JPH09291249A - Pigment dispersion, photosetting pigment-dispersed resist composition for color filter using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pigment dispersion with improved fine dispersion stability even in an elevated pigment concentration in a nonaqueous solvent. SOLUTION: This pigment dispersion contains pigments, solvent, pigment dispersant and, when needed, a binder resin where a modified novolak resin having at least one of a structural unit represented by the formula (X is a divalent hydrocarbon of 2-4 carbon atoms; i is an integer of 1-100; j is an integer 2-3; R is H, an alkyl of 1-4 carbon atoms, phenyl or furfuryl; R<1> is an alkyl or an aromatic group; n is an integer of 0-2) is used as a pigment dispersant in an amount of at least 0.2 pts.wt. per 100 pts.wt. of pigment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment dispersion which uses a non-aqueous solvent in the industrial field of pigment-dispersed resists, inks, paints, etc. The present invention relates to a photocurable pigment-dispersed resist composition for a color filter.

[0002]

2. Description of the Related Art Generally, organic and inorganic pigments are widely used in pigment-dispersed resists, inks, paints, and the like for the purpose of coloring, shading, preventing rust, protecting inner layers, and the like. These coated materials and printed materials are required to have high optical density, coloring power, transparency or surface smoothness, and sufficient fluidity necessary for coating, printing or handling. Also, these properties must be maintained even after long-term storage. For that purpose, the dispersion stability must be excellent even if the pigment particles are made fine and contained in a high concentration. However, even if the pigment particles are once finely dispersed, they are easily re-agglomerated, so that it is often difficult to obtain a stable fine dispersion. In particular, in the field of pigment-dispersed resists, in which the pigment particles are becoming finer due to the increasing demand for higher transmittance of visible light and higher contrast for color liquid crystal display devices in recent years, the pigment particle size is at least the wavelength of visible light. Since it is necessary to make the content below, the specific surface area of the pigment particles becomes considerably larger than usual, and it becomes difficult to obtain a stable fine dispersion. Also, R (red), G (green), B
Since two or more kinds of pigments are mixed and used in each pigment dispersion resist to obtain a spectrum suitable for the pixels of the three primary colors of (blue), heteroaggregation easily occurs and dispersion becomes more difficult.

Various methods of using pigment dispersants have been developed to solve these problems. For example, Japanese Patent Application Laid-Open No. 60-237403 discloses a method in which a derivative of an organic pigment or dye having a basic functional group or the like is used as a pigment dispersant. However, this method has a problem in that although the pigment dispersion effect is good, the application range is limited because the color tone of the pigment dispersion resist is changed by the coloring of the pigment dispersant itself.

Further, in JP-A-3-212601, etc., an ionic or nonionic surfactant, specifically, a long-chain alkylamine acetate, a quaternary ammonium salt, a high molecular polycarboxylic acid, A method using a polyoxyethylene derivative, a sorbitan ester of a long-chain fatty acid or the like as a pigment dispersant is disclosed.

However, this method has some problems in stabilizing the dispersion of the pigment, but has a problem in that a satisfactory effect cannot be obtained.

Due to these problems, the selection and combination of pigments are limited, and the pigments must be used without satisfactory pigment dispersion stability.

[0007]

The present invention has been made to solve these problems. That is, by using a substantially colorless novel pigment dispersant that is not a dye derivative, a pigment dispersion having improved fine dispersion stability even when the pigment concentration is high in a non-aqueous solvent, and a color filter using the same The present invention provides a photocurable pigment-dispersed resist composition for use.

[0008]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have found that the above problems can be solved by the following specific compound group, and have completed the present invention. Was.

That is, in the present invention, in a pigment dispersion containing (1) a pigment, a solvent, a pigment dispersant, and optionally a binder resin, the constitutional unit represented by the general formula (1) is used as the pigment dispersant. The present invention relates to a pigment dispersion comprising at least 0.2 part by weight of a modified novolac resin having at least one, with respect to 100 parts by weight of a pigment.

[0010]

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(In the formula, X is a divalent hydrocarbon group having 2 to 4 carbon atoms, i is an integer in the range of 1 to 100,
j is an integer in the range of 2 to 3, R is a hydrogen atom, and the number of carbon atoms is 1.
An alkyl group, a phenyl group or a furfuryl group in the range of 4 to 4, R ¹ is an alkyl group or an aromatic group, and n is an integer of 0 to 2) The present invention also provides (2) above (1). It relates to a photocurable pigment-dispersed resist composition for a color filter, which comprises the pigment dispersion described above, a radically polymerizable compound, and a photopolymerization initiator.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, by using the above-mentioned specific modified novolac resin in which a structure obtained by ring-opening addition of an alkylene oxide to an aromatic hydroxyl group of a polyhydric phenol is introduced as a pigment dispersant, The pigment agglomeration and structural viscosity of the fine concentration dispersion are suppressed, and high fluidity during handling, coating, printing, and manufacturing of inks, paints, pigment-dispersed resists, etc. High stability is obtained. The reason is
It is considered that this is because the site adsorbed to the pigment (novolak resin part) and the site solvated in the molecule (polyalkylene oxide chain part) are structurally concentrated. As a result, a coated material or a printed material having high optical density, coloring power, transparency or surface smoothness can be obtained. Further, when the condensation reaction of novolac formation is carried out after the addition of alkylene oxide to phenol, the reaction rate is usually decreased due to the high molecular weight of the phenol component, but in the present invention, the reactivity of novolac formation is high. Since a high polyphenol is used, the reaction rate does not decrease.

The pigment, solvent, pigment dispersant of the present invention,
Further, a pigment dispersion containing a binder resin, if necessary, containing a modified novolak resin as a pigment dispersant, and a photocurable pigment-dispersed resist composition for a color filter using the pigment dispersion will be described in detail.

As the novolak resin used for obtaining the modified novolac resin of the present invention, polyhydric phenols and, if necessary, novolak resins derived from monohydric phenols and aldehydes can be used.

Here, the polyhydric phenols are those in which one aromatic ring has two or three aromatic hydroxyl groups. In addition, the monohydric phenol refers to a compound composed of one or a plurality of aromatic rings, and one aromatic ring has only one aromatic hydroxyl group.

As the polyphenols, catechol,
Di- or trihydroxybenzenes such as resorcinol, hydroquinone, trihydroxybenzene, etc., or their alkyl-substituted or aromatic-substituted compounds can be used. Among these polyhydric phenols, those not alkyl-substituted or aromatic-substituted are preferable from the viewpoint of reactivity. These polyhydric phenols may be used alone or in 2
A mixture of more than one species can be used.

The monohydric phenols used as necessary include phenols usually used in the production of novolac resins, or cresol, xylenol, trimethylphenol, propylphenol, butylphenol, amylphenol, hexylphenol, octylphenol, nonylphenol, dodecyl. Alkyl-substituted phenols such as phenol, monohydroxydiphenylmethanes or phenols having an aromatic substituent such as phenylphenol can be used. Further, dihydroxydiphenylmethanes such as bisphenol A and bisphenol F, hydroxybiphenyls and the like can also be used. Further, halogen-substituted compounds of the above-mentioned monohydric phenols such as chlorine-substituted phenol and bromine-substituted phenol can also be used. These monohydric phenols may be used alone or in combination of two or more. From the viewpoint of reactivity, as the monohydric phenols, phenol and phenols in which the meta position is substituted with one alkyl group are preferable.

As the aldehydes, those commonly used in the production of novolak resins can be used without particular limitation. Specific examples thereof include lower aliphatic aldehydes such as formaldehyde, paraformaldehyde, trioxane, cyclic formal, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde and glyoxal, and aromatic aldehydes such as furfural and phenylaldehyde. . These aldehydes may be used alone or in combination of two or more.

The novolak resin is synthesized by the conventional method in the presence of an acid catalyst such as paratoluenesulfonic acid, perchloric acid, hydrochloric acid, nitric acid, sulfuric acid, chloroacetic acid, oxalic acid, phosphoric acid, etc. It can be carried out by reacting with a compound at 80 to 130 ° C. The progress of the reaction can be followed by measuring the molecular weight by gel permeation chromatography (GPC).

The modified novolak resin of the present invention can be obtained by ring-opening addition of an alkylene oxide to the aromatic hydroxyl group of the thus obtained novolak resin by a conventional method.

As the alkylene oxide, ethylene oxide, propylene oxide or butylene oxide may be used alone or in combination of two or more.

In addition to the ring-opening addition of alkylene oxides after synthesizing the novolac resin in this way, first, the alkylene oxides are ring-opening added to the aromatic hydroxyl group of the above-mentioned polyhydric phenols, and aldehydes are added to this. The modified novolak resin of the present invention can also be obtained by synthesizing a novolak resin by adding a phenol and other phenols as necessary.

The ring-opening addition reaction of the alkylene oxides can be carried out by a conventional method.

In the general formula (1), X has 2 to 2 carbon atoms.
A divalent hydrocarbon group in the range of 4, i is an integer in the range of 1 to 100, j is 2 or 3, R is a hydrogen atom, an alkyl group having a carbon number of 1 to 4, phenyl Group or furfuryl group, R ¹ is an alkyl group or an aromatic group, and n is 0
2 to 2. However, these structures and appropriate values are different depending on the type of pigment used, the specific surface area and particle diameter of the pigment particles, the properties of the pigment surface treatment agent, the polarity of the dispersion medium, etc.
It is preferable to optimize it according to the application. Even if the value of i exceeds the above range, the pigment dispersibility cannot be further improved. Moreover, the number of i (addition number) of 2 to 3 polyalkylene oxide chains bonded to one polyhydric phenol ring may be the same or different within the range of 1 to 100. When a plurality (n = 2) of R ¹ groups are bonded to the polyhydric phenol ring, the R ¹ groups may be the same or different.

The modified novolac resin of the present invention exhibits a good pigment dispersing effect if it has at least one constitutional unit represented by the general formula (1).

The modified novolak resin of the present invention preferably has a number of nuclei in the range of 2 to 20, since it is difficult to control the molecular weight when the number of nuclei is large.

As the pigment to be used in the present invention, general inorganic or organic pigments can be used. As organic pigments, phthalocyanine, azo, anthraquinone, quinacridone, dioxazine, anthrapyrimidine, anthanthrone, indanthrone, flavanthrone,
Examples include pigments such as perylene pigments, thioindigo pigments, isoindolinone pigments, triphenylmethane pigments, and carbon black. Examples of the inorganic pigment include extender pigments such as barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, aluminum hydroxide, silicon dioxide and titanium dioxide, and magnetic iron oxide. These organic and inorganic pigments can be used alone or in combination of two or more.

The solvent of the present invention may be any solvent that dissolves the resin component in the pigment dispersion or the resin component used together with the pigment dispersion, and may be appropriately selected from known ones according to the application. .

Further, as the binder resin of the present invention,
Various known binder resins used in the fields of pigment-dispersed resists, paints, and offset printing ink compositions can be used.

In order to obtain the pigment dispersion of the present invention, it is desirable that the modified novolac resin is contained as a pigment dispersant in an amount of at least 0.2 part by weight based on 100 parts by weight of the pigment.
If it is less than this range, a sufficient pigment dispersion effect cannot be obtained.
Even if it is used in an amount of more than 100 parts by weight, the pigment dispersion effect is not improved any further.

However, the pigment dispersion effect differs depending on the type of pigment, the specific surface area and particle diameter of the pigment particles, the properties of the pigment surface treatment agent, the polarity of the dispersion medium, etc., so it is necessary to optimize in each case. .

Next, the photocurable pigment-dispersed resist composition for color filters using the pigment dispersion of the present invention will be specifically described.

When the modified novolac resin of the present invention is used in a photocurable pigment-dispersed resist composition for a color filter by radical polymerization, pay attention to the content of the polyvalent phenol-derived aromatic hydroxyl group contained in the modified novolac resin. There is a need. This is because the radical polymerization inhibitory action may appear. In this application, it is preferable to use a modified novolak resin in which the aromatic hydroxyl group derived from the polyhydric phenol does not remain. However, conversely, it is also possible to control undesired radical polymerization during storage and improve storage stability.

As the pigment used in the photocurable pigment-dispersed resist composition for a color filter using the pigment dispersion of the present invention, those known in this field can be used. Specifically, as the red pigment, anthraquinone-based C.I. I. Pigment Red 177, C.I. I. Pigment Red 168 and green pigments include halogenated phthalocyanine C.I. I. Pigment Green 7, C.I. I. Pigment Green 36 and a blue pigment such as β-type phthalocyanine C.I. I. Pigment Blue 1
5: 3, ε-type phthalocyanine-based C.I. I. Pigment Blue 15: 6, and disazo C.I. I. Pigment Yellow 83, isoindolinone-based C.I. I.
Pigment Yellow 139, and dioxazine-based C.I. I. Pigment Violet 23, a chromophthalic C.I. I. Pigment Violet 37 or the like can be shown.

With respect to these pigments, in order to increase the light transmittance while keeping the optical density of the coating film high, it is necessary that the particle diameter is 400 nm or less, which is the lower limit of the wavelength of visible light, preferably 1/2 of the lower limit. Is 200 nm or less, more preferably about 100 nm.

By using the modified novolak resin of the present invention, even such fine pigments can be dispersed and stabilized. In order to obtain a spectrum suitable for each pixel of the three primary colors of R, G, and B, for example, yellow pigments are combined with red and green pigments, purple pigments are combined with blue pigments, and two or more kinds of red pigments are used. A plurality of pigments can be used in combination.

Further, the pigment dispersion of the present invention containing the above-mentioned inorganic pigment can be used in a pigment dispersion resist using an inorganic pigment used for an overcoat material of a color filter.

When the pigment dispersion of the present invention is used in a photocurable pigment-dispersed resist composition for a color filter,
The modified novolak resin is added to 0.2 per 100 parts by weight of the pigment.
˜100 parts by weight, preferably 1 to 50 parts by weight.

As the solvent used in the photocurable pigment-dispersed resist composition for a color filter using the pigment dispersion of the present invention, a known solvent can be used as long as it is an organic solvent capable of dissolving the resin component used in this field. be able to.

Specific examples include glycol ethers such as ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, dipropylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether. Glycol monoether acetates such as ether acetate, ketones such as cyclohexanone and methyl ethyl ketone, N,
Examples include amides such as N-dimethylacetamide and N-methylpyrrolidone, lactones such as γ-butyrolactone, and acetates such as butyl acetate. These may be used alone or in combination of two or more in consideration of the solubility of the resin component and the coating suitability of the composition.

The binder resin used in the photocurable pigment-dispersed resist composition for a color filter using the pigment dispersion of the present invention is known as long as it is compatible with the organic solvent used. Things can be used. As a use of the photocurable pigment-dispersed resist for a color filter, a resin having little coloring is preferable, and examples thereof include an acrylic resin, a styrene resin, a urethane resin, and an epoxy resin.

If it is necessary to develop the coating film with an alkali to form pixels after photocuring by radical polymerization, a binder resin having an acidic functional group introduced therein may be used. Acrylic resins for this use are copolymers of a monomer having an ethylenically unsaturated double bond and (meth) acrylic acid, styrene resins are copolymers of styrene and maleic anhydride, (Meth) acrylic acid derivative, or a half ester obtained by reacting an acid anhydride ring of these copolymers with an alcohol. As urethane resin,
Those obtained by introducing a carboxyl group with dimethylolpropionic acid or the like are exemplified. If a (meth) acryloyl group is introduced, photocurability can also be imparted. Examples of the epoxy resin include a resin obtained by subjecting an acid component to an epoxy group by epoxy esterification and then reacting an acid anhydride with a generated hydroxyl group. If (meth) acrylic acid is used as the acid component, photocurability can be imparted. In addition, heat curing after photocuring by adding an amino resin or the like is also possible. These may be used alone or in combination of two or more.

Polyfunctional (meth) acrylates can be used as a radically polymerizable compound for preparing a photocurable pigment-dispersed resist composition for a color filter using the pigment dispersion of the present invention. Specifically, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, glycerin di (meth) acrylate, trimethylolpropane di (meth) ) Acrylate, trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate,
Trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tri (meth) acrylate, ditrimethylolpropane penta (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate Acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, di (meth) acrylate of ester of hydroxypivalic acid and neopentyl glycol, di (meth) acrylate of adipic acid and 1,6-hexanediol. (Meth) acrylate, bisphenol A ethylene oxide adduct di (meth) acrylate, bisphenol A propylene oxide adduct di (meth) Polyfunctional compounds such as acrylate, di (meth) acrylate of ethylene oxide adduct of tetrabromobisphenol A, di (meth) acrylate of ethylene oxide adduct of isocyanuric acid, tri (meth) acrylate of ethylene oxide adduct of isocyanuric acid ( (Meth) acrylates and bisphenol A
Type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, polycarboxylic acid glycidyl ester, polyol polyglycidyl ester, alicyclic or aliphatic epoxy resin by modification with rosin or drying oil, amine epoxy resin, triphenol Examples thereof include polyfunctional epoxy (meth) acrylates obtained by reacting an epoxy group such as a methane type epoxy resin and a dihydroxybenzene type epoxy resin with (meth) acrylic acid. These may be used alone or in combination of two or more.
Monofunctional (meth) acrylates can be used in combination with these. In order to increase the curing speed, it is preferable to use acrylates among the (meth) acrylates.

As a photopolymerization initiator for radical polymerization for preparing a photocurable pigment-dispersed resist composition for a color filter using the pigment dispersion of the present invention, acetophenone-based, benzoin ether-based, benzophenone-based, thioxanthone-based Known photopolymerization initiators such as can be used. Specifically, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, 1-
Hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1
Acetophenone-based initiators such as-(4-morpholinophenyl) -butanone and 1-phenylpropanedione-2- (o-ethoxycarbonyl) oxime; benzoin ether-based initiators such as benzoin and benzoin methyl ether; benzophenone; o-benzoyl Methyl benzoate,
4-phenylbenzophenone, bis (4-dimethylaminophenyl) ketone, 4,4'-dichlorobenzophenone, 4-benzoyl-4'-methyl-diphenylsulfide, 3,3 ', 4,4'-tetra (t-butyl Benzophenone initiators such as peroxycarbonyl) benzophenone and 2,4,6-trimethylbenzophenone; thioxanthones such as isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone and 1-chloro-4-propoxythioxanthone Initiator, or dibenzoyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,
2'-bis (o-chlorophenyl) -4,5,4 ',
5'-tetraphenyl 1,2-bisimidazole, 10
Examples include initiators such as -butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, camphorquinone, and methylphenylglyoxyester, and titanocene compounds.
These can be used alone or in combination of two or more.

Further, as a benzophenone-based or thioxanthone-based initiator, or a hydrogen abstraction-type initiator such as a dicarbonyl compound, α-hydrogen such as triethanolamine or methyl 4-dimethylaminobenzoate serving as a hydrogen donor is used. The tertiary amines possessed can be used as an accelerator. Further, a dye having a sensitizing effect on long-wavelength light such as xanthene, acridine, oxazine, and cyanine may be added. These may be used alone or in combination of two or more.

Further, stabilizers such as hadroquinone, hydroquinone methyl ether, catechol and picric acid can be used.

To prepare a photocurable pigment-dispersed resist composition for a color filter using the pigment dispersion of the present invention, various additives such as a lubricant and a surfactant are used in addition to the above-mentioned materials. You can

Table 1 shows the preferable ranges of the content of the components in the photocurable pigment-dispersed resist composition for a color filter of the present invention.

[0049]

[Table 1]

Of these components, the pigment, the modified novolac resin, the whole amount or a part of the solvent, and if necessary, a part or the whole of the binder resin are mixed and kneaded by using a bead mill or a three-roll mill. The pigment dispersion of the present invention can be obtained with. The remaining solvent and binder resin,
A radically polymerizable compound and a photopolymerization initiator are added, and the mixture is further kneaded or sufficiently stirred, and filtered or centrifuged if necessary to obtain a photocurable pigment-dispersed resist composition for a color filter of the present invention. be able to.

When the pigment dispersion of the present invention is used in fields other than pigment-dispersed resists such as inks and paints, various binder resins conventionally used in those fields,
Solvents and additives can be used.

[0052]

The present invention will be described below with reference to examples. They do not limit the invention unless it departs from the spirit and scope. "Parts" in the description indicate parts by weight.

[Pigment Dispersant] Pigment Dispersant 1 256 parts of phenol, 50 parts of phenol, and formalin are added to a reaction vessel in which resorcinol is added with an average of 45.4 mol of ethylene oxide (22.7 mol per hydroxyl group). 40 parts and 5 parts of oxalic acid dihydrate were added to obtain 95
The mixture was stirred at -100 ° C. for 15 hours and distilled under reduced pressure to obtain a modified novolac resin (pigment dispersant 1). The weight average molecular weight measured by GPC was 16,000.

Pigment Dispersant 2 Instead of the polyether in the synthesis of Pigment Dispersant 1,
Propylene oxide in resorcinol on average 34.
A modified novolak resin having a weight average molecular weight of 17,000 (pigment dispersion) was prepared in the same manner as in the synthesis of Pigment Dispersant 1 except that 256 parts of polyether added with 4 moles (17.2 moles per hydroxyl group) was used. Agent 2) was obtained.

Pigment Dispersant 3 Instead of the polyether in the synthesis of Pigment Dispersant 1,
Butylene oxide in resorcinol is 27.8 on average
A modified novolak resin (pigment dispersant having a weight average molecular weight of 17,000) was used in the same manner as in the synthesis of Pigment Dispersant 1 except that 256 parts of a polyether having 1 mol (13.9 mol per hydroxyl group) added was used. 3) was obtained.

Pigment Dispersant 4 Instead of the polyether in the synthesis of Pigment Dispersant 1,
Propylene oxide is 7.0 on average in resorcinol
A modified novolak resin (pigment having a weight average molecular weight of 5,100) was used in the same manner as in the synthesis of Pigment Dispersant 1 except that 61.9 parts of a polyether having a mole (3.5 moles per hydroxyl group) added was used. A dispersant 4) was obtained.

Pigment Dispersant 5 Instead of the polyether in the synthesis of Pigment Dispersant 1,
On average 10 propylene oxide in resorcinol
Weight average molecular weight of 32,000 in the same manner as in the synthesis of Pigment Dispersant 1 except that 741 parts of polyether added with 3.4 mol (51.7 mol per hydroxyl group) was used.
A modified novolak resin (pigment dispersant 5) of was obtained.

Pigment Dispersant 6 Instead of the polyether in the synthesis of Pigment Dispersant 2,
Propylene oxide in hydroquinone is 34.
A modified novolac resin having a weight average molecular weight of 15,000 (pigment dispersion) was prepared in the same manner as in the synthesis of Pigment Dispersant 2 except that 256 parts of polyether added with 4 moles (17.2 moles per hydroxyl group) was used. Agent 6) was obtained.

Pigment Dispersant 7 Instead of the polyether in the synthesis of Pigment Dispersant 2,
A weight average molecular weight of 14 was obtained in the same manner as in the synthesis of Pigment Dispersant 2 except that 256 parts of polyether in which propylene oxide was added to catechol on average 34.4 mol (17.2 mol per hydroxyl group) was used. 1,000 modified novolak resin (pigment dispersant 7) was obtained.

Pigment Dispersant 8 13.4 parts of resorcinol and 50 parts of phenol in a reaction vessel.
Part, formalin 40 parts, and oxalic acid dihydrate 5 parts were added, and the mixture was stirred at 95 to 100 ° C. for 7 hours and distilled under reduced pressure to obtain a novolak resin. To this, 1,700 parts of ethylene oxide (50 mol per hydroxyl group) was added under pressure to obtain a modified novolac resin (pigment dispersant 8) having a weight average molecular weight of 39,000.

Pigment Dispersant 9 10 parts of phenol in the synthesis of Pigment Dispersant 2 was
A weight average molecular weight of 18, in the same manner as in the synthesis of Pigment Dispersant 2 except that 11.5 parts of cresol was used.
000 modified novolak resins (pigment dispersant 9) were obtained.

Pigment Dispersant 10 A weight average molecular weight of 20 was obtained in the same manner as in the synthesis of Pigment Dispersant 2 except that 5 parts of phenol in the synthesis of Pigment Dispersant 2 were replaced with 12.1 parts of bisphenol A.
000 modified novolak resins (pigment dispersant 10) were obtained.

Pigment Dispersant 11 Weight average molecular weight 12,000 in the same manner as in the synthesis of Pigment Dispersant 2 except that 5 parts of formalin in the synthesis of Pigment Dispersant 2 were replaced with 5 parts of furfural. To obtain a modified novolak resin (pigment dispersant 11).

[Comparative Pigment Dispersant] Pigment Dispersant 12 Pigment Dispersant 12 was a polyether having a hydroxyl group at one end obtained by adding 22.7 moles of ethylene oxide to butanol on average.

Pigment Dispersant 13 A commercially available sorbitan fatty acid ester compound was used as Pigment Dispersant 13.

[Pigment Dispersion and Photocurable Pigment Dispersion Resist Composition for Color Filter] Examples 1 to 13 and Comparative Examples 1 and 2 Pigment Dispersants 1 to 11 and Comparative Pigment Dispersant (Pigment Dispersant 1
2, 13) was kneaded by a bead mill by the method described above to prepare a pigment dispersion having the composition shown in Table 2. A radical polymerizable compound and a photopolymerization initiator were added thereto, and the mixture was further kneaded. Finally, a photocurable pigment-dispersed resist composition for a color filter having the composition shown in Table 3 was obtained. Here, propylene glycol monomethyl ether acetate is used as a solvent, methacrylic acid and benzyl methacrylate are used as a binder resin in a copolymerization component, and an acrylic resin having an acid value of 100 mgKOH / g and a weight average molecular weight of 45,000 is used as a radical polymerizable compound. Is trimethylolpropane triacrylate (Kyoeisha Chemical Co., Ltd.)
Manufactured by TMP-A) and 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one (manufactured by Ciba-Geigy Co., IRGACURE-9) as a photopolymerization initiator.
07) was used. Table 4 shows the types of pigments used in the R, G, and B pigment dispersion resists and the weight% of all pigments.
It was shown to. In the preparation of the pigment dispersion composition, as shown in Table 2, the amount of the solvent used was increased or decreased according to the amount of the pigment dispersant used so that the total amount of the composition was 100% by weight. Also in the preparation of the resist composition, the total amount of the composition was similarly adjusted to 100% by weight. In Comparative Example 3, the equivalent amount of the pigment dispersant was replaced with propylene glycol monomethyl ether acetate without using the pigment dispersant.

[0067]

[Table 2]

[0068]

[Table 3]

[0069]

[Table 4]

[Evaluation Test] Table 5 shows the properties of the pigment dispersion and the photocurable pigment-dispersed resist composition for a color filter and the evaluation results of the cured film.

(1) Viscoelasticity The viscosity of the obtained pigment dispersion and the photocurable pigment-dispersed resist composition for a color filter, TI (thixotropy.
Index) and stored in a dark place at a constant temperature of 40 ° C. for 1 month, and examined changes in viscosity and TI over time. The measurement was performed at 25 ° C. using a rotational viscometer manufactured by Haake. Low viscosity, TI close to 1.0, little change over time,
A pigment-dispersed resist composition having no problem in spin coating suitability is considered to have excellent viscoelasticity. 3, Viscosity and TI are slightly high, or spin coating suitability is possible although these changes with time are slightly large. , 1 was markedly high, TI was not suitable for spin coating, and was highly unstable over time. The case where sedimentation or separation of the pigment was observed was also indicated by 1.

(2) Transmittance The photocurable pigment-dispersed resist composition for each color filter was spin-coated on a glass substrate, heated to 100 ° C. for 2 minutes, and then exposed to ultraviolet light of 200 mJ / cm ^2. To form a cured film having a thickness of 0.9 to 1.1 μm. With respect to the glass substrate on which the cured film was formed, the transmission spectrum of visible light was measured with reference to the glass substrate. Table 5 shows the transmission range (R: 610 nm, G: 540 nm, B: 4) of each color coating film.
50 nm). The values of the transmittance in Table 5 are conversion values when the thickness of the cured film is 1.0 μm. The higher the transmittance, the better.

By using the modified novolak resin of the present invention, the viscoelasticity of the pigment fine dispersion and the photocurable pigment-dispersed resist composition for a color filter was improved, and a cured film having high transmittance was obtained. On the other hand, in the comparative example, the viscoelasticity was poor and the transmittance was low.

[0074]

[Table 5]

[0075]

By using the modified novolac resin of the present invention, pigment aggregation and structural viscosity in a pigment fine dispersion and a photocurable pigment-dispersed resist composition for a color filter are suppressed, and spectral characteristics resulting from pigment dispersibility are suppressed. , Performance such as storage stability is improved.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Ishikawa 1-23-37 Edobori, Nishi-ku, Osaka City Inside Sakata Inks Co., Ltd.

Claims (2)

[Claims] 1. A pigment dispersion containing a pigment, a solvent, a pigment dispersant, and optionally a binder resin, and a modified novolac resin having at least one constitutional unit represented by the general formula (1) as the pigment dispersant. At least 0.2 part by weight based on 100 parts by weight of the pigment. Embedded image (In the formula, X is a divalent hydrocarbon group having a carbon number of 2 to 4, i is an integer of 1 to 100, j is an integer of 2 to 3, and R is a hydrogen atom. , An alkyl group having 1 to 4 carbon atoms, a phenyl group or a furfuryl group, R ¹ is an alkyl group or an aromatic group, and n is an integer of 0 to 2) 2. A photocurable pigment-dispersed resist composition for a color filter, which comprises the pigment dispersion according to claim 1, a radically polymerizable compound, and a photopolymerization initiator.