JPH0859718A - Method for preventing polymer from yellowing - Google Patents

Abstract

PURPOSE: To prevent a polymer from yellowing due to the irradiation with light by adding a specific thiophenol compound, etc., to a photopolymerizale composition containing a cationic dye having the absorption in a near infrared region and a boron-based catalyst. CONSTITUTION: This method for preventing a polymer from yellowing is to add one or more compounds of (i) a thiophenol compound of the formula, Ar1 -SH [Ar1 is a (substituted)phenyl], (ii) an organic amine compound of formula II (R5 and R6 are each a tertiary alkyl or together form a ring; R7 is an alkyl), (iii) a phenol compound of the formula, Ar2 -OH (Ar2 is an alkyl-substituted phenyl) and (iv) a benzotriazole compound of formula III [R is H, OH or a (substituted)alkyl] to a photopolymerizable composition comprising (A) a polymerizable unsaturated compound, (B) a cationic dye of the formula, D<+> .A<-> (D<+> is a cation having the absorption in a near infrared region; A<-> is various anions) and (C) a boron-based catalyst of formula I (R1 to R4 are each an alkyl, an aryl, etc.; Z<+> is a quaternary ammonium ion, etc.).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for preventing yellowing of a polymer, and more particularly to a method for improving yellowing of a polymer in a photopolymerization system.

[0002]

2. Description of the Related Art Currently, photopolymerization is used in various fields such as curing and printing of coating films, resin relief printing, printing substrate preparation, resists and photomasks. Photopolymerization can be carried out even at room temperature, and the polymerization time is short. Therefore, active development has been carried out from the viewpoints of energy saving and space saving. Among these photopolymerization techniques, near infrared photopolymerization has recently attracted attention.

Near-infrared photopolymerization initiator (JP-A-5-1946)
No. 19), for example, is a combination of a near-infrared light absorbing cation dye and a boron-based catalyst, which is decomposed by irradiation of near-infrared light to cause the color of the cation dye to disappear and to coexist. Polymerization of a polymerizable unsaturated compound such as a (meth) acrylate compound is initiated, and near-infrared light has a longer wavelength than ultraviolet light used for conventional photopolymerization, and thus safety of light ( It does not generate ozone, has a low risk of skin cancer, etc.), has a good economical light source, and has excellent light transmittance, so it is a thick film system that was difficult with conventional ultraviolet light. Alternatively, the colored composition or the like has a feature that it can be photopolymerized. However, when this composition was irradiated with light to carry out polymerization, there was a drawback that a trace amount of a coloring substance generated during a photoreaction may discolor the polymer.

[0004]

The object of the present invention is to provide a method for improving the yellowing of a polymer in photopolymerization.

[0005]

As a result of investigations to solve this problem, the present inventors found that the polymer is colored yellow due to the cationic dye which is a component of the photopolymerization initiator. In order to improve it, by adding at least one of the thiophenol compound, organic amine compound, phenol compound and triazine compound shown below to a cationic dye having an absorption in the near infrared region and a boron-based catalyst. It was found that a photopolymerization initiator which does not cause yellowing of the polymer was obtained, and the present invention was completed.

The cationic dye of the present invention is a compound represented by the general formula (1).

[0007]

[Image Omitted] D ⁺ · A ⁻ (1) (In the formula, D ⁺ is a cation having absorption in the near infrared wavelength region, and A ⁻ represents various anions.)

The cation having absorption in the near-infrared light region herein is a cation having absorption in the wavelength region of 740 nm or more, and preferably a compound having absorption in the wavelength region of 780 nm or more. Near-infrared light has a long wavelength and is excellent in light transmittance as compared with ultraviolet light that is generally used in the past, therefore, it is difficult to use conventional ultraviolet light for various light-hiding properties such as various pigment-containing compositions, Good photopolymerization can be performed even for thick compositions and the like. The cationic dye is not particularly limited as long as it has absorption in the near infrared region, and for example, methine, polymethine, indoline, cyanine, xanthene, oxazine, thiazine, diarylmethane, triarylmethane, and pyrylium-based cationic dyes. Examples include cations. Specifically, for example, Table 1 and Table 2
Examples include cations as shown in.

[0009]

[Table 1]

[0010]

[Table 2]

The boron-based catalyst of the present invention has the general formula (2)
Is a compound represented by.

[0012]

Embedded image

(In the formula, R ₁ , R ₂ , R ₃ and R ₄ are each independently an alkyl group, an aryl group, an allyl group, an aralkyl group, an alkenyl group, an alkynyl group, a heterocyclic group, a substituted alkyl group and a substituted group. Represents an aryl group, a substituted allyl group, a substituted aralkyl group, a substituted alkenyl group, a substituted alkynyl group, or a halogen atom, and Z ⁺ represents a quaternary ammonium cation, a quaternary pyridinium cation, a quaternary quinolinium cation, a phosphonium cation or Indicates a metal ion.)

Specific examples of the boron anion include n-butyltriphenylboron ion, n-octyltriphenylboron ion, n-butyltrianisylboron ion, di-n-dodecyldiphenylboron ion, tetraphenylboron ion and triphenyl. Examples thereof include naphthylboron ion and tetrabutylboron ion. Among them, triphenylalkylboron anion is particularly preferable from the viewpoint of easy availability and reactivity.

Z ^{+ in the} general formula (2) is a quaternary ammonium cation, a quaternary pyridinium cation, a quaternary quinolinium cation, a phosphonium cation or a metal ion, and the quaternary ammonium cation has four substituents. Are each independently a hydrogen atom, an alkyl group, an aryl group, an allyl group, an aralkyl group, an alkenyl group, an alkynyl group,
The ammonium cation is a heterocyclic group, a substituted alkyl group, a substituted aryl group, a substituted allyl group, a substituted aralkyl group, a substituted alkenyl group or a substituted alkynyl group, and specific examples of the ammonium cation include tetramethylammonium ion and tetramethylammonium ion. Tetraalkylammonium io such as butylammonium ion can be mentioned.

Further, the thiophenol compound effective in preventing yellowing constituting the present invention is represented by the general formula (3), and specific examples include thiophenol, 4-hydroxythiophenol and 1,4- Examples include dimercaptobenzene and the like.

[0017]

## STR00009 ## Ar ₁ --SH (3) (In the formula, Ar ₁ represents a phenyl group or a substituted phenyl group.)

The organic amine compound of the present invention is a compound represented by the general formula (4) and generally called hindered amines. As a specific example, bis- (1,2,
2,6,6-pentamethyl-4-piperidyl) sebacate and the like can be mentioned.

[0019]

[Chemical 10] (In the formula, R ₅ and R ₆ each independently represent a tertiary alkyl group, and R ₅ and R ₆ may form a cyclic structure. R ₇ represents an alkyl group.)

The phenolic compound of the present invention is represented by the general formula (5), and specific examples thereof include 2,6-di-t.
-Butyl-p-cresol, 2,2'-methylenebis (6-t-butyl-p-cresol) and the like.

[0021]

Embedded image Ar ₂ —OH (5) (In the formula, Ar ₂ represents an alkyl-substituted phenyl group.)

The benzotriazole compound of the present invention is
It is represented by the general formula (6), and specific examples are 1, 2, 3
Examples thereof include benzotriazole and 3-hydroxy-1,2,3-benzotriazole.

[0023]

[Chemical 12] (In the formula, R is a hydrogen atom, a hydroxyl group, an alkyl group,
A substituted alkyl group is shown. )

When the near-infrared photopolymerization initiator containing one or more of the above compounds is irradiated with light, discoloration of the photolyzed dye is prevented and the polymer is not colored yellow. The yellowing-preventing compound of the present invention is preferably used alone or in combination of two or more kinds. The function of the anti-yellowing agent of the present invention is not necessarily clear, but it is presumed that it controls the decomposition of the cationic dye by the photoreaction to change into a yellowing substance.

The cationic dye represented by the general formula (1) and the boron-based catalyst represented by the general formula (2) in the present invention are practically used by using 0.001% by weight or more of the entire polymerizable composition. Photopolymerization can be performed. If it is less than that, the polymerization may be very slow, or the polymerization may be insufficiently completed. The anti-yellowing agent of the present invention is a cationic dye of 0.01
The object of the present invention can be achieved by adding more than a mole. It is preferably in the range of 0.1 to 10 mol. If it is too small, the function of preventing yellowing may be insufficient, and if it is too large, the physical properties of the polymer may be impaired.

The polymerization initiator of the present invention can be photopolymerized by allowing a polymerizable unsaturated compound to coexist. Examples of the polymerizable unsaturated compound that can be used in that case include generally used radically polymerizable monomers such as various (meth) acrylic compounds and vinyl compounds, and oligomer compounds. Radical-polymerizable monomers are all customary ethylenically unsaturated compounds, in particular acrylic or methacrylic acid esters of monohydric or polyhydric alcohols or 4- (meth) acryloyloxyl group-containing aromatic polycarboxylic acids and their acids. 2,2-bis (4- (3-methacryloxy-2-hydroxypropoxy), which is a reactant known from U.S. Pat. No. 3,066,112, such as anhydrides and these esters also include so-called urethane acrylates or methacrylates. ) -Phenyl) propane and di (methacryloxyethyl) trimethylhexamethylenediurethane,
2,2-bis (4-methacryloxypolyethoxyphenyl) propane, tetramethylolmethane trimethacrylate, tetramethylolmethane tetramethacrylate,
It also includes dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, 4- (meth) acryloyloxymethoxycarbonylphthalic acid and its acid anhydride, 4- (meth) acryloyloxyethoxycarbonylphthalic acid and its acid anhydride, and the like.

[0027]

EXAMPLES The present invention will now be specifically described by way of examples, but the present invention is not limited to these examples without departing from the gist of the present invention.

Example 1 Near-infrared light absorbing cation dye of Table 1, No. 3 (counter ion is n-
Butyltriphenylboron anion) 0.5 wt% and boron-based catalyst tetrabutylammonium n-butyltriphenylboron 1.0 wt% were dissolved to form a basic solution.
0.5w of 1,2,3-benzotriazole in the basic solution
The sample with No. It was set to 1.

[Decoloring test] A sample prepared with the above composition was placed in a 10 ml sample bottle, and the wavelength was 700 to 95.
A halogen lamp having a spectral distribution in the range of 0 nm was irradiated until the blue color of the dye disappeared. The change in color of the decolorized solution was visually observed. The change in hue is shown in Table 3.

[Polymerization test] 10 g of pentaerythritol triacrylate was added to the above sample and mixed sufficiently to prepare a polymerized sample. Each sample was applied to an aluminum substrate in a thickness of 250 μm, a transparent cover glass was placed on the sample, and the halogen lamp used in the above-described decoloring test was irradiated for 15 minutes. The hue of the polymerized sample was visually observed. The results are also shown in Table 3.

(Example 2) 2,6-di-t- was added to the basic solution.
Sample No. was prepared by adding 0.5 wt% of butyl-p-cresol. And 2. A color erasing test and a polymerization test were conducted in the same manner as in Example 1. The results are also shown in Table 3.

Example 3 Sample N was prepared by adding 0.5 wt% of 4-hydroxythiophenol to the basic solution.
o. It was set to 3. A color erasing test and a polymerization test were conducted in the same manner as in Example 1. The results are also shown in Table 3.

(Example 4) 1,2,3-benzotriazole and bis- (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate were added to the basic solution at 0.5% each.
Sample No. was added with wt%. It was set to 4. Example 1
A decoloring test and a polymerization test were conducted in the same manner as in. The results are also shown in Table 3.

(Example 5) Bis- (1,2,2) was added to the basic solution.
2,6,6-pentamethyl-4-piperidyl) sebacate and 2,4-hydroxythiophenol were each added to 0.
Sample No. with 5 wt% added It was set to 5. A color erasing test and a polymerization test were conducted in the same manner as in Example 1. The results are also shown in Table 3.

Example 6 Sample No. 3 was prepared by adding 0.5 wt% each of 1,2,3-benzotriazole and 4-hydroxythiophenol to the basic solution. It was set to 6. A color erasing test and a polymerization test were conducted in the same manner as in Example 1. The results are also shown in Table 3.

(Example 7) 1,2,3-benzotriazole, 4-hydroxythiophenol, and bis- (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate were added to the basic solution in an amount of 0. Sample No. with 5 wt% added It was set to 7. A color erasing test and a polymerization test were conducted in the same manner as in Example 1. The results are also shown in Table 3.

(Example 8) Sample No. 7 was the same as in Example 7 except that the dye of Complex No. 1 in Table 1 (the anion was tosylate anion) was used as the cationic dye.
8 was synthesized. A color erasing test and a polymerization test were conducted in the same manner as in Example 1. The results are also shown in Table 3.

Comparative Example 1 Sample No. 1 was prepared by adding no additive to the basic solution. a. A color erasing test and a polymerization test were conducted in the same manner as in Example 1. The results are also shown in Table 3.

(Comparative Example 2) Sample No. 8 was obtained by adding no additive to Example 8. b. A color erasing test and a polymerization test were conducted in the same manner as in Example 1. The results are also shown in Table 3.

Comparative sample No. a and No. When the halogen lamp was irradiated, the blue color of the dye disappeared and it was colored yellow, but the sample No. b of Examples 1 to 8 in which the additive was added was used. 1 to 8 did not become almost yellow.
Comparative sample No. a and No. In b, the polymer was colored yellow, but the sample N of Examples 1 to 8 in which an additive was added was used.
o. 1 to 8 were not colored.

[0041]

[Table 3] ×: Dark yellow Δ: Yellow ○: Almost colorless and transparent ◎: Colorless and transparent

[0042]

The conventional near-infrared photopolymerization system has a drawback that when polymerized by irradiation with light, a slight amount of a coloring substance generated during photoreaction discolors the polymer. The yellowing of the polymer can be improved. The near-infrared photopolymerization system according to the present invention can be used in various fields such as curing and printing of coating films, resin letterpress, printing substrate preparation, resists and photomasks, and has high industrial utility value.

Front Page Continuation (72) Inventor Yutoshi Minohara, Toyota City, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor, Nobuhiro Ito, Toyota City, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. A photopolymerizable compound comprising a polymerizable unsaturated compound, a cationic dye represented by the general formula (1) having absorption in the near infrared region, and a boron-based catalyst represented by the general formula (2). The composition contains a thiophenol compound represented by the general formula (3), an organic amine compound represented by the general formula (4), and a general formula (5).
A method for preventing yellowing of a polymer, comprising adding at least one compound selected from the group consisting of a phenol compound represented by the formula (1) and a benzotriazole compound represented by the general formula (6). Embedded image D ⁺ · A ⁻ (1) (In the formula, D ⁺ is a cation having an absorption in the near infrared wavelength region, and A ⁻ represents various anions.) (In the formula, R ₁ , R ₂ , R ₃ and R ₄ are each independently an alkyl group, an aryl group, an allyl group, an aralkyl group, an alkenyl group, an alkynyl group, a heterocyclic group, a substituted alkyl group, a substituted aryl group, A substituted allyl group, a substituted aralkyl group, a substituted alkenyl group, a substituted alkynyl group, or a halogen atom, Z ⁺ is a quaternary ammonium cation, 4
Grade pyridinium cation, quaternary quinolinium cation,
Indicates a phosphonium cation or a metal ion. Ar ₁ --SH (3) (In the formula, Ar ₁ represents a phenyl group or a substituted phenyl group.) (In the formula, R ₅ and R ₆ each independently represent a tertiary alkyl group, and R ₅ and R ₆ may form a cyclic structure. R ₇ represents an alkyl group.) Ar ₂ —OH (5) (In the formula, Ar ₂ represents an alkyl-substituted phenyl group.) (In the formula, R is a hydrogen atom, a hydroxyl group, an alkyl group,
A substituted alkyl group is shown. )