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WO 2005/12I882 PCT/KR2005/001681
Description DISPLAY DEVICE USING PRINTED CIRCUIT BOARD AS
SUBSTRATE OF DISPLAY PANEL
Technical Field
[ I | The present invention relates to a display device using a printed circuit board
(PCB) as a substrate of a display panel. More particularly, the present invention relates to a display device capable of improving the response speed and image quality thereof by directly connecting pixels or segments of a display panel to a driving circuit through a via hole formed in a PCB.
Background Art
[2| Generally, display devices arc classified into emissive display , such as CRTs,
PDPs, LEDs, or OLEDs, and non- emissive display , such as LCDs. The emissive display represents the high response speed, but the image becomes faint in a bright place. In contrast, the non- emissive display represents the low response speed although it can clearly display the image in the bright place.
[3] Among other things, an cleclrochromic display (ECD) is a non- emissive display ,
such as an LCD, capable of adjusting the color of an clcctrochromic material through controlling the chemical reaction of the clcctrochromic material by applying an electric signal to the clcctrochromic material.
(4) FIG. I is a schematic view illustrating a structure of a display panel of an ECD.
Referring to FIG. I, the display panel I of the ECD includes a lower electrode I I
formed on a lower glass substrate 10, an electrochromic layer 12 formed on an upper
surface of the lower electrode 11 and including an clcctrochromic material changing its
color depending on an electric signal applied thereto, an electrolyte layer 13 formed on
the electrochromic layer 12 and including ions related to the clcctrochromic reaction,
an ion storage 14 formed on the electrolyte layer 13 for storing ions having polarity op
positc to that of the ions related to the electrochromic reaction, an upper electrode 15
formed on the ion storage 14, and an upper glass substrate 16 formed on the upper
electrode 15. Generally, at least one of the lower electrode 11 and the upper electrode
15 is a transparent electrode, such as indium tin oxide (ITO) electrode. The ion storage
14 can be omitted and the electrolyte layer 13 can be replaced with an ionic liquid
layer including ionic liquid.
|5) If voltage is applied to the display panel I, current flows from the electrochromic
layer 12 to the ion storage 14, thereby coloring the electrochromic layer 12. In contrast, if the current flows from the ion storage 14 to the electrochromic layer 12, the electrochromic layer 12 is decolored. The above coloring and decoloring reactions of the

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electrochromic layer 1 2 may occur with the current flow inverse to the above current How depending on materials of the cicclrochromic layer 12.
|6| FIG. 2a is a view illustrating a layout of the clcctrochromic layer for displaying
numerical characters with 7-scgmcnls, and FIG. 2b is a view illustrating a layout of a conventional lower electrode lor applying an electric signal to the clcctrochromic layer shown in FIG. 2a.
[7| As shown in FIG. 2b, lengths of electrodes corresponding to segments are different
from each other. In general, an electrode resistance value (for example, 200 O ) of a scgmcnl (a) is higher than an electrode resistance value (for example, 100 O ) of a segment (d) by two limes. In this case, the maximum current for the segments (d and a) is 10mA and 5mA, respectively, under the same coloring voltage of I.0V,so the response speed of the segment (a) is slower than the that of the segment (d) by two times. Accordingly, the overall response speed of the display device may be slowcred while varying the coloring degree for each segment, thereby degrading the image quality of the display device.
[8| The above problem may occur in various display devices in addition to the ECD.
For instance, display devices, such as the LCDs, OLEDs or PDPs, have wirings on each pixel electrode for applying an electric signal to a display panel. Jn this case, the line width becomes narrowed as the number of pixels increases, thereby increasing the resistance. Accordingly, the response speed of the display device is slowcred and the non-uniformity of the pixel image is occurred.
Disclosure
[9| The present invention is directed to a display device using a printed circuit board
(PCB) as a substrate of a display panel that substantially obviates one or more problems due to limitations and disadvantages of the related art.
[10] It is an object of the present invention to provide a display device capable of
improving operational characteristics thereof by reducing resistance of electrodes through directly applying an electric signal to pixels or segments of a display pane) by way of a via hole formed in a PCB.
[11] To achieve this object and other advantages in accordance with the purpose of the
invention, as embodied and broadly described herein, there is provided a display
device comprising: a printed circuit board (PCB) formed with a via hole and used as a
substrate; a display panel having an electrode, which applies an electric signal to a
pixel or a segment, aligned adjacent to one side of the via hole formed in the PCB; a
driving circuit section for applying an electric signal lo the display panel; and a wiring
section for electrically connecting the electrode of the display panel lo the driving
circuit section through the via hole.
[ 12] According to one preferred embodiment of the present invention, the driving circuit

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section is formed in the PCB in opposition to the display panel.
| 13] According to another preferred embodiment of the present invention, the display
device further includes an clcctrochromic layer aligned on the electrode in such a manner that a color thereof is changed according to the electric signal applied thereto from the electrode, an electrolyte layer aligned on the clcctrochromic layer and including ions related to an clcctrochromic reaction, an ion storage, which stores ions having polarity opposite to thai of ions related to the clcctrochromic reaction, aligned on the electrolyte layer, and a second electrode aligned on the ion storage. The ion storage can be omitted and the electrolyte layer can be replaced with an ionic liquid layer including ionic liquid.
[ 14] According to further another preferred embodiment of the present invention, the
via hole includes a metal wiring section formed at an outer peripheral portion of the via hole, and an inner peripheral portion of the via hole is empty or filled with a metal or a PCB laminate material.
[15] According to further another preferred embodiment of the present invention, the
display device further includes a passivation layer formed at a connection part between the PCB and the electrode. The passivation layer includes an oxide layer or a nitride layer.
| 16] According to the present invention, the electric signal of the driving circuit is
directly applied to the electrode through the via hole of the PCB, so the length of the electrode line used for wiring can be significantly reduced, thereby improving the response speed of the display device.
Description of Drawings
[ 17| The accompanying drawings, which arc included to provide a further un-
derstanding of the invention and arc incorporated in and constitute a part of this application, illustrate cmbodimcnl(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:
[ 18] FIG. 1 is a schematic view illustrating a basic structure of a display panel of an
ECD.
[19] FJG. 2a is a view illustrating a layout of an electrochromic layer for displaying
numerical characters with 7-segmcnls.
[20] FIG. 2b is a view illustrating a layout of a conventional lower electrode for
applying an electric signal to an clcctrochromic layer shown in FIG. 2a.
[211 FIG. 3 is a schematic view illustrating a structure of a display device using a PCB
as a substrate of a display panel according to a preferred embodiment of the present invention.
[22] FJG. 4 is a view illustrating a detailed structure of a via hole according to a
preferred embodiment of the present invention.

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[231 FIG. 5 is a schematic view illustrating a structure of a display device using a PCB
as a substrate of a display panel according to another embodiment of the present invention.
{2-4-1 FIG. 6 is a view illustrating a structure ol a passivation layer according to a
preferred embodiment of the present invention.
1251
126] 20: display panel, 21: lower electrode
1271 22: clcclrochromic layer, 23: electrolyte layer
[281 24: ion storage, 25: upper electrode
[291 30: PCB, 32: via hole
(30j 34: metal wiring, 36: driving circuit section
[311 50: passivation layer
Mode for Invention
[32| Reference will now be made in detail to the preferred embodiment of the present
invention, examples of which arc illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
[331 FIG. 3 is a schematic view illustrating a structure of a display device using a PCB
as a substrate of a display panel according to a preferred embodiment ol the present invention.
[ 34] Referring to FIG. 3, a display panel 20 of an ECD is mounted on a PCB 20. The
PCB 30 is a double-side PCB provided at a lower surface thereof with a driving circuit section 36. An electric diving signal generated from the driving circuit section 36 is directly applied to a lower electrode 21 of the display panel by way of a wiring 34 and a via hole 32.
[35] Electronic parts of the driving circuit section 36 can be formed in a separate PCB
such that they are electrically connected to the wiring 34 without directly making contact with the PCB 30 . This structure is also within the scope of the present invention.
[36] The structure of the display panel 20 shown in FTG. 3 corresponds to the structure
of the display panel 1 shown in FIG. 1. That is, a lower electrode 21, an clectrochromic
layer 22, an electrolyte layer 23, an ion storage 24, an upper electrode 25, and an upper
glass structure 26 of the display panel 20 are identical to those of the display panel 1
shown in FIG. I.
[37] However, according to the present invention, the lower electrode 21 is directly
connected to the via hole 32 without forming the lower glass substrate 10 (see, FIG 1) between the display panel 20 and the PCB 30. In addition, the via hole 32 is electrically connected to the wiring 34.

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[38] According lo the above structure, the lower electrode can he formed with a shape
identical to the shape of the clcctrochromic layer. For instance, in a case of a 7-scgmcnl display, the conventional clcctrochromic layer has a shape as shown in FIG. 2a and the conventional lower electrode has a shape as shown in FIG. 2b by taking the wiring into consideration. However, according to the structure of the display device shown in FIG 3, the wiring is directly connected lo the lower electrode 2 1 through the via hole 32 from the lower surface of the PCB 20. Thus, the lower electrode 2 I can be formed with the shape identical to the shape of the clcctrochromic layer, so that the length of the electrode wiring can be reduced. As a result, ihc resistance can be reduced and the response speed of the display device can be improved. In addition, since the segment electrodes arc identically Formed, the coloring/decoloring of the segments can be uniformly realized.
[ 39] Jn one embodiment of die present invention, the upper electrode 25 plays the role
of a common electrode. However, it is also possible to employ the lower electrode 22
installed on the upper surface of the PCB 30 as a common electrode.
[4-0] Preferably, the lower electrode 21 includes a metal electrode. Jn addition, a
transparent electrode (for example, an ITO layer) can be used for the lower electrode 21. If the metal electrode is used as the lower electrode 21, the response speed of the display device can be further improved due to the low resistance value of the metal electrode.
[41] Preferably, the PCB 30 is made from FR4, GETEX, Teflon, or ceramic, but the
present invention is not limited thereto. Materials that represent low reactivity with
respect lo an electrolyte and superior heat-resistant characteristics at device processing
temperature can be used for fabricating the PCB 30 without limitations. If the deviccis
processed under the high-lempcraturc condition, it is preferred to use ceramic as a
material for the PCB. In addition, a flexible PCB is used for a flexible display.
[42] Preferably, the wiring 34 is made from metal, but the present invention is not
limited thereto. Any conductive materials can be used for fabricating the wiring 34 without limitations.
[43] The via hole 32 is provided to electrically connect the lower electrode 21 lo the
wiring 34. FIG. 4 shows the detailed structure of the via hole 32. Referring lo FIG. 4, the via hole 32 includes an outer peripheral portion 40 and an inner peripheral portion 42. The outer peripheral portion 40 is a metal wiring section for electrically connecting the wiring 34 formed at an underside of the PCB 30 to the lower electrode 22. Jn addition, the inner peripheral portion 42 is a cavity, which is empty or filled with a PCB laminate material or a metal, such as Cu, Au or Pt. Materials filled in the via hole 32 must not react with the electrolyte while preventing the defect caused by a difference of a thermal expansion coefficient between the materials and the PCB 30 or

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Ihc lower electrode 2 I even if Ihe materials arc repeatedly shrunk and expanded due to temperature variation II the inner peripheral portion 42 is (Tiled with the metal or the PCB laminate material, the electrolyte can he prevented from being leaked
[-4—4-1 It is also possible to form a passivation layer between the PCB 30 and the
electrolyte in order to prevent the chemical reaction therebetween.
[45] FIG. 5 is a schematic view illustrating a structure of a display device using a PCB
as a substrate of a display panel according to another embodiment of the present invention.
[46] Referring to FIG. 5, a passivation layer 50 is further interposed between an
electrolyte 23 and a PCB 30 in addition to the structure shown in FJG. 4. Preferably, the passivation layer 30 is made from an oxide layer (for example, SiO ) or a nitride layer (for example, SiN) in such a manner that a connection part between the PCB and the lower electrode is not exposed to the exterior. FIG. 6 shows a structure of the passivation layer in detail.
|47| Although the present invention has been described in relation to the electrochromic
device, the present invention is applicable for other display devices. For instance, the present invention is used for an LCD (liquid crystal display), a PDP (plasma display panel), an LED (light emitting diode), an EL (electroluminescent display), an OLED (organic LED), an elcctrophorclic display, or display devices used for displaying images by applying electric signals to pixel electrodes.
[48] For example, if the present invention is utilized for a passive matrix display device,
since the wiring is directly connected to thc lower electrode formed on the upper surface of the PCB by passing through the PCB from the lower portion of the PCB, the length of the electrode wiring is significantly reduced and the difference of the resistance values of the pixels can be reduced.
Industrial Applicability
[49] According to the present invention, the electric signal of the driving circuit is
directly applied to the lower electrode through the via hole of the PCB, so the length of the electrode line used for wiring can be significantly reduced, thereby improving the response speed of the display device.
[50] Jn addition, since the pixel electrodes or segment electrodes arc uniformly formed,
the coloring/decoloring of the pixel electrodes can be uniformly realized, so that the image quality can be improved.
[51] Although a preferred embodiment of the present invention has been described for
illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

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Claims
[ 1 | A display device comprising:
a printed circuil hoard (PCB) formed with a via hole and used as a substrate: a display panel having an electrode, which applies an electric signal to a pixel or a segment, aligned adjacent to one side of the via hole formed in the PCB; a driving circuit section lor applying an electric signal to the display panel: and a wiring section for electrically connecting the electrode of the display panel to the driving circuit section through the via hole.
[2] The display device as claimed in claim I, wherein the driving circuit section is
formed in the PCB in opposition to the display panel.
[3] The display device as claimed in claim J, further comprising an eleclrochromic
layer aligned adjacent to the electrode in such a manner that a color thereof is changed according to the electric signal applied thereto from the electrode, an electrolyte layer aligned adjacent to the elcctrochromic layer and including ions related to an eleclrochromic reaction, and a second electrode aligned adjacent lo the electrolyte layer.
|4| The display device as claimed in claim 1, further comprising an elcctrochromic
layer aligned adjacent to the electrode in such a manner (hat a color thereof is changed according to the electric signal applied thereto from the electrode, an ionic liquid layer aligned adjacent to the eleclrochromic layer and including ions related lo an elcctrochromic rcaclion, and a second electrode aligned adjacent to the ionic liquid layer.
|5] The display device as claimed in claim 3, further comprising an ion storage,
which stores ions having polarity opposite lo thai of ions related lo the eleclrochromic rcaclion, aligned adjacent lo the electrolyte layer.
[6] The display device as claimed in claim 4, further comprising an ion storage,
which stores ions having polarity opposite lo that of ions related to the elcctrochromic reaction, aligned adjacent to the ionic liquid layer.
[7] The display device as claimed in any one of claims 1 lo 6, wherein the via hole
includes a metal wiring section formed at an outer peripheral portion of the via hole, and an inner peripheral portion of the via hole is filled with a metal or a PCB laminate material.
[8] The display device as claimed in any one of claims 1 lo 6, wherein the via hole
includes a metal wiring section formed at an outer peripheral portion of the via hole, and an inner peripheral portion of the via hole is empty.
[9] The display device as claimed in any one of claims 1 to 6, further comprising a
passivation layer formed at a connection part between the PCB and the electrode.

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[10] The display device as claimed in claim 9, wherein the passivation layer includes
an oxide layer or a nitride layer.