JPH0812897A - Production of halogenated gallium phthalocyanine crystal - Google Patents

Abstract

PURPOSE:To provide a method for producing halogenated gallium phthalocyanine crystals, having simple process, not requiring complicate equipment and capable of stably producing crystals having good electrophotographic characteristics at a low cost. CONSTITUTION:A halogenated gallium phthalocyanine is subjected to dry powdering by stirring or mechanical strain in the presence of an inert gas to provide the objective halogenated gallium phthalocyanine having diffraction peaks at 7.5 deg., 16.7 deg., 25.6 deg. and 28.4 deg. of Bragg angle (2theta+ or -0.2 deg.) in CuK<F- characteristic X ray diffraction spectrum and having >=0.5 half height width at the peak of 7.5 deg. Bragg angle and 0.4-0.6 strength ratio of the peak of 28.4 deg. Bragg angle to the peak of 7.5 deg. Bragg angle.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a halogenated gallium phthalocyanine crystal suitable for use in an electrophotographic photoreceptor.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for extending the photosensitive wavelength region of organic photoconductive materials to the wavelength of a semiconductor laser of near infrared rays and using it as a photoconductor for digital recording such as a laser printer. From the viewpoint, squarylium compounds, triphenylamine-based trisazo compounds, phthalocyanine compounds (JP-A-48-
34189 and 57-14874) have been proposed as organic photoconductive materials for semiconductor lasers. When an organic photoconductive substance is used as a photosensitive material for a semiconductor laser, first, the photosensitive wavelength range is extended to a long wavelength, then, the sensitivity and durability of the formed photoreceptor are good. Required. In order to meet these requirements, vigorous research and development have been attempted on the above-mentioned organic photoconductive materials, and especially for phthalocyanine compounds, regarding their crystal form and electrophotographic characteristics,
Many reports have been made. Generally, phthalocyanine compounds show several crystal types depending on the difference in production method and treatment method, and it is known that the difference in crystal type has a great influence on the photoelectric conversion characteristics of the phthalocyanine compound. Regarding the crystal form of the phthalocyanine compound, for example, when looking at copper phthalocyanine, in addition to the stable β form, α, ε, π, x, ρ, γ, δ and other crystal forms are known. The mold is mechanical strain, sulfuric acid treatment,
It is known that they can be mutually transformed by an organic solvent treatment and a heat treatment (for example, US Pat. No. 2,7,7).
70,629, 3,160,635, 3,
708,292 and 3,357,989). Further, the metal-free phthalocyanine is known to have crystal forms such as α, β, γ and x. Furthermore, regarding chlorogallium phthalocyanine, the journal of the Electrophotographic Society,
26 (3), 240 (1987), a crystal form of chlorogallium phthalocyanine having a diffraction peak at a specific Bragg angle is described, but the crystal form is different from that of the present invention. There is no description about the application of. On the other hand, JP-A-59-44053,
The Shinkyo Giho CPM 81-69, 39 (1981), etc.
There is a report on application to electrophotography, and JP-A-1-221459 describes a chlorogallium phthalocyanine having a diffraction peak at a specific Bragg angle and an electrophotographic photoreceptor using the same.

[0003]

However, the previously proposed phthalocyanine compound and the above-mentioned chlorogallium phthalocyanine do not necessarily have sufficient photosensitivity, and the dispersibility in the binder resin or the dispersion liquid is not sufficient. There is also a problem in the stability of the image, and image defects such as fog and black spots are likely to occur, and therefore further improvement has been desired. The present invention has been made in view of the above circumstances of the conventional art. That is, an object of the present invention is to provide a method for stably producing a halogenated gallium phthalocyanine crystal having good characteristics with simple steps, low cost, and without requiring complicated equipment. . Another object of the present invention is to provide a method for producing a halogenated gallium phthalocyanine crystal exhibiting excellent electrophotographic properties with high sensitivity, dispersibility in a binder resin and excellent stability of a dispersion liquid. It is in.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have carried out dry pulverization of halogenated gallium phthalocyanine obtained by synthesis by stirring or mechanical strain in the presence of an inert gas. By doing
It was found that a gallium phthalocyanine halide crystal having high sensitivity and durability can be easily obtained as a photoconductive material. Furthermore, when this halogen gallium phthalocyanine crystal is used as a charge generating material for a photoconductor, electrophotography with excellent characteristics can be achieved. They have found that a photoconductor can be obtained, and completed the present invention. That is, the present invention relates to a method for producing a halogenated gallium phthalocyanine crystal, which comprises subjecting the gallium phthalocyanine halide to dry pulverization by stirring or mechanical strain in the presence of an inert gas to obtain CuKα characteristic X-rays. Bragg angle (2θ ± 0.2 °) of 7.5 in the diffraction spectrum
Has diffraction peaks at °, 16.7 °, 25.6 ° and 28.4 °, the half value width at the peak of Bragg angle 7.5 ° is 0.5 or more, and the peak at Bragg angle 7.5 °. To obtain a halogenated gallium phthalocyanine crystal having a peak intensity ratio at a Bragg angle of 28.4 ° in the range of 0.4 to 0.6.

The present invention will be described in detail below. The raw material halogenated gallium phthalocyanine is synthesized by a known method. For example, the phthalonitrile method in which phthalonitrile or diiminoisoindoline and a metal chloride are heated and melted or heated in the presence of an organic solvent, phthalic anhydride is heated and melted with urea and a metal chloride or heated in the presence of an organic solvent. By a method of reacting cyanobenzamide with a metal salt at a high temperature, a method of reacting dilithium phthalocyanine with a metal salt, or the like. As the raw material gallium phthalocyanine halide, the Bragg angle (2θ ±
Those having strong diffraction peaks at least at 11.0 °, 13.5 ° and 27.1 ° are preferably used. As the organic solvent used in the above synthesis method, α-chloronaphthalene, β-chloronaphthalene, methoxynaphthalene, diphenylethane, ethylene glycol, dialkyl ether, quinoline, sulfolane, dimethyl sulfoxide, dichlorobenzene, dichlorotoluene, etc. Active high boiling solvents are desirable.

The halogenated gallium phthalocyanine obtained by any of the above synthetic methods is dry-ground by stirring or mechanical strain in the presence of an inert gas. As a crushing device for stirring or mechanical straining force,
A vibration mill, automatic mortar, planetary ball mill, sand mill, attritor, ball mill or the like can be used. Among these pulverizers, the vibration mill is desirable because it can obtain high pulverization efficiency. In order to carry out dry pulverization in the presence of an inert gas, it is sufficient to fill the pot with the inert gas. As a result, aggregation of halogenated gallium phthalocyanine crystals and adhesion or coating to the inner wall of the pot can be prevented, and efficient pulverization can be performed, and pulverization can be performed until a smaller particle size is achieved. Therefore, the sensitivity of the gallium phthalocyanine halide crystal can be further increased. Further, since it is not affected by oxygen and moisture in the air, it is effective in preventing deterioration of the pigment such as oxidation and decomposition.

When the inert gas is not used, the gallium phthalocyanine halide crystals adhere to the inner wall of the pot or cause coating, so that the gallium phthalocyanine halide crystals aggregate, and a long crushing time is required. Further, it is not possible to reduce the grain size of the resulting gallium phthalocyanine halide crystals as compared with the case of using an inert gas, and as a result, the sensitivity when using it as an electrophotographic photosensitive material becomes low. . Further, since aggregates of gallium phthalocyanine halide crystals are likely to remain, black spots, white spots, etc. occur when the photoconductor is manufactured, which adversely affects image quality. Examples of the inert gas used in the present invention include helium of Group 0 of the periodic table,
Besides neon, argon, krypton, xenon, radon, nitrogen and the like can be used, and these can be used alone or in combination. In the present invention, when the dry pulverization is performed as described above, the obtained gallium gallium phthalocyanine crystal has an average particle size of 0.01 to 0.20 μm.
It is preferable to adjust the crushing time so as to obtain m. If the average particle size is larger than 0.20 μm, the sensitivity becomes insufficient, and if it is made smaller than 0.01 μm,
Not very efficient as it requires very long milling
Contamination due to abrasion of the pot and the crushed media increases, resulting in image quality defects, which is not preferable.

The gallium phthalocyanine halide crystal obtained as described above has a Bragg angle (2θ ± 0.2 °) of at least 7.5 with respect to CuKα characteristic X-rays.
It has major diffraction peaks at 0 °, 16.7 °, 25.6 ° and 28.4 °, and the Bragg angle 7.
The half width at the peak of 5 ° is 0.5 or more, and the Bragg angle 2 with respect to the peak at the Bragg angle of 7.5 ° is 2
The peak intensity ratio at 8.4 ° is 0.4 to 0.6. The halogenated gallium phthalocyanine crystal obtained by the above processing method of the present invention is useful as a charge generating material in an electrophotographic photoreceptor.

Next, an electrophotographic photosensitive member using the halogenated gallium phthalocyanine crystal produced according to the present invention will be described. The electrophotographic photosensitive member may have a single-layer photosensitive layer, or may have a laminated structure in which a charge-generating layer and a charge-transporting layer are functionally separated. In the case of an electrophotographic photoreceptor having a laminated structure, a photosensitive layer in which at least a charge generation layer and a charge transport layer are laminated is provided on a conductive support, and the order of lamination is whichever is on the support side. May be. As the conductive support, any material can be used as long as it is used in an electrophotographic photoreceptor.
Further, if necessary, the surface of the conductive support can be subjected to various treatments within a range that does not affect the image quality. For example, surface anodizing treatment, surface roughening treatment by liquid honing, chemical treatment, coloring treatment and the like can be performed.

The charge generating layer is composed of the gallium phthalocyanine halide crystal produced as described above and a suitable binder resin. The binder resin may not be used. As the charge generating material, other known charge generating materials may be used in combination with the gallium halide phthalocyanine crystal. On the other hand, as the binder resin, any known resin can be used. Examples thereof include polycarbonate, polystyrene, polyester, methacrylic acid ester polymer, polyvinyl butyral, polyacetal, vinyl acetate polymer, vinyl chloride-vinyl acetate copolymer, cellulose ester, cellulose ether, polybutadiene, polyurethane, and epoxy resin. The compounding ratio of the charge generating material and the binder resin is 40: 1 to 1: 4, preferably 20: 1 to 1: 2. When the ratio of the charge generating material is too high, the stability of the coating solution is lowered, and when it is too low, the sensitivity is lowered, so that the above range is preferable. The charge generation layer can be formed by dispersing the halogenated gallium phthalocyanine crystal in an organic solvent solution of a binder resin and applying the dispersed solution. As the organic solvent, methanol, ethanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, benzene, Toluene, xylene, chlorobenzene,
Examples thereof include organic solvents such as dimethylformamide and dimethylacetamide, or mixed solvents thereof. As a dispersing means, a method such as a sand mill, a colloid mill, an attritor, a ball mill, a dyno mill, a co-ball mill or a roll mill can be used. As a coating method, a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, a curtain coating method, or the like can be used. The thickness of the charge generation layer is 0.01 to 5 μm.
m, preferably about 0.03 to 2 μm.

The charge transport layer is composed of a charge transport material and a film-forming resin.
N'-diphenyl-N, N'-bis- (m-tolyl) benzidine, N, N'-bis- (p-tolyl) -N, N '
-Bis- (p-ethylphenyl) -3,3'-dimethylbenzidine, 4-diethylaminobenzaldehyde-
Any known compounds such as 2,2-diphenylhydrazone and p- (2,2-diphenylvinyl) -N, N'-diphenylaniline can be used. Examples of the film-forming resin include polycarbonate, polyarylate, polystyrene, polyester, styrene-acrylonitrile copolymer, polysulfone, polymethacrylic acid ester, styrene-methacrylic acid ester copolymer, and polyolefin. Among these, polycarbonate is preferable in terms of durability. The compounding ratio (weight) of the charge transport material and the film-forming resin is 5: 1 to 1: 5, preferably 3: 1 to 1: 3. If the ratio of the charge transport material is too high, the mechanical strength of the charge transport layer will decrease, and if it is too low, the sensitivity will decrease, so the above range is preferred. Further, when the charge transport material has a film forming property, the film forming resin can be omitted. The charge-transporting layer is formed by dissolving the charge-transporting material and the film-forming resin in a suitable solvent and applying the solution.
The thickness is preferably 5 to 50 μm, and more preferably 10 to 40 μm. As a coating method for these photosensitive layers, any of the above-mentioned methods can be used.

When the photosensitive layer has a single layer structure, the photosensitive layer is composed of a photoconductive layer containing the above-mentioned gallium phthalocyanine halide crystal and a charge transport material in a film forming resin.
Here, as the charge-transporting material, any known material can be used, and as the film-forming resin, the same material as described above is used, and the photosensitive layer is formed by any one of the above-mentioned coating methods. To be done. In that case, the compounding ratio (weight) of the charge transport material and the film-forming resin is 1:20 to 5: 1, and the compounding ratio (weight) of the gallium phthalocyanine halide crystal and the charge transport material is 1:10. It is preferably set to about 10: 1. Further, the electrophotographic photoreceptor may be provided with an undercoat layer between the photosensitive layer and the conductive support, if necessary. The subbing layer is effective for preventing unnecessary injection of charges from the support, and has an effect of improving the charging property of the photoconductor. Further, it also has the function of improving the adhesiveness between the photosensitive layer and the support. Further, the electrophotographic photoreceptor may be provided with a protective layer on the photosensitive layer in order to improve printing durability. The electrophotographic photosensitive member using the halogenated gallium phthalocyanine crystal produced by the present invention is effectively used in an electrophotographic copying machine, and further, a laser beam printer, an LED printer, a CRT printer,
It can be applied to a micro film reader, plain paper FAX, electrophotographic plate making system, and the like.

[0013]

The present invention will be described in more detail with reference to the following examples. In the examples, "part" means "part by weight". Synthesis Example (Synthesis of chlorogallium phthalocyanine) 30 parts of 1,3-diiminoisoindoline (parts by weight, the same applies hereinafter) and 9.1 parts of gallium trichloride were placed in 230 parts of quinoline and reacted at 200 ° C. for 4 hours. After that, the product was filtered off, washed with N, N-dimethylformamide and methanol, and then the wet cake was dried to obtain 28 parts of crystals of chlorogallium phthalocyanine. The powder X-ray diffraction pattern of the obtained chlorogallium phthalocyanine crystal is shown in FIG. The elemental analysis values were as follows. CHNCl theoretical value% 62.22 2.61 18.14 5.74 actual value% 62.18 2.67 18.02 5.75 The average particle size of the chlorogallium phthalocyanine crystal at this time was determined by a laser diffraction scattering method. When measured with a particle size distribution measuring device (LA700, manufactured by Horiba, Ltd.), it is 20.0μ.
It was m.

Example 1 5 parts of the chlorogallium phthalocyanine crystal obtained in the above synthesis example was placed in an alumina pot together with 25 parts of alumina beads, filled with nitrogen gas and sealed. Attach this to a vibration mill (MB-1 type, manufactured by Chuo Kakoki Co., Ltd.),
Milled for 100 hours. A powder X-ray diffraction diagram of the obtained chlorogallium phthalocyanine crystal is shown in FIG. 1, a spectrum spectrum diagram is shown in FIG. 2, and an infrared absorption spectrum diagram is shown in FIG. From the measurement result of the powder X-ray diffraction, the half width at the peak of the Bragg angle of 7.5 ° is 0.59, and the peak intensity ratio of the Bragg angle of 28.4 ° to the peak of the Bragg angle of 7.5 ° is 0.58. It was confirmed. The average particle size of the obtained chlorogallium phthalocyanine crystal was measured and found to be 0.15 μm.

Example 2 5 parts of the chlorogallium phthalocyanine crystal obtained in the above-mentioned synthesis example was placed in a glass ball mill together with 30 parts of glass beads, filled with argon gas and sealed. This was set on a ball mill stand and pulverized for 120 hours. The powder X-ray diffraction pattern of the obtained chlorogallium phthalocyanine crystal showed a spectrum similar to that of FIG. At this time, the half width at the peak of Bragg angle of 7.5 ° is 0.5.
4, the peak intensity ratio of the Bragg angle of 28.4 ° to the Bragg angle of 7.5 ° was 0.43. The average particle size of the obtained chlorogallium phthalocyanine crystal was measured and found to be 0.18 μm.

Comparative Example 1 5 parts of the chlorogallium phthalocyanine crystal obtained in the above synthesis example was placed in an alumina pot together with 25 parts of alumina beads and sealed as it was without being filled with an inert gas. This was mounted on a vibration mill and pulverized for 100 hours. At that time, a large amount of chlorogallium phthalocyanine crystal aggregates were observed in the pot. The powder X-ray diffraction pattern of the obtained chlorogallium phthalocyanine crystal is shown in FIG. At this time, the half value width at the peak of the Bragg angle of 7.5 ° is 0.
26, the peak intensity ratio at the Bragg angle of 28.4 ° to the peak at the Bragg angle of 7.5 ° was 0.20. The average particle size of the chlorogallium phthalocyanine crystal was measured and found to be 0.27 μm.

Comparative Example 2 5 parts of the chlorogallium phthalocyanine crystal obtained in the above-mentioned synthesis example was put into a glass ball mill together with 30 parts of glass beads and sealed as it was without being filled with an inert gas. This was set on a ball mill stand and pulverized for 120 hours. At that time, a large amount of chlorogallium phthalocyanine crystal aggregates were observed in the pot. The powder X-ray diffraction pattern of the obtained chlorogallium phthalocyanine crystal showed the same spectrum as in FIG. Bragg angle 7.5 at this time
The full width at half maximum at the peak of ° was 0.31, and the peak intensity ratio at the Bragg angle of 28.4 ° to the peak at the Bragg angle of 7.5 ° was 0.25. The average particle size of the obtained chlorogallium phthalocyanine crystal was measured and found to be 0.35 μm.

Application Example 1 First, wet honing treatment of an aluminum pipe was performed as follows. A 40 mmφ × 319 mm mirror surface aluminum pipe was prepared, and 10 kg of an abrasive (Greendesic GC # 400, Showa Denko KK) was suspended in 40 liters of water using a liquid honing device, and the suspension was pumped to 6 liters. Liquid is sent to the gun at a flow rate of liter / minute, spraying speed is 60 mm / minute, air pressure is 0.85 kgf / cm ^2.
Then, the aluminum pipe was moved in the axial direction while being rotated at 120 rpm, and the wet honing treatment was performed. The center line average roughness Ra at this time was 0.16 μm.
Next, polyvinyl butyral resin (S-REC BM-
8 parts of S, Sekisui Chemical Co., Ltd.) was added to 152 parts of n-butyl alcohol and dissolved by stirring to prepare a 5 wt% polyvinyl butyral solution. Next, 100 parts of a 50% toluene solution of tributoxyzirconium acetylacetonate (ZC540, manufactured by Matsumoto Trading Co., Ltd.), 10 parts of γ-aminopropyltriethoxysilane (A1100, manufactured by Nippon Unicar Co., Ltd.) and n. -Butyl alcohol 13
The solution obtained by mixing 0 parts was added to the above-mentioned polyvinyl butyral solution and stirred with a stirrer to prepare a coating liquid for forming an undercoat layer. This coating solution was applied onto an aluminum pipe by dip coating and dried by heating at 165 ° C. for 10 minutes to give a film thickness of 1.
An undercoat layer of 0 μm was formed. On the other hand, polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.)
To a solution prepared by dissolving 3 parts of 100 parts of a mixed solution of xylene / n-butyl acetate = 1/5 in advance, 3 parts of the chlorogallium phthalocyanine crystal obtained in Example 1 was added, and the mixture was dispersed in a sand mill for 24 hours to obtain the above xylene. / Diluted with n-butyl acetate mixed solution to prepare a charge generation layer forming coating solution having a solid content concentration of 3.0% by weight. The obtained coating liquid was applied onto the undercoat layer with a ring coater and dried by heating at 100 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.20 μm. A charge transport layer was formed on the formed charge generation layer. That is, N. N'-bis- (p-tolyl) -N. N '
Using 4 parts of -bis- (p-ethylphenyl) -3,3'-dimethylbenzidine as a charge transport material, 6 parts of polycarbonate Z resin and 40 parts of monochlorobenzene, the resulting solution was dissolved by a dip coating device. Coating on the charge generation layer, heating and drying at 120 ° C. for 60 minutes, film thickness 2
A charge transport layer having a thickness of 0 μm was formed to prepare an electrophotographic photoreceptor.

Application Example 2 An electrophotographic photosensitive member was prepared in the same manner as in Application Example 1 except that the chlorogallium phthalocyanine crystal obtained in Example 2 was used as the charge generating material.

Reference Example 1 An electrophotographic photosensitive member was prepared in the same manner as in Application Example 1 except that the chlorogallium phthalocyanine crystal obtained in Comparative Example 1 was used as the charge generating material. Reference Example 2 An electrophotographic photosensitive member was produced in the same manner as in Application Example 1 except that the chlorogallium phthalocyanine crystal obtained in Comparative Example 2 was used as the charge generation material. Reference Example 3 An electrophotographic photoreceptor was prepared in the same manner as in Application Example 1 except that the chlorogallium phthalocyanine obtained in Synthesis Example was used as the charge generation material.

Using a laser printer remodeling scanner (XP-11 remodeling machine, manufactured by Fuji Xerox Co., Ltd.) on these electrophotographic photoreceptors, the grid applied voltage-at 20 ° C. and 50% RH was used. Charged with a 600 V scorotron charger (A), and using a 780 nm semiconductor laser to irradiate 10.0 erg / cm ² of light to discharge for 1 second (B), and after 3 seconds, 50 erg / cm.
The potential of each part was measured by the process (C) of erasing the red LED light of No. ² to remove the electric charge. The higher the potential VH in (A), the higher the receptive potential of the photoconductor, and thus the higher the contrast, and the lower the potential VL in (B), the higher the sensitivity, and the lower the potential in (C) VRP. It can be said to be a photoconductor with little residual potential, image memory and less fog.
Further, the potential of each part after charging and exposure was repeated 5000 times was also measured. Furthermore, for these electrophotographic photoreceptors,
The image quality was evaluated using a laser printer (XP-11, manufactured by Fuji Xerox Co., Ltd.) under the environment of 30 ° C. and 85% RH. Table 1 regarding the charge generation materials used
Table 2 shows the results of the above measurement and evaluation.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

EFFECTS OF THE INVENTION Since the present invention has the above-mentioned constitution, the process is simple, complicated equipment is not required, cost can be reduced, and a halogenated gallium phthalocyanine crystal having good characteristics can be stabilized. There is an effect that can be obtained. The halogenated gallium phthalocyanine crystal produced according to the present invention has excellent electrophotographic characteristics and is useful as a charge generating material, and an electrophotographic photoreceptor using the same exhibits high sensitivity and good electrophotographic characteristics. It also has excellent image quality characteristics without fog or black spots.

[Brief description of drawings]

FIG. 1 shows a powder X-ray diffraction diagram of a chlorogallium phthalocyanine crystal obtained in Example 1.

2 is a spectroscopic spectrum diagram of the chlorogallium phthalocyanine crystal obtained in Example 1. FIG.

3 shows an infrared absorption spectrum of the chlorogallium phthalocyanine crystal obtained in Example 1. FIG.

FIG. 4 shows a powder X-ray diffraction diagram of a chlorogallium phthalocyanine crystal obtained in a synthesis example.

5 shows a powder X-ray diffraction pattern of the chlorogallium phthalocyanine crystal obtained in Comparative Example 1. FIG.

Claims (1)

[Claims] 1. A Bragg angle (2θ ± 0.2 °) of 7 in a CuKα characteristic X-ray diffraction spectrum is obtained by subjecting a gallium phthalocyanine halide to dry grinding by stirring or mechanical strain in the presence of an inert gas. It has diffraction peaks at 0.5 °, 16.7 °, 25.6 °, and 28.4 °, the half-value width at the Bragg angle of 7.5 ° is 0.5 or more, and the Bragg angle of 7.5 °.
A method for producing a gallium phthalocyanine halide crystal, which comprises obtaining a gallium phthalocyanine halide crystal having a peak intensity ratio of a Bragg angle of 28.4 ° with respect to the peak of 0.4 to 0.6.