JP4804518B2 - Polyester composite monofilament - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is suitable for an electromagnetic shielding screen, and more specifically, used for an electromagnetic shielding screen of a plasma display (PDP), and has excellent dimensional stability, weaving property, abrasion during weaving, and scum suppressing effect. It relates to monofilaments.

  Conventionally, as described in Patent Document 1, Patent Document 2, Patent Document 3, and the like, mesh fabrics using polyester monofilaments have been used as substitutes for inorganic fibers such as natural fibers and stainless steel for screen printing. Since these require printing accuracy such as electronic circuit printing, it is important that they have high mesh and high strength. In addition, even if the strength is high, the one using a copolyester having a flexible structure as a sheath component as in Patent Document 1 in consideration of weaving properties has become the mainstream.

Japanese Patent No. 2580816 JP-A-62-215013 JP-A-2-127513

These are all referred to high-strength and high-modulus monofilaments.Because of their high strength, when weaving, the fiber surface tends to be scraped off by wrinkles, or a lot of white powder scum is generated and cannot be used practically. There wasn't. (C rebound rate is high).
Furthermore, since stretching is performed at as high a stretching ratio as possible in order to achieve high strength, there are many problems such as the occurrence of pirn due to stress relaxation in the winding package and the generation of many lines in the mesh fabric. It was.

  As a measure for eliminating panning, for example, Patent Document 4 and Patent Document 5 improve the stretching method. However, none of them have been improved completely, and there are still many products with a high C reaction rate.

Japanese Patent Laid-Open No. 11-1000072

JP 2001-355123 A

  On the other hand, with the advancement of information technology in recent years, the demand for plasma displays (hereinafter referred to as PDPs) as industrial or home displays is increasing. As described in Non-Patent Document 1, a mesh plated with a conductive material is used between the plasma generation plate and the surface protection plate of the PDP in order to shield electromagnetic waves caused by plasma. In addition, as the mesh, a conductive material is printed on a transparent film in a grid pattern, and a metal monofilament or organic monofilament mesh fabric is sputter-deposited with nickel, copper or the like as described in Patent Document 6, and then conductive. There is a method of depositing carbon. The former can increase the aperture ratio of the mesh, but has the disadvantage that the electromagnetic wave shielding performance tends to be worse than that of the mesh fabric and the advantage that a light interference pattern (moire) is less likely to occur. The latter is characterized in that the electromagnetic wave shielding performance is good, but the aperture ratio is reduced and moire is likely to occur, but the image contrast is good. The aperture ratio of the mesh is required to be 50% or more in consideration of visible light transmittance. Therefore, it is required to use monofilaments with fineness. In addition, high strength performance such as screen printing is not required, but strength, elongation and flexibility that are stable during weaving and processing are required. Moreover, since it is a display use, it is absolutely necessary to avoid mixing of scum and fiber surface shavings. Monofilaments used for screen printing applications as described in Patent Documents 1 to 5 have high strength and low elongation, so they are poor in flexibility and scraped with scissors during weaving, and shavings are mixed into the mesh openings to lower the aperture ratio. There was a problem such as letting. In addition, the metal monofilament as in Patent Document 6 is not practical because of its high cost.

Katsuya Yasuo, Hitachi Chemical Technical Report NO. 33, 1999-7, p. 9-16

Japanese Patent No. 2892339

  In view of the problems of the prior art, the present inventors have an object to stably provide polyester monofilaments having physical properties and weaving properties suitable for PDP applications and the like.

  That is, (1) A mesh fabric has a large opening and a high A reaction rate in watermark inspection (no occurrence of fineness spots or white powder scum). (2) Fiber surface wear due to wrinkles during weaving In addition, a polyester monofilament suitable for PDP use that has a moderate elastic modulus and strength and is excellent in form stability when made into a mesh fabric is provided. For the purpose.

  As a result of intensive studies to solve the above problems, the present inventors have found the following and have reached the present invention. (1) The initial elastic modulus greatly contributes to maintaining the shape stability of the electromagnetic wave shielding screen and measures against breakage during the production of the mesh fabric. (2) Elongation at 2.5 cN / dtex greatly contributes to fiber surface wear due to wrinkles during weaving, countermeasures against scum generation, and countermeasures against punning.

  That is, the present invention is a polyester composite comprising a core-sheath type composite polyester having an initial elastic modulus of 80 to 100 cN / dtex and an elongation at a strength of 2.5 cN / dtex of 5 to 8%. The main point is monofilament. Moreover, the effect is further improved by using polyester obtained by copolymerizing polyethylene glycol as the sheath component.

  Since the composite monofilament of the present invention has the physical properties within the range of the present invention, there is no punning after winding of the monofilament, and the fiber surface is not scraped by wrinkles and no scum is generated when weaving the mesh fabric. For this reason, when a mesh fabric is made using the composite monofilament of the present invention, the light transmittance necessary for the screen for PDP can be obtained, and the product pass rate from the viewpoint that the shape stability performance is good. The conventional 30% could be improved to 90% or more. Moreover, the mesh fabric manufactured using the filament of the present invention has an appropriate elastic modulus and strength, is excellent in shape retention, and is suitable for PDP applications.

  The present invention is described in detail below. It is important that the monofilament of the present invention takes a core-sheath type composite form. The core-sheath type indicates a form in which the core component is completely covered with the sheath component and is not exposed on the surface, and the core-sheath component does not necessarily have to be arranged concentrically. The cross-sectional shape is not particularly limited, but a perfect circle is preferable in consideration of spinning, weaving stability, and aperture ratio.

  As the core component, it is preferable to use polyester mainly composed of polyethylene terephthalate. The intrinsic viscosity of the polyester is not particularly limited, but is preferably in the range of 0.65 to 0.75 from the viewpoint of spinnability and from the viewpoint of maintaining a high elastic modulus like the polyester monofilament of the present invention. Among them, it is preferable to use a polyester having a higher degree of polymerization than the sheath component polyester.

  As the sheath component, polyester mainly composed of polyethylene terephthalate is preferably used, but for the purpose of imparting flexibility to the monofilament, it is more preferable to use polyester copolymerized with polyethylene glycol. The molecular weight of the polyethylene glycol may be appropriately selected within a range in which it is easy to completely copolymerize in the molecular chain of the polyester, and a molecular weight of about 400 to 1000 is preferred. The copolymerization rate is not particularly limited, but is preferably about 3 to 7% in order to maintain the flexibility, elastic modulus, and strength of the monofilament. In addition, since polyester polymerized by the direct continuous polymerization method has few spots of polymer physical properties and the polymerizability in the fibers is uniform, it is effective for improving the abrasion resistance.

  The monofilament of the present invention preferably has a breaking elongation of 25 to 35% from the viewpoint of preventing frictional abrasion due to wrinkles on the filament surface during weaving, and has a breaking strength of 4 from the viewpoint of molding stability of the mesh fabric. It is preferably 5 to 6.0 cN / dtex. In addition, monofilaments for printing screen meshes suitable for precision printing applications such as IC substrate patterns are required to have a breaking strength exceeding 6.0 cN, so the breaking elongation is less than 25%, and the surface can be scraped by wrinkles. There are many.

Moreover, in addition to said structure, it is preferable that the ratio of a core component and a sheath component is 40: 60-70: 30. If it is 40:60 or more, it is easy to obtain a breaking strength suitable for PDP electromagnetic shielding screen applications, and if it is 70:30 or less, the effect of a flexible sheath component is exhibited, and the occurrence of friction scraping due to wrinkles during weaving It is preferable at the point which becomes easy to prevent.
In particular, the core component has a higher degree of polymerization than the sheath component, the core component has an intrinsic viscosity within the above range, and the sheath component is a copolymer of the third component, and the ratio of the core component to the sheath component is this. When it is within the range, it is easy to obtain a composite monofilament satisfying the initial elastic modulus and the elongation at a strength of 2.5 cN / dtex of the present invention.
If the ratio exceeds 70:30 as described in Patent Document 1, the monofilament becomes rigid and friction scraping due to wrinkles is likely to occur, and shavings tend to be mixed into the mesh fabric to reduce the mesh opening ratio. There is.

In the present invention, the initial elastic modulus of the composite monofilament needs to be 80 to 100 cN / dtex. Here, the initial elastic modulus is a point A in which a monofilament having an initial length of 200 mm is subjected to a tensile test at a strain rate of 100% / min, and after obtaining the SS curve of FIG. And the slope of point B are calculated by the following method.
Initial elastic modulus (cN / dtex) = (strength at point A−strength at point B) / [(elongation at point A−elongation at point B) / 100]
When the initial elastic modulus is less than 80 cN / dtex, the mesh fabric strength is weak and the shape retention is poor. When it exceeds 100 cN / dtex, the monofilament is hard and brittle, and there is a problem that the fiber surface is easily scraped by wrinkles during weaving.

Next, the SS curve of the composite monofilament in the present invention is preferably in the shape of the curve Y in FIG. 2 between the yield point Y1 and the yield point Y2.
That is, the SS curve of the composite monofilament in the present invention has two distinct inflection points, where Y1 is the first yield point with low elongation and Y2 is the second yield point with high elongation. It is preferable that the point Y2 has a convex shape below the line connecting the yield point Y1 and the yield point Y2 as shown by the curve Y in FIG. The curve between the first yield point Y1 and the second yield point Y2 is preferably a curve that has a convex shape in the direction of the elongation axis (downward in FIG. 2) than the straight line connecting Y1 and Y2. As shown in FIG. 2, in the present invention, it is important that the elongation at a strength of 2.5 cN / dtex is 5 to 8%.

Here, with reference to FIG. 2, the difference between the conventional monofilament and the thing of this invention is demonstrated. First, a conventional monofilament has a shape as indicated by a curve X in FIG. The present invention preferably takes a shape such as a curve Y.
Between the yield point Y1 and the yield point Y2, the elongation force of the amorphous chain in the fiber is expressed. In the case of the curve X, it is considered that the degree of orientation of the amorphous part is higher than that of the curve Y. The present inventors have found that if the molecular orientation of this part is high, punning is likely to occur during monofilament production, and fiber surface wear becomes severe due to wrinkles during weaving. That is, it is preferable that the degree of orientation of the molecules in the amorphous part is low, but this allows the molecules in the amorphous part in the filament to move freely to some extent even when tension is applied from the outside. As a result, since the filament itself can have flexibility and flexibility, it is considered that it is possible to prevent panning and scoring. In particular, in the present invention, attention was paid to the fact that the elongation at a strength of 2.5 cN / dtex greatly contributes to measures such as punning and shaving. When the elongation is less than 5% at a strength of 2.5 cN / dtex, even if the shape is convex below the line connecting the yield point Y1 and the yield point Y2 as in the curve Y, the fiber surface is caused by wrinkles during weaving The problem arises that the shaving increases. When the elongation exceeds 8%, the rate of occurrence of scraping by wrinkles is reduced, but the strength is low and the elongation is high, so the shape retention as a mesh fabric is poor.

  Furthermore, the SS curve of the composite monofilament has a convex shape below the line connecting the yield point Y1 and the yield point Y2 as shown by the curve Y in FIG. 2 between the yield point Y1 and the yield point Y2, and the strength 2 A composite filament having an SS curve as shown in FIG. 2 having an elongation at 5 cN / dtex of 5 to 8% is more preferable.

  As a specific method for obtaining the composite monofilament of the present invention, a conventionally known composite spinning method can be employed. That is, the polymers that respectively form the core component and the sheath component are melted independently, weighed, merged so as to take the core-sheath structure with the flow dividing plate at the mouthpiece, discharged from the same discharge hole, and the oil agent after cooling And so-called undrawn yarn is wound up. The undrawn yarn is drawn at a draw ratio at which the elongation becomes 30 + -3% (30 plus or minus 3%) in the drawing step. At this time, after drawing heat with a drawing roller, the film is drawn, led to a second roller at room temperature, and then heat-set while applying 3 to 6% overfeed with the third roller, and wound into a pan. The composite monofilament of the present invention can be obtained. This method is preferred because heat stress is set while the strain in the molecular chain due to stretching is relaxed, so that no panic generation occurs. Here, as described in Patent Document 4, what is important is a point different from a general method in which relaxation heat treatment is performed while overfeed is applied after stretching heat setting. Even if a relaxation heat treatment is performed after the stretching heat setting, the stress strain in the molecular chain is not eliminated, and as a result, there arises a problem that warp and weft muscles are generated by meshing the mesh fabric.

  Therefore, when producing the filament of the present invention, the core-sheath type composite polyester whose core component has a higher degree of polymerization than the sheath component is melt-spun, and then the obtained undrawn yarn is drawn after being given heat of drawing. It is preferable to use a method for producing a core-sheath type polyester composite monofilament by heat setting after setting to normal temperature and applying overfeed. At this time, it is preferable to use a polyester having an intrinsic viscosity of 0.65 to 0.75 as the core component and a polyester obtained by copolymerizing a third component such as polyethylene glycol as the sheath component. Furthermore, it is more preferable to melt-spin the ratio of the core component and the sheath component as 40:60 to 70:30.

  The fineness of the composite monofilament of the present invention is not particularly limited, but for use in PDP applications, the mesh opening ratio should be 50% or more, preferably 60% or more. For this purpose, the fineness is preferably 22 dtex or less, more preferably 10 dtex or less. Within this range, the image is not shielded, and it is possible to have good electromagnetic shielding properties after plating with a conductive material after weaving the mesh fabric. In addition, 2 dtex or more is preferable from the viewpoint of production and handling.

  The composite monofilament of the present invention is woven at a density of 110 to 150 mesh to form a mesh fabric. Thereafter, the surface is vapor-deposited with nickel and copper, and then vapor-deposited with conductive carbon. The obtained conductive mesh is introduced between the front transparent glass substrate and the back substrate of the PDP, and is installed between the front and back transparent substrates with a resin adhesive or the like. At this time, the mesh fabric is introduced with a certain bias angle to prevent moire. The electromagnetic wave shielding light-transmissive window material for PDP is formed by this method.

  Hereinafter, the present invention will be described in more detail by way of examples. The characteristic values in the following examples are measured by the following methods.

(1) Intrinsic viscosity Intrinsic viscosity [η] was measured by a conventional method at 20 ° C. in a mixed solvent of phenol / tetrachloroethane = 6/4.

(2) Using an initial elastic modulus autograph tensile tester (manufactured by Shimadzu Corporation), a tensile test was carried out until the fracture occurred at an initial length of 200 mm, a strain rate of 100% / min, and an initial load of 1/30 cN / dtex. The initial elastic modulus was calculated by the method described above.

(3) Elongation at a strength of 2.5 cN / dtex (hereinafter referred to as E2.5)
In the tensile test described above, the elongation at a strength of 2.5 cN / dtex was determined.

(4) Breaking strength and breaking elongation The breaking strength and breaking elongation were determined by the tensile test described above.

(5) Abrasion and scum generation due to wrinkles When weaving a 130 mesh mesh fabric using the composite monofilament, weigh whether the fiber surface is worn by wrinkles or whether white powder scum is generated. It was evaluated according to the following criteria whether the mesh fabric was inspected and whether white powder adhered to the ridges and healds.
◎: No wrinkle wear or scum generation ○: No warpage or scum generation after weaving 5000m in the warp direction △: Some wear or scum is observed ×: There is much wear or scum

(6) A reaction rate In the mesh weaving process, the A reaction rate of the mesh fabric is the result of watermark inspection of warp breakage, warp spots, loosening, etc. due to clogging of white powder scum or wrinkles due to wrinkles in the mesh fabric structure. The inspection specialist will give a score and make a decision. Among the mesh fabrics, those having an A reaction rate of 90% or more were accepted. Those having an A reaction rate of less than 90% cannot be put into the next vapor deposition step.

(7) Mesh fabric performance A A mesh fabric raised as an anti-spatter was sputter-deposited with a conductor such as nickel, copper and carbon to produce an electromagnetic wave screen for PDP. The mesh fabric has good shape retention and good opening and can be used for PDP. ◎, can be used but has a slight problem with opening, ○ and shape holding and opening are insufficient. △, the thing which cannot be used was evaluated as x.

(Examples 1-3, 5)
Polyethylene terephthalate polymer having an intrinsic viscosity of 0.688 is used as a core component, and a copolymer polyester obtained by copolymerizing 4.8% by weight of polyethylene glycol having an intrinsic viscosity of 0.668 and an average molecular weight of 600 is used as a sheath component. It was. The polyester is melt-metered so as to have a core-sheath ratio shown in Table 1, and a composite monofilament having a concentric core-sheath structure is discharged from a nozzle having a nozzle hole diameter of 0.45 mm. After cooling, an oil agent is applied at 1500 m / min. Once wound up. Next, the undrawn yarn was drawn at a draw ratio shown in Table 1 between a roller heated to 83 ° C. and a roller not heated, and then between a non-heated roller and a 130 ° C. heating plate. The overfeed (OF) described in No. 1 was applied to wind up the pan. In all cases, there was no panning, and the SS curve in the tensile test had the shape of curve Y in FIG. Further, the initial elastic modulus and the elongation at a strength of 2.5 cN / dtex were within the scope of the present invention as shown in Table 1. Next, when a 130-mesh mesh fabric was woven using the monofilament, the determinations shown in Table 1 were made, and both were useful for an electromagnetic wave shielding screen for PDP.

Example 4
A composite monofilament was produced in the same manner as in Example 1 except that polyester having an intrinsic viscosity of 0.637 was used as the sheath component polyester. Since the monofilament has a sheath component that is not a flexible copolyester, it has been slightly scraped by wrinkles, but can be used for mesh fabrics.

(Comparative Examples 1-4, 6-7)
When stretched under the conditions described in Table 1 in the same manner as in Example 1, Comparative Examples 1 and 5 had an initial elastic modulus or elongation at a strength of 2.5 cN / dtex outside the scope of the present invention. Occasionally, wear due to wrinkles was large and the A reaction rate was low. Comparative Example 2 was not attractive because there was no shaving due to wrinkles and the A modulus was high, but the elastic modulus was low, so the mesh fabric had no shape retention. In Comparative Example 3, the initial elastic modulus was too high, and the surface was scraped with a ridge during weaving, and the light transmittance was low due to the scum mixing. In Comparative Example 4, the initial elastic modulus was low and scum was not generated, but the shape stability when the mesh was formed was poor. In Comparative Example 6, since the initial elastic modulus and strength were high and the elongation was low, scraping due to wrinkles during weaving occurred frequently, and the weaving property was extremely poor. Although the comparative example 7 had a low core component ratio and good weaving properties, the elastic modulus and strength were low, and the shape stability of the mesh fabric was poor.

(Comparative Example 5)
A single monofilament using only polyester having an intrinsic viscosity of 0.688 was wound up at 1500 m / min. The stretching heating roller temperature was set to 85 ° C., stretching was performed with a 130 ° C. heating roller at the magnification shown in Table 1, and then 3% overfeed was applied to the 140 ° C. heating roller, followed by winding. The SS curve of the monofilament has the shape of curve X in FIG. 2. When a mesh fabric was made using the monofilament, surface scraping due to wrinkles occurred frequently, and the A reaction rate was extremely poor at 35%. .

It is the schematic diagram which showed the method of calculating the SS curve and the initial stage elasticity modulus in the tension test of the composite monofilament of this invention. It is a schematic diagram of the SS curve in the tensile test of the composite monofilament of the present invention.

Explanation of symbols

Y1 1st yield point Y2 2nd yield point Curve X SS curve of conventional monofilament Curve Y SS curve of the composite monofilament of the present invention

Claims (9)

A polyester composite monofilament composed of a core-sheath type composite polyester, having an initial elastic modulus of 80 to 100 cN / dtex and an elongation at a strength of 2.5 cN / dtex of 5 to 8% (however, initial elasticity The elongation at the rate and strength of 2.5 cN / dtex is in the tensile test at a strain rate of 100% / min). The SS curve of the composite monofilament has two yield points, and the curve between the first yield point Y1 and the second yield point Y2 has a convex shape below the straight line connecting Y1 and Y2. The polyester composite monofilament according to claim 1, which is a curve. The polyester composite monofilament according to claim 1 or 2, wherein the sheath component is a polyester copolymerized with polyethylene glycol. The polyester composite monofilament according to any one of claims 1 to 3, wherein the core component is a polyester having an intrinsic viscosity of 0.65 to 0.75. The polyester composite monofilament according to any one of claims 1 to 4, wherein the ratio of the core component to the sheath component is 40:60 to 70:30. A mesh fabric comprising the polyester composite monofilament according to any one of claims 1 to 5. A mesh fabric obtained by depositing the surface of the mesh fabric according to claim 6 with nickel or copper. An electromagnetic wave shielding mesh fabric comprising the mesh fabric according to claim 6 or 7. An electromagnetic wave shielding light-transmitting window material comprising the mesh fabric according to any one of claims 6 to 8.

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