KR20110134478A - Process of preparing copper phthalocyanine particles exhibiting alpha crystallographic form - Google Patents

Abstract

Provided is a process for preparing copper phthalocyanine (CuPc) particles exhibiting an alpha crystallographic form, which method comprises: (a) adding crude copper phthalocyanine particles containing at least 50% by weight of particles exhibiting a beta crystallographic form to one or more functional groups; Dissolving at least a portion of the crude CuPc in acid by mixing with an acid in the presence of CuPc particles substituted by; And (b) precipitating at least a portion of the dissolved CuPc in the medium. By adding CuPc derivatives to the acid-paste step for the alpha-crystalline form of CuPc phase inversion in the beta crystallographic form, the overall process time for producing epsilon-CuPc-based blue pigments, as well as the performance of the color filter pigments containing them It can be improved.

Description

The manufacturing method of the copper phthalocyanine particle which shows an alpha crystalline form {PROCESS OF PREPARING COPPER PHTHALOCYANINE PARTICLES EXHIBITING ALPHA CRYSTALLOGRAPHIC FORM}

This application claims the benefit of European Patent Application No. 09155545.8, filed March 18, 2009, which is incorporated herein by reference.

FIELD OF THE INVENTION The present invention generally relates to copper phthalocyanine (CuPc) and methods of making the same. In particular, the present invention relates to a new efficient and economical method for producing CuPc pigments with improved dispersibility for color filters used to display color images and CuPc pigments produced therefrom.

Phthalocyanine-based organic pigments are excellent in terms of fixability and performance. Therefore it is usually used as a blue colorant for paints or plastic materials. Among the pigments, copper phthalocyanine is more preferable because it is very stable and has various fixability. In addition, copper phthalocyanine has several crystal forms. Among these crystalline forms, the crystalline forms known for practical use include the alpha-, beta- and epsilon-crystalline forms of copper phthalocyanine. It is common practice to use beta crystalline forms to express greenish blue and alpha crystalline forms to express reddish blue. In addition, epsilon crystalline forms are used when a reddish blue color is required than produced using alpha crystalline forms.

Various methods have been proposed to produce phthalocyanine pigments with each crystalline form. A typical method for preparing epsilon crystalline copper phthalocyanine is the solvent salt milling method, in which copper phthalocyanine particles representing the alpha crystalline form and copper phthalocyanine particles representing the epsilon crystalline form are milled in an organic solvent. Regarding a method for producing alpha-type copper phthalocyanine from beta type, a coloring method using sulfuric acid which is one of mineral acids is known in the art. That is, the acid-paste method (a method of treating crude (crude) copper phthalocyanine when dissolved in a large amount of concentrated sulfuric acid) and the acid-slurry method (a large amount of sulfuric acid with an insufficient concentration to dissolve the pigment to form a sulfate) Method for treating crude copper phthalocyanine).

The products obtained by the acid-paste method or the acid-slurry method generally have low crystal quality and are prepared in the form of aggregates which do not exhibit the desired performance characteristics. In order to achieve optimum application properties, so-called finishes are carried out, for example in solvents, with the addition of surface-active agents. In addition, in order to improve the performance characteristics, it has been proposed in the art to produce pigment preparations using phthalocyanine derivatives substituted by polar groups such as sulfuric acid, carboxylic acid or sulfonamide groups.

For example, US Pat. No. 3024247 discloses chlorinating phthalocyanine to produce an amorphous phthalocyanine colorant, followed by acid-pasting phthalocyanine and mixing phthalocyanine monosulfonic acid with an acid-pasted aqueous slurry. The general method of making is described.

U. S. Patent No. 5534055 also discloses a process for preparing alpha phase metal phthalocyanine pigments from crude metal phthalocyanine pigments. Such methods include: (a) acid-pasting or acid swelling the crude metal phthalocyanine pigment; (b) dry milling the acid-paste or acid-swelled metal phthalocyanine pigment; (c) finishing the milled metal phthalocyanine pigment by thoroughly mixing the milled metal phthalocyanine pigment with the finishing solvent mixture; And (d) separating the alpha phase metal phthalocyanine pigment. After acid-pasting beta CuPc to produce precipitated CuPc, dry milling the precipitated CuPc with a stabilizer to produce alpha CuPc is performed in the presence of a sulfonamide derivative of CuPc as a stabilizer. .

U.S. Patent No. 6031030 also discloses a process for preparing a paint concentrate, the method comprising: (a) milling or acid-pasting crude metal phthalocyanine to reduce the particle size to form a modified crude metal phthalocyanine; And (b) kneading the mixture of the modified crude metal phthalocyanine and the paint carrier comprising at least one solvent to prepare a paint concentrate containing metal phthaloisin in the form of pigments dispersed in the paint carrier. . It is described to mill the crude CuPc in the presence of a fluidizing agent such as sulfonated CuPc to produce alpha CuPc.

However, the above-mentioned methods for producing alpha crystalline copper phthalocyanine produce very large particles, which is problematic in that a considerable time is required to reduce the particle size and phase-shift to epsilon in a subsequent kneading step. In addition, the performance (eg, contrast ratio) of color filter pigments prepared by the acid-paste process of the prior art has certain disadvantages due to the low dispersibility of the pigments produced. Therefore, there has been a strong desire in the art to develop an efficient alpha crystalline copper phthalocyanine production method that is suitable for carrying out the kneading step in a more efficient manner and improves the performance of the final pigment for color filters.

In order to solve the problems with the existing manufacturing methods (e.g., long process time, relatively low dispersibility, contrast ratio, etc.) of the manufactured color filter pigments, the inventors of the present invention have a phase from beta crystallographic form to alpha crystallographic form. It has been found that the addition of some additives, such as CuPc derivatives, to the acid-paste step for conversion can improve the performance of the final color filter pigments and the overall process time for producing blue pigments.

1 is a transmission electron microscope (TEM) image of copper phthalocyanine particles prepared by the method according to Example 1 and exhibiting an alpha crystallographic phase.
FIG. 2 is a TEM image of copper phthalocyanine particles prepared by the method according to Example 2 and exhibiting an alpha crystallographic phase.
3 is a TEM image of copper phthalocyanine particles prepared by the method according to Comparative Example 1 and showing an alpha crystallographic phase.

Hereinafter, the present invention will be described in detail.

It is an object of the present invention to prepare CuPc particles having alpha crystalline form as intermediates for producing copper phthalocyanine particles having epsilon form, and since the particle size of the particles thus prepared is very small and dispersibility is improved, The performance of the generated color filter is improved. Another object of the present invention is to provide a method for preparing alpha-type copper phthalocyanine having a reduced particle size, which shortens the time required to obtain epsilon crystalline copper phthalocyanine with high crystallographic purity. In this regard, the present invention seeks to develop a new, more efficient method for producing copper phthalocyanine that satisfies the aforementioned features.

Acid-paste operation refers to an operation in which at least a portion of the crude CuPc is dissolved in a suitable acid (dissolution step) and the dissolved CuPc is precipitated in a suitable medium (precipitation step).

In the dissolution step, preference is given to using sulfuric acid, chlorosulfonic acid and polyphosphoric acid, in particular inorganic acids such as concentrated sulfuric acid or sulfuric acid monohydrate. These acids are usually used in the form of an aqueous solution. If sulfuric acid is used, the concentration of sulfuric acid should be at least 90% by weight, preferably at least 95% by weight. Preference is given to using sulfuric acid concentrated at about 96% by weight. There is no limitation on the amount of aqueous solution used in the dissolution step. However, for economic reasons, the concentration of the ground crude copper phthalocyanine can be maintained within a range that allows the mixture to be prepared to be agitated or pulverized and incorporated. Specifically, the amount of the aqueous solution used is 2 to 20 times preferably 5 to 15 times based on the weight of the crude pigment. The temperature at which the dissolution step is carried out is usually 0 to 100 ° C., preferably 5 to 60 ° C., more preferably 10 to 40 ° C. (eg room temperature). The time for which the dissolution step is carried out is generally 30 minutes to 5 hours, in particular 1 hour to 3 hours, with about 2 hours being suitable.

In the precipitation step, the precipitation medium used may consist of water, an organic solvent or a mixture thereof, preferably water, in particular distilled water. The ratio of the precipitation medium to the acid / CuPc mixture resulting from the dissolution step is generally from 1 to 50, preferably from 5 to 20 (eg about 10). The temperature at which the precipitation step is carried out is from 0 to 100 ° C., in particular from 5 to 60 ° C., more specifically from 10 to 50 ° C., and working at room temperature is also suitable.

When the acid / CuPc mixture resulting from the dissolution step is added to the precipitation medium, at a rate of 1 to 100 g of acid / CuPc mixture per kg of precipitation medium within 1 minute to 1 hour, preferably per kg of precipitation medium within 5 to 30 minutes It is usually added at a rate of 1 to 100 g of the acid / CuPc mixture, for example at a rate of 10 g of the acid / CuPc mixture per kg of precipitation medium within about 10 minutes. Precipitation can occur under turbulent flow conditions.

Next, the mixture resulting from the dissolution step is filtered, washed with water and dried. Preferably, the washing operation is performed with distilled water, more preferably with distilled water having a pH of 6 or more. Any filtration or drying method known in the art can be used for the filtration step and the drying step. For example, the filtration step may be carried out using a gravity system, and the drying step may be carried out in an oven, for example at a temperature of 120 ° C.

Such acid-paste manipulation is described, for example, in Ullman's Encyclopedia of Industrial Chemistry, Fifth Completely Revised Edition, 1992, Volume A20, pp. 225-226.

In a first embodiment of the invention, copper phthalocyanine (CuPc) particles exhibiting alpha crystalline form are prepared by the following steps:

(a) dissolving at least a portion of the crude CuPc in an acid by mixing the crude copper phthalocyanine particles containing at least 50% by weight of particles exhibiting a beta crystallographic form with an acid in the presence of CuPc particles substituted by one or more functional groups. step; And

(b) precipitating at least a portion of the dissolved CuPc in the medium. According to a particular embodiment, the average number of functional groups per CuPc molecule is between 0.5 and 2, preferably about 1.

In the dissolution step (a), it is preferred to dissolve the crude CuPc completely in acid. In said dissolving step (a), the weight ratio of copper phthalocyanine substituted by one or more functional groups to crude copper phthalocyanine is generally at least 0.01, preferably at least 0.03, more preferably at least 0.05. This ratio is generally at most 0.3, preferably at most 0.2, more preferably at most 0.15.

According to some specific embodiments, the functional group is at least one selected from -SO ₃ M, -SO ₂ NR ₁ R _2, and -R ₃ -NR ₄ R ₅ , wherein R ₁ and R ₂ are independent of each other, May be selected from the group consisting of hydrogen, alkyl, alkenyl, aryl or cycloalkyl; M can be a proton, ammonium cation or metal cation; R ₃ is a single bond, alkylene or arylene, wherein the alkylene and arylene may be substituted by one or more substituents; R ₄ and R ₅ are independent of each other and may be hydrogen, alkyl, alkenyl, aryl or cycloalkyl or together form a condensed structure containing one or more of —CO—, —SO ₂ — and —N═N— Can be formed.

중에서 선택되는 하나 이상의 작용기에 의해 치환될 수 있으며, 가장 구체적으로, 작용기는 -S0₃H,

또는 이들의 혼합물일 수 있다. 다른 구현예에 의하면, 작용기에 의해 치환된 CuPc 입자는 상이한 작용기에 의해 치환된 CuPc 2종 이상의 혼합물, 예를 들면, -SO₃H에 의해 치환된 CuPc 입자 및

에 의해 치환된 CuPc 입자의 혼합물이다.More specifically, the copper phthalocyanine particles are -S0 ₃ H, -SO ₂ NHR ₁ Wherein R ₁ is hydrogen, alkyl, alkenyl, aryl or cycloalkyl; and

It may be substituted by one or more functional groups selected from, and most specifically, the functional group is -S0 ₃ H,

Or mixtures thereof. According to another embodiment, the CuPc particles substituted by a functional group are a mixture of two or more types of CuPc substituted by different functional groups, for example CuPc particles substituted by -SO ₃ H and

It is a mixture of CuPc particles substituted by.

In another embodiment, the copper phthalocyanine particles exhibiting an ε-crystallographic form to be used as blue pigments comprise copper phthalocyanine particles exhibiting an alpha crystalline form prepared according to the first embodiment in the presence of an organic liquid at a temperature of at least 50 ° C. It is prepared by heating and optionally milling in the presence of beads. By milling operation is meant a process in which solids are treated by attrition, grinding, etc. to achieve a reduction in particle size as defined herein. Dry milling refers to a process that is substantially free of liquid while processing solids by crushing, grinding, etc. to achieve particle size reduction as defined herein. However, a small amount of solvent may be added.

In another embodiment, crystal phase inversion and size reduction may occur simultaneously. In this embodiment, the kneading step is carried out in the presence of at least one liquid and at least one inorganic salt. Preferably, the kneading step is carried out under temperature conditions which indicate a temperature profile over time in which at least two of the derivatives of temperature (dT / dt) with respect to time are zero. Two temperature values with zero derivatives differ by more than 10 ° C. According to another embodiment, the kneading step is performed under a temperature distribution that is constantly changing or at least once (stepping).

Specific conditions of the kneading or heating step (eg, time, organic liquid, liquid, beads, inorganic salts, etc.) are described in PCT applications PCT / EP2008 / 065448 and PCT / EP2008 / 062266, all of which are herein incorporated in their entirety. Incorporated by reference.

By adding CuPc derivatives in the acid-paste step, the process of the invention can produce alpha crystalline copper phthalocyanine having a small average primary particle size of 140 nm or less, preferably 100 nm or less. In addition, the addition of such CuPc derivatives in the acid-paste process improves the dispersibility of the pigment particles, which improves the contrast ratio of the color filter produced from the pigment particles.

(식 중 R₁은 수소, 알킬, 알케닐, 아릴 또는 사이클로알킬이며, 바람직하게는

임) 중에서 선택되는 하나 이상의 작용기에 의해 치환된 CuPc 입자는 용해 단계(a)에 존재할 수 있는 한편, -SO₃H에 의해 치환된 CuPc 입자가 혼련 또는 가열 단계 도중에, 특히는 혼련 단계 도중에 추가로 첨가되어도 된다.In another embodiment, CuPc particles substituted by one or more functional groups are added during the kneading or heating step as well as during the acid-paste step. For example, -S0 ₃ H, -SO ₂ NHR ₁ and

Wherein R ₁ is hydrogen, alkyl, alkenyl, aryl or cycloalkyl, preferably

CuPc particles substituted by one or more functional groups selected from the group may be present in the dissolution step (a), while the CuPc particles substituted by -SO ₃ H are further added during the kneading or heating step, in particular during the kneading step. It may be added.

The invention also relates to alpha crystalline copper phthalocyanine particles obtainable according to the process of the invention. This embodiment relates to the use of copper phthalocyanine particles obtainable according to the process of the invention for the production of copper phthalocyanine particles exhibiting epsilon crystallographic form. It also relates to a color filter comprising copper phthalocyanine particles exhibiting epsilon crystallographic form obtainable by the process of the invention.

Example

Example  1 (beta- CuPc Wow Phthaloimidomethyl - CuPc Mountain- Paste )

20 g of crude copper phthalocyanine and 1 g of phthalimidomethyl (PIM) -substituted copper phthalocyanine were added to 200 g of 95 wt% sulfuric acid in a 1 L glass beaker. In addition, the resulting mixture was stirred for 2 hours at 30 ° C. with a stirring impeller (Teflon centrifuge, rotational speed: 300 rpm) to prepare a sulfate suspension or sulfate solution in sulfuric acid. The suspension or solution was poured into 2 L of water to give alpha crystalline copper phthalocyanine, then washed twice with distilled water and dried under hot air. After grinding the resulting solid, alpha crystalline copper phthalocyanine was obtained almost quantitatively in terms of crystallographic yield, which was confirmed by XRD studies.

Example  2 (beta) CuPc Wow Monosulfonate - CuPc Mountain- Paste )

Copper phthalocyanine particles exhibiting the alpha crystallographic form were obtained in the same manner as in Example 1 except that 1 g of monosulfonate-CuPc particles was added instead of phthalimidomethyl-CuPc particles.

Example  3 (beta) CuPc Wow Monosulfonate - CuPc Wow Phthaloimidomethyl - CuPc Mountain- Paste )

Alpha crystals in the same manner as in Example 1, except that 0.5 g of monosulfonate-CuPc particles and 0.5 g of phthalimidomethyl-CuPc particles were added instead of 1 g of phthalimidomethyl-CuPc particles. Copper phthalocyanine particles are obtained which show a morphological form.

Comparative example  1 (beta) CuPc Only mountains Paste )

In the same manner as in Example 1, except that no CuPc derivative was added, copper phthalocyanine particles showing an alpha crystallographic form were obtained. Several dried samples of copper phthalocyanine particles exhibiting alpha crystallographic morphology were analyzed by transmission electron microscopy (TEM) to find that their average particle size was greater than 140 μm (FIG. 3).

As shown in the TEM images of FIGS. 1 to 3, the average particle size of the alpha-CuPc particles produced using the method of the present invention (Examples 1 and 2) is about 97 nm in the conventional acid-paste process ( It is considerably smaller than the average particle size (ie greater than 140 μm) of the alpha-CuPc particles produced by Comparative Example 1). By reducing the size of the alpha-CuPc particles to be kneaded, the kneading time can be significantly shortened while the dispersibility of the resulting particles can be improved.

Example  4 (in alpha crystalline form Epsilon  Copper as crystalline form Phthalocyanine  decision Phase change )

To a laboratory scale kneader, 50 g of copper phthalocyanine particles showing alpha crystallographic form and 12 g of epsilon type copper phthalocyanine obtained from Example 1 or 2 were added together with 80 g of diethylene glycol and 400 g of sodium chloride. This mixture was kneaded at 130 ° C. for 2 hours at a rotational speed of 50 rpm (first step), and then for 8 hours at 80 ° C. at the same rotational speed (second step). The particles obtained after the kneading operation were purified by filtration and dried at a temperature of 80 ° C. and a pressure of 10 ⁴ Pa.

Example  5 ( Monosulfonate - CuPc In alpha crystalline form in the presence of Epsilon  Copper as crystalline form Phthalocyanine  decision Phase change )

Copper phthalocyanine particles exhibiting epsilon crystallographic morphology were obtained from the alpha-CuPc obtained from Example 3 in the same manner as in Example 4. However, prior to the kneading step, instead of the first step, alpha crystalline copper phthalocyanine and epsilon copper phthalocyanine were treated in diethylene glycol for 2 hours at 130 ° C., and 6.2 g of MS-CuPc was added during the kneading step.

Example  6 ( Monosulfonate - CuPc In alpha crystalline form in the presence of Epsilon  Copper as crystalline form Phthalocyanine  decision Phase change )

Copper phthalocyanine particles exhibiting epsilon crystallographic morphology were obtained from the alpha-CuPc obtained from Example 1 in the same manner as in Example 4. However, prior to the kneading step, instead of the first step, alpha crystalline copper phthalocyanine and epsilon type copper phthalocyanine were treated in diethylene glycol for 2 hours at 130 ° C., and 6.2 g of MS-CuPc was added during the kneading step.

Example  7 ( Monosulfonate - CuPc In alpha crystalline form in the presence of Epsilon  Copper as crystalline form Phthalocyanine  decision Phase change )

In the same manner as in Example 4 except that 6.2 g of MS-CuPc was added during the kneading step, from the alpha-CuPc obtained from Example 1, copper phthalocyanine particles exhibiting epsilon crystallographic form were obtained.

Example  8 ( Cetyltrimethyl Ammonium Monosulfo CuPo From alpha crystalline form to epsilon crystalline form in the presence of copper Phthalocyanine  decision Phase change )

From the alpha-CuPc obtained from Example 1, copper phthalocyanine particles exhibiting epsilon crystallographic form were obtained in the same manner as in Example 4, except that 6.2 g of cetyltrimethyl ammonium monosulfo CuPc was added during the kneading step. Obtained.

Comparative example  2 ( PIM - CuPc  And Ms - CuPc While adding In alpha crystalline form Epsilon  Copper as crystalline form Phthalocyanine  decision Phase change )

From the alpha-CuPc obtained from Comparative Example 1, copper phthalocyanine particles exhibiting epsilon crystallographic form were obtained in the same manner as in Example 4 except that PIM-CuPc and MS-CuPc were added sequentially during the kneading step. Obtained.

Example  9. In the color filter  Particle test

Color filters were prepared using the epsilon-type copper phthalocyanine pigment particles prepared according to Examples 4 to 8 and Comparative Example 2 as pigments. The contrast ratio and luminance of the color filter thus prepared are summarized in Table 1 below. As shown in Table 1, these results compared with those of Comparative Example 2, Examples 4 to 8 resulted in an improvement in the contrast ratio by about 4 to 21%. Furthermore, when color filters were prepared from Example 5 (PIM-CuPc and MS-CuPc were added in the acid-paste step while MS-CuPc was further added in the kneading step), these color filters were prepared in Example 6 ( Only PIM-CuPc was added in the acid-paste step while MS-CuPc was added in the kneading step), resulting in improved contrast ratio and brightness. The color filter prepared from Example 7 (using MS-CuPc) also had improved results compared to the color filter prepared from Example 8 (using cetyltrimethyl ammonium monosulfo CuPc).

Contrast Ratio (a.u. *) Luminance (a.u.) Comparative Example 2 5630 Not measured Example 4 5850 Not measured Example 5 6815 18.44 Example 6 6625 18.27 Example 7 6815 18.20 Example 8 6673 18.19

* Arbitrary unit

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Accordingly, the present disclosure is intended to embrace all such modifications and variations that fall within the scope of the appended claims and their equivalents.

If the disclosure of any of the patent documents, patent applications and publications incorporated herein by reference is in conflict with the present invention to the extent that it can produce an ambiguous expression, the present invention prevails.

Claims (15)

(a) dissolving at least a portion of the crude CuPc in an acid by mixing crude copper phthalocyanine particles containing at least 50% by weight of particles exhibiting a beta crystallographic form with an acid in the presence of CuPc particles substituted by one or more functional groups. ; And
(b) precipitating at least a portion of the dissolved CuPc in the medium
Method of producing copper phthalocyanine (CuPc) particles exhibiting an alpha crystallographic form comprising a. The method of claim 1, wherein the acid is sulfuric acid at a concentration of at least one, preferably greater than 90% by weight, selected from the group consisting of sulfuric acid, chlorosulfonic acid and polyphosphoric acid. The method of claim 1 or 2, wherein the medium is one or more selected from water, organic solvents, or mixtures thereof. The method according to claim 1, wherein the average number of functional groups per molecule of CuPc is between 0.5 and 2, preferably about 1. 5. A copper phthalocyanine particle exhibiting an alpha crystallographic form produced by the method according to any one of claims 1 to 4, wherein at least two of the derivative (dT / dt) of temperature versus time is zero At least two temperatures associated with a temperature profile with a temperature profile of zero, comprising kneading under specified temperature conditions that differ by at least 10 ° C, wherein at least 50% by weight of the particles are liquid and one The manufacturing method of the copper phthalocyanine particle which shows the epsilon crystallographic form which shows an alpha crystallographic form in the presence of the above inorganic salt. A method for producing copper phthalocyanine (CuPc) particles exhibiting epsilon crystallographic form comprising a heating step of heating an alpha crystalline form prepared by the method according to claim 1 at a temperature of 50 ° C. or higher. The method of claim 5 or 6, wherein the CuPc particles substituted by one or more functional groups are further added during the kneading or heating step. The method according to any one of claims 1 to 7, wherein the functional group is at least one member selected from the group consisting of -SO ₃ M, -SO ₂ NR ₁ R ₂ and -R ₃ -NR ₄ R ₅ , R ₁ and R ₂ are each independently of each other hydrogen, alkyl, alkenyl, aryl or cycloalkyl; M is a proton, ammonium cation or metal cation; R ₃ is a single bond, alkylene or arylene, wherein the alkylene and arylene may be substituted by one or more substituents; R ₄ and R ₅ are independent of each other and are hydrogen, alkyl, alkenyl, aryl or cycloalkyl, or together form a condensed structure containing one or more of —CO—, —SO ₂ — and —N═N— To form. The compound of claim 8, wherein the functional group is -SO ₃ H, -SO ₂ NHR ₁ , wherein R ₁ is hydrogen, alkyl, alkenyl, aryl or cycloalkyl; or

How to be. The CuPc particles substituted by functional groups according to claim 8 or 9 are mixtures of two or more CuPc particles substituted by different functional groups, preferably CuPc particles substituted by -SO ₃ H and

And a mixture of CuPc particles substituted with. The method of claim 7, wherein

CuPc particles substituted by are present in step (a), and CuPc particles substituted by —SO ₃ H are further added during the kneading or heating step. Copper phthalocyanine particles exhibiting an alpha crystallographic form obtainable by the method according to any one of claims 1 to 4 and 8 to 10. The copper phthalocyanine particle of claim 12 which has an average particle size of 100 nm or less. Use of the copper phthalocyanine particles according to claim 12 or 13 for producing copper phthalocyanine particles exhibiting epsilon crystallographic form. Color filter comprising copper phthalocyanine particles exhibiting epsilon crystallographic form obtainable by the method according to any one of claims 5 to 7 and 11.

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