JPH06128854A - Printing substrate - Google Patents

Abstract

PURPOSE:To obtain a printing substrate having the printing quality comparable to that of coated paper and high tear strength by forming an ink fixing layer capable of manifesting a specific surface roughness on one side of a nonwoven fabric composed of polyolefinic three-dimensional netlike fiber. CONSTITUTION:This printing substrate having high printing quality is obtained by subjecting a polyolefin (preferably polyethylene) three-dimensional netlike fiber nonwoven fabric to calendering, then coating at least one side thereof with preferably a carboxylated styrene-butadiene-based latex, subsequently drying the coated latex with hot air, then carrying out the water-resistant treatment and forming an ink fixing layer having 0.4-0.7 surface roughness (an SMD value measured with a KES(R) surface tester). This substrate has better ink receiving properties and a higher grade than those of a conventional nonwoven fabric.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing substrate made of a non-woven fabric excellent for printing, and more particularly to a printing substrate optimal for bar code printing, oil-based offset printing and the like.

[0002]

2. Description of the Related Art Printing technology on paper has started in letterpress printing, which was invented in the middle of the 15th century, and in the era of offset printing through gravure printing. In addition to paper, the printing base material is synthetic paper made of stretched film. Or, cloth or the like is used.
With regard to paper as a printing substrate, technological progress has been made in coated paper and art paper made of pulp, and satisfactory printability has been obtained, but the paper has drawbacks such as poor water resistance and insufficient tear strength. Can be a problem.

As a printing substrate having improved water resistance, synthetic papers made of polypropylene film, polyester film and the like containing an inorganic filler and stretched have been proposed. These synthetic papers have excellent water resistance but are stretched. Since the tear strength peculiar to the film is small, the film is easily torn, and there is a problem that the film is torn from the part particularly in the use such as a business form having a punch hole.

In recent years, various non-woven fabrics having water resistance and large tear strength have been put on the market. Nonwoven fabrics, especially long-fiber non-woven fabrics produced by the spunbond method and polyolefin non-woven fabrics produced by the flash-spinning method, have high tear strength and are therefore being used for this purpose. However, non-woven fabrics made by the spunbond method or by flash spinning are
Since there are fibers having a certain diameter on the surface, the surface always has unevenness. Therefore, when these non-woven fabrics are used for printing, it is impossible to eliminate the influence of the unevenness of the fibers, and uneven printing of the ink occurs due to surface unevenness at the time of barcode or oil-based offset printing.

Another problem is that the surface of the polyolefin nonwoven fabric is particularly poor in ink acceptability, so that ink acceptability is poor during bar code printing or oil-based offset printing.
There are points that do not get on the surface cleanly. As a countermeasure, in order to improve ink acceptability, a method of providing an ink fixing layer on the surface of a polyolefin three-dimensional reticulated fiber nonwoven fabric is disclosed in JP-A-3-234869.

Although the printing substrate provided with such an ink fixing layer certainly improves the ink acceptability, the quality after printing is not always good, and the surface of the printed substrate after printing has a polyolefin nonwoven fabric under the ink fixing layer. Since the surface of the ink-fixing layer is exposed to the surface irregularities, the surface of the base material becomes irregular after printing, and the quality of the printed product deteriorates.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of the prior art, and not only has good ink acceptability at the time of bar code or oil-based offset printing, but also the conventional paper. It is to provide an excellent printing base material having a printing quality equivalent to.

[0008]

As a result of various investigations in view of the above problems, the present inventors have found that good printing quality can be obtained by setting the surface roughness of a printing substrate to a specific value. The invention was reached. That is, in the present invention, an ink fixing layer is provided on at least one side of a polyolefin three-dimensional reticulated fiber nonwoven fabric, and the surface roughness of the ink fixing layer (SMD value measured by a KES surface tester) is 0.4 to.
It is a printing base material characterized by being 0.7.

The polyolefin three-dimensional reticulated fiber nonwoven fabric used in the present invention is a polyolefin non-woven fabric having a three-dimensional reticulated structure, and can be produced by using a normal polyolefin flash spinning technique. That is, the polyolefin three-dimensional reticulated fiber non-woven fabric used in the present invention is, for example, a three-dimensional polyolefin composed of a polyolefin polymer dissolved in a solvent under high temperature and high pressure, and then discharged into a low temperature and low pressure region while simultaneously flushing the solvent. And a polyolefin fiber fibrillated into a mesh,
Next, this fiber is deposited on a plate-like or mesh-like support, made into a web, and then heat-bonded by an embossing roll or a calender roll to produce the fiber.

At this time, a polyolefin three-dimensional reticulated fiber nonwoven fabric having various physical properties can be obtained by changing the thermal bonding conditions, and tearing as a nonwoven fabric is achieved by adjusting the temperature of the embossing roll or calender roll, the bonding pressure and the bonding time. The strength, tensile strength, and surface smoothness can be adjusted to some extent. Polyethylene, polypropylene and the like are used as the polyolefin used in the present invention, and polyethylene is preferable from the viewpoint of surface smoothness.

The basis weight of the polyolefin three-dimensional network fiber nonwoven fabric used in the present invention is preferably 40 to 100 g / m ² .
If the basis weight of the nonwoven fabric is less than 40 g / m ^2, it is difficult to uniformly provide the ink fixing layer due to poor dispersibility of the polyolefin three-dimensional network fiber nonwoven fabric, and the basis weight is 100 g / m ^2.
If it exceeds m ² , the overall thickness becomes too large. The surface roughness in the present invention is a value measured by a KES surface tester. The KES surface tester is a part of the KES-FB series designed to measure the texture of cloth,
This device measures the surface characteristics of cloth. This device has a calculation circuit capable of measuring the geometrical roughness of the cloth surface, the coefficient of friction and its variation. The surface roughness used in the present invention is KE
Among the values that can be measured by the S surface tester, the measured value of surface roughness using a contactor is used. In the present invention, the surface roughness uses an average value of three times of the background.

The non-woven fabric using the polyolefin three-dimensional reticulated fiber non-woven fabric has a surface roughness of about 1 to 1.5. When the non-woven fabric is provided with a fixing layer having good ink acceptability, the non-woven fabric is a base material. The surface roughness becomes smaller than that. That is, the surface becomes smooth. The ink fixing layer used in the present invention can be provided by using a known technique generally used in the paper industry. The ink fixing layer is usually obtained by applying a coating liquid mainly composed of a synthetic copolymer latex and a pigment with a blade coater, a roll coater, an air knife coater or the like. To make the surface smooth, it is particularly preferable to use a gate roll coater or a bar coater. Further, in order to make the surface smooth, it is possible to apply multiple layers.

Examples of the synthetic copolymer latex of the ink fixing layer used in the present invention include carboxylated styrene / butadiene latex, acrylic synthetic copolymer latex, vinyl acetate copolymer latex and saran copolymer latex. Can also be used. Particularly, when adhesive strength and water resistance are required, use of carboxylated styrene-butadiene latex is preferable.

The synthetic copolymer latex is preferably used in an amount of 10 to 40 parts by weight based on 100 parts by weight of the pigment. 10
If the amount is less than part by weight, the adhesive strength of the fixing layer becomes low. If it exceeds 40 parts by weight, the ink setting property particularly during printing obviously deteriorates, and a show-through phenomenon occurs during printing with an oil-based offset printing machine. As the pigment of the ink fixing layer used in the present invention, all the raw materials used in the ordinary paper coating field can be used. Examples of pigments include inorganic pigments such as clay, calcium carbonate, titanium oxide, and talc. In addition, it is preferable in the coating process to use a water-soluble binder at the same time. As the water-soluble binder, starch, casein, polyvinyl alcohol and the like which are usually used in paper coating can be used. In addition, for example, a dispersant, a defoaming agent, a lubricant, a water-proofing agent, a coloring agent, etc. can be used in combination and can be used as necessary.

When the polyolefin three-dimensional network fiber nonwoven fabric provided with the ink fixing layer of the present invention is used for printing, ordinary bar code printing, oil-based offset printing, gravure printing, flexographic printing, silk screen printing, etc. can be used. , Both can be handled in the same way as ordinary paper. However, since the ink fixing layer does not have the ability to retain the ink solvent, it is preferable to use a synthetic paper ink with a small amount of special ink solvent, especially in oil-based offset printing.

The printing substrate of the present invention needs to have an ink fixing layer on at least one side, and preferably has ink fixing layers on both sides. When the ink fixing layer is on one side, there is no problem in printing, but since the coating surface is on one side, the ink fixing layer has a two-layer structure, and the flatness as a printing substrate is impaired and curling easily occurs. When both sides of the ink fixing layer are provided, there is an advantage that curling does not easily occur, which is preferable.

If necessary, it is possible to provide a multi-layer coating layer having two or more layers on one side. In this case, it is preferable that the under layer is a barrier layer having a shielding effect against the solvent of the oil-based offset ink and the top layer is the ink fixing layer. When an ink fixing layer is provided on a non-woven fabric made of general three-dimensional reticulated fibers, the surface roughness measured by a KES surface tester is 1-1.
It is about 5, and at this level, the surface irregularities of the base material float on the surface after oil-based offset printing, which is not preferable.

The basis weight of the ink fixing layer used in the present invention is preferably 10 to 30 g / m ² per side. If it is less than 10 g / m ² , the ink fixing layer cannot be formed uniformly and the ink acceptability may be poor. Even if it exceeds 30 g / m ² , there is no problem in ink acceptability, but when forming the ink fixing layer, it becomes difficult to dry, so the coating speed decreases,
Productivity drops.

The polyolefin nonwoven fabric made of three-dimensional network fibers having a surface roughness of 0.4 to 0.7 according to the present invention has no conspicuous surface irregularity even after printing, and a print quality comparable to that of coated paper can be obtained. The polyolefin three-dimensional reticulated fiber nonwoven fabric constituting the present invention can be obtained by further calendering an ordinary thermally bonded nonwoven fabric. Calendering is normal metal
Combinations of metal rolls, metal-cotton rolls, metal-resin rolls and the like can be used. The calendered smooth non-woven fabric obtained from the combination of metal-metal rolls has a surface roughness of 0.5- by a KES surface tester.
It is about 0.9, and a printing substrate can be obtained by providing an ink fixing layer by a known method on the smooth nonwoven fabric obtained by this method.

In the case of a polyolefin three-dimensional reticulated fiber nonwoven fabric, if pressure is applied from above and below during calendering, the overall thickness decreases and distortion occurs. Therefore, the linear pressure of the metal roll is 30 to 100 kg / cm and the temperature is 30. ~ 80 ° C
It is preferable to process it to some degree. When an ink fixing layer is provided on a calendered polyolefin three-dimensional reticulated fiber nonwoven fabric, the surface roughness by a KES surface tester is 0.4 to
Must be 0.7.

When the surface roughness is less than 0.4, it is necessary to reduce the surface roughness of the polyolefin three-dimensional network fiber nonwoven fabric to 0.45 or less by calendering. When calendered, the surface roughness of the nonwoven fabric certainly lowers, but since distortion remains inside, when coating to provide an ink fixing layer and heating and drying, the distortion is released and the surface becomes uneven. It is not preferable because it is newly generated and the surface flatness is lowered.

Surface flatness, when viewed as a printing substrate,
For example, when base materials are stacked on a flat plate when performing oil-based offset printing, for example, the surface becomes uneven due to partial waviness rather than fine surface irregularities, making it difficult to feed the print. There is. The surface roughness is 0.
When it exceeds 7, the surface roughness after printing becomes conspicuous and the printing quality deteriorates, which is not preferable.

Further, since the printing substrate according to the present invention uses a non-woven fabric made of three-dimensional reticulated fibers as a substrate, it has a feature that it has a higher tear strength than general coated paper or synthetic paper made of a stretched film. . The tear strength varies depending on the thermal bonding conditions, but it is preferably at least 300 g or more. Especially when it is used for bar code printing or business form, punch holes are often punched, and it has a characteristic that it is less likely to tear than punch holes.

[0024]

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 sheet of the present invention will be described. Surface roughness is 20 cm x 20
Prepare a sample with a size of cm. As the tester, a KES-FB4 surface tester manufactured by Kato Tech (with an automatic calculation function) is used. The sample is set on the tester with a load of 400 g, and the contactor for surface roughness detection with a load of 10 g is brought into contact with the sample to start the device. The background of the sample was measured three times, and the average thereof was used as the surface roughness.

The surface quality after printing was evaluated by observing the solid-printed surface state using an RI tester with an oily ink of Tack 15 and setting 5 as the best and 1 as the lowest.

[0026]

Example 1 and Comparative Example 1 A web made of polyethylene three-dimensional reticulated fibers was used as a nonwoven fabric using Luxer H2040XW (trade name) manufactured by Asahi Kasei Kogyo Co., Ltd. In Example 1, a calender machine composed of metal-metal rolls was used. Calendered. The temperature of the metal roll is 40 ° C and the linear pressure is 40
It was processed at 6 m / min at kg / cm. Then, as Comparative Example 1, a polyolefin three-dimensional reticulated fiber non-woven fabric which was not calendered was used.

20g / m ^{2 was} coated on one side with a Meyer bar using the coating liquid having the composition shown below, and immediately at 105 ° C.
It was dried with hot air under the condition of 30 seconds. Then, water resistance treatment was performed using an aqueous solution of zinc sulfate and a supercalender at 60 ° C. Next, in order to evaluate the printability, an RI tester was used to perform solid printing using the oil-based ink of Tack 15, and the surface condition was observed. The results are shown in Table 1. In the printing substrate of the present invention, the surface is smooth even after printing and unevenness does not occur on the printed surface, whereas in the nonwoven fabric of Comparative Example 1, unevenness that is considered to be due to fiber aggregates on the surface. Occurred and the quality was degraded.

SBR latex (trade name: L-1622 manufactured by Asahi Chemical Industry Co., Ltd.) 20 parts Clay (trade name: UW-90 manufactured by EMC Co.) 70 parts Calcium carbonate (trade name: Brilliant 15 manufactured by Shiraishi Industry Co., Ltd.) 15 parts Titanium oxide (trade name: A-110, manufactured by Sakai Industry Co., Ltd.) 15 parts Casein (ammonia aqueous solution) 5 parts Dispersant: antifoaming agent 2 parts Total 127 parts

[0029]

[Table 1]

[0030]

Examples 2-3, Comparative Examples 2-3 Polyethylene three-dimensional reticulated fiber nonwoven fabric was used as a product of Asahi Kasei Kogyo Co., Ltd. under the trade name Luxer H2030XW, and the surface roughness was varied by changing the calendering temperature and linear pressure. A non-woven fabric was obtained. The same coating solution as in Example 1 was used to apply 15 g / m ² on both sides using a Meyer bar, and it was dried with a hot air dryer. The evaluation results are shown in Table 2.

[0031]

[Table 2]

[0032]

INDUSTRIAL APPLICABILITY The printing base material of the present invention has better ink acceptability in bar code and oil-based offset printing than a printing base material using a conventional non-woven fabric, and has a printing quality equivalent to that of conventional paper. It is an excellent printing sheet having

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Claims (1)

[Claims] 1. A printing substrate, wherein an ink fixing layer is provided on at least one surface of a polyolefin three-dimensional reticulated fiber nonwoven fabric, and the surface roughness of the ink fixing layer surface is 0.4 to 0.7. .