FILM FORMATION AND EVALUATION

This invention relates to the formation of films on the surfaces of substrates and to the evaluation of characteristics of such films.

Coatings are widely used in both industrial and domestic environments to enhance the functionality and add-on value of bulk materials and articles and to enhance the appearance of structures. Other applications include non-continuous coatings such as inks. Organic coatings are particularly widely used in many industrial protective/decorative applications, such as automobile top clear coatings, automotive and decorative paints and lacquers, etc, and in inks. Other types of organic coatings include, for example, protective and anticorrosive coatings, adhesive and release coatings, environmental barrier coatings, electric conductive/optic transparent coatings and scratch resistant hard coatings. Although such coatings may consist solely of organic components, other coatings may contain inorganic elements such as metal oxide pigments, conductive metal particles, inorganic particle fillers, clays such as vermiculite and similar well known inorganic particles.

There are also many forms of inorganic coatings which may contain organic binders or alternatively may be formed from aqueous dispersions. Other forms of inorganic coatings may be formed by the direct application of the coating materials to substrates using techniques such as sputtering and chemical or physical vapour deposition.

The ability to test new combinations of ingredients for coating materials or new processing conditions, especially rapidly and in large numbers of samples, to discover next generation materials or new, cost-effective manufacturing methods is high on the agenda of many manufacturers to enable them to obtain commercial advantages over competitors. Also of significant importance is the ability to test existing formulations for performance drift, especially when substituting alternative ingredients or alternatively-sourced ingredients.

Such aspirations also apply more generally to other materials such as structural materials, particularly when at least some of the properties of interest of such materials may be determined from film samples of such materials.

There have been attempts to generate and test samples of materials in high numbers, for example as disclosed in US 6482264 B1 , US 2003/0224105 A1, US 2004/0071888 A1 and DE 10136448 A1. These publications disclose a variety of methods of depositing and spreading samples on substrates to form films, including in some, spreading the liquid samples using non-contact methods, for example

spinning or oscillating the substrate or using an air knife to spread the liquid samples or spraying the liquid samples onto the substrate.

Such methods suffer from the disadvantage that, owing to the small amounts of liquid deposited on the substrates, the uniformity of the films formed may vary significantly and, consequently, the measured parameters may not be accurately determined. Whilst this may not be significant for some materials or for screening materials, for example on a pass/fail basis, it may, however, in other applications be more critical. For example, in determining colour specifications for paints, lacquers, inks etc, the thickness and uniformity of the film may significantly affect the colour determination process. Additionally, the amount of shear the sample is subjected to during spreading may affect the dispersion of pigment particles and, therefore, the uniformity of the resultant colour of the film sample.

Another problem that may significantly affect the quality of data generated from the analysis of samples arises owing the potential variability in the amounts of ingredients that are used to make the samples. For example, the viscosities of liquids vary with fluctuations in ambient temperature. Although the change in viscosity in real terms may be relatively small, it may result in the amount, ie weight, of a sample ingredient used to make the sample being significantly different, for example of the order of 4-5 wt%, and at times up to 15-20 wt%, on a day-to-day basis. Owing to the small size of the samples, such differences in weight deposited may lead to significant differences in the uniformity of the films formed on the substrates between batches or day to day basis thus leading to doubts concerning the reproducibility of samples and the data generated therefrom. It may also lead to time consuming practises such as having to re-calibrate equipment on a relatively frequent basis.

It is an object of the present invention to reduce or obviate at least one of the aforementioned disadvantages.

According to a first aspect of the present invention, a method of forming a film on a surface of a substrate comprises dispensing a liquid sample to be formed into a film at a sample location position on the substrate surface and subjecting the liquid sample to a controlled gas flow to spread the sample substantially uniformly away from said sample location position relative to the substrate surface to form a film thereon.

More particularly, according to the first aspect of invention, a method of forming a film on a surface of a substrate comprises dispensing a liquid sample to be formed into a

film at a sample location position on the substrate surface and subjecting the liquid sample to a controlled gas flow directed substantially normal to the substrate surface and preferably generally centrally of the sample to spread the sample substantially uniformly away from said sample location position relative to the substrate surface to form a film thereon.

The controlled gas flow used in the methods according to the invention comprises a gas flow that is controlled in both pressure and duration. Preferably, the gas flow is at a pressure in the range 0.5 to 10 bar, more particularly in the range 1 to 5 bar. Preferably, the gas flow has duration in the range 0.5 to 10 seconds, more particularly in the range 0.5 to 3 seconds.

Preferably, the gas flow is generated with a substantially uniform cross-section, preferably circular. The height at which the gas flow is generated above the substrate is optimised in accordance with the pressure used and the viscosity of the liquid sample(s) being dispensed onto the substrate. For a given sample viscosity, variation in the height at which the gas flow is generated above the sample will affect the gas pressure and gas flow duration parameters which will have to be adjusted up or down as the height increases or decreases to ensure uniform flow of the sample to form the film.

Preferably, the gas flow is a diffuse gas flow. In a preferred embodiment of the invention, said method further comprises generating a liquid sample comprising at least two liquid ingredients by dispensing said ingredients to a sample preparation location, gravimetrically controlling the dispensation of at least one of said ingredients and, if necessary, mixing said sample ingredients. Preferably, when generating a liquid sample, the method comprises volumetrically dispensing a major ingredient of said sample and gravimetrically controlling the dispensation of at least one minor ingredient of said sample. More preferably, said major ingredient comprises at least 50 wt% and up to 99 wt%, more especially at least 70 wt% of a target weight for said sample. Preferably, to achieve the target weight of said sample, said at least one minor ingredient is dispensed under gravimetric control in two stages, wherein, in the first stage, a major proportion of said minor ingredient is dispensed at a faster rate than the rate at which a remaining minor proportion of said minor ingredient is dispensed in the second stage.

It will be appreciated that more than one minor ingredient may be added to the major ingredient.

Preferably, in the first gravimetrically-controlled stage of sample generation, between

50 wt% and 98 wt%, more preferably between 50 wt% and 96 wt%, and more especially between 50 wt% and 95 wt% of the ingredient target weight is dispensed. Preferably, in the second gravimetrically-controlled stage of sample generation, up to 2 wt%, more preferably up to 4 wt%, and more especially up to 5 wt% of the ingredient target weight is dispensed.

Preferably, the weight of a first ingredient dispensed is measured and used to adjust the weight of a second ingredient dispensed to the sample preparation location wherein the required relative proportions of said ingredients in the sample is achieved.

Using this technique, it has been found that, by using a volumetric dispensation of the major ingredient of the sample, ±50mg of a target weight for the major ingredient may be achieved. Using the feedback of the weight of the major ingredient to adjust the target weight(s) of the or each minor ingredient to maintain proportionality, about ±5mg of a target weight thereof may be achieved.

If the weight of the major ingredient is less than the target weight therefor, the target weight(s) of the or each minor ingredient is adjusted and the or each minor ingredient is added to the major ingredient under gravimetric control. Similarly, If the weight of the major ingredient is more than the target weight therefor, the target weight(s) of the or each minor ingredient is adjusted and the or each minor ingredient is added to the major ingredient under gravimetric control provided that, if the total weight to be dispensed it greater than a predetermined figure, the sample is aborted.

Preferably, during the sample generation, the first volumetric dispensation occurs in not more than 15 seconds/gram (s/g) of sample dispensed, more preferably in not more than 12 s/g, and is typically about 8 s/g. Preferably, the first gravimetrically- controlled stage occurs at a rate of at least 1.5 mg/s, more preferably at a rate of at least 2 mg/s. Preferably, the second gravimetrically-controlled stage occurs at a rate of not more than 1 mg/s, more preferably at a rate of not more than 0.6 mg/s.

In an alternative embodiment, the major ingredient of said sample may also be dispensed under gravimetric control, if desired, also using a two-stage process as described in the preceding paragraphs.

In a yet further alternative embodiment, the major ingredient of said sample may dispensed in two stages, a first volumetric stage and a second gravimetric stage.

The first stage is a volumetric dispensation as described in the preceding paragraphs wherein preferably at least 70% by weight, more preferably at least 80% by weight

and, more especially at least 90% by weight, of the major ingredient is dispensed volumetrically. The second stage is a gravimetric stage which may be a single stage or a two-stage process as described in the preceding paragraphs wherein not more than 30% by weight, more preferably not more than 20% by weight and, more especially not more than 10% by weight of the minor ingredient is dispensed gravimetrically.

Some applications may require the preparation of relatively large amounts of samples: such applications may include, for example, identical samples that may be subjected to varying processing conditions such as curing, drying or polymerisation or to varying environmental conditions such as wear testing or weathering of the samples. Preferably, however, in other applications the prepared liquid sample weight is not more than 50Og, preferably not more than 25Og. In a particularly preferred embodiment, the prepared liquid sample weight is not more than 100g, more preferably not more than 10g, and especially not more than 5g. Although target weights of less than 0.1g, may be envisaged in some applications, in applications relating to relatively viscous and/or thixotropic systems, such as paints etc, realistically, the target weight is preferably not less than 0.1g, more particularly not less than 1g.

Although the liquid sample may be dispensed onto the surface of the substrate gravimetrically, for example as hereinbefore described with reference to sample preparation, in a preferred embodiment of the first aspect of the invention, the amount of liquid sample that is dispensed at said sample location position is volumetrically controlled. Preferably, the amount of sample that is dispensed onto the surface of the substrate is in the range 1 μl to 10ml, more preferably in the range 1μl to 1ml, more particularly in the range 10μl to 500μl and especially in the range

50μl to 300μl.

The methods of the invention include forming a plurality of films on the substrate surface by dispensing at least two liquid samples at sample positions on said surface that are in space relationship from one another and forming films from said samples. Conveniently, the number of samples dispensed on said surface is not more than 100, preferably not more than 50, and especially not more than 30. Alternatively, depending on the test to which the films are to be subjected and space availability in test equipment, it may be necessary to dispense as many samples as it is practicable to do so on to said surface.

Preferably, the films formed on the substrate surface are discrete from one another. Alternatively, at least some of the films formed on the substrate surface may overlap with adjacent films provided that the non-overlap area has a surface area sufficient to enable a desired characterisation test to be performed. The surface area of the or each film formed is preferably at least 0.1 mm ² , more preferably at least 1 mm ² especially at least 5 mm ² . The maximum extent of the or each film formed is preferably not more than 1000 mm ² , especially not more than 500 mm ² . In embodiments in which at least some adjacent films may overlap, preferably, films that do overlap have a non-overlapped surface area of at least 0.1 mm ² , more preferably at least 1 mm ² especially at least 5 mm ² . The area covered by the or each film will be determined by the amount of liquid sample dispensed, the viscosity of the sample and the pressure and duration of the gas flow used to form the film. Typically, the area of the or each film is 100 to 400 mm ² , more preferably 150 to 350 mm ² . It will be appreciated, however, that film area may be application dependent and may by higher or lower that the ranges quoted.

Although it is preferred to form an array of films on the surface of a single substrate, in alternative embodiments, single or multiple films may be formed on the surfaces of an array of substrates.

In some embodiments of the invention, the samples may be deposited directly on to the surface of substrate. For example, this procedure may be adopted if a single type of sample, which may be pre-prepared as a relatively large batch, is being subjected to varying processing conditions such as curing, drying or polymerisation or to varying environmental conditions such as wear testing or weathering of the films. The procedure may also be adopted if ingredients for each sample are deposited on the surface of the substrate and, if necessary, are mixed thereon.

Alternatively, samples may be prepared separately, mixed if necessary and an amount greater than that to be dispensed drawn from the prepared samples. Each sample may be prepared individually and/or serially; alternatively, a number of samples may be prepared in parallel. The sample preparation may include a mixing step if required. The sample may be stirred, shaken, vibrated or otherwise agitated to effect mixing. When the sample is thixotropic in nature, for example paints, effective mixing may be particularly difficult to achieve, especially in small samples. To mix such samples, it is preferred to subject the sample to a three dimensional reciprocating motion such as that imparted

by conventional paint can shaker equipment used to mix tinters into base paints to customers' requirements.

Once the filrh(s) is formed, at least one characteristic of the film is determined. Without being limited to the following examples, the characteristic may be physical, eg colour, transparency, scratch resistance, wear; chemical, eg environmental stability/resistance; mechanical, eg strength, modulus; or electrical, eg resistance, conductivity.

In a particularly preferred embodiment of the invention, a method of forming and evaluating a plurality of films on a surface of a substrate comprises: (a) forming a plurality of liquid samples

(b) dispensing a proportion of at least two samples at respective sample location positions on the substrate surface;

(c) subjecting each sample to a controlled gas flow to spread the sample substantially uniformly away from the respective sample location position relative to the substrate surface to form a film thereon; and

(d) determining at least one characteristic of at least one of the films formed on the substrate surface.

In another particularly preferred embodiment of the invention, a method of forming and evaluating a plurality of films on a surface of a substrate comprises: (a) generating a plurality of liquid samples each comprising at least two liquid ingredients by dispensing said ingredients to respective sample preparation locations, gravimetrically controlling the dispensation of at least one of said ingredients at each location and, if necessary, for each sample mixing said sample ingredients; (b) dispensing a proportion of at least two samples at respective sample location positions on the substrate surface;

(c) subjecting each sample to a controlled gas flow to spread the sample substantially uniformly away from the respective sample location position relative to the substrate surface to form a film thereon; and (d) determining at least one characteristic of at least one of the films formed on the substrate surface.

The features of the invention described previously apply mutatis mutandis to these particularly preferred embodiments of the invention as the context permits.

The invention also includes apparatus by which the methods of the invention may be performed.

More particularly, according to a second aspect of the invention, apparatus for forming a film on a surface of a substrate comprises a substrate support means, a dispensing system for dispensing at least one liquid sample at a sample location position on a surface of a substrate supported by said substrate support means during operation of said apparatus, a gas flow system for delivering, during operation of said apparatus, a controlled gas flow to spread the sample substantially uniformly away from said sample location position relative to the substrate surface to form a film thereon.

In a preferred form of apparatus according to the second aspect of the invention, said apparatus comprises a substrate support means, a dispensing system for dispensing at least one liquid sample at a sample location position on a surface of a substrate supported by said substrate support means during operation of said apparatus, a gas flow system for delivering, during operation of said apparatus, a controlled gas flow to spread the sample substantially uniformly away from said sample location position relative to the substrate surface to form a film thereon, wherein a delivery nozzle of said gas flow system is, during operation of the apparatus, located to deliver said controlled gas flow substantially normal to the substrate surface and preferably generally centrally of a sample located thereon.

Preferably, the dispensing system preferably comprises a dispensing tip and means for applying vacuum or pressure to said tip whereby, in use, liquid may be aspirated into said tip or dispensed therefrom.

The gas flow system of the apparatuses according to the invention preferably is capable of delivering a gas flow that is controlled in both pressure and duration.

Preferably, the gas flow is at a pressure in the range 0.5 to 10 bar, more particularly in the range 1 to 5bar. Preferably, the gas flow has duration in the range 0.5 to 10 seconds, more particularly in the range 0.5 to 3 seconds. This is achieved in accordance with the invention by the computer-controlled operation of a pressure regulator and a solenoid valve both located in the gas flow line connected to a source of pressurised gas. Alternatively, a mass flow controller connected to a source of pressurised gas may be used.

Preferably, the delivery nozzle of said gas flow system delivers a diffuse gas flow.

Conveniently, this may be achieved by providing the delivery nozzle with a gas diffuser in the form of a metal, metal oxide or ceramic sinter or frit having a plurality of

θ holes passing through it. The holes in the sinter or frit may have a diameter in the range 100-200 microns, more particularly in the range 120-180 microns, typically about 150 microns. Suitable metal frits are Retimet™ metal foam frits available from Dunlop. Apparatus according to the second aspect of the invention further comprises an ingredient dispensing system for dispensing at least two liquid ingredients at a sample preparation location, said system being operable to control gravimetrically the dispensation of at least one of said ingredients.

The ingredient dispensing system preferably comprises a reservoir for containing a liquid ingredient, a motive means for dispensing, during use, a liquid ingredient from said reservoir, a balance mechanism on which is beatable an ingredient receptacle, a feedback loop connected between said balance mechanism and said motive means and including a computer means for controlling said motive means whereby, in use, said motive means is controlled by said computer means to dispense a target weight of at least one ingredient, the final amount of ingredient dispensed being controlled in response to weight changes detected by the balance mechanism. Preferably, said motive means is controlled by said computer means such that, in use, the rate at which the ingredient is dispensed is controlled.

Preferably, said reservoir comprises a syringe locatable relative to said motive means such that the plunger thereof is movable by said motive means.

Conveniently, the motive means comprises a stepper motor. Other, less preferred, motive means may be for example hydraulically- or gas-operated piston and cylinder mechanisms.

Preferably, said apparatus also comprises a tray mechanism interposable between said reservoir and the balance mechanism whereby, in use, extraneous drips of liquid from said reservoir are prevented from reaching an ingredient receptacle on said balance mechanism.

Preferably, the ingredient dispensing system comprises a second reservoir for containing a liquid ingredient, a second motive means for dispensing, during use, a liquid ingredient from said second reservoir, said computer means, in use, controlling said second motive means to dispense a liquid ingredient volumetrically from said second reservoir and controlling said first motive means to dispense a liquid ingredient gravimetrically from said first reservoir using feedback from said balance mechanism.

Conveniently, the second motive means comprises a peristaltic pump. Other, less preferred, second motive means may be for example an HPLC or a hydraulically- or gas-operated piston and cylinder mechanism.

Preferably, said computer means is programmed to adjust the weight of at least one ingredient dispensed by operation of said first motive means in response to a weight signal receivable from the balance mechanism representing the weight of an first ingredient dispensed by operation of said second motive means wherein the required relative proportions of said ingredients in the sample is achieved.

Preferably, to achieve a target weight of a sample, said computer means is programmed to control said first motive means to dispense at least one ingredient gravimetrically using feedback from said balance mechanism in two stages, wherein, in the first stage, a major proportion of said minor ingredient is dispensed at a faster rate than the rate at which a remaining minor proportion of said minor ingredient is dispensed in the second stage. Accordingly, it is preferred that said computer is programmed to control said first motive means, in the first gravimetrically-controlled stage, to dispense between 50 wt% and 98 wt%, more preferably between 50 wt% and 96 wt%, and more especially between 50 wt% and 95 wt% of a target weight for an ingredient. Preferably, said computer is programmed to control said first motive means, in the second gravimetrically-controlled stage, to dispense up to 2 wt%, more preferably up to 4 wt%, and more especially up to 5 wt% of a target weight for an ingredient.

Preferably, said computer is programmed to control said second motive means to dispense an ingredient volumetrically in not more than 15 s/g, more preferably in not more than 12 s/g and typically in about 8 s/g. Preferably, said computer is programmed to control said first motive means to dispense a first portion of a target weight of an ingredient in a first gravimetrically-controlled stage at a rate of at least 1.5 mg/s, more preferably at a rate of at least 2 mg/s. Preferably, said computer is programmed to control said first motive means to dispense a second portion of a target weight of an ingredient in a second gravimetrically-controlled stage at a rate of not more than 1 mg/s, more preferably at a rate of not more than 0.6 mg/s.

In an alternative embodiment, said computer is programmed to control said second motive means to dispense a major ingredient under gravimetric control, preferably using a two-stage process as described in the preceding paragraphs.

The apparatuses of the invention include automated handling equipment for indexing said substrate support and said dispensing system relative to one another whereby,

in use, at least two liquid samples may be deposited on a substrate surface at sample positions on said surface that are in space relationship from one another. Conveniently, the number of samples dispensed on said surface is not more than 100, preferably not more than 50, and especially not more than 30. Alternatively, depending on the test to which the films are to be subjected and space availability in test equipment, it may be necessary to dispense as many samples as it is practicable to do so on to said surface.

In a preferred embodiment of the invention, said sample receptacle comprises a well plate containing at plurality of wells each capable of receiving ingredients of samples. Sample ingredients are dispensed, for example as described previously, in the wells and the wells are sealed. The samples in the wells are then subjected to a mixing step.

Alternatively, and especially for larger sample sizes, individual receptacles, eg pots, having a capacity of for example up to 55Og may be used. If preferred, such individual receptacles may be supported in racks for parallel or serial processing.

Preferably, the well plate is sealed using a heat sealable foil. The sealed well plate may then be subjected to an appropriate motion, as hereinbefore described, to effect mixing of the sample ingredients.

Preferably, the foil used to seal a well plate is penetrable by for example a dispensing tip whereby, in use, quantities of liquid samples in the wells may be aspirated into said dispensing system for dispensing on a surface of a substrate for subsequent testing.

Alternative sealing means for the wells, or for individual pots, may be used. For example, a sealing plate having individual seals for surrounding each well may be clamped to the well plate. In that instance, the sealing plate may be provided with a plurality of sample ports or other sample access means positioned to permit samples in the wells to be accessed. Individual pots may be fitted with lids, again with sample access means being provided.

In a particularly preferred embodiment of the invention, apparatus for forming and evaluating a plurality of films on a surface of a substrate comprises a substrate support means, a dispensing system for dispensing at least one liquid sample at a sample location position on a surface of a substrate supported by said substrate support means during operation of said apparatus, a gas flow system for delivering, during operation of said apparatus, a controlled gas flow to spread the sample substantially uniformly away from said sample location position relative to the

substrate surface to form a film thereon and equipment for determining a property of interest of at least one film.

In another particularly preferred embodiment of the invention, apparatus for forming and evaluating a plurality of films on a surface of a substrate comprises an ingredient dispensing system for dispensing at least two liquid ingredients at a sample preparation location, said system being operable to control gravimetrically the dispensation of at least one of said ingredients, a substrate support means, a dispensing system for dispensing at least one liquid sample at a sample location position on a surface of a substrate supported by said substrate support means during operation of said apparatus, a gas flow system for delivering, during operation of said apparatus, a controlled gas flow to spread the sample substantially uniformly away from said sample location position relative to the substrate surface to form a film thereon and equipment for determining a property of interest of at least one film.

The features of the invention described previously apply mutatis mutandis to these particularly preferred embodiments of the invention as the context permits.

As discussed earlier, coatings may be made of a wide variety of materials and, within the context of the present invention, films may be made from both organic and inorganic materials provided the materials are in liquid form, or in solution or dispersed in a liquid carrier. Typical applications include adhesives, polymers, resins, inks, metal solutions, starches, dispersions, including nanoparticle dispersions, etc. In many such applications, the materials may be either conductive or non-conductive.

A particularly preferred application for the methods and apparatuses of the present invention is in the formation and characterisation of films of coating compositions. Such coating compositions particularly include paints, lacquers, varnishes and the like. In this context, the term "paint" is used to mean coatings for painting the interior and exterior surfaces of structures such as buildings, fences and bridges, for both decorative and/or protective purposes. Paints typically comprise a carrier liquid and a film forming binder polymer together with other components such as additives including thickeners and for coloured paints, pigments. The carrier liquid can comprise water, organic solvent or a mixture of water and organic solvent. The binder polymer may be in the form of a dispersion of particles in the carrier liquid, whereby the polymer exists in particulate form or it may be dissolved in the carrier liquid and be a solution.

Colour may be conveniently defined using CIE {L ^* a*b*) 1976 standard (CIELAB) and differences from a defined point in the colour space defined using CIEDE2000 (δE2000).

As will be appreciated, paint recipes (or other coloured liquids such as inks) may be defined by measuring the CIELAB values of films formed using the paint (or inks etc) made to a particular recipe and variations from such recipes, for example, owing to changes in ingredients or ingredient sources, may be identified by determining

δE2000 values for films. In determining δE2000 values for films, a δE2000 value of around 1 is noticeable to a human observer. Accordingly, δE2000 values of less than 1, more preferably less than 0.5, are desirable when comparing films with reference CIELAB parameters.

Accordingly, the present invention may be used to explore new recipes or to reformulate recipes following changes in ingredients or ingredient sources or to check in-store formulation practises easily and rapidly. The present invention also includes at least one array of films, more preferably a library of films comprising at least two arrays of films each on a substrate, wherein each film is uniformly located with reference to a sample location position in the array.

The present invention also includes at least one array of films, more preferably a library of films comprising at least two arrays of films each on a substrate, wherein a CIELAB value or a δE2000 value is identified for each film. Preferably, the films are paints films.

The invention will now be illustrated by reference to the accompanying drawings and following examples. In the drawings: Figure 1 is a schematic plan view of a sample preparation station;

Figure 2 is a schematic side view of apparatus for gravimetrically dispensing sample ingredients; and

Figure 3 is a schematic plan view of a sample dispensation and film testing station.

The apparatus in accordance with the invention that is described below with reference to the drawings has been particularly designed to prepare and dispense paints and to form films from paints and is described in that context. Although some of the features of the apparatus are particularly adapted to handling paint ingredients and samples, it will be appreciated that the apparatus is generically applicable to

other liquid sample systems and is not intended to be limited specifically to paint samples.

A sample preparation station 10 is shown in Figure 1. The station 10 has a base plate 11 on which is mounted an automated XYZ handling system 12, for example a robotic movement arm available from Tecan Limited which services two dispense stations 14, 16. The system 12 is provided with two sets of grippers (not shown). The first set of grippers is used to load/unload well plates 18 (see Figure 2) from a well plate storage unit 20 located between the dispense stations 14, 16 to each of the dispense stations 14, 16. The second set of grippers is used to load/unload syringes 22 (see Figure 2) from a syringe storage unit 24 located between the dispense stations 14, 16 to each of the dispense stations 14, 16. A pneumatically-operated heated foil plate sealer 26, for example a a plate sealer model number AB-0384-240 available from Abgene for sealing well plates 18 is provided at one end of the station 10. The well plate storage unit 20 is designed to accommodate thirty five well plates 18. The well plates 18 are conveniently clear plastic microtitre plates each having twenty four wells 28 available from VWR International. The wells 28 are arranged in a 6x4 array and each well 28 has a capacity of about 3.5g. The well plates 18 are bar coded to enable well plate/sample tracking to be performed. The syringe storage unit 24 is designed to hold up to one hundred 10ml syringes 22, each containing a liquid paint tinter solution 30 (see Figure 2). The unit 24 is temperature and humidity controlled to prevent the paint tinter solutions from drying out.

Each dispense station 14, 16 (see Figure 2) has a four decimal place rapid response balance 32, for example a Mettler SAG 40 available from Mettler Limited. A well plate holder 34 is provided on the balance 32 for holding a well plate 18 in a fixed location. Each dispense station 14, 16 has an automated XY handling system (not shown) on which is mounted a syringe carrier 36 consisting of a frame 38 on which is mounted a micro-stepping stepper motor 40, for example VEXTA 2-phase, 2 amp stepper motor available from The Oriental Motor Company.

The motor 40 is mounted on the frame 38 for reciprocating movement towards and away from the frame 38. In use, a flange (not shown) on the upper end of the syringe plunger 42 engages a slot in the body of the motor 40 and a flange 46 on the upper end of the syringe body 44 engages the frame whereby movement of the motor 40 towards the frame 38 causes liquid to be dispensed from the syringe 22

and slight movement of the motor 40 away from the frame 38 imposes a slight negative pressure on the liquid in the syringe 22 to prevent the formation of extraneous drops of liquid on the nozzle 48 of the syringe 22. Although shown as separate in Figure 2, the frame 38 also has mounted thereon a drip tray 50 which is pneumatically operable to be interposed between the nozzle 48 and a well plate 18.

Each dispense station 14, 16 is provided with at least one peristaltic pump (not shown), for example a peristaltic pump model number 520S/R available from VWR International. The peristaltic pumps are connected to a base paint reservoir (not shown) which may be either mounted on the base plate 11 of the station 10 or externally thereof. The peristaltic pump(s) at each dispense station 14, 16 are mounted on the base plate 11 with the or each outlet nozzle (not shown) being mounted on the respective XY handling system.

A bar code reader (not shown) is also provided on the base plate 11 of the station 10.

A computer 52 (see Figure 2) is provided to control operation of the sample preparation station 10. In addition to controlling the XYZ and XY handling systems, the computer system controls the peristaltic pumps and the stepper motors 40 and the drip trays 50 and is provided with a feedback loop 54 from the balance 32. The computer also records the well plate bar codes and maintains a record of the sample recipes located in each well 28 of the well plates 18. In operation, an operator loads the station 10 with the well plates 18, foil seals, base paint and disposable tinter syringes 22. The computer 52 is programmed with the required sample recipes and operation of the system is initiated. The XYZ handling system 12 loads each balance 32 at the respective dispensing stations 14, 16 with a well plate 18, each well plate 18 being passed by the bar code reader on route to the dispensing station 14, 16.

The computer 52 calculates a dispense volume for each well based on the required base paint ingredient weight for each recipe and controls the XY handling system to move the discharge nozzle of the peristaltic pump over each well 28 in the well plate 18 and operates the peristaltic pump to discharge the calculated amount of base plate ingredient for that well 18. As each well 18 is filled with the base paint ingredient, the final weight of the base paint ingredient in the well is recorded by the computer 52. The computer 52 then calculates, based on the final weight of base paint ingredient in each well 18, the weight(s) of tinter ingredients) that has to be added to each well 28 to complete the recipe for each well 28.

The XYZ handling system 12 is then operated to load each dispense station 14, 16 with a syringe 22 containing the required tinter ingredient 30. The XY handling system at each dispense station 14, 16 is then operated to position the syringe 22 over each well in sequence to dispense using the stepper motor 40 the required weight of tinter ingredient 30 in each well 28. At the start of dispensing the tinter ingredient 30 into a well 28, the drip tray 50 is withdrawn from beneath the nozzle 48 of the syringe 22 and at the end of the dispense of the tinter ingredient 30, the drip tray 50 is replaced beneath the nozzle 48 of the syringe 22. Additionally, the computer 52 controls the stepper motor 40 to dispense the tinter ingredient 30 from the syringe 22 relatively rapidly until a major proportion of the tinter ingredient 30 is dispensed and then to control it to dispense the tinter ingredient 30 relatively slowly until the target weight for the tinter ingredient 30 is achieved. At the end of the discharge, the stepper motor 40 is reversed to impose a slightly negative pressure on the tinter ingredient 30 remaining in the syringe 22 to prevent drips. The final weight of the tinter ingredient 30 dispensed into a well 28 is recorded.

As a syringe 22 is exhausted, the XYZ handling system 12 is operated to remove the exhausted syringe from the relevant dispense station 14, 16, dispose of it and to collect and insert a fresh syringe 22.

It will be appreciated that, depending on the recipes for the paint samples loaded in the computer 52, not every well 28 will necessarily receive an amount of a particular tinter ingredient 30. Similarly, paint recipes may well require the inclusion of two or three tinter ingredients to achieve a particular colour, for example. In such instances, the computer 52 will operate the apparatus to locate in sequence syringes 22 containing different tinter ingredients 30 for dispensation into at least one of the wells 28.

Once all of the samples in a well plate 18 have been completed, the XYZ handling system 12 is operated to remove the completed well plate 18 from the respective dispense station 14, 16 and move it to the plate sealer 26 at which it is sealed with a foil lid. Following completion of all of the well plates 18 for a particular set of recipes, the well plates 18 are manually loaded in batches of, for example, ten in a paint shaker device, for example a VIBA 25 available from Collomix, which is then operated to shake the well plates 18 to mix the ingredients of each sample therein.

Referring to Figure 3, a film generation and testing station 110 is shown. The station 110 has a base plate 111 at one end of which is locatable a ball screw driven stacker

112, for example Labman Automation. The stacker 112 has thirty sliding trays 114 on each of which is beatable a well plate 18 and a respective substrate 116 in the form of an A4 card available from Leneta to receive twenty four samples in a 6x4 array (to match the number of samples in a well plate 18). Each substrate 116 is bar coded similarly to the well plates 18 to enable paint substrate/films to be identified.

The station 110 has mounted longitudinally on the base plate 111 a tray puller mechanism 118 for engaging with a tray 114. The mechanism 118 has a rail 118A mounted beneath the base plate 111. A gripper 118B is mounted on the rail for reciprocal movement on the rail 118A and in a slot (not shown) in the base plate 111 whereby, in operation, the gripper 118B grips a tray 114 positioned opposite the gripper 118B by the stacker 112 to pull it on to the upper surface of the base plate 111.

A sample aspiration means 120, for example a MINIPREP™ robot available from Tecan Limited, is located towards the end of the base plate 111 at which the stacker 112 is located. Located adjacent the aspiration means 120 is a rack 122 for seven hundred disposable tips (not shown) each capable of holding for example 150μl of sample.

A gas flow system 124 is located on the base plate 111 over the path that a substrate 116 takes during movement of a tray 114 on which it is located by the puller mechanism 118. The gas flow system 124 has four delivery nozzles 126, each being circular and having an inside diameter of 6 mm. The centres of the nozzles 126 are spaced such that each nozzle 126 will be located concentrically with respective centres of four sample locations on the substrate 116 when the substrate 116 is positioned under the system 124. The orientation of each nozzle 126 is such that a gas flow from the nozzle 126 is normal to the surface of the substrate 116. Fixed into the end of each nozzle 126 is a frit (not shown), for example a Retimet™ metal foam frit available from Dunlop, to ensure the gas flow from the nozzle 126 is diffuse and even on to the respective sample.

In many applications, an air flow will be delivered by the gas flow system 124. The air may be obtained from a compressed air cylinder or compressor/reservoir equipment as required. If it is desired to use other gases, then a suitable supply of the compressed gas, eg a gas cylinder, may be used. Typically, air or gas pressures of around 2 to 6 bar will be required.

The gas flow system 124 delivers a controlled gas flow using a pressure control and delivery system such as a pressure regulator and solenoid valve (not shown)

controlled by the computer 52. Alternatively, a mass flow controller may be used to control the air flow.

Film analysis equipment 128 is located at the end of the base plate 111 remote from the stacker 112. Typically, the equipment 128 may be a spectrophotometer, for example a Mercury ME available from Datacolor mounted on an automated Y handling system 130. In this instance, the spectrophotometer 128 is used to measure the colour of each film individually. Alternatively, or additionally, the equipment 128 may consist of or include a suitable camera to capture an image of either individual films or of the whole or a substantial part of the substrate 116. In this instance, colour information of the films may be obtained by sampling within a digitised colour image of the films or of the substrate containing the films using known methods.

The operation of the film generation and testing station is controlled using a computer, for example computer 52 used to control the sample preparation station 10. Alternatively, a separate computer may be used provided it is either in communication with computer 52 to obtain details of sample recipes and identification or such information is separately downloaded to it.

In operation, an operator loads each of the trays 114 with a sealed well plate 18 containing samples and a substrate. Under control of the computer 52, the stacker 112 moves a first tray 114 to a position at which it is engaged by the tray puller mechanism 118 which moves the tray over the base plate 111 to a first location adjacent the aspiration means 120 and releases the tray. The aspiration means 120 is then operated to engage with a syringe a disposable tip, to move the tip to a first sample location in the well plate 18, to penetrate the foil seal over the respective well 28 with the tip and to aspirate typically about a 100 μl portion of the sample from the well 28 into the tip. To ensure the tip is wetted to aid dispensation of the sample onto the substrate 116, the sample in the tip may be discharged back into the well 28. This cycle of aspiration/discharge is preferably performed for a total of three iterations. Following the fourth aspiration, the aspiration means 120 moves over the substrate 116 and dispenses the sample from the tip at a sample location position on the substrate 116. The aspiration means 120 then disposes of the tip into a waste receptacle (not shown) mounted on the base plate 111.

Once four samples have been dispensed onto the substrate 116 in a first line of sample location positions, the tray puller mechanism118 re-engages the tray 114

moves it back towards the stacker 112 to locate the first row of four samples underneath the gas flow system 124. A controlled gas flow is then delivered simultaneously from each of the nozzles 126 to spread the four samples to form films therefrom. This process is then repeated a further five times to dispense subsequent rows of four samples and to form films from them on the substrate to complete the 6x4 array of samples on the substrate.

Once all of the films have been formed, the tray 114 is relocated on the stacker 112, which is then indexed to move the next tray into position and the film formation process is repeated. This process is repeated for each of the trays 114. Typically, for paint samples, the processing of thirty trays (with twenty four samples per substrate) will take about seven hours by which time the paint film formed on the first substrate 116 will be dry and may be analysed.

Under control of the computer 52, the stacker 112 moves a first tray 114 to a position at which it is engaged by the tray puller mechanism 118 which moves the tray over the base plate 111 to a second location adjacent the XY handling system 120. Under control of the computer 52, the system 120 moves the spectrophotometer 128 to each sample location position on the substrate 116 located on its tray 114 to measure and record the colour of the sample. Example 1

Using the apparatus and methods described above, water-based latex paint recipes were formulated and made into arrays of films. The samples were formed into films using a gas flow of 3 bar for 3 seconds. The colours of the films were analysed using the spectrophotometer and the δE2000 values from an appropriate reference colour* were determined.

One sample recipe is shown in Table 1 below. The tinters used were made up as 1% weight of pigment in base paint to avoid trying to dispense very small quantities of pigments. In formulating the sample, the actual weights of tinters dispensed was the weights dispensed following adjustment of the target weights by the computer based on the actual weight of the base paint dispensed and gravimetric control of the weights of tinters being dispensed. As can be seen, good control of the target weights was achieved.

The δE2000 value (difference in colour space from reference to sample) for the sample = 0.125.

Example 2

Using the apparatus and methods described above, solvent-based alkyd resin paint recipes were formulated and made into arrays of films. The samples were formed into films using a gas flow of 3 bar for 3 seconds. The colours of the films were analysed using the spectrophotometer and the δE2000 values from an appropriate reference colour* were determined.

One sample recipe is shown in Table 2 below. The tinter used was made up as 1% weight of pigment in base paint to avoid handling very small quantities of pigment. In formulating the sample, the actual weight of tinter dispensed was the weight dispensed following adjustment of the target weight by the computer based on the actual weight of the base paint dispensed and gravimetric control of the weight of tinter being dispensed. As can be seen, good control of the target weights was achieved.

The δE2000 value (difference in colour space from reference to sample) for the sample = 0.265.

Table 1

Table 2

* The reference colours used in both Examples were established by conventionally making samples, on typically a 1 litre or 1 US gallon (3.8 litres) scale, of appropriate specific recipes but very accurately measuring the ingredients for such samples.