JP5260452B2 - Al alloy reflective film with excellent hot water resistance and sputtering target - Google Patents

Description

  The present invention relates to an Al alloy reflective film; and an automotive lamp, a lighting tool, a decorative part using the Al alloy reflective film; and an Al alloy sputtering target.

  Since pure Al has a high reflectance (about 88%), it is used as a reflective film for automobile lamps, lighting fixtures, decorative parts, and the like. However, since pure Al is an amphoteric metal, it is vulnerable to acids and alkalis. Therefore, when a reflective film made of pure Al (pure Al reflective film) is used for an automotive lamp or the like, the reflective film may deteriorate in a short period of time and a high reflectance may not be maintained over a long period of time.

  As a method for maintaining the high reflectance of the pure Al reflective film for a long period of time, there is a method of forming a protective film resistant to acid or alkali on the surface of the pure Al reflective film. However, the above method has a problem that the productivity of the product is lowered.

  In addition, a method for alloying Al with other elements is also disclosed. For example, Patent Document 1 discloses an Al alloy reflective film to which transition elements of Group IIIa, Group IVa, Group Va, Group VIa, Group VIIa, and Group VIIIa of the periodic table are added. Patent Document 2 discloses an Al alloy reflective film in which Mg is added to Al. Further, Patent Document 3 discloses an Al alloy reflective film in which Mg and rare earth elements are added to Al.

JP-A-7-301705 JP 2007-72427 A JP 2007-70721 A

  Incidentally, automotive lamps such as headlamps and rear lamps have a problem that condensation and water droplets are easily generated inside. The reason for this is that when outside air containing moisture enters the interior of an automotive lamp, it is heated by the heat generated by the light source when it is lit, while it is cooled by outside air or rain when it is not lit. This is because cooling is repeated. The occurrence of dew condensation causes the reflection film provided in the automobile lamp to be transparent and the reflectance to decrease. For this reason, there is a strong demand for a reflective film that is excellent not only in high reflectivity but also in hot water resistance.

  The problem of dew condensation similar to the above occurs not only in automobile lamps but also in reflective films provided in lighting fixtures and decorative parts such as downlights, fluorescent lamps, and organic EL lighting fixtures using organic EL.

  The present invention has been made in view of the circumstances as described above, and its object is to have high reflectivity and an environment in which it is repeatedly heated and cooled, such as an automotive lamp, without a protective film. It is to provide an Al alloy reflective film excellent in warm water resistance, which is difficult to reduce the reflectance even when dew condensation occurs when exposed to water, and an Al alloy sputtering target useful for forming such an Al alloy reflective film. .

  The Al alloy reflective film of the present invention that has solved the above problems is a group consisting of Gd, La, Y, Sc, Tb, Lu, Pr, Nd, Pm, Ce, Dy, Ho, Er, and Tm (hereinafter, At least one element selected from group A) may be 2.5 to 6 atomic%; Cr, Cu, Ag, Ni, Co, Mn, Si, Mo, V, Fe, and Be It contains at least one element selected from the group consisting of the following groups (hereinafter sometimes referred to as group B) with 15 atomic% or less (not including 0%), with the balance being Al and inevitable impurities. And

  In the above Al alloy reflective film, those containing 3.0 atomic% or less of Cr and those containing 10.0 atomic% or less of Cu and / or Ag are preferred embodiments of the present invention.

  The present invention also includes an automotive lamp, a lighting fixture, and a decorative part provided with the Al alloy reflective film.

  In addition, the sputtering target of the present invention that can solve the above problems is a group (group A) consisting of Gd, La, Y, Sc, Tb, Lu, Pr, Nd, Pm, Ce, Dy, Ho, Er, and Tm. And at least one element selected from the group consisting of Cr, Cu, Ag, Ni, Co, Mn, Si, Mo, V, Fe, and Be (group B) It contains at least one element selected from 20 atomic% or less (excluding 0%), and the balance is Al and inevitable impurities.

  Since the Al alloy reflective film of the present invention is composed of a predetermined element group, it has a high reflectance and is excellent in hot water resistance. Therefore, the Al alloy reflective film of the present invention is suitably used for products that are used in an environment where condensation easily occurs due to repeated heating and cooling, such as automotive lamps, lighting fixtures, and decorative parts.

  In order to provide an Al alloy reflective film excellent in resistance to dew condensation environment (warm water resistance) required for automobile lamps and the like as well as having high reflectance, the present inventors have made extensive studies. I have done it. As a result, it has been found that the intended purpose can be achieved by using an Al- (group A)-(group B) alloy reflective film to which a rare earth element belonging to group A and an element belonging to group B are added. Was completed.

  Before describing the constituent features of the present invention in detail, first, the background to the present invention will be described.

  The present inventors can maintain a high reflectance over a long period of time without a reflective film, and as a reflective film excellent in alkali resistance, acid resistance, heat resistance, etc., Al- (containing a rare earth element of group A) Group A) An alloy film has already been filed (Japanese Patent Application No. 2009-048222). Here, the alkali resistance means that it does not corrode even in an alkaline environment and the reflectance does not decrease; the acid resistance means that it does not corrode even in an acidic environment and the reflectance does not decrease. Further, the moisture resistance means resistance under a high-temperature and high-humidity environment, and means that it does not corrode under the environment and the reflectance does not decrease.

  However, in the subsequent research, the above Al alloy reflective film is inferior in warm water resistance, and in the warm water resistance test (warm water immersion test) simulating the dew condensation environment, the transparency of the film and the significant decrease in reflectivity were observed. It has been found that innumerable pinholes may be formed in the initial stage of immersion. The reason for this is unknown in detail, but Al dissolves preferentially from the weak or thin part of the Al natural oxide film (functioning as a protective film) and elutes, which is oxidized and hydroxylated. It is presumed that the formation of a film through which oxygen enters and the oxidation of the Al film proceeds is the main cause of film transparency.

  Accordingly, the present inventors have made extensive studies in order to provide a novel Al alloy reflective film that maintains both high reflectance and good alkali resistance while also having hot water resistance. As a result, it was found that the addition of an element belonging to Group B to the Al alloy reflective film improves the hot water resistance of the Al alloy reflective film, thereby completing the present invention.

  That is, the Al alloy reflective film of the present invention is selected from the group consisting of Gd, La, Y, Sc, Tb, Lu, Pr, Nd, Pm, Ce, Dy, Ho, Er, and Tm (group A). At least one selected from the group consisting of 2.5 to 6 atomic%; Cr, Cu, Ag, Ni, Co, Mn, Si, Mo, V, Fe, and Be (group B); It is characterized by containing 15 atomic% or less (not including 0%) of seed elements, with the balance being Al and inevitable impurities.

  Hereinafter, the Al alloy reflective film of the present invention (hereinafter sometimes simply referred to as an Al alloy film) will be described in detail.

(Group A elements)
The Al alloy film of the present invention contains a group A element. The element of group A is a group obtained by removing Sm, Eu, and Yb from a rare earth element group [usually, an element group obtained by adding a lanthanoid element, Sc, and Y]. According to the experimental results of the present inventors, the group A element in the rare earth element group improves the alkali resistance, acid resistance, moisture resistance and the like, and the group B element (details will be described later). This is because it has been confirmed that even when used in combination, these effects are not deteriorated. The group A elements may be used alone or in combination of two or more.

  The reason why the above characteristics are improved by the addition of Group A element is not clear in detail, but is presumed as follows. For example, in an acidic environment, it is considered that the immersion potential of the Al alloy film is lower than the immersion potential of pure Al, and the dissolution rate of Al is reduced. Similarly, in an alkaline environment, it is considered that group A elements were precipitated and concentrated as hydroxides on the surface of the Al alloy film, which became a protective film, and the dissolution rate of Al was reduced.

  In contrast, Eu, Sm, and Yb rare earth elements not included in group A do not improve alkali resistance. These elements are considered to be inferior in the effect of reducing the dissolution rate of Al as compared with the elements of Group A because these elements are ionized and dissolved in the solution in an alkaline environment and do not precipitate on the surface of the Al alloy film.

  The above action is observed in all of the rare earth elements belonging to Group A, and the difference in the action depending on the type of element (the superiority or inferiority of the effect) is hardly seen. However, some of the above elements are liable to be colored or discolored and impair the appearance of the reflective film. Therefore, it is preferable to avoid the use depending on the purpose of use of the Al alloy film. Specifically, among the elements of group A, Gd, La, Y, Sc, Tb, and Lu (hereinafter sometimes referred to as Gd to Lu) are difficult to be colored even when precipitated on the surface of the Al alloy film. Although the color change is small after immersion in alkali, elements other than Gd to Lu, such as rare earth element hydroxides such as Ce, have a color such as yellow or brown, and discoloration when concentrated on the surface of the Al alloy film. There is a case.

  Considering the acid resistance and alkali resistance of the Al alloy film, the manufacturing cost of the sputtering target used for film formation, etc., the group A element added to Al is preferably Gd, La, Y, Tb, Lu, and Gd, La, Y is more preferred.

  In order to effectively exert the above-described action by addition of an element of group A, the content of the above-described element (single amount when used alone is a total amount when both are included) is 2.5 atomic% or more 6 Atomic% or less. A preferable content is 2.8 atomic% or more and 5.5 atomic% or less, and more preferably 3.0 atomic% or more and 5.0 atomic% or less.

  By setting the group A element content to 2.5 atomic% or more, the alkali resistance of the Al alloy film is sufficiently improved. Further, by setting the content of the element of group A to 6 atomic% or less, it is possible to prevent a decrease in reflectance (less than 70%) immediately after the formation of the Al alloy film.

(Group B elements)
The Al alloy film of the present invention further contains a group B element in addition to the group A element. That is, the present invention has the greatest feature in using an Al- (group A)-(group B) alloy film, and thereby the hot water resistance of the Al alloy film is enhanced. An Al alloy film containing both group A and group B elements is not disclosed in the above-mentioned patent document.

  Group B elements may be used alone or in combination of two or more.

  Although the detailed reason why the hot water resistance of the Al alloy film is improved by using the elements of Group A and Group B in combination is unknown, the element of Group B is dissolved in Al when the Al alloy film is immersed in warm water. As a result, it is presumed that the Al alloy film becomes difficult to oxidize.

  The effect of improving resistance to warm water by the elements of group B is effectively exhibited in a small amount. Specifically, the content of the element of group B in the Al alloy film (single amount in the case of a single substance, and the total amount in the case of including both) is generally 0.1 atomic% or more (more preferably Is preferably 0.3 atomic% or more, more preferably 0.5 atomic% or more.

  From the viewpoint of improving hot water resistance, the higher the content of Group B elements, the better. However, if the content is excessive, the reflectance immediately after film formation decreases (less than 70%), so the upper limit is 15 atoms. % Or less. The preferable content is 12 atomic% or less, more preferably 10 atomic% or less, still more preferably 7.0 atomic% or less, and still more preferably 5.0 atomic% or less.

  Strictly speaking, the upper limit of the preferable content of group B varies depending on the type of element of group B. For example, when Cr is used as an element of group B, the Cr content should be controlled to 3.0 atomic% or less (more preferably 2.0 atomic% or less, more preferably 1.5 atomic% or less). Is preferred. If the Cr content exceeds 3.0 atomic%, the reflectivity immediately after the formation of the Al alloy film may be remarkably reduced. In consideration of the balance between the reflectivity immediately after the film formation and the hot water resistance, Atomic% or less is preferable.

  Further, when Ag and / or Cu is used as an element of group B, the content of these elements (single amount when used alone or total amount when both are included) is 10.0 atomic%. It is preferable to control to below (more preferably 7 atomic% or less, still more preferably 5 atomic% or less, and still more preferably 3 atomic% or less). Ag and Cu generally tend to have a lower reflectivity lowering effect immediately after film formation than Cr, but when their content exceeds 10.0 atomic%, reflection immediately after film formation of an Al alloy film. The rate may decrease significantly. Strictly speaking, as shown in the examples described later, when Ag is contained alone, the upper limit is allowable up to 11.0%.

  The Al alloy reflective film of the present invention contains both the group A and the group B, and is the balance Al and inevitable impurities.

(Use of Al alloy reflective film)
The Al alloy reflective film of the present invention has high reflectivity immediately after film formation and is extremely excellent in hot water resistance, etc., as will be demonstrated in the examples described later. It is suitably used for lamps, lighting fixtures, or decorative parts. Further, it has been confirmed that the Al alloy reflective film of the present invention exhibits good alkali resistance, acid resistance and the like even without a protective film. As a result, the automotive lamp using the Al alloy reflective film of the present invention can not only withstand long-time use (excellent in durability) but also can reduce production costs.

(Al alloy sputtering target)
The Al alloy film of the present invention is desirably formed by a sputtering method using a sputtering target. This is because a thin film having excellent in-plane uniformity of components and film thickness can be easily formed as compared with a thin film formed by ion plating, electron beam vapor deposition or vacuum vapor deposition. In particular, it is preferably formed by a DC sputtering method using a direct current (DC) power source cathode.

  In order to form the Al alloy film by a sputtering method, 2.5 to 8 atomic% of at least one element of the group A described above and 20 elements of at least one element of the group B described above are used as the sputtering target. A sputtering target containing at most atomic% (not including 0%) and the balance being Al and inevitable impurities is used. Unlike the Al alloy reflective film described above, the upper limit of the content of each element in the sputtering target is slightly increased. This is because when the Al alloy sputtering target having the same composition as that of the Al alloy film described above is used, the yield decreases, and therefore it is preferable to set a large amount in anticipation of the yield decrease. The detailed reason for the decrease in yield is unknown, but the elements of Group A and Group B once incorporated into the Al alloy by sputtering are regenerated by newly sputtered particles in the subsequent sputtering process. This is probably because the composition (content) of the Al alloy film is changed by sputtering. The yield is calculated from the following formula.

（上記式中、Ａ／Ｂとは、Ａおよび／またはＢを意味する。）

(In the above formula, A / B means A and / or B.)

  The shape of the sputtering target is not particularly limited, and may be processed into an arbitrary shape (such as a square plate shape, a circular plate shape, or a donut plate shape) according to the shape or structure of the sputtering apparatus.

  Moreover, the manufacturing method of the said sputtering target is also not specifically limited, Although various methods, such as a melt casting method, a powder sintering method, and a spray forming method, can be applied, It is preferable to apply the spray forming method. The Al alloy sputtering target manufactured by the spray forming method is excellent in the uniformity of the component structure, and as a result, an Al alloy reflective film having a uniform component structure can be formed.

(Substrate)
In applying the Al alloy reflective film of the present invention to a reflector such as an automotive lamp, the Al alloy reflective film may be formed on a substrate. The material of the base used is not particularly limited as long as it is normally used in the field of automotive lamps and lighting fixtures provided with an Al alloy reflective film, and examples thereof include resin and glass. Examples of the resin include polycarbonate resins, acrylic resins, polyester resins such as PET (polyethylene terephthalate) and PBT (polybutylene terephthalate), ABS resins, epoxy resins, acetal resins, and alicyclic hydrocarbon resins. It may be a mixture of resins.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

(Manufacture of test bodies 1 to 33)
Using a DC magnetron sputtering apparatus, an Al alloy film having the composition shown in Table 1 was formed on a 20 mm × 50 mm glass substrate (Corning # 1737). Details of the film forming method are as follows.

As a sputtering target for forming an Al alloy film, a composite sputtering target in which a chip of a desired metal element (a metal element to be added) is attached to a pure Al sputtering target having a diameter of 100 mm is attached to an electrode in a chamber of a sputtering apparatus. The chamber was evacuated so that the pressure in the chamber was 1.3 × 10 ⁻³ Pa or less. When forming a pure Al film, a pure Al sputtering target was used as a sputtering target.

Next, Ar gas was introduced into the chamber, and the pressure in the chamber was adjusted to 2.6 × 10 ⁻¹ Pa. Thereafter, sputtering was performed by applying an output of 260 W to a sputtering target with a direct current (DC) power source, and an Al alloy film having a desired composition was formed on one surface of the substrate, to obtain test bodies 1 to 33.

  At this time, the composition of the Al alloy film was adjusted by changing the metal element species and the number of chips attached to the pure Al sputtering target, and the film formation time was adjusted to 150 nm.

  The specimens 1 to 33 were subjected to composition analysis, measurement of reflectance immediately after film formation, and hot water resistance test by the following methods.

<Composition analysis>
The composition of the Al alloy film of the test body was measured by ICP (Inductively Coupled Plasma) emission spectrometry. That is, the Al alloy film is dissolved with an acid, and the amounts of Al and additive elements in the resulting solution are measured by ICP emission analysis, normalized to 100%, and the composition of the Al alloy film did.

<Measurement of reflectivity immediately after film formation>
The reflectance with a wavelength in the range of 250 nm to 800 nm was measured for the test specimen formed on the glass substrate, and the visible light reflectance was calculated in accordance with JIS R 3106.

<Warm water resistance test>
A specimen (20 mm × 50 mm) formed on a glass substrate was immersed in 30 ° C. ion exchange water for 30 hours. A sample photograph obtained by photographing the test specimen after immersion with a digital camera was binarized with the image processing software so that the transparent portion became black, and then the area of the black portion (transparent portion) was obtained with the image analysis software. Thereafter, the film remaining rate was calculated according to the following formula (1).
Membrane remaining rate (%)
= 100 × (20 × 50−transparent area (mm ² )) / (20 × 50)
... Formula (1)

Moreover, the reflectance after immersion in each test body was measured in the same way as the above-mentioned reflectance measurement, and the reflectance fall rate was computed according to following formula (2).
Reflectivity decrease rate (%)
= 100 × (Reflectance immediately after film formation−Reflectance after hot water resistance test) / Reflectance immediately after film formation (2)

<Alkali resistance test>
Mask the specified area of the test specimen deposited on the glass substrate and combine the masked part (masking part) and the non-masked part (exposed part) in a 1% by weight aqueous KOH solution for 5 minutes. After stacking, washing with water and drying, the masking was removed. When the Al alloy film was dissolved and the glass substrate was seen through in less than 5 minutes, the immersion was terminated at that time.

  After the masking removal, the level difference between the masking portion and the exposed portion was measured using a surface roughness measuring device (Dektak 6M), and this was taken as the dissolution amount (nm). Thereafter, the dissolution rate (nm / sec) was calculated from the immersion time (sec) and the dissolution amount (nm). That is, the dissolution rate was determined using the formula: dissolution amount / immersion time = dissolution rate.

  Table 2 shows the reflectivity immediately after film formation, the results of warm water resistance test (film remaining rate and reflectivity reduction rate), and the alkali resistance test result of each test specimen.

<Pass / fail judgment>
With respect to the reflectance immediately after film formation, the reflectance of 80% or more was evaluated as ◎, the reflectance of 55% or more and less than 80% was evaluated as ◯, and the reflectance of less than 55% was evaluated as ×.

  For the hot water resistance test, the film remaining rate after the hot water resistance test was 90% or more, ◎, 85% or more and less than 90%, and ○ or less than 85%. Moreover, the thing with a reflectance fall rate after a warm-water resistance test of less than 30% was made into (circle), the thing of 30% or more and less than 40% was made into (triangle | delta), and 40% or more was made into x.

  For the alkali resistance test, based on the dissolution rate of the Al-4.1 atomic% Gd film (test body 30) as a reference (◎), the intermediate between the Al-4.1 atomic% Gd film (test body 30) and the pure Al film. In the case of, the case of less than or equal to that of a pure Al film is indicated as ×.

  And what evaluated all the evaluation results more than (circle) was set as the pass.

Specimens 1 to 17 and 21 to 28 are Al alloy films containing both group A elements of 2.5 to 6 atom% and group B elements of 15 atom% or less. It was found that the film was excellent in reflectivity, hot water resistance, and alkali resistance immediately after film formation. Specifically, the reflectance immediately after film formation exceeds 80%, the film remaining ratio after the hot water resistance test is 85% or more, and the reflectance reduction ratio is 30% or less, and the alkali resistance higher than that of the pure Al film is satisfied. did.
did.

  Test bodies 18 to 20 are examples in which the content of Cu or Ag exceeds 10.0 atomic% or the content of Cr exceeds 3.0 atomic%, although the Al alloy film has excellent hot water resistance, It turned out that the reflectance immediately after a film | membrane falls a little (evaluation is (circle)). Specifically, although the film residual ratio after the warm water resistance test was 85% or more and the reflectance reduction ratio was 30% or less, the reflectance immediately after the film formation was in the range of 75 to 80%.

  On the other hand, the following specimens that do not satisfy the requirements of the present invention have the following problems.

  Specimen 29 is an example in which the content of group B element exceeds 15 atomic%, and the hot water resistance is good, but the reflectivity immediately after film formation is significantly reduced (below 50%). It was.

  The test body 30 is an example that does not include an element of group B. Since it contains Group A elements, the reflectivity immediately after film formation is high, and the film remaining rate is ◎ in the hot water resistance test, but the reflectivity decrease rate after the hot water resistance test may exceed 30%. I understood.

  The test body 31 is a conventional example using a pure Al reflective film. Although the reflectivity immediately after film formation is very high, it was found that the elution of Al could not be sufficiently suppressed in the hot water resistance test, the film remaining rate was less than 85%, and the reflectivity reduction rate exceeded 30%. . Moreover, it turned out that alkali resistance is also bad.

  The test body 32 is an example containing Sn instead of the group B element. Compared with the inventive examples containing Group B elements, the reflectance immediately after film formation was slightly reduced (evaluation was ◯), and Al elution could not be sufficiently suppressed in the hot water resistance test, and the film remaining rate was 85. It was found that the reflectivity reduction rate exceeded 30%.

  Although the test body 33 contains the element of group B, it falls below 2.5 atomic% of the element of group A, and therefore satisfies the film residual rate of 85% or more and the reflectance reduction rate of 30% or less after the hot water resistance test. It was found that the alkali resistance deteriorates.

Claims (7)

2.5 to 6 atomic% of at least one element selected from the group consisting of Gd, La, Y, Sc, Tb, Lu, Pr, Nd, Pm, Ce, Dy, Ho, Er, and Tm;
15 at% or less (not including 0%) of at least one element selected from the group consisting of Cr, Cu, Ag, Ni, Co, Mn, Si, Mo, V, Fe, and Be;
An Al alloy reflective film for automotive lamps, lighting fixtures, or decorative parts having excellent hot water resistance , characterized in that the balance is Al and inevitable impurities.   The Al alloy reflective film according to claim 1, containing 3.0 atomic% or less of Cr.   The Al alloy reflective film according to claim 1, containing 10.0 atomic% or less of Cu and / or Ag. An automotive lamp having excellent hot water resistance, comprising the Al alloy reflective film according to claim 1. The lighting fixture excellent in warm water resistance provided with the Al alloy reflective film in any one of Claims 1-3. A decorative part excellent in hot water resistance, comprising the Al alloy reflective film according to claim 1. It is a sputtering target used for manufacture of Al alloy reflective film in any one of Claims 1-3,
2.5 to 8 atom% of at least one element selected from the group consisting of Gd, La, Y, Sc, Tb, Lu, Pr, Nd, Pm, Ce, Dy, Ho, Er, and Tm;
20 atomic% or less (excluding 0%) of at least one element selected from the group consisting of Cr, Cu, Ag, Ni, Co, Mn, Si, Mo, V, Fe, and Be;
A sputtering target characterized in that the balance is Al and inevitable impurities.