JPH1053737A - Ink for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink for ink jet printing which shows a small change in viscosity being one physical property with varying ambient temperature by mixing a dye with a solvent and specifying the viscosity of the resulting mixture. SOLUTION: 0.1-20 dye which colors a substrate is dissolved in a solvent medium selected from water containing at least one solvent selected among diethylene glycol monobutyl ether acetate, tripropylene glycol monomethyl ether, n-decane or dimethul sulfoxide, 1,4-dioxane and propylene carbonate and 1-50wt.% at least one nonvolatile organic solvent selected among glycerol, glycols and polyglycols to obtain an ink for ink jet recording having a ratio of the viscosity at 5 deg.C to that at 40 deg.C of 1.0-3.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet recording ink used for an ink-jet printer which uses, for example, a terminal printer for a personal computer, a printer for a calculator, a printer for a register, and performs recording by ink droplets.

[0002]

2. Description of the Related Art In an ink jet recording system, ink droplets are ejected by various methods, and recording is performed by causing the ink droplets to adhere to a recording material. As one recording method, Japanese Patent Publication 2-51
As disclosed in Japanese Unexamined Patent Publication No. 734, pressure is applied to a chamber called a pressure chamber filled with ink by a pressure generating means to cause the ink to be ejected from the pressure chamber through a minute nozzle and installed at a position facing the nozzle. There is a method of recording by attaching the recording material to the recording material.

[0003] By the way, the values of viscosity, surface tension and specific gravity, which are physical properties of ink, change depending on the environmental temperature. In particular, the temperature dependence of the viscosity of the ink is large, and the viscosity value at 5 ° C. of the ink we have conventionally developed is about four times or more the viscosity value at 40 ° C.

[0004]

By the way, the pressure generating capability of the above-mentioned pressure generating means is generally constant even when the environmental temperature changes, or decreases as the temperature decreases. In addition, the viscosity of the ink becomes a viscous resistance and becomes a resistance of ink ejection. Therefore, as the viscosity increases, the amount and speed of the ejected ink decrease. As described above, the viscosity of the ink increases as the temperature decreases, and therefore, the ink ejection amount and the ejection speed decrease at low temperatures.

[0005] If the ink ejection amount is large, the recording density increases, and if the ink ejection amount is small, the recording density decreases. The greater the temperature dependence of the viscosity of the ink, the more the ejection characteristics of the recording head, such as the amount of ink ejected and the speed of ejection, are greatly affected by the environmental temperature.

[0006] Even if the viscosity of the ink changes due to the environmental temperature, in order to prevent a change or deterioration of the recording quality, a mechanism capable of discharging ink corresponding to the viscosity of the ink to a printer or a recording head, such as a heating means for the recording head, etc. There is a way to attach. However, when such a mechanism is attached,
It is not an appropriate method because of the increased cost and size of the printer.

Therefore, the present invention has been made to solve such a problem, and the present invention has been made to
By providing an ink with a small change in viscosity that greatly affects the ink ejection characteristics among the physical properties of the ink, the recording quality is stable against changes in environmental temperature,
An object is to provide an inexpensive and small-sized inkjet printer.

[0008]

The ink-jet recording ink of the present invention is an ink-jet recording ink comprising at least a dye for coloring a recording material and a solvent dissolving the dye. Viscosity and 40
The ratio of the viscosity at ° C is 1.0 or more and 3.5 or less.

According to the present invention, since the temperature dependency of the ink is small, even if the environmental temperature changes, a stable ejection characteristic can be maintained without providing a special mechanism in the printer or the recording head. This has the effect of keeping the recording quality constant. Further, there is no increase in cost and size of the printer using the ink jet recording method.

In this case, the ratio of the viscosity at 5 ° C. to the viscosity at 40 ° C. of the ink is desirably 1.0 or more and 2.5 or less, which can further reduce the temperature dependence of the ink. Quality can be kept constant.

Further, the solvent itself for dissolving the ink dye,
It is preferable to use one having a relatively small ratio of the viscosity at 5 ° C. to the viscosity at 40 ° C. For example, preferred solvents include diethylene glycol monobutyl ether acetate, tripropylene glycol monomethyl ether, and n-decane. When the solvent for dissolving the dye is water, a solvent other than water, which has a small ratio of the viscosity at 5 ° C. to the viscosity at 40 ° C., for example, dimethyl sulfoxide, 1,4-dioxane, propylene carbonate, etc. is added. It is desirable that the temperature dependency of the ink can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described using one embodiment of the present invention.

The present invention relates to an ink jet recording ink comprising a dye for coloring a recording material and a solvent for dissolving the dye, and a component adjusting agent such as a surfactant for adjusting the surface tension of the ink. Preservatives, pH adjusters and the like can be added.

The amount of the dye to be used as a coloring agent in the ink of the present invention is determined by the required recording density and color value.
20 wt%, desirably 0.1 to 5 wt% is added. Dyes can be added alone or in combination.

Dyes used for coloring include water-soluble dyes such as C.I. I. DirectBlack (hereinafter D
Bk) -38, DBk-71, DBk-74, DBk-
75, DBk-90, DBk-112, DBk-11
7, DBk-154, DBk-169, Acid Bl
ack (hereinafter, ABk) -2, ABk-24, ABk-3
1, black dyes such as ABk-52. Color dyes include C.I. I. Direct Yellow (hereinafter D
Y) -27, DY-28, DY-33, DY-39, D
Y-58, DY-86, DY-88, DY-98, DY
-132, DY-142, DY-144, Acid Y
yellow (hereinafter AY) -11, AY-17, AY-2
3, AY-25, Diret Red (hereinafter DR)-
1, DR-2, DR-4, DR-9, DR-11, DR
-13, DR-17, DR-20, DR-227, Ac
id Red (AR) -1, AR-14, AR-3
2, AR-51, AR-52, AR-87, AR-9
2, AR-94, AR-249, AR-289, Dir
ect Blue (hereinafter DB) -1, DB-8, DB-
71, DB-76, DB-78, DB-80, DB-8
6, DB-90, DB-199, Acid Blue
(Hereinafter AB) -9, AB-22, AB-93, AB-1
There are 12 etc. Oily dyes include black dyes such as C.I.
I. SolventBlack (hereinafter SBk) -3, S
Bk-7, SBk-22, SBk-45, SBk-50
Etc. Color dyes include C.I. I. Solve
nt Yellow (hereinafter SY) -19, SY-61,
SY-82, SY-93, Solvent Red (hereinafter SR) -8, SR-18, SR-49, SR-81,
Solvent Blue (hereinafter SB) -2, SB-
5, SB-36, SB-70, etc., but are not limited to these, and can be selected as needed. As the solvent component in the ink of the present invention, a solvent having a small ratio of the viscosity at 5 ° C. to the viscosity at 40 ° C. (hereinafter referred to as a temperature viscosity coefficient α _5/40 for simplicity) is used alone or as a mixture of two or more. can do. Examples of the solvent include organic solvents such as diethylene glycol monobutyl ether acetate, tripropylene glycol monomethyl ether, and n-decane.

A single solvent or a plurality of solvents having a small temperature viscosity coefficient α _5/40 can be added to an ink using water as a solvent. Examples of the solvent include dimethyl sulfoxide, 1,4-dioxane, propylene carbonate and the like. Is raised.

In addition, an organic solvent can be added to impart moisturizing properties to the ink, and examples of the organic solvent include non-volatile organic solvents such as glycerin, glycols and polyglycols. The amount of the organic solvent to be added can be in the range of 1 to 50% by weight based on the total weight of the ink.

The combination of the components in the ink is determined depending on whether the emphasis is placed on the ink or the recording quality item.
In the ink of the present invention, the temperature viscosity coefficient α _5/40 is 1.0
As described above, the temperature viscosity coefficient α is set to 3.5 or less.
_It is configured such that _5/40 is not less than 1.0 and not more than 2.5. As an example, inks were prepared from the compositions shown in Table 1 below, and the viscosity values at 5 ° C., 25 ° C., and 40 ° C.,
Discharge characteristics and recording quality of the determination result of the ink at each temperature, and the temperature viscosity coefficient alpha _5/40 of ink calculated from the values of viscosity of the 5 ° C. and 40 ° C., the value of the temperature viscosity coefficient alpha _5/40 solvent It is shown in Table 2.

[0019]

[Table 1]

[0020]

[Table 2]

FIG. 1 is a graph showing a comparison between the temperature dependence of the viscosity of the ink of the present embodiment and the ink developed by the related art. A line a indicates the ink of the present embodiment, and a line b indicates the conventional ink as a comparative example. Comparative Example b
Is about 4 times the viscosity value η _{5b at} 5 ° C. with respect to the viscosity value η _{40b at} 40 ° C., whereas the ink of the present embodiment has a viscosity value η _{5a at} 5 ° C. = 4.9 mPa · s, 40 The viscosity at ℃ η _40a = 1.7 mPa · s, and η _5a was 2.9 times η _40a , indicating that the temperature characteristics of the ink viscosity were improved.

The methods for determining the ejection characteristics, recording density and recording stability in Table 2 are as follows.

(1) Discharge characteristics: 5 ° C., 25 ° C. and 40 ° C.
In the environment described above, the ink is ejected from the nozzle having an inner diameter of 60 μm for a unit time, and the ejected ink weight per ejection obtained from “total weight of ejected ink / number of times of ink ejection” is measured. 5 ° C and 4 for weight
The change rate of the ejected ink weight at 0 ° C. is determined, and the determination is made based on the following criteria.

○ −Change rate of ejected ink weight is within ± 5% Δ−Change rate of ejected ink weight is within ± 10% × −Change rate of ejected ink weight is larger than ± 10% (2) Recording density: ( The ink was ejected under the same conditions and ejection method as in 1), the optical density of the recorded portion of what was recorded on commercial copy paper was measured, and the optical densities at 5 ° C and 40 ° C were compared with the optical densities at 25 ° C. Judge based on the following criteria.

○ -Change rate of optical density is within ± 5% △ -Change rate of optical density is within ± 10% × -Change rate of optical density is more than ± 10% (3) Recording stability: (2) The ink is ejected and recorded in the same manner as that described above for 100 copy sheets, and the determination is made based on the following criteria.

○ _—No abnormality × _—No ejection or occurrence of recording disturbance As described above, when the temperature viscosity coefficient α _5/40 of the ink is _set to 1.0 or more and 3.5 or less, the weight of the ejected ink Is hardly changed, and the quality of recording is not degraded. Therefore, good recording quality is maintained even when the environmental temperature at which the printer operates is changed. The solvent used, dimethyl sulfoxide, has a temperature viscosity coefficient α _5/40 of 2.0 and is a solvent having a small temperature dependence of viscosity.

[0027]

EXAMPLES Examples 1 to 5 showing the compositions are shown below.
This example will be described in detail using the inks of (Tables 3 to 7) and Comparative Examples 1 and 2 (Tables 8 and 9).

The components described for the inks of Examples 1 to 5 and Comparative Examples 1 and 2 were weighed and added so that the total amount became 100 g, and the mixture was heated and stirred at about 70 ° C. After the temperature of the ink returned to room temperature, it was filtered through a membrane filter having a pore size of 0.8 μm to prepare each ink.

[Example 1]

[0030]

[Table 3]

Embodiment 2

[0032]

[Table 4]

[0033]

Embedded image

[Embodiment 3]

[0035]

[Table 5]

Embodiment 4

[0037]

[Table 6]

Embodiment 5

[0039]

[Table 7]

Comparative Example 1

[0041]

[Table 8]

[Comparative Example 2]

[0043]

[Table 9]

5 ° C., 25 ° C. and 40 ° C. for each of the above inks
, The viscosity of the ink at each temperature and the determination results of the recording quality, the temperature viscosity coefficient α _{5/40 of} the ink calculated from the viscosity values at 5 ° C. and 40 ° C., and the temperature viscosity coefficient α of the solvent Table 10 shows the values of _5/40 . Table 11 also shows inks of comparative examples. The ejection characteristics, recording density, and recording stability in each table were determined in the same manner as described above.

[0045]

[Table 10]

[0046]

[Table 11]

The ink of Example 1 was an ink to which 1,4-dioxane was added as a solvent, and had a temperature viscosity coefficient α _5/40 of 2.7.

The ink of Example 2 is an ink to which propylene carbonate is added as a solvent, and has a temperature viscosity coefficient α
_5/40 is 2.6.

The ink of Example 3 was an ink to which triethylene glycol was added as a solvent, and had a temperature viscosity coefficient α _5/40 of 3.1.

The ink of Example 4 is an ink containing glycerin as a solvent, and has a temperature viscosity coefficient α _5/40 of 2.9.

The ink of Example 5 was an ink to which n-decane was added as a solvent, and had a temperature viscosity coefficient α _5/40 of 2.4. Thus, the temperature viscosity coefficient α of the ink
_{If 5/40} is 1.0 or more and 3.5 or less, the change in the weight of the ejected ink becomes sufficiently small, and the recording quality is not degraded.

On the other hand, the ink of Comparative Example 1 is an ink to which propylene glycol is added as a solvent, and has a temperature viscosity coefficient α _5/40 of 3.7.

The ink of Comparative Example 2 was an ink in which ethyl lactate was added as a solvent, and had a temperature viscosity coefficient α
_5/40 is 3.8.

In each of the comparative examples in which the temperature viscosity coefficient α _5/40 is 3.5 or more, the change in the weight of the ejected ink is large, and the printing quality of recording is deteriorated. Thus, the temperature viscosity coefficient α _5/40 of the solvent used in the comparative example is larger than the temperature viscosity coefficient α _5/40 of the example, which causes an increase in the temperature viscosity coefficient α of the ink. I understand.

[0055]

As described above, according to the present invention, even when the environmental temperature changes, the change in the viscosity of the physical characteristics of the ink is small, and the ink discharge characteristics can be stabilized. An inkjet printer that maintains stable recording quality regardless of a temperature change can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the temperature dependence of the viscosity of ink.

Claims (6)

[Claims] 1. An ink jet recording ink comprising at least a dye for coloring a recording material and a solvent for dissolving the dye, wherein the viscosity of the ink at 5 ° C.
An ink jet recording ink having a viscosity ratio at 1.0 ° C. of 1.0 or more and 3.5 or less. 2. The ink for ink jet recording according to claim 1, wherein the ratio of the viscosity at 5 ° C. to the viscosity at 40 ° C. of the ink is 1.0 or more and 2.5 or less. ink. 3. The ink jet recording ink according to claim 1, wherein the solvent for dissolving the dye contains at least one of diethylene glycol monobutyl ether acetate, tripropylene glycol monomethyl ether and n-decane. Ink for inkjet recording. 4. The ink for ink jet recording according to claim 1, wherein the solvent dissolving the dye is water, and dimethyl sulfoxide is used as a solvent other than water.
An ink jet recording ink comprising at least one of 1,4-dioxane and propylene carbonate. 5. The ink jet recording ink according to claim 1, further comprising a non-volatile organic solvent in an amount of 1 to 50% by weight based on the total weight of the ink. Recording ink. 6. The ink for ink jet recording according to claim 5, wherein said nonvolatile organic solvent contains at least one of glycerin, glycols and polyglycol.