GB2251085A - Color toner for slide preparation - Google Patents

Abstract

A color toner for use in preparing color slides comprises 20 % or less by volume with a particle diameter of 12 mu m or more, a volume average particle diameter d50 whose cumulative volume distribution is 50 % of 4 to 9 mu m and a melt index Mi of 10 to 30. with the proviso that the relation of (MI >/= 4.0 d50 - 18) is satisfied i.e. the shaded area is unsatisfactory. The color toner is capable of giving a clear fixed color image so that the slide can be used in an overhead projector. <IMAGE>

Description

2231035 COLOR TONER FOR SLIDE PREPARATION

FIELD OF THE INVENTION

The present invention relates to color toners f or f orming images with an electrophotographic method on color slides used for overhead projectors (OHP), etc.

BACKGROUND OF THE INVENTION

When f orming a color image on a transparent sheet used for a slide projector by an electrophotographic method, developers for use in usual electrophotography have conventionally been employed. These developers comprise a color toner and a carrier. The color toner is produced by kneading and dispersing a binder resin (e.g., polystyrene, styrenebutadiene copolymer or polyester) and a pigment or dye (e.g., carbon black or phthalocyanine blue) as a colorant, and then grinding the dispersion to 10 gm to 30 gm to obtain toner particles. On the other hand, the carrier is composed of carrier particles which have an average particle diameter of 500 gm or less provided that the particle diameter of carrier is larger than that of the toner particles. As the carrier, glass beads, iron powder, nickel powder, ferrite powder, and those obtained by resin coating thereof can be used.

However, when the color slides prepared by using the usual developers for use in electrophotography are projected on an overhead projector, it is difficult to obtain clear color images. This is because, as shown in Fig. 2, gaps are present 1 - in the fixed image formed on the transparent sheet, unevennesses are formed on the surface of the fixed image and thus the light is scattered. In this regard, various attempts, for example fixing at a fixing temperature higher than the usual temperature of from 120 to 2200C, or lowering the fixing speed, or lowering the weight-average molecular weight of the binder resin below the usual range (i.e., Mw = 10,000 to 350,000) have been made.

However, if the fixing temperature is raised the power consumption becomes extremely large, and if the molecular weight of the binder resin is lowered then new problems arise such as internal blocking or offsetting during fixing.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a color toner f or use in a color slide, which is capable of giving a clear fixed color image with OHP, etc., with little power consumption during fixing and without extreme decrease in the molecular weight of the binder resin.

The above and other objects of the present invention have been attained by using a specific color toner. That is, the present invention is a color toner for use in a color slide f or f orming a color image on a transparent sheet by an electrophotographic method, wherein 20 % or less by volume of said color toner has a particle diameter of 12 tm or more, and wherein said color toner has the volume average particle diameter d5o whose cumulative volume distribution is 50 % of 4 to 9 gm and the melt index MI of 10 to 30, with the proviso that the relation of (MI: 4.0 x d.50 - 18) is satisfied.

The said particle diameters of color toner particles are measured using a Coulter Counter Model TAII made by Coulter Electronics, Inc. and the said melt index MI is measured under the conditions of 135C of temperature, 2160 g of loading and 15 seconds of time by using a melt indexer made by Toyo Seiki Co,, Ltd. according to JIS K-7210.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, Fig. 1 is a sectional view of a typical fixed image formed using the color toner of the present invention, Fig. 2 is a sectional view of a typical fixed image using the color toner of the prior art, and Fig. 3 is a graph showing the relationship between the melt index MI and the volume average particle diameter d50 Of the color toner of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

If the volume average particle diameter d.50 of the color toner is larger than 9 gm, the degree of deposition of the toner on the fixed surface decreases and the surface properties worsen because unevennesses remain on the surface of the fixed image. Also, if the volume percentage of toner particles having a particle diameter of 12 4m or more is more than 20 the larger particle diameter toner will remain and surface properties will worsen. As a result, when projecting on an OHP there is light scattering that prevents reproduction of a clear fixed color image. On the other hand, if the volume average particle diameter d.50 is smaller than 4 gm or the melt index MI is higher than 30, it becomes difficult to use the toner because of internal blocking or offsetting during fixing.

In the present invention, the toner particles must be arranged so that the volume average particle diameter d5o whose cumulative volume distribution is 50 % is from 4 to 9 gm and the melt index MI is from 10 to 30, with the proviso that the relation of (XI: 4.0 x d.50 - 18) is satisfied (Fig. 3).

Fig. 1 is a sectional view of a typical f ixed image formed by using the color toner of the present invention. As is clear f rom Fig. 1, the melt adhesion between toner particles and the transparent sheet and between toner particles each other, no gaps inside the image, and the smoothness of the image surface are confirmed.

In another side view, the characteristic f eature of the present invention is based on the findings that the larger particle diameter toners must have higher melt indexes.

That is, when the toner particle diameter is large, it is easy to form a gap between the transferred toner particles. In this case, therefore, it is required to use the material having a high MI which is capable of filling the gap as toner. on the other hand, when the oner particle diameter is small, the gap is hardly formed between the transferred toner particles. Therefore, it can be easy to obtain the surface gloss necessary for the color forming property on an OHP without the material having a high MI. In view of the above findings, color toners of the shaded region in Fig. 3 are excluded from the present invention.

Binder resins used in the color toners of the present invention have a weight-average molecular weight of from 10, 000 to 350,000 and include homopolymers or copolymers of styrenes such as styrene and chlorostyrene, mono-olefins such as etylene, propylene, butylene and isobutylene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate, a-methylene aliphatic monocarboxylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and dodecyl methacrylate, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, and vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone. Typical examples are polystyrene, a styrene-alkyl acrylate copolymer, a styrene-alkyl methacrylate copolymer, a styrene-acrylonitrile copolymer, a styrenebutadiene copolymer, and a styrene-maleic anhydride copolymer. In addition, polyesters, polyurethanes, polyamides, modified rosins and the like can be used.

Typical examples of te colorants for the color toners of the present invention are carbon black, Nigrosine dye, Aniline blue, Charchoyl Blue, Chrome Yellow, Ultramarine Blue, Du Pont oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue, Malachite Green oxalate, Lamp black, Rose Bengale, C. I. Pigment Red 48:1, C.I. Pigment Red 122, C.I. Pigment Red 57:1, C.I. Pigment Yellow 97, C.I. Pigment Yellow 12, C.I. Pigment Blue 15:1 and C.I. Pigment Blue 15:3. Further, dyes which are excellent in light-fastness and heat resistance and pigments which are easy to be primary dispersed are preferred for the colorants.

The weight ratio of the colorant to the binder resin in the toner composition of the present invention is generally in the range of from 3:97 to 15:85.

The binder resin and colorant to be used in the present invention are not limited to the above-enumerated examples. If desired, the color toner of the present invention may further contain an internal charge control agent or a magnetic powder. Specific examples of the internal charge control agent include Nigrosine dyes, quaternary ammonium salts, triphenyl methane compounds, salitylic acid metal complex compounds, and metal azo compounds. Specific examples of the magnetic powder include alloys or compounds containing a ferromagnetic element such as iron, cobalt, or nickel (e.g., magnetite, ferrite), and those obtained by surface treating thereof with surface treating agents such as silane coupling agents or aluminum coupling agents and those obtained by polymer coating thereof. The magnetic powder which can be used in the present invention preferably has a particle diameter of from 0.5 to 1 gm.

- 6 Further, resins. used for preventing offsetting such as polyethylene, polypropylene and waxes can also be used.

The color toner of the present invention can be made by melt fusion of the above ingredients, then kneading followed by cold hardening, grinding and classifying.

The color toner obtained can also be used with external additions such as aqueous silica particles, metal oxide particles, polyvinylidene fluoride particles and polymethyl methacrylate particles.

The color toner of the present invention can also be used singly as a single component developer, or it can be used mixed with a carrier as a two component developer.

The carriers which can be used in the case of the two component developer include iron, nickel, cobalt, iron oxide, ferrite, glass beads and silicone particles having an average particle diameter of up to 500 pm, and as required the surfaces of the above particles may be coated with a fluorine resin, an acrylic resin, a silicone resin, etc.

When forming the fixed image on a transparent sheet using the color toner of the present invention, it is preferred that heat roller is employed for the fixing process at temperature of 140 to 2200C and speed of 80 to 300 mm/sec.

As the transparent sheet, films having heat resistance higher than 100'C such as polyester, polysulfone, polyphenyl oxide, polyimide, polycarbonate, cellulose ester and polyamide, and the surface treated products thereof can be used.

7 The present invention is described in greater detail with reference to the following Examples and Comparative Examples. All parts are by weight.

In the following examples, the particle diameter of color toner was measured using a Coulter Counter Model TAII made by Coulter Electronics, Inc. and the melt index MI of color toner was measured under the conditions of 1350C of teTperature, 2160 g of loading and 15 seconds of time by using a melt indexer made by Toyo Seiki Co., Ltd. according to JIS K7210.

EXAMPLE 1

Styrene-n-butyl methacrylate copolymer (weight-average molecular weight: 80,000) 85 parts Copper phthalocyanine- 10 parts Propylene wax 5 parts The above ingredients were melt kneaded, ground and then classified to obtain blue colored toner particles having a volume average particle diameter d5o of 9 gm, in which the volume percentage of toner having a particle diameter of 12 gm or more is 18 %.

To 100 parts of the blue particles were added 0.5 part of hydrophobic colloidal silica to obtain blue toner. The measured value of the melt in. dex MI of this toner was 28, and the relation of (MI 2: 4.0 x d.50 - 18) was satisfied.

8 - Then this blue toner was mixed with an iron carrier having an average particle diameter of 100 gm to prepare a developer composition.

The thus prepared developer composition was loaded in an electronic copying machine having a two component magnetic brush developing apparatus (5030, produced by Fuji Xerox Co., Ltd.), and a blue fixed image was formed on a polyethylene terephthalate film using a 2.0 cm x 2. 0 cm solid original. The fixing temperature was set at 1900C.

The gross value of the sample obtained was 43 when measured in the following manner. Using a gross meter (Gross Meter Model GM26D made by Murakami Shikisai Gijutsu Kenkyusho), the angle of incident light on the sample was set at 75', the ratio of the intensity of the light reflected from the sample to the intensity of the incident light was measured, and error correction was done with the standard gross value of a standard plate (mirror surface polished plate) at 89.

Then the sample was set on an overhead projector (OHP Z-1, produced by Fuji Xerox Co., Ltd.) and projected, and when the color reproduction was examined by visual observation, a clear blue image had been reproduced.

EXAMPLE 2

A developer composition was prepared in the same manner as in Example 1 except that instead of the styrene-n-butyl methacrylate copolymer (weightaverage molecular weight: 80,000) and the copper phthalocyanine of the toner composition in Example 1, styrene-n-butyl methacrylate copolymer (weightaverage molecular weight: 100,000) and C.I. Pigment Red 48:1 were respectively added in the same amounts. The toner obtained had a volume average particle diameter d50 of 8 gm, and the volume percentage of toner having a particle diameter of 12 gm or more was 15 %. Also, the measured value of the melt index MI of this toner was 23, and the relation of (MI i 4.0 x dso 18_) was satisfied.

Using this developer, a fixed image was formed in the same manner as in Example 1, and when the gross value and color reproduction were examined, the gross value was 40 and a clear red image was reproduced in the same manner as in Example 1.

EXAMPLE 3

A developer composition was prepared in the same manner as in Example 1 except that instead of the copper phthalocyanine of the toner composition in Example 1, C.I. Pigment Yellow 12 was added in the same amount. The toner obtained had a volume average particle diameter d.50 of 8.5 gm, and the volume percentage of toner having a particle diameter of 12 gm or more was 17 %. Also, the measured value of the melt index MI of this toner was 28, and the relation of (MI k 4.0 x d.50 - 18) was satisfied.

Using this developer, a fixed image was formed in the same manner as in Example 1, and when the gross value and color reproduction were examined, the gross value was 46 and a clear yellow image was reproduced in the same manner as in Example 1.

EXAMPLE 4

A developer composition was prepared in the same manner as in Example 1 except that instead of the styrene-n-butyl methacrylate copolymer (weightaverage molecular weight: 80,000) and the copper phthalocyanine of the toner composition in Example 1, styrene-n-butyl methacrylate copolymer (weightaverage molecular weight: 130,000) and C.I. Pigment Red 122 were respectively added in the same amounts. The toner obtained had a volume average particle diameter d.50 of 4 gm, and the volume percentage of toner having a particle diameter of 12 gm or more was 16 %. Also, the measured value of the melt index MI of this toner was 10, and the relation of (MI k 4.0 x d50 18) was satisfied.

Using this developer, a fixed image was formed in the same manner as in Example 1, and when the gross value and color reproduction were examined, the gross value was 43 and a clear red image was reproduced in the same manner as in Example 1.

EXAMPLE 5

A developer composition was prepared in the same manner as in Example 4 except that instead of C.I. Pigment Red 122 of the toner composition in Example 4, C.I. Pigment Red 57 was added in the same amount. The toner obtained had a volume average -particle. diameter d5o of 7 gm, and the volume percentage of toner having a particle diameter of 12 gm or more was 18 %. Also, the measured value of the melt index MI of this toner was 10, and the relation of (MI 4.0 x d50 - 18) was satisfied.

11 - Using this developer, a fixed image was formed in the same manner as in Example 1, and when the gross value and color reproduction were examined, the gross value was 40 and a clear red image was reproduced in the same manner as in Example 4.

EXAMPLE 6

A developer composition was prepared in the same manner as in Example 1 except that instead of the styrene-n-butyl methacrylate copolymer (weightaverage molecular weight: 80,000) and the copper phthalocyanine of the toner composition in Example 1, styrene-n-butyl methacrylate copolymer (weightaverage molecular weight: 110,000) and C.I. Pigment Blue 15:1 were respectively added in the same amounts. The toner obtained had a volume average particle diameter d_90 of 4 pm, and the volume percentage of toner having a particle diameter of 12 gm or more was 16 %. Also, the measured value of the melt index MI of this toner was 30, and the relation of (MI: 4.0 x d5o 18) was satisfied.

Using this developer, a fixed image was formed in the same manner as in Example 1, and when the gross value and color reproduction were examined, the gross value was 64 and a clear blue image was reproduced in the same manner as in Example 1. COMPARATIVE EXAMPLE 1 Blue toner was prepared with the same constituent ingredients as in Example 1 except that the volume average particle diameter d.50 was 11 im and the volume percentage of toner having a particle diameter of 12 4m or more was 33 %.

The measured value of the melt index MI of this toner was 28, and the relation of (MI 2: 4. 0 x d50 - 18) was satisf ied.

Using this developer, a fixed image was formed in the same manner as in Example 1, and when the gross value and color reproduction were examined, the gross value was 34, but in regard to color reproduction, the product was a blue image with gray in it that had insufficient clarity.

COMPARATIVE EXAMPLE 2 Red toner was prepared with the same constituent ingredients as in Example 2 except that the volume average particle diameter d.50 was 10.5 gm and the volume percentage of toner having a particle diameter of 12 gm or more was 26 %. The measured value of the melt index MI of this toner was 23, and the relation of (MI 2: 4. 0 x d.50 - 18) was not satisfied.

Using this developer, a fixed image was formed in the same manner as in Example 2, and when the gross value and color reproduction were examined, the gross value was 25, and the projected image was black, it being absolutely impossible to reproduce a red image.

COMPARATIVE EXAMPLE 3 Yellow toner was prepared with the same constituent ingredients as in Example 3 except that the volume average particle diameter d5o was 9 pm and the volume percentage of toner having a particle diameter of 12 pm or more was 22 The measured value of the melt index MI of this toner was 28, and the relation of (MI 2: 4.0 x d5o - 18) was satisfied.

13 - Using this developer, a fixed image was formed in the same manner as in Example 3, and when the gross value and color reproduction were examined, the gross value was 35, but in regard to color reproduction, the product was a yellow image with gray in it that had insufficient clarity.

COMPARATIVE EXAMPLE 4 A developer composition was prepared in the same manner as in Example 1 except that instead of the styrene-n-butyl methacrylate copolymer (weight- average molecular weight: 80,000) and the copper phthalocyanine of the toner composition in Example 1, styrene-n-butyl methacrylate copolymer (weightaverage molecular weight: 120,000) and C.I. Pigment Red 48:1 were respectively added in the same amounts. The toner obtained had a volume average particle diameter d5o of 8 gm, and the volume percentage of toner having a particle diameter of 12 gm or more was 18 %. Also, the measured value of the melt index MI of this toner 'was 12, and the relation of (MI: 4. 0 x d5o 18) was not satisfied.

Using this developer, a fixed image was formed in the same manner as in Example 1, and when the gross value and color reproduction were examined, the gross value was 35 while color reproduction was an unsatisfactory dark purple image.

COMPARATIVE EXAMPLE 5 A developer composition was prepared in the same manner as in Comparative Example 4 except that instead of C. I. Pigment Red 48:1 of the toner composition in Comparative Example 4, C.I. Pigment Yellow 97 was added in the same amount. The toner obtained had a volume average particle diameter d5o of 3 im, and the volume percentage of toner having a particle diameter of 12 gm or more was 15 %. Also, the measured value of the melt index MI of this toner was 15, and the relation of (MI 2: 4. 0 x d5o - 18) was satisfied.

Using this developer, a fixed image was formed in the same manner as in Comparative Example 4, and when the gross value and color reproduction were examined, the gross value was 45 and although there was color development with the overhead projector, it was impossible to use because the extremely poor flowability of the toner caused blocking.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims (6)

1._ A color toner for use in a color slide for forming a color image on a transparent sheet by an electrophotographic method, wherein 20% or less by volume of said color toner has a particle diameter of 12 gm or more, and wherein said color toner has a volume average particle diameter d5o, whose cumulative volume distribution is 50 %, of 4 to 9 gm and a melt index MI of 10 to 30, with the proviso that MI: ( (4. 0 x d50) - 18].

2. A color toner as claimed in claim 1, wherein the particles comprise colorant and a binder resin in a weight ratio in the range of from 3:97 to 15:85.

3. A color toner as claimed in claim 2, wherein the binder resin has a weight average molecular weight of from 10,000 to 350,000.

4. A color toner as claimed in any preceding claim, in admixture with a carrier for use as a two-component developer.

5. A color toner substantially as hereinbefore described in any one of Examples 1 to

6.

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