Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2~7591
~VO 95/01583 PCT/US94/06718
COLOR LIQUID CI~YSTAL DISPLA~
t RAcKGRouND OF THF lNVFNTION
Field of the Jnvention
The invention relates to color displays and, more particularly, to color liquid
crystal displays (LCDs) lltili~in~ optically coupled microlens matrices, therebycollecting a greater percentage of the available light to illllmin~te the matrix of liquid
crystal elements and matrix of color filter elements. The invention also isolates the
LCD medium from the color filter so that the substances used in the color filter, such as
the dyes, need not be inert to the liquid crystal medium.
T)iscussion of the Prior Art
Prior art LCD systems typically have color filter dyes deposited directly onto the
glass substrate of the LCD. This requires that the substances used in the color filter,
primarily the dyes, be inert to the liquid crystal medium. Furtherrnore, in order to
achieve o~lil.lulll wide viewing angles for users, the spacing of each liquid crystal cell
or elennlon~ i.e., the cell gap, must be adjusted to an optimum value for the color of the
particular cell.
2 o SUMl\~A~Y OF THF TNVFNTION
In accordance with the invention there is provided a color LCD comprising a
matrix of liquid crystal elements positioned within a liquid crystal medium layer
disposed bc;Lwc;c;ll sandwiching transparent layers of material inert to the liquid crystal
medium. The color LCD further comprises a ulliÇOllll light source, a matrix of color
2 5 filter elements colle~ollding to the matrix of liquid crystal elements, and first and
second matrices of microlens elements corresponding to the matrix of liquid crystal
elements and to the matrix of color filter elements. One of the matrices of microlens
elements is disposed on each side of the matrix of liquid crystal elements.
Corresponding elements of the liquid crystal matrix, the color filter matrix and the first
3 o and second microlens matrices are optically coupled to one another and to the uniform
light source to provide a viewable color display. The uniform light source preferably
comprises a diffuse uniform light source.
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At least some of the individual lens elements of the microlens matrices are
preferably shaped to reduce chromatic aberration for the color of the light to be
transmitted therethrough. The color filter elements can comprise additive color dye dots
or subtractive color dye dots.
Further, the lens elements of at least one of the microlens matrices are preferably
larger in cross-sectional area than are the liquid crystal elements in order to utilize a
greater portion of the available light than could be utilized without the use ofmicrolenses. The color filter elements are also preferably larger in cross-sectional area
than are the liquid crystal elements.
The color filter elements can comprise one or more dyes which are reactive with
the liquid crystal medium. The color filter layer can be positioned between the light
source and the liquid crystal matrix, such as between the light source and the first
microlens matrix, or between the first microlens matrix and one of the transparent layers
sandwiching the LCD matrix. The color filter layer can ~ltern~tively be positioned to
color filter the light after it has passed through the liquid crystal matrix.
OF~TF.CTS AND ADVANTAGF.S O~ THE PRF~ENT rNVF~TION
One object of the present invention is to utilize a higher percentage of available
light in producing a color LCD.
2 o Another object of the instant invention is to minimi7~ chromatic aberrations in a
color LCD.
One advantage of the present invention is that relatively high intensity is
m~int~ined over wide viewing angles on the color LCD of the invention.
Another advantage of the invention is that color filters comprising substances
2 5 which are reactive with LCD media can be Utili~
Yet another advantage of the invention is that a lower cost color LCDis
producible in accordance therewith.
Still another advantage of the invention is that monochrome LCD glass can be
used in providing a color LCD.
3 0 Other objects, features and advantages of the invention will become a~,p~ to
those skilled in the art from the description of the preferred embodiment, claims and
drawings hereof, wherein like numerals refer to like elements.
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~'O 95/01583 PCT/US94/06718
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BF~TFF DFSCRTPTION OF THF DRAW~GS
Fig. 1 schematically illustrates a preferred embodiment of the invention with the
matrix of color filter elements positioned between the input microlens matrix and the
5 LCD matrix;
Fig. 2 schematically shows an embodiment of the present invention having the
matrix of color filter elements disposed between the LCD matrix and the output
microlens matrix;
Fig. 3 schematically depicts a third embodiment wherein the matrix of color
0 filter elements is placed between the diffuse light source and the input microlens plate;
and
Fig. 4 sch~m~tically illustrates light paths for corresponding microlens matrix
elemente and LCD matrix elements.
nFSC~TPTION OF THF Pl~FFFRRFn EM~OnTMF~T
As can be seen in Fig. 1, a light source 10 provides uniform and preferably
diffuse light through a diffuser 12 and through a color filter layer 14 which may
comprise typical additive colors, subtractive colors or additive colors comprising paired
layers of subtractive colors, such as disclosed in U.S. application Ser. No. 08/081,915
2 o filed June 22, 1993 entitled "Color Filter Display." Various choices for the color filter
dots or elements are well-known and they are disposed in a matrix in a well-known
manner. Each color dot is optically coupled with a corresponding individual microlens
in a first or input matrix of microlenses on layer 16.
Optically coupled to the color dot and microlens matrices is layer 18 comprising2 5 a matrix of liquid crystal elements or cells sandwiched between two solid transparent
layers 20 and 22. A second or output microlens matrix 24 is optically coupled to the
color filter matrix 14, the first microlens matrix 16, and the LCD element matrix 18. In
the preferred embodiment, each microlens is preferably corrected for chromatic
aberration in accordance with the color of the dot through which it will transmit light.
3 o Thus, the individual color elements of filter layer 14 are disposed to be in registry with
corresponding individual microlenses in layers 16 and 24 and individual LCD elements
or cells in layer 18, so that good ~ nment of the color filters and lenses is achieved and
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any chromatic aberration corrected. For example, for a particular green filter dot,
corresponding individual microlenses in layer 16 and in layer 24 are corrected to
minimi7e chromatic aberration of green light. Chromatic aberration correction isanalogous for the red and blue filtered light. The dots of the filter can be surrounded by
5 black bands as known in the art, if desired.
Fig. 2 schem~tically illu~ Les an ~It~rn~tive embodiment of the invention
wherein the color filter layer 14 is disposed b~lw~ell layer 18 of liquid crystal elements
and the second or output microlens matrix 24.
Fig. 3 sehem~tically shows another embodiment of the invention wherein the
0 color filter layer 14 is positioned belw~tll the light diffuser 12 and first or input
microlens matrix 16.
All three embolliment~ illustrated utilize e~enti~lly the same combination of
optical components. Those skilled in the art will appreciate that a particular
embodiment may be the most desirable for a particular application or that m~nllf~çturing
5 of one embodiment may be easier or less costly than another. Microlens opticalcharacteristics can be adjusted to co.llpellsate for color filter placement, if nece~S~ry.
Fig. 4 sçhem~tie~lly depicts the light paths for corresponding microlens and
LCD matrix element~ in accordallce with the invention. Although not shown in Fig. 4
for the sake of clarity, the color filter matrix 14 is positionable in several places, within
2 o the light path of Fig. 4 as illustrated in Figs. 1, 2 and 3.
In contrast, typical prior art designs require deposition of the color filter layer
directly onto the common electrode surface of the LCD. This layer must then be
optically aligned with the active matrix of the LCD and held in precise ~ ;nment during
subsequent sealing operations. This is usually difficult for a normally black display
2 5 glass. Mi~ nment of these layers results in a loss of color purity in the subsequent
display and hence the loss of the entire, relatively expensive, active matrix glass.
Since, in practicing the present invention, the color filter layer is not deposited
on the LCD substrate, a wider variety of ms~teri~l~ or substances and processes can be
considered for using in constructing the color filter layer. Appropriate choices can save
3 o money, decrease m~nnf~cturing steps, increase assembly accuracy, and add to the
durability of the product. Too, particular dyes which would not be available because
they would react with the LCD medium and which are very resistant to fading can be
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VO 95/01583 PCT/US94/06718
used. Therefore, a much broader wliverse of dyes can be used to create the color layer.
Such dyes may be more stable toward heat as well as light over a normal range ofenvironments to be encountered by the display.
Another advantage of the invention is that the use of a matrix of color filter dots
deposited onto a microlens plate elimin~tes a need for a complicated gap adjustment. In
the conventional LCD, the cell gap spacing is adjusted for each color in order to
optimize the contrast and viewing angle characteristics of the display. This cell gap
adjustment is done typically by depositing additional clear layers of various thickness
over or under the color filter layer. Although cell gap adjustment is nPcess~ry in the
pler~lled embodiment, yields are increased as a result of se~dling the cell gap
adjll~tment from the color filter fabrication.
Furthermore, in accordance with the invention, since light travels through the
LCD with near perpendicular ~li nment a wide viewing angle is provided through
various designs available for the output microlens plate 24.
In addition, in practicing the invention, a monochrome LCD glass, lower in cost
than a color panel, can be utilized simply by ch~n~in~ the lens and filter layers which
are used with the glass, thereby re~lu~ing the number and variety of components that
must be hlvt;ll~olied. In this way by practicing the invention, a single LCD glass can be
used for monochrome, diagonal stripe color, vertical stripe color, or quad color dot
2 o arrangements depending on the lens filter plate to which it is mated.
As either additive or subtractive color filter m~teri~lc can be utilized the
advantages of each can be applied to any specific application. Thus, the color filter dots
can be produced by, for example, a color printing process in which a printing press or
silk screen process is used to deposit a matrix of color dots onto a plate in registry with
2 5 the microlens matrix thereon. Alternatively, the color p~ttern~ can be created using a
photolithographic process using p~tterne(l polymer layers which are either pre- or post-
dyed. The patterns can also be created using color photographic processes such as are
utilized to m~nllf~cture color transparencies.
This invention has been described herein in considerable detail in order to
3 o comply with the Patent Statutes and to provide those skilled in the art with the
information needed to apply the novel principles and to construct and use such
specialized components as are required. However, it is to be understood that the
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WO 95101583 2 ~ ~ ~ 5 9 ~ -6- PCT/US94/06711
invention can be carried out by specifically different equipm~nt and devices, and that
various modifications, both as to the equipment details and operating procedures, can be
accomplished without departing from the scope of the invention itself.
