JP2017068219A - Electrode structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode structure that suppresses reflection of incident light from outside, prevents generation of interference fringes, and minimizes scattering of light.SOLUTION: An electrode structure comprises an Al metallic layer which has a tapered side face and is made of Al or an Al alloy, and an antireflection layer disposed on a transparent substrate in the described order. The Al metallic layer has a taper length of -0.10 to 0.35 μm, inclusive, and a reflectance of 50% or less in a visible light range. The electrode structure exhibits a value represented by [(Haze of the electrode)-(Haze of the transparent substrate)] of 1.0% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode structure. In particular, the present invention relates to an electrode structure in which reflection of light incident from the outside is suppressed and light scattering and interference fringes are suppressed.

  Hereinafter, the electrode structure of the present invention will be described by taking as an example the case where it is applied to an input device, particularly a touch panel sensor, but the present invention is not limited to this.

  As an electrode used for a touch panel sensor, use of, for example, an Al-based metal electrode exhibiting a low electric resistance has been studied. However, since the metal electrode has high reflectance of incident light from the outside and is visible to the naked eye of the user, an antireflection layer is laminated on the metal film constituting the metal electrode, or the metal film is blackened Etc. are adopted. However, even if the reflection of incident light is suppressed in this way, interference fringes and light scattering may occur locally as another problem.

  The light scattering is generally evaluated by a haze ratio (also referred to as haze), and the lower the haze ratio, the more the light scattering is suppressed. The following techniques can be cited as techniques for suppressing the increase in haze ratio.

  For example, Patent Document 1 discloses that the etching quality of the aluminum pattern layer is improved by setting the thickness of the aluminum oxide film formed on the surface of the electrode made of the aluminum pattern layer to a certain value or less. It has been shown that defects such as jaggedness and disconnection in the line contour portion are eliminated, and as a result, increase in conductivity variation and haze (cloudiness value) can be suppressed. However, a specific wiring shape is not shown.

  In Patent Document 2 and Patent Document 3, silver nanowires are metal electrode materials that have flexibility and high light transmission and are hardly visible, and can be applied to touch panels, solar cells, flexible liquid crystal displays, and the like. It has been shown. By using this silver nanowire for wiring, the wiring can be made invisible. However, the haze ratio of the silver nanowire shown in Patent Document 2 is 3.7%, and the silver nanowire shown in Patent Document 3 is used. The haze rate of the wire exceeds 1.0%, and at this haze rate, light may be scattered and appear white and cloudy. Therefore, there is a demand for more reliably suppressing light scattering.

  In any of the above Patent Documents 1 to 3, no countermeasures against interference fringes have been studied.

JP 2011-070536 A JP 2013-144822 A JP 2013-199691 A

  The present invention has been made paying attention to the circumstances as described above, and its purpose is to suppress reflection of incident light from the outside, to prevent generation of interference fringes, and to suppress light scattering. It is to establish an electrode structure.

  In the electrode structure of the present invention that can solve the above problems, an electrode including an Al-based metal layer made of Al or an Al alloy having a tapered side surface and an antireflection layer in this order is formed on a transparent substrate, The taper length of the Al-based metal layer is −0.10 μm or more and 0.35 μm or less, and the reflectance in the visible light region is 50% or less, and [(the haze ratio of the electrode) − (of the transparent substrate The haze ratio)] is 1.0% or less. Hereinafter, this [(the haze ratio of the electrode) − (the haze ratio of the transparent substrate)] may be referred to as a “difference in the haze ratio”.

  In a preferred embodiment, the taper angle of the Al-based metal layer is 20 to 100 degrees.

  In a preferred embodiment, the antireflection layer includes at least one of a nitride film of Al or an Al alloy and a nitride film of a refractory metal element. The antireflection layer may further contain a transparent conductive film.

  The present invention also includes an input device having the electrode structure and a touch panel sensor having the electrode structure.

  According to the present invention, the reflection of light incident from the outside can be suppressed by setting the taper length of the Al-based metal layer, which is a conductive layer, within a certain range and keeping the difference between the haze ratios of the electrode and the transparent substrate below a certain value. At the same time, it is possible to provide an electrode structure in which generation of interference fringes is prevented and light scattering is suppressed.

FIG. 1 is a schematic sectional view showing an example of the electrode structure of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of an electrode structure that does not satisfy the requirements of the present invention.

  The inventors of the present invention have an electrode structure including a metal film as an electrode on a transparent substrate, in which reflection of external light is suppressed, generation of interference fringes can be prevented, and light scattering is suppressed. I have been studying to get it. As a result, an electrode including an Al-based metal layer made of Al or an Al alloy having a tapered side surface and an antireflection layer in this order is formed on the transparent substrate, and the Al-based metal layer includes: The taper length is −0.10 μm or more and 0.35 μm or less, the reflectance in the visible light region is 50% or less, and [(the haze ratio of the electrode) − (the haze ratio of the transparent substrate)] is 1. The present inventors have found that the above characteristics can be achieved by satisfying 0.0% or less, and the present invention has been completed.

  Hereinafter, the electrode structure of the present invention will be described in detail with reference to FIG. However, the electrode structure of the present invention is not limited to FIG.

[Al-based metal layer made of Al or Al alloy with side taper]
FIG. 1 is a schematic sectional view showing an example of the electrode structure of the present invention. In FIG. 1, a tapered Al-based metal layer 2 is formed on a transparent substrate 1, and an antireflection layer 3 is further formed thereon. The tapered Al-based metal layer 2 is symmetrical in FIG. 1, and the shape of the Al-based metal layer 2 varies depending on the taper angle θ. The Al metal layer 2 serves as a low electrical resistance layer and a conductive layer. In FIG. 1 and FIG. 2 described later, the side of the transparent substrate 1 on which the Al-based metal layer 2 and the like are laminated is referred to as the front side 1a of the transparent substrate, and the opposite side is referred to as the back side 1b of the transparent substrate.

  One of the features of the present invention is that the taper length D of the Al-based metal layer 2 is in the range of −0.10 μm or more and 0.35 μm or less. It has been found that when the taper length exceeds 0.35 μm, interference fringes are generated and visibility is inferior. The taper length is preferably 0.25 μm or less, more preferably 0.20 μm or less. On the other hand, when the taper length is less than −0.10 μm, that is, as shown in FIG. 2, the contact end region between the Al-based metal layer 2 and the transparent substrate 1 may be located sufficiently inside the end portion of the antireflection layer 3. The generation of interference fringes and an increase in haze ratio were observed. In FIG. 2, light incident from the back side 1b of the transparent substrate is scattered by the contact end regions B1 and B2 of the Al-based metal layer 2 and the antireflection layer 3, or light incident from the front side 1a of the transparent substrate is Al. This is considered to be due to irregular reflection in the acute angle spaces X1 and X2 formed by the side surface of the metallic metal layer 2 and the transparent substrate 1. Therefore, in the present invention, the taper length is set to −0.10 μm or more. The taper length is preferably 0 μm or more.

  Further, the taper angle θ of the Al-based metal layer 2 shown in FIG. 1 is preferably in the range of 20 to 100 degrees. The unit of the taper angle is also expressed by “°” or “deg” which means “degree”. By setting the taper angle to 20 degrees or more, in the contact end regions A1 and A2 of the Al-based metal layer and the transparent substrate in FIG. 1, light scattering can be reduced and haze rate increase can be suppressed. Then, it becomes easy to suppress [(the haze ratio of the electrode) − (the haze ratio of the transparent substrate)] described later within a specified range. The taper angle is more preferably 40 degrees or more, and still more preferably 50 degrees or more. On the other hand, by setting the taper angle to 100 degrees or less, light incident from the back side 1b of the transparent substrate is scattered by B1 and B2 in FIG. 2, or light incident from the front side 1a of the transparent substrate is shown in FIG. It is possible to suppress irregular reflection at X1 and X2 and suppress an increase in the haze ratio. As a result, in this case, [(the haze ratio of the electrode) − (the haze ratio of the transparent substrate)] is within a specified range. It is preferable because it is easy to suppress. The taper angle is more preferably 90 degrees or less.

  The Al-based metal layer is made of Al, that is, pure Al and the balance of inevitable impurities, or made of Al alloy, that is, Al, alloy elements, and the balance of inevitable impurities. The alloy element is not particularly limited, and can be used by appropriately controlling the type and content. Examples of the alloy element include one or more of rare earth elements, refractory metal elements, Ni, Cu, Si, Ge, Zr, and the like. The rare earth element includes lanthanoid elements, that is, 15 elements from La to Lu, and scandium and yttrium. The refractory metal element means a metal having a melting point of 1200 ° C. or higher, such as Mo, Ti, Ta, W, Cr, and Mn. Examples of the Al alloy include Al-Nd such as Al-2 atomic% Nd, Al-Ni-La such as Al-2 atomic% Ni-0.35 atomic% La, Al-0.2 atomic% Ni-0.5. Al-Ni-Ge-Nd such as atomic% Ge-0.2% Nd, Al-Si such as Al-1 atomic% Si, Al-Cu such as Al-0.5 atomic% Cu, or the like can be used. .

  The thickness of the Al-based metal layer is preferably 100 nm or more and more preferably 150 nm or more in order to achieve a low electrical resistivity. However, if the thickness of the Al-based metal layer exceeds 500 nm, the workability may be lowered or the substrate may be warped. Therefore, the thickness of the Al-based metal layer is preferably 500 nm or less.

[Antireflection layer]
The electrode according to the present invention includes an antireflection layer. Since this antireflection layer is included, a low reflection electrode structure can be realized. The type of the antireflection layer is not particularly limited as long as it can achieve a reflectance of 50% or less of the electrode structure in the visible light region.

  In order to easily achieve the reflectance, it is preferable that the antireflection layer includes at least one of an Al or Al alloy nitride film and a refractory metal element nitride film. Hereinafter, these nitride films may be referred to as “metal nitride films”.

  The refractory metal element means a metal having a melting point of 1200 ° C. or higher, such as Mo, Ti, Ta, W, Cr, and Mn. These metals can be used alone or alloys based on these metals. In this specification, the “nitride film” is sufficient if at least nitrogen is contained in Al, an Al alloy, and a refractory metal element, and is not necessarily a nitride satisfying the stoichiometric composition. For example, when Mo nitride is represented by MoNx, x may be about 0.1 to 0.95.

  In order to suppress the electrical resistivity while easily achieving the reflectance, it is preferable to use Mo or Ti as the refractory metal element. That is, at least one of a nitride film of Mo or Mo alloy and a nitride film of Ti or Ti alloy is preferable, and a nitride film of Mo or Mo alloy is more preferable. The Mo alloy preferably contains at least one of Nb, W, Ti, V, and Cr. For example, a Mo—Nb alloy, a Mo—W alloy, a Mo—Ti alloy, a Mo—V alloy, a Mo—Cr alloy, etc. Is mentioned. In view of wet etching processability, a Mo—Nb alloy is more preferable.

  The thickness of the metal nitride film is preferably 5 nm or more from the viewpoint of ensuring low reflectance. More preferably, it is 10 nm or more. However, if the thickness of the metal nitride film exceeds 80 nm, the reflectivity increases, and the productivity may be reduced. Therefore, the thickness of the metal nitride film is preferably 80 nm or less. More preferably, it is 50 nm or less.

[Transparent conductive film if necessary]
In order to further reduce the reflectance, a transparent conductive film may be formed on the metal nitride film, that is, on the opposite side of the metal nitride film from the transparent substrate side, if necessary. The transparent conductive film is not particularly limited as long as it is usually used in the technical field of the present invention, but preferably contains at least one of In or Zn. For example, in view of workability, In—Zn—O, Zn—Al—O, Zn—O, In—O, and the like represented by IZO are more preferable.

  The thickness of the transparent conductive film is preferably 25 nm or more in order to effectively exhibit the low reflectance effect. More preferably, it is 35 nm or more. However, when the thickness of the transparent conductive film exceeds 100 nm, the reflectivity is increased, and an etching residue may be caused. Therefore, the thickness is preferably set to 100 nm or less. More preferably, it is 80 nm or less.

[Transparent substrate]
The transparent substrate constituting the electrode structure of the present invention is usually used in the technical field of the present invention and is not particularly limited as long as it has transparency. For example, a glass substrate constituting a color filter substrate or a cover glass, A film substrate, a quartz substrate, etc. are mentioned.

  The electrode structure of the present invention including the antireflection layer satisfies a reflectance in the visible light region of 50% or less. The reflectance is preferably 30% or less, more preferably 10% or less. Since the influence of the transparent substrate on the reflectivity of the electrode structure is negligible, the reflectivity is equal to the reflectivity of the electrode, that is, the laminate including the Al-based metal layer and the antireflection layer.

  In the electrode structure of the present invention, the difference in haze ratio obtained by [(the haze ratio of the electrode) − (the haze ratio of the transparent substrate)] is suppressed to 1.0% or less. The difference in haze ratio is preferably 0.7% or less, more preferably 0.5% or less, and most preferably no difference, that is, 0%.

  The electrode structure of the present invention has a basic structure in which the Al-based metal layer and the antireflection layer are laminated in this order on a transparent substrate. For the purpose of further reducing electrical resistivity and reflectance, Other layers may be laminated.

  The electrode structure of the present invention is preferably applied to an input device. This input device includes both an input device having an input means in a display device such as a touch panel; and an input device having no display device such as a touch pad. Specifically, an input device for operating the device by combining the various display devices and the position input means and pressing a display on the screen, or a display device separately installed corresponding to the input position on the position input means The electrode structure of the present invention can also be applied to the electrode structure of an input device that operates.

  The method for obtaining the electrode structure of the present invention is not particularly limited. The electrode structure of the present invention can be obtained, for example, by the following method.

  The formation of the Al-based metal layer on the transparent substrate is performed by a sputtering method using a sputtering target from the viewpoints of thinning, homogenization of alloy components in the film, and easy control of the amount of added elements. It is preferable to form a film.

  The sputtering target to be used may be an Al or Al alloy sputtering target corresponding to the Al-based metal layer to be formed. The shape of the sputtering target is not particularly limited, and may be any shape depending on the shape and structure of the sputtering apparatus, for example, a square plate shape, a circular plate shape (also called a disk shape), a donut plate shape, a cylindrical shape, etc. What was processed can be used.

The conditions of the sputtering method of the Al-based metal layer are not particularly limited. For example, when the target is a circular plate having a diameter of 4 inches, the following range may be mentioned.
-(Ar) gas pressure during film formation: 1 to 4 mTorr
Ar gas flow rate: 5-50sccm
・ Sputtering power: 100-2000W
-Substrate temperature: room temperature to 200 ° C
・ Deposition temperature: room temperature to 200 ° C
・ Achieving vacuum: 1 × 10 ^-5 Torr or less

After forming the Al-based metal layer, an antireflection layer is formed on the Al-based metal layer. When forming a metal nitride film as the antireflection layer, it is preferable to employ a reactive sputtering method containing nitrogen gas from the viewpoints of productivity and film quality control. The conditions of the reactive sputtering method include, for example, the following ranges when the target is a circular plate having a diameter of 4 inches.
・ Atmosphere gas: Nitrogen gas, Ar gas ・ Substrate temperature: Room temperature to 200 ° C.
・ Deposition temperature: room temperature to 200 ° C
-Nitrogen gas flow rate during film formation: 5-50% of Ar gas
・ Sputtering power: 100-2000W
・ Achieving vacuum: 1 × 10 ^-5 Torr or less

  When a transparent conductive film is further formed as the antireflection layer, the transparent conductive film may be formed under conditions usually used in the technical field of the present invention.

  After a laminated film of the Al metal layer and the antireflection layer is formed on the transparent substrate, an electrode pattern is formed by patterning the laminated film by photolithography and wet etching. In order to easily make the taper shape of the Al-based metal layer into the shape prescribed in the present invention, for example, the above-mentioned photolithography conditions are controlled, specifically, for example, surface treatment is performed before resist application to improve adhesion with the resist. Or adjusting the etching shape of the laminated film of the antireflection layer and the Al-based metal layer by adjusting the temperature of resist baking performed after applying the resist.

  Conditions that are usually used in the technical field of the present invention can be appropriately employed as manufacturing conditions for electrode structures other than those described above.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be implemented with modifications within a range that can meet the purpose described above and below. They are all included in the technical scope of the present invention.

  In this example, an Al—Nd film as an Al-based metal layer and a laminated film of an Al—Cu nitride film and an IZO film, which is a transparent conductive film, were formed in this order as an Al-based metal layer on a transparent substrate. Thereafter, electrodes having various taper angles and taper lengths of the Al-based metal layer were formed, and electrode structures were obtained as samples. Using this sample, the reflectance, the presence or absence of interference fringes, and the difference in haze rate in the visible light region were evaluated. Details of the preparation of the sample and the evaluation of the characteristics are shown below.

(1) Preparation of sample (1-1) Film formation of Al-based metal layer First, a glass substrate as a transparent substrate, specifically, an alkali-free glass plate having a diameter of 4 inches and a plate thickness of 0.7 mm was used. On the surface of the glass substrate, an Al-2 atomic% (at%) Nd film having each film thickness shown in Table 1 was formed as an Al-based metal layer by DC magnetron sputtering. Specifically, before the film formation, the atmosphere in the chamber is once adjusted to an ultimate vacuum of 3 × 10 ⁻⁶ Torr, and then a 4 inch diameter disk having the same component composition as the Al-2 at% Nd film. Sputtering was performed using the mold sputtering target under the following conditions.
(Sputtering conditions)
Ar gas pressure: 2 mTorr
Ar gas flow rate: 10sccm
・ Sputtering power: 500W
-Substrate temperature: Room temperature-Film formation temperature: Room temperature-Film thickness: 100-500 nm

(1-2) Formation of Antireflection Layer (Al-7 at% Cu Nitride Film) On the Al-2 at% Nd film, an Al-7 at% Cu alloy target was used under the following reactive sputtering conditions. A film was formed by reactive sputtering with N ₂ to form an Al-7 at% Cu nitride film having a thickness of 50 nm.
(Reactive sputtering conditions)
・ (Ar + N ₂ ) gas pressure: 2 mTorr
Ar gas flow rate: 10sccm
・ N ₂ gas flow rate: 5 sccm
・ Sputtering power: 500W
・ Substrate temperature: Room temperature ・ Film formation temperature: Room temperature

(1-3) Film formation of antireflection layer (IZO film) After forming an Al-7 at% Cu nitride film as described above, the surface is then transparent under the following sputtering conditions by DC magnetron sputtering. An IZO film having a thickness of 50 nm was formed as the conductive film. Before forming the transparent conductive film, the atmosphere in the chamber is once adjusted to an ultimate vacuum of 3 × 10 ⁻⁶ Torr, and then a disk type having the same composition as the transparent conductive film and having a diameter of 4 inches. The IZO sputtering target was used.
(Sputtering conditions)
・ Gas pressure: 2mTorr
Ar gas flow rate: 18 sccm
・ O ₂ gas flow rate: 1 sccm
・ Spatter power: 250W
・ Substrate temperature: Room temperature ・ Film formation temperature: Room temperature

(1-4) Formation of electrode pattern The laminated film of the Al-based metal layer and the antireflection layer thus obtained is subjected to patterning by photolithography and wet etching, and the taper angle and taper length shown in Table 1 are obtained. An electrode having a grid pattern with a wiring width of 4 μm, a wiring interval of 300 μm, and perpendicular to the vertical and horizontal directions was prepared. The taper angle and taper length shown in Table 1 control the photolithography conditions. Specifically, the surface treatment is performed before the resist coating to improve the adhesion with the resist, and the resist baking temperature after the resist coating is controlled. Changed by changing. In Table 1, No. No. 11 is an etching process without an IZO film. The taper shape was slightly different from 1-10.

Measurement of taper angle and taper length of Al-based metal layer The taper angle and taper length were obtained by observing the wiring cross section with SEM (Scanning Electron Microscope). The taper length is as shown in FIG. 1 when the shape of the Al-based metal layer 2 in the laminated section is a trapezoid, that is, the contact end region between the Al-based metal layer 2 and the transparent substrate 1 is the end of the antireflection layer 3. The case where the position is located outside is a positive value, and the shape of the Al-based metal layer 2 in the laminated section is an inverted trapezoid, that is, the contact end region between the Al-based metal layer 2 and the transparent substrate 1 is the antireflection layer 3. The case where it located inside the edge part of was obtained as a negative value.

(2) Evaluation of characteristics (2-1) Reflectance of electrode structure The reflectance in the visible light region of the electrode structure is based on JIS R 3106, and the visible light reflectance is spectrally divided by light having a wavelength of 380 to 780 nm with a D65 light source. It measured using the photometer (The JASCO Corporation make: Visible and ultraviolet spectrophotometer "V-570"). Specifically, the reflected light intensity (measured value) of the sample with respect to the reflected light intensity of the reference mirror is calculated as “reflectance” (= [reflected light intensity of sample / reflected light intensity of reference mirror] × 100%). did. In this example, when the reflectance of the sample at each wavelength of λ = 450 nm, 550 nm, and 650 nm was measured, the case where the reflectance was 50% or less and more than 30% in all wavelength regions, Since the reflection is suppressed, it is passed as “good”, particularly when the reflectance is 30% or less, the reflection of incident light from the outside is sufficiently suppressed as “excellent”. The case where the reflectance was more than 50% was judged as rejected because the reflection of incident light from the outside was not suppressed and was “bad”.

(2-2) Presence / absence of interference fringes With the light of the fluorescent lamp applied from the antireflection layer side of the sample, the surface of the antireflection layer side of the sample was visually observed to evaluate the presence / absence of interference fringes. Those having no interference fringes were evaluated as “good”, and those having interference fringes were evaluated as “bad”.

(2-3) Difference of haze ratio About each of the electrode obtained by said method and a glass substrate, the haze ratio was measured on condition of the following. Then, [(the haze ratio of the electrode) − (the haze ratio of the glass substrate)], that is, the difference between the haze ratios was obtained. When the difference in haze ratio is 1% or less, light scattering is suppressed as “good”, and when the difference in haze ratio exceeds 1%, light scattering occurs and evaluated as “bad”. .
(Measurement conditions of haze ratio)
Measuring device: Haze meter NDH2000 (Nippon Denshoku Industries Co., Ltd.)
・ Measurement method: Conforms to JIS K 7136 (with compensation opening)
・ Optical conditions: Light source, halogen bulb (D65 light)

  These results are shown in Table 1.

  Table 1 shows the following. No. in Table 1 In 1-3, 5-7 and 11, reflection of incident light from the outside was suppressed, interference fringes were not observed, and the difference in haze ratio was small, so that light scattering was suppressed. In contrast, no. In 4, 8, and 9, reflection of incident light from the outside was suppressed, but interference fringes occurred because the taper length exceeded the specified range. No. In No. 10, reflection of incident light from the outside is suppressed, but since the taper length is less than the specified range, interference fringes also occur in this case.

  Furthermore, no. 9 and no. No. 10 had a haze ratio difference of more than 1%, and light scattering was likely to occur. This No. 9 and 10; From the comparison with 1 to 3 and 5 to 7, it can be seen that it is preferable to control the taper angle within the recommended range in order to suppress the difference in haze ratio to 1% or less.

1 Transparent substrate 1a Front side 1b of transparent substrate 2 Back side of transparent substrate 2 Al-based metal layer 3 Antireflection layer D Tapered length of Al-based metal layer θ Taper angles A1 and A2 of Al-based metal layer Contact between Al-based metal layer and transparent substrate Edge regions B1 and B2 Contact end regions X1 and X2 of the Al-based metal layer and the antireflection layer Acute angle space formed by side surfaces of the Al-based metal layer and the transparent substrate

Claims (6)

An electrode including an Al-based metal layer made of Al or an Al alloy having a tapered side surface and an antireflection layer in this order is formed on the transparent substrate,
The taper length of the Al-based metal layer is −0.10 μm or more and 0.35 μm or less, and the reflectance in the visible light region is 50% or less, and [(the haze ratio of the electrode) − (the transparent substrate The haze ratio)] is 1.0% or less.   The electrode structure according to claim 1, wherein the taper angle of the Al-based metal layer is 20 to 100 degrees.   The electrode structure according to claim 1, wherein the antireflection layer includes at least one of a nitride film of Al or an Al alloy and a nitride film of a refractory metal element.   The electrode structure according to claim 3, wherein the antireflection layer further includes a transparent conductive film.   An input device having the electrode structure according to claim 1.   A touch panel sensor having the electrode structure according to claim 1.