JPH0624835B2 - Neutral paper printing method and wetting liquid circulation device for neutral paper printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is most suitable for a neutral paper printing method for printing using neutral paper, and is suitable for printing using neutral paper. The present invention relates to a wetting liquid circulating device for neutral paper printing, which circulates the applied wetting liquid between a storage dish and a storage container.

[Background technology]

In offset printing, a wetting liquid is applied to the non-image areas of the planographic printing plate to prevent oily printing ink from adhering to enable clear printing.

In such offset printing, acid paper has been used in the past, but the acid paper that has been printed has a marked change over time. Therefore, printing using neutral paper has become popular.

However, since the pigment contained in neutral paper, such as calcium carbonate, is alkaline, if this calcium carbonate dissolves into the wetting liquid via the ink roller, the storage capacity of the storage dish will be small and the pH value of the wetting liquid will change. However, this may cause the W / O balance of the printing ink to be lost.

The details are as follows. As the wetting liquid, for example, an etching liquid diluted five times with water is supplied to the storage dish. This wetting liquid has a pH of about 4, and when acidic paper is used, the pH rises to about 5.5, but is stable there and does not rise any further. On the other hand, in neutral paper, alkaline substances come out, so the pH rises above 5.5, and the printed matter begins to stain from around pH 6.

The etching liquid contains ferrocyan ion,
A non-sensitized film is formed by reacting with the zinc oxide applied to the printing plate. However, this reaction progresses when the pH is within about 5.5, and when it exceeds about pH 6, the ferrocyan ion does not react with zinc oxide, and the ferrocyan does not contribute, and it is the same state as when printing only with water. Become.

As a result, stains are generated on the entire printing paper, and the ink is bridged in the details of the image lines, resulting in entanglement of the image lines.

Increasing the capacity of the storage tray will slow down the fouling of the wetting liquid, but this will not be easy as it requires a major design change of the printing machine.

This is remarkable when printing using an electrophotographic printing original plate containing organic or inorganic photo-semiconductor particles.

Further, it is possible to separately provide a storage tank for storing a large amount of the wetting liquid, and circulate the wetting liquid between this storage tank and the storage tray for the wetting liquid, but a drive source such as a pump is required for circulation. This is necessary, and the heat generated by driving the pump heats the wetting liquid, which causes a problem that the wetting liquid cannot be maintained at an appropriate temperature.

In consideration of the above facts, the present invention is a neutral paper printing method and a neutral paper printing method capable of maintaining clear printing by preventing stains and temperature changes of a wetting liquid even when printing using neutral paper. The aim is to obtain a wetting liquid circulation device for paper printing.

It should be noted that the neutral paper referred to here is one in which an alkaline pigment such as calcium carbonate is used as a filler, and the pH value of the paper measured by the cold water extraction method is in the range of about 5.5 to about 10. Therefore, the printing method of the present invention has a remarkable effect particularly when printing on a neutral paper having a pH value in the range of about 6 to about 9.

[Outline and Action of Invention]

The neutral paper printing method according to the present invention is a neutral paper printing method of applying a wetting liquid in a storage dish to a lithographic plate while circulating the wetting liquid between a wetting liquid storage dish and a storage container, The temperature of the circulating wetting liquid is increased by pumping up more wetting liquid than the amount sent to the wetting liquid storage tray from the storage container, and returning the surplus to the storage container in the middle of the pipeline that connects the wetting liquid storage tray and the storage container. Is characterized by being dispersed.

Further, the wetting liquid circulation device for neutral paper printing according to the present invention is used in a printing machine in which a roller immersed in a wetting liquid applies the wetting liquid to a lithographic plate, and a reservoir for storing the wetting liquid and this reservoir. A storage container that stores more wetting liquid, and a circulation means that circulates the wetting liquid between the storage container and the storage dish,
Adjusting means for adjusting a flow rate to a branch passage for returning a part of the wetting liquid circulated by the circulation means to the storage container, the adjusting means being provided in a pipe line communicating the storage container and the storage dish. .

According to the present invention, in addition to the wetting liquid storage dish, a storage container for storing a large amount of the wetting liquid is separately provided and the wetting liquid is circulated. As a result, even if the wetting liquid in the wetting liquid storage dish is contaminated, it is removed by circulation and diluted with a large amount of wetting liquid, so that the contamination can be made inconspicuous.

Further, a larger amount than the wet flow rate supplied to the wetting liquid storage tray is pumped from the storage container, and the surplus portion is returned to the storage container in the middle of the pipeline connecting the wetting liquid storage tray and the storage container. As a result, even if the heat generated when pumping up the wetting liquid, for example, the heat generated from the pump when pumping up with the pump, is transferred to the wetting liquid, a large amount of the wetting liquid absorbs this heat, so that the wetting liquid storage tray It is possible to prevent the temperature of the sent wetting liquid from rising rapidly.

As the wetting liquid of the present invention, it is preferable to use a wetting liquid having a buffering capacity and containing a Ca ion chelating agent at a pH of about 5.5 or less.

For example, potassium hydrogen phthalate and sodium hydroxide, potassium dihydrogen phosphate and sodium hydroxide, sodium citrate and sodium hydroxide, potassium dihydrogen citrate and hydrochloric acid or sodium hydroxide, succinic acid and sodium tetraborate, and citric acid. Potassium dihydrogen acid and sodium tetraborate,
A buffer solution having a desired pH value can be obtained by appropriately combining aqueous solutions such as tartaric acid and sodium tartrate, acetic acid and sodium acetate, and disodium hydrogen phosphate and citric acid.
Moreover, as a chelating agent for Ca ions, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA),
Various substances such as uramil diacetic acid (UDA) can be used.

Therefore, in the present invention, the circulation means circulates the wetting liquid from the wetting liquid storage container to the storage dish, and even when the pH value is changed to the alkali side by the neutral paper, substantially The same as when the volume of the wetting liquid increases, the degree of change in the pH value of the wetting liquid decreases, and printing without contamination can be continued for a long period.

When a motor pump is used as the circulation means, a bear coil induction motor, a condenser running motor, or the like can be applied, and as the pump, a centrifugal type vortex pump used in the circulator of the fish watching tank can be used. The pump is preferably acid resistant.

[Embodiment of the Invention] FIG. 1 shows an offset printing machine 10 to which the present invention is applied. In this offset printing machine 10, the lithographic plate 14 installed on the mounting table 12 is wound around the plate cylinder 20 through the etching section 16 and the prewetting section 18, and the image is transferred to the plate cylinder 20 and then the plate discharge section 22. It is a composition that is sent to.

A form roller 23 is in contact with the plate cylinder 20 so that printing ink is applied to the plate cylinder 20.
4 are arranged in contact with each other, and an impression cylinder 26 is in contact with a lower portion of the blanket cylinder 24.

A paper feed unit 28 is provided in the lateral direction of the impression cylinder 26, and the printing paper 3
0s are stored in layers. The printing paper 30 in the paper supply unit 28 is supplied from the uppermost portion between the blanket cylinder 24 and the impression cylinder 26, and after being printed with an image, sent to the discharge unit 22.

Rollers 34, 36, 38 and 40 are sequentially brought into contact with the upper portion of the plate cylinder 20, and the roller 40 is immersed in the wetting liquid storage tray 42.

As shown in FIG. 2, the storage dish 42 has a shallow dish shape with an open upper side, and a weir 44 is provided near one end in the longitudinal direction to partition the storage section 45 and the discharge section 46.
The weir 44 keeps the dampening liquid stored therein at a constant level and allows the overflowing dampening liquid to flow to the discharge portion 46.

One end of a forward pipe 50 is attached to a bracket 48 protruding from a part of the storage dish 42 toward the central portion. The forward opening of the forward pipe 50 has its axis centered vertically and is directed downward, and the wetting liquid pumped to the central portion of the water surface of the stored wetting liquid flows down to cause a large wave motion on the water surface of the wetting liquid. It does not cause it.

The return pipe 52 connected to the bottom surface of the discharge portion 46 has a function of discharging the overflowing wetting liquid by gravity.

As shown in FIG. 3, the other end of the forward pipe 50 is connected to the storage container 5
4 is penetrated into the wetting liquid 56 in the storage container 54. The tip of this immersion portion is formed as a diameter-expanded portion 58, which increases the pumping speed of the wetting liquid 56 and enables a high head.

A pump 60 is provided in the expanded diameter portion 58, and the control device 6
The wetting liquid 56 is pressure-fed into the outflow pipe 50 by the control of 2. The control device 62 is provided with a switch 64 and a phase control dial 66 so that the amount of pressure feeding can be changed. Further, the return pipe 52 for guiding the return liquid from the storage dish 42 is attached such that its tip portion penetrates the storage container 54.

In addition, as shown in FIG.
The valve element 74 is attached, and the opening / closing amount of the valve element 74 is controlled by the cock 76. A return pipe 78 is connected to the valve body 74, and a tip end portion of the valve body 74 communicates with the inside of the storage container 54.

Therefore, in this embodiment, by adjusting the cock 76, a part of the wetting liquid 56 sent from the pump 60 is sent to the storage dish 42, and the rest is returned to the storage container 5 via the return pipe 78.
It is possible to return to 4. Therefore, it becomes possible to adjust the pump 60 so as to send out a sufficient amount of pressure and to supply only the necessary amount to the storage tray 42.

Further, an additional bottle 68 is attached to the opening 70 on the top surface of the storage container 54 in an inverted state. The valve body 72 is attached to the neck portion of the additional bottle 68, and the valve rod 72A of the valve body 72 is immersed in the wetting liquid 56 and hits the contact rod 73 of the storage container 54 to remove the additional bottle 68. It is open. The neck portion 68A of the additional bottle 68 is the storage container 5
It is soaked in the wetting liquid 56 in the container No. 4, and when the wetting liquid level decreases, the additional wetting liquid in the additional bottle 68 flows into the storage container 54, and the liquid level is always kept constant.

Here, the storage amount of the dampening liquid 56 in the storage container 54 is determined by the storage tray 4
2 is larger than the storage amount in the storage container 54, and the wetting liquid 56 is circulated between the storage container 54 and the storage tray 42.
The substantial amount of the dampening liquid stored in the storage dish 42 is the total of the storage amounts of the storage dish 42 and the storage container 54.

Next, the operation of this embodiment will be described.

When the offset printing machine 10 is in operation, the planographic plate 1 is supplied.
4 is wound around the plate cylinder 20 and ink is applied from the form roller 23. In this case, the rollers 34 to 40 successively transfer the wetting liquid in the storage dish 42 and apply it to the non-image area of the planographic plate 14 to prevent ink from adhering to the non-image area. The image lines on the planographic printing plate 14 are transferred to the rubber body 24, and further transferred to the printing paper 30 supplied from the paper supply unit 28 to perform printing.

When neutral paper is used as the printing paper 30, the calcium carbonate contained in the neutral paper flows out to the wetting liquid in the storage tray 42 via the blanket cylinder 24, the plate cylinder 20 and each roller, so that the wetting liquid approaches the alkali. Becomes

However, in this embodiment, since the wetting liquid 56 in the storage container 54 is circulated with the storage tray 42 via the forward pipe 50 and the return pipe 52 during printing, the substantial storage amount of the wetting liquid in the storage tray 42 is large. This prevents the pH value of the wetting liquid from changing rapidly. As a result, a good printing state can be maintained even when printing a large number of sheets.

The level of the wetting liquid in the storage tray 42 is kept constant by the weir 44, and the wetting liquid level can be arbitrarily changed by making the height of the weir 44 adjustable. For this purpose, as a simple method, the weir 44 can be made of synthetic resin clay such as epoxy resin or polyamide resin.

Here, when the pump 60 circulates, heat may be generated by the operation of the pump 60, and this heat may warm the circulating wetting liquid. The temperature of the wetting liquid is maintained at an appropriate temperature, but it is appropriate. In this embodiment, the amount of the wetting liquid fed by the drive of the pump 60 is larger than the amount actually fed to the storage tray 42.

For this reason, the amount of the wetting liquid that receives this heat is larger than that of the generated heat, so that the temperature of the wetting liquid does not rise so much and is kept at an appropriate temperature.

The excess amount of the wetting liquid sent to the return pipe 78 depends on the opening / closing amount of the valve body 74 opened / closed by adjusting the cock 76.
And is returned to the storage container 54. Therefore, an appropriate amount of the moistening liquid having an appropriate temperature is sent to the storage dish 42,
It is possible to circulate the wetting liquid in an optimal state without any dirt or temperature change.

According to the experimental results of the present invention, when printing is performed using only the 200 cc storage tray 42 without using the storage container 54, the print stain occurs in about 3 hours of printing time, and the storage tray 42 is 400 cc. In such a case, the print stain occurred after 6 to 9 hours, but by using the storage container 54 of 2.5 together, clear printing could be performed for 20 hours or more.

〔The invention's effect〕

As described above, the neutral paper printing method and the wetting liquid circulation device for neutral paper printing according to the present invention prevent a stain and a temperature change of the wetting liquid even when printing using neutrons, and perform clear printing. It has an excellent effect that can be maintained.

[Brief description of drawings]

FIG. 1 is a sectional side view showing an offset printing machine to which the present invention is applied, FIG. 2 is a perspective view showing a wetting liquid storage tray according to the present embodiment, and FIG. 3 is a sectional view showing a storage container according to the present embodiment. FIG. 4 and FIG. 4 are sectional views showing the circulation system of this embodiment. 10 ... Offset printing machine, 14 ... Planographic printing, 42 ... Reservoir, 44 ... Weir, 45 ... Reservoir, 50 ... Outgoing pipe, 52 ... Returning pipe, 54 ... Reservoir container, 56 ... Wetting liquid, 60 ... Pump.

Claims (2)

[Claims] 1. A neutral paper printing method for applying a wetting liquid in a storage dish to a lithographic plate while circulating the wetting liquid between a wetting liquid storage dish and a storage container, which is sent to the wetting liquid storage dish. A characteristic is that the temperature of the circulating wetting liquid is dispersed by pumping up more wetting liquid than the amount from the storage container and returning the surplus to the storage container in the middle of the pipeline that connects the wetting liquid storage dish and the storage container. And neutral paper printing method. 2. A reservoir immersed in a wetting liquid, which is used in a printing machine for applying the wetting liquid onto a lithographic plate, and a storage tray for storing the wetting liquid, and a storage container storing a larger amount of the wetting liquid than the storage tray. A circulation means for circulating the wetting liquid between the storage container and the storage dish, and a part of the wetting liquid circulated by the circulation means provided in a pipe line communicating the storage container and the storage dish And a adjusting means for adjusting the flow rate to the branch path for returning to the neutralizing paper.