JPS62288044A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To apply high image quality ink jet recording to general-purpose recording paper regardless of paper quality, by a method wherein a recording liquid droplet is adhered to recording paper preheated and the recording paper is held to a heated state even after recording to rapidly evaporate the liquid component contained in the recording liquid droplet to fix a solvent and dye remaining onto the recording paper. CONSTITUTION:A recording liquid droplet is adhered to preheated recording paper in a state where it rises by the surface tension of said liquid droplet and held to a heated sate even after ink jet recording to rapidly evaporate the liquid component contained in the recording liquid droplet while the adhered state is held to reduce the volume of the recording liquid droplet and the solvent and dye mainly remaining on the recording paper is fixed to the recording paper. The solvent component other than the dye mainly remaining on the recording paper at the time of fixing under heating is pref. glycerine, diethylene glycol, thiodiglycol or a mixture thereof and the total mixing amount with the recording liquid is pref. 5-20%. The pH of the recording liquid is 6-10 and the preheating or heating temp. of the recording paper is desirably within a range, from the min. b.p. of the solvent contained in the recording liquid to 140 deg.C.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Industrial Application Field] The present invention applies heat energy to a recording liquid to cause a state change, and the pressure change accompanying the state change causes the recording liquid ejection port to open. Regarding the device used for inkjet (hereinafter referred to as thermal inkjet) recording, which ejects recording liquid from a recording liquid to form a dot image on a recording paper facing the recording liquid discharge port, please refer to the following for more details. The present invention relates to a thermal inkjet recording device that can perform high-quality recording on recording paper regardless of paper quality.

[Prior art] As a conventional example of a thermal inkjet recording device, the US HEW
The May 1985 issue of the LETT-PACKARD Company Journal introduces the structure of the recording device and recording head in detail, and it is an effective means for realizing an inkjet recording device that has a simple structure and is capable of high-speed, high-density recording. be.

Further, as a representative example of an inkjet recording apparatus having a heating drying means for recording liquid, Japanese Patent Application Laid-open Nos. 55-69464 and 5
No. 5-84670, etc., which heats the entire platen that supports the recording paper with a heating element installed inside the platen, thereby heating the recording paper from the back side, drying the recording liquid, and eliminating unnecessary bleeding, paper wrinkles, and unspecified problems. This is an effective means for preventing stains caused by the recording liquid and realizing high-resolution and high-quality image recording.

[Problems to be Solved by the Invention] However, in conventional thermal inkjet recording devices, the recording liquid recorded on the recording paper does not dry well, and when recording on commercially available general-purpose recording paper such as medium-quality paper, Unnecessary bleeding, paper wrinkles, and stains caused by unfixed recording fluid occur.

Furthermore, since the thin film circuit that generates thermal energy for ejecting the recording liquid is adjacent to the recording liquid through a thin protective layer, the components of the recording liquid are required to ensure the durability of the protective layer and the thin film circuit. , PH value, etc. are limited. Therefore, it is not preferable to use a strong alkaline solution in the recording liquid as a means for chemically accelerating the fixation and drying of the recording liquid on the recording paper, since this significantly deteriorates the durability of the protective layer and the thin film circuit.

In addition, during the manufacturing process of commercially available and medium-quality paper, which is a typical general-purpose recording paper, properties vary widely depending on the configuration and processing method of raw material valves, mixed fillers, wire parts of paper machines, size presses, etc. Therefore, the inkjet recording characteristics are completely different not only depending on the manufacturer and production lot, but also on the front and back sides of the same paper. That is, since the absorbency of the recording liquid differs, the print quality is greatly influenced by the paper quality. Japanese Patent Publication No. 55-69464
No. 55-84670, etc. are concerned only with the recording paper heating means and structure of the platen section, and simply combining this technology with thermal inkjet recording will not be able to produce high resolution and high resolution on various general purpose recording papers regardless of the paper quality. It is technically insufficient to realize high-quality thermal inkjet recording.

[Means for Solving the Problems] The present invention solves these problems by ejecting recording liquid from a recording liquid ejection port to form a dot image on a recording paper facing the recording liquid ejection port. In a thermal inkjet recording device, recording liquid droplets are deposited on a preheated recording paper in a bulging state due to their surface tension, and the recording paper is heated and held to maintain the adhering state even after inkjet recording. The liquid component contained in the droplet is rapidly vaporized to reduce the volume of the recording droplet, and the solvent and dye mainly remaining on the recording paper are fixed onto the recording paper.

The solvent component other than the dye contained in the recording liquid and mainly remaining on the recording paper during the heat fixing is glycerin, diethylene glycol, thiodiglycol, or a mixture thereof, and the total amount mixed in the recording liquid is 5 to 20%. It is preferable.

Further, it is desirable that the recording liquid has a pH of 6 to 10, and the preheating and heating temperature of the recording paper is preferably higher than the lowest boiling temperature of the solvent contained in the recording liquid and lower than 140°C.

The above-mentioned commercially available and medium-quality papers include Japanese Industrial Standards Printing Paper A and 8, Japanese Industrial Standards Writing and Drawing Paper (letter paper, drawing paper, Ghent paper, etc.), Japanese Industrial Standards Coated Paper (coated paper, etc.), etc. The present invention can also be applied to lower-grade recording paper such as medium-quality paper or lower quality paper.

Direct dyes for inkjet recording include: C,1, Direct Black 19 C,1, Direct Black 22 C,1, Direct Black 154 C,1, Direct Yellow 12 C,1, Direct Yellow 26 C,1 , Direct Red 13 C,1, Direct Red 17 C,1, Direct Blue 8 C,1, Direct Blue 90, etc.As acid dyes, C,1, Acid Black 52 C,1, Acid Yellow 17 C,1 , Acid Yellow 25 C,1, Acid Red 37 C,1, Acid Red 52 C,R, Acid Blue 22, etc.

[Function] According to the present invention, the recording droplets attached to the preheated general-purpose recording paper do not erode the recording paper fibers, and are not diffused or absorbed onto the recording paper surface by capillary action due to surface tension. Immediately after adhering to the recording paper, heating and drying begins while maintaining the adhesion state, and the volume of the recording droplets rapidly decreases and the droplets mainly remain on the recording paper without vaporizing. By fixing the solvent and dye on the recording paper, there is no need to use a strong alkaline recording liquid that would damage the durability of the protective layer and thin film circuit of the recording head, and eliminates bleeding and paper wrinkles caused by unnecessary recording liquid. This enables high-quality thermal inkjet recording without any blemishes.

[Example code] The present invention will be explained in detail based on examples.

First, a recording liquid suitable for the thermal inkjet recording apparatus of the present invention will be explained.

First, various recording liquids as described below were produced as prototypes.

<Recording liquid a> Dye...C, 1, Direct Black 1541% Solvent...Water *Remaining amount <Recording liquid B> Dye...C, 1, Direct Black 1541% Solvent...Glycerin X0% Water
*Remaining amount <Recording liquid C> Dye...C, R, Direct black 221% solvent.
...Glycerin 10% methyl alcohol 10% water
*Remaining amount <Recording liquid d> Dye: C, 1, Direct Black 1541% Solvent: Thiodiglycol 10% Water
*Remaining amount recording liquid e> Dye...C, 1, Direct Black 1541% Solvent...Diethylene glycol 10% water
*Remaining amount <Recording liquid f> Dye...C, 1, Direct Black 1541% Solvent...Triethylene glycol 10% water
*Remaining amount <Recording liquid g> Dye...C, 1, Direct Black 1541% Solvent...Polyethylene glycol 10% water
*Remaining amount recording liquid h> Dye...C, 1, Direct Black 1541% Solvent...Glycerin 5% Diethylene glycol 3% Thiodiglycol 2% Water *Remaining amount recording liquid i> Dye...C, 1. Direct Black 1541% Solvent: Glycerin 5% Polyethylene Glycol 5% Water *Remaining amount [Note] In addition to the above ingredients, 0.2% of Proxel was added as a preservative to each recording liquid.

The commercially available medium-quality paper shown in Table 1 was preheated and heated to room temperature or 130°C, and the recording liquid was ejected using a thermal inkjet method at a speed of about 4 m/see with a droplet diameter of about 10011 m. It was attached to recording paper.

Table 1 Table 2 shows the results of examining the recording conditions.

Table 2 From the results shown in Table 2, each recording liquid has extremely better drying properties when recorded on recording paper that has been preheated to 130°C. There was no phenomenon in which the paper surface was stained with unfixed recording liquid or stuck to hands when touched.

Furthermore, recording liquids a, b, c, d, e, and h provided better printing with less bleeding than printing at room temperature. When using other recording liquids, it was possible to read the recorded characters although there was some smearing compared to the above-mentioned recording liquid.

Also, when recording images on high-density recording paper at room temperature,
There were cases where wrinkles appeared on the recording paper and the wrinkles did not recover even if the recording liquid dried after recording, and unfixed recording liquid flowed on the paper surface and smeared the recorded image. These problems did not occur when recording on paper.

From the above results, recording liquid a to which no solvent was added and recording liquids a, b, c, to which glycerin, diethylene glycol, thiodiglycol, or a mixture thereof was added as a solvent component,
It was found that d, e and h are effective recording liquids for this recording apparatus.

Next, the recording paper preheating/heating temperature appropriate for drying and fixing the recording liquid will be described. Table 3 shows the results of thermal inkjet recording of the recording liquid C on the recording papers shown in Table 1 that had been preheated and heated to various temperatures under the same ejection conditions as in Table 2, and the recording conditions were examined.

Table 3: If the preheating/heating temperature of the recording paper exceeds 140°C, the recording paper and recording liquid will emit smoke during recording, and if it exceeds 160°C, the moisture in the recording paper will be completely removed and it may break when bent. . Further, if the groove is not 80° C., the drying properties of the recording liquid are poor, and it takes time for the recording liquid to be fixed on the recording paper, and the print quality is poor.

Therefore, the recording paper preheating/heating temperature is higher than the lowest boiling point of the solvent contained in the recording liquid (in the case of recording liquid C, the boiling point of methyl alcohol).
It has been found that a temperature of 140° C. or lower is desirable.

Furthermore, the appropriate mixing amount of the solvent was studied as follows. Table 4 shows the results of inkjet recording in the same manner as in Table 3, using several types of recording liquids prepared by varying the amount of solvent mixed in based on the recording liquid.

Table 4 [Note* Only glycerin is mixed as a solvent.

*The mixing amount of dye for each recording liquid is C and I.

Direct black 1541%.

*Added 0.2% Proxel as a preservative.

*The rest is water.

*Solvent content of 0% is the same as recording liquid a.

From the results in Table 2 above, a recording liquid applicable to the inkjet recording apparatus of the present invention was found, but the recording liquid for inkjet recording contains a high boiling point solvent to prevent clogging of the recording liquid ejection port. It is well known that this is necessary. Therefore, in Table 4, the recording liquid a and the recording liquid with a solvent content of 5% in the groove are applicable, but not practical.

In Table 4, even if the amount of solvent mixed was increased, there was almost no effect on bleeding. If 5 to 10% of solvent is mixed in with the recording liquid ejection port, recording liquid ejection failure will occur if left for a long time, but the drying properties are good and it can be used for the time being.
At 10% or more, there was no problem of poor ejection. If the amount of solvent mixed exceeds 20%, the drying properties of the recording liquid will be poor and immediate drying properties will not be obtained.

Similar results were obtained even when the amount of solvent mixed in was varied based on recording liquids C, dSe, and h, and it was found that the amount of solvent mixed in was preferably 5 to 20%.

In addition, in order to investigate the relationship between the PH degree of the recording liquid and the print quality,
The following recording liquid was prepared based on the recording liquid sample, and inkjet recording was performed in the same manner as in Table 2. The results are shown in Table 5.

<Recording liquid j> C,1, Acid Black 52 1% Glycerin 10% Acetic acid 1% Proxel 0.2% Water
Remaining amount PH = 5.5 <Recording liquid 1> C, R, Direct black 191% Glycerin 10% Proxel 0.2% = 17- Water Remaining amount PH = 8 <Recording liquid m> C, 1, Direct black 1541% glycerin
10% Proxel 0.2% water
Remaining amount PH = 10 Recording liquid n> C, 1, Direct black 1541% glycerin
10% potassium hydroxide 0.2% Proxel
0.2% water Remaining amount PH=11.2 Table 5 As in Table 2, bleeding and recording liquid drying properties are better when inkjet recording is performed on recording paper preheated to 130°C. At this time, if the pH of the recording liquid is less than 6, bleeding will occur and various parts of the apparatus will be oxidized, which is not practical.

In addition, since the recording liquid is strongly alkaline at a pH of 11 or higher, it erodes the recording paper fibers and is absorbed into the paper surface, causing smearing, and also protects the thin film circuit that generates thermal energy for ejecting the recording liquid. The durability of the protective layer deteriorated significantly. From the above results, it has been found that the pH of the recording liquid is preferably about 6 to 1O.

Second, the configuration of a thermal inkjet recording apparatus using the above-mentioned recording liquid will be explained.

FIG. 1 is a schematic overall configuration diagram showing an embodiment of a thermal inkjet recording apparatus of the present invention.

In FIG. 1, the recording head 5 is guided by the carriage guide 6 and moves in the direction of the arrow (■) while receiving the recording liquid from the recording liquid tank 15 through the recording liquid supply vibrator 16, and the paper feed roller 2 and the guide roller 4 Thermal inkjet recording is performed on recording paper that is fed intermittently with a line feed in synchronization with the recording head 5.

In FIG. 2, the recording head 5 has a plurality of recording liquid ejection ports 1.
3 is provided, and a dot image is formed on the recording paper 3 by means of recording liquid discharge means such as piezoelectric element control, electric field control, charge control, and thermal ink jet recording. The recording head 5 of this example is a thermal inkjet recording head equipped with 32 recording liquid ejection ports in one vertical row with an interval of 240 dpi, and has approximately 90 J
Recording droplets with a diameter of Jm are ejected.

The fixed platen 1 is suitably made of a material with good heat diffusion such as an aluminum alloy or a thermally conductive plastic material, and in this example, an aluminum alloy plate with an average thickness of 1 mm and a size of approximately 250 mm x 30 mm is used. Recording head 5 on fixed platen 1
As shown in FIG. 2, a heating element 12 is provided on the back surface not facing the . The heating element 12 has a rated voltage of 30V and an average resistance value of 22Ω at normal temperature.
It is appropriate to arrange five PTC thermistors for heaters evenly, or to use a sheath heater of about 100V and 250W.

By preheating and heating the recording paper 3, the recording paper 3 is curled along the shape of the fixed platen 1. In order to remove this curl, the recording paper 3 is wound around a curl removing roller 14 after inkjet recording, and the curl is removed by curling it in the opposite direction to the curling direction, and the recording paper 3 is taken out in a flat state. be able to.

21 Using the thermal inkjet recording apparatus of this example, the preheating time before recording was 4 seconds on Table 1 and other various commercially available medium-quality papers.
Recording liquid b, C% d, e, ks with heating time of 4 seconds after recording
When 1% and m were recorded by thermal inkjet,
High-quality image recording could be achieved regardless of the paper quality and the front and back sides of the paper, and the recording ink dried sufficiently, with no paper wrinkles, unnecessary bleeding of dots, or stains due to unfixed recording liquid.

Furthermore, even when a near-neutral recording liquid such as 1 is used as the recording liquid in thermal inkjet recording as in this example, high print quality and sufficient recording liquid drying properties can be obtained, and the recording liquid ejection from the recording head It does not chemically impair the durability of the thin film circuit that performs this function and the protective layer that protects the thin film circuit. Furthermore, the recording liquid in the recording head section is heated by the heating and drying means for the purpose of fixing the recording liquid onto the recording paper, thereby reducing the viscosity of the recording liquid in a low-temperature environment and improving the recording liquid ejection performance. In the thermal inkjet recording of this example, the thermal energy required to change the state for ejecting the recording liquid could be reduced by about 5%.

Although this example is a monochrome thermal inkjet recording device, it is obvious that the present invention can also be applied to a color inkjet recording device.

[Effects of the Invention] As described above, according to the thermal inkjet recording apparatus of the present invention, high-quality inkjet recording can be performed on commercially available general-purpose recording paper such as medium-quality paper regardless of the paper quality.

In addition to improving printing quality, we are also able to improve recording liquid ejection performance in low-temperature environments, and chemically improve the durability of the thin film circuit in the recording head that ejects the recording liquid and the protective layer that protects the thin film circuit. In addition, the energy required for ejecting the recording liquid can be reduced.

In particular, thermal inkjet allows for easy high-density multiplication of recording liquid ejecting sections and enables high-density inkjet recording.The present invention is therefore useful for improving device reliability and recording image quality and diversifying compatible recording papers. The effect is great.

[Brief explanation of drawings]

FIG. 1 is a schematic overall configuration diagram showing an embodiment of an inkjet recording apparatus of the present invention. FIG. 2 is a partial side view of FIG. 1. 4...Guide roller 6...Carriage guide 8...Paper feed gear or higher

Claims (4)

[Claims] (1) Heat energy is applied to the recording liquid to cause a state change, and the pressure change accompanying the state change causes the recording liquid to be ejected from the recording liquid ejection port to form a dot image on the recording paper facing the recording liquid ejection port. In an inkjet recording apparatus, recording droplets are deposited on a preheated recording paper in a swollen state due to their surface tension, and the recording paper is heated and held to maintain the adhering state even after inkjet recording. An inkjet recording apparatus characterized in that the volume of the recording droplet is reduced by rapidly vaporizing a liquid component contained in the droplet, and the solvent and dye mainly remaining on the recording paper are fixed onto the recording paper. (2) The solvent component other than the dye contained in the recording liquid and mainly remaining on the recording paper during the heat fixing is glycerin, diethylene glycol, thiodiglycol, or a mixture thereof, and the total amount mixed in the recording liquid is 5 to 20%. %
An inkjet recording apparatus according to claim 1, characterized in that: (3) The inkjet recording apparatus according to claim 1, wherein the recording liquid has a pH of 6 to 10. (4) The inkjet recording apparatus according to claim 1, wherein the preheating and heating temperature of the recording paper is higher than the lowest boiling temperature of a solvent contained in the recording liquid and lower than 140°C.