JP2511300B2 - Thermal recording label paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a heat-sensitive recording label paper, and more particularly to a heat-sensitive recording label paper having excellent punching properties and excellent recording sensitivity.

<Prior Art> Generally, a heat-sensitive recording material having a heat-sensitive recording layer mainly composed of a colorless or light-colored leuco dye and a developer that reacts with a leuco dye to develop a color is disclosed in Japanese Examined Patent Publication No. 45-14035. Has been widely used. A thermal printer or the like having a built-in thermal head is used to perform recording on this thermal recording medium, but such a thermal recording method does not generate noise at the time of recording as compared with other conventional recording methods. Because it does not require developing and fixing, is maintenance-free, has a relatively inexpensive and compact device, and produces a very clear color, it can be used for computer output, facsimiles, calculators, measuring instruments, etc. Widely used as recorder paper and ticket paper for vending machines.

In recent years, one of the fields of application of the above-mentioned thermal recording has rapidly spread, and POS systems (Point
It can be used as a label with the increase in the number of sale. The heat-sensitive recording type labels used in these POS systems are mainly used for price display and bar code display of fresh foods and often come in contact with water, food wraps, oils, etc. For the purpose of preventing, for example, as shown in JP-A-57-188392, a protective layer is provided on the thermosensitive coloring layer, or a back layer or an under layer is provided to prevent the invasion of chemicals from the back side to improve the image stability. It has an enhanced structure.

The above-mentioned heat-sensitive recording label paper is, for example, in Japanese Utility Model Publication Sho 53-89.
As shown in No. 334, the back surface is adhesively processed with a release paper having a pressure-sensitive adhesive layer on the back surface, and after the print processing is performed on the front surface as required, the label is printed by a punching machine having a rotary cutter or the like. Punched into shape.

In recent years, in the above-mentioned processing step, particularly in the punching step, attempts have been made to increase the punching speed of the label paper in order to improve the productivity, and also an attempt to shorten the width of punching scraps called skeletons at the time of punching and improve the yield. Has been done. However, the rationalization of this punching process increases the mechanical impact force on the skeleton during punching, which makes it easier for the skeleton to break, which makes it difficult to remove the skeleton from the label, so-called scrap lifting, and conversely reduces productivity. It is the cause.

On the other hand, among the characteristics required for a label, the recording characteristics such as a bar code printer tend to be compact and energy saving, so that it is possible to obtain high density color development with low energy, that is, high The demand for higher sensitivity is increasing. However, as is clear from the layer structure of the thermosensitive recording label paper, the protective layer on the thermosensitive coloring layer impairs the heat transfer efficiency, and thus it is a very difficult proposition to increase the sensitivity. In order to increase the sensitivity, various proposals have been made to increase the recording sensitivity by studying materials such as leuco dyes, developers and sensitizers used in the thermosensitive coloring layer. However, there is an undeniable decrease in heat transfer efficiency due to the protective layer, and as a method of increasing the recording sensitivity in the heat-sensitive recording label paper, the heat energy applied from the heat-sensitive head should be used as effectively as possible. It is considered important to take a method of improving the adhesiveness of the surface of the recordable label paper.

As means for improving the adhesion with the thermal head,
For example, in Japanese Examined Patent Publication No. 52-20142, the surface of thermosensitive recording paper with a Beck smoothness of 20 with a super calender method is used.
The method of surface treatment is stored for 0 to 1000 seconds. Further, in JP-A-61-179786, in order to improve the adhesion to the head, the support contains 10% or more of a pigment, and
The internal binding force measured according to RC-308 is 0.5 to 2.5 kg-c
It is stated that it is set to m. That is, a method has been proposed in which a support having a weak internal bonding force is used to increase flexibility, improve adhesion to a head, and improve recording sensitivity. However, the above proposal describes a thermal recording material having a structure in which a thermosensitive coloring layer is provided only on a support, and like a thermosensitive recording label paper, a constitution in which a protective layer is provided on the coloring layer is used. It's not about things.

As described above, as a thermal recording type label paper, in recent years,
Despite the urgent need to simultaneously satisfy the two requirements of rapid improvement of processing characteristics and improvement of recording characteristics, the mechanical characteristics at the time of punching have not been examined, and the thermal recording type At present, no study has been made on means for improving the recording sensitivity in the label form, and therefore, a heat-sensitive recording label paper which satisfies the processing characteristics and the recording characteristics at the same time has not yet been developed.

<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned problems, and specifically, scraping failure does not occur during punching processing, that is, processing characteristics without cutting skeleton. The present invention relates to a heat-sensitive recording type label paper which is not only excellent but also has high heat sensitivity during heat-sensitive recording.

<Means for Solving the Problems> In the present invention, (1) a thermosensitive coloring layer containing a colorless or pale leuco dye and a developer as a main component and a protective layer are sequentially provided on the surface of a paper support, and the backside of the paper support is provided. The back layer is provided with a back layer, and the interlaminar strength (according to Tappi UM-403) of the laminate is larger than 2.5 kg-cm, and the Beck smoothness of the protective layer surface (according to JIS P8119) is large. Thermal recording label paper characterized by being 700 seconds or more, and (2)
An underlayer, a thermosensitive coloring layer containing a colorless or pale leuco dye and a color developer as a main component, and a protective layer were sequentially provided on a paper support to form a laminated structure, and the interlayer strength (Tappi UM-
The heat-sensitive recording label paper according to claim 1, wherein the protective layer has a Beck smoothness (according to JIS P8119) of 700 seconds or more.

First, the interlayer strength, which is a constituent feature of the present invention, will be described.

Conventionally, the mechanical properties of thermal recording type label paper, which have an influence on the skeleton breakage phenomenon during punching, include tensile breaking strength (JIS-P8113) and tear strength (JIS-P8116) that have been tested in paper-related fields. ). However, as a result of diligent research by the inventors of the present invention with respect to an increase in punching speed in recent years and an increase in punching failure phenomenon due to a decrease in skeleton width, as a result of the above-mentioned skeleton breakthrough phenomenon and tensile rupture strength and tear strength, It was found that this skeleton breaking phenomenon was basically due to the weak interphase strength of the thermosensitive recording type label, which had no correlation with the mechanical properties. This is because the rupture phenomenon is not fundamentally related to the tensile strength in the vertical and horizontal directions of the label paper or the strength when tearing the label paper, and the rupture phenomenon is the impact applied in the thickness direction of the label paper during punching. It means that it must be regarded as a mechanical behavior against force, and due to the impact force in the thickness direction that occurs when the skeleton is peeled off from the release paper immediately after punching, a crack is generated between the layers of the skeleton and the skeleton is formed in this crack part. It can be analyzed that breakage occurs due to the concentration of the winding tensile stress. That is, the present inventor has clarified that the interlaminar strength of the thermosensitive recording label paper is an important mechanical property value in order to improve the punching property.

As the method for measuring the interlaminar strength, it is most effective to evaluate using the internal bond tester described in Tappi-UM403, and in order to perform punching work without problems regardless of the punching speed or the width of the skeleton. Found that it is necessary to increase the interlaminar strength of the laminate constituting the thermosensitive recording label paper to exceed 2.5 kg-cm.

In order to increase the interlaminar strength above 2.5 kg-cm, it is first necessary to make the interlaminar strength of the support paper 2.5 kg-cm or more. Furthermore, since the cohesive failure strength between the layers of the coating layer itself and the adhesive strength between the coating layer and the support also affect the interlayer strength, the interlayer strength of the heat-sensitive recording label paper itself is increased beyond 2.5 kg-cm. That is an absolute requirement.

The paper used as the support in the present invention is not limited to the type and composition of the pulp, additives, etc., but the type and composition of the pulp, and the beating conditions such that the paper interlaminar strength is 2.5 kg-cm or more. Those produced by appropriately selecting the type and amount of the paper-strengthening agent, the wet pressing conditions, the drying conditions, and the like are applied.

Further, the interlayer strength of the coating layer itself and the adhesive strength with the support are aimed by using a binder as described below used for each coating layer by appropriately selecting the type and amount thereof. The interlayer strength of the label paper can be obtained.

Next, the smoothness, which is another component of the present invention, will be described.

As described above, in the present invention, the paper interlaminar strength is 2.5k.
Although it is a necessary condition to use a paper support with g-cm or more, the use of such a support is disclosed in JP-A-61-19797.
As described in No. 86, since the recording paper lacks flexibility, the matching property with the thermal head becomes poor and the recording characteristics deteriorate.

As a result of diligent study on the deterioration of the recording characteristics, the present invention shows that in a thermosensitive recording type label paper having an interlaminar strength exceeding 2.5 kg-cm, the Beck smoothness of the protective layer surface measured according to JIS P8119 is 700. More than a second, preferably 1000
It was found that the recording characteristics were sufficiently satisfied by processing for more than 2 seconds.

In order to produce such a thermal recording type label paper having a smoothness of 700 seconds or more, for example, using a super calender, a machine calender or a gloss calender, the protective layer coated surface is passed through so as to come into contact with a metal nip roll. It can be done on paper. However, since stronger surface treatment is required as compared with the smoothing treatment of general thermal recording paper, it is important to appropriately set various conditions such as paper moisture, roll pressure, treatment temperature, and treatment speed.

For example, regarding the moisture value of the paper among the above processing conditions, it is preferable to set the moisture content of the thermosensitive recording label paper to 7 to 10% before the smoothing treatment, whereby the smoothing treatment can be easily achieved. it can.

That is, if the water content is less than 7%, a very high nip pressure is required to obtain the desired smoothness, and a plurality of nip treatments are required, resulting in a slight decrease in productivity. On the other hand, if the water content exceeds 10%, the coating layer may be transferred to the nip roll during smoothing treatment depending on the surface treatment conditions and the material of the surface layer, which may stain the roll or protect it in the wound state. It is not preferable because the layer may adhere to the back surface, which may cause a so-called blocking phenomenon, which may cause a trouble in production.

The water content value as described above can be adjusted to a predetermined value by weakening the drying conditions at the time of coating or by passing it through a humidity controller before the smoothing treatment.

The heat-sensitive color forming layer of the heat-sensitive recording type label paper of the present invention contains a colorless or light-colored leuco dye developer.
Typical leuco dyes used are crystal violet lactone, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-.
Chlorofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-pyrrolidino-6-methyl-7-
Anilinofluorane, 3-piperidino-6-methyl-7
-Anilinofluorane, 3-cyclohexylmethylamino-6-methyl-7-anilinofluorane, 3-ethylisoamylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chloroanilino )
Fluoran, 3-dibutylamino-7- (o-chloroanilino) fluorane and the like are included, but are not limited thereto.

Further, as a color developer which reacts with the above leuco dye to develop color, α-naphthol, β-naphthol, 4-t-butylphenol, 4-t-octylphenol, 4-phenylphenol, 2,2-bis (p- Hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl)
Butane, 4,4'-cyclohexylidene diphenol, 2,2
-Bis (2,5-dibromo-4-hydroxyphenyl) propane, 4,4'-isopropylidenebis (2-t-butylphenol), 2,2'-methylenebis (4-chlorophenol), 4,4'- Sulfonyldiphenol, 4,4'-
There are derivatives such as thiobisphenol, 4,4′-thiobis (2-methylphenol), benzoic acid, salicylic acid, and gallic acid, but not limited to these.

Further, in the present invention, in order to improve recording sensitivity, various conventional heat-fusible substances may be added to the heat-sensitive color forming layer, if necessary. Examples of the heat-fusible substance include organic compounds having an appropriate melting point. Examples thereof include higher fatty acid amides such as stearic acid amide, animal waxes such as beeswax and shellac wax, vegetable waxes such as carnauba wax, and montan wax. Waxes such as mineral wax, paraffin wax, microcrystalline wax, etc., higher fatty acids, higher fatty acid esters, aromatic carboxylic acid esters such as dimethyl terephthalate, diphenyl phthalate, alkylnaphthalene derivatives, alkyl dipheniu derivatives, alkyl A terphenyl derivative or the like is used.

Further, in the present invention, inorganic and organic pigments as a conventional filler, for example, heavy and light calcium carbonate, aluminum hydroxide, titanium oxide, zinc oxide, barium sulfate, talc, clay, satin white, kaolinite,
The sharpness of the color image can be improved by adding polyolefin particles, polystyrene particles, urea-formalin resin particles and the like.

In addition, various kinds of surfactants, antifoaming agents, antioxidants, ultraviolet absorbers and the like can be added as required. Further, by using a binder for binding on the support, a thermosensitive coloring layer is formed. Examples of the binder include casein, gelatin, polyvinyl alcohol, polyvinylpyrrolidone, starch, modified starch, isobutylene-maleic anhydride resin, diisobutylene-maleic anhydride resin, styrene-maleic anhydride resin, polyacrylamide, modified polyacrylamide. , Carboxymethyl cellulose,
Methyl cellulose, hydroxyethyl cellulose, vinyl acetate, acrylic ester, vinyl chloride-vinyl acetate copolymer, emulsion such as SBR and NBR, latex, etc. may be used alone or in combination.

In preparation of the heat-sensitive color developing layer coating material, the leuco dye, the color developer, and the heat-fusible substance optionally added are pulverized by a media type wet disperser to prepare a dispersion liquid. At this time, it is desirable that the particle size of the leuco dye, the color developer and the heat-fusible substance, which are the materials to be dispersed, be 5 μm or less, preferably 3 μm or less. Further, it is preferable to add about 0.2% to 10% of a water-soluble polymer substance as a dispersant to water as the dispersion medium.

Since the protective layer, the back layer and the under layer are provided for the purpose of preventing chemicals from entering the thermosensitive coloring layer, it is basically necessary to use a polymer binder having good film-forming property as a main component. . As the polymer binder, basically, a water-soluble or water-insoluble resin binder which is a material used for the thermosensitive coloring layer can be used, but it does not allow the entry of lipophilic chemicals such as plasticizers and oils. For the purpose of prevention, water-soluble resins are preferable. However, since the water-soluble resin binder tends to have poor water resistance, when imparting water resistance, an emulsion, latex, or the like may be mixed with the water-soluble resin binder, or glyoxal, chrome alum, or melamine resin. , Melamine formaldehyde resin, polyamide resin, polyamide-epichlorohydrin resin and the like are preferably used after adding a waterproofing agent. Further, various surfactants and antifoaming agents can be added as necessary.

In addition to the above-mentioned film-forming polymer binder, the protective layer may be made of an inorganic or organic pigment, zinc stearate, calcium stearate, a lubricant such as a fluororesin, or the like, if necessary, in order to obtain matching with the thermal head. It is desirable to add a release agent.

Each layer having the composition as described above is formed by a known coating method such as air knife coating, roll coating, bar coating, or blade coating.
It is formed as a coating layer by sequentially applying a coating material to the front surface or the back surface of the support and drying it.

The layer structure of the heat-sensitive recording type label paper of the present invention is, as described above, a laminated structure in which a thermosensitive coloring layer and a protective layer are sequentially provided on the surface of the paper support and a back layer is provided on the back surface of the paper support, or a paper support. It is based on a laminated structure in which an under layer, a thermosensitive coloring layer, and a protective layer are sequentially provided on the body.For example, a back layer is provided on the back surface of the support, and an under layer, a thermosensitive coloring layer, and a protective layer are provided on the support surface. There is no problem if the back layer and the under layer are used in combination as in the laminated structure sequentially provided.

<Example> Next, the present invention will be described in detail with reference to Examples and Comparative Examples. In addition, all the parts showing the composition are parts by weight.

Using 80 parts of LBKP and 20 parts of NBKP, varying the beating degree with a beating machine, and changing the type and amount of sizing agent, band, paper strengthening agent, four types of A to D with different physical properties shown in Table-1. The paper support was made on a Fourdrinier paper machine. In Table 1, the weight is measured according to JIS P8124, the tensile strength is measured according to JIS P8113, and the tensile strength is measured according to JIS P8116.

A mixture having the following composition was dispersed using a sand mill to prepare dispersions [A] to [C].

[A] liquid [B] liquid [C] liquid Using the dispersion liquids of [A] to [C] obtained as described above, a thermosensitive coloring layer coating material having the following composition was prepared.

A paint having the following composition was prepared as the under layer or the back layer.

Furthermore, 30% is added to 100 parts of the under layer or back layer paint.
5 parts of zinc stearate dispersion liquid (Hydrin Z-7-30, manufactured by Chukyo Yushi Co., Ltd.) was added to prepare a coating material for the protective layer.

Using the paper supports A to D, the back layer coating material was applied and dried on the back surface so that the dry coating amount was 5 g / m ^2, and then the heat-sensitive coloring layer coating material and the protective layer coating material were each applied on the front surface in a dry coating amount of 7 g / m ^2.
They were sequentially applied and dried such that m ^2, 4g / m ^2. Further, this coated product was subjected to moisture conditioning so that the water content was 5 to 12%, and then smoothed with a super calender so that the surface of the protective layer was in contact with the metal roll. The heat-sensitive recording type label sheets of Comparative Examples 1 to 4 were manufactured.

Also, using paper supports A to D, an under layer, a thermosensitive coloring layer and a protective layer were respectively applied on the surface in a dry coating amount of 3 g / m ² , 7 g / m ² ,
The coated product was sequentially coated and dried to 4 g / m ^2, and the coated product was conditioned to a moisture content of 4 to 11%, and then smoothed in the same manner as in Examples 3 and 4 and Comparative Examples 5-8
A heat-sensitive recording label paper was produced.

The thermal recording type label paper of the obtained Examples and Comparative Examples was applied with a thermal printing device manufactured by Matsushita Electronic Components Co., Ltd.
/ Dot, pulse width 1.0 msec., Printing density was measured by Macbeth reflection dark clock RD-94, and recording sensitivity was evaluated.

Furthermore, the heat-sensitive recording type label papers of the examples and comparative examples were subjected to an adhesive processing with a ball tack number 4 adhesive force specified by JIS Z0237 after using an emulsion type adhesive as the release paper, and then at a speed of 70 m / min. A punching test was performed under the condition of a skeleton width of 3 mm.

Table 2 shows the results. In Comparative Examples 4 and 8, characteristics such as Beck's smoothness and interlayer strength could not be evaluated because coating dust adhered to the roll during super calender treatment and blocking occurred during winding. Also table-
In the evaluation of the punching characteristics in No. 2, the skeleton was cut during the punching process and normal punching work could not be continued.

As can be seen from Table-2, the heat-sensitive recording type label paper of the present invention has not only good punching characteristics but also excellent recording characteristics.

<Effects of the Invention> The heat-sensitive recording label paper of the present invention has excellent performance satisfying processing characteristics and recording characteristics at the same time.
Therefore, there is an effect that excellent productivity can be obtained without sacrificing recording characteristics.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-16185 (JP, A) JP 49-60744 (JP, A) JP 61-179786 (JP, A)

Claims (2)

(57) [Claims] 1. A laminated structure in which a thermosensitive coloring layer mainly composed of a colorless or light-colored leuco dye and a color developer and a protective layer are sequentially provided on the surface of a paper support, and a back layer is provided on the back surface of the paper support.
The interlayer strength of the laminate (according to TappiUM-403) is 2.5 kg.
A thermosensitive recording label paper which is larger than -cm and has a Bekk smoothness (according to JIS P8119) of the protective layer surface of 700 seconds or more. 2. An underlayer, a thermosensitive color-developing layer containing a colorless or pale leuco dye and a color developer as a main component, and a protective layer are sequentially provided on a paper support, and the interlayer strength of the laminate ( A heat-sensitive recording label paper, characterized in that it has a large TappiUM-403) of more than 2.5 kg-cm and a Bekk smoothness (according to JIS P8119) of the protective layer surface of 700 seconds or more.