JPH05188525A - Improved phototypesetting paper - Google Patents

Abstract

PURPOSE: To obtain photographic composing paper having improved image forming characteristics. CONSTITUTION: This photographic composing paper includes a white reflective base and image forming units which are applied on this base, exhibit at least the max. density of 2.0 and exhibit a contrast of >=2.0 through a 0.75logE exposure area where fogging is measured from the min. exposure necessary for embodying the density exceeding 0.2. This photographic composing paper includes a tabular silver halide grain emulsion. The coefft. of fluctuation of this emulsion is <15% per total grain groups of the emulsion indicating ECD exceeding 0.1μm. The grain groups exceeding 97% of the projection area has <0.2μm average thickness and a tabular degree exceeding 25.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to photography, and more particularly to improved photographic paper.

[0002]

Phototypesetting paper is a photographic product intended to form a black maximum density silver image on a white minimum density background. The image is visualized by reflection from a white support. A common name for a "paper" support with respect to a reflective support is the historical legacy from the early days when the support was virtually completely paper. White reflective plastics are nowadays provided as a reinforcing or even a complete replacement for reflective supports.

To obtain the impression of a black image on a white background, the exposed areas exhibit a density of at least 2.0 and the unexposed areas exhibit a uniform low density, typically less than 0.1,
And it is necessary to have a sharp boundary between the exposed and unexposed areas. A maximum density of 2.0 has been chosen in the art, since it is not possible to identify densities above 2.0 when observing reflection points. A minimum density of less than 0.1 is a fog level that has been found convenient. To obtain a sharp boundary between exposed and unexposed areas (ie, the eye is unable to distinguish intermediate densities), phototypesetting papers are usually constructed to have a contrast of at least 2.0. It

The choice of silver halide emulsion layer units to be coated on the reflective support is dictated by their density and contrast requirements. Maximum density and contrast requirements dictate the coverage of silver halide coating for the selected emulsion. Referring to FIG. 1, a series of characteristic curves were similarly prepared by coating the same silver halide emulsion (but varying silver halide coating coverage) on the same support. Indicates that. These emulsions were coated on a film support so that the full range of maximum densities could be measured. Curves B, C and D are 75, 50 and 25% of the silver halide coverage of curve A, respectively.
The coating amount is shown. It can be seen that the maximum density and the contrast decrease as the silver halide coating amount gradually decreases.

The silver halide to be coated per unit area required to achieve a particular maximum image density depends on the covering power of the emulsion. The covering power is usually
It is defined as the maximum image density divided by developed silver (typically reported in units of g / m ² or mg / dm ² ) per unit area.

Tabular grains have been observed in silver bromide photographic emulsions and silver bromoiodide photographic emulsions at the time when enlarged grains and grain replicas were observed, but with photographic advantages such as improved speed and The relationship between the granularity and the increased covering power both in the absolute sense and as the binder curing function,
Faster developability, increased thermal stability, increased resolution of blue and negative blue imaging speeds, and improved image sharpening in single and multiple emulsion layer formats Is the average tabularity relational expression D / t ² > 25 (where D is the equivalent circular diameter (ECD) of tabular grains in micrometers (μm)). , And t is the thickness of the tabular grains in .mu.m) recognized in the early 1980s as being achieved from silver bromide and silver bromoiodide emulsions occupied by tabular grains satisfying Was not known until.

Due to their increased covering power, high (D / t
² > 25) The tabularity emulsion was immediately put to use for phototypesetting paper. Wilgus et al., US Pat. No. 4,434,226 (see columns 54, line 58 to column 56, line 21) and Kofron et al., US Pat. No. 4,439,520 (columns, lines 31 to 31). 75, line 62)
Reported a comparison of the above properties of phototypesetting paper prepared with high tabularity emulsions and conventional low tabularity emulsions. According to this comparison, the high tabularity emulsions achieved higher maximum densities at low silver coverages. With reference to FIG. 1, it can be seen that even greater reductions were achieved at equal maximum silver coverages. The tabular grain emulsions of recent commercial phototypesetting paper samples have an average ECD of 2.1 μm and an average tabular grain thickness of 0.087 μm.
And COV 43% are indicated.

Despite their early attempts at phototypesetting paper, tabular grain emulsions were not ideally suited for that application. The reason is the maximum concentration of 2.0
The emulsions still showed a contrast of less than 2.0 when coated with a silver coverage sufficient to achieve This has been solved by the well-known contrast enhancing methods of incorporating contrast enhancing dopants (particularly rhodium) into the tabular grains. Such dopants have the drawback of reducing photographic speed. This is shown in FIG. Characteristic curves E and F were similarly prepared except that the emulsion used to create curve F was rhodium doped. Both curves show the same maximum density, but the contrast of curve E is much lower than that of curve F. However, the improvement in contrast in curve F has been achieved by a significant reduction in speed, as evidenced by the increased exposure required to achieve density production above fog.

Concerns about the dispersity of early tabular grain emulsions have largely focused on the presence of a significant population of inconsistent grain shapes in the tabular grains consistent with the desired grain structure. FIG. 3 is an optical micrograph of an early high aspect ratio tabular silver bromoiodide grain emulsion first provided by Wilgus et al. And Kofron et al., Where various grains can be present in the high aspect ratio tabular grain emulsion. It indicates that there is a property. It can be seen that most of the total grain projected area is occupied by tabular grains such as grain 101, but there are also inconsistent grains. Particle 103
Indicates a non-tabular grain. The particles 105 are fine particles.
Grain 107 refers to grains that are merely nominally referred to as tabular grains having inconsistent thicknesses. Although not shown in FIG. 3, rods also constitute a common inconsistent grain population in tabular silver bromide grains and tabular silver bromoiodide grain emulsions.

Although the presence of inconsistent grain shapes in tabular grain emulsions still hinders the achievement of narrow grain dispersities,
As tabular grain preparation methods have come to reduce unintentional inclusion of inconsistent grain shapes, there has been growing interest in reducing the dispersity of tabular grains. It must be understood that the tabular grains themselves, which were sought even by the surface examination of Fig. 3, also show a wide range of equivalent circular diameters.

Techniques for quantifying the degree of grain dispersion that have been applied to nontabular and tabular grain emulsions have been described for obtaining a statistically significant sampling of the projected area of individual grains, corresponding to each grain. The average ECD of the sampled particles is calculated by calculating the standard deviation of the particle population.
Divide by and multiply by 100 to obtain the coefficient of variation (COV) of the particle population as a percentage. High monodispersity with regular non-tabular grains (COV <10%, although emulsions can be obtained, COV of less than 20% is obtained even with very carefully controlled precipitation of tabular grain emulsions. Rarely could it be achieved Research Disclosure , Vol.
232, August 1983, Item 23212 (corresponding to French Patent 2,534,036 to Mignot) discloses the preparation of tabular silver bromide grain emulsions having a COV range of 15 or less. Research Disclosure is Kenneth Mason Publicat
ions, Ltd. (Dudley Annex, 21a North Street, Emswort
h, Hampshire P010 7DQ, England).

Saitou et al., US Pat. No. 4,797,35
11.1% in Example 9 of Example 4 (Example)
The COV of this is reported, but this number is not comparable to the number reported by Mignot. Saitou et al. Simply report that the selected tabular grain population is within the COV range. Inconsistent grain populations within the emulsion are excluded from these COV calculations because they have a strong impact on grain dispersity and overall COV. Saitou
Sampling the total grain population of these emulsions yields significantly higher COV. According to Saitou et al.'S note on the emulsion of Example 9, a COV of 21.3% was observed when the COV was based on the total grain population.

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a phototypesetting paper having improved imaging properties. A more specific objective is to provide improved speed phototypesetting paper. Another object is to provide a phototypesetting paper that exhibits improved contrast, especially improved shoulder contrast.

[0014]

SUMMARY OF THE INVENTION In one aspect, the present invention provides a white reflective support, as well as a coating coated thereon, exhibiting a maximum density of at least 2.0 and a fog of greater than 0.2. Is directed to a phototypesetting paper comprising imaging layer units exhibiting a contrast of 2.0 or greater through a 0.75 log E exposure area measured from the minimum exposure required to achieve The imaging layer unit comprises a tabular silver halide grain emulsion having a grain halide content of 0 to 5 mole percent chloride, 0 to 15 mole percent iodide and 80 to 100 mole percent bromide, based on total silver. Become.

The phototypesetting paper has tabular grain emulsions having a coefficient of variation of less than 15% per total grain population of emulsions having an equivalent circular diameter of greater than 0.1 μm, and an equivalent circular diameter of greater than 0.1 μm. More than 97% of the projected area of the total grain population of the emulsion is characterized by tabular grains having an average thickness of less than 0.2 µm and a tabularity of greater than 25.

The present invention is directed to an improved phototypesetting paper. This phototypesetting paper is coated on a conventional white reflective support, as well as the support, with a maximum density of at least 2.0.
2. Through a 0.75 log E exposure range measured from the minimum exposure required to achieve a density above 0.2 and fog.
The image forming layer unit has a contrast of 0 or more.

This phototypesetting paper has an image forming layer unit of 0.
An emulsion containing tabular grains having an average thickness of less than 2 µm and an average tabularity of greater than 25 is used. These emulsions, which contain thin tabular grains and exhibit high tabularity, provide a high level of silver covering power that is of particular interest for use in tabular grain emulsions in phototypesetting paper.

The present invention characterizes phototypesetting papers containing thin, high tabular grain tabular grain emulsions, (1) increasing the proportion of the total grain population occupied by thin tabular grains, and (2). Improved by the use of tabular grain emulsions prepared by the novel method which increase the monodispersity of the total grain population forming the image forming layer units. The phototypesetting paper of the present invention is
A coefficient of variation for tabular grain emulsions of less than 15% (preferably less than 10%) is shown per total grain population of emulsions having equivalent circular diameters of greater than 0.1 μm. The low coefficient of variation of the total grain population having an equivalent circular diameter greater than 0.1 μm provides an emulsion in which the tabular grain population occupies all or nearly all of the total projected area of grains having an equivalent circular diameter greater than 0.1 μm. , And by reducing the dispersity observed in the tabular grain population itself. These phototypesetting papers consist essentially of, in their emulsion layer units, tabular grains of high or low tabular grains with a high tabularity and an equivalent circular diameter of greater than 0.1 μm per total grain population. Thin tabular silver halide grain emulsions are used.

When precipitated by the method described below, the presence of particles having an equivalent circular diameter of 0.1 μm or less is present in a negligible amount. However, in the preparation of emulsions for phototypesetting paper, small diameter particles (sometimes "dust") are used to match the specific profile of the characteristic curve.
It is recognized that the compounding of small amounts) is commonly practiced. These small grains can range in size up to 0.1 μm, but are typically Lippmann emulsions having a mean grain equivalent circular diameter of about 0.05 μm. Particles with an equivalent circular diameter of 0.1 μm or less
It is too small to contribute significantly to the trapping or scattering of light in the visible spectrum. Their role in the presence of these compounded small particles is closer to the image modifier than the role of the imaging particle population.

The phototypesetting paper of the present invention was realized by the discovery and optimization of a novel precipitation method for low grain dispersity tabular grain emulsions. These methods produce 0 chloride per total silver.
-5 mol%, iodide 0-15 (preferably 0-5) mol% and bromide 80-100 (preferably 90-10).
Emulsions suitable for use in phototypesetting paper having a grain halide content of 0) mol% can be prepared. The grain population can consist essentially of silver bromide as the single silver halide. In some cases silver iodide and / or silver chloride may also be present in the grains. The presence of iodide is particularly beneficial for increasing emulsion speed, even when present in very small amounts per silver (eg, 20.1 mol%). However, high levels of iodide form thermal images and are preferably avoided. Therefore, it is preferable to limit iodide to less than 5 mol% (optimally less than 3 mol%) based on silver.

A population of grains consisting essentially of tabular grains having an average thickness in the range of 0.080 to 0.2 μm and an average tabularity of greater than 25 (as defined above) is formed by the precipitation described below. Within the scope of the law. These ranges represent any average tabular grain ECs suitable for photographic use.
It is also possible to select D. In other words, the invention is applicable to the full range of average ECD's of conventional tabular grain emulsions. An average ECD of about 10 μm is typically considered the upper limit for photographic use. For most applications tabular grains exhibit average ECD's of 5 µm or less. High EC
It is generally preferred that the average ECD of the tabular grains be at least about 0.4 μm, as D contributes to achieving higher average aspect ratios and tabularities.

Both the stated average tabular grain thicknesses and average tabular grain aspect ratios within the tabularity range are preferred. The average tabular grain aspect ratio to tabular grains of the coprecipitated grain population of the present invention is preferably in the range of 5 to 100 or more. Average aspect ratios in this range include medium (5-8), and high (> 8) average aspect ratio tabular grain emulsions. Average tabular grain aspect ratios in the range of about 10 to 60 are preferred for most photographic applications.

While average aspect ratios have been used extensively in the art to sterically characterize tabular grain emulsions, the property of positioning tabular grain populations, excluding nontabular grain populations, has been Average tabularity (D / t ² above) provides a fair and good quantitative measure. The emulsion of the present invention is
Include tabular grain populations exhibiting tabularities in excess of 25. The typical average tabularities of these emulsions range up to about 500. Since tabularity increases exponentially with a decrease in average tabular grain thickness, it can be understood that very high tabularity falls in the range of up to 1000 or more.

The emulsions intended for use are (a) initially forming a population of grain nuclei, (b) ripening a portion of the grain nuclei in the presence of a ripening agent, and (c) post-ripening grains. The discovery of an improved method for preparing tabular grain emulsions by carrying out growth and their optimization made them possible. Minimal COV co-precipitated grain population emulsions consisting essentially of tabular grains satisfying the requirements of the invention resulted from the discovery of special techniques for forming grain core populations.

To achieve the lowest possible grain dispersity, the first step involves the formation of silver halide grain nuclei under conditions that promote uniformity. Bromide ions are added to the dispersing medium before grain nucleation. While other halides can be added to the dispersion medium with silver prior to the introduction of silver, the halogen ions in the dispersion medium consist essentially of bromide ions.

When the aqueous silver salt solution and the aqueous halide solution are simultaneously introduced into a dispersion medium containing water and a hydrophilic colloid peptizer, balanced double jet precipitation of grain nuclei is particularly preferable. One or both of the chloride and iodide salts can be introduced via the bromide jet or as a separate aqueous solution via another jet. The chloride and / or iodide concentrations are preferably limited to below the above total levels during grain nucleation.

Although silver nitrate is the most commonly utilized silver salt, commonly used halide salts are ammonium halide and alkali metal (eg, lithium, sodium or potassium) halides. The ammonium counterion does not act as a ripening agent because the dispersion medium is at an acidic pH, ie below 7.0.

Uniform nucleation can be achieved by introducing the Lippmann emulsion into the dispersing medium without introducing the aqueous silver salt and the aqueous halide salt via separate jets. Lippmann emulsion particles typically have an average ECD of less than 0.05 μm, so that a small fraction of the initially introduced Lippmann particles serve as deposition sites while all of the remaining Lippmann particles precipitate on the grain core surface. As it does, it dissociates into silver ions and halogen ions. A technique for using small amounts of preformed silver halide grains as a feedstock for emulsion precipitation is described by Mignot U.S. Pat. No. 4,334,012, Saito.
4,301,241 and Solberg et al., 4,4.
No. 33,048.

The low COV emulsions intended for use can be prepared by forming a population of grain nuclei containing parallel twin planes in the presence of a selected surfactant prior to ripening. Specifically, the dispersity of the tabular grain emulsion of the present invention can be determined by introducing parallel twin planes into grain nuclei in the presence of one or a combination of polyalkylene oxide block copolymer surfactants. It can be reduced. Polyalkylene oxide block copolymers, and especially those intended for use in preparing the emulsions of this invention, are generally well known and widely used for a variety of purposes. They are generally recognized as falling within the broader category of nonionic surfactants.
Molecules that function as surfactants must contain at least one hydrophilic unit and at least one lipophilic unit linked together. For a review of block copolymer surfactants, see IR Schmolka, "A Review of Block Polymer Sur
factant's, J. Am., Oil Chem. Soc ., Vol.54, No.3, 1
977, pages 110-116, and AS Davidsohn and B. Milwidsky, Synthetic Detergents , John Wiley.
& Sons, NY1987, pages 29-40, in particular pages 34-36.

One class of polyalkylene oxide block copolymer surfactants found to be useful in the preparation of these emulsions is at least 4% of the copolymer molecular weight.
It consists of two terminal lipophilic alkylene oxide block units linked by hydrophilic alkylene oxide block units. These surfactants are hereinafter referred to as category S-I surfactants.

Category S-I surfactants contain at least two terminal lipophilic alkylene oxide block units linked by hydrophilic alkylene oxide block units, and have the following scheme (I):

[0032]

[Chemical 1]

Where LAO1 in each case represents a terminal lipophilic alkylene oxide block unit, and HA
O1 represents a hydrophilic alkylene oxide block linking unit) and can be represented simply and schematically.

It is generally preferred to select HAO1 so that the hydrophilic block units make up 4 to 96% based on the total molecular weight of the block copolymer.

Of course, it is recognized that the above block scheme I is only one example of a polyalkylene oxide block copolymer having at least two terminal lipophilic block units linked by hydrophilic block units. .. In a common variant structure, three or four terminal lipophilic groups are introduced by inserting a trivalent amine linking group into one or both of the boundaries between LAO1 block units and HAO1 block units of polyalkylene oxides. Can bring

In the simplest embodiment, the category S-I polyalkylene oxide block copolymer surfactant first comprises a block repeating unit of an oligomer or polymer which condenses ethylene glycol and ethylene oxide to serve as a hydrophilic block unit. Generate, then 1,
Prepared by completing the reaction with 2-propylene oxide. Propylene oxide is added to each end of the ethylene oxide block unit. To generate a lipophilic block repeat unit, at least 6 1,
2-Propylene oxide repeating units are required. The resulting polyalkylene oxide block copolymer surfactant has the following (II),

[0037]

[Chemical 2]

Where x and x'are each at least 6 and can be up to 120 or more, and y is the hydrophilicity required for the ethylene oxide block units to retain surface activity. And chosen to maintain a lipophilic balance). In general, it is preferred to select y such that the hydrophilic block units make up 4 to 96 wt% of the total block copolymer. When x and x'are within the above range,
y can range from 2 to 300 or more.

In general, any Category S-I surfactant block copolymer which retains the dispersing properties of the surfactant can be used. It has been found that these surfactants are sufficiently effective to dissolve or physically disperse in the reaction vessel. Dispersion of the polyalkylene oxide block copolymer is typically facilitated by the vigorous agitation used in making tabular grain emulsions. Generally, a molecular weight of less than about 16,000 (preferably less than about 10,000)
Surfactants having a are intended for use.

The second category (hereinafter, category S-
II surfactant), the polyalkylene oxide block copolymer surfactant contains two terminal hydrophilic alkylene oxide block units linked by a lipophilic alkylene oxide block unit, and has the following scheme (III ),

[0041]

[Chemical 3]

(Wherein HAO2 in each case represents a terminal hydrophilic alkylene oxide block unit, and LA
O2 represents a lipophilic alkylene oxide block linking unit) and can be represented simply as shown schematically.

It is generally preferred to choose LAO2 so that the lipophilic block units make up 4 to 96% based on the total molecular weight of the block copolymer.

Of course, the above block diagram (III) is
It is recognized that this is only one example of a category S-II polyalkylene oxide block copolymer having at least two terminal hydrophilic block units linked by lipophilic block units. In a common variant structure, insertion of a trivalent amine linking group at one or both of the interfaces between LAO2 block units and HAO2 block units can result in 3 or 4 terminal hydrophilic groups.

In the simplest embodiment, the category S-II polyalkylene oxide block copolymer surfactant is prepared by first condensing 1,2-propylene glycol and 1,2-propylene oxide to obtain a lipophilic block unit. It is prepared by forming a block repeating unit of an oligomer or polymer that serves as the compound and then completing the reaction with ethylene oxide. Ethylene oxide is added to each end of the 1,2-propylene oxide block unit. At least 13 1,2-propylene oxide repeat units are required to produce a lipophilic block repeat unit. The resulting polyalkylene oxide block copolymer surfactant has the following formula (IV):

[0046]

[Chemical 4]

Where x is at least 13 and can be up to 490 or more, and y and y'are the hydrophilicity and the ethylene oxide block units required to retain surface activity. Selected to maintain a lipophilic balance).
It is generally preferred to choose x such that the lipophilic block units make up 4 to 96 wt% of the total block copolymer. When x is in the above range, y and y'can range from 1 to 320 or more.

Any category S-II block copolymer surfactant that retains the dispersing properties of the surfactant can be used. It has been found that these surfactants are sufficiently effective to dissolve or physically disperse in the reaction vessel. Dispersion of the polyalkylene oxide block copolymer is typically facilitated by the vigorous agitation used in making tabular grain emulsions. Generally, a molecular weight of about 3
Surfactants having less than 10,000, preferably less than about 20,000 are contemplated for use.

Third category (hereinafter category S-II
I surfactant), the polyalkylene oxide surfactant contains at least three terminal hydrophilic alkylene oxide block units linked by lipophilic alkylene oxide block linking units, and has the following formula (V):

[0050]

[Chemical 5]

Where HAO3 in each case represents a terminal hydrophilic alkylene oxide block unit, LOL represents a lipophilic alkylene oxide block linking unit, z is 2 and z'is 1 or 2. ) Can be represented simply and schematically.

The polyalkylene oxide block copolymer surfactant used is represented by the following formula (VI):

[0053]

[Chemical 6]

(Wherein HAO3 represents a terminal hydrophilic alkylene oxide block unit in each case, LAO3 represents a lipophilic alkylene oxide block unit in each case, L represents a linking group such as an amine or a diamine,
z is 2 and z'is 1 or 2).

The linking group L can take any convenient form. In general, it is preferable to choose a linking group that is itself lipophilic. If z + z 'equals 3, then the linking group must be trivalent. Amines can be used as trivalent linking groups. When an amine is used to form the linking unit L, the polyalkylene oxide block copolymer surfactant used has the formula (VII):

[0056]

[Chemical 7]

Where HAO3 and LAO3 are as defined above; R ¹ , R ² and R ³ independently contain a hydrocarbon linking group, preferably 1 to 10 carbon atoms. Selected from an alkylene group or a phenylene group;
And a, b and c are independently 0 or 1). In order to avoid steric hindrance, it is generally preferred that at least one (optimally at least two) of a, b and c is 1. The amine having a hydroxy functional group involved in the oxyalkylation reaction (preferably a secondary or tertiary amine) is
It is the preferred starting material for producing a polyalkylene oxide block copolymer satisfying formula (VII).

When z + z 'is equal to 4, the linking group must be tetravalent. Diamine is the preferred tetravalent linking group. When the linking unit L is formed using a diamine, the polyalkylene oxide block copolymer surfactant used has the following formula (VIII):

[0059]

[Chemical 8]

Wherein HAO3 and LAO3 are as defined above; R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are independently a hydrocarbon linking group, preferably 1 carbon atom. Selected from alkylene or phenylene groups containing 10 to 10; and d, e, f and g are independently 0 or 1). In general, LAO3 is preferably chosen such that the LOL lipophilic block units account for 4 to less than 96% of the molecular weight of the copolymer, preferably 15 to 95%, optimally 20 to 90%.

Fourth category (hereinafter category S-IV
Referred to as surfactant), the polyalkylene oxide block copolymer surfactant used contains at least three terminal lipophilic alkylene oxide block units linked by hydrophilic alkylene oxide block linking units, and The following formula (IX),

[0062]

[Chemical 9]

Where LAO4 in each case represents a terminal lipophilic alkylene oxide block unit, HOL represents a hydrophilic alkylene oxide block linking unit, z is 2 and z ′ is 1 or 2. ), It can be represented simply and schematically.

The polyalkylene oxide block copolymer surfactant used is represented by the following formula (X):

[0065]

[Chemical 10]

(Wherein HAO4 in each case represents a hydrophilic alkylene oxide block unit, LAO4 in each case represents a terminal lipophilic alkylene oxide block unit, L'represents a linking group, for example an amine or diamine, z is 2 and z'is 1 or 2).

The linking group L'can take any convenient form. In general, it is preferable to choose a linking group that is itself hydrophilic. If z + z 'equals 3, then the linking group must be trivalent. Amines can be used as trivalent linking groups. When an amine is used to form the linking unit L ′, the polyalkylene oxide block copolymer surfactant used has the following formula (XI):

[0068]

[Chemical 11]

Where HAO4 and LAO4 are as defined above; R ¹ , R ² and R ³ independently contain a hydrocarbon linking group, preferably 1 to 10 carbon atoms. Selected from an alkylene group or a phenylene group;
And a, b and c are independently 0 or 1). In order to avoid steric hindrance, it is generally preferred that at least one (optimally at least two) of a, b and c is 1. The amine having a hydroxy functional group involved in the oxyalkylation reaction (preferably a secondary or tertiary amine) is
It is the preferred starting material for producing polyalkylene oxide block copolymers satisfying formula (XI).

When z + z 'equals 4, the linking group must be tetravalent. Diamine is the preferred tetravalent linking group. When a diamine is used to form the linking unit L ′, the polyalkylene oxide block copolymer surfactant used has the following formula (XII):

[0071]

[Chemical 12]

Where HAO4 and LAO4 are as defined above; R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are independently a hydrocarbon linking group, preferably 1 carbon atom. Selected from alkylene or phenylene groups containing 10 to 10; and d, e, f and g are independently 0 or 1). In general, it is preferred that LAO4 be chosen such that the HOL hydrophilic block units account for 4-96%, preferably 5-85% of the molecular weight of the copolymer.

In its simplest form, category S-III
And S-IV polyalkylene oxide block copolymer surfactants use ethylene oxide repeating units to form hydrophilic (HAO3 and HAO4) block units, and 1,2-propylene oxide repeating units. Form lipophilic (LAO3 and LAO4) block units. At least 3 propylene oxide repeat units are required to produce a lipophilic block repeat unit. When so formed, H-HAO3-LAO
The 3- or H-LAO4-HAO4- group has the following formula (XIIIa) or (XIIIb), respectively:

[0074]

[Chemical 13]

Where x is at least 3 and can be up to 250 or more, and y
Are selected such that the ethylene oxide block units maintain the balance of lipophilicity and hydrophilicity necessary to retain surface activity). y can be chosen such that the sum of the hydrophilic block units constitutes 4 to 96 wt% (optimally 10 to 80 wt%) of the total block copolymer. In this case, the lipophilic alkylene oxide block linking unit containing the 1,2-propylene oxide repeating unit and the linking moiety is 4 to 4% of the total weight of the block copolymer.
96% (optimally 20-90%). Within the above range, y can range from 1 (preferably 2) to 340 or more.

The overall molecular weight of the polyalkylene oxide block copolymer surfactants of category S-III and S-IV exhibits a molecular weight of more than 1,100, preferably at least 2,000. Generally, any such block copolymer that retains the dispersing properties of the surfactant can be used. It has been found that these surfactants are sufficiently effective to dissolve or physically disperse in the reaction vessel. Dispersion of the polyalkylene oxide block copolymer is typically facilitated by the vigorous agitation used in making tabular grain emulsions. Generally, Category S-III surfactants having a molecular weight of less than about 60,000, preferably less than about 40,000 are contemplated for use and have a molecular weight of less than 50,000, preferably about 3
Category S-IV surfactants having less than 10,000 are contemplated for use.

Industrial surfactant manufacturers have found that, in their overwhelming majority of products, to form lipophilic and hydrophilic block units of nonionic block copolymer surfactants on a cost basis. 2-Propylene oxide repeating units and ethylene oxide repeating units have been chosen. However, if the desired lipophilicity and hydrophilicity are retained, any of the category SI, S-II, S-III and S-IV surfactants may optionally contain other alkylene oxide repeat units. It is recognized that it can be substituted. For example, the propylene oxide repeating unit is
The following formula (XIV),

[0078]

[Chemical 14]

Wherein R ⁹ is a hydrocarbon group, such as an alkyl group containing 1 to 10 carbon atoms or 6 carbon atoms.
Are lipophilic groups such as aryl groups such as phenyl and naphthyl containing up to 10).

Similarly, the ethylene oxide repeat unit has the formula (XV)

[0081]

[Chemical 15]

Wherein R ¹⁰ forms hydrogen or the above R ⁹ further having one or more polar substituents, eg 1, 2 or 3 or more hydroxy and / or carboxy groups. Type is a hydrophilic group such as a hydrocarbon group) and is only one of a group of repeating units.

In each of the surfactant categories,
Each block unit contains a single alkylene oxide repeat unit selected to impart the desired hydrophilic or lipophilic character to the block unit. The hydrophilic-lipophilic balance value (HLB) of commercially available surfactants is generally available and can be considered in selecting the appropriate surfactant.

Only very low levels of surfactant are required when parallel twin planes are introduced into the grain nuclei to reduce the grain dispersity of the resulting emulsion. A surfactant weight concentration of about 0.1% is contemplated based on the interim silver weight (ie, the weight of silver present in the emulsion while the twin planes are introduced into the grain nuclei). The preferred minimum concentration of surfactant is 1% based on the immediate silver weight. A wide range of surfactant concentrations has been observed to be effective. A surfactant concentration of more than 100% of the current silver weight when using a category S-I surfactant,
Alternatively, surfactant concentrations above 50% of the immediate silver weight when using category S-II, S-III or S-IV surfactants did not realize additional benefits. However, when a category SI surfactant is used, the surfactant concentration is 200% or more of the current silver weight, or the category S-II, S-III or S-IV is used.
It is believed that a surfactant concentration of 100% or more of the immediate silver weight with a surfactant can be used.

The method of manufacture is compatible with both of the two most common techniques for introducing parallel twin planes into grain nuclei. The preferred and most common of these techniques are to produce a population of grain nuclei that eventually grow into tabular grains, while at the same time
This is a method of introducing parallel twin planes in the same precipitation step. In other words, grain nucleation occurs under the conditions leading to twinning. The second method is to generate a stable grain nucleus population and then adjust the pAg of the interim emulsion to a level that leads to twinning.

Regardless of which method is adopted,
It is advantageous to introduce twin planes into the grain nuclei in the early stages of precipitation formation. It is contemplated that less than 2% of the total silver used to prepare the tabular grain emulsion will be used to obtain a grain core population with parallel twin planes. It is usually convenient to prepare the grain nucleus population with parallel twin planes using at least 0.05% of the total silver amount, although this can be achieved even in lower amounts. The later the introduction of the parallel twin planes after the formation of the stable grain nucleus population is delayed, the greater the tendency of the grain dispersity to increase.

At the stage of introducing parallel twin planes in the grain nuclei during or shortly after the initial grain nucleation, the lowest achievable level of grain dispersity in the final emulsion is achieved by controlling the dispersing medium. It

The pAg of the dispersion medium is less than 10% COV
In order to achieve the above, the range is preferably maintained in the range of 5.4 to 10.3, optimally in the range of 7.0 to 10.0. 1
At pAgs above 0.3, there is a trend towards increasing ECD and thickness dispersity of the tabular grains. Any convenient conventional technique for monitoring and adjusting pAg can be used.

A reduction in particle dispersity was also observed as a function of the pH of the dispersion medium. Both the occurrence of non-tabular grains and the dispersity of the thickness of the non-tabular grain population are such that the pH of the dispersion medium at the time when parallel twin planes are introduced into the grain nuclei is less than 6.0. It was observed that the number decreased. The pH of the dispersion medium can be adjusted by any convenient conventional method. Strong mineral acids, such as nitric acid, can be used for this purpose.

Particle nucleation and growth occur in a dispersing medium comprising water, dissolved salts and conventional peptizers.
Hydrophilic colloid peptizers such as gelatin and gelatin derivatives are specifically contemplated. 20-800 (optimally 40-600) per mole of silver introduced during the nucleation step
It was observed that a deflocculating agent concentration of grams produced an emulsion with the lowest level of grain dispersity.

The formation of grain nuclei containing parallel twin planes takes place at the precipitation temperatures customary for photographic emulsions, especially in the temperature range 20 to 80 ° C., and 20 to 60.
The temperature range of ° C is optimal.

Once the population of grain nuclei containing parallel twin planes has been generated as described above, the next step is to reduce the dispersity of the population of grain nuclei by aging. The purpose of aging the grain nuclei containing parallel twin planes is Himmelright,
U.S. Pat. No. 4,477,565 and Nott
orf, U.S. Pat. No. 4,722,886. Ammonia or thioether with a concentration of about 0.01 to 0.1 N constitutes a preferred ripening agent group.

Instead of introducing a silver halide solvent to induce ripening, it is possible to achieve the ripening step by adjusting the pH to a high level, for example above 9.0. This type of aging method is disclosed by Buntaine and Brady, US Pat. No. 5,013,641 (issued May 7, 1991).
In this method, the post-nucleation aging step uses a base such as an alkali hydroxide (eg, lithium hydroxide, sodium hydroxide or potassium hydroxide) to bring the pH of the dispersion medium to 9.0.
This is done by adjusting over time and then digesting briefly (typically 3-7 minutes). At the end of the ripening step, the emulsion is brought to the acidic pH range (eg, below 6.0) normally selected for silver halide precipitation by adding a conventional acidifying agent, eg, mineral acid (eg, nitric acid). Return again.

No matter how the aging period is shortened, some reduction in the degree of dispersion will occur. At least about 20 of total silver
It is preferred to continue aging until the% solubilizes and redeposits on the remaining particle nuclei. The longer the maturation period, the fewer the remaining nuclei. This is
It means that in the subsequent growth step, the additional silver halide precipitation required to prepare the tabular grains of the desired ECD is gradually reduced. From another perspective, long ripening reduces the size of the emulsion composition in terms of total grams of silver precipitated. Optimum ripening varies as a function of the individual requirements of the desired emulsion and can be adjusted to the desired level.

Upon completion of nucleation and ripening, further emulsion growth can be carried out in any conventional manner compatible with achieving the desired final average grain thickness and ECD. The halide introduced during grain growth can be chosen independently of the halide chosen for nucleation. The tabular grain emulsions can contain grains of the same or different silver halide composition.

When the coating amount is selected so as to achieve a maximum density of 2.0 or more, an emulsion capable of exhibiting a contrast of more than 2.0 can be prepared by the above-mentioned preparation method, but in some cases, it is usually used in the emulsion. The contrast of the emulsions used can be further increased by incorporating one or more contrast enhancing agents. For example, Group VIII metal dopants known to improve contrast such as rhodium, ruthenium or iridium can be introduced during grain formation. The dopant can be added to the reaction vessel before the start of precipitation, but is preferably added after the formation of parallel twin planes during grain growth.

The metal can be added to the reaction vessel as a simple salt or coordination complex (eg, a tetracoordination complex, preferably a hexacoordination complex). Both the ligand of the complex and the complex-forming metal ion can form part of the product particle. In a preferred mode of addition, rhodium, ruthenium or iridium can be added in the form of a simple salt of a halide, preferably chloride and / or bromide. In another preferred embodiment of the addition, the ammonium or alkali metal hexahalorhodiate complex, hexahalolydiate complex or hexahaloruthenate complex (the halide is preferably chloride or bromide)
In this state, rhodium, iridium or ruthenium can be added.

Any amount of dopant up to about 1 × 10 ^-5 Group VIII metal gram atom per mole of silver can be used. To achieve a more significant improvement in contrast, it is typically at least 10 per mole of silver.
^-9 (preferably at least 10 ^-8 ) metal gram atom concentrations of Group VIII metal ions are expected. To avoid excessive desensitization of the emulsion, it is preferred to limit the Group VIII metal ion concentration to less than 10 ^-6 metal gram atoms per silver mole. Research Disclosure , Vol.308, December 1989,
Item 308119, Section I, paragraph D provides a summary teaching metal dopants. Evans et al., US Pat. No. 5,024,931 discloses the effectiveness of various iridium oligomers as dopants.

In optimizing the process for making tabular grains at minimum dispersity levels, the optimization conditions can be varied by the action of iodide incorporated in the grains and the choice of surfactant and / or peptizer. Admitted.

While any of the conventional hydrophilic colloid peptizers can be used, it is preferred to use a gelatin peptizer during precipitation. Gelatin peptizers are usually divided into so-called "regular" gelatin peptizers and so-called "oxidized" gelatin peptizers. Regular gelatino-peptizers contain at least 30 micromoles per gram, and usually fairly high concentrations of natural methionine.

The term oxidized gelatino-peptizer means a gelatino-peptizer containing less than 30 micromoles of methionine per gram. Regular gelatino-peptizers become oxidized gelatino-peptizers when treated with strong oxidants as taught by Maskasky, US Pat. No. 4,713,323 and King et al., 4,942,120. Will be converted. The oxidant attacks the divalent sulfur atom of the methionine moiety and converts it to the tetravalent or, preferably, hexavalent state. It has been found that methionine concentrations of less than 30 micromolar per gram exhibit the behavioral characteristics of oxidized gelatino-peptizers, but it is preferred to reduce the methionine concentration to less than 12 micromolar per gram. Generally, any of the effective oxidations can reduce methionine below detectable levels. In rare cases, gelatin may originally contain low levels of methionine, and it is convenient to express the actually distinguishable feature at the methionine level rather than whether or not the oxidation step was performed. It is understood that the term "regular" or "oxidation" is used.

When an oxidized gelatin peptizer is used, it is preferred to keep the pH below 5.2 during twin plane formation to achieve a minimum (less than 10%) COV. Minimum COV if regular gelatin peptizer is used
The pH is kept below 3.0 during the formation of twin planes in order to achieve

When a regular gelatin and a category S-I surfactant are used before the post-ripening grain growth, the category S-I surfactant contains a hydrophilic block (for example, HAO1) as a surfactant. 4-9 of total molecular weight
6% (preferably 5-85%, optimally 10-80%)
Is chosen to occupy. X and x '(in formula II) are at least 6, and the surfactant has a minimum molecular weight of at least 760, optimally at least 1,000 and a maximum molecular weight of 16,000 or less, preferably 10,000.
It is preferably less than.

When the category S-I surfactant is replaced by a category S-II surfactant, the latter is such that the lipophilic block (eg LAO2) is 4 to 96% (preferably 15%) of the total molecular weight of the surfactant. ~ 95%, optimally 20 ~
90%). X in formula (IV) is at least 13, and the surfactant has a minimum molecular weight of at least 800, optimally at least 1,000 and a maximum molecular weight of 30,000 or less, preferably 20,000.
It is preferably less than.

When a Category S-III surfactant is selected for this step, it has lipophilic alkylene oxide block linking units (LOL) of 4-96% of the total molecular weight of the surfactant, preferably 15-95%. , Optimally 20 ~
Selected to account for 90%. In the ethylene oxide and 1,2-propylene oxide embodiments shown in formula (XIIIa), x can range from 3 to 250, y can range from 2 to 340, and the minimum molecular weight of the surfactant is 1,2. Over 100, optimally at least 2,000,
Maximum molecular weight is 60,000 or less, preferably 40,000
It is less than 0. The concentration level of the surfactant is preferably limited as the iodide concentration increases.

When a Category S-IV surfactant is selected for this step, it has a hydrophilic alkylene oxide block linking unit (HOL) of 4% of the total molecular weight of the surfactant.
~ 96%, preferably 5-85%, optimally 10-80
Chosen to account for%. In the ethylene oxide and 1,2-propylene oxide embodiments shown in formula (XIIIb), x can range from 3 to 250, y can range from 2 to 340, and the minimum molecular weight of the surfactant is 1,2. 1
00, optimally at least 2,000, with a maximum molecular weight of 50,000 or less, preferably less than 30,000.

If an oxidized gelatin peptizer is used prior to post-ripening grain growth, and no iodide is added during post-ripening grain growth, the hydrophilic block (eg HAO1) is the total surfactant. 4-35% of molecular weight (optimally 10-3
Minimal COV emulsions can be made with Category S-I surfactants selected to account for 0%). The minimum molecular weight of surfactants is x and x '(formula II)
Continues to be determined by the minimum value of 6 In an optimized embodiment, x and x '(Formula II) are at least 7. Minimal COV emulsions with Category S-II surfactants chosen such that the lipophilic block (eg LAO2) accounts for 40-96% (optimally 60-90%) of the total surfactant molecular weight. Can be manufactured. The minimum molecular weight of the surfactant continues to be determined by the minimum of 13 of x (formula IV). The same molecular weight ranges as with the regular gelatin peptizers described above are applicable to both category SI and S-II surfactants.

The polyalkylene oxide block copolymer surfactant can optionally be removed from the emulsion after it has been completely prepared. Any convenient cleaning procedure commonly used, such as Research Disclo
sure , Vol.308, December 1989, Item 308, 119, Section
The procedure specifically described in II can be used. The polyalkylene oxide block copolymer surfactant constitutes a detectable component of the final emulsion when present in concentrations greater than 0.02% based on total silver.

In addition to the features described above, the phototypesetting paper of the present invention has a conventional form, for example, Research Disclosure , It.
It can be constructed according to the embodiment shown in em 308, 119. According to Item 308, 119, the emulsion was washed (Section II) and chemically sensitized (Sectio).
n III) and spectrally sensitized (Section IV, but G
And L section), and one or more antifoggants, sensitizers (Section VI) and hardeners (Sect)
ion X). Each of the dye image-forming layer units comprises in the emulsion layer or in an adjacent layer a dye releasing or forming coupler as well as other photographically useful group releasing couplers such as those described in Section VII. It may contain one or more couplers, including both. The emulsion layers and other layers of the photographic element are coated with coating aids (Sectio
n XI), plasticizers and lubricants (Section XII),
An antistatic layer (Section XIII) can be included, as well as a matting agent (Section XVI). Any conventional reflective support can be used, such as any of the various reflective supports described in Section XVII. The emulsion can be prepared using conventional coating and drying operations, and S
Any of the additional layers described in Section XV can be used, such as subbing layers and overcoat layers. Conventional exposure and processing as specifically described in Sections XVIII and XIX (D), respectively, are also contemplated.

[0110]

The present invention can be more fully understood by referring to the following specific examples. In each case, the tabular grains accounted for greater than 97% of the total grain projected area in the emulsion. In each case, no particles having an equivalent circular diameter of less than 0.1 μm are present, or are present in negligible amounts without the reported numerical particle parameters.

Comparative Example 1 (AgBr, Saitou et al., Example 9 of US Pat. No. 4,797,354) Into a 4 L reaction vessel, an aqueous gelatin solution (1 L of water, 7 g of deionized alkali-treated gelatin, 4.5 g of potassium bromide) was used. And 1.2 mL of 1N potassium hydroxide, pBr1.42
Is added), and while maintaining the temperature at 30 ° C., 25 mL of an aqueous silver nitrate solution (containing 8.0 g of silver nitrate) and 25 mL of an aqueous potassium bromide solution (containing 5.8 g of potassium bromide) are added at a rate of 25 mL / min. Simultaneously added over 1 minute. Next, an aqueous gelatin solution (containing 1950 mL of water, 90 g of deionized alkali-treated gelatin, 15.3 mL of 1N aqueous potassium hydroxide solution and 3.6 g of potassium bromide) was added thereto, and the temperature of the mixture was raised to 75 ° C. over 10 minutes. Raised. Then, it was aged for 50 minutes.

Next, the above mixture was transferred to a 12 L reaction vessel, and 200 mL of an aqueous silver nitrate solution (containing 90 g of silver nitrate) was added to 20 mL.
It was added at a rate of mL / min. Twenty-five seconds after the start of addition of silver nitrate, 191.6 mL of an aqueous potassium bromide solution (containing 61.2 g of potassium bromide) was added thereto at a rate of 20 mL / min, and at the same time, the addition of both solutions was completed. Then, the resulting mixture was stirred for 2 minutes, and then 2,000 mL of an aqueous silver nitrate solution (containing 900 g of silver nitrate) and 2,000 mL of an aqueous potassium bromide solution were added.
(Containing 636.9 g of potassium bromide) was simultaneously added to the mixture at a rate of 40 mL / min for the first 20 minutes and at a rate of 60 mL / min for the next 20 minutes. The mixture was then stirred for 1 minute, after which the silver halide emulsion thus obtained was washed and redispersed. These emulsion grains consisted essentially of silver bromide.

The grain characteristics of this emulsion were as follows. Average grain ECD: 1.20 μm Average grain thickness: 0.162 μm Average aspect ratio: 7.4 Average tabularity: 45.7 Coefficient of variation based on total grains: 21.3%.

This emulsion comprises sodium thiocyanate 70
mg / mole, potassium tetrachloroaurate 2.4 mg / mole,
Sodium thiosulfate pentahydrate 3.2 mg / mole, Dye
A: 3-ethyl-5- [N- (4-sulfobutyl) -4
Sensitized with-(1H) pyridylidene] rhodanine pyridinium salt 60 mg / mole and heat treated for 35 minutes at 65 ° C. To finish the emulsion, 5-methyl-s-triazole (2,3a) -pyrimidin-7-ol 300 mg / mole
Was added.

Example 2 (AgBr, AKT-731) In a 4 L reaction vessel, a gelatin aqueous solution [1 L of water, 2.5 g of alkali-processed oxidized gelatin and 4.0 mL of 4N nitric acid solution was added.
And 1.12 g of sodium bromide and 1.57% by weight of PLURONIC ™ -31R1 (x = of Formula II, based on the total silver weight introduced by the start of the post-ripening grain growth step).
25, x '= 25, y = 7) and a pAg of 9.39] are added thereto, while maintaining these temperatures at 45 ° C., 8.3 mL of an aqueous solution of silver nitrate is added thereto.
An aqueous solution of sodium bromide (containing 1.44 g of sodium bromide) in the same amount as (containing 2.26 g of silver nitrate) was added simultaneously at a constant rate over 1 minute. Then, after mixing for 1 minute, 14.2 mL of an aqueous sodium bromide solution (containing 1.46 g of sodium bromide) was added to the mixture. The mixture temperature was raised to 60 ° C. over 9 minutes. At this point, 65 mL of an ammoniacal aqueous solution (containing 6.7 g of ammonium sulfate and 48 mL of 2.5N sodium hydroxide solution) was added to the reaction vessel and mixed for 9 minutes.

Next, an aqueous gelatin solution 10 was added to this mixture.
5.5mL (16.7g of alkali-treated oxidized gelatin and 4N
(Containing 22 mL of nitric acid solution) was added over 2 minutes. Thereafter, 25 mL of the silver nitrate aqueous solution (containing 6.8 g of silver nitrate) and the same amount of the sodium bromide aqueous solution (containing 4.4 g of sodium bromide) were added at a constant rate for 10 minutes.

Next, 225 mL of an aqueous silver nitrate solution (silver nitrate 6
1.1 mL) and the same amount of sodium bromide aqueous solution (containing 38.9 g of sodium bromide), 2.5 mL / min
And a constant gradient starting from a rate of 2.6 mL / min was added simultaneously to the mixture over 30 minutes. Next, 469 mL of an aqueous silver nitrate solution (containing 127.4 g of silver nitrate) and 466 mL of an aqueous sodium bromide solution (containing 80.5 g of sodium bromide)
Was simultaneously added to the mixture at a constant rate over 37.5 minutes. The silver halide emulsion thus obtained was washed.

This emulsion was sensitized and finished like the emulsion of Example 1. The grain characteristics of this emulsion are as follows. Average grain ECD: 1.26 μm Average grain thickness: 0.144 μm Average aspect ratio of grain: 8.8 Average tabularity of grain: 60.8 Coefficient of variation based on total grain: 6.3%.

Comparative Example 3 (AgBr _0.99 I _0.01 + Rh,
AKT-720) After the emulsion was transferred to a 12 L reaction vessel, 159 μg of ammonium hexachlororhodium (III) ate was added over 25 minutes.
Was repeated, and Example 1 was repeated except that an additional 1 mol% potassium iodide was added to the aqueous potassium bromide solution for subsequent precipitation. The emulsion thus prepared contained 1 mol% iodide and 7.23 × 10 ⁻⁸ mol ammonium hexachlororhodium (III) ate per mol silver.

This emulsion was sensitized and finished like the emulsion of Example 1. The grain characteristics of this emulsion are as follows. Average grain ECD: 1.30 μm Average grain thickness: 0.148 μm Average aspect ratio of grains: 8.8 Average tabularity of grains: 59.3 Variation coefficient based on total grains: 19.2%.

Example 4 (AgBr _0.99 I _0.01 + Rh, A
KT-728) In a 4 L reaction vessel, an aqueous gelatin solution (1 L of water, 1 g of alkali-treated gelatin, 1 mL of 4N nitric acid solution, and 2.44 g of sodium bromide was used, and x = 3 in the formula (II).
Surfactant PLURO satisfying 2, y = 9 and y ′ = 9
NIC ™ -L63, containing 3.47 wt% based on the total weight of silver introduced by the start of post-ripening grain growth, and exhibiting a pAg of 9.71) and a temperature of 45 ° C. 6.7mL of silver nitrate aqueous solution
(Containing 0.91 g of silver nitrate) and the same amount of aqueous sodium bromide solution (containing 0.63 g of sodium bromide) were simultaneously added at a constant rate over 1 minute. After mixing for 1 minute, the temperature of the mixture was raised to 60 ° C over 9 minutes. At that point, 28.5 mL of aqueous ammoniacal solution in the reaction vessel
(Containing 1.68 g of ammonium sulfate and 11.8 mL of 2.5N sodium hydroxide solution) were added and mixed for 9 minutes. Then, add 88.7 mL of gelatin aqueous solution to the mixture.
(16.7 g of alkali-treated gelatin and 4N nitric acid solution 5.
3 mL) was added over 2 minutes.

Next, 31.6 μg of ammonium hexachlororhodium (III) was added over 2.5 minutes. Thereafter, 7.5 mL of an aqueous silver nitrate solution (containing 1.0 g of silver nitrate) and 7.3 mL of an aqueous sodium bromide solution (0.6 mg of sodium bromide)
8 g) was added at a constant rate over 5 minutes. Next, 474.7 mL of silver nitrate aqueous solution (containing 129 g of nitrate)
And 473.6 mL of an aqueous halide solution (containing 81 g of sodium bromide and 1.3 g of potassium iodide) at the same time over a period of 64 minutes with a constant gradient starting from rates of 1.5 mL / min and 1.6 mL / min, respectively. Added to the mixture. Next, 253.3 mL of an aqueous silver nitrate solution (silver nitrate 68.
(Containing 9 g) and 251.1 mL of an aqueous silver halide solution (containing 43 g of sodium bromide and 0.7 g of potassium iodide) were simultaneously added to the above mixture at a constant rate over 19 minutes. The silver halide emulsion thus obtained contained 1 mol% of iodide and 7.23 × 10 ⁻⁸ mol of ammonium hexachlororhodium (III) per mol of silver.

The grain characteristics of this emulsion are as follows. Average grain ECD: 1.58 μm Average grain thickness: 0.118 μm Average aspect ratio of grains: 13.4 Average tabularity of grains: 113.5 Coefficient of variation based on total grains: 10.4%.

Example 5 (AgBr _0.99 I _0.01 + Rh, A
KT-730) The amount of PLURONIC ™ -L63 added was 5.
Example 4 was repeated except that it was increased to 21% by weight.
The silver halide emulsion thus obtained contained 1 mol% of iodide and 7.23 × 10 ⁻⁸ mol of ammonium hexachlororhodium (III) per mol of silver.

This emulsion was sensitized and finished like the emulsion of Example 1. The grain characteristics of this emulsion are as follows. Average grain ECD: 1.35 μm Average grain thickness: 0.153 μm Average aspect ratio of particles: 8.8 Average tabularity of grains: 57.7 Coefficient of variation based on total grains: 7.0%.

Example 6 (AgBr _0.99 I _0.01 + Rh, A
KT-729) 6.94 with added PLURONIC ™ -L63
Example 4 was repeated except that the weight percent was increased. The silver halide emulsion thus obtained contains 1 iodide per mol of silver.
% And ammonium hexachlororhodium (III) 7.23.times.10.sup.- ⁸ mol.

The grain characteristics of this emulsion are as follows. Average grain ECD: 1.22 μm Average grain thickness: 0.186 μm Average aspect ratio of grain: 6.6 Average tabularity of grain: 35.3 Coefficient of variation of total grain: 6.3%.

Example 7 (AgBr _0.99 I _0.01 + Ir, A
KT-761) Example 5 was repeated, except that 0.235 mg of potassium hexachloroiridium (IV) ate was added instead of ammonium hexachlororhodium (III) ate. The silver halide emulsion thus obtained contained 1 mol% of iodide per mol of silver and 4.3 × 10 6 potassium hexachloroiridium (IV).
^-7 mol.

The grain characteristics of this emulsion are as follows. Average grain ECD: 1.33 μm Average grain thickness: 0.159 μm Average aspect ratio of particles: 8.4 Average tabularity of grains: 52.6 Coefficient of variation based on total grains: 7.7%.

Coating and Processing The emulsion of Comparative Example 1 was compared to the emulsion of Example 2 for the purpose of comparing silver bromide. The emulsion of Comparative Example 3 was compared to the emulsion of Example 5 for the purpose of comparing silver bromoiodide. The Example 5 emulsion was chosen for comparison with the emulsion of Comparative Example 3 on the basis of their similarity in average grain ECD, thickness and aspect ratio.

A comparison of these emulsions compares 21.5 on a transparent film support, which allows an accurate determination of maximum density.
Based on an equivalent silver coverage of 2 mg / dm ² (200 mg / ft ² ) and a silver coverage of 10.76 mg / dm ² (100 mg / ft ² ) on a white reflective support. These coatings were each treated with Developer A listed in Table XV for 1 minute at 35 ° C and then with Fixer A listed in Table XVI for 30 seconds.

Table XV Composition of Developer A (g) Water 539.0 Potassium hydroxide (45.5% solution) 178.8 Sodium metabisulfite 145.0 Sodium bromide 12.0 2-Butene-dioic acid ( Z) Homopolymer (50% solution) 13.0 Pentetic acid * pentasodium salt (40% solution) 15.0 Sodium hydroxide (50% solution) 56.0 Benzotriazole 0.4 1-Phenyl -5-Mercaptotetrazole 0.05 Boric acid 6.94 Diethylene glycol 110.0 Hydroquinone 75.0 4-Hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone 2.9 Potassium carbonate (47% solution) 120.0

Table XVI Composition of Fixer A (g) Ammonium thiosulfate 155.0 Sodium metabisulfite 190.0 Sodium acetate / acetic acid 25.0 Sodium borate pentahydrate 11.8 Ammonium sulphate 6.6

The photographic response for the Comparative Example 1 and Example 2 coatings with a 1/10 second exposure at 3000 ° K light temperature is shown in FIG. 4 and summarized in Table XVII. The excellent photographic performance exhibited by Comparative Emulsion 1 or more of the present emulsions (Emulsion 2)
Not only the contrast but also the speed with harmonious fog is evident.

In each of Tables XVII, XVIII and XIX, speed was measured at a density above 1.0 fog. Contrast was measured as the slope between a first point at a density of 0.2 above fog and a second point on the characteristic curve showing an exposure 0.75 log E above the first point.

Table XVII Emulsion Fogging Speed Contrast 1 (Comparison) 0.04 153 1.13 2 (Invention) 0.04 213 1.46

Comparative Emulsion 3 and Emulsion 5 were compared in FIG. Again, the excellent photographic performance exhibited by Emulsions 3 and above of the present emulsion (Emulsion 5) is evident not only in contrast, but also in speed and fog. The sharp shoulder contrast exhibited by Emulsion 5 is particularly noticeable. The results are summarized in Table XVIII.

Table XVIII Emulsion Fog Speed Contrast 3 (Comparison) 0.06 221 1.375 (Invention) 0.05 233 1.70

Optimally sensitized Comparative Emulsion 3 and Example 5 were further evaluated under this condition, as high intensity, short exposures are commonly used in graphic arts products. The results of the 10 ^-5 second exposed coatings are shown in Figure 6 and are summarized in Table XIX. The advantages of Emulsion 5 over Comparative Emulsion 3 were maintained even under high-intensity exposure conditions.

Table XIX Emulsion Fogging Speed Contrast 3 (Comparison) 0.03 145 1.805 (Invention) 0.03 160 1.94

[0141]

INDUSTRIAL APPLICABILITY The phototypesetting paper is a flat plate which is substantially free of non-tabular grains, thin (<0.2 μm), high (> 25) tabularity and high monodispersity (COV <15%). It has been found that a number of advantages can be realized when constructed using tabular grain emulsions having tabular grains as compared to conventional phototypesetting papers containing tabular grain emulsions. High speed and high contrast are observed when compared to similarly configured phototypesetting papers in which the tabular grains only exhibit conventional coefficients of variation. A particularly marked increase in contrast is observed in the shoulder region of the characteristic curve from maximum density to an optical density of about 0.4 below maximum density. A reduced granularity is also observed.

[Brief description of drawings]

FIG. 1 is a graph plotting optical density against exposure for various silver coatings.

FIG. 2 is a graph plotting optical density against exposure for the same emulsion with and without contrast enhancing dopants.

FIG. 3 is an optical photograph replacing an enlarged view of a conventional tabular grain emulsion.

FIG. 4 is a photographic response curve of the coatings of Example 1 (control) and Example 2 (invention) when exposed to 3000 ° K light temperature for 1/10 seconds.

FIG. 5 is a photographic response curve of each coating of Example 3 (control) and Example 5 (invention) similar to FIG.

FIG. 6 Example 3 (control) and Example 5 by high-intensity and short-time exposure
(Invention) Fig. 4 is a photographic response curve of each coating. 1 to 6 show 3.9 logE with an increase of 0.15 logE.
Is a characteristic curve obtained by plotting the optical density as a function of the exposure dose over the exposure area of (E is the exposure dose measured in lumen second (ms)).

 ─────────────────────────────────────────────────── ————————————————————————————————————————————————————————————— In Inventor Mommy Coming New York, USA 14450, Fairport, Great Garland Rise 15

Claims (1)

[Claims] 1. A white reflective support, as well as at least 2. through a 0.75 log E exposure area measured on the support with a minimum exposure required to produce a density above 0.2 fog. It has a maximum density of 0 and a contrast of 2.0 or more, and contains 0 to 5 mol% of chloride per total silver and 0.
A phototypesetting paper comprising image-forming units comprising tabular silver halide grain emulsions having halide content grains consisting of .about.15 mol% iodide and 80 to 100 mol% bromide and having a size of greater than 0.1 .mu.m. The tabular grain emulsion has a coefficient of variation of less than 15% per total grain population in a tabular grain emulsion having an equivalent circular diameter, and greater than 97% of the projected area of the total grain population in the tabular grain emulsion. ,
Photographic typesetting paper, characterized in that it is comprised of tabular grains having an equivalent circular diameter of more than 0.1 μm and an average thickness of less than 0.2 μm and a tabularity of more than 25.