JP2005072255A - Electromagnetic wave shielding sheet for plasma display and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding sheet for PDP and a method of manufacturing the same in which durability such as moisture-proof property and anti-migration property is improved without deterioration in the electrical characteristics. <P>SOLUTION: The electromagnetic wave shielding sheet for plasma display is characterized in comprising a base material, a conductive film formed on the base material, and electrodes which are electrically in contact with the conductive film and in that the conductive film has a multilayer structure in which an oxide layer and a metal layer are alternately laminated in the (2n+1) layers in total [n: an integer equal to 1 or larger] from the side of base material and the metal layer is mainly formed of Ag with inclusion of Bi. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electromagnetic wave shielding sheet for PDP, which is installed on the observer side of a PDP to protect the main body of a plasma display panel (hereinafter referred to as PDP) and has an electromagnetic wave shielding ability to shield electromagnetic noise generated from the PDP, and It relates to the manufacturing method.

  Conventionally, electromagnetic waves harmful to the human body have been generated from the front surface of the PDP. As an optical filter for shielding this electromagnetic wave, an electromagnetic wave shielding sheet in which a conductive film is provided on a substrate such as a plastic film is disposed on the PDP observer side.

The electromagnetic wave shielding ability of the electromagnetic wave shielding sheet can be improved by reducing the sheet resistance of the conductive film. One method for reducing sheet resistance is to use pure Ag as the material for the conductive film. However, pure Ag has practical problems in terms of moisture resistance and migration resistance.
On the other hand, moisture resistance and migration resistance are improved by doping pure Ag with specific impurities. Currently, for example, Ag: Pd, Ag: Au, Ag: Cu, Ag: Ag alloys such as Pd: Cu and Ag: Nd have been proposed (see, for example, Patent Document 1).
International Publication No. 98/13850 Pamphlet

  However, although these Ag alloys have improved durability such as moisture resistance and migration resistance due to doping of impurities, they cannot avoid deterioration of electrical characteristics such as specific resistance. Further, the deterioration of the electrical characteristics deteriorates the optical characteristics such as luminous transmittance. Therefore, it is necessary to improve durability without deteriorating electrical characteristics.

  An object of the present invention is to provide an electromagnetic wave shielding sheet for PDP having improved durability such as moisture resistance and migration resistance without impairing electrical characteristics, and a method for producing an electromagnetic wave shielding sheet for PDP.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have replaced conventional Ag alloys such as Ag: Pd, Ag: Au, Ag: Cu, Ag: Pd: Cu, and Ag: Nd. By using an Ag: Bi alloy, it has been found that an electromagnetic wave shielding sheet with improved durability such as moisture resistance and migration resistance can be obtained while maintaining the same electrical characteristics as when pure Ag is used. Based on the findings, the present invention has been completed.
That is, the present invention is an electromagnetic wave shielding sheet for a plasma display having a base, a conductive film formed on the base, and an electrode that is in electrical contact with the conductive film. The conductive layer has a multilayer structure in which oxide layers and metal layers are alternately stacked in total (2n + 1) layers [n is an integer of 1 or more], and the metal layer is a metal layer containing Ag as a main component and containing Bi. An electromagnetic wave shielding sheet for PDP is provided.
Further, the present invention provides a multilayer structure in which an oxide layer and a metal layer containing Ag as a main component and containing Bi are alternately stacked in total (2n + 1) layers [n is an integer of 1 or more]. Provided is a method for producing an electromagnetic wave shielding sheet for PDP, wherein a conductive film is formed and an electrode is formed on the conductive film.

The electromagnetic wave shielding sheet for PDP of the present invention is suitable for PDP having high electromagnetic wave shielding ability and excellent durability such as moisture resistance and migration resistance.
In addition, the production method of the present invention provides an electromagnetic wave shielding sheet for PDP having high electromagnetic wave shielding ability and excellent durability such as moisture resistance and migration resistance.

Hereinafter, the present invention will be described in detail.
≪Electromagnetic wave shielding sheet for PDP≫
The electromagnetic wave shielding sheet for PDP of the present invention has a base, a conductive film formed on the base, and an electrode that is in electrical contact with the conductive film, and has the ability to shield electromagnetic waves emitted from the PDP. (High conductivity, that is, low sheet resistance).

  The resistance value of the electromagnetic wave shielding sheet for PDP of the present invention is 0.4 to 3.5Ω, particularly 0.5 to 2.5Ω, and more preferably 0.5 to 1.5Ω for electromagnetic wave shielding performance. Is preferred.

Moreover, since the electromagnetic wave shielding sheet for PDP of the present invention is disposed on the front surface of the PDP, the visible light transmittance is preferably 40% or more so that the display is not difficult to see.
The visible light reflectance of the electromagnetic wave shielding sheet for PDP of the present invention is preferably less than 6%, particularly preferably less than 3%.

<Substrate>
In the present invention, the base material includes glass plates (including tempered glass such as air-cooled tempered glass and chemically tempered glass), polyethylene terephthalate (PET), triacetyl cellulose (TAC), polycarbonate (PC), and polymethyl. Examples thereof include transparent plastic materials such as methacrylate (PMMA).

<Conductive film>
In the present invention, the conductive film is a conductive film having a multilayer structure in which a total of (2n + 1) layers of oxide layers and metal layers are alternately laminated from the substrate side (hereinafter also referred to as a multilayer film). n is an integer greater than or equal to 1, 2-6 are preferable and 3-6 are the most preferable.

Examples of the oxide layer include a layer mainly composed of an oxide of one or more metals selected from the group consisting of Bi, Zr, Al, Ti, Sn, In, Nb, and Zn. Preferably, the layer is composed mainly of an oxide of one or more metals selected from the group consisting of Ti, Sn, In, Nb, and Zn. In particular, since the absorption is small and the refractive index is around 2, a layer mainly composed of ZnO is preferable. In addition, a layer mainly composed of TiO ₂ or Nb ₂ O ₅ is preferable because it has a large refractive index and is easily obtained with a small number of layers having a preferable color tone.
The oxide layer may be composed of a plurality of thin oxide layers. For example, instead of the oxide layer mainly composed of ZnO, a layer mainly composed of SnO ₂ and a layer mainly composed of ZnO can be formed.

The oxide layer (ZnO film) containing ZnO as a main component preferably contains one or more metals other than Zn. The one or more metals are present in the ZnO film mainly in an oxide state.
Preferred examples of the one or more metals include Sn, Al, Cr, Ti, Si, B, Mg, Ga, and Y.
The content ratio of the total amount of one or more metals in the ZnO film is 1-10 atomic% with respect to the total amount of the metal and the total amount of Zn because the moisture resistance of the obtained conductive film is improved. preferable. By being 1 atomic% or more, the internal stress of ZnO can be sufficiently reduced, and the adhesion between the ZnO film and the metal layer containing Ag as a main component can be maintained. As a result, moisture resistance is improved. Moreover, moisture resistance can be maintained by setting it as 10% or less. This is considered to be because the crystallinity of ZnO can be maintained and the compatibility with Ag can be maintained by setting the ratio of the contained metal other than Zn to a certain level. In consideration of obtaining a ZnO film having a low internal stress stably and with good reproducibility, and considering the crystallinity of ZnO, the metal content is more preferably 2 to 6 atomic%.

  The geometrical thickness of the oxide layer (hereinafter simply referred to as the film thickness) is 20 to 60 nm (particularly 30 to 50 nm) for the oxide layer closest to the substrate and the oxide layer farthest from the substrate, and other oxides. The layer is preferably 40 to 120 nm (particularly 40 to 100 nm).

The metal layer is a metal layer containing Ag as a main component and containing Bi. By using Ag as a main component, a metal layer having a small specific resistance and a small absorption of visible light can be obtained. Moreover, it can be set as the metal layer excellent in durability, such as moisture resistance and migration resistance, by containing Bi.
Here, the migration resistance means the performance of suppressing the diffusion and aggregation of silver. When silver aggregates, the moisture resistance becomes poor, and at the same time, the aggregated portion becomes white and the appearance becomes poor. Such migration (aggregation) is likely to occur under high temperature and high humidity conditions, and the presence of chlorine is considered to accelerate the migration (aggregation).
The content ratio of Bi is preferably 0.1 to 1.0 atomic% with respect to the total amount of Bi and Ag. By setting it to 0.1 atomic% or more, the durability of silver can be improved. If it is the range up to 1.0 atomic%, the moisture resistance improves as the content ratio increases. On the other hand, if it is 1.0 atomic% or less, the production efficiency is high (the film forming speed is high), and a high visible light transmittance can be maintained. From the above viewpoint, the Bi content is particularly preferably 0.2 to 0.6 atomic% with respect to the total amount of Bi and Ag.

  The total thickness of the metal layers is, for example, 25 to 60 nm (especially 25 to 50 nm) when the resistance value target of the obtained electromagnetic shielding sheet is 1.5Ω, and 35 when the resistance value target is 0.9Ω. It is preferable to set it to -80 nm (especially 35-70 nm). As for the film thickness of each metal layer, the total film thickness is appropriately distributed according to the number of metal layers. As the number of metal layers increases, the specific resistance of each metal layer increases, so that the total film thickness tends to increase as a result of decreasing the resistance.

  The film thickness of the conductive film, that is, the total film thickness of the oxide layer and the metal layer is not particularly limited, and is appropriately determined according to the above-described total film thickness of the oxide layer and the total film thickness of the metal layer. . For example, when the number of metal layers is 2 (n = 2), 160 to 200 nm (particularly 180 to 190 nm), and when the number of metal layers is 3 (n = 3), 230 to 330 nm (particularly 250 to 300 nm), the metal layer When the number is 4 (n = 4), 300 to 400 nm (especially 340 to 390 nm), when the number of metal layers is 5 (n = 5), 370 to 500 nm (especially 420 to 470 nm), and the number of metal layers is 6 ( In the case of n = 6), it is preferable that it is 440-600 nm (especially 520-570 nm).

In the present invention, it is preferable to combine an oxide layer containing ZnO as a main component and containing an Al oxide or Sn oxide as an oxide layer with respect to a metal layer containing Ag as a main component and containing Bi.
An oxide layer containing ZnO as a main component and containing an oxide of Al or an oxide of Sn has good compatibility with the metal layer, and the moisture resistance is improved by combining the two.
As will be described later, for example, such an oxide layer can be formed by a sputtering method using a ZnO target doped with at least one metal other than Zn or an oxide of the metal. Al is preferably selected as the metal other than Zn because the film forming rate by sputtering is fast.
In addition, an oxide layer made of ZnO and Al oxide and a metal layer made of Ag and Bi are extremely compatible.
The reason for this is thought to be that Al has the same crystal structure as Ag and Bi. For this reason, even when Al is precipitated at the grain boundary or interface of ZnO, it is considered that the compatibility at the atomic level interface with Ag or Bi is improved.

  In the present invention, as the conductive film, by using a multilayer film in which a total of (2n + 1) layers (n is an integer of 1 or more) are alternately stacked on the substrate with an oxide layer, a metal layer, and an oxide layer, A low sheet resistance value, a low reflectance, and a high visible light transmittance can be obtained.

As a multilayer film in which (2n + 1) layers (n is an integer of 1 or more) are alternately laminated on the substrate with oxide layers, metal layers, and oxide layers, three layers (n = 1), five layers ( Examples of the multilayer film include n = 2), 7 layers (n = 3), 9 layers (n = 4), 11 layers (n = 5), and 13 layers (n = 6). In particular, it is preferably a multilayer conductive film having n of 3 or more, that is, 7 or more layers. Among them, when n is an integer of 3 to 6, that is, when the multilayer film is 7 layers, 9 layers, 11 layers, or 13 layers, the resistance value can be sufficiently lowered and the near-infrared shielding ability can also be imparted. . Therefore, it is not necessary to separately provide a near infrared shielding resin film.
Further, by adopting such a configuration, the color tone viewed from the observer side is preferable (not reddish).

When n is an integer of 3 or more, that is, the conductive film is a multilayer film having 7 or more layers, and the conductive film has at least three metal layers, the metal layer closest to the substrate and the most substrate among the metal layers It is preferable that the film thickness of the metal layer between the metal layer far from the substrate is larger than the film thickness of the metal layer closest to the substrate and larger than the film thickness of the metal layer farthest from the substrate. Moreover, it is preferable that the thickness of the metal layer closest to the base is the same as the thickness of the metal layer farthest from the base.
Similarly for the oxide layer, the thickness of the oxide layer between the oxide layer closest to the base and the oxide layer farthest from the base is larger than the thickness of the oxide layer closest to the base, And it is preferable that it is larger than the film thickness of the oxide layer farthest from the substrate. Moreover, it is preferable that the thickness of the oxide layer closest to the substrate and the thickness of the oxide layer farthest from the substrate are the same.

More specifically, the film thickness of the metal layer closest to the substrate is 8 to 15 nm (preferably 9 to 11 nm), and the film thickness of the metal layer between the metal layer closest to the substrate and the metal layer farthest from the substrate. Is appropriately adjusted to satisfy the required optical performance from the range of 10 to 16 nm (preferably 13 to 16 nm), and the thickness of the metal layer farthest from the substrate is 8 to 15 nm (preferably 9 to 11 nm). .
The thickness of the oxide layer closest to the substrate is 20 to 60 nm (preferably 30 to 50 nm), and the thickness of the metal layer between the oxide layer closest to the substrate and the oxide layer farthest from the substrate is The thickness of the oxide layer farthest from the substrate is 40 to 100 nm (preferably 70 to 90 nm), and the thickness is appropriately adjusted to satisfy the required optical performance from the range of 20 to 60 nm (preferably 30 to 50 nm). .

FIG. 1 shows an example of an electromagnetic wave shielding sheet 1 having nine layers of conductive films. For convenience of explanation, each dimensional ratio is different from the actual one.
As shown in FIG. 1, the electromagnetic wave shielding sheet 1 basically includes a base 2 and a nine-layer conductive film 3.
The conductive film 3 includes, from the base 2 side, an oxide layer 4 (first layer) mainly composed of first ZnO, a metal layer 5 (second layer) mainly composed of first Ag, An oxide layer 6 (third layer) containing ZnO as a main component, a metal layer 7 (fourth layer) containing second Ag as a main component, and an oxide layer 8 (fifth layer) containing third ZnO as a main component Eye), metal layer 9 mainly composed of third Ag (sixth layer), oxide layer 10 principally composed of fourth ZnO (seventh layer), metal mainly composed of fourth Ag This is a multilayer film having a nine-layer structure in which a layer 11 (eighth layer) and an oxide layer 12 (ninth layer) containing fifth ZnO as a main component are sequentially formed. By setting it as such a structure, the color tone seen from the observer side becomes a preferable thing (it does not become reddish).

In the present invention, a protective film 13 such as an oxide film or a nitride film is preferably provided on the conductive film 3 as shown in FIG. By providing this protective film 13, the conductive film 3 can be protected from moisture. Also, an adhesive for bonding an arbitrary resin film (moisture-proof film, anti-scattering film, anti-reflection film, protective film for near-infrared shielding, etc., functional film such as a near-infrared absorbing film) on the conductive film 3 It is possible to protect the oxide layer (particularly a layer containing ZnO as a main component) of the conductive film 3 from (especially an alkaline adhesive).
Specific examples of the protective film 13 include metal oxide films and nitride films such as Sn, In, Ti, and Si.
In particular, when an oxide layer mainly composed of ZnO is used as the uppermost layer of the conductive film 3, it is particularly preferable to use an indium-tin oxide (ITO) film as the protective film 13.
The thickness of the protective film 13 is preferably 2 to 30 nm, and particularly preferably 3 to 20 nm.

<Electrode>
The electrode is provided so as to be in electrical contact with the conductive film so that the electromagnetic wave shielding effect of the conductive film is exhibited.
The electrode is preferably disposed on the entire periphery of the conductive film in order to secure the electromagnetic wave shielding effect of the conductive film.
As the electrode material, a lower resistance is superior in terms of electromagnetic shielding performance. For example, an Ag paste (a paste containing Ag and glass frit) or a Cu paste (a paste containing Cu and glass frit) applied and fired is preferably used.

<Various resin films>
"Moisture-proof film"
In the electromagnetic wave shielding sheet for PDP of the present invention, it is preferable that a moisture-proof resin film (moisture-proof film) is provided on the conductive film in order to protect the conductive film from moisture.
There is no restriction | limiting in particular as a moisture-proof film, What is generally used for the electromagnetic wave shielding sheet for PDP can be used, For example, plastic films, such as PET and a polyvinylidene chloride, are mentioned.

"Resin prevention resin film"
In the electromagnetic wave shielding sheet for PDP of the present invention, particularly when a glass plate is used as a substrate, a resin film for preventing scattering is provided on the front surface side (observer side) and / or the back surface side (PDP side) of the electromagnetic wave shielding sheet. It is preferable that
There is no restriction | limiting in particular as a film for scattering prevention resin, The thing generally used for the electromagnetic wave shielding sheet for PDP can be used. In particular, good results can be obtained by using a urethane resin film having self-healing properties and self-healing properties that prevent self-healing when scratched.

"Anti-reflection resin film"
In the electromagnetic wave shielding sheet for PDP of the present invention, an antireflection resin film is preferably provided on the front side (observer side) and / or the back side (PDP side) of the electromagnetic wave shielding sheet.
There is no restriction | limiting in particular as a resin film for reflection prevention, The thing generally used for the electromagnetic wave shielding sheet for PDP can be used. In particular, good results can be obtained by using a fluororesin film. The resin film having a low refractive index can be a colored film for color tone adjustment.
Further, a thin film having a low refractive index may be formed on the front side (observer side) and / or the back side (PDP side) of the electromagnetic wave shielding sheet instead of the antireflection resin film.
Since the antireflection resin film or the low refractive index thin film (antireflection layer) reduces the reflectance of the obtained electromagnetic wave shielding sheet and provides a preferable reflection color, the antireflection layer itself reflects in the visible region. The wavelength with the lowest rate is preferably 500 to 600 nm, particularly 530 to 590 nm.

  From the viewpoint of preventing scattering and reflection of the electromagnetic wave shielding sheet itself, as an anti-scattering and anti-reflection resin film having the functions of the above-described anti-scattering resin film and anti-reflection resin film, Arctop (manufactured by Asahi Glass Co., Ltd.) It is preferable to use a product name. ARCTOP (trade name) is an anti-reflective treatment by forming a low-refractive index anti-reflective layer made of an amorphous fluoropolymer on one side of a polyurethane-based soft resin film having self-repairing properties and anti-scattering properties. Is given.

"Near-infrared shielding film"
In the electromagnetic wave shielding sheet for PDP of the present invention, a near infrared shielding film may be provided on the front surface side (observer side) and / or the back surface side (PDP side) of the electromagnetic wave shielding sheet.
There is no restriction | limiting in particular as a near-infrared shielding film, The thing generally used for the electromagnetic wave shielding sheet for PDP can be used.
Also, instead of a near-infrared shielding film, a near-infrared absorbing substrate is used, a pressure-sensitive adhesive added with a near-infrared absorber is used during film lamination, a near-infrared absorber is added to an antireflection resin film, etc. It is possible to use a method such as having a function or using a conductive film having a near infrared reflection function.

In the electromagnetic wave shielding sheet for PDP of the present invention, a resin film such as a moisture-proof film, an anti-scattering resin film, an anti-reflection resin film or the like can be used as a colored film for color tone adjustment as appropriate.
For example, the conductive film may appear colored depending on the film design such as the film thickness, but by making the resin film its complementary color film, the overall color tone can be neutralized.

<Support substrate>
In the electromagnetic wave shielding sheet for PDP of the present invention, a transparent supporting base material (hereinafter simply referred to as a supporting base material) having higher rigidity than the base body is provided on the back surface side (PDP side) of the electromagnetic wave shielding sheet. Also good.
In the electromagnetic wave shielding sheet for PDP of the present invention, by providing a support base material, even if the base material is a plastic such as PET, warping may occur due to a temperature difference that occurs on the opposite side of the surface on the PDP side. Absent.
Examples of the material for the supporting base include the same materials as the base material described above.

When providing various resin films and / or supporting substrates, it is preferable that the various resin films and / or supporting substrates are laminated on the substrate and / or the conductive film via an adhesive layer.
As the pressure-sensitive adhesive of the pressure-sensitive adhesive layer, a commercially available pressure-sensitive adhesive can be used, and preferred specific examples include acrylic ester copolymer, polyvinyl chloride, epoxy resin, polyurethane, vinyl acetate copolymer, Examples thereof include pressure-sensitive adhesives such as styrene-acrylic copolymer, polyester, polyamide, polyolefin, styrene-butadiene copolymer rubber, butyl rubber, or silicone resin. In particular, an acrylic pressure-sensitive adhesive is preferably used because good moisture resistance is obtained.
The pressure-sensitive adhesive layer may contain additives having various functions such as an ultraviolet absorber.
In addition, the lamination of a resin film may be possible by heat bonding without using an adhesive or an adhesive.

<Colored ceramic layer>
In the PDP electromagnetic wave shielding sheet of the present invention, it is preferable that a colored ceramic layer for concealing the electrode so as not to be directly visible from the observer side is formed on the observer side of the electrode. The colored ceramic layer only needs to be provided closer to the observer than the electrode, and can be formed, for example, by printing on a supporting substrate or by sticking a colored tape.

  The electromagnetic wave shielding sheet for PDP of the present invention may be installed on the PDP observer side, and the arrangement position is not particularly limited. For example, it may be installed away from the PDP surface, or may be directly attached to the PDP surface.

<First Embodiment>
Hereinafter, 1st Embodiment of the electromagnetic wave shielding sheet for PDP of this invention is described.
In FIG. 2, the typical schematic sectional drawing which shows the layer structure of one embodiment of the electromagnetic wave shielding sheet for PDP of this invention is shown. In FIG. 2, 21 is a substrate, 22 is a conductive film, and 23a and 23b are electrodes.
In this embodiment, a protective film 25 is provided on the conductive film 22 with an adhesive layer 24 interposed therebetween.
Further, a support base 27 is provided on the base 21 via an adhesive layer 26, and a colored ceramic is provided between the base 21 and the support base 27 on the observer side (person side) of the electrodes 23a and 23b. Layers 28a, 28b are provided.
Furthermore, a resin film 30 for preventing scattering and preventing reflection is provided on the support base 27 via an adhesive layer 29.

In the present embodiment, the scattering / antireflection resin film 30 is provided on the most human side of the electromagnetic wave shielding sheet. As the anti-scattering and anti-reflection resin film 30, the above-mentioned ARCTOP (trade name, manufactured by Asahi Glass Co., Ltd.) is preferably used.
The anti-scattering and anti-reflection resin film 30 may be mixed with a near-infrared absorber to give a near-infrared shielding effect. In the electromagnetic wave shielding sheet of the present invention, near-infrared rays can be shielded by the conductive film 22, but the shielding effect is further improved by using such a resin film.

  In FIG. 2, the base 21 and the conductive film 22 on the support base 27 are provided except for the left and right ends in the drawing in order to form a ground terminal for grounding the electrode 23 in this portion. . In order to reduce the ground resistance and ensure a high electromagnetic wave shielding effect, a large number of ground terminals are preferably provided around the entire periphery of the electromagnetic wave shielding sheet.

  In this embodiment, the scattering prevention and antireflection resin film 30, for example, the above-mentioned ARCTOP (trade name, manufactured by Asahi Glass Co., Ltd.) is adhered to the most human side surface of the electromagnetic wave shielding sheet. Instead, the antireflection treatment may be performed by a method of forming a low refractive index film directly on the outer surface of the support base 27.

Second Embodiment
Next, 2nd Embodiment of the electromagnetic wave shielding sheet for PDP of this invention is described. In the embodiments described below, the same reference numerals are given to the components corresponding to the above embodiments, and the detailed description thereof is omitted.

FIG. 3 is a schematic cross-sectional view showing the layer structure of another embodiment of the electromagnetic wave shielding sheet of the present invention. In the present embodiment, the base 21, the conductive film 22, and the electrodes 23 a and 23 b are sequentially laminated on the person side of the support base 27 via the pressure-sensitive adhesive layer 31, and the pressure-sensitive adhesive layer 32 is interposed on the conductive film 22. The anti-scattering and anti-reflection resin film 30 is laminated.
With such a configuration, since the protective effect of the conductive film 22 is obtained by the anti-scattering and anti-reflection resin film 30, the protective film 25 in the first embodiment may not be provided.

≪Method for producing electromagnetic wave shielding sheet for PDP≫
In the electromagnetic wave shielding sheet for PDP of the present invention, a total of (2n + 1) layers [n is an integer of 1 or more] of oxide layers and metal layers containing Ag as a main component and Bi are alternately laminated on a substrate. In this way, a multi-layered conductive film is formed and an electrode is formed on the conductive film.

The method for forming the conductive film (oxide layer, metal layer) on the substrate is not limited, and for example, sputtering, vacuum deposition, ion plating chemical vapor deposition, or the like can be used. Among these, sputtering can be suitably used because of its good quality and stability of characteristics.
Formation of the conductive film by sputtering can be performed as follows, for example. First, an argon gas mixed with oxygen gas is introduced into the surface of the substrate using an oxide layer target (for example, ZnO doped with at least one metal other than Zn or an oxide of the metal), and pulse sputtering is performed. To form an oxide layer. Next, using a target material of Ag alloy doped with Bi, argon gas is introduced and pulse sputtering is performed to form a metal layer. By repeating this operation and finally forming an oxide layer by the same method as described above, a conductive film having a (2n + 1) layer structure is formed.
In order to set the Bi content ratio in the metal layer to 0.2 to 0.6 atomic% based on the total amount of Bi and Ag, the Bi content ratio in the Ag: Bi alloy is set to Bi and Ag. It is preferable to set it as 0.2-1 atomic% with respect to the total amount of, and it is more preferable to set it as 0.3-0.6 atomic%.

  The electrode can be formed by, for example, applying and baking Ag paste (a paste containing Ag and glass frit) or Cu paste (a paste containing Cu and glass frit) on the conductive film.

  Examples are given below to explain the invention in more detail. The present invention is not limited by these examples.

Example 1
[Production of support substrate]
An electromagnetic wave shielding sheet for PDP having the configuration shown in FIG. 2 was produced by the following procedure.
First, a glass plate having a thickness of 2.5 mm was cut into 98 cm × 68 cm, chamfered, washed, and screen-printed with ink for forming a colored ceramic layer on the entire periphery of the glass plate. Next, for the purpose of glass strengthening treatment, this glass plate was heated to 660 ° C. and then subjected to air cooling strengthening to produce a support base 27 on which the colored ceramic layers 28a and 28b were formed.

[Formation of conductive film by sputtering]
Next, a polyethylene terephthalate (PET) having a thickness of 100 μm is used as the base material 2 (base material 21 in FIG. 2), and the conductive film 3 having the structure shown in FIG. A conductive film 22) was formed by the following procedure.
First, dry cleaning using an ion beam for the purpose of cleaning the surface of the substrate 2 was performed as follows. First, about 30% oxygen was mixed with Ar gas, and power of 100 W was applied. The substrate surface was irradiated with Ar ions and oxygen ions ionized by an ion beam source.

Next, using a zinc oxide target doped with 5% by mass of alumina on one side of the surface of the substrate 2 subjected to the dry cleaning treatment, 3% by volume of oxygen gas was mixed with argon and introduced, and 0.35 Pa of Pulse sputtering with a frequency of 100 kHz, a power density of 4.8 w / cm ² , and an inversion pulse width of 1 μsec was performed under pressure to form a zinc oxide film 4 (thickness 40 nm).
Next, using an Ag alloy target doped with 0.5 atomic% Bi, argon gas was introduced, pulse sputtering with a frequency of 100 kHz, a power density of 0.4 w / cm ² , and an inversion pulse width of 5 μsec at a pressure of 0.5 Pa. The Ag alloy film 5 (thickness 13 nm) was formed.
Under this condition, the content ratio of Bi in the Ag alloy film is 0.25 atomic% with respect to the total amount of Bi and Ag.

Next, using a zinc oxide target doped with 5% by mass of alumina, 3% by volume of oxygen gas was mixed and introduced into argon, at a pressure of 0.35 Pa, a frequency of 100 kHz, a power density of 4.8 w / cm ² , Pulse sputtering with an inversion pulse width of 1 μsec was performed to form a zinc oxide film 6 (thickness 80 nm).
Next, using an Ag alloy target doped with 0.5 atomic% Bi, argon gas was introduced, pulse sputtering with a frequency of 100 kHz, a power density of 0.4 w / cm ² , and an inversion pulse width of 5 μsec at a pressure of 0.5 Pa. The Ag alloy film 7 (thickness 16 nm) was formed.

Next, using a zinc oxide target doped with 5% by mass of alumina, 3% by volume of oxygen gas was mixed and introduced into argon, at a pressure of 0.35 Pa, a frequency of 100 kHz, a power density of 4.8 w / cm ² , Pulse sputtering with an inversion pulse width of 1 μsec was performed to form a zinc oxide film 8 (thickness 80 nm).
Next, using an Ag alloy target doped with 0.5 atomic% Bi, argon gas was introduced, pulse sputtering with a frequency of 100 kHz, a power density of 0.4 w / cm ² , and an inversion pulse width of 5 μsec at a pressure of 0.5 Pa. The Ag alloy film 9 (thickness 16 nm) was formed.

Next, using a zinc oxide target doped with 5% by mass of alumina, 3% by volume of oxygen gas was mixed and introduced into argon, at a pressure of 0.35 Pa, a frequency of 100 kHz, a power density of 4.8 w / cm ² , Pulse sputtering with an inversion pulse width of 1 μsec was performed to form a zinc oxide film 10 (thickness 80 nm).
Next, using an Ag alloy target doped with 0.5 atomic% Bi, argon gas was introduced, pulse sputtering with a frequency of 100 kHz, a power density of 0.4 w / cm ² , and an inversion pulse width of 5 μsec at a pressure of 0.5 Pa. The Ag alloy film 11 (thickness 13 nm) was formed.

Next, using a zinc oxide target doped with 5% by mass of alumina, 3% by volume of oxygen gas was mixed and introduced into argon, at a pressure of 0.35 Pa, a frequency of 100 kHz, a power density of 4.3 w / cm ² , Pulse sputtering with an inversion pulse width of 1 μsec was performed to form a zinc oxide film 12 (thickness 35 nm).

Next, an ITO target (indium: tin = 90: 10) is used as a protective film on the zinc oxide film 12, and 3% by volume of oxygen gas is mixed and introduced into argon, and the frequency is set at a pressure of 0.35 Pa. Pulse sputtering with 100 kHz, power density of 0.5 w / cm ² and inversion pulse width of 1 μsec was performed to form an ITO film 13 (thickness 5 nm) to obtain an electromagnetic wave shielding film.

  An adhesive material (P0280, manufactured by Lintec Corporation) was applied to the obtained electromagnetic shielding film so as to have a thickness of 25 μm, and attached to the surface of the prepared support substrate 27 on the side where the colored ceramic layers 28a and 28b were formed. .

  Then, for the purpose of protecting the electromagnetic wave shielding film, a protective film 25 (trade name ARCTOP CP21, manufactured by Asahi Glass Co., Ltd.) was bonded to the side of the electromagnetic wave shielding film opposite to the side where the support base 27 was bonded. In a part of the outer peripheral portion of the conductive film, a portion where the protective film was not bonded was left for the purpose of taking out the electrode.

[Electrode formation]
Next, Ag paste (trade name AF4810, manufactured by Taiyo Ink Co., Ltd.) is screen-printed with nylon mesh # 180 and emulsion thickness 20 μm on the exposed portion of the electromagnetic shielding film exposed (outer periphery of the conductive film), and hot air circulation is performed. It was dried in an oven at 85 ° C. for 35 minutes to form an electrode.

  Next, a transparent soft adhesive film is applied to the back surface of the support substrate 27 (the opposite surface to which the electromagnetic wave shielding film is bonded) on a polyurethane soft resin film (trade name ARCTOP URP2199) for the purpose of preventing reflection and preventing glass scattering. Were bonded together to obtain an electromagnetic wave shielding sheet for PDP. Normally, a colorant is added to the resin film to achieve color tone correction, Ne cut, and the like to improve color reproducibility. However, since this evaluation is not performed in this verification, no color was given.

Comparative Example 1
An electromagnetic wave shielding sheet for PDP was obtained in the same manner as in Example 1, except that the Bi-doped Ag alloy target in Example 1 was changed to an Ag alloy target doped with 1% by mass of Pd.

Comparative Example 2
An electromagnetic wave shielding sheet for PDP was obtained in the same manner as in Example 1 except that the Bi-doped Ag alloy part in Example 1 was changed to Ag having a purity of 99.9%.

Test example 1
About the electromagnetic wave shielding sheet for PDP created in Example 1 and Comparative Examples 1 and 2, the luminous transmittance and sheet resistance were measured by the following procedures, and a high temperature and high humidity resistance test and a NaCl dropping test were performed.

"Visibility"
The luminous transmittance (stimulus value Y defined in JIS Z 8701) was measured with a spectrophotometer UV3150PC manufactured by Shimadzu Corporation.
The luminous transmittances of the PDP electromagnetic wave shielding sheets of Example 1 and Comparative Example 2 were 61.1% and 62.2%, respectively. On the other hand, the luminous transmittance of the electromagnetic wave shielding sheet for PDP of Comparative Example 1 was as low as 55.0%.

"Sheet resistance"
The sheet resistance was measured with an eddy current resistance measuring device SRM12 manufactured by Nagy.
The sheet resistance of the electromagnetic wave shielding sheet for PDP of Example 1 was 0.85Ω. In contrast, the sheet resistance of the PDP electromagnetic shielding sheet of Comparative Example 1 was as high as 1.15Ω. Moreover, the sheet resistance of the electromagnetic wave shielding sheet for PDP of Comparative Example 2 was 0.81Ω.

"High temperature and humidity resistance test"
In an accelerated test under standing in a high-temperature and high-humidity environment, the deterioration of luminous transmittance (optical characteristics) and sheet resistance (electrical characteristics), and changes in appearance (whether white spots or cloudiness occurred) were investigated. After leaving it in an environment of 60 ° C.-90% for 100 hours, visual observation was performed, and the luminous transmittance and sheet resistance were evaluated in the same manner as described above.
The electromagnetic wave shielding sheet for PDP of the present invention and Comparative Example 1 had no appearance defects and no change in luminous transmittance and sheet resistance. In contrast, the electromagnetic wave shielding sheet for PDP in Comparative Example 2 has white spots and cloudiness, large changes in luminous transmittance and sheet resistance before and after the test, and large changes in optical characteristics and electrical characteristics. confirmed.

"NaCl drop test"
About deterioration of Ag film | membrane, the corrosion degree by NaCl aqueous solution was compared and migration resistance was evaluated.
5 μL of a 2 mass% NaCl aqueous solution was dropped on the conductive film before the protective film 25 of the PDP electromagnetic shielding sheet of Example 1 and Comparative Examples 1 and 2 was bonded, and dried at room temperature. After drying, the protective film 25 was bonded and left for 100 hours in a constant temperature and humidity chamber having a humidity of 60% and a temperature of 90 ° C. The sheet was taken out from the thermo-hygrostat and observed from the protective film side, and the areas of the portions (deteriorated portions) that were discolored around the NaCl aqueous solution dropping portion were compared. As a result, it was confirmed that the area of the discolored portion of Experimental Example 1 was equivalent to that of Comparative Example 1 and was smaller than that of Comparative Example 2.

  As is clear from these results, the PDP electromagnetic shielding sheet of Example 1 has a higher luminous transmittance (optical characteristics) than the PDP electromagnetic shielding sheet of Comparative Example 1 using Ag doped with Pd, and The sheet had low sheet resistance (electrical characteristics) and had moisture resistance and migration resistance superior to the electromagnetic wave shielding sheet for PDP of Comparative Example 2 using pure Ag.

It is a typical schematic sectional drawing of an example of the electrically conductive film formed on the base | substrate in this invention. It is a typical schematic sectional drawing which shows the layer structure of the 1st embodiment of the electromagnetic wave shielding sheet for PDP of this invention. It is a typical schematic sectional drawing which shows the layer structure of the 2nd embodiment of the electromagnetic wave shielding sheet for PDP of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electromagnetic wave shielding sheet, 2 ... Base | substrate, 3 ... Conductive film, 4 ... Oxide layer, 5 ... Metal layer, 6 ... Oxide layer, 7 ... Metal layer, 8 ... Oxide layer, 9 ... Metal layer, 10 ... Oxide layer, 11 ... metal layer, 12 ... oxide layer, 13 ... protective film, 21 ... substrate, 22 ... conductive film, 23a and 23b ... electrode, 24 ... adhesive layer, 25 ... protective film, 26 ... adhesive Layer 27, supporting substrate 28a and 28b, colored ceramic layer, 29 adhesive layer, 30 anti-scattering and anti-reflection resin film, 31 adhesive layer, 32 adhesive layer

Claims (6)

An electromagnetic wave shielding sheet for plasma display having a substrate, a conductive film formed on the substrate, and an electrode in electrical contact with the conductive film,
The conductive film is a conductive film having a multilayer structure in which a total of (2n + 1) layers [n is an integer of 1 or more] are laminated alternately from the base side on the oxide layer and the metal layer,
An electromagnetic wave shielding sheet for plasma display, wherein the metal layer contains Ag as a main component and contains Bi.   The electromagnetic wave shielding sheet for a plasma display according to claim 1, wherein the content ratio of Bi is 0.2 to 0.6 atomic% with respect to the total amount of Bi and Ag.   The electromagnetic wave shielding sheet for plasma display according to claim 1 or 2, wherein the oxide layer contains ZnO as a main component.   The electromagnetic wave shielding sheet for plasma display according to claim 3, wherein the oxide layer mainly composed of ZnO contains one or more metals other than Zn.   On the substrate, an oxide layer and a metal layer containing Ag as a main component and containing Bi are alternately stacked in total (2n + 1) layers [n is an integer of 1 or more] to form a multi-layered conductive film, Electrode is formed on this electrically conductive film, The manufacturing method of the electromagnetic wave shielding sheet for plasma displays as described in any one of Claims 1-4 characterized by the above-mentioned. The method for producing an electromagnetic wave shielding sheet for plasma display according to claim 5, wherein the metal layer is formed by sputtering using an Ag: Bi alloy as a target.

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