JPH03153773A - Ink composition - Google Patents

Abstract

PURPOSE:To prolong the life of hue of an ink compsn. which is solid at room temp. and comprising a vehicle and a colorant by using the colorant comprising an oil-sol. black dye and an oil-sol. yellow dye in a specified ratio. CONSTITUTION:An ink compsn. which is solid at room temp. comprises a vehicle and a colorant, and is jetted through an ink jet apparatus at room temp. or higher when used, contains a colorant comprising an oil-sol. black dye in an amt. of 1.0-10.0wt.% based on the compsn. and an oil-sol. yellow dye in an amt. of 5.0-25.0wt.% based on the black dye. The vehicle comprises a first component which alone does not dissolve the colorant and a second component which has an m.p. at least 10 deg.C higher than that of the first component, dissolves the colorant, has a compatibility with the first component above the m.p., and forms a homogeneous phase contg. the colorant and the first component, the wt. ratio of the first to second component being (10:1)-(1:1).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ink composition used in an inkjet recording device. More specifically, the present invention relates to an ink composition that is solid at room temperature and is used for inkjet recording at a temperature higher than room temperature.

[Prior Art] Inkjet recording is excellent in quietness during recording and high-speed printing performance. BACKGROUND ART Liquid ink compositions based on water or the like have conventionally been used as ink compositions for inkjet recording. However, since ink is recorded by soaking into the paper, it has the disadvantage that when recording on paper where ink easily soaks, bleeding occurs, and the periphery of the recorded dots becomes unclear and the print quality deteriorates. .

For this reason, as an ink composition that provides good print quality regardless of paper quality, U.S. Patent No. 4390369.44849
Publication No. 48.4659383, JP-A-58-10827
Using a hot-melt ink composition based on a wax or the like that is solid at room temperature as shown in Publication No. 1, the solid ink is melted by heating at high temperatures and is ejected, then cooled and solidified on recording paper to form recording dots. Hot-melt inkjet recording methods have been proposed.

[Problems to be Solved by the Invention] However, although conventional hot melt ink compositions have good compatibility with recording paper and drying properties after printing, they cannot be heated and melted in the ink reservoir (ink tank). Since the ink is supplied to the inkjet head in a high-temperature molten state, the ink may change to brown due to thermal deterioration of the dye, accelerated fading, or coloring due to the heat of the vehicle, resulting in a difference between the print color when new ink is added and the color that has passed over a long period of time. This poses a problem in that the printed color differs from that printed later.

This problem becomes a serious problem when the residence time of the ink in the molten state increases.

In order to avoid this problem, a method has been adopted in which when the printer standby time exceeds a certain time, the temperature of the ink reservoir (ink tank) and head is lowered to near the melting point of the ink, but in this case, printing becomes possible. I have another ill IM that will take some time to develop.

The present invention is intended to solve these problems, and its purpose is to provide an ink composition that has a long life of discoloration due to heat.

[Means for Solving the Problems] The ink composition of the present invention has the following properties:
In an ink composition that is solid at room temperature and is composed of a vehicle and a coloring material and is ejected from an inkjet recording device, the ink composition contains an oil-soluble black dye and an oil-soluble yellow dye as the coloring materials, and the ink composition contains an oil-soluble black dye and an oil-soluble yellow dye as the coloring materials. The weight ratio is 5.0 to 25.0 weight percent with respect to the oil-soluble black dye,
The oil-soluble black dye is added to the ink composition in an amount of 1.0 to 10.
It is characterized by containing 0 weight percent.

In addition, in an ink composition that is solid at room temperature in which a vehicle and a coloring material are ejected from an inkjet recording device at a temperature higher than room temperature, the ink composition has the following properties: (b) has a melting point 10°C or more higher than the first component, dissolves the colorant, is compatible with the first component above the melting point, and forms a uniform phase containing the colorant and the first component; (c) the weight ratio of the first component and the second component is between 10=1 and 1:1; (d) the coloring material is an oil-soluble black dye and an oil-soluble yellow dye, the weight ratio of the oil-soluble yellow dye to the oil-soluble black dye is 5.0 to 25.0 weight percent, and the oil-soluble black dye is 1.0 weight percent to the ink composition. It is characterized by containing ~10.0% by weight.

The ratio of the oil-soluble yellow dye to the oil-soluble black dye may be any value from 1.0 to 25.0 weight percent as long as the hue of the ink composition is true black, depending on the hue of the black dye. From the perspective of improving discoloration life, 5.0 to 15.0
Weight percent is more preferred.

According to experiments conducted by the present inventors, with conventional hot melt ink, in the initial stage after ink is added to the ink reservoir (ink tank), the vehicle changes color to brown due to high temperature before the black dye changes color. It was discovered that the color of the composition was changed to brown, and then, when the progress of the discoloration of the vehicle slowed down, the discoloration of the black dye became significant and the discoloration was accelerated. Therefore,
When a yellow dye was added between 5.0 and 25.0 weight percent, the ink hue at the time of ink preparation became closer to true black than before, and the yellow dye and the vehicle component also faded. This was contradictory, and the time it remained black became longer.

[Function] By containing the oil-soluble yellow dye, the ink composition of the present invention has high-temperature heat resistance of the yellow dye at the same level as that of the vehicle. Therefore, the fading of the yellow dye and the fading of the vehicle conflict with each other, resulting in a change in the hue of the ink. It extends the lifespan of change.

[Example] Before giving examples here, an outline of the "a'b° color system used to evaluate hue will be described.

Color measurement applies photoelectric principles to measure the intensity of light reflected or transmitted from an object, and then displays the color as three numerical values calculated using a prescribed method. The L″a″b° color system is one of them, and the value of Lo is expressed as the lightness index, ao, b
The value of o is called the chromaticness index, and these three numbers L''a'b' represent the position of the spatial coordinate point as shown in Figure 4.For example, CL', ao, bo) = ( 73,
The color indicated by 5, 17, 3, 31° 4) is bright orange,
The color indicated by (35, 3, -25, 6, 25, 9) is dark green.

FIG. 5 shows the correspondence between ao, bo, hue, and saturation. In the figure, YR is orange, R is red, RP is reddish-purple, P is purple, PB
means blue-purple, B means blue, BG means blue-green, G means green, and YG means yellow-green. As seen from Figures 4 and 5, L
The closer the angle is to 0, a=0, and b=0, the more true black it is.

As a result of various experiments, the process of discoloration of ink compositions has been
Proceed as shown in the diagram. As can be seen from this figure, as time passes, ao changes little, but bo gradually increases. In other words, it can be seen that the color changes to yellow or orange.

In this example, evaluation was performed focusing on changes in the bo value. According to experiments conducted by the inventors, it was around when the b° value exceeded 5 that the discoloration became visible to the naked eye. Evaluation was made in terms of life time.

In the evaluation method described below, the L° value was not evaluated in this example because it depends on the thickness of the ink composition.

The present invention will be explained below with reference to Examples, but is not limited thereto.

The ink composition according to claim 1 of the present invention can be prepared by a known method, by mixing a vehicle component and a colorant,
Above the melting point of the vehicle component, preferably 5 to 15% above the melting point
Heating bath at a temperature as high as °C [! ! ! Thereafter, a backward-dissolving composition is heated at that temperature, and if necessary, it is filtered through a filter in a high-temperature molten state, and then cooled.

The ink composition according to claim 2 can also be prepared by a known method, by mixing the first component, the second component, and the coloring material, and preparing the ink composition at a temperature higher than the melting point of the second component, preferably 5 to 15% higher than the melting point. '
After heating and melting at a temperature as high as C<, a backward-melting composition is prepared by heating at that temperature, and if necessary, the composition is filtered through a filter under the high temperature melting state, and then cooled.

The physical properties of the ink include the temperature during printing operation (80 to 200
The viscosity at 1 °C) is determined by
A pressure of 5.0 mPa·S or less is required, and a range of 2.0 to 10°0 mPa·S is more preferable in order to realize even higher responsiveness. Since the surface tension affects meniscus formation near the nozzle, it is preferably 50 mN/m or less, and more preferably 35 mN/m or less in order to promote high permeability of the print I& on the recording paper.

The vehicle component according to claim 1 is selected from ketones, amides, waxes, fatty acids and the like. A plurality of these can be used in combination as long as there is no problem with the physical properties of the ink.

As the ketones, waxy dialkyl ketones are preferable, and specifically, stearon (Kaohwax T-1) is preferable.
: Manufactured by Kao Corporation), Lauron, etc. are selected. Moreover, these can also be used in combination of two or more types depending on the case.

Further, as the amides, saturated or unsaturated fatty acid amides are preferable, and specifically, erucic acid amide, lauric acid amide, stearic acid amide, palmitic acid amide, behenic acid amide, brassic acid amide, amide HT
-P, C (manufactured by Lion Corporation) fatty acid amide -3, T
, P (manufactured by Kao Corporation), etc. are selected. Moreover, these can also be used in combination of two or more types depending on the case.

Further, as the wax, for example, paraffin or paraffin wax selected from petroleum waxes, carnauba wax, candelilla wax, montan wax, etc. are selected.

Specifically, (paraffin) n-paraffin and isoparaffin (paraffin wax) having 23 to 32 carbon atoms No. 140. 150. 155 HNP-3, 9, 10, 11, 12, 16SP-014
5,3040,3035 (Microcrystalline wax, others) Hi-Mi
c-2045, 1045 Curt wax - 3735, 3640 (all manufactured by Nippon Seiro Co., Ltd.) (Montan wax and its derivatives) Hoechst wax - 8, SW, E, LP (manufactured by Hoechst Co., Ltd.), etc. are selected. .

The fatty acid preferably has 15 or more carbon atoms, such as valmitic acid, stearic acid, behenic acid, sebacic acid, and oleic acid.

Moreover, these can also be used in combination of two or more types depending on the case.

Some of the vehicle components described in claim 2 overlap with the vehicle components described above, but as the first component,
It is necessary that the coloring material is not dissolved and the melting point is lower than that of the second component. For example, a solid wax selected from paraffin, paraffin wax, microcrystalline wax, or a combination thereof such as petroleum wax having a melting point of 70° C. or less is preferable. In some cases, two or more types can be used in combination.

Specifically, (paraffin) n-paraffin and isoparaffin having 23 to 32 carbon atoms.

(Paraffin wax) No. 115. 120. 125. l 30.
135゜140.150,155 HNP-3,9,10,11,16 SP-0145,1035,3040゜3035.01
10 (Microcrystalline wax, others) Hi-Mi
c-2045, 1045 CARTOWAX-3025, 3735°3640 (all manufactured by Nippon Seiro Co., Ltd.), etc.

The properties required for the second component are to dissolve the coloring material and to
fatty acid amide,
Aromatic amides, aromatic sulfonamides, etc. satisfy these conditions.

Specifically, erucic acid amide, lauric acid amide, palmic acid amide, stearic acid amide, palmitic acid amide, behenic acid amide, brassic acid amide, acetamide, benzamide, propionamide, oleic acid amide, ricinoleic acid amide -〇 , HT-P, C (manufactured by Lion Corporation) fatty acid amide-S, T, P, C,0 (Kao (
Co., Ltd.) op-toluenesulfonamide, etc.

The coloring material is preferably one that has compatibility with the vehicle, water resistance, and does not sublimate due to heat, bleed, or migrate to printing paper.

Specifically, (Black Dye 14) C, 1, Solvent Black 3. 22. 23 Sumiblast Frack-○ (BKG), 3BA (Sumip
last Black G (BKG), 3BA) (
Sumisol Black ARsol (Sumisol Black ARsol) Sumisol Chemical Industry Co., Ltd.
(Same as above) AiShine Ba5e EX (Orient Chemical Co., Ltd.) (Aizen)
5pilon Black RLH) (Hodogaya Chemical Industry Co., Ltd.)
izen 5pilOn Black GMH5pec
ial) (same as above) (yellow dye) C, 1, Solvent Yellow 19. 21. 61゜0 Manufacturer) Manufacturer) Manufactured by Aiz
en 5pilon Yellow GRH5p
(ecial) Isisyspiron Yellow C-GW) I
(Aizen 5pilon Yellow C
-GNHnew) (manufactured by Hodogaya Chemical Industry Co., Ltd.) SUMI BLAST IE o-GG, FC (Sun+1plast Yellow GG, F
C) (manufactured by Sumima Kagaku Kogyo Co., Ltd.) In addition, the ink composition of the present invention may optionally contain various surfactants as antioxidants and surface tension modifiers in order to prevent fundamental thermal oxidative deterioration of the vehicle. It can also be added depending on the situation.

In addition to these, inorganic compounds such as silicon compounds such as silica may also be added to the ink composition of the present invention, if necessary.

(Example) Ink compositions having the compositions shown in Table 1 from 1nkl to 1nk6 were prepared, and 10g of each was placed in a sample bottle and
It was placed in a constant temperature bath at ℃. Thereafter, sampling was carried out at regular intervals, and the samples were dropped onto a heated slide glass, covered with a cover glass, and cooled to prepare a slide.

The hue of this prepared ink composition was measured using a color difference meter CR-110 manufactured by Minolta Camera Co., Ltd., and changes in the hue b value of the ink composition depending on the time it was placed in a constant temperature bath were examined. This situation is shown in FIG.

Further, Table 2 shows the ink discoloration lifespan according to the above.

(Comparative Example) Ink compositions having the compositions shown in Table 1 from 1nk7 to 1nklO were prepared in the same manner as in the examples, and 10 g of each was placed in a sample bottle and placed in a constant temperature bath at 150°C. Thereafter, sampling was carried out at regular intervals, and the samples were dropped onto a heated slide glass, placed on a cover glass, and cooled to prepare a slide. The hue of this prepared ink composition was measured using a color difference meter CR-110 manufactured by Minolta Camera Co., Ltd., and the change in the hue b value of the ink composition depending on the time it was placed in a constant temperature bath was examined. This situation is shown in FIG.

Further, Table 2 shows the ink discoloration lifespan according to the above.

As is clear from the results shown in Table 2 and FIGS. 1 and 2, it is obvious that the ink composition of the present invention has a small change in b° value over time and a long ink discoloration life.

[Effects of the Invention] As described above, in an ink composition that is solid at room temperature and is composed of a vehicle and a coloring material and is ejected from an inkjet recording device at a temperature higher than room temperature, the ink composition acts as a coloring material. The ink contains an oil-soluble black dye and an oil-soluble yellow dye, the weight ratio of the oil-soluble yellow dye to the oil-soluble black dye is 5.0 to 25.0% by weight, and the ink contains an oil-soluble black dye. By containing 1.0 to 10.0% by weight based on the composition, or in an ink composition that is solid at room temperature and consists of a vehicle and a coloring material that are ejected from an inkjet recording device at a temperature higher than room temperature. The ink composition consists of (a) a first component in which the colorant is insoluble when used alone, and (b) a melting point 10°C or more higher than the first component, which dissolves the colorant and is compatible with the first component above the melting point. (c) the weight ratio of the first component and the second component is 10:1;
(d) Contains an oil-soluble black dye and an oil-soluble yellow dye as coloring materials, and the weight ratio of the oil-soluble yellow dye to the oil-soluble black dye is 5.0 to 1. By including the oil-soluble black dye in an amount of 1.0 to 10.0 weight percent based on the ink composition, the ink discoloration life is significantly extended.

This also has the effect that the lifespan of prints printed with the ink composition is longer than the lifespan of prints made with conventional hot-melt inkjet recording devices.

[Brief explanation of the drawing]

FIG. 1 shows one of the ink compositions (inks 1 to 6) of the present invention.
The process of discoloration at 50°C is expressed as b in the L″a′b° color system.
Diagram shown by ° values. FIG. 2 shows a conventional hot-melt ink composition (ink
7 to 10) at 150°C is L'a'b
゛A diagram shown using the b° value of the color system. FIG. 3 is a diagram showing a typical discoloration process of a hot melt ink composition using ao and b° values of the L'a'b° color system. Figure 4 is a diagram showing the color space and color coordinates in the L'a″b° color system. Figure 5 is a diagram showing the correspondence between ao and b° values, hue, and saturation.

Claims (2)

[Claims] (1) In an ink composition that is solid at room temperature and consists of a vehicle and a coloring material that is ejected from an inkjet recording device at a temperature higher than room temperature, the ink composition contains an oil-soluble black dye and an oil-soluble yellow coloring material as the coloring materials. dye, and the weight ratio of the oil-soluble yellow dye to the oil-soluble black dye is from 5.0 to
25.0 weight percent, and the ink composition contains 1.0 to 10.0 weight percent of the oil-soluble black dye based on the ink composition. (2) In an ink composition that is solid at room temperature and is composed of a vehicle and a coloring material and is ejected from an inkjet recording device at a temperature higher than room temperature, the ink composition has the following properties: (b) a homogeneous phase that has a melting point 10°C or more higher than the first component, dissolves the colorant, is compatible with the first component above the melting point, and also contains the colorant and the first component. (c) the weight ratio of the first component and the second component is from 10:1 to 1:
(d) contains an oil-soluble black dye and an oil-soluble yellow dye as coloring materials, and the weight ratio of the oil-soluble yellow dye to the oil-soluble black dye is 5.0 to 25.0. An ink composition comprising 1.0 to 10.0 weight percent of the oil-soluble black dye based on the weight of the ink composition.