Ion-absorbing silicate coloring pigments

Abstract

This invention belongs to the field of coloring pigments and their preparation technology, specifically relating to an ion-absorbing silicate coloring pigment. The general formula of its initial raw materials is: x AX 1 / δ · m MX 2 / δ · n SiX 4 / δ · y REX 2或3 / δ A carbon source is added, and the mixture is calcined at 900-1500℃ in an inert or reducing atmosphere for 1-50 h to obtain an ion-absorbing silicate coloring pigment. The resulting pigment can achieve continuous coloring in the blue-green to red-orange visible light region under sunlight. This ion-absorbing silicate inorganic coloring pigment is non-toxic, exhibits strong absorption in the blue-green light region with a wide absorption band, and overcomes the shortcomings of the aforementioned functional luminescent pigments, such as weak light absorption, extremely poor coloring performance, and unstable coloring. It also possesses many advantages that make it an ideal coloring pigment, including abundant and inexpensive raw materials, stable physicochemical properties, simple synthesis conditions, good compatibility with glass and ceramics, and environmental friendliness during preparation and use.

Description

Technical Field

[0001] This invention belongs to the field of coloring pigments and their preparation technology, specifically relating to an ion-absorbing silicate coloring pigment. Background Technology

[0002] Pigments can be categorized into coloring pigments, functional pigments, and white pigments. Coloring pigments impart color to objects, and their properties primarily depend on color (hue, brightness, saturation) and color rendering properties (tinting strength, hiding power). Functional pigments refer to pigments with specific functionalities (such as luminescent pigments, pearlescent pigments, rust-preventing pigments, magnetic pigments, conductive pigments, and heat-resistant pigments). Their core requirement is to exert specific functional effects in the applied materials or products through their own chemical composition, crystal structure, or physical properties, while coloring is only auxiliary, or even completely absent. For example, luminescent pigments can store energy after being exposed to light and emit light in the dark (phosphorescent pigments), or emit fluorescence under specific conditions (such as ultraviolet light irradiation) (fluorescent pigments), thus being used in fields such as low-light illumination indicators or anti-counterfeiting.

[0003] Coloring pigments achieve their coloring effect through the selective absorption and scattering (reflection) of visible light: for example, as the absorption wavelength extends from 430 nm to 530 nm, the color changes from yellow to orange. Orange-red The red evolution refers to the absorption of blue-green light and reflection of yellow-red light by yellow-red pigments. Currently widely used traditional yellow-red inorganic coloring pigments still face several bottlenecks that urgently need to be addressed: 1) Most contain toxic elements, such as molybdenum chromium red (PbCr2O4 and PbMoO4), realgar (α-As4S4), red lead (Pb3O4), cinnabar (HgS), and cadmium red (CdS). 1-x Se x ), etc.; coating its surface with a layer of SiO2 / ZrSiO4 can reduce its toxicity and increase its operating temperature, but it still cannot avoid environmental pollution and harm to organisms during preparation and use. 2) Newly developed low-toxicity alternative warm-toned pigments, such as Ca 1-x La x Ta(O, N)3 orange-red pigments and rare earth sulfide (such as γ-Ce2S3) yellow-orange-red pigments are expensive and their stability needs improvement. The color development of these pigments is related to the band gap absorption of the matrix itself, and their advantage lies in their high color development efficiency based on intrinsic absorption. However, pigments require band gap absorption to be confined to the visible light region. Such narrow-bandgap inorganic pigments are rare, and discovering new narrow-bandgap materials is extremely difficult. Therefore, developing inorganic yellow-red pigments that are non-toxic to the environment and organisms and have pure color development is an urgent priority in pigment research.

[0004] In contrast, most inorganic materials are wide-bandgap materials with their absorption limit in the ultraviolet region, and there are many types. Their body color is white, and they cannot be directly used as coloring pigments. In this case, specific ions can be doped into the wide-bandgap material, utilizing the absorption of visible light by these ions to achieve coloration. For example, photoluminescent materials emit fluorescence (usually visible light) of a specific color by absorbing incident light of a specific wavelength (usually ultraviolet light). Among them, wide-excitation-bandgap luminescent materials, such as long-afterglow materials and luminescent materials for white LEDs, can extend their absorption limit to the blue-green region to achieve coloration. Examples include alkaline earth aluminosilicate white LEDs and long-afterglow luminescent materials, such as SrAl₂O₄:Eu,Dy, Ca₂MgSi₂O₇:Eu,Dy, Sr₂SiO₄:Eu, and Sr₃SiO₅:Eu, whose absorption limits can reach 480 nm. Theoretically, these wide-excitation-bandgap luminescent materials can meet the requirements of coloring pigments, but their visible light absorption and reflection depend on the activator (such as Eu). 2+ The activator doping level is very low, around ~1 mol%, resulting in extremely poor visible light absorption and reflection capabilities, two orders of magnitude weaker than the aforementioned narrow bandgap coloring pigments, leading to extremely poor coloring performance. Secondly, luminescent materials are typically used under conditions of strong excitation, such as the excitation density of LED lighting, which can reach 2000 kW / m². 2 The pigments are used under normal lighting or sunlight, and their maximum excitation density does not exceed 1 kW / m³. 2 Furthermore, due to their strong luminescence, the radiative transition emission superimposed on the reflected light severely interferes with color rendering. Their color and color rendering properties fluctuate greatly with different irradiation environments, failing to meet the color stability requirements of coloring pigments. When measuring the color rendering data of these luminescent materials using conventional spectrometers, accurate data is often unavailable. Therefore, these luminescent materials can be used as functional luminescent pigments, such as in long-afterglow luminescent toys and anti-counterfeiting inks, utilizing their luminescent properties rather than as coloring pigments, because their coloring power, hiding power, and other color rendering properties are very poor and unstable. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides an ion-absorbing inorganic silicate coloring pigment with performance comparable to narrow bandgap coloring pigments, while overcoming the three drawbacks of the aforementioned functional luminescent pigments. Under visible light irradiation, it achieves blue-green-green-yellow-orange-red coloration and tinting. This pigment possesses advantages such as excellent coloring effect and stable chemical properties.

[0006] The technical solution of the present invention is as follows:

[0007] An ion-absorbing silicate coloring pigment, the initial raw material has the following general formula:

[0008] xAX 1 / δ ·mMX 2 / δ·nSiX 4 / δ yREX 2或3 / δ

[0009] Where A is Li + Na + K + 、Rb + Cs + NH4 + One or more of the following; M is Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Zn 2+ One or more of the following; RE is a colorant or a mixture of a colorant and an auxiliary colorant, wherein the colorant is Eu. 2+ Yb 2 + Ce 3+ Cr 3+ One or more of the auxiliary colorants Sm 3+ 、Nd 3+ Al 3+ B 3+ Fe 3+ One or more of them; X is O 2- Or by F - Cl - ,Br - I - S 2- N 3- One or more substitutes for O 2- And the substitution amount does not exceed 40% of m+y; δ is the valence state of element X, REX 2或3 / δ The values ​​of subscripts 2 and 3 in the expression will depend on the valence state of RE. When RE is divalent, the expression is REX. 2 / δ When RE is trivalent, the expression is REX. 3 / δ m, n, x, and y represent mole fractions, where x = 0.01-0.2, m+y = 1.7-3.3, n = 0.8-1.2, and y = 0.001-1.0. Preferably, m+y is between 1.7-2.3 or 2.7-3.3. A carbon source is added to the initial raw materials, and the mixture is calcined at 900-1500 °C under an inert or reducing atmosphere for 1-50 h to obtain an ion-absorbing silicate coloring pigment. The resulting pigment can achieve continuous coloring in the blue-green to red-orange visible light region under sunlight.

[0010] There are two ways to add the C source: when it is directly mixed in, the molar amount of C added is the same as that of the divalent colorant, and the C source is powdered C, preferably C5-C7 organic sugar; when it is placed independently as a reducing agent during calcination, the molar amount of C source added is 10-30 times that of y, and the C source is granular or blocky activated carbon.

[0011] The beneficial effects of this invention are as follows: This ion-absorbing silicate inorganic coloring pigment is non-toxic, exhibits strong absorption in the blue-green light region with a wide absorption band, and overcomes the shortcomings of the aforementioned functional luminescent pigments, such as weak light absorption, extremely poor coloring performance, and unstable color. It also possesses numerous advantages that make it an ideal coloring pigment, including abundant and inexpensive raw materials, stable physicochemical properties, simple synthesis conditions, good compatibility with glass and ceramics, and environmental friendliness during preparation and use. Attached Figure Description

[0012] Figure 1 This is the reflectance spectrum of Example 1;

[0013] Figure 2 This is the reflectance spectrum of Example 4;

[0014] Figure 3 This is the reflectance spectrum of Example 5;

[0015] Figure 4 This is the reflectance spectrum of Example 6;

[0016] Figure 5 This is the reflectance spectrum of Example 20;

[0017] Figure 6 This is the reflectance spectrum of Example 21. Detailed Implementation

[0018] The following specific embodiments illustrate the different compositions of the multi-component sulfides of the present invention and their luminescent properties.

[0019] Comparative Example 1: Commercial Sr2SiO4:Eu yellow phosphor for LEDs.

[0020] Example 1: NH4Cl (98%), BaCO3 (98%), SiO2 (98%), Eu2O3 (99%), and Fe2O3 (98%) were used as initial raw materials, with initial raw material C added directly. The raw materials were weighed according to the table below, ground thoroughly for 30 minutes, placed in a corundum tube, and then placed in a resistance furnace. The furnace was filled with N2 gas, and the sample was heated to 1250 °C at a rate of 10 °C / min, held at that temperature for 4 h, and then cooled to room temperature. After grinding, the target product was obtained. Compared with Comparative Example 1, its performance indicators are shown in the table below, and the reflectance spectrum is shown in [Table missing]. Figure 1The color measurement conditions for all embodiments of this invention are kept consistent.

[0021] Using a similar method, Examples 2 through 22 can be obtained.

[0022] The above embodiments employ a solid-state reaction method. The initial raw materials can be halides, oxides, sulfides, nitrides, or complex salts containing the elements mentioned in the technical solution, such as carbonates, oxalates, nitrates, acetates, and sulfates. The calcination temperature is between 1100-1500 °C, adjusted according to the amount of material, particle size, and reactivity. For example, in Example 1, the initial raw materials are Ba(NO3)2, tetraethyl orthosilicate (TEOS), Eu(NO3)3, and Fe(NO3)3. Precursors are prepared via a sol-gel method, and the calcination temperature can be reduced to 1100 °C. Using micron-sized raw materials, the calcination temperature in Example 7 can reach 1450 °C. The calcination time is between 1-50 h, adjusted according to the amount of material and the reactivity of the initial raw materials. A shorter calcination time is required when the amount of material is small and the initial raw materials have high reactivity.

[0023] In the above embodiments, halides were the most effective choice for component AX, typically fluorides and chlorides, while bromides and iodides were more expensive. Oxides (such as Li₂O, Example 3) also showed good results, while sulfides and nitrides had poor stability, increasing the difficulty of preparation. Component xAX (x=0.01-0.2) acted as a co-solvent, lowering the reaction temperature by 10-50 °C, and also made the pigment color more vibrant, further improving pigment performance (absorbance, hiding power, tinting strength) by 7-23%. The optimal addition amount x was between 0.01 and 0.2, and the specific optimal addition amount needed to be adjusted according to the initial raw material particle size, reactivity, and reaction temperature. When the initial raw material particle size was coarse, the reactivity was low, and the reaction temperature was high, the x value approached 0.2. Conversely, the x value approached 0.01.

[0024] In the above embodiments, component MX is selected from oxides (MO) which offer the best overall performance (coloring effect and cost). Replacing the oxides with partial sulfides and nitrides, with the substitution amount not exceeding 40% of m+y, can significantly adjust the color tone towards a warmer hue. However, increasing the substitution amount will raise the cost. M=Ca 2+ 、Sr 2+ and Ba 2+ It is the element with the best overall performance (coloring effect and cost) and can be used as a matrix component; and component Ca 2+ 、Sr 2+ and Ba 2+ These pigments can be substituted for each other, and the absorption edge can be adjusted to a large extent. As shown in Examples 4-6, the properties of the obtained pigments are shown in the table below, and their reflectance spectra are shown in... Figures 2-4 Sr 2+Replace Ca 2+ Its color is clearly biased towards warm tones. 2+ Replace Ba 2+ and Ca 2+ Replace Ba 2+ Furthermore, the color development pattern is not very regular. Due to the small ionic radius, Mg... 2+ and Zn 2+ It cannot be used independently as a matrix material; a small amount of Mg 2+ (<10 mol%) Ca substitution 2+ 、Sr 2+ Ba 2+ It can increase the purity of red color development by 5-10%, while a small amount of Zn 2+ (<10 mol%) Ca substitution 2+ 、Sr 2+ Ba 2+ This can improve color rendering by 7-13%. For mMX, if a portion of mMX is selected as a halide and used in combination with AX (not exceeding 5%), such as Li2CO3+MgF2, or CaF2, SrF2, BaF2, etc., the phase will be purer and the performance will be better. The m+y value has a significant impact on the color rendering and coloring performance of pigments, and can also affect the calcination temperature and particle size of pigments. The larger the m+y value, the warmer the hue of the pigment (as shown in Examples 20-21, whose reflectance spectra are shown in...). Figures 5-6 The optimized value is between 1.7 and 2.3 or 2.7 and 3.3. Within this range, the pigment phase composition is usually not pure, and all phases exhibit good color development performance. It should be noted that even when the m+y value exceeds this range, good color development performance is still achieved, but due to the presence of more impurities, it may result in some waste of initial raw materials from an economic perspective.

[0025] In the above embodiments, the best overall performance (coloring effect and cost) is achieved by using oxides (SiO2) for component SiX. Replacing oxides with some sulfides and nitrides can significantly adjust the color hue towards a warmer tone, but this increases cost. For nSiX, if a portion of nSiX is selected as a halide and used in combination with AX (not exceeding 2%), such as Li2CO3+K2SiF6, it can effectively adjust the pigment particle morphology, which is particularly beneficial for applications. The n value also affects the pigment calcination temperature and color hue; the warmer the n value, the higher the calcination temperature and the warmer the color hue. The optimized n value is between 0.8 and 1.2. Within this optimized range, the pigment phase composition is usually not pure, and all phases exhibit good color rendering performance. It should be noted that even with n values ​​outside this range, good color rendering performance is still achieved, but due to the presence of more impurities, it may result in some waste of initial raw materials from an economic perspective.

[0026] In the above embodiments, trivalent REs in component REX are best selected from oxides (RE2O3) for their overall performance (coloring effect and cost), while divalent REs are preferably selected from sulfides (such as EuS). Regarding Eu... 2+ Yb 2+ 、Sm 3+ 、Nd 3+ Al 3+ Fe 3+ Halides such as fluorides or chlorides can also be used, while nitrides can significantly adjust the color tone towards a warmer hue, but this increases cost. Using a method similar to Examples 1-11, the colorant is changed to Yb. 2+ Ce 3+ Cr 3+ Colorant Ce 3+ The color shows a clear blue shift, leaning towards a cooler tone, and the colorant Yb... 2+ The coloration of Eu 2+ Similar in color, leaning towards warm tones, but with slightly less light absorption than Eu. 2+ As in Examples 12-18, its color is similar to that of the colorant Eu. 2+ Different. Co-doping with colorant combinations can significantly improve absorbance by 13-35%, such as Ce. 3+ +Eu 2+ Yb 2+ +Eu 2+ Ce 3+ +Yb 2+ However, this will increase costs. Auxiliary colorant Sm 3+ 、Nd 3+ It will significantly quench, thereby eliminating the color fluctuation of the obtained pigment under different lighting conditions and enhancing the application performance of the pigment. Its addition amount does not exceed y / 3. However, the influence of various component parameters, such as xAX, mMX, nSiX, and yREX, on the pigment color follows a similar pattern to that in Examples 1-11. For example, for yREX, the larger the y value, the warmer the hue, and its optimized value is between 0.1 and 1.0.

[0027] Using a method similar to that in Examples 1-22, the effects of other parameters not listed in Examples 1-22 on color, absorbance, and tinting strength can also be obtained. When A=Rb + or Cs + When, with A=K + Similar results were obtained, but Rb + and Cs + The price is relatively high. Performance is better when used in combination A, such as A=Li. + and NH4 + The combination of these factors can result in a more uniform product particle size, and while maintaining the color, the calcination temperature can be appropriately reduced by 25-50 ℃. When M contains a portion of Be...2+ or Cd 2+ While these elements will not affect the sample's performance, they may present challenges in application due to environmental concerns. X=Br - or I - When, with X=Cl - Similar results were obtained, but Br - and or I - The price is relatively high.

[0028] The data and results for each embodiment are shown in Table 1 below:

[0029] Table 1

[0030]

[0031]

[0032]

[0033]

[0034]

Claims

1. An ion-absorbing silicate coloring pigment, characterized in that, The general formula for the initial raw material of the ion-absorbing silicate coloring pigment is as follows: xAX 1 / δ ·mMX 2 / δ ·nSiX 4 / δ ·yREX 2或3 / δ Where A is Li + Na + K + 、Rb + Cs + NH4 + One or more of the following; M is Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Zn 2+ One or more of the following; RE is a colorant or a mixture of a colorant and an auxiliary colorant, wherein the colorant is Eu. 2+ Yb 2+ Ce 3 + Cr 3+ One or more of the auxiliary colorants Sm 3+ 、Nd 3+ Al 3+ B 3+ Fe 3+ One or more of them; X is O 2- Or by F - Cl - ,Br - I - S 2- N 3- One or more substitutes for O 2- And the substitution amount does not exceed 40% of m+y; δ is the valence state of element X, REX 2或3 / δ The values ​​of subscripts 2 and 3 in the expression will depend on the valence state of RE. When RE is divalent, the expression is REX. 2 / δ When RE is trivalent, the expression is REX. 3 / δ m, n, x, and y are mole fractions, x = 0.01-0.2, m+y = 1.7-3.3, n = 0.8-1.2, and y = 0.001-1.

0. A C source is added to the initial raw materials, and the mixture is calcined at 900-1500 °C in an inert or reducing atmosphere for 1-50 h to obtain an ion-absorbing silicate coloring pigment. The obtained pigment can achieve continuous coloring in the blue-green to red-orange visible light region under sunlight.

2. The ion-absorbing silicate coloring pigment according to claim 1, characterized in that, m+y is between 1.7 and 2.3 or between 2.7 and 3.

3.

3. The ion-absorbing silicate coloring pigment according to claim 1 or 2, characterized in that, in, There are two ways to add the C source: when it is directly mixed in, the molar amount of C added is the same as that of the divalent colorant; when it is placed independently as a reducing agent during calcination, the molar amount of C source added is 10-30 times that of y.

4. The ion-absorbing silicate coloring pigment according to claim 3, characterized in that, in, There are two ways to add the carbon source: when it is directly mixed in, the carbon source is powdered carbon, which is a C5-C7 organic sugar; when it is placed independently as a reducing agent during calcination, the carbon source is granular or blocky activated carbon.

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