JPS63242678A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To enhance recording density and to improve dot reproducibility even in high speed recording, by providing a thermal color forming layer on a paper support wherein an intermediate layer containing white pigment, a film forming polymer and a petroleum resin is provided on base paper. CONSTITUTION:In thermal recording paper constituted by providing a thermal color forming layer on a support, a paper support is formed by providing an intermediate layer containing white pigment, a film forming polymer and a petroleum resin on base paper. The base paper is prepared mainly from natural pulp by a papermaking process but a synthetic fiber, synthetic pulp or an inorg. fiber can be partially mixed with the base paper. As the white pigment, inorg. pigment such as kaolin or baked kaolin and org. pigment such as a urea/ formalin resin are designated but one having oil absorbancy of 10-150cc/100g is pref. As the film forming polymer, a polymer emulsion of SBR or MBR is especially pref. The petroleum resin is a hydrocarbon resin obtained by copolymerizing 5 or more C unsaturated aromatic or aliphatic hydrocarbons formed as byproducts by the cracking of naphtha and pref. has MW of 500-5,000.

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, a thermal pen, etc. More specifically, the present invention relates to a thermal recording paper on which recording is performed using a thermal head, a thermal pen, etc. The present invention relates to a thermal recording paper that does not cause piling to the head, has good dot reproducibility even in high-speed recording, and provides clear, high-density recording.

(Prior art) In recent years, facsimiles, printers, etc. have made remarkable progress.
In particular, a thermal recording method using a thermal head and a thermal recording paper coated with a colorless dye such as ristal violet lactone and a 7-ethanol compound, as described in Japanese Patent Publication Sho μj-/≠032, It is widely used in these devices.

This thermal recording method has many advantages such as primary color development on the recording paper, no need for development, simplification of the recording device, low costs for the recording paper and recording device, non-innocuous recording, and no noise. It established its position as a low-speed recording method. However, a major drawback of thermosensitive recording is that the recording speed is slower than other recording methods such as electrostatic recording, and at present it has not been adopted to the extent of high-speed recording.

In thermal recording, the most important reason why high-speed recording is not possible is that heat conduction between the thermal head and the thermal recording paper in contact with the head is not sufficient, and sufficient recording temperature cannot be obtained. The thermal head, which is a collection of dot-shaped electrical resistance heating elements, generates heat in response to recording signals, melting and coloring the thermosensitive coloring layer in contact with the thermal head. In order to obtain clear and high-density recording, it is necessary to have good dot reproducibility, that is, to ensure that the thermal head and thermosensitive coloring layer are in close contact with each other as much as possible, so that heat conduction is carried out efficiently, and the dots are fully compatible with the n1 high-speed recording signal. It is necessary that completely colored dots corresponding to the shape of the dot heating element of the thermal head are formed on the thermosensitive coloring layer. but,
At present, only a few percent of the heat generated by the thermal head is transferred to the thermosensitive coloring layer, and the efficiency of heat transfer is extremely low.

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.

Japanese Patent Publication No. 0/II describes that the surface of the heat-sensitive coloring layer is subjected to surface treatment for a Bekk smoothness of 200 to 1000 seconds. Japanese Patent Application Laid-open No. 3 μm 115253 discloses a Bekk smoothness of 200 to io.

At 0 seconds, it can only cope with a thermal nozzle of about j-t milliseconds, and for high-speed recording of 7 milliseconds or less, the surface of the thermosensitive coloring layer must be smoothed to a Bekk smoothness of 1100 seconds or more. It is stated that it is necessary.

If the Bekk smoothness is set to 1ioo seconds or more, color fog will occur due to pressure, so please prepare the base paper beforehand.
Bekk smoothness is improved to 200 seconds or more to prevent color development. Tokukai Akira! J-/! 60r&
Then, the surface roughness Ra of the surface of the thermosensitive coloring layer is /, 2μTr
L or less, gloss level 2! It is stated that it should be less than or equal to 1.

The conventional techniques for improving the smoothness mentioned above improve the smoothness of the heat-sensitive coloring layer only by calender treatment such as super calender, machine calender, cross calender, etc. Calendar treatment is performed on only the base paper, on the base paper and thermal paper, or on the thermal paper only. Thermal paper whose smoothness has been improved through these calender treatments has an increase in sticking and piling as the smoothness improves and the recording density improves, so in reality, the smoothness does not reach an appropriate level. The recording density, sticking, and turning are perfectly balanced. In the prior art, regardless of the level of smoothness, the recording density or fc is not practical for high-speed recording in terms of recording stability.

Sticking is when the thermal head and thermosensitive coloring layer adhere to each other.
Piling is a phenomenon in which a peeling sound is generated and the dot reproducibility is reduced. Piling is a phenomenon in which the thermal melt of the thermosensitive coloring layer is deposited on the thermal head, causing a decrease in recording density and dot reproducibility. Both of these phenomena interfere with stable recording.

Another disadvantage of calendering thermal paper is that color fogging occurs due to pressure, and the density of the background portion of the recording paper increases.

-Currently, there is a limit to the calendering of base paper due to the occurrence of so-called bulges, wrinkles, etc. caused by uneven basis weight. As mentioned above, the smoothing of the heat-sensitive coloring layer and the improvement of recording density by calendering are inevitably limited, and a product that is sufficiently satisfactory for high-speed recording has not been obtained.

(Object of the Invention) The object of the present invention is to provide a thermal recording paper which improves the above-mentioned drawbacks, that is, a thermal recording paper 'ff- which has a high recording density and good dot reproducibility even in high-speed recording.

(Structure of the Invention) The present inventors have conducted intensive studies to improve these drawbacks, and as a result, we have developed a paper support with an intermediate gold film containing a white pigment, a film-forming polymer, and a petroleum resin on a base paper. It has been found that the above characteristics can be obtained by providing a thermosensitive coloring layer on the body.

The petroleum resin used in the present invention is a hydrocarbon resin copolymerized with unsaturated aromatic hydrocarbons or aliphatic hydrocarbons having 5 or more carbon atoms, which are by-produced during naphtha decomposition, and has a molecular weight of 600'- , t, 000 is preferred.

That is, cyclopentadiene, intene, methylstyrene, etherstyrene, dimethylstyrene, methylintene, methylpropenylbenzene, etc. and 1 as a starting material.
It is preferable that maleic anhydride be added thereto. In addition, the whiteness of the paper support is particularly required.
The Jb field@-1lc is preferably hydrogen-decorated and has the following properties.

Petroleum resin is preferably used in combination with conventionally known coating materials such as white pigments and film-forming polymers, and its high water resistance significantly improves the flatness after coating the heat-sensitive layer.
Extremely high color density can be obtained. The amount of petroleum resin applied depends on the white pigment and film-forming polymer used together, but O12~! , Of/m2.

In the present invention, the white pigment used in the middle layer includes kaolin,
Inorganic pigments such as calcined kaolin, talc, calcium carbonate, barium sulfate, and titanium oxide, and organic pigments such as urea-formalin resin, acrylic resin, and polystyrene resin are listed, but their oil absorption is 10~/jOCc/100? , preferably 30 to rOcc//009. Film-forming polymers used in the intermediate layer include water-soluble polymers such as starch, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and polyacrylamide, and SBR%MBR%SMBR.

Although NBR, styrene/acrylic ester, and MMA/acrylic ester polymer emulsions are used,
Polymer emulsions of SBR and MBR are particularly preferred.

Also, if necessary, melamine formaldehyde, urea formaldehyde, polyamide polyurea.

Waterproofing agents such as polyamide polyamine epichlorohydrin can be added.

In addition, it is also possible to add dyes, fluorescent dyes, antifoaming agents, and the like. As a coating method for forming such an intermediate layer, conventionally known methods such as blade coating, air knife coating, gravure coating, dip coating, and par coating are used.

The coating amount of the intermediate layer is in the range λ~20 t/m2b, preferably ψ~/O17m2.

The base paper used in the present invention is made entirely of natural pulp.
However, it is also possible to mix some sweet acid fibers, synthetic fibers, or inorganic fibers.

Natural pulps include softwood pulp, hardwood pulp, straw pulp, nisperton pulp, bagasse pulp, etc.
It is also possible to use hardwood pulp, but hardwood pulp is more preferable because it has short fibers and is easily smooth. Pulp is beaten using beaters, disc refiners, conical refiners, Jordan refiners, etc.
(C, S, F) of OO-2OO is preferred, and particularly preferably ≠OQ~300 (COS, F).

In addition, the following chemicals can be added as raw materials other than Nogulup. That is, as a sizing agent, rosin, nografine wax, higher fatty acid salt, alkenyl succinate, fatty acid anhydride, styrene maleic anhydride copolymer,
Alkyl ketene dimer epoxidized fatty acid amide, reaction product of maleic anhydride copolymer and polyalkylene polyamine as a softening agent, V class ammonium salt of higher fatty acid, talc, clay, kaolin, calcium carbonate, barium sulfate as a pigment, oxidation Titanium, aluminum sulfate, aluminum chloride salt, polyamide polyamine epichlorohydrin as a fixing agent, dyes, fluorescent dyes, antistatic agents, antifoaming agents, etc. can all be added as necessary.

Note that it is desirable to control the amount of the sizing agent added so that the sizing degree of the paper support after paper making is 30 t/@2 or less in terms of lump sizing degree, preferably 20 to IOf/TrL2.

After mixing these raw materials, the base paper used in the present invention is made into paper using a fourdrinier paper machine or cylinder paper machine.
The basis weight is JO-1097m2. In addition, by on-machine calendering or off-machine supercalendering, the density can be o, to-o, or It/cTn3.
Those that have been carefully finished are used.

Next, the heat-sensitive coating liquid used in the 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 finely divided color formers or color developers can be achieved by using balls of different particle sizes at an appropriate mixing ratio and dispersing them for a sufficient amount of time. nru. It is also effective to use a light model sand mill (trade name: Dyno Mill).

The obtained dispersion of f'1 color former and color developer is mixed with inorganic pigments, waxes, higher fatty acid amides, metal soap, and if necessary, ultraviolet absorbers, antioxidants, latex binders, etc. Add it to make a coating liquid. These additives may be added at the time of dispersion.

The coating liquid generally has an applied amount of coloring agent of O, Kf/? F
It is coated on the support so that it becomes L2 to /, Ot/rIL2.

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. To give a specific example, n is (1) triarylmethane thread-forming adduct, for example, J,J-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone)%j(ri). 1-dimethylaminophenyl)-J-(/, λ-dimethylindole 3
3-(p-dimethylaminophenyl)-j-(2-phenylindol-3-yl)
Phthalide, 3,3-bis-(p-ethylcarbazole-
(2) Diphenylmethane compounds, such as μ, Hiro - bis-dimetelaminobenzhydrin benzyl ether, N-halophenyl leuco auramine, N-2゜μ, j-trichlorophenyl leuco auramine, etc.: (3) xanthine compounds, such as rhodamine B-anilinolactam, 3-diethylamino-7
-Dibenzylaminofluorane, 3-diethylamine-
7-Butylaminofluorane, 3-diethylamine-7
-(λ-chloroanilino)fluorane, 3-diethylamino-6-methyl-tuanilinofluorane, 3-piperidino-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-anilinofluoran Oran, 3-cyclohexyl-methylamino-t-methyl-7-anilinofluorane, 3-diethylamino-6-
Chloro-7-(β-ethoxyethyl)aminofluorane, 3-diethylamine-6-chloro-7-(γ-chloropropyl)aminofluorane, 3-diethylamino-4
-chloro-7-anilinofluorane, 3-N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7-phenylfluorane, etc.; (4) thiazine compound, For example, benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.; (5) Spiro compounds, such as 3-
Examples include methyl-spiro-dinaphthopyran, 3-ether-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 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 carbon fermentation conductors are preferred, and bisphenols are particularly preferred. Specifically, as phenols, p
-octylphenol, p-tert-ifruphenol, p-phenylphenol, λ, 2bis(p-hydroxy)furonoξ, /, /-bis(p-hydroxyphenyl)pentane, /, /-bis(p- hydroxyphenyl)hexane, x,z-bis(p-hydroxyphenyl)hexane, /,/-his(p-hydroxyphenyl)
- coethylhexane, 2. Examples include Corbis(gu-hydroxy-3,j-dichlorophenyl)pronone.

Aromatic carboxylic acid derivatives include p-hydroxybenzoic acid, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate,
3. ! - Di-α-methylbenzyl salicylic acid and carboxylic acid, these polyvalent metal salts and the like are commonly used.

These color developers are 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. It is preferable to add the agent in a state in which it is fused to the surface of the agent particles.

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 metalstones include polyvalent metal salts of higher fatty acids, ie, zinc stearate, aluminum stearate, calcium stearate, and sub81 oleate.

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

It is preferable that these pigments have an oil absorption of 60 total/100 or more and an average particle diameter of 5 μm or less. For oil-absorbing inorganic pigments, dry weight@j-jOMg,
Preferably, it is desirable to blend in a weight ratio of 10-HiroO.

These ingredients are dispersed in a binder and applied. The most common types of pinter are those that are water-bathable. Copolymers, polyacrylic acid, starch derivatives casein, gelatin, etc. are available.

(9) In order to impart water resistance to these binders, a water-resistant agent (gelling agent, cross-linking agent) is added to create an emulsion of a hydrophobic polymer, specifically (3) styrene-butadiene rubber latex, acrylic resin. Emulsions etc. can also be added.

The binder is added to the recording layer in an amount of 10 to 30 dry weights. Furthermore, various auxiliary agents such as antifoaming agents, fluorescent dyes, and colored dyes can be added to the blood as appropriate and necessary.

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

The amount of the coating liquid forming the recording layer to be applied to the support is not limited, but is usually 3 to 1 by dry weight! t/1rL
2, preferably in the range of 44 to 1097 m''.

(Effects of the Invention) The effects obtained by the thermal recording paper according to the present invention, which uses a paper support having an intermediate layer consisting of a white pigment, a film-forming polymer, and a petroleum resin on a base paper, are as follows: This increases the contact area with the head, making it possible to achieve uniform recording density and good dot reproducibility.

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

Example LBKPro part and NBKP part 20 parts were refined to a Canadian threeness mark of 310 using a disc refiner, and then 270 parts of tal, 1 part of rosin, and 2 parts of sulfuric acid band [
was added in weight percent to the bone-dry pulp, and a base paper of 60'//m2 in area was made using a Fourdrinier paper machine. Thereafter, it was adjusted to a thickness of tμ by a super calender.

An intermediate layer having the composition shown in Table 1 was applied onto the base paper using an air knife coater to obtain a paper support according to the present invention. (Sample shop 7~μ). Similarly, a paper support coated with an intermediate layer to which no petroleum resin was added and a paper support without an intermediate layer were prepared as comparative examples. (Sample & j~ri).

A thermal coating liquid was applied to the paper supports of Examples and Comparative Examples to obtain thermal paper. Thermal recording was performed on this thermal paper and the recording density was measured.

These results are shown in Table 2. The method for producing the heat-sensitive coating liquid, the method for coating it, and the method for measuring the heat-sensitive recording density are shown below.

Method for producing heat-sensitive coating liquid Crystal violet lactone 20 was dispersed day and night in a JOOl ball mill with an aqueous solution of 9f10 polyvinyl alcohol (saponification degree 1 degree polymerization degree 200).

Similarly, 2,2-bis(≠-hydroxyphenyl)propane was dispersed overnight in a 30073 ball mill with 20Jf 10% polyhinyl alcohol aqueous solution. Both dispersions were mixed with crystal violet lactone and 2,2-bis (≠
-hydroxyphenyl)propane ratio is / S jit
Mix the mixture so that the ratio is equal to the ratio, and then add
j) C9 light calcium carbonate was added and sufficiently dispersed to form a coating liquid.

How to apply heat-sensitive coating liquid: Apply solids to one side of the paper sheet using an air knife coater.
It was applied to a t/y of 12, dried in a zo 0c hot air dryer, and machine calendered.

Measuring method of thermosensitive recording density Recording speed 1 dot λ milliseconds, recording density main scanning direction j
Dots/fl, 6 dots/ho in the sub-scanning direction, energy of the thermal head! Solid coloring was performed at O millijoules/m2. The recording density was determined by measuring the reflection density of Alonm and is shown in Table 1.

Also, the reproducibility of the dots shown in Table 1 was determined visually and indicated by the symbols shown below.

Symbol Tod reproducibility ○ Good △ Slightly problematic in practice c%
It is clear that it has a sexual nature.

Claims (2)

[Claims] (1) In a thermosensitive recording paper having a thermosensitive coloring layer provided on a support, the support is a paper support in which an intermediate layer containing a white pigment, a film-forming polymer, and a petroleum resin is provided on a base paper. A thermal recording paper featuring (2) The coating amount of the intermediate layer is 2 to 20 g/m^2, and the coating amount of the petroleum resin is 0.2 to 3 g/m^2. Thermal recording paper.