JP5424577B2 - Continuous ink jet recording ink composition - Google Patents

Description

  The present invention relates to an ink composition for continuous ink jet recording. More specifically, the present invention relates to an ink composition for continuous ink jet recording having a wide temperature range capable of satisfactorily printing by suppressing droplet tailing and satellite.

  The ink jet recording methods currently used are roughly classified into two types: a continuous method and an on-demand method. Here, the continuous method means that only ink droplets necessary for recording image formation are landed on a recording medium by causing ink droplets to continuously fly and deflecting the flight path with an electric force. The ink jet recording system is characterized in that the remaining ink droplets are collected and repeatedly used. On the other hand, the on-demand system is an ink jet recording system characterized in that only ink droplets necessary for recording image formation are intermittently ejected and landed on a recording medium as it is.

  Because of these differences in principle, continuous recording devices always eject ink droplets, so they are more responsive than timed and can be recorded at higher speeds. is there. In addition, even when fast-drying ink is used, there is a feature that the ejection reliability is high. Therefore, there are a large number of recording media, and for fields where recording is performed for a long time, and non-absorbing recording media. In fields where fast drying ink is required, it is mainly used for industrial purposes.

  The ink composition used in the continuous method is generally of a low viscosity type. This is to facilitate the collection of ink that has not been used for recording image formation, as described above, and when ink having a high viscosity is used, the ink stays in the middle of the collection channel. However, such a low-viscosity ink has a problem that it is not necessarily appropriate in terms of obtaining good recording performance for the following reason.

  In the ink jet recording system, a recorded image is obtained by collecting a large number of colored dots formed by ink droplets landing on the surface of a recording medium. And, the size of each dot is uniform and the shape is uniform, resulting in obtaining a beautiful recorded image. Therefore, in order to obtain good recording performance, the shape (flying shape) while the ink droplets ejected from the recording head are flying is important. The flying shape for ensuring that the ink droplets land on the recording location is preferably a perfect spherical shape. For flying shapes such as those with tails (tailing) or those with broken droplets (satellite), This is not preferable because it causes variations in the position of the dots and the size and shape of the dots, resulting in difficult reading. Furthermore, the low viscosity ink has a problem that the tailing and satellite are likely to occur.

  In particular, in the ink jet recording method, an ink droplet generation method in which ink is quickly filled into a nozzle and ejected from the nozzle under pressure is disadvantageous from the viewpoint of tailing and satellite generation.

  As one means for solving such a problem, a method in which a cellulose derivative is contained in an ink is known. However, the cellulose derivative has a high affinity for moisture, and if it is contained in a large amount in the ink for the purpose of preventing tailing and satellite, there is a problem that the hygroscopicity is increased accordingly. In particular, in the continuous method, while ink is repeatedly ejected and collected, moisture in the air is absorbed to cause separation of the colorant and precipitation of the resin (sowering).

  Therefore, the present applicant has so far proposed an ink composition for continuous ink jet recording containing propylene glycol monomethyl ether and / or propylene glycol monoethyl ether in order to prevent ink sowing. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 10-204346

  However, even the ink composition described in Patent Document 1 has a limit in increasing the cellulose derivative content. As a result, when used in a specific temperature range, droplet tailing and satellite may still occur. In such a case, problems such as deterioration in printing quality and printing stability have occurred.

  Accordingly, an object of the present invention is to obtain an ink composition for ink jet recording which can reduce the occurrence of tailing and satellites while maintaining a viscosity suitable for a continuous type recording apparatus.

  As a result of intensive studies on the fixing resin (binder resin), the present inventors have found that when a styrene-maleic acid-based resin having a specific acid value is used as a binder in combination, even if a large amount of cellulose derivative is used, soringing is caused. It has been found that the performance drop does not occur, the size and flying shape of ink droplets are uniform, and tailing and satellites can be reduced, and the present invention has been completed.

  That is, the present invention is (1) an ink composition for continuous ink jet recording comprising a colorant, a resin and a solvent, wherein the resin contains a styrene-maleic acid resin and a cellulose derivative, and the styrene -It relates to an ink composition for continuous ink jet recording, wherein the acid value of the maleic resin is 60 to 320 mgKOH / g.

  The cellulose derivative preferably contains one or more cellulose acetate alkylates having 1 to 6 carbon atoms.

  The cellulose acetate alkylate is preferably cellulose acetate butyrate and / or cellulose acetate propionate.

  According to the ink composition for continuous ink jet recording of the present invention, the size and flying shape of ink droplets are uniform, and a continuous ink composition for ink jet recording with good print quality can be obtained. .

  Hereinafter, the present invention will be described in more detail.

  Examples of the colorant used in the ink composition for inkjet recording of the present invention include C.I. I. Solvent Black 22, 23, 27, 29, 34, 43, 47, 123, C.I. I. Solvent Yellow 19, 21, 23, 32, 61, 79, 80, 81, 82, C.I. I. Solvent Red 8, 35, 83, 84, 100, 109, 118, 119, 121, 122, 160, C.I. I. Examples thereof include oil-soluble metal-containing dyes such as Solvent Blue 25, 55 and 70. These colorants can be used alone or in admixture of two or more.

  The content of these colorants in the ink composition is preferably in the range of 3 to 15% by mass. When the content of the colorant is less than 3% by mass, the color density decreases. On the other hand, when the content exceeds 15% by mass, it becomes difficult to use from the viewpoint of ink viscosity and fluidity.

  The styrene-maleic acid resin used in the present invention is obtained by copolymerizing a maleic acid monomer and the like with a styrene monomer as an essential component. Here, examples of the styrenic monomer include styrene, α-methylstyrene, vinyltoluene, and derivatives thereof. The maleic acid monomers include maleic anhydride and maleic acid, aliphatic or alicyclic alkyl esters having 1 to 18 carbon atoms, alkyl amides having 1 to 18 carbon atoms, and 2 to 4 carbon atoms. And hydroxyalkyl esters. The styrene-maleic acid resin can be produced by a known method using these monomer components.

  The styrene-maleic acid resin obtained by polymerizing the above monomer components preferably has an acid value of 60 to 320 mgKOH / g, more preferably 65 to 300 mgKOH / g. When the acid value of the styrene-maleic acid-based resin is lower than the above range, the re-solubility of the ink in the solvent is insufficient, and further, it is difficult to be charged as a continuous ink-jet recording ink composition, and discharge stability and intermittent There is a tendency to lack discharge properties. On the other hand, when the acid value is higher than the above range, the compatibility with the cellulose derivative is lowered, and the stability tends to be impaired.

  From the viewpoint of imparting chargeability, the copolymerization ratio (mass ratio) of the styrene monomer and the maleic monomer is preferably 90:10 to 30:70. Furthermore, the weight average molecular weight of the styrene-maleic acid resin is preferably 4,000 to 20,000 from the viewpoint of imparting ink viscosity and chargeability.

  Examples of the cellulose derivative used in the present invention include nitrocellulose (nitro group-substituted), cellulose acetate, cellulose acetate propionate, lower acyl group-substituted products such as cellulose acetate butyrate, and lower alkyl-substituted products such as methylcellulose and ethylcellulose. Can be mentioned.

  There are various cellulose derivatives having different molecular weights, substitution degrees with respect to hydroxyl groups, and the like, but it is preferable to select various types according to the viscosity of the target ink composition for inkjet recording. For example, cellulose acetate butyrate or cellulose acetate propionate is preferable from the viewpoint of solubility in a solvent and compatibility with a styrene-maleic acid resin, and the degree of substitution of acetyl group, butyryl group or propyl group (3 glucose units). When the number of hydroxyl groups is completely substituted with a certain substituent, those having a substitution degree of 100%) are 0.6 to 20% and 32 to 53%, respectively.

  The content ratio (mass ratio) of the styrene-maleic acid resin and the cellulose derivative, particularly cellulose acetate butyrate or cellulose acetate propionate in the ink composition for inkjet recording of the present invention is 10:90 to 50:50. It is preferable that the ratio is 20:80 to 30:70. When the content of the styrene-maleic acid-based resin exceeds the above range, the droplets are not well-organized and tend to be less than the appropriate viscosity range. There is a tendency to exceed.

  The total content of the styrene-maleic acid resin and the cellulose derivative, which are resin components in the ink composition for ink jet recording of the present invention, is preferably 3 to 10% by mass in the ink composition for ink jet recording. When the total content of these resins is less than 3% by mass, the scratching property is deteriorated.

  Examples of the solvent used in the present invention include methanol, ethanol, n-propanol, isopropanol, n-butanol, amyl alcohol, benzyl alcohol, cyclohexanol, diacetone alcohol and the like monovalent alcohols, ethylene glycol monomethyl ether, diethylene glycol mono Alkylene ether monoalkyl ethers such as ethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monoethyl ether, alkylene glycol monoacetates such as ethylene glycol monoacetate, propylene glycol monoacetate, Ethylene glycol, diethylene glycol, trimethylene glycol , Triethylene glycol, tetraethylene glycol, polyethylene glycol, a dihydric alcohol such as propylene glycol, ketones such as acetone and methyl ethyl ketone, methyl lactate, butyl lactate, .gamma.-butyrolactone and the like.

  Examples of other additives include pH adjusters, viscosity adjusters, rust inhibitors, antifoaming agents, silicone surfactants, fluorine-containing surfactants, and other surfactants.

  In order to prepare the ink composition for continuous ink jet recording of the present invention from the above various materials, a colorant, a styrene-maleic acid resin, a cellulose derivative, a solvent, and various additives as necessary are contained in a sealed container. The mixture can be obtained by stirring, mixing and dissolving uniformly, and then filtering with a membrane filter.

  The viscosity of the ink composition for continuous ink jet recording obtained is preferably about 2.0 to 5.0 mPa · s at 25 ° C.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to this. Unless otherwise specified, “part” and “%” mean “part by mass” and “% by mass”, respectively.

Examples 1-9 and Comparative Examples 1-3
<Preparation of ink composition for continuous ink jet recording>
The compositions shown in Table 1 below (the mixing ratio of each component represents mass%) were stirred and uniformly dissolved in a closed container, and then filtered through a 10 μm membrane filter. Examples 1 to 9 and Inkjet recording ink compositions of Comparative Examples 1 to 3 were obtained.

（＊１）スチレン−マレイン酸系樹脂Ａ：重量平均分子量１６，０００、酸価１９９ｍｇＫＯＨ／ｇ、スチレン／マレイン酸のｉｓｏ−ブチルアルコールハーフエステル＝３９／６１（重量比）
（＊２）スチレン−マレイン酸系樹脂Ｂ：重量平均分子量９，５００、酸価２６５〜３００ｍｇＫＯＨ／ｇ、スチレン／無水マレイン酸＝５０／５０（重量比）、実施例３では、酸価が２９０、実施例９では、酸価が３００ものを使用。
（＊３）スチレン−マレイン酸系樹脂Ｃ：重量平均分子量１５，０００、酸価６６ｍｇＫＯＨ／ｇ、スチレン／マレイン酸のｉｓｏ−ブチルアルコールハーフエステル＝８０／２０（重量比）
（＊４）スチレン−マレイン酸系樹脂Ｄ：重量平均分子量１５，０００、酸価３５ｍｇＫＯＨ／ｇ、スチレン／マレイン酸のｉｓｏ−ブチルアルコールハーフエステル＝８９／１１（重量比）
（＊５）バイロン１０３：ポリエステル樹脂：東洋紡績株式会社製
（＊６）ＣＡＢ３８１−２：セルロースアセテートブチレート：アセチル基置換度１３．５％、ブチリル基置換度３８．０％、イーストマンケミカル社製
（＊７）ＣＡＰ４８２−０．５：セルロースアセテートプロピオネート：２．５％、プロピル基置換度４６．０％、イーストマンケミカル社製
（＊８）オラゾールブラックＲＬＩ：ソルベントブラック２９：チバ・スペシャリティ・ケミカルズ株式会社製
（＊９）ＴＳＦ４４４５：シリコーン系添加剤：東芝シリコーン株式会社製

(* 1) Styrene-maleic acid resin A: weight average molecular weight 16,000, acid value 199 mgKOH / g, styrene / maleic acid iso-butyl alcohol half ester = 39/61 (weight ratio)
(* 2) Styrene-maleic acid resin B: weight average molecular weight 9,500, acid value 265-300 mgKOH / g, styrene / maleic anhydride = 50/50 (weight ratio), in Example 3, acid value 290 In Example 9, an acid value of 300 was used.
(* 3) Styrene-maleic acid resin C: weight average molecular weight 15,000, acid value 66 mgKOH / g, styrene / maleic acid iso-butyl alcohol half ester = 80/20 (weight ratio)
(* 4) Styrene-maleic acid resin D: weight average molecular weight 15,000, acid value 35 mgKOH / g, styrene / maleic acid iso-butyl alcohol half ester = 89/11 (weight ratio)
(* 5) Byron 103: Polyester resin: manufactured by Toyobo Co., Ltd. (* 6) CAB381-2: Cellulose acetate butyrate: acetyl group substitution degree 13.5%, butyryl group substitution degree 38.0%, Eastman Chemical Co., Ltd. (* 7) CAP482-0.5: cellulose acetate propionate: 2.5%, propyl group substitution degree 46.0%, manufactured by Eastman Chemical Co. (* 8) Orazole Black RLI: Solvent Black 29: Ciba・ Specialty Chemicals Co., Ltd. (* 9) TSF4445: Silicone additive: Toshiba Silicone Co., Ltd.

<Performance evaluation>
The viscosity, ejection stability, intermittent stability, and adhesiveness of each ink composition for inkjet recording were evaluated by the following methods. The results are shown in Table 2.

[viscosity]
Using an ELD viscometer manufactured by Tokyo Keiki Co., Ltd., measurement was performed at a measurement temperature of 25 ° C. and a measurement rotation speed of 100 rpm.

[Discharge stability]
Using a continuous ink jet printer (Domino A300), it was continuously operated at room temperature for 100 hours and printed on a stainless steel substrate.
A: Characters are clearly printed during continuous operation B: Characters are printed but difficult to read C: Characters are not printed

[Intermittent discharge]
Using a continuous ink jet printer (A300 manufactured by Domino), after 100 hours of continuous operation, the ink was ejected again after 50 hours and printed on a stainless steel substrate.
A: Characters are printed neatly B: Characters are printed but difficult to read C: Characters are not printed

[Adhesiveness]
After the cello tape (registered trademark) (transparent beautiful color manufactured by Sumitomo 3M Co., Ltd.) was pressed 5 times against the stainless steel base material, it was immediately peeled off.
A: No peeling at all B: Some peeling off C: Most peeling off

  As shown in Table 2, in Examples 1 to 9 having a predetermined configuration of the present invention, since the ejection stability and intermittent stability are good, the flying shape of the ink droplet is close to a true sphere, and tailing and satellite It has been found that the occurrence of is effectively suppressed. On the other hand, in Comparative Examples 1 to 3, since ejection stability and intermittent stability were poor, it was found that character formation failure occurred due to ink droplet tailing and satellite generation. In particular, it was found from Comparative Example 1 that when a resin D (acid value 35) having an acid value of 60 or less was used, various functions such as ejection stability were lowered. From Comparative Example 2, styrene-maleic acid resin is essential for the present invention, and from Comparative Example 3, cellulose acetate alkylate must be contained even when styrene-maleic acid is contained. It was found that the discharge stability and the intermittent stability were inferior.

  From the above, it was shown that the continuous ink-jet recording ink composition according to the present invention has a good flying shape in a viscosity range suitable for the ink-jet recording ink composition.

  By using the ink composition according to the present invention in a continuous ink jet recording system, it is possible to effectively prevent tailing and satellite of ink droplets when ejected from a nozzle while suppressing performance degradation due to souring. Therefore, it is possible to obtain a high-quality printed matter.

Claims (3)

A continuous ink-jet recording ink composition comprising a colorant, a resin, and a solvent,
As the resin, including a styrene-maleic acid resin and a cellulose derivative,
The acid value of the styrene-maleic acid resin is 60 to 320 mgKOH / g,
A continuous ink composition for inkjet recording, wherein the content ratio (mass ratio) of the styrene-maleic acid resin and the cellulose derivative is 10:90 to 50:50. The ink composition for continuous ink jet recording according to claim 1, wherein the cellulose derivative contains one or more cellulose acetate alkylates having 1 to 6 carbon atoms. The ink composition for continuous ink jet recording according to claim 2 , wherein the cellulose acetate alkylate is cellulose acetate butyrate and / or cellulose acetate propionate.