JP2023154268A - Protective film, housing with protective film, and electronic apparatus using the same - Google Patents

Abstract

To provide a protective film having optimum gloss feeling and brightness feeling as well as durability such as abrasion and solvent resistance, the protective film being suitable for a housing for housing an electronic component.SOLUTION: This invention relates to a protective film for a housing for an electronic component, wherein: the film thickness is 3 μm or more; and Flop Index (FI) is 9 to 13 and 60° glossiness is 10 to 50.SELECTED DRAWING: Figure 1

Description

The present invention relates to a protective film for a housing for accommodating electronic components.

2. Description of the Related Art Conventionally, outer casings for accommodating electronic components such as semiconductor devices have often been manufactured by injection molding thermoplastic resin.
In recent years, the market for electronic devices such as smartphones, tablets, and portable notebook computers has been expanding, but in these applications, there has been rapid progress in making them smaller, lighter, and thinner, and conventional molding Plastic casings are no longer suitable. This is because if the wall thickness of a conventional resin casing is made thin, its strength will be weak. Therefore, metal housings such as magnesium and aluminum are increasingly being used, which can ensure strength and satisfy requirements such as electromagnetic shielding and heat dissipation. Additionally, metal casings are easy to recycle.
Recently, in addition to durability such as abrasion resistance and solvent resistance, advanced design such as a combination of brightness and matteness is often required in order to improve the appearance, and protect the housing. In many cases, countermeasures are taken with coating agents.

Patent Document 1 discloses a pre-coated aluminum alloy plate for a housing that is made of polyester resin, acrylic resin, epoxy resin, or polyurethane resin and has excellent scratch resistance using resin beads made of acrylic resin or fluororesin. is disclosed.
Patent Document 2 describes a precoat used for the housings of electrical and electronic devices such as notebook computers, which has excellent wear resistance and scratch resistance by adding hard inorganic aggregate such as silica to the resin film. An aluminum alloy plate is disclosed.

Japanese Patent Application Publication No. 2004-98624 Japanese Patent Application Publication No. 2010-228279

However, with conventional pre-coated alloy plates, it is difficult to achieve both optimal gloss and brightness, and to satisfy the performance of the protective film, that is, durability such as abrasion resistance and solvent resistance. there were.
Furthermore, conventionally, it has been possible to determine whether the glossiness is good or bad by measuring the glossiness using a gloss meter or the like, but the glossiness has to be determined by human visual observation. However, in recent years, it has become possible to quantify the brightness using products such as those manufactured by X-rite and the BYK-mac i manufactured by BYK.

The present invention has been made in view of the above circumstances, and provides a casing for accommodating electronic components that has optimal gloss and brightness, and also has durability such as abrasion resistance and solvent resistance. The purpose is to provide a protective film suitable for

The present invention is a protective film for a casing for accommodating electronic components, which has a thickness of 3 μm or more, a Flop Index (FI) of 9 to 13, and a 60° glossiness of 10 to 50.

According to the present invention, it is possible to provide a protective film that has optimal gloss and brightness, has durability such as abrasion resistance and solvent resistance, and is suitable for housings for housing electronic components. did it.

FIG. 1 is a schematic cross-sectional view of an electronic device according to an embodiment. FIG. 2 is a diagram illustrating a Flop Index (FI) according to the present embodiment.

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated in detail.

[Protective film]
The protective film of the present invention is a protective film for a housing for accommodating electronic components. The protective film is located on the outermost surface of the housing, which is the side where the electronic components are housed, that is, the surface opposite to the inner surface.

[Film thickness]
The thickness of the protective film is 3 μm or more, preferably 4 μm or more, and more preferably 7 μm or more. If the thickness of the protective film is 3 μm or more, wear resistance and solvent resistance can be improved.
On the other hand, the thickness of the protective film is preferably 20 μm or less. When forming a protective film with a thickness exceeding 20 μm, it is not preferable because bubbles tend to remain on the coated surface when the coating for forming the protective film is applied and baked, and the appearance of the cured film tends to be poor.

<Flop Index (FI)>
The FI of the protective film is used as an index indicating the brightness. The higher the FI, the higher the glitter feeling, and the lower the FI, the lower the glitter feeling. The FI of the protective film of the present invention is 9 to 13, preferably 10 to 13, and more preferably 12 to 13. If the FI of the protective film is within this range, the desired performance of the protective film, such as its brightness, abrasion resistance, and solvent resistance, can be effectively optimized.
Incidentally, FI is measured on the surface of the coating film using a multi-angle colorimeter "BYK-mac i" manufactured by BYK Instruments. FI, that is, Flop Index is calculated by the following formula (1).

The FI measurement system is shown in Figure 2. In FI, light (incident light) is irradiated at an incident angle of 45° to the perpendicular direction of the surface to be measured, and the light reflected at a certain angle (regularly reflected light) is detected by a detector and quantified. It is calculated using the lightness L ^* . L ^* is the lightness L ^* in the L ^* a ^* b ^* color system specified in JIS Z8729, and L ^* _15° , L ^* _45° , and L ^* _110° are the values in the perpendicular direction of the surface to be measured, respectively. On the other hand, L ^* is observed at offset angles of 15°, 45°, and 110° from the specularly reflected light of light incident at an angle of 45°.

<60°gloss>
The 60° glossiness of the protective film of the present invention is from 10 to 50, preferably from 10 to 20, more preferably from 11 to 17, even more preferably from 14 to 15. If the 60° glossiness is 10 to 50, the glossiness of the protective film will be improved, and the abrasion resistance and solvent resistance will be improved.

FI and 60° gloss can be adjusted by adjusting the amount of wax or inorganic filler added in the protective film. Specifically, when the amount of wax or inorganic filler added is increased, the FI and 60° glossiness decrease, and when the amount of wax or inorganic filler added is decreased, the FI and 60° glossiness are improved. It can also be adjusted by changing the thickness of the protective film. Specifically, when the thickness of the protective film is increased, the FI increases and the 60° gloss level decreases. When the thickness of the protective film is made thinner, the opposite tendency occurs.
In addition, FI and 60° gloss can also be adjusted by adjusting the average particle diameter of the wax or inorganic filler.

<Method for manufacturing protective film>
The protective film of the present invention is formed as a cured film by applying a protective film-forming paint to a housing base material, and volatilizing and drying the liquid medium in an oven or the like.

<Coating for forming a protective film>
Paints for forming a protective film include general solvent-based paints, water-based paints, thermosetting paints such as solvent-free paints, as well as UV-curable paints, and although not particularly limited, recent years Considering environmental regulations, especially VOC regulations, water-based paints, solvent-free paints, and UV-curable paints are preferred. However, since the molecular weight of the constituent materials of solvent-free paints and UV-curable paints is low, the strength of the cured paint film is low, and the performance is not satisfactory as a protective film for a housing that requires strong durability. Hard to obtain. On the other hand, water-based paints include water-soluble and water-dispersible paints, and the latter is mainly called an emulsion type. Emulsion-type paints allow the constituent materials to have high molecular weights and provide a highly durable protective film.

(Composition of paint for forming a protective film)
Next, the structure and materials of the coating for forming a protective film will be described. Components of the paint include a base agent, a curing agent, a solvent, a wax, an inorganic filler, and the like.

(base agent)
Examples of the main resin include epoxy resin, acrylic resin, polyester resin, urethane resin, etc. Epoxy resin is particularly preferable for a protective film that requires durability including abrasion resistance.

(Epoxy resin)
The epoxy resin is preferably a bisphenol type, novolac type, naphthalene type, biphenyl type epoxy resin, or the like. Among these, bisphenol A type epoxy resin is more preferable in consideration of processability, abrasion resistance, and adhesion with the housing after forming a protective film. The epoxy resin preferably has a weight average molecular weight of 2,500 to 70,000. When the weight average molecular weight is less than 2500, the amount of unreacted substances such as bisphenol A remains large, and physical properties such as durability may not be obtained sufficiently. On the other hand, if the weight average molecular weight exceeds 70,000, sufficient adhesion to the housing may not be obtained. In the present invention, commercially available bisphenol A epoxy resins include, for example, JER1007, JER1009, and JER1010 manufactured by Mitsubishi Chemical Corporation.

(Acrylic modified epoxy resin)
Since an epoxy resin alone cannot be dissolved or dispersed in water, a stable water-based paint can be obtained by modifying it with an acrylic resin or an acrylic monomer having a carboxyl group. Acrylic modified epoxy resin is a composite resin obtained using an ethylenically unsaturated monomer and an epoxy resin, and examples of its manufacturing methods include (a) graft polymerization method, (b) esterification method, and (u) ) direct polymerization method, etc. That is,
(a) Graft polymerization method: Using a radical polymerization initiator in the presence of an epoxy resin, (meth)acrylic acid ["acrylic acid" and "methacrylic acid" are collectively written as "(meth)acrylic acid"] . Same below. This is a method of obtaining an acrylic-modified epoxy resin in which an acrylic polymer is grafted onto an epoxy resin by polymerizing ethylenically unsaturated monomers containing carboxyl group-containing monomers such as [0010] as an essential component.
(a) Esterification method: An acrylic polymer having a carboxyl group is obtained by polymerizing an ethylenically unsaturated monomer containing a carboxyl group-containing monomer such as (meth)acrylic acid as an essential component, and a part of this carboxyl group and This is a method for obtaining an acrylic modified epoxy resin by subjecting a portion of the epoxy groups in the epoxy resin to an esterification reaction in the presence of a basic compound as a catalyst.
(c) Direct polymerization method: Part of the epoxy groups in the epoxy resin is subjected to an esterification reaction with the carboxyl group of a carboxyl group-containing monomer such as (meth)acrylic acid, and this reaction product and the carboxyl group-containing monomer are used as essential components. This is a method of obtaining an acrylic modified epoxy resin by copolymerizing with an ethylenically unsaturated monomer.

Furthermore, acrylic modified epoxy resin can also be obtained by combining the above methods. For example, there is a method in which an ethylenically unsaturated monomer is polymerized in the presence of an epoxy resin to perform graft polymerization, followed by an esterification reaction by adding a basic compound, or a method in which an epoxy resin is reacted with (meth)acrylic acid, etc. Examples include a method of directly polymerizing an ethylenically unsaturated monomer in the presence of a substance, followed by an esterification reaction.

(Ethylenically unsaturated monomer)
As the ethylenically unsaturated monomer used in the present invention, it is preferable to use a carboxyl group-containing monomer and other ethylenically unsaturated monomers.
Examples of carboxyl group-containing monomers include (meth)acrylic acid, maleic acid, itaconic acid, and fumaric acid.
Other ethylenically unsaturated monomers include:
Methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl ( Alkyl (meth)acrylates such as meth)acrylate, 2-ethylhexyl (meth)acrylate;
Hydroxyl groups such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate, hydroxyhexyl (meth)acrylate, etc. an ethylenically unsaturated monomer having;
Aromatic monomers such as styrene and methylstyrene;
N-hydroxyalkyl (meth)acrylamide such as N-hydroxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-hydroxybutyl (meth)acrylamide;
N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, N-(n-,iso)butoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, N-ethoxyethyl (meth)acrylamide , N-alkoxyalkyl (meth)acrylamide such as N-(n-,iso)butoxyethyl (meth)acrylamide;
and (meth)acrylamide.

Considering the solution stability of the acrylic-modified epoxy resin, suitability for coating, processability when forming a coating film, and adhesion to the housing, the ethylenically unsaturated monomer should have a carboxyl group concentration of 2.7 to 2.7. It is preferable to mix it so that it becomes 7.1 mmol/g. If the carboxyl group concentration is less than 2.7 mmol/g, the water dispersibility may decrease and the storage stability as a water-based paint may be impaired. On the other hand, if the carboxyl group concentration is higher than 7.1 mmol/g, it may be difficult to obtain workability, metal adhesion, and durability when forming a protective film. The carboxyl group concentration in the present invention is a theoretical value determined from the amount of carboxyl group-containing monomers contained in the composition of the ethylenically unsaturated monomer, and refers to the number of moles of carboxyl groups present per unit weight. be.

The ethylenically unsaturated monomer is preferably used in a weight ratio with the epoxy resin such that the ethylenically unsaturated monomer/epoxy resin is 10/90 to 50/50. If the weight ratio of the ethylenically unsaturated monomer is less than 10, the solution stability may be reduced or the coating properties may be poor. Furthermore, if the weight ratio of the ethylenically unsaturated monomer is greater than 50, the processability when forming a protective film, the adhesion to the casing, and the durability may be poor.
As the radical polymerization initiator used when polymerizing the ethylenically unsaturated monomer, it is preferable to use, for example, an organic peroxide, a persulfate, an azobis compound, or a redox system in which these are combined with a reducing agent. In the present invention, peroxide-based initiators are preferred, and benzoyl peroxide is particularly preferred.

The radical polymerization initiator is preferably used in an amount of 1 to 10 parts by weight, more preferably 1 to 6 parts by weight, based on a total of 100 parts by weight of ethylenically unsaturated monomers. Incidentally, reaction conditions such as temperature and time during polymerization are not special, and known conditions can be used. It is important to obtain an acrylic-modified epoxy resin by appropriately adjusting reaction conditions so that the viscosity properties when made into a water-based paint are optimal.
In the above method, basic compounds used as catalysts during the esterification reaction include alcohol amines such as dimethylethanolamine (dimethylaminoethanol), ethanolamine, diethanolamine, aminomethylpropanol, trimethylamine, triethylamine, butylamine, etc. Examples include alkylamines such as morpholine, ammonia, and the like.

The basic compound is preferably used in the reaction in a proportion of 1 to 80 moles, more preferably 5 to 60 moles, per 100 moles of the carboxyl group-containing monomer. Note that the reaction conditions such as temperature and time during the esterification reaction are not special, and the reaction can be carried out using known conditions, but the reaction may be carried out as appropriate to optimize the fluidity of the resulting aqueous paint. It is important to adjust the conditions and obtain an acrylic modified epoxy resin.
The resulting acrylic-modified epoxy resin can be made into an aqueous dispersion using a conventional method. Specifically, this is a method in which the carboxyl groups present in the acrylic-modified epoxy resin are neutralized with a basic compound or the like to impart hydrophilicity. More specifically, there is a method of adding a basic compound to an acrylic-modified epoxy resin and then adding an aqueous medium such as water to form an aqueous dispersion, and a method of adding a basic compound to an acrylic-modified epoxy resin to form an aqueous dispersion. Examples include a method of adding a medium to form an aqueous dispersion.

(Organic solvent)
The water-based paint used for forming the protective film of the present invention preferably contains 5 to 30% by weight of an organic solvent for the purpose of improving coating properties.
The organic solvent used in the reaction step when obtaining the acrylic modified epoxy resin may be contained as it is, or may be added separately as necessary.
The organic solvent is not particularly limited, but relatively highly hydrophilic solvents as shown below are preferred. Specifically, for example,
Methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, sec-amyl alcohol, n-octanol, 2- Alcohols such as ethyl-1-hexanol and tridecanol;
Glycols such as ethylene glycol, diethylene glycol, 1,3-butylene glycol;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, methylpropylene glycol, methylpropylene diglycol, propylpropylene glycol, propylpropylene diglycol, butyl Glycol ethers such as propylene glycol and dipropylene glycol monomethyl ether;
Examples include acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, 3-methoshibutyl acetate, ethylene glycol monobutyl ether acetate, and 3-methyl-3-methoxybutyl acetate.
In the present invention, from the viewpoint of the storage stability of the water-based paint and the rate of solvent volatilization during coating, the organic solvent used is an alkylene glycol monoalkyl ether whose alkyl group has 1 to 6 carbon atoms, or an alkyl group whose carbon number is 1 to 6. is preferably 1 to 10, and it is more preferable to use both in combination.

(hardening agent)
If necessary, one or more curing agents such as phenol resins can be added to the protective film-forming coating material for the purpose of improving the curability and metal adhesion of the coating film.
In addition to self-crosslinking, the phenol resin can react with carboxyl groups in the acrylic-modified epoxy resin. Moreover, when the acrylic modified epoxy resin has hydroxyl groups, the phenol resin can also react with those hydroxyl groups. Furthermore, when the ethylenically unsaturated monomer contains an amide monomer and the acrylic modified epoxy resin has a crosslinkable functional group derived from this amide monomer, it can also react with these crosslinkable functional groups.
The phenolic resins used in the present invention include trifunctional phenolic compounds such as phenol, m-cresol, and 3,5-xylenol, and difunctional phenolic compounds such as o-cresol, p-cresol, and p-tert-butylphenol. Examples include those obtained by reacting formaldehyde in the presence of an alkali catalyst. In this case, the above-mentioned phenol compounds may be used alone or in combination of two or more.
As the above-mentioned phenol resin, one in which a part or all of the methylol groups generated by addition of formaldehyde is etherified with an alcohol having 1 to 12 carbon atoms is also preferably used.
When a curing agent is used, it is preferably used in an amount of 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the main agent, for example, an acrylic modified epoxy resin.

(wax)
The wax used in the present invention is used to ensure wear resistance. The wax exists dispersedly in the paint for forming a protective film.
As such waxes, animal and vegetable waxes such as lanolin and carnauba, paraffin wax, microcrystalline wax, petrolatum such as white vaseline, and synthetic wax-based polyethylene wax can be used. In order to obtain high abrasion resistance, granular wax is preferable, and in this embodiment, it is preferable to use polyethylene wax, which has a high melting point and can exist as particles in the coating film after drying and curing.

The average particle size of the polyethylene wax is preferably about 3 to 6 μm. If the particle size is too large, the cured coating film itself becomes lumpy, the appearance and feel of the coating film deteriorates, and it cannot be used as a protective film. On the other hand, if it is too small, it will be embedded in the coating film and will not exhibit wear resistance, which is not preferable.

Note that the average particle diameter is a volume average particle diameter, and can be measured by a conventionally known method such as laser diffraction.

The amount of polyethylene wax used is preferably 4 to 25 parts by weight based on the total of 100 parts by weight of the base resin and curing agent. If it is less than 4 parts by weight, it is difficult to obtain sufficient abrasion resistance of the protective film, while if it is more than 25 parts by weight, the strength of the protective film tends to decrease.

(Inorganic filler)
The inorganic filler used in the present invention is added to the paint for forming a protective film in order to adjust the FI and gloss of the protective film.
Examples of the type of inorganic filler include various inorganic substances, and are not particularly limited, but silica fine particles are preferred. The shape of the silica fine particles is not particularly limited and may be spherical, hollow, porous, rod-like, plate-like, fibrous, or irregularly shaped. Preferably what is possible.

Commercially available products that can be used as the silica fine particles include, for example, the Silicia series manufactured by Fuji Silysia Co., Ltd. (Silysia 250N, Thylysia 350, Thylysia 370, Thylysia 380, Thylysia 420, Thylysia 440). ”, etc.), Cylohovic series (“Cylohovic 100”, “Cylohovic 200”, “Cylohovic 702”, “Cylohovic 4004”, etc.), Cylosphere series (“Cylosphere 1504”, “ SYLOID series manufactured by Grace Japan (``CYLOID W300'', ``CYLOID W500'', etc.), ACEMATT series manufactured by Evonik Degussa Japan (``ACEMATT HK460'', ``ACEMATT HK400'', ``ACEMATT OK412'') , "ACEMATT OK520", "ACEMATT OK607", "ACEMATT TS100", "ACEMATT 3200", "ACEMATT 3300", "ACEMATT 3600", etc.), NIPGEL series manufactured by Nippon Silica Kogyo Co., Ltd. ("NIPGEL A Z-200” etc.) , NIPSIL series ("NIPSIL E-200A", "NIPSIL SS-50B", "NIPSIL SS-178B", etc.), Mizusawa Chemical's Mizukashiru series ("Mizukashiru P-73", "Mizukashiru P-526", etc.) ), the AEROSIL series ("AEROSIL 200", "AEROSIL R805", "AEROSIL R972", etc.) manufactured by Nippon Aerosil Co., Ltd., and the like.

The average particle diameter of the silica fine particles is not particularly limited, but is preferably 2 to 9 μm, more preferably 3 to 7 μm. If the average particle diameter is smaller than 2 μm, the matting function tends to be insufficient, and if it is larger than 9 μm, the paint becomes lumpy and tends to remain on the protective film when it dries.
In addition, the said average particle diameter is a volume average particle diameter.

The amount of silica fine particles used is preferably 1 to 25 parts by weight based on 100 parts by weight of the base resin and curing agent. When the amount is less than 1 part by weight, the matting function tends to be insufficient. On the other hand, when it is more than 25 parts by weight, the viscosity of the paint becomes too high, and fluidity tends to decrease, making painting difficult. Furthermore, the filler is not sufficiently dispersed, and when the paint dries, it becomes lumpy and tends to remain on the protective film.

Similarly to the above-mentioned inorganic filler, fine polymer particles can also be used to adjust FI and gloss. The addition amount and average particle diameter are preferably in the same range as the inorganic filler. The inorganic filler and the polymer fine particles may be used together.

(Other ingredients)
A solvent, a surfactant, an antifoaming agent, etc. may be added to the coating material for forming a protective film in the present invention, if necessary, to improve coating properties.

(Painting method)
Coating methods include roll coating, spray coating, curtain coating, spin coating, die coating, dip coating, etc., and are not particularly limited and can be appropriately selected depending on the purpose.

(Baking conditions)
In order to obtain the protective film of the present invention, it is necessary to bake the applied paint. As a baking method, an electric oven, an infrared oven, a gas oven, etc. can be used as appropriate.
The baking temperature is preferably 180 to 220°C, more preferably 190 to 200°C. The baking time is preferably 40 to 120 seconds, more preferably 50 to 80 seconds. If the baking temperature exceeds 220° C. or the baking time exceeds 120 seconds, the coating film tends to become yellowish and colored, which is inappropriate for the appearance of the housing. Furthermore, if the baking temperature is lower than 180°C or the baking time is shorter than 40 seconds, the drying and curing properties of the paint tend to be insufficient, and the performance as a protective film such as wear resistance and solvent resistance decreases. do.

[Case]
Various metals such as aluminum, magnesium, and titanium, as well as composite resins of polycarbonate resin and acrylonitrile-butadiene-styrene resin, are used as the base material for the casing, but there is a balance between strength, portability, and cost. Aluminum and magnesium are more preferred for notebook computers and smartphones, which are important materials. The thickness of the housing base material is not particularly limited, but it is preferably 0.2 mm to 0.8 mm since it is necessary to achieve both strength and portability.
The coating layer of the housing may be formed from a single layer or from a plurality of layers. An example of a layer formed from multiple layers is to provide a resin layer (undercoat layer) containing a pearlescent pigment or colored pigment on the surface of the housing base material depending on the desired gloss or matte feel. A laminated structure may be used in which a transparent resin layer (overcoat layer) is formed on top. In this case, the protective film is formed on the surface of the top coat.
An example of a single layer is a single resin that does not contain a filler or contains an inorganic filler to provide transparency, and is used when it is desired to form a resin layer that does not require coloring. Formed in layers.

[Electronics]
The electronic device of the present invention has electronic components housed inside a casing covered with the protective film of the present invention. Its shape, structure, size, etc. can be selected as appropriate.
The electronic components to be stored include circuit boards, transistors, ICs, CPUs, and the like.
The electronic devices are not particularly limited, and include, for example, personal computers (laptop computers, desktop computers), telephones, smartphones, copy machines, facsimile machines, various printers, digital cameras, televisions, videos, CD devices, DVD devices, etc. Can be mentioned. Among these, notebook computers and smartphones are particularly preferred because they are portable and can be used.

Examples and comparative examples according to the present invention will be described. Unless otherwise specified, "part" means "part by weight" and "%" means "% by weight" as a unit of blending amount. The blending amounts of raw materials (excluding solvents) listed in the Examples section and the tables are non-volatile content equivalent values unless otherwise specified.

[Manufacture example 1]
<Production of phenolic resin (A) solution>
(1) Ion exchange water 48 parts (2) 25% sodium hydroxide aqueous solution 31 parts (3) Bisphenol A 68 parts (4) Formalin 145 parts (5) n-butanol 26 parts (6) Butyl acetate 26 parts (7) 20% aqueous hydrochloric acid solution 36 parts (8) Ion exchange water Use 120 parts for each wash. Washed 4 times.
(9) 52 parts of n-butanol

Charge (1) to (4) into a four-necked flask and react at 60°C for 3 hours under a nitrogen stream, then add (5) and (6) and cool. After cooling to below 55°C, adjust pH to 5 using (7). After leaving for about 30 minutes and discarding the aqueous phase, wash with water in step (8). Washing with water is carried out by adding (8), stirring for 15 minutes, standing for 15 minutes, and then discarding the aqueous phase, which is repeated four times. After washing with water, (9) was charged and dehydrated to obtain a phenol resin (A) solution with a non-volatile content concentration of 50%.

[Manufacture example 2]
<Preparation of base paint>
(1) Diethylene glycol monobutyl ether 40 parts (2) Ethylene glycol monobutyl ether 32 parts (3) JER1009 (manufactured by Mitsubishi Chemical Corporation) 170 parts (4) 25% sodium hydroxide aqueous solution 0.12 parts (5) Methacrylic acid 0 .6 parts (6) Hydroquinone 0.01 parts (7) Diethylene glycol monobutyl ether 34 parts (8) n-butanol 16 parts (9) Methacrylic acid 23 parts (10) Styrene 29 parts (11) Ethyl acrylate 6 parts (12 ) Benzoyl peroxide 3.7 parts (13) Benzoyl peroxide 0.31 part (14) Benzoyl peroxide 0.31 part (15) Benzoyl peroxide 0.31 part (16) Dimethylaminoethanol 9 parts (17) Ion Exchange water 164 parts (18) Ion exchange water 348 parts (19) Surface conditioner 10 parts (20) Phenol resin (A) solution obtained in Production Example 1 21 parts

Charge (1) to (6) into a four-necked flask, raise the internal temperature to 125°C, proceed with the reaction under a nitrogen stream, and cool when the acid value becomes 0.2 mgKOH/g or less. Add (7) and (8) at ℃. A mixture of (9) to (12) previously mixed in a dropping funnel was added dropwise at 117°C to 123°C over 1 hour. After the dropwise addition is completed, (13), (14), and (15) are added every 45 minutes while maintaining the internal temperature at 117°C to 120°C. Cooling is started 45 minutes after the addition of (15), and when the temperature reaches 80°C, premixed (16) and (17) are added dropwise over 30 minutes, and then (18) is added dropwise over 50 minutes. After standing for a day and night, Surfynol 104A (manufactured by Nissin Chemical Industry Co., Ltd.) as (19) was added and stirred. (20) was added and stirred to obtain a base paint with a nonvolatile content concentration of 24%.

[material]
The following materials were prepared.
Silica fine particles 1: Fuji Silysia Chemical amorphous silica fine particles "Silysia 420" average particle diameter 2.7 μm
Silica fine particles 2: Fuji Silysia Chemical amorphous silica fine particles "Silysia 350" average particle diameter 3.9 μm
Silica fine particles 3: Fuji Silysia Chemical amorphous silica fine particles "Silysia 250N" average particle diameter 5.0 μm
Silica fine particles 4: Fuji Silysia Chemical amorphous silica fine particles "Silysia 370" average particle diameter 6.4 μm
Silica fine particles 5: Fuji Silysia Chemical amorphous silica fine particles "Silysia 380" average particle diameter 9.0 μm
Polyethylene wax: “MPP-611AL” manufactured by MicroPowders, average particle diameter 4.5 μm, melting point 112°C

[Examples, comparative examples]
The above polyethylene wax was added to 416.7 parts (100 parts as resin content) of the base paint (non-volatile content concentration 24%) prepared in Production Example 2, and stirred for 10 minutes with a mixer. Subsequently, silica particles are added and stirred with a mixer for 10 minutes.
The resulting paint was applied to an aluminum plate with a thickness of 0.24 mm using a wire bar coater, and baked in an oven set at 190° C. for 1 minute to obtain a protective film having the thickness shown in the table. Comparative examples were also carried out using the formulations listed in the table and the same coating and baking conditions.

[Evaluation of physical properties of protective film]
The various physical properties of the protective film in the following items were evaluated for the coated plates obtained in Examples and Comparative Examples.

[FI]
The coating surface is measured using a multi-angle colorimeter "BYK-mac i" manufactured by BYK Instruments.
[60°gloss]
The coating surface is measured using a "VG7000" gloss meter manufactured by Nippon Denshoku Industries Co., Ltd.
[Abrasion resistance evaluation method]
Using MODEL7 RCA Abrasion Wear TESTER manufactured by NORMAN TOOL, the number of times of wear when the underlying material begins to be visible is recorded and evaluated.
<Evaluation criteria>
◎ (Excellent): 30 times or more ○ (Good): 10 to 29 times ×: (Not practical) 9 times or less [Solvent resistance evaluation method]
A piece of gauze folded in four is fixed in a 2-pound hammer, and the protective film is rubbed with methyl ethyl ketone soaked in as a solvent. Record and evaluate the number of reciprocations of the hammer when the underlying material begins to show.
<Evaluation criteria>
◎ (Excellent): 200 times or more 〇 (Good): 50 to 199 times ×: (Not practical) 49 times or less

The evaluation results are shown in Tables 1 and 2.

[Summary of results]
In Example 1, the amount of silica fine particles 2 added was 10 parts by weight and 4 parts by weight of polyethylene wax based on the total of 100 parts by weight of the main agent and curing agent, and the FI, 60° gloss, and abrasion resistance were and solvent resistance were both good.
In Examples 2 to 5, the particle size of the silica fine particles was varied, and although the FI decreased as the particle size increased, the wear resistance and solvent resistance were both at acceptable levels.
In Examples 6 to 11, the amount of polyethylene wax added was varied, and as the amount added increased, both FI and 60° gloss decreased, but both solvent resistance and abrasion resistance were at an acceptable level, especially A protective film with extremely excellent wear resistance was obtained.
In Examples 12 to 17, the thickness of the protective film was varied, but as the film thickness increased, both the abrasion resistance and solvent resistance tended to improve, and especially at 8 μm or more, all of the protective films were excellent. I was able to get
Comparative Example 1 contained neither polyethylene wax nor silica fine particles in the protective film, but the 60° gloss was too high and the abrasion resistance was very poor, so it was rejected.
Comparative Example 2 did not contain polyethylene wax in the protective film, but had poor abrasion resistance and was rejected.
In Comparative Example 3, the amount of polyethylene wax added was increased to 30 parts, but while the abrasion resistance was very good, the solvent resistance was decreased and it was rejected.
In Comparative Example 4, the film thickness was set to 1 μm, but the 60° gloss was too high and both the abrasion resistance and solvent resistance were very poor, and the film was rejected.
In Comparative Example 5, the particle diameter of the silica fine particles was varied to the smallest 2.7 μm, and although the physical properties and FI were at an acceptable level, the 60° gloss was too high and failed.
In Comparative Examples 6 and 7, the amount of silica fine particles 2 added in Example 1 was varied to 12.5 parts by weight and 15 parts by weight, respectively, based on the total of 100 parts by weight of the main agent and curing agent.
FI, abrasion resistance, and solvent resistance all passed, but the 60° gloss was insufficient.

The present invention is not limited to the above-described embodiments and examples, and design changes can be made as appropriate without departing from the spirit of the present invention.

1: Electronic equipment 2: Protective film 3: Housing base material 4: Electronic components

Claims (6)

A protective film for a housing for accommodating electronic components,
A protective film having a film thickness of 3 μm or more, a Flop Index (FI) of 9 to 13, and a 60° glossiness of 10 to 50. The protective film according to claim 1, characterized in that it is formed from a paint for forming a protective film. The protective film according to claim 2, which contains 1 to 25 parts by weight of silica fine particles based on a total of 100 parts by weight of the main agent and curing agent contained in the coating for forming a protective film. The protective film according to claim 2, which contains 4 to 25 parts by weight of polyethylene wax based on 100 parts by weight of the base agent and curing agent contained in the protective film-forming paint. A casing having a protective film according to any one of claims 1 to 4. An electronic device in which an electronic component is housed inside the casing according to claim 5.