JP2658123B2 - Photosensitive lithographic printing plate precursor - Google Patents

Description

The present invention relates to a photosensitive lithographic printing plate precursor,
In particular, the present invention relates to a photosensitive lithographic printing plate precursor having extremely high photosensitivity in the ultraviolet or visible range and hardly subject to curing inhibition by oxygen.

[Prior Art] Photosensitive resins which cause a change in solubility upon irradiation with light are widely used in the fields of printing and electronic materials, especially as photosensitive printing plates and photoresists. In these fields, recently, the exposure technology by scanning with a laser beam has remarkably developed, and accordingly, photosensitive materials suitable for the above-described exposure method, that is, photosensitive materials having high sensitivity to visible light are required. . Conventionally known photosensitive resins have a photosensitive wavelength region mainly in the ultraviolet region, have insufficient sensitivity, and do not have suitability for laser exposure.

Various studies have been made on photosensitive resins having high sensitivity to visible light. There are various types of photosensitive resins, such as photodimerization type, photopolymerization type, and photodecomposition type. To achieve high sensitivity, photopolymerization type based on the chain reaction mechanism is advantageous. Many studies on photosensitive resins relate to photopolymerization type, especially to photoradical polymerization type. As for the photopolymerization type, various photopolymerization initiator systems with high efficiency have been found, and quite satisfactory photosensitive characteristics can be obtained under ideal exposure conditions. However, the photo-radical polymerization composition generally has a serious weakness that the curing is significantly inhibited in the presence of oxygen (air), and sufficient sensitivity cannot be obtained. It is difficult to use. To avoid this problem, perform the exposure in a vacuum or inert gas,
Alternatively, measures such as providing an oxygen-blocking and transparent coating on the surface of the photosensitive resin are taken, but in these cases, the operation becomes complicated, and if the coating is provided on the surface, the resolution is deteriorated. There are various problems. Various additives have also been proposed for reducing the influence of oxygen, but none of them have sufficient effects even if they have some effects.
No satisfactory effect has yet been found.

A so-called ene-thiol composition based on an addition reaction between an unsaturated group and a thiol group is known as a photocurable composition which is less affected by oxygen. This composition is also based on a chain reaction similar to that of the photopolymerization type, and has the possibility of increasing the sensitivity, but there is less research than the photopolymerization type. In this composition, an aromatic ketone such as benzophenone is known as a photoinitiator, but in this case, even if the influence of oxygen is small, the original sensitivity is insufficient, and almost no photosensitivity in the visible region. It is not suitable as a photosensitive material for a laser because it does not have the above.

[Problems to be Solved by the Invention] As described above, a photosensitive resin composition having high photosensitivity to visible light even in the presence of oxygen, in particular, a photosensitive lithographic printing plate precursor has not yet been found and developed. Is longing for.

The present inventor has focused on ene-thiol-based compositions that have little research while having advantages in curability in the presence of oxygen, and as a result of repeated studies on improving sensitivity and expanding the photosensitive area, found that certain compounds The inventors have found that very good results can be obtained when used as a photoinitiator, and have reached the present invention.

[Means for Solving the Problems] The present invention is a photosensitive lithographic printing plate precursor comprising the following components as essential components of a photosensitive layer.

(A) a compound having at least two ethylenically unsaturated bonds, (b) a polythiol compound represented by the following general formula (I), R (SH) _n (I) (where R is an n-valent organic residue) a radical, n is an integer from 2 to 6) (c) iron complex salt represented by the following formula (II), [Cp-Fe ⁺ -Ar] X ^-. (II) (wherein, Cp is This represents an unsubstituted or substituted cyclopentadienyl group, Ar represents an unsubstituted or substituted aromatic hydrocarbon, and X represents an acid residue.) Hereinafter, the present invention will be described in detail.

In the photosensitive lithographic printing plate precursor according to the invention, the compound having at least two ethylenically unsaturated bonds of the component (a), which is the first essential component, has compatibility with other components in the present composition. The structure is not particularly limited as long as it is a compound, but a vinyl group or an allyl group is an ether, an ester,
Or those containing urethane bonds, and (meth)
Those in the form of acrylic acid derivatives are common. (Meta)
Acrylic acid derivatives have heretofore rarely been used as components of the ene / thiol-based photosensitive composition, but can be suitably used in the composition of the present invention. There are no particular restrictions on the molecular weight, other than monomeric, oligomer,
Prepolymer forms can also be used. In applications where the present composition is used as a film, it is particularly preferable to include a polymer having an unsaturated group in a side chain or a main chain, also serving as a binder.

Specific examples of such unsaturated compounds include (meth) acrylic acid esters of polyhydric alcohols such as pentaerythritol tri (meth) acrylate, pentaenthritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, and ethylene. Glycol di (meth) acrylate, hexanediol di (meth) acrylate, etc., a compound having a plurality of epoxy groups and an addition reaction product of (meth) acrylic acid, allyl ester of polybasic acid such as diallyl phthalate, triallyl isocyanurate, etc. Allyl (meth) acrylate (co) polymer, (meth)
Glycidyl (meth) acrylate or allyl glycidyl ether added to (co) polymers such as acrylic acid and maleic acid, and unsaturated compounds having a hydroxyl group such as allyl alcohol and 2-hydroxyethyl (meth) acrylate (Poly) urethanes obtained by polyaddition of diisocyanates with polyisocyanates, and unsaturated polyesters obtained by polycondensation reaction of maleic acid and diols. One of these substances may be used alone, or two or more of them may be used in combination.

Next, the component (b), which is the second essential component, is a polythiol compound represented by the general formula (I).

R (SH) _n (I) Here, n is an integer of 2 to 6, and R represents an n-valent organic residue. There is no particular limitation on the structure of R.
It may contain an ester bond, an ether bond, or the like in addition to the carbon bond, and may have a substituent such as a hydroxyl group or a halogen. The molecular weight and the like are not particularly limited, but those having 2 to 30 carbon atoms are generally used, and the photocurable composition of the present invention may be substantially treated at room temperature (0 to 40 ° C). When used as a non-fluid composition, those having a boiling point of about 150 ° C. or more at atmospheric pressure are preferred.

Examples of such compounds include di (2-mercaptoethyl) ether, 1,6-hexanedithiol, ethylene glycol dithioglycolate, ethylene glycol dithiopropionate, 1,4-butanediol dithiopropionate, trimethylolpropane There are tris (thioglycolate), trimethylolpropane tris (β-thiopropionate), pentaerythritol tetrakis (thioglycolate), pentaerythritol tetrakis (β-thiopropionate) and the like. Among these,
Those having a thiopropionate structure are particularly preferred.

Component (c), which is the third essential component, is a component that acts as a photoinitiator, and is a component that is a remarkable feature in the present invention. The component (c) is a complex salt containing divalent iron represented by the general formula (II).

In the formula, C _p represents a cyclopentagenenyl group, and as a substituent, an alkyl group having 1 to 8 carbon atoms,
It may have 8 alkenyl groups. Ar represents an aromatic hydrocarbon coordinated to an iron atom, which may be a condensed cyclic one, or an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, 1 carbon atom
It may have an alkoxy group of 8, a cyano group, a halogen, a phenoxy group, a phenyl group, a monocarboxylic acid ester group having 2 to 6 carbon atoms, an alkanoyl group having 2 to 5 carbon atoms, or a benzoyl group. . Examples of Ar include benzene, toluene, xylene, cumene, chlorobenzene, anisole, biphenyl, naphthalene, methylnaphthalene, pyrene and the like. X represents an acid residue, and preferred examples include halogen, ClO ₄ , BF ₄ , PF ₆ , As
F _6, SbF _6, and the like.

Such a complex salt is a substance originally proposed as a photocationic polymerization initiator such as an epoxy resin (J. Rad. Curing, Oct. 1).
986, p.26), The structure of X = PF ₆ is provided by Ciba-Geigy in “IRGACUR
It is sold under the trade name E "261. This substance is preferably used for the purposes of the present invention.

Although the above compound was developed as a photocationic polymerization initiator as described above, the present inventor has found that this substance is also effective as a photoradical initiator, and that an ene-thiol curing reaction based on a radical chain mechanism is performed. Was found to start very efficiently. This compound has a wavelength from the ultraviolet
It has a wide range of photosensitive wavelengths, covering the visible range of 500 nm, and exhibits good sensitivity to various light sources. A remarkable feature of the initiator is that highly efficient sensitization is possible with other photosensitizers. Therefore, the combined use of a suitable photosensitizer is extremely effective. Although good photosensitivity can be obtained by using the compound (c) alone, the sensitivity can be greatly improved by using a sensitizer in combination. Can be set arbitrarily over the entire visible region from the ultraviolet region to a wavelength of approximately 700 nm.

Preferred sensitizers are aromatic carbonyl compounds or dyes such as xanthene, thioxanthene, thiazine, acridine, oxazine, cyanine, and merocyanine, such as Michler's ketone, 4,4'- Bis (diethylamino) benzophenone,
Benzanthrone, thioxanthone, eosin Y, erythrosine, rhodamine B, rhodamine 6G, methylene blue, Nile blue, acridine yellow, acridine orange and the like. When a red dye such as rhodamine or eosin is used, good photosensitivity is imparted to blue to green light having a wavelength of about 500 nm, so that an image can be formed by, for example, an argon laser (oscillation wavelengths of 488 and 514.5 nm). When a blue dye such as Nile Blue is used, good sensitivity to red light having a wavelength of 600 to 700 nm is imparted. For example, a helium-neon laser (having an oscillation wavelength of 63 nm) is used.
3 nm).

Since the photosensitive lithographic printing plate precursor according to the invention has a so-called ene-thiol composition based on an addition reaction between the unsaturated group of the component (a) and the thiol group of the component (b), the components (a) and (b) Generally, the ratio is used in the vicinity of a ratio at which the unsaturated group and the thiol group are equivalent, but this is not strict, and there is no particular problem if the molar ratio of the two is in the range of 4: 1 to 1: 4. There is no. In the case of using a component having an unsaturated group which is susceptible to radical polymerization, such as a (meth) acryloyl group, as the component (a), a polymerization curing reaction using only the unsaturated group may be performed in parallel with the addition reaction with the thiol. In this case, (a) :( b) = about 100: 1 (a)
The components can also be used in excess.

The amount of the photoinitiator component (c) is not particularly limited, but is preferably 0.05% to 20% by weight, more preferably 0.05% by weight based on the whole composition, in order to exert the effect of the present invention particularly remarkably.
It is advisable to mix it in the range of 0.1 to 10% by weight. When the amount of the component (c) is less than the above range, the amount of radicals that initiate a curing reaction when irradiated with actinic light is small, so that the photocurability of the composition is significantly reduced, and Even when an excessive amount exceeding the above range is used, the photosensitivity is reduced due to the effect of shielding effective light and the like.

When a photosensitizer is further used in addition to the above components, the preferable addition amount of the photosensitizer varies depending on the type of the photosensitizer, but generally ranges from 0.05 to 5% by weight based on the whole composition. It is.

The photosensitive lithographic printing plate precursor according to the invention preferably contains a storage stabilizer in addition to the above components. The composition of the present invention generally has insufficient storage stability, and when no stabilizer is added, insolubilization or sensitivity change is likely to occur even in a dark place. Acids and radical inhibitors are effective as stabilizers, and particularly preferred are acids, for example, phosphoric acid, acetic acid, formic acid, propionic acid,
Glycolic acid, lactic acid, benzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, malic acid, tartaric acid, citric acid and the like. Among these, preferred are carboxylic acids,
Particularly, it is a polybasic carboxylic acid, and among them, malonic acid is preferable. The preferred addition amount of the acid as a stabilizer is,
Although it depends on the types of the components (a) and (b), it is generally from 0.1 to 50% by weight, more preferably the total amount of the composition.
It is in the range of 0.5 to 20% by weight. If the addition amount is less than the above range, the stabilizing effect becomes insufficient, and if an excessive amount exceeding the above range is used, the curing reaction is accelerated,
Stability may be worsened rather.

The photosensitive lithographic printing plate precursor according to the invention has, in addition to the above-mentioned components, an organic polymer substance which is compatible with the above-mentioned components and has a film-forming ability, in order to impart a film-forming ability. Can be contained. For many uses such as PS plates and photoresists, it is preferable to use such a binder material in combination to impart film-forming ability to the photocurable composition.

As such a polymer substance, any substance may be used as long as it is soluble in a solvent and has compatibility with each component of the composition, but particularly preferred is water, or an aqueous solution of an alkali or an acid. It is a polymeric substance that is soluble and therefore allows development with aqueous developers. Examples of such polymers include copolymers containing unsaturated carboxylic acids such as (meth) acrylic acid and maleic acid as one component, polyvinyl alcohol, polyvinylpyrrolidone, copolymerized nylon, and alkali-soluble novolak resins. In order to obtain particularly high photosensitivity, it is preferable to use a polymer having an unsaturated group in the side chain or main chain. In this case, this polymer can be regarded as the component (a). Examples of such a polymer are as already described in the description of the component (a). Particularly, in a copolymer such as (meth) acrylic acid and maleic acid, an amount equivalent to a carboxyl group or less is used. Those to which an amount of glycidyl (meth) acrylate is added are excellent in both photosensitivity and water developability and are preferable.

The photosensitive lithographic printing plate precursor according to the invention may further contain various additives such as a thermal polymerization inhibitor, an adhesion improver, a plasticizer, and a filler, if necessary.

The photocurable composition of the present invention is a printing plate, a photoresist,
Although it has a very wide range of uses such as paints, printing inks and adhesives, particularly useful uses are plate materials for lithographic printing and photosensitive image forming materials such as photoresists. In these applications, it is general that the photocurable composition of the present invention is dissolved in a solvent to form a solution, which is coated on a support by a known method, dried and used as a film.

The support used here is generally a planar material that does not cause a significant dimensional change, and examples thereof include metals such as aluminum, copper, zinc, and iron, polyester, polystyrene, polymethyl methacrylate, and nylon. And the like, glass, silicon, silicon oxide, ceramic and the like. A material obtained by laminating two or more thin films of these materials, or a thin film of another material formed on the surface of a certain material by means of vapor deposition or the like can also be used. In addition, the surface of the support as described above can be used after being subjected to treatments such as graining, electrolytic etching, chemical etching, electrolytic oxidation, corona discharge, and the like, or provided with a coating such as an adhesive layer and an antihalation layer. You can also.

A negative type (or a positive type) using a support coated with an ink repellent silicone rubber layer (or a silicone rubber layer coated on the coating film of the photosensitive composition of the present invention).
It is also possible to produce a waterless lithographic printing plate.

The major feature of the photosensitive lithographic printing plate precursor of the present invention is that it shows good curability even in the presence of oxygen, and shows a practically sufficient high sensitivity as it is, but further remarkable high sensitivity if oxygen is cut off. can get. As a method for blocking oxygen, a method in which exposure is performed in a vacuum or in an atmosphere of an inert gas such as nitrogen or carbon dioxide, or a solution of an oxygen-blocking and soluble polymer such as polyvinyl alcohol is coated on the photosensitive composition film. And a method in which a transparent and oxygen-blocking plastic film such as polyester, polyvinyl alcohol, and polyvinylidene chloride is adhered to the surface of the photosensitive film. When used as a dry film resist, the support film acts as an oxygen barrier layer, so that a remarkably high sensitivity can be obtained even though a relatively thick photosensitive resin film is used.

The image-forming material using the photosensitive lithographic printing plate precursor according to the invention may be formed into an image by a conventional photographic method, that is, a method of exposing a negative film in close contact, or a method of projection exposure, or a method of scanning exposure with a laser beam. After exposure, an image can be formed by dissolving and removing unexposed portions with a solvent that dissolves the photosensitive layer. The resulting image has good ink depositability and acid resistance and can be suitably used as a printing plate or a resist.

Hereinafter, the present invention will be described based on examples and comparative examples. Here, "parts" means parts by weight. All operations in the examples and comparative examples were performed in a dark room under red light.

(Synthesis of polymer for binder) (A) 30 parts of styrene, 30 parts of ethyl acrylate, 40 parts of methacrylic acid, 50 parts of ethyl alcohol, methyl ethyl ketone
50 parts were mixed, 1 part of azobisisobutyronitrile was added, and the mixture was reacted at 80 ° C. for 8 hours with stirring. The obtained polymer solution was used as it was (without separating the polymer) for preparing the composition.

(B) After carrying out the polymerization reaction exactly as in (A),
The resulting polymer solution was diluted with 100 parts of ethyl alcohol and 100 parts of methyl ethyl ketone, and 40 parts of glycidyl methacrylate and 1 part of pyridine were added thereto.
The reaction was performed at 8 ° C. for 8 hours. The resulting solution was used as is (without separating the polymer) in the preparation of the composition.

(C) 20 parts of allyl methacrylate, methyl methacrylate 20
, 50 parts of methacrylic acid, 100 parts of ethyl alcohol and 100 parts of methyl ethyl ketone, 1 part of azobisisobutyronitrile was added, and the mixture was reacted at 80 ° C for 4 hours with vigorous stirring. The obtained polymer solution was used as it was in the preparation of the composition.

Examples 1 to 8 and Comparative Examples 1 and 2 100 parts (as a solid content) of a polymer (B) for a binder and each component of a thiol, a photoinitiator, a photosensitizer and a stabilizer were mixed with an ethyl alcohol / methyl ethyl ketone mixed solution ( 1/1)
To prepare a solution having a solid content of about 15%. After graining, the aluminum plate surface-treated with an aqueous solution of sodium metasilicate was dried using a wire bar coater to a coating thickness of about 15%. It was applied to a thickness of 5 μm, and dried at 80 ° C. for 2 minutes in an electric heat ventilation dryer to prepare a PS plate.

On the obtained PS version, 21 steps tablet (Stou
ffer) and a test chart negative film,
Exposure was performed under the following conditions to examine the photosensitive characteristics. Some of the samples were also tested for photosensitivity after storage in a 50 ° C. electrothermal dryer for two weeks.

(1) Using a 3Kw ultra-high pressure mercury lamp ("Jetlight" 3300, manufactured by Oak Manufacturing Co., Ltd.), expose for 1 second or 5 seconds from a distance of 1m.

(2) Using a 60 W tungsten lamp, expose for 5 seconds from a distance of 25 cm.

(3) Argon laser light beam (spot diameter 50 μm) that mainly emits visible light having wavelengths of 488 nm and 514.5 nm
Then, scanning exposure is performed under the conditions of a light amount of 10 mW on the plate surface, a scanning speed of 150 m / sec, and a scanning line density of 90 lines / mm.

After exposure as described above, development was performed with a 1% aqueous solution of sodium carbonate. Sensitivity is as shown in Table 1. All of the compositions based on the composition of the present invention showed good sensitivity and good image reproducibility. In particular, when a photosensitizer is used in combination, the sensitivity is much higher. When a dye was used as a sensitizer (Examples 4 to 8),
Excellent photosensitivity to visible light is obtained. The storage stability is insufficient when no stabilizer is added, but is very good when an acid is added as a stabilizer.

When only a conventionally known aromatic carbonyl compound was used as a photoinitiator (Comparative Examples 1 and 2), the photosensitivity was significantly inferior to the composition of the present invention.

Example 9 50 parts of polymer for binder (A) (as solid content), 25 parts of pentaerythritol triacrylate ("A-TMM-3" manufactured by Shin-Nakamura Chemical Co., Ltd.), 25 parts of TMTP, and 2 parts of "IRGACURE" 261 , 1 part of rhodamine 6G and 2 parts of malonic acid were dissolved in ethyl alcohol to prepare a solution having a solid concentration of about 15%, and a PS plate was prepared in the same manner as in Examples 1 to 8.

The obtained PS plate was exposed under the exposure condition (2) in Examples 1 to 8, and developed with a 1% aqueous sodium carbonate solution.
The number of curing steps of the step tablet was 6.

Example 10 100 parts of polymer for binder (C) (as solid content), B
DTP 20 parts, "Irgacure" 261) 2 parts, Rhodamine 6G
One part was dissolved in ethyl alcohol to prepare a solution having a solid content of about 15%. A PS plate was prepared in the same manner as in Examples 1 to 8, exposed under the exposure condition (2), and developed with a 1% aqueous sodium carbonate solution. The step tablet curing stage number was 5.

Comparative Example 3 In Example 9, the thiol component (TMPT) was not used and instead pentaerythritol triacrylate was used.
A PS plate was prepared in the same manner except that the amount was increased to 50 parts and malonic acid was excluded.

The PS plate was exposed and developed under the exposure conditions of (2) in Examples 1 to 8, and was not exposed at all, and no image was obtained. The PS plate has a thickness of 9 mm on the photosensitive layer surface.
A μm polyethylene terephthalate film (“Lumirror” manufactured by Toray Industries, Inc.) was brought into close contact with the film, exposed under the same conditions from above the film, peeled and developed, and found to be photosensitive. there were.

That is, in the photopolymerizable photosensitive layer composition containing only an ethylenically unsaturated compound without containing a thiol component as a reaction component, while exhibiting considerable sensitivity under oxygen blocking, the sensitivity is extremely poor in the presence of oxygen. You can see that.

[Effects of the Invention] As described above, the photosensitive lithographic printing plate precursor according to the present invention exhibits extremely high sensitivity to ultraviolet or visible light even in the presence of oxygen, and particularly to long wavelength light such as for laser scanning exposure. It is extremely useful for printing plates and photoresists that require high sensitivity.

Claims (5)

(57) [Claims] 1. A photosensitive lithographic printing plate precursor comprising the following components as essential components of a photosensitive layer. (A) a compound having at least two ethylenically unsaturated bonds, (b) a polythiol compound represented by the following general formula (I), R (SH) _n (I) (where R is an n-valent organic residue) a radical, n is an integer from 2 to 6) (c) iron complex salt represented by the following formula (II), [Cp-Fe ⁺ -Ar] X ^-. (II) (wherein, Cp is Represents an unsubstituted or substituted cyclopentadienyl group, Ar represents an unsubstituted or substituted aromatic hydrocarbon, and X represents an acid residue.) 2. The photosensitive lithographic printing plate precursor as claimed in claim 1, further comprising a sensitizer. 3. The photosensitive lithographic printing plate precursor according to claim 1, further comprising a stabilizer. 4. A sensitizer comprising an aromatic carbonyl compound, a xanthene type, a thioxanthene type, an acridine type,
The photosensitive lithographic printing plate precursor according to claim 2, which is at least one dye selected from oxazine, thiazine, cyanine, and merocyanine. 5. The photosensitive lithographic printing plate precursor according to claim 3, wherein the stabilizer is an acid.