JPH0241380A - Radiation-curable paint - Google Patents

Abstract

PURPOSE: To provide a radial ray-hardening paint for a magnetic recording medium having excellent practival durability and electromagnetic converting characteristics even in high temperature and high moisture conditions in which prepolymer obtained by reaction of polyisocyanate and polyol with a specific acrylate compound is included.

CONSTITUTION: A paint includes prepolymer obtained by reaction of (A) polyisocyanate comprising 2,4-tolylenediisocyanate or the like, (B) polyol comprising polyester diol, polyether diol, polycaprolactin diol or the like, and (C) acrylate compound of a molecular weight of 140-3000 (favorably 200-1000) expressed by a formula I [R¹ is H, methyl; R² is a formula III (x is 2-30; y is 3-10; m is 1-20; n is 0-20)].

COPYRIGHT: (C)1990,JPO

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radiation-curable coating material, and more specifically, to a radiation-curable coating material suitable for producing magnetic recording media such as magnetic tapes and magnetic disks by mixing magnetic powder. Regarding radiation-curable paints.

[Conventional technology]

What about magnetic recording media in general? A magnetic layer is formed by applying a magnetic paint consisting of magnetic powder, a polymer, a solvent, and various additives onto a substrate such as a realester film.

In recent years, as a method for manufacturing such magnetic recording media, radiation-curable polymers having acrylic double bonds have been used as polymers.
A method is known in which a magnetic paint prepared by mixing this with magnetic powder, a solvent, etc. is applied onto a substrate, and this coating film is cured by radiation irradiation (for example, JP-A-56-25230, JP-A-56- Publication No. 124119, JP-A-50-77
433, etc.). The magnetic paint obtained by mixing and dispersing magnetic powder etc. into these radiation-curable polymers is
It is expected to be effective in improving the hot life of a magnetic paint, reducing the amount of solvent used, simplifying the manufacturing process of magnetic recording media, and reducing energy consumption for curing the magnetic paint.

However, in recent years, with the further expansion of its uses, the performance of magnetic recording media has come to be required to have practical durability under harsher conditions such as high temperature and humidity. however,
The magnetic recording medium using the magnetic paint described above could not maintain sufficient practical durability and electromagnetic conversion characteristics under high temperature and high humidity conditions.

[Problem to be solved by the invention]

Therefore, an object of the present invention is to provide a radiation-curable coating material that provides a magnetic recording medium that maintains excellent practical durability and electromagnetic conversion characteristics even under harsh conditions such as high temperature and humidity.

[Means to solve the problem]

That is, the present invention has the following characteristics: (field) 1+? Liisocyanate (B) polyol and (ψ General formula (1) below % formula % (1) [wherein R1 is a hydrogen atom or a methyl group R2 is a formula
Represents a group represented by A sol formed by reacting compounds with a molecular weight of 140-300G? The present invention provides a radiation-curable paint characterized by containing a remer.

Used in this invention? Liisocyanate (hereinafter referred to as “(A)
2.4-tolylene diisocyanate, 2.6-)lylene diisocyanate, 4.4'
-diphenylmethane diisocyanate, m-phenylene diisocyanate, xylylene diisocyanate), tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diincyanate ester, 1.4-
cyclohexylene zoisocyanate), 4.4'-zocyclohexylmethane zoisocyanate), 3.3'-dimethyl-4,4'-piphenylene zoincyanate, 3.3
'-dimethoxy-4,4'-piphenylene zoisocyanate, 3,3'-cyclo4゜41-piphenylene zoisocyanate, 1,5-s7talene zoisocyanate)
, 1.5-7-trahydronaphthalenezoincyanate, isophorone diisocyanate, etc., preferably 2.4
-) lylene diisocyanate, 4,4'-zophenylmethane diisocyanate, 44'-dicyclohexylmethane diisocyanate, and the like. These alone are
Alternatively, two or more types can be used in combination.

Used in this invention? Diol (hereinafter referred to as "component (B)")
), for example? Lyesterzool,? Rietherzoor,? Examples include relatively high-molecular diols such as ricazololactone diol.

? As the lyesterzool, for example, - general formula (厘-1
) (In the formula, 13 is an alkylene group having 2 to 10 carbon atoms.
R4 is a polybasic acid residue described later, h is an integer of 1 to 30, and X is an integer of 1 to 10. Ethylene glycol / lyethylene glycol, 7°c2 helene glycol, ? Lysolopylene glycol, tetramethylene glycol? Polyhydric alcohols such as ritetramethylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, geltaric acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, 7-maric acid, Examples include diols obtained by reacting with polybasic acids such as superic acid, azobic acid, methylazopic acid, sepathic acid, and oxalic acid.

Diol-1 is also available as a commercial product), such as "Nitsu? Ran 40091," Nitsu? Ran 4oo21, [
Etsu? Run 4 (1101, "Nitsu? Run 40401,"
Nitsu? Run 40321, ``Etsu?Ran 40421, [Etsu?Ran 4060'', ``Nitsu?Ran 40701, ``Nitsu?Ran 143'', ``Nitsu?Ran 150'', ``Nitsu?Ran 50181, [Nitsu?Ran 50191,'' Nitsu?Run 5
035J (manufactured by Nippon?Liurethane) and the like.

Of the above diol-1? Ridero Girenger Recall,
? Diols obtained by reacting ritetramethylene glycol etc. with azobic acid are preferred, and corresponding commercial products include "Nira?U/40091" and "Nirazelan 40Q".
2'' etc.

Also,? As the rietherzool, for example, the general formula (
厘-2) I(0+130-), H(1-2) (In the formula, R3 is the same as above, and the amount is an integer of 1 to 50) (hereinafter referred to as "diol-2") Specifically, broken ethylene glycol,? Lipropylene glycol? Examples include ritetramethylene glycol.

Diol-2 is available as a commercial product and is available under the name “PEG
#200 1, [PEG14300 1, “PR1Jk
400 1, l'-PE (46001, [PEG143
00, ``D, 4001, ``D-700J.

"D'-10001, [D-12001, "n-200
0J (manufactured by NOF Corporation), [PTMG650J (
Du? P'rMG 1000 1, PT
Examples include MG20001 and l'-PTMG3000J (manufactured by Mitsubishi Chemical Industries, Ltd.).

Of these diol-2? Litetramethylene glycol? Commercially available products such as lyethylene glycol [P
TMG 3000 1, [PTMG 1000 1, l
'-PE(44001, "Pg(4200"), etc. are preferred.

moreover,? As ricaderolactone zool, for example, the general formula (Seal-3) (where IN and X are the same as above, and j and j'
is an integer of 1 to 30) (hereinafter referred to as "diol-3"). This diol-3 is, for example, casirolactone, ethylene glycol, or Rideropyrene glycol? It can be obtained by reacting with ritetramethylene glycol or the like.

Diol-3 is also available as a commercial product, such as “Plaxel 203AL1,” “Plaxel 203,” “f2xel 205,” “Graphcel 205ml,” “f Lafcel 212,” “Plaxel 212AL1,” “Plaxel 220.” , [f Rough Cell 220ALJ (manufactured by Daicel Chemical Industries, Ltd.), among others, "f Rough Cell 205^L", "Plaxel 212", etc. are preferred.

In the present invention, at least one diol selected from these diol-1, diol-2 and diol-3 ↓ 5 to 99 mol% in the component (B),
In particular, it is preferable to use 5 to 95 moles. This value is 5
If the molar amount is less than 9, the coating film obtained by applying and curing the radiation-curable paint tends to lose its flexibility.
If it exceeds 9 mol%, the resulting coating film tends to lose its curability.

In addition, as component (B), the following may be listed as necessary. Diols can be used.

(11 diols containing polar groups such as carboxylic acid groups, carboxylic acid metal bases, sulfone dispersion groups, sulfonate metal bases, phosphoric acid groups, etc. in the molecule. Here, the polar groups contained in the obtained prepyrimer are i It is preferable to set it as less than 10-' equivalent i/f.

(2) Diol having multiple (meth)acryloyl groups in the molecule. For example, diols represented by general formula (II-4) can be exemplified.

CHl [wherein, R5 is +CH2CH10+c, (-CH2C
l(O+.

(k indicates an integer from 1 to 20), CH.

(However, W and W' are independently a group represented by -CH2CM- or Ra is a hydrogen atom or a methyl group.) These diols are available as commercial products, for example, Esther 40EM1, "Eng? Kishester 70P people", [Eng? Kishester 200PA1, "Eng.?
Xyester 80 MF', [Eng? xyester 30
02 Ml, [Eng? Xyester 3002AJ (and above,
(manufactured by Kyoeisha Yushisha Co., Ltd.), and [2? Preferred examples include Kishester 3002A1 and Kishester 70PAJ.

(3) A diol that is an oxyalkylene bisphenol derivative. For example, (broken) oxyethylene pisphenol ether and (/su) oxypropylene bisphenol A ether represented by the general formula (■-5) can be exemplified.

(Summer-5) (In the formula, R? and HM may be the same or different, C217'c is an alkylene group having 3 carbon atoms, ' and p may be the same or different, and 1 to 20 ) These are available as commercial products, for example [D movie]
350FJJDA-4001, 1'-DB-9001
, "DB-4001", "Dmu-<ooo" (manufactured by NOF Corporation), and the like.

(4) Ethylene glycol, soropylene glycol, tetramethylene glycol, 1.6-Φsameethylene glycol, glycerin, 12.3--f! Low molecular weight dE such as 1,2,3-butanetriol and 1,2,3-butanetriol
' Riolu.

In addition, in the present invention, #1 of these (B) components may include ethylenezoamine, tetramethylenecyamine, hexamethylenecyamine, A-roughenylenezoamine, 4,4'-diaminodiphenylmethane, etc. Reamine may also be used in combination.

Next, a compound represented by the general formula (summer) (hereinafter "(
4-hydroxybutyl acrylate, 6-hydroxydecyl acrylate, 10
-Hydroxydecyl acrylate, ? Liethylene glycol acrylate? Lysolobylene glycol acrylate? Examples include ritetramethylene glycol acrylate, lactone-modified 2-hydroxyethyl (meth)acrylate represented by the following structural formula (m), and the like.

(In the formula, R1 and y are the same as above, and p is 1 to 2
Among these components (C), preferred are lactone-modified 2-hydroxyethyl (meth)acrylate and the like. These are available commercially,
For example, "Plaxel FM1, l-Plaxel FA" (manufactured by Daicel Chemical Industries, Ltd.) can be mentioned.

In the present invention, these components (C) can be used alone or in combination of two or more.

The molecular weight of the compound represented by general formula (1) is 140 to
It is preferably 3,000, particularly 200 to 1,000.

If the molecular weight is less than 140, sufficient practical durability and electromagnetic conversion characteristics of the magnetic recording medium obtained when the resulting radiation-curable paint is used as a magnetic paint for a magnetic recording medium may not be obtained. If it exceeds 3,000, a problem arises in that the mechanical strength of the coating film obtained by applying and curing the radiation-curable paint is significantly reduced.

Lure used in the radiation-curable coating of the present invention? Rimmer is
For example, it can be manufactured by the following manufacturing method.

First, in the first step, component (A) and component (B) are reacted. In this first step reaction, component (A) is used in stoichiometric excess with respect to the total amount of component (B), and both are bonded together through a urethane bond, with an incyanate group at the end of the molecule. Produces urethane.

Next, in the second step, the ??generated in the first step? Add component (C) to urethane? The reaction is carried out at a ratio of approximately 5 to 2 equivalents of α5 to 1 equivalent of incyanate group possessed by urethane. Through this second step,? At the end of urethane (C
) Ingredients are combined via urethane bonds to create the desired solé? Rimmer is obtained.

The reaction in the first step is usually carried out using a catalyst such as copper naphthenate, cobalt naphthenate, zinc naphthenate, h-butyltin laurate, or triethylamine. These catalysts were used in a total amount of 100% of the starting materials used in the first step.
It is preferable to use α01 to 1 part by weight based on the weight part. Moreover, it is preferable that the reaction temperature is usually 30 to 80°C.

The reaction in the second step can be carried out in the presence of the same catalyst as above. Was the catalyst formed in the first step? It is preferably used in an amount of α01 to 1 part by weight per 100 parts by weight of urethane. The reaction in the second step is preferably 30~
Performed at 80°C.

Here, the reactions in the first and second steps can be carried out sequentially without isolating the products of each step.

When carrying out the reaction in each step, a solvent such as methyl ethyl ketone, cyclohexanone, toluene, tetrahydrofuran, methyl imbutyl ketone, dioxane, etc. can be used as necessary.

Solle used in the present invention obtained as described above? Remer〇 number average molecular weight is about 1 (LOOO~100,000
, particularly preferably about 1 (LOOO to 8α000).If the number average molecular weight is less than about 1o, ooo, the strength of the resulting coating film obtained by curing the radiation-curable paint tends to decrease; This not only increases the viscosity of the solution when preparing it as a paint, making it difficult to handle, but also increases the amount of solvent required to reduce the viscosity, especially when used as a magnetic paint.

Does the radiation-curable paint of the present invention have any requirements? Lipinyl petitral? Lipinyl acetal? urethane,
? Riester, engineering? xy resin, engineered xy urethane resin,
? vinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl propionate copolymer, vinyl chloride-
Polymer compounds such as vinyl acetate-acrylic acid ester copolymer, vinylidene chloride-acrylonitrile copolymer, phenoxy resin, nitrocellulose, nitrified cotton, acrylonitrile-zotazoene-styrene copolymer, and the like can also be blended.

These polymer compounds may have a sulfonic acid group, a sulfonated metal base, a hydroxyl group, a radiation polymerizable unsaturated bond, and the like.

Furthermore, the radiation-curable coating material of the present invention may contain a low-molecular polymer having a radiation-polymerizable unsaturated bond.

When using the radiation-curable paint of the present invention as a magnetic paint, the magnetic powder to be mixed is γ-?・Snow 03, F・3
04.7 - Iron oxide with an oxidation state intermediate between F@203 and F.304, containing Co - F@203, F.3 containing Co
04s Iron oxide in an oxidation state intermediate between Co-containing γ-F@203 and Fa3Q4, iron oxide further containing a metal element such as a transition metal element, iron oxide containing Co oxide or hydroxide Those formed with a coating layer mainly composed of
CrO2, the surface of CrO2 is reduced to Cr! Examples include those in which a 03 layer is formed, metals such as F., Co, and N1, alloys thereof, and those in which metal elements or metal elements such as transition metal elements are contained therein. Are these magnetic powders gray? It is usually used in an amount of 200 to 700 parts by weight per 100 parts by weight of reamer.

Solvents used in preparing the radiation-curable paint of the present invention include ketones such as acetone, methyl ethyl ketone, methyl imbutyl ketone, and cyclohexanone; esters such as ethyl formate, ethyl acetate, and butyl acetate; methanol, and ethanol. Alcohols such as , inzoronoQnol, and citanol; Aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; Aliphatic hydrocarbons such as hexa/, heptane; Examples include glycol ethers such as dioxane. How much of these solvents should be used? It is usually 200 to 2,500 parts by weight per 100 parts by weight of reamer.

Soy, when preparing the radiation-curable paint of the present invention, Cagrilic acid, Cabric acid, Lauric acid, Myristic acid, IQ Lumitic acid, Stearic acid, Oleic acid, Elaidic acid, Linoleic acid, Rilunic acid, Stearolic acid, Dispersants such as lecithin, organic titanium compounds, and organic silane compounds; Lubricants such as molybdenum disulfide, graphite, and silicone oil; abrasive agents such as aluminum oxide, chromium oxide, and silicon oxide; cargo grac graft? Conductive fine powder such as Rimmer: Su? Natural surfactants such as nin; nonionic surfactants such as alkylene oxide, glycerin, and glycidol; cationic surfactants such as higher alkyl amino acids, quaternary ammonium salts, bilysin, phosphoniums, and sulfoniums; cardan Anionic surfactants containing acidic groups such as acids, sulfonic acids, phosphoric acids, sulfuric ester groups, phosphoric ester groups, etc. Ampholytic surfactants such as amino acids, amino sulfonic acids, sulfuric acid or phosphoric esters of amino alcohols: Antistatic agents such as black; antirust agents such as phosphoric acid, sulfamide, bilicin, dicyclohexylamine nitrite, and cyclohexylammonium casenate can be blended.

When manufacturing a magnetic recording medium using the radiation-curable paint of the present invention as a magnetic paint, the film to be coated may be, for example: Liethylene terephthalate, etc.? Riester;? Lipropylene etc.? Liolefin; cellulose triacetate,
Cellulose derivatives such as Selmies diacetate:? Licarmenate;? Vinyl chloride:? Examples include liimide; non-magnetic metals such as aluminum and copper; and paper. Furthermore, the radiation-curable coating material of the present invention can be used as an undercoat, totsuzo coat, back coat, etc. when manufacturing magnetic recording media.

The radiation used for crosslinking and curing the radiation-curable paint of the present invention includes electron beams, γ-rays, neutron beams, β-rays,
Examples include X-rays and X-rays, but electron beams are particularly preferred from the viewpoint of controlling the radiation dose and ease of introducing the radiation irradiation device into the manufacturing process. The electron beam used has an accelerating voltage of 100~ from the viewpoint of penetrating power.
It is preferable to use a 750 KV electron beam accelerator and irradiate the coating film so that the absorbed dose of the electron beam is α5 to 30 megarads.

Note that the mechanical properties of the radiation-curable paint of the present invention after curing vary depending on the radiation curing conditions, etc., but usually have an elastic modulus of 10ζ/傂2 or more and a breaking strength of 9 ok/r:m.
The above, and adjust the appropriate amount so that the elongation at break is 7% or more. Used with select rimmer.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

In addition, in the following synthesis examples, the molecular weight is a value determined by an osmotic pressure method.

Also, the gray of each synthesis example? The solution viscosity of the reimer was measured at 25°C using a B-type viscometer manufactured by Tokyo Keiki Co., Ltd. for a 40% by weight solution in the solvent used in the synthesis of the previlmer in each example.
This is the value measured at (Senna size + CP).

Synthesis of Prepilimer Synthesis Example 1 ■ In a flask equipped with a thermometer, a stirrer, and a reflux condenser, 141.5f of 4*'4'-dicyclohexylmethanezoinocyanate and 1.5f of diptyltin dilaurate were added.
2T and a mixed solvent of methyl ethyl ketone and cyclohexanone (volume ratio 50:50) at 200F were added and heated to 60°C. This is a copolymer of azobic acid and butanediol, while being careful not to raise the temperature of the system from the dropping funnel. Liesterzool (manufactured by Nippon Riuretan Co., Ltd., Nitsuran 4009, hereinafter referred to as Liesterzool (1)) 8F1.8f, l? Lyoxyethylene bisphenol ether (DA-3 manufactured by Nippon Oil & Fats Co., Ltd.)
5op) 12tst, acrylic acid adduct of bisphenol alkylene oxide derivative (manufactured by Kyoeisha Yushi Co., Ltd., Polyoxyester 3002A, hereinafter referred to as "specific hydroxy compound (1)") 32-4? and a mixed solvent of methyl ethyl ketone and cyclohexanone (volume ratio 5
Drop a uniform mixture of 0:50') 400t,
After completion of the dropwise addition, the mixture was reacted at 60° C. for 4 hours. Next, e-caprolactone-modified 2-hydroxyethyl acrylate (manufactured by Daicel Chemical Co., Ltd., Zolaxel FA) having the following formula structure was added to this.
-51 molecular weight approximately 686) 12.76F was added, and further 6
The reaction was carried out at 0°C for 4 hours.

After the expansion was completed, it was confirmed by infrared absorption spectrum that no isocyanate groups remained in the system. Pres obtained in this way? The remer is referred to as polymer (1). Polymer (1
) has a molecular weight of 43×104 and a solution viscosity of 23.800e.
It was p.

Synthesis Example 2 In a flask equipped with a thermometer, a stirrer, and a reflux condenser,
2.4-Toluene diisocyanate 12α5f, sibutyltin laurate 1.2f and tetrahydrofuran 2
00f was added and heated to 60°C. Add one drop to this using the funnel, being careful not to raise the temperature of the system. Litetramethylene glycol (manufactured by Mitsubishi Chemical Industries, Ltd., FTMG)
looo) 21 &6 F, /lioxyalkylene pisphenol A ether (manufactured by NOF Corporation, DA-4
00) 3 a 6 f, 12.5 F of acrylic acid adduct of ethylene glycol zoglycisol ether derivative (manufactured by Kyoeisha Yushi Co., Ltd., 40 gM of polyester) and 350 f of tetrahydro-72 were uniformly mixed and the mixture was added dropwise. After the dropwise addition was completed, the mixture was reacted at 60° C. for 2 hours. Next, ethylene glycol-luminium, 8F and tetrahydro 7ran 5
The solution dissolved in 0t was added dropwise, and after the dropwise addition was completed, the reaction was allowed to proceed for 2 hours. Finally, a compound IL1f'i whose main structure is represented by the formula % was added, and the mixture was further reacted at 60° C. for 4 hours.

After reaction route T, it was confirmed by infrared absorption spectrum that no incyanate groups remained in the system. Did you get it like this? The remer is referred to as polymer (2).

The molecular weight of polymer (2) is 4.5X10', and the solution viscosity is 2
It was 6,500cp.

Example 1 A magnetic paint having the following composition was prepared using the polymer (1) obtained in Synthesis Example 1.

Co-containing -F@201 80 parts by weight polymer (1120 parts by weight (solid content equivalent)) This was coated to a thickness of 15 μm/6 μm on the ester film, subjected to magnetic field orientation treatment, and left at room temperature overnight. After drying, the coating film was irradiated with an electron beam using an electro-curtain type electron beam accelerator at an acceleration voltage of 160 kilodalt and an absorbed dose of 7 megarads to cure the coating film, thereby obtaining a magnetic cured coating film.

Separately, in the above composition, except for excluding the magnetic powder, a paint having the same composition was applied to the glass plate so that the dry film thickness of the paint was 40 to 60 μm, and the thickness was 100 μm.
Each film was coated to a thickness of 40 to 50 μm on the Lyester film, dried overnight at room temperature, and then irradiated with an electron beam at an accelerating voltage of 180 kilodal and an absorbed dose of 5 megarad to cure the coating, making it non-magnetic. A coating film was obtained.

In order to evaluate various properties of the obtained magnetic paint, magnetic cured coating, and non-magnetic cured coating, the following tests (1) to (9) were conducted as follows.

Magnetic paint・・・・・・Test (1) Magnetic cured coating・
......Tests (3) to (6) Non-magnetic cured coating (
(substrate glass plate)...Tests (I) and (8) Non-magnetic cured coating (substrate double-broken ester film)...
...Test (9) The results of these tests are shown in Table 1.

il+ filtration test: It was observed whether the magnetic paint could be 100% filtered in 1 minute using a filter having an average pore size of 2 μm.

(2) Gloss test: Measure the gloss of the magnetic cured coating film at a reflection angle of 45° using a digital gloss needle (Newly manufactured by Murakami Color Technology Research) 1. If the gloss is 70-90, ◎, 50-70 In the case of t-0, the case of 30 to 50 was evaluated as Δ, and the case of 30 or less was evaluated as ×.

(3) Surface observation: Observe the surface of the magnetic cured coating using a scanning electron microscope. ○ indicates a state in which aggregation is observed in a portion of the test sample, Δ indicates a state in which some agglutination is observed in the rest of the test sample, and × indicates a state in which aggregation is observed over the entire surface of the test sample. evaluated.

Adhesion test: Adhesive tape is pasted on the surface of the magnetic cured coating, and after adhering uniformly to the entire surface, the condition is observed when it is instantly peeled off.The magnetic cured coating is completely peeled off from the substrate. If it was peeled off, it was evaluated as ×, if it peeled off slightly, it was evaluated as Δ, if it was hardly peeled off, it was evaluated as ○, and if no peeling was observed at all, it was evaluated as ◎.

Powder shedding test: The amount of powder shedding was measured when the magnetic cured coating was sheered 20 times on 11000 emery paper at 25° C. and 50% relative humidity.

Squareness ratio (Br/Bn+) test: Toei Kogyo K K If!
oo to external magnetic field using vsM-3 type.

Magnetic properties were measured using Os. (Br = residual magnetic flux density, Bm = maximum residual magnetic flux density) Breaking strength, elongation, initial modulus test: Strip-shaped test piece (0.5 m x 10 csc x 40 to 60 μm) 1-cut out from a non-magnetic cured coating and cut out at room temperature. Measurements were made at a tensile speed of 50 m/min. Note that the following conditions were used as measurement conditions.

Initial modulus ■ 25℃ 50% relative humidity Initial modulus ■ 60℃ 50% relative humidity Breaking strength and elongation
25℃ 50% relative humidity (8) Tetrahydrofuran (T
HF) Extraction residue test: The non-magnetic cured coating film was subjected to THF Soxhlet extraction for 24 hours, and the proportion of extraction residue was measured.

(9) Bending test: Is the non-magnetic cured coating applied to the substrate? Cut each piece of Lyester film into a short piece with a width of 11 cm at 25°C, fix both ends, bend it from outside the center, and then immediately restore it to its original state 20 times per second.The bending part becomes transparent. It was observed whether peeling or destruction of the cured coating occurred. Those that withstood flexing for 500 hours were rated as ◎, those that withstood 400 hours of flexing as ○, those that withstood 900 hours of flexing as Δ, and those that did not withstand 300 hours of flexing as ×.

The measurement conditions are as follows. The case was used.

50% Relative Humidity ■ 60°C 80% Relative Humidity Examples 2 to 4 In each example, a magnetic cured coating film was obtained in the same manner as in Example 1, except that a magnetic coating material having the following composition was used. Also on a glass plate? A non-magnetic cured coating film was formed on the Lyester film in the same manner as in Example 1 using a coating material having the same composition except that it did not contain magnetic powder. The properties of the obtained magnetic paint, magnetic cured coating, and non-magnetic cured coating were evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Composition of magnetic paint of Example 2> Co-containing 7-Fe2O270X parts by weight Polymer (1) 30 parts by weight (solid content equivalent) <Composition of magnetic paint of Example 3> Co-containing -Fe103 80 parts by weight polymer (2) 20 parts by weight (solid content equivalent) Tetrahydrofuran 200 parts by weight
Composition of magnetic paint of Example 4> Co-containing -F@Tomi 03 70 parts by weight polymer (
2) 30 parts by weight (solid content equivalent) Tetrahydrofuran 200 parts by weight or less [Effects of the invention] The radiation-curable paint of the present invention has excellent practical durability and excellent electromagnetic conversion characteristics even under harsh conditions of high temperature and humidity. Give a medium.

that's all

Claims (1)

[Claims] 1. (A) polyisocyanate (B) polyol and (C) the following general formula (I) CH_2=CR^1COOR^2 (I) [wherein R^1 is a hydrogen atom or a methyl group] , R^2 is a formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (x is a number from 2 to 30, y is a number from 3 to 10, m is a number from 1 to 20, and n is a number from 0 to 20). A radiation-curable paint characterized by containing a prepolymer obtained by reacting a compound having a molecular weight of 140 to 3,000 represented by the following formula.