JPS647017B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a material for coating an optical glass fiber for light transmission (hereinafter referred to as an optical fiber). Due to the nature of optical fibers, a plastic coating is applied immediately after spinning the glass matrix. A known plastic coating is one in which a flexible first coating layer is first provided on the surface of the optical fiber, and a second coating layer with good abrasion resistance is further provided on the outside thereof. The first coating layer in this two-layer plastic coating has good adhesion to the optical fiber and excellent flexibility to maintain the initial strength of the optical fiber. It is desired that the optical fiber has a refractive index as large as possible compared to the refractive index of the optical fiber to prevent an increase in transmission loss as much as possible. However, many of the conventional primary coating layers described above lack adhesion to optical fibers, flexibility, and refractive index, and materials with excellent flexibility and adhesion generally have poor refractive index. The drawback is that it tends to drop. As a result of intensive studies from the above viewpoint, the inventors found that when a specific polymerizable unsaturated compound is blended into the main component such as various acrylic oligomers, a coating layer with high refractive index as well as adhesion and flexibility is achieved. After discovering that it was possible to form a polyurethane resin, he completed this invention. That is, the present invention provides a main component consisting of an oligomer having at least two polymerizable carbon-carbon double bonds in one molecule and a reactive diluent having at least one double bond similar to the above in one molecule. The present invention relates to a coating material for optical fiber, characterized in that diphenyl phosphate of hydroxyalkyl (meth)acrylate is blended into the coating material. In this specification, (meth)acrylate or a compound name containing this term is a general term for acrylate and methacrylate.
This means that it can be either one or both. One of the main components used in this invention is an oligomer having at least 2, usually 2 to 5, preferably 2 to 3 polymerizable carbon-carbon double bonds in one molecule; In addition to (meth)acrylate oligomers containing an acrylic group or methacrylic group as a double bond, those having a polymerizable carbon-carbon double bond other than an acrylic group or a methacrylic group such as 1,4-polybutadiene oligomers are included. Those that give particularly good results in flexibility after curing are selected. Specifically, urethane (meth)acrylate oligomers such as polyester polyol-based urethane (meth)acrylate oligomers, polyether polyol-based urethane (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, polyester (meth)acrylate oligomers, and polyether Examples include (meth)acrylate oligomers, polybutadiene (meth)acrylate oligomers, and 1,4-polybutadiene oligomers. These oligomers are generally viscous at room temperature, and their number average molecular weight is
It is about 200 to 50,000. The above number average molecular weight is a value determined by gel permeation chromatography using polystyrene as a reference material. Hereinafter, the term "number average molecular weight" in this specification refers to a value determined by the same method as above. Another main component used in this invention is a compound that is liquid at room temperature and has at least one polymerizable carbon-carbon double bond in one molecule, which acts as a diluent for the above-mentioned oligomer. A (meth)acrylate compound having an acrylic group or a methacrylic group as a double bond is preferably used. In addition, allyl esters having an allyl group as the above-mentioned double bond can also be used. Among (meth)acrylate compounds, mono(meth)acrylate compounds having a long-chain aliphatic group such as a long-chain alkyl group or a long-chain polyoxyalkylene group in the molecular skeleton are desirable because they give good results for the flexibility of the cured product. In addition, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, etc. have two or more acrylic or methacrylic groups (the normal upper limit is 5) in the molecule. It is also possible to use poly(meth)acrylate compounds having the following properties. Representative examples of the above mono(meth)acrylate compounds include those represented by the following general formula. The carbon number of the long chain aliphatic group in these compounds is 7 or more, preferably 10 to 100.
In cases where the aliphatic group contains both an alkyl group and a polyoxyalkylene group, as in the following general formula (B), the total number of carbon atoms in the aliphatic group may be within the above range. [In the formula, R ₁ is hydrogen or a methyl group, R ₂ is an alkyl group, and R ₃ is an alkylene group] The amount of the above-mentioned reactive diluent used is based on the total amount of the main material component, that is, the amount of the above-mentioned oligomer. 20-70% by weight
It is preferable that the amount be within the range of 10 to 10. If the amount is too large, it is not desirable because it may impair curability and film properties of the cured product. The diphenyl phosphate of hydroxyalkyl (meth)acrylate used in this invention has the following chemical structural formula. [R ₁ is hydrogen or a methyl group, R ₃ is an alkylene group] The number of carbon atoms in the alkylene group (R ₃ ) in the above structural formula is generally about 2 to 10. This compound polymerizes and hardens together with the main material component, and increases the refractive index of the polymerized and cured product because its own refractive index (1.529) is much larger than the refractive index of silica glass (1.46 or less). , thereby suppressing an increase in transmission loss. In addition, it has the characteristic that the adhesion and flexibility of the main component to the optical fiber surface are not significantly impaired by the blending of such compounds. The blending amount of the diphenyl phosphate is 5 to 50 parts by weight based on 100 parts by weight of the main ingredient.
The amount is preferably 10 to 30 parts by weight. If the amount is too small, the above effects cannot be obtained, and if the amount is too large, problems such as deterioration of the mechanical strength of the cured product will occur. The coating material of the present invention can be easily and quickly cured with radiation such as ultraviolet rays by using a photopolymerization initiator as a polymerization initiator together with the above-mentioned components. As the above-mentioned photopolymerization initiator, various kinds of initiators and sensitizers that are generally used as initiators and sensitizers for ultraviolet curable coatings can be used. For example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, 2-methylbenzoin, benzophenone, Michler's ketone, benzyl, benzyl dimethyl ketal, benzyl diethyl ketal, anthraquinone, methylanthrquinone, diacetyl, acetophenone, diphenyldis Examples include rufido, anthracene, etc., and those used in combination with small amounts of sensitizing aids such as amines. Further, the coating material of the present invention can be thermally cured by using a thermal polymerization initiator instead of or together with the photopolymerization initiator. Examples of the thermal polymerization initiator include peresters such as tertiary butyl peroctoate and tertiary butyl perpivalate, percarbonate esters such as bis-(4-tertiary butylcyclohexyl)-peroxydicarbonate, and benzoyl peroxide. diacyl peroxides such as, dialkyl peroxides such as di-tert-butyl peroxide and dicumyl peroxide, cyclohexanone peroxide,
Examples include peroxide-based polymerization initiators such as hydroperoxides such as methyl ethyl ketone peroxide and cumene hydroperoxide, and combinations thereof with metal promoters such as cobalt-salts of 2-ethylhexanoic acid and naphthenic acid, and others. Azo compounds and the like can also be used. The amount of these polymerization initiators used is based on the main material components.
It is about 1 to 10 parts by weight per 100 parts by weight. If this amount is too small, curability cannot be satisfied. Further, even if the amount exceeds the predetermined amount, no further improvement in the curing speed can be expected, and it is practically preferable to use the amount within the above range. The optical fiber coating material of the present invention has each of the above-mentioned components as essential components, and, if necessary, adhesion imparting agents such as a silane coupling agent and various conventionally known additives are blended therewith. From the viewpoint of coating workability, the overall viscosity is desirably adjusted within the range of 1,000 to 10,000 centipoise/25°C. When applying this coating material to an optical fiber, the above-mentioned material is coated on the surface of the optical fiber immediately after spinning by an appropriate means so that the thickness after curing is 10 to 200 μm, and then a polymerization initiator is applied. Depending on the type, it may be cured by heating or by irradiation with ultraviolet rays, electron beams, etc. By coating and curing polyamide resin or a general thermosetting or ultraviolet or electron beam curing material on the primary coating layer formed in this way, a secondary coating layer is provided, which provides optical fibers with good strength. A fiber coating is obtained. As detailed above, according to the present invention, it is possible to provide a coating material for optical fibers that is useful as a primary coating for optical fibers, has excellent adhesion and flexibility, and has low transmission loss due to its high refractive index. . 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 Polyester polyol-based urethane with a number average molecular weight of 1900 obtained by reacting 2 moles of 2-hydroxyethyl acrylate with a reaction product of 1 mole of polyester polyol synthesized from ethylene glycol and adipic acid and 2 moles of tolylene diisocyanate. To 30 parts of acrylate oligomer, Aronix M113 (trade name, manufactured by Toagosei Co., Ltd.) (acrylate having a long chain aliphatic group represented by the above general formula (B); in the general formula (B), R ₁ = hydrogen, R ₂ = nonyl group, R ₃ = 70 parts of ethylene group (n=25) were added, and 17 parts of diphenyl phosphate of hydroxyethyl acrylate and 5 parts of benzyl dimethyl ketal were added thereto, mixed uniformly, and the mixture had a viscosity of 3600 centipoise/25°C. The coating material for optical fibers of this invention was prepared. Comparative Example A comparative optical fiber coating material was obtained in the same manner as in Example 1, except that diphenyl phosphate of hydroxyethyl acrylate was not blended at all. Example 2 Instead of polyester polyol-based urethane acrylate, a polyether obtained by reacting 2 moles of 2-hydroxyethyl acrylate with a reaction product of 1 mole of polytetramethylene ether glycol having a number average molecular weight of 1000 and 2 moles of isophorone diisocyanate. An optical fiber coating material of the present invention having a viscosity of 3100 centipoise/25° C. was obtained in the same manner as in Example 1, except that 30 parts of the urethane acrylate oligomer was used. Example 3 Instead of Aronix M113, Nippon Kayaku Co., Ltd. trade name TC120S (acrylate having a long chain aliphatic group represented by the above general formula C; R ₁ in the general formula C) was used.
= hydrogen, R ₃ = pentamethylene group, n = 2) to 70
An optical fiber coating material of the present invention having a viscosity of 3,800 centipoise/25° C. was obtained in exactly the same manner as in Example 1, except that the coating material for optical fibers was used in the same manner as in Example 1. In order to investigate the performance of the materials of the above Examples and Comparative Examples, each material was coated on a glass plate to a thickness of 100 μm and then cured using two 80 W/cm high pressure mercury lamps. Adhesion and properties of the cured product peeled from the glass plate were measured by the following methods. The results were as shown in the table below. <Adhesion> Measured by a square tape peel test method. In the table, the denominator indicates the total number of squares, and the numerator indicates the number of the coatings remaining without peeling out of the above number. <Characteristics of cured product> Hardness is measured using a Shore hardness tester A type.
Young's modulus and elongation were measured by a tensile test method using dumbbell No. 3 according to JIS K-6911. In addition to the above tests, actual optical fiber coating tests were conducted using each material. That is, after coating the surface of a 125 μm thick optical fiber immediately after spinning to a thickness of 50 μm, it is cured by irradiating ultraviolet rays using two 80 W/cm high pressure mercury lamps, and a coating of 0.85 μm is applied to the optical fiber coating. Transmission loss of light at wavelength (d
B/Km) was investigated. The results were as shown in the table below.

[Table] As is clear from the above table, according to the present invention, it is possible to provide an optical fiber coating material that has excellent adhesion and flexibility and has less transmission loss.

Claims (1)

[Claims] 1 A main component consisting of an oligomer having at least two polymerizable carbon-carbon double bonds in one molecule and a reactive diluent having at least one double bond in one molecule similar to the above, and a hydroxyalkyl (meth) ) A coating material for optical glass fiber, characterized in that it contains acrylate diphenyl phosphate.