Core-sheath composite monofilament for screen gauze

Abstract

The problem to be solved by the invention is to provide a core-sheath composite monofilament for a screen gauze, the core-sheath composite monofilament having excellent abrasion resistance when woven into a high-definition mesh fabric and excellent anti-halation effects when forming a printing pattern on a screen without requiring a dyeing process. This core-sheath composite monofilament for a screen gauze satisfies requirements (a) to (c). (a) The reflectance in the entire region having an optical wavelength of 300 to 450 nm is 20.0% or less. (b) Only the core section contains a light-absorbing agent. (c) The breaking strength is between 7.0 cN / dtex and 9.0 cN / dtex.

Description

TECHNICAL FIELD

[0001] The present invention relates to a core-sheath composite monofilament for a screen gauze. Specifically, the present invention relates to a core-sheath composite monofilament for a screen gauze having an excellent halation preventing effect when a printing pattern is formed by exposure without dyeing the screen gauze.BACKGROUND ART

[0002] As a woven fabric for screen printing, a mesh woven fabric made of natural fibers such as silk or inorganic fibers such as stainless steel has been widely used as a screen gauze.

[0003] In recent years, synthetic fiber meshes excellent in flexibility, durability, and cost performance are preferably used. Among them, polyester monofilaments, which are excellent in dimensional stability, are highly suitable for screen applications and thus widely used.

[0004] In addition, in high-definition screen printing applications such as electrodes and wiring printing of electronic components, against the background of increasing demand for global clean energy such as multilayer ceramic capacitors and solar cells, growth expansion and rigorous demand for high definition printing are remarkable, and thus advancement of monofilaments for a screen gauze has been required.

[0005] A general plate-making process includes stretching and fixing a screen gauze prepared using a monofilament to a printing plate frame, scouring the screen gauze to remove unnecessary substances such as an oil agent attached to the monofilament, applying and drying an ultraviolet curable resin, and then exposing the screen gauze with ultraviolet rays having a wavelength of 300 to 450 nm in a state where a positive film in which a pattern to be printed is drawn in black is brought into close contact with the screen gauze.

[0006] The ultraviolet curable resin overlapping the pattern part of the positive film is not solidified, and the ultraviolet curable resin in the other part is exposed to ultraviolet rays and solidified by a photochemical reaction. Therefore, by washing the plate after the exposure with water, the ultraviolet curable resin in the pattern part of the positive film is washed away, thereby obtaining a negative film.

[0007] In screen printing, in order to perform more precise and fine printing, how to solidify the ultraviolet curable resin according to the pattern of the positive film is an important problem.

[0008] When the ultraviolet reflectance of the screen gauze is high, so-called halation, in which ultraviolet rays are irregularly reflected on the surface of the screen gauze and the pattern part not requiring exposure is exposed, occurs, and as a result, the printing accuracy is significantly deteriorated.

[0009] As a method for preventing this irregular reflection, a method of weaving monofilaments into a screen gauze and then dyeing the screen gauze is generally employed.

[0010] However, the light wavelength region of the ultraviolet curable resin or the ultraviolet irradiation lamp used in the plate-making process varies depending on the platemaking company in order to prevent irregular reflection.

[0011] Furthermore, dyes to be used for dyeing and color tone settings are also selectively used for each platemaking company, and thus the types of ultraviolet curable resins and dyes are enormous.

[0012] Moreover, in the dyeing process, discharge of waste liquid imposing a high environmental load is a serious problem in various places.

[0013] Under such circumstances, in order to eliminate the dyeing process of the screen gauze, various studies have been made on a spun-dyed monofilament for a screen gauze, which is colored by adding a pigment in the yarn-making process stage.

[0014] For example, Patent Document 1 discloses an invention in which the fiber cross section of a monofilament has a core-sheath composite structure, and a light-absorbing substance is contained in the core component.

[0015] Furthermore, Patent Document 2 discloses an invention of a polyester monofilament having a small fineness and a high strength for high-definition screen printing, in which an organic compound-based pigment is contained in the entire transverse cross-section of the fiber.PRIOR ART DOCUMENTSPATENT DOCUMENTS

[0016] Patent Document 1: International Publication No. 2005 / 118927 Patent Document 2: Japanese Patent Laid-open Publication No. 2022-144471 SUMMARY OF THE INVENTIONPROBLEMS TO BE SOLVED BY THE INVENTION

[0017] Patent Document 1 proposes that a light-absorbing agent is contained in a core component in a core-sheath composite monofilament. However, in order to prevent halation in a wide range of light wavelength regions of various types of ultraviolet curable resins and ultraviolet irradiation lamps, it is necessary to contain a higher concentration of the light-absorbing agent.

[0018] Furthermore, in order to obtain the strength of the monofilament necessary for the dimensional stability of the screen gauze, it has been necessary to draw the monofilament at a high ratio. However, the fiber surface of the monofilament, which contains the light-absorbing agent at a high concentration and is drawn at a high ratio, is easily scraped due to high orientation of the crystal structure, causing yarn breakage in the yarn-making process and the weaving process.

[0019] Furthermore, Patent Document 2 proposes that an organic compound-based pigment is contained in the entire fiber to suppress the reflectance at an ultraviolet light wavelength. However, the organic compound-based pigment is exposed on the fiber surface, and powdery scum colored in the yarn-making process or the weaving process is generated, which causes deterioration of yarn making properties and many defects of the screen gauze.

[0020] Therefore, an object of the present invention is to obtain a core-sheath composite monofilament for a screen gauze that eliminates a dyeing process of the screen gauze and has strength necessary for high-definition screen printing, by reducing the reflectance in the entire region of a light wavelength of 300 nm to 450 nm.SOLUTIONS TO THE PROBLEMS

[0021] In order to solve the above-mentioned problems, the present invention employs the following configurations. 1. A core-sheath composite monofilament for a screen gauze, satisfying the requirements (a) to (c): (a) a reflectance in the entire region of a light wavelength of 300 nm to 450 nm is 20.0% or less; (b) a light-absorbing agent is contained only in the core; and (c) a strength at break is 7.0 cN / dtex to 9.0 cN / dtex. 2. The core-sheath composite monofilament for a screen gauze according to the above 1, wherein a maximum reflectance in a region of a light wavelength of 300 nm to 450 nm is 1.3 times or less of an average reflectance. 3. The core-sheath composite monofilament for a screen gauze according to the above 1 or 2, wherein two or more types of light-absorbing agents having different absorption peaks at a light wavelength of 300 nm to 450 nm are contained only in the core, and a total content of the light-absorbing agents in the core is 0.1 wt% to 0.8 wt%. 4. The core-sheath composite monofilament for a screen gauze according to the above 1 or 2, containing a polyester. EFFECTS OF THE INVENTION

[0022] According to the present invention, it is possible to provide a core-sheath composite monofilament that eliminates a dyeing process of a screen gauze, exhibits an excellent halation preventing effect when a printing pattern is formed by exposure, and is suitable for high-definition screen printing.EMBODIMENTS OF THE INVENTION

[0023] The monofilament for a screen gauze of the present invention has a composite cross section composed of a core and a sheath.

[0024] The resin constituting the core and the sheath may be any melt-spinnable resin. Examples of the resin include polyolefins such as polyethylene and polypropylene, or modified polyolefins containing these as main components; polyamides such as nylon 6 and nylon 66, or modified polyamide copolymers containing these as main components; aromatic polyesters such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; aliphatic polyesters such as polylactic acid and polybutylene succinate; and copolymerized polyesters containing these as main components, polyarylate, polybenzazole, wholly aromatic polyesters, and wholly aromatic polyamides.

[0025] Among them, the resin used for the core is preferably a polyester mainly composed of polyethylene terephthalate (hereinafter, referred to as PET) from the viewpoint of dimensional stability and production cost.

[0026] PET is preferably a polyester containing terephthalic acid as a main acid component and ethylene glycol as a main glycol component, and having repeating units of ethylene terephthalate in an amount of 90 mol% or more.

[0027] The resin used for the core preferably does not contain a copolymerization component because the copolymerization component inhibits orientation of fibers, and a satisfactory original yarn strength for a high-definition screen printing application cannot be obtained in some cases.

[0028] In addition, titanium dioxide as a matting agent, fine silica or alumina particles as a lubricant, a hindered phenol derivative as an antioxidant, a flame retardant, an antistatic agent, and the like can be added to the resin as necessary.

[0029] Since the resin to be used for the core of the present invention is mainly responsible for the strength of the monofilament, the content of an additive of inorganic particles represented by titanium oxide to be added as a matting agent is preferably less than 0.6 wt%.

[0030] Meanwhile, the resin to be used for the sheath is preferably polyester mainly composed of PET.

[0031] PET is preferably a polyester containing terephthalic acid as a main acid component and ethylene glycol as a main glycol component, and having repeating units of ethylene terephthalate in an amount of 90 mol% or more.

[0032] Since the resin to be used for the sheath is mainly responsible for the abrasion resistance of the monofilament, it is preferable to add about 0.1 wt% to 0.5 wt% of inorganic particles represented by titanium oxide.

[0033] The transverse cross-section of the core-sheath composite monofilament of the present invention is preferably a round cross section from the viewpoint of uniformity of the opening of the screen gauze.

[0034] The core-sheath composite monofilament of the present invention also preferably has a core-sheath composite fiber structure in which the core is covered with the sheath and the core is disposed so as not to be exposed to the surface in the transverse cross-section of the fiber, and the core and the sheath are preferably disposed concentrically.

[0035] In addition, the composite volume ratio of the core to the sheath is 50 : 50 to 95 : 5 from the viewpoint of achieving both the scum suppressing effect by the sheath and the increase in strength by the core.

[0036] When the same type of resin is employed for the core and the sheath, the phenomenon of peeling at the composite interface hardly occurs, and thus the composite volume ratio is preferably 70 : 30 to 90 : 10.

[0037] When different types of resins are employed for the core and the sheath, the composite volume ratio is preferably 50 : 50 to 70 : 30 from the viewpoint of suppressing peeling at the composite interface and maintaining the strength of the monofilament.

[0038] In the core-sheath composite monofilament of the present invention, the reflectance in the entire region of a light wavelength of 300 nm to 450 nm is 20.0% or less, and more preferably 15.0% or less. The lower limit value is not particularly limited, but it is basically necessary to mix a large amount of pigment in order to lower the reflectance, and mixing of a large amount of pigment impairs the strength of the yarn. Therefore, it is necessary to set the reflectance in consideration of the required strength and reflectance of the yarn. When the photosensitive resin is cured with ultraviolet rays in the plate-making process, the photosensitive resin is usually irradiated with light having a light wavelength of 300 nm to 450 nm. Since the light wavelength region is selected by a platemaking company depending on compatibility with the ultraviolet curable resin, in order to prevent halation, it is important to suppress reflection against the entire region of the corresponding light wavelength. The reflectance is a reflectance measured at every 10 nm in a light wavelength range of 300 nm to 450 nm as described later. When the maximum value of the measured values is 20.0% or less, that is, when the reflectance of the entire region is 20.0% or less, reflection of ultraviolet light is suppressed, and a clear printing pattern can be obtained without occurrence of halation.

[0039] In addition, when the maximum reflectance which is the maximum value of the measured values of the reflectance is set to 1.3 times or less of the average reflectance which is the average value of the measured values of the reflectance, occurrence of halation can be suppressed.

[0040] In the present invention, the core-sheath composite monofilament contains a light-absorbing agent only in the core for the purpose of suppressing halation when a printing pattern is formed and reproducing the printing pattern with high definition with an ultraviolet curable resin.

[0041] When the core-sheath composite monofilament contains the light-absorbing agent in the sheath, the light-absorbing agent exposed on the fiber surface falls off in a powder form and emerges as powdery scum colored in the yarn-making process and the weaving process to induce yarn breakage. Therefore, the light-absorbing agent is not contained in the sheath.

[0042] The light-absorbing agent has an absorption peak specific to the light wavelength. When two or more types of light-absorbing agents having different absorption peaks at a light wavelength of 300 nm to 450 nm are contained in the core, uniform light absorption in a wide range of light wavelength becomes possible.

[0043] Moreover, since the total amount of the light-absorbing agent to be contained in order to achieve a reflectance of 20.0% or less in the entire region of a light wavelength of 300 nm to 450 nm is small as compared with the case of containing one type of light-absorbing agent, it is possible to suppress deterioration of the strength of the core-sheath composite monofilament. More preferably, when light-absorbing agents having absorption peaks different from each other by 50 nm or more in the light wavelength region are combined, light absorption in a wide range of light wavelength becomes possible, and the content of the light-absorbing agent can be reduced.

[0044] The total content of the light-absorbing agent in the core is preferably 0.1 wt% to 0.8 wt%. When the content is 0.1 wt% or more, a sufficient halation preventing effect can be obtained, and when the content is 0.8 wt% or less, a core-sheath composite monofilament having both sufficient strength and abrasion resistance for realizing precise and fine screen printing can be obtained. The total content of the light-absorbing agent in the core is more preferably 0.2 wt% to 0.4 wt%.

[0045] As the light-absorbing agent, a conventionally known light-absorbing agent that is well dispersed in a molten resin and enables coloring in the melt spinning stage can be used.

[0046] In general, a red or yellow warm-colored screen gauze is widely used because it has good ultraviolet absorbability from a high wavelength side of visible light. The light-absorbing agent of the present invention preferably exhibits a color tone similar to the warm color.

[0047] Examples of the warm color light-absorbing agent include organic pigments such as benzene azo-based condensed polycyclic pigments (monoazo, disazo, and the like), heterocyclic azo-based condensed polycyclic pigments (thiazole azo, benzothiazole azo, quinoline azo, pyridine azo, imidazole azo, thiophene azo, and the like), anthraquinone-based condensed polycyclic pigments, and isoindoline-based condensed polycyclic pigments; titanium oxide-based inorganic pigments having iron or aluminum as a ligand; and dyes such as indigoid dyes, triphenylmethane dyes, xanthene dyes, alizarin dyes, acridine dyes, and cyanine dyes.

[0048] In the screen printing, in order to improve the accuracy of the printing pattern, a method of increasing the tension for stretching the gauze to reduce the distance between the screen gauze and the printing target is generally adopted.

[0049] During stretching of the gauze, the strength per monofilament is improved in order to increase the tension.

[0050] Furthermore, the demand of the printing industry is severe, and the tension to be applied to the yarn is not always proportional to the fineness in the weaving process that requires a screen gauze having a high mesh and a small fineness, that is, a screen gauze having a high weave density. It is important that the strength per monofilament is high, and a higher strength at break is required as the monofilament becomes thinner accordingly.

[0051] The core-sheath composite monofilament of the present invention has a strength at break of 7.0 cN / dtex or more from the viewpoint of suppressing deterioration of weaving properties and occurrence of gauze elongation and obtaining high dimensional stability.

[0052] Meanwhile, the orientation and degree of crystallinity are required to be suppressed from the viewpoint of abrasion resistance. Therefore, the strength at break is preferably 9.0 cN / dtex or less and 8.8 cN / dtex or less.

[0053] The fineness of the core-sheath composite monofilament of the present invention is preferably 2.0 dtex to 10.0 dtex.

[0054] In the case of a high-mesh screen gauze of #420 or more (420 yarns per 2.54 cm) suitable for precision printing, the mesh grid space per yarn is very small. Therefore, when monofilaments having a fineness of more than 10 dtex are used, the opening (aperture) per grid is very small.

[0055] As a result, scum is easily generated due to the friction between the reed and the monofilament, and as a result, it becomes difficult to obtain a screen gauze of #420 or more.

[0056] Furthermore, the fineness is preferably 8.0 dtex or less for the screen gauze of #450 or more, and 6.0 dtex or less for the screen gauze of #500 or more.

[0057] The lower limit of the fineness is preferably 2.0 dtex or more from the viewpoint of weaving properties, particularly, running properties of the weft in a Sulzer loom.

[0058] In the present invention, the monofilament preferably has a strength at 5% elongation of 4.5 cN / dtex to 6.5 cN / dtex.

[0059] When the strength at 5% elongation is 4.5 cN / dtex or more, deterioration of elongation at the time of weaving and gauze elongation at the time of printing are less likely to occur, and high dimensional stability is obtained. When the strength at 5% elongation is 6.5 cN / dtex or less, fibrillation of crystal orientation of fibers is less likely to occur, so that abrasion resistance is likely to be improved.

[0060] As a method for melt-spinning the core-sheath composite monofilament for a screen gauze of the present invention, a conventionally known melt spinning method may be employed.

[0061] Examples of the melting method include a pressure melter method and an extruder method, but melting by an extruder method is preferable from the viewpoint of uniform melting and prevention of retention.

[0062] The resins of the core component and the sheath component are melted by separate melt extruders. The separately melted polymers are passed through respective pipelines, dispensed, and then fed to a spinneret pack. At this time, the pipeline passage time is preferably within 30 minutes from the viewpoint of preventing thermal degradation. Both polymers fed to the pack are merged in the above-described spinneret, combined into a core-sheath form, and discharged through the spinneret.

[0063] Thereafter, the core-sheath composite monofilament for a screen gauze of the present invention can be produced by a direct spinning-drawing method in which cooling and oiling are performed and drawing is subsequently performed without once winding.

[0064] The monofilament yarn can be once wound as an undrawn yarn in the spinning process, and then subjected to the drawing process again. However, a direct spinning-drawing method is preferable in which drawing is performed directly in connection with the spinning process from the viewpoint of reducing the guide through which the yarn passes in the production process to suppress the yarn from being scraped.

[0065] The drawing process is preferably multi-stage drawing using three or more pairs of rollers.

[0066] The temperature of the drawing roller before the final drawing roller in the multi-stage drawing is preferably 130°C or less, more preferably 110°C or less to suppress crystallization during drawing. The temperature of the final drawing roller is preferably 130°C or more, and more preferably 180°C or more. When the temperature of the final drawing roller is 130°C or less, it is difficult to control fiber surface orientation, and crystallization of fibers hardly proceeds, so that a high-strength polyester monofilament cannot be obtained. On the other hand, when the temperature of the final drawing roller exceeds 230°C, fusion is likely to occur in the final drawing roller, and yarn making properties are deteriorated, which is not preferable.

[0067] In the winding process, the yarn is wound in the form of a pirn or a cheese, whereby the core-sheath composite monofilament for a screen gauze of the present invention can be obtained.

[0068] Examples of the resin of the core component include various types of resins as described above, but polyester is preferable from the viewpoint of dimensional stability. Among them, PET is preferable from the viewpoint of cost and spinning operability. When the component of the core is PET, the intrinsic viscosity IV thereof is preferably 0.90 to 1.50. When the intrinsic viscosity IV is 0.90 or more, a core-sheath composite monofilament having both sufficient strength and elongation can be produced. The intrinsic viscosity IV is more preferably 0.95 or more. The upper limit of the intrinsic viscosity IV is preferably 1.50 or less from the viewpoint of ease of forming such as melt extrusion. The upper limit of the intrinsic viscosity IV is more preferably 1.30 or less in consideration of the production cost and the influence of decrease in the molecular weight caused by molecular chain breakage due to heat or shear force during the process.

[0069] Examples of the resin of the sheath component include various types of resins as described above, but it is preferably the same component as the resin of the core component from the viewpoint of peeling at the composite interface, polyester is preferable from the viewpoint of cost and spinning operability, and PET is more preferable.

[0070] When the resin component of the core and the sheath is PET, it is preferable that the intrinsic viscosity IV of PET of the sheath component is lower than the intrinsic viscosity IV of PET of the core component, and the difference in intrinsic viscosity IV is set to 0.20 to 1.00 from the viewpoint of obtaining good abrasion resistance and sufficient strength.

[0071] When the difference in intrinsic viscosity IV is 0.20 or more, the degree of orientation and the degree of crystallinity of PET of the sheath component, that is, PET molecular chains on the fiber surface can be suppressed, resulting in good abrasion resistance. Furthermore, since the sheath component bears a shear stress on an inner wall surface of a spinneret discharge hole of the melt spinning, a shear stress received by the core component is reduced. Accordingly, since the core component has a low degree of molecular chain orientation and is spun in a uniform state, the strength of the finally obtained monofilament is improved.

[0072] Meanwhile, in order for the monofilament to have high strength, the sheath component is also required to be appropriately oriented. Therefore, the original yarn strength is obtained by setting the difference in the intrinsic viscosity IV to 1.00 or less. A more preferred difference in intrinsic viscosity IV is 0.30 to 0.70.

[0073] As described above, the light-absorbing agent is contained only in the core component.

[0074] Examples of the method for adding the light-absorbing agent include a method in which pellets prepared by blending a light-absorbing agent in a meltable resin are melt-spun, and a method in which spinning is performed while high-concentration master pellets having a content of about 2 to 20 times a predetermined content and a normal resin are melt-kneaded and diluted.

[0075] In the latter case, the master pellets and normal resin pellets may be mixed in a state of a pellet and kneaded by a melt extruder, or may be separately melted by a melt extruder and then kneaded in a transportation pipeline of the molten polymer or a spinning pack. In any case, it is preferable to use a static mixer in order to ensure dispersion uniformity of the light-absorbing agent.EXAMPLES

[0076] The evaluations of Examples and Comparative Examples were measured by the following methods.(1) Fineness

[0077] Monofilaments were wound up into a 500-m skein, and a value obtained by multiplying the mass (g) of the skein by 20 was defined as the fineness.(2) Strength at break (cN / dtex), strength at 5% elongation (cN / dtex)

[0078] The strength at break and the strength at 5% elongation were measured according to JIS L1013 (2010) using Tensilon UCT-100 manufactured by ORIENTEC CO., LTD.(3) Intrinsic viscosity IV

[0079] Regarding ηr in the definition formula, in 10 mL of o-chlorophenol (hereinafter abbreviated as "OCP") having a purity of 98% or more at a temperature of 25°C, 0.8 g of a sample was dissolved. The relative viscosity ηr was determined according to the following formula using an Ostwald viscometer at a temperature of 25°C, and the intrinsic viscosity IV was calculated. ηr = η / η 0 = t × d / t 0 × d 0 Intrinsic viscosity IV = 0.0242 ηr + 0.2634 In the formula, η is the viscosity of a polymer solution, η0 is the viscosity of OCP, t is the dropping time of the solution (second), d is the density of the solution (g / cm 3< ), t0 is the dropping time of OCP (second), and d0 is the density of OCP (g / cm 3< ). (4) Abrasion resistance

[0080] The monofilament is fixed in air at a tension of 5 g, and one reed dent made of SUS (thickness: 65 µm) is pressed against the monofilament from above to fix the monofilament at an angle of 2° with respect to the horizontal. The reed dent is reciprocated in a range of 3.2 cm at a speed of 133 m / min with respect to the fiber axis direction, and the reciprocation is stopped after 20 seconds. The position rubbed with the reed dent was observed using VHX-D500 manufactured by KEYENCE CORPORATION, the abrasion state of the position was evaluated as follows in the SEM image, and ranks S and A were rated as passed.

[0081] S...There is no deformation or fluff scraping on the surface of the monofilament, and there is no problem.

[0082] A...Although there are thin streaks on the surface of the monofilament in the longitudinal direction of the fiber, there is no problem in quality.

[0083] B...There is fluff scraping on the surface of the monofilament.(5) Weaving properties

[0084] The presence or absence of a problem in the process of obtaining a screen gauze having a warp density and a weft density of 460 mesh (460 yarns / 2.54 cm) from monofilaments was evaluated as follows, and ranks S and A were rated as passed.

[0085] S...There is almost no fluff scraping or powdery scum, and there is no problem.

[0086] A...Although there are fluff scraping and powdery scum, there is no problem in quality.

[0087] B...There are significant fluff scraping and powdery scum.(6) Reflectance

[0088] A monofilament having a length of 10000 m was wound around a plate having a length of 6 cm and a width of 6 cm without any gap. The reflectance was measured at every 10 nm in a light wavelength range of 300 nm to 450 nm using a V750 spectrophotometer manufactured by JASCO Corporation in accordance with a photoengraving process (JIS Z8722:2009). The maximum value of the measured values of the reflectance was defined as the maximum reflectance, and the average of the measured values was defined as the average reflectance.(7) Absorption peak wavelength of pigment

[0089] A monofilament containing only one type of pigment and having a length of 10000 m was wound around a plate having a length of 6 cm and a width of 6 cm without any gap. The reflectance was measured every 5 nm in a light wavelength range of 300 nm to 500 nm using a V750 spectrophotometer manufactured by JASCO Corporation in accordance with a photoengraving process (JIS Z8722:2009). The wavelength at the minimum value of the measured values of the reflectance was defined as the absorption peak wavelength.(8) Halation

[0090] A fine pattern was printed on the screen gauze obtained in the same manner as described in the above (5), and the screen gauze was observed with an electron microscope for evaluation, and ranks S and A were rated as passed.

[0091] S...The halation preventing effect is great. There is almost no blur of the fine pattern, and there is no problem.

[0092] A...There is a halation preventing effect. There is blur of the fine pattern, but there is no problem in quality.

[0093] B...Halation occurs. The blur of the fine pattern is significant.(9) Printing accuracy

[0094] The screen gauze obtained in the same manner as described in (5) was stretched on a 30 cm × 30 cm printing plate frame. A 50 µm line pattern was formed on the obtained mesh woven fabric at intervals of 50 µm with a photosensitive emulsion, and the state after printing was observed and determined according to the following indices. Ranks S and A were rated as passed.

[0095] S...Line reproduction is favorable.

[0096] A... Irregularities are observed at the boundary of the line, but there is no problem.

[0097] B...The irregularities of the boundary of the line are severe, and the line is partially disconnected.(Example 1)

[0098] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 having an absorption peak at 450 nm and Pigment Brown 48 having an absorption peak at 300 nm were mixed therein at a ratio of 1 : 4. The mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the core.

[0099] As the component of the sheath, polyethylene terephthalate having an intrinsic viscosity IV of 0.50 and containing 0.4 wt% of titanium oxide was employed.

[0100] The polyester as the core component and the polyester as the sheath component were each melted at a temperature of 297°C using an extruder. Then, the core component and the sheath component were dispensed by pumping at a polymer temperature of 275 to 285°C so that the core-sheath volume ratio (core component to sheath component) was 80 : 20, and fed into a melt spinning pack. A yarn was spun by feeding the respective components into a known composite spinneret so as to form a core-sheath type structure. The polyester monofilament discharged from the spinneret was positively heated and kept at a certain temperature so that the ambient temperature immediately below the spinneret was 300°C. Thereafter, the polyester monofilament was cooled by a yarn cooling blower, and taken up by non-heated first godet rolls while applying a spinning oil agent. The polyester monofilament was taken over first hot rolls heated to a temperature of 90°C, second hot rolls heated to a temperature of 90°C, and third hot rolls heated to a temperature of 190°C without being wound up temporarily, so that the polyester monofilament was drawn and heat-set. The draw ratios of the second hot roll and the third hot roll were 4.90 times. Furthermore, the polyester monofilament was taken over two non-heated godet rolls having a surface roughness of 0.8 S, and then wound into a package while the winding tension was kept at 0.417 g / dtex by controlling the number of spindle revolutions to obtain a core-sheath composite monofilament having a fineness of 6.0 dtex. The characteristics of the core-sheath composite monofilament are as shown in Table 1. The maximum reflectance in a region of a light wavelength of 300 nm to 450 nm was 10.2%, that is, the reflectance in the entire region was 10.2% or less. Thus, excellent abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Examples 2 and 3)

[0101] Yarns were made and wound in the same manner as in Example 1 except that the draw ratios were 4.70 and 5.90 times. The characteristics of the core-sheath composite monofilaments are shown in Table 1. In Example 2, the printing accuracy was slightly deteriorated, and in Example 3, the abrasion resistance was slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Examples 4 and 5)

[0102] A core-sheath composite monofilament having a fineness of 3.1 dtex and a core-sheath composite monofilament having a fineness of 13.0 dtex were obtained in the same manner as in Example 1 except that the discharge amount was changed. The characteristics of the core-sheath composite monofilament are shown in Table 1. In Example 4, the weaving properties were slightly deteriorated, and in Example 5, the printing accuracy was slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Examples 6 and 7)

[0103] Yarns were made and wound in the same manner as in Example 1 except that the intrinsic viscosity IV of the polyethylene terephthalate pellets for the core component was each set to 1.50 and 0.90, and the draw ratio was changed to 5.20 times. The characteristics of the core-sheath composite monofilaments are as shown in Table 1. In Example 7, the abrasion resistance and the weaving properties were slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Example 8)

[0104] Yarns were made and wound in the same manner as in Example 1 except that the master pellets contained in the core component polyester and the polyethylene terephthalate pellets were blended at a ratio of 1 : 99, and the content of the light-absorbing agent was changed to 0.10 wt%. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 1. The halation preventing effect and the printing accuracy were slightly deteriorated, but sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Example 9)

[0105] Yarns were made and wound in the same manner as in Example 1 except that the master pellets contained in the core component polyester and the polyethylene terephthalate pellets were blended at a ratio of 7 : 93, and the content of the light-absorbing agent was changed to 0.70 wt%. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 1. The abrasion resistance and the weaving properties were slightly deteriorated, but sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Example 10)

[0106] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. A core-sheath composite polyester monofilament having a fineness of 6.0 dtex was obtained by making yarns in the same manner as in Example 1 except that the obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 8 : 92 using a blending apparatus, and 0.80 wt% of a light-absorbing agent was contained in the component of the core. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 1. All of the abrasion resistance, the weaving properties, and the printing accuracy were deteriorated, but the abrasion resistance and halation suppressing effect that can be employed for screen gauze applications were obtained.(Example 11)

[0107] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 20 wt% of Pigment Yellow 150 having an absorption peak at 450 nm, Pigment Brown 48 having an absorption peak at 300 nm, and Pigment Red 101 having an absorption peak at 390 nm were mixed therein at a ratio of 1 : 2 : 2. The mixture was supplied to a twin-screw kneading extruder to obtain master pellets. A core-sheath composite polyester monofilament having a fineness of 6.0 dtex was obtained by making yarns in the same manner as in Example 1 except that the obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 3 : 97 using a blending apparatus, 0.60 wt% of a light-absorbing agent was contained in the component of the core, and the draw ratio was set to 5.2 times. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 1, and an excellent abrasion resistance and halation suppressing effect for screen gauze applications were obtained. (Comparative example 1)

[0108] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 0.96 and containing 0.5 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the core.

[0109] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.50, containing 0.4 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 0.50 and containing 0.4 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the sheath.

[0110] The polyesters of the core component and the sheath component were made into yarns, and the yarns were wound in the same manner as in Example 1 to obtain a core-sheath composite monofilament having a fineness of 6.0 dtex. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 2, and a deterioration of the abrasion resistance, generation of colored powdery scum during weaving, and yarn breakage occurred.(Comparative example 2)

[0111] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 0.96 and containing 0.5 wt% of titanium oxide were blended at a ratio of 10 : 90 using a blending apparatus, and 1.00 wt% of a light-absorbing agent was contained in the component of the core. A core-sheath composite monofilament having a fineness of 6.0 dtex was obtained by making yarns and winding in the same manner as in Example 1 except that the draw ratio was 4.30 times. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 2, the strength was low, and sufficient accuracy in screen printing could not be obtained.(Comparative example 3)

[0112] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the core. A core-sheath composite polyester monofilament having a fineness of 6.0 dtex was obtained by making yarns and winding in the same manner as in Example 1 except that the draw ratio was 5.00 times. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 2, halation occurred, and sufficient accuracy in screen printing could not be obtained.(Comparative Example 4)

[0113] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 5 wt% of Pigment Yellow 150 and Pigment Brown 48 were mixed therein at a ratio of 1 : 4. The mixture was supplied to a twin-screw kneading extruder to obtain master pellets. A core-sheath composite polyester monofilament having a fineness of 6.0 dtex was obtained by making yarns and winding in the same manner as in Example 1 except that the obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 1 : 99 using a blending apparatus, and 0.05 wt% of a light-absorbing agent was contained in the component of the core. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 2, halation occurred, and sufficient accuracy in screen printing could not be obtained.

Examples

example 1

(Example 1)

[0098]Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 having an absorption peak at 450 nm and Pigment Brown 48 having an absorption peak at 300 nm were mixed therein at a ratio of 1 : 4. The mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the core.

[0099]As the component of the sheath, polyethylene terephthalate having an intrinsic viscosity IV of 0.50 and containing 0.4 wt% of titanium oxide was employed.

[0100]The polyester as the core component and the polyester as the sheath component were...

examples 2 and 3

(Examples 2 and 3)

[0101]Yarns were made and wound in the same manner as in Example 1 except that the draw ratios were 4.70 and 5.90 times. The characteristics of the core-sheath composite monofilaments are shown in Table 1. In Example 2, the printing accuracy was slightly deteriorated, and in Example 3, the abrasion resistance was slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.

examples 4 and 5

(Examples 4 and 5)

[0102]A core-sheath composite monofilament having a fineness of 3.1 dtex and a core-sheath composite monofilament having a fineness of 13.0 dtex were obtained in the same manner as in Example 1 except that the discharge amount was changed. The characteristics of the core-sheath composite monofilament are shown in Table 1. In Example 4, the weaving properties were slightly deteriorated, and in Example 5, the printing accuracy was slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.

TECHNICAL FIELD

[0001] The present invention relates to a core-sheath composite monofilament for a screen gauze. Specifically, the present invention relates to a core-sheath composite monofilament for a screen gauze having an excellent halation preventing effect when a printing pattern is formed by exposure without dyeing the screen gauze.BACKGROUND ART

[0002] As a woven fabric for screen printing, a mesh woven fabric made of natural fibers such as silk or inorganic fibers such as stainless steel has been widely used as a screen gauze.

[0003] In recent years, synthetic fiber meshes excellent in flexibility, durability, and cost performance are preferably used. Among them, polyester monofilaments, which are excellent in dimensional stability, are highly suitable for screen applications and thus widely used.

[0004] In addition, in high-definition screen printing applications such as electrodes and wiring printing of electronic components, against the background of increasing demand for global clean energy such as multilayer ceramic capacitors and solar cells, growth expansion and rigorous demand for high definition printing are remarkable, and thus advancement of monofilaments for a screen gauze has been required.

[0005] A general plate-making process includes stretching and fixing a screen gauze prepared using a monofilament to a printing plate frame, scouring the screen gauze to remove unnecessary substances such as an oil agent attached to the monofilament, applying and drying an ultraviolet curable resin, and then exposing the screen gauze with ultraviolet rays having a wavelength of 300 to 450 nm in a state where a positive film in which a pattern to be printed is drawn in black is brought into close contact with the screen gauze.

[0006] The ultraviolet curable resin overlapping the pattern part of the positive film is not solidified, and the ultraviolet curable resin in the other part is exposed to ultraviolet rays and solidified by a photochemical reaction. Therefore, by washing the plate after the exposure with water, the ultraviolet curable resin in the pattern part of the positive film is washed away, thereby obtaining a negative film.

[0007] In screen printing, in order to perform more precise and fine printing, how to solidify the ultraviolet curable resin according to the pattern of the positive film is an important problem.

[0008] When the ultraviolet reflectance of the screen gauze is high, so-called halation, in which ultraviolet rays are irregularly reflected on the surface of the screen gauze and the pattern part not requiring exposure is exposed, occurs, and as a result, the printing accuracy is significantly deteriorated.

[0009] As a method for preventing this irregular reflection, a method of weaving monofilaments into a screen gauze and then dyeing the screen gauze is generally employed.

[0010] However, the light wavelength region of the ultraviolet curable resin or the ultraviolet irradiation lamp used in the plate-making process varies depending on the platemaking company in order to prevent irregular reflection.

[0011] Furthermore, dyes to be used for dyeing and color tone settings are also selectively used for each platemaking company, and thus the types of ultraviolet curable resins and dyes are enormous.

[0012] Moreover, in the dyeing process, discharge of waste liquid imposing a high environmental load is a serious problem in various places.

[0013] Under such circumstances, in order to eliminate the dyeing process of the screen gauze, various studies have been made on a spun-dyed monofilament for a screen gauze, which is colored by adding a pigment in the yarn-making process stage.

[0014] For example, Patent Document 1 discloses an invention in which the fiber cross section of a monofilament has a core-sheath composite structure, and a light-absorbing substance is contained in the core component.

[0015] Furthermore, Patent Document 2 discloses an invention of a polyester monofilament having a small fineness and a high strength for high-definition screen printing, in which an organic compound-based pigment is contained in the entire transverse cross-section of the fiber.PRIOR ART DOCUMENTSPATENT DOCUMENTS

[0016] Patent Document 1: International Publication No. 2005 / 118927 Patent Document 2: Japanese Patent Laid-open Publication No. 2022-144471 SUMMARY OF THE INVENTIONPROBLEMS TO BE SOLVED BY THE INVENTION

[0017] Patent Document 1 proposes that a light-absorbing agent is contained in a core component in a core-sheath composite monofilament. However, in order to prevent halation in a wide range of light wavelength regions of various types of ultraviolet curable resins and ultraviolet irradiation lamps, it is necessary to contain a higher concentration of the light-absorbing agent.

[0018] Furthermore, in order to obtain the strength of the monofilament necessary for the dimensional stability of the screen gauze, it has been necessary to draw the monofilament at a high ratio. However, the fiber surface of the monofilament, which contains the light-absorbing agent at a high concentration and is drawn at a high ratio, is easily scraped due to high orientation of the crystal structure, causing yarn breakage in the yarn-making process and the weaving process.

[0019] Furthermore, Patent Document 2 proposes that an organic compound-based pigment is contained in the entire fiber to suppress the reflectance at an ultraviolet light wavelength. However, the organic compound-based pigment is exposed on the fiber surface, and powdery scum colored in the yarn-making process or the weaving process is generated, which causes deterioration of yarn making properties and many defects of the screen gauze.

[0020] Therefore, an object of the present invention is to obtain a core-sheath composite monofilament for a screen gauze that eliminates a dyeing process of the screen gauze and has strength necessary for high-definition screen printing, by reducing the reflectance in the entire region of a light wavelength of 300 nm to 450 nm.SOLUTIONS TO THE PROBLEMS

[0021] In order to solve the above-mentioned problems, the present invention employs the following configurations. 1. A core-sheath composite monofilament for a screen gauze, satisfying the requirements (a) to (c): (a) a reflectance in the entire region of a light wavelength of 300 nm to 450 nm is 20.0% or less; (b) a light-absorbing agent is contained only in the core; and (c) a strength at break is 7.0 cN / dtex to 9.0 cN / dtex. 2. The core-sheath composite monofilament for a screen gauze according to the above 1, wherein a maximum reflectance in a region of a light wavelength of 300 nm to 450 nm is 1.3 times or less of an average reflectance. 3. The core-sheath composite monofilament for a screen gauze according to the above 1 or 2, wherein two or more types of light-absorbing agents having different absorption peaks at a light wavelength of 300 nm to 450 nm are contained only in the core, and a total content of the light-absorbing agents in the core is 0.1 wt% to 0.8 wt%. 4. The core-sheath composite monofilament for a screen gauze according to the above 1 or 2, containing a polyester. EFFECTS OF THE INVENTION

[0022] According to the present invention, it is possible to provide a core-sheath composite monofilament that eliminates a dyeing process of a screen gauze, exhibits an excellent halation preventing effect when a printing pattern is formed by exposure, and is suitable for high-definition screen printing.EMBODIMENTS OF THE INVENTION

[0023] The monofilament for a screen gauze of the present invention has a composite cross section composed of a core and a sheath.

[0024] The resin constituting the core and the sheath may be any melt-spinnable resin. Examples of the resin include polyolefins such as polyethylene and polypropylene, or modified polyolefins containing these as main components; polyamides such as nylon 6 and nylon 66, or modified polyamide copolymers containing these as main components; aromatic polyesters such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; aliphatic polyesters such as polylactic acid and polybutylene succinate; and copolymerized polyesters containing these as main components, polyarylate, polybenzazole, wholly aromatic polyesters, and wholly aromatic polyamides.

[0025] Among them, the resin used for the core is preferably a polyester mainly composed of polyethylene terephthalate (hereinafter, referred to as PET) from the viewpoint of dimensional stability and production cost.

[0026] PET is preferably a polyester containing terephthalic acid as a main acid component and ethylene glycol as a main glycol component, and having repeating units of ethylene terephthalate in an amount of 90 mol% or more.

[0027] The resin used for the core preferably does not contain a copolymerization component because the copolymerization component inhibits orientation of fibers, and a satisfactory original yarn strength for a high-definition screen printing application cannot be obtained in some cases.

[0028] In addition, titanium dioxide as a matting agent, fine silica or alumina particles as a lubricant, a hindered phenol derivative as an antioxidant, a flame retardant, an antistatic agent, and the like can be added to the resin as necessary.

[0029] Since the resin to be used for the core of the present invention is mainly responsible for the strength of the monofilament, the content of an additive of inorganic particles represented by titanium oxide to be added as a matting agent is preferably less than 0.6 wt%.

[0030] Meanwhile, the resin to be used for the sheath is preferably polyester mainly composed of PET.

[0031] PET is preferably a polyester containing terephthalic acid as a main acid component and ethylene glycol as a main glycol component, and having repeating units of ethylene terephthalate in an amount of 90 mol% or more.

[0032] Since the resin to be used for the sheath is mainly responsible for the abrasion resistance of the monofilament, it is preferable to add about 0.1 wt% to 0.5 wt% of inorganic particles represented by titanium oxide.

[0033] The transverse cross-section of the core-sheath composite monofilament of the present invention is preferably a round cross section from the viewpoint of uniformity of the opening of the screen gauze.

[0034] The core-sheath composite monofilament of the present invention also preferably has a core-sheath composite fiber structure in which the core is covered with the sheath and the core is disposed so as not to be exposed to the surface in the transverse cross-section of the fiber, and the core and the sheath are preferably disposed concentrically.

[0035] In addition, the composite volume ratio of the core to the sheath is 50 : 50 to 95 : 5 from the viewpoint of achieving both the scum suppressing effect by the sheath and the increase in strength by the core.

[0036] When the same type of resin is employed for the core and the sheath, the phenomenon of peeling at the composite interface hardly occurs, and thus the composite volume ratio is preferably 70 : 30 to 90 : 10.

[0037] When different types of resins are employed for the core and the sheath, the composite volume ratio is preferably 50 : 50 to 70 : 30 from the viewpoint of suppressing peeling at the composite interface and maintaining the strength of the monofilament.

[0038] In the core-sheath composite monofilament of the present invention, the reflectance in the entire region of a light wavelength of 300 nm to 450 nm is 20.0% or less, and more preferably 15.0% or less. The lower limit value is not particularly limited, but it is basically necessary to mix a large amount of pigment in order to lower the reflectance, and mixing of a large amount of pigment impairs the strength of the yarn. Therefore, it is necessary to set the reflectance in consideration of the required strength and reflectance of the yarn. When the photosensitive resin is cured with ultraviolet rays in the plate-making process, the photosensitive resin is usually irradiated with light having a light wavelength of 300 nm to 450 nm. Since the light wavelength region is selected by a platemaking company depending on compatibility with the ultraviolet curable resin, in order to prevent halation, it is important to suppress reflection against the entire region of the corresponding light wavelength. The reflectance is a reflectance measured at every 10 nm in a light wavelength range of 300 nm to 450 nm as described later. When the maximum value of the measured values is 20.0% or less, that is, when the reflectance of the entire region is 20.0% or less, reflection of ultraviolet light is suppressed, and a clear printing pattern can be obtained without occurrence of halation.

[0039] In addition, when the maximum reflectance which is the maximum value of the measured values of the reflectance is set to 1.3 times or less of the average reflectance which is the average value of the measured values of the reflectance, occurrence of halation can be suppressed.

[0040] In the present invention, the core-sheath composite monofilament contains a light-absorbing agent only in the core for the purpose of suppressing halation when a printing pattern is formed and reproducing the printing pattern with high definition with an ultraviolet curable resin.

[0041] When the core-sheath composite monofilament contains the light-absorbing agent in the sheath, the light-absorbing agent exposed on the fiber surface falls off in a powder form and emerges as powdery scum colored in the yarn-making process and the weaving process to induce yarn breakage. Therefore, the light-absorbing agent is not contained in the sheath.

[0042] The light-absorbing agent has an absorption peak specific to the light wavelength. When two or more types of light-absorbing agents having different absorption peaks at a light wavelength of 300 nm to 450 nm are contained in the core, uniform light absorption in a wide range of light wavelength becomes possible.

[0043] Moreover, since the total amount of the light-absorbing agent to be contained in order to achieve a reflectance of 20.0% or less in the entire region of a light wavelength of 300 nm to 450 nm is small as compared with the case of containing one type of light-absorbing agent, it is possible to suppress deterioration of the strength of the core-sheath composite monofilament. More preferably, when light-absorbing agents having absorption peaks different from each other by 50 nm or more in the light wavelength region are combined, light absorption in a wide range of light wavelength becomes possible, and the content of the light-absorbing agent can be reduced.

[0044] The total content of the light-absorbing agent in the core is preferably 0.1 wt% to 0.8 wt%. When the content is 0.1 wt% or more, a sufficient halation preventing effect can be obtained, and when the content is 0.8 wt% or less, a core-sheath composite monofilament having both sufficient strength and abrasion resistance for realizing precise and fine screen printing can be obtained. The total content of the light-absorbing agent in the core is more preferably 0.2 wt% to 0.4 wt%.

[0045] As the light-absorbing agent, a conventionally known light-absorbing agent that is well dispersed in a molten resin and enables coloring in the melt spinning stage can be used.

[0046] In general, a red or yellow warm-colored screen gauze is widely used because it has good ultraviolet absorbability from a high wavelength side of visible light. The light-absorbing agent of the present invention preferably exhibits a color tone similar to the warm color.

[0047] Examples of the warm color light-absorbing agent include organic pigments such as benzene azo-based condensed polycyclic pigments (monoazo, disazo, and the like), heterocyclic azo-based condensed polycyclic pigments (thiazole azo, benzothiazole azo, quinoline azo, pyridine azo, imidazole azo, thiophene azo, and the like), anthraquinone-based condensed polycyclic pigments, and isoindoline-based condensed polycyclic pigments; titanium oxide-based inorganic pigments having iron or aluminum as a ligand; and dyes such as indigoid dyes, triphenylmethane dyes, xanthene dyes, alizarin dyes, acridine dyes, and cyanine dyes.

[0048] In the screen printing, in order to improve the accuracy of the printing pattern, a method of increasing the tension for stretching the gauze to reduce the distance between the screen gauze and the printing target is generally adopted.

[0049] During stretching of the gauze, the strength per monofilament is improved in order to increase the tension.

[0050] Furthermore, the demand of the printing industry is severe, and the tension to be applied to the yarn is not always proportional to the fineness in the weaving process that requires a screen gauze having a high mesh and a small fineness, that is, a screen gauze having a high weave density. It is important that the strength per monofilament is high, and a higher strength at break is required as the monofilament becomes thinner accordingly.

[0051] The core-sheath composite monofilament of the present invention has a strength at break of 7.0 cN / dtex or more from the viewpoint of suppressing deterioration of weaving properties and occurrence of gauze elongation and obtaining high dimensional stability.

[0052] Meanwhile, the orientation and degree of crystallinity are required to be suppressed from the viewpoint of abrasion resistance. Therefore, the strength at break is preferably 9.0 cN / dtex or less and 8.8 cN / dtex or less.

[0053] The fineness of the core-sheath composite monofilament of the present invention is preferably 2.0 dtex to 10.0 dtex.

[0054] In the case of a high-mesh screen gauze of #420 or more (420 yarns per 2.54 cm) suitable for precision printing, the mesh grid space per yarn is very small. Therefore, when monofilaments having a fineness of more than 10 dtex are used, the opening (aperture) per grid is very small.

[0055] As a result, scum is easily generated due to the friction between the reed and the monofilament, and as a result, it becomes difficult to obtain a screen gauze of #420 or more.

[0056] Furthermore, the fineness is preferably 8.0 dtex or less for the screen gauze of #450 or more, and 6.0 dtex or less for the screen gauze of #500 or more.

[0057] The lower limit of the fineness is preferably 2.0 dtex or more from the viewpoint of weaving properties, particularly, running properties of the weft in a Sulzer loom.

[0058] In the present invention, the monofilament preferably has a strength at 5% elongation of 4.5 cN / dtex to 6.5 cN / dtex.

[0059] When the strength at 5% elongation is 4.5 cN / dtex or more, deterioration of elongation at the time of weaving and gauze elongation at the time of printing are less likely to occur, and high dimensional stability is obtained. When the strength at 5% elongation is 6.5 cN / dtex or less, fibrillation of crystal orientation of fibers is less likely to occur, so that abrasion resistance is likely to be improved.

[0060] As a method for melt-spinning the core-sheath composite monofilament for a screen gauze of the present invention, a conventionally known melt spinning method may be employed.

[0061] Examples of the melting method include a pressure melter method and an extruder method, but melting by an extruder method is preferable from the viewpoint of uniform melting and prevention of retention.

[0062] The resins of the core component and the sheath component are melted by separate melt extruders. The separately melted polymers are passed through respective pipelines, dispensed, and then fed to a spinneret pack. At this time, the pipeline passage time is preferably within 30 minutes from the viewpoint of preventing thermal degradation. Both polymers fed to the pack are merged in the above-described spinneret, combined into a core-sheath form, and discharged through the spinneret.

[0063] Thereafter, the core-sheath composite monofilament for a screen gauze of the present invention can be produced by a direct spinning-drawing method in which cooling and oiling are performed and drawing is subsequently performed without once winding.

[0064] The monofilament yarn can be once wound as an undrawn yarn in the spinning process, and then subjected to the drawing process again. However, a direct spinning-drawing method is preferable in which drawing is performed directly in connection with the spinning process from the viewpoint of reducing the guide through which the yarn passes in the production process to suppress the yarn from being scraped.

[0065] The drawing process is preferably multi-stage drawing using three or more pairs of rollers.

[0066] The temperature of the drawing roller before the final drawing roller in the multi-stage drawing is preferably 130°C or less, more preferably 110°C or less to suppress crystallization during drawing. The temperature of the final drawing roller is preferably 130°C or more, and more preferably 180°C or more. When the temperature of the final drawing roller is 130°C or less, it is difficult to control fiber surface orientation, and crystallization of fibers hardly proceeds, so that a high-strength polyester monofilament cannot be obtained. On the other hand, when the temperature of the final drawing roller exceeds 230°C, fusion is likely to occur in the final drawing roller, and yarn making properties are deteriorated, which is not preferable.

[0067] In the winding process, the yarn is wound in the form of a pirn or a cheese, whereby the core-sheath composite monofilament for a screen gauze of the present invention can be obtained.

[0068] Examples of the resin of the core component include various types of resins as described above, but polyester is preferable from the viewpoint of dimensional stability. Among them, PET is preferable from the viewpoint of cost and spinning operability. When the component of the core is PET, the intrinsic viscosity IV thereof is preferably 0.90 to 1.50. When the intrinsic viscosity IV is 0.90 or more, a core-sheath composite monofilament having both sufficient strength and elongation can be produced. The intrinsic viscosity IV is more preferably 0.95 or more. The upper limit of the intrinsic viscosity IV is preferably 1.50 or less from the viewpoint of ease of forming such as melt extrusion. The upper limit of the intrinsic viscosity IV is more preferably 1.30 or less in consideration of the production cost and the influence of decrease in the molecular weight caused by molecular chain breakage due to heat or shear force during the process.

[0069] Examples of the resin of the sheath component include various types of resins as described above, but it is preferably the same component as the resin of the core component from the viewpoint of peeling at the composite interface, polyester is preferable from the viewpoint of cost and spinning operability, and PET is more preferable.

[0070] When the resin component of the core and the sheath is PET, it is preferable that the intrinsic viscosity IV of PET of the sheath component is lower than the intrinsic viscosity IV of PET of the core component, and the difference in intrinsic viscosity IV is set to 0.20 to 1.00 from the viewpoint of obtaining good abrasion resistance and sufficient strength.

[0071] When the difference in intrinsic viscosity IV is 0.20 or more, the degree of orientation and the degree of crystallinity of PET of the sheath component, that is, PET molecular chains on the fiber surface can be suppressed, resulting in good abrasion resistance. Furthermore, since the sheath component bears a shear stress on an inner wall surface of a spinneret discharge hole of the melt spinning, a shear stress received by the core component is reduced. Accordingly, since the core component has a low degree of molecular chain orientation and is spun in a uniform state, the strength of the finally obtained monofilament is improved.

[0072] Meanwhile, in order for the monofilament to have high strength, the sheath component is also required to be appropriately oriented. Therefore, the original yarn strength is obtained by setting the difference in the intrinsic viscosity IV to 1.00 or less. A more preferred difference in intrinsic viscosity IV is 0.30 to 0.70.

[0073] As described above, the light-absorbing agent is contained only in the core component.

[0074] Examples of the method for adding the light-absorbing agent include a method in which pellets prepared by blending a light-absorbing agent in a meltable resin are melt-spun, and a method in which spinning is performed while high-concentration master pellets having a content of about 2 to 20 times a predetermined content and a normal resin are melt-kneaded and diluted.

[0075] In the latter case, the master pellets and normal resin pellets may be mixed in a state of a pellet and kneaded by a melt extruder, or may be separately melted by a melt extruder and then kneaded in a transportation pipeline of the molten polymer or a spinning pack. In any case, it is preferable to use a static mixer in order to ensure dispersion uniformity of the light-absorbing agent.EXAMPLES

[0076] The evaluations of Examples and Comparative Examples were measured by the following methods.(1) Fineness

[0077] Monofilaments were wound up into a 500-m skein, and a value obtained by multiplying the mass (g) of the skein by 20 was defined as the fineness.(2) Strength at break (cN / dtex), strength at 5% elongation (cN / dtex)

[0078] The strength at break and the strength at 5% elongation were measured according to JIS L1013 (2010) using Tensilon UCT-100 manufactured by ORIENTEC CO., LTD.(3) Intrinsic viscosity IV

[0079] Regarding ηr in the definition formula, in 10 mL of o-chlorophenol (hereinafter abbreviated as "OCP") having a purity of 98% or more at a temperature of 25°C, 0.8 g of a sample was dissolved. The relative viscosity ηr was determined according to the following formula using an Ostwald viscometer at a temperature of 25°C, and the intrinsic viscosity IV was calculated. ηr = η / η 0 = t × d / t 0 × d 0 Intrinsic viscosity IV = 0.0242 ηr + 0.2634 In the formula, η is the viscosity of a polymer solution, η0 is the viscosity of OCP, t is the dropping time of the solution (second), d is the density of the solution (g / cm 3< ), t0 is the dropping time of OCP (second), and d0 is the density of OCP (g / cm 3< ). (4) Abrasion resistance

[0080] The monofilament is fixed in air at a tension of 5 g, and one reed dent made of SUS (thickness: 65 µm) is pressed against the monofilament from above to fix the monofilament at an angle of 2° with respect to the horizontal. The reed dent is reciprocated in a range of 3.2 cm at a speed of 133 m / min with respect to the fiber axis direction, and the reciprocation is stopped after 20 seconds. The position rubbed with the reed dent was observed using VHX-D500 manufactured by KEYENCE CORPORATION, the abrasion state of the position was evaluated as follows in the SEM image, and ranks S and A were rated as passed.

[0081] S...There is no deformation or fluff scraping on the surface of the monofilament, and there is no problem.

[0082] A...Although there are thin streaks on the surface of the monofilament in the longitudinal direction of the fiber, there is no problem in quality.

[0083] B...There is fluff scraping on the surface of the monofilament.(5) Weaving properties

[0084] The presence or absence of a problem in the process of obtaining a screen gauze having a warp density and a weft density of 460 mesh (460 yarns / 2.54 cm) from monofilaments was evaluated as follows, and ranks S and A were rated as passed.

[0085] S...There is almost no fluff scraping or powdery scum, and there is no problem.

[0086] A...Although there are fluff scraping and powdery scum, there is no problem in quality.

[0087] B...There are significant fluff scraping and powdery scum.(6) Reflectance

[0088] A monofilament having a length of 10000 m was wound around a plate having a length of 6 cm and a width of 6 cm without any gap. The reflectance was measured at every 10 nm in a light wavelength range of 300 nm to 450 nm using a V750 spectrophotometer manufactured by JASCO Corporation in accordance with a photoengraving process (JIS Z8722:2009). The maximum value of the measured values of the reflectance was defined as the maximum reflectance, and the average of the measured values was defined as the average reflectance.(7) Absorption peak wavelength of pigment

[0089] A monofilament containing only one type of pigment and having a length of 10000 m was wound around a plate having a length of 6 cm and a width of 6 cm without any gap. The reflectance was measured every 5 nm in a light wavelength range of 300 nm to 500 nm using a V750 spectrophotometer manufactured by JASCO Corporation in accordance with a photoengraving process (JIS Z8722:2009). The wavelength at the minimum value of the measured values of the reflectance was defined as the absorption peak wavelength.(8) Halation

[0090] A fine pattern was printed on the screen gauze obtained in the same manner as described in the above (5), and the screen gauze was observed with an electron microscope for evaluation, and ranks S and A were rated as passed.

[0091] S...The halation preventing effect is great. There is almost no blur of the fine pattern, and there is no problem.

[0092] A...There is a halation preventing effect. There is blur of the fine pattern, but there is no problem in quality.

[0093] B...Halation occurs. The blur of the fine pattern is significant.(9) Printing accuracy

[0094] The screen gauze obtained in the same manner as described in (5) was stretched on a 30 cm × 30 cm printing plate frame. A 50 µm line pattern was formed on the obtained mesh woven fabric at intervals of 50 µm with a photosensitive emulsion, and the state after printing was observed and determined according to the following indices. Ranks S and A were rated as passed.

[0095] S...Line reproduction is favorable.

[0096] A... Irregularities are observed at the boundary of the line, but there is no problem.

[0097] B...The irregularities of the boundary of the line are severe, and the line is partially disconnected.(Example 1)

[0098] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 having an absorption peak at 450 nm and Pigment Brown 48 having an absorption peak at 300 nm were mixed therein at a ratio of 1 : 4. The mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the core.

[0099] As the component of the sheath, polyethylene terephthalate having an intrinsic viscosity IV of 0.50 and containing 0.4 wt% of titanium oxide was employed.

[0100] The polyester as the core component and the polyester as the sheath component were each melted at a temperature of 297°C using an extruder. Then, the core component and the sheath component were dispensed by pumping at a polymer temperature of 275 to 285°C so that the core-sheath volume ratio (core component to sheath component) was 80 : 20, and fed into a melt spinning pack. A yarn was spun by feeding the respective components into a known composite spinneret so as to form a core-sheath type structure. The polyester monofilament discharged from the spinneret was positively heated and kept at a certain temperature so that the ambient temperature immediately below the spinneret was 300°C. Thereafter, the polyester monofilament was cooled by a yarn cooling blower, and taken up by non-heated first godet rolls while applying a spinning oil agent. The polyester monofilament was taken over first hot rolls heated to a temperature of 90°C, second hot rolls heated to a temperature of 90°C, and third hot rolls heated to a temperature of 190°C without being wound up temporarily, so that the polyester monofilament was drawn and heat-set. The draw ratios of the second hot roll and the third hot roll were 4.90 times. Furthermore, the polyester monofilament was taken over two non-heated godet rolls having a surface roughness of 0.8 S, and then wound into a package while the winding tension was kept at 0.417 g / dtex by controlling the number of spindle revolutions to obtain a core-sheath composite monofilament having a fineness of 6.0 dtex. The characteristics of the core-sheath composite monofilament are as shown in Table 1. The maximum reflectance in a region of a light wavelength of 300 nm to 450 nm was 10.2%, that is, the reflectance in the entire region was 10.2% or less. Thus, excellent abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Examples 2 and 3)

[0101] Yarns were made and wound in the same manner as in Example 1 except that the draw ratios were 4.70 and 5.90 times. The characteristics of the core-sheath composite monofilaments are shown in Table 1. In Example 2, the printing accuracy was slightly deteriorated, and in Example 3, the abrasion resistance was slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Examples 4 and 5)

[0102] A core-sheath composite monofilament having a fineness of 3.1 dtex and a core-sheath composite monofilament having a fineness of 13.0 dtex were obtained in the same manner as in Example 1 except that the discharge amount was changed. The characteristics of the core-sheath composite monofilament are shown in Table 1. In Example 4, the weaving properties were slightly deteriorated, and in Example 5, the printing accuracy was slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Examples 6 and 7)

[0103] Yarns were made and wound in the same manner as in Example 1 except that the intrinsic viscosity IV of the polyethylene terephthalate pellets for the core component was each set to 1.50 and 0.90, and the draw ratio was changed to 5.20 times. The characteristics of the core-sheath composite monofilaments are as shown in Table 1. In Example 7, the abrasion resistance and the weaving properties were slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Example 8)

[0104] Yarns were made and wound in the same manner as in Example 1 except that the master pellets contained in the core component polyester and the polyethylene terephthalate pellets were blended at a ratio of 1 : 99, and the content of the light-absorbing agent was changed to 0.10 wt%. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 1. The halation preventing effect and the printing accuracy were slightly deteriorated, but sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Example 9)

[0105] Yarns were made and wound in the same manner as in Example 1 except that the master pellets contained in the core component polyester and the polyethylene terephthalate pellets were blended at a ratio of 7 : 93, and the content of the light-absorbing agent was changed to 0.70 wt%. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 1. The abrasion resistance and the weaving properties were slightly deteriorated, but sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.(Example 10)

[0106] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. A core-sheath composite polyester monofilament having a fineness of 6.0 dtex was obtained by making yarns in the same manner as in Example 1 except that the obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 8 : 92 using a blending apparatus, and 0.80 wt% of a light-absorbing agent was contained in the component of the core. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 1. All of the abrasion resistance, the weaving properties, and the printing accuracy were deteriorated, but the abrasion resistance and halation suppressing effect that can be employed for screen gauze applications were obtained.(Example 11)

[0107] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 20 wt% of Pigment Yellow 150 having an absorption peak at 450 nm, Pigment Brown 48 having an absorption peak at 300 nm, and Pigment Red 101 having an absorption peak at 390 nm were mixed therein at a ratio of 1 : 2 : 2. The mixture was supplied to a twin-screw kneading extruder to obtain master pellets. A core-sheath composite polyester monofilament having a fineness of 6.0 dtex was obtained by making yarns in the same manner as in Example 1 except that the obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 3 : 97 using a blending apparatus, 0.60 wt% of a light-absorbing agent was contained in the component of the core, and the draw ratio was set to 5.2 times. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 1, and an excellent abrasion resistance and halation suppressing effect for screen gauze applications were obtained. (Comparative example 1)

[0108] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 0.96 and containing 0.5 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the core.

[0109] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.50, containing 0.4 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 0.50 and containing 0.4 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the sheath.

[0110] The polyesters of the core component and the sheath component were made into yarns, and the yarns were wound in the same manner as in Example 1 to obtain a core-sheath composite monofilament having a fineness of 6.0 dtex. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 2, and a deterioration of the abrasion resistance, generation of colored powdery scum during weaving, and yarn breakage occurred.(Comparative example 2)

[0111] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 0.96 and containing 0.5 wt% of titanium oxide were blended at a ratio of 10 : 90 using a blending apparatus, and 1.00 wt% of a light-absorbing agent was contained in the component of the core. A core-sheath composite monofilament having a fineness of 6.0 dtex was obtained by making yarns and winding in the same manner as in Example 1 except that the draw ratio was 4.30 times. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 2, the strength was low, and sufficient accuracy in screen printing could not be obtained.(Comparative example 3)

[0112] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 was mixed therein, and the mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the core. A core-sheath composite polyester monofilament having a fineness of 6.0 dtex was obtained by making yarns and winding in the same manner as in Example 1 except that the draw ratio was 5.00 times. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 2, halation occurred, and sufficient accuracy in screen printing could not be obtained.(Comparative Example 4)

[0113] Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 5 wt% of Pigment Yellow 150 and Pigment Brown 48 were mixed therein at a ratio of 1 : 4. The mixture was supplied to a twin-screw kneading extruder to obtain master pellets. A core-sheath composite polyester monofilament having a fineness of 6.0 dtex was obtained by making yarns and winding in the same manner as in Example 1 except that the obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 1 : 99 using a blending apparatus, and 0.05 wt% of a light-absorbing agent was contained in the component of the core. The characteristics of the core-sheath composite polyester monofilament are as shown in Table 2, halation occurred, and sufficient accuracy in screen printing could not be obtained.

Examples

example 1

(Example 1)

[0098]Polyethylene terephthalate, having an intrinsic viscosity IV of 0.70, containing 0.1 wt% of titanium oxide, and polymerized and pelletized by an ordinary method, was freeze-pulverized. Then, 10 wt% of Pigment Yellow 150 having an absorption peak at 450 nm and Pigment Brown 48 having an absorption peak at 300 nm were mixed therein at a ratio of 1 : 4. The mixture was supplied to a twin-screw kneading extruder to obtain master pellets. The obtained master pellets and polyethylene terephthalate pellets having an intrinsic viscosity IV of 1.19 and containing 0.5 wt% of titanium oxide were blended at a ratio of 4 : 96 using a blending apparatus, and 0.40 wt% of a light-absorbing agent was contained in the component of the core.

[0099]As the component of the sheath, polyethylene terephthalate having an intrinsic viscosity IV of 0.50 and containing 0.4 wt% of titanium oxide was employed.

[0100]The polyester as the core component and the polyester as the sheath component were...

examples 2 and 3

(Examples 2 and 3)

[0101]Yarns were made and wound in the same manner as in Example 1 except that the draw ratios were 4.70 and 5.90 times. The characteristics of the core-sheath composite monofilaments are shown in Table 1. In Example 2, the printing accuracy was slightly deteriorated, and in Example 3, the abrasion resistance was slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.

examples 4 and 5

(Examples 4 and 5)

[0102]A core-sheath composite monofilament having a fineness of 3.1 dtex and a core-sheath composite monofilament having a fineness of 13.0 dtex were obtained in the same manner as in Example 1 except that the discharge amount was changed. The characteristics of the core-sheath composite monofilament are shown in Table 1. In Example 4, the weaving properties were slightly deteriorated, and in Example 5, the printing accuracy was slightly deteriorated, but in all cases, sufficient abrasion resistance and a halation suppressing effect for screen gauze applications were obtained.

Claims

1. A core-sheath composite monofilament for a screen gauze, satisfying the requirements (a) to (c): (a) a reflectance in the entire region of a light wavelength of 300 nm to 450 nm is 20.0% or less; (b) a light-absorbing agent is contained only in the core; and (c) a strength at break is 7.0 cN / dtex to 9.0 cN / dtex.

2. The core-sheath composite monofilament for a screen gauze according to claim 1, wherein a maximum reflectance in a region of a light wavelength of 300 nm to 450 nm is 1.3 times or less of an average reflectance.

3. The core-sheath composite monofilament for a screen gauze according to claim 1 or 2, wherein two or more types of light-absorbing agents having different absorption peaks at a light wavelength of 300 nm to 450 nm are contained in only the core, and a total content of the light-absorbing agents in the core is 0.1 wt% to 0.8 wt%.

4. The core-sheath composite monofilament for a screen gauze according to claim 1 or 2, comprising a polyester.

Images