JPS63188087A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To obtain sharp high density recording having good dot reproducibility, by providing a thermal color forming layer to a support obtained by providing a thermoplastic resin layer to a pigment coated paper by a heat-melting extrusion method. CONSTITUTION:In thermal recording paper wherein a thermal color forming layer is provided on a support, the support is formed by providing a thermoplastic resin to pigment coated paper by a melt-extrusion method. As the pigment coated paper, cast coat paper is desirable. As the thermoplastic resin, a homopolymer of an alpha-olefin such as polyethylene or polypropylene, a copolymer of alpha-olefins or a mixture of polyethylene, polystyrene and polyvinyl chloride such as a mixture of various polymers is used. When polyethylene is used, the thickness of the resin layer is desirably 10mum or more. By this method, the thermal recording paper having good dot reproducibility, especially, the dot reproducibility in a low density region and high sensitivity can be obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a thermal recording paper for performing thermal recording using a thermal head, a thermal gun, etc., and is particularly suitable for high-speed halftone recording. In recording, the present invention also relates to thermal recording paper that has good dot reproducibility and provides clear, high-density recording.

(Prior art) In recent years, facsimile machines, printers, etc. have made remarkable progress, and in particular, heat-sensitive recording technology coated with colorless dyes such as ristal violet lactone and phenol compounds, as described in Tokuko Shosan J-/Sen 032, etc. A thermal recording system using a combination of paper and a thermal head is widely used in these devices.

With the thermal recording method, the recording paper only develops primary color.

It has many advantages such as no development is required, the recording device can be simplified, the cost of the recording paper and recording device is low, and there is no impact and no noise, and it has established itself as a low-speed recording method. Furthermore, recently, devices have appeared that apply the thermal recording method to record halftones of television images and the like.

In order to perform such halftone recording, the thermal recording medium is required to have dot reproducibility, particularly in a low density region, and high sensitivity.

In thermal recording, a major cause of poor dot reproducibility and sensitivity is insufficient heat conduction between the thermal head and the thermal recording paper in contact with it. The heating element, which is a collection of dot-shaped electrical resistance heating elements, generates heat equal to the amount of heat generated by the recording signal, and melts and colors the heat-sensitive coloring layer that is in contact with the heat.In order to obtain clear recording, , good dot reproducibility, that is, the thermal head and thermosensitive coloring layer are in close contact as much as possible, heat conduction is efficient, and the dots of the thermal head are completely colored on the thermosensitive coloring layer, corresponding to the shape of the heating element. It is necessary that the dots are formed in a manner similar to that shown in FIG.

Several methods have been proposed for improving the smoothness of the thermosensitive coloring layer so that the thermal head and the thermosensitive coloring layer come into close contact as much as possible.゛Special public show j2-20/'
No. I describes that the Bekk smoothness of the surface of the recording medium is set to 200 to 1000 seconds by using a super calender or the like.

Japanese Patent Application Laid-Open No. 2003-110033 describes a method in which undercoated paper is used as a support.

JP-A-11-/! tart describes a method for adjusting the surface roughness and glossiness of a recording medium to a specific range. However, the method of increasing smoothness through surface treatment hardly improves the dot reproducibility in the low density range, and on the contrary, the recording density decreases due to the accumulation of hot melt on the head (so-called Adhesion between the recording medium and the head tends to cause peeling noise and a drop in dot reproducibility (so-called sticky ink). Also, a method using undercoated paper as a support, especially JP-A-Sho TP
- A film-forming polymer layer such as POA, SBR, etc. is provided on a cast coated paper such as that seen in rsr≠l, or a pigment coated layer such as that seen in baryta paper 1% Kaisho 4/-/3gtO. Although there is a slight effect of improving dot reproducibility on supports and the like compared to uncoated paper, it is still insufficient. In addition, the method of adjusting the surface roughness and glossiness of the recording medium to a specific range is subject to limitations on the heat-sensitive coloring layer, coating method, etc., and dot reproducibility and sensitivity in the low density region are not necessarily satisfactory. .

(Object of the Invention) The object of the present invention is to provide a thermal recording paper that improves the above-mentioned drawbacks, that is, a thermal recording paper that has good dot reproducibility, especially in a low density region, and is highly sensitive. This is done by providing the following.

(Structure of the Invention) As a result of intensive research to improve these drawbacks, the present invention has developed a heat-sensitive paper, which is made by providing a heat-sensitive coloring layer on a support made of pigment-coated paper with a polyolefin resin formed by hot-melt extrusion. The purpose of the present invention has been achieved by using the recording paper.

The types of inorganic and organic pigments for the pigment-coated paper used in the present invention include calcined kaolin, kaolin, Merck, barium sulfate, titanium oxide, light calcium carbonate, aluminum oxide, magnesium carbonate, diatomaceous earth, hydrated silicic acid, Examples include anhydrous silicic acid, aluminum silicate, magnesium silicate, calcium silicate, magnesium aluminosilicate, sodium pluminosilicate, polystyrene resin, urea-formalin resin, etc., but are not particularly limited.

The average particle size of the pigment is 7゛~10μ, preferably λ
~tμ is also good.

In addition, in the coating layer, the binder for the pigment is not particularly limited and may be any commonly used binder, such as casein, starch, starch derivatives, P V
Water-soluble polymers such as A, CMC, and hydrophobic polymer emulsions such as SBRlMBR and acrylic resins are used.

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

The coating amount of the coating layer is J y / m 2 or ≠ oy
/z 2. .

In addition, the coating methods include air knife coating method, blade coating method, gravure coating method, roll coating coating method,
Conventionally known coating methods such as spray coating, dip coating, bar coating, and extrusion coating can be used. It is desirable to carry out a treatment such as cross calendering or super calendering after coating.

Particularly for purposes of the present invention, cast coated papers are desirable.

Thermoplastic resins used in the present invention include polyethylene homopolymers of α-olefins such as polypropylene, copolymers of these α-olefins, and mixtures of these various polymers. Mention may be made of olefins, polystyrene and vinyl chloride. Among these, polyethylene is particularly preferred in terms of cost and properties. The molecular weight of the thermoplastic resin is not particularly limited as long as extrusion coating is possible, and is usually 10,000.
~λ00000. When polyethylene is used as the thermoplastic resin, low density polyethylene, high density polyethylene, or a blend of low density polyethylene and high density polyethylene can be used.

It is also possible to fill the thermoplastic resin on the side where the heat-sensitive coloring layer is provided with inorganic white pigments such as titanium oxide, zinc oxide, barium sulfate, etc., and it is necessary to disperse these pigments in the resin. It is also possible to use zinc stearate and other surfactants as dispersants. It is also possible to use inorganic colorants such as turquoise and cobalt blue, organic colorants, and fluorescent whitening agents, which are desirable in order to increase the degree of whiteness.

The surface of the thermoplastic resin layer is usually molded to a mirror surface during extrusion coating.

Further, a thermoplastic resin is provided on the opposite side (back side) to the thermosensitive coloring layer in order to balance the curl.

The thickness of the thermoplastic resin layer is I/C, 10 to 10 on both sides.
It is preferably about 110-4 AOp.

In addition, before extrusion coating the thermoplastic resin onto the coated paper, it is preferable to pre-treat the coated paper in order to strengthen the adhesion between the coated paper (both sides) and the resin coating layer. The pretreatment may be freely selected from among corona discharge treatment, glow discharge treatment, ultraviolet irradiation treatment, flame treatment using gas flame, and the like. From the viewpoint of simplicity, corona discharge treatment is preferred.

In addition, in order to improve the adhesion between this thermoplastic resin layer and the thermosensitive coloring layer attached thereon, the surface of the thermoplastic resin layer may be subjected to surface treatment such as corona discharge, or further surface treatment. Subsequently, an undercoat layer containing the same binder as the thermosensitive coloring layer may be provided.

Further, it is possible to provide an antistatic layer containing an ionic organic antistatic agent such as an alkali metal salt of a polymerizable carboxylic acid, a floidal silicate agent, etc. on the thermoplastic resin layer on the back side, if necessary.

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. Using a ball mill as an example, obtaining a finely divided color former or developer is achieved by using balls of different particle sizes at an appropriate mixing ratio and dispersing for a sufficient amount of time. . It is also effective to use a model sand mill (trade name: Dyno Mill).

The resulting dispersion of color forming agent and color developer is mixed and coated with inorganic pigments, waxes, higher fatty acid amides, metal soap, and if necessary, ultraviolet absorbers, antioxidants, latex binders, etc. Make it into a liquid. There is no problem in adding these additives at the time of dispersion.

The coating liquid generally has a coating amount of 0.2y/color former.
It is coated onto the support at a rate of 2 to 1.0 l/m2.

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 such as 3,3-bis(p-dimethylaminophenyl)-4-dimethylaminophthalide (
crystal violet lactone), J-(p-dimethylaminophenyl)-j-(/, nodimethylindol-3-yl)phthalide, j-(p-dimethylaminophenyl)-j-(2-phenylindole- 3-il) Lid I) Do,! ,! -bis-(D-ethelcarbasol-3-yl)-3-dimethylaminophthalide, 3.
3-bis-(2-phenylindol-3-yl)-1
-dimethylaminophthalide, etc.; (2) Diphenylmethane compounds, such as Hiroshi, -bis-dimethelaminobenzhydrin benzyl ether, N-halophenylleucoauramine, N-2゜French, 7-)! J dichloroenyl leukoolamine, etc.; (3) xanthine compounds, such as rhodamine B-anilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-butylaminofluorane, 3-diethylamino -7-(2-chloroanilino)fluorane, 3
-diethylamino-t-methyl-7-anilinofluorane, 3-pyridino-t-methyl-7-anilinofluorane, 3-ethyl-tolylamino-4-methyl-7-anilinofluorane, 3-cyclohexyl-methylamino -6-Methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-(β-ethoxyethyl)aminofluorane, 3-diethylamino-t-chloro-7-
(r-chloropropyl)aminofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, J-
N-cyclohexyl-N-methylamino-4-methyl-
7-anilinofluorane, 3-diethylamino-7-phenylfluorane, etc.; (4) Thiazine compounds, such as benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, etc.; (5) Spiro compounds,
For example, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-benzylspiro-
dinaphthopyran, 3-methylnaphtho-(3-methoxy-
Examples include 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 carboxylic acid derivatives are preferred, and bisphenols are particularly preferred. Specifically, p
-octylphenol, p-tert-ithylphenol, p-phenylphenol, co,2bis(p-hydroxy)furonoξone, /,/-bis(p-hydroxyphenyl)intane, /,/-bis(p- hydroxyphenyl)hexane, 2. -monobis(p-hydroxyphenyl)hexane, l,l-bis(p-hydroxyphenyl)
Examples include -coethylhexane, 2-bis(≠-hydroxy-3.!-dichlorophenyl)propane, and the like.

Aromatic carboxylic acid derivatives include p-hydroxybenzoic acid, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate,
3. ! Examples of -di-α-methylbenzyl salicylic acid and carboxylic acid include polyvalent metal salts thereof.

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.

Examples of 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.

Examples of the metal soap include polyvalent metal salts of higher fatty acids, such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

Inorganic pigments include kaolin, calcined kaolin, Merck,
Examples include waxite, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide, and barium carbonate.

It is preferable that these inorganic pigments have an oil absorption of AO ml/1001 or more and an average particle diameter of Jμ or less. It is desirable that the oil-absorbing inorganic pigment be incorporated into the recording layer in an amount of 0% by dry weight, preferably 10-4 cO.

These are applied dispersed in a binder. Water-soluble binders are commonly used, such as reeds, polyvinyl alcohol, droxyethyl cellulose, and hydroxypropyl cellulose.

Examples include ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, inbutylene-maleic anhydride copolymer, polyacrylic acid, starch derivative casein, and gelatin.

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 in an amount of 10 to 30% by dry weight. 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, groove coating, and extrusion coating can be used.

The amount of the coating liquid forming the recording layer applied to the support is not limited, but is usually 3 to try/m2 by dry weight,
It is preferably in the range of 4' to /Op/m2.

Also, after coating the recording layer, the thermal recording paper contains moisture! ≠00 under conditions of weight percent or more and 12 weight/1'-cent or less
Surface treatment is carried out by passing the paper through a pressure device that combines a metal roll and an elastic roll heated to a temperature above C to 0C so that the surface of the heat-sensitive recording layer comes into contact with the metal roll.

(Examples of the Invention) The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto.

Example 1゜100 copies of LBKP sent to Canadian Freeness 3jOCC
After beating, 1.0 part of rosin, 6 parts of sulfuric acid,
Added 10 parts of talc as a filler and made fourdrinier paper with a basis weight of 7.
A base paper of oy/m2 was made.

A coating liquid having the following formulation was applied to this base paper using an air knife coater so that the solid content was 7 p/m2.

[Coating liquid prescription]

Dry in a hot air dryer so that the solid-liquid concentration is 30% and the water content is 7% by weight.
Pressure treatment was performed using an elastic roll.

Next, corona discharge treatment was applied to both sides of this coated paper, and high-density polyethylene (density 6
0g110n3MI=/Jy/10min) to resin thickness 20
A resin layer having a matte surface was formed by melt extrusion coating.

Next, a melt extruder was used to coat the coated surface with low-density polyethylene containing 10% by weight of anatase titanium dioxide and a trace amount of ultramarine (density O6 λ3/cm2, MI=
7F/10 minutes) with a resin thickness of 20 mμ,
A resin layer consisting of a glossy surface was formed. Next, this surface was subjected to a corona discharge treatment, and then a heat-sensitive coating liquid was applied by the method described below to obtain a heat-sensitive recording paper.

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

[Production method of heat-sensitive coating liquid]

20 ~ of crystal violet lactones were dispersed overnight in a 300 J-lumil with a 100 l aqueous solution of ribinyl alcohol (degree of saponification, t% degree of polymerization j00). Similarly, 2,2-bis(Hiro-hydroxyphenyl)propane λ
OK4 and KJ with 10% polyvinyl alcohol aqueous solution
Dispersion was carried out overnight in an OOl ball mill. Both dispersions were mixed so that the ratio of crystal violet lactone and 2,2-bis(≠-hydroxyphenyl)propane was l:j weight ratio, and further, j ~ slight amount of calcium carbonate was added to the mixed liquid -2QK4. was added and sufficiently dispersed to form a coating liquid.

[How to apply heat-sensitive coating liquid]

Apply solids to the intermediate layer coated paper using an air knife coater.
/ m2, apply it! Dry in a hot air dryer at o 0c to a moisture content of 7 wt.ξ-cents,
The heat-sensitive recording surface was brought into contact with a metal roll heated to ≦O0C, and pressure treatment was performed using an elastic roll.

Example 2゜ Cast coated paper (Espricor manufactured by Sanyo Okaei Pulp Co., Ltd.) FPtμ, Riy/m was used as a replacement for the pigment coated paper of Example 1.
Example 2 was prepared by applying polyethylene laminate and heat-sensitive coating liquid in the same manner as in Example 1 using Example 2).

Comparative Example 16 Comparative Example 1 was obtained by directly coating the base paper produced in Example 1 with the same polyethylene laminate and heat-sensitive coating liquid as in Example 1.

Comparative Example 2 Comparative Example 2 was prepared by directly applying a heat-sensitive coating liquid to the coated paper produced in Example 1.

Comparative Example 3 Comparative Example 3 was prepared by directly applying a heat-sensitive coating liquid to the base paper produced in Example 1.

The heat-sensitive layer develops color at a recording speed of 1 millisecond per dot and a recording density in the main direction! dots)/m, sub-scanning direction t dots/1m
, a solid color develops with the energy of the thermal head of 2 omJ/tight,
The color density was determined by measuring the reflection density of A/Onm.

The reproducibility of dots was determined by using the same device as described above and changing the energy of the thermal head to achieve an image density of 0. /-0° solid coloring was performed and visually judged.

As is clear from the results in Table 1 and Table 7, the thermal recording material of the present invention has the characteristics of good dot reproducibility in the low density region and high color development sensitivity, and is particularly suitable for halftone recording. It is characterized by excellent effects when

Claims (3)

[Claims] (1) A thermosensitive recording paper comprising a thermosensitive coloring layer provided on a support, characterized in that the support is pigment-coated paper with a thermoplastic resin applied by melt extrusion. (2) The thermal recording paper according to claim 1, wherein the coated paper is cast coated paper. (3) The thermoplastic resin is polyethylene and has a thickness of 10
The thermosensitive recording paper according to claim 1, characterized in that it has a particle diameter of μ or more.