WO2010105982A2

WO2010105982A2 - Process of preparing copper phthalocyanine particles exhibiting alpha crystallographic form

Info

Publication number: WO2010105982A2
Application number: PCT/EP2010/053184
Authority: WO
Inventors: Hyunsu Lee; Jai Won Park; Kisuck Jung; Sangmin Han; Dongyoon Kim; Hyunsuk Jeong
Original assignee: Solvay Sa
Priority date: 2009-03-18
Filing date: 2010-03-12
Publication date: 2010-09-23
Also published as: TWI466956B; CN102356130A; CN102356130B; WO2010105982A3; JP2015143368A; JP2012520914A; TW201100497A; KR20110134478A

Abstract

There is provided a process of preparing copper phthalocyanine (CuPc) particles exhibiting an alpha crystallographic form, which comprises the following steps: (a) mixing crude copper phthalocyanine particles containing at least 50 wt % of particles exhibiting a beta crystallographic form with an acid in the presence of CuPc particles substituted by at least one functional group, such that at least part of the crude CuPc is dissolved in the acid; and (b) precipitating at least part of the dissolved CuPc in a medium. By adding CuPc derivatives in the acid-pasting step for the phase conversion from beta to alpha crystallographic type CuPc, the entire process time of producing blue pigments based on epsilon-CuPc, as well as the performance of the color filter pigment containing them, can be improved.

Description

Process of Preparing Copper Phthalocyanine Particles Exhibiting Alpha

Crystallographic Form

[0001] The present application claims the benefit of the European application no. 09155545.8 filed on March 18, 2009, herein incorporated by reference.

Technical Field

[0002] The present invention is generally related to copper phthalocyanine (CuPc) and processes of preparing the same. More particularly, the present invention is related to a new efficient and economical process of preparing CuPc pigments with better dispersibility for color filters, which are used for displaying colour images and the CuPc pigments prepared thereby.

Background Art

[0003] A phthalocyanine based organic pigment is excellent in terms of fastness and performance. Thus, it is typically employed as a blue colorant for paints or plastics. Among pigments, copper phthalocyanine is very stable and further desirable since it possesses a variety of fastness. Further, copper phthalocyanine has many crystal forms. Among such crystal forms, those known to have actual applications include alpha, beta and epsilon crystal forms of copper phthalocyanine. It is a common practice to use the beta crystal form to impart a greenish blue colour, while using the alpha crystal form to impart a reddish blue colour. Further, the epsilon crystal form is employed when a blue colour, which is more reddish than that produced using the alpha crystal form, is required.

[0004] Various methods have been proposed for producing a phthalocyanine pigment with each crystal form. A typical process of producing epsilon crystal form copper phthalocyanine is the solvent salt milling process, wherein copper phthalocyanine particles exhibiting alpha crystal form and copper phthalocyanine particles exhibiting epsilon crystal form are milled in an organic solvent. As to a process of preparing alpha form copper phthalocyanine from the beta form, pigmentation processes using sulfuric acid, which is one of the mineral acids, have been known in the art. That is, an acid pasting process (treating crude copper phthalocyanine when dissolved in a large amount of concentrated sulfuric acid) and an acid slurry process (treating crude copper phthalocyanine with a large amount of sulfuric acid having a concentration insufficient for dissolving the pigment to form a sulfate) are used.

[0005] The products obtained by the acid pasting or slurry process are generally of poor crystal quality and are produced in the form of agglomerates, which do not display the desired performance properties. In order to subsequently achieve optimum application properties, the so-called finish is carried out in, for example, solvents while adding surface-active agents. Further, to improve the performance properties, it has been proposed in the art to produce pigment preparations by using phthalocyanine derivatives substituted by polar groups such as sulfonic acid, carboxylic acid or sulfonamide groups.

[0006] For example, U.S. Patent No. US 3024247 describes a general process of acid-pasting phthalocyanines and blending a phthalocyanine monosulfonic acid with a water slurry of acid-pasted, after chlorinated phthalocyanines to produce non-crystallizing phthalocyanine coloring matters.

[0007] Further, U.S. Patent No. US 5534055 discloses a process of preparing alpha-phase metal phthalocyanine pigments from crude metal phthalocyanine pigments. Such a process comprises the following steps: (a) acid pasting or acid swelling a crude metal phthalocyanine pigment; (b) dry milling the acid-pasted or acid-swelled metal phthalocyanine pigment; (c) finishing the milled metal phthalocyanine pigment by thoroughly mixing the milled metal phthalocyanine pigment with a finishing solvent mixture; and (d) isolating the alpha-phase metal phthalocyanine pigment. After acid pasting beta CuPc to produce precipitated CuPc, dry milling of precipitated CuPc with stabilizer to produce alpha CuPc is conducted in the presence of sulfonamide derivative of CuPc as a stabilizer.

[0008] U.S. Patent No. US 6031030 also discloses a process of preparing a paint concentrate, which comprises the following steps: (a) milling or acid pasting a crude metal phthalocyanine to reduce the particles size thereof, thereby forming a modified crude metal phthalocyanine; and (b) kneading a mixture of the modified crude metal phthalocyanine together with a paint vehicle comprising one or more paint solvents to provide a paint concentrate containing the metal phthalocyanine in a pigmentary form dispersed in the paint vehicle. Milling crude CuPc in the presence of a fluidising agent such as a sulfonated CuPc is described to produce alpha CuPc.

[0009] However, the above-described methods of preparing alpha crystal form copper phthalocyanine have problems in that they produce very large particles, thereby requiring a significant amount of time to conduct particle size reduction and phase conversion into epsilon form in the subsequent kneading step. Further, the performance of color filter pigments (e.g., contrast ratio) prepared from the acid pasting method of the prior art has certain drawbacks due to the poor dispersibility of the resultant pigment. Thus, there has been a strong desire in the art to develop a method of effectively preparing alpha crystal form copper phthalocyanine, which is proper for conducting kneading in a more efficient manner, as well as to improve the performance of a final pigment for color filter.

Disclosure of Invention

[0010] In order to resolve the problems in the conventional preparation process (e.g., longer process time, relatively low dispersibility, contrast ratios from the resultant color filter pigment, etc.), the inventors of the present invention discovered that the performance of the final color filter pigment and the entire process time for producing blue pigments may be improved when some additives such as CuPc derivatives were added in the acid- pasting step for the phase conversion from beta to alpha crystallographic type.

[0011] Hereinafter, the present invention is described in detail.

[0012] Thus, the purpose of the present invention is to prepare, as an intermediate for producing copper phthalocyanine particles having epsilon form, CuPc particles having alpha crystal form, the particle size of which is very small and the dispersibility of which is better, thereby providing better performance of the color filter produced from the CuPc pigments. Further, it is another purpose of the present invention to provide a process of preparing alpha form copper phthalocyanine having a reduced particle size, which needs a shorter time to obtain the epsilon crystal form copper phthalocyanine with a high crystallographic purity. In this regard, the present invention is directed to developing a new and more efficient process of preparing copper phthalocyanine, which satisfies the above- mentioned features.

[0013] Acid pasting refers to the dissolution of at least part of the crude CuPc in suitable acids (dissolution step) and precipitation of the dissolved CuPc in suitable media (precipitation step).

[0014] In the dissolution step, preference is given to using inorganic acids such as sulfuric acid, chlorosulfonic acid and polyphosphoric acids, especially concentrated sulphuric acid or sulphuric acid monohydrate. The acids are usually used in the form of an aqueous solution. If sulfuric acid is used, then its concentration should be equal to or greater than 90% by weight, preferably equal to or greater than 95% by weight. It is preferable to use concentrated sulfuric acid at about 96% by weight. The amount of aqueous solution to be used in the dissolution step is not limited. However, for economic reasons, the concentration of ground crude copper phthalocyanine may be kept in such a range wherein the resulting mixture may be stirred or ground and incorporated. Specifically, the amount of aqueous solution used is 2 to 20 times, preferably 5 to 15 times, by weight based on crude pigment. The temperature of the dissolution step is usually from 0 to 100°C, preferably from 5 to 60°C, more preferably from 10 to 40°C, for example room temperature. The duration of the dissolution step is in general of from 30 minutes to 5 hours, in particular from 1 to 3 hours, duration of around 2 hours being suitable.

[0015] In the precipitation step, the precipitation medium employed may comprise water, organic solvents or mixtures thereof, preferably water, especially distilled water. The ratio of precipitated medium to the mixture acid / CuPc resulting from the dissolution step is generally from 1 to 50, preferably from 5 to 20, for example around 10. The temperature of the precipitation step may be from 0 to 100°C, in particular from 5 to 60°C, more particularly from 10 to 50°C, working at room temperature being also suitable. The mixture acid / CuPc resulting from the dissolution step is usually added to the precipitation medium at a rate of 1 to 100 g of mixture acid / CuPc per kg of the precipitation medium in 1 minute to 1 hour, preferably at a rate of 1 to 100 g (mixture acid / CuPc) / kg (precipitation medium) in 5 to 30 minutes, for example about 10 g (mixture acid CuPc) / kg (precipitation medium) in about 10 minutes. The precipitation may take place under turbulent flow conditions.

[0016] The mixture resulting from the dissolution step is then filtered, washed with water and dried. Preferably, the washing is conducted with distilled water, more preferably with distilled water having a pH of at least 6. Any filtering or drying method known in the art may be used for the filtering and the drying steps. For example, filtering may be done using a gravity system and drying may be conducted in an oven at a temperature of, for example, 120⁰C.

[0017] Such acid pasting treatment is described, for instance, in Ullmann's Encyclopedia of Industrial Chemistry, Fifth Completely Revised Edition, 1992, Volume A20, pp. 225-226.

[0018] In a first embodiment of the present invention, copper phthalocyanine (CuPc) particles exhibiting the alpha crystallographic form are prepared by:

(a) mixing crude copper phthalocyanine particles containing at least 50 wt % of the particles exhibiting the beta crystallographic form with an acid in the presence of CuPc particles substituted by at least one functional group, such that at least part of the crude CuPc is dissolved in the acid; and

(b) precipitating at least part of the dissolved CuPc in a medium. In specific embodiments, the average number of functional groups per CuPc molecule is 0.5 to 2, preferably about 1.

[0019] In the dissolution step (a), the crude CuPc is preferably completely dissolved in the acid. In said dissolution step (a), the weight ratio of the copper phthalocyanine substituted by at least one functional group to the crude copper phthalocyanine is generally higher than or equal to 0.01 , preferably higher than or equal to 0.03, and more preferably higher than or equal to 0.05. Such a proportion is generally lower than or equal to 0.3, preferably lower than or equal to 0.2, more preferably lower than or equal to 0.15.

[0020] In some specific embodiments, the functional group is at least one selected from -SO3M, -SO2NR1R2 and -Rs-NR₄Rs, wherein: Ri and R2 are independent of one another and can be selected from the group consisting of hydrogen, alkyl, alkenyl, aryl or cycloalkyl; M can be a proton, ammonium cation or metal cation; R3 can be a single bond, alkylene or arylene, wherein said alkylene and arylene may be substituted by at least one substituent ; and R₄ and R5 are independent of one another and can be hydrogen, alkyl, alkenyl, aryl, cycloalkyl or collectively form a condensed structure containing at least one of -CO-, -SO2- or -N=N-.

[0021] More specifically, the particles of copper phthalocyanine may be substituted by at least one functional group selected from -SO3H, -

SO₂NHRi and

, wherein Ri is hydrogen, alkyl, alkenyl, aryl or cycloalkyl. Most specifically, the functional group is -

SO3H,

or a mixture thereof. In another embodiment, the CuPc particles substituted by a functional group is a mixture of at least two different substituted CuPc, for instance a mixture of CuPc particles substituted by -SO3H and CuPc particles substituted by

[0022] In another embodiment, copper phthalocyanine particles exhibiting a ε crystallographic form to be used as a blue pigment is prepared by heating the copper phthalocyanine particles exhibiting an alpha crystallographic form prepared according to the first embodiment at a temperature higher than or equal to 50°C in the presence of an organic liquid and optionally milling in the presence of beads. Milling, as defined herein, means a process by which the solids are subjected to attrition, grinding, etc. to achieve particle size reduction. Dry milling, as defined herein, means a process by which the solids are subjected to attrition, grinding etc. to achieve particle size reduction while being substantially free of liquid. However, a low level of solvent may be added.

[0023] In yet another embodiment, the crystal phase conversion and size reduction can take place simultaneously. In this embodiment, kneading is conducted in the presence of at least one liquid and at least one inorganic salt. Preferably, kneading is conducted under certain temperature conditions such that the temperature profile as a function of time exhibits at least two derivatives of temperature with respect to time (dT/dt) being equal to 0. The two temperatures are associated with the derivatives equal to 0 differing by at least 10°C. In another embodiment, kneading is conducted under a constantly changing temperature profile or at least one time (stepwise).

[0024] The specific conditions of the kneading or heating step (e.g., duration, organic liquid, liquid, beads, inorganic salts, etc.) are described in PCT Application Nos. PCT/EP2008/065448 and PCT/EP2008/062266, all of which are incorporated herein by reference in their entirety.

[0025] By adding CuPc derivatives during the acid pasting, the process of the present invention can lead to alpha crystal form copper phthalocyanine having a smaller averaged primary particle size of not more than 140 nm, preferably not more than 100 nm. Further, a better dispersibility of the pigment particles can be obtained when such CuPc derivatives are added in the acid pasting process, which leads to an improved contrast ratio of the resultant color filter prepared from the pigment particles. [0026] Further, in another embodiment, CuPc particles substituted by at least one functional group are added during the kneading or heating step as well as in the acid pasting step. For example, CuPc particles substituted by at least one functional group selected from -SO3H, -SO2NHR1 and

, wherein Ri is hydrogen, alkyl, alkenyl, aryl or

cycloalkyl, preferably

, may be present in dissolution step (a) while CuPc particles substituted by -SO3H may be further added during the kneading or heating step, particularly during the kneading step.

[0027] The present invention is also related to alpha crystal form copper phthalocyanine particles obtainable according to the process of the present invention. This embodiment is directed to the use of the copper phthalocyanine particles obtainable according to the process of the present invention for the preparation of copper phthalocyanine particles exhibiting the epsilon crystallographic form. Also, it is related to a color filter comprising copper phthalocyanine particles exhibiting the epsilon crystallographic form obtainable by the process of the present invention.

Examples

[0028] Example 1 (Acid-pasting beta-CuPc and phthaloimidomethyl-CuPc)

[0029] 2Og of the crude copper phthalocyanine and 1g of phthaloimidomethyl (PIM)-substituted copper phthalocyanine are added to 200 g of 95 wt % sulfuric acid in a 1 L glass beaker. Further, the resultant mixture is stirred by a stirring impeller (Teflon centrifugator, rotation speed of 300 rpm) at 3O⁰C for 2 hours to prepare a suspension or solution of sulfate in the sulfuric acid. The suspension or the solution is poured into 2L of water to obtain an alpha crystal form copper phthalocyanine, which is then washed twice with distilled water, and dried under hot air. After pulverizing the resulting solid, the alpha crystal form copper phthalocyanine is obtained almost quantitatively in terms of crystallographic yield, which is confirmed by a XRD study.

[0030] Example 2 (Acid-pasting beta-CuPc and monosulfonated-CuPc)

[0031] Copper phthalocyanine particles exhibiting alpha crystallographic form were obtained in an identical manner to that of Example 1 , except that 1 g of monosulfonated-CuPc particles was added instead of phthaloimidomethyl-CuPc particles.

[0032] Example 3 (Acid-pasting beta-CuPc and monosulfonated- and phthaloimidomethyl-CuPc particles)

[0033] Copper phthalocyanine particles exhibiting alpha crystallographic form were obtained in a manner identical to that of Example 1 , except that 0.5g of monosulfonated-CuPc particles and 0.5g of phthaloimidomethyl-CuPc particles were added instead of 1g of phthaloimidomethyl-CuPc particles.

[0034] Comparative Example 1 (Acid-pasting beta-CuPc only)

[0035] Copper phthalocyanine particles exhibiting alpha crystallographic form were obtained in an identical manner to that of Example 1 , except that no CuPc derivative was added. Upon analyzing some dried samples of the resultant copper phthalocyanine particles exhibiting alpha crystallographic form with the transmission electron microscope (TEM), they were shown to have a mean particle size of more than 140 μm (Figure 3).

[0036] As shown in the TEM images of Figures 1-3, the average particle size of the resultant alpha-CuPc particles using the process of the invention (examples 1 and 2), i.e., about 97 nm, is significantly less than that prepared by the conventional acid pasting process (comparative example 1), i.e., more than 140 μm. By reducing the size of the alpha-CuPc particles to be kneaded, the kneading time can be significantly reduced while the dispersibility of the resultant particles can be improved.

[0037] Example 4 (Crystal phase conversion of copper phthalocyanine from alpha crystal form to epsilon crystal form) [0038] To a lab-scale kneader, 50 g of the copper phthalocyanine particles exhibiting an alpha crystallographic form, obtained from example 1 or 2, and 12 g of the epsilon-type copper phthalocyanine are added with 80 g of diethylene glycol and 400 g of sodium chloride. The mixture is kneaded for 2 hours at 13O⁰C with the rotation speed of 50 rpm (1^st stage), and then for 8 hours at 80 ⁰C with the identical rotation speed (2^nd stage). After kneading, the resultant particles are purified by filtration and dried at temperature of 8O⁰C and pressure of 10⁴ Pa.

[0039] Example 5 (Crystal phase conversion of copper phthalocyanine from alpha crystal form to epsilon crystal form in the presence of monosulfonated- CuPc)

[0040] Copper phthalocyanine particles exhibiting an epsilon crystallographic form were obtained in a manner identical to that of Example 4 from alpha- CuPc obtained from Example 3. However, prior to the kneading step, the alpha crystal form copper phthalocyanine and the epsilon-type copper phthalocyanine were treated at 130°C for 2 hours in diethylene glycol instead of 1^st stage and 6.2g of MS-CuPc were added during the kneading step.

[0041] Example 6 (Crystal phase conversion of copper phthalocyanine from alpha crystal form to epsilon crystal form in the presence of monosulfonated- CuPc)

[0042] Copper phthalocyanine particles exhibiting an epsilon crystallographic form were obtained in a manner identical to that of Example 4 from alpha- CuPc obtained from Example 1. However, prior to the kneading step, the alpha crystal form copper phthalocyanine and the epsilon-type copper phthalocyanine were treated at 130°C for 2 hours in diethylene glycol instead of 1^st stage and 6.2g of MS-CuPc were added during the kneading step.

[0043] Example 7 (Crystal phase conversion of copper phthalocyanine from alpha crystal form to epsilon crystal form in the presence of monosulfonated- CuPc)

[0044] Copper phthalocyanine particles exhibiting an epsilon crystallographic form were obtained in a manner identical to that of Example 4 from alpha- CuPc obtained from Example 1 , except that 6.2g of MS-CuPc were added during the kneading step.

[0045] Example 8 (Crystal phase conversion of copper phthalocyanine from alpha crystal form to epsilon crystal form in the presence of cetyltri methyl ammonium monosulfo CuPc)

[0046] Copper phthalocyanine particles exhibiting an epsilon crystallographic form were obtained in a manner identical to that of Example 4 from alpha- CuPc obtained from Example 1 , except that 6.2g of cetyltrimethyl ammonium monosulfo CuPc were added during the kneading step.

[0047] Comparative Example 2 (Crystal phase conversion of copper phthalocyanine from alpha crystal form to epsilon crystal form while adding PIM-CuPc and MS-CuPc)

[0048] Copper phthalocyanine particles exhibiting an epsilon crystallographic form were obtained in an identical manner to that of Example 4, from alpha-CuPc obtained from comparative example 1 , except that PIM-CuPc and MS-CuPc were sequentially added during the kneading step.

[0049] Example 9. Test of the particles in color filters

[0050] Color filters were fabricated using as pigments the ε form copper phthalocyanine pigment particles prepared according to Examples 4 to 8 and Comparative Example 2. The contrast ratio and brightness of the resulting color filters are summarized in Table 1 below. These results show that Examples 4 to 8 yielded improvements in contrast ratio by approximately 4 to 21 %, compared to those of Comparative Example 2, as shown in Table 1. Further, when color filters were fabricated from Example 5 (where PIM-CuPc and MS-CuPc were added in the acid- pasting step while MS-CuPc was further added in the kneading step), they yielded better results in contrast ratio and brightness compared to Example 6 (where PIM-CuPc alone was added in the acid-pasting step while MS-CuPc was further added in the kneading step). The color filters fabricated from Example 7 (utilizing MS-CuPc) also yielded improved results compared to those of Example 8 (utilizing cetyltrimethyl ammonium monosulfo CuPc).

[0051] Table 1.

^*arbitrary unit

Brief Description of Figures in the Drawings

[0052] Fig. 1 is an image from a Transmission Electron Microscope (TEM) for the copper phthalocyanine particles exhibiting alpha crystallographic phase prepared by the method according to Example 1. [0053] Fig. 2 is an image from a TEM for the copper phthalocyanine particles exhibiting alpha crystallographic phase prepared by the method according to Example 2. [0054] Fig. 3 is an image from a TEM for the copper phthalocyanine particles exhibiting alpha crystallographic phase prepared by the method according to Comparative Example 1.

Industrial Application

[0055] It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

[0056] Should the disclosure of any of the patents, patent applications, and publications that are incorporated herein by reference conflict with the present disclosure to the extent that it might render a term unclear, the present disclosure shall take precedence.

Claims

1. A process of preparing copper phthalocyanine (CuPc) particles exhibiting an alpha crystallographic form, comprising:

(a) mixing crude copper phthalocyanine particles containing at least 50 wt % of particles exhibiting a beta crystallographic form with an acid in the presence of CuPc particles substituted by at least one functional group, such that at least part of the crude CuPc is dissolved in the acid; and

(b) precipitating at least part of the dissolved CuPc in a medium.

2. The process of Claim 1 , wherein the acid is at least one selected from the group consisting of sulfuric acid, chlorosulfonic acid and polyphosphoric acid, preferably sulfuric acid with a concentration of greater than 90% by weight.

3. The process of Claim 1 or 2, wherein the medium is at least one selected from water, organic solvents or mixtures thereof.

4. The process of any one of Claims 1-3, wherein the average number of functional groups per CuPc molecule is 0.5 to 2, and preferably about 1.

5. A process of preparing copper phthalocyanine particles exhibiting an ε crystallographic form comprising kneading the copper phthalocyanine particles exhibiting an alpha crystallographic form prepared according to the process of any one of Claims 1 -4 under certain temperature conditions such that the temperature profile as a function of time exhibits at least two derivatives of temperature with respect to time (dT/dt) being equal to 0, with at least two temperatures being associated with at least the derivatives equal to 0, differing by at least 10°C, wherein more than or equal to 50 wt % of the particles exhibit an α crystallographic form in the presence of a liquid and at least one inorganic salt.

6. A process of preparing copper phthalocyanine (CuPc) particles exhibiting an ε crystallographic form, comprising a heating step by heating at a temperature higher than or equal to 50°C an alpha crystallographic form prepared according to the process of any one of Claims 1 -4.

7. The process of Claim 5 or 6, wherein the CuPc particles substituted by at least one functional group are further added during the kneading or heating step.

8. The process of any one of Claims 1-7, wherein the functional group is at least one selected from the group consisting of -SO3M, -SO2NR1R2, and -Rs-NR₄Rs, wherein Ri and R2 are independent of one another and are hydrogen, alkyl, alkenyl, aryl, or cycloalkyl; M is a proton, ammonium cation, or metal cation; R3 is a single bond, alkylene or arylene, wherein said alkylene and arylene may be substituted by at least one substituent; and R₄ and R5 are independent of one another and are hydrogen, alkyl, alkenyl, aryl, cycloalkyl, or collectively form a condensed structure containing at least one of -CO-, -SO2-, and -N=N-.

9. The process of Claim 8, wherein the functional group is -SO3H, -SO2NHR1 or

, wherein Ri is hydrogen, alkyl, alkenyl, aryl or cycloalkyl.

10. The process of Claim 8 or 9, wherein the CuPc particles substituted by a functional group is a mixture of at least two different substituted CuPc particles, preferably a mixture of CuPc particles substituted by -SO3H and CuPc particles

substituted by

11. The process of Claim 7, wherein CuPc particles substituted by

-

are present in step (a), and wherein CuPc particles substituted by -SO3H are further added during the kneading or heating step.

12. Copper phthalocyanine particles exhibiting the alpha crystallographic form obtainable by the process of any one of Claims 1 -4 and 8-10.

13. The copper phthalocyanine particles according to Claim 12, wherein the particles have an averaged particle size of not more than 100 nm.

14. Use of the copper phthalocyanine particles according to Claim 12 or 13 to prepare copper phthalocyanine particles exhibiting the epsilon crystallographic form.

15. A color filter comprising the copper phthalocyanine particles exhibiting the epsilon crystallographic form obtainable by the process of any one of Claims 5- 7 and 11.