JPH06136307A - Recording ink - Google Patents

Abstract

PURPOSE:To provide an ink having a sufficient rate of penetration into paper and good printing quality. CONSTITUTION:A recording ink having a contact angle with paper of 30-60 deg.. This angle is preferably represented in terms of a forward contact angle as measured when the paper is immersed in an ink at a speed of 100mm/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based ink for ink jet recording and can be used as a water-based ink for water-based writing instruments.

[0002]

2. Description of the Related Art It is known that among the properties of water-based inks for ink jet recording, penetrability into paper and the speed of drying have a significant influence on the quality of images drawn on paper. Penetration to paper is related to the contact angle of the ink on the paper. Conventionally, the contact angle of ink with paper is 14
A large ink of 0 ° or more has been proposed, but since the penetration time to the paper is extremely long, fixing is not sufficient immediately after printing because a special drying means is not used, and the image is rubbed, the offset, the trace of the paper feed roller. However, there is a problem in that the color overlapping portion and the color boundary portion are damaged during color printing.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink which has a sufficient rate of permeation into paper and has good printing quality.

In particular, in the case of color printing, it is an object of the present invention to obtain a print on a plain paper in which a color overlapping portion or a color boundary does not bleed, characters are sharp, and feathering is small.

[0005]

The structure of the present invention for solving the above problems has a contact angle with respect to paper of 30 ° or more, and 6
The recording ink is 0 ° or less.

Ink jet inks include dyes of 0.5 to
With a basic formulation of 5 wt% and 5 to 30 wt% of the wetting agent, the balance is pure water, the contact angle of the ink with the paper is 90 ° to 150 °.
Since it is large and the penetration is remarkably slow, the drying has been insufficient and various problems have conventionally occurred without a drying means such as an infrared heater or hot air drying.

Therefore, a method has been proposed in which various penetrants are added to carry out permeation drying, but an appropriate level changes depending on the type and amount of the penetrant, so a unified index has been desired.

In the present invention, the dynamic contact angle is measured from the change in tension when the paper is immersed in the ink liquid at a predetermined speed and then pulled up, and the appropriate value is determined regardless of the type and amount of the penetrant. It was found that the contact angle range was good.

The dynamic contact angle was measured using a dynamic contact angle measuring device DCA-20 manufactured by Orientec Co., Ltd.

2 cm of Ricoh type 6200 paper and Xerox 4024 paper are used as standard PPC plain paper.
The dynamic contact angle was obtained from the change in tension when the product was cut into a width, immersed at a speed of 100 mm / min for 10 mm, and immediately pulled up at the same speed. Since the ink penetration phenomenon is considered to be determined by the advancing contact angle (Q _A ), it was determined from the advancing tension (F _A ) during immersion as in equation (1).

CosQ _A = F _A / P · γ _L (1) P: perimeter of paper (4.02 cm) γ _L : surface tension of ink The present invention will be specifically described below with reference to Examples.

[0012]

EXAMPLES FIG. 1 shows a penetrant A (nonionic surfactant).
And the advancing contact angle changes for various inks with different amounts of penetrant B (anionic surfactant) added.

FIG. 2 shows the drying time when these inks were used for printing on a Ricoh PPC paper Type 6200 paper with a HP color printer Deskwriter C. If the drying time was 5 seconds or less, the above-mentioned defects due to insufficient drying did not occur.

FIG. 3 similarly shows the Deskwriter C
Represents the change in print quality when printed with. (Level 10
Is extremely good, 8 is good, 6 is an acceptable level, and 5 or less is an unacceptable level. This printing quality was evaluated by emphasizing the feathering of the character portion.

The composition of the above ink was as follows.

(Composition of penetrant A-based ink) (% by weight) Dye Direct Black 154 3.0 Diethylene glycol 7.5 Glycerin 2.5 Penetrant A (nonionic surfactant: heptaethylene glycol alkyl ether) 1 to 1.5 Ion-exchanged water balance (composition of penetrant B-based ink) (wt%) Dye Acid Blue 249 2.0 Diethylene glycol 7.5 Glycerin 2.5 Penetrant B (anionic surfactant: dioctyl sulphate) Sodium succinate) 0.1-1.5 Ion-exchanged water balance

[0017]

The effects of the present invention described above are summarized as follows.

(1) When ink having a contact angle of 60 degrees or less with paper is used, image rubbing due to insufficient drying property, set-off, traces of paper feed rollers, color overlapping portion during color printing,
Bleeding does not occur at the color boundary.

(2) When ink having a contact angle of 30 degrees or more with paper is used, it is possible to prevent print quality, particularly feathering of the character portion.

(3) As a constraint condition for this contact angle, the paper is specified as plain paper for PPC, and the contact angle to the paper is specified as the advancing contact angle, so that the proper composition of the recording ink is determined, and sufficient drying is achieved. In addition, printing with less feathering can be obtained.

(4) By specifying the contact angle measurement conditions, the appropriate contact angle required for the recording ink is specified, the appropriate composition is determined, and printing that is sufficiently dry and less feathering can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a penetrant content of ink and a contact angle.

FIG. 2 is a graph showing the relationship between the contact angle of ink and the drying time.

FIG. 3 is a graph showing a relationship between an ink contact angle and print quality (feathering).

Claims (3)

[Claims] 1. A recording ink having a contact angle with paper of 30 degrees or more and 60 degrees or less. 2. The recording ink according to claim 1, wherein the contact angle is an advancing contact angle on plain paper for PPC. 3. The recording ink according to claim 1, wherein the contact angle is a value measured by the advancing contact angle when the paper is immersed in the ink liquid at a speed of 100 mm / min.