JP2003147248A - Ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink composition having dispersibility of an ink pigment and ink stability superior to those of a conventional polylactic acid ink. SOLUTION: This ink composition comprises a hydroxyacid-based polyester represented by formulas (1) [wherein, X is a <=20C alkyl group, a cycloalkyl group, an aryl group, an arylalkyl group, hydrogen, hydroxy group, nitro group, amino group, an acyl group, sulfonic acid group, an alkoxy group or a halogen; M is lithium, sodium, potassium or an amine represented by formula (3) (wherein, R<2> to R<5> are each independently hydrogen, an alkyl group, a phenyl group or benzyl group); m1 is an integer of 0-3; m2 is an integer of 1-4; m1 and m2 satisfy the relation of 1<=m1+m2<=4; and n1 is an integer of >=1] and/or (2) [wherein, R<1> is a <=20C alkylidene group; M is lithium, sodium, potassium or an amine represented by formula (3)] an including a sulfonic acid-containing structure, the ink pigment and a solvent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates generally to ink compositions, and more particularly to ink compositions modified to be biodegradable.

[0002]

2. Description of the Related Art With the increasing awareness of environmental problems in recent years, products using natural materials or biodegradable synthetic materials have been actively developed.

[0003] When biodegradable films such as polylactic acid films have been used as packaging materials due to the current trends in the world, conventionally used urethane-based, acrylic-based, aromatic polyesters and the like have been used as ink binders. It is necessary to use biodegradable ink instead of non-biodegradable ink.

In view of the above circumstances, the present applicant has already proposed a biodegradable ink using lactic acid type polyester as an ink binder (Japanese Patent Laid-Open No. 8-92518).

A biodegradable ink using a resin containing polycaprolactone, polylactic acid, or polyvinyl alcohol as an ink binder (Japanese Patent Laid-Open No. 8-319).
No. 445), a biodegradable ink using a biodegradable copolymer having ester and amide groups as an ink binder (JP-A-9-132709), and a biodegradable fat usable as an ink binder. Thermosetting biodegradable resin composition containing an aromatic polyester resin as a main component (JP-A-10-251368) and a biodegradable magnetic ink composition using an aliphatic polyester as an ink binder (JP-A-10-25439). Gazette) has already been disclosed.

[0006]

However, the above ink composition has problems in the dispersibility of the ink pigment and the stability of the ink, and it has been desired to develop a biodegradable ink excellent in these properties. Therefore, it is an object of the present invention to provide an ink composition that is superior to conventional polylactic acid inks in terms of ink pigment dispersibility and ink stability. Another object of the present invention is to provide an ink composition having biodegradability.

[0007]

The present invention provides the following formula (1):
And / or a hydroxy acid-based polyester containing a sulfonate-containing structure represented by the formula (2) in the molecular chain,
Since it is an ink composition containing an ink pigment and a solvent, it is possible to provide an ink composition having excellent dispersibility of the ink pigment and stability of the ink.

[0008]

[Chemical 5]

[In the formula (1), X is an alkyl group having 20 or less carbon atoms, a cycloalkyl group, an aryl group, an arylalkyl group, or hydrogen, a hydroxyl group, a nitro group, an amino group, an acyl group, a sulfonic acid group, an alkoxyl group. Represents a group and halogen, and M represents lithium, sodium, potassium or an amine represented by the following formula (2). Also, m
1 is an integer of 0 to 3, m2 is an integer of 1 to 4, and m1 + m2 satisfies the relationship of 1 ≦ m1 + m2 ≦ 4. N1 represents an integer of 1 or more. ]

[0010]

[Chemical 6]

[In the formula (2), R ¹ represents an alkylidene group having 20 or less carbon atoms, M represents lithium, sodium,
It shows potassium or an amine represented by the following formula (3). ]

[0012]

[Chemical 7]

[In the formula (3), R ² , R ³ , R ⁴ and R ⁵ each independently represent hydrogen, an alkyl group, a phenyl group or a benzyl group. The hydroxy acid-based polyester preferably contains a sulfonate-containing structure represented by the following formula (4).

[0014]

[Chemical 8]

[In the formula (4), M represents lithium, sodium, potassium or an amine represented by the above formula (3). N2 represents an integer of 1 or more. ]Also,
In the hydroxy acid-based polyester, the concentration of sulfonate is preferably 5 to 100 equivalents / 10 ⁶ g.

When the hydroxy acid type polyester is a lactic acid type polyester, it is preferable that the polyester contains 80 mol% or more of lactic acid residues.

Further, in this case, when the above-mentioned hydroxy acid type polyester contains L-lactic acid residue and D-lactic acid residue, the number of moles of L-lactic acid residue (L) and D-lactic acid residue. The molar ratio (L / D) of the number of moles (D) of the group is preferably 1 to 9.

The reduced viscosity (η _{SP / C} ) of the hydroxy acid type polyester is preferably 0.3 to 1.5 dl / g.

Further, the glass transition point (Tg) of the hydroxy acid type polyester is preferably 35 to 60 ° C.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The ink composition of the present invention will be described in detail below.

(Hydroxy Acid Polyester) The ink composition of the present invention contains a hydroxy acid polyester having a sulfonate-containing structure represented by the following formula (1) and / or formula (2) in the molecular chain. Has been.

The sulfonate-containing structure represented by the formula (1) has the following structure.

[0023]

[Chemical 9]

In the formula (1), X is an alkyl group having 20 or less carbon atoms, a cycloalkyl group, an aryl group, an arylalkyl group, or hydrogen, a hydroxyl group, a nitro group, an amino group, an acyl group, a sulfonic acid group, an alkoxyl group. And halogen, and M represents lithium, sodium, potassium or an amine represented by the following formula (3). In the formula (1), M is preferably lithium, sodium or potassium from the viewpoint of dispersibility of the ink pigment.

In the formula (1), _m1 in (X) m1
Is the number of bonds to the aromatic ring of X, which represents the above substituent, and m1 is an integer of 0 to 3. In addition, (SO ₃ M) _m2
M2 in is the number of bonds to the aromatic ring of SO ₃ M representing a sulfonate, m2 is an integer of 1 to 4,
m1 + m2 satisfies the relationship of 1 ≦ m1 + m2 ≦ 4. N1 represents an integer of 1 or more.

Here, two or more substituents represented by X can be bonded to one aromatic ring. In this case, the substituent represented by X, which is bonded, may have two or more kinds of different structures, or may have only one kind of structure. The same applies to the sulfonate represented by SO ₃ M.

The sulfonate-containing structure represented by the above formula (1) may be contained in the hydroxy acid polyester regardless of the main chain or side chain of the molecular chain of the hydroxy acid polyester. The other main constituents include a hydroxy acid residue described later.

That is, the sulfonate-containing structure represented by the above formula (1) is located between the molecular chains of the hydroxy acid type polyester and / or at the terminal of the molecular chain.
Therefore, when the structure is located between the molecular chains, both of the COO- groups of the other sulfonate-containing structure represented by the above formula (1) or (4) are combined with a hydroxy acid residue or the like described later. When the structure is located at the terminal of the molecular chain, one of the COO-groups is a hydroxy acid residue or the like described later, and the other of the COO-groups is hydrogen, an alkyl group, a hydroxyalkyl group or the like. Will be combined with.

The sulfonate-containing structure represented by the formula (2) has the following structure.

[0030]

[Chemical 10]

In the formula (2), R ¹ represents an alkylidene group having 20 or less carbon atoms, M represents lithium, sodium,
It shows potassium or an amine represented by the following formula (3). In the formula (2), M is preferably lithium, sodium or potassium from the viewpoint of dispersibility of the ink pigment.

Here, the sulfonate-containing structure represented by the formula (2) may be bound to one end of the molecular chain of one hydroxy acid type polyester, and may be contained at one or both ends of the molecular chain.

It is sufficient that the hydroxy acid type polyester used in the present invention contains either one of the sulfonate-containing structures represented by the above formula (1) or (2) in the molecular chain. The structure may be contained.

The amine represented by the formula (3) has the following structure.

[0035]

[Chemical 11]

In the formula (3), R ² , R ³ , R ⁴ and R ⁵ each represent a substituent, and each independently represent hydrogen, an alkyl group, a phenyl group or a benzyl group.

In the formula (3), R ² , R ³ and R ⁴
R ⁵ and R ⁵ can each independently select the kind of the substituent, and R ² , R ³ , R ⁴ and R ⁵ may represent the same substituents as other substituents, and are different from each other. It may represent a substituent. Further, the amine represented by the formula (3) is 2 in one hydroxy acid type polyester.
It is possible to adopt different structures of more than one kind, or to adopt only one kind of structure.

The hydroxy acid type polyester used in the present invention preferably contains a sulfonate-containing structure represented by the following formula (4).

[0039]

[Chemical 12]

In the formula (4), M represents lithium, sodium, potassium or an amine represented by the above formula (3). In the formula (4), M is preferably lithium, sodium or potassium from the viewpoint of dispersibility of the ink pigment.

The sulfonate-containing structure represented by the above formula (4) may be contained in the hydroxy acid polyester regardless of the main chain or side chain of the molecular chain of the hydroxy acid polyester. The other main component is a residue of a hydroxy acid described later.

That is, the sulfonate-containing structure represented by the above formula (4) is located between the molecular chains of the hydroxy acid type polyester and / or at the terminal of the molecular chain.
Therefore, when the structure is located between the molecular chains, both of the COO- groups of the other sulfonate-containing structure represented by the above formula (1) or (4) are combined with a hydroxy acid residue or the like described later. When the structure is located at the terminal of the molecular chain, one of the COO-groups is a hydroxy acid residue or the like described later, and the other of the COO-groups is hydrogen, an alkyl group, a hydroxyalkyl group or the like. Will be combined with.

(Production Method of Hydroxy Acid-Based Polyester) The hydroxy acid-based polyester used in the present invention is produced by copolymerizing a sulfonate-containing compound represented by the following formula (5) with a hydroxy acid described below. To be done.

[0044]

[Chemical 13]

In the formula (5), R ⁶ and R ⁷ each independently represent hydrogen, an alkyl group or a hydroxyalkyl group, and M represents lithium, sodium, potassium or the amine represented by the formula (2). In the formula (5), M is preferably lithium, sodium or potassium from the viewpoint of dispersibility of the ink pigment.

In the formula (5), R ⁶ and R ⁷ can be selected independently of each other, and R ⁶ and R ⁷ may be the same or different.

Here, it is preferable to copolymerize using a sulfonate-containing compound represented by the following formula (6).

[0048]

[Chemical 14]

In the formula (6), R ⁶ and R ⁷ each independently represent hydrogen, an alkyl group or a hydroxyalkyl group, and M represents lithium, sodium, potassium or the amine represented by the above formula (3). In the formula (6), M is preferably lithium, sodium or potassium from the viewpoint of dispersibility of the ink pigment.

The obtained copolymer may contain a block copolymer and / or a random copolymer of the sulfonate-containing compound represented by the above formula (5) or (6).

The sulfonate-containing compound represented by the above formula (5) or (6) is not limited to one type, but two or more types can be copolymerized.

The hydroxy acid type polyester of the present invention is a polyester having a hydroxy acid content of 60 mol% or more in all components (diol, dicarboxylic acid, hydroxy acid, etc.), and the hydroxy acid component is preferably 70 mol% or more. , And more preferably 80 mol% or more.

The hydroxy acid used in the present invention is a compound having an alcoholic hydroxy group and a carboxyl group in one molecule. Examples of hydroxy acids include glycolic acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 16-hydroxyhexadecanoic acid, 2-hydroxy-2-methylbutyric acid and 10-, in addition to the above-mentioned lactic acid.
Hydroxystearic acid, malic acid, citric acid, gluconic acid and the like are used. Further, an intramolecular ester of a hydroxy acid such as caprolactone and a cyclic ester formed by losing a water molecule from an α-hydroxy acid such as lactide are also used.

Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and orthophthalic acid, and bisphenol-
A, an aromatic diol such as an alkylene oxide adduct of bisphenol-A and the like may be copolymerized in a small amount.

Further, not only one type of the above hydroxy acid but also two or more types can be copolymerized.

The copolymerization of the sulfonate-containing compound and the hydroxy acid is not particularly limited, and a conventionally known method can be used. For example, lactide, which is a dimer of lactic acid, and the above-mentioned sulfonate-containing compound are melt-mixed and heated by a known ring-opening polymerization catalyst such as tin octylate or aluminum acetylacetonate. And a method of performing direct dehydration polycondensation by heating and decompression. The hydroxy acid type polyester used in the present invention can be obtained by adding the sulfonate-containing compound between the start of polymerization and the end of polymerization.

(Composition of Hydroxy Acid Polyester) The hydroxy acid polyester obtained as described above has a sulfonate concentration of 5 to 100 in the polyester.
It is preferably equivalent weight / 10 ⁶ g. 5 equivalents / 10 ⁶ g
When it is less than the above range, it tends to be impossible to obtain better ink pigment dispersibility and ink stability. Also, 100
When the amount is more than 10 ⁶ g, there is a tendency that a biodegradable ink having better biodegradability and coating film physical properties cannot be obtained.
If the concentration of the sulfonate is 5 equivalent / 10 ⁶ g or more, the hydroxy acid other than lactic acid described below may be 0%.

When the hydroxy acid type polyester obtained as described above is a lactic acid type polyester, it is preferable that the lactic acid residue is contained in an amount of 80 mol% or more. More preferably, it is 90 mol% or more. If it is less than 80 mol%, better biodegradability and coating film physical properties tend not to be obtained. From the viewpoint of mass, the content of lactic acid residue is preferably 90% by mass or more, and more preferably 95% by mass or more, 9
Most preferably, the content is 7% by mass or more.

When the hydroxy acid type polyester contains L-lactic acid residue and D-lactic acid residue,
The molar ratio (L / D) of the number of moles of L-lactic acid residue (L) and the number of moles of D-lactic acid residue (D) is preferably 1 to 9. It is more preferably 1 to 5.6. If L / D exceeds 9, the solubility of the polyester in the solvent used tends to make it difficult to use the polyester as a binder for ink. When L / D is less than 1 (excess of D-lactic acid), it tends to be difficult to manufacture at lower cost.

As the lactic acid, any of L-lactic acid, D-lactic acid and DL-lactic acid can be used.

(Physical properties of hydroxy acid type polyester)
The hydroxy acid-based polyester obtained as described above
The reduced viscosity of tel (η _{SP / C}) Is 0.3-1.5 dl / g
Preferably there is. Reduced viscosity is less than 0.3 dl / g
If it is too low, it may cause ink cissing during printing.
Yes, and if the reduced viscosity is higher than 1.5 dl / g,
When the ink viscosity increases and better printability cannot be obtained.
There is a match.

The reduced viscosity was measured at a sample concentration of 0.
It is a value measured using an Ubbelohde viscous tube at 125 g / 25 ml, a measurement solvent chloroform, and a measurement temperature of 25 ° C.

The hydroxy acid type polyester preferably has a glass transition point (Tg) of 35 to 60 ° C. More preferably, it is 40 to 55 ° C. 35-6
Within the range of 0 ° C, better adhesion strength to the biodegradable film and blocking resistance can be obtained.

The glass transition point Tg can be adjusted, for example, by changing the ratio of the copolymerization component of the hydroxy acid type polyester. The glass transition point is a value measured by the DSC (differential scanning calorimeter) method.

The hydroxy acid type polyester preferably has biodegradability. Here, the term "biodegradable" refers to the property of being converted into a low molecular weight compound by the metabolism of organisms in the process of decomposition.

(Ink Composition) The ink composition of the present invention is obtained by mixing the above hydroxy acid type polyester with an ink pigment and a solvent.

The ink pigment used in the present invention is not particularly limited as long as it is a commonly used one, and for example, titanium oxide, calcium carbonate, barium sulfate, yellow iron oxide,
Red iron oxide, carbon black, aluminum powder, mica,
Examples include inorganic pigments such as titanium powder, azo pigments, phthalocyanine pigments, and various organic pigments. These may be used alone or in combination of two or more.

The solvent used in the present invention is preferably methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, butyl acetate, toluene, from the viewpoints of solubility, workability, drying rate, etc. of the hydroxy acid type polyester. Xylene, isopropyl alcohol, etc. are used. These may be used alone or in combination of two or more.

(Method for producing ink composition) The ink composition of the present invention is not particularly limited as long as it is a conventionally known method.
It is produced by a commonly used method. For example, the hydroxy acid polyester is dissolved in the solvent,
An ink composition can be produced by a method in which the above-mentioned ink pigment is mixed with this and dispersed using a ball mill, a paint shaker or the like.

Here, it is preferable that the above-mentioned respective components are mixed in an amount of 1 to 1000 parts by mass of the ink pigment and 100 to 2000 parts by mass of the solvent with respect to 100 parts by mass of the hydroxy acid type polyester. More preferably, the ink pigment 2 to 100 parts by mass of the hydroxy acid-based polyester.
500 parts by mass and 200 to 1500 parts by mass of the solvent.

In addition to the above components, if necessary,
A cross-linking agent such as polyfunctional isocyanate, polyfunctional epoxy and melamine, a pigment dispersant, a viscosity modifier and the like can be added.

[0072]

EXAMPLES Hereinafter, the ink composition of the present invention will be described in more detail with reference to examples.

(Example 1) 500 parts of DL-lactide, 5
-3.56 parts of ethylene glycol diester of sodium sulfo-isophthalic acid and 0.1 part of tin octylate as a ring-opening polymerization catalyst were charged into a 4-neck flask and heated at 190 ° C for 1 hour under a nitrogen atmosphere to perform ring-opening polymerization. By doing so, a polyester resin (i) containing a sulfonate in the main chain of the molecular chain was obtained.

Next, the above polyester resin (i) 100
Parts were dissolved in a mixed solvent consisting of 100 parts of methyl ethyl ketone (MEK) and 100 parts of ethyl acetate, and 100 parts of carbon black were mixed and dispersed in a ball mill to obtain a black ink composition (I).

(Example 2) 500 parts of DL-lactide, 3
-1.62 parts of sodium sulfo-n-propanol and 0.1 part of tin octylate as a ring-opening polymerization catalyst were placed in a four-necked flask and heated at 190 ° C for 1 hour under a nitrogen atmosphere,
By ring-opening polymerization, a polyester resin (ii) containing a sulfonate at the end of the molecular chain was obtained.

With respect to the polyester resin (ii), a black ink composition (II) was prepared in the same manner as in Example 1.

(Example 3) 500 parts of DL-lactide, 5
-0.89 parts of ethylene glycol diester of sodium sulfo-isophthalic acid and 0.1 part of tin octylate as a ring-opening polymerization catalyst were charged in a four-necked flask and heated at 190 ° C for 1 hour under a nitrogen atmosphere to perform ring-opening polymerization. By doing so, a polyester resin (iii) containing a sulfonate at the terminal of the molecular chain was obtained.

Regarding the polyester resin (iii),
A black ink composition (III) was prepared in the same manner as in Example 1.
Was produced.

(Example 4) 500 parts of DL-lactide, 5
-Sodium sulfo-isophthalic acid ethylene glycol diester (12.46 parts) and tin octylate (0.1 part) as a ring-opening polymerization catalyst were charged into a 4-necked flask and heated at 190 ° C for 1 hour in a nitrogen atmosphere to perform ring-opening polymerization. By doing so, a polyester resin (iv) containing a sulfonate at the terminal of the molecular chain was obtained.

With respect to the polyester resin (iv), a black ink composition (IV) was prepared in the same manner as in Example 1.

(Comparative Example 1) 500 parts of DL-lactide, 2.25 parts of glycolic acid as a polymerization initiator, and 0.1 part of tin octylate as a ring-opening polymerization catalyst were placed in a four-necked flask under a nitrogen atmosphere at 190 parts. A ring-opening polymerization was carried out by heating at 0 ° C. for 1 hour to obtain a polyester resin (v). Also for the polyester resin (v), a black ink composition (V) was produced in the same manner as in Example 1.

Comparative Example 2 Byron RV103 (R) (v), an aromatic polyester resin manufactured by Toyobo Co., Ltd.
Using i), a black ink composition (VI) was obtained in the same manner as in Example 1.

The composition and physical properties of the polyester resins of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 1 below.

<Evaluation of Ink Performance and Biodegradability> Using the ink compositions obtained in the above Examples and Comparative Examples, printing was performed on a poly L-lactic acid film with a gravure printing machine to obtain a printing film. Ink performance (ink pigment dispersibility, ink stability, printability, adhesion) using this printing film
And the biodegradability was evaluated as follows.
The ink stability, printability, adhesiveness, and biodegradability were evaluated on a scale of 5 to 5 (very good) to 1
It was evaluated as (poor). Practically 4 or more is a passing level.

1) Ink pigment dispersibility: The dispersibility of the ink pigment was evaluated with a gloss meter. 2) Ink stability: Visually check the change with time of the ink,
The degree of presence or absence of ink pigment separation and sedimentation was visually evaluated.

3) Printability: Gravure printing was performed on a poly L-lactic acid film, and the presence or absence of cissing of the ink was visually evaluated.

4) Adhesiveness: The cross-cut was cut, and the adhesiveness was evaluated by peeling Cellotape (R). 5) Biodegradability: the above print film 10 cm x 10 cm
The poster (garbage disposal machine, manufactured by Mitsui Home Co., Ltd. (MA
M)), and after 14 days, the morphology (degree of decomposition) of the sample was visually evaluated. Those with a large degree of decomposition were considered good.

The results are shown in Table 1.

[0089]

[Table 1]

The reduced viscosity was 0.125 as the sample concentration.
g / 25ml, measurement solvent chloroform, measurement temperature 25 ℃
The measurement was performed using an Ubbelohde viscosity tube. The glass transition point was measured by the DSC method. In addition, in Table 1, the lactic acid residue defines the charged amount. However, 5
It was confirmed by NMR at 00 MHz that the polyester resin of Examples and Comparative Examples also contained the same amount of lactic acid residue.

Further, the molar ratio of L-lactic acid and D-lactic acid in the polyester resin is obtained from the charged amount. It was confirmed to be the same as that determined using SEPA-200 manufactured by Seisakusho. The sulfonate concentration was calculated from the charged amount.

As shown in Table 1, the ink compositions of Examples 1 to 4 were particularly excellent in ink pigment dispersibility and ink stability as compared with the ink compositions of Comparative Examples 1 and 2.

The embodiments and examples disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

[0094]

As described above, according to the present invention, since the hydroxy acid type polyester having the sulfonate-containing structure is contained in the ink composition, the dispersibility of the ink pigment and the stability of the ink are improved. It is possible to provide a particularly biodegradable ink composition having excellent properties.

The ink composition of the present invention can be used, for example, for printing labels, packaging films and the like having a biodegradable film such as a polylactic acid film as a base material, and is widely used as a biodegradable ink for paper. Can be used.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Miyamoto             2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. (72) Inventor Tayota Hotta             2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. (72) Inventor Toshiyuki Kaku             1-5-1 Taito, Taito-ku, Tokyo Toppan stamp             Imprint Co., Ltd. (72) Inventor Kazuki Okuyama             2-3-13, Kyobashi, Chuo-ku, Tokyo Toyo             Nki Manufacturing Co., Ltd. (72) Inventor Akira Suzuki             2-3-13, Kyobashi, Chuo-ku, Tokyo Toyo             Nki Manufacturing Co., Ltd. F-term (reference) 4J029 AA02 AB01 AC01 AC02 AD01                       AD10 AE18 BH02 DB01 EA01                       EA02 EA03 EA05 EH03 FA18                       HA03A                 4J039 AE06 BA04 BA06 BA13 BA16                       BA18 BA30 BA35 BA37 BC39                       BC60 BE01 BE12 CA07 EA45

Claims (7)

[Claims] 1. An ink composition comprising a hydroxy acid-based polyester having a sulfonate-containing structure represented by the following formulas (1) and / or (2) in a molecular chain, an ink pigment, and a solvent. object. [Chemical 1] [In the formula (1), X is an alkyl group having 20 or less carbon atoms, a cycloalkyl group, an aryl group, an arylalkyl group or hydrogen, a hydroxyl group, a nitro group, an amino group, an acyl group, a sulfonic acid group, an alkoxyl group and a halogen. And M represents lithium, sodium, potassium or an amine represented by the following formula (3). Also, m1 is 0 to 3
M2 is an integer of 1 to 4 and m1 + m
2 satisfies the relationship of 1 ≦ m1 + m2 ≦ 4. Also, n1
Represents an integer of 1 or more. ] [Chemical 2] [In the formula (2), R ¹ represents an alkylidene group having 20 or less carbon atoms, and M represents lithium, sodium, potassium or an amine represented by the following formula (3). ] [Chemical 3] [In the formula (3), R ² , R ³ , R ⁴ and R ⁵ each independently represent hydrogen, an alkyl group, a phenyl group or a benzyl group. ] 2. The ink composition according to claim 1, wherein the hydroxy acid-based polyester has a sulfonate-containing structure represented by the following formula (4) in the molecular chain. [Chemical 4] [In the formula (4), M represents lithium, sodium, potassium or an amine represented by the above formula (3). N2 represents an integer of 1 or more. ] 3. The ink composition according to claim 1, wherein the concentration of the sulfonate of the hydroxy acid-based polyester is 5 to 100 equivalents / 10 ⁶ g. 4. The ink composition according to claim 1, wherein the hydroxy acid-based polyester contains 80 mol% or more of lactic acid residues. 5. The hydroxy acid polyester is L
-Lactic acid residue and D-lactic acid residue are included, and the molar ratio of the number of moles of L-lactic acid residue (L) and the number of moles of D-lactic acid residue (D) (L
/ D) is 1-9, The ink composition of Claim 4 characterized by the above-mentioned. 6. The ink composition according to claim 1, wherein the hydroxy acid-based polyester has a reduced viscosity (η _{SP / C} ) of 0.3 to 1.5 dl / g. . 7. The ink composition according to claim 1, wherein the hydroxy acid-based polyester has a glass transition point (Tg) of 35 to 60 ° C.