JP2006120379A - Black conductive film of display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a black conductive layer of display devices which is capable of fully shielding a white layer and also suppressing the occurrence of air bubbles, even when being covered with a glass film. <P>SOLUTION: In a display device using a black layer, the effect of the hue of a bus electrode 30 on a display quality is suppressed properly, since the black layer is formed on the viewing side, in comparison to the case where a bus electrode is formed with a high-brightness material, such as a thick-film silver. In addition, since the bus electrode 30 is formed with the black layer 38 and a white layer 40 coated on it that has a width smaller than that of the black layer 38, the white layer 40 is shielded by the black layer 38 from the viewing side, while the white layer 40 ensures conductivity required for the bus electrode 30, thereby its display quality is improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a black conductive film provided on one surface of a substrate in order to generate visible light in an airtight space of a display device.

  For example, in a display device such as a plasma display panel (PDP), a flat airtight space formed between a pair of substrates is divided into a plurality of light emitting sections and the inside of the plurality of light emitting sections. A plurality of electrodes for selectively emitting light are provided on the inner surface of the substrate or the like (see, for example, Patent Document 1). In the PDP described in Patent Document 1, a plurality of pairs of discharge electrodes covered with a glass film are provided along one direction on the inner surface side of one substrate, and discharge occurs between parallel electrode pairs on the inner surface. This is what is called an AC type surface discharge structure in which ultraviolet rays are generated and the phosphors in the light emitting section emit light with the ultraviolet rays. In this structure, in order to observe visible light generated in the light emitting section through one substrate provided with a discharge electrode, the discharge electrode is made of a transparent conductive film made of ITO (indium tin oxide) or the like that is transparent to visible light. A bus electrode (bus wiring) for constituting and supplementing the conductivity is provided so as to overlap the transparent conductive film.

By the way, in the structure as described above, the bus electrode is positioned on the viewing side. Therefore, in order to suppress the influence of the color tone on the display, for example, the decrease in color purity and contrast, the brightness of the bus electrode should be kept as low as possible while keeping the conductivity of the bus electrode as high as possible. That is, a black conductive film is desired. In order to satisfy such a condition, in Patent Document 1 and the like, the bus electrode is configured in a two-layer structure, a black layer is formed on the viewing side (that is, the substrate side), and the conductivity and brightness are higher than that. A black conductive film provided with a high white layer has been proposed. The lightness of the conductive film increases as the content of conductive particles such as silver is increased in order to increase the conductivity. Therefore, the lightness should be kept low enough to ensure conduction between the white layer and the transparent conductive film. A lower black layer is provided between them to shield the white layer from the viewing side. The white layer is composed of a material having high conductivity such as thick film silver, and the black layer is obtained by mixing an appropriate amount of a black pigment such as cobalt trioxide (Co ₃ O ₄ ) into the thick film silver, for example. Composed of materials.

  In particular, in the above-described Patent Document 1, the black layer is formed of an insulating material that does not contain conductive particles (that is, the same material as the black matrix layer), and the film thickness is reduced while significantly reducing the brightness. By sufficiently reducing the thickness, conduction between the white layer and the transparent conductive film is ensured. Therefore, there is an advantage that the brightness on the viewing side is extremely low.

In the present application, “brightness” is a measure of the reflectance of the object surface and means the brightness of the color. For example, it is standardized by CIE (International Lighting Commission) and JIS Z8729. Also, it is represented by the lightness index L value defined in the L ^* a ^* b ^* color system adopted. The L value is quantified, for example, with ideal black and white as 0 and 100, respectively. However, “white” and “black” in the white layer and the black layer do not mean ideal white and black, respectively, but merely represent the relative brightness.
JP 2000-251744 A

  However, in the conventional two-layer structure, the white layer and the black layer of the black conductive film including those described in Patent Document 1 have their edges in the width direction positioned at the same position. It was provided. The black conductive film such as the bus electrode reduces the light emitting area of the display device, so that it is desirable to make the width as small as possible. If the white layer and the black layer are formed with the minimum width dimensions that can be formed, the width dimensions are necessarily the same. Therefore, in the observation direction inclined with respect to the surface of the substrate, that is, the display surface, the edge of the white layer located above the black layer is not sufficiently shielded by the black layer, so that the effect of providing the black layer is sufficient. There was a problem that could not be obtained. In one aspect described in the above-mentioned Patent Document 1, since the black matrix layer is provided entirely between the discharge electrode pairs adjacent to each other, the black layer happens to be white at one edge in the width direction of the bus electrode. Although it is made larger than the layer, since the edge of the other width direction edge of the black layer and the white layer is located at the same position, the shielding property at the other edge of the white layer becomes insufficient. .

  In addition, if an end edge is located at the same position, the white layer stacked on the black layer has a slightly larger width dimension, and the black layer's shielding effect is further reduced, and the black layer When the conductive film is covered with the glass film, there is also a problem that bubbles are generated in the glass film due to the gas remaining between the portion of the white layer protruding outside the black layer and the substrate. When forming using the thick film printing method, due to the sagging of the paste for constituting the white layer, etc., when forming using photo etching, due to the wraparound of light during exposure, etc. However, the width dimension of the white layer can be increased. Incidentally, it is desirable that the glass film covering the black conductive film be made as thin as possible in order to lower the operating voltage. However, if bubbles are present, the glass film is likely to be damaged due to a heating process during manufacture or voltage application during use. So it cannot be made thinner. These problems are not limited to the black conductive film of the PDP, and may occur in common in various types of display devices that observe visible light generated in an airtight space through a substrate.

  The present invention has been made in the background of the above circumstances, and the object of the present invention is to provide a display device that can sufficiently protect the white layer by the black layer and is less likely to generate bubbles even when covered with a glass film. The object is to provide a black conductive film.

  In order to achieve such an object, the gist of the present invention is that a display device of a type in which visible light generated in an airtight space is observed through a substrate constituting a part of its outer wall is positioned on the airtight space side. A black conductive film extending along one direction provided to generate the visible light on one surface of the substrate, comprising: (a) a black layer located on one surface side of the substrate; and (b) the black And a white layer which is laminated on the layer so as to be located on the inner side in the width direction and has higher brightness and conductivity than the black layer.

  In this way, the black conductive film in which the white layer is stacked on the black layer is stacked so that the white layer is positioned on the inner side in the width direction of the black layer positioned on the viewer side. Compared to the case where the edges in the direction are formed at the same position, or the case where the white layer protrudes beyond the black layer, the shielding property by the black layer is further enhanced. Moreover, even when covered with a glass film, since no gas can exist between the white layer and the substrate, the generation of bubbles in the glass film is suppressed.

  In the present invention, the “black conductive film” means having a predetermined conductivity required according to the type of the display device and exhibiting black on the viewing side. The conductivity of the black conductive film varies depending on the application and, as is clear from the structure described in the claims, the black layer and the white layer are laminated so that the whole exhibits a black color. Absent.

  Further, in the case where the “black layer” is laminated on the transparent conductive film, it is required to have conductivity for ensuring conduction between the transparent conductive film and the white layer, but does not have the transparent conductive film. In a structure, for example, a structure in which the black conductive film itself forms a discharge electrode or the like, the black layer may be configured to be insulative. In addition, even when the black layer requires electrical conductivity, if the display device has necessary electrical conductivity in an assembled state, an insulating property is described as described in Patent Document 1. It can be composed of materials.

  In addition, the “black layer” means that the brightness is low enough that the color tone of light emission in the display device is not substantially affected, for example, a black matrix layer can be formed. That is, it is not limited to a completely black one having a lightness of 0. For example, a case where gray or black-brown is exhibited depending on the type of black pigment or conductive particles is included in the “black layer” in the claims. . The “white layer” means that the brightness is sufficiently higher than that of the black layer. That is, it is not limited to a completely white color having a lightness of 100. For example, a case where a yellow color or the like is formed by thick film silver is also included in the “white layer” in the claims. In the display device to which the present invention is applied, the color tone of the white layer that is not observed from the viewing side is not particularly limited. However, in order to increase the efficiency by increasing the ratio of the light emitted in the airtight space to the viewer side as much as possible, the white layer must have as high a reflectance as possible. It is desirable that the brightness is as high as possible.

  Here, the black conductive film preferably has a trapezoidal cross-sectional shape as a whole in the longitudinal direction. In this way, the width of the white layer is increased as much as possible while ensuring sufficient shielding by the black layer, so that the conductivity can be further increased while keeping the brightness of the black conductive film low. it can. That is, the cross-sectional shape of the black conductive film can be appropriately determined in a range in which the white layer is located on the inner side of the black layer in the width direction. For example, the width dimension of the white layer is significantly larger than the width dimension of the black layer. Although it is possible to make it smaller, the trapezoidal shape as described above is most preferable. The “trapezoid” is not limited to a complete trapezoidal shape, but may be any as long as it has a substantially trapezoidal outline as a whole. For example, a shape in which a small dent or the like exists between the black layer and the white layer may be used. Further, the side surface corresponding to the trapezoidal leg (the side connecting the upper base and the lower base) may be convex. The boundary between the leg and the bottom may be a curved line.

  Preferably, when the black conductive film has a trapezoidal cross section as described above, the angle between the leg and the perpendicular to the bottom is incident when the design viewing angle in the display device is α. This is a value larger than the refraction angle in the substrate at the angle α / 2. In this way, since the white layer on the black layer cannot be observed in the range of the viewing angle that is planned, the shielding effect by the black layer can be obtained more reliably.

Preferably, the black layer is made of an insulating material or a conductive material containing a black pigment, a Cr film, or the like. Examples of black pigments include pyrochlore oxides such as tribasic cobalt oxide (Co ₃ O ₄ ), ruthenium oxide (RuO ₂ ), Fe—Cr—Mn pigments, Cu—Cr—Mn pigments, and the like. The insulating material is composed of these black pigments and glass, and the conductive material is further composed of Ag—Pd, Ag—Cu, Ag, Ag—Pt or the like. Of these, an insulating material containing cobalt trioxide as a black pigment is most preferable. If this is done, the reason is not clear, but the brightness of the black layer is further lowered and a relatively high conductivity is obtained for the entire bus electrode as compared with the case where other pigments are used.

  Preferably, the white layer is made of a thick film conductor material containing Ag, Al, Cu, Cr or the like as a conductive component.

  Preferably, the black conductive film is a PDP bus electrode. That is, it is provided on a transparent conductive film made of ITO or the like. In this case, more preferably, the black layer is provided with a film thickness in the range of 0.5 to 30 (μm) using an insulating material. In this way, a black conductive film having a lower brightness than that obtained when the black layer is made of a conductive material can be obtained. At this time, the black layer provided with an extremely thin thickness as described above has sufficient conductivity to ensure conduction between the white layer and the transparent conductive film after the formation of the bus electrode. There is no problem even if it is made of materials.

  Preferably, the black conductive film constitutes a discharge electrode pair provided for generating a display discharge in the PDP. That is, the present invention can be applied to a PDP regardless of whether or not a transparent conductive film is provided. Further, the present invention can be applied to an organic EL display device, an inorganic EL display device and the like in addition to the PDP.

  Preferably, the black conductive film includes a step of forming a black coating film for forming the black layer on the substrate, and a white coating film for forming the white layer. Forming the black conductive film by firing the black coating film and the white coating film, and forming the thin film on the top so that both ends in the width direction are located inside the black coating film. The manufacturing process is a process including

  Preferably, the black conductive film has a step of forming a black coating film for forming the black layer on the substrate, and a shrinkage ratio than that of the black coating film for forming the white layer. It is manufactured by a process including a step of forming a large white coating film on the black coating film with the same width dimension and a step of firing the black coating film and the white coating film to generate the black conductive film. . In this way, while forming the black coating film and the white coating film with the same width dimension, the width dimension of the black layer is made larger than the width dimension of the white layer to obtain the black conductive film as described above. it can.

  The process for forming the black coating film and the white coating film is not particularly limited. For example, a known appropriate method such as a thick film screen printing method or a photo-etching method can be used.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a diagram showing a main part of a PDP 8 in which a bus electrode 30 is constituted by a black conductive film of the present invention, and FIG. 2 is a diagram showing a cross section along the longitudinal direction of the write electrode 18. The PDP 8 is classified as an AC type surface discharge PDP having a three-electrode structure, and is arranged along one direction in an airtight space formed between the front plate 10 and the back plate 12 arranged in parallel to each other. A plurality of discharge spaces 16 defined by longitudinal barrier ribs 14 are provided.

  On the back plate 12, a plurality of write electrodes 18 are provided so as to be covered with an overcoat 32 along the partition wall 14. On the other hand, the front plate 10 is covered with a dielectric layer 20 made of a low softening point glass such as borosilicate glass and a protective film 22 made of magnesium oxide (MgO) along the other direction orthogonal to the one direction. A plurality of pairs of display discharge electrodes (sustain electrodes) 24a and 24b are provided. The plurality of discharge spaces 16 are divided into a plurality of light emitting sections formed for each pair of the display discharge electrodes 24a and 24b. In addition, phosphor layers 26 are provided separately for each discharge space 16 on the inner surface of the back plate 12 and the surface of the barrier ribs 14.

  The display discharge electrode 24 is an ITO (Indium Tin Oxide) formed by a thin film process or the like for the purpose of generating surface discharge over a wide range and minimizing the shielding of display light emitted through the front plate 10. A transparent electrode 28 made of indium tin) or ATO (antimony tin oxide) or the like, that is, a transparent conductive film, and on the transparent electrode 28 at the outer end position in the width direction for each pair in order to supplement the conductivity. And a bus electrode 30 provided on the substrate. In FIG. 1 and FIG. 2, reference numeral 34 denotes an undercoat for suppressing the reaction between the writing electrode 18 and the back plate 12 made of soda, lime and glass. .

  The PDP 8 configured as described above generates a write discharge between the write electrode 18 and the display discharge electrode 24a, for example, for each frame of image display, so that the PDP 8 can be selected from the plurality of light emitting sections. A light emitting section to emit light in a frame is selected, a display discharge is generated between the display discharge electrodes 24a and 24b in the selected light emitting section, and the discharge is maintained until a predetermined end time of each frame ( One image is displayed by generating a discharge continuously. Then, by repeating these selection and sustain discharge, a desired moving image is continuously displayed. The details of the driving method are not necessary for understanding the present embodiment, and will not be described.

  FIG. 3 is an enlarged view illustrating the configuration of the bus electrode 30 on the inner surface 36 of the front plate 10 of the PDP 8, and FIG. 4 is a view illustrating a cross section thereof. 3 and 4, the dielectric layer 20 and the protective film 22 that cover the bus electrode 30 are omitted. 1 and 2, the bus electrode 30 is composed of two layers made of two different materials. Of the two layers, the lower layer fixed to the transparent electrode 28 is a low brightness black layer 38 exhibiting black, and the upper layer laminated thereon is a high brightness white layer 40 exhibiting white to yellow. Therefore, the bus electrode 30 is black in the viewing direction indicated by the arrow, and in this embodiment, the bus electrode 30 corresponds to a black conductive film.

The black layer 38 is a thick film having, for example, a thickness dimension of about 1 (μm) and a width dimension of about 74 (μm), and is made of glass such as PbO—SiO ₂ —B ₂ O _3. And black pigments such as cobalt trioxide (Co ₃ O ₄ ). For this reason, it has a relatively low lightness, for example, about the same as a black matrix layer (not shown in FIG. 1) normally provided between pixels, for example, an L value of about 28. The white layer 40 is a thick film having a thickness dimension of about 4 (μm) and a width dimension of about 66 (μm), such as a PbO—SiO ₂ —B ₂ O ₃ system. It consists of glass and silver. Therefore, for example, it has a relatively high lightness of about L value 85, and reflects most of the light that travels toward the bus electrode 30 among the visible light generated inside, so that the viewing side of the bus electrode 30 is constituted by the black layer 38. Therefore, the light emission efficiency is not lowered. The white layer 40 has a high conductivity of, for example, about 2.4 (μΩ · cm).

  Further, as is clear from the relationship of the width dimensions, the white layer 40 is provided with a narrower width than the black layer 38. For this reason, the bus electrode 30 as a whole has a substantially trapezoidal cross section in which the width dimension becomes narrower toward the upper surface thereof as shown in FIG. 4, and its legs are perpendicular to the normal of the surface 36 of the front plate 10. For example, the inclination is about θ = 40 degrees. The width dimensions of the black layer 38 and the white layer 40 are the respective maximum values, that is, the width dimension at the interface with the transparent electrode 28 in the black layer 38, and the width dimension at the interface with the black layer 38 in the white layer 40. is there.

  Note that the black layer 38 formed with an extremely thin film thickness as described above provides conduction between the white layer 40 and the transparent electrode 28 even though it is made of an insulating material such as glass and black pigment. It has sufficient conductivity not to interfere. This is presumably because the conductive component in the transparent electrode 28, the conductive component in the white layer 40, etc. diffuse into the black layer 38 when the black layer 38 and the white layer 40 are laminated and fired. Therefore, the function as the bus electrode 30 that supplements the conductivity of the transparent electrode 28 is ensured in the same manner as in the prior art in which the black layer 38 is made of a conductive material.

  According to the bus electrode 30 configured in this way, since the viewing side is configured by the black layer 38, compared to the case where the bus electrode is configured by a material with high brightness such as thick film silver, The color tone of the bus electrode 30 is preferably suppressed from affecting the display quality. In addition, since the bus electrode 30 is composed of the black layer 38 and the white layer 40 having a narrower width than that of the black layer 38, the white layer 40 has a conductivity required as the bus electrode 30. The white layer 40 is shielded from the viewing side by the black layer 38 while ensuring the display quality, thereby improving the display quality.

  Moreover, the bus electrode 30 has a substantially trapezoidal cross section whose legs are inclined by θ. When the viewing angle of the PDP 8 is α = 160 degrees, the θ is the front plate when the incident angle is α / 2. 10 is set to a value equal to or larger than the refraction angle a. Therefore, within the range of the viewing angle α, as is apparent from FIG. 4, it is not possible to observe light having an incident angle from the inside of the PDP 8 to the front plate surface 36 of a or more, so the white layer 40 is completely shielded, Higher display quality can be obtained.

  Further, since the laminated lower layer, that is, the black layer 38 has a larger width dimension than the upper layer, that is, the white layer 40, according to the bus electrode 30 of this embodiment, the upper layer as in the conventional two-layer structure is used. Gas entrainment between the substrate and the substrate cannot occur. Incidentally, the width of the lower layer, that is, the upper layer, that is, the white layer 54, is lower than that of the black layer 52 although the conventional bus electrode 50 is formed in the same width dimension as schematically shown in FIG. In some cases, the dimensions increased. In such a cross-sectional shape, a gap is generated between the white layer 54 and the front plate surface 36. Therefore, when the glass paste for forming the dielectric layer 20 is applied onto these, a gas is introduced into the gap. Is caught and remains after the baking treatment. The micrographs of the bus electrode 30 of the present embodiment and the conventional bus electrode 50 are shown in FIGS. 6 and 7, respectively. Unlike the bus electrode 30 of the present embodiment, in the conventional example, the width dimension of the white layer 54 is larger than the width dimension of the black layer 52, and it can be seen that the structure is easy to entrain gas. Conventionally, such a shape is caused by the sagging of the paste for forming the white layer 54 in the case of the screen printing method, and in the case of the photo etching method, the white layer 54 and One reason is that light wraps around the side of the black layer 52 when the black layer 52 is stacked and exposed collectively.

  The bus electrode 30 of this embodiment is formed by using, for example, a thick film screen printing method or a photo etching method. For example, in the case of the thick film screen printing method, the opening width dimension of the screen for forming the white layer 40 is made smaller than the screen for forming the black layer 38, and the cross-sectional shape shown in FIG. It can be formed by applying a paste for forming both layers 38 and 40. In the case of the photo-etching method, the exposure width of the exposure mask for forming the white layer 40 is made smaller than the exposure width of the exposure mask for forming the black layer 38, and the exposure process is performed in a separate process. It can form by performing each.

  In addition to adjusting the width dimensions when forming the black layer 38 and the white layer 40 as described above, in any of the forming methods, the firing shrinkage rate is the same as that of the white layer 40. There is also a method in which pastes are prepared so as to be relatively smaller than each other (that is, so that the residual ratio is relatively large) and laminated with the same width dimension. In this case, the white layer 40 becomes narrower than the black layer 38 in accordance with the difference in the firing shrinkage rate, so that the substantially trapezoidal cross section is obtained. According to this method, since a common screen making and exposure mask are used, there are advantages in that the manufacturing cost is reduced and the alignment at the time of formation is facilitated. The firing shrinkage rate can be adjusted, for example, by changing the solid content, resin content, and solid content particle size in the paste. The shrinkage rate is set to about 15 (%) for the black layer 38 and about 25 (%) for the white layer 40, for example.

  As mentioned above, although this invention was demonstrated in detail with reference to drawings, this invention can be implemented also in another aspect, A various change can be added in the range which does not deviate from the main point.

It is a figure which notches one part and shows the principal part structure of PDP provided with the black electrically conductive film of one Example of this invention. It is a figure which shows the cross section along the longitudinal direction of the write-in electrode in FIG. It is a schematic diagram which shows the step which formed the bus electrode in the manufacturing process of PDP of FIG. It is a figure which expands and shows the cross section of a bus electrode. It is a figure which shows the cross section of the conventional bus electrode typically. It is a microscope picture corresponding to FIG. 6 is a photomicrograph of the conventional bus electrode shown in FIG.

Explanation of symbols

10: Front plate, 28: Transparent electrode, 30: Bus electrode, 38: Black layer, 40: White layer

Claims (2)

In a display device of the type that observes visible light generated in an airtight space through a substrate constituting a part of its outer wall, it is provided to generate the visible light on one surface of the substrate located on the airtight space side. A black conductive film extending along one direction,
A black layer located on one side of the substrate;
A black conductive film for a display device, comprising: a white layer laminated on the black layer so as to be positioned on the inner side in the width direction, and having a brightness and conductivity higher than that of the black layer. 2. The black conductive film of a display device according to claim 1, wherein a cross-sectional shape perpendicular to the longitudinal direction forms a trapezoid as a whole.