-sensitive recording sheet, which comprises peeling off and providing a heat-sensitive recording layer containing a leuco compound and an organic acid that develops a color by reacting with the leuco compound on the ionomer resin layer.

The sheet-like base material mainly composed of cellulose used in the present invention includes those commonly used as base materials for heat-sensitive recording sheets, such as paper and nonwoven fabric. The thickness of the base material is arbitrary.

On the above sheet-like base material. As the adhesive located at , adhesives such as thermoplastic or thermosetting resins, such as synthetic rubber-based or vinyl acetate-based thermoplastic resins, polyurethane-based or epoxy-based thermosetting resins, etc. may be used. I can do it. The adhesive is applied to a sheet-like base material, for example, in a thickness of 1 to 10 g/m'' by a conventional method such as coating.

The ionomer resin used in the present invention is Teha, ethylene α
, β-unsaturated carboxylic acid (or its 6-ester) copolymer in which part of the aqueous carboxyl group is replaced with sodium or zinc. The ionomer resin layer has a thickness of 1 to log/m', preferably 2 to
6 g/m".

The heat-sensitive recording layer provided on the above-mentioned ionomer layer will be explained next.

Leuco compound The leuco compound blended into the heat-sensitive recording layer is a colorless or light-colored substance that develops color by reacting with an organic acid, and includes triphenylmethane, triphenylmethane phthalide, fluoran, leuco auramine, diphenylmethane,
Phenothiazine, Hue. Examples include various derivatives such as noisazine, spiropyran, impirin, and indigo.

Preferred leuco compounds include, for example, crystal violet lactone, 3-diethylamino-6-methyl-
7-anilinofluorane, 3-(N-ethyl-P-}luidino)-6-methyl-7-anilinofluorane, 3-
Jetylamino-6-methyl-7-(ortho, p-dimethylanilino)fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-(N-cyclohecyl-N-methylamino)-6-methyl-7- Anilinofluorane, 3-jethylamino~7-(orthochloroanilino)fluorane, 3-jethylamino-7-(
Metatrifluromethylanilino) fluorane, 3-
Jethylamino-6-methyl-chlorofluorane, 3
-jethylamino-6-methyl-fluorane, 3-(N
-isoaminoC'-N-ethylamino)-6-methyl-
Examples include 7-anilinofluoran and 3-dibutylamino-6-methyl-7-anilinofluoran.

The leuco compound is 3 to 20% by weight of the solid content in the heat-sensitive recording layer.
(hereinafter abbreviated as %) is preferably used.

Organic acid (or its ester) The organic acid to be blended into the heat-sensitive recording layer is a substance that is solid at room temperature, melts when heated and becomes a color developer when it comes into contact with a leuco compound, and includes various phenolic substances and fatty acids. , aromatic carboxylic acids, etc.

The amount of the organic acid used is generally 1 to 40% of the total solid content of the heat-sensitive recording layer.

Specifically, the organic acids include the following.

Gallic acid, salicylic acid, l-hydroxy-2-naphthoic acid, O-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxy-p-toluic acid, 3,5-xylenol, thymol, p-tert-butylphenol, 4- Hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, α-
Naphthol, β-na7}-)Lt, fJtecol, resorcinol, hydroquinone, 4-tert-cutyltecol, 4.4゜-sec-butylidenephenol, 2
．． 2"-dihydroxydiphenyl, 2,2゜-methylenebis(4-methyl-(i-tert-butylphenol), 2.2゜-bis(4-hydroxyphenyl)
Broban (also known as bisphenol A), 4.4'-
Isobropylidene bis(2-tert-butylphenol), pyrogallol, phloroglucin, phloroglucincarboxylic acid, p-methylphenol, p-phenylphenol, 4.4″-cycloheylidene diphenol, 4,4° -isopropylidene dicatechol, 4.4° -benzylidene diphenol, 4.4°
-isopropylidene bis(2-chlorophenol), 3
-Phenylsalicyl M, 3.5-? -di-tert-butylsalicylic acid, l-odicy-2-naphthoic acid, gallic acid ester, salicylic acid ester, p-hydroxybenzoic acid ester, 4-hydroxyphthalic acid ester, 2-(
4-hydroxyphenyl)-2-(3°-hydroxyphenyl)furopane, 4,4°-dihydroxy-3.
One type or a mixture of two or more types of 3°-diisobrobyldiphenyl-2,2'-propane.

Binder A binder is usually added to the thermosensitive recording layer. The binder mainly consists of a water-soluble binder, which isolates and fixes the coloring agent separated into fine particles from each other, and includes polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, Examples include casein, gelatin, starch and their derivatives. The amount of the binder used is preferably 1 to 35%, preferably 10 to 30% of the total solid content of the heat-sensitive recording layer.

Other additives The heat-sensitive recording layer may contain other additives as necessary, such as inorganic or organic additives such as clay, calcium carbonate, synthetic silica, aluminum hydroxide, talc, titanium oxide, zinc oxide, etc.
i-based materials, waxes, antioxidants for storage stability, ultraviolet absorbers, various fatty acid metal salts to prevent stickiness,
A water resistance agent, phenol resin, surfactant, etc. can be added to improve water resistance.

Furthermore, a thermofusible substance that promotes color development can also be added as necessary.

The heat-sensitive recording sheet of the present invention can be produced, for example, by the following method.

Production of a synthetic resin film provided with an ionomer resin layer A synthetic resin film provided with an ionomer resin layer, which is a feature of the present invention, can be produced as follows.

(1) A biaxially oriented polypropylene film, which is a resin film base material, is roughened and an ionomer resin is extruded and laminated, or it is dissolved in a solvent or made into an emulsion and coated using a known method. and laminate them.

(2) When using a biaxially oriented polypropylene film as a film-like base material made of resin, either the ionomer resin layer and the polypropylene resin are integrated into a film by coextrusion*, or the ionomer resin layer and the polypropylene resin are formed into a film before the stretching of the polypropylene resin is completed. The ionomer laminate film may be made by extrusion laminating the resin layers or by completing the stretching after coating with a solvent or emulsion based ionomer resin.

As the synthetic resin film base material, conventionally known materials can be used, such as polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, polystyrene, nylon, cellulose diacetate, cellulose triacetate, and the like. The thickness is arbitrary.

It is also possible to add additives that are commonly used in these resin films and resins, such as antioxidants, antistatic agents, slip agents, etc.

Although the synthetic resin film provided with the ionomer resin layer of the present invention can be produced by the above-mentioned production methods, the present invention is not limited to these production methods.

Application of adhesive and peeling and bonding In the present invention, an adhesive such as a rubber-based adhesive is bonded to a resin film-like base material provided with the ionomer resin layer and a sheet-like base material mainly composed of cellulose. It is first coated on the laminating side of the latter, and after drying, the two laminated surfaces are overlapped and heated and pressed from one or both sides, or they are integrated by applying pressure without heating, and then the film-like base is applied. The material is peeled off and the ionomer resin layer is transferred to the latter sheet-like substrate.

Form of heat-sensitive recording layer In the present invention, a heat-sensitive recording layer is provided on the ionomer resin layer. The paint for the heat-sensitive recording layer contains the above-mentioned leuco compound. and,
An organic acid, a binder, and additives such as pigments and sensitivity adjusters as necessary are mixed in an aqueous medium containing a binder such as polyvinyl alcohol at an appropriate concentration using a pole mill or a sand grinder. It is generally prepared by grinding and dispersing.

It is advantageous from the point of view of coloring efficiency to make each of the structural substances as fine as possible, and preferably to have a particle size of 0.5 to 3 .mu.m. The heat-sensitive paint thus obtained is applied onto the above-mentioned ionomer resin layer and dried to obtain the heat-sensitive recording sheet of the present invention.

Coating can be done using a regular blade coater, air knife coater,
This can be done using a bar coater, reverse roll coater, or the like.

The amount of paint applied is not particularly limited, but is usually 2~
12 g/m', preferably in the range 3-10 g/m''.

〔Effect of the invention〕

With the present invention, we have developed a method that could not be put to practical use in the past because the adhesion would deteriorate significantly if a water-based heat-sensitive recording layer forming coating liquid was directly applied to the surface of a highly smooth resin film-like substrate. It is possible to solve this problem and provide a heat-sensitive recording sheet with extremely excellent dot reproducibility. Furthermore, according to the Kaizo method described in claim (2), the ionomer resin is provided on the highly smooth synthetic resin film base material and transferred onto the adhesive layer, so that the ionomer resin layer is smooth. The heat-sensitive recording layer formed thereon can have extremely high smoothness.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples.

Example 1 a) Production of a synthetic resin film provided with an ionomer resin layer One side of a 200μ thick l-axis stretched polypropylene film obtained by stretching a polypropylene sheet extruded from a T-die 5 times in the uniaxial direction. was subjected to corona discharge treatment. Next, an ionomer emulsion, Chemipearl S (Mitsui Petrochemical Il), was applied to this corona discharge treated surface so that the solid content after drying was 2 g/m', and immediately after drying, it was applied in the lateral direction at an effective magnification of 9 times. Stretching treatment was performed to achieve this. The ionomer-coated surface was then subjected to a corona discharge treatment to obtain a 20 μm thick PP film with a surface tension of 50 dyne/cm and laminated with an ionomer.

b) Application and peeling of adhesive Apply a rubber adhesive to a 50 g/m'' high-quality paper so that the solid content after drying is 2 g/m', and apply the solvent to an infrared dryer. After evaporation, the ionomer layer was laminated with the ionomer laminated layer OPP film obtained in step a>, and pressurized while heating at 100° C., and then the OPP film was peeled off to transfer the ionomer layer to high-quality paper.

C) Manufacture of heat-sensitive recording sheet A coating solution was prepared by separately shaking solutions A and B of the following composition in a paint shaker (Toyo Seiki Kai) for 10 hours.

Solution A: Leuco dye 3-dibutylamino-6 methyl-7-anilinofluorane Zinc stearate Polyvinyl alcohol 12% liquid Water 5g 5g 40g 50g Solution B: Bisphenol A 10g Zinc stearate 3g Polyvinyl alfal 12% solution 40g Water
47g then 100g of liquid A
, 100g of liquid B and 50g of 12% polyvinyl alcohol liquid
, synthetic silica P-832 (manufactured by Mizusawa Chemical Co., Ltd.) 15 g, water 60
The heat-sensitive recording layer forming coating solution obtained by adding and stirring the ionomer was coated using a Mayer bar so that the coated amount after drying was 8 g/m'', and then dried. A thermosensitive recording sheet was obtained.

Comparative Example 1 A heat-sensitive recording sheet was obtained in the same manner as in Example 1, except that the heat-sensitive recording layer-forming coating liquid was directly applied to 50 g/m'' high-quality paper without using an adhesive or an ionomer.

Comparative Example 2 A heat-sensitive recording sheet was obtained in the same manner as in Example 1, except that the heat-sensitive recording layer or coating liquid was directly applied to an OPP film subjected to a corona discharge treatment without using an adhesive or an ionomer.

Comparative Example 3 Coated Silica D-527 (manufactured by Mizusawa Chemical) 70g Baked Kai Clay 30g Polyvinyl Alcohol 12% liquid 300g Water
1 6 0
g Make a coating liquid by dispersing with a homomixer using the above assembly 5 0
g/m' high-quality paper with a dry coating weight of 6 g/m'.
After coating and drying, the heat-sensitive coating liquid of Example 1 was applied thereon to obtain a heat-sensitive recording sheet.

The sheets obtained in the above Examples and Comparative Examples were subjected to surface treatment using a test calender under the conditions shown in Table 1.

The properties of the obtained heat-sensitive recording sheet were investigated by the following method.

The results are shown in Table 1.

a) Adhesion between heat-sensitive recording layer and support A cellopeal test was conducted using a commercially available mending tape.
Adhesion was visually determined.

b) Dot reproducibility and image density Commercially available thermal head KFT-2 1 6-8MPDI
(manufactured by Kyocera) with 0 printing power. 7 W/dat
Pulse period 5. Solid printing was performed under conditions of 0 ms and pulse width of 0.3 ms, and the density and background density of the resulting image were measured using a Macbeth densitometer RD-914, and dot reproducibility was visually determined.

C) Moisture resistance, heat resistance For those printed with b), 40°C, 90% R
After storage for 24 hours at 60° C. and 30% RH, the background density and image density were measured.

d) Paper passing/discharging properties Paper passing and recording were carried out on a practical thermal facsimile machine (Fujitsu 1l FF-2000) in an atmosphere of 20°C and 65% RH, and the paper passing properties and paper discharging properties were evaluated according to the following criteria. evaluated.

○ No trouble The paper is stuck in the xi position and cannot be ejected.

Claims (2)

[Claims] (1) A heat-sensitive recording sheet formed by sequentially providing an adhesive layer, an ionomer layer, and a heat-sensitive recording layer on a sheet-like base material containing cellulose as a main component. (2) An ionomer resin layer is provided on a synthetic resin film-like base material, and then a sheet-like base material whose main component is cellulose and has an adhesive layer on one side is bonded to the adhesive layer and the ionomer resin layer. After superimposing and integrating them in such a manner, the film-like base material is peeled off, and a heat-sensitive recording layer containing a leuco compound and an organic acid that reacts with the leuco compound to develop a color is provided on the ionomer resin layer. A method for producing a heat-sensitive recording sheet characterized by: