JPH05339528A - Ink composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which ensures less load on a transfer system and is excellent not only in printing quality after transfer but also in wear and water resistances of recording images irrespective of the type of paper by employing a specific phthalic ester as a vehicle. CONSTITUTION:The title composition is used in a recording system in which ink is discharged from an ink jet recording head to an intermediate transfer medium at a temperature higher than room temperature, and in which the ink is transferred from the medium to testing paper. The composition comprises a vehicle and a colorant, in which at least one member selected from among o- and m-phthalic diesters each having a melting point of 50 deg.C or higher is used as the vehicle. Each of the diesters has a substituent containing at least a cyclohexyl or an aryl group. This composition ensures clear profile and excellent printing quality irrespective of the properties of paper, and a recorded image composed of records having excellent wear and water resistances can be obtained from the composition.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an ink composition used in an ink jet recording system. More specifically, an ink composition (hereinafter referred to as an ink composition used in an inkjet recording method in which ink is ejected from an inkjet recording head to an intermediate transfer medium under a temperature higher than room temperature, and the ink is further transferred from the intermediate transfer medium to a recording sheet. , And "ink" together).

[0002]

2. Description of the Related Art Inkjet recording is excellent in quietness and high-speed printing at the time of recording. As an ink composition used in an inkjet recording system so far, a liquid ink composition based on water or the like or a natural ink composition has been used. A room temperature solid ink composition based on wax has been used. However, since the recording is performed directly on the recording paper, in the case of the former, various types of recording paper such as bond paper, PPC paper, and recycled paper are formed from the viewpoint of forming a recorded image due to stains in the fibers of the paper. Print quality tends to vary. Further, the latter is, for example, US Pat. No. 4,390,369, 448.
Ink compositions such as those described in Japanese Patent No. 4948 and Japanese Patent Application Laid-Open No. 58-108271 have been proposed to improve the former drawback, but the adaptability to the paper type is improved, but the ink composition at the time of recording is improved. Since the droplets are rapidly cooled and solidified in a state of being raised on the surface of the recording paper, the adhesive strength and the ink strength are low, and there are drawbacks such that they are easily peeled off or deformed due to external friction or pressure.

Further, in order to solve such a problem, US Pat.
538156, JP-A-57-70668, JP-A-57-123065, and JP-A-59-2.
No. 25958, JP-A No. 62-92849, and the like, the same ink is used to eject from a recording head onto an intermediate carrier (intermediate transfer medium) that is not absorptive. A method of compensating for the drawbacks of the inkjet recording method of recording directly on the recording paper by performing transfer to a target recording medium (recording paper etc.) after applying a means such as evaporating Called) is proposed.

[0004]

When an ink composition based on water is used as the ink composition used in such an ink jet transfer system, good printing is achieved irrespective of the quality of the recording paper. Although there is a tendency for quality to be obtained, (1) it takes time to obtain an appropriate viscosity due to water evaporation on the transfer medium, and high-speed output cannot be performed,
(2) It takes a long time to dry the ink after the transfer, (3) the transfer of the ink from the intermediate transfer medium onto the recording paper is likely to be insufficient, and the transfer background stain is easily generated. (4) the recording after the transfer There are problems such as the lack of water resistance of the image, and the conventional problems still not solved.

In contrast to this method, when the hot-melt ink composition proposed so far is used, it is difficult to maintain the state of the ink on the intermediate transfer medium, and the temperature for maintaining the proper state is maintained. There is a problem that the control range is extremely narrow. Specifically, when the ink that has been once cooled and solidified on the intermediate medium is reheated to be transferred, or when the intermediate transfer medium is preheated before the ink is ejected to maintain the molten state, , The change in viscosity of the molten ink due to the heating temperature is too large, and the viscosity is lowered when the heating temperature is too high, causing printing blur on the recording paper after transfer, and the transfer from the intermediate transfer medium to the recording paper is caused when the heating temperature is low. The problem is that it is incomplete and transfer stains are likely to occur.

The present invention is intended to solve the above-mentioned problems, and aims at: a load on a transfer system is small; a print quality after transfer to all paper types is good; An object of the present invention is to provide an ink composition used in an inkjet transfer system, which has good print abrasion resistance and water resistance on a recording paper.

[0007]

According to the ink composition of the present invention, an ink is ejected from an ink jet recording head onto an intermediate transfer medium at a temperature higher than room temperature, and further the ink is transferred from the intermediate transfer medium to a recording paper. An ink composition for use in a recording method comprising a vehicle and a coloring material, the vehicle comprising at least one kind of phthalic acid diesters having a melting point of 50 ° C. or higher and ortho or meta coordinates. It is characterized in that a phthalic acid ester is used, and the substituent of the phthalic acid diester coordinated to the ortho or meta position contains at least a cyclohexyl group or an aryl group.

The ink composition of the present invention will be described below.

The inventors of the present invention have been studying a room temperature solid ink composition for ink jet recording for recording directly on a recording sheet, and among them, among them, a phthalic acid diester coordinated to the ortho position and the meta position is shown. They found a unique thermal behavior characteristic of the class.

Conventionally used room temperature solid ink compositions such as natural waxes are melted and solidified at a specific temperature according to external heating and cooling. However, although the above materials have a temperature (melting point) at which they start melting at a specific temperature when heated, they do not show the temperature (freezing point) of changing from a liquid to a solid when cooled from a high temperature, and thus become high with cooling. It exists as a viscous liquid in a viscous state, and has the property of gradually solidifying (so-called supercooling property). This property, as a normal temperature solid ink composition for ink jet recording which is directly recorded on a recording sheet up to now, may cause printing bleeding or the like, but when used in an ink jet transfer system,
It has a very remarkable effect.

The phthalate compound used in the ink composition of the present invention is preferably a compound having an ortho-position, a meta-position or a para-position, and a compound having an ortho-position and a meta-position. Para-coordinated phthalate ester (so-called terephthalate ester) has poor supercooling properties compared to other coordinated products, and when cooled from a heated and melted state, the temperature almost reaches the freezing point. In that case, the crystalline solid state is exhibited. Therefore, when the ink composition is used in the inkjet transfer method of the present invention, the ink composition is solidified on the intermediate transfer medium and causes transfer failure.

The phthalate compound used in the present invention preferably has a melting point between 50 ° C and 150 ° C. Further, those having a melting point of 70 to 120 ° C. are more preferable.

When a phthalate compound having a melting point lower than 50 ° C. is used, it causes significant problems in the use as a recording material obtained and in the storage environment. Specifically, it is conceivable that the atmosphere around the bag easily exceeds 50 ° C. or reaches the vicinity thereof, such as when a recorded matter is contained in the bag in the vehicle. In such a case, bleeding of the recorded image due to remelting of the ink, blurring, or deterioration of the recorded matter due to adhesion with other recording paper or the like occurs.

On the contrary, when a phthalate compound having a melting point of more than 150 ° C. is used, the heating temperature of the recording head in the ink jet recording apparatus becomes extremely high. You will need it.
Further, since the thermal stability of the material itself at high temperature is lowered, the reliability of the ink composition under a long-term use condition becomes a problem.

Regarding the melting point range of 70 to 120 ° C., there is a high possibility that the ink composition is most balanced with respect to the above problems.

The content is preferably 50 wt% or more, more preferably 70 wt% or more. Content is 5
When the amount is less than 0 wt%, the amount of other vehicle material relatively increases, which may cause an increase in viscosity beyond the viscosity value that can be ejected by the recording head, resulting in ink ejection failure from the recording head. Will cause it. On the contrary, when the content is 50 wt% or more, preferable viscosity characteristics are exhibited, and the ink ejection stability of the recording head is improved. Furthermore, when the content is 70 wt% or more, it becomes possible to obtain an ink composition having a lower viscosity, and a high frequency response of the recording head becomes possible.

As the vehicle constituting the ink composition of the present invention, a resin, an additive and the like are appropriately contained in addition to the phthalate compound.

With respect to the resin as a vehicle, the addition amount thereof has a great influence on the viscosity characteristics of the ink composition, and also has a great contribution to the abrasion resistance of the print. When the content exceeds 50 wt%, the print abrasion resistance and the like tend to improve, but the amount of other vehicle materials added relatively decreases, causing an increase in viscosity above the allowable viscosity and causing ink ejection failure. I will end up.

[0019]

Like the conventional hot melt ink composition, the ink composition of the present invention is ejected from an ink jet recording head to an intermediate transfer medium which is not subjected to temperature control such as heating under a temperature higher than room temperature. It After that, 0.
In a short time within 3 seconds to 10 seconds, the intermediate transfer medium exhibits supercooling characteristics with cooling due to heat being taken away, and exhibits a highly viscous liquid state. After that, the ink is transferred from the intermediate transfer medium to the recording paper under an appropriate pressure to form a recorded image.

The obtained recorded image is transferred to the fibers of the surface of the recording paper under pressure from the intermediate transfer medium in a viscous and viscous liquid state as an ink composition, so that bleeding occurs during transfer. Ink is pushed into the recording paper fibers and fixed in an extremely sharp image contour, and further solidifies with the lapse of time.

[0021]

EXAMPLES Next, the present invention will be described with reference to examples.

The ink composition of the present invention can be prepared by a known method, and various vehicles are mixed with a coloring material, a resin, etc., and the melting point of the vehicle or higher, preferably 80 to 160.
It can be obtained by heating and melting at 0 ° C, stirring with heating at that temperature to obtain a homogeneously dissolved composition, optionally filtering through a filter under a high temperature molten state, and then cooling.

As the physical properties of the ink, the viscosity at an operating ink temperature of about 50 to 150 ° C. is 50.0 millipascal second (hereinafter, referred to as the viscosity of the ink supply stability and the ink droplet formation flight stability under the high speed response of the recording head). mPa · s) or less) is necessary, and 20.0 to 3.0 mPa · s is more preferable for achieving even higher response (for realizing response of 4 to 10 KHz or more).
Further, the viscosity measurement temperature is appropriately determined according to the characteristics of the vehicle used for the ink composition. The surface tension affects the meniscus formation in the vicinity of the nozzle, and is preferably 50 millinewton per meter (mN / m) or less.

The melting point used for the ink vehicle is 50.
Specific examples of various phthalic acid ester compounds having a temperature of up to 150 ° C. include the following.

[0025]

[Table 1]

The resin is preferably selected from polyamide resins, alkyd resins, polyester polyol resins and the like, and is preferably compatible with the phthalate ester compound.

The colorant is preferably selected from oil-soluble dyes, pigments and disperse dyes having heat resistance and water resistance.

Specifically, [black dye] C.I. I. Solvent Black 3,22,23,45 [yellow dye] C.I. I. Solvent Yellow 19, 21, 62, 79,
83 [Red, magenta dye] C.I. I. Solvent Red 8,49,81,82,8
3, 84, 89, 91, 100, 109,
121, 127 C.I. I. Day Super Red 9 [Blue, Cyan Dye] C.I. I. Solvent Blue 11, 12, 25, 36, 4
4, 45, 49, 55, 73, [pigment] carbon black, phthalocyanine blue and the like.

The addition amount of the coloring material is preferably 10 wt% or less, and more preferably 5 wt% or less in consideration of the flight stability and proper viscosity of the head under high-speed response.
Further, two or more kinds of dyes can be appropriately mixed and used for adjusting the color tone.

Further, from the viewpoint of thermal stability, it is possible to appropriately add a general antioxidant or the like.

Next, a specific example of the embodiment will be shown.

Example 1 Composition Weight Percentage Vehicle: Bis- (4-benzyloxycarbonylphenyl) isophthalate 80.0 Resin: Polyester resin 8.0 Polyester polyol resin 8.5 Colorant: C.I. I. Solvent Black 45 3.0 Additive: Antioxidant (Hindered Phenol) 0.5 Melt the mixture of the above components at 140 ° C., stir and mix for 3 hours, and then mix with a pore size of 5 μm in a high temperature molten state. Pressure filtration using a tetrafluoride polyethylene membrane filter gives a viscosity of 20.0 mPas at a temperature of 120 ° C.
An ink composition having s and a surface tension of 29.0 mN / m was obtained.

Next, an ink-on-demand type (impulse type) ink jet recording head compatible with heated and melted ink was used, and after the recording head was attached to an ink jet transfer type recording apparatus, the recording head was kept at 130 ° C. The ink composition prepared in 1 was filled. And bond paper (Nina Bond), PPC (Xerox 4024
Paper) and recycled paper ("Yamayuri" manufactured by Honshu Paper Co., Ltd.) were used to transfer and record bit images, characters, etc., and then the following evaluations A1 to A6 were performed. The results of using the ink composition of Example 1 were all "adequate" or higher.

-Evaluation Method-A1. Ejectability: The viscosity value (η) of the ink composition prepared with a predetermined composition is: 5.0 ≦ η ≦ 20.0 ... Suitable (⊚) 20.0 <η ≦ 50.0・ Appropriate (○) ・ 50.0 <η ... Classify and evaluate according to unsuitable (×).

A2. Transfer medium smearing property: Degree of ink remaining on the intermediate transfer medium after transfer recording: No ink remains even when observing the surface with a microscope.
・ Appropriate (◎) ・ Although it is confirmed by microscopic observation, almost no ink residue is visually observed. ・ ・ ・ Appropriate (○) ・ Clear ink residue is visually observed ・ ・ ・ Inappropriate (×) Classify and evaluate.

A3. Paper type compatibility: The clarity of printing after transfer recording to 3 types of recording paper, the degree of difference between recording papers, -There is no difference in quality between recording papers, and a clear recorded image is shown-・
・ Suitable (⊚) ・ Slight difference between recording papers is recognized, but it feels preferable as a recording image ・ ・ ・ Suitable (○) ・ Clearly different recorded image depending on the type of recording paper ・.. Classify and evaluate according to unsuitability (x).

A4. Print rubbing resistance: After being left at room temperature for 24 hours after transfer recording to various recording papers, whether or not stains are generated by rubbing the printed surface with a cross-cut tester equipped with a clip with a load of 100 to No contamination due to a load of 200 g ・ ・ ・ Suitable (⊚) ・ No contamination due to a load of 50 to 100 g ・ ・ ・ Appropriate (○) ・ Stain generation due to a load of 50 g or less ・ ・ ・ Inappropriate (×)

A5. Water resistance: After transfer recording to various types of recording paper and leaving it at room temperature for 24 hours, soak each sample in a beaker containing pure water for 1 hour, and then check if there is a residual state of ink recording image on the recording paper.・ There is almost no change from before leaving it ・ ・ ・ Suitable (◎) ・ Although it is slightly thin, characters etc. can be clearly seen ... Appropriate (○) ・ Ink image cannot be confirmed at all ・ ・ ・ Unsuitable (×) ) Classify and evaluate by.

A6. Environmental storability: Changes in the ink recorded image after the recording material after transfer recording is left for 24 hours in an environment of 45 ° C. and taken out are: ・ No change from before being left ... Some changes can be seen, but hardly visible
・ ・ Appropriate (○) ・ Bleeding, blurring, etc. are visually observed compared to before leaving ... Classify and evaluate according to unsuitable (×).

Example 2 Table 2 shows Examples 2-1 to 2-10 in the same manner as in Example 1.
The ink composition shown in was obtained.

[0041]

[Table 2]

Also in Example 2, when A1 to A6 were evaluated in the same manner as in Example 1, as shown in Table 3 below, all of the results were "appropriate" or higher.

[0043]

[Table 3]

Comparative Example Ink compositions of Comparative Examples C-1 to C-5 shown in Table 2 above were prepared as Comparative Examples in the same manner as in Example 1.

For these comparative examples, as in Example 1, A
When the evaluations of 1 to A6 were performed, the results shown in Table 3 above according to the individual characteristics were obtained.

A brief description of each is as follows.

C-1: Bis-used as a vehicle
The addition amount of (4-benzyloxycarbonylphenyl) isophthalate (melting point: 105 to 112 ° C.) was 40.0 w.
Since it was t%, the addition amount of the resin used as another vehicle was relatively increased and the viscosity value as the ink composition was 50.
It was over 0 mPa · s, which caused defective ink ejection.

C-2: A vehicle having a melting point of 50 ° C.
Since lower bis- (2,2,2-trifluoroethyl) phthalate (melting point: 41 ° C.) was used, the evaluation A6 (environmental preservation) as the ink composition was “unsuitable”.

C-3: Since dimethyl terephthalate (melting point: 142 ° C.) coordinated to the para position was used as a vehicle, ejection from the recording head was possible, but it solidified rapidly on the intermediate transfer medium. The transfer onto the recording paper was impossible.

C-4: An ink composition based on water, which has been generally used in the past, was prepared, and transfer recording was carried out by ejecting the ink at room temperature, and the above evaluations A1 to A6 were carried out.
However, it was "unsuitable" in terms of scumming resistance, paper type compatibility, and water resistance, which resulted in confirming the conventional problems.

C-5: A normal temperature solid ink composition was prepared using the natural wax materials shown in US Pat. No. 4,390,369 and US Pat. No. 4,484,948, and the above evaluations A1 to A6 were carried out. It was difficult to control the temperature for maintaining the liquid state above, and the state of the recorded matter after the transfer recording after that showed a remarkable variation, which greatly affected the background stain property and the paper type compatibility. In addition, in the scratch resistance evaluation of the recorded matter with a preferable print quality, only the same scratch resistance as the ordinary temperature solid ink composition of the conventional direct recording is shown,
It was "unsuitable".

[0052]

As described above, in the ink composition of the present invention, the ink is ejected from the ink jet recording head to the intermediate transfer medium at a temperature higher than room temperature, and further the ink is ejected from the intermediate transfer medium to the recording paper. An ink composition comprising a vehicle and a coloring material, which is used in a transfer recording method, wherein the vehicle is at least one selected from phthalic acid diesters having a melting point of 50 ° C. or higher and ortho or meta positions. The phthalic acid ester is characterized by using different kinds of phthalic acid esters, and the phthalic acid diesters coordinated to the ortho or meta position contain at least a cyclohexyl group or an aryl group.

From these characteristics, the ink composition of the present invention has a clear contour and shows good print quality regardless of the quality of the recording paper, and a recorded image with good abrasion resistance and water resistance of the recorded matter is obtained. It has the effect of being

Further, since the ink composition of the present invention uses a monomolecular solid organic material as a vehicle, it has a higher molecular weight with respect to thermal stability at high temperatures than natural wax and the like.
It has a remarkable effect that it has a great decrease in viscosity when melted, can add a relatively large amount of materials such as resin, and has an extremely stable thermal structure because it has an aromatic skeleton. There is.

Further, the ink composition of the present invention has a significantly better solubility with respect to a dye as a coloring material than that of a natural wax ink, but on the other hand, it is used in various ink tank members and head constituent materials. It has a special effect of hardly invading the plastic material.

Furthermore, since the ink composition of the present invention has the property of its supercooling property, the volume shrinkage of the recording head and its surroundings during solidification in the storage container filled with ink and heated is relaxed. Therefore, it has a special effect that the occurrence of mechanical damage of the recording head member due to the rapid volume shrinkage during solidification of the conventional room temperature solid ink composition based on natural wax can be almost ignored. is doing.

Claims (2)

[Claims] 1. A vehicle and a coloring material used in a recording system in which ink is ejected from an inkjet recording head onto an intermediate transfer medium at a temperature higher than room temperature, and then the ink is transferred from the intermediate transfer medium to a recording sheet. An ink composition comprising: an ink composition comprising, as a vehicle, at least one phthalic acid ester selected from phthalic acid diesters having a melting point of 50 ° C. or higher and coordinated to the ortho or meta position. Composition. 2. The ink composition according to claim 1, wherein the substituent of the phthalic acid diester coordinated to the ortho or meta position contains at least a cyclohexyl group or an aryl group.