JPH05107929A - Developing method - Google Patents

Abstract

PURPOSE:To enable fixing with low energy and prolonging of the life of a developer by using the two-component developer contg. a carrier having a prescribed apparent density. CONSTITUTION:A toner is a thermal dissociation type capsule toner and the carrier is a ferrite or magnetite carrier having <=2.5g/cm<2> apparent density. The essential component of the shell material of the capsule of the toner is constituted of a resin having at least one of a thermal dissociation urethane bond, thiol urethane bond or S-thiourethane bond. Further, the thermal dissociation type urethane resin has >=30% number of the bonds by the reaction of a phenolic hydroxyl and/or thiol group among the bonds to which the total isocyanate groups and/or isothiocyanate groups contribute. The softening point of the capsule toner is 80 to 150 deg.C. The carrier may be subjected to a coating treatment by a resin and the coating film thickness in such a case is >=1.5mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method used in plain paper copying machines, laser printers, plain paper facsimiles and the like. More specifically, it relates to a method of developing an electrostatic charge image suitable for a reprographic system that employs a magnetic brush development method when the toner is a heat dissociation type capsule toner, and in particular, a two-component toner used in the magnetic brush development method. The present invention relates to a developing method using a developer.

[0002]

2. Description of the Related Art When an image is formed in a copying machine or a laser beam printer,
The Carlson method is generally used (US Pat. Nos. 2,221,776, 2,297,691 and 2,357,809; "Electro
photography ": p22-p41, RMShaffert 1965, The Focal P
ress). In electrophotography, an electrostatic latent image formed by optical means is first developed in a developing process and then transferred to a recording medium such as recording paper in a transferring process, and further, in a fixing process, generally high heat and high heat are applied. An image is formed by fixing with a fixing roller system having pressure. In such a conventional image forming method, the temperature of the heating element of the fixing device is very high and a large pressure is required during the process from the formation of the electrostatic latent image to the fixing to the recording medium. It is the current situation.

On the other hand, since the photoconductor and the developing device need to be kept at room temperature, it is necessary to keep a considerable distance between the fixing section and the photoconductor and the developing device. It is necessary to remove the heat generated from the outside of the system. Noise and heat generated by the forced heat dissipation device are also a cause of environmental damage in offices and the like. The fixing step exists independently, usually at a high temperature of around 200 ° C. and at 2 Kg /
Since fixing is performed with a fixing device having a linear pressure of cm or more, expensive heat-resistant resin and heat-resistant rubber are required around the fixing device. Also, when fixing at such a high temperature, the paper curls,
It has been pointed out that troubles such as jamming are likely to occur, and the paper absorbs heat depending on the thickness of the paper, resulting in defective fixing.

Further, if the fixing temperature is high, it takes time to reach the set temperature, and quick printing cannot be performed. Therefore, it is not suitable for a device such as a facsimile machine which requires quick printing. On the other hand, with conventional toners, which try to fix at a fixing temperature of about 100 ° C. or less, it is not possible to expect the resin in the toner to soften due to heat. A linear pressure is required, and in that case, not only a large-scale fixing device is used, but also the fixing strength is inferior to that of heat fixing, and problems such as paper wrinkling occur.

From these viewpoints as well, development of a new system and a toner adapted thereto is expected. In order to meet such expectations, the effectiveness of using a thermal dissociation type capsule toner as a toner is being evaluated. The thermal dissociation type encapsulated toner is a toner containing a shell having a property that the shell structure is weakened by heat and a core material that can be fixed by low linear pressure at low temperature (Japanese Patent Application No. 3-1).
4231). In this way, the thermal dissociative capsule toner is
Since the properties of the toner are significantly different from those of conventional toner, in order to use the toner as a two-component developer together with a magnetic carrier, development of a developing method using a magnetic carrier suitable for it is required.

[0006]

In order to solve the above-mentioned problems, the developing method of the present invention is a method for developing a latent image on an image carrier using a two-component developer comprising toner particles and a magnetic carrier. In above, the toner is a thermal dissociation type capsule toner, and the carrier is a ferrite or magnetite carrier having an apparent density of 2.5 g / cm ³ or less. Here, in the toner, the main component of the shell material of the capsule is a heat dissociable urethane bond, a thiol urethane bond,
Alternatively, it is composed of a resin having at least one bond of s-thiourethane bond. Furthermore, in the heat dissociable urethane resin, which is the main component of this shell material, among the bonds involving all the isocyanate groups and / or isothiocyanate groups, the number of the bonds due to the reaction with the phenolic hydroxyl group and / or the thiol group is the number. Is 30% or more. The softening point of the capsule toner is 80 ° C to 15 ° C.
Those at 0 ° C. are used. The ferrite or magnetite carrier may be coated with a resin, and the thickness of the coating layer formed by the coating treatment in that case is 1.5 μm or more.

The toner used in the present invention is a thermal dissociation type capsule toner. The thermal dissociation type capsule toner is a toner having a shell having a property that the shell structure is weakened by heat and containing a core material that can be fixed by pressure at low temperature.
That is, the structure of the shell changes due to heat, and the core material is released and fixed when pressure is applied.

Such a capsule toner can usually be easily obtained by the following manufacturing method. (1) A spray drying method (spray drying method) in which the core substance is dispersed in a non-polymer aqueous solution or a polymer emulsion and then the dispersion is spray-dried, and (2) around the core substance from a mixed aqueous solution of an ionic polymer colloid. Phase separation method (coacervation method) in which micro-capsules are formed from simple emulsion through complex emulsion by causing phase separation in
(3) The core material solution or dispersion is dispersed in a W / O or O / W type emulsion system, and at the same time, the shell material monomer (A) is collected at the interface, and in the next step, the monomer (B) and the monomer at the interface are collected. In addition to the interfacial polymerization method in which (A) reacts, an in situ polymerization method, a liquid hardening coating method, an air suspension coating method, an electrostatic coalescence method, a vacuum vapor deposition coating method and the like can be mentioned. In the present invention, the capsule toner produced by the interfacial polymerization method or the spray drying method is preferably used. In the interfacial polymerization method, not only the functional separation of the core material and the shell material is easy, but also a uniform toner can be produced in an aqueous system, and a substance having a low softening point can be used for the core material. A toner having desirable properties can be obtained.

As the shell material, a styrene resin (JP-A-48)
-80407), a polyamide resin (JP-A-58)
-66948), an epoxy resin (JP-A-59-59).
No. 148066), a polyurethane resin (Japanese Patent Laid-Open No. Sho 5)
No. 7-179860), polyurea-based resins (JP-A No. 62-150262), and many others have been devised. Examples of the heat-pressure fixing substance contained in the core material include thermoplastic resins having a glass transition point (Tg) of 10 ° C. or higher and 50 ° C. or lower, such as polyester resin, polyamide resin, polyester polyamide resin, and vinyl resin. ..

With respect to the thermal characteristics of the core material, the structure and thermal characteristics of the shell material are significantly involved in the fixability of the toner as a whole. Since it has both storage stability and low-temperature fixability, it is a very preferable material in the image forming method of the present invention. The main component of such a shell material is a resin having at least one bond of thermal dissociative urethane bond, thiol urethane bond, or s-thiourethane bond. Furthermore, in the heat dissociable urethane resin, which is the main component of this shell material, among the bonds involving all the isocyanate groups and / or isothiocyanate groups, the number of the bonds due to the reaction with the phenolic hydroxyl group and / or the thiol group is the number. Is 30% or more. For example, an isocyanate compound and / or an isothiocyanate compound and a phenolic hydroxyl group and / or
Alternatively, a resin obtained by a reaction with a compound having a thiol group or the like is preferably used (Japanese Patent Application No. 14231/1991).
issue).

More specifically, for example, the capsule toner comprises a heat-meltable core material containing at least a colorant and an outer shell provided so as to cover the surface of the core material. The main component of the shell is (1) a monovalent isocyanate compound and / or an isothiocyanate compound in an amount of 0 to 30 mol% of the whole isocyanate compound and / or an isothiocyanate compound, and (2) a divalent or higher valent isocyanate compound and / or an isothiocyanate compound. The thiocyanate compound is 100 to 70 mol% of the whole isocyanate compound and / or isothiocyanate compound, and (3) the compound having one active hydrogen which reacts with the isocyanate group and / or the isothiocyanate group is an isocyanate group and / or an isothiocyanate group. 0 to 30 mol% of all compounds that react with, (4) isocyanate groups and Alternatively, a compound having two or more active hydrogens capable of reacting with an isothiocyanate group is used in 100 to 70 mol% of all compounds capable of reacting with an isocyanate group and / or an isothiocyanate group, and (1) + (2) 3) + (4), which is made of a resin that is reacted in a ratio of 1: 1 to 1:20 with respect to the number of moles, and in the resin, all the isocyanate groups and / or isothiocyanate groups are involved. Capsule toners in which at least 30% or more in the number are bonds exhibiting thermal dissociation are mentioned.

The bond exhibiting thermal dissociation is preferably a bond derived from the reaction of a phenolic hydroxyl group and / or a thiol group with an isocyanate group and / or an isothiocyanate group. Specifically, the monovalent isocyanate compound of (1) above includes ethyl isocyanate, octyl isocyanate, 2-chloroethyl isocyanate, chlorosulfonyl isocyanate, cyclohexyl isocyanate, n-dodecyl isocyanate, and butyl isocyanate. , N-hexyl isocyanate, lauryl isocyanate, phenyl isocyanate, m-chlorophenyl isocyanate, 4-chlorophenyl isocyanate, p-cyanophenyl isocyanate, 3,4-dichlorophenyl isocyanate, o-tolyl isocyanate, isocyanic acid m-tolyl, p-tolyl isocyanate, p-isocyanate
-Toluenesulfonyl, 1-naphthyl isocyanate, o-nitrophenyl isocyanate, m-nitrophenyl isocyanate, p-nitrophenyl isocyanate, phenyl isocyanate, p-bromophenyl isocyanate, o-methoxyphenyl isocyanate, isocyanate Acid m-methoxyphenyl, p-methoxyphenyl isocyanate,
Examples thereof include monovalent isocyanate compounds such as ethyl isocyanato acetate, butyl isocyanato acetate, and trichloroacetyl isocyanate.

Examples of the divalent or higher valent isocyanate compound (2) include, for example, 2,4-tolylene diisocyanate, 2,4-tolylene diisocyanate dimer, and 2,6-tolylene diisocyanate.
Tolylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 3,3'-dimethyl-diphenyl-4,4'-diisocyanate, 3, 3'-Dimethyl-diphenylmethane-
Aromatic isocyanate compounds such as 4,4'-diisocyanate, metaphenylene diisocyanate, triphenylmethane-triisocyanate, polymethylenephenyl isocyanate, etc., Aliphatic compounds such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, dimer acid diisocyanate, etc. Alicyclic isocyanate compounds such as isocyanate compounds, isophorone diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4 (or 2,6) diisocyanate, 1,3- (isocyanatomethyl) cyclohexane Examples thereof include isocyanate compounds such as an adduct of 3 mol of diisocyanate and 1 mol of trimethylolpropane. Examples of the compound having an isothiocyanate group include compounds such as phenyl isothiocyanate, xylylene-1,4-diisothiocyanate, and ethylidyne diisothiocyanate. Among them, a compound in which an isocyanate group is directly bonded to an aromatic ring is preferably used because it has an effect of lowering the thermal dissociation temperature after the urethane bond is formed.

The monovalent isocyanate compound and / or isothiocyanate compound (1) described above can be used up to 30 mol% of the whole isocyanate compound and / or isothiocyanate compound while also controlling the molecular weight of the outer shell resin. If it exceeds mol%, the storage stability of the capsule toner deteriorates, which is not preferable.

Examples of the compound (3) having one active hydrogen which reacts with the isocyanate group and / or the isothiocyanate group include methyl alcohol, ethyl alcohol,
Aliphatic alcohols such as propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, t-butyl alcohol, pentyl alcohol, hexyl alcohol, cyclohexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, lauryl alcohol, stearyl alcohol, phenol , O-cresol, m-cresol, p-cresol, 4-butylphenol, 2-sec
-Butylphenol, 2-tert-butylphenol, 3
-Tert-butylphenol, 4-tert-butylphenol, nonylphenol, isononylphenol, 2-propenylphenol, 3-propenylphenol, 4-
Propenylphenol, 2-methoxyphenol, 3-
Methoxyphenol, 4-methoxyphenol, 3-acetylphenol, 3-carbomethoxyphenol, 2
-Chlorophenol, 3-chlorophenol, 4-chlorophenol, 2-bromophenol, 3-bromophenol, 4-bromophenol, benzyl alcohol,
1-naphthol, 2-naphthol, 2-acetyl-1-
Examples thereof include compounds such as aromatic alcohols such as naphthol and amides such as ε-caprolactam.

Among them, the phenol derivative represented by the following formula (I) is preferably used.

[Chemical 1] (In the formula, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are independently H, or an alkyl group having 1 to 9 carbon atoms, an alkenyl group, an alkoxy group, an alkanoyl group, a carboalkoxy group, or an aryl group. Or halogen.)

Among the compounds having two or more active hydrogens that react with the isocyanate group and / or the isothiocyanate group of the above (4), the divalent or higher valent alcohol compound is
For example, catechol, resorcin, hydroquinone, 4-
Methylcatechol, 4-t-butylcatechol, 4-acetylcatechol, 3-methoxycatechol, 4-phenylcatechol, 4-methylresorcin, 4-ethylresorcin, 4-t-butylresorcin, 4-hexylresorcin, 4-chloro Resorcin, 4-benzylresorcin, 4-acetylresorcin, 4-carbomethoxyresorcin, 2-methylresorcin, 5-methylresorcin, t-butylhydroquinone, 2,5-di-t-butylhydroquinone, 2,5-di- t-amylhydroquinone, tetramethylhydroquinone, tetrachlorohydroquinone, methylcarboaminohydroquinone, methylureidohydroquinone, benzonorbornene-3,6-
Diol, bisphenol A, bisphenol S, 3,3 '
-Dichlorobisphenol S, 2,2'-dihydroxybenzophenone, 2,4-dihydroxybenzophenone, 4,4 '
-Dihydroxybenzophenone, 2,2'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl, 2,2'-dihydroxydiphenylmethane, 3,4-bis (p-hydroxyphenyl) hexane, 1,4-bis (2- ( p-hydroxyphenyl) propyl) benzene, bis (4-hydroxyphenyl) methylamine, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 1,
5-dihydroxyanthraquinone, 2-hydroxybenzyl alcohol, 4-hydroxybenzyl alcohol,
2-hydroxy-3,5-di-t-butylbenzyl alcohol, 4-hydroxy-3,5-di-t-butylbenzyl alcohol, 4-hydroxyphenethyl alcohol, 2
-Hydroxyethyl-4-hydroxybenzoate, 2
-Hydroxyethyl-4-hydroxyphenyl acetate, resorcin mono-2-hydroxyethyl ether,
Hydroxyhydroquinone, gallic acid, ethyl 3,4,5-trihydroxybenzoate and the like can be mentioned. Among them, a catechol derivative represented by the following formula (II) or a resorcin derivative represented by the following formula (III) is preferably used.

[0018]

[Chemical 2] (In the formula, R ₆ , R ₇ , R ₈ , and R ₉ independently represent H, or an alkyl group having 1 to 6 carbon atoms, an alkenyl group, an alkoxy group, an alkanoyl group, a carboalkoxy group, an aryl group, or halogen. Show.)

[Chemical 3] (In the formula, R ₁₀ , R ₁₁ , R ₁₂ , and R ₁₃ independently represent H, or an alkyl group having 1 to 6 carbon atoms, an alkenyl group, an alkoxy group, an alkanoyl group, a carboalkoxy group, an aryl group, or halogen. Show.)

Other compounds having at least one functional group other than a hydroxyl group which reacts with an isocyanate group and / or an isothiocyanate group and having at least one phenolic hydroxyl group include, for example,
o-hydroxybenzoic acid, m-hydroxybenzoic acid, p
-Hydroxybenzoic acid, 5-bromo-2-hydroxybenzoic acid, 3-chloro-4-hydroxybenzoic acid, 4-chloro-2-hydroxybenzoic acid, 5-chloro-2-hydroxybenzoic acid, 3,5-dichloro -4-Hydroxybenzoic acid, 3-methyl-2-hydroxybenzoic acid, 5-methoxy-2-hydroxybenzoic acid, 3,5-di-t-butyl-4-hydroxybenzoic acid, 4-amino-2-hydroxy Benzoic acid, 5-amino-2-hydroxybenzoic acid, 2,
5-dinitrosalicylic acid, sulfosalicylic acid, 4-hydroxy-3-methoxyphenylacetic acid, catechol-4-
Carboxylic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,4
-Dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, m-hydroxycinnamic acid, p-hydroxycinnamic acid, 2-amino-4-methylphenol, 2-amino-5-methylphenol 5,
-Amino-2-methylphenol, 3-amino-2-naphthol, 8-amino-2-naphthol, 1-amino-
2-naphthol-4-sulfonic acid, 2-amino-5-naphthol-4-sulfonic acid, 2-amino-4-nitrophenol, 4-amino-2-nitrophenol, 4-amino-2,6-dichlorophenol , O-aminophenol, m-aminophenol, p-aminophenol, 4
-Chloro-2-aminophenol, 1-amino-4-hydroxyanthraquinone, 5-chloro-2-hydroxyaniline, α-cyano-3-hydroxycinnamic acid, α-cyano-4-hydroxycinnamic acid, 1-hydroxynaphthoene Acid, 2-hydroxynaphthoic acid, 3-hydroxynaphthoic acid, 4-hydroxyphthalic acid and the like can be mentioned.

Further, polythiol compounds having one or more thiol groups in one molecule include ethanethiol, 1
-Propanethiol, 2-propanethiol, thiophenol, bis (2-mercaptoethyl) ether, 1,2
-Ethanedithiol, 1,4-butanedithiol, bis (2-mercaptoethyl) sulfide, ethylene glycol bis (2-mercaptoacetate), ethylene glycol bis (3-mercaptopropionate), 2,2-
Dimethylpropanediol bis (2-mercaptoacetate), 2,2-dimethylpropanediol bis (3-mercaptopropionate), trimethylolpropane tris (2-mercaptoacetate), trimethylolpropane tris (3-mercaptopropionate) ), Trimethylolethanetris (2-mercaptoacetate), trimethylolethanetris (3-mercaptopropionate), pentaerythritol tetrakis (2
-Mercaptoacetate), pentaerythritol tetrakis (3-mercaptopropionate), dipentaerythritol hexakis (2-mercaptoacetate), dipentaerythritol hexakis (3-mercaptopropionate), 1,2-dimercaptobenzene ,
4-methyl-1,2-dimercaptobenzene, 3,6-dichloro-1,2-dimercaptobenzene, 3,4,5,6-tetrachloro-1,2-dimercaptobenzene, xylylenedithiol, 1 Examples include 3,3,5-tris (3-mercaptopropyl) isocyanurate.

In the heat dissociable outer shell resin used in the present invention, the heat dissociable bonds include all isocyanate groups and / or
Alternatively, among the bonds involving isothiocyanate groups, the number is at least 30% or more, preferably 50%. If the number of the bonds that undergo thermal dissociation is less than 30% of the number of bonds involving all isocyanate groups and / or isothiocyanate groups, the capsule shell strength will not be sufficiently reduced during heat and pressure fixing, leading to excellent fixing performance of the core material. I can't.

In the encapsulated toner of the present invention, of the bonds involving all the isocyanate groups and / or isothiocyanate groups, the number of bonds due to reaction with a phenolic hydroxyl group and / or a thiol group is 30%.
Within the range of less than the phenolic hydroxyl group and /
Or a compound having a functional group which reacts with an isocyanate group other than a thiol group, for example, malonic acid esters, active methylene group-containing compounds such as acetoacetic acid esters, oximes such as methyl ethyl ketone oxime, carboxylic acids, polyols, polyamines, Aminocarboxylic acid, aminoalcohol and the like can be used as the shell forming substance.

In the present invention, the compound (3) having one active hydrogen that reacts with the isocyanate group and / or isothiocyanate group is 30 mol% of the whole compound that reacts with the isocyanate group and / or isothiocyanate group.
However, if it exceeds 30 mol%, the storage stability of the capsule toner deteriorates, which is not preferable. Further, an isocyanate compound and / or an isothiocyanate compound [(1) + (2)] constituting the outer shell, an isocyanate group and / or
Or a compound that reacts with an isothiocyanate group [(3) +
The molar ratio of (4)] is preferably 1: 1 to 1:20 so that unreacted isocyanate groups do not remain.

In the production of the capsule toner, the outer shell is preferably formed by interfacial polymerization or in-situ polymerization. For example, the core particles as the core substance and the number average particle size are 1% of the number average particle size of the mother particles. It may be carried out by a dry method in which the outer shell particles of / 8 or less and the child particles of the outer shell forming material are stirred at high speed in an air stream to form the outer shell.

The outer shell resin can be produced without a catalyst, but when a catalyst is used, a tin-based catalyst such as dibutyltin dilaurate, 1,4-diazabicyclo [2.2.2] octane, N, N,
Known urethane catalysts such as amine-based catalysts such as N-tris (dimethylaminopropyl) -hexahydro-S-triazine can be used.

The resin used as the core material of the capsule toner in the present invention has a glass transition point (Tg) of 10 ° C. or higher and 50 or higher.
Thermoplastic resins such as polyester resins, polyester / polyamide resins, polyamide resins and vinyl resins having a temperature of not higher than 0 ° C. are mentioned, and vinyl resins are particularly preferable. Glass transition point
If the temperature is less than 10 ° C, the storage stability of the capsule toner deteriorates, and
If the temperature exceeds ℃, the fixing strength of the capsule toner deteriorates, which is not preferable.

Examples of the monomer constituting the vinyl resin include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-
Styrene or styrene derivatives such as ethylstyrene, 2,4-dimethylstyrene, p-chlorostyrene, vinylnaphthalene, etc., such as ethylene, propylene, butylene,
Ethylenically unsaturated monoolefins such as isobutylene and the like, vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl formate and vinyl caproate, for example acrylic acid,
Methyl acrylate, ethyl acrylate, acrylic acid n-
Propyl, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate,
Amyl acrylate, cyclohexyl acrylate, n-octyl acrylate, isooctyl acrylate, decyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, methoxyethyl acrylate, 2-hydroxyethyl acrylate, acrylic acid Glycidyl, 2-chloroethyl acrylate, phenyl acrylate, α-chloromethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, T-Butyl methacrylate, amyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, decyl methacrylate, lauryl methacrylate, methacrylic acid Ethylenic monocarboxylic acids and their esters such as 2-ethylhexyl acid salt, stearyl methacrylate, methoxyethyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate and the like. , An ethylenic monocarboxylic acid substitution product such as acrylonitrile, methacrylonitrile, acrylamide, etc., an ethylenic dicarboxylic acid such as dimethyl maleate and the substitution product thereof, vinyl ketones such as vinyl methyl ketone, for example vinyl methyl ether Vinylidene halides such as vinylidene chloride and N-vinyl compounds such as N-vinylpyrrole and N-vinylpyrrolidone. is there. Preferably, of the components constituting the resin for the core material according to the present invention, styrene or a styrene derivative is preferably 50 to 90 parts by weight for forming the main skeleton of the resin, and ethylene is used for adjusting the thermal characteristics such as the softening temperature of the resin. The monocarboxylic acid and its ester are preferably used in an amount of 10 to 50 parts by weight.

When a cross-linking agent is added to the monomer composition constituting the resin for the core material according to the present invention, known cross-linking agents can be used appropriately (combination of two or more if necessary). .. When the amount of these cross-linking agents used is large, the toner is less likely to be melted by heat, resulting in poor heat fixing property or heat pressure fixing property. Further, when the amount used is small, it is difficult to prevent the offset phenomenon in which a part of the toner adheres to the roller surface without being completely fixed to the paper and is transferred to the next paper in the thermal pressure fixing. Further, the amount of these crosslinking agents used is preferably 0.001 to 15% by weight (more preferably 0.1 to 10% by weight) based on the polymerizable monomer. If necessary, the core material may contain one or more known anti-offset agents for the purpose of improving offset resistance in heat and pressure fixing. The ratio of these offset preventing agents to the resin in the core material is preferably 1 to 20% by weight.

Although the colorant is contained in the core material of the encapsulated toner of the present invention, all the dyes, pigments and the like used in the conventional colorant for toner can be used. Usually, about 1 to 15 parts by weight is used with respect to 100 parts by weight of the resin in the core material.

In the outer shell material of the capsule toner of the present invention, as a charge control agent, a metal-containing dye such as a metal complex of an organic compound having a carboxyl group or a nitrogen group, which has been conventionally used in toner, nigrosine, etc. May be added in an appropriate amount. Further, this charge control agent may be mixed with a toner and used.

If desired, the capsule toner of the present invention may contain a fluidity improver, a cleaning improver and the like. Further, an additive for adjusting the developability, for example, fine particle powder of a polymer of methacrylic acid methyl ester may be used. Further, a small amount of carbon black may be used for toning and resistance adjustment. The softening point of the capsule toner in the present invention is preferably 80 ° C. or higher and 150 ° C. or lower, but if it is lower than 80 ° C., the offset resistance deteriorates, and if it exceeds 150 ° C., the fixing strength deteriorates, which is not preferable. The particle size of the capsule toner in the present invention is not particularly limited, but the average particle size is usually 3 to.
It is set to 30 μm. The thickness of the outer shell of the capsule toner is 0.01 ~
1 μm is preferable, and if it is less than 0.01 μm, blocking resistance is deteriorated, and if it exceeds 1 μm, heat melting property is deteriorated, which is not preferable.

Carrier particles used in the magnetic brush development method are generally ore reduced iron powder produced by reducing iron ore, mill scale reduced iron powder produced by reducing mill scale, and molten copper are fine pores. Conventionally used are spherical atomized iron powder that has flowed out of the powder and is cooled and powdered, and iron nitride powder that has been denitrified after nitriding and crushing copper flakes. Further, a ferrite carrier obtained by granulating / drying and firing a ferrite powder containing Fe ₂ O ₃ as a main raw material is also used. The iron powder type carrier is oxidized by moisture in the air and Fe ₂ O ₃ so-called rust is generated on the surface, so it is covered with a stable oxide thin film of relatively high resistance by forced oxidation. It can be adjusted. The iron powder type carrier has a lower resistance than the ferrite carrier and is more likely to produce an image density, but has a large true specific gravity and low fluidity, so that the developer life is generally inferior to that of the ferrite carrier.

On the other hand, the ferrite carrier has a true specific gravity of 30 to 40% smaller than that of the iron powder type carrier, electric resistance and magnetic properties can be largely changed, and it is spherical and has good fluidity and little residual magnetization. It has features such as being able to. Therefore, the ferrite carrier is easier to adjust the image than the iron powder type carrier and is suitable for extending the life of the developer, but it has not yet reached the level enough to satisfy the demand. Further, it is necessary to consider the performance of the core particles and the performance of the toner in order to extend the life of the developer. That is, when a ferrite carrier is used as a core particle, Fe ₂ O ₃ , NiO, CuO, CoO, M, which is a raw material of ferrite, is used.
gO, ZnO, MnCO ₃ , BaCO ₃ , SrCO ₃ ,
It is necessary to select a material such as Li ₂ CO ₃ and CdO in which the composition ratio and composition uniformity are important and the chemical change is small.

Magnetite (Fe ₂ O ₃ ) is also a kind of ferrite and is also called iron ferrite. 100% of Fe ₂ O ₃ is used as a raw material, and a carrier is produced from this using a dry method similar to the production of ferrite described later. The magnetite carrier has magnetic characteristics, especially maximum magnetization larger than that of ferrite, and FeO having a low resistance inside the carrier. FeO has a relatively low resistance, so that the resistance becomes lower than that of the ferrite carrier, and the image density is easy to appear. Since its performance is similar to that of a ferrite type, it is effective as a reversal developing type developer having a small effective developing potential width and has recently been noted.

The core particles that can be used in the present invention are magnetite carriers or ferrite carriers, and other than Fe ₂ O ₃ , NiO, CuO, CoO,
MgO, ZnO, MnCO ₃ , BaCO ₃ , SrC
Raw materials such as O ₃ , Li ₂ CO ₃ and CdO are used. other,
As additives, SiO ₂ , CaCO ₃ , TiO ₂ , Sn
_{O 2, PbO, V 2 O} 5, Bi 2 O 5, Al 2 O 3 and the like may also be used.

The ferrite carrier is generally manufactured by a dry method in which the raw materials are mechanically mixed, calcined and finely pulverized, and then granulated and fired at a high temperature. That is, several metal oxides of the main raw material are mixed with other metal oxides as an additive as the case may be, then dried and baked, and then a binder such as polyvinyl alcohol, a defoaming agent, a dispersant and the like are added. Add slurry for granulation. Granules obtained by atomizing and drying the slurry are heated to 900-1 in an electric furnace.
After firing at 300 ° C., crushing and classification are performed to produce core particles.

The apparent density of the carrier is: JIS-Z25
It is measured by a measuring method according to No. 04 (Apparent density test method for metal powder). Generally, the apparent density of ferrite carrier or magnetite carrier is 2.5 to 3.5 (g /
cm ³ ), which is slightly lighter than the iron powder carrier of 2.5 to 4.5. However, the present carrier used in the invention is an apparent density is further reduced, preferably usually 2.5 g / cm ³ or less require 1.0~2.4g / cm ^3. When the apparent density exceeds 2.5 g / cm ³ , the force applied to the toner becomes too large and the shell of the capsule toner used in the present invention is easily damaged. Also, the density is 1.0 g / cm ³
If it is less than 1.0 g, undesired phenomena such as too low saturation magnetization, easy carrier damage due to lack of carrier strength, and easy carrier scattering may occur. / Cm ³ or more is preferable.

Such a low apparent density carrier is used in the production of the carrier, such as the particle size of the metal oxide as the raw material, the type and amount of the dispersant and the binder, the addition of the extender, the conditions for slurrying, and the powder mist drying. It can be achieved by controlling the conditions and firing conditions. Further, a resin-coated carrier in which a resin coating layer is provided on the surface of core particles such as a ferrite carrier and a magnetite carrier has been devised, and it is possible to reduce the possibility that the toner adheres to the surface of the carrier particles and makes the toner charging unstable. It has recently attracted attention because it has the potential of further improving the durability of the developer, adjusting the triboelectric charging property of the toner, and reducing the environmental dependence of the charging property. The performance required for the resin material for coating is that the coating layer on the surface of the core particles has sufficient abrasion resistance and heat resistance, and that the coating layer has sufficient adhesion to the core particles. In addition, it is required that the coating layer has a good anti-sticking property so that the toner particles do not stick to the surface of the carrier particles, and that the toner is easily provided with a desired polarity and magnitude of chargeability. Fluororesin as the resin material,
Acrylic resin, styrene acrylic resin, silicone resin,
Polyester resin, polybutadiene resin, etc. are used,
Preferred are styrene acrylic resin and silicone resin.

The method of coating the carrier is to dissolve the resin in an organic solvent or the like, or to use a solution prepared as an aqueous resin emulsion, and apply the solution to the surface of the particles by the dipping method, the atomization method or the like,
The thickness is usually 0.1 μm due to drying and / or heat curing.
Generally, a resin film having a thickness of 1.0 μm is formed. However, as the coated carrier used for the capsule toner in the present invention, a coating layer having a thickness of 1.5 μm or more is usually used. Coating layer thickness is 1.5μm
The following is not enough to smooth the surface irregularities of the carrier, the fluidity is low and the force applied to the capsule toner is large, so that the shell is easily worn and damaged, and the developer life is shortened. Not preferable. On the other hand, the coat layer of the carrier is worn by the sleeve on the magnet roll in the developing unit, but by thickening the coating layer, the fluidity is improved and the reduction of the film thickness due to abrasion can be suppressed, which is effective in extending the service life. .. Therefore, it is more preferably 2.0 μm or more. On the other hand, thickening the coating layer requires coating the resin multiple times or increasing the concentration of the resin solution.In the former case, the manufacturing process is complicated, and in the latter case, uneven coating film is a problem. Therefore, the thickness of the coating layer is practically 5.0 μm.

When the developing method of the present invention is carried out by using the two-component developer comprising the above-mentioned thermal dissociative capsule toner of the present invention and the carrier having the above-mentioned apparent density, the developing apparatus and method to be used. As the above, a conventionally known one can be used as it is. That is, a normal developing method in which toner having a polarity opposite to that of the latent image on the image carrier is developed by Coulomb force, and toner having the same polarity as the latent image on the image carrier is applied with a bias voltage to utilize Coulomb repulsion force. The latent image on the image carrier can be developed by a reversal development method of developing. In this case, the compounding amount of the toner particles and the carrier is usually 1/99 to 20/80. The developing method of the present invention can be used for developing a latent image formed on a photoconductor as an image bearing member, a latent image formed on a dielectric, or the like. After the developing process is completed by the developing method of the present invention as described above, the toner image is transferred and fixed on a recording medium such as recording paper by a conventionally known method.

[0041]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Production Example 1 Production Example of Capsule Toner 70.0 parts by weight of styrene, 2-ethylhexyl acrylate
30.0 parts by weight, divinylbenzene 1.0 part by weight, carbon black "# 44" (manufactured by Mitsubishi Kasei) 10.0 parts by weight, 2,2'-
4.0 parts by weight of azobisisobutyronitrile and 9.5 parts by weight of 4,4'-diphenylmethane diisocyanate "Millionate MT" (manufactured by Nippon Polyurethane Industry Co., Ltd.) were added, and the mixture was put into an attritor (manufactured by Mitsui Miike Kakoki) and heated to 10 ° C. And dispersed for 5 hours to obtain a polymerizable composition. 30% by weight of this in 800 g of an aqueous colloidal solution of 4% by weight of tricalcium phosphate prepared in a glass separable flask having a volume of 2 liters.
Was added and the mixture was emulsified and dispersed for 2 minutes at 5 ° C. and a rotation speed of 10,000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). A four-neck glass lid was attached, a reflux type cooling tube, a thermometer, a dropping funnel with a nitrogen introducing tube, and a stainless steel stirring rod were attached, and the glass was placed in an electric heating mantle.
Resorcin 22.0 g, diethyl malonate 3.6 g, 1,4-diazabicyclo [2.2.2] octane 0.5 g, ion-exchanged water 40 g
Prepare a mixed solution of and mix with a dropping funnel while stirring.
It dripped over minutes. Then, while continuing stirring under nitrogen, the temperature was raised to 80 ° C. and reacted for 10 hours. 10% after cooling
Dissolve the dispersant in aqueous hydrochloric acid, filter, wash with water, and then
The mixture was dried at 20 ° C. under reduced pressure at 20 mmHg for 12 hours and classified by an air classifier to obtain a capsule toner having an average particle diameter of 9 μm and a resin having a thermally dissociable urethane bond. The glass transition point derived from the resin in the core material is 30.2 ° C, and the softening point is 130.
It was 0 ° C.

Production Example 2 Production Example of Capsule Toner Copolymer 10 comprising 75 parts by weight of styrene and 25 parts by weight of n-butyl acrylate and having a softening point of 75.3 ° C. and a glass transition point of 40.5 ° C.
0 Parts by weight of copper phthalocyanine “Suikaprint Cyanine Bl
ue GN-O "(Sumitomo Chemical Co., Ltd.) 6 parts by weight and polypropylene wax" Bi- scol 550p "(Sanyo Kasei Co., Ltd.) 5 parts by weight are premixed, melt-kneaded by a twin-screw extruder, and cooled. Then, it was crushed. 40 parts by weight of this kneaded product, 50 parts by weight of styrene, 15 parts by weight of n-butyl acrylate, 2,2'-
3 parts by weight of azobis (2,4-dimethylvaleronitrile),
Adduct of 3 moles of 2,4-tolylene-diisocyanate and 1 mole of trimethylolpropane "Takenate D-102"
(Takeda Pharmaceutical Co., Ltd.) 9.0 parts by weight, xylylene-1,4-
The mixture was mixed with 0.5 part by weight of diisothiocyanate to obtain a polymerizable composition. 4% by weight of tricalcium phosphate prepared in advance in a glass separable flask having a volume of 2 liters.
The amount of 30% by weight was added to 800 g of the aqueous colloidal solution of and the rotation speed was 10,000 rpm at 5 ° C using the TK homomixer.
And emulsified and dispersed for 2 minutes.

A four-necked glass lid was attached, and a reflux type cooling tube, a thermometer, a dropping funnel with a nitrogen introducing tube, and a stainless steel stirring rod were attached and installed in an electric heating mantle. Four
-Acetylcatechol 27.4 g, dimethyl malonate 4.0 g,
A mixed solution of 0.8 g of 1,2-ethanedithiol, 0.5 g of 1,4-diazabicyclo [2.2.2] octane and 40 g of ion-exchanged water was prepared and added dropwise from a dropping funnel over 30 minutes while stirring. Then, while continuing stirring under nitrogen, the temperature was raised to 80 ° C. and reacted for 10 hours. After cooling, dissolve the dispersant in 10% aqueous hydrochloric acid, filter, wash with water, dry under vacuum at 20 mmHg for 12 hours at 45 ° C, classify with a wind classifier, and heat the outer shell with an average particle size of 9 μm. A capsule toner made of a resin having a dissociative urethane bond was obtained. This capsule toner 10
0 parts by weight of hydrophobic silica fine powder "Aerosil R-972"
0.4 parts by weight (manufactured by Aerosil Co., Ltd.) were added and mixed to obtain a capsule toner according to the present invention. The glass transition point derived from the resin in the core material was 35.4 ° C, and the softening point was 133.5 ° C.

Production Example 3 Production Example of Ferrite Carrier 55 mol% Fe ₂ O ₃ , 25 mol% ZnO, NiCO ₃
20 mol% is pulverized and mixed by a wet ball mill for 10 hours,
After drying, it was kept at 950 ° C. for 4 hours. This was crushed with a wet ball mill for 24 hours to 3 μm or less. The slurry is granulated and dried, and then 1200 ° C in an electric furnace in a nitrogen atmosphere.
After holding at ℃ for 6 hours, crush and classify to 60-100μ
m. When the magnetic properties of this granulated carrier were measured, the value of magnetization at 3000 Oe was 75 emu, and the coercive force and residual magnetization were 0. Moreover, the apparent density is 2.3.
Met.

Production Example 4 Production Example of Magnetite Carrier Fe ₂ O ₃ was ground and mixed in a wet ball mill for 10 hours,
After drying, it was kept at 950 ° C. for 4 hours. This was pulverized with a wet ball mill for 24 hours to have a size of 5 μm or less. The slurry is granulated and dried, and then 1200 ° C in an electric furnace in a nitrogen atmosphere.
After holding at ℃ for 6 hours, crush and classify to 60-100μ
m. When the magnetic properties of this granulated carrier were measured, the value of magnetization at 3000 Oe was 75 emu, and the coercive force and residual magnetization were 0. Moreover, the apparent density is 2.2.
Met.

Production Example 5 Production Example of Coated Carrier Using the ferrite carrier obtained in Production Example 3, 15% by weight of the coating silicone resin composition was coated on the carrier using a fluidized bed, and further at 150 ° C. After baking for 3 hours, a resin-coated carrier was obtained. The apparent density of the resin-coated carrier is 2.15 g / cm ³ ,
The resistance is 3 × 10 ¹² Ωcm and the saturation magnetization is 75.
It was emu / g. Further, the thickness of the coating material of the coated carrier was calculated to be 2.0 μm by calculating the total coating material weight with a carbon analyzer.

Production Example 6 Production Example of Coated Carrier Using the magnetite carrier obtained in Production Example 4, the fluororesin composition for coating was applied to the carrier in an amount of 1 with respect to the carrier.
Coating was performed at 5% by weight, and baking was further performed at 150 ° C. for 3 hours to obtain a resin-coated carrier. The apparent density of the resin-coated carrier is 2.00 g / cm ³ , the resistance is 2 × 10 ¹² Ωcm, and the saturation magnetization is 75 em.
It was u / g. The thickness of the coating material of the coated carrier was 2.5 μm as a result of measuring and measuring the total coating material weight with a carbon analyzer.

Example 1 92 parts by weight of the resin-coated carrier obtained in Production Example 5 was mixed with 8 parts by weight of the capsule toner obtained in Production Example 1, and the mixture was stirred with a V blender for about 8 hours to give a developer. Obtained. Copying was performed using a commercially available OPC-equipped copying machine equipped with a stirrer at a copying speed of 12 sheets / min while using the above developer and intermittently supplying capsule toner.
No deterioration of the image was observed even when the size was changed to 4 and the development of 100,000 sheets was performed, and a copy having good image quality was obtained. Further, the fixing property of the toner was evaluated by a gauze rubbing test to be 10
It was sufficiently fixed at a heat roller surface temperature of 0 ° C.

Example 2 92 parts by weight of the resin-coated carrier obtained in Production Example 6 was mixed with 8 parts by weight of the capsule toner obtained in Production Example 2 and mixed with a V blender for about 8 hours to stir the developer. Obtained. When the above-mentioned developer was used and intermittently replenishing the capsule toner, copying was carried out by a commercially available OPC-equipped copying machine similar to that of Example 1 equipped with a stirrer. No deterioration of the image was observed even after the operation, and a copy with good image quality was obtained.

Comparative Production Example 1 Production Example of Ferrite Carrier 55 mol% Fe ₂ O ₃ , 25 mol% ZnO, NiCO ₃
20 mol% is pulverized and mixed by a wet ball mill for 10 hours,
After drying, it was kept at 950 ° C. for 4 hours. This was crushed with a wet ball mill for 24 hours to be 10 μm or less. This slurry was granulated and dried, held at 1200 ° C. for 6 hours, and then pulverized and classified to 60 to 100 μm. When the magnetic properties of this granulated carrier were measured, the value of magnetization at 3000 Oe was 75 emu, and the coercive force and residual magnetization were 0. Moreover, the apparent density was 2.9.

Comparative Production Example 2 Production Example of Magnetite Carrier Fe ₂ O ₃ was ground and mixed in a wet ball mill for 10 hours,
After drying, it was kept at 950 ° C. for 4 hours. This was crushed with a wet ball mill for 24 hours to be 10 μm or less. This slurry is granulated and dried, and then 120 times in a nitrogen atmosphere in an electric furnace.
After holding at 0 ℃ for 6 hours, crush and classify to 60-100
μm. When the magnetic properties of this granulated carrier were measured, the value of magnetization at 3000 Oe was 75 emu, and the coercive force and residual magnetization were 0. Moreover, the apparent density is 2.
It was 9.

Comparative Production Example 3 Production Example of Coated Carrier Using the ferrite carrier obtained in Comparative Production Example 1, 5% by weight of the coating silicone resin composition was coated on the carrier using a fluidized bed, and further 150 3 at ℃
After baking for a period of time, a resin-coated carrier was obtained. The apparent density of the resin-coated carrier is 2.80 g / c.
m ³ , resistance was 2.5 × 10 ¹² Ωcm, and saturation magnetization was 75 emu / g. Further, the thickness of the coating material of the coated carrier was calculated and measured by the carbon analyzer in the same manner as in Production Examples 4 and 5, and 1.
It was 0 μm.

Comparative Production Example 4 Production Example of Coated Carrier Using the ferrite carrier obtained in Comparative Production Example 1, 15% by weight of the silicone resin composition for coating was coated on the carrier using a fluidized bed, and further 150 A resin-coated carrier was obtained by baking at 3 ° C for 3 hours. The apparent density of the resin-coated carrier is 2.75 g / cm.
³ , the resistance was 4 × 10 ¹² Ωcm, and the saturation magnetization was 75 emu / g. Further, the thickness of the coating material of the coated carrier was calculated to be 2.0 μm by calculating the total coating material weight with a carbon analyzer.

Comparative Production Example 5 Production Example of Coated Carrier Using the magnetite carrier obtained in Comparative Production Example 2,
The carrier is coated with the coating silicone resin composition in an amount of 15% by weight using a fluidized bed and further at 150 ° C.
After baking for 3 hours, a resin-coated carrier was obtained.
The apparent density of the resin-coated carrier is 2.9 g / cm.
³ , the resistance was 2 × 10 ¹² Ωcm, and the saturation magnetization was 75 emu / g. The thickness of the coating material of the coat carrier was 2.0 μm as a result of calculating and measuring the total coating material weight with a carbon analyzer.

Comparative Example 1 92 parts by weight of the resin-coated carrier obtained in Comparative Production Example 3 was mixed with 8 parts by weight of the capsule toner obtained in Production Example 1, and the mixture was stirred with a V blender for about 8 hours to develop the developer. Got When a copying machine equipped with a commercially available OPC equipped with a stirrer was used to copy the toner using the above-mentioned developer and intermittently supplying the capsule toner, image deterioration was observed at 20,000 sheets of A4 size. An increase in density and a decrease in gradation were observed, and background fogging occurred and a black core was observed. Further, toner agglomeration occurred in the developer.

Comparative Example 2 92 parts by weight of the resin-coated carrier obtained in Comparative Production Example 4 was mixed with 8 parts by weight of the capsule toner obtained in Production Example 2, and the mixture was stirred with a V blender for about 8 hours to develop the developer. Got When copying was performed using a commercially available OPC-equipped copier equipped with a stirrer while using the above-mentioned developer and intermittently supplying capsule toner, image deterioration was observed at 50,000 sheets of A4 size. An increase in density and a decrease in gradation were observed.

Comparative Example 3 92 parts by weight of the resin-coated carrier obtained in Comparative Production Example 5 was mixed with 8 parts by weight of the capsule toner obtained in Production Example 1, and the mixture was stirred with a V blender for about 8 hours to develop the developer. Got When copying was performed using a commercially available OPC-equipped copier equipped with a stirrer while using the above-mentioned developer and intermittently supplying capsule toner, image deterioration was observed at 50,000 sheets of A4 size. An increase in density and a decrease in gradation were observed.

[0059]

INDUSTRIAL APPLICABILITY By using a two-component developer containing a carrier having a predetermined apparent density in the present invention, development suitable for the heat dissociative capsule toner in the present invention can be carried out, and low energy fixing and development can be performed. The life of the agent can be extended.

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Claims (6)

[Claims] 1. A method of developing a latent image on an image carrier using a two-component developer comprising toner particles and a magnetic carrier, wherein the toner is a heat dissociative capsule toner and the carrier has an apparent density of 2 A development method characterized in that the carrier is a ferrite or magnetite carrier of 0.5 g / cm ³ or less. 2. The toner according to claim 1, wherein the main component of the shell material of the capsule is a resin having at least one bond of a heat dissociable urethane bond, a thiol urethane bond, or an s-thiourethane bond. Claim 1
The developing method described. 3. The heat dissociable urethane resin, which is the main component of the shell material according to claim 2, has a phenolic hydroxyl group and / or a thiol group among bonds involving all isocyanate groups and / or isothiocyanate groups. The developing method according to claim 2, wherein the number of bonds by the reaction with is 30% or more. 4. The developing method according to claim 1, wherein the capsule toner according to claim 1 has a softening point of 80 ° C. to 150 ° C. 5. The developing method according to claim 1, wherein the ferrite or magnetite carrier according to claim 1 is coated with a resin. 6. The developing method according to claim 5, wherein the coating layer formed by the coating treatment according to claim 5 has a thickness of 1.5 μm or more.