JP2008275801A - Display device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device in which an optical diffraction index of a transparent conductive film is optimized and optical transmittance of pixels is enhanced. <P>SOLUTION: The display device is provided with an electrode formed on a pixel area of a substrate. The electrode is composed of transparent conductive film which transmits light. The transparent conductive film is composed of metal oxide and contains nitride. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device and a manufacturing method thereof, and more particularly to a display device including a transparent conductive film electrode in a pixel and a manufacturing method thereof.

  For example, a liquid crystal display device has a pair of substrates made of glass, for example, opposed to each other with liquid crystal as an envelope, and has pixels arranged in a matrix on the liquid crystal side surface of these substrates.

  The area where each of these pixels is arranged becomes a liquid crystal display area, and an electric field is independently generated in each of the pixels, and the liquid crystal molecules of the pixel are caused to behave according to the strength of the electric field. To control.

  Each pixel is provided with a pair of electrodes, and an electric field having an intensity corresponding to a difference in potential applied to each electrode is generated in each pixel.

  Here, each of the electrodes functions as an electrode to which a reference potential is applied on one side (hereinafter sometimes referred to as a counter electrode), and on the other side, a potential corresponding to luminance (gradation) information is applied. It functions as an electrode (hereinafter sometimes referred to as a pixel electrode).

  In this case, for example, a backlight is provided on the back surface, and each pixel has a pixel electrode on the liquid crystal side surface of one substrate and a counter electrode on the liquid crystal side surface of the other substrate ( In some cases, the vertical electric field method is used, and each of the electrodes must be formed of a transparent conductive film. This is because the light from the backlight must be transmitted through one of the electrodes, the liquid crystal, and the other of the electrodes.

  Similarly, a backlight is provided on the back surface, and each pixel includes a pixel electrode and a counter electrode on the liquid crystal side surface of one substrate (sometimes referred to as a horizontal electric field method). In the case where the electrodes are formed in a comb-like shape and are arranged so as to be separated and meshed with each other, it is not always necessary to form the transparent conductive film. It is possible to improve the light transmittance.

  In addition, a liquid crystal display device called a so-called IPS (In Plain Switching) method, which is a form of a horizontal electric field method, has a counter electrode disposed in, for example, a large area of a pixel, and the counter electrode is disposed on the counter electrode through an insulating film. The pixel electrodes formed so as to overlap each other are formed by an electrode group in which a large number of pixel electrodes are juxtaposed in a direction intersecting the longitudinal direction. Even in this case, there is a demand that at least the counter electrode must be formed of a transparent conductive film. This IPS (In-Plane-Switchin) type liquid crystal display device is disclosed in detail, for example, in Patent Document 1 below.

Further, a so-called reflective liquid crystal display device that does not include a backlight and recognizes an image using external light such as the sun is also known. Such a liquid crystal display device is formed with a light reflecting plate on the liquid crystal side surface of the substrate opposite to the side observed by an observer, and the light reflecting plate usually serves as a counter electrode or a pixel electrode. However, even in this case, there is a demand that the other electrode must be formed of a transparent conductive film.
JP 2002-49049 A

  In any of the liquid crystal display devices having such a configuration, it has been continuously demanded to improve the light transmittance of the pixel.

  In this case, a method of changing the metal composition of the transparent conductive film is considered. However, when the transparent conductive film is formed by, for example, a sputtering method, the composition ratio is determined in advance, and thus cannot be realized by the sputtering method. There was a restriction.

  In addition, a method of adjusting the film thickness of the transparent conductive film is considered, but it is sufficient when it is desired to reduce the sheet resistance or when the underlying layer forming the transparent conductive film has a step. There was a restriction that it could not be thinned.

  An object of the present invention is to provide a display device in which the light refractive index of a transparent conductive film is optimized and the light transmittance of a pixel is improved without the above-described restrictions.

  Further, an object of the present invention is to provide a method for manufacturing a display device in which the light refractive index of a transparent conductive film is optimized and the light transmittance of a pixel is improved without the above-described restrictions.

   Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

(1) A display device according to the present invention includes, for example, an electrode formed in a pixel region of a substrate, and the electrode is formed of a transparent conductive film that transmits light,
The transparent conductive film is made of a metal oxide and contains a nitride.

(2) The display device according to the present invention is, for example, on the premise of the configuration of (1), wherein the ratio of the nitride of the transparent conductive film to the oxide is 10% or less.

(3) The display device according to the present invention is based on, for example, the configuration of (1), and the transparent conductive film is composed of at least one metal oxide of In, Sn, and Zn metal oxides. It is characterized by that.

(4) A display device according to the present invention, for example, on the premise of the configuration of (1), includes a thin film transistor that is turned on by a scanning signal from a gate signal line in the pixel region of the substrate,
The electrode is a pixel electrode to which a video signal from a drain signal line is supplied through the turned-on thin film transistor.

(5) The display device according to the present invention is based on the configuration of (1), for example, and a thin film transistor that is turned on by a scanning signal from a gate signal line in the pixel region of the substrate, A pixel electrode to which a video signal from a drain signal line is supplied,
The electrode may be a counter electrode that generates an electric field between the pixel electrode and the pixel electrode.

(6) A method of manufacturing a display device according to the present invention includes, for example, a step of forming a transparent conductive film on a substrate by a sputtering method,
Forming an electrode in each pixel by the transparent conductive film,
In forming the transparent conductive film, nitrogen gas is contained in the atmosphere.

(7) The method for manufacturing a display device according to the present invention is based on, for example, the configuration of (6), and the transparent conductive film is formed of at least one metal oxide of In, Sn, and Zn metal oxides. It is characterized by being.

  In addition, this invention is not limited to the above structure, A various change is possible in the range which does not deviate from the technical idea of this invention.

  According to the display device configured as described above, the light refractive index of the transparent conductive film can be optimized and the light transmittance of the pixel can be improved.

  In addition, according to the manufacturing method of the display device configured as described above, it is possible to obtain a liquid crystal display device in which the light refractive index of the transparent conductive film is optimized and the light transmittance of the pixel is improved.

  Embodiments of a display device according to the present invention will be described below with reference to the drawings.

<Schematic configuration diagram>
FIG. 2 is a schematic plan view showing a liquid crystal display device which is an embodiment of the display device according to the present invention.

  First, there is a liquid crystal display panel PNL, and this liquid crystal display panel PNL is configured by using a substrate SIUB1 and a substrate SUB2 which are arranged to face each other with a liquid crystal (not shown) interposed therebetween.

  The liquid crystal is sealed by a sealing material SL that also serves to fix the substrate SUB2 to the substrate SUB1, and a region surrounded by the sealing material SL is configured as a liquid crystal display region AR.

  In the liquid crystal display area AR, for example, on the liquid crystal side surface of the substrate SUB1, the gate signal lines GL extending in the x direction and juxtaposed in the y direction in the drawing, and extending in the y direction and juxtaposed in the x direction. Each drain signal line DL is formed.

  Pixels are respectively formed in regions (pixel regions) surrounded by the adjacent gate signal lines GL and the adjacent drain signal lines DL, whereby the pixels are arranged in a matrix in the liquid crystal display region AR. Will be.

  For example, as shown in an enlarged view (a portion in a solid line circle frame in the drawing) of the pixel indicated by a symbol PIX in the drawing (a portion in a dotted line circle frame in the drawing) with an equivalent circuit, the pixel is separated from the gate signal line GL. A thin film transistor TFT that is turned on by a signal (scanning signal), a pixel electrode PX to which a signal (video signal) from the drain signal line DL is supplied via the turned on thin film transistor TFT, and, for example, in parallel with the gate signal GL The counter electrode CT is connected to the arranged common signal line CL and generates an electric field between the pixel electrode PX and the counter electrode CT.

  Both the pixel electrode PX and the counter electrode CT are formed on the liquid crystal side surface of the substrate SUB1, and the liquid crystal molecules behaved by the electric field generated between these electrodes. Sometimes called a method.

  The gate signal line GL extends, for example, at one end on the left side in the figure beyond the seal material SL, and is connected to a scanning signal drive circuit composed of a plurality of semiconductor devices CH (V) mounted around the left side of the substrate SUB1. They are connected and supplied with the scanning signal.

  The drain signal line DL extends, for example, at one end on the upper side in the figure beyond the seal material SL, and is a video signal drive comprising a plurality of semiconductor devices CH (H) mounted on the upper periphery of the substrate SUB1. The video signal is supplied by being connected to a circuit.

  The common signal lines CL are connected to each other via a common line CLC, for example, on the right end side thereof, and the common line CLC extends, for example, beyond the sealing material SL on the upper end side thereof, and the upper side of the substrate SUB1. Is connected to a terminal CLT formed in the circuit.

  A reference signal serving as a reference for the video signal is supplied to the counter electrode CT via the terminal CLT, the common line CLC, and the common signal line CL.

  In the above-described embodiment, the liquid crystal display panel PNL has a configuration in which the semiconductor devices CH (V) and CH (V) are mounted on the substrate SUB1. However, the present invention can also be applied to a structure in which a semiconductor device formed by a so-called tape carrier method is used and the semiconductor device is connected to the periphery of the substrate SUB1 through an anisotropic conductive film, for example. .

  In addition, the liquid crystal display device applied to this invention is not limited to what was mentioned above as a structure of the pixel. For example, a pixel electrode made of a transparent conductive film is formed in almost the entire pixel region of the substrate SUB1, and a counter electrode made of a common transparent conductive film is formed in each pixel region of the substrate SUB2, and a liquid crystal is generated by an electric field generated between these electrodes. It may be a pixel configuration called a so-called vertical electric field method for driving the.

<Pixel configuration>
FIG. 3 is a block diagram showing an embodiment of one of the above-described pixels, FIG. 3 (a) is a plan view, and FIG. 3 (b) is a line bb in FIG. 3 (a). Sectional drawing and FIG.3 (c) are sectional drawings in the cc line | wire of Fig.3 (a).

  First, as shown in FIG. 3A, the gate signal line GL and the common signal line CL are formed in parallel with a relatively large distance on the liquid crystal side surface (front surface) of the substrate SUB1.

  A counter electrode CT made of a transparent conductive material is formed in a region between the gate signal line GL and the common signal line CL. The counter electrode CT is configured by containing a nitride (Nitride) in a material of ITO (Indium Tin Oxide), for example. As will be described in detail later, the counter electrode CT configured as described above has a higher optical refractive index than an ITO film containing no nitride, but reflects light at the interface with the substrate SUB1. The amount can be greatly reduced.

  The counter electrode CT is formed so as to be superimposed on the common signal line CL at the side portion on the common signal line CL side, thereby being electrically connected to the common signal line CL.

  An insulating film GI (see FIGS. 3B and 3C) is formed on the surface of the substrate SUB1 so as to cover the gate signal line GL, the common signal line CL, and the counter electrode CT. Yes. This insulating film GI functions as a gate insulating film of the thin film transistor TFT in a formation region of the thin film transistor TFT described later, and the film thickness and the like are set accordingly.

  An amorphous semiconductor layer AS made of, for example, amorphous silicon is formed on the upper surface of the insulating film GI where it overlaps with a part of the gate signal line GL. The semiconductor layer AS is a semiconductor layer of the thin film transistor TFT.

  The semiconductor layer AS is a region other than the region where the thin film transistor TFT is formed, and below the drain signal line DL, the connection layer JC that electrically connects the drain signal line DL and the drain electrode DT of the thin film transistor TFT. It may also be formed below and below the portion of the source electrode ST of the thin film transistor TFT that extends beyond the region where the thin film transistor TFT is formed. The semiconductor layer AS having such a pattern is formed by forming the thin film transistor TFT by, for example, a registry flow method. For example, the drain signal line DL can be formed with a small level difference, and the so-called inconvenience of the step disconnection can be avoided.

  Then, a drain signal line DL is formed extending in the y direction in the figure, and this drain signal line DL has an extension part (connection part JC) extending in part to the thin film transistor TFT side. The existing portion is connected to the drain electrode DT of the thin film transistor TFT formed on the semiconductor layer AS.

  Further, the source electrode ST formed simultaneously with the formation of the drain signal line DL and the drain electrode DT is opposed to the drain electrode DT on the semiconductor layer AS, and from the semiconductor layer AS to the pixel region. It is formed with an extending portion that extends slightly to the side. This extending portion is formed so as to reach a pad portion PD connected to a pixel electrode PX described later.

  When the semiconductor layer AS is formed on the insulating film GI, for example, the surface thereof is formed by doping a high concentration impurity. For example, the drain electrode DT and the source electrode ST are patterned. After the formation, the high-concentration impurities formed in regions other than the formation region of the drain electrode DT and the source electrode ST are etched using the drain electrode DT and the source electrode ST as a mask. This is because a high-concentration impurity remains between the semiconductor layer AS and the drain electrode DT and the source electrode ST, and this impurity layer is formed as an ohmic contact layer.

  By doing so, the thin film transistor TFT constitutes a so-called inverted staggered MIS (Metal Insulator Semiconductor) type transistor using the gate signal line GL as a gate electrode.

  Note that the transistor having the MIS structure is driven so that the drain electrode DT and the source electrode ST are switched by application of the bias. However, in the description of this specification, the transistor is connected to the drain signal line DL for convenience. The side connected to the drain electrode DT and the side connected to the pixel electrode PX are called the source electrode ST.

  A protective film PAS (see FIGS. 3B and 3C) is formed on the surface of the substrate SUB1 so as to cover the thin film transistor TFT. This protective film PAS is made of, for example, a silicon nitride film, and is provided to avoid direct contact of the thin film transistor TFT with the liquid crystal. Further, the protective film PAS is provided as an intervening layer between the counter electrode CT and a pixel electrode PX, which will be described later, and a capacitor provided between the counter electrode CT and the pixel electrode PX together with the insulating film GI. It also functions as a dielectric film of the element.

  A pixel electrode PX made of a transparent conductive material is formed on the upper surface of the protective film PAS, and the pixel electrode PX is formed in a region overlapping the formation region of the counter electrode CT. The pixel electrode PX is formed so as to have an electrode group composed of a large number of strip-shaped electrodes in which a large number of slits are juxtaposed in a direction intersecting the longitudinal direction thereof, and both ends thereof are connected to each other. Has been. A pixel having such a configuration is called a so-called IPS (In-Plane-Switching) method.

  In this case, each electrode of the pixel electrode PX, for example, divides the pixel region into two parts in the upper and lower parts in the drawing, and extends in the + 45 ° direction with respect to the traveling direction of the gate signal line GL, for example The other region is formed so as to extend in the −45 ° direction. A configuration in which a so-called multi-domain method is adopted, and when the longitudinal direction of the slit formed in the pixel electrode PX (longitudinal direction of each electrode of the pixel electrode PX) is single, the problem that coloring occurs depending on the viewing direction is eliminated. It has become.

  The pixel electrode PX is configured by, for example, a material of ITO (Indium Tin Oxide) containing nitride (Nitride), like the counter electrode CT. As will be described in detail later, the pixel electrode PX configured in this manner has a higher optical refractive index than an ITO film containing no nitride, but the light at the interface with the protective film PAS. The amount of reflection can be greatly reduced.

  Thus, an alignment film ORI1 (see FIGS. 3B and 3C) is formed on the surface of the substrate SUB1 on which the pixel electrode PX is formed so as to cover the pixel electrode PX. This alignment film ORI1 is a film that is in direct contact with the liquid crystal and, together with the alignment film formed on another substrate (indicated by reference numeral SUB2 in FIG. 1), determines the initial alignment direction of the molecules of the liquid crystal. .

  A polarizing plate PL1 (see FIGS. 3B and 3C) is formed on the surface of the substrate SUB1 opposite to the liquid crystal. The polarizing plate PL1 is provided together with the polarizing plate formed on the other substrate SUB2 in order to visualize the behavior of liquid crystal molecules.

<Counter electrode CT, pixel electrode PX>
As described above, the counter electrode CT and the pixel electrode PX are made of a transparent conductive material in which a nitride (Nitride) is contained in an ITO (Indium Tin Oxide) material, for example.

  The conventional counter electrode CT and pixel electrode PX are made of a transparent conductive material that does not contain nitride.

  Here, when the manufacturing method of the film | membrane (transparent conductive film) which consists of this conventional transparent conductive material is shown, it was formed, for example by sputtering method, for example, was accelerated using the mixed sintered compact target of indium oxide and tin oxide Ions are made to collide with the target, and the transparent conductive material that has jumped out is made to volume on the substrate. As a sputtering gas in this case, an argon gas mixed with, for example, water vapor (or oxygen) is used.

For example, when the glass substrate SUB1 has a substrate size of, for example, 1500 mm × 1850 mm, the substrate temperature is room temperature, the film forming pressure is 0.67 Pa, the water vapor flow rate is 10 sccm, the argon (Ar) flow rate is 200 sccm, and the input power density is The transparent conductive film is formed under a film forming condition of 10 kw / cathode. Here, 1 sccm indicates a flow rate of 1 cm ³ of gas in a standard state per second.

  In this case, the transparent conductive film is formed at a rate of, for example, 2.2 nm / second.

  And the light transmittance of the transparent conductive film (ITO film) having a film thickness of 80 nm formed on the substrate under the film forming conditions described above was about 89.1%. The light transmittance is the light transmittance including the substrate, and the used light has a wavelength of 550 nm. Further, when the thickness of the ITO film was 50 nm, the light transmittance was 90.0%. In this case, the optical refractive index of the ITO film was 2.00.

On the other hand, the transparent conductive film (ITO film) used in the above examples was in its film formation, and a sputtering gas containing nitrogen such as N ₂ O or N ₂ was added. It is in. The film formation conditions other than the sputtering gas were the same as in the prior art, and the formation rate of the ITO film formed thereby was the same as in the prior art.

<Consideration of Transparent Conductive Film According to the Present Invention>
In the transparent conductive film thus formed, the light transmittance of the material film of the ITO film having a thickness of 50 nm formed on the substrate was 89.5%. The light transmittance having this value is slightly lower than that of the conventional case, but it can be confirmed that the light refractive index is 2.11 and is larger than the conventional light refractive index.

  According to the result of measuring this transparent conductive film by, for example, RBS (Rutherford backscattering analysis), it can be confirmed that the ratio (N / O) of nitrogen (N) to oxygen (O) is about 3%.

  This has shown that the optical refractive index of this transparent conductive film improves by containing nitrogen in a transparent conductive film. However, it has been found that when the ratio of nitrogen (N) / oxygen (O) is greater than 10%, the light transmittance and conductivity are decreased, and the function as a transparent conductive film is impaired. The ratio (N / O) of (N) to oxygen (O) is preferably within 10%.

  FIG. 1 is a table showing relative white luminance data for each sample, showing the material, thickness (nm), light refractive index, and light transmittance of the transparent conductive film based on the data described above. Here, the relative white luminance means data corresponding to the light transmittance of a liquid crystal display panel using the transparent conductive film as an electrode.

  Among the samples, samples 1 to 3 show transparent conductive films not containing nitrogen, and samples 4 and 5 show transparent conductive films containing nitrogen. In the table, sample Ref. Indicates a transparent conductive film containing no nitrogen and having a thickness of 80 nm.

  The relative white luminances of Samples 4 and 5 are 101.31% and 101.61%, respectively, both of which are larger than the relative white luminance of the transparent conductive film not containing nitrogen. .

  From this, in the liquid crystal display device according to the above-described embodiment, the optical refractive index of each transparent conductive film of the pixel electrode and the counter electrode can be optimized and the light transmittance of the pixel can be improved. In this case, the light transmittance of the pixel can be improved despite a slight decrease in the light transmittance.

  This is presumed that, for example, when a transparent conductive film is formed having an interface with a glass substrate or a silicon nitride film, the reflected light at the interface is greatly reduced.

  Sample 1 and Sample 2 show the case where the thickness of the ITO film is reduced from 80 nm to 50 nm, respectively, and the light transmittance of the ITO film itself is improved by 1% from 89.1% to 90.0%. However, it turns out that the light transmittance (relative white luminance) as the panel (or pixel) is equivalent or rather lowered, such as 99.68% or 100.32%, respectively. This is because even if the light transmittance of the ITO film itself is improved, reflection (interface reflection) at the interface with other materials (glass substrate or silicon nitride film) is increased, so-called effective light transmittance is decreased. It shows that it will end.

  On the other hand, Sample 3 and Sample 4 are nitride films containing ITO films (indicated by ITON in the table) with a film thickness of 50 nm, and the light transmittance of the ITO film itself is Compared with the case of the sample 1 and the sample 2, it is 0.5% smaller from 90.0% to 89.5%. However, the optical refractive index is increased from 2.00 to 2.11 as compared with the case of Sample 1 and Sample 2, and the relative white luminance is also greatly increased to 101.31% or 101.61%. It turns out that This means that the influence of interface reflection with other materials can be reduced by adjusting the optical refractive index of the ITO film by containing nitride.

  Thus, a liquid crystal display device can be obtained in which the light refractive index of a transparent conductive film such as an ITO film is optimized and the light transmittance of the pixel is improved.

<Other Examples>
In the above-described embodiments, the transparent conductive film is made of an ITO film containing nitride (Nitride). However, since the same effect can be obtained with other transparent conductive films such as IZO (Indium Zinc Oxide), the present invention can also be applied to the other transparent conductive films. In addition, the transparent conductive film can also be applied to those composed of at least one metal oxide of In, Sn, and Zn metal oxides.

  In the above-described embodiments, the present invention is applied to the counter electrode CT and the pixel electrode PX. However, the present invention may be applied to only one of these electrodes.

  In the above-described embodiments, the present invention is applied to electrodes of a so-called IPS (In-Plane-Switching) type liquid crystal display device. However, it can also be applied to electrodes of other liquid crystal display devices such as a so-called TN type.

  In the above-described embodiments, the liquid crystal display device is taken as an example. However, the present invention can also be applied to other display devices such as an organic EL display device. An organic EL display device includes a phosphor layer sandwiched between a pair of electrodes in each pixel, and at least one of the phosphor layers that emits light due to a current flowing through each electrode is formed of a transparent conductive film. This is because the present invention can be applied to the formation of the transparent conductive film.

  Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically.

It is the table | surface which showed the effect of the display apparatus by this invention compared with the former. 1 is an overall configuration diagram showing an embodiment of a display device according to the present invention. It is a block diagram which shows one Example of the pixel of the display apparatus by this invention.

Explanation of symbols

  PNL: Liquid crystal display panel, SUB1, SUB2: Substrate, CH (H): Semiconductor device (video signal driving circuit), CH (V): Semiconductor device (scanning signal driving circuit), GL: Gate signal line , DL: drain signal line, CL: common signal line, PIX: pixel, TFT: thin film transistor, PX: pixel electrode, CT: counter electrode, DT: drain electrode, ST: source electrode, AS ... Semiconductor layer, PD ... Pad part, GI ... Insulating film, PAS1 ... Protective film, ORI1 ... Alignment film, PL1 ... Polarizing plate.

Claims (7)

A display device comprising an electrode formed in a pixel region of a substrate, the electrode comprising a transparent conductive film through which light is transmitted,
The said transparent conductive film is comprised from the metal oxide, and nitride is contained, The display apparatus characterized by the above-mentioned.   The display device according to claim 1, wherein a ratio of the nitride of the transparent conductive film to the oxide is 10% or less.   The display device according to claim 1, wherein the transparent conductive film is made of at least one metal oxide of In, Sn, and Zn metal oxides. A thin film transistor that is turned on by a scanning signal from a gate signal line is provided in the pixel region of the substrate,
The display device according to claim 1, wherein the electrode is a pixel electrode to which a video signal from a drain signal line is supplied through the turned-on thin film transistor. A thin film transistor that is turned on by a scanning signal from a gate signal line and a pixel electrode that is supplied with a video signal from a drain signal line through the turned on thin film transistor are provided in the pixel region of the parliament.
The display device according to claim 1, wherein the electrode is a counter electrode that generates an electric field between the electrode and the pixel electrode. Forming a transparent conductive film on the substrate by a sputtering method;
Forming an electrode in each pixel by the transparent conductive film,
A method for manufacturing a display device, wherein nitrogen gas is contained in the atmosphere when forming the transparent conductive film.   The method of manufacturing a display device according to claim 6, wherein the transparent conductive film is made of at least one metal oxide of In, Sn, and Zn.

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