JPH0693132B2 - Electrophotographic toner - Google Patents

Description

The present invention relates to a toner used in electrophotography, electrostatic printing and the like, and more particularly to an electrophotographic toner suitable for a heat fixing method.

[Conventional technology]

Conventionally, as the electrophotographic method, many methods are known as described in U.S. Pat.No. 2,297,691, Japanese Patent Publication No. 4223910 and Japanese Patent Publication No. 43-24748, but photoconductive methods are generally known. After forming an electric latent image on the photoconductor by various means using a conductive substance, developing the latent image with a toner, and transferring the toner image to a transfer material such as paper, if necessary. It is fixed by heating or pressure to obtain a copy. Various developing methods for visualizing an electric latent image using toner are known. For example, U.S. Pat.
No. 2618552, magnetic brush method described in 063
No. 2221 and the cascade development method described in the specification.
Many developing methods such as the powder method, the fur brush developing method, and the liquid developing method described in the specification of 776 are known. As the toner used in these developing methods,
A fine powder in which a dye or pigment is dispersed in a natural or synthetic resin is used. Further, it is known to use a developing fine powder to which a third substance is added for various purposes.

The developed toner image is transferred and fixed on a transfer material such as paper, if necessary.

As a method for fixing the toner image, a method of heating and melting the toner by a heater or a heat roller to fuse and solidify it on the support, a method of softening or dissolving the binder resin of the toner with an organic solvent and fixing it on the support, pressurization There is known a method of fixing the toner to the support by the method.

Toners are selected with materials suitable for each fixing method,
Generally, the toner used for a particular fixing method cannot be used for another fixing method. In particular, it is almost impossible to transfer the toner used in the heat fusion fixing method using a heater, which has been widely used in the past, to the heat roller fixing method, the solvent fixing method, the pressure fixing method and the like. Therefore, toner suitable for each fixing method has been researched and developed.

Various magnetic recording methods are known in which a magnetic latent image is formed and developed with a magnetic toner.

Although various methods and devices have been developed for the process of fixing the toner image on paper, the most general method at present is
This is a so-called thermal roll fixing system in which heat and pressure are applied at the same time, and this is a method of fixing the toner image on the image receiving sheet by bringing the image receiving sheet carrying the toner image into contact with a heated roller.

In recent years, a heat roll type fixing method having good thermal efficiency has become the majority of commercially available copying machines as the copying work becomes more efficient, energy is saved, and the copying machine is made smaller and has higher performance.
Most of these copiers try to fix the toner on the paper by thermocompression bonding with a heating roller.The non-contact heating method using heat rays allows the heating element to obtain a satisfactory fixed image at a lower temperature. However, there are many advantages such as higher speed, but this method also has various problems. As one of the big ones, if the roller is kept at a temperature at which the toner should be sufficiently fixed to the holding member such as paper, the toner is fused not only on the paper but also on the heat roll, which causes the repeated copying. There is a serious problem due to the so-called offset contact method in which the heat roll becomes dirty and cannot be completely removed by the blade or the cleaning web that should keep the roll clean, and the paper also becomes dirty at last.

Various measures have been attempted for fixing devices and toners in order to solve or alleviate this problem, but it cannot be said that they have been sufficiently solved.

As the fixing device, a material such as Teflon or silicon having excellent surface peeling property is used. Alternatively, a device such as applying oil such as silicone oil to the roller has been made, and most of the hot roller fixing devices of currently commercialized copying machines apply oil in some form. However, the oil application causes problems such as oil stains on the sheet and troubles due to complication of the fixing device and an increase in cost.

As the toner, a method of adding a small amount of wax such as low-molecular weight polyethylene or polypropylene that is sufficiently melted when heated to increase the releasability is also used, but it is effective in preventing offset, but aggregation of the toner is effective. However, it is difficult to say that this is sufficient, because adverse effects such as an increase in the property, instability in the charging characteristics, and a decrease in the durability have been observed. As other methods, various attempts have been made to improve the binder resin. JP-B-51-23354 proposes a toner using a crosslinked polymer as a binder resin. According to that method, the improvement of offset resistance and anti-sticking property is remarkable, but on the other hand, if the degree of cross-linking is increased, the fixing point rises, and therefore the fixing temperature is sufficiently low and the anti-offset property and anti-sticking property are low. Good fixing properties and sufficient fixing characteristics have not been obtained. Further, the cross-linked polymer is difficult to disperse the pigment and is difficult to be compatible with other polymers, and thus it is difficult to obtain good developing characteristics for a toner using the cross-linked polymer as a binder resin. There is a problem.

In general, in order to measure high-speed fixing, it is necessary to lower the molecular weight of the resin and lower the softening point, which is contrary to the measures for improving the offset resistance. In addition, this inevitably lowers the glass transition point of the resin and causes undesired development in which the toner is blocked during storage. However, in the case of conventional low-speed and medium-speed machines that do not require low-temperature fixing so much, practical measures are taken by measures such as the improvement of the fixing device as described above and the improvement of the toner, such as crosslinking and the use of releasable additives. The level didn't matter. However, basically, the above contradiction has not been solved, and under the present circumstances, a toner capable of fixing at an extremely low temperature and having a wide fixing temperature range and good offset resistance and blocking resistance has not been obtained.

In order to satisfy the contradictory properties of low-temperature fixability and blocking resistance, that is, storage stability, one resin ensures low-temperature fixability and the other resin provides offset resistance and blocking resistance. There is. For example, in JP-A-56-27156, the styrene content is low,
A developing powder composed of a styrene copolymer having a large average molecular weight and a styrene copolymer having a larger average molecular weight and a smaller styrene content than the styrene content of the former styrene copolymer is described. The former styrene copolymer is a fixing component,
The latter is a blocking resistant component. In addition, JP-A-58
In Japanese Patent Laid-Open No. 106552, a weight average molecular weight that contributes to fixability is 50,000 or more, a resin having a Tg (glass transition point) of 70 ° C. or less and a weight average molecular weight that contributes to blocking resistance is 50,000 or more, and Tg There is a description of a dry developing toner composed of a blend of resins at 70 to 80 ° C. In addition, JP-A-58-203453
In the publication, a low temperature softening resin having a softening point of 80 to 120 ° C.,
There is a description of a toner in combination with a high temperature softening resin having a softening point of 140 ° C. or higher.

However, conventionally, the disclosed technology is based on the average molecular weight or the composition ratio as a comprehensive evaluation value from a macroscopic point of view of a resin having a molecular weight distribution from a low molecular weight to a high molecular weight region. However, it does not refer to the thermal characteristics in the fixing temperature range, but to fix the fixing property and the offset property. Even in an attempt to limit the thermal characteristics and improve the fixing property, the inventors described the thermal development over the entire toner with only one representative value (for example, softening point) showing the thermal overall characteristics of the toner. However, it is intended to solve the problems of the present toner. However, in reality, development having the same softening point but completely different toner characteristics can sufficiently occur.

In the present invention, by analyzing the physical properties and thermal characteristics of the toner and defining them, it is possible to first obtain a toner that can satisfy low-temperature fixing property, cold offset resistance, hot offset resistance and storage stability. There is a place where you can.

The objects of the present invention are listed below.

(1) An object of the present invention is to provide a dry toner suitable for a heat roll fixing method that does not apply oil.

(2) The object of the present invention is to sufficiently fix at a lower temperature,
An object of the present invention is to provide a toner capable of lowering energy, particularly suitable for high-speed fixing, sufficiently preventing offset, and having a wide fixing temperature range.

(3) It is an object of the present invention to provide a toner having an acceptable agglomeration temperature and free from blocking during storage and use.

(4) An object of the present invention is to provide a toner having stable electric characteristics under various humidity conditions and good moisture resistance.

(5) It is an object of the present invention to provide a toner having a sufficient image density, a clear image, a high resolution, and an image quality free of background fog and having excellent developing characteristics.

(6) An object of the present invention is to provide a toner having excellent durability against repeated use and capable of stably maintaining a good quality image as described in the preceding paragraph.

(7) An object of the present invention is to provide a toner having excellent powder characteristics such as fluidity and cohesiveness, and good replenishment and storage stability.

(8) An object of the present invention is to provide a toner having almost no carrier contamination in a two-component developer due to adhesion to the carrier, fusion or the like.

(9) An object of the present invention is to provide a one-component magnetic toner having good dispersibility of magnetic powder.

(10) An object of the present invention is to provide a toner having a high commercial value, which is excellent in overall conditions in which various performances required for the toner are well balanced.

[Means and Actions for Solving Problems]

A feature of the present invention is that the pour point is in the range of 70 to 110 ° C. and the gradient (1 × 10 ² ) of the flow line is in the range of −2.0 to −6.0, and the pour point is the above. , But the gradient of the flow line is in the range of -7.0 to -10.0 (B)
The use of a binder resin whose main component is a mixture of

The weight ratio of the resin (A) and the resin (B) in the present invention is 1:10.
~ 8: 10, preferably 2:10 to 7:10, more preferably 3:10 to
It is in the range of 7:10.

Moreover, the preferable range of the pour point is 75 to 105 ° C., and the more preferable ranges of the gradient (1 × 10 ² ) of the resin (A) and the resin (B) are −2.5 to −5.0 and −7.0 to −9.5, respectively. is there.

The pour point and the gradient of the flow straight line (1 × 10 ² ) in the present invention can be obtained by the following measuring method.

Using the flow tester OFT-500 type (manufactured by Shimadzu Corporation),
With a die (nozzle) diameter of 1.0 mm and a thickness of 1.0 mm, a load of 100 kg is applied, and after preheating time of 120 seconds, extrusion load of 30 kg is 5 ° C /
A plunger drop amount-temperature curve (hereinafter referred to as a softened S-shaped curve) of the toner drawn when the temperature is raised at a constant speed for a minute is obtained.
Use 2.0g of fine powder as the sample toner, and make the plunger cross-sectional area 1.0cm ² . Softened S-curve is usually first
The curve is as shown. As the temperature rises at a constant rate, the toner is gradually heated and starts to flow out. (Plunger descending A → B) When the temperature is further raised, the toner in the molten state largely flows out (B → C → D), and the plunger descending is stopped and completed. (D → E) The height H of the softening S curve represents the total outflow amount, and the temperature T _O corresponding to the point C of H / 2 represents the softening point of the toner.

At this time, the point B, which is the starting point of the plunger descent, is the pour point. At the same time, the melt viscosity is measured at 1.5 ° C intervals by an automatic measuring device built into the device. (However, for the formula for deriving the melt viscosity, refer to Shimadzu Review, Vol. 39, Issue 3.4). The result is calculated as the viscosity-temperature function by the least squares method, and a straight line is obtained. To get

log VI = 1 × T + m Flow straight line VI: Melt viscosity (poise), l: Gradient, T: Temperature (° C.) m: Viscosity interception Within the range specified in the present invention as the binder resin of the developer of the present invention Resins of can be used. For example, polyester resin, epoxy resin, styrene acrylic resin,
Butyral resin, styrene-butadiene resin, etc.

The production examples of the resins that can be used as the resins (A) and (B) are shown below.

Production example 1 The polymerizable monomer composition composed of the above materials was added dropwise to 200 parts by weight of xylene heated to the reflux temperature over 4 hours. Furthermore, while refluxing xylene, the temperature is 138 to 144 ° C.
The reaction was carried out for 4 hours to complete the polymerization. After completion of the polymerization, xylene was removed while heating under reduced pressure to obtain a styrene-n-butyl acrylate copolymer crosslinked with divinylbenzene [hereinafter referred to as "resin (A1)"]. The obtained resin (A1) had a flow line gradient (l × 10 ² ) of −4, a pour point of 100 ° C., a glass transition point of 67 ° C., and a gel permeation chromatography chromatogram. Had a maximum at a molecular weight of about 18,000.

Production example 2 Styrene-n was prepared in the same manner as in Production Example 1 using the above materials.
-Butyl acrylate copolymer [hereinafter referred to as "resin (A2)"
]] Was obtained. The obtained resin (A2) had a flow line gradient (l × 10 ² ) of −2.4 and a pour point of 109 ° C.,
It has a glass transition point of 72 ° C and a molecular weight of about 2500 in the gel permeation chromatography chromatogram.
It had a maximum at 0.

Production Example 3 Styrene-n was prepared in the same manner as in Production Example 1 using the above materials.
-Butyl acrylate copolymer [hereinafter referred to as "resin (A3)"
]] Was obtained. The obtained resin (A3) has a flow line gradient (l × 10 ² ) of −5.3, a pour point of 85 ° C., a glass transition point of 61 ° C., and a gel permeation chromatography chromatogram. Molecular weight of about 12000
Had a maximum value at.

Production Example 4 The above materials were introduced into a polymerization reaction vessel having a stirring means and the inside of the vessel was replaced with nitrogen gas, the temperature was gradually raised with stirring, the reaction was carried out at a temperature of 150 ° C for 5 hours, and the temperature was raised to 190 ° C. Warm and react for 4 hours to react with polyester resin [hereinafter,
"Resin (A4)" is obtained. Obtained resin (A4)
Has a flow line gradient (l × 10 ² ) of −3.4, a pour point of 91 ° C., a glass transition point of 64 ° C., and a maximum value of about 20,000 in the chromatogram of gel permeation chromatography. Had.

Production Example 5 Styrene-n was prepared in the same manner as in Production Example 1 using the above materials.
-Butyl acrylate copolymer [hereinafter referred to as "resin (A5)"
]] Was obtained. The obtained resin (A5) has a flow line gradient (l × 10 ² ) of −1.2 and a pour point of 125 ° C.
It has a glass transition point of 75 ℃ and a molecular weight of about 3500 in the gel permeation chromatography chromatogram.
It had a maximum at 0.

Production Example 6 Styrene-n was prepared in the same manner as in Production Example 1 using the above materials.
-Butyl acrylate copolymer [hereinafter referred to as "resin (B1)"
]] Was obtained. The obtained resin (B1) had a flow line gradient (l × 10 ² ) of −9.0, a pour point of 79 ° C., a glass transition point of 62 ° C., and a gel permeation chromatography chromatogram. At about 45,000
Had a maximum value at.

Production Example 7 Styrene-n was prepared in the same manner as in Production Example 6 using the above materials.
-Butyl acrylate copolymer [hereinafter referred to as "resin (B2)"
]] Was obtained. The obtained resin (B2) had a flow line gradient (l × 10 ² ) of −9.3, a pour point of 74 ° C., a glass transition point of 58 ° C., and a gel permeation chromatography chromatogram. Molecular weight at about 34,000
Had a maximum value at.

Production Example 8 After the above materials were introduced into a container and mixed, 25 parts by weight of sodium hydroxide was gradually added, and the pressure was reduced after the heat generation was finished to remove the remaining monomers. Then, 3 parts by weight of xylene was added, the precipitate was filtered off, and xylene was removed from the filtrate by depressurization to obtain an epoxy resin [hereinafter referred to as "resin (B
3) ”]] was obtained. The obtained resin (B3) had a flow line gradient (l × 10 ² ) of −7.2, a pour point of 87 ° C., a glass transition point of 68 ° C., and a gel permeation chromatography chromatogram. At about molecular weight
It had a maximum at 3000.

Production Example 9 Using the above materials, a polyester resin [hereinafter referred to as "resin (B4)"] was obtained in the same manner as in Production Example 4. The obtained resin (B4) had a flow line gradient (l × 10 ² ) of −8.5, a pour point of 94 ° C., a glass transition point of 71 ° C., and a gel permeation chromatography chromatogram. Had a maximum at a molecular weight of about 23,000.

Production Example 10 Styrene-2 using the above materials in the same manner as in Production Example 1.
-Ethylhexyl acrylate copolymer [hereinafter referred to as "resin (B5)"] was obtained. The obtained resin (B5) has a flow line gradient (l x 10 ² ) of -13 and a pour point of 65. ℃, the glass transition point is 55 ℃, the molecular weight in the chromatogram of gel permeation chromatography is about
It had a maximum at 26000.

Examples of the charge control agent used in the toner of the present invention include organic metal compounds which are organic salts or complexes containing divalent or higher valent metals. Al, Ba, Ca, C as effective metal species
Examples include polyvalent compounds such as d, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Sn, Sr, and Zn. As the organometallic compound, carboxylate salts, alkoxylates, organometallic complexes and chelate compounds of the above metals are effective, and examples thereof include zinc acetate, magnesium acetate, calcium acetate, aluminum acetate, magnesium stearate, calcium stearate and stearin. Examples thereof include aluminum acid acid, aluminum isopropoxide, aluminum acetylacetonate, iron (III) acetylacetonate, and chromium 3,5 ditertiarybutylsalicylate. Among them, acetylacetone metal complexes and salicylic acid metal salts are particularly preferable. The addition amount is preferably 0.2 to 10% by weight based on the binder resin.

If necessary, a colorant and a fluidity modifier may be added to the toner of the present invention, and the charge control agent and the fluidity modifier may be mixed (externally added) with the toner and used. Conventionally known dyes and pigments can be used as the colorant, and colloidal silica, fatty acid metal salts and the like can be used as the fluidity modifier.

Further, when it is desired to obtain a magnetic toner, magnetic fine particles may be added to the toner. Does the magnetic substance show magnetism,
Any material that can be magnetized, such as fine metal powders of iron, manganese, nickel, cobalt, chromium, alloys and compounds of various ferrites, manganese, etc., and other ferromagnetic alloys such as magnetite, are conventionally known as magnetic materials. You can use what you have. The content thereof is appropriately 20 to 150% by weight, preferably 30 to 90% by weight, more preferably 40 to 85% by weight, based on the binder resin.

Further, polyolefins such as low-molecular weight polyethylene and low-molecular weight polypropylene can be added to the toner in order to make the releasability from the heat fixing roll more complete.

Hereinafter, the present invention will be specifically described with reference to resin production examples, examples and comparative examples, but these do not limit the present invention. All used parts are parts by weight.

(Example 1) Pour point 100 ° C Flow line gradient (l x 10 ² ) -4.0 styrene-acrylic resin (A1) ... 25 parts Pour point 79 ° C Flow line gradient (l x 10 ² ) -9.0 styrene - a mixture of the acrylic resin (B1) ...... 75 parts of magnetite (Fe ₃ O ₄₎ ...... 65 parts low molecular weight polypropylene ...... 5 parts di Shari butyl salicylic acid chromium complex ...... 2 parts (in parts by weight) the formulation The mixture was heated and kneaded with a roll. After allowing this to cool, it was made into a coarsely pulverized product, finely pulverized by an ultrasonic jet mill, and classified by an air classifier to obtain toner particles having an average diameter of about 13 μm. Colloidal silica (Aerosil R-972) was added to this toner to give a one-component toner.

In order to check the electrophotographic characteristics, an electrophotographic copying machine of a one-component developing system using the toner as a developer (Canon NP-
When it was supplied to 400 RE) and subjected to a copy test, a sufficient image density and a development durability of 50,000 or more sheets were obtained, and no problem in fixing property occurred. Also, in order to see the heat fixing property in detail, only the fixing unit of the copying machine was prepared separately, and the fixing test was conducted on the separately prepared unfixed image on the transfer paper by changing the roller set temperature with the different fixing device. The practical fixing temperature is 145 ° C, the offset phenomenon does not occur in a wide temperature range, and the offset generation temperature is
The 230 ° C fixability was also excellent. Further, this toner was left in an atmosphere of 50 ° C. for a long time, but no blocking or caking was observed. Further, there was no problem with the developability in a high humidity atmosphere and the developability in a low humidity atmosphere.

However, the minimum practical fixing temperature refers to the minimum temperature at which a fixed image that can be practically sufficiently endured can be obtained without cold offset to the heat roller.

Next, Examples 2 to 5 and Comparative Examples 1 and 2 using Resin A and Resin B shown in Table 1 and Table 2 below will be described.

Example 2 A toner was obtained in the same manner as in Example 1 except that the resins A1 and B1 in Example 1 were replaced with the resins A2 and B2 in Table 1.

When the obtained toner was tested in the same manner as in Example 1, sufficient performance was exhibited in terms of image quality, offset resistance, and storage stability.

By the way, the minimum practical fixing temperature was 135 ° C., and the toner had a fairly good fixing property.

(Example 3) Table 1 Resin A3 + resin B4 (A3: B4 = 5: 10) 100 parts of magnetite (Fe ₃ O ₄₎ heating and kneading 60 parts of polyethylene wax 3 parts iron acetylacetonate 5 parts mixture of the above formulation in a roll did. The particles were coarsely pulverized, pulverized several times, and classified to obtain 5 to 20 μm toner particles, and colloidal silica was further added. When a copy test was conducted in the same manner as in Example 1, sufficient performance could be confirmed. Also, a fixing test with an external fixing device and 50 ° C
There was no problem in the high temperature storage test.

(Example 4) The same procedure as in Example 1 was repeated except that magnetite, which is a magnetic powder, was excluded from the toner blending method, and 8.0 parts of carbon black was added. A toner having a diameter of 9.2μ was obtained. 20 parts of this toner was mixed with 80 parts of carrier iron powder (Nippon Iron Powder EFV200 / 300) and supplied to a Canon copier NP-6000 for development test. As a result, the initial image and the 30,000-sheet durability image were sufficient, and the fixability was better than in Example 1. The minimum practical fixing temperature by the separate fixing device shown in Example 1 was 135 ° C, and the offset generation temperature was 225 ° C. The storage test also showed sufficient performance.

(Example 5) Resin (A1) of Table 1 in Example 1: resin (B1) = 3.3: 10
Instead of resin (A3): resin (B3) = 2:10, toner was formed in the same manner and electrophotographic characteristics were evaluated.
The initial image and the durable image were extremely good and had no problems. Further, the fixing test, the storage test and the high-humidity test using another fixing device were almost the same as in Example 1 and good results were obtained without any problems.

Comparative Example 1 A toner was obtained in the same manner as in Example 1 except that the resins A5 and B5 in Table 1 were used instead of the resins A1 and B1. When colloidal silica was added to this toner and a test was conducted in the same manner as in Example 1, sufficient performance was exhibited in initial developability, durability and storability. However, the fixing point of another fixing device is 183 ° C.
That is, it was clearly too high, which was not practical.

It is clear that this is not suitable for high-speed fixing toner.

Comparative Example 2 A toner was manufactured in the same manner as in Example 5 except that the resins B1 and B4 were used instead of the resins A3 and B3, and colloidal silica was added to make a one-component toner. The T ₁ of this toner was as low as 98 ° C., which caused concern about hot offset properties and storage stability.

When the electrophotographic characteristics were tested in the same manner as in Example 1, the hot offset increased with the durability, and the toner deposited and deposited on the heat roller frequently contaminates the transfer paper.

Further, the toner showed a tendency to aggregate during storage, and many granular lumps were generated, so that the toner was not broken by simple vibration.

〔The invention's effect〕

In the electrophotographic toner of the present invention, as described above,
By selecting resins A and B having a specific pour point and flow straight line, excellent low-temperature fixability, fixing with low energy is possible, especially suitable for high-speed fixing, offset is prevented, and the fixing temperature range is wide, Blocking is hard to occur,
Has excellent durability against repeated use,
A good image is stably maintained, and various powder properties such as fluidity are excellent, replenishability and storability are good, and there is no adhesion or contamination on the toner holding member or the electrostatic latent image surface. In the two-component developer, there is almost no carrier contamination due to adhesion to the carrier, fusion, etc., and in the one-component magnetic toner, the dispersibility of the magnetic powder is good and the mechanical property of the electrostatic image forming surface is good. It has a good cleaning property of the photosensitive surface by reducing wear. The toner of the present invention is an excellent toner in which various performances required as a toner are balanced as described above, and the industrial significance of the present invention is great.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the temperature by a flow tester and the plunger drop amount, and the pour point B and the like are shown.

Claims (2)

[Claims] 1. A resin (A) having a pour point in the range of 70 to 110 ° C. and a flow line gradient (l × 10 ² ) in the range of −2.0 to −6.0, and a pour point of 70 to 110 ° C. And a binder resin whose main component is a mixture of a resin (B) having a flow line gradient (l × 10 ² ) in the range of −7.0 to −10.0. Photographic toner. 2. The weight ratio of the resin (A) to the resin (B) is 1:10 to.
The electrophotographic toner according to claim 1, which is in a range of 8:10.