From Disposable to Reusable-New Plate Making SystemLowers Printing Cost withReduced Impact on EnvironmentMITSURU TABUCHI*1
HIROAKI IKEDA*1
FUMINORI FURUYASHIKI*2

This paper introduces a new reusable plate system that can save material cost and reduce environmental impact
by writing and erasing images repeatedly. This system comprises an anodized aluminum plate with high printability
and a thermosensitive polymer, assuring the high quality and high durability required in commercial offset printing.
In addition, by installing the reusable plate system close to the printing press, an integrated plate making andprinting process is realized, and the work flow of the entire process is made more efficient.

near the printing press, integration of plate making andprinting process is realized without lowering the productivity of the printing press, and the efficiency of work
flow is improved.
Plate recycling effects are not limited to reduction ofplate material cost. Since the aluminum material can beused repeatedly, supposing that 100 plates are made perday, the annual consumption of aluminum material isdramatically reduced to 50 kg from about 1 000 kg, which
contributes greatly to reducing impact on the environment. This paper describes the basic performance of thenew plate making system, together with the future output of this technology.

1. Introduction
To meet market demands for lower cost and shorter
delivery terms, the printing industry has recently been
adopting new ideas such as a CTP (computer-to-plate)system capable of making plates directly by laser fromimage data, work flow for efficient management of production control, and a digital system.
Another new technology is Computer to Press capableof making plates and printing in one system by combining the hitherto different processes. However, in thisComputer to Press for imaging directly on the printing
plate and printing on the printing press, the press issmall and low in speed, and thus differs from the large
high-speed offset printing presses used in commercial
printing.
Accordingly, Computer to Press has the followingproblems.
Expensive laser imaging devices must be installed ineach printing unit, making the initial investment costvery high.
The printing machine must be stopped during platemaking, lowering the operation factor of the printing
machine.
Existing plates on the market for Computer to Press
are higher in cost than other plates for CTP or PS.
The environments (vibration, dust, etc.) of the printing press give rise to various problems in plate making
work, and the plate making quality is limited.
The reusable plate system introduced in this paper,
which is intended to realize integration of plate making
and printing process by overcoming the above problems,
is a versatile printing system applicable to diversified
printing processes.
Accordingly, by installing the reusable plate system

2. Principle of plate recycling process
The plate recycling process is as explained with reference to Fig. 1
1.
(1) Preparation of material
The material for the printing plate needs to havesufficient durability to withstand repeated making
and high printing quality, and an anodized aluminumwith excellent retention of water is used. For recycling, this aluminum plate 0.1 to 0.3 mm in thickness
must be transported between the printing press andthe plate making machine, but because of its thinness it is likely to be deformed or flawed duringtransportation. Accordingly, the aluminum plate is
installed on a sleeve which can be mounted on theplate cylinder of the printing press, and the aluminum plate is conveyed together with the sleeve. Thisprevents deformation or creation of flaws in the platematerial that could occur at the time of exchange ofprinting press and plate making machine, and satisfactory printability equivalent to that in the existing
PS and CTP is realized.

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Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 42 No. 2 (Apr. 2005)*1 Hiroshima Research & Development Center, Technical Headquarters*2 SOCIO DIAMOND SYSTEMS CO., LTD.

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1 Preparation of material

2 Polymer application

Polymer

3 Halogen lamp for heating

4 Infrared laser device for
imaging

Crystallization of polymer
orientation by heat control

Randomization of polymer
orientation by laser irradiation

Polymer hardening

Increase ofpolymer solubility

Anodised aluminum

5 Development
Alkalinedeveloping solution

7 Printing

6 Image type
Printing
element

Fig. 1 Plate recycling process

Non-printing
element

Ink

8 Image erasure
Water

Stripping solution

Through positive polymer using orientation control technology by heat,
both high print durability and ease of erasure for recycling are achieved.

(7) Erasure of image
By using the alkaline aqueous solution as stripping
solution, the polymer in the printing area can be dissolved, the ink on the polymer is simultaneously strippedfrom the plate surface, and the printing area can be removed efficiently. Further, by washing in water, theerasure waste liquid on the plate surface can be removed,
and the same state as that of the grain plate in initialstate can be obtained. After this process is finished,preparation of the next plate is completed.

(2) Polymer application
As material for printing image, liquid polymer isapplied on the aluminum plate which is integrated withthe sleeve. Printing element material is required tohave print durability for the printing plate and ease oferasing images for recycling, and a positive polymer isused because it facilitates control of the film strengthof printing images and forming of images independently. The polymer can be handled in room light, anddoes not require any special storage facility.
(3) Heating
Polymer orientation is crystallized by temperature
control of the plate through heating with a halogen
lamp, and a printing area layer with excellent print
durability of high hardness and very low solubility isformed.
(4) Imaging
By emitting infrared laser radiation to the portion corresponding to non-printing area, thepolymer is instantly heated to a high temperatureand its orientation is randomized, thereby increasing the solubility for developing solution of thepolymer. By using a light absorbing dye for the polymer, the material is designed to obtain a highabsorption characteristic of laser oscillation wavelength of 830 nm.
(5) Development
By alkaline developing solution, the polymer in thenon-printing area is dissolved and removed, and theimage in laser writing is developed, thus completingthe plate making process as printing plate.
(6) Printing
As in conventional plate composition, the same
print setting as in existing offset printing is possible,and commercial ink and dampening water can be used.

3. Construction and specifications of reusable platesystem
This section refers to the construction of the concept
machine shown in Fig. 22, RPS-X1 (reusable plate system). The RPS-X1 consists of three stations for (1) image
erasure, (2) polymer coating and drying, and (3) imaging and developing. The printing plate moves
sequentially through these stations in its sleeve envelope, and undergoes plate making and recycling process.
Clean air supply device
Laser imagingmachine
Plate sleeve

Elevating device
Imageerasing station
Coating anddrying station

Developing andimaging station

Fig. 2 Outline of concept machine RPS-X1
Consisting of three stations, the printing plate is sequentiallyprocessed, regenerated and completed in each process.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 42 No. 2 (Apr. 2005)

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The processing devices of the system are installed onan elevating stage which moves up and down. The elevating stage moves in accordance with the diameter sizeof the printing plate, and each processing device is set
in an appropriate position to the plate surface, so that it
is applicable to a plate sleeve of a different diameter.
Conventionally, the plate making device is installed
in a prepress room with a relatively favorable environment, but in this system it is installed in a printing shop.
Accordingly, a clean air supply facility is required andinstalled to prevent dust deposits which are the maincauses of plate making defects.
The printing plate is used when mounted on a plate
3 the plate sleeve can be desleeve. As shown in Fig. 3,tached from the plate cylinder of the printing press inthe axial direction. After being detached from the printing press, the plate sleeve is installed in the RPS-X1,
and the plate is regenerated and mounted again on theprinting press. Since the printing sleeve is made of lightweight resin, it can be easily handled and carried.
Handling of the printing plate is thus very easy in theplate recycling process.
The main specifications are shown in Table 1
1. Theprinting plate can be used repeatedly in a cumulative
total of 500 000 plates until the performance deteriorates due to abrasion of the grain plate of the material.
By minimizing accumulation of erasure residue, it has
been verified that the plate can be reused up to 20 times.

As a result, while maintaining the productivity of
the conventional offset printing press, a superior system is realized that is applicable to small lots of
25 000 copies on average. It can also reduce the printing material cost and improve the efficiency of workflow.

4. Performance verification result(1) Number of times of regeneration
Fig. 4 shows print samples of first print and print
after 20 times of plate making. The image is a standard offset print of 2400 dpi, 175 lpi, and after 20times, the print quality is unchanged, and it has been
confirmed that no image deterioration results fromrepeated making.
(2) Print durability
In the printing plate after 20 times of recycling,
the durability was tested at a printing speed of 60000 copies/hour. Taking a sample from each copy
of printing, changes of dot percentage were measured, and no decline of dot percentage due toabrasion of image area was found in either highlight or shadow area.
In the halftone dot on paper of highlight area
where the effects of abrasion are likely to appear, nodot loss or skip were observed as shown in Fig. 55,
and the same print durability as in ordinary CTP
material was confirmed.

Sleeve can be detached in theplate cylinder axial direction inthis printing unit.

Plate sleeve

Reusable plate system

Offset printing press

Fig. 3 Handling of printing plate by sleeve
By use of a lightweight sleeve, the plate sleeve can be easily handled
and carried between the printing press and plate making machine.
Initial print

Table 1 Basic specifications of RPS-X1
Main body size

(mm)

Main body weight(kg)System

H 1 600 x W 2 300 x D 2 200
1 500
One-cylinder system

Printing element material
Non-printing element material
Image resolution

After 20 times of remaking

Fig. 4 Print samples
After 20 times of repeated plate making, no deterioration was foundin print quality (2 400 dpi, 175 lpi).

(dpi)

Print durability
Number of times of remaking

Thermal polymer
Aluminum grain plate
2 400

16 000 copies

More than 100 000 copies/image

125 000 copies

225 000 copies

Fig. 5 Harftone dot on paper (5% area) in durability test
No dot loss or skip were observed in highlight area showing a first signof deterioration of print durability.

20 times(cumulative prints: within 500 000 copies)

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 42 No. 2 (Apr. 2005)3

Trimmingallowance

Cutting
Trimming
off
allowance

Size:
BT 2
Trimming
allowance

Trimming
allowance

Trimming allowance:
110 mm
(A great deal ofwaste of paper)
Trimming allowance:
3.1 mmSize:
AY 1Fig. 7 Reduction of waste of paper by variable printing length
By cutting off according to image size, excessive trimming allowanceis eliminated and waste of paper is reduced.

Fig. 6 Concept model of variable printing length offset
printing press MAX-V
May 2004, appearance of MAX-V shown at business fair.
Waste of paper is reduced by variable printing length.

5. Concept and future outlook

Imaging

Plate recycling technology has realized reduction ofplate material cost and lowering of impact on the environment while maintaining the conventional level ofprinting productivity, and the new system is suited toprinting needs of small lots in the present diversifiedapplications.
From the viewpoint of realizing reduction of cost, lowering of environmental impact and shortening ofprocess, the following specific future applications arebeing considered.
(1) Use in web offset printing press of variable printing
lengthThe reusable plate making system, which is regarded as part of a system ranging from plate making
to printing, is being developed at present to realize acombined system with commercial web offset printing press of variable printing length as shown in Fig
Fig.. 6(MAX-V concept machine).
In web offset printing, the print size is limited and,depending on the pattern size, waste of paper may beincreased, but by varying the diameter of the platesleeve, flexibility is possible with changes in printing
length. As a result, one printing press can handle
printing jobs of multiple sizes, and waste of paper isreduced as shown in Fig. 77.
The reusable plate system is applicable to changes
in plate sleeve diameter, and in a system combinedwith MAX-V, waste is eliminated and running costs
are reduced substantially.
(2) Enhanced productivity with multicylinder system
The concept machine RPS-X1 is designed to makeplates sequentially, but an effective method of improving the making speed is to make plates simultaneously
in parallel processes. This is realized by themulticylinder system shown in Fig. 88.

Developing

Polymercoatinganddrying

Imageerasure

Fig. 8 Multicylinder system
By simultaneous and parallel processing of plate making steps,
productivity of the plate making process is improved.

(3) Future outlook
Conventional photography is being replaced bydigital cameras, the printing process is being replacedby the digital system that is applicable to versatile
printing needs. The object of this development, which
is not limited to digital concept for printing data or
printing process control, is to realize an integrated
process of plate making and printing.
Accordingly, through technical development of reusable plate materials and development of a reusable
plate system realizing the plate recycling process, theconcept has been realized. Henceforth, continuous
efforts will be concentrated on development of a total
printing system that envisages efficiency and versatility of printing information including creation of
printing information and after-treatment of printedmaterials.

Mitsuru Tabuchi

Hiroaki Ikeda

Fuminori Furuyashiki

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 42 No. 2 (Apr. 2005)

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