Exemplary embodiments of the present invention can be understood in more detail from the following detailed description taken in conjunction with the accompanying drawings, in which:
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the following exemplary embodiments but includes various applications and modifications. In addition, the size of the layers and regions of the attached drawings along with the following embodiments are simplified or exaggerated for precise explanation or emphasis and the same reference numeral represents the same component.
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The shielding layer 20 includes a polymer material and a clay-based material dispersed onto the polymer material. The shielding layer 20 prevents the malfunctioning of the display device due to static electricity and impurities through the polymer material and the clay-based material.
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For the liquid crystal display device, the static electricity might be generated during the fabricating thereof as follows. During fabricating the liquid crystal display device, a polarizing plate is attached to the substrate 10. The polarizing plate is transferred with a protecting film attached thereon and then is attached to the substrate 10 after separating the protecting film. During separating the protecting film, the static electricity is generated and a large amount of charges 30 due to the static electricity inflows from the polarizing plate to the substrate 10. The charges 30 form unnecessary electric fields to induce the malfunctioning of the display device.
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The conductive polymer material included in the shielding layer 20 is, for example, a graft copolymerizing product obtained by grafting the main chain of polystyrene sulfonic acid with aniline monomers. That is, the shielding layer 20 includes, for example, aqueous polystyrene sulfonic acid graft polyaniline (polystyrene sulfonic acid-g-polyaniline; which will be referred to by ‘PSSA-g-PANI’ hereinafter) represented by the following chemical formula 1.
In PSSA-g-PANI, the main chain of polystyrene sulfonic acid includes a first portion (1) which is not concerned with polyaniline and a second portion (2) which is concerned with polyaniline. The first portion (1) is aqueous because of styrene sulfonic acid which is not concerned with polyaniline. For the second portion (2), hydrogen combined with nitrogen in a portion of an aniline functional group provides electrons to oxygen combined with sulfur included in sulfonic acid to exhibit a polarized state to show the conductivity. Accordingly, when the shielding layer 20 is formed by using PSSA-g-PANI, the shielding layer 20 can be formed using an aqueous solution because of the first portion (1) and the shielding layer 20 can exhibit the conductivity because of the second portion (2).
The shielding layer 20 may further include, for example, a trace amount of ethyl tri-methoxy silane represented by the following chemical formula 2.
Also, the shielding layer 20 may further include, for example, a trace amount of tetra-ethyl ortho-silicate represented by the following chemical formula 3.
Ethyl tri-methoxy silane and tetra-ethyl ortho-silicate function as a curing agent that cures the aqueous solution state of the shielding layer 20 to a solid state layer.
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The clay-based material includes various inorganic cations such as, for example, sodium cation (Na+), magnesium cation (Mg2+), calcium cation (Ca2+), and the like and the plate-shaped layers 25 can be integrated strongly through an electrostatic combination with the inorganic cations. For example, the clay-based material includes at least one of montmorillonite, bentonite, hectorite, fluorohectorite, saponite, beidelite, nontronite, stevensite, vermiculite, volkonskoite, magadite and kenyalite.
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At each pixel area, a thin film transistor 400 and a pixel electrode 160 are formed. The thin film transistor 400 includes a gate electrode 111, a source electrode 141 and a drain electrode 142. The gate electrode 111 is branched from the gate line 110. The source electrode 141 is branched from the data line 140. The drain electrode 142 faces the source electrode 141 and is electrically connected to the pixel electrode 160. The pixel electrode 160 occupies most of the region of the pixel area except the thin film transistor 400.
On the second substrate 200, a common electrode 230 corresponding to the pixel electrode 160 is formed. The pixel electrode 160 and the common electrode 230 have an interaction and form an electric field between the first and the second substrates 100 and 200.
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On the source electrode 141 and the drain electrode 142, a passivation layer 150 to protect the channel region is formed. At the passivation layer 150, a contact hole 150h exposing a portion of the drain electrode 142 is formed. On the passivation layer 150, the pixel electrode 160 is formed and the pixel electrode 160 is electrically connected to the drain electrode 142 through the contact hole 150h. On the pixel electrode 160, a first shielding layer 170 and a first alignment layer 180 are formed.
On the second substrate 200, a light shielding pattern 210 and a color filter 220 are formed. The light shielding pattern 210 is formed to cover the regions corresponding to the boundary of the pixel regions and the thin film transistor 400. Except the covered regions, the light shielding pattern 210 is opened. The light shielding pattern 210 blocks the transmission of the light not controlled at the pixel electrode 160. The color filter 220 is formed to fill the opened region of the light shielding pattern 210. The color filter 220 includes blue/red/green filters corresponding to the three primary colors of light to display color image. On the color filter 220, an over-coating layer is formed to protect the color filter 220 and to planarize the second substrate 200.
On the color filter 220 or the over-coating layer, the common electrode 230 is formed. On the common electrode 230, a second shielding layer 240 and a second alignment layer 250 are formed. Between the first and the second alignment layers 180 and 250, a liquid crystal layer 300 in which liquid crystal 301 is aligned is provided. The initial alignment direction of the liquid crystal 301 can be controlled by the first and the second alignment layers 180 and 250.
During the operation of the liquid crystal display device, when a gate on signal is applied to the gate line 110, the thin film transistor 400 is turned on. Into the data line 140, data signals according to the image information is transferred and applied to the pixel electrode 160. At the same time, a common voltage is applied to the common electrode 230. An electric field according to the applied voltage difference between the pixel electrode 160 and the common electrode 230 is generated and functions onto the liquid crystal layer 300. The liquid crystal 301 has a dielectric anisotropy and the alignment direction of the liquid crystal 301 is changed according to the electric field. The liquid crystal 301 has a refractive anisotropy and a light transmitting the liquid crystal 301 exhibits transparency corresponding to the alignment direction of the liquid crystal 301 to display an image.
During operation, the liquid crystal layer 300 is exposed to various impurities and can be contaminated. When the liquid crystal 301 is contaminated, the quality of the externally displaying image during the operation of the liquid crystal display device can be deteriorated. One of the factors which may cause contamination of the liquid crystal 301 is the color filter 220. The color filter can be formed, for example, by patterning color photoresist including a pigment. As described above, the photoresist may include various chemical components such as, for example, a polymer resin, an organic solvent and a photoactive compound and so the impurities can be originated from the photoresist.
The first and the second shielding layers 170 and 240 includes, for example, the clay-based material having the plate-shaped layers, and the plate-shaped layers are distributed and dispersed within the first and the second shielding layers 170 and 240. The plate-shaped layers block the movement of the impurities and prevent the contamination of the liquid crystal 300 due to the passage of the impurities through the first and the second shielding layers 170 and 240. As described above, the clay-based material may be prepared by using various mineral including, for example, montmorillonite and can include an inorganic cation such as a sodium ion.
During the operation of the liquid crystal display device, static electricity might be generated and a large amount of charges from the first and the second substrates 100 and 200 might inflow into the liquid crystal layer 301. When the charges inflow, the electric field applied to the liquid crystal layer 301 might be changed to thereby cause malfunctioning of the liquid crystal display device.
The first and the second shielding layers 170 and 240 include a conductive polymer material, and the charges inflowing due to the static electricity diffuse within the shielding layers. As the result, the charges are present within the first and the second shielding layers 170 and 240 and cannot move to the liquid crystal layer 300. As explained above, the conductive polymer material includes an aqueous polyaniline graft copolymer produced by grafting the main chain of polystyrene sulfonic acid with an aniline monomer. That is, the polymer material include, for example, PSSA-g-PANI represented by chemical formula 1.
When the thickness of the first and the second alignment layers 180 and 250 are too thick, the intensity of the electric field functioning from the pixel electrode 160 and the common electrode 230 to the liquid crystal 301 might be weakened. In addition, when the thickness of the first and the second alignment layers 180 and 250 is too thick, a uniform thickness may not be accomplished and the uniform alignment of the liquid crystal 301 may not be accomplished. Considering this point, the preferred thickness of the first and the second alignment layers 180 and 250 may be about 1000 angstroms (Å). For example, the thickness of the first and the second shielding layers 170 and 240 corresponding to the first and the second alignment layers 180 and 250 may be from about 500 Å to about 2000 Å.
Both of the first and the second shielding layers 170 and 240 need not to be formed together, but one of the first and the second shielding layers 170 and 240 can be formed if necessary. For example, when considering the contamination of the liquid crystal display device due to the impurities mainly caused by the color filter 222 formed on the second substrate 200, the first shielding layer 170 can be omitted and only the second shielding layer 240 can be formed.
PSSA-g-PANI included in the first and the second shielding layers 170 and 240 can be prepared through, for example, a reaction of a copolymer of styrene sulfonic acid and aminostyrene with aniline.
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As described above, in manufacturing PSSA-g-PANI, the conductivity can be controlled, for example, by controlling the amount of aminostyrene in the copolymer of styrene sulfonic acid and aminostyrene or by controlling the amount of reacting aniline with the copolymer of styrene sulfonic acid and aminostyrene. For example, the conductivity of the shielding layer which may prevent the malfunctioning of the liquid crystal display device due to generated static electricity is about 10−9 S/cm to about 10−1 S/cm.
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On the source electrode 141 and the drain electrode 142, a passivation layer 150 is formed by applying the same method of forming the gate insulating layer 120. The passivation layer 150 is patterned to form a contact hole 150h exposing the drain electrode 142. On the patterned passivation layer 150, a transparent conductive layer utilizing, for example, indium zinc oxide (IZO) or indium tin oxide (ITO) is deposited and then is patterned to form a pixel electrode 160.
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The color filter 220 is formed by coating color photoresist on the second substrate 200 and then patterning the color photoresist layer. The color filter 220 fills the region where the light shielding layer is removed through the patterning of the light shielding layer. The patterning with respect to the color photoresist layer is implemented three times for red/green/blue. A transparent layer is deposited on the color filter 220 to form a common electrode 230.
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The clay-based material 172 is mixed by from about 5% to about 20% by weight with respect to the aqueous solution 171. When the amount of the clay-based material 172 is used too much, the physical property of the polymer material included in the aqueous solution 171 might be changed.
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The second shielding layer 240 illustrated in
According to exemplary embodiments of the present invention, a shielding layer is provided onto a substrate which may prevent the malfunctioning of a display device induced by a contamination due to impurities and static electricity.
Having described the exemplary embodiments of the present invention, it is further noted that it is readily apparent to those of reasonable skill in the art that various modifications may be made without departing from the spirit and scope of the invention which is defined by the metes and bounds of the appended claims.
Number | Date | Country | Kind |
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10-2006-65991 | Jul 2006 | KR | national |