JP4864546B2 - Organic EL display device and manufacturing method thereof - Google Patents

Description

  The present invention relates to an organic EL (Electro Luminescence) display device and a manufacturing method thereof.

  In an organic EL element, a hole transport layer, a light emitting layer, and an electron injection layer made of an organic material are laminated between an anode electrode (hereinafter referred to as “anode electrode”) and a cathode electrode (hereinafter referred to as “cathode electrode”). It emits light when a low voltage direct current is applied. The organic EL element is excellent in moving image display because of its high response speed from application of direct current to light emission. Further, since the organic EL element is a self-luminous element, an auxiliary light source as in the case of a liquid crystal display element is unnecessary, and attention is paid in that it is suitable for a thin display device.

  Organic EL display devices using organic EL elements are classified into a passive matrix drive type and an active matrix drive type in which each pixel is provided with a switch element according to a method for applying and driving a low voltage direct current. Furthermore, it is distinguished according to the direction in which the light emission from the organic EL element is extracted, and is divided into a bottom emission type in which the organic EL element is taken out to the side of the substrate on which the organic EL element is laminated and a top emission type in which the laminated substrate is taken away from It is done.

  Examples of an active matrix drive type top emission type organic EL display device are disclosed in Japanese Patent Application Laid-Open No. 2005-285395 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2005-322564 (Patent Document 2).

In Patent Document 1, a reflection plate is formed of an Al-based metal so as to cover an upper surface of a portion other than a contact hole of an interlayer insulating film, and an anode having a thickness of 100 nm made of ITO covers the upper side of the reflection plate. A low-voltage direct current from the drain electrode of the TFT is applied to the organic EL layer through this transparent anode.
JP 2005-285395 A JP 2005-322564 A

  In the organic EL display device disclosed in Patent Document 1, in order to improve the light extraction efficiency and obtain a bright organic EL display device, the film thickness of the ITO film called “anode” in optical design It is desirable to reduce the thickness and to a specific film thickness. However, when this ITO film becomes thin, the resistance value increases. In addition, the coverage with the ITO film at the contact hole or the stepped portion of the reflector is reduced. As a result, light emission failure or non-light emission is caused by an increase in resistance value or disconnection. Therefore, if the thickness of the ITO film is reduced and the reflector made of an Al-based metal is also made thinner to compensate for the decrease in coverage, the reflectivity of the reflector decreases and the light extraction efficiency deteriorates. End up.

  In the organic EL display device disclosed in Patent Document 2, the “lower electrode” serving as an anode electrode has a three-layer structure of ITO-Ag-ITO. Here, it is considered that the Ag film plays the role of a reflective film. If the Ag film is used, the reflectance is high and the contact resistance with the ITO film as the transparent conductive film is also kept low. However, in such a structure, low resistance electrical connection is required between the transparent conductive film and the reflective film, and the materials of the reflective metal film and the transparent conductive film are limited.

  Further, the present inventors have found that the amount of moisture and gas released increases when the metal film and the organic resin come into contact with each other and heat is applied. On the other hand, the organic EL layer is vulnerable to moisture. If the contact structure between the metal film and the organic resin film is included in the organic EL display device, moisture or gas is generated in the organic EL display device due to heat generated by long-term driving or high-temperature use environment such as under the sun. The EL layer deteriorates.

  In the structure of Patent Document 1, the “reflector 50” made of metal and the “interlayer insulating film 36” made of organic resin are in contact with each other. In the structure of Patent Document 2, the side surface of the Ag film included in the “lower electrode 15” is in contact with the “insulating film 16” made of an organic resin. Therefore, in any of Patent Documents 1 and 2, moisture and gas are generated due to heat generated by long-term driving or a high-temperature use environment such as in the sun, and the organic EL layer is deteriorated.

  Therefore, an object of the present invention is to provide an organic EL display device with high reliability and long life.

  In order to achieve the above object, an organic EL display device according to the present invention includes a substrate, a plurality of thin film transistors formed on the main surface of the substrate, and a planarizing film made of an organic resin that covers the upper sides of the plurality of thin film transistors. And a plurality of anode electrodes disposed on the planarizing film and electrically connected to each of the plurality of thin film transistors, and the plurality of anode electrodes are individually insulated and isolated from an organic resin. An organic EL layer disposed above the anode electrode so as to be electrically connected to the anode electrode, and disposed above the organic EL layer so as to be electrically connected to the organic EL layer. The anode electrode includes three layers of a lower transparent conductive film, a reflective metal film, and an upper transparent conductive film in order from the side close to the substrate, and the reflective gold Film top surface, all of the lower surface and side surfaces are coated with a transparent conductive film.

  According to the present invention, the upper surface, the lower surface, and the side surface of the reflective metal film are all covered with the transparent conductive film, and as a result, there is no place where the metal film and the film made of organic resin are in direct contact. The generation of moisture and gas inside can be reduced, and a highly reliable and long-life organic EL display device can be realized.

  As a result of intensive studies for extending the lifetime of the organic EL layer used in the organic EL display device, the inventors have compared the transparent conductive film with the metal film and the organic resin film being in contact with each other. It has been found that when the organic resin film is in contact with the organic resin film, the amount of moisture and gas released is significantly less, and the life of the organic EL layer is extended. Based on this knowledge, the following invention was made.

(Embodiment 1)
(Constitution)
With reference to FIG. 1 and FIG. 2, the organic EL display device in Embodiment 1 based on this invention is demonstrated.

  The organic EL display device according to the present embodiment includes a substrate, a plurality of thin film transistors formed on a main surface of the substrate, a planarization film made of an organic resin, covering the upper side of the plurality of thin film transistors, and the planarization film A plurality of anode electrodes electrically connected to each of the plurality of thin film transistors, a separation membrane made of an organic resin, which is formed to individually isolate and isolate the plurality of anode electrodes, An organic EL layer disposed above the anode electrode so as to be electrically connected to the anode electrode; and a cathode electrode disposed above the organic EL layer so as to be electrically connected to the organic EL layer. The anode electrode includes three layers of a lower transparent conductive film, a reflective metal film, and an upper transparent conductive film in order from the side close to the substrate, and the reflective metal film has an upper surface, a lower surface, and a lower transparent film. All the fine side is coated with a transparent conductive film.

  A plan view of this organic EL display device is shown in FIG. 1, and a sectional view thereof is shown in FIG. This organic EL display device is an active matrix organic EL display device using TFTs as switching elements. FIG. 1 shows a region corresponding to three pixels. FIG. 2 representatively shows one pixel taken out and cut. This organic EL display device includes a glass substrate 1 as a substrate, and a silicon nitride film 2 and a silicon oxide film 3 are provided in order from below so as to cover the surface of the glass substrate 1. Alternatively, the glass substrate 1 combined with the silicon nitride film 2 and the silicon oxide film 3 may be regarded as a “substrate”.

  A plurality of TFTs are provided on the main surface of the glass substrate 1. In FIG. 2, only one of the plurality of TFTs is representatively displayed. The TFT includes a polysilicon film 7, a gate insulating film 5, a gate electrode 6, a source electrode 11 and a drain electrode 12. The polysilicon film 7 has a channel region 7a in the center, and has a source region 7b and a drain region 7c at both ends. The gate insulating film 5 is provided so as to cover the upper side of the polysilicon film 7. A gate electrode 6 is disposed on the gate insulating film 5. A first interlayer insulating film 8 is provided so as to cover the upper side of the gate electrode 6. A source electrode 11 and a drain electrode 12 are disposed above the first interlayer insulating film 8. The source electrode 11 and the drain electrode 12 penetrate the first interlayer insulating film 8 and are electrically connected to the source region 7b and the drain region 7c, respectively. A second interlayer insulating film 13 is provided so as to cover the upper side of the source electrode 11 and the drain electrode 12.

  On the upper side of the second interlayer insulating film 13, a planarizing film 15 made of an organic resin is provided so as to cover the upper side of the above-described plurality of TFTs. A plurality of anode electrodes 16 are provided above the planarizing film 15 and are electrically connected to each of the TFTs through the connection holes 14. In FIG. 2, only one of the plurality of anode electrodes 16 is representatively displayed. The separation membrane 17 is made of an organic resin, and is formed so as to insulate and isolate the plurality of anode electrodes 16 individually. The organic EL layer 18 is disposed above the anode electrode 16 so as to be electrically connected to the anode electrode 16. The organic EL layer 18 has a three-layered structure of a hole transport layer 18a, a light emitting layer 18b, and an electron transport layer 18c in order from the bottom. The cathode electrode 19 is disposed on the upper side of the organic EL layer 18 so as to be electrically connected to the organic EL layer 18. The anode electrode 16 includes three layers of a lower transparent conductive film 16a, a reflective metal film 16b, and an upper transparent conductive film 16c in order from the side close to the glass substrate 1. The reflective metal film 16b is covered with a transparent conductive film on the upper surface, the lower surface, and the side surfaces.

(Action / Effect)
In the organic EL display device according to the present embodiment, the upper surface, the lower surface, and the side surface of the reflective metal film 16b are all covered with the transparent conductive film, and as a result, there is no place where the metal film and the film made of organic resin are in direct contact. It has a configuration. Therefore, it is possible to reduce the generation of moisture and gas inside the organic EL display device due to a high temperature use environment such as heat generation under long-term driving or under hot weather. Thereby, the organic EL display device according to the present embodiment can be a highly reliable and long-life organic EL display device.

  Further, since the upper transparent conductive film 16c and the lower transparent conductive film 16a are directly electrically connected without passing through the reflective metal film 16b, a material such as Al having a high contact resistance with respect to the transparent conductive film is used as the reflective metal film 16b. Even when used, the resistance of the anode electrode 16 can be reduced, and an organic EL display device with high luminous efficiency can be obtained. As described above, in the present embodiment, it is possible to use a material such as Al for the reflective metal film 16b without any problem. Therefore, the reflective metal film 16b is preferably made of aluminum or an alloy containing aluminum as a main component. This is because the light reflectance of the reflective metal film 16b can be increased.

  Alternatively, the reflective metal film 16b is preferably made of silver or an alloy containing silver as a main component. This is because the electric resistance of the reflective metal film 16b can be lowered by such a configuration.

  The lower transparent conductive film 16a and the upper transparent conductive film 16c are preferably made of any material selected from the group consisting of IZO (Indium Zinc Oxide), ITO (Indium Tin Oxide), and ZnO. This is because a transparent conductive film can be easily formed.

  Moreover, since the upper transparent conductive film 16c and the lower transparent conductive film 16a are directly electrically connected without passing through the reflective metal film 16b, the reflective metal film 16b may not contribute to the electrical connection. Therefore, it is possible to reduce the ratio of the additive and mixture conventionally added to the reflective metal film 16b for electrical connection. As a result, the reflectivity of the reflective metal film 16b is improved and the light extraction efficiency is improved. improves.

  In the present embodiment, the lower transparent conductive film 16a is preferably thicker than the upper transparent conductive film 16c. This can be said from the viewpoint of optical design. Thus, if the film thickness of the upper transparent conductive film 16b is optimized to be thin, the light extraction efficiency is improved. Since conduction is sufficiently achieved by the lower transparent conductive film, an organic EL display device free from defective light emission due to increased resistance or disconnection of the anode electrode 16 can be obtained.

  In addition, as shown in FIG. 3, it is preferable that the outer peripheral side surface of the reflective metal film 16b is tapered. This is because if the outer peripheral side surface of the reflective metal film 16b is tapered, the coverage of the upper transparent conductive film 16c is improved. Therefore, when an Al-based metal or the like that increases the contact resistance between the reflective metal film 16b and the transparent conductive film is used as the material of the reflective metal film 16b, the reflective metal film 16b has a film thickness of the upper transparent conductive film 16c. Even when the thickness is significantly thicker than the above, the resistance of the anode electrode 16 can be reduced, and an organic EL display device with high luminous efficiency can be obtained.

(Embodiment 2)
(Production method)
A method for manufacturing an organic EL display device according to the second embodiment of the present invention will be described with reference to FIGS.

  The manufacturing method of the organic EL display device in the present embodiment includes a step of forming a plurality of thin film transistors on the main surface of the substrate, a step of forming a planarizing film with an organic resin so as to cover the upper side of the plurality of thin film transistors, A plurality of anode electrodes each including three layers of a lower transparent conductive film, a reflective metal film, and an upper transparent conductive film are provided on each of the plurality of thin film transistors, in order from the side closer to the substrate, on the flattening film. Forming a separation membrane with an organic resin so as to expose a part of the plurality of anode electrodes through the opening while individually isolating and isolating the plurality of anode electrodes; Forming an organic EL layer on the upper side of the anode electrode so as to be electrically connected to the anode electrode in the opening; and The upper side of the organic EL layer to connect and forming a cathode electrode. In the step of forming the plurality of anode electrodes, the reflective metal film is formed so that the upper surface, the lower surface, and the side surface are all covered with the transparent conductive film.

  Hereinafter, a method for manufacturing an organic EL display device according to the present embodiment will be described for each process with reference to the drawings. As shown in FIG. 4, first, a plurality of thin film transistors (TFTs) are formed on the main surface of the substrate. Here, the “substrate” refers to a glass substrate 1 and a silicon nitride film 2 and a silicon oxide film 3 combined. Since FIG. 4 is a cross-sectional view of a region corresponding to one pixel, only one TFT is displayed, but a large number of TFTs are actually formed over the entire display region. The formation of the TFT can be performed using a known technique.

  Next, as shown in FIG. 5, a second interlayer insulating film 13 is formed. The second interlayer insulating film 13 is a silicon nitride film and can be formed by a CVD method. A lower portion of the connection hole 14 is formed so as to penetrate the second interlayer insulating film 13 using a photoengraving technique and an etching technique. Further, as shown in FIG. 5, a planarizing film 15 is formed with an organic resin so as to cover the upper side of the plurality of TFTs. The planarizing film 15 can be formed of a photosensitive acrylic resin. The upper portion of the connection hole 14 is formed so as to penetrate the planarizing film 15 by photolithography. Then, baking is performed at 230 ° C.

  Further, as shown in FIG. 6, a plurality of anodes each including three layers of a lower transparent conductive film 16a, a reflective metal film 16b, and an upper transparent conductive film 16c in order from the side close to the substrate above the planarizing film 15. The electrode 16 is formed so as to be electrically connected to each of the plurality of TFTs. The lower transparent conductive film 16a is continuously formed by sputtering so that the thickness is 200 nm by IZO and the reflective metal film 16b is 50 nm by Al alloy. An island-like resist film is formed on the reflective metal film 16b initially formed in a wide range by this sputtering method so as to cover only a small area as compared with the lower transparent conductive film 16a by using a photoengraving technique. . Using this resist film as a mask, the reflective metal film 16b is etched using an etching technique so as to remain only in a desired region as shown in FIG. In this etching, the edge of the reflective metal film 16b, that is, the outer peripheral side surface can be tapered by appropriately selecting an etching solution. For example, when the reflective metal film 16b is made of aluminum, the outer peripheral side surface can be tapered by using an etching solution with a high acetic acid ratio. Thereafter, the resist film is removed. After that, UV treatment and cleaning treatment with ozone water are performed. The upper transparent conductive film 16c is formed by sputtering so as to have a thickness of 20 nm with IZO. By forming the upper transparent conductive film 16c, the entire reflective metal film 16b is covered with the upper transparent conductive film 16c. Thereafter, a resist pattern for the anode electrode 16 is formed over a wider area than the reflective metal film 16b by using a photoengraving technique. The upper transparent conductive film 16c and the lower transparent conductive film 16a are simultaneously etched by the etching technique to remove the resist pattern. In this way, the anode electrode 16 is obtained in which the reflective metal film 16b is completely encased by the transparent conductive film made of IZO and has a desired shape as a whole. The anode electrode 16 is electrically connected to the TFT through the connection hole 14.

  Further, as shown in FIG. 7, a separation membrane 17 is formed of an organic resin so that a part of the plurality of anode electrodes 16 is exposed through the opening while the plurality of anode electrodes 16 are individually insulated and isolated. . The separation membrane 17 can be formed of a photosensitive polyimide resin. It is formed using photolithography and baked at 230 ° C. In the separation film 17, the metal mask used when the organic EL layer 18 is formed by a vacuum deposition method in the subsequent process and the surface of the anode electrode 16 where the organic EL layer 18 is to be formed are not in contact with each other. Also plays the role of rib material to make it. In order to increase the cleanliness of the surface of the anode electrode 16, a cleaning process using UV processing, chelation, ozone water, or the like is performed.

  Next, as shown in FIG. 8, an organic EL layer 18 is formed on the anode electrode 16 so as to be electrically connected to the anode electrode 16 in the opening. The organic EL layer 18 is formed in a state where the vacuum atmosphere is maintained after the vacuum heat dehydration treatment. The organic EL layer 18 is a layer of an organic material including a hole transport layer 18a, a light emitting layer 18b, and an electron transport layer 18c, and has a property of emitting light when a voltage is applied.

  Further, a cathode electrode 19 is formed on the upper side of the organic EL layer 18 so as to be electrically connected to the organic EL layer 18. The cathode electrode 19 is formed while maintaining a vacuum atmosphere. In this way, an organic EL display device having the structure shown in FIG. 2 can be obtained. Furthermore, in order to protect the upper surface of the organic EL display device, it is preferable to cover the upper side with a cover glass or to form a protective layer.

(Action / Effect)
According to the method for manufacturing an organic EL display device in the present embodiment, the organic EL display device described in the first embodiment can be obtained. That is, the organic EL display device can be manufactured so that the upper surface, the lower surface, and the side surface of the reflective metal film 16b are all covered with the transparent conductive film, and there is no place where the metal film and the film made of the organic resin are in direct contact. . Therefore, it is possible to manufacture an organic EL display device in which generation of moisture and gas inside due to high-temperature usage environments such as heat generation under long-term driving and under hot weather is reduced.

  In order to obtain the organic EL display device having the structure shown in FIG. 3 in the first embodiment, in the step of forming the anode electrode 16 as shown in FIG. 6, as shown in FIG. What is necessary is just to form so that the outer peripheral side surface may become tapered. If the reflective metal film 16b is formed in this way, the upper transparent conductive film 16c is also tapered. If such steps are included, the organic EL display device having the structure shown in FIG. 3 in the first embodiment can be obtained.

  In the first and second embodiments, the example in which the top gate type single gate TFT is employed as the switch element of the active matrix organic EL display device has been described. However, the switch element may be any element having a switch function. For example, a bottom gate TFT, a thin film diode, or an organic transistor may be used. The organic EL display device to which the present invention is applied is not limited to the active matrix type, and may be a passive matrix type organic EL display device having no switching elements.

  The organic EL display device exemplified in the first and second embodiments is a top emission type, but may be a bottom emission type.

  In the first and second embodiments, IZO is used for the transparent conductive film. However, a transparent conductive film such as ITO or ZnO may be used. If electrical connection is possible, the upper transparent conductive film 16c and the lower transparent conductive film are used. The material may be different from 16a. Further, since the film thickness of the upper transparent conductive film 16c should be determined from the configuration of the organic EL layer, the refractive index of the transparent conductive film itself, and the absorption coefficient, it may be different from those shown in the first and second embodiments. Good. Furthermore, since the lower transparent conductive film 16a should be determined in consideration of the covering property and the electric resistance, it may be different from those shown in the first and second embodiments.

  In the first and second embodiments, the organic EL layer 18 is described as a three-layered structure including the hole transport layer 18a, the light emitting layer 18b, and the electron transport layer 18c. However, the organic EL layer 18 is a single layer of the light emitting layer 18b. It may be a multilayer film including the light emitting layer 18b.

  In the first and second embodiments, an example in which an acrylic resin is used for the planarization film 15 and a polyimide resin is used for the separation film 17 is described. However, the planarization film 15 and the separation film 17 are made of the same material. For example, any one of acrylic resin, polyimide resin, epoxy resin, and the like may be used.

  The organic EL element can be sealed by a combination (not shown) of an inert gas and a sealing material, but may be a laminated structure such as a silicon nitride film or an organic resin.

  The present invention relates to an organic EL display device, but is also applicable to a display device and a semiconductor device having a structure in which a metal film and an organic resin are in contact with each other. Other types of display devices can be applied to, for example, transflective and reflective liquid crystal display devices. In the case of a liquid crystal display device, application of the present invention reduces moisture mixing into the liquid crystal, so that variation in the storage capacity of the liquid crystal can be suppressed, and a liquid crystal display device with extremely low image sticking can be obtained.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

It is a top view of the organic electroluminescence display in Embodiment 1 based on this invention. It is arrow sectional drawing regarding the II-II line | wire in FIG. It is sectional drawing of the preferable example of the organic electroluminescent display apparatus in Embodiment 1 based on this invention. It is explanatory drawing of the 1st process of the manufacturing method of the organic electroluminescence display in Embodiment 2 based on this invention. It is explanatory drawing of the 2nd process of the manufacturing method of the organic electroluminescence display in Embodiment 2 based on this invention. It is explanatory drawing of the 3rd process of the manufacturing method of the organic electroluminescence display in Embodiment 2 based on this invention. It is explanatory drawing of the 4th process of the manufacturing method of the organic electroluminescence display in Embodiment 2 based on this invention. It is explanatory drawing of the 5th process of the manufacturing method of the organic electroluminescence display in Embodiment 2 based on this invention. It is explanatory drawing of the modification of 1 process included in the manufacturing method of the organic electroluminescence display in Embodiment 2 based on this invention.

Explanation of symbols

  1 glass substrate, 2 silicon nitride film, 3 silicon oxide film, 5 gate insulating film, 6 gate electrode, 7 polysilicon film, 7a channel region, 7b source region, 7c drain region, 8 first interlayer insulating film, 11 source electrode , 12 Drain electrode, 13 Second interlayer insulating film, 14 Connection hole, 15 Planarization film, 16 Anode electrode, 16a Lower transparent conductive film, 16b Reflective metal film, 16c Upper transparent conductive film, 17 Separation film, 18 Organic EL layer , 18a hole transport layer, 18b light emitting layer, 18c electron transport layer, 19 cathode electrode.

Claims (6)

A substrate,
A plurality of thin film transistors formed on the main surface of the substrate;
Covering the upper side of the plurality of thin film transistors, and a planarizing film made of an organic resin;
A plurality of anode electrodes disposed on the planarization film and electrically connected to each of the plurality of thin film transistors;
A plurality of anode electrodes, each of which is formed so as to be insulated and isolated, and a separation membrane made of an organic resin;
An organic EL layer disposed on the anode electrode so as to be electrically connected to the anode electrode;
A cathode electrode disposed on the organic EL layer so as to be electrically connected to the organic EL layer;
The anode electrode includes three layers of a lower transparent conductive film, a reflective metal film, and an upper transparent conductive film in order from the side close to the substrate,
The reflective metal film top surface, all of the lower surface and side surfaces are coated with a transparent conductive film, the previous SL lower transparent conductive film and the upper transparent conductive film in contact with each other at the site extending outward from the reflective metal layer An organic EL display device in which the separation film and the reflective metal film are not in contact with each other .   The organic EL display device according to claim 1, wherein the lower transparent conductive film is thicker than the upper transparent conductive film.   The organic EL display device according to claim 1, wherein the reflective metal film is made of aluminum or an alloy containing aluminum as a main component.   The organic EL display device according to claim 1, wherein the reflective metal film is made of silver or an alloy containing silver as a main component.   5. The organic EL display device according to claim 1, wherein the lower transparent conductive film and the upper transparent conductive film are made of any material selected from the group consisting of IZO, ITO, and ZnO. Forming a plurality of thin film transistors on the main surface of the substrate;
Forming a planarization film with an organic resin so as to cover the upper side of the plurality of thin film transistors;
A plurality of anode electrodes each including three layers of a lower transparent conductive film, a reflective metal film, and an upper transparent conductive film are provided on each of the plurality of thin film transistors, in order from the side closer to the substrate, on the flattening film. Forming to be electrically connected;
Forming a separation membrane with an organic resin so as to expose a part of the plurality of anode electrodes through the opening while individually isolating and isolating the plurality of anode electrodes;
Forming an organic EL layer above the anode electrode so as to be electrically connected to the anode electrode in the opening;
Forming a cathode electrode on the upper side of the organic EL layer so as to be electrically connected to the organic EL layer,
In the step of forming the plurality of anode electrodes, the reflective metal film is formed such that the upper surface, the lower surface, and the side surface are all covered with a transparent conductive film, and the lower transparent conductive film and the upper transparent conductive film are A method for manufacturing an organic EL display device , wherein the separation film and the reflective metal film are not in contact with each other, and are formed so as to be stacked in contact with each other at a portion extending outward from the reflective metal film .

Images