Arylazoaniline blue dyes for color filter array element

A thermally-transferred color filter array element comprising a transparent support having thereon a thermally-transferred image comprising a repeating mosaic pattern of colorants in a receiving layer, one of the colorants being a phenyl or thienyl azoaniline blue dye. In a preferred embodiment, the dye has the following formula: ##STR1## wherein R.sup.1 and R.sup.2 each independently represents hdyrogen; a substituted or unsubstituted alkyl group of from 1 to about 6 carbon atoms; a cycloalkyl group of from about 5 to about 7 carbon atoms; or a substituted or unsubstituted aryl or hetaryl group of from about 6 to about 10 carbon atoms; PA1 R.sup.3 represents hydrogen or a substituted or unsubstituted alkyl or alkoxy group of from 1 to about 10 carbon atoms; PA1 R.sup.2 may be taken together with R.sup.1 to form a 5- or 6-membered ring; PA1 R.sup.1 or R.sup.2 may be combined with R.sup.3 or may be joined to the carbon atom of the benzene ring at a position ortho to the position of attachment of the anilino nitrogen to form a 5- or 6-membered ring; PA1 R.sup.4 represents hydrogen, a substituted or unsubstituted alkyl or alkoxy group of from 1 to about 10 carbon atoms, halogen, sulfonamido or acylamido; PA1 R.sup.5 represents nitro, cyano, fluorosulfonyl, alkylsulfonyl, arylsulfonyl, acyl, alkoxycarbonyl, carbamoyl, sulfamoyl, trifluoromethyl or halogen; PA1 R.sup.6 represents nitro, cyano, acyl, trifluoroacetyl, dicyanovinyl or tricyanovinyl; and PA1 J represents --S-- or --CH.dbd.CR.sup.5 --.

This invention relates to the use of an arylazoaniline blue dye in a 
thermally transferred color filter array element which is used in various 
applications such as a liquid crystal display device. 
In recent years, thermal transfer systems have been developed to obtain 
prints from pictures which have been generated electronically from a color 
video camera. According to one way of obtaining such prints, an electronic 
picture is first subjected to color separation by color filters. The 
respective color separated images are then converted into electrical 
signals. These signals are then operated on to produce cyan, magenta and 
yellow electrical signals. These signals are then transmitted to a thermal 
printer. To obtain the print, a cyan, magenta or yellow dye-donor element 
is placed face to face with a dye-receiving element. The two are then 
inserted between a thermal printing head and a platen roller. A line type 
thermal printing head is used to apply heat from the back of the dye-donor 
sheet. The thermal printing head has many heating elements and is heated 
up sequentially in response to the cyan, magenta and yellow signals. The 
process is then repeated for the other two colors. A color hard copy is 
thus obtained which corresponds to the original picture viewed on a 
screen. Further details of this process and an apparatus for carrying it 
out are contained in U.S. Pat. No. 4,621,271 by Brownstein entitled 
"Apparatus and Method For Controlling A Thermal Printer Apparatus," issued 
Nov. 4, 1986, the disclosure of which is hereby incorporated by reference. 
Another way to thermally obtain a print using the electronic signals 
described above is to use a laser instead of a thermal printing head. In 
such a system, the donor sheet includes a material which strongly absorbs 
at the wavelength of the laser. When the donor is irradiated, this 
absorbing material converts light energy to thermal energy and transfers 
the heat to the dye in the immediate vicinity, thereby heating the dye to 
its vaporization temperature for transfer to the receiver. The absorbing 
material may be present in a layer beneath the dye and/or it may be 
admixed with the dye. The laser beam is modulated by electronic signals 
which are representative of the shape and color of the original image, so 
that each dye is heated to cause volatilization only in those areas in 
which its presence is required on the receiver to reconstruct the color of 
the original object. Further details of this process are found in GB 
2,083,726A, the disclosure of which is hereby incorporated by reference. 
Liquid crystal display devices are known for digital display in electronic 
calculators, clocks, household appliances, audio equipment, etc. There has 
been a need to incorporate a color display capability into such monochrome 
display devices, particularly in such applications as peripheral terminals 
using various kinds of equipment involving phototube display, mounted 
electronic display, or TV-image display. Various attempts have been made 
to incorporate a color display using a color filter array into these 
devices. However, none of the color array systems for liquid crystal 
display devices so far proposed have been successful in meeting all the 
users needs. 
One commercially available type of color filter array which has been used 
in liquid crystal display devices for color display capability is a 
transparent support having a gelatin layer thereon which contains dyes 
having the additive primary colors red, green and blue in a mosaic pattern 
obtained by using a photolithographic technique. To prepare such a color 
filter array element, a gelatin layer is sensitized, exposed to a mask for 
one of the colors of the mosaic pattern, developed to harden the gelatin 
in the exposed areas, and washed to remove the unexposed (uncrosslinked) 
gelatin, thus producing a pattern of gelatin which is then dyed with dye 
of the desired color. The element is then recoated and the above steps are 
repeated to obtain the other two colors. This method contains many labor 
intensive steps, requires careful alignment, is time consuming and very 
costly. Further details of this process are described in U.S. Pat. No. 
4,081,277. 
In addition, a color filter array element to be used in a liquid crystal 
display device may have to undergo rather severe heating and treatment 
steps during manufacture. For example, a transparent electrode layer, such 
as indium tin oxide, is usually vacuum sputtered onto the color filter 
array element. This may take place at temperatures elevated as high as 
200.degree. C for times which may be one hour or more. This is followed by 
coating with a thin alignment layer for the liquid crystals, such as a 
polyimide. Regardless of the alignment layer used, the surface finish of 
this layer in contact with the liquid crystals is very important and may 
require rubbing or may require curing for several hours at an elevated 
temperature. These treatment steps can be very harmful to many color 
filter array elements, especially those with a gelatin matrix. 
It is thus apparent that dyes used in color filter arrays for liquid 
crystal displays must have a high degree of heat and light stability above 
the requirements desired for dyes used in conventional thermal dye 
transfer imaging. 
While a blue dye may be formed from a mixture of one or more magenta and 
one or more cyan dyes, not all such combinations will produce a dye 
mixture with the correct hue for a color filter array. Further, when a dye 
mixture with the correct hue is found, it may not have the requisite 
stability to light. It would be desirable to obtain a single blue dye of 
the correct hue rather than using a mixture of dyes. 
EP 235,939, JP 61/227,092, JP 60/031,565, JP 61/268,494, JP 62/099,195 and 
JP 62/132,684 relate to the use of various arylazoaniline blue dyes for 
thermal dye transfer. However, these references do not describe the use of 
these dyes for color filter array elements. 
It would be desirable to provide a color filter array element having high 
quality, good sharpness and which could be obtained easily and at a lower 
price than those of the prior art. It would also be desirable to provide 
such a color filter array element having a blue dye of the correct hue and 
which would have good stability to heat and light. 
These and other objects are achieved in accordance with this invention 
which comprises a thermally transferred color filter array element 
comprising a transparent support having thereon a thermally transferred 
image comprising a repeating mosaic pattern of colorants in a receiving 
layer, one of said colorants being a phenyl or thienyl azoaniline blue 
dye. 
In a preferred embodiment of the invention, the dye has the following 
formula: 
##STR2## 
wherein R.sup.1 and R.sup.2 each independently represents hydrogen; a 
substituted or unsubstituted alkyl group of from 1 to about 6 carbon atoms 
such as methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl or such 
alkyl groups substituted with hydroxy, acyloxy, alkoxy, aryl, aryloxy, 
cyano, acylamido, alkoxycarbonyl, alkoxycarbonyloxy, phthalimido, 
succinimido, sulfonamido, halogen, etc.; a cycloalkyl group of from about 
5 to about 7 carbon atoms such as cyclopentyl, cyclohexyl, 
p-methylcyclohexyl, etc.; or a substituted or unsubstituted aryl or 
hetaryl group of from about 6 to about 10 carbon atoms such as phenyl, p 
tolyl, m chlorophenyl, p-methoxyphenyl, m bromophenyl, o-tolyl, naphthyl, 
3 pyridyl, o-ethoxyphenyl, etc., or such groups substituted as above., 
R.sup.3 represents hydrogen or a substituted or unsubstituted alkyl or 
alkoxy group of from 1 to about 10 carbon atoms such as methyl, ethyl, 
propyl, isopropyl, butyl, pentyl, hexyl, methoxy, ethoxy, isopropoxy, 
etc., or such alkyl or alkoxy groups substituted with hydroxy, acyloxy, 
alkoxy, aryl, aryloxy, cyano, acylamido, alkoxycarbonyl, 
alkoxycarbonyloxy, phthalimido, succinimido, sulfonamido, halogen, etc.; 
R.sup.2 may be taken together with R.sup.1 to form a 5- or 6-membered ring 
such as morpholine, pyrrolidine, piperidine, oxazoline, pyrazoline, etc.; 
R.sup.1 or R.sup.2 may be combined with R.sup.3 or may be Joined to the 
carbon atom of the benzene ring at a position ortho to the position of 
attachment of the anilino nitrogen to form a 5 or 6 membered ring, thus 
forming a polycyclic system such as 1,2,3,4-tetrahydroquinoline, 
julolidine, 2,3-dihydroindole, benzomorpholine, etc.; 
R.sup.4 represents hydrogen; a substituted or unsubstituted alkyl or alkoxy 
group of from 1 to about 10 carbon atoms such as those listed above for 
R.sup.3; halogen such as chlorine, bromine, fluorine, etc.; 
sulfonamido or acylamido; 
R.sup.5 represents nitro, cyano, fluorosulfonyl, alkylsulfonyl, 
arylsulfonyl, acyl, alkoxycarbonyl, carbamoyl, sulfamoyl, trifluoromethyl 
or halogen; 
R.sup.6 represents nitro, cyano, acyl, trifluoroacetyl, dicyanovinyl or 
tricyanovinyl; and 
J represents -S- or -CH=CR.sup.5 -. 
In a preferred embodiment of the invention, R.sup.1 and R.sup.2 are each 
independently hydrogen, ethyl, n-propyl, benzyl, cyclohexyl, -(C.sub.2 
H.sub.4 O).sub.2 C.sub.2 H.sub.2, or may be taken together to form a 
morpholino group. In another preferred embodiment of the invention, 
R.sup.3 is hydrogen or methoxy and R.sup.4 is -NHCOCH.sup.3. In yet 
another preferred embodiment of the invention, R.sup.5 is cyano or 
trifluoromethyl and R.sup.6 is nitro or cyano. In yet still another 
preferred embodiment of the invention, J is S or -CH=CR.sup.5 - wherein 
R.sup.5 is nitro or cyano. 
Specific blue dyes useful in the invention include the following: 
__________________________________________________________________________ 
##STR3## 
R.sup.1 
R.sup.2 R.sup.3 
R.sup.5 
R.sup.6 
J 
__________________________________________________________________________ 
1 C.sub.2 H.sub.5 
CH.sub.2 C.sub.6 H.sub.5 
H CN NO.sub.2 
CHCHNO.sub.2 
2 C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
H CF.sub.3 
NO.sub.2 
CHCHCN 
3 n-C.sub.3 H.sub.7 
n-C.sub.3 H.sub.7 
H CN NO.sub.2 
CHCHNO.sub.2 
4 H c-C.sub.6 H.sub.11 
OCH.sub.3 
CN NO.sub.2 
CHCHNO.sub.2 
5 C.sub.2 H.sub.5 
(C.sub.2 H.sub.4 O).sub.2 C.sub.2 H.sub.5 
H CN NO.sub.2 
CHCHNO.sub.2 
6 H C.sub.2 H.sub.5 
OCH.sub.3 
CN CN S 
##STR4## 
__________________________________________________________________________ 
The dye-receiving layer of the color filter array element of the invention 
may comprise, for example, sucrose acetate or polymers such as a 
polycarbonate, a polyurethane, a polyester, a polyvinyl chloride, a 
polyamide, a polystyrene, an acrylonitrile, a polycaprolactone or mixtures 
thereof. The dye-receiving layer may be present in any amount which is 
effective for the intended purpose. In general, good results have been 
obtained at a concentration of from about 0.25 to about 5 g/m.sup.2. 
In a preferred embodiment of the invention, the receiving layer comprises a 
polycarbonate binder having a T.sub.g greater than about 200.degree. C. as 
described in Application Ser. No. 334,269 of Harrison et al., filed Apr. 
6, 1989, the disclosure of which is hereby incorporated by reference. The 
term "polycarbonate" as used herein means a polyester of carbonic acid and 
one or more glycols or dihydric phenols. In another preferred embodiment, 
the polycarbonate is derived from a bisphenol component comprising a 
diphenyl methane moiety. Examples of such polycarbonates include those 
derived from 4,4'-(hexahydro-4,7-methanoindene-5-ylidene)bisphenol, 
2,2',6,6'-tetrachlorobisphenol-A and 4,4'(2-norbornylidene)bisphenol. 
In another preferred embodiment of the invention, the mosaic pattern which 
is obtained by the thermal transfer process consists of a set of red, 
green and blue additive primaries. 
In another preferred embodiment of the invention, each area of primary 
color and each set of primary colors are separated from each other by an 
opaque area, e.g., black grid lines. This has been found to give improved 
color reproduction and reduce flare in the displayed image. 
The size of the mosaic set is normally not critical since it depends on the 
viewing distance. In general, the individual pixels of the set are from 
about 50 to about 300 .mu.m. They do not have to be of the same size. 
In a preferred embodiment of the invention, the repeating mosaic pattern of 
dye to form the color filter array consists of uniform, square, linear 
repeating areas, with one color diagonal displacement as follows: 
##STR5## 
In another preferred embodiment, the above squares are approximately 100 
.mu.m. 
As noted above, the color filter array elements of the invention are used 
in various display devices such as a liquid crystal display device. Such 
liquid crystal display devices are described, for example, in UK Patent 
Nos. 2,154,355; 2,130,781; 2,162,674 and 2,161,971. 
A process of forming a color filter array element according to the 
invention comprises 
(a) imagewise-heating a dye-donor element comprising a support having 
thereon a dye layer as described above, and 
(b) transferring portions of the dye layer to a dye-receiving element 
comprising a transparent support having thereon a dye-receiving layer, 
the imagewise-heating being done in such a way as to produce a repeating 
mosaic pattern of dyes to form the color filter array element. 
Various methods can be used to supply energy to transfer dye from the dye 
donor to the transparent support to form the color filter array of the 
invention. There may be used, for example, a thermal print head. A high 
intensity light flash technique with a dye-donor containing an energy 
absorPtive material such as carbon black or a non-subliming light 
absorbing dye may also be used. This method is described more fully in 
U.K. Application No. 8824366.2 by Simons filed Oct. 18, 1988, the 
disclosure of which is hereby incorporated by reference. 
Another method of transferring dye from the dye-donor to the transparent 
support to form the color filter array of the invention is to use a heated 
embossed roller as described more fully in U.K. Application No. 8824365.4 
by Simons filed Oct. 18, 1988, the disclosure of which is hereby 
incorporated by reference. 
In a preferred embodiment of the invention, a laser is used to supply 
energy to transfer dye from the dye-donor to the receiver as described 
more fully in U.S. Ser. No. 259,080, filed Oct. 18, 1988 of DeBoer 
entitled "Color Filter Array Element Obtained by Laser induced Thermal Dye 
Transfer", the disclosure of which is hereby incorporated by reference. 
If a laser or high intensity light flash is used to transfer dye from the 
dye-donor to the receiver, then an additional absorptive but non-volatile 
material is used in the dye-donor. Any material that absorbs the laser or 
light energy may be used su:h as carbon black or non-volatile 
infrared-absorbing dyes or pigments which are well known to those skilled 
in the art. Cyanine infrared absorbing dyes may also be employed with 
infrared diode lasers as described in DeBoer Application Ser. No. 221,163 
filed July 19, 1988, the disclosure of which is hereby incorporated by 
reference. 
A dye-donor element that is used to form the color filter array element of 
the invention comprises a support having thereon a blue dye as described 
above along with other colorants su:h as imaging dyes or pigments to form 
the red and green areas. Other imaging dyes can be used in such a layer 
provided they are transferable to the dye receiving layer of the color 
array element of the invention by the action of heat. Especially good 
results have been obtained with sublimable dyes. Examples of additive 
sublimable dyes include anthraquinone dyes, e.g., Sumikalon Violet RS.RTM. 
(Sumitomo Chemical Co., Ltd.), Dianix Fast Violet 3R-FS.RTM. (Mitsubishi 
Chemical Industries, Ltd.), Sumickaron Diazo Black 5G.RTM. (Sumitomo 
Chemical Co., Ltd.), and Miktazol Black 5GH.RTM. (Mitsui Toatsu Chemicals, 
Inc.); direct dyes such as Direct Dark Green B.RTM. (Mitsubishi Chemical 
Industries, Ltd.) and Direct Brown M.RTM. and Direct Fast Black D.RTM. 
(Nippon Kayaku Co. Ltd.); acid dyes such as Kayanol Milling Cyanine 
5R.RTM. (Nippon Kayaku Co. Ltd.); and basic dyes such as Aizen Malachite 
Green.RTM. (Hodogaya Chemical Co., Ltd.). Examples of subtractive dyes 
useful in the invention include the following: 
##STR6## 
or any of the dyes disclosed in U.S. Pat. No. 4,541,830. The above cyan, 
magenta, and yellow subtractive dyes may be employed in various 
combinations, either in the dye-donor itself or by being sequentially 
transferred to the dye image-receiving element, to obtain the other 
desired red and green additive primary colors. The dyes may be mixed 
within the dye layer or transferred sequentially if coated in separate dye 
layers. The dyes may be used at a :overage of from about 0.05 to about 1 
g/m.sup.2. 
The imaging dye, and an infrared or visible light-absorbing material if one 
is present, are dispersed in the dye-donor element in a polymeric binder 
such as a cellulose derivative, e.g., cellulose acetate hydrogen 
phthalate, :ellulose acetate, cellulose acetate propionate, cellulose 
acetate butyrate, cellulose triacetate; a polycarbonate; poly(styrene co 
acrylonitrile), a poly(sulfone) or a poly(phenylene oxide). The binder may 
be used at a coverage of from about 0.1 to about 5 g/m.sup.2. 
The dye layer of the dye-donor element may be coated on the support or 
printed thereon by a printing technique such as a gravure process. 
Any material can be used as the support for the dye-donor element provided 
it is dimensionally stable and can withstand the heat generated by the 
thermal transfer device such as a laser beam. Such materials include 
polyesters su:h as poly(ethylene terephthalate); polyamides; 
polycarbonates; glassine paper; condenser paper; cellulose esters; 
fluorine polymers; polyethers; polyacetals; polyolefins; and polyimides. 
The support generally has a thickness of from about 2 to about 250 .mu.m. 
It may also be coated with a subbing layer, if desired. 
The support for the dye image-receiving element or color filter array 
element of the invention may be any transparent material such as 
polycarbonate, poly(ethylene terephthalate), cellulose acetate, 
polystyrene, et:. In a preferred embodiment, the support is glass. 
After the dyes are transferred to the receiver, the image may be treated to 
further diffuse the dye into the dye-receiving layer in order stabilize 
the image. This may be done by radiant heating, solvent vapor, or by 
contact with heated rollers. The fusing step aids in preventing fading 
upon exposure to light and surface abrasion of the image and also tends to 
prevent crystallization of the dyes. Solvent vapor fusing may also be used 
instead of thermal fusing. 
Several different kinds of lasers could be used to effect the thermal 
transfer of dye from a donor sheet to the dye-receiving element to form 
the color filter array element, such as ion gas lasers like argon and 
krypton; metal vapor lasers such as copper, gold, and cadmium; solid state 
lasers such as ruby or YAG; or diode lasers su:h as gallium arsenide 
emitting in the infrared region from 750 to 870 nm. However, in practice, 
the diode lasers are preferred because they offer substantial advantages 
in terms of their small size, low cost, stability, reliability, 
ruggedness, and ease of modulation. In practice, before any laser can be 
used to heat a dye-donor element, the laser radiation must be absorbed 
into the dye layer and converted to heat by a molecular process known as 
internal conversion. Thus, the construction of a useful dye layer will 
depend not only on the hue, sublimability and intensity of the image dye, 
but also on the ability of the dye layer to absorb the radiation and 
convert it to heat. 
Lasers which can be used to transfer dye from the dye-donor element to the 
dye image receiving element to form the color filter array element in a 
preferred embodiment of the invention are available commercially. There 
can be employed, for example, Laser Model SDL-2420-H2.RTM. from 
Spectrodiode Labs, or Laser Model SLD 304 V/W.RTM. from Sony Corp. 
The following example is provided to illustrate the invention.

EXAMPLE 
A blue dye-donor was prepared by coating on a gelatin subbed transparent 
175 .mu.m poly(ethylene terephthalate) support a dye layer containing blue 
dye 1 illustrated above (0.22 g/m.sup.2) in a cellulose acetate propionate 
(2.5% acetyl, 46% propionyl) binder (0.26 g/m.sup.2) coated from a 
1-propanol, 2-butanone, toluene and cyclopentanone solvent mixture. The 
dye layer also contained Raven Black No. 1255.RTM. (Columbia Carbon Co.) 
(0.21 g/m.sup.2) ball-milled to submicron particle size, FC-431.RTM. 
dispersing agent (3M Company) (0.01 g/m.sup.2) and Solsperse.RTM. 2400 
dispersing agent (ICI Corp.) (0.03 g/m.sup.2). 
A control blue dye-donor was prepared as described above except that it 
contained a mixture of the cyan dye illustrated above (0.64 g/m.sup.2) and 
the magenta dye illustrated above (0.21 g/m.sup.2) to form a dye having a 
blue hue. 
A dye receiver was prepared by spin-coating the following layers on a 53 
.mu. thick flat surfaced borosilicate glass: 
(1) Subbing layer of duPont VM 651 Adhesion Promoter as a 1% solution in a 
methanol water solvent mixture (0.5 .mu.m thick layer equivalent to 0.54 
g/m.sup.2), and 
(2) Receiver layer of a polycarbonate of 
4,4'-(hexahydro-4,7-methanoindene-5-ylidene)bisphenol, as described in 
U.S. Application Ser. No. 334,269, of Harrison et al. referred to above, 
from methylene chloride solvent (2.5 g/m.sup.2). 
The dye-donor was placed face down upon the dye-receiver. A 
Mecablitz.RTM.Model 45 (Metz AG Company) electronic flash unit was used as 
a thermal energy source. It was placed 40 mm above the dye-donor using a 
45 degree mirror box to concentrate the energy from the flash unit to a 
25.times.50 mm area. The dye transfer area was masked to 12.times.42 mm. 
The flash unit was flashed once to produce a transferred transmission 
density of 1.4 at the maximum absorption of the dye mixture. 
The same flash transfer procedure was used for the control coating 
producing a transferred transmission density of 1.4 at the maximum density 
of the dye mixture. 
Each transferred area was then treated with a stream of air saturated with 
methylene chloride vapor at 22.degree. C for 10 minutes to further diffuse 
the dyes into the dye-receiving layer. 
The Red and Green Status A densities of the transferred area were read. 
Each transferred area was then placed in an oven at 180.degree. C, 25% RH 
for one hour and the densities were then re read to determine the percent 
dye loss. The following results were obtained: 
______________________________________ 
Red Status A density 
Green Status A Density 
Receiver 
Init. Heated % Loss 
Init. Heated 
% Loss 
______________________________________ 
Control 
1.83 0.70 62 1.47 1.29 12 
Invention 
1.43 1.36 5 1.11 1.11 0 
______________________________________ 
The above results indicate that the receiver containing the blue dye 
according to the invention had better stability to heat than the control 
receiver containing a mixture of dyes to form a blue dye. 
The invention has been described in detail with particular reference to 
preferred embodiments thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.