Development of Rapid Dry Photothermographic Materials with Water-base Emulsion Coating

Method Yasuhiro Yoshioka, Katsutoshi Yamane and Tomoyuki Ohzeki

Digital & Photo Imaging Materials Research Laboratories, Fuji Photo Film Co., Ltd. Minamiashigara-shi, Kanagawa / Japan

Abstract

The new system of the dry laser imager DRYPIX-7000 and the dry photothermographic imaging film DI-HL has been developed as a new generation of dry imaging system for health imaging. The system has the highest specifications, amazingly rapid output of first print (65 seconds), the highest throughput (180 sheets per hour for 14 x 17-in), and the shortest start up time (15 minutes from power off condition). These features were achieved by the combination of the excellent technologies introduced in the new imaging film and the laser imager.

In DI-HL, new high-activity heat-developer and new heat-development accelerator were introduced in order to realize rapid processing and high throughput. Quite new yellow dye forming tone control agent was employed for excellent image tone reproduction. Image stabilizer, high purity silver behenate and new SBR latex binder were designed for image keeping stability. And the film is produced with water-base emulsion coating method, so much friendly to environment.

In DRYPIX-7000 imaging apparatus, laser exposure and heat development are carried concurrently in order to realize high throughput.

Figure 1. Dry laser imager DRYPIX-7000 and photothermographic film DI-HL

Introduction

In recent years, digitalization of health imaging is proceeding rapidly by development and spread of heals imaging technologies such as computed tomography (CT), nuclear magnetic resonance imaging (MRI), computed radiography (CR). These digital images were printed out to laser imagers connected to the network system in the hospital. On the other hand, increasing in concern over the global environment, importance of dry laser imagers are increasing further. This system does not use any chemical solutions for processing and does not put out any waste and residue. In 1995 the first dry imager and films were introduced from Minnesota Mining and Manufacturing Co., but the film was produced with a large amount of organic solvent. In this background dry laser imager FM-DP L and film DI-AL were released in 1999 from Fuji Film Medical. Co., Ltd. The dry photothermographic film DI-AL is produced with water-base emulsion coating method. 1-3 This technology is much echo-friendly one that does not use a plenty of organic solvent in the manufacturing process.

Figure 2. Manufacturing processes of solvent-base and water-base coated photothermographic films

in Organic Solvent

Aqueous Dispersion Coating

Organic Solvent Coating

Dry up

Silver Salt

AgBr

Organic Materials

SBR Latex Binder

Prepared separately

Prepared together

Silver SaltAgBr

Mixing Coating

PVB resin

Coating

Organic materials exist homogeneously

in Water

in Water

Organic materials exist as solid dispersion

Protective Layer

Emulsion Layer

Solvent

OrganicMaterials

Film Support

Film Support

Protective Layer

Emulsion LayerSimple !

in Organic Solvent

Aqueous Dispersion Coating

Organic Solvent Coating

Dry up

Silver Salt

AgBr

Organic Materials

SBR Latex Binder

Prepared separately

Prepared together

Silver SaltAgBrSilver SaltAgBr

Mixing Coating

PVB resin

Coating

Organic materials exist homogeneously

in Water

in Water

Organic materials exist as solid dispersion

Protective Layer

Emulsion Layer

Solvent

OrganicMaterials

Film Support

Film Support

Protective Layer

Emulsion LayerSimple !

2004 International Symposium on Silver Halide Technology

28

FM-DP L system was highly regarded for high quality image, constancy of printing and easy operation, but recently demands on processing speed and image tone quality were increasing. Then we have developed the new system of the dry laser imager DRYPIX-7000 and the dry imaging film DI-HL. In this presentation we will talk about organic chemical compounds introduced in DI-HL mainly.

Image forming mechanism of photothermographic materials

The image forming mechanism of the photothermographic materials was shown in Fig.3.4

Figure 3. Image forming mechanism of photothermographic materials

First of all, latent images are formed on silver halide grains by laser exposure of the film. The film is heated about 120 ﾟ C, then silver behenate get mobility by phase transition. Silver ion is translated from silver behenate to phthalazine, and carried to the silver halide with latent image. Then silver ion is reduced to metal silver by heat-developer and silver filament is growing up there. Unexposed silver halide is not developed by the action of poly-halides anti fogging agent.

In the water-base coated photothermographic materials, rate determining step is the earlier period of the silver cluster growth. To realize rapid processing, it is important how to accelerate the reduction of silver ion at the earlier period without increasing fog and degradation of image keeping stability.

Technologies introduced in DI-HL

Development acceleration technologies, image-tone control technologies and image stabilizing technologies have been developed for the photothermographic film DI-HL. 1) Development acceleration technologies

We developed a new reducing agent for heat-developer which is o-bisphenol compound with tert-alkyl groups at the 2,2'-position. This compound has high activity, and is able to reduce over 6-equivalent silver ions. We also

developed quite new naphthol compound as a development accelerator. This compound works as a strong reducing agent at the earlier period of the development process, and then works as an electron transfer intermediate from bisphenol developer to silver ion. Adding about 3 mol% of the accelerator against heat-developer, developing speed is amazingly accelerated as shown in Fig.3..

Figure 3. Effect of development accelerator

Figure 4. Mechanism of development acceleration

2) Image-tone control technologies The color tone of the silver image depends on the size

of the developed silver particles. In the photothermographic materials with water-base emulsion coated method, we can control the size of silver particles by changing the Na+/ NH4

+ ratio. If Na+ is increased the silver particles decrease the size, and spectral absorption of blue light region increases and red light region decreases. If NH4

+ is increased the silver particles increase the size, and spectral absorption of blue light region decreases and red light region increases. We

・ ・・

Silver ion carrierPhthalazine

Silver ion sourceSilver behenate

Silver complex

Silver ion

Developero-Bisphenol

exposure

Photo CenserSilver halide

heatLatent image

DevelopedSilver

Silver filament growth

heatAnti fogging agent

Poly-halidesNo image

Heat solventPhthalic acid

・・ ・・・・

Silver ion carrierPhthalazine

Silver ion sourceSilver behenate

Silver complex

Silver ion

Developero-Bisphenol

exposure

Photo CenserSilver halide

heatLatent image

DevelopedSilver

Silver filament growth

heatAnti fogging agent

Poly-halidesNo image

Heat solventPhthalic acid

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

-0.5 0.0 0.5 1.0 1.5 2.0 2.5

－ｌｏｇＥ

Ｄvis

Accelerator×0.03 eq

Developer×1 eq

Accelerator×0.03 eq

effectDeveloper×1 eq

Opt

ical

den

sity

exposure → largesmall ←

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

-0.5 0.0 0.5 1.0 1.5 2.0 2.5

－ｌｏｇＥ

Ｄvis

Accelerator×0.03 eq

Developer×1 eq

Accelerator×0.03 eq

effectDeveloper×1 eq

Opt

ical

den

sity

exposure → largesmall ← exposure → largesmall ←

・ ・

AcceleratorActive Developer

②② electron mediatorelectron mediatorSilver image

①① reinforce latent imagereinforce latent image

O H

R R

R' O H

･OR R

R' O HO

R

R

R

R' O H

Ａｇ＋

Ａｇ Higher oxidantsＡｇ＋ Ａｇ＋

OH

O R

C O N HR

O

O R

C O NHR

･O H

R R

R' O H

･OR R

R' O H

O

R

R

R

R' O H

Ａｇ＋

Ａｇ

Ａｇ＋

Without Accelerator

With AcceleratorＡｇ＋

0Ag cluster growth → catalytic activity up Catalyze electron transfer → reaction speed up

120℃ 120℃

Select high-activity reducing agent

Introduce new developing accelerator

fast fast

slow

・・ ・・

AcceleratorActive Developer

②② electron mediatorelectron mediatorSilver image

①① reinforce latent imagereinforce latent image

O H

R R

R' O H

･OR R

R' O HO

R

R

R

R' O H

Ａｇ＋

Ａｇ Higher oxidantsＡｇ＋ Ａｇ＋

OH

O R

C O N HR

O

O R

C O NHR

･O H

R R

R' O H

･OR R

R' O H

O

R

R

R

R' O H

Ａｇ＋

Ａｇ

Ａｇ＋

Without Accelerator

With AcceleratorＡｇ＋

0Ag cluster growth → catalytic activity up Catalyze electron transfer → reaction speed up

120℃ 120℃

Select high-activity reducing agent

Introduce new developing accelerator

fast fast

slow

2004 International Symposium on Silver Halide Technology

29

can not increase both of the blue and the red absorption at once.

We found 2,2'-tert-alkyl-4,4'-methyl substituted o-bisphenol developer formed yellow dye during heat development at high density region. It reveals that two of one electron oxidized radicals are dimerized and oxidized to yellow dye. Furthermore we found p-bisphenol substituted with hindered alkyl groups at the 2,2',6,6'-position formed yellow dye at low density region. These compounds made us to control image tone as we like.

Figure 5. Yellow dye forming developer and tone controller

3) Image stabilizing technologies Usually to use high activity developer degenerates

image keeping stability. So we must develop the method to improve image keeping stability at the same time. We introduced three technologies in DI-HL, a new type of image stabilizer, high purity silver behenate, and improved SBR latex binder.

The image stabilizer is a triphenylphosphinoxide derivative, which makes the hydrogen-bonded complex with developer after heat-development, and thereby developer is inactivated. High purity silver behenate has a higher phase transition temperature and decrease silver ion supply in film keeping. The SBR latex is reduced the content of surfactant and inorganic salts as less as possible.

Figure 6. Image stabilizing technologies

Figure 7. Mechanism of phosphinoxide image stabilizer

Figure 8. Combination effect of image stabilizing technologies

DI-HL

Figure 9. Dark keeping stability of DI-HL and comparative organic solvent-base photothermographic materials

ComparativeFresh 1d 3d 7d

Fresh 1d 3d 7d

Dark keeping at 60℃

0

0.5

1

1.5

2

2.5

3

350 400 450 500 550 600 650 700 750 800

波長（ｎｍ）

吸光

度（ａｂｓ．）

0

0.5

1

1.5

2

2.5

3

350 400 450 500 550 600 650 700 750 800

波長（ｎｍ）

吸光度

（ａｂｓ．）

O H O H

C H 3C H3

R' O

R

O H

R

RR

O O H

R'

R'

O H R' O H

R

O

R

HO

R'

R

R

C H2HO O H C HHO O

Yellow color forming

Ａｇ＋

Ａｇ＋

DI-AL DI-HL

O O H

C H3C H3

R'･

D= 2.5

D = 1.5

D = min

Low density

High density

Absorption spectra

λ (nm) λ (nm)

abso

rptio

n

abso

rptio

n

0

0.5

1

1.5

2

2.5

3

350 400 450 500 550 600 650 700 750 800

波長（ｎｍ）

吸光

度（ａｂｓ．）

0

0.5

1

1.5

2

2.5

3

350 400 450 500 550 600 650 700 750 800

波長（ｎｍ）

吸光度

（ａｂｓ．）

O H O H

C H 3C H3

R' O

R

O H

R

RR

O O H

R'

R'

O H R' O H

R

O

R

HO

R'

R

R

C H2HO O H C HHO O

Yellow color forming

Ａｇ＋

Ａｇ＋

DI-AL DI-HL

O O H

C H3C H3

R'･

D= 2.5

D = 1.5

D = min

Low density

High density

Absorption spectra

λ (nm) λ (nm)

abso

rptio

n

abso

rptio

n

・

Light

Heat

・

Image stabilizer inactivation

High purity silver behenate Improved SBR latex binder

Developer

suppressionstabilization

FogOrganic

silver salt

Silver halide

・・

Light

Heat

・・

Image stabilizer inactivation

High purity silver behenate Improved SBR latex binder

Developer

suppressionstabilization

FogOrganic

silver salt

Silver halide

O H O

R'R'

RR

H

OP

R ''

RR

R

P

O

R

RR

OH OH

R

R'R'

R

R''

Complex

StabilizerDeveloper Hydrogenbond

Crystal structure

inactivemelting

Heat

Complexformation

Separate soliddispersion

Heat

O H O

R'R'

RR

H

OP

R ''

RR

R

P

O

R

RR

OH OH

R

R'R'

R

R''

Complex

StabilizerDeveloper Hydrogenbond

Crystal structure

inactivemelting

Heat

Complexformation

Separate soliddispersion

Heat

60℃-50%　：　0, 1, 3days

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d

Dmin

High purity silver behenate

Improved SBR

Image stabilizer

Silver behenate high purity high purity high purity high purity convensionalconvensionalconvensionalconvensional

SBR latex im proved convensional im proved convensional im proved convensional im proved convensional

Im age stabilizer with with without without with with without without

60℃-50%　：　0, 1, 3days

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d Fr 1d 3d

Dmin

High purity silver behenate

Improved SBR

Image stabilizer

Silver behenate high purity high purity high purity high purity convensionalconvensionalconvensionalconvensional

SBR latex im proved convensional im proved convensional im proved convensional im proved convensional

Im age stabilizer with with without without with with without without

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Combination of these technologies we can realize both of the developing ability and keeping stability.

Advancement in dry imager DRYPIX-7000

In order to shorten the processing time we change the inner layout of apparatus shown in Fig.10. In this layout the film transfer pass is very short and exposure part and developing part is placed closely. In this apparatus heat development begin from the top of the film sheet before the exposure does not finish the end of the sheet. The time table of the developing process is shown in Fig.11.

Figure 10. Internal structure of the dry imagers

Figure 11. Processing time table and laser-heater layout

Conclusion

We developed the system of dry laser imager DRYPIX-7000 and new photothermographic material DI-HL. Combination of the new imager and film, we can get high quality diagnosis image with high productivity. Table 1. System performance of dry imagers and films

References

1. T. Tsuzuki, A. Hatakeyama and K. Nakajima, Proc. ISIS'02 International Congress of Imaging Science 2002, Tokyo, pg.27

2. K. Yamane and S. Yamashita, Proc. ISIS'02 International Congress of Imaging Science 2002, Tokyo, pg.29

3. H. Tsuzuki, The Chem. Record, Vol.3,322-328(2004) 4. H, Maekawa, M. Yoshiokane, H. Fujiwara and I. Toya, J.

Imaging Sci. and Technol., 45, 365(2001)

Biography

Yasuhiro Yoshioka was born in 1955 in Tokyo Japan. In 1980 he was graduated from the graduated course of chemistry division of The University of Tokyo, and obtained a degree of Master of Science. In the same year, he joined Ashigara Research Laboratories of Fuji Photo Film Co., Ltd.

250 kg203 kgImager weight(kg)

0.78 m30.62 m3Imager volume(m3)

30 min15 minTime for rising from power off condition (minutes)

150 sec65 secTime for first print output(seconds)

130 sheets180 sheetsContinuous processing rate (14x17 inch sheets/hour)

FM-DP LDI-AL

DRYPIX-7000DI-HL

ImagerFilm

250 kg203 kgImager weight(kg)

0.78 m30.62 m3Imager volume(m3)

30 min15 minTime for rising from power off condition (minutes)

150 sec65 secTime for first print output(seconds)

130 sheets180 sheetsContinuous processing rate (14x17 inch sheets/hour)

FM-DP LDI-AL

DRYPIX-7000DI-HL

ImagerFilm

2004 International Symposium on Silver Halide Technology

31

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