Non-calcined pencil lead

Abstract

The invention provides a non-calcined pencil lead, which can achieve high visibility and line performance of easy writing even on a tablet, and pencil writability / line characteristics at the same time. The non-calcined pencil lead according to the present disclosure contains at least a body material, a pigment, and a water-soluble resin, and is characterized in that the range of the intensity ratio (G / D) of the G peak (near 1580 cm <-1 >) to the D peak (near 1350 cm <-1 >) in the Raman spectrum of a writing line is set to 5-20%, and the range of the intensity ratio (G / D) of the writing line is set to 20% or more, the range of the intensity ratio (G / D) of the writing line is set to 0.5-1.5.

Description

Technical Field

[0001] This instruction manual pertains to unburnt pencil leads. Background Technology

[0002] Traditionally, calcined pencil leads are typically manufactured as follows: graphite and clay are mixed to form a core, which is then sintered at a high temperature of around 1000°C to obtain the core body. Oil or similar substances are then impregnated into the pores created in the core body. This type of calcined pencil lead utilizes the impregnated oil to fix the graphite onto the paper surface, and due to the good erasing properties of the eraser, it is widely used (see, for example, Patent Document 1). However, calcined pencil leads require heating to around 1000°C to sinter the clay used as the bonding material, which is energy-intensive.

[0003] In addition, existing non-calcined pencil leads are manufactured as follows: wax or resin is used as a binder, mixed with various inorganic or organic pigments, shaped into a core shape using an extrusion molding machine, and then dried as needed (see, for example, Patent Document 2).

[0004] The bonding material for such unburnt pencil leads is wax or resin. The lines of these pencils have a high gloss, resulting in poor visibility, especially when writing on writing surfaces such as whiteboards, where the color often fades due to the gloss. On the other hand, colored pencils have high visibility, but the writing feel is heavy and the lines cannot be erased.

[0005] On the other hand, as a pencil lead that suppresses reflection, calcined pencil leads made from 10 parts of earthy graphite, 20 parts of clay, 20 parts of carbon black, 50 parts of calcium carbonate powder, 3 parts of binder (xanthan gum), and 120 parts of water are known (see, for example, Patent Document 3). On the other hand, calcined pencil leads with a tip strength / core bending strength of 0.6 or more and 1.5 or less, a writing resistance value of 65 N or less, and an R-value (intensity ratio: G / D) based on Raman spectroscopy of 0.15 or more and 0.55 or less are known (see, for example, Patent Document 4).

[0006] However, the anti-reflection effect of the calcined pencil lead in Patent Document 3 is not sufficient, and its elimination effect is also low, leaving room for improvement. Patent Document 4 mentions an R-value (intensity ratio: G / D) based on Raman spectroscopy in its calcined pencil lead. Although it discloses calcined pencil lead, the embodiments do not provide the R-value (intensity ratio: G / D), and its inventive subject matter and technical concept (solution and its effects) differ from this disclosure.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2007-138031

[0010] Patent Document 2: Japanese Patent Application Publication No. 2012-52109

[0011] Patent Document 3: Chinese Patent Announcement No. 109385147

[0012] Patent Document 4: Japanese Patent Application Publication No. 2023-95065 Summary of the Invention

[0013] The problem the invention aims to solve

[0014] This disclosure aims to solve the problems in the prior art, and the purpose of this disclosure is to provide a non-calcined pencil lead that can highly balance the line performance of high visibility and easy writing even on a writing board, as well as the line characteristics of high pencil writeability and / or line erasure rate.

[0015] Solution for solving the problem

[0016] The inventors conducted in-depth research on the aforementioned existing problems and found that, in non-calcined pencil leads containing at least a binder material, pigment, and water-soluble resin, the G peak (1580 cm⁻¹) in the Raman spectrum of the resulting writing lines can be obtained by... -1 (nearby) and D peak (1350cm) -1 By setting the range of peak intensity ratio (G / D) of the writing line to be 2.0 or higher (near the target area) and the range of peak intensity ratio (G / D) of the writing line to be 0.5 to 1.5 as specified, a non-calcined pencil lead that solves the above-mentioned problem can be obtained, thus completing this disclosure.

[0017] That is, the non-calcined pencil lead of this disclosure is characterized by being a non-calcined pencil lead containing at least a binder material, pigment, and water-soluble resin, and the resulting writing lines exhibit a G peak (1580 cm⁻¹) in the Raman spectrum. -1 (nearby) and D peak (1350cm) -1 The range of peak intensity ratio (G / D) of the near area is set to 5% to 20% or higher, and the range of intensity ratio (G / D) of the writing line is set to 20% or higher or higher, which is between 0.5 and 1.5.

[0018] The material having a strength ratio (G / D) of 2.0 or higher is preferably flake graphite with an average particle size of 5 to 20 μm.

[0019] The material having a strength ratio (G / D) in the range of 0.5 to 1.5 is preferably selected from at least one of carbon black, earthy graphite, and plant-derived black pigments.

[0020] The effects of the invention

[0021] According to this disclosure, a non-calcined pencil lead is provided that can highly balance line performance such as high visibility and easy writing even on a writing board, as well as line characteristics such as high pencil writeability and / or line erasure rate.

[0022] The purpose and effects of this disclosure are recognized and obtained by using the constituent elements and combinations specifically pointed out in the claims. The foregoing general description and the following detailed description are both exemplary and illustrative, and do not limit the disclosure as set forth in the claims. Attached Figure Description

[0023] Figure 1 This is a perspective view schematically showing the appearance of an unburnt pencil lead as an example of an embodiment of this disclosure. Detailed Implementation

[0024] The embodiments of this disclosure will now be described in detail. However, it should be noted that the technical scope of this disclosure is not limited to the various embodiments detailed below, but extends to the invention as described in the claims and its equivalents. Furthermore, this disclosure can be implemented based on the content disclosed in this specification and common technical knowledge in the field (including design considerations and obvious aspects).

[0025] The non-calcined pencil lead of this embodiment is characterized by being a non-calcined pencil lead containing at least a binder material, pigment, and water-soluble resin, and exhibiting the G peak (1580 cm⁻¹) in the Raman spectrum of the written lines. -1 (nearby) and D peak (1350cm) -1 The range of peak intensity ratio (G / D) of the near area is set to 5% to 20% or higher, and the range of intensity ratio (G / D) of the writing line is set to 20% or higher or higher, which is between 0.5 and 1.5.

[0026] As the filler material used in this embodiment, there are no particular limitations as long as it is a filler material commonly used in non-calcined pencil leads, and it can be used arbitrarily. Examples of suitable filler materials include white materials such as boron nitride, kaolin, talc, mica, and calcium carbonate. Colored filler materials can also be used depending on the hue of the solid drawing material, and mixtures of various materials can also be used. In particular, from the perspective of its physical properties, shape, and the effects of this disclosure, boron nitride, kaolin, talc, flake graphite, sericite, and mica are preferred.

[0027] The total content of these body materials is not particularly limited as long as it is in a specified ratio of the intensity ratio (G / D) of the Raman spectrum of the writing lines being 2.0 or higher and the intensity ratio (G / D) being 0.5 to 1.5. It is preferably 30 to 80% by mass relative to the total amount of unburned pencil lead, and particularly preferably 50 to 70% by mass.

[0028] Examples of pigments used in this embodiment include carbon black, earthy graphite, plant-derived black pigments, titanium dioxide, iron black, Prussian blue, ultramarine, Blue No. 1, iron oxide red, yellow iron oxide, chromium oxide, chromium hydroxide, zinc oxide, zirconium oxide, cobalt oxide, fish scale foil, bismuth oxychloride, and mica titanium, as well as azo-based organic pigments such as diazo yellow AAA and pyrazolone orange, cyano-based organic pigments such as phthalocyanine blue and phthalocyanine green, high-grade organic pigments such as quinacridone red, coloring pigments such as fanalcolor, and fluorescent pigments. In addition to pigments, dyes such as Blue No. 2, Blue No. 404, Red No. 2, Red No. 3, Red No. 102, Red No. 104, Red No. 105, Red No. 106, DPP red, Yellow No. 4, Yellow No. 5, and Green No. 3 can also be used, either alone or in mixtures of two or more.

[0029] As a usable plant-derived black pigment, a carbonized pigment obtained by charring bamboo, wood, or other plants at a temperature of 250°C or higher is used. There are no particular limitations on plant-derived carbon black pigments; for example, black charcoal, white charcoal, machine-made charcoal, bamboo charcoal, and fly ash can be used. Among these, bamboo charcoal and white charcoal, represented by binchotan charcoal, are preferred. Bamboo charcoal, made from bamboo, has more fine pores compared to other types of charcoal. Furthermore, bamboo charcoal contains more glassy substances than wood charcoal, thus exhibiting the effect of better wetting with water-soluble resins that act as binders, further enhancing the effectiveness of this disclosure.

[0030] In particular, from the perspective of their physical properties, shape and the effects of this disclosure, carbon black, earthy graphite, bamboo charcoal, binchotan charcoal and coconut shell charcoal are preferred examples.

[0031] There are no particular restrictions on the total amount of these pigments as long as they are in a specified proportion such that the intensity ratio (G / D) in the Raman spectrum of the above-mentioned writing lines is 2.0 or more and the intensity ratio (G / D) is 0.5 to 1.5. It is preferably 20 to 50% by mass relative to the total amount of unburned pencil lead, and particularly preferably 30 to 40% by mass.

[0032] As the water-soluble resin used in this embodiment, water-soluble polymers such as sodium carboxymethyl cellulose (CMC-Na), ammonium carboxymethyl cellulose, polyvinyl alcohol (PVA), methyl cellulose, hydroxypropyl cellulose, xanthan gum, echogum, etherified starch, polyacrylamide, and polyacrylic acid can be used.

[0033] In particular, from the perspective of their physical properties, shape and the effects of this disclosure, preferred examples include sodium carboxymethyl cellulose (CMC-Na), polyvinyl alcohol (PVA), xanthan gum, polyacrylic acid, and polyacrylamide.

[0034] The content of these water-soluble resins is not particularly limited as long as it is in a specified proportion such that the intensity ratio (G / D) in the Raman spectrum of the writing lines is 2.0 or higher and the intensity ratio (G / D) is 0.5 to 1.5. It is preferably 5 to 30% by mass relative to the total amount of uncalcined pencil lead, and particularly preferably 10 to 20% by mass.

[0035] The non-calcined pencil lead of this embodiment contains at least the above-mentioned body material, pigment and water-soluble resin. In addition to the above components, in order to adjust the wear of the lead, it may contain appropriate amounts of lubricants such as metal soap, PTFE particles, hydrocarbon wax, wax esters, etc.

[0036] Examples of usable metallic soaps include zinc stearate, barium stearate, aluminum stearate, magnesium stearate, zinc laurate, and zinc 12-hydroxystearate.

[0037] The non-calcined pencil lead of this embodiment can be manufactured to the desired physical properties using the following manufacturing method. Specifically, a mixture is prepared by adding a specified water-soluble resin to a substance formed by mixing a specified pigment as powder with a binder material and then kneading. At this time, a low alcohol (with fewer than 5 carbon atoms, C5) such as ethanol and a solvent such as water may be added as needed. The prepared mixture is then extruded into pencil leads of a specified shape and size using a plunger-type or screw-type extruder. Furthermore, if a solvent is used, the solvent is subsequently dried (approximately 40°C for 24 hours) to remove it. Through this molding process, a pencil lead with the desired physical properties is obtained. Figure 1 The unburnt pencil lead 10 shown has a core 11 with a generally cylindrical shape.

[0038] The molded core is a porous body with pores derived from the microstructure of the pigment and extender materials. These pores can remain intact or, after heating at 60–200°C for 12 hours, can be impregnated with oils or greases as needed. Lower alcohols such as ethanol or water can be used as solvents.

[0039] As usable oils and fats, preferred substances include oily substances that are liquid at room temperature, such as liquid paraffin, spindle oil, silicone oil, α-olefin oligomers and squalane, vegetable oils such as palm oil and olive oil, and animal oils such as lard. Among these, silicone oil is particularly good, and examples include dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, cyclic dimethyl silicone oil, polyether-modified silicone oil, methylstyrene-modified silicone oil, and alkyl-modified silicone oil.

[0040] As described above, the non-calcined pencil lead of this embodiment can be manufactured using at least a binder material, pigment, and water-soluble resin through the aforementioned manufacturing method, etc., to produce the G peak (1582 cm⁻¹) in the Raman spectrum of the written lines. -1 ) and D peak (1350cm) -1 The strength ratio (G / D) of the writing line is set to be 5% to 20% or more, and the strength ratio (G / D) of the writing line is set to be 0.5 to 1.5 or more. With this configuration, a non-calcined pencil lead that can highly balance the line performance of high visibility and easy writing even on a writing board, as well as the line characteristics of high pencil writeability and / or line erasure rate, is obtained for the first time.

[0041] Raman spectroscopy, based on the method of Raman spectroscopy, is mainly used for structural analysis of carbon materials. The D peak (1350 cm⁻¹) is a key indicator. -1 The peaks near the G peak (1580 cm⁻¹) originate from the diamond structure (sp³ bonds). -1 The peaks (nearby) originate from the graphite structure (sp2 bonds).

[0042] In this embodiment, the range of intensity ratio (G / D) of the writing line in the Raman spectrum of 2.0 or above is set to 5 to 20% in 100%, preferably 10 to 15%, and the range of intensity ratio (G / D) of the writing line in the Raman spectrum of 0.5 to 1.5 is set to 20% or above, preferably 30 to 50%.

[0043] Non-calcined pencil leads possessing these writing line characteristics can be prepared by appropriately combining suitable components and their contents from the aforementioned types of body materials, pigments, and water-soluble resins, and then by combining suitable mixing and manufacturing methods.

[0044] Preferably, as a material with a strength ratio (G / D) of 2.0 or higher, flake graphite with an average particle size of 5 to 20 μm is preferred. In addition, as a material with a strength ratio (G / D) in the range of 0.5 to 1.5, at least one of plant-derived black pigments such as carbon black, earthy graphite, and bamboo charcoal which is amorphous carbon is preferred.

[0045] It should be noted that the average particle size mentioned in this specification refers, for example, the median particle size (D50) on a volume basis as measured using a particle size analyzer [Microtrac HRA9320-X100 (manufactured by Nikkiso Co., Ltd.)].

[0046] By reducing the intensity ratio (G / D) of the writing lines in the Raman spectrum from 2.0 or higher to 5-20% in 100%, a black color with low crystallinity and low gloss due to diffuse light reflection caused by the amorphous structure is produced. Furthermore, by setting the intensity ratio (G / D) of the writing lines from 0.5 to 1.5 to 20% or higher in 100%, the gloss of the lines can be suppressed. In this embodiment, since the amorphous carbon core is formed using carbon black, bamboo charcoal, or the like as pigments, and then oil is impregnated in the form of a porous core through cross-linking or the like, a pencil lead with intact amorphous carbon residue, high visibility, light writing properties, high core strength, and high line erasure properties can be obtained.

[0047] The resulting unburnt pencil lead possesses the following excellent properties: it forms highly visible lines with a line brightness L* of 40 or less and a 60° gloss value of 25 or less; it reduces the halo effect when writing on a writing board; in addition, the line removal rate is 85% or more, and the coefficient of dynamic friction is 0.230 or less.

[0048] In this disclosure, the structure is configured such that it contains at least the aforementioned extender material, pigment, and water-soluble resin, and the Raman spectrum of the written lines contains the G peak (1580 cm⁻¹). -1 (nearby) and D peak (1350cm) -1 The range of peak intensity ratio (G / D) of the near-terminal area is set to 5-20% or higher, and the range of intensity ratio (G / D) of the writing line is set to 0.5-1.5 or higher, thereby obtaining a non-calcined pencil lead that can highly balance the line performance of high visibility and easy writing even on a writing board, as well as the line characteristics of high pencil writeability and line erasure rate.

[0049] Example

[0050] Next, this disclosure will be described in more detail through examples and comparative examples, but this disclosure is not limited to the following examples, etc.

[0051] (Examples 1-4 and Comparative Examples 2 and 3: Manufacturing of non-calcined pencil leads)

[0052] The non-calcined pencil leads of each embodiment and comparative example have the composition shown in Table 1 below.

[0053] Equal masses of water were added to the raw materials of the uncalcined pencil leads of Examples 1-4 and Comparative Examples 2 and 3 shown in Table 1 below. The mixture was then mixed using a planetary mixer, and moisture was adjusted while kneading with a two-roll mill. The mixture was then shaped into fine threads using a hydraulic plunger extruder. Examples 1-4 and Comparative Examples 2 and 3 were dried at 180°C for 3 hours to remove moisture, yielding black pencil lead porous bodies with a diameter of 2.5 mm. These black pencil lead porous bodies were impregnated in silicone oil at 80°C, allowing the silicone oil to penetrate into the internal pores, resulting in black uncalcined pencil leads. The oil penetration rates (mass %) are shown in Table 1 below (the same applies below).

[0054] (Comparative Example 1: Manufacturing of calcined pencil leads)

[0055] Equal amounts of water were added to each of the raw materials for calcined pencil leads shown in Table 1 below. The mixture was then combined using a planetary mixer, with moisture adjustment performed simultaneously using a two-roller kneading process. The mixture was then shaped into fine threads using a hydraulic plunger extruder and dried at 150°C for 3 hours to remove moisture, yielding black pencil lead bodies with a diameter of 2.6 mm. These porous black pencil lead bodies were then calcined at 1000°C in a reducing atmosphere for 5 hours to obtain porous black pencil lead bodies with a diameter of 2.5 mm. Finally, these porous black pencil lead bodies were immersed in silicone oil at 80°C, allowing the silicone oil to penetrate the internal pores, resulting in black calcined pencil leads.

[0056] (Comparative Example 4: Manufacturing of Non-calcined Colored Pencil Leads)

[0057] In Comparative Example 4 (using wax), the same mass of water was added to each raw material (using wax) and mixed using a planetary mixer. Moisture was adjusted while simultaneously using a two-roll mill. The mixture was then shaped into fine threads using a hydraulic plunger extruder and dried at 180°C for 3 hours to remove moisture, yielding porous black pencil leads with a diameter of 2.5 mm. These porous black pencil leads were then immersed in silicone oil at 80°C, allowing the silicone oil to penetrate the internal pores, thus obtaining the non-calcined colored pencil leads.

[0058] For the uncalcined pencil leads, calcined pencil leads, and uncalcined colored pencil leads obtained in Examples 1-4 and Comparative Examples 1-4, the G peak (1580 cm⁻¹) in the Raman spectrum of the writing lines was measured using the following method. -1 (nearby) and D peak (1350cm) -1 The range of peak intensity ratio (G / D) of the near area is 2.0 or higher, and the range of peak intensity ratio (G / D) of the written line is 0.5 to 1.5.

[0059] Raman Spectroscopic Analysis of Writing Lines

[0060] Writing lines were set in a Raman microscope (XploRA, manufactured by Horiba Manufacturing Co., Ltd.), and measurements were performed using a 532 nm laser wavelength. Measurement conditions were: acquisition time 0.1 seconds, cumulative measurements 10 times, 10% neutral density filter, 20x objective lens magnification, 500mm confocal aperture, 100μm slit width, and measurement wavelength 100–3000 cm⁻¹. -1 The writing lines used for the measurement were transferred onto a glass slide and flattened using a spatula. Within the obtained peak, the 1580 cm⁻¹ peak in the spectrum was selected. -1 The intensity of the nearby peak is defined as the G peak, and the peak intensity at 1350 cm⁻¹ in the spectrum is used to define the peak intensity. -1 The intensity of the nearby peak is defined as the D peak, and the intensity ratio (G / D) of the writing line is defined. The distribution over a 0.1 mm × 0.1 mm area is determined by mapping the peak ratio of the D peak and the G peak at two locations.

[0061] In addition, the brightness L* value, 60° gloss, reflectivity under photographic capture, coefficient of dynamic friction, and line elimination rate (elimination property) of the writing lines of the non-calcined pencil leads, calcined pencil leads, and non-calcined colored pencil leads obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were measured and evaluated using the methods described below.

[0062] These results are shown in Table 1 below.

[0063] (Method for measuring luminance L*)

[0064] For writing lines, the surface brightness (bright / dark) of the ink reservoir component inside the cylinder is evaluated using a colorimeter SC-P (manufactured by Suga Test Instruments Co., Ltd.) under the following measurement conditions, according to the evaluation criteria below.

[0065] [Optical Conditions] Reflectance Measurement: Diffuse Light Illumination, 8° Light Reception

[0066] According to condition c of JIS Z 8722

[0067] Evaluation Criteria:

[0068] A: Under 37

[0069] B: Greater than 37 and less than 42

[0070] C: 42 and above

[0071] (Method for determining 60° gloss)

[0072] Specular gloss was determined according to JIS Z 8741-1997. The 60° gloss was evaluated according to the following evaluation criteria.

[0073] A: Under 22

[0074] B: Greater than 22 and less than 30

[0075] C: 30 and above

[0076] (Evaluation of glare from the photo)

[0077] For photographs of lines taken at a height of 30cm with the light source placed at a 30° angle, confirm the following evaluation criteria.

[0078] Evaluation Criteria:

[0079] ○: The halo around the lines is small, the lines are darker, and they are clearly visible.

[0080] △: A halo with lines, the lines appearing slightly gray.

[0081] ×: The halo around the lines is large, and the lines appear gray.

[0082] (Method for determining the coefficient of kinetic friction)

[0083] The average value of the total friction force in the line drawn using the line drawing machine as specified in JIS S 6005:2007 and JIS S 6006:2007, divided by the writing load (n=10), is taken as the "dynamic friction coefficient".

[0084] (Method for determining line elimination rate)

[0085] The lines written in the abrasion test were erased with an eraser (EP-105E) for 5 cycles under a 12N load. The concentration after erasure was measured, and the line erasure rate (n=10) was calculated using the following formula.

[0086] Line removal rate (%) = (Line concentration - Post-removal concentration) / Line concentration × 100

[0087] [Table 1]

[0088]

[0089] The values ​​*1 to *15 in Table 1 above are described below.

[0090] *1: Average particle size 10μm, manufactured by Japan Graphite Industry Co., Ltd.

[0091] *2: Average particle size 10μm, manufactured by Takehara Chemical Industry Co., Ltd.

[0092] *3: Average particle size 2μm, manufactured by Kyoritsu Materials Co., Ltd.

[0093] *4: Average particle size 10nm, manufactured by Mitsubishi Chemical Corporation

[0094] *5: Average particle size 2μm, manufactured by Japan Graphite Industry Co., Ltd.

[0095] *6: Average particle size 5μm, manufactured by Ezaki Glico Co., Ltd.

[0096] *7: Pigment Blue 15, manufactured by Dai Nippon Seika Co., Ltd.

[0097] *8: Manufactured by Miki Chemical Industry Co., Ltd.

[0098] *9: Manufactured by ANDOH PARACHEMIE CO., LTD.

[0099] *10: Manufactured by ANDOH PARACHEMIE CO., LTD.

[0100] *11: Manufactured by Japan Paper Corporation

[0101] *12: Kuraray Corporation

[0102] *13: Manufactured by Sanjing Chemical Company

[0103] *14: Made by Nippon Shokubai Co., Ltd.

[0104] *15: Viscosity 100CS, manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0105] The results in Table 1 above clearly confirm that, compared with Comparative Examples 1 to 4 which fall outside the scope of this disclosure, Examples 1 to 4 which fall within the scope of this disclosure have obtained non-calcined pencil leads that can highly balance line performance with high visibility and easy writing even on a writing board, as well as pencil writing / line characteristics.

[0106] Industrial availability

[0107] This disclosure can be used for non-calcined pencil leads.

Claims

1. A non-calcined pencil lead, characterized in that, It is a non-calcined pencil lead containing at least a binder material, pigment, and water-soluble resin. The Raman spectrum of the resulting writing lines shows that the intensity ratio of the G peak to the D peak (G / D) is greater than 2.0, ranging from 5% to 20%. Furthermore, the intensity ratio of the writing lines with a G / D of 0.5 to 1.5 is set to be greater than 20%. The G peak is at 1580 cm⁻¹. -1 Nearby, peak D is at 1350cm -1 nearby.

2. The non-calcined pencil lead according to claim 1, characterized in that, The material with a strength ratio (G / D) of 2.0 or higher is flake graphite with an average particle size of 5-20 μm.

3. The non-calcined pencil lead according to claim 1 or 2, characterized in that, The material with a strength ratio (G / D) in the range of 0.5 to 1.5 is selected from at least one of carbon black, earthy graphite, and plant-derived black pigments.

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