JPH01188394A - Image fixing method - Google Patents

Abstract

PURPOSE:To strengthen the adhesion of an ink to a recording material and obtain a favorable fixed image, by adding a pH-varying substance to an ink image formed on the recording material. CONSTITUTION:A pH-varying substance is added to an ink image, whereby the pH of the ink is varied, the viscosity of the ink is enhanced, and the ink is solidified, resulting in a higher adhesion of the ink to a recording material. The ink to be used is one the viscosity of which is increased by a variation in the pH thereof, particularly, one the fixation of which is strengthened by the addition of an alkaline pH-varying substance and the viscosity of which is increased with increase in pH thereof. This method is particularly suitable for an ink which has a property that the ink increases in viscosity in the vicinity of an anode when an electric current is passed, in addition to the above- mentioned properties. For example, an ink has a gel state in a wide sense in which a liquid dispersion is maintained by a crosslinked substance, and an ink contains a high molecular weight electrolyte. Thus, the fixability of an ink image is augmented by the addition of the pH-varying active substance, and an image with higher quality and excellent durability can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a method for more strongly fixing an ink image on a recording medium.

[Prior Art] Conventionally, methods for strengthening the adhesion of ink to a recording medium include thermal fixing such as heating using a heating roller, heating using infrared irradiation, pressure fixing using a pressure roller, and the like.

[Problems to be Solved by the Invention] However, among the above conventional examples, in the case of thermal fixing, a large amount of electrical energy is required for heating the rollers, lighting the infrared lamp, etc. Further, in the case of pressure fixing, there are disadvantages in that a device such as a pressure roll becomes large and the image has a peculiar gloss.

An object of the present invention is to provide an image fixing method that can firmly adhere an ink image to a recording medium without using a large amount of energy or a large-sized device.

[Means to solve the problem]

As a result of intensive research in line with this objective, the inventors of the present invention found that the adhesion of ink to a recording medium can be strengthened by changing the pH value, especially by adding an alkaline substance, and in particular, the adhesiveness can be changed by energization. Ink that sticks to the recording medium (i.e., it is sandwiched between an anode and a cathode, and is given adhesiveness on the anode side only between the electrodes that are energized, forming an image depending on the energized area) The present inventors have discovered that by adding an alkaline substance to an image using an ink that can be produced, the adhesion of the ink to a recording medium can be strengthened and a good fixed image can be obtained, leading to the present invention.

That is, the present invention adds a pH value changing substance to an ink image to change the pH value of the ink, increase the viscosity of the ink, and solidify the ink, thereby increasing the adhesion of the ink to the recording medium. This is a fixing method.

The method of the present invention is applicable to images with a wide variety of inks.

As is clear from the effect of the pH value changing agent, the ink to which this method is applied can be
Any ink whose viscosity increases, and among such inks, the fixing is enhanced by the addition of an alkaline pH value changing substance. This will improve the results. Among these, it is suitable for inks that also have the property of increasing viscosity near the anode side when energized. Specifically, it is an ink having a broadly defined gel state in which a liquid dispersion medium is held by a crosslinked structure substance, or an ink containing a polymer electrolyte.

- The liquid dispersion medium of the ink having a gel state in a broad sense, to which the present invention is preferably applied, is one in which various inorganic or organic solvents that are liquid at room temperature are used, but in particular volatile ones. A relatively low solvent (e.g., equivalent to or lower than water) is used.

The present invention is particularly preferably applicable to those in which a hydrophilic dispersion medium such as water or a water-containing dispersion medium is used as the liquid dispersion medium, and a hydrophilic (natural or synthetic) polymer or the like is used as the crosslinked structure substance.

Examples of such hydrophilic polymers include guar gum,
Plant-based polymers such as locust bean gum, gum arabic, taragant, carrageenan, pectin, mannan, and starch; Microbial-based polymers such as xanthan gum, dextrin, succinucan, and curdlan; Animal-based polymers such as gelatin, casein, albumin, and collagen. Polymers: Cellulose polymers such as methyl cellulose, ethyl cellulose, and hydroxyethyl cellulose, or starch polymers such as soluble starch, carboxymethyl starch, and methyl starch, alginate polymers such as propylene glycol alginate, and alginate, and their geosaccharides. Semi-synthetic polymers such as derivatives of polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl methyl ether, carboxyvinyl polymer, sodium polyacrylate, etc.Other vinyl polymers such as polyethylene glycol, ethylene oxide, propylene oxide block copolymers, etc. Synthetic polymers may be used alone or in combination of two or more as necessary.

Usually 0.2 to 50 parts per 100 parts of liquid dispersion medium,
In particular, the present invention is particularly suitably applicable to ink images containing 0.5 to 30 parts of hydrophilic polymer.

Further, the ink containing a polymer electrolyte to which the present invention can be preferably applied is one containing a polymer electrolyte which is a polymer having a dissociative group in the polymer chain.

Polyelectrolytes are synthesized by introducing dissociative groups into natural products such as alginic acid and gelatin, and ordinary polymers such as polystyrene sulfonic acid and polyacrylic acid, which dissociate into polymer ions when dissolved in water. It is cited as a representative example.

An ink whose fixing is enhanced by the addition of an acidic pH value changing substance has an improved viscosity due to a decrease in pH value, such as an ink made of gelatin and water.

The pH value changing substance used in the present invention may be organic or inorganic, but among these substances, alkaline substances include:
Those with a pH value of 7.1 or higher in an aqueous solution, preferably pH
The pH value is 7.5 or more, more preferably the pH value is 8 or more. Specifically, sodium hydroxide, potassium hydroxide, ammonia, ammonium hydroxide, calcium hydroxide, barium hydroxide, copper hydroxide, magnesium hydroxide, ferric hydroxide, aluminum hydroxide, or methylamine, ethylamine. , octylamine, cetylamine, dibutylamine, dimethylamine, trimethylamine, allylamine, dibrobylamine, aniline, methylaniline, triethanolamine, and other electron pair donors (Lewis bases).

On the other hand, among the pH value changing substances, p
The H value is 6.9 or less, preferably the pH value is 6.5 or less, and more preferably the pH value is 6 or less.

Specifically, electron pair acceptors (Lewis acids) such as hydrochloric acid, nitric acid, acetic acid, hydrocyanic acid, chloric acid, hypozinc acid, carbolic acid, sulfuric acid, sulfurous acid, carbonic acid, oxalic acid, hydrogen sulfide, phosphoric acid, and boric acid etc.

Methods for adding these pH value changing substances to a recording medium on which an ink image has been formed include spraying vaporized gas, spray coating by mixing with chlorofluorocarbon gas, etc.
Roll application in liquid state by roll coating, etc.
Any method that brings the pH-changing substance into contact with the ink image may be used, such as impregnation coating in which felt or the like is impregnated and applied.

The amount of the pH value changing substance to be added is not particularly limited and may be selected as appropriate.

The reason why ink fixation is enhanced by the present invention is presumed to be as follows.For example, in the case of an ink containing a crosslinked product of polyvinyl alcohol and borate ions, the crosslinking between the OH group of polyvinyl alcohol and borate ions It is thought that the increase in the alkaline side causes the increase in the viscosity of the ink, thereby strengthening its adhesion to the recording medium.

In addition, in the case of ink containing a polymer electrolyte, taking amino acids as an example, a change in pH value causes some of the -NHz' ions of the amino acids to become -NH2, and changes in the dissociation state of the amino acids cause the adhesive property to change. It is thought that there will be a difference.

〔Example] Example 1 First, an example of making the ink used in this example will be shown.

Component A was uniformly dissolved while being heated to 80 to 90° C., and then component B was added and stirred to obtain gel-like ink 2.

Using this ink 2, image output and ink fixation enhancement are performed in the first step.
This was done as shown in the figure. That is, stainless steel 20mm
An ink carrying roll 1 consisting of a cylindrical roll of φ (surface roughness Is) and an intermediate transfer roll 4 consisting of an iron cylindrical roll (20 mm φ) whose surface is plated with hard chrome are opposed to each other with a gap of 2 mm at the ink transfer position. The first consisting of
Using the image recording apparatus shown in the figure, the ink 2 of the present invention was put into the ink container 3 of this apparatus.

The ink carrying roll 1 is rotated at a rotation speed of 20 rpm in the direction of the arrow to form a layer of fluid ink on the roll 1, and while in contact with this layer, the intermediate transfer roll 4 is rotated in the direction of the arrow B at about 18 rpm. It was rotated at a rotation speed of . The thickness of the ink 2 was controlled by a regulating means 10. At this time, with a thickness of 1 mm,
If electrical energy is not supplied to the layer of ink 2 from the recording electrode 5 made of copper (gold plating) whose width is the same as the length of the transfer roll 4 (in the direction parallel to the rotation axis), the intermediate transfer roll 4 Substantially no ink 2 was transferred onto the intermediate roll 4, although a small amount of water was transferred onto it.

On the other hand, when 40V was applied using the recording electrode 5 as an anode and the ink carrying roll 1 as a cathode, the ink 2 was transferred onto the intermediate transfer roll 4. PH of transferred ink
was 3.

On the other hand, approximately 1 mm of fluoropolymer paint FC-721 (manufactured by Sumitomo 3M Co., Ltd.) is applied as a water-repellent coating film on the polyimide film, and then an ordinary electrophotographic method is applied using an electrophotographic toner mainly composed of polyamide resin. Using a dry copying machine, the printing plate 13 on which the toner image has been formed is wound around the plate cylinder 6, brought into contact with the ink on the intermediate transfer roller 4, and rotated in the direction of the arrow. Only the ink was transferred.

Next, when the brush cylinder (urethane rubber surface) 7 was rotated in the direction of arrow B in contact with the plate 13, the plate 13
The upper ink was transferred to the brush cylinder 7. Next, plus body 7
When the recording material 8 is conveyed in the direction of arrow E with the OHP sheet (Mylar sheet) sandwiched between the pressure roller (surface silicone rubber) 9 and the toner image on the plate 13 and the toner image on the plate 13 on the recording material 8. A similar ink image was formed. Ammonia gas is applied to this ink image 11 by a spray 12,
When the ink image 11 was rubbed with a finger after one minute, the ink image 11 was not disturbed.

Example 2 An ink image was formed in the same manner as in Example 1, except that an aluminum plate was used as the recording medium 8 and IN NaOH was used as the alkaline pH-changing substance.

When I rubbed it with my finger one minute after recording, there was no disturbance in the image.

〔Effect of the invention〕

As explained above, the fixability of the ink image was strengthened by adding the pH value changing substance. This makes it possible to form images of better quality and durability than in the conventional example.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of an apparatus for carrying out the method of the invention. 1: Ink carrying roll 2: Ink 3: Ink container 4: Intermediate transfer roll 5 Varnish spray
6: Plate cylinder 7: Brush cylinder 8: Recording material 9: Pressure roll lO: Regulating means 11: Ink image 12: P
Patent applicant for H-change agent applicator Canon Co., Ltd.

Claims (1)

[Scope of Claims] 1) An image fixing method characterized by applying a pH value changing substance to an ink image formed on a recording medium. 2) The image fixing method according to claim 1, wherein the ink has a property that the viscosity becomes higher when the pH value is high than when the pH value is low, and the pH value changing substance is an alkaline substance.