JPS6335438A - Coating material for optical glass fiber - Google Patents

Abstract

PURPOSE:To obtain the titled coating material having excellent curability and giving a tough cured product, by compounding a (meth)acrylate oligomer, a specific mixture and a polymerization initiator. CONSTITUTION:A mono(meth)acrylate compound of formula (R is H or methyl) is mixed with a compound taking the state of a low-viscosity liquid at normal temperature (2-2,000cps at 25 deg.C), containing >=1 polymerizable C-C double bond in one molecule and having a molecular weight of 150-5,000 [e.g. 2- ethylhexyl (meth)acrylate] at a weight ratio of 1:10-10:1 to obtain a mixture B. 100pts.wt. of a curable component composed of (A) 20-80wt% (meth)acrylate oligomer having a number-average molecular weight of 500-10,000 [e.g. epoxy (meth)acrylate oligomer] and (B) 80-20wt% above mixture B is compounded with (C) 1-10pts.wt. of a polymerization initiator (e.g. benzoin) to obtain a coating material for optical glass fiber and having a viscosity of 1,000-10,000cps (25 deg.C).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to materials for coating optical glass fibers for light transmission.

[Conventional technology]

Optical glass fibers (hereinafter simply referred to as optical fibers) used as optical transmission media usually have a diameter of 20 mm.
0 μm or less and the material is brittle, so scratches are likely to occur on the surface during manufacturing, cable production, and storage (these scratches become a source of stress concentration, and when stress is applied from the outside) The disadvantage is that the optical fiber easily breaks.

For this reason, it is extremely difficult to use optical fiber as it is as a medium for optical transmission. Therefore, conventionally, attempts have been made to coat the surface of an optical fiber with a resin, thereby maintaining the initial strength immediately after manufacturing the optical fiber and producing an optical fiber that can withstand long-term use.

Examples of such resin coating materials include those using thermosetting resins such as silicone resin, epoxy resin, and urethane resin, and those using ultraviolet rays such as epoxy (meth)acrylate, urethane (meth)acrylate, and polyester (meth)acrylate. Those using curable resin are known.

[Problem that the invention seeks to solve]

However, the above-mentioned thermosetting materials require a long time to cure and dry, resulting in poor productivity for optical fibers.Due to insufficient curing, the adhesion between the coating and the optical fiber is impaired, resulting in poor long-term reliability. I have a tendency to chip. In addition, although the above-mentioned UV-curable materials exhibit relatively good curability, the toughness of the cured product is inferior, which is determined by a comprehensive evaluation of the elongation of the cured product and mechanical strength such as tensile strength and tensile modulus. , which causes a decrease in the reliability of optical fibers.

Therefore, the present invention solves the above-mentioned conventional problems, improves the productivity of optical fibers by providing excellent curability, and greatly contributes to improving the reliability of optical fibers by providing excellent toughness of the cured product. The present invention aims to provide an industrially useful coating material for optical fibers.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors used various (meth)acrylate oligomers as the main ingredient of this type of coating material, and one of the reactive diluents used in combination with the main ingredient. When a specific mono(meth)acrylate compound having an isobornyl skeleton is used as a component, it can be quickly cured by applying it to the surface of an optical fiber and then heating it or irradiating it with ultraviolet rays or electron beams. This invention was made based on the knowledge that it has very good elongation and excellent toughness, and greatly contributes to improving the long-term reliability of optical fibers.

That is, this invention comprises: A) 20 to 80% by weight of a (meth)acrylate oligomer; B) b1) a mono(meth)acrylate represented by the following formula; [wherein R is hydrogen or a methyl group] and b2) a compound that is a liquid with low viscosity at room temperature and contains one or more polymerizable carbon-carbon double bonds in one molecule, and has at least an action as a reactive diluent for the A component together with the BL component. and the gravity ratio of the above 71 components and the b2 structure is 1 = 10 ~
The present invention relates to an optical fiber coating material characterized in that a polymerization initiator is contained in a curable component consisting of a mixture of 80 to 20% by weight in a ratio of 10:1.

In addition, in this specification, the (meth)acryloyl group refers to an acryloyl group and/or a methacryloyl group,
(Meth)acrylate means acrylate and/or methacrylate, and (meth)acrylic acid means acrylic acid and/or methacrylic acid, respectively.

In addition, the number average molecular weight described in this specification refers to a value measured by gel permeation chromatography (GPC) using polystyrene as a standard, and viscosity refers to a value measured by a Brookfield viscometer. , respectively.

[Structure and operation of the invention]

The meth)acrylate oligomer as component A used in this invention has two or more (meth)acryloyl groups, usually up to five (meth)acryloyl groups in the molecule, and particularly preferably has a small number of (meth)acryloyl groups.
Both have (meth)acryloyl groups at both ends of the molecule, and generally have a number average molecular weight of 500 to 10,000, preferably 1
,000 to about 7,000 oligomers.

Examples of such (meth)acrylate oligomers include epoxy (meth)acrylate oligomers, urethane (meth)acrylate oligomers, and polyester (meth)acrylate oligomers. You may use a mixture of more than one species.

The mono(meth)acrylate compound as the bl component, which is one of the B components used in this invention, has an isobornyl skeleton in the molecule represented by the above formula, and a (meth)acryloyl group is attached to it in one or more combinations. This compound serves as a reactive diluent for the component A together with component b2, which will be described later, and greatly contributes to improving the toughness, especially the elongation, of the cured product.

That is, since component A is generally solid or highly viscous liquid at room temperature, it cannot be used alone as a curable material that does not contain a solvent, and requires an appropriate reactive diluent. Here, if only component b2, which will be described later, is used as the above-mentioned diluent, the toughness of the cured product, especially the elongation, will inevitably decrease, but if component b1, described above is used as a part of the reactive diluent, this drawback will be avoided. Rather, the effect is that the elongation of the cured product becomes better and the toughness is improved.

Note that this b1 component is effective in imparting elongation to the cured product, but in order to obtain good results in tensile strength, hardness, etc. along with this elongation, the above b1 component and the b2 component described below are combined in a reactive manner. It is also used as a diluent.

This mono (meth)acrylate compound as component b1 can be obtained by reacting the hydroxyl group of isopoldiol with (meth)acrylic acid.

As mentioned above, the b2 component used in this invention is
Together with component b1, it acts as a reactive diluent for at least component A, but it also contributes as a component for adjusting the flexibility and hardness of the cured film.

As such two components, a compound having one or more, preferably 1 to 3 polymerizable carbon-carbon double bonds in the molecule and which is a liquid with a low viscosity at room temperature is used. The above-mentioned low viscosity liquid refers to one whose viscosity is in the range of about 2 to 2.000 centipoise/25°C. This compound is not limited to one type, but two or more types can be used in combination, but when used in combination, the properties of the mixture as described above are sufficient. Therefore, even if one of the compounds is solid or has high viscosity at room temperature Good.The molecular weight of this b2 component is usually 150 to 5.0.
It is about 00.

Specific examples of the above b2 component include 2-ethylhexyl (meth)acrylate, (meth)acrylate of tetrahydrofurfuryl alcohol caprolactone adduct, nonylphenol ethylene, which has a (meth)acryloyl group as a polymerizable carbon-carbon double bond. Oxide adduct (meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, bisphenol diethylene glycol di(meth)acrylate, hydrogenated bisphenol triethylene glycol di(meth)acrylate, trimethylolpropane tri( Epoxy synthesized from meth)acrylate, pentaerythritol tri(meth)acrylate, and bisphenol diglycidyl ether (
Examples include mono- and poly(meth)acrylates such as meth)acrylate.

In addition, as the b2 component, allyl esters such as diallyl adipate, diallyl phthalate, triallyl trimellitate, triallyl isocyanurate, styrene,
Vinyl compounds such as vinyl acetate, N-vinylpyrrolidone, N-N-dimethylacrylamide, N-N-dimethylaminopropylacrylamide, N-N-dimethylaminoethyl acrylate can also be used.

The curable component used in this invention consists of the above-mentioned A component and B component (bl component and b2 component). 20% by weight, and the weight ratio of the b1 structure and b2 component constituting component B is 1:10 to 10:1.
should be within the range of If you deviate from this range, you will not be able to obtain good results in properties such as elongation and tensile strength of the cured product, or in viscosity properties as a coating material.
Undesirable.

In the present invention, a polymerization initiator is further blended with such curable components to obtain an optical fiber coating material. As the polymerization initiator, a photopolymerization initiator that can rapidly cure the coating material by irradiation with ultraviolet light is preferred.

As this photopolymerization initiator, various kinds of initiators and aggravating agents that are generally used as initiators and aggravating agents for ultraviolet curable coatings can be used. For example, benzoin, benzoin methyl ether, hendiin ethyl ether, hendiin isopropyl ether, benzoin isobutyl ether, 2-methylbenzoin, benzophenone, Michler's ketone, benzyl, benzyl dimethyl ketal, henzyl diethyl ketal, anthraquinone, methylanthraquinone, 2
・2-Jethoxyacetophenone, 2-methylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, anthracene, 1,1-dichloroacetophenone, methylorthobenzoylbenzoate, etc., and small amounts of sensitizing aids such as these and amines Examples include those used in combination with.

Further, as the above polymerization initiator, it is also possible to use a thermal polymerization initiator, and specific examples thereof include peresters such as tertiary butyl peroctoate and tertiary butyl pervivalate, bis-(4-tertiary percarbonates such as (butylcyclohexyl)-veroquine dicarbonate, diacyl oxides such as benzoyl peroxide, dialkyl peroxides such as di-tert-butyl peroxide and dicumyl peroxide, cyclohexanone peroxide,
Hydroperoxides such as methyl ethyl ketone peroxide and cumene hydroperoxide, and 2-
Examples include peroxide-based polymerization initiators such as those in combination with metal promoters such as cobalt-n salts of ethylhexanoic acid and naphthenic acid, and other azo compounds can also be used.

The amount of these polymerization initiators to be added is as described in A above.

Usually 1 part by weight of the curable component consisting of component B
The amount is approximately 1 to 10 parts by weight, preferably 1 to 5 parts by weight. If the amount is too small, the curability cannot be satisfied, and even if the amount exceeds 1, no further improvement in the curing speed can be expected.

The optical fiber coating material of the present invention contains the above-mentioned curable component and polymerization initiator as essential components, and optionally contains acrylic resin, polyamide resin, polyester resin, polyether resin, polyurethane resin, polyamideimide. Various modifying resins such as resins, silicone resins, and phenol resins, and various additives such as organic silicon compounds and surfactants may be blended. The overall viscosity is preferably adjusted to a range of 1.000 to 10.000 centipoise (25° C.) from the viewpoint of coating workability.

The coating material for optical fibers of the present invention having such a structure is usually coated with an inner layer coating which is softer than this material, and then coated with the outer layer coating material, rather than directly coating the surface of the optical fiber. It is desirable to apply it as a coating. The coating thickness at this time is usually 50 to 30 mm after curing.
It is recommended that the coating thickness be 0 μm (after coating, depending on the type of polymerization initiator, it may be cured by heating or by irradiation with ultraviolet rays, electron beams, etc.).

Furthermore, on the coating layer formed in this way, as the outermost layer, a tough coating such as an ordinary ultraviolet curable coating such as epoxy (meth)acrylate or urethane (meth)acrylate, or a thermoplastic resin coating such as polyethylene or nylon is used. By forming a coating having the following properties, it is possible to obtain an optical fiber coating with even better fiber strength.

〔Effect of the invention〕

As described above, in this invention, while the (meth)acrylate oligomer as the A component is used as the main ingredient of the coating material, the specific monomer as the BL component is used as a part of the reactive diluent of the A component. By using a (meth)acrylate compound, it has good curability and contributes to improving the productivity of optical fibers, and the cured product has excellent toughness evaluated by properties such as elongation and tensile strength. It is possible to provide an industrially extremely useful optical fiber coating material that greatly contributes to improving the long-term reliability of optical fibers.

〔Example〕

EXAMPLES Below, examples of the present invention will be described in more detail. In addition, in the following, parts shall mean parts by weight.

Example 1 A polyester polyol having a hydroxyl group at both ends of the molecule consisting of a reaction product of polyethylene glycol and adipic acid was reacted with tolylene diisocyanate and further reacted with 2-hydroxyethyl acrylate to obtain a number average molecular weight of 2,000. 50 parts of polyester urethane acrylate oligomer, isobornyl monoacrylate (
R=hydrogen in the above formula; the same applies hereinafter) 20 parts, bisphenol A diethylene glycol diacrylate 15 parts, N-
15 parts of vinyl-2-pyrrolidone, 3 parts of benzophenone and 1 part of diethylaminoethanol were mixed, and the mixture had a viscosity of 3 parts.
．． 000 centipoise (25°C) coating material for optical fiber was obtained.

Example 2 Number average molecule ill obtained by reacting polyoxytetramethylene glycol with tolylene diisocyanate and further reacting with 2-hydroxyethyl acrylate, 300
polyether urethane acrylate oligomer 40
parts, 30 parts of epoxy acrylate with a number average molecular weight of 450 obtained by reacting bisphenol A epoxy resin with acrylic acid, 10 parts of isobornyl monoacrylate, 20 parts of N-vinyl-2-pyrrolidone, 3 parts of benzophenone, and 1 part of diethylaminoethanol. 2. parts to a viscosity of 2.
000 centipoise (25°C) coating material for optical fiber was obtained.

Example 3 Number average molecule i2,0 obtained by reacting acrylic acid with a polyester polyol having hydroxyl groups at both molecular ends, which is a reaction product of polypropylene glycol and phthalic anhydride.
00 polyester acrylate oligomer 50 parts, isobornyl monoacrylate 20 parts, bisphenol F
20 parts of diethylene glycol diacrylate, 10 parts of N-vinyl-2-pyrrolidone, 3 parts of benzophenone and 1 part of diethylaminoethanol were mixed to give a viscosity of 5°0.
00 centipoise (25°C) coating material for optical fiber was obtained.

Comparative Example 1 Example 1 except that isobornyl monoacrylate-1- was not blended, the number of blended parts of bisphenol A diethylene glycol diacrylate was 25 parts, and the number of blended parts of N-vinyl-2-pyrrolidone was 25 parts. Similarly, the viscosity is 2.5.
00 centipoise (25°C) coating material for optical fiber was obtained.

Comparative Example 2 A viscosity of 1,500 centipoise (25
℃) coating material for optical fiber was obtained.

Comparative Example 3 Isobornyl monoacrylate was not blended, the number of blended parts of bisphenol F diethylene glycol diacrylate was 30 parts, and the blended number of N-vinyl-2-pyrrolidone was 2 parts.
The viscosity was 4.50 in the same manner as in Example 3 except that the part was 0 part.
A coating material for optical fiber of 0 centipoise (25° C.) was obtained.

In order to examine the performance of each of the optical fiber coating materials of Examples 1 to 3 and Comparative Examples 1 to 3, the following tests were conducted.

Test Example 1 Each coating material was applied to a thickness of 0.2 fl on a glass plate, and then cured using a high-pressure mercury lamp (80 W/cm).
The amount of ultraviolet irradiation required for complete curing and the tensile strength, elongation, and flexibility of the cured film were measured.

The results were as shown in the table below. Note that tensile strength and elongation were measured in accordance with JIS K7113. In addition, the flexibility was evaluated as ◯ if the cured film peeled off from the glass plate was not damaged when it was bent 180 degrees, and × if it was damaged. This flexibility is an index of the toughness of the cured film, which is determined by the tensile strength and elongation of the cured film.

Test Example 2> An inner layer material (an oligomer synthesized from polyoxytetramethylene glycol with a number average molecular weight of 12,000, tolylene diisocyanate, and 2-hydroxyethyl acrylate) and tetrahydrofurfuryl alcohol were applied to the surface of an optical fiber with a diameter of 125 μm. The diameter after coating is 25 mm.
After coating to a thickness of 0 μm and curing at a linear speed of 100 m/min using a high-pressure mercury lamp of 16 Q W / cm, each light of Examples 1 to 3 and Comparative Examples 1 to 3 was applied for the outer layer. Each fiber coating material was applied so that the diameter after coating was 400 μm, and cured at the same speed using the same high-pressure mercury lamp as above.

The optical fiber coated body thus obtained was prepared in Example 1.
Those using the optical fiber coating materials of Comparative Examples 1 to 3 had good bobbin winding characteristics and lateral pressure characteristics, and no increase in transmission loss was observed, but the cases using the optical fiber coating materials of Comparative Examples 1 to 3 However, both of the above characteristics were inferior, and a significant increase in transmission loss was observed.

Note that the bobbin winding characteristics are the results obtained by examining the increase in transmission loss when the bobbin is wound on a drum with a diameter of 30 cm (tension: 80 g), and the lateral pressure characteristics are the results obtained by examining the increase in transmission loss when the bobbin is wound on a drum with a diameter of 30 cm (tension: 80 g).
An optical fiber is sandwiched between the two with a length of 6Q cm round trip,
The increase in transmission loss was investigated by applying a load from above.

Claims (2)

[Claims] (1) A) (meth)acrylate oligomer 20-80
B) b1) A mono(meth)acrylate compound represented by the following formula; ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, R is hydrogen or a methyl group] and b2)
It consists of a compound that is liquid with a low viscosity at room temperature and contains one or more polymerizable carbon-carbon double bonds in one molecule and has at least an action as a reactive diluent for the component A, together with the component b1, and An optical glass characterized by containing a polymerization initiator in a curable component consisting of 80 to 20% by weight of a mixture of component b1 and component b2 in a weight ratio of 1:10 to 10:1. Coating material for fiber. (2) The coating material for optical glass fibers according to claim (1), wherein the number average molecular weight of the (meth)acrylate oligomer as component A is in the range of 500 to 10,000.