Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2001-02-07
2004-01-20
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S139000, C349S152000, C349S192000
Reexamination Certificate
active
06680759
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrode structure of a display panel and an electrode forming method, and more particularly, to an electrode structure of a display panel, for example, a plasma display panel (PDP), a liquid crystal display panel (LCD), an electro luminescence display (EL) or the like, in which electrodes are formed on a substrate through etching, and an electrode forming method.
2. Description of the Related Art
In a display panel of this kind, generally, electrodes are often formed through etching. In the case where the electrodes are to be formed on the substrate through etching, first, a layer of an electrode material such as ITO, SnO
2
, Cr, Cu or Ag is uniformly formed over the whole surface of the substrate by evaporation, sputtering or printing such as slot coating, then a resist pattern having a geometry of the electrodes is formed on the electrode material layer by photolithography or the like, and the electrode material layer is etched by pouring an etching solvent like a shower over the resist pattern, i.e., by a so-called spray etching.
In recent years, particularly, a so-called conveyer type inline manufacturing system has been the mainstream of display panel manufacturing apparatus as mass production has been demanded. In the inline manufacturing system, processing is continuously carried out while delivering a panel substrate on a conveyer line. For this reason, the spray etching is also carried out by spraying the etching solvent sequentially onto substrates by a spray device provided in a fixed position while delivering the substrates through the conveyer line.
In the above-mentioned display panel, electrodes having a geometry as shown in
FIG. 12
are formed on the substrate, for example.
FIG. 12
shows an example of electrodes formed on a glass substrate on a front face side of a 3-electrode surface discharge type PDP. In this PDP, a plurality of pairs of electrodes X and Y for generating a main discharge (surface discharge) for display are provided in a horizontal direction on a central part (display region) of a substrate
11
. These electrodes X and Y are divided into a plurality of blocks and are collected and converged for each block on ends of the substrate
11
(outside the display region).
In this example, the electrodes X are converged on one side of the substrate
11
(the left side in the figure) and the electrodes Y are converged on the other side of the substrate
11
(the right side in the figure). The electrodes X and Y are connected to flexible cables
34
at terminal portions
33
on a substrate end on said one side and on a substrate end on said other side, respectively, with use of an anisotropic conductive adhesive or the like and are connected to drivers.
In
FIG. 12
, for simplicity of description, eight display lines (a display line represented by a pair of electrodes X and Y) form one block (or group) and the electrodes X and Y of each block are converged on the terminal portions
33
on one side and on the other side.
12
. In an actual display panel having 480 display lines, for example, the display lines are divided into four blocks, each block having 120 display lines, through the division of the display line depends upon the performance of drivers. In each of the blocks, 120 electrodes X and 120 electrodes Y are converged on the terminal portions
33
on one side and on the other side and are connected to the flexible cables
34
at the terminal portions
33
, respectively.
In the above-mentioned display panel, as the size is increased and high definition is sought for, the width of electrodes is reduced. Consequently, the shape and the dimension of the electrodes obtained after etching are required to have higher precision and uniformity.
However, when the electrode material layer is etched by the spray etching method while delivering the substrate by means of the inline manufacturing system, the etching solvent is excessively supplied to a block boundary portion B of the resist pattern formed on the electrode material layer and the electrode material layer is over-etched in this portion. This problem is now described.
FIG. 13
is a view illustrating the details of an end of the substrate on which the electrodes X and Y are formed. Hereinafter, for convenience, rectilinear portions of the electrodes X and Y arranged in almost parallel in the display region of the substrate will be referred to as discharge electrode portions
51
, and oblique portions of the electrodes X and Y which extend from the discharge electrode portions
51
, converge in a predetermined number for each block and reach the terminal portions
33
at the end of substrate will be referred to as lead electrode portions
52
.
As shown in
FIG. 13
, at the end of the substrate, the discharge electrode portions
51
of either X or Y electrodes of the electrode pairs alone (for example, only the Y electrodes) are led out by the lead electrode portions
52
and reach the terminal portions
33
. Consequently, with regard to the Y electrodes, electrode distances between the electrodes are smaller in the terminal portions
33
than in the display region. In the block boundary portion B, however, since the lead electrode portions
52
of Y electrodes in adjacent blocks extend obliquely in such directions as to keep away from each other (i.e., in opposite directions) with the block boundary portion B interposed therebetween, the electrode distances are greater in the terminal portions
33
than in the display region. Furthermore, an electrode interval (a gap) between the electrodes X and Y of each electrode pair which acts as a discharge slit (discharge portion) is smaller than the electrode distances in the terminal portions, and an electrode interval (a gap) between the electrodes X and Y of adjacent electrode pairs which acts as an inverse slit (non-discharge portion) is greater than the electrode distances in the terminal portions. In other words, the electrode distances are little different in the central part of the substrate and are much greater in the block boundary portions at the end of the substrate. This difference in the electrode distances (i.e., in the density of the electrodes) at the end of the substrate causes a problem during etching.
FIG. 14
is a view illustrating the details of an end of the substrate on which the resist pattern for forming the above-described electrodes is provided. As shown in
FIG. 14
, when the resist pattern for the electrodes, that is, a resist pattern
51
a
for forming the discharge electrode portions, a resist pattern
52
a
for forming the lead electrode portions and a resist pattern
33
a
for forming the terminal portions, is provided and the spray etching is carried out while delivering the substrate
11
in a direction of an arrow K, a flow in a relative direction shown by an arrow F is generated in the etching solvent for the following reason.
FIG. 15
is a view illustrating a section taken along the line A-A′ in FIG.
14
. In general, the resist patterns
51
a
,
52
a
and
33
a
have hydrophobicity and has the property of repelling etching solvent
36
. For this reason, the etching solvent
36
does not get on the resist patterns
51
a,
52
a
and
33
a
easily and swells over the electrode material layer
31
. Accordingly, the etching solvent
36
flows in the direction shown by the arrow F without getting over the resist patterns
51
a
,
52
a
and
33
a.
In
FIG. 14
, attention will be paid to the block boundary portion B of the resist pattern. At the substrate end, the interval between terminal electrodes in the block boundary portion is larger than the interval between terminal electrodes which are not positioned in the block boundary portion, and has a larger area for receiving the etching solvent. Consequently, the inflow of the etching solvent into the block boundary portion B is larger. In the display region, however, the electrode interval in the block boundary portion B is equal to the electrode distances of other electro
Fujitsu Hitachi Plasma Display Limited
Kim Robert H.
Schechter Andrew
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