JPS61139485A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To eliminate the lowering of temperature during the high-energy color-forming period by a method in which an intermediate layer composed of an inorganic and/or organic pigment having a specific oil absorption value is provided on a paper supporter,a nd a thermal color-forming layer is laminated on the intermediate layer. CONSTITUTION:An intermediate layer composed of an inorganic pigment and/or an organic pigment having an oil absorption of 30-50muml/100g (specified by JIS-K-5101) is provided on a paper supporter. A thermal color-forming layer is then laminated on the intermediate layer to form a thermal recording paper. As the inorganic pigment and/or organic pigment, baked kaolin, kaolin, talc, synthetic silica, natural silica, polystyrene resin, polyethylene resin, etc., may be used, having an average grain size of 1-10mum, more prefrably of 2-6mum. As the paper supporter, ones having internal bonding forces of 0.5-2.5kg.cm (specified by TappiRC-308) are preferably used.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a thermal recording paper on which recording is performed using a thermal head, thermal pen, etc. The invention relates to a thermal recording paper having an intermediate layer coated with a pigment.

(Prior art) Thermosensitive recording paper has a thermosensitive coloring layer that can be colored by heating.
It is installed on a support such as paper, synthetic paper, or plastic film, and is suitable for use in heat-resistant devices such as calculators, thermal printers of computer terminals, medical measuring instruments, recorders, thermal facsimile machines, automatic ticket vending machines, etc. Widely used as recording material. Thermosensitive recording materials usually contain a color-forming substance such as a colorless or light-colored leuco dye, a lactone, a lactam, or a spiropyran-based color-forming dye, and a color-developing substance that causes the color-forming substance to develop color when heated, such as naphthol,
Catechol, resorcinol, a, 4t'-isopropyritine diphenol, g, l-cyclohexyritine diphenol, benzoic acid, p-71 nylphenol, etc. are separately pulverized and dispersed using a ball mill, attritor, sound mill, etc., and then the resin is Manufactured by adding and mixing a binder, and adding surfactants, antifoaming agents, wax, inorganic pigments, etc. as necessary to prepare a heat-sensitive coloring layer forming liquid, which is then applied to paper and dried. It had been.

The heat-sensitive recording paper thus obtained is heated with a heating resistor, a thermal head made of a nichrome wire, etc., to form a colored image. A method has been proposed in which an intermediate layer made of an inorganic or organic pigment is coated between the paper support and the thermosensitive coloring layer in order to reduce the amount of residue deposited on the thermal head of the thermosensitive recording paper.

A method of coating an inorganic pigment such as calcium carbonate with an oil absorption of ik"+d/"'g or more as an intermediate layer (% Kosho 57-J-
29Ir) or a method using an organic pigment urea-formaldehyde resin as an intermediate layer (Japanese Patent Application Laid-Open No. 17-703♂
No. 92) etc.

However, when the above-mentioned intermediate layer is coated, there is a drawback that when the heat-sensitive recording layer is colored with high energy, the coloring component is absorbed by the intermediate layer, resulting in a decrease in the coloring density.

(Object of the Invention) An object of the present invention is to provide a heat-sensitive recording paper that has improved the above-mentioned drawbacks, that is, a heat-sensitive recording paper that does not reduce the color density even when it is colored with high energy.

(Structure of the Invention) The present inventors conducted intensive research to improve these drawbacks, and as a result, the oil absorption amount (JI) between the support and the thermosensitive coloring layer was
S K-r10/1g) is JOrd/10
The present object was achieved by interposing an intermediate layer consisting of a pigment of 01i or more and less than 10w1710017. In other words, by using pigments with low oil absorption, the coloring component is prevented from penetrating into the intermediate layer during coloring.
It has been found that thermal recording paper with high color density can be obtained even when printed with high energy.

The types of inorganic and organic pigments used in the present invention include calcined kaolin, kaolin, talc, barium sulfate, titanium oxide, light calcium carbonate, synthetic silica, natural silica,
Polystyrene resin, polystyrene resin, urea-formalin resin, etc., preferably calcined kaolin, kaolin, talc, may be used alone or in combination.

The average particle size of the pigment is /~70μ, preferably λ
~buμ is good.

Binders used in the present invention include water-soluble polymers such as starch, starch derivatives, CMC, and polyvinyl alcohol, and hydrophobic polymer emulsions such as SBR,
Examples include MBR and acrylic resin, and any water-soluble and hydrophobic polymer compounds similar to these can be used in the present invention.

Furthermore, surfactants, dispersants, thickeners, waterproofing agents, antifoaming agents, etc. can be added as necessary.

The coating amount of the intermediate layer according to the present invention is 3 g/g@2 to 2017/, WL2.゛In addition, as a coating method, conventionally known coating methods such as air knife coating method, blade coating method, gravure coating method, roll coating coating method, spray coating method, dip coating method, bar coating method, extrusion coating method, etc. is available.

Paper supports used in the present invention include Tapp iR,
The internal bonding force defined by C-40♂ is θ,! ~Ko,
! It is preferable to have faith. The internal bond strength is ko, t~
- When it is 1 or more, the compressibility of the paper decreases and the color density decreases. Moreover, if it is less than 0,6 or 9·α, problems such as paper breakage may occur during the coating process.

Next, the heat-sensitive coating liquid used in the present invention will be described.

Generally, a heat-sensitive coating liquid is prepared by separately dispersing a color former and a color developer in a water-soluble polymer solution using means such as a ball mill. Taking a ball mill as an example, in order to obtain a finely divided color former or color developer, balls of different particle sizes are used in an appropriate mixing ratio, and this is achieved by dispersing them for a sufficient amount of time. be done. It is also effective to use a model sand mill (trade name: Dyno Mill).

The resulting dispersion of color former and color developer is mixed, and inorganic pigments, waxes, higher fatty acid amides, metal soap, and if necessary, ultraviolet absorbers, antioxidants, latex binders, etc. are added to form a coating liquid. shall be. There is no problem in adding these additives at the time of dispersion.

The coating liquid generally has a coating amount of θ0.2 as a coloring agent! 9
/ff! 2 to θ11/−2.

The color forming agent used in the present invention is not particularly limited as long as it is used in general pressure-sensitive recording paper, heat-sensitive recording paper, etc. Specific examples include (1)) IJ arylmethane compounds, for example! ,! -bis(p-dimethylaminophenyl)-g-dimethylaminophthalide (
crystal violet lactone), 3-(p-dimethylaminophenyl)-3-(/,2-dimethylindol-3-yl)phthalide, 3-(1)-dimethylaminophenyl)-j-(12-phenyl) Indole-3
-yl)phthalide, 3,3-bis-(p-ethylcarbazol-3-yl)-3-dimethylami7phthalide, 3
．． 3-bis-(2-phenylindol-3-yl)-
! -dimethylaminophthalide, etc.; (2) Diphenylmethane compounds, such as g,4t-bis-dimethylaminobenzhydrin benzyl ether, N-hac2 phenylleucoolamine, N-2゜41, j-) Chlorophenylleukoolamine etc.; (3) xanthine compounds such as rhodamine B-anilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamine-7-butylaminofluorane, 3-diethylamino-7 -(2-chloroanilino)fluoran,
3-diethylamine-≦-methyl-2-anilinofluorane/, 3-pi is saginoh-6-methyl-anilinofluorane, 3-ethyl-tolylamino-g-methyl-7-
Anilinofluorane, 3-cyclohexyl-methylamino-bu-methyl-2-anilinofluorane, 3-diethylamino-6-chloro-7-(β-ethoxyethyl)aminofluorane, 3-diethylamino-echloro-7
-(γ-chloropropyl)aminofluorane, 3-diethylamine-6-chloro-7-anilinofluorane, j
-N-cyclohexyl-N-methylamino-methyl-7-anilinofluorane, 3-diethylamine-2-
(4) Thiazine compounds, such as benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, etc.; (5) Spiro compounds, such as 3-methyl-spiro-dinaphthopyran, 3-
Examples include ethyl-spiro-dinaphthopyran, 3-benzylspiro-sina7topyran, 3-methylnaphtho-(3-methoxy-benzo)-spiropyran, and mixtures thereof. These are determined by the application and desired properties.

The color developer used in the present invention includes phenol derivatives,
Aromatic carzenic acid derivatives are preferred, and bisphenols are particularly preferred. Specifically, as phenols, -
p-octylphenol, p-tert-fluorphenol, p-phenylphenol, co, λ bis(p-hydroxy)propane, /I/-bis(p-hydroxyphenyl)hantane, /, /-bis(p- hydroxyphenyl)hexane, 2. Corbis(p-hydroxyphenyl)hexane, /, /-bis(p-hydroxyphenyl)
-Coethylhexane, co-2-bis(couhydroxy-3,t-dichlorophenyl)propane, etc. are available.

Aromatic carzenic acid derivatives include p-hydroxybenzoic acid, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate,
3. For j-di-α-methylbenzylsalicylic acid and carboxylic acid, polyvalent metal salts thereof can be used.

These color developers may be added as a eutectic with a thermofusible substance with a low melting point in order to melt at a desired temperature and cause a color reaction, or the low melting point compound may be added to the surface of the color developer particles. It is preferable to add it in a fused state.

Waxes include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax, and higher fatty acid amides such as stearic acid amide, ethylene bisstearamide, and higher fatty acid esters.As metal soaps, high-grade Examples include fatty acid polyvalent metal salts, such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

Examples of inorganic pigments include kaolin, calcined kaolin, PKR,
Quartzite, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide, barium carbonate, etc. are included.

These inorganic pigments have an oil absorption of 607/1009 or more and an average particle size! It is preferable that it is less than μm. Regarding oil-absorbing inorganic pigments, the dry weight of the recording layer is high! 0% by weight,
Preferably, /Q-g is blended in an amount of 0% by weight.

These are dispersed in a binder and applied. Binders are generally water-soluble, such as polyvinyl alcohol, hydroxyethylcellulose, hydroxypropylylulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and imbutylene-maleic anhydride copolymer. Polymers, polyacrylic acid, starch derivatives casein, gelatin, etc. can be used.

In addition, water-resistant agents (gelling agents, cross-linking agents) are added to these binders for the purpose of imparting water resistance, and emulsions of hydrophobic polymers, specifically styrene-butadiene rubber latex, acrylic resin emulsions, etc. etc. can also be added.

The binder reacts in the recording layer at a dry weight of 70-30%. Furthermore, various auxiliary agents such as antifoaming agents, fluorescent dyes, and colored dyes can be added to the coating liquid as appropriate and necessary.

The coating liquid for forming such a recording layer is a blade coating method,
Conventionally known coating methods such as air knife coating, gravure coating, roll coating, spray coating, dip coating, bar coating, and extrusion coating can be used.

The amount of the coating liquid that forms the recording layer to be applied to the support is not limited, but it is usually 3~/r9/r on a dry weight basis.
fn2, preferably in the range of Z to 10/i/fF12.

The present invention will be specifically explained below using Examples, but the present invention is not limited thereto.

Table 1 shows the interlayer formulation and the internal bonding strength of the paper support in Examples and Comparative Examples.

After thoroughly stirring the intermediate layer coating liquid, apply an air knife to a high-quality paper with a basis weight of 4tj 9/fn2 using a postwar 109/frL2
It was applied and dried at /aoOc.

A thermal coating liquid was applied to the paper support coated with the intermediate layer of Examples and Comparative Examples to obtain thermal recording paper.

The method for producing and applying the heat-sensitive coating liquid is shown below.

Method for producing heat-sensitive coating liquid 20 kq of crystal violet lactone was dispersed overnight in a 3001 ball mill with an aqueous solution of 10 polyvinyl alcohol (saponification degree 9/polymerization degree 100).

Similarly, 9 was dispersed in 2,2-bis(4t-hydroxyphenyl)propane 20 and a 70% polyvinyl alcohol aqueous solution in 3 oz; g-lumil overnight. Both dispersions were mixed in 1. Crystal violet lactone and co, λ-
The ratio of bis(couhydroxyphenyl)propane is /:!
The mixtures were mixed in the same weight ratio, and a slight amount of calcium carbonate (j kg) was added to 20 kg of the mixed liquid and sufficiently dispersed to prepare a coating liquid.

How to apply heat-sensitive coating liquid: Apply solids to one side of base paper using an air knife coater at t/l.
/ rn 2, and placed in a machine calendar in a JOOCO hot air dryer.

The color development of the heat-sensitive layer is determined by the recording speed/comiseconds per dot and the recording density in the main scanning direction! Dot/■, 4 dots/cod in sub-scanning direction, energy of thermal head jOmJ/11Ia2 and rO
A solid color was developed at mJ/vm2, and the color density was ≦70, and the reflection density was measured.

Claims (2)

[Claims] (1) In thermal recording paper in which a thermosensitive coloring layer is provided on a paper support, there is an oil absorption amount (J
(specified in IS K-5101) is 30ml/100
1. A thermosensitive recording paper characterized by interposing an intermediate layer consisting of an inorganic and/or organic pigment of 50 ml/100 g or more and less than 50 ml/100 g. (2) Internal bonding force of paper support (Tappi RC-30
8) is 0.5 to 2.5 kg·cm.