JPH07119098B2 - Polyester film for wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a polyester film for a wiring board, more specifically, a polyester for a wiring board having improved adhesion to a conductive layer, a resistor layer, an insulating layer and a printing ink layer. Regarding

[Conventional technology]

The biaxially stretched polyester film has been used as a flexible wiring board or a membrane switch by taking advantage of its excellent electric insulation, heat resistance, dimensional stability and chemical resistance. Especially in recent years, in addition to the method of laminating and latching copper, conductive paste, conductive ink, low antibody ink,
A method of printing an ink for an insulator and a marking ink is used. Along with this, a method of providing a polyester having improved adhesiveness with various inks, for example, a polyester-based copolymer thin film (for example, JP-A-62-162540).
Japanese Laid-Open Patent Publication No. 62-173253) or a method of applying a urethane resin (for example, Japanese Laid-Open Patent Publication No. 62-173253).

[Problems to be solved by the invention]

However, the above-mentioned conventional polyester films have the drawbacks that the adhesiveness is still insufficient, that they stick to each other when annealed to impart dimensional stability or heated to cure the ink. there were.

It is an object of the present invention to provide a polyester film for a wiring board, which has good adhesion to inks or polymer pastes for conductors, low antibodies, or insulators and does not cause film sticking to each other.

[Means for solving problems]

The present invention provides a polyester copolymer (b) obtained by crosslinking inorganic particles (a) having an average particle diameter of 0.08 to 2.2 µm on at least one surface of a biaxially stretched polyester film having a center line average roughness of 0.02 to 0.50 µm. And a coating layer comprising a component mainly composed of (1) and having a ratio (D / d) of the average particle size (D) of the inorganic particles (a) to the layer thickness (d) in the range of 1.1 to 80. Is a polyester film for wiring boards.

The polyester used for the biaxially stretched polyester film of the present invention is ethylene terephthalate, ethylene α, β
-Bis (2-chlorophenoxy) ethane-4,4'-dicarboxylate, ethylene α, β-bis (phenoxy)
The main constituent is at least one structural unit selected from ethane-4,4'-dicarboxylate and ethylene 2,6-naphthalate units.

Further, within the range that does not inhibit the present invention, preferably 10 mol%
Other components than the above may be copolymerized as long as they are within the above range.

The polyester film used in the present invention contains the above composition as a main component, but within a range not impairing the object of the present invention,
Other polymers may be blended, antioxidants,
Inorganic or organic additives such as heat stabilizers, lubricants, UV absorbers and nucleating agents may be added to the extent that they are usually added.

The polyester film constituting the film of the present invention,
It is at least biaxially oriented by a conventional method, and the thickness is preferably 2 to 600 μm, more preferably 25 to 250 μm, and excellent in handleability in practical use as a base material.

The biaxially stretched polyester film of the present invention is required to have a center line average roughness of 0.02 to 0.50 μm, preferably 0.05 to 0.15 μm, and more preferably 0.08 to 0.13 μm. If the center line average roughness is too small, the films are easily fixed to each other by heating, which is not preferable. On the other hand, if the center line average roughness is too large, the uniformity of coating of various inks and polymer pastes deteriorates, and the electrical insulating property deteriorates, which is not preferable.

The biaxially stretched polyester film having the above-mentioned centerline average roughness can be produced by a known method such as a method of adding inorganic particles to polyester to form a film.

The coating layer of the present invention comprises a component mainly composed of a polyester copolymer (b) crosslinked with the inorganic particles (a). The coating layer is within a range that does not impair the objects and effects of the present invention.
Although substances other than (a) and (b) may be added, (a)
The addition amount of substances other than (b) is less than 40% by weight in the coating layer,
It is preferably less than 20% by weight, more preferably less than 5% by weight. The substances added other than (a) and (b) are not particularly limited, but representative examples include various resins such as urethane resin, non-crosslinkable polyester resin, acrylic resin, vinyl resin, styrene resin, and defoaming agent. Agents, coatability improvers, thickeners, antistatic agents, antioxidants, ultraviolet absorbers, dyes,
Although pigments can be used, when a crosslinkable polyester copolymer grafted with an acrylic macromer is used as the polyester copolymer (b), an acrylic resin, particularly a water-dispersible acrylic resin is used. Is preferred.

Further, the thickness (d) of the coating layer in the present invention is not particularly limited as long as the ratio (D / d) to the average particle diameter (D) of the inorganic particles is 1.1 to 80, but it is 0.005 to 0.30 μm. Is preferable, and the range of 0.01 to 0.1 μm is more preferable.

Here, the crosslinked polyester copolymer is a polyester copolymer obtained by adding and blending a known crosslinking agent that reacts with carboxyl groups and hydroxyl groups at the polyester terminal to crosslink the polyester, and crosslinks by heating, ultraviolet rays, electron beams or the like. Examples thereof include those in which a reactive group is introduced into a polyester copolymer, and the polyester copolymer is self-crosslinked by heating alone or by using a crosslinking catalyst.

The former polyester copolymer is a usual polyester copolymer having a carboxyl group and a hydroxyl group at the terminal and is obtained by polycondensing a dicarboxylic acid component and a glycol component, and is not particularly limited.

The dicarboxylic acid component is an aromatic, aliphatic, or alicyclic dicarboxylic acid, such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid,
Adipic acid, sebacic acid, succinic acid, glutaric acid, 1,3
-Cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, dodecanedicarboxylic acid, azelaic acid and the like can be mentioned. Further, a metal sulfonate-containing dicarboxylic acid may be used as a copolymerization component in order to make the polyester copolymer water-soluble or to impart water-based dispersibility. Examples thereof include metal salts such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene 2,7-dicarboxylic acid and 5 (4-sulfophenoxy) isophthalic acid.

The glycol component to be reacted with the above dicarboxylic acid is an aliphatic glycol having 2 to 8 carbon atoms, or 6 to 6 carbon atoms.
12 alicyclic glycols, and specific examples include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1, 2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4
-Cyclohexanedimethanol, p-xylylene glycol, diethylene glycol, triethylene glycol and the like. Polyethylene glycol, polypropylene glycol, or polytetramethylene glycol may be used as part of these glycol components.

The polyester copolymer obtained from the above dicarboxylic acid and glycol component is used by being dissolved or dispersed in water or an organic solvent or a mixed solvent of water and an organic solvent.

These copolymerized polyesters preferably have many terminal groups from the viewpoint of crosslinkability, and have a hydroxyl value of 3 to 200 mgKOH / g polymer, preferably 5 to 100 mgKOH / g polymer. When the hydroxyl value is 3 or less, the reactivity is poor, and when it exceeds 200, the toughness of the coating film is poor. When the glass transition point of the copolyester is 10 to 90 ° C, preferably 40 to 70 ° C, suitable moisture-resistant adhesion is exhibited.

The cross-linking agent for cross-linking the polyester copolymer is not particularly limited as long as it reacts with a carboxyl group at the terminal, a hydroxyl group and becomes three-dimensional, but representative examples are methylolated or alkylolated urea-based and melamine-based. , Acrylamide-based and polyamide-based resins, and epoxy compounds, isocyanate compounds, aziridine compounds and the like. Among them, it is preferable to use a methylolated melamine or an isocyanate compound in terms of adhesion to a substrate, particularly wet adhesion. The amount of the cross-linking agent to be added is appropriately selected depending on the type of the cross-linking agent, but it is preferable to add it in an amount equivalent to the terminal amount of the normal polyester copolymer, usually 2 to 30 parts in solid content ratio with respect to the polyester copolymer, It is preferably 5 to 20 parts.

Further, the particularly preferable reactive group-introduced polyester copolymer is the following compound having a functional group such as a reactive functional group, a self-crosslinking functional group and a hydrophilic group in the polyester copolymer which is a trunk polymer. It was introduced. Examples of the compound having a carboxyl group or a salt thereof, or an acid anhydride group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and macromers thereof. On the other hand, as a compound having an amide group or an alkylolated amide group, acrylamide,
Methacrylamide, N-methyl methacrylamide, methylol acrylamide, methylol methacrylamide, ureido vinyl ether, β-ureido isobutyl vinyl ether, ureido ethyl acrylate and the like and macromers thereof can be mentioned. Further, as the compound having a hydroxyl group, β-hydroxyethyl methacrylate,
β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β-hydroxyvinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate, etc. And their macromers. Examples of the compound having an epoxy group include glycidyl acrylate, glycidyl methacrylate, and macromers thereof. It goes without saying that macromers obtained by copolymerizing various monomers may be used.

Among these reactive groups, methacrylic acid, acrylic acid, methylol acrylamide, in terms of adhesion with the coating material,
Grafted products of glycidyl acrylate or glycidyl methacrylate or macromers thereof are particularly preferred.

The polyester copolymer having these reactive groups can be crosslinked by heating after coating, but it is more preferable to use a crosslinking catalyst together because crosslinking is further promoted. As the crosslinking catalyst, ammonium chloride, ammonium nitrate, citric acid, oxalic acid, p-toluenesulfonic acid, dialkyltin complex and the like can be used. The amount of the crosslinking catalyst added is 0.5 to 5 parts, preferably 1 to 3 parts, based on the solid content of the polyester copolymer.

The polyester copolymer having a cross-linking agent and the polyester copolymer having a reactive group introduced are applied to a substrate and then heated,
Although it is crosslinked by ultraviolet rays, electron beams, etc., a method of heating is generally used.

The heating is not particularly limited as long as it can be crosslinked to such an extent that the object of the present invention can be achieved, but is usually 60 to 260 ° C. for 0.1 second to
It is 15 minutes, preferably 1 second to 2 minutes at 100 to 240 ° C. In the case where the base film is a biaxially stretched polyester film, it is more preferable that it be crosslinked at high temperature if it is dried and heat-treated after being applied in the manufacturing process.

The average particle size (D) of the inorganic particles (a) used in the present invention is
The thickness is 0.08 to 2.2 μm, preferably 0.08 to 0.6 μm. When the average particle diameter (D) is less than 0.08 μm, the blocking resistance of the film becomes insufficient, and further, the cohesiveness of the particles is increased, so that the generation of coarse foreign matters deteriorates the electric insulating property, which is not preferable. On the other hand, those exceeding 2.2 μm are not preferable because the film surface is remarkably roughened and the electrical insulating property is similarly deteriorated.

The average particle size as used herein is measured using a centrifugal sedimentation type particle size distribution measuring device (SA-CP2 type manufactured by Shimadzu Corporation).

The type of the inorganic particles (a) in the present invention is not particularly limited, but typical particles include talc, kaolin, heavy or light or synthetic calcium carbonate, titanium oxide, silica, lithium fluoride, calcium fluoride, and sulfuric acid. Mention may be made of barium, alumina, zirconia, calcium phosphate or natural or synthetic swelling or non-swelling mica. However, among them, from the viewpoint of dispersibility, it is preferable to use an inorganic colloid which is present in the form of a colloid in water from the viewpoint of dispersibility in a coating material.

The term “inorganic colloid” as used herein is defined in the Kyoritsu Publishing Chemical Dictionary, and contains 10 ⁵ to 10 ⁹ atoms in one particle. Depending on the element, it is obtained as a metal colloid, an oxide colloid, or a hydroxide colloid. As the metal colloid, gold, palladium, platinum, silver, sulfur and the like are preferably used, and as the oxide colloid, hydroxide colloid, carbonate colloid and sulfate colloid, zinc, magnesium, silicon, calcium, aluminum and strontium are used. , Barium, zirconium, titanium, manganese, iron, cobalt, nickel,
Oxide colloids such as tin, hydroxide colloids, carbonate colloids, and sulfate colloids are preferably used in the present invention. For example, a silicic acid colloid obtained by adding silicon tetrahalide to water or gradually adding concentrated hydrochloric acid to an aqueous solution of an alkali silicate is very preferably used in the present invention.

The average particle size of the inorganic colloid is 0.08-0.6 μm, preferably
It is desirable that the thickness is in the range of 0.11 to 0.3 μm, more preferably 0.15 to 0.25 μm. This has an average particle size of 0.08-0.6μ
When it is m, the stability is excellent in the aqueous solution of the inorganic colloid particles, which is preferable.

In the film of the present invention, the ratio (D / d) of the average particle diameter (D) of the inorganic particles of the coating layer to the coating layer thickness (d) must be 1.1 to 80. Preferably 2.0-40, more preferably
It is in the range of 3.0 to 15. If the (D / d) is less than 1.0, the slipperiness and blocking resistance of the laminated film deteriorate, which is not preferable. On the other hand, when the (D / d) is 80 or more, the abrasion resistance of the easy-adhesion layer is deteriorated and powder is generated, which is a product defect, which is not preferable.

Next, a typical method for producing the film of the present invention will be described, but the method is not limited thereto.

First, a biaxially stretched polyester film as a base material is prepared. If necessary, this film may be subjected to corona discharge treatment in air or various atmospheres. The anchor treatment may be performed using a known anchor treatment agent such as urethane resin or epoxy resin, but it is not particularly necessary. After coating the coating layer on the film by a known method such as gravure coating, reverse coating, or spray coating, the coating layer is coated at 60 ° C to 260 ° C for 0.1 sec to 15 sec.
Dry for about a minute.

The coating layer may be formed separately and laminated later. However, the coating layer is preferably insufficient in strength, and thus a method of directly coating the substrate film is preferable.

Further, it can be applied in the manufacturing process of the base film. That is, specifically describing one example, at least one surface of the polyester film after stretching in one direction is applied, and after drying or stretching in the perpendicular direction while drying, heat treatment is performed or stretching in the perpendicular direction is performed. After
This is a method of re-stretching in one direction and heat treatment. This method is particularly preferable because the coating layer can be applied thinly and uniformly, and the crosslinking of the polyester copolymer proceeds rapidly and highly.

The characteristic values used in the present invention are based on the following measuring methods and evaluation criteria.

(1) Blocking resistance Fifty sheets of 100 μm-thick, size A4 film having a predetermined coating layer on both sides of the film are stacked and left for 60 minutes in a hot air oven at an ambient temperature of 170 ° C. The samples are gradually cooled at room temperature and then peeled one by one. At that time, as in the case before the heat treatment without sticking to each other, those that can be peeled off are judged as “◯”, and the others are judged as “x”.

(2) Adhesion at normal temperature After coating and curing the following four types of coating materials i) to iv) on a predetermined coating layer, put a 1 mm square so-called burdock,
180 with the cellophane tape (manufactured by Nichiban Co., Ltd.)
Forcible peeling was performed in the ° direction, and the judgment was made according to the following criteria. That is, "○" indicates that less than 15% of the total peeled area is peeled off, and "x" indicates that it is peeled off more. Further, when the peeled area was less than 5%, it was judged as "A". However, the first
The table shows the result when the adhesion is the worst among the four types of paints.

i) Nihon Atchison ED450SS (50%) ML-25089 (50%) was applied by 7 μm by screen printing method, and then UV irradiation device (80W / cm × 3 lights, height 150mm, 7-8m / min treatment).
Cured.

ii) “Vylox” 1400 manufactured by DuPont was applied to a thickness of 6 μm and then heat cured.

iii) 100 parts of UVA-9119 of Seiko Advance Co., Ltd. 40 parts of SVX-120 was applied to 4 μm and then cured in the same manner as in i).

iv) Toyo Ink FD-SS (ink) 100 parts FD Reducer P 5 parts was applied to 4 μm and then cured in the same manner as i).

(3) Moisture resistance adhesion The above-mentioned four kinds of coating materials i) to iv) were applied on the coating layer and cured, and the film was left at 85 ° C and 95% RH for 4 days, and then the same as in (2). Evaluation was performed and judged.

(4) Abrasion resistance After the surface of the coating layer of the tape-shaped film was repeatedly contacted with a metal (SUS) fixed guide (5 mmφ) 100 times,
The amount of scratches adhering to the film was observed, and the number of scratches was judged as follows.

◯: Scratch is small (good durability), ×: Scratch is large (durability is poor) (5) Coating layer thickness d (μm) A cellophane tape is attached to the coating layer, and the coating layer at the end of the cellophane tape is dimethylformamide. Dissolve and remove with a solvent such as. Next, the cellophane tape was peeled off, and the boundary between the surface protected by the cellophane tape and the surface removed by dissolution was measured with an ET-10 high-precision level difference measuring instrument manufactured by Kosaka Laboratory Ltd. to obtain the thickness.

When the above method was difficult, a transmission electron microscope HU-12 manufactured by Hitachi, Ltd. was used to observe the ultrathin section of the laminated film to determine the thickness.

(6) Center line average roughness In accordance with JIS-B-0601, using a stylus type surface roughness meter SD-3 type made by Kosaka Laboratory Ltd., cutoff 0.25 mm, measurement length
The average roughness Ra (μm) was measured at 1 mm.

(7) Dielectric breakdown characteristics Electrodag 450SS from Japan Acheson Co., Ltd., film thickness 25 μm
Apply to UV lamp 120W / cm × 2 lamps 6m / min (height 150m
m) after radiation curing, according to ASTM D-149A,
Dielectric breakdown voltage 2000V · Ac / □ was measured at n = 50. When the variation except the maximum and minimum exceeded 40% of the average breakdown voltage, it was marked as “x”, and when smaller than that, it was marked as “◯”.

〔Example〕

The present invention will be described using the following examples and comparative examples, but the present invention is not limited to these examples.

Examples 1 to 6 and Comparative Examples 1 to 6 Polyethylene terephthalate having an intrinsic viscosity of 0.64 has an average particle size.
0.008% of 0.15 μm silicon oxide (Comparative Example 1), 0.018%
(Examples 1, 4 to 6, Comparative Examples 3 to 6), 0.035% (Example 2), 0.06% (Example 3), 0.14% (Comparative Example 2) added, the resin melted at 285 ° C., surface It was extruded on a cooling drum at a temperature of 50 ° C. The film thus obtained was stretched in the longitudinal direction at 90 ° C. by a factor of 3.8, the surface was subjected to corona discharge treatment, and then a coating composition having the following composition was applied by a gravure coating method using water as a solvent. After that, while drying the paint,
The film was stretched 3.3 times at 100 ° C. and further heat-treated in an atmosphere at 220 ° C. while being relaxed in the lateral direction by 4%.

The composition of the paint used is as follows.

A. Methacrylic acid and glycidyl acrylate 20 mol% each
Water-dispersible polyester copolymer grafted in macromer form (trade name: Takamatsu Yushi Co., Ltd. PES Resin 604)
G) 100 parts by weight B. Melamine-based cross-linking agent (trade name: Nikalac MW10LF) 8 parts by weight C. Silica sol (however, the average particle size is shown in Table 1) 2.5
Parts by weight Various physical properties of the obtained film were evaluated. The results are shown in Table 1.

As can be seen from Table 1, good characteristics are exhibited only in the range of the present invention. Further, especially in the case of Example 2, the blocking resistance and the dielectric breakdown characteristics were particularly good.

Example 6 A film was formed by the same method as in Example 2. However, the paint was applied by a gravure coating method on a heat-treated biaxially stretched film, not by a uniaxially stretched film, and dried at 150 ° C. The film thus obtained was similarly evaluated. The adhesiveness was slightly inferior to that of Example 2, but similarly showed good characteristics.

[Effects of the Invention] In the present invention, since a predetermined coating layer is provided on the biaxially stretched polyester film having a specific center line average roughness, the following excellent operational effects are exhibited, and as a wiring substrate. It is suitable.

(1) Excellent adhesion to various inks and polymer pastes.

(2) The adhesiveness hardly changes even in a high temperature and high humidity atmosphere.

(3) Excellent blocking resistance.

Claims (3)

[Claims] 1. A polyester copolymer (b) crosslinked with inorganic particles (a) having an average particle diameter of 0.08 to 2.2 μm on at least one side of a biaxially stretched polyester film having a center line average roughness of 0.02 to 0.50 μm. ) Is the main component,
A polyester for a wiring substrate, which is provided with a coating layer having a ratio (D / d) of the average particle diameter (D) of the inorganic particles (a) to the layer thickness (d) of 1.1 to 80. the film. 2. The polyester film for a wiring board according to claim 1, wherein the coating layer is stretched. 3. The polyester film for a wiring board according to claim 1, wherein the polyester copolymer is grafted with a crosslinkable acrylic acid or methacrylic acid compound.