Establishment of Water-based
C o a t i n g Te c h n o l o g y i n
Perfecting Printing for Short
Time Delivery
SHINICHI FUJIMOTO*1SHINYA KOBAYASHI*1
KAZUHIKO HAMAMOTO*1

HAJIME YAGI*1
KAZUTADA DEJIMA*1
MASAYUKI EDA*2

The mainstream in the sheet-fed perfecting press industry is for short time delivery, and sales of sheet-fed perfecting presses that enable printing on both-side surfaces simultaneously are increasing rapidly. However, a problem for short time delivery is ink drying. Both-side water-based coating is a technology that may solve this problem.
The establishment of this technology has enabled us to propose a printing method for short time delivery to ourcustomers who are considering establishing their technical superiority in an effort to survive in their industry andpave the way for further expansion of sales of sheet-fed perfecting presses.

The mainstream in the sheet-fed perfecting press industry is for short time delivery that enables prompt
delivery of printed matters, and sales of sheet-fed perfecting presses that permit simultaneous both-side
surface printing of books, magazines, catalogs, leaflets,
etc., are expanding rapidly. Mitsubishi Heavy Industries,Ltd. (MHI) mobilized its techniques to meet the market
needs, and in 2003 a sheet-fed perfecting press "Tandem Perfector" consisting of the world's first such uniquemachines was introduced to the market, realizing highquality both-side surface printing and receiving
consistently high evaluation from customers since its
introduction.
However, the greatest difficulty for short time delivery is ink drying. The both-side water-based coating is atechnology that may solve this problem. The establishment of this technology has enabled MHI to propose a
printing method for short time delivery to its customers
who are considering establishing their technical superiority for the survival of their industry using sheet-fed
perfecting presses, thus paving the way for further expansion of sales of sheet-fed perfecting presses.
This paper introduces MHI's leading edge both-sidewater-based coating technology.

unable to reduce further time, and the need could not beanswered for short time delivery that would enable theprinted products to be shipped on the same day the order was issued.
Meanwhile, there is the ultraviolet (UV) printing
method that may be able to realize short time delivery.
The greatest advantage of UV printing, which uses ink
that is totally different in composition from oil-based ink,
is that the ink used dries (cures) instantly as ultraviolet
radiation is irradiated on the printed surface. This makes
the drying process after both-side printing unnecessary.
In addition, the printed ink film is hard and excels inabrasion resistance, contributing to surface protection.
However, the introduction ratio of UV printing is stillaround 10% among companies using sheet-fed perfecting presses. The reasons why oil-based ink users ingeneral cannot decide to introduce the UV printing are
as follows:(1) UV dryer is expensive.
(2) UV ink is twice as expensive as oil-based ink.
(3) The materials necessary just for UV printing are allexpensive.
(4) Printing techniques for UV ink differ from those foroil-based ink and are difficult.
(5) Gloss of the print is inferior (approximately 30% lessthan that of oil-based ink printing).

2. Present printing process and related problems

3. Technologies for achieving short time delivery

Until now, one side surface printing at printing companies has needed for front face printing, drying, backface printing and drying. Oil-based ink used in both-side
surface printing requires 8 to 12 hours to dry so that aminimum of two days is necessary before starting post
press process (cutting, folding, etc.).
The introduction of the perfecting press has shortened the time for both-side printing and ink drying,enabling the post press process to be done on the following day. However, the conventional printing method wasAttention has been given to water-based coating as
an alternative method to UV printing. According to thismethod, a water-based coating is applied over undriedoil-based ink so that the ink drying process can be eliminated as the water-based ink dries fast. Water-based
coating is used throughout the world as a means to enhance gloss and protect print surface. This method could
be more acceptable to general users than UV printing.
The advantages of this method as compared with the UV
printing are as follows:

1. Introduction*1 Paper & Printing Machinery Division*2 Hiroshima Research & Development Center, Technical Headquarters

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 43 No. 3 (Sep. 2006)

1

Front surface drying unit

Front surface printing unit

Front surface coating unit

Back surface coating unit

Back surface drying unit

Back surface printing unit

Fig. 1 Both-sides water-based coating facility configuration(1) The cost of facilities for this method is about the same
as for UV printing.
(2) Running costs are lower.
(3) No special printing techniques are required.
(4) Gloss of the print can be improved (approximately40% improvement compared with oil-based print).
For the above reason, the techniques of water-based
coating for the perfecting press have been developed.
Facility-wise, a water-based coating unit and a drying unit (including drying device) are to be added to theFig. 1
perfecting press (Fig.
1).

that has roughened surface and is treated with non-adFig. 3
hesive coating (Fig.
3).
However, if the water-based coating over the backside print surface is not completely dried, thewater-based coating surface may be exfoliated when thepressure of the ceramic jacket is applied at time of front
surface printing, as shown by the enlarged sample photoFig. 4(Fig.
4). In the present development, the following measures were taken for machine and materials in order toimprove the on-machinery drying efficiency of the water-based coating:

4. Technical problems and solutions
4.1 Optimization of paper feeding in back surface
drying unit
The printed paper passing the first transfer cylinder
in the back surface drying unit has the previously applied water-based coating that is about to arrive at thedrying unit, so that undried coated surface is in contact
with the cylinder surface. Therefore, in order to preventthe printed surface from contamination and abrasion
damage, air is blown up from inside the cylinder while
the printed paper is locally supported by means of aspring. In this way, stable high-speed paper transfer ofFig. 2
up to 11 000 sheets per hour is achieved (Fig.
2).
4.2 Optimization of the drying system
With the perfecting press, the printed back-side surface is pressed against the impression cylinder. To
prevent the back-side surface print image from beingtransferred to the impression cylinder at this time, theimpression cylinder is provided with a ceramic jacket

Impression cylinder(provided withceramic jacket)

Transfercylinder

Fig. 3 Front surface printing unit
Back surface coating unit/Impression cylinder
Wound by spring

Dryingdevice

Sheet-floatingcylinder(1st transfercylinder)

1 : Water-based coat/ink interface exfoliation
2 : Cohesion destruction in ink film
3 : Exfoliation at ink/paper interface

Air blowing-outsurface

1
Verticallighting

2

3

Appearance of
sheet-floating cylinder
Fig. 2 Back surface drying unit

Fig. 4 Enlarged photo of sample print surfaceMitsubishi Heavy Industries, Ltd.
Technical Review Vol. 43 No. 3 (Sep. 2006)

2HighIR pass
: Plot: actually measured value

Temperature: Curve: calculated value

Low
Paper surface passage back surface drying unit

Aqueous coating

Time

Impression loadfrom ceramic jacket

Fig. 5 Temperature distribution of paper surface on machine: IR-A (relative strength): IR-C (relative strength): Water (absorptivity): IR-B (relative strength): IR-D (relative strength): Ink - yellow (absorptivity)

Approx. 100 m

IR lamp type (relative strength)
Water absorptivity HighGroove as enlarged

Anilox roller

Absorptivity

Relative strength

HighInk (yellow)
absorptivity

Plate cylinder
Chamber
PrintingplateLow

Low
Short
Wave-length ( m)PumpLong

Impression cylinder

Fig. 6 Relative strength of IR and ink/water absorptivities

VarnishFig. 7 Chamber coater supply system(1) Approach from the standpoint of machinery
The principle of drying of the water-based coating is
evaporation of moisture in the varnish, and it is therefore necessary to raise the temperature of the varnish
on the paper efficiently in order to accelerate moistureevaporation. In the present development, the optimallayout of the infrared ray (IR) lamp and hot air units
was determined following calculations and measurements of the temperature of the paper surface while it
Fig. 5was passing the back surface drying unit (Fig.
5).
The temperature of the paper surface rises as thewater-based coating and ink absorb IR. For this reason, an IR lamp that suits the IR absorption
wave-length domains of moisture and ink was selected
Fig. 6so as to improve the energy efficiency (Fig.
6).
(2) Approach from the standpoint of materials
Printing materials to suit both-side coating requirethat the water-based coating should have an appropriate balance between quick-drying performance andgloss (surface smoothness) and that the ink should
be of quick-setting performance by high-concentration
pigment type. Concerning these printing materials,
materials for exclusive use in both-side printing thatsatisfy the above-mentioned performances were developed in cooperation with Toyo Ink Mfg. Co., Ltd.
Regarding the ceramic jacket, surface roughness
configuration that would have effective non-adhesiveness on water-based coating was studied, and aceramic jacket that would be most suitable for bothside water-based coating was selected accordingly.
4.3 Optimization of water-based coating supplysystem
The chamber coater system was adopted for the water-based coating supply section. This method, whichtransfers the aqueous varnish filled in the grooves on
the anilox roller onto the printing cylinder, ensures stablesupply of water-based coating whose characteristics areFig. 7
easily changed by the external environment (Fig.
7).
Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 43 No. 3 (Sep. 2006)

3Table 1 Specifications

Gloss

High

: Prior print surface (w/aqueous coating): Posterior print surface (w/aqueous coating): Ink only

Low
0

Four-color ink coverage (%)

Max. printing speed (sheet/h)

11 000Applied ink coverage (%)

0 - 280Gloss

40 - 60
Front/back same level

Ink/aqueous varnish

Exclusive use materials
development
Joint development withToyo Ink Mfg. Co., Ltd.
Special-purpose jacket used

Ceramic jacket
Varnish supply method

Chamber coater system

HighFig. 8 Equalization of front and back surface print quality (gloss)

The introduction of both-sides water-based coating
enables printing companies to meet needs for short timedelivery, making it easier to procure job orders and improving business chances. It also reduces loss resulting
from failure of products by limiting in-machine print
damage through improvement of surface protection.
Especially in the United States and Europe, wherewater-based coating is widely used, demands for thistechnology are already high. It is therefore intended toincrease the overseas market share of MHI's printing
machines by introducing this newly developed type inthe shortest possible time.
In the future, it is intended to globalize usable materials and improve their performances. MHI is determined
to continue to introduce to the market more productsthat will meet its customers' needs.

Water-based coating thickness can be controlled by
the number of grooves on the anilox roller. Normally, theback-side printing surface receives impression pressure
from the ceramic jacket, so its gloss is seriously degraded
compared with the front-side surface. However, equalization of front surface gloss and back surface gloss wasaccomplished by changing the number of grooves on theanilox roller -- in other words, by changing the varnish
Fig. 8supply film thickness (Fig.
8).

5. Conclusion
This development work has established the both-sides
water-based coating technology to the specifications
Table 1
shown below (T1).

Shinichi Fujimoto

Hajime Yagi

Shinya Kobayashi

Kazutada Dejima

Kazuhiko Hamamoto

Masayuki Eda

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 43 No. 3 (Sep. 2006)

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