DE1472913B2 - LIQUID ELECTROPHOTOGRAPHIC DEVELOPER - Google Patents

Description

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The invention relates to a liquid electrophotographic developer from a carrier liquid, a pigment, a control agent and optionally a dispersant.

Liquid electrophotographic developer comprising two types of toner particles in an insulating liquid suspended of different charge and which also have a dispersant already known (e.g. U.S. Patent 3,078,231). Also from U.S. Patent 3,010,842 liquid developers containing two toners of different polarity are known.

With these well-known developers it was previously not possible to get optimal results with regards to to achieve maximum image density and a clear background.

This is achieved according to the invention.

The object of the invention is to provide a clean surface and a maximum image density that has been achieved so far not achieved quality.

The invention relates to a liquid electrophotographic Developer from a carrier liquid, a pigment, a control agent and optionally a dispersant characterized in that it is a control means which is the opposite Has polarity like the control substance, and the pigment not or less than the control substance wetted, contains.

While the control substance is permanently fixed to the surface of the developer, this one To impart charge, the control agent is dispersed in the carrier liquid. Essential for the tax means is that it does not wet the control substance in the pigment so that what is present in liquid form is dispersed or dissolved control agent acts like a second developer with opposite polarity that is due to the non-wettability of the control substance on the pigment cannot combine with it. That means So that the control substance and control agent are not miscible with one another, so that they are in the desired Relationships to the pigment remain. The intended goal is achieved because there are more developer particles are driven down to the desired image surface parts and because the underground surfaces shielded against contact with pigment particles.

For the separate deposition of the two oppositely acting developer components it is essential that that pigment particles and the shielding medium remain moveable. This is going through reached the optionally added dispersant, through which the force of attraction between the developer components is weakened, even if they carry an opposite charge. The pigment particles are therefore even if the oppositely charged components of the developer flow together, separate from the shielding medium, as they are in the field of the opposite parts of the charged surface move. The shielding medium migrates into the underground surfaces, and at least in part due to the influence of the induced field.

During this development, the pigment substance is deposited on the areas where it is due to the Field of the image is attracted to the photoconductor surface, while the shielding medium is on the Subsurface areas deposited at least in part under the influence of the induced field. With the As the developer builds up on the image surfaces, the induced field lines are changed with the result that the repellent medium and a pigment deposited on it is released, whereby the Surface is cleaned.

During the development process, a shielding substance is deposited on the surface, on which developer particles can be deposited, but this shielding substance is released or releases the pigment particles when and how the induced field is changed.

This leaves a clean surface. Movement or washing can intensify this cleaning process.

To explain the invention it should be pointed out that the developer according to the invention consists of must consist of five parts, namely:

A. the carrier liquid, which, as usual, is an insulating medium such as a hydrocarbon, commonly used in liquid electrophotographic developers;

B. a pigment, preferably of the same polarity as the desired final developer particle, d. H. with a sign of charge that corresponds to the sign of the charge to be developed Face is opposite;

C. a controlling coating (control substance), which the pigment particles in relation to the to be developed Surface charges in the opposite direction or increases its charge, if it is already with charged with the desired polarity;

D. a dispersing agent that the dispersion of the mixture of the ingredients B + C in the Supports carrier A and creates a finer suspension (Note: D can be a control means for B, so that in this case C is not used);

E. a control means with a charge polarity that corresponds to the resulting particle charge according to the Combination of B and C is opposite; or a control means of the opposite (Polarity) effect on the control substance (C) that has been applied to the pigment and in which Carrier liquid is present in dissolved form when the particle is already coated and as a developer opposite sign acts. So if C as Cp for positive or as Cn for negative When referring to properties, E is hereinafter sometimes referred to as Cn and Cp, respectively.

Examples of B, C, D and E are given below.

Example for B

Speaks Color Index pigment uncharged,
if A and B are mixed Soot or printer CI. 77266 black negative CI. 77266 Peerless black .... positive CI. 50440 Monolite black ... positive CI. 74160 Irgalite Fast Blue .... positive CI. Purple 1 Vivid magenta negative CI. 42040 Brilliant green ...... negative

B e i s ρ i e 1 for C

(1) The vegetable and animal oils on the list reverse the following pigments negative or make them more negative.

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linseed oil Pigments to a Color Index oils Sunflower oil negative particles
• with these oils Saffron Oil to obtain Tung oil Tall oil Peanut oil soot Corn oil Vivid magenta CI. 42040 Soybean oil Brilliant green CI. 45160 Poppy seed oil Rose red CI. 77266 Oiticica oil soot CI. 77266 lanolin soot Castor oil Boiled linseed oil

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(2) The following mineral oils and resins form positive particles when placed on List 45 pigments be applied.

B. P. Viscostatic Irgalite Fast CI. 74160 Engine lubricating oil Brilliant blue Polymetharyl acid CI. 42040 butyl ester Coates brilliant green Various Wed CI. 50440 mineral lubricating oils Monolite black bitumen CI. 15865 (based on petroleum) Ruby toner RO 13 / 2 B rose red

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B e i s ρ i e 1 e for D

The following alkyd resins can be used 65, the product of B and C without reduction to disperse their effectiveness as a developer.

X) Isophthalic acid alkyd resin modified with semi-dry Safflower oil up to 60% and with varnish jpenzin to a content of 60% of non-volatile substances diluted.

Y) An alkyd resin esterified with dental rythritol, modified up to 70% with linseed oil and with mineral spirits diluted to a non-volatile content of 70%.

Z) A pentalrythritol-esterified alkyl resin modified to 72% with linseed oil.

B e i s ρ i e 1 e for E

(1) The following agents can be added to reduce the subsoil if they are added to the Developer product from B and C are introduced, with B + C being negatively charged.

(a) The positive-making substances from C (2) above,

(b) soluble in or miscible with the carrier liquid,

(c) Pigments that are strongly positive but are present in lower concentrations,

(d) bitumen (petroleum based).

(2) The following agents can be added to the developer to clean the image background, when the developer product of B and C is positively charged.

(a) All negative making oils,

(b) low concentrations of negative pigments dispersed with any D-series alkyd resin are.

The polymer system consists of four parts. For a reversal developer to develop positive ones Image areas are required:

A. As a liquid insulating carrier medium,
C as the control substance forming the charge (e.g. a vegetable oil),

D. as a dispersant (e.g. an alkyd resin),

E. as a means of cleaning the substrate, usually a control means, the opposite of C is (e.g. bitumen).

The following examples illustrate the effect of the components in the system described. The charts show the behavior of the various systems if the order in which the components are added, changed and the developer is checked after each change.

Table I.

Effect of the order of wetting
on the polarity

Developer i

Ig pigment (B):

Brilliant green (CI. 42040). "

3 g negative oxygen (Cn):
Sunflower oil.

2 g dispersant (D):

Alkyd resin, such as isophthalic acid alkyd resin, modified with semi-dry safflower oil up to 60% and diluted with mineral spirits to a non-volatile content of 60%.

5 g underground cleaner (Cp), which is a positive control agent:
Viscostatic engine oil, this cleans the under-

reason, but tends to charge a pigment particle when used alone.

Developer 2

1 g pigment (B):

Brilliant green, e.g. CI. 42040.
5 g positive control substance (Cp):
Viscostatic engine oil.

2 g dispersant (D):

Alkyd resin, e.g. B. Isophthalic acid alkyd resin modified with semi-dry safflower oil up to 60% and with mineral spirits to a content of 60% diluted in non-volatile substances.

3 g underground cleaner (Cn), which has a negative

Control means is:

Sunflower oil.

Developer 1 is a reversal developer which consists of negative developing particles and is based on irradiated or illuminated surfaces.

Developer 2 is a direct developer, which consists of positively developing particles and is based on the im Dark (i.e. unexposed) parts of the surface that are shielded from radiation or lighting are deposited.

Table II
Pigment (B)

1 g »Brillfast« Vivid Magenta 3964:

CI. Purple 10.

3 g negative control substance (Cn):
Sunflower oil.

2 g dispersant (D):

An alkyd resin, such as isophthalic acid alkyd resin, modified with semi-dry safflower oil up to 60% and diluted with mineral spirits to a non-volatile content of 60%.
6 g underground cleaner (Cp), which has a positive
Control means is:
Viscostatic engine oil

Components and order polarity Subsurface density sensitivity
(arbitrary units) AWAY. negative 0.4 very weak 1.0 A + B + Cn negative 0.5 weak 2.0 A + B + Cn + D negative 2.6 - 3.0 A + B + Cn + D + Cp negative 0.3 strong 6.0 A + B + Cp zero 0.0 no picture A + B + Cp + D negative 0.5 very weak 1.0. A + B + Cp + D + Cn negative 0.4 weak 2.0

This pigment can be made positive if the sequence and relative amounts of Cp and Cn can be changed since the results given above are not the only possible ones. It should be noted that the positive and negative control means or control substances have the property opposite To form charges. The pigment used in this example can be negative or positive depending on whether the negative or the positive tax means or the tax substance on the Pigment is applied. Many pigments respond in this way, but they can do so in other ways changed and then kept in the desired state. In many cases the pigment is itself heavily charged, counteracts the tendency to change its charge in the opposite direction and slowly, but with a noticeable decrease in uncharged responsiveness, returns to its natural state Polarity back.

If the pigment has a natural polarity and the control agent is such that it does the Moving the load to a higher value in that direction will give the best results. Table II shows a negative pigment, and further that a maximum uncharged response and a low one Subsurface density (subsurface pollution) is only achieved if the correct and complete sequence is applied.

Provided that the pigment and the first control agent have sufficient affinity for one another, is It is often possible to make developer by grinding B, C, D and E together and doing just one Fraction of the desired amount of E.

The following recipe specifies a reversal developer for exposed areas. All components can because of the affinity between B and Cn are married together. The one when you leave out one of the ingredients the resulting effect is shown in Table III.

Developer 3

Ig pigment (B):
"Kohinoor"printer's ink C. 1.77 266,

100 g.
3 g control substance (Cn):

Sunflower oil, 300 g.
2 g dispersant:

Alkyd resin, such as isophthalic acid alkyd resin, modified with semi-dry safflower oil up to 60% and diluted with mineral spirits to a non-volatile content of 60%, 200 g.
5 g substrate cleaner and control agent (Cp):
Viscostatic motor oil, 500 g.

All components are ground. 10 g of the concentrate are dispersed in 100 g of hydrocarbon carrier liquid (A). The relocated underground

Cleaner (Cp) can be made by adding 10 grams of the viscostatic motor oil to the hydrocarbon mixture be dispersed. This dispersion is used as a pre-exchange bath either before or after exposure, or with or without evaporation drying; The values for the Reflection densities are like for this developer if the bringing together is done little by little follows:

polarity image
density Under reason- Components density
(without preceding negative 0.0 to wash negative 0.06 with Cp) A + B negative 0.57 0.0 A + B + Cn negative 0.54 0.04 A + B + Cn + D negative 0.53 0.44 A + B + Cn + D + Cp 0.04 A + B + Cp + D + Cn 0.09

As shown above, if one surface polarity is strongly developed, the other is only weakly developed because of the structure of the fields, and this influence is used according to the invention to achieve a maximum contrast through a strong image precipitation and a weak precipitation which controls the background to reach.

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Claims (1)

Claim: Liquid electrophotographic developer composed of a carrier liquid, a pigment, a Control substance and optionally a dispersant, characterized in that it contains a control means which has the opposite polarity as the control fabric and which Pigment not wetted or wetted less than the control substance.