Note: Descriptions are shown in the official language in which they were submitted.
~.2~;ZZ
INFORMATION CARRIER AND PROCESS
FOR ITS MANUFACTU~
BACKGROUND OF THE INVENTION
The present invention relates to an infor-
mation earrier eomprising a reeording layer ap-
plied to a support, and to a proeess for its
manufaeture.
- The prior art teaehes produetion o~ pro-
jeetion images with intensity-modulated light by
light-seattering.
In the case of vesicular films, light is
seattered by tiny bubbles ~vesicles) formed in
softenable layers by the eombined action of light
and heat upon aromatie diazo eompounds. Vesieular
films are in use and yield images of very high
contrast in conventional projectors. It is not
possible, however, to produce metal matrices from
a vesieular film and to duplicate the image by
embossing with the aid of sueh metal matrices.
z
In the case of frost imagesinthermoplastic
materials, light is scattered by irregular surface
deformations formed in the photoconductive thermo~
plastic layers by electrostatic charging~ image-
wise exposure, and heating.
Frost images have not been known to be
used in practice, which is probably due to the
fact t~at their contrast is not sufficient for
conventional projectorsO
As a consequence of the expansion of
microfilm techniquest especially of micropublish-
ing, i.e. the publication of new and hitherto
unpublished information in the form of micro-
copies for sale and for distribution to the public
as by a publishing house, modern recording sys-
tems are not only required to have certain sensi-
tometric properties, but it is also desired that
the master copies should lend themselves readily
to duplication, so that large numbers of copies
can be produced from them. For this purpose,
embossing techniques are preferred, where struc-
tured surfaces carrying information are transferred
onto an embossable medium by pressure.
There is a demand for easy-to-handle infor-
mation carriers on which the information is re-
corded ln the form of surface structures which
may be reproduced by embossing and can be read
out by conventional projectors.
~.2~
Description of the Prior Art
Images with grating-like screening may be
produced by the ZOD ~zero order diffraction) tech-
nique described in the journal "Laser und Opto-
Elektroni]c", No. 3/1976, pages 16 and 17. Three
nickel matrices are produced from three relief
images which correspond, for example, to three
primary-color grating patterns in three photore-
sist layers r and colorless thermoplastic films
of f for example, polyvinyl chloride are embossed
with these matrices. The three films are super-
imposed mechanically, and on projection with
conventional projectors, colored projection images
are oktained from the colorless relief images.
The grating-shaped screening is effected with re-
lief gratings of rectangular cross-section, the
grating periods bein~ approximately 1.5 ~m. The
grating-li~e screening is periodical, both with
respect to the grating distance, i.e. the density
of the structures, and the grating depth for a
certain color, i.e. the amplitude of the informa-
tion. ~or each color separation, in magénta,
~ellow and cyan, a separate nickel matrix with
different relief depths is made, from which
separate embossed images are produced. The relief
depths differ, the relief depth being the greatest
for the cyan separation and the smallest for the
yellow separation. These color separation images
are screened. The embossed images are superimposed
to form a three-layered relief image from which
colored images can be projected. The technique
described yields very bright color images with
high resolution. The relief images can be dupli-
cated relatively cheaply and rapidly by embossing.
A disadvantage which has hindered the intro-
duction of this technique is the expensive produc-
tion process requiring three completely separate
operations for producing the individual embossed
relief images corresponding to the color separa-
tions. A further disadvantage is the necessity
for putting together in register the three separate
relief~images to form the duplicate image required
for the colored projection.
If it is desired that the projection image
produced by the ZOD technique include, among
other colors, the color blac~, this color is pro-
duced by the mechanical superposition of three
films corresponding to the color separations for
magenta, yellow and cyan. If only a black-and-
white image is to be produced, two sinusoidal
relief gratings of exactly predetermined relief
depth are placed cross-wise upon each other in
the black areas of the image. High precision is
2Q required to produce the gratings.
U.S. Patent Nos. 3,615,476 and 3,~15,486
disclose processes for the recording of informa-
tion in polymers or polymer systems which can be
- photo-chemically hardened. A reproduction of an
electromagnetio image in the form of a shadow-
image, which is either directly visible or may
be made visible by light, is obtained by subject-
ing the exposed recording layer to a treatment of
heat and/or vapor. This treatment results in a
softening and swelling of the recording layer in
the exposed areas without removing any o~ it.
After this treatment, the exposed areas are dis-
tinctl~ higher than the unexposed areas and dis-
play micro deformations. ~hen viewed from above,
the deformations are directly visible due to light
~.2~
scatteringO If the recording layer, which may be
either self-supporting or disposed on a support,
is transilluminated with light, the exposecl areas
become ~isihle as a shadow image due to their
light-scattering effect.
SUMM~RY OP T~-IE lNVENTION
It is the object of the present invention to provide an information
carrier of simple structure which, upon projection, yields black-and-white
images representing a positive or negative projection image of the original.
This object is achieved in that the recording layer contains in
selected areas of its surface certain structures, image-wise arranged and
statistically distributed, which scatter the light irradiated during projection
of the information carrier and whose thickness is reduced as compared with
the original thickness of the recording layer.
The scattered-light technique has the advantage of making it possible,
simply by appropriately dosing the exposure energy, to produce structures
in the photoresist layer which yield either a positive or a negative projection
image of a given original.
Stated more specifically, the present invention provides, according
to a first aspect, an information carrier comprising an exposed and developed
relief image on a recording layer, for example a photoresist layer, disposed
on a support wherein said exposed and developed relief image comprises, in
selected areas of the surface of the recording layer information-wise shaped
statistically distributed structures of light-scattering centers of graded
densities, said structures being irregularly distributed with regard to their
mutual distances and depths, said light-scattering centers scattering the
light irradiated for projection of the information carrier thereby forming a
grey/white projected image, said structures having a thickness which is reduced
as compared with the thickness of the recording layer prior to exposure and
development of the relief imageO
According to another aspect, the invention provides a process for
the manufacture of an information carrier as claimed in claim 1 comprising an
exposed and developed relief image on a recording layer, for example a photo-
--6--
resist layer, disposed on a support, comprising the step of e~posing thesurface of said recordlng layer through a scattering image transparency with
graded densities of scattering centers ~o obtain in selected areas of the
surface, :information-wise shapedl statistically distributed structures, sai,d
structures being irregularly distributed with regard to their mutual distances
and their depths, and the step of developing the recording layer with an
alkaline medium to form out said structures.
'~J~ 6a-
~.2~
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention will be
explained in detail by reference to the attached
drawings:
In the drawings,
Figure 1 shows, in section, a diagrammatic
arrang~ment for exposing an information carrier
through an original,
Figure 2 shows, in section, a diagrammatic
arrangement for exposing another information
carrier through an original,
Figure 3 shows an information carrier
comprising light scattering and diffracting struc-
tures,
Figure 4 shows a color wedge comprising
scattering centers of graded density distributed
over the length of the wedge,
Figures 5 and 6 show the relationship be-
tween the density of the projection image and the
density of the original,
Figure 7 shows an arrangement for producing
light-scattering structures in the photoresist
- layer, and
Figure 8 shows a further arrangement for
producing light-scattering surface structures
in a pnotoresist layer.
DETAILED DESCRIPTION OF THE PREFERRED EMsoDIMENTs
For the production of the scattering struc-
tures, photoresist layers are used, high-resolu-
tion photoresistlayers comprising o quinone dia-
zides being preferred in view of the small size
of the scattering centers. The pho~oresist layers
should have a thickness of at least 2 ~m~
The simplest method, which is therefore pre-
ferred in practice, is by contact exposure under
an original comprising a black-image separation
film under conditions which will be specified
hereinafter.
Figure 1 is a diagrammatic representation,
in section, oE an arrangement for exposing an
information carrier 1 through a master copy 6
of the type described. A medium section of the
master copy 6 is covered by an alpha-numerical
and/or image information 7 which comprises a plur-
ality of light-impermeable spots indicated by
points. If the information carrier 1, which is
shown positioned under the master copy 6 in Figure
1 and whichconsists of a supporting layer 5 with
a recording layer 2, e.g. a photoresist layer,
coated thereon, is exposed, light passes through
the areas of the master copy 6 t~ the right and
to the left of the image information 7, without
causing an information-wise distribution of the
intensity in the corresponding portions of the
recording layer 2.
In the middle section, which carries the
image information 7, the incident light rays (in-
dicated by arrows) are weakened or barred in
accordance with the arrangement of the light~
- 9 -
impermeable spots, so that, after exposure, an
image wise or information wise distribution of the
intensity results on the surface of the recording
layer 2 in the corresponding section of the infor-
mation carrier 1 below. The thus exposed informa-
tion carrier 1 is then treated with an aqueous-
alkaline solution which dissolves away the exposed
portions, so that in the middle section an arrange-
ment of structures 3 is obtained whose degree of
deformation corresponds to the distribution of
light i~tensity previously falling on the surface
of the recording layer 2, whereas to the left and
to the right of the middle section, the recording
layer 2, is substantially removed after alkaline
development. As regards their distance from each
other and their depth, the structures 3 are irreg-
ularl~ distributed, or, in other words, their
density and amplitudes correspond to a statistical,
i.e. absolutely irregular, distribution. The
ori~inal thickness of the recording layer 2, prior
to development, is indicated by a broken line.
For the sake of clarity, the thickness of the
recording layer 2 relative to the support 5 is
shown grossly exaggerated in the figures. When
the invention is utili~e~ in practice, the support
is considerably thicker than the recording layer.
During projection of the information carrier 1,
the irradiated light is scattered by the structures
3, so that the scattering structures appear as
dark images in the projection, when the information
carrier is reproduced through a lens.
The maximum contrast which can be achieved
by the structures 3 during projection is, inter
alia, a function of the projection lens which
is used. The lower the light intensity of the lens,
the higher the contrast. ~ practicable system
-10-
must be adapted to conventional projection lenses
with a light intensity of about l : 2.8, which
means -that the scattered light must be deflected
at an angle of 20 or more to the optical axis.
The light scattering structures in the recording
layer 2 must be adapted to fullfil this require-
ment.
The scattering angle requirement can be
easily complied with under the following conditions:
If photoresists such as those marketed by Messrs.
Shipley Comp. Inc., ~ewton, Massachusetts~ USA,
are exposed to actinic light of 400 nm through a
silver halide original, for which e.g., step II
with a nominal densit~ of 0.35 of the color test
wedge 8 diagrammatically shown in Figure 4 may be
used, followed by a~ueous alkaline development
and projection with a lens of a light intensity
of 1 : 2,8 t maximum densities of more than l are
obtained. Such a test wedge is composed of
black-pigmented layers which stepwise are applied
as sections 9 and whose density increases from
step I to step X. Obviously, such a test wedge
may also comprise more or less than 10 section5,
and the density increase from step to step may
vary with different types of test wedges.
The density of the scattering centers in
the individual steps of the test wedge increases
to such a degree that, starting approximately
with step VII, the density is such that only a
few areas are free from scattering centers and form
scattering holes, whereas the other areas of the
step appear a uniform black to the view. After
transition from scattering centers to scattering
holes, the number of holes decreases to such an
extent that step X of the test wedye appears a
uniform black, as indicated in Figure 4.
Surprisingly, practically iden-ticaldensities
are achieved if transparent spacing films of up
to 15 ~m thickness are positioned between the
photoresist layer and the scattering film during
exposure. This means that close contact or distance
between recording layer 2 and scattering film are
not critical during contact exposure. The projec-
tion images show a neutral black color shade. If
a nickel matrix is produced from the surface struc-
ture of the photoresist layer and used for embossing
- a thermoplastic polyvinyl chloride film, the em-
bossed image produces projection images of the same
density.
Comparable results are achieved when using
other known scattering films designed as color
test wedges comprising several steps and having,
e.g., a nominal density of 0.45 at step III.
Common criteria for scattering films which
are suitable for producing maximum projection den-
sities are that they should contain scattering cen-
ters of ~ut 1 ~m dimension or diameter, with a r~e of
variation between 0.5 and 2 ~m, and that the dis-
tances between scattering centers, projected on
the surface of the photoresist layer, should be
about 1.5 ,um, with a range of variation between
0.6 and 4 ~m. Such scattering films have trans-
parencies between 0.25 and 0.65.
Scattering images which are rich in con~
trast may also be produced with scattering films
of higher densities, but only after relatively
long exposure times. By using test wedges r dif-
ferent tone values may be reproduced in the pro-
jection images.
~,.24~.Z~
-12-
The above described scattered image tech-
ni~ue yields good sensitometric results and is
distinguished by a particular ease and reliability
of performance. This is by no means a matter of
course, since, according to other known techniques,
high~precision sinoidal relief gratings comprising
about 600 lines per mm and having an exact relief
depth of 0.87 ~m, which is stated to be the optimum
depth, are required for the production of black-
and-white projecticn images ~M.T. Gale, Opt. Comm.
l~, 1976, 2~2).
The combined information-wise exposure and
scattered-light exposure through a master copy 6
is explained in the following by reference to
the arrangement for exposing an information carrier
l which is diagrammatically shown in Figure 2.
In this case, a black color ~eparation film
is used, which may be a silver halide film of the
original and which simultaneously serves as the
original and the scattering film. The image areas
on the recording layer 2 corresponding to the
transparent areas of the original are thus opti-
cally masked. For example, in the middle section
according to Figure 2, the master copy 6 may com-
prise optical densities of about 2 after exposure
and development, which corresponds to transpar~
encies of OoOl and less, whereas the neighboring
sections to the right and left thereof, which
corre~pond to the black or gray image areas of the
original, are only slightly exposed, up to trans-
parencies between 0.25 and 0.65 for black, andbelow 0.25 for gray, a slight overlapping with
the black areas being possible in the case of gray.
Alternatively, different tone values may
be reproduced with the aid of known screening
techniques,
Furthermore, the described scattering image technique may be very
advantageously combined with the technique of reproducing color images by means
of rectangular relief gratings with different relief depths in one plane, as
described ln Canadian Patent Application Serial No. 293,120 Eiled
December 15, 1~77 and Canadian Patent Application Serial No. 3087353 filed
July 28, 1978, both in the name of lloechst Aktiengesellschaft. If colored
images containing black image elements are to be recorded, a black color
separation is superimposed. This is achieved, in a relatively simple manner,
by exposing the photoresist layer through a scattering film and a black color
separation film in such a manner that light-scattering surface structures are
formed in the black image areas only. This technique may also be employed
if the photoresist layer was previously superficially exposed in the form of a
screen.
Figure 3 shows an information carrier 1 which contains deflecting
structures ~ in its middle region, which may be produced by exposure under a
relie~ grating, while the neighboring regions to the right and left thereof
contain scattering structures 3. During projection, the middle region appears
colored, whereas the other regions are dark.
Figures 5 and 6 show density cha:racteristics which illustrate the
density D2 of the projection image as a function of the density Dl of the image
information on the color separation original. These density characteristics
will be referred to in connection with Examples 1 and 3 below. A positive
projection image is obtained by exposing the material first, image-wise,
through a separation original of the image information which has a density
Dl, and then, uniformly, through a scattering film.
-13-
~.2~L~2~
Alternatively, the sequence of these steps may be
reversed. If image-wise or information-wise
exposure and scattered~light exposure of the re-
cording layer are performed simultaneously, either
a negative or a positive projection image may be
obtained, depending on the exposure time.
The density characteristics shown in Figure
5 appear at different exposure energies~ On the
ordinate, the density D2 f the projection image,
which was obtained with a lens of a light intensity
of 1 : 2.8, is plotted as a function of the density
Dl of the scattering film. Changes in the density
Dl of the scattering film are produced by means
o a test wedge, the indi~idual steps of which are
placed one after the other on separate information
carriers 1 for exposure. If ~he irradiated energy
corresponds to 324 mWs/cm2, a negative projection
image of the color separation original is obtained,
and with an energy corresponding to 1800 mWs/cm2, a
positîve projection image results. In the case
of a negative projection image, the dark and light
areas of the original are reversed, whereas they
are unreversed in the positive projection image.
- It is not necessary for the information
to be contained in the scattering film itself.
The density characteristic of Figure 6 was pro-
duced by image-wise exposing first through the
separation original and then, uniformly, through
step III of a known test wedge used as the scat-
tering film.
I~ images of high quality, e.g. screenedcolored images, are to be produced, a scattering
film is used which is optimally adjusted to a
maximum density of the scattering image. This
-15-
scattering film may be a briefly exposed and devel-
oped silver halide film or a pigment layer. This
layer is coated with a photoresist layer which is
so colored that it is impermeable to light within
the short wave spectral range, and the photoresist
layer is then removed in the black areas only.
Alternatively, an impermeable metal layer, e.g.
an aluminum layer, may ~e vapor-deposited on the
scattering layer and then coated with a photore-
sist layer. By image-wise exposure, development,
and etching, the black image areas are removed
down to the scattering layer.
Alternatively, the light-scattering sur-
face structures in the recording layer may be
produced by the arrangement shown in Figure 7,
in which the rays of a light source 13 are directed,
by a lens 14, upon a screen 15 consisting of re-
flecting particles~ such as glass chips, and are
deflected by the screen upon the recording layer.
Purthermore, a perforated screen may be reproduced
on the recording layer with the aid of a light
source.
~igure 8 shows an arrangement in which the
- rays of a laser 16, e.g. an ~V laser, are deflected
by a mirror 18 in the direction of an electro-
optical deflector 17. The electro-optical deflec-
tor 17, which is controlled by a random pulse
generator 19, transmits the rays in accordance
with the signals received from it and deflects
them in the directionof the recording layer on the
information carrier 1.
f~
-16-
Example 1
A 5 ~m -thick photoresist layer is applied
to a 50 ~m thick polyester film which serves as
the support. It is then exposed in a printing
frame under a silver halide film original 10 with
graded densities.
.Eigure 5 shows the silver halide film
original 10 carrying the letter "A" as image infor-
mation. As indicated diagrammatically, the den-
sity Dl of the image information on the silver
film original 10 corresponds to one of the steps
VII to IX of the test wedge 8 shown in Figure 4
and thus contains a certain number of scattering
holes. The other areas of the silver film ori
ginal 10 correspond to the density of one of the
sections II to IV of the test wedge 8.
In a first test, an energy corresponding
to 324 mWs/cm2 is beamed upon the photoresist
layer, and in a second test, a new photoresist la-
yer is irradiated with 1,800 mWs/cm2. For this
purpose, the actinic light o a mercury vapor lamp
is collimated by means of a lens and is passed
through a blue-colored glass with a rnaximum trans-
mission at a wave length o~ 400 nm. Aqueous-
alkaline development follows. Upon projection
with a lens of a light intensity of 1 : 2.8, a
projection irnage with neutrally colored areas of
graded densities is obtained. With an irradiated
energy of 324 mWs/cm2, a negative image is obtained,
and with an energy o~ 1,800 mWs/cm2 a positive
image of the original results. An irradiated
energy of 324 mWs/cm2 corresponds to a short ex-
posure time during which the image information
Z~2
in the form of the letter "A" transmits very lit-
tle light, whereas in the other areas the light
is scattered by the scatteriny centers. ~fter
development, the information carrier yields a
projection image 11 which is shown in Figure 5a
and in which the image information appears light,
whereas the other areas are dark, which means
that the projection image is a negative copy of
the silver halide film original.
Using an irradiated energy of 1,800 mWs/cm2,
which means that the exposure time is about 5.6
times that used in the first test, the areas of
the recording layer on the information carrier
co~ered by the image information are not burned
in, but structures are burned into the recording
layer in the areas oppositetothe scattering holes.
During projection! these structures form scattering
centers and appear dark, as indicated in Figure 5b.
Due to the long exposure time, the areas of the
2Q information carrier lying outside of the image
information which are positioned opposite to the
scattering centers of the silver halide film ori-
ginal are also exposed, so that the originally
- formed structures are leveled and the resulting
projection image shows a positive reproductlon 12
of the silver halide film original 10.
In order to determine the densities of the
images, the intensities in different areas of the
projection images are measured by means of a photo-
electric cell. The thus calculated optical den-
sities D2 f the projection images are shown in
Fiyure 5 as functions of the densities Dl of the
test wedge used. Maximum values of about 1 are
obtained.
2;2
By vaporization techniques, the relief irn-
ages in the photoresist layer are provided with a
thin copper layer, then a nickel layer of up to
about 40 ~m is electro-deposited thereon so that
an embossing die results. This die is used at
about 130C, in a press, to emboss polyvinyl
chloride film. Upon projection, the thus obtained
embossed images also show neutrally colored areas
of graded densities, whose contrast substantlally
resembles that of the projection images o the
original information carrier.
Example 2
An image is recorded under the conditions
stated in Example 1, the silver halide film ori-
ginal showing the photographic negative of a land-`
scape. After a short exposure, i.e. with an energy
of 324 mWs/cm2, and aqueous-alkaline development,
an image of the landscape in the correct tonal
values is projected from the structured photo-
resist layer.
Example 3
A 3 ,um thick photoresist layer disposed ona support consisting of a 50 ~m thick polyester
film is irradiated with an energy of 710 mWs/cm2
through an ungrained step wedge with 2 mm wide
steps. The step wedge consists of a transparent
yellowish film whose optical density at a wave
length of 400 nm is 0.26; thus, densities of 0.26,
0.52, 0.78 and 1.04 may be adjusted for this wave
length by superimposing one, two, three, or four
films. Then a test wedge with a density of 0.45
is superimposed and light of an energy of 500 mWs/cm2
2;2
--19--
i5 irradiated (Figure 6). After ayueous-alkaline
development of the pho-toresist layer, projection
yields an image containing neutrally colored
areas of graded densities. I'he optical densities
D2 are calculated from the light intensities
measured in the individual areas. In Figure 4,
these optical densities D2 are shown as functions
of the optical densities Dl of the test wedge.
The projection image i8 a positive image, image
areas of high density in the original being re-
produced by image areas of high density in the
projection image.
Example 4
A 3 ,um thick photoresist layer is applied
to a transparent support and irradiated with light
of an energy of 150 mWs/cm2 through a screened,
transparent original. The subject on the original
is dissected by a screen comprising 80 screen
elements per cm. Then, the material is exposed
again to light of an energy of 150 mWs/cm2, this
time through a scattering original, e.g, a test
wedge. After aqueous-alkaline development, the
pro~ection image of the information carrier, like
the original used, reproduces continuous tones
by screen dots of appropriate darkness. The op-
tical density in the center of a screen dot is
1 15
Example 5
A smooth, transparent polyester film is
coated with a 2.5 ~m thick photoresist layer by
whirler-coating anddrying. In a contact arrange~
ment, the resulting photoresist layer is exposed
-20-
to light of 250 mT1~s/cm2 ener~y under a glass plate
containing a screen composed of 600 metal wire
lines per mm. The exposure time is adjusted to
the projection c019x "green". Subsequentlyr the
material is exposed, in register, under color
separation originals which are transparent only
in the image areas of the respective color separa-
tion o~iginal and in the white areas, the irradi-
ated light energies being 75 mWs/cm2 for red,
95 mWs/cm2 for yellow, and 130 mWs/cm2 for blue.
The black color separation original is a silver
halide film which was exposed in such a manner
that the light areas have maximum optical density
and the black areas have an optical density of up
to 0.45 ater development, For exposure under the
black color separation film, a light energy of
300 mWs/cm2 is irradiated. After aqueous-alkaline
de~elopment, the structured photoresist layer
yields a colored projection image in which the
black image areas are reproduced by an optical
density of 0.95 which is neutral in color.
The projection colors do not quite corres-
pond to the original colored image, because the
times of exposure under the color separation
ori~inals are corrected to take into account
the different indices of refraction of photore-
sist layer and embossed film. A thin copper
layer is vapor-deposited on the relief image,
and the copper layer is then, in turn, electro~
plated with a nickel la~er of up to ~0 ~m thick-
ness. The resulting metal matrix is separated from
the photoresist layer and used for embossing a
highly transparent polyvinyl chloride film at
130C in a press. The embossed image thus ob-
~ JL~
tained shows a colored projection image which cor-
responds to the original colored image and which
contains dark image areas corresponding to the
black image areas of the original~
The foregoing detailed description is to be
clearly understood as given by way of illustration
and example only, the spirit and scope of this
invention being limited solely by the appended
claims.
