JPH0311916B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an antistatic screen gauze for printing, which is free from troubles such as ink streaks and splashes during printing and has excellent fiber-making properties. Screen gauze is a fabric used for screen printing and VDT screens, and is a fabric woven from monofilament fibers. The fibers used to make this screen gauze are mostly synthetic fibers such as polyamide and polyester, and a small amount of natural fibers such as silk are also used. For example, screen gauze made of polyamide fibers has good ink permeability, so it has beautiful edges and is used for general printing such as curved surface printing and halftone dot printing that take advantage of its moderate elongation. In addition, screen gauze made of polyester fibers has excellent dimensional stability, so it is used for delicate and precise printing such as printed wiring. However, the above-mentioned natural fibers and synthetic fibers used in conventional screen gauze generally have electrical insulating properties, but have the disadvantage of being electrostatically charged due to friction or the like. Therefore, even with screen gauze, problems occur during printing due to charging of the gauze. In other words, due to the electrification of the gauze,
Problems such as adhesion of dust and ink streaks and splashes occur when the plate separates, which are major drawbacks of screen printing. In order to prevent these electrostatic problems with gauze, measures such as (a) applying an antistatic agent and (b) using metal fibers have been taken. However, in the method (a) above, the effect is not only temporary;
This was not a good solution as it caused problems with ink permeability. In addition, in the method (b) above, although it has excellent electrical conductivity and has a remarkable effect on preventing static electricity, other fibers (natural fibers or synthetic fibers)
When used in combination with metallic fibers, they have poor passability during high-order processing during weaving, and when used alone, they lack the elasticity of natural fibers and synthetic fibers, and their ink retention is poor. Because of the poor quality, it is difficult to obtain a good screen gauze. Furthermore, as another solution, there is also known a method of using a synthetic fiber whose surface is coated with conductive metal powder or conductive carbon black fine powder mixed with resin. However, even in this method, conductive metal powder or conductive carbon black fine powder is exposed on the fiber surface, which makes it difficult to pass through high-order processing. There was a problem that the powder would fall off, and since the thickness of the fibers was uneven, there was a major drawback in that the opening, which was the lifeblood of screen gauze, varied. In order to overcome the drawbacks of such conventionally known methods, the present inventors have developed a screen that has excellent antistatic properties and is highly durable without impairing the excellent features of conventional screen gauze. The present invention was arrived at as a result of extensive research into screen gauze having electrical properties. That is, an object of the present invention is to provide an antistatic screen gauze for printing that does not have the drawbacks of the conventional screen gauze for printing described above, and that can prevent troubles such as ink splatters and splashes during printing. It is in. The antistatic screen gauze for printing of the present invention comprises a conductive thermoplastic synthetic polymer A containing conductive carbon black (hereinafter referred to as "conductive polymer A") and a non-conductive thermoplastic fiber-forming synthetic polymer. B (hereinafter,
A composite fiber consisting of a non-conductive polymer (hereinafter referred to as B), in which at least the surface layer of the fiber is made of the non-conductive polymer, and at a DC voltage of 1 kV.
A conductive composite fiber having a specific resistance of less than 10 ⁵ Ω・cm is used for the weft yarn, and the conductive composite fiber is uniformly distributed throughout the fabric, and the mixing ratio thereof is
It is characterized by being 0.5 to 25% by weight and having a frictional charging voltage of 2 _kV or less. Hereinafter, the conductive screen gauze of the present invention will be specifically explained. Conductive fibers containing conductive carbon black are generally produced by composite spinning a thermoplastic synthetic polymer containing conductive carbon black and a non-conductive thermoplastic fiber-forming synthetic polymer. Although it can be obtained as a composite fiber with electrical conductivity (for example, Japanese Patent Publication No. 52-31450, Japanese Patent Application Laid-Open No. 1983-1989)
1337, etc.), the composite form of the conductive composite fiber used in the screen gauze of the present invention is suitable for conductive fibers from the viewpoints of screen gauze performance, antistatic durability, and high-order processing passability during fiber manufacturing. It is undesirable for the polymer A to be exposed on the fiber surface. That is, it is necessary that the fiber surface be completely covered with the non-conductive synthetic polymer B containing no conductive carbon black. As long as the fiber surface layer is entirely made of the non-conductive polymer B, its composite form may be a core-sheath type such as double, triple, or quadruple, or a matrix dispersion type. Alternatively, it may be of a streak-like distributed type. The thermoplastic synthetic polymer in which the conductive carbon black is dispersed may be any extrudable synthetic polymer and does not particularly require fiber-forming properties. Suitable polymers include, for example, polyamides, polyesters, polyacrylics, polyethers, polyolefins and copolymers thereof. On the other hand, considering the strength of the conductive fibers and other fiber materials constituting the screen gauze, fiber-forming polymers that do not contain conductive carbon black are
Polyester or polyamide are most suitable. The polyester here refers to polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or polyesters containing these as main components, and ethylene glycol is used within a range (usually 10 mol% or less) that does not significantly affect the basic properties of polyester. , a small amount of a polymer diol such as butanediol and a dicarboxylic acid such as isophthalic acid or terephthalic acid may be copolymerized. Also,
A mixed polyester obtained by mixing one or more types of PET, PBT, or a polyester obtained by copolymerizing these with a small amount of a polyester-forming monomer may be used. In addition, polyamide is poly ε-capramide (nylon 6), polyhexamethylene adipamide (nylon 66), or polyamide containing these as main components, and is within a range that does not significantly affect the basic properties of polyamide (usually 10 (mol% or less) of a copolymerization component. Alternatively, a mixed polyamide obtained by mixing polyamide with a small amount of other polyamide may be used. Furthermore, in order to improve the light resistance and weather resistance of the filament, additives such as ultraviolet absorbers, oxidative decomposition inhibitors, and photodegradation inhibitors may be optionally added and contained. If necessary, a matting agent such as titanium oxide or kaolinite may also be added. As the conductive carbon black used in the present invention, known conductive carbon blacks such as
"Vulcan" C manufactured by Cabot Carbon Co., Ltd., "Continex" ISAF manufactured by Toyo Continental Carbon Co., Ltd., etc. can be used. Needless to say, the most important characteristic of the conductive composite fiber of the present invention is the conductivity of the filament, and the specific resistance of the filament is at least 10 ⁵
Must be smaller than Ω・cm. More preferably, it is 10 ⁴ Ω·cm or less. If fibers with a resistance of 10 ⁵ Ω·cm or more are used, sufficient antistatic properties cannot be obtained for the screen gauze. The specific resistance referred to here is calculated by cutting a thread made of conductive fibers deoiled with carbon tetrachloride to a total density of about 1000 denier into a length of 10 cm, and applying conductive resin to both ends to make an electrode. The resistance is measured when a DC voltage of 1000V is applied under the conditions of ℃ and 65%RH, and the value is converted to specific resistance (Ωcm). In addition, the mixing ratio of the conductive composite fibers in the screen gauze (versus the entire fabric) may be 0.5% by weight or more in order to obtain sufficient antistatic properties (2 kV or less, which will be described later). On the other hand, if the mixing ratio exceeds 25% by weight or if it is also used in warp yarns, the weavability of the screen gauze will deteriorate. The antistatic screen gauze of the present invention is woven in the same manner as ordinary screen gauze, using the conductive fibers as part of the weft threads. It is necessary that the conductive conjugate fibers are uniformly arranged throughout the fabric; if this arrangement is uneven, antistatic properties will occur, making the fabric unsuitable for use as a screen gauze. In order to uniformly arrange the conductive conjugate fibers, a method may be adopted in which m conductive conjugate fibers are arranged as weft threads for every n other fibers. (Here n,
m is a positive integer of 1 or more. ) The frictional charging voltage of the antistatic screen gauze of the present invention is:
In order to overcome the problems of dust adhesion and ink splashing and splashing caused by electrostatic charging of the gauze, which is the object of the present invention.
It needs to be 2kV or less. If the voltage exceeds 2kV, it is difficult to sufficiently prevent the above-mentioned problems due to charging. The frictional charging voltage of antistatic screen gauze is calculated by comparing the sample (screen gauze) and the target fabric (cotton plain weave Kanakin No. 3).
After leaving it in an atmosphere of 20℃ and 30%RH for more than 24 hours, attach the test fabric and the target fabric to a Kyoto University Kaken type rotary static tick tester in an atmosphere of 20℃ and 30%RH, and rotate the rotor ( 400 rpm) and measured the frictional charging voltage after 60 seconds. The antistatic screen gauze of the present invention can sufficiently prevent obstacles such as ink streaks and splashes during printing, has durable antistatic properties, and has excellent passability through high-order processing during weaving. It is useful as a screen gauze because it has excellent ink retention and permeability. This screen gauze is also useful as an electromagnetic wave absorbing screen such as a VDT screen. Next, the present invention will be further explained by examples. Example Polyester terephthalate with an intrinsic viscosity of 0.65 in orthochlorophenol was used as the sheath component, and polycapramide with a relative viscosity of 2.55 in 98% sulfuric acid at 25°C containing 35% by weight of conductive carbon black was used as the core component. Composite spinning was performed in a conventional manner and hot drawing was performed to obtain a 15 denier monofilament conductive composite fiber. The weight ratio of the non-conductive sheath and the conductive core was 95:5, resulting in a double core-sheath cross-sectional structure. The specific resistance of the obtained conductive composite fiber A is at a DC voltage of 1 kV.
It was 3.8×10 ³ Ω・cm. A 15-denier polyethylene terephthalate monofilamentro was used for the warp yarn, and the monofilamentro and the aforementioned conductive composite fiber A were mixed for the weft yarn as shown in Table 1.
The mesh screen gauze was woven in a conventional manner. Table 1 shows the mixing ratio of conductive composite fiber A in the weft yarn and the frictional charging voltage.

[Table] As can be seen from Table 1, the antistatic screen gauze of the present invention (invention Nos. 1 to 3) has excellent antistatic properties. In addition, when weaving screen gauze, its process passability is good at all levels shown in Table 1, and it is inferior to the No. 1 comparison (conventional screen gauze) in terms of textile physical properties. Nakatsuta. Invention No.
For screen gauze Nos. 1 to 3, during screen printing, there was no adhesion of dust due to electrostatic charge on the gauze, and no ink streaks or splashes occurred when the plate separated. Comparison No.
No. 1 caused the above-mentioned charging problem and was unsuitable as a screen gauze. Comparison No. 2 also shows slight ink streaks and splashes, and it can be said that a frictional charging voltage of 2 kV or less is required.

Claims (1)

[Scope of Claims] 1. A composite fiber consisting of a conductive thermoplastic synthetic polymer A containing conductive carbon black and a non-conductive thermoplastic fiber-forming synthetic polymer B, which comprises at least a fiber surface layer. consists of the non-conductive thermoplastic fiber-forming synthetic polymer B, and 1
A conductive composite fiber having a specific resistance of less than 10 ⁵ Ω·cm at a DC voltage of kV is used for the weft yarn;
The conductive composite fibers are uniformly distributed throughout the fabric,
And the mixing rate is 0.5 to 25% by weight,
and an antistatic screen gauze for printing, characterized by a frictional charging voltage of 2 _kV or less. 2. The antistatic screen gauze for printing according to claim 1, wherein the non-conductive thermoplastic fiber-forming synthetic polymer B is polyester. 3. The antistatic screen gauze for printing according to claim 1, wherein the non-conductive thermoplastic fiber-forming synthetic polymer B is polyamide.