JPH08199467A - Nonwoven fabric used as substrate to bee coated and heat-sensitive recording material - Google Patents

Abstract

PURPOSE: To obtain a heat-sensitive recording material capable of carrying out precise printing such as bar code printing without any unevenness of color development by coating a nonwoven fabric having a specific surface roughness and a specified air permeability as a substrate to be coated with a recording liquid for heat-sensitive recording. CONSTITUTION: This nonwoven fabric is formed by carrying out the flash spinning of a high-density polyethylene, depositing the resultant fibers on a wire net, providing fibrillated reticulated fibers, then passing the formed fibers through heated embossing rollers and further treating the fibers by a felt calender. The resultant nonwoven fabric has a surface roughness of at least one surface within the range of 0.3-0.9 and an air permeability within the range of 10-1000sec/100cc. Furthermore, the heat-sensitive recording material is prepared by coating the nonwoven fabric as a substrate to be coated with a coating liquid for an undercoating layer, hot-air drying the coated liquid, then coating the prepared nonwoven fabric with a coating liquid for a heat- sensitive recording layer and subsequently hot-air drying the coated nonwoven fabric. The obtained heat-sensitive recording material has >=50sec surface smoothness and <=0.7 surface roughness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-woven fabric excellent as a support for coating, and more specifically, in heat-sensitive coating on a non-woven fabric, strike-through of the coating liquid hardly occurs, and it is smooth and has few defects. The present invention relates to a nonwoven fabric used as a substrate from which a heat-sensitive recording layer can be obtained. The present invention relates to a heat-sensitive recording material obtained by applying a heat-sensitive recording layer to this non-woven fabric, which is excellent in strength and water resistance, has no uneven coloring, and is capable of precise printing such as bar code printing. Is.

[0002]

2. Description of the Related Art Printing technology has started in letterpress printing, which was invented in the middle of the 15th century, and through gravure printing, has entered the age of offset printing. In addition to paper, synthetic paper made of synthetic resin-based stretched film, cloth, and the like are used as the printing substrate. With regard to paper as a printing substrate, technological progress has been made in the paper-making technology for coated paper and art paper made of pulp, and printability has been obtained that does not hinder the general process. Defects such as tearability may be a problem. As a printing base material having improved water resistance, synthetic paper made of polypropylene film, polyester film or the like containing an inorganic filler and stretched is proposed. However, although these synthetic papers are excellent in water resistance, they have a low tear strength peculiar to a stretched film and are therefore easily broken. In particular, in applications such as business forms that have punched holes, there is a drawback in that they will tear from the punched holes. In addition, there is a problem that when it is used for outdoor use, it needs to be reinforced with a vinyl chloride sheet, a fiber woven fabric or the like.

In recent years, various non-woven fabrics having water resistance and large tear strength have been put on the market as printing base materials to replace synthetic paper. In particular, long-fiber non-woven fabrics produced by the spunbond method and polyolefin non-woven fabrics produced by flash-spinning method have high tear strength, and thus have been proposed for this application. Recently, also in the use of thermal recording media, studies have been conducted to use a nonwoven fabric as a support from the viewpoint of strength and water resistance. However, since the surface of the spunbonded nonwoven fabric or the nonwoven fabric produced by flash spinning may have voids due to unevenness due to the fiber diameter or dispersion unevenness due to the manufacturing method, a heat-sensitive layer is coated on the nonwoven fabric. When processed, it has the problems that unevenness will occur on the surface of the heat-sensitive layer, and that the coating liquid will penetrate and strike through the pores, providing smoothness and uniformity suitable for printability. Moreover, a thermosensitive recording medium having a satisfactory non-woven fabric as a support has not been provided yet.

[0004]

The object of the present invention is to solve the above-mentioned problems of the prior art and to use it as a substrate to be coated which has a uniform color developability and enables precision printing such as bar code printing. Another object of the present invention is to provide a heat-sensitive recording material in which a heat-sensitive recording layer is formed on the nonwoven fabric and the improved non-woven fabric substrate.

[0005]

As a result of various investigations in view of the above problems, the present inventors have found that a specific surface roughness and air permeability can be obtained by joining fibers forming a non-woven fabric by a special method. It was found that a good heat-sensitive coating layer can be obtained by using such a nonwoven fabric, and the present invention was completed.

That is, in the present invention, a nonwoven fabric used as a support for coating, that is, a substrate to be coated has a surface roughness of at least one surface of 0.3 to 0.9 and an air permeability of 1
A thermoplastic non-woven fabric characterized by 0 to 1000 sec / 100 cc, and a coated thermosensitive recording layer having a smoothness of 50 sec or more and a surface roughness of 0.7 or less was applied to at least one surface of the non-woven fabric. It is a thermosensitive recording medium characterized by the above. The above-mentioned surface roughness, air permeability and smoothness are based on the measuring methods defined in the Examples section described later.

In the present invention, the non-woven fabric used as the substrate to be coated is preferably a long-fiber thermoplastic non-woven fabric excellent in water resistance and strength. More preferable non-woven fabrics include polyolefin non-woven fabrics having a three-dimensional network structure, multi-component spun-bonded non-woven fabrics such as polyethylene-polypropylene, and polyethylene terephthalate spun-bonded non-woven fabrics disclosed in Japanese Patent Publication No. 1-47588. These non-woven fabrics become non-woven fabrics having the surface roughness and air permeability of the present invention by joining fibers together.

The air permeability of the non-woven fabric used as the substrate to be coated is 10 to 1000 seconds / 100 cc, preferably 30 to
It is 100 seconds / 100cc. Non-woven fabric has air permeability of 10 seconds /
If it is less than 100 cc, the thermosensitive recording layer permeates and uniform coloring cannot be obtained, and the smoothness of the thermosensitive recording layer is lowered, so that the thermal head is hard to contact during printing, and a portion that does not develop color (hereinafter referred to as missing) This is more likely to occur. If the air permeability of the non-woven fabric exceeds 1000 seconds / 100 cc, the surface of the non-woven fabric becomes film-like and the tear strength is lowered, or the non-woven fabric becomes corrugated, which is not preferable.

The surface roughness of the non-woven fabric is 0.3-
It is 0.9, preferably 0.4 to 0.7. The non-woven fabric is
When the surface roughness is 0.9 or more, the unevenness of the non-woven fabric affects the surface state of the heat-sensitive recording layer, resulting in blank spots during printing or unevenness on the printed surface, which is preferable in terms of the quality of the printed matter. Absent. If the surface roughness is 0.3 or less, the nonwoven fabric becomes wavy, which is not preferable.

The non-woven fabric as the substrate to be coated of the present invention has an air permeability of 10 seconds or more and has a very dense surface, so that the coating liquid hardly penetrates and is smooth. As compared with the method of applying to a normal non-woven fabric or woven fabric, there is almost no need for a sealing layer, and the surface as a heat-sensitive recording material is smooth, so that uneven coloring and blanking during printing are very small. Also,
The nonwoven fabric of the present invention is preferably one that has been subjected to corona treatment or electron beam treatment in order to improve adhesiveness,
A fiber treatment agent such as an antistatic agent, a water repellent, and an anti-scratch agent may be added.

Next, the method for producing the non-woven fabric for a substrate to be coated of the present invention will be described. Here, the flash-spun nonwoven fabric will be described in detail, but the nonwoven fabric of the present invention is not limited thereto. The flash-spun nonwoven fabric used in the present invention can be manufactured by using a normal polyolefin flash-spinning technique. Flash-spun nonwoven fabrics are, for example, three-dimensional, reticulated fibrillated polyolefin fibers made of polyolefin by dissolving a polyolefin polymer in a solvent at high temperature and high pressure, and then discharging the solvent at low temperature and low pressure while simultaneously flashing the solvent. Then, the fiber can be obtained by placing the fiber on a plate-like or net-like support, forming a web, and then thermally bonding the fibers with an embossing roll or a felt calender. At this time, a polyolefin nonwoven fabric having various physical properties can be obtained by changing the thermal bonding conditions,
The surface roughness and air permeability can be adjusted to some extent by adjusting the temperature of the embossing roll or felt calender, the bonding pressure, and the bonding time.

However, in order to achieve the surface roughness and air permeability of the present invention, it is difficult to carry out the joining method using a usual calender roll or felt calender. For example, joining with a calender roll not only tends to result in insufficient strength, but also partially forms a film, which causes waviness in the nonwoven fabric and makes coating difficult. or,
When thermal bonding is performed using a felt calender, the pore size of the surface layer of the non-woven fabric becomes too large and the air permeability becomes 10 seconds / 100 cc or less, resulting in penetration of the coating liquid and strike-through.

The non-woven fabric used for the substrate to be coated of the present invention can be basically prepared by increasing the density of the constituent fibers before joining the fibers and then joining the fibers. Non-woven fabric by joining the first stage with a calender roll or embossing roll to a web porosity of 50 to 80%, smoothing the surface, increasing the fiber density, and then joining with a felt calender. It has been found that the diameter of the pores of No. 1 becomes smaller and the air permeability can be made 10 seconds / 100 cc or more.

For example, in the case of a polyethylene web having a basis weight of 50 to 70 g / m ² obtained by the flash spinning method, it is at least once between a rubber roll having a rubber hardness of 90 ° or more and a smooth metal roll heated to 135 ° C. or more. With a linear pressure of 50 kg / cm2, the porosity is 60-8.
A 0% temporary bond resistance is obtained. The surface roughness is 0.3 to 0.7 and air permeability is obtained by secondarily bonding the temporary bonding cloth with a felt calender at a heating temperature of 132 to 142 ° C. and a contact time of 1 to 10 seconds. The degree can be 10 seconds / 100cc or more. Further, this nonwoven fabric has a tear strength about 10 times that of the film-based synthetic paper having the same weight.

Also for the spunbonded nonwoven fabric, the nonwoven fabric of the present invention can be obtained by selecting the type of calender roll and the heat and pressure conditions. The basis weight of the nonwoven fabric used for these substrates to be coated is preferably 30 g / m ² or more. When it is 30 g / m ² or less, a part where the air permeability is less than 10 seconds / 100 cc tends to be included.

Next, a thermal recording material using the above-mentioned nonwoven fabric as a substrate to be coated will be described in detail. The thermal recording medium
It is preferable to have an undercoat layer and a heat-sensitive recording layer on at least one surface of the nonwoven fabric. That is, as the thermal recording material, one or more undercoat layers containing a resin and / or a pigment as a main component are provided to improve the recording image quality, and the surface roughness of the undercoat layer is 0.7 or less. Is preferred. For that purpose, it is preferable that the surface tension of the undercoating agent made of a resin and / or a pigment is equal to or higher than the critical surface tension of the surface of the nonwoven fabric. For example, if the critical surface tension of the polyolefin non-woven fabric is 38 dyne / cm, a smooth undercoat layer can be obtained by adjusting the undercoating agent to 40 to 50 dyne / cm.

The coating amount of the undercoat layer after drying is 0.1 to 10 g / m ² , preferably 0.5 to 5 g / m ² .
It is desirable to set it to m ² . As the pigment used in the undercoat layer, known pigments such as kaolin, clay, talc, calcium carbonate, titanium oxide and aluminum hydroxide can be used, and the particle size is preferably 20 μm or less. As the resin used for the undercoat layer, starch,
Known resins such as casein, polyvinyl alcohol, gum arabic, acrylic acid ester copolymer, styrene acrylic acid copolymer, styrene butadiene copolymer, urea resin, ethylene vinyl acetate copolymer, and epoxy acrylate are used.

The heat-sensitive layer is a layer containing, as components, a color former and a color former that develops color by contacting the color former.
As a combination of these color-forming substances, a known combination method can be applied, and JP-B-41-14510,
The combination described in Japanese Patent Application Laid-Open No. H2-120081 is used. For example, in the combination of a basic dye and a coloring agent, a basic dye such as a triallylmethane dye, a spiro dye, a diphenyl dye, a thiazine dye, an aromatic carboxylic acid, an aromatic carboxylic acid and a polyvalent metal, And a coloring agent such as an organic acidic substance.

The heat-sensitive layer is a layer containing the above-mentioned color former and binder. The heat-sensitive layer may further contain an inorganic pigment, an ultraviolet absorber, a sensitizer, an anti-sticking agent, a defoaming agent or a dispersant as an auxiliary agent in the coating liquid. As the binder of the heat-sensitive layer, starch, casein, polyvinyl alcohol, gum arabic, acrylate copolymer, styrene-acrylic acid copolymer, styrene-butadiene copolymer, urea resin, ethylene vinyl acetate copolymer, etc. are used as the heat-sensitive layer. The total solid content of 3 to 30% by weight is preferable.
The coating amount of the heat sensitive layer is not particularly limited, but is preferably ^{2 to} 12 g / m ² , and more preferably 3 to 10 g.
/ M ² .

The method for forming the undercoat layer and the heat-sensitive layer is not particularly limited, and a conventional technique can be used. For example, using the nonwoven fabric of the present invention as a support, an appropriate coating device such as an air knife coater, a blade coater, a bar coater, or a gravure coater can be used for the coating liquid for the undercoat layer or the heat-sensitive layer. These coatings The heat-sensitive recording layer of the present invention has a surface roughness of 0.7.
It is below, and the smoothness is formed to be 50 seconds or more. When the surface roughness of the heat-sensitive recording layer is 0.7 or more, uneven coloring or missing is caused during printing. Further, if the smoothness is 50 seconds or less, the image quality may deteriorate. In order to improve the smoothness of the heat-sensitive recording layer, calendering may be performed at the stage of applying the undercoat layer or the heat-sensitive layer. A particularly preferable range of the heat-sensitive layer is that the surface roughness of the heat-sensitive recording layer is smaller than the surface roughness of the non-woven fabric support, which means that the recording layer is uniform, and uneven coloring during printing or No missing. An overcoat layer may be provided for the purpose of protecting the dry heat recording layer. Furthermore,
It is also possible to add various known techniques in the field of heat-sensitive recording materials such as adhesive processing.

[0021]

EXAMPLES The present invention will be described in detail below with reference to examples. Prior to the description of the examples, methods for measuring various physical properties of the nonwoven fabric and the thermal recording medium of the present invention will be described. (1) Surface Roughness Prepare a sample with a size of 20 cm × 20 cm from the base material. A KES-FB4 surface tester manufactured by Kato Tech (with an automatic calculation function) is used as the tester. 400 samples for testing
A load of 10 g is set and the contactor for detecting surface roughness applied with a load of 10 g is brought into contact with the sample to start the device. The background of the sample is measured three times, and the average thereof is used as the surface roughness. (2) Air Permeability This is the time taken for 100 cc of air to be measured by the Gurley Air Permeability Measuring Machine specified in JIS-P-8117. The unit of measurement is expressed in seconds. It shows that it is difficult to pass through and the pore size is small. (3) Beck's smoothness According to the Beck's smoothness test method defined by JIS-P-8119. The unit of measurement is expressed in seconds, and the larger the value, the smoother the surface. (4) Thermal printing test A thermal recording material is printed using a thermal paper color tester TH-PMD manufactured by Okura Electric Co., Ltd., and blanking and color uniformity during printing are visually evaluated.

◯: There is no missing in the printed portion and there is no uneven coloring. Δ: Partially missing. Or, there is slight color unevenness that can be visually recognized. Poor: Occurrence of missing spots on the printed part and overall scraping. Or, uneven coloring is conspicuous and the color is whitish. (5) Bar code printability A BC-8 type machine manufactured by Autonics was used as a printing machine, and a bar code reading test (N = 20) was carried out to determine whether or not the thermal recording material was actually printed.

◯: Bar code reading rate is 95% or more. Δ: Bar code reading rate is 70 to 90%. X: Bar code reading rate is 65% or less. (6) Unit weight and thickness According to JIS-L-1096 method, The measurement was performed. However, the load for measuring the thickness was 100 g / cm ² . (7) Porosity (%)

Example 1 A solvent composed of high-density polyethylene polymer (MI = 0.8) and Freon 11 was discharged from a nozzle at a low temperature and a low pressure area under high temperature and high pressure conditions to flush the solvent and deposit it in a wire mesh form. , Fibrillated reticulated fiber, and a silicone rubber roll with rubber hardness 70 °
Linear pressure 50kg / cm with a flat metal roll heated to 0 ℃
And press it with a silicone rubber roll with a hardness of 90 ° so that the metal roll surface faces the silicone rubber roll side.
The protrusion height is 0.04 mm and the protrusion area is 22%. The linear pattern pressure is 50 kg / cm with a grid pattern embossing roll to make the web porosity 70%, and then the felt calender at 135 ° C is used for one side. Both sides were treated with a contact time of 4 seconds each. Basis weight 57
A polyethylene nonwoven fabric having a g / m ² thickness of 0.17 mm and a porosity of 65% was obtained (nonwoven fabric A). The surface roughness (SMD) of the flat surface of the nonwoven fabric was 0.7.

Using the non-woven fabric A as a substrate to be coated, the coating amount for the undercoat layer described below has an adhesion amount of 2 g / m after drying.
² with a Mayer bar, and dry with a hot air dryer at 100 ° C for 1 minute. Then, the thermal recording layer coating liquid is dried with a Mayer bar so that the adhesion amount after drying is about 2 g / m ^2. The coating was applied and dried with a hot air dryer at 60 ° C. for 3 minutes to obtain a heat-sensitive recording material.

Composition of coating liquid for undercoat layer PVA 10% aqueous solution (trade name N-300: manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 50 parts calcium carbonate (trade name Brilliant # 1500: Shiraishi Industry Co., Ltd.) 25 parts water 25 parts for thermosensitive recording layer Preparation of coating liquid 90 parts of solution A and 90 parts of solution B, 30 parts of silicon oxide pigment (trade name Mizushikaru P-527: manufactured by Mizusawa Chemical Co., Ltd.), PVA
200 parts of a 10% aqueous solution was stirred and mixed to prepare a coating liquid for a heat-sensitive recording layer.

Composition of liquid A 3- (N-ethyl-N-isoamyl) amyl-6-methyl-7-phenylaminofluorane 10 parts 1,2-bis (phenoxy) ethane 25 parts Methylcellulose 5% aqueous solution 20 parts water 40 parts Composition of liquid B 4,4-isopropylidenediphenol 30 parts 5% aqueous solution of methylcellulose 40 parts Water 20 parts Evaluation of nonwoven fabric A as a substrate to be coated and evaluation results of a thermal recording medium using nonwoven fabric A are shown. Shown in 1. As is clear from Table 1, the non-woven fabric A causes penetration and strike-through during coating,
Moreover, since the surface of the obtained thermal recording material is smooth and the thickness of the recording layer is uniform, uneven coloring or missing is not caused, and it is a base material capable of precise printing such as bar coating printing. there were.

[Embodiment 2] Hole diameter: 0.25 mm, number of holes: 100
Discharge rate 850 g / min using 0 rectangular spinneret
Polyethylene terephthalate with an intrinsic viscosity of 0.75 is melted at a temperature of 290 ° C and is spun at a spinning speed of 390 by air sucker.
A web having a basis weight of 100 g / m ² was formed at 0 m / min.
This web (birefringence 0.062) was set to a temperature of 185 ° C for the upper metal roll and a temperature of 80 ° C for the lower paper roll using a pair of smooth rolls, and thermocompression bonding was performed on both sides at a linear pressure of 70 kg / cm. A polyethylene terephthalate nonwoven fabric having a thickness of 0.16 mm and a porosity of 45% was obtained (nonwoven fabric B). The surface roughness (SMD) of the non-woven fabric was 0.8.

Using the non-woven fabric B as the substrate to be coated, a thermosensitive recording medium was prepared under the same conditions as in Example 1, and the evaluation of the non-woven fabric B as the substrate to be coated and the thermosensitive recording medium using the non-woven fabric (B) The evaluation results of are shown in Table 1. As is clear from Table 1, the non-woven fabric B has no unevenness in color development because the heat-sensitive recording material obtained has a smooth surface and has a smooth surface and has a uniform recording layer thickness. It was a base material to be coated which could be printed accurately by bar coating or the like without causing any scratches.

[Example 3] The temperature of the upper metal roll and the temperature of the lower paper roll of the non-woven fabric A were set to 50 ° C and 30 ° C using a pair of smooth rolls, and thermocompression bonding was performed on both sides at a linear pressure of 70 kg / cm. A polyethylene nonwoven fabric having a thickness of 0.17 mm and a porosity of 61% was obtained (nonwoven fabric C). The surface roughness (SMD) of the non-woven fabric was 0.4.

Table 1 shows the evaluation results obtained by preparing and evaluating the heat-sensitive recording material by forming the heat-sensitive recording layer on the substrate to be coated with the nonwoven fabric C under the same method and conditions as in Example 1. The non-woven fabric C does not cause permeation or strike-through during coating, has a smooth surface, and the surface of the obtained thermosensitive recording medium is smooth and the recording layer has a uniform thickness, so that uneven coloring or lack of spots does not occur. It was a base material that could be printed with precision printing.

Example 4 After corona treatment was applied to one surface of the nonwoven fabric A, potassium 3-methoxybutyl phosphate was applied by a spray method so as to be 0.4% of the dry weight of the nonwoven fabric. A polyethylene nonwoven fabric having a half-life of 1.5 seconds as described in L-1092 was obtained (nonwoven fabric D).

A heat-sensitive recording material was prepared by coating the surface of the nonwoven fabric D with the heat-sensitive recording layer under the same method and conditions as in Example 1.
The evaluation results are shown in Table 1 together with the evaluation of the coated substrate of the nonwoven fabric D. The non-woven fabric D does not cause permeation or strike-through during coating and has a smooth surface, and the surface of the obtained thermosensitive recording medium is smooth and the recording layer has a uniform thickness, so that uneven coloring or lack of clearing does not occur, and bar coating It was a base material that could be printed with precision printing.

[Embodiment 5] A solvent composed of high-density polyethylene polymer (MI = 0.8) and Freon 11 was discharged from a nozzle to a low-temperature low-pressure region under high temperature and high pressure conditions to flush the solvent and deposit it in a wire mesh form. , Fibrillated reticulated fiber, and a silicone rubber roll with rubber hardness 95 °
Linear pressure 20kg / cm with a flat metal roll heated to 0 ℃
And press it with a silicone rubber roll with a hardness of 90 ° so that the metal roll surface faces the silicone rubber roll side.
The protrusion height is 0.04 mm, the protrusion surface is 22%, and the linear pattern embossing roll is applied at a linear pressure of 80 kg / cm to make the porosity of the web 65% and then with a felt calender at 132 ° C. Both sides were treated with a contact time of 5 seconds on each side. Basis weight 57
A polyethylene nonwoven fabric having a g / m ² thickness of 0.17 mm and a porosity of 65% was obtained (nonwoven fabric E). The surface roughness (SMD) of the flat surface of the nonwoven fabric was 0.3.

A heat-sensitive recording material was prepared by coating the heat-sensitive recording material using the nonwoven fabric E by the method described in Example 1. Table 1 shows the evaluation results of the non-woven fabric E as a substrate to be coated and the evaluation results of the thermal recording medium using the non-woven fabric E. As is clear from Table 1, the non-woven fabric E does not cause permeation or strike-through during coating, has a smooth surface, and has a smooth surface of the resulting thermosensitive recording medium and has a uniform recording layer thickness. It was a base material to be coated which could be printed accurately by bar coating or the like without causing any scratches.

[Comparative Example 1] A solvent consisting of high-density polyethylene polymer (MI = 0.8) and Freon 11 was discharged from a nozzle to a low-temperature low-pressure region under high temperature and high pressure conditions to flush the solvent and deposit it in a wire mesh form. After making fibrillated reticulated fiber, contact time is 5 with a felt calender at 138 ° C.
Both sides were processed in seconds. A polyethylene nonwoven fabric having a basis weight of 62 g / m ² thickness of 0.20 mm and a porosity of 67% was obtained (nonwoven fabric a).
The surface roughness (SMD) of the non-woven fabric was 1.2.

Using the non-woven fabric a as a substrate for coating, a heat-sensitive recording layer was formed on the surface under the same method and conditions as in Example 1 and evaluated. Table 1 shows the evaluation results of the base material to be coated of the non-woven fabric a and the thermosensitive recording medium made of the non-woven fabric a. As can be seen from Table 1, the non-woven fabric a has a large surface roughness of 1.2 and a low air permeability, so that the undercoat coating liquid permeates to the back face of the non-woven fabric and is used as a base material to be coated on the heat-sensitive recording layer. Was unsuitable.

[Comparative Example 2] The temperature of the upper metal roll and the temperature of the lower paper roll of the non-woven fabric a were set to 50 ° C and 30 ° C using a pair of smooth rolls, and thermocompression bonding was performed on both sides at a linear pressure of 70 kg / cm. A polyethylene nonwoven fabric having a thickness of 0.17 mm and a porosity of 61% was obtained (nonwoven fabric b). The surface roughness (SMD) of the non-woven fabric was 0.7.

Table 1 shows the results of evaluation and evaluation of a thermosensitive recording medium using the nonwoven fabric b under the same method and conditions as in Example 1. The nonwoven fabric b was unsuitable as a coating substrate for the heat-sensitive recording layer because the undercoat coating liquid penetrated to the back surface of the nonwoven fabric.

[Comparative Example 3] Pore diameter 0.25 mm, number of holes 100
Discharge rate 850 g / min using 0 rectangular spinneret
Polypropylene with a melting temperature of 190 ° C by air sucker at a spinning speed of 5000 m / min and a basis weight of 100 g / m ²
Formed a web of. This web was set to a temperature of 155 ℃ for the upper metal roll and a temperature of 80 ℃ for the lower paper roll using a pair of smooth rolls, and thermocompression bonding was performed on both sides at a linear pressure of 70 kg / cm to obtain a porosity of 0.18 mm. A 43% polypropylene nonwoven fabric was obtained (nonwoven fabric c). The surface roughness (SMD) of the non-woven fabric was 0.9.

Using the nonwoven fabric c, a thermal recording material was prepared by the same method and under the same conditions as in Example 1 and the performance was evaluated. Table 1 shows the evaluation results. The non-woven fabric c was a material that was completely unsuitable as a coating base material for the heat-sensitive recording layer because the undercoat coating liquid penetrated to the back surface of the non-woven fabric.

[Comparative Example 4] Pore diameter 0.25 mm, number of holes 100
Discharge rate 850 g / min using 0 rectangular spinneret
And polyethylene terephthalate with an intrinsic viscosity of 0.75 at a melting temperature of 290 ° C and a spinning speed of 500 by air sucker.
A web (birefringence index 0.097) having a basis weight of 100 g / m ² was formed at 0 m / min. This web is heated to a temperature of the upper metal embossing roll 155 using a pair of embossing rolls.
℃, the temperature of the lower rubber roll set to 30 ℃, linear pressure 70kg
Thermocompression bonding on one side at a thickness of 0.18 mm and porosity of 60
% Polyethylene terephthalate nonwoven fabric was obtained (nonwoven fabric d). The surface roughness (SMD) of the non-woven fabric was 2.5.

A heat-sensitive recording material was prepared using the nonwoven fabric d under the same method and conditions as in Example 1 and the evaluation results shown in Table 1 were obtained.
In this non-woven fabric, the coating liquid for undercoat escaped to the surface of the non-woven fabric, and a smooth thermosensitive recording medium could not be obtained.

[Comparative Example 5] A basis weight of 57 g / m ² and a thickness of 0.
A 18 mm Tyvek T1056D (trade name, manufactured by E. I. DuPont) (nonwoven fabric c) was used to prepare a dry heat recording medium under the same conditions and conditions as in Example 1, and the nonwoven fabric was used as a substrate to be coated. Was prepared. The surface roughness of this substrate is
At 1.3, the air permeability was large, and as contrasted with Table 1, it was not possible to obtain a heat-sensitive recording material having satisfactory smoothness and surface roughness.

[0045]

[Table 1]

[Examples 6 to 7 and Comparative Example 6] Using the thermoplastic nonwoven fabric (E) obtained above as a support, the undercoat layer coating solution was applied in various amounts to obtain a hot air dryer. After drying at 100 ° C for 1 minute at 100 ° C, apply the coating liquid for the thermal recording layer with a Mayer bar so that the adhesion amount after drying will be about 1 g / m ^2, and dry at 60 ° C for 3 minutes with a hot air dryer to obtain a thermal recording. Got the body

Table 2 shows the evaluation results of the non-woven fabric and the heat-sensitive recording material which became the support. Since the surface roughness of Example 6 of the present invention was low, both the thermal printing test and the bar code printability were excellent. In addition, since the surface roughness and Beck's smoothness of Example 7 are inferior to those of Example 6, the color printing was excellent even though there was slight color unevenness in the thermal printing test. On the other hand, in Comparative Example 6, due to the surface roughness and the smoothness of the surface outside the scope of the claims of the present application, uneven coloring was conspicuous and the bar code printability was poor.

[0048]

[Table 2]

[0049]

INDUSTRIAL APPLICABILITY The non-woven fabric having a specific surface roughness and air permeability of the present invention is excellent as a support for a thermosensitive recording medium, because the coating liquid at the time of thermosensitive coating does not penetrate and the surface is smooth. Further, the heat-sensitive recording material of the present invention is excellent in tear strength, water resistance and printability, and is unprecedented.

Claims (2)

[Claims] 1. A non-woven fabric used as a substrate to be coated, characterized in that at least one surface has a surface roughness of 0.3 to 0.9 and an air permeability of 10 to 1000 seconds / 100 cc. Thermoplastic non-woven fabric. 2. The surface roughness of at least one surface is 0.3 to.
A coating thermal recording layer having a surface smoothness of 50 seconds or more and a surface roughness of 0.7 or less is applied to at least one side of a nonwoven fabric having a permeability of 0.9 and an air permeability of 10 to 1000 seconds / 100 cc. A thermosensitive recording medium characterized in that