JPH02124981A - Pigment - Google Patents

Abstract

PURPOSE:To prepare a pigment with high coloring and hiding power and suitable for use in automobile exterior coating by covering a substrate material exhibiting metallic luster by surface metal layer with a layer of a transparent inorg. compd., thereby enabling the interference color to be utilized. CONSTITUTION:On the surfaces of a substrate material of granular shape, pref. of scaly shape like mica, a layer of a metal such as Ag, Au, Cu, Pd, Ni, etc., is formed by plating, vapor depositing, etc., and then on said metal layer a covering layer of a transparent inorg. compd. (TiO2 is most desirable) is formed, giving a pigment. The resulting pigment develops color by interference between the light reflected at the surface of said inorg. compd. layer and the light passed through said inorg. compd. layer and reflected at the surface of said metal layer.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a novel pigment that utilizes interference color.

The pigments of this invention are particularly useful in automotive exterior paints.

[Prior Art] Metallic finishes using so-called metallic paints containing metal powder such as aluminum foil are often used for finishing coating of automobiles, home appliances, and the like. However, aluminum foil has low brightness and is difficult to use as a light color. Therefore, in recent years, the use of burr mica, which has a mica surface coated with a titanium dioxide layer, has been increasing.

As shown in FIG. 8, this Burl mica pigment has a structure in which the surface of mica 100 is coated with a titanium dioxide layer 101. In this pearl mica, the incident light is reflected light A that is reflected on the surface of the titanium dioxide layer 101 and the reflected light A that is reflected on the surface of the titanium dioxide layer 101
It is divided into 1 and 1. The light incident on the titanium dioxide layer 101 is separated into reflected light B that is reflected at the interface with the mica 100 and transmitted light that passes through the mica 100.

The interference between the reflected light A and the reflected light B produces various colors. For example, when the titanium dioxide layer 101 with a thickness of 120 to 135 nm is formed, the interference color between reflected light A and reflected light B is blue.

However, a part of the transmitted light passes through the burr mica pigment and is reflected on the surface of the base 102, and then passes through the burr mica pigment again and exits as reflected light C from the titanium dioxide layer 101 on the incident side. Since this reflected light C is mixed with reflected light B to become white light, the interference between reflected light A and reflected light B becomes correspondingly weaker, resulting in a disadvantage that the interference color becomes weaker.

In addition, burr mica has weak coloring power and hiding power, and is poor in practical use. For example, in the case of top-coat metallic paint for automobiles, conventionally the paint is applied with two coats and one bake. However, metallic paints using Burr Lumica usually require a concealing film thickness of 200 μm or more, and in conventional painting processes, the underlying color is exposed. Therefore, uneven coating is noticeable and repair painting is not easy. Therefore, as seen in JP-A No. 59-215857, for example, a method such as first forming a color base layer similar to the paint color of the paint containing burr mica, and then applying a metallic coating with the paint containing burr mica is used. The current situation is that

However, this method requires the same number of color base paints as the top coat colors, and also increases the number of painting steps, resulting in increased man-hours and high costs.

Colored mica pigments are known as a solution to this problem. As shown in FIG. 9, this pigment has an iron oxide layer 202 (
FezO3, etc.) is coated. According to this colored mica pigment, since the interference color and the object color of iron oxide develop, the coloring power and hiding power are improved compared to Burl mica.

Furthermore, as shown in FIG. 10, JP-A-60-60163 discloses that a pigment is prepared by first forming a low-order titanium oxide layer 301 on the surface of mica 300, and then forming a titanium dioxide layer 302. Japanese Patent Publication No. 61225264 discloses a paint using this pigment. According to such a pigment (hereinafter referred to as black var pigment), the low-order titanium oxide layer 301 exhibits a blackish-brown color, so that transmitted light is absorbed and reflected light C is reduced. Therefore, the interference between the reflected light A and the reflected light B is not hindered, and a strong interference color is obtained, so that the coloring power and the hiding power are improved.

[Problems to be Solved by the Invention] With the colored mica pigment described above, various colors can be obtained by changing the thickness of the titanium dioxide layer 201 and by changing the crystal form of the iron oxide layer 202. However, since this pigment is based on the object color of iron oxide, it is limited to a range from red to yellow. Furthermore, the iron oxide itself has a cloudy color, which is less clear than the interference color produced optically. Mica pigments modified with metals such as cobalt, copper, chromium, and cadmium have also been developed, but they have problems in terms of toxicity and durability, and none have yet been put to practical use.

On the other hand, since black var pigment develops color by interference color, it can produce vivid color and has higher coloring power and hiding power than var mica. However, when used as an automobile paint, the coloring power and hiding power are still not sufficient. In other words, even when the black var pigment is contained to the limit of the physical properties of the coating film, the thickness of the hiding film is 80 to 10
It is as high as 0 μm, which is not practical.

In view of the above-mentioned current situation, the development of pigments having strong interference colors and high tinting power and hiding power is strongly desired, especially in the field of top coatings for automobiles. The present invention aims to meet this need.

[Means for Solving the Problems] The pigment of the present invention has a metal layer on at least a portion of the surface,
It consists of a substrate that has a metallic luster due to the metal layer, and a transparent inorganic compound coating layer formed to cover the substrate surface. It is characterized by a structure in which color is generated by interference with reflected light.

The substrate can be in the form of particles or scales, and scales are particularly desirable. If it is in the form of scales, it will be oriented in a layered manner in the applied wet coating film, and a coating film with excellent flop properties and hiding power can be formed. Typical examples of such substrates include natural mica and synthetic mica, but other examples include glass flakes and molybdenum disulfide. In addition, its size is as follows when used for paint:
It is preferable to have a thickness of 0.5 to 2 μm and an average particle size of 50 μm or less.

This substrate has a metal layer on at least a portion of its surface, and has a metallic luster due to the metal layer. Although the metal layer may be formed only on a part of the surface of the base, it is desirable that it be formed on the entire surface. As a result, the light transmitted through the inorganic compound coating layer is almost completely reflected by the metal layer, resulting in a strong interference color. Note that the entire base body can also be made of metal. Metals constituting such a metal layer include silver, gold, copper, palladium, nickel, cobalt, nickel-phosphorus, nickel-boron, nickel-cobalt-phosphorus, nickel-tungsten-phosphorus, silver-gold, and cobalt-phosphorus. Examples include metals or alloys such as.

A transparent inorganic compound coating layer is formed on the surface of the substrate. The material for this inorganic compound coating layer is selected from titanium dioxide, iron oxide, aluminum hydroxide, chromium hydroxide, etc., but a material with a large refractive index is desirable, and titanium dioxide is most recommended. By changing the type and thickness of this inorganic compound coating layer, interference colors of various tones can be obtained.

Note that metal can also be attached in the form of islands to the surface of the inorganic compound coating layer. In this way, the intensity of the light reflected on the surface of the inorganic compound coating layer increases, so that a strong interference color can be obtained.

To manufacture the pigment of the present invention, a metal layer is first formed on a substrate such as mica. This metal layer can be formed by a plating method such as electroplating or electroless plating, or a PVD method such as vapor deposition or sputtering.

In addition, the inorganic compound coating layer is formed by attaching an aqueous solution of a non-R salt to the substrate surface, and then depositing a water-containing layer by hydrolysis.
It can be formed by a conventionally known method, such as heating at a predetermined temperature. For example, when forming a titanium dioxide layer, the titanyl sulfate method or the titanium tetrachloride method described in Japanese Patent Publication No. 43-25644 or the like can be used.

As an example of the eleventh aspect of the present invention, there is one in which a metal layer is formed between the mica of pearl mica and the titanium dioxide layer. Therefore, it is conceivable to produce the pigment of the present invention using pearl mica as a starting material. However, it is usually difficult to pass through the titanium dioxide layer and form a metal layer on the mica surface.

However, as a result of intensive research, the present inventors discovered that a metal layer is formed on the mica surface by passing through the titanium dioxide layer under special conditions, and developed a method for forming a metal layer using this formation. established. The method will be explained below.

First, a titanium dioxide layer of a predetermined thickness is formed on the mica surface by a known titanyl sulfate method or the like. If commercially available pearl mica is used, this step can be omitted.

Next, this pearl mica is subjected to chromium treatment.

That is, a chromium compound is deposited on the surface of the titanium dioxide layer. This step is carried out by a method in which chromium hydroxide is precipitated by hydrolyzing a solution of soluble chromium salts such as chlorides or sulfates, as seen in Japanese Patent Publication No. 60-3345, or in Japanese Patent Publication No. 59-3345. 78265, chromium is subjected to hydroxide, carbonate, phosphate or methacrylate complexation from a solution containing iron or manganese ions and chromium ions. According to experiments conducted by the present inventors, as detailed in the Examples below, it was discovered that the plating metal does not precipitate on the surface of the titanium dioxide layer, but rather precipitates on the interface between the mica and the titanium dioxide layer. It has been found that the deterioration is significantly delayed, and it is inferred that this inhibitory effect has a major influence.

Thereby, a metal layer can be formed on the surface of the base made of mica. Incidentally, with pearl mica treated with alumina, untreated pearl mica, etc., precipitation of plating metal at the interface does not occur.

In addition, when silver is precipitated as the above-mentioned suppression effect depending on the amount of chromium compound precipitated, the weight of burr mica is 100% by weight.
In this case, it is necessary to configure the structure so that the amount of chromium compound precipitated in terms of metallic chromium is 0.05 to 5% by weight. If the amount of chromium compound precipitated is less than 0.05% by weight, silver will precipitate on the surface of the titanium dioxide layer, making it impossible to obtain the desired interference color. Moreover, if it exceeds 5% by weight, the color of chromium will appear and become yellowish, which is not preferable. Especially from 0°15
A range of 0.30% by weight is desirable.

Further, when silver is deposited on the interface as a metal layer using the above method, if the weight of pearl mica is 100% by weight, silver can be deposited in a range of 1 to 100% by weight.

If it is less than 1% by weight, the interference color will be weak and the coloring power will be poor;
If the amount exceeds 0% by weight, silver particles of several micrometers in size will precipitate on the surface of the titanium dioxide layer, making it impossible to obtain the desired color development. 0.1~
A range of 10% by weight is particularly desirable. In this range,
The particle size of the precipitated silver particles is in the range of 10 to 500 nm, and the maximum interference color is obtained.

[Effect] The action of the pigment of the present invention will be explained based on FIG.

The pigment of the present invention is composed of a substrate 1 having a metal layer 10 on at least a portion of its surface, and a transparent inorganic compound coating layer 2 formed to cover the surface of the substrate 1. in this case,
The metal layer 10 is formed on the entire surface of the base 1.

When light is incident on this pigment, a part of the incident light is reflected on the surface of the inorganic compound coating layer 2 and becomes reflected light A1. Also,
The rest of the incident light passes through the inorganic compound coating layer 2 and passes through the metal layer 1.
The light is reflected at 0, transmits through the inorganic compound coating layer again, and becomes reflected light A2. Here, a predetermined interference occurs between the reflected light A1 and the reflected light A2 according to the optical thickness (geometric thickness x refractive index) of the inorganic compound coating layer 2, and an interference color is generated.In the present invention, the metal layer Since 10 has metallic luster, almost all of the light that passes through the inorganic compound coating layer 2 and reaches the metal layer 10 is totally reflected without any loss.Therefore, the reflected light A2
Since the intensity of the reflected light A1 becomes maximum, the interference with the reflected light A1 also becomes maximum, resulting in a strong interference color.

If the metal layer 10 is formed on the entire surface of the substrate 1, no light will pass through this pigment, and almost all of the incident light will contribute to the interference, resulting in the maximum interference color.

This interference color can be made into various tones by simply adjusting the thickness of the inorganic compound coating layer 2. Further, the metallic luster of the metal layer 10 is visible from the surface. Therefore, this pigment is used as a metallic pigment of various colors.

Ordinary colored pigments develop their color by absorbing light. When the three primary colors are mixed, the mixed color approaches black as much as possible.

In other words, the more primary colors are mixed, the lower the saturation becomes. On the other hand, the object color of the pigment of the present invention is an achromatic color with metallic luster, which develops color due to interference. Since interference color is an optical color, when three primary colors are mixed, the mixed color approaches white as much as possible. That is, in the pigment of the present invention, the mixed color approaches the metallic color of the metal layer as much as possible. And the saturation is not reduced by mixing primary colors. Therefore, even when a plurality of colors are mixed, the pigment of the present invention has high chroma and provides a clear color tone.

[Effects of the Invention] Therefore, the pigment of the present invention produces a strong interference color that conventional mica pigments do not have, so it has high coloring power and excellent hiding properties, and it can be used simply by adjusting the thickness of the inorganic compound coating layer. It is extremely useful as a pigment for top coats of automobiles because it can easily obtain various color tones and can create metallic coatings with unprecedented bright colors.

Furthermore, in conventional metallic paints, metallic paints of various colors are produced by mixing organic pigments and aluminum powder. Therefore, color separation may occur due to differences in the composition and electrical properties of the pigments. Furthermore, in order to turn colored pigments into paints, a dispersion process using a ball mill or the like is essential, and the number of man-hours required to turn them into paints is large.

However, if the pigment of the present invention is used, even if a plurality of primary colors are mixed, the composition will be the same, so color separation will not occur. Further, a dispersion process is not required, and the number of man-hours can be significantly reduced.

[Example] Hereinafter, this will be explained in detail using examples.

As shown in FIG. 1, the pigment of this example consists of a mica 1 as a base, a silver coating 10 as a metal layer formed on the entire surface of the mica 1, and an inorganic compound formed on the surface of the silver coating 10. It is composed of a titanium dioxide layer 2 as a covering layer. This pigment and the pigments of comparative examples will be described in detail below while explaining the manufacturing method. Note that parts hereinafter refer to parts by weight, and % refers to % by weight.

(Formation of pearl mica) Commercially available mica powder (thickness 0.5-1.0 um, particle size)
A titanium dioxide layer was formed by the titanyl fiiiit acid method using a titanium dioxide layer (O ~ 50 μm). Specifically, 150 CI of mica powder was added to 750 m52 of an aqueous titanyl sulfate solution containing 67% titanium dioxide, and the mixture was rapidly heated to boiling and boiled under reflux for about 4.5 hours. The product was isolated by filtration and washing with water to pH 5.0.

The amount of mica powder added was varied in six steps to form a titanium dioxide layer, and six types of pearl mica with different thicknesses of the titanium dioxide layer were prepared. The obtained pearl mica was embedded in a resin, sliced with a microtome, and then observed with a transmission electron microscope to measure the thickness of the titanium dioxide layer, which is shown in Table 1 along with the color tone of each.

(Chromium treatment) 100Q of each of the above pearl mica was suspended in 1 volume of distilled water, and while maintaining II at 4.5 with a 2% NaOH aqueous solution, 92g of Fe50+ 7H20 and KCr (
100ml of an aqueous solution containing 17g of SO4)212H20
5! and 100 m of an aqueous solution containing 1.5 g of NaH2PO42H20! Q was added over a period of 60 minutes at 50°C. Next, the DH was adjusted to 5.0 with a 2% NaOH aqueous solution, and the mixture was further stirred for 60 minutes. After filtering and washing with water, it was dried at 130°C. In this case, the chromium compound is precipitated as a phosphate.

The amounts and addition times of the two types of aqueous solutions added to the suspension were varied in four stages to obtain four types of chromium-treated pearl mica each having a different amount of chromium compound precipitated. The amount of chromium compound deposited on each of these four types of chromium-treated pearl mica was measured by plasma elemental analysis. This chromium treatment was carried out in the same manner for the above six types of pearl mica, resulting in a total of 24 types of chromium-treated pearl mica. In addition, samples without chromium treatment and those with alumina treatment in place of chromium treatment are shown for comparison, and each sample N
o, are shown in Table 2.

(Formation of metal layer) Each sample 151 shown in Table 2 was mixed with 450 ml of distilled water.
Suspend in rJ and stir. Add this to Ginpa (AC7) at room temperature.
Distilled water was added to 50 g of NOa and 50 m of a 28% ammonia aqueous solution to make a total amount of >30 rrl, and the mixture was stirred for 5 minutes. Next, formalin solution (
35% formalin solution 9mC1 with distilled water total volume 40m,
Q) 20° C. was added all at once, and the mixture was stirred for 55 minutes.

That is, electroless plating was performed. After filtration, washing with water, and drying at 120° C., 36 types of pigments of Examples and Comparative Examples were obtained. Sample No. 1 of this pigment is substituted with sample No. in Table 2.

In addition, the content of AQN (h is 100 (7 and 300q
Sample 7 marked with * in Table 2
14 types of pigments were obtained by electroless plating in the same manner. Sample No. 1 is shown in Table 3. In addition, three types of red, green, and black pearls were selected from among the black pearls disclosed in JP-A No. 61-225264, and samples No., B-1, B-2, and B-2, respectively, were selected.
It was designated as B-3.

(Structure of Pigment) The structure of the pigment of sample No. 5-C-3 was investigated using a transmission electron microscope. The micrographs are shown in FIGS. 2 to 5. These photographs were taken with the pigment peeled off at the interface between the titanium dioxide layer 2 and the mica 1.

As schematically shown in FIGS. 6 and 7, it is observed that the titanium dioxide layer 2 is formed by columnar titanium dioxide particles 20 having a height of 10 to 1100 nm and a diameter of 2 to 5 nm, arranged in an orderly manner. . Further, a concentric circular surface to which nothing is attached was observed on the surface of the mica 1, and silver particles 1] were precipitated around it. This is presumed to indicate that the silver particles 11 are precipitated around the titanium dioxide particles 20. As a result, as shown in FIGS. 6 and 7, it is presumed that the silver particles 11 are deposited in the gaps between the titanium dioxide particles 20 between the titanium dioxide layer 2 and the mica 1.

(Painting) Using each of the 53 types of samples mentioned above and the 6 types of pearl mica shown in Table 1 that are not chromium-treated or silver-plated, they are mixed in the following formulation (solid content except for organic solvents) using a high-speed dispersor. Each base paint was prepared by stirring and dispersing.

Sample pigment 3.20% Acrylic resin 18.78% Melamine resin 8.05% Anti-settling agent 1.96% Additive 0.42% Organic solvent 67.59% Total 100.00% The acrylic resin is as follows. With a monomer composition of, Mw=27000
．． A resin of Mn-12000 was used.

(Left below) Styrene 20.0% n-butyl methacrylate 15.0% ethylhexyl methacrylate 20.0% stearyl methacrylate
15.0% Butyl acrylate 13.5%
Hydroxyethyl methacrylate 15.0% melamine resin is n-butylated melamine resin (ru-van20sE
J Mitsui Toatsu Chemical Co., Ltd.) was used, and an amide wax was used as the anti-settling agent.

The PWC of mica pigment is 10%.

(Color measurement) Each paint obtained from each sample pigment was applied to the surface of the gray intermediate coating film using a bar coater so that the dry film thickness was 15 μm, and baking was dried. The color tone of the obtained painted surface was measured using a colorimeter (rSM-3, manufactured by Suga Test Instruments Co., Ltd.), and the lab values are shown in Table 4. Note that two types of color measurement were performed: MCH corresponding to the color tone viewed from the front and CH corresponding to the color tone viewed from an oblique direction.

(Hiding power) Each paint was applied to a black and white hiding test paper in gradually changing film thickness, and the film thickness at which it was no longer possible to distinguish between white and black is shown in Table 4 as the hiding film thickness.

(Coating film physical properties) Each base paint was applied by air spray to the steel plate on which the electrodeposition coating film and intermediate coating film had been formed so that the dry film thickness was 15 μm, and after a flash time of several minutes, wet coating was applied. - On-wet acrylic-melamine resin clear paint was applied by air spray to a dry film thickness of 35 μm. Then, it was baked at 140° C. for 23 minutes to prepare a test piece. A water resistance test and a weather resistance test were conducted on this test piece, and the results are shown in Table 4.

The composition of the clear paint and the acrylic resin used in the clear paint is shown below. Two types of water resistance tests were conducted: one was immersion in hot water at 40°C for 10 days, and the other was immersion in hot water at 80°C for 10 hours, and the appearance of the coated surface was visually judged. In addition, the weather resistance test was performed using a QLIV tester.
A 00 hour acceleration test was conducted and the color difference between after and before the test was measured.

[Clear paint composition] Acrylic resin 38.25% Melamine resin 16.40% Additives 1.24% Organic solvent 45.11% Total 100.00% [Acrylic resin composition] Styrene 30.0% n-butyl methacrylate 15. 0% ethyl acrylate
20.0% butyl acrylate
17.5% hydroxyethyl methacrylate 15.0%
Acrylic acid 2.5% total 100.0%Mw=1
6000. Mn=7000 (Evaluation) The pigment of this example (C series) has a black and white hiding film thickness of 21 to 48 μm at PWC-10%, whereas the black pearl (B series) has a thickness of 93 to 101 μm and 1 burr mica (M series). ) is 320 to 410 μm.

That is, it is clear that the pigment of the present invention has excellent coloring power and hiding power.

Furthermore, the color difference after the weather resistance test of the pigment of this example is equivalent to that of Burl Mica, and no deterioration in weather resistance due to chromium treatment and silver plating is observed, and excellent performance is maintained. Regarding water resistance and weather resistance, the C series pigments are superior to the A series pigments which were not subjected to chromium treatment, and it is clear that these properties are improved by chromium treatment.

It can be seen that the C series pigments have a large difference between MCH and CH and exhibit good flip 70 tube characteristics. Furthermore, as is clear from the black and white hiding film thickness of the D series pigments, it can be seen that as the amount of silver plating increases, the hiding film thickness becomes smaller. This is because the amount of light incident on the pigment that is totally reflected by the silver plating layer increases, resulting in increased interference.

In addition, pigments made of silver-plated pearl mica without chromium treatment and alumina-treated pearl mica (A series)
The flip-flop characteristics are smaller and the hiding film thickness is larger than those treated with chromium. Although the drawings are omitted for these pigments, as a result of microscopic observation, silver particles were precipitated on the surface of the titanium dioxide layer.

In other words, the pigment of this example can be said to be sufficiently practical even when used as a top coat for automobiles.

(Color mixture) Among the pigments of this example described above, 1-C-3 (silver color),
2-C-3 (gold), 3-C-3 (red), 5-C-
3 (blue) and 6-C-3 (green) were selected, and paints were prepared in the same manner as in the examples.

Then, mix each paint so that the pigment ratio is as shown in Table 5, and apply 25ml of each paint to art paper.
I applied it with a l applicator and baked it to dry. The color tone was measured in the same manner as in the examples, and the results are shown in Table 5.

As described above, with the pigment of this example, pigments with various tones can be obtained simply by changing the thickness of the titanium dioxide layer, and tones over a golden range can be obtained simply by mixing them. Since each of these colors can be achieved using only interference colors, the color mixture becomes an additive color mixture, and a bright color tone without turbidity can be obtained. Furthermore, since each color can be obtained using mica pigment alone, problems such as color separation do not occur. When turning it into a paint, it is dispersed only by stirring, so the conventional dispersion process, which requires a lot of man-hours, is no longer necessary, and the number of man-hours required for turning it into a paint is significantly reduced.

[Brief explanation of drawings]

FIGS. 1 to 7 relate to pigments according to one embodiment of the present invention.
The figure is a schematic cross-sectional view, Figures 2, 3, 4, and 5 are micrographs showing the crystal structure, Figure 6 is an enlarged cross-sectional view of the main part, and Figure 7 is the main part. FIG. FIGS. 8, 9 and 10 are schematic cross-sectional views of conventional pigments. 1... Mica (substrate) 2... Titanium dioxide layer (inorganic compound coating layer) 10...
・Silver coating (metal layer) 11...Silver particles 20...Titanium dioxide particles Patent applicant Toyota Motor Corporation Agent
Patent Attorney Hiroshi Okawa Figure 1 Figure 6 Figure 3 Figure 5 II Figure 2 Figure 41

Claims (1)

[Claims] (1) Consists of a substrate having a metal layer on at least a portion of the surface and having a metallic luster due to the metal layer, and a transparent inorganic compound coating layer formed to cover the surface of the substrate, and a transparent inorganic compound coating layer formed on the surface of the inorganic compound coating layer. 1. A pigment characterized in that it develops color by interference between reflected light and light transmitted through the inorganic compound coating layer and reflected by the metal layer.