 |
Claims  |
|
|
What is claimed is:
1. A method for fabricating a micropolarizer, comprising the steps of:
providing a first polarized film having a first polarization state, P1 and
coated with photoresist;
exposing the film to a source of electromagnetic radiation through a mask
having a first predetermined pattern;
removing parts of the first film exposed to the electromagnetic radiation
through the mask;
repeating the providing, exposing and removing steps with a second
polarized film having a second polarization state, P2 and coated with
photoresist and using a mask having a second predetermined pattern that is
an inverse of the first predetermined pattern;
aligning the first polarized film and the second polarized film so that the
removed parts of the first film are aligned with those parts of the second
film that were not removed;
laminating the aligned first and second films to one another.
2. A method of fabricating a micropolarizer, comprising the steps of:
providing a first film having a first pattern of optically active and
non-optically active parts;
providing a second film having a second pattern of optically active and
non-optically active parts; wherein the optically active parts of the
second film affect light differently than the optically active parts of
the first film and the first pattern is an inverse of the second pattern;
thereafter, aligning the first and second films so that the optically
active parts of the first film are aligned with and overlap the
non-optically active parts of the second film and vice versa; and
laminating the aligned first and second films to one another.
3. The method of claim 2, wherein the providing step includes providing the
first film as a first set of optically active parts mounted on a first
substrate according to the first pattern and providing the second film as
a second set of optically active parts mounted on a second substrate
according to the second pattern.
4. The method of claim 3, wherein the laminating step is carried out by
contacting and laminating the optically active parts of one of the first
and second films to the substrate layer of the other of the first and
second films.
5. The method of claim 3, wherein the laminating step is carried out by
contacting and laminating the optically active parts of each of the first
and second films to the substrate layer of the other of the first and
second films to provide a layer of interposed optically active parts of
the first and second films, the interposed optically active parts being
sandwiched between the respective substrate layers.
6. The method of claim 3, wherein the laminating step is carried out by
contacting and laminating the substrate layers of the first and second
films to one another.
7. The method of claim 2, wherein the providing step includes providing the
first film as a first set of optically active parts mounted on a first
side of a common substrate according to the first pattern and providing
the second film as a second set of optically active parts mounted on a
second side of the common substrate according to the second pattern.
8. The method of claim 2, wherein the optically active parts of each of the
first and second films are quarter wave retarders having respective
optical axes oriented 90.degree. from each other; and wherein the
laminating step includes laminating a sheet of polarizer to the laminated
first and second films.
9. The method of claim 8, wherein the sheet of polarizer is a linear
polarizer.
10. A method for fabricating a micropolarizer, comprising the steps of:
providing a first film coated with a protective mask having a predetermined
pattern that exposes preselected parts of the first film;
thereafter, treating the first film to affect the preselected parts of the
first film to provide a pattern of polarized and unpolarized parts of the
first film, the polarized parts of the first film having a first
polarization state, P1;
repeating the providing and treating steps with a second film coated with a
protective mask to provide a pattern of polarized and unpolarized parts of
the second film, the polarized parts of the second film having a second
polarization state, P2, and, using a mask having a second predetermined
pattern that is an inverse of the first predetermined pattern;
thereafter, aligning the treated first and second films so that the
polarized parts of the first film are aligned with and overlap the
unpolarized parts of the second film and vice versa; and
laminating the aligned first and second films to one another.
11. The method of claim 10, wherein the first film comprises a polarized
film having the first polarization state, P1, and the second film
comprises a polarized film having the second polarized state, P2; and
wherein the treating step is carried out by treating the first and second
films to remove the polarization state of the respective preselected
exposed parts of each of the first and second films
12. The method claim of 11, wherein the first and second films each
comprise a polarized PVA film.
13. The method of claim 11, wherein the first and second films are
cholesteric liquid crystal polarizers of P1 and P2 polarization states
respectively.
14. The method of claim 10, wherein the step of treating each of the first
and second films to remove the polarization state of the respective
preselected exposed parts is carried out by applying a solvent or an
etchant solution to the respective preselected exposed parts.
15. The method of claim 10 wherein each of the first and second films
comprise a stretched PVA film without a dichroic effect and wherein the
treating step is carried out by applying an iodine solution to the
respective exposed parts of the first and second films to cause a dichroic
effect at each respective exposed part, the stretched PVA of the first
film polarizing light according to the first polarization state, P1, after
treatment and the stretched PVA of the second film polarizing light
according to the second polarization state, P2, after treatment.
16. The method of claim 15, wherein the iodine solution comprises a
solution of iodine and potassium iodide and comprising the further step of
applying a stabilizing solution to the respective preselected parts after
application of the iodine solution.
17. The method of claim 10, wherein the providing step includes mounting
each of the first and second films on a respective substrate layer.
18. The method of claim 17, wherein the laminating step is carried out by
contacting and laminating one of the first and second films to the
substrate layer of the other of the first and second films.
19. The method of claim 17, wherein the laminating step is carried out by
contacting and laminating the substrate layers of the first and second
films to one another.
20. The method of claim 10, wherein the aligning and laminating steps are
carried out by mounting each of the first and second films to a common
substrate layer interposed between the first and second films.
21. The method of claim 10, wherein the first and second polarization
states are linear polarization states oriented 90.degree. from one
another.
22. The method of claim 10, wherein the first film comprises a polarized
film having the first polarization state, P1, and the second film
comprises a polarized film having the second polarization state, P2;
wherein the providing step includes mounting each of the first and second
films on a respective substrate layer; and
wherein the treating step is carried out by etching away the respective
preselected parts of each of the first and second films to provide a
pattern of polarized parts mounted on each respective substrate layer.
23. The method claim of 22, wherein the etching step is carried out by
chemically etching away the respective preselected parts of each of the
first and second films.
24. The method of claim 22, wherein the etching step is carried out by
photochemically etching away the respective preselected parts of each of
the first and second films.
25. The method of claim 22, wherein the etching step is carried out by
laser etching away the respective preselected parts of each of the first
and second films.
26. The method of claim 22, wherein the etching step is carried out by
reactive ion etching away the respective preselected parts of each of the
first and second films.
27. The method of claim 22, wherein the laminating step is carried out by
contacting and laminating the polarized parts of one of the first and
second films to the substrate layer of the other of the first and second
films.
28. The method of claim 22, wherein the laminating step is carried out by
contacting and laminating the polarized parts of each of the first and
second films to the substrate layer of the other of the first and second
films to provide a layer of interposed polarized parts of the first and
second films, the interposed polarized parts being sandwiched between the
respective substrate layers.
29. The method of claim 22, wherein the laminating step is carried out by
contacting and laminating the substrate layers of the first and second
films to one another.
30. The method of claim 22, wherein the first and second films are mounted
on a common substrate layer.
31. A method for fabricating a patterned polarizer film, comprising the
steps of:
providing a first film coated with a protective mask having a predetermined
pattern that exposes preselected parts of the first film; and
thereafter, treating the first film to affect the preselected parts of the
first film to provide a pattern of polarized and unpolarized parts of the
first film, the polarized parts of the first film having a first
polarization state, P1.
32. The method of claim 31, wherein the first film comprises a polarized
film having the first polarization state, P1; and wherein the treating
step is carried out by treating the first film to remove the polarization
state of the preselected exposed parts of the first film.
33. The method of claim 32, wherein the first film comprises a polarized
PVA film.
34. The method of claim 32, wherein the first film comprises a cholesteric
liquid crystal polarizer.
35. The method of claim 32, wherein the first film comprises a half-wave
retarder.
36. The method of claim 32, wherein the first film comprises a quarter-wave
retarder.
37. The method of claim 31, wherein the step of treating the first film to
remove the polarization state of the preselected exposed parts is carried
out by applying an etchant or a solvent solution to the preselected
exposed parts.
38. The method of claim 31, comprising the further step of laminating the
first film to a sheet of polarizer.
39. The method of claim 38, wherein the first film is a retarder and
wherein the sheet of polarizer comprises a sheet of linear polarizer.
40. The method of claim 31, wherein the first film comprises a polarized
film having the first polarization state, P1;
wherein the providing step includes mounting the first film on a substrate
layer; and
wherein the treating step is carried out by etching away the preselected
parts of the first film to provide a pattern of polarized parts mounted on
the substrate layer.
41. The method of claim 40, wherein the etching step is carried out by
chemically etching away the preselected parts of the first film.
42. The method of claim 40, wherein the etching step is carried out by
photochemically etching away the preselected parts of the first film.
43. The method of claim 40, wherein the etching step is carried out by
laser etching away the preselected parts of the first film.
44. The method of claim 40, wherein the etching step is carried out by
reactive ion etching away the preselected parts of the first film.
45. A method of fabricating a micropolarizer, comprising the steps of:
providing a first film having a first pattern of polarized and unpolarized
parts, the polarized parts of the first film having a first polarization
state, P1;
providing a second film having a second pattern of polarized and
unpolarized parts, the polarized parts of the second film having a second
polarization state, P2, and wherein the first pattern is an inverse of the
second pattern;
thereafter, aligning the first and second films so that the polarized parts
of the first film are aligned with and overlap the unpolarized parts of
the second film and vice versa; and
laminating the aligned first and second films to one another.
46. The method of claim 45, wherein the providing step includes mounting
each of the first and second films on a respective substrate layer.
47. The method of claim 46, wherein the laminating step is carried out by
contacting and laminating the first and second films to one another.
48. The method of claim 46, wherein the laminating step is carried out by
contacting and laminating the first and second films to the substrate
layer of the other of the first and second films.
49. The method of claim 46, wherein the laminating step is carried out by
contacting and laminating the substrate layers of the first and second
films to one another.
50. The method of claim 45, wherein the aligning and laminating steps are
carried out by mounting each of the first and second films to a common
substrate layer interposed between the first and second films.
51. The method of claim 45, wherein the first and second polarization
states are linear polarization states oriented 90.degree. from one
another.
52. The method of claim 45, wherein the first and second polarization
states are left and right circular polarization.
53. The method of claim 45, wherein the providing step includes providing
the first film as a first set of polarized parts each having the first
polarization state, P1, and the first set being mounted on a first
substrate according to the first pattern and providing the second film as
a second set of polarized parts each having the second polarization state,
P2, and the second set being mounted on a second substrate according to
the second pattern.
54. The method of claim 52, wherein the laminating step is carried out by
contacting and laminating the polarized parts of one of the first and
second films to the substrate layer of the other of the first and second
films.
55. The method of claim 52, wherein the laminating step is carried out by
contacting and laminating the polarized parts of each of the first and
second films to the substrate layer of the other of the first and second
films to provide a layer of interposed polarized parts of the first and
second films, the interposed polarized parts being sandwiched between the
respective substrate layers.
56. The method of claim 52, wherein the laminating step is carried out by
contacting and laminating the substrate layers of the first and second
films to one another. |
|
 |
|
 |
Claims |
|
|
|
Description |
|
|
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of polarizers and the high throughput
mass manufacturing of a new class of polarizars called micropolarizers.
Micropolarizers have been developed for use in spatial multiplexing and
demultiplexing image elements in a 3-D stereo imaging and display system.
2. Description of Related Art
This invention is related to my co-pending application Serial No.
07/536,190 entitled "A System For Producing 3-D Stereo Images" filed on
even date herewith which introduces a fundamentally new optical element
called a micropolarizer. The function of the micropolarizer is to
spatially multiplex and spatially demultiplex image elements in the 3-D
stereo imaging and displaying system of the aforementioned co-pending
application. As shown in FIG. 1, the micropolarizer (.mu.Pol) 1, 2 is a
regular array of cells 3 each of which comprises a set of microscopic
polarizers with polarization states P1 and P2. The array has a period p
which is the cell size and is also the pixel size of the imaging or
displaying devices.
It is possible to turn unpolarized light into linearly polarized light by
one Of three well known means: 1) Nicol prisms; 2) Brewster Angle
(condition of total internal reflection in dielectric materials); and 3)
Polaroid film. These are called linear polarizers. The Polaroids are
special plastic films which are inexpensive and come in very large sheets.
They are made of polyvinyl alcohol (PVA) sheets stretched between 3 to 5
times their original length and treated with iodine/potassium iodide
mixture to produce the dichroic effect. This effect is responsible for
heavily attenuating (absorbing) the electric field components along the
stretching direction while transmitting the perpendicular electric field
components. Therefore, if P1 is along the stretching direction of the PVA
sheets, it is not transmitted, where as only P2 is transmitted, producing
polarized light. By simply rotating the PVA sheet 90 degrees, P1 state
will now be transmitted and P2 will be absorbed.
The aforementioned three known means for producing polarized light have
always been used in situations where the polarizer elements have large
areas, in excess of 1 cm.sup.2. However, for 3-D imaging with .mu.Pols
using 35 mm film, to preserve the high resolution, the .mu.Pol array
period p may be as small as 10 micron. Therefore, there is no prior art
anticipating the use of or teaching how to mass produce .mu.Pols having
such small dimensions.
SUMMARY OF THE INVENTION
The present invention provides a means for high through put mass
manufacturing of micropolarizer arrays. To use the .mu.Pols in consumer
3-D photography, and printing applications, the economics dictate that the
cost of .mu.Pols be in the range of 1 to 5 cents per square inch. For this
reason, the low cost PVA is the basis for the manufacturing process.
The present invention also provides a flexible .mu.Pols manufacturing
process which can be adapted to low and high resolution situations as well
as alternative manufacturing methods, each of which may be advantageous in
certain applications and adaptable to processing different polarizer
materials. The present invention further provides an electronically
controllable .mu.Pol.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration of a micropolarizer array according to the
present invention.
FIGS. 2 and 3 illustrate fabrication processes of linear micropolarizers
using, respectively, bleaching and selective application of iodine.
FIG. 4 shows final alignment and lamination processes for making linear
micropolarizers.
FIG. 5 illustrates a process for fabricating linear micropolarizers by
means of etching.
FIG. 6 illustrates a method for patterning micropolarizer by mechanical
means.
FIG. 7 shows final alignment and lamination processes for making linear
micropolarizers by the etching method.
FIG. 8 shows final alignment and lamination processes for making circular
micropolarizers by the etching method.
FIGS. 9 and 10 illustrate processes for making linear and circular
polarizers eliminating an alignment step.
FIGS. 11 and 12 illustrate photo-lithographic patterning steps.
FIG. 13 illustrates an automated high through-put process for continuous
production of micropolarizer sheets by photo-lithographic means.
FIG. 14 illustrates an automated high throughput process for continuous
production of micropolarizer sheets by direct application of bleaching ink
or iodine-based ink.
FIG. 15 illustrates an active electronically controllable micropolarizer
based on electro-optical effect of liquid crystals.
DETAILED DESCRIPTION
Since its invention by E. Land in the 1930's, polyvinyl alcohol (PVA) has
been the polarizer material of choice. It is available from several
manufacturers including the Polaroid Corporation. It comes as rolls 19
inches wide and thousands of feet long. The PVA, which is 10 to 20 micron
thick, is stretched 3 to 5 times original length and treated with iodine
to give it its dichroic (polarizing) property. The PVA treated in this
manner crystallizes and becomes brittle. The processes below employ
certain chemical properties of the PVA. These are: i) resistance to
organic solvents and oils; ii) water solubility, 30% water and 70% ethyl
alcohol; iii) bleaching of the dichroic effect in hot humid atmosphere and
by means of caustic solutions; iv) manifestation of dichroic effect by
painting the PVA in iodine/potassium iodide solution; and v) the
stabilization of the dichroic effect in boric acid solution. The starting
PVA material comes laminated to a clear plastic substrate which protects
the brittle PVA and facilitates handling and processing. The substrate is
made either of cellulose aceto bytyrate (CAB) or cellulose triacetate
(CTA), and is typically 50 to 125 micron thick. CAB and CTA are
ultra-clear plastics and at the same time they are good barriers against
humidity. For some applications, large glass plates are also used as
substrates. Although other polymers, when stretched and treated by
dichroic dyes, exhibit similar optical activity to that of PVA and may be
fabricated into micropolarizers following the methods taught here, only
PVA is considered in the manufacturing processes described in the present
invention.
The physical principles on which the polarization of light and other
electromagnetic waves, and the optical activity which produces phase
retardation (quarter wave and half wave retarders) are described in books
on optics, such as: M. Born and E. Wolf, Principles of Optics Pergamon
Press, London, fourth edition, 1970; F. S. Crawford, Jr., Waves
McGraw-Hill, New York, 1968; and M. V. Klein, Optics, Wiley, New York,
1970. There are several important facts used in this invention:
1. Two linear polarizers with their optical axis 90 degrees from each other
extinguish light.
2. A linear polarization which is 45 degrees from the optical axis of a
quarter wave retarder is converted into a circular polarization.
3. A linear polarization which is 45 degrees from the optical axis of a
half wave retarder is converted into a linear polarization rotated 90
degrees.
4. Two linear polarization states, P1 and P2, 90 degrees from each other,
are converted into clockwise and counter-clockwise circular polarization
states by means of a quarter waver retarder.
5. A circular polarization is converted into a linear polarization by means
of a linear polarizer.
6. A clockwise circular polarization is converted into a counter-clockwise
polarization by means of a half-wave retarder.
The process for producing the micropolarizers, .mu.Pols, 1, 2 in FIG. 1 is
described in FIG. 2 which starts with a sheet of linear polarizer 5
laminated onto a clear substrate 4. The laminate is coated with
photosensitive material 6 called photoresist. This can be one of several
well known liquid photoresists marketed by Eastman Kodak and Shipley, or
in the form of a dry photoresist sheet called Riston from the Du Pont
Company. The latter is preferred because complete laminated rolls of the
three materials 3, 5, 6 can be produced and used to start the .mu.Pols
process. The photoresist is subsequently exposed and developed using a
mask having the desired pattern of the .mu.Pols cell 3 producing a pattern
with polarization parts protected with the photoresist 6 and unprotected
parts 7 exposed for further treatment. These exposed parts 7 are treated
for several seconds with a caustic solution, e.g., a solution of potassium
hydroxide. This bleaching solution removes the dichroic effect from the
PVA so that the exposed parts 8 are no longer able to polarize light. The
photoresist is removed by known strippers, which have no bleaching effect,
thus the first part 9 of the .mu.Pols fabrication is produced.
Alternatively, FIG. 3 shows a method for making linear .mu.Pols by starting
with a laminate of PVA 10 which is stretched but does not yet have the
dichroic effect, i.e., it has not yet been treated with iodine, and the
substrate 4. Following identical steps as above, windows 7 are opened in
the photoresist revealing part of the PVA. The next step is to treat the
exposed parts with a solution of iodine/potassium iodide and subsequently
with a boric acid stabilizing solution. The exposed parts 11 of the PVA
become polarizers while those protected with the photoresist remain
unpolarizers. Stripping the photoresist completes the first part of the
process.
As illustrated in FIG. 4, a complete .mu.Pol is made using two parts 13, 14
produced by either the process of FIG. 2 or FIG. 3 except that part 13 has
polarization axis oriented 90 degrees from that of part 14. The two parts
are aligned 15 so that the patterned polarizer areas do not over lap, and
then laminated together to from the final product 16. The .mu.Pol 16 is
laminated with the PVA surfaces facing and in contact with each other. The
.mu.Pol 17 is laminated with the PVA of part 13 is in contact with the
substrate of part 14. The .mu.Pol 18 is laminated with the substrates of
both parts are in contact with each other. Finally, it is possible to
produce the .mu.Pol 19 with only one substrate onto which two PVA films
are laminated and patterned according to the process described above.
The above process leaves the patterned PVA film in place and achieves the
desired result by either bleaching it or treating it with iodine solution.
The processes described in FIGS. 5 and 6 achieve the desired result by the
complete removal of parts of the PVA. In FIG. 5, the starting material is
any PVA film 20 (linear polarizer, quarter wave retarder, or half wave
retarder) or any non-PVA optically active material laminated to a
substrate. As described above, windows 7 in the photoresist are opened.
The exposed PVA 7 is removed 21 by means of chemical etching (30%
water/70% ethyl alcohol solution), photochemical etching, eximer laser
etching or reactive ion etching. Stripping the photoresist, the first part
22 of the .mu.Pols process is completed.
The removal of PVA can also be accomplished by mechanical cutting or
milling means. FIG. 6 illustrates the process which uses a diamond cutter
66 mounted on a motor driven shaft 74. In one embodiment, the PVA 68 is
sandwiched between two polymers, such as poly-methyl methacrylate, PMMA,
film 67, and the sandwich is laminated onto a substrate 69. The diamond
saw is used to cut channels. The channel width and the distance between
the channels are identical. The PMMA serves to protect the top PVA surface
from abrasion and protects the substrate from being cut by the saw. Next
the PMMA on top of the PVA and in the channel is dissolved away, leaving
the part 71 with clean substrate surface 70. This part can be used as is
to complete the .mu.Pol fabrication or the original substrate 69 is
removed by dissolving away the rest of the PMMA, after having attached a
second substrate 72. This part which consists of the patterned PVA 68
laminated to the substrate 72 is used in a subsequent step to complete the
.mu.Pol.
Even though this process is mechanical in nature, it has been shown in
Electronic Business, May 14, 1990, page 125, that channels and spacings as
small as 5 micron can be made using diamond discs manufactured by Disco
HI-TEC America Inc., of Santa Clara, Calif. Realizing that using only one
disc makes the process slow and costly, the arrangement in FIG. 6 is used
where many discs 73 in parallel 75 is preferred. Each disc has its center
punched out in the shape of a hexagonal so that it can be mounted on a
shaft 74 with a hexagonal cross section. Hundreds of such discs are
mounted on the same shaft and are spaced apart by means of spacers 76
whose diameters are smaller than those of the discs. The diameter
difference is used to control the cutting depth. The spacers also have
hexagonal centers. The cutting discs and the spacers have the same
thickness in order to obtain identical channel width and channel spacing.
The discs and spacers are mounted on the shaft tightly to prevent lateral
motion, while the hexagonal shaft prevents slipping. The discs are made to
rotate between 20,000 and 50,000 RPM and the laminate is cut in continuous
fashion, thus achieving high through put.
To complete making a whole .mu.Pol the parts 22, 71, 72 prepared by the PVA
removal methods are used as in FIG. 7. If the PVA is a linear polarizer,
then, parts 23, 24 have patterned polarizers which are oriented 90 degrees
from each other, and when aligned 25, and laminated together, complete
linear .mu.Pols 26,27,28, 29 result. If the PVA is quarter wave retarder,
then the parts 30, 31 of FIG. 8 have patterned retarders with optical axes
oriented 90 degrees from each other, and when aligned 32 and laminated to
a sheet of linear polarizer 33, complete circular .mu.Pols 34, 35, 36
result.
Up until now all .mu.Pols have been made using two patterned parts aligned
to each other and then laminated as in FIGS. 4, 7, and 8. It possible make
.mu.Pols with a single patterned part 38 or 40 in FIGS. 9 and 10, and
without the alignment step. In FIG. 9, the single patterned part 38
consists of a patterned half-wave retarder on a substrate 4. It is mounted
simply on a sheet of polarizer 39 with no alignment necessary and a
complete .mu.Pols results. If a linear polarizer sheet 39 is used, the
result is a linear .mu.Pols. If a circular polarizer sheet 39 is used, the
result is a circular .mu.Pols. In FIG. 10 the single patterned part 40 has
a linear polarizer which is simply mounted on a circular polarizer sheet
41 to produce a complete .mu.Pols.
FIG. 11 shows the apparatus 42 used for contact printing of the laminate 46
made of photoresist, PVA, and its substrate. The apparatus consists of a
vacuum box 47, and a vacuum pump 48 attached thereto. The top of box is
flat surface with vacuum holes which hold the laminate flat during
exposure. The mask 45 with its emulsion facing down, makes direct contact
with the photoresist surface with the aid of the top glass cover 44. The
very high intensity UV lamp 43 is then turned on for 30 to 60 seconds to
expose the photoresist. The laminate is subsequently removed for
development and the rest of the .mu.Pols fabrications processes as
described in FIGS. 2, 3, and 5. This printing process using apparatus 46
is automated for large area .mu.Pols production as shown in FIG. 12. The
laminate 46 is furnished in a large roll, is fed to apparatus 42 when the
vacuum pump 48 is off and the mask and cover 44 are open. By means of an
electronic controller, the following automatic sequences are carried out:
(1) the vacuum is turned on; (2) the cover and mask are lowered; (3) the
lamp is turned on for certain period of time; (4) the lamp is turned off;
(5) the mask and cover are lifted; (6) the vacuum is turned off; and (7)
the laminate is advanced. These steps are repeated until the whole roll is
finished. The exposed roll 49 is then processed further. This exposure
apparatus is simple and has no critical alignment requirements.
The fully automated embodiment in FIG. 13 is used for continuous mass
production. The raw roll of laminate 46 enters from the right and the
finished roll 56 of .mu.Pols exists from the left. As one laminate segment
is exposed, it is advanced to the left, developed and rinsed in station
50. Said segment is then further advanced to the left to be dried in
station 51, and advanced further to section 52. This station carries out
the most critical .mu.Pols process by one of three methods discussed above
in connection with FIGS. 2, 3, and 5. These are:
1. Bleaching by means of potassium hydroxide then rinsing.
2. Polarizing by means of iodine/potassium iodide solution, boric acid
stabilizing solution, then water/methyl alcohol rinse.
3. Dry or wet etching of the PVA.
After the rinsing step in station 52, the segment is advanced to station 53
for drying and heat treatment. The photoresist stripping and rinsing is
done in 54 and the final drying step in 55. The finished roll 56 is
laminated with a polarizer sheet according to FIGS. 9 and 10 complete the
.mu.Pols.
The photolithographic printing used above involves several steps:
1. Application of the photoresist
2. Baking
3. Making contact with the mask
4. Exposure
5. Development
6. Rinsing
7. Drying
8. Post baking
9. Stripping
10. Rinsing
11. Drying
These steps have been eliminated by using the mechanical method described
in FIG. 6. They are also completely eliminated by using the embodiment
illustrated in FIG. 14. This apparatus 57 promises to be the least
expensive high volume manufacturing process for .mu.Pols. It consists of a
plate drum 58 to which a plate a fixed, a blanket drum 59 which has a
rubber surface, and an impression drum 60. The inks from ink fountains 62,
65, are transferred to the plate by means of rollers 63, 64. The pattern
is transferred from the plate to the blanket drum which in turn it
transfers to the PVA laminate 61. The rotation of the blanket drum and the
impression drums draws in the laminate, and blanket rubber surface
pressing on the laminate causes proper printing. Although the hardware is
similar to that used in offset printing press, the process is different
from offset printing. The principal difference is in the ink formulation.
In offset printing slightly acidic water is used in fountain 65, and an
oil-based paint (linseed oil, pigments, binder, and other additives) is
used in fountain 62. These are not intended to interact with the paper.
The pigments in the oil based solution will remain bonded to the paper,
and the water evaporates. In the .mu.Pols printing process, on the other
hand, the oil based solution is clear and is not intended to remain, while
the water based solution is intended to interact with the PVA and
permanently modify it, by bleaching it or by endowing it with the dichroic
property. Another difference is the use of the negative image on the plate
to print a positive image of the pattern on the PVA laminate, whereas in
the offset printing, the opposite occurs. The plates are made by means
which are well known in the offset printing industry.
The .mu.Pols process using apparatus 57 has three embodiments which depend
on the content of the water based solutions in fountain 65, while fountain
62 contains a fast drying clear oil solution:
1. Selective Bleaching: The water based solution contains a bleaching agent
such as potassium hydroxide or sodium hydroxide which applied selectively
as pattern on the polarized PVA. Where applied, the solution removes the
iodine and its polarizing effect. Rinsing and drying steps follow this
bleaching step.
2. Selective Dichroism: The water based solution contains a
iodine/potassium iodide which is applied selectively as a pattern on the
unpolarized PVA. Where applied, the solution turns the PVA into a
polarizer. This step is followed by a stabilizing step using a boric acid
solution and subsequently rinsing using a methyl alcohol solution and
drying steps.
3. Selective Etching: The water based solution contains a clear polymer
| | |
