Hot-melt resin composition coating method

Abstract

To provide a coating method for forming a thin hot-melt resin composition and a coating surface with no hole.SOLUTION: A hot-melt resin composition coating method includes a process in which a hot-melt resin composition heated so as to become a viscosity of 100 to 1,000 Pa s is discharged from a head part of a hot-melt resin composition discharge nozzle with a hydraulic pressure of 0.2 to 1.0 MPa by air, which is heated to an atomization temperature of -100 to +100°C relative to a heating temperature of the hot-melt resin composition, at a discharge rate of 0.04 to 0.1 g / sec.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for applying a hot melt resin composition. [Background technology]

[0002] BACKGROUND ART Conventionally, in electronic circuit mounting substrates, insulating moisture-proof coatings are applied using coating agents to protect exposed metal parts of electronic components such as IC chips and chip coils from moisture, dust, corrosive gases, and the like.

[0003] In recent years, the packaging density of electronic components has increased, leading to higher integration. Coating agents have become an important factor in ensuring the reliability of electronic circuit boards for these electronic components. The coating agents used on electronic circuit boards are mainly moisture-curing, UV-curing, and solvent-drying types.

[0004] On the other hand, conventional coating agents require the use of solvents, which are hazardous to the human body and undesirable from the viewpoint of the working environment. Therefore, Patent Document 1 proposes coating electronic circuit boards with hot-melt resin compositions.

[0005] However, it is not easy to apply a hot-melt resin composition thinly to an electronic circuit mounting board without forming holes in the coated surface, and there is a need to find coating conditions under which a hot-melt resin composition can be applied thinly and with good reproducibility without forming holes in the coated surface. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-50859 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, an object of the present invention is to find a method for applying a hot melt resin composition to form a thin coating surface without pores. [Means for solving the problem]

[0008] As a result of intensive research conducted by the present inventors to solve the above problems, they discovered that a hot melt resin composition can be applied thinly to a coating surface without forming holes by discharging the hot melt resin composition under specific conditions. Based on this finding, the present inventors conducted further research and completed the present invention.

[0009] That is, the present invention provides the following method for applying a hot melt resin composition. Section 1. A method for applying a hot melt resin composition, comprising the step of: heating a hot melt resin composition to a viscosity of 100 to 1,000 Pa s; and discharging the composition from the head of a nozzle for discharging the hot melt resin composition at a hydraulic pressure of 0.2 to 1.0 MPa using air heated to an atomization temperature that is −100 to +100°C relative to the heating temperature of the hot melt resin composition, at a discharge rate of 0.04 to 0.1 g / sec. Section 2. Item 2. The method according to Item 1, wherein the moving speed of the head portion relative to the surface to be coated is 100 to 300 mm / sec. Section 3. Item 3. The method according to item 1 or 2, wherein the distance between the hot melt resin composition discharge port in the head and the surface to be coated is 5 to 150 mm. Section 4. The hot melt resin composition is Contains a thermoplastic resin (A) and a liquid softener (B), Item 4. The method according to Item 3, wherein the melt viscosity (η1) at 160°C is 20,000 mPa s or less, the melt viscosity (η2) at 180°C is 10,000 mPa s or less, and the ratio (η1 / η2) of the melt viscosity (η1) at 160°C to the melt viscosity (η2) at 180°C is 1.0 to 5.0. [Effects of the Invention]

[0010] According to the method for applying a hot melt resin according to the present invention as described above, the hot melt resin composition can be applied thinly and the coated surface can be formed without pores. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, the term "containing" is a concept that encompasses all of "comprise," "consist essentially of," and "consist only of." Furthermore, in this specification, when a numerical range is expressed as "A to B," it means A or more and B or less.

[0012] The method for applying a hot melt resin composition of the present invention includes a step of discharging a hot melt resin composition heated to a viscosity of 100 to 1,000 Pa s from the head of a nozzle for discharging hot melt resin compositions at a liquid pressure of 0.2 to 1.0 MPa using air heated to an atomization temperature that is −100 to +100°C relative to the heating temperature of the hot melt resin composition, at a discharge rate of 0.04 to 0.1 g / sec.

[0013] When applying, the hot-melt resin composition is heated to reduce its viscosity. By heating, the viscosity of the hot-melt resin composition is increased to 100 Pa·s or more, preferably 200 Pa·s or more, more preferably 250 Pa·s or more, and even more preferably 280 Pa·s or more. If the viscosity is less than 100 Pa·s, the composition will not form a thin film.

[0014] On the other hand, the viscosity of the hot melt resin composition when heated is 1,000 Pa·s or less, preferably 800 Pa·s or less, more preferably 600 Pa·s or less, and even more preferably 550 Pa·s or less. If the viscosity of the hot melt resin composition is higher than 1,000 Pa·s, a thick film will be formed.

[0015] The heating temperature of the hot-melt resin composition is not particularly limited, and may be appropriately adjusted so that the hot-melt resin composition to be used has the above-mentioned viscosity. Specifically, the heating temperature is preferably 160 to 250°C, more preferably 180 to 240°C, and even more preferably 190 to 230°C.

[0016] The heated hot melt resin composition is in a molten state, and air heated to a predetermined temperature is blown onto the molten composition at a predetermined pressure, thereby discharging the hot melt resin composition from the head of the nozzle for discharging the hot melt resin composition.

[0017] The nozzle for discharging the hot melt resin composition and the head thereof may be any of a wide variety of known nozzles and are not particularly limited.

[0018] The temperature of the air sprayed onto the hot melt resin composition (hereinafter, this temperature will also be referred to simply as the "atomization temperature") is -100°C or higher, preferably -80°C or higher, more preferably -50°C or higher, and even more preferably -30°C or higher, relative to the heating temperature of the hot melt resin composition. Furthermore, the air temperature is 100°C or lower, preferably +80°C or lower, more preferably +50°C or lower, even more preferably +30°C or lower, relative to the heating temperature of the hot melt resin composition. If the atomization temperature is lower than -100°C relative to the heating temperature of the hot melt resin composition, the hot melt will not easily come out of the nozzle, resulting in an uneven film. On the other hand, if the atomization temperature exceeds +100°C relative to the heating temperature of the hot melt resin composition, holes may form in the film, potentially making it impossible to protect the substrate.

[0019] The air pressure (liquid pressure) applied to the hot melt resin composition when it is discharged from the hot melt resin composition discharge nozzle is 0.2 to 1.0 MPa, preferably 0.2 to 0.8 MPa, and more preferably 0.2 to 0.5 MPa. If the air pressure is less than 0.2 MPa or exceeds 1.0 MPa, the coated surface of the hot melt resin composition will become uneven or holes will be formed on the coated surface.

[0020] In this specification, the pressure required to spray the hot melt resin composition as a mist after the hot melt resin composition is discharged from the head of the nozzle for discharging the hot melt resin composition using the above-mentioned liquid pressure is defined as the atomization pressure. The atomization pressure is not particularly limited and may be adjusted appropriately depending on the setting of the above-mentioned liquid pressure. Specifically, the atomization pressure is preferably 0.01 to 0.5 MPa, more preferably 0.05 to 0.4 MPa, and even more preferably 0.1 to 0.3 MPa.

[0021] The amount of hot-melt resin composition discharged per unit time from the head of the above-mentioned hot-melt resin composition discharge nozzle (hereinafter simply referred to as "discharge nozzle") is 0.04 to 0.1 g / sec, preferably 0.04 to 0.08 g / sec, and more preferably 0.04 to 0.07 g / sec. If this amount is less than 0.04 g / sec, the film will have many defects. On the other hand, if this amount exceeds 0.1 g / sec, the film will become too thick.

[0022] When the hot melt resin composition is discharged from the head of the discharge nozzle, a predetermined amount of the hot melt resin composition is stored in the head while being discharged. The amount of the hot melt resin composition stored in the head is not particularly limited. For example, it is preferably 0.003 to 0.009 mL, and more preferably 0.005 to 0.006 mL.

[0023] In this specification, the moving speed of the discharge nozzle relative to the surface to be coated when applying a hot melt resin composition is defined as the moving speed of the head of the discharge nozzle when the surface to be coated is viewed from above with the head of the discharge nozzle on the near side.

[0024] The moving speed of the head is preferably 100 mm / sec or more, more preferably 200 mm / sec or more, and even more preferably 300 mm / sec or more. By setting the moving speed to 100 mm / sec or more, the hot melt resin composition can be applied thinly.

[0025] The moving speed of the head is preferably 300 mm / sec or less, more preferably 200 mm / sec or less, and even more preferably 300 mm / sec or less. By setting the moving speed to 300 mm / sec or less, a sufficient film thickness of the hot-melt resin composition can be obtained on the coated surface.

[0026] The distance between the discharge port in the head of the discharge nozzle through which the hot melt resin composition is discharged and the surface to be coated (hereinafter, this distance is also referred to as "clearance" in this specification) is preferably 5 to 150 mm, more preferably 5 to 50 mm, and even more preferably 5 to 19 mm. By adopting such a configuration, an appropriate film thickness of the hot melt resin composition can be obtained.

[0027] The application width during application (generally corresponding to the head width of the nozzle portion) is preferably 1 to 10 mm, and more preferably 3 to 5 mm.

[0028] The hot melt resin composition used in the present invention can be a wide variety of known hot melt resin compositions and is not particularly limited. However, it is preferable to use one that contains a thermoplastic resin (A) and a liquid softener (B), has a melt viscosity (η1) at 160°C of 20,000 mPa·s or less, a melt viscosity (η2) at 180°C of 10,000 mPa·s or less, and has a ratio (η1 / η2) of the melt viscosity (η1) at 160°C to the melt viscosity (η2) at 180°C of 1.0 to 5.0.

[0029] Such a hot melt resin composition will be described below.

[0030] (Thermoplastic resin (A)) The thermoplastic resin (A) is not particularly limited as long as it is a thermoplastic resin, and examples thereof include polystyrene-based resins, polyolefin-based resins, polyester-based resins, polyurethane-based resins, etc. Among these, polystyrene-based resins and polyolefin-based resins are preferred, with polystyrene-based resins being more preferred, in that they have even better electrical insulation and moisture resistance.

[0031] The thermoplastic resins may be used alone or in combination of two or more.

[0032] Examples of polystyrene-based resins include homopolymers or copolymers of styrene-based monomers such as styrene, α-methylstyrene, and chlorostyrene; and styrene-based block copolymers, which are block copolymers of styrene-based monomers and olefin-based monomers such as ethylene monomers, propylene monomers, and butylene monomers.

[0033] Examples of styrene-based block copolymers include styrene-based thermoplastic elastomers, more specifically, styrene-butylene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), and the like.

[0034] Alternatively, a hydrogenated styrene block copolymer may be used. Examples of the hydrogenated styrene block copolymer include block copolymers obtained by block copolymerizing a vinyl aromatic hydrocarbon with a conjugated diene compound and hydrogenating all or part of the blocks based on the conjugated diene compound in the resulting block copolymer. Specific examples of the hydrogenated styrene block copolymer include styrene-ethylene / butylene-styrene copolymer (SEBS), styrene-ethylene / propylene-styrene copolymer (SEPS), styrene-ethylene / ethylene / propylene-styrene copolymer (SEEPS), styrene-ethylene / butylene / styrene-styrene copolymer ("SEBSS"), and styrene-ethylene / propylene / styrene-styrene copolymer ("SEPSS"). Among these, in terms of further improving the bleed-out resistance of the hot melt resin composition, styrene-butylene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), styrene-ethylene / butylene-styrene copolymer (SEBS), styrene-ethylene / propylene-styrene copolymer (SEPS), and styrene-ethylene / ethylene / propylene-styrene copolymer (SEEPS) are preferred, and styrene-ethylene / butylene-styrene copolymer (SEBS), styrene-ethylene / propylene-styrene copolymer (SEPS), and styrene-ethylene / ethylene / propylene-styrene copolymer (SEEPS) are more preferred.

[0035] The styrene-ethylene / butylene-styrene copolymer (SEBS), styrene-ethylene / propylene-styrene copolymer (SEPS), styrene-ethylene / ethylene / propylene-styrene copolymer (SEEPS), etc. are preferably those having a triblock structure as the main structure. Here, a triblock structure refers to a styrene-based block copolymer in which the terminal styrene units in the structure of the styrene-based block copolymer form an endblock phase, and the ethylene / butylene units, ethylene / propylene units, and ethylene / ethylene / propylene units form a midblock phase in each of the copolymers, and is also referred to as an ABA type. When such a styrene-based block copolymer having a triblock structure as the main structure is used, the adhesion between a coating formed from the hot melt resin composition and an electronic circuit mounting board is further improved when the hot melt resin composition contains a tackifier (D) described below.

[0036] The weight average molecular weight (Mw) of the styrene block copolymer is preferably 20000 to 200000. When the weight average molecular weight (Mw) of the styrene block copolymer is within the above range, the foaming suppression property during application is further improved.

[0037] In this specification, the weight average molecular weight (Mw) of the styrene-based block copolymer is a measured value obtained by using a gel permeation chromatography measuring device and converting it into standard polystyrene.

[0038] The weight average molecular weight (Mw) of the styrene-based block copolymer can be measured, for example, using the following measuring device and under the following measuring conditions. Measurement equipment: Waters product name "ACQUITY APC" Measurement conditions: Column ·ACQUITY APC XT45 1.7μm×1 piece ·ACQUITY APC XT125 2.5μm×1 piece ·ACQUITY APC XT450 2.5μm×1 piece Mobile phase: tetrahydrofuran 0.8 mL / min Sample concentration: 0.2% by mass Detector: Refractive index (RI) detector Standard material: Polystyrene (Waters, molecular weight: 266-1,800,000) Column temperature: 40°C RI detector temperature: 40℃

[0039] Commercially available styrene block copolymers can be used, including, for example, Kraton's trade names "MD-1648," "G-1645," and "G-1650" for styrene-ethylene / butylene-styrene copolymers (SEBS), Kuraray's trade name "Septon 2004" for styrene-ethylene / propylene-styrene copolymers (SEPS), and Kuraray's trade name "Septon 4033" for styrene-ethylene / ethylene / propylene-styrene copolymers (SEEPS).

[0040] The styrene-based block copolymer may be used alone or in combination of two or more.

[0041] The styrene content of the styrene block copolymer is preferably 10% by mass or more, and more preferably 20% by mass or more, based on 100% by mass of the styrene block copolymer. When the lower limit of the styrene content of the styrene block copolymer is within the above range, the curing time after application of the hot melt resin composition is further shortened, and tack-free properties are further improved. Furthermore, the styrene content of the styrene block copolymer is preferably 50% by mass or less, and more preferably 40% by mass or less, based on 100% by mass of the styrene block copolymer. When the upper limit of the styrene content of the styrene block copolymer is within the above range, adhesion between the coating formed from the hot melt resin composition and the electronic circuit mounting board is further improved.

[0042] In this specification, the "styrene content" of a styrene block copolymer refers to the content (mass %) of styrene blocks in the styrene block copolymer.

[0043] In this specification, the styrene content in the styrene-based block copolymer can be calculated, for example, by a method using proton nuclear magnetic resonance spectroscopy or infrared spectroscopy in accordance with JIS K6239.

[0044] The polyolefin resin is not particularly limited, and examples thereof include olefin copolymers such as polyethylene, polypropylene, polybutene, polymethylpentene, ethylene-propylene copolymer, ethylene-octene copolymer, and ethylene-butene copolymer, as well as olefin block copolymers which are block copolymers of these resins. Among these, it is preferable to use an olefin block copolymer.

[0045] As the polyolefin resin, commercially available products can be used, such as an olefin block copolymer (OBC) under the trade name "Infuse D9807" manufactured by The Dow Chemical Company.

[0046] The content of the thermoplastic resin (A) in the hot melt resin composition is preferably 15% by mass or more, and more preferably 19% by mass or more, based on 100% by mass of the hot melt resin composition. When the lower limit of the content of the thermoplastic resin (A) in the hot melt resin composition is within the above range, the curing time after application of the hot melt resin composition is further shortened, and tack-free properties are further improved. Furthermore, the content of the thermoplastic resin (A) in the hot melt resin composition is preferably 34% by mass or less, and more preferably 25% by mass or less, based on 100% by mass of the hot melt resin composition. When the upper limit of the content of the thermoplastic resin (A) in the hot melt resin composition is within the above range, adhesion between the coating formed from the hot melt resin composition and the electronic circuit mounting board is further improved.

[0047] (Liquid softener (B)) The hot melt resin composition preferably contains a liquid softener (B). In this specification, the term "liquid" refers to a state in which the composition exhibits fluidity at room temperature (5 to 35°C).

[0048] The liquid softener (B) is not particularly limited, and examples thereof include paraffinic process oil, naphthenic process oil, aromatic process oil, liquid paraffin, hydrocarbon synthetic oil, etc. Among these, paraffinic process oil, naphthenic process oil, liquid paraffin, and hydrocarbon synthetic oil are preferred in terms of more excellent heat stability, and paraffinic process oil, naphthenic process oil, and hydrocarbon synthetic oil are more preferred. Paraffinic process oil is even more preferred in terms of further improving coatability.

[0049] Commercially available paraffinic process oils can be used, such as "PW-32" manufactured by Idemitsu Kosan Co., Ltd., "Diana Fresia S32" manufactured by Idemitsu Kosan Co., Ltd., "PS-32" manufactured by Idemitsu Kosan Co., Ltd., and "PS-90" manufactured by Idemitsu Kosan Co., Ltd. By using paraffinic process oil, the increase in melt viscosity of the hot melt resin composition at low temperatures can be suppressed, and the ratio (η1 / η2) of the melt viscosity at 160°C (η1) to the melt viscosity at 180°C (η2) can be further reduced, thereby further improving the foam suppression during application.

[0050] The dynamic viscosity of the liquid softener (B) is 30 mm at 40°C. 2 / S or more is preferable, 50mm 2 / S or more is preferable, 70mm 2 / S or more is more preferable, 90mm 2 / S or more is particularly preferred. When the lower limit of the kinematic viscosity is in the above range, in a viscoelasticity measurement of the hot-melt resin composition in a temperature range of -40°C to 130°C, the temperature at the intersection of the temperature-storage modulus G' curve and the temperature-loss modulus G'' curve in a temperature range of 50°C or higher does not become too low, and high-temperature flow resistance is further improved. In addition, the upper limit of the kinematic viscosity of the paraffinic process oil is not particularly limited, and is preferably 450 mm 2 / S or less is preferable, 300mm 2 / S or less is preferable, 200mm 2 / S or less is more preferable, and 150 mm2 / S or less is particularly preferred.

[0051] In this specification, the kinematic viscosity is a value measured using a viscometer and a measurement method described in JIS Z8803. For example, when a single-cylinder rotational viscometer is used, if the viscosity value of a liquid is η, then: [Kinematic viscosity](mm 2 / s)=η(mPa·s) / (liquid density)(g / cm 3 ) It can be calculated by the following formula.

[0052] In this specification, the density is a value measured by the method described in JIS Z8804.

[0053] In this specification, high-temperature flow resistance refers to the following characteristic. That is, when a hot-melt resin composition is exposed to high temperatures, it melts and begins to flow. This flow refers to the hot-melt resin composition being applied to an electronic circuit mounting board and flowing out of the board. In other words, high-temperature flow resistance is an indicator of whether a hot-melt resin composition melts and flows in a high-temperature environment (e.g., 80°C or higher). Hot-melt resin compositions usually have a softening point, but because they actually melt and begin to flow at temperatures lower than the softening point, it is necessary to distinguish between softening point and high-temperature flow resistance. Therefore, if the electronic circuit mounting board to be used is exposed to high temperatures, the high-temperature flow resistance must be equal to or higher than the environmental temperature. High-temperature flow resistance can be used as an indicator of whether a hot-melt resin composition is suitable for application to an electronic circuit mounting board.

[0054] As the naphthenic process oil, commercially available products can be used, such as "N-90" manufactured by Idemitsu Kosan Co., Ltd., "Diana Fresia N28" manufactured by Idemitsu Kosan Co., Ltd., "Diana Fresia U46" manufactured by Idemitsu Kosan Co., Ltd., and "Diana Process Oil NR" manufactured by Idemitsu Kosan Co., Ltd.

[0055] Commercially available liquid paraffin can be used, such as "P-100" manufactured by MORESCO and "Kaydol" manufactured by Sonneborn.

[0056] As the hydrocarbon synthetic oil, commercially available products can be used, such as "Lucant HC-10" and "Lucant HC-20" manufactured by Mitsui Chemicals, Inc.

[0057] The liquid softener (B) may be used alone or in combination of two or more.

[0058] The content of the liquid softener (B) in the hot melt resin composition is preferably 100 parts by mass or more, more preferably 110 parts by mass or more, and even more preferably 120 parts by mass or more, based on 100 parts by mass of the thermoplastic resin (A). When the lower limit of the liquid softener (B) content is within the above range, the foaming suppression ability of the hot melt resin composition is further improved, and foaming of the lead wires of the mounted electronic components during application is further suppressed. Furthermore, the content of the liquid softener (B) in the hot melt resin composition is preferably 500 parts by mass or less, more preferably 450 parts by mass or less, even more preferably 400 parts by mass or less, particularly preferably 300 parts by mass or less, and most preferably 200 parts by mass or less, based on 100 parts by mass of the thermoplastic resin (A). When the upper limit of the liquid softener (B) content is within the above range, the decrease in the melt viscosity of the hot melt resin composition is further suppressed, and the foaming suppression ability is further improved. Furthermore, by setting the upper limit of the liquid softener (B) content within the above range, in a viscoelastic measurement of the hot melt resin composition in the temperature range of -40°C to 130°C, the temperature at the intersection of the temperature-storage modulus G' curve and the temperature-loss modulus G'' curve in the temperature range of 50°C or higher will not be too low, further improving high-temperature flow properties, and further suppressing flow at high temperatures of the hot melt resin composition applied to an electronic circuit mounting board. Furthermore, by setting the upper limit of the liquid softener (B) content within the above range, an increase in the dielectric loss tangent, which is an electrical property of the hot melt resin composition, will be further suppressed, making the composition even more suitable for use in electronic circuit mounting boards.

[0059] (Wax (C)) The hot melt resin composition may contain a wax (C). By containing the wax (C), the ratio (η1 / η2) of the melt viscosity (η1) at 160°C to the melt viscosity (η2) at 180°C can be further reduced, which further improves the ability to suppress foaming during application and further improves tack-free properties.

[0060] The wax (C) is not particularly limited, and examples thereof include mineral waxes such as paraffin wax and microcrystalline wax; polyolefin waxes such as polyethylene wax, polypropylene wax and Fischer-Tropsch wax; and vinyl acetate waxes such as ethylene-vinyl acetate copolymer (EVA) wax. Among these, vinyl acetate waxes, polyethylene waxes, polypropylene waxes and Fischer-Tropsch waxes are preferred, with paraffin wax and Fischer-Tropsch wax being more preferred, in terms of further improving foam suppression.

[0061] The wax (C) may be used alone or in combination of two or more kinds.

[0062] Commercially available products can be used as the wax (C). Examples of commercially available paraffin waxes include "64-66C" manufactured by PetroChina Corporation, and examples of commercially available Fischer-Tropsch waxes include "SX105" manufactured by Nippon Seiro Co., Ltd.

[0063] The melting point of wax (C) is preferably 60°C or higher, more preferably 90°C or higher. When the lower limit of the melting point of wax (C) is within the above range, in a viscoelastic measurement of the hot melt resin composition in the temperature range of -40°C to 130°C, the temperature at the intersection of the temperature-storage modulus G' curve and the temperature-loss modulus G'' curve in the temperature range of 50°C or higher is not too low, further improving high-temperature flow resistance and further suppressing flow at high temperatures of the hot melt resin composition applied to an electronic circuit mounting board. The upper limit of the melting point of wax (C) is not particularly limited, and is approximately 115°C.

[0064] The content of wax (C) in the hot melt resin composition is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less, based on 100 parts by mass of thermoplastic resin (A). When the upper limit of the wax (C) content is within the above range, the hot melt resin composition is even less likely to become hard or brittle. There is no particular restriction on the lower limit of the wax (C) content, but it is preferably 0 parts by mass or more, and more preferably 25 parts by mass or more. When the lower limit of the wax (C) content is within the above range, foaming suppression during application is even more improved, and the insulation reliability of the mounting board is even more improved.

[0065] (Tackifier (D)) The hot melt resin composition may contain a tackifier (D). By containing the tackifier (D), the adhesion between the coating formed from the hot melt resin composition and the electronic circuit mounting board is further improved.

[0066] As the tackifier, naturally occurring tackifiers, petroleum resin-based tackifiers, and hydrogenated petroleum resin-based tackifiers can be suitably used.

[0067] Examples of naturally occurring tackifiers include rosin-based tackifiers and terpene-based tackifiers.

[0068] Examples of rosin-based tackifiers include unmodified rosins such as tall rosin, gum rosin, and wood rosin, polymerized rosin, disproportionated rosin, hydrogenated rosin, maleic acid-modified rosin, and fumaric acid-modified rosin. Furthermore, esterified rosin-based tackifiers obtained by esterifying these rosin-based tackifiers can also be used, and specific examples include glycerin esters, pentaerythritol esters, methyl esters, ethyl esters, butyl esters, and ethylene glycol esters of rosin-based tackifiers.

[0069] Examples of the terpene tackifier include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; and modified terpene resins such as terpene phenol resins, styrene-modified terpene resins, and hydrogenated terpene resins.

[0070] Examples of petroleum resin-based tackifiers include petroleum resins such as C5 petroleum resins, C9 petroleum resins, C5C9 petroleum resins, and dicyclopentadiene petroleum resins. Also included are hydrogenated petroleum resins obtained by adding hydrogen to these petroleum resins, specifically hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated dicyclopentadiene resins, and hydrogenated C5C9 resins.

[0071] The C5 petroleum resin is a petroleum resin made from the C5 fraction of petroleum. The C9 petroleum resin is a petroleum resin made from the C9 fraction of petroleum. The C5C9 petroleum resin is a petroleum resin made from the C5 fraction and C9 fraction of petroleum. Examples of C5 fractions include cyclopentadiene, isoprene, and pentane. Examples of C9 fractions include styrene, vinyltoluene, and indene. As the C5 petroleum resin and C5C9 petroleum resin, those containing dicyclopentadiene (DCPD) in the skeleton, which is derived from cyclopentadiene, a type of C5 fraction, can be suitably used.

[0072] As the tackifier (D), terpene tackifiers and hydrogenated products thereof are preferred, as they further improve the adhesion between the coating formed from the hot melt resin composition and the electronic circuit mounting board.

[0073] The tackifier (D) may be used alone or in combination of two or more.

[0074] Commercially available products can be used as the tackifier (D). Commercially available terpene-based tackifiers include terpene resins "YS Resin TO-85" and "YS Resin TO-125" manufactured by Yasuhara Chemical Co., Ltd. Modified terpene resins that are terpene-based tackifiers include terpene phenol resins "YS Polystar" manufactured by Yasuhara Chemical Co., Ltd. and "Sylvareth 1150" manufactured by Arizona Chemical Co., Ltd. Hydrogenated petroleum resins that are petroleum resin-based tackifiers include "Imarve P-145" manufactured by Idemitsu Kosan Co., Ltd.

[0075] The content of the tackifier (D) in the hot melt resin composition is preferably 180 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 130 parts by mass or less, per 100 parts by mass of the thermoplastic resin (A). When the upper limit of the content of the tackifier (D) is within the above range, the tack-free properties of the hot melt resin composition are further improved. There is no particular limitation on the lower limit of the content of the tackifier (D), and it may be 0 parts by mass or 90 parts by mass.

[0076] (Solid softener (E)) The hot melt resin composition may contain a solid softener (E). By containing the solid softener (E), the high-temperature flow resistance of the coating formed from the hot melt resin composition can be further improved.

[0077] The solid softener (E) is not particularly limited, and examples thereof include triethylene glycol tribenzoate, trimethylolethane tribenzoate, glycerol tribenzoate, sucrose benzoate, pentaerythritol tetrabenzoate, 2,2-dimethyl-1,3-propanediol dibenzoate, triethylene glycol dibenzoate, glycerol tribenzoate, 2-hydroxymethyl-2-methyl-1,3-propanediol tribenzoate pentaerythritol tetrabenzoate, and neopentyl glycol dibenzoate.

[0078] The solid softener (E) is preferably a solid softener that recrystallizes in the hot-melt resin composition. Examples of such solid softeners include benzoate ester plasticizers that are solid at room temperature, such as cyclohexanedimethanol dibenzoate. Furthermore, the solid softener (E) is more preferably a solid softener that is solid at ambient temperature and has a softening point above 60°C. Examples of such solid softeners include 1,4-cyclohexanedimethanol dibenzoate (including cis- and trans-isomers).

[0079] Commercially available products can be used as the solid softener (E). Commercially available cyclohexanedimethanol dibenzoate products include Benzoflex 352 manufactured by Eastman Co.

[0080] The solid softener (E) may be used alone or in combination of two or more.

[0081] The content of the solid softener (E) in the hot melt resin composition is preferably 60 parts by mass or less, more preferably 30 parts by mass or less, based on 100 parts by mass of the thermoplastic resin (A). When the upper limit of the content of the solid softener (E) is within the above range, the high-temperature flow resistance of the hot melt resin composition is further improved. There is no particular limitation on the lower limit of the content of the solid softener (E), and it may be 0 parts by mass or 20 parts by mass.

[0082] (Antioxidant (F)) The hot melt resin composition may contain an antioxidant (F).

[0083] Antioxidants include 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2,4-bis(octylthiomethyl)-o-cresol, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethoxy]-2,4-bis(octylthiomethyl)-o-cresol, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, and 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethoxy]-2,4-bis(octylthiomethyl)-o-cresol. Examples of antioxidants include hindered phenol-based antioxidants such as 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)]phenyl acrylate, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)]acrylate, and tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane; sulfur-based antioxidants such as dilauryl thiodipropionate, lauryl stearyl thiodipropionate, and pentaerythritol tetrakis(3-laurylthiopropionate); and phosphorus-based antioxidants such as tris(nonylphenyl)phosphite and tris(2,4-di-t-butylphenyl)phosphite.

[0084] The antioxidant (F) may be used alone or in combination of two or more.

[0085] The content of the antioxidant (F) in the hot melt resin composition is preferably 2 parts by mass or less, more preferably 1.0 part by mass or less, based on 100 parts by mass of the thermoplastic resin (A). There is no particular lower limit to the content of the antioxidant (F), and it may be 0 part by mass or 0.5 part by mass.

[0086] (Other additives) The hot melt resin composition may contain other additives, such as color pigments and flame retardants, to the extent that the addition of these additives does not substantially impair the object of the present invention.

[0087] The color pigment may be an inorganic pigment such as titanium oxide.

[0088] Examples of the flame retardant include phosphate ester flame retardants, melamine flame retardants, and inorganic flame retardants such as magnesium hydroxide.

[0089] The total content of the other additives in the hot melt resin composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of the thermoplastic resin (A). The total content of the other additives is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, per 100 parts by mass of the thermoplastic resin (A). By keeping the total content of the other additives within the above range, the hot melt resin composition exhibits even better foam suppression during application, a shorter curing time after application, and better tack-free properties and bleed-out resistance, while also imparting desired performance to the hot melt resin composition.

[0090] The hot-melt resin composition has a melt viscosity (η1) at 160°C of 20,000 mPa·s or less. If η1 exceeds 20,000 mPa·s, the hot-melt resin composition will not have a viscosity suitable for application using a dispenser, and the generation of bubbles in the lead wires of components will not be suppressed, resulting in an unsatisfactory coating film, which will reduce the reliability of electronic components and result in poor foam suppression. The melt viscosity (η1) of the hot-melt resin composition at 160°C is preferably 16,000 mPa·s or less, more preferably 15,000 mPa·s or less. The melt viscosity (η1) of the hot-melt resin composition at 160°C is preferably 1,000 mPa·s or more, more preferably 6,000 mPa·s or more.

[0091] The hot-melt resin composition has a melt viscosity (η2) of 10,000 mPa·s or less at 180°C. If η2 exceeds 10,000 mPa·s, the hot-melt resin composition will not have a viscosity suitable for application using a dispenser, and the generation of bubbles in the lead wires of components will not be suppressed. This will result in an unsatisfactory coating, which will reduce the reliability of electronic components and result in poor foam suppression. The melt viscosity (η2) of the hot-melt resin composition at 180°C is preferably 6,000 mPa·s or less, more preferably 4,000 mPa·s or less. The melt viscosity (η2) of the hot-melt resin composition at 180°C is preferably 500 mPa·s or more, more preferably 2,000 mPa·s or more.

[0092] In this specification, the "melt viscosity" refers to the viscosity of a hot-melt resin composition in a molten state after heating at a certain temperature. The melt viscosity (η1) at 160°C and the melt viscosity (η2) at 180°C are values ​​measured by heating and melting the hot-melt resin composition and measuring the viscosity in the molten state at 160°C and 180°C, respectively, using a Brookfield RVT viscometer (spindle No. 27).

[0093] The hot melt resin composition has a ratio (η1 / η2) of the melt viscosity (η1) at 160°C to the melt viscosity (η2) at 180°C of 1.0 to 5.0. If η1 / η2 exceeds 5.0, the foaming suppression effect of the hot melt resin composition when applied decreases. Furthermore, η1 / η2 is preferably 4.5 or less, more preferably 4.0 or less, even more preferably 3.5 or less, and particularly preferably 3.0 or less. Furthermore, η1 / η2 is preferably 1.5 or more, more preferably 2.0 or more.

[0094] In this specification, the ratio (η1 / η2) of the melt viscosity at 160°C (η1) to the melt viscosity at 180°C (η2) is a value measured by the following measurement method. That is, a hot-melt resin composition is heated and melted, and the viscosities in the molten state at 160°C and 180°C are measured using a Brookfield RVT viscometer (spindle No. 27), and these are designated as η1 and η2, respectively. Based on the measurement results, the ratio η1 / η2 of the melt viscosities at 160°C and 180°C is calculated to determine the value.

[0095] In a viscoelasticity measurement performed over a temperature range of -40°C to 130°C, the hot-melt resin composition preferably has a temperature at the intersection (hereinafter simply referred to as "intersection") between the temperature-storage modulus G' curve and the temperature-loss modulus G'' curve in a temperature range of 50°C or higher of 80°C or higher, more preferably 90°C or higher. When the lower limit of the temperature at the intersection falls within the above range, the high-temperature flow resistance is further improved, making the composition more suitable for use in electronic circuit mounting substrates. There are no particular limitations on the upper limit of the intersection, but it is preferably 130°C or lower, more preferably 120°C or lower.

[0096] The temperature of the intersection can be measured by the following method. Specifically, a hot-melt resin composition is heated to 180°C to melt it and then dropped onto a release-treated PET film. Next, another release-treated PET film is prepared and placed on top of the hot-melt resin composition so that the release-treated surface is in contact with the hot-melt resin composition, and the film is compressed by a heat press to a thickness of 1 mm. Next, the hot-melt resin composition sandwiched between the PET films is left to stand at 23°C for 24 hours. The release film is then removed to prepare a sample for dynamic viscoelasticity measurement.

[0097] Using the sample prepared as described above, dynamic viscoelasticity measurements (heating process) are performed using a dynamic viscoelasticity measuring device in rotational shear mode at a frequency of 1 Hz, in the temperature range of -40°C to 130°C, and at a heating rate of 5°C / min. The temperature (°C) at the intersection of the temperature-storage modulus G' curve and the temperature-loss modulus G'' curve obtained by the measurement is measured in the temperature range of 50°C or higher.

[0098] The dynamic viscoelasticity measuring device is not particularly limited, but examples thereof include a rotational rheometer (product name "AR-G2") manufactured by TA Instruments.

[0099] The temperature of the intersection can be adjusted, for example, by the following method. Specifically, to adjust the temperature of the intersection to a large extent, a wax with a high melting point and a narrow molecular weight distribution can be used, and a liquid softener with a high kinematic viscosity can be used. To adjust the temperature of the intersection to a small extent, a wax with a low melting point and a broad molecular weight distribution can be used, and a liquid softener with a low kinematic viscosity can be used.

[0100] The hot melt resin composition is a hot melt resin composition for electronic circuit mounting boards. The electronic components mounted on the electronic circuit mounting board are not particularly limited, and examples include IC chips. The hot melt resin composition is suitable for use in electronic circuit mounting boards on which IC chips are mounted as electronic components. Generally, when the electronic component is an IC chip, when the hot melt resin composition is applied to the electronic circuit mounting board, air is forced out of the gaps between the lead wires of the IC chip during application, forming bubbles that appear on the surface, which can reduce insulation reliability. Because of the above-described configuration, the hot melt resin composition has excellent foaming suppression properties during application, a short curing time after application, and excellent tack-free properties and bleed-out resistance, making it useful as a hot melt resin composition for electronic circuit mounting boards.

[0101] The hot melt resin composition is solid at room temperature (5 to 35° C.). Because the hot melt resin composition is solid within the above temperature range, it takes a short time to cure after application and has excellent tack-free properties.

[0102] The method for coating an electronic circuit mounting board with a hot melt resin composition is not particularly limited, and can be performed by a conventionally known method, such as melting the hot melt resin composition at a temperature of about 150 to 180°C and discharging it onto the surface of the electronic circuit mounting board using a dispensing machine to form a coating.

[0103] The coating thickness is preferably 700 μm or more, more preferably 1000 μm or more, and even more preferably 1500 μm or more. When the lower limit of the coating thickness is within the above range, the insulation reliability of the coated electronic circuit mounting board is further improved. Furthermore, the coating thickness is preferably 4000 μm or less, more preferably 3000 μm or less, and even more preferably 2000 μm or less. When the upper limit of the coating thickness is within the above range, tackiness is further improved. Hot melt resin compositions differ from potting compositions in that they have a thickness within the above range and do not require the provision of a frame (case) on the electronic circuit mounting board when coating.

[0104] Although the embodiments of the present invention have been described above, the present invention is not limited to these examples, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention. [Example]

[0105] Hereinafter, the embodiments of the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0106] The hot melt resin compositions used were those having the compositions shown in Table 1 below.

[0107] [Table 1]

[0108] The hot melt resin composition was applied to a 100 mm x 100 mm x 75 μm nipper release film under the conditions shown in Table 2 below. The on-off valve stroke in Table 2 refers to the amount of hot melt resin composition maintained and stored in the nozzle head when the hot melt resin composition is dispensed. The on-off valve stroke increases or decreases the hot melt storage volume by 0.0003 mL per graduation. A film thickness of 300 μm or less after application was considered acceptable, and the condition of the formed coating film was evaluated according to the following criteria, with 〇〇, 〇, or △ being considered acceptable. The lower the moisture permeability value, the more moisture-impermeable it is, which indicates a good coating film has been formed, protecting the circuitry of the substrate to which the hot melt is applied. 〇〇: 300μm or less, moisture permeability 4.0g / m 2 -24 hours or less No holes formed in the film after application 〇 :110~150μm Moisture permeability 6.0~8.0g / m 2 No holes formed on the film after 24 hours of application △ :50~90μm Moisture permeability 40~50g / m 2 No holes formed on the film after 24 hours of application ×: Holes are formed in the film after application

[0109] [Table 2]

Claims

1. A method for applying a hot melt resin composition, comprising a step of discharging a hot melt resin composition heated to a viscosity of 100 to 1,000 Pa s from a head of a nozzle for discharging the hot melt resin composition at a liquid pressure of 0.2 to 1.0 MPa using air heated to an atomization temperature that is −100 to +100° C. relative to the heating temperature of the hot melt resin composition, at a discharge rate of 0.04 to 0.1 g / sec.

2. 2. The method according to claim 1, wherein the moving speed of the head portion relative to the surface to be coated is 100 to 300 mm / sec.

3. 3. The method according to claim 1, wherein the distance between the hot melt resin composition discharge port in the head and the surface to be coated is 5 to 150 mm.

4. The hot melt resin composition is Contains a thermoplastic resin (A) and a liquid softener (B), The method according to claim 3, wherein the melt viscosity (η1) at 160°C is 20,000 mPa s or less, the melt viscosity (η2) at 180°C is 10,000 mPa s or less, and the ratio (η1 / η2) of the melt viscosity (η1) at 160°C to the melt viscosity (η2) at 180°C is 1.0 to 5.0.

Images