Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

1

Comparative studies of gloss development in electrophotography and offset printing
Yoshihisa KITANO*， Toshiharu ENOMAE▲** and Akira ISOGAI***Fuji Xerox Co. Ltd., 2274 Hongo, Ebina-shi, Kanagawa 243-0494, Japan
E-mail: kitano.yoshihisa@fujixerox.co.jp**The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
E-mail: enomae@psl.fp.a.u-tokyo.ac.jp
E-mail: aisogai@mail.ecc.u-tokyo.ac.jp▲

IS&T Member

Abstract
The difference between the formation processes of the printed surface topography in offset
printing and electrophotography is clarified. Understanding the formation processes isimportant because the printed surface topography is closely related to the print gloss.
Furthermore, the formation process in offset printing is applied to electrophotography. The
experiments are carried out using matte-coated paper.
From the results, the key difference between the surface topography formation in offset
printing and electrophotography was found to lie in the different behaviors of the ink andtoner, respectively, on the paper surfaces. We, therefore, imitated the offset printing process
in electrophotography by maintaining a low toner viscosity so that the toner could flow on thepaper surface. This resulted in a printed surface topography that was more consistent withthe paper surface topography; subsequently, the printed surface gloss became moreconsistent with the paper gloss.
Keywords Electrophotography; Gloss; Matte-coated paper; Offset printing; Paper surface
topography, Printed surface topography.

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

2

INTRODUCTION
In recent years, many color printers possessing the qualities of high speed and high image
quality have been commercially introduced1–3. These printers allow easy and fast printing,and they can also adapt to the digitalization of the printing procedure easily. Due to thesefeatures, these printers are used for small volume print jobs in the printing market. However,the correlation between print gloss and paper gloss in electrophotographic products has
been known to be inferior to that in offset printing products4. In other words,
electrophotography produces high print gloss even on low-gloss matte-coated paper, which
results in a texture quite different from offset printing products and may yield an unnaturalimpression. It is desirable, therefore, that print gloss changes according to the paper gloss inelectrophotographic products, similar to offset printing products, so that the prints appear
more natural.
In offset printing, studies have been carried out mainly on the mechanism of gloss
development on high-gloss paper. For example, it has been shown that when ink istransferred to paper, topographical unevenness, called split patterns, forms on thedeposited ink surface5. Some of these split patterns persist on the printed surface even after
the ink dries, and this is known to affect the print gloss. Furthermore, changing the ink
vehicle absorbency of the coated paper by altering its surface and internal structure has also
been found to affect the print gloss6. Another study showed through cross-sectional
observations of printed samples that the amount of absorbed ink affects the formation of theprinted surface topography7. In these studies, however, there has been little clarification
about the mechanism of gloss development on low-gloss paper.
With regard to electrophotography, several studies have attempted to develop fusing
technologies that provide high print gloss8. Pettersson and Fogden clarified that the amountof toner that is transferred has a significant influence on the printed surface topography9. Ide
and Kurimoto reported that uniformity in print gloss was obtained by using a clear toner10.
Kurimoto and Watanabe demonstrated through cross-sectional observations how the height
and uniformity of the toner layer are different between the outputs of electrophotography
and offset printing11. Very few attempts have been made, however, to study how print gloss
changes according to paper gloss in electrophotography.
This study was intended to clarify gloss development mechanisms in offset printing and how
these mechanisms are different from those in electrophotography. In our previous studies,
we showed how paper and printed surface topographies differ in offset printing andelectrophotography. In one of these studies, Pearson’s correlation coefficient was used to
examine the relationship between the surface topographies of a coated paper surface andits printed surface at the same location4. Four kinds of coated papers possessing different
glosses were used. In offset printing, the correlation coefficient was high for every kind ofcoated paper except the cast-coated paper. In electrophotography, however, the correlation

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

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coefficient was low for all the four kinds of papers. This result implies that in order to change
the print gloss in accordance with the paper gloss, the printed surface topography should
follow the paper surface topography. The present work examines the formation process ofprinted surface topography in offset printing and electrophotography and the reason for thegloss development being different between these two printing technologies. We also
attempted to apply the formation process of the printed surface topography in offset printing
to electrophotography. This experiment was carried out using matte-coated paper, whose
surface topography was expected to have a significant influence on the formation of theprinted surface topography.

EXPERIMENTAL DETAILS
Printing Trials
Offset printing was performed using the universal printability tester （ KRK, Tokyo,
MPT6000）, and dampening water was not applied. The printing speed was 2.8 m/s and theprinting pressure was 11.8 kN/m. The ink kneading temperature was 25 °C and the ambient
temperature was 20 °C–25 °C. The ink used in the printing trials was cyan ink (Toyo Ink
Manufacturing, Tokyo, TK high-unity MZ). These printing conditions and the ink type werebased on those employed in common-sheet-fed offset printing presses. The amount of ink
supplied to the kneader was 0.1 mL, which was the volume required to reproduce Japan
Color 200112 standards. Under this condition, 1.2 g/m2 of ink was transferred to thematte-coated paper to cover the entire surface, and the thickness of the ink layer after drying
was approximately 0.8 µm when printed on cast-coated paper.
Electrophotographical printing was performed using a color laser printer (Fuji Xerox, Tokyo,
DC1250). This printer has a hot roll fusing system containing two metal rolls covered withsilicon rubber and heated by halogen lamps inside the rolls. As the standard printing
condition, the printing speed was set to 130 mm/s; the printing load, 1275 N; and the printing
temperature, 160 °C. The cyan toner was used in the printing trials; its amount was adjusted
so that the average thickness of the toner layer was approximately 4.0 µm when printed on
cast-coated paper.
The commercial matte-coated paper (Oji Paper, Tokyo, OK matte coat) of a basis weight of
127.5 g/m2 was used. In the experiment for evaluating the paper surface topography and theink distribution on the printed surface, the ink layer was solidified using liquid nitrogen atgiven intervals. The samples were then dried for two days in a freeze dryer (Tokyo Rikakikai,Tokyo, EYELA FDU-830).
In the experiment for examining the relationship between the fusing parameters and theprinted surface topography in electrophotography, the printing load and temperature wereconsidered to be variable fusing parameters. One of the two parameters was changed at a

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

4

time, while the other parameter was maintained at the standard level mentioned above.
Printed samples were obtained for three levels of every parameter. The values employed
were as follows: printing loads of 981, 1275 (standard level), and 1569 N and printing
temperatures of 150 °C, 160 °C (standard level), and 170 °C.
In the experiment to study the formation process of printed surface topography in offset
printing and to apply it in electrophotography, printed samples were heated in an oven at
160 °C for 30 s so that the toner on the paper recovered its viscosity. The fusing parameters
were set to a printing load of 981 N and a printing temperature of 150 °C.
Printed Sample Characterization
Three-dimensional profiles of the paper surface and its printed surface at the same location
were examined using a laser microscope (Keyence, Osaka, VK-8500). The sampling pitchin the height direction was 0.02 µm. The specular gloss of the paper and printed samples at
60° was measured using the gloss meter (Nippon Denshoku, Tokyo, VG2000).
Immediately after printing, the printed surface was observed using a laser microscope(Keyence, Osaka, VF-7500). The analog image output from the laser microscope wastransferred via a digital video camera into a computer so that the topographical changes in
the printed surface could be observed. From these images, the reflected light distribution
was calculated using image processing software (Media Cybernetics, Washington DC,
Image-Pro Plus).
For the examination of the relationship between paper surface topography and lightness
images of the prints, the paper surface topography and color images of the prints wereobserved using a laser microscope (Keyence, Osaka, VK-8500). The intensity of illumination
was set to be constant for all the color images available as RGB data. These data wereassumed to be sRGB and converted to L*a*b* images.
For the quantification of the similarity between the paper and printed surface topographies,
Pearson’s correlation coefficients were calculated from the data of five sets of locations
using the image processing software. The results were averaged for each kind of sample.
To determine the extent to which the paper surface topography was maintained after
printing, Fourier transform was carried out for the topographical images of the specified
areas of the paper surface and for those of the corresponding areas of the printed surface of
the identical paper. Using the radially averaged power spectrum (RAPS) 13, the gain definedby the following transfer function (Eq. (1)) was calculated.

Gain(dB) = 20 log(

RAPS(Printed surface topography))
RAPS(Paper surface topography)(1)Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

5

If the gain is 0 dB, the surface topographies before and after printing are completely
identical. The gains larger and smaller than 0 dB imply that the printed surfaces are rougherand smoother than the paper surfaces, respectively. The gain was calculated for fivelocations on the paper and printed surfaces.

RESULTS AND DISCUSSION
Surface Topography and Initial Gloss Dynamics for Matte-coated Paper
Topographical images of the paper and printed surfaces for the standard printing condition
are shown in Figure 1. In offset printing, the paper surface topography has a significant
influence on the printed surface topography. In electrophotography, the large-scaleroughness is preserved on the printed surface. The small-scale roughness, however, ishidden by the toner, causing the printed surface to be considerably smoother than the paper
surface.
Figure 2 shows the gloss dynamics, that is, changes in the print gloss of the matte-coatedpaper immediately after printing, in both electrophotography and offset printing. In offset
printing, the gloss changed with time; it increased for approximately 10 s immediately after
printing and subsequently decreased for several minutes. In other words, the printed surface
topography continued to change during the entire period of time. In electrophotography, thegloss did not change with time. This result shows that in offset printing, the printed surface
topography develops during some period of time after the ink has been transferred onto thepaper. In electrophotography, on the other hand, the printed surface topography isestablished during the fusing procedure, that is, in the fusing nip.
Mechanisms of Gloss Development in Offset Printing
In order to clarify the mechanism of gloss development in offset printing, the changes insurface topography during increases and decreases in the gloss were examined14–15.
Printed Surface Topography during Increase in Print Gloss
Using the laser microscope, the printed surface topography was observed immediately after
the ink transfer. As shown in Figure 3, many white spots were visible. This observation
indicates that the printed surface was very uneven. This uneven topography was formed by
splits in the ink layer occurring at the nip exit.
Figure 4 shows how the white spot area ratio (the ratio of the total area occupied by whitespots to the total surface area) and the gloss changed with time. The white spot area ratio
decreased for the initial several tens of seconds, reflecting the decrease in the topographicalunevenness. After this process, the white spot area ratio barely changed. The print gloss, on
the other hand, increased for the first several tens of seconds and then reached an

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

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equilibrium state; subsequently, it decreased for several hundreds of seconds. In otherwords, the time during which the white spot area ratio decreased was consistent with thatduring which the print gloss increased. This result suggests that the increase in print gloss
resulted from the decrease in the unevenness of the printed surface topography.
Printed Surface Topography during Decrease in Print Gloss
In order to examine the process of decrease in the print gloss, the microdynamics of theprinted surface topography after the ink transfer was observed using the laser microscope.
The light source was positioned so that the direction of light was as close and parallel as
possible to the surface plane. This positioning reduced the light incident on the ink layer.
The illumination intensity was set so that a sufficient amount of light was reflected from thesurface for recording the details of the topography. The result of these observations isshown in Figure 5. The reflected light profiles were measured along the direction ofillumination. Therefore, the reflected light profiles represented the printed surface
topography to some extent16. By closely studying the profiles, the roughness pattern wasobserved to repeat regularly with a wavelength of several micrometers on the printed
surface.
The paper surface and printed surface were observed using SEM, as shown in Figure 6. Insome areas of the printed surface, coating pigments of the paper surface were exposed.
This result suggests that the pigment coating layer exposed on the printed surface is likely tobe observed as high-frequency roughness in the reflected light profile analysis. Morespecifically, the roughness hidden by the ink layer was revealed as the ink film became
thinner with the penetration of the ink vehicle.
Relationship between Printed Surface Topography and Ink Distribution
On the other hand, the paper roughness may cause an ink flow that can lead to uneven ink
distribution. It is known that the thickness of an ink layer correlates well with the density ofcolor according to the Kubleka-Munk theory. In other words, the concave areas with more
ink are expected to appear densely colored, and the convex areas with less ink are
expected to appear lighter. With these assumptions, the time change of the relationshipbetween the paper surface topography and the luminosity distribution on the printed surface
was examined. The correlation coefficient between the paper surface topography and thelightness images on the printed surface was calculated, and a quantitative analysis was
carried out. For one sheet, eight locations were chosen for the correlation coefficient
calculation because the correlation level was expected to vary depending on the choice ofthe location. The average and variance of the correlation coefficients for the sheet were
calculated and compared between the samples, and the results are shown in Figure 7.
Although no correlation was apparent between the paper surface topography and theluminosity distribution immediately after the ink transfer, the correlation coefficient increased
with time. This result indicates that ink flows according to the paper surface topography andKitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

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concentrates in the concave areas of the paper surface, thus making those areas appear
dark. The driving force for wetting the surfaces of the concave areas is considered to be thesurface tension of the ink and not the gravity.
Formation Process of Printed Surface Topography in Offset Printing
From the above results, it is concluded that in offset printing on matte-coated paper, gloss isdeveloped along with the formation of the printed surface topography through the processes
described below. When ink is transferred to the paper, topographical unevenness of theprinted surface results from inhomogeneous ink layer splits. This unevenness disappears
during the initial several tens of seconds. Concurrently, the ink flows along the paper surface,
and the printed surface becomes smoother than the paper surface.
For the next several hundred seconds, the ink vehicle penetrates the paper and causes theshape of the printed surface to gradually become increasingly similar to that of the paper
surface. In other words, the roughness hidden by the ink layer so far becomes apparent andprominent as a result of the ink vehicle penetration.
Mechanisms of Gloss Development in Electrophotography
In order to clarify the mechanism of gloss development in electrophotography, therelationship between the paper and the printed surface topographies was examined byvarying the fusing parameters, namely, the load and temperature of the nip17.
Relationship between Nip Load and Printed Surface Topography
The paper surface topography and printed surface topography resulting from different nip
loads were observed with the laser microscope, and the correlation coefficients between thepaper and the printed surface topographical images were calculated; these correlation
coefficients are shown in Figure 8. The correlation coefficient shows a tendency to decrease
with the nip load. The relationship between the nip load and the print gloss is shown in
Figure 8. The print gloss, on the other hand, shows a tendency to increase with a decreasein the nip load. The above result shows that the level of influence of the paper surface
topography on the printed surface topography changes with the nip load.
Relationship between Nip Temperature and Printed Surface Topography
The paper surface topography and printed surface topography resulting from different nip
temperatures were observed with the laser microscope, and the correlation coefficients
between the paper and the printed surface topographical images were calculated; thesecoefficients are shown in Figure 9. The correlation coefficient between the paper and theprinted surface topographical images increases with a decrease in the nip temperature. The
relationship between the nip temperature and the print gloss is shown in Figure 9. As the nip
temperature decreases, the small-scale roughness becomes apparent on the printed
surface and the gloss decreases. The above result shows that the level of influence of theKitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

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paper surface topography on the printed surface topography changes with the nip
temperature.
Relationship between Paper Surface Topography and Unfused Surface Topography
It was shown through the result for all the parameter values, that the lesser the fusing
energy applied to the toner, the more was the influence of the paper surface topography on
the printed surface topography. This implies that the unfused surface topography follows thepaper surface topography to a certain extent, and the printed surface topography becomesdifferent from the paper surface topography when heat and pressure are applied. With thisassumption, the relationship between the paper surface topography and the unfusedsurface topography was examined.
The paper surface topography, unfused surface topography, and printed surface topography
were observed using the laser microscope, as shown in Figure 10. The unfused surface wascovered with toner particles larger than those covering the fused surface. Two-dimensional
Fourier transform was carried out for the images of these surfaces. Using RAPS, it was
examined if there were any peak frequencies other than those corresponding to the tonerparticle size. In this observation, the transform equation was not used because the tonerparticle diameter on the unfused/printed surface was homogeneous and the gain would
have an intense peak of the diameter and apparently interfere with the output (the dividendof the transfer function occupied by the unfused/printed surface topography).
The result of the frequency analysis is shown in Figure 11, and the peak frequencies of theimage of each surface are presented in Table 1. As this result indicates, there are no
similarities in the peak frequencies in the high-frequency range. This is because it is difficult
to reproduce a paper surface roughness smaller than the toner diameter on unfused/printed
surfaces. In the low-frequency region, however, the paper and unfused surfaces have someconsistent peak frequencies, whereas no consistent frequencies are observed between thepaper and the printed surfaces.
This result confirms our hypothesis by suggesting that the influence of the paper surface ismaintained, to a certain extent, on the unfused surface topography; the printed surface
topography becomes different from the paper surface topography when heat and pressure
are applied.
Formation Process of Printed Surface Topography in Electrophotography
From the above results, it is concluded that in electrophotography using matte-coated paper,
the printed surface topography is formed through the processes described below.
Before the toner on the surface is fused, the low-frequency roughness, that is, roughness
greater than the size of the toner particles distributed over the unfused surface, ischaracteristically similar to that of the paper surface. The pressure and heat applied to thetoner result in a toner layer shape that is different from that of the paper surface topography

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

9through processes such as coalescence and flowing. The degree of change in the toner
shape is dependent on the amount of applied heat energy and the viscosity of the melted
toner. Through this process, the printed surface topography becomes smoother than thepaper surface topography.
Application of Formation Process of Printed Surface Topography to Offset Printing inElectrophotography
Formation Process of Printed Surface Topography
The above results indicate that in offset printing, the printed surface topography follows thepaper surface topography through the following two steps.
Step 1: Smoothing out the topographical unevenness of the printed surface caused by ink
layer splits immediately after printing.
Step 2: Inducing ink flow along the paper surface and causing the ink vehicle to penetrate
the paper.
Through these two steps, the printed surface topography is obtained; thus, the printed
surface topography is modestly influenced by ink and significantly influenced by the paper
surface topography.
It was assumed that the following steps would enable such printed surface topographies to
be available in electrophotography by applying the formation mechanisms of the printed
surface topography in offset printing. First, a low fuser nip temperature and a low load wereapplied to reduce the excess smoothing of the toner while maintaining the influence of thepaper surface topography. Second, the toner viscosity was kept low to allow the printed
surface topography to follow the paper surface topography. Furthermore, one apparent
difference between the printed surface topography in the offset printing and theelectrophotography outputs pertains to the thickness of the ink/toner layer11. Therefore, theamount of toner was adjusted so that the thickness of the toner layer was approximately 2.0µm on cast-coated paper.
Printed Surface Topography Resulting from Imitated Offset Printing Mechanisms
Using a laser microscope, the topography of the paper surface as well as the topography ofthe printed surface resulting from imitated the offset printing mechanisms described earlier
was observed. The results are shown in Figure 12.
Table 2 shows the correlation coefficient between the paper and the printed surface
topographical images with 60° print gloss. The tran sfer function that is calculated when thepaper and printed surface topographies are applied as the input and output, respectively, isshown in Figure 13. This result indicates that when the formation process responsible for thesurface topography in offset printing is studied and applied to electrophotography, theKitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

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correlation coefficient increases, print gloss decreases, and gain of the transfer function
approaches zero. In other words, the surface topography and print gloss become moreconsistent with the original paper surface topography.

CONCLUSION
In this research, the difference between the formation processes of printed surface
topography in offset printing and electrophotography was clarified using matte-coatedpaper.
In offset printing, the formation of printed surface topography occurs through the following
processes. The ink is transferred to the paper, and the topographical unevenness of theprinted surface results from ink layer splits. This unevenness is smoothed out during theinitial several tens of seconds. Furthermore, the ink flows along the paper surface, and theprinted surface becomes smoother than the paper surface. For the next several hundreds of
seconds, the ink vehicle penetrates the paper and causes the printed surface to gradually
become increasingly similar to the paper surface. In other words, the roughness initiallyhidden by the ink layer becomes apparent as a result of the ink vehicle penetration.
In electrophotography, the formation of printed surface topography takes place through thefollowing processes. Before the toner on the surface is fused, low-frequency roughness, thatis, roughness greater than the size of the toner particles distributed over the unfused surface,is characteristically similar to that of the paper surface. The pressure and heat applied to thetoner provide the toner layer with a shape different from that of the paper surface
topography through processes such as coalescence and flow. The change in the toner
shape is dependent on the applied heat energy and the viscosity of the melted toner.
The formation process of the printed surface topography in offset printing was studied andapplied to electrophotography. It was found that by this application, the printed surface
topography became more consistent with the paper surface topography. The results of thisresearch, therefore, have opened the door to a new technology for controlling a print gloss
matching the paper gloss.

References
1.

J.

Takagi, On-demand full color digital xerography printing system—Color DocuTech

60, Journal of the imaging society of Japan 40, 145 (2001).
2.

T. Shibutani, Single path duplex electrophotographic printer, Journal of the imaging

society of Japan 40, 150 (2001).
3.

M. Anzai, Overview on plateless digital printing methods, Journal of the imaging societyof Japan 40, 140 (2001).

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

4.

11

Y. Kitano, T. Enomae and A. Isogai, Analysis of printed surface topography inelectrophotograpy and offset printing, Journal of the imaging society of Japan 44, 450(2005).
5.

T. Enomae, M. Teramoto, F. Onabe, S. Hayano, H. Naito, K. Takano and K. Kamada,“Mechanisms of print gloss development,” International Printing and Graphic Arts
Conference (Svannah, GA, USA, 2001) pp. 1–8.
6.

Y. Arai and K. Nojima, “Coating structure of cast coated paper for obtaining high print

gloss,” Proceedings of the 64th Pulp and Paper Research Conference (TAPPI, Japan,1997), pp. 47–55.
7.

H. Uchimura, Y. Ozaki, S. Maruyama and A. Sawatari, Observation of the printing ink

transferred and penetrated into the paper, Journal of printing science and technology 39, 48(2002).
8.

J. C. Briggs, J. Cavanaugh, M-K. Tse and D. A. Telep, “The effect of fusing on gloss inelectrophotography,” Proc. IS&T’s NIP14 (IS&T, Springfield, VA, 1998) pp.456-461.
9.

T. Pettersson and A. Fogden, Leveling during toner fusing: Effects of surface

roughness and gloss of printed paper, Journal of imaging science and technology 50, 202(2006).
10.

O. Ide and M. Kurimoto, Image quality improvement with surface structure modificationin xerography, Journal of the imaging society of Japan 38, 103 (1999).
11.

M. Kurimoto and F. Watanabe, Cross-sectional observation of color hardcopy images,

Journal of the imaging society of Japan 35, 131 (1996).
12.

M. Kaji, S. Otake and Y. Azuma, Colorimetric Characteristics of Process Color Prints

Produced Under the Japan Color Conditions: Conversion Trials from L*a*b* Values to CMY
Dot Percent Values Recent Progress in Color Management and Communications (IS&T,
Springfield, VA 1998) pp. 62–67.
13.

R. Ulichney, Digital Halftoning (MIT Press, Cambridge, MA, 1988).

14.

Y. Kitano, T. Enomae and A. Isogai, Mechanisms of gloss development withmatte-coated paper in offset printing, Journal of printing science and technology 42, 105(2005).
15.

Y. Kitano, T. Enomae and A. Isogai, Mechanisms of gloss development withmatte-coated paper in offset printing (2) Post-printing micro-dynamics of ink film, Journal of
printing science and technology 43, 346 (2006).
16.

Y. Osawa, Image Processing (CG-ARTS, Tokyo, 1997).

17.

Y. Kitano, T. Enomae and A. Isogai, Mechanisms of gloss development withmatte-coated paper in electrophotography, Journal of the imaging society of Japan 45, 504(2006).

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

100 µm(a) Paper surface(b) Printed surface

12

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

13(c) Paper surface(d) Printed surface

Fig.1 Topographical images of paper surface and printed surface for the standard printing
condition taken during offset printing (a and b) and electrophotography (c and d)
on a height scale of 10 µm and assigned to 8-bit gray levels.

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

60

60° Print gloss

50

Electrophotography

40
30
Offset printing

20
10
0

100
200
Elapsed time after printing (s)300

Fig.2 Dynamic print gloss for matte-coated paper.

14

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

500 µm

Fig.3 Printed surface topography recorded immediately after ink transfer.

15

10

25

8

23
Print gloss

6

21

4

19
White spot area

20Print gloss

White spot area (%)

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

17
15

0

20
40
60
80
Elapsed time after printing (s)Fig.4 Dynamic print gloss and change in white spot area for matte-coated paper.

16

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

80

Lightness

70
60
50
40
30
0

100
200
Position (μm)

300

0

100
200
Position (μm)300(a) 30 s

80

Lightness

70
60
50
40
30

(b) 180 s
Fig.5 Profiles of ink density 30 s (a) and 180 s (b) after printing.

17

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

5 µm(a) Paper surface(b) Printed surface
Fig.6 Scanning electron microphotographs of paper (a) and printed (b) surfaces.

18

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

Correlation coefficient

0.5
0.4
0.3
0.2
0.1
0
0

100
200
300
Elapsed time after printing (s)400

Fig.7 Change in correlation coefficient between images of paper surface profileand distribution of ink lightness.

19

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

1

100

0.8

80

0.6

60

0.4

40

Correlation
coefficient

0.2

20

0

0
981

1275
Load (N)Fig.8 Effect of nip load.

1569

Print gloss

Correlation coefficient

Print gloss

20

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

100

Correlation coefficientFig.9 Effect of load temperature.
Print gloss
0.8

80

0.6

60

0.4

40

0.2

Correlation
coefficient

0

20
0

150
160
170
Temperature (℃)

Print gloss

1

21

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

100 µm(a) Paper surface(b) Unfused surface

22

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

23(c) Printed surface
Fig.10 Topographic images of paper, unfused, and printed surfaces on a height scale of 20
μm assigned to 8-bit gray levels.

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

Radialy averaged power

100.000
10.000Unfused surface
1.000
0.100

Paper surface

0.010

Print surface

0.001
0

50
100
150
Frequency (1/mm)

200

Fig.11 Frequency characteristics of surface topography.

24

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

25

100 µm(a) Paper surface(b) Printed surface
Fig.12 Topographical images of paper surface and printed surface formed inelectrophotography following offset printing mechanisms on a height scale of 10 μm andassigned to 8-bit gray levels.

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

50Offset printing

Gain (dB)

-5
-10
-15

Offset-likeelectrophotography

-20
-25

Generalelectrophotography

-30
-35
-40
1

10

100

Frequency (1/mm)

Fig.13 Comparison of transfer functions.

1000

26

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

Table 1 Peak frequency of surface topography.
Paper

UnfusedPrintedsuface (1/mm)

surface (1/mm)

surface (1/mm)

13.5

13.5

26.9

26.9
40.4

60.6

40.4

60.6
67.3
80.7

87.5

87.5

107.7

107.7

121.2
134.6
141.3

141.3

161.5

161.5

148.1
168.2
188.4
195.2

27

Kitano, Y., Isogai, A., Enomae, T., "Comparative Studies of Gloss Development in Electrophotography and Offset Printing",
J Imaging Science Technology, 52(1), 10504-1-10504-10(2008).

28

Table 2 Comparison of print gloss and correlation coefficients between paper and printed
surface topography.

Offset printing

General

Offset-likeelectrophotographyelectrophotography

Print gloss

19.1

51.3

44.2

Correlation

0.88

0.66

0.78

coefficient