KR100252025B1 - Transparent film for use in electrophotographical copier - Google Patents

Abstract

PURPOSE: A transparent film for electronic-photographic copying machines is provided to achieve excellent interfacial resistance, toner adhesion, curling resistance, and coherence between layers. CONSTITUTION: A transparent film for electronic-photographic copying machines comprises an image layer formed of coating compositions that contains polyester film, methyl methacrylate-butyl methacrylate copolymer as a thermoplastic polymer that is to coat the polymer film, an acrylic acid-methacrylic acid polymer as a thermohardening polymer, a cross linker, an anti-static agent, and further polyester resin. The polyester resin has the average molecular weight of 18,000-23,000, the glass transition temperature of 63-67 deg.C, and the softening temperature of 130-150 deg.C.

Description

Transparent film for use in electrophotographic copier

The present invention relates to a transparent film for an electrophotographic copier, and in particular, has excellent toner adhesion, curling resistance, and antistatic property, and the delamination between the base film and the image receiving layer is greatly reduced, and thus electrophotographic. A film suitable for use for a type copier.

At present, a number of copiers have been developed for forming toner images on transparent polymer substrates using electrophotographic methods, and the image receiving layers of the film media used in these copiers have good quality images, toner adhesion, and high temperature during fusion. Curling (the phenomenon in which the film medium loses flatness and forms bending in the up and down directions) has to have high resistance to resistance, antistatic properties and good transport in the copier.

However, conventional image carrier layers of film carriers are not suitable for use as film carriers for electrophotographic copiers because of their large drawbacks in at least one of the desired properties.

That is, Japanese Patent Laid-Open Nos. 60-6460 and 60-13074 disclose a method of applying an acrylic copolymer or a thermosetting polyurethane resin on a transparent polymer substrate to improve toner adhesion. By the way, the film produced by the above method has good toner adhesion when used in a specific copier, but does not have sufficient toner adhesion when used in a different type of electrophotographic copier with different toner types and fixing conditions. There is a problem.

Japanese Patent Application Laid-open No. Hei 4-348353 discloses a method of mixing and applying a main resin and the same resin, that is, a polyester resin and a polystyrene resin in an appropriate ratio in order to improve toner adhesion. The film produced by the toner was improved in toner adhesion in various copiers, but its antistatic property and transportability in the copier were poor.

In general, there is a method of curing the soft resin binder and a method of using a thermoplastic polymer having a high glass transition temperature in order to suppress the curling phenomenon, but the film produced by the method is poor in adhesion of the toner image.

Japanese Patent Publication Nos. 51-34734, US Pat. Nos. 3,854,942 and 4,489,122 disclose the use of antistatic agents to suppress the generation of static electricity in order to improve the transportability in the copier, and to form protrusions on the film surface using the mat agent. A method of reducing the interfacial area of a film is disclosed. However, the film produced by the above method may cause toner adhesion to be degraded, resulting in loss of image during handling or use, and in case of stacking, an antistatic agent may be transferred to an adjacent film medium, resulting in an unradiated area. .

US Pat. No. 4,480,003 discloses the use of conductive polymers for effective antistatic properties, and US Pat. No. 4,711,816 describes a primer layer containing an antistatic agent, an image receiving layer, and two layers on one side of the substrate. A method of having a structure is disclosed, which has a problem that the process is complicated.

In addition, Korean Patent Application No. 95-4716 discloses a film in which an image receiving layer including a thermoplastic polymer, a thermosetting polymer as a crosslinking agent, and an antistatic agent is formed on a base film so as to have good toner adhesion, curling resistance, and antistatic property. It is. However, such a film has a disadvantage in that an interlayer separation phenomenon easily occurs between the base film and the image receiving layer.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a transparent film for an electrophotographic copier, which has excellent toner adhesion, curling resistance, and antistatic property, and greatly reduces the delamination between the base film and the image receiving layer.

1 is a schematic cross-sectional view of a transparent film for an electrophotographic copier in which an image receiving layer is formed on both sides of a base film according to an embodiment of the present invention.

In order to achieve the above object, the present invention contains a polyester base film, and a methyl methacrylate-butyl methacrylate copolymer as a thermoplastic polymer, an acrylic acid-methacrylic acid ester polymer as a thermosetting polymer, a crosslinking agent, an antistatic agent, and a polyester resin. To provide a transparent film for an electrophotographic copier characterized in that the coating composition comprises an image receiving layer formed by coating on the base film.

That is, the present invention is characterized by further preventing a separation phenomenon between the transparent base film and the image receiving layer by further containing a polyester resin having the same functional group as the base film in the image receiving layer. 1 shows a transparent film for an electrophotographic copier in which an image receiving layer 2 is formed on both sides of a base film 1 according to one embodiment of the present invention, and the present invention will be described in more detail with reference to this. Let's do it.

In the present invention, the base film must be flexible and thermally stable, and have a transparency suitable for use for overhead projection (OHP). That is, the thermal stability should be sufficient at 120 to 200 ° and the visible light should be well transmitted. Polyesters are suitable as film substrates suitable for the above requirements, preferably biaxially oriented polyethylene terephthalates. The thickness of the base film is preferably 50 to 200 μm. In the present invention, the image receiving layer 2 includes a coating composition containing a thermoplastic polymer, a thermosetting polymer, an antistatic agent, a crosslinking agent, a polyester and the like. 1) formed by coating and drying on it.

In the coating composition, a methyl methacrylate-butyl methacrylate copolymer is used as the thermoplastic polymer. The methyl methacrylate-butyl methacrylate copolymer has good affinity with toner to act as a binder. In addition, since the methyl methacrylate-butyl methacrylate copolymer has excellent adhesion to polyesters, especially polyethylene terephthalate, the coating composition for an image receiving layer may be applied without forming a prime layer on the base film. In other words, in order to improve the adhesion between the substrate and the image receiving layer, it is common to apply a prime layer, but the thermoplastic copolymer used in the present invention has very good adhesion to the polyethylene terephthalate as the base material, and thus the prime layer is unnecessary. The weight average molecular weight of the methyl methacrylate-butyl methacrylate copolymer is preferably 50,000 to 500,000.

Preferred thermosetting polymers are acrylic acid-methacrylic acid esters, which serve to make the image receiving layer very hard and to also provide excellent curling resistance, blocking resistance and scratch resistance.

The thermoplastic polymer and thermosetting polymer added for the purpose as described above should be appropriately adjusted in their content so as to achieve the desired effect. Experimental results of the present inventors found that the weight ratio of the acrylic acid-methacrylic acid ester and the methyl methacrylate-butyl methacrylate copolymer is preferably from 50: 1 to 1:50.

A crosslinking agent is added for the crosslinking reaction of the thermosetting polymer, and the amount and type of the crosslinking agent does not adversely affect the performance of the thermoplastic polymer in the image receiving layer which gives good toner adhesion, and is suitable for the characteristics of the radiation medium of the present invention. It needs to be adjusted.

Factors to consider in selecting the appropriate crosslinking agent and its amount of use are the type of functional groups present in the thermosetting polymer, whether or not the catalyst is used in the crosslinking reaction, the amount and the amount of the desired curing time and curing temperature for the image receiving layer. .

Crosslinking agents useful in the present invention include aldehydes such as formaldehyde resins, melamine-formaldehyde resins, urea-formaldehyde resins, and the like, isocyanates, blocked isocyanates and the like. As a preferable crosslinking agent, it is a melamine-formaldehyde resin, and this resin contributes also to the adhesive force improvement between a base film and an image receiving layer.

In addition, the amount of the crosslinking agent added in the present invention is preferably 5 to 60% by weight based on the weight of the thermosetting polymer. This is because when the amount of the crosslinking agent is less than 5% by weight, the crosslinking reaction is insignificant, and when the amount of the crosslinking agent is greater than 60% by weight, the negative effect on the thermoplastic polymer increases, resulting in poor toner adhesion.

The catalyst used for the purpose of promoting the initiation of the crosslinking reaction in the present invention is preferably 0.1 to 10% by weight relative to the total solid weight of the coating composition. Suitable catalysts are preferably acids or blocked acids, especially citric acid, formic acid, zinc chloride, trichloroacetate, and the like when the aldehyde is a crosslinking agent. When the isocyanate is a crosslinking agent, an organic tin compound is generally used, but the crosslinking agent itself may initiate a desired crosslinking reaction without using a catalyst.

In the present invention, nitrite, sulfate, ammonium salt and the like can be used as an antistatic agent. In particular, quaternary fatty acid amine ethoxylates are preferred, which materials exhibit excellent antistatic properties in the polymer resins of the present invention. In addition, the addition amount of the antistatic agent is 5 to 40% by weight relative to the total solids in the coating composition, because the use of less than 5% by weight of the present invention is insignificant, if it exceeds 40% by weight is poor thermal stability to be.

On the other hand, since the antistatic agent is a liquid itself, there is a problem that can separate the base film and the image receiving layer. In order to solve this problem, the present invention may further contain a polyester resin having the same functional group as the base film in the image receiving layer.

The polyester resin contained in the image receiving layer preferably has a molecular weight of 18,000 to 23,000, a glass transition temperature of 63 to 67 °, and a softening temperature of 130 to 150 °. Glass transition temperature is 63 ?? Less than or softening temperature is 130 ?? This is because the image receiving layer may melt when the base film is heated to a high temperature in the copier. On the other hand, when the glass transition temperature exceeds 67 ° or the softening temperature exceeds 150 °, there is a problem in that the toner is hardly fixed to the image receiving layer. The content of the polyester resin is preferably 0.01 to 1.0% by weight based on the total solids.

Fine particles may also be added to reduce the friction between the films to improve sliding properties, the choice of which is dependent on the polymer substrate applied and the desired result, the amount being 0.1 to 10 relative to the total solids. % By weight is suitable. Preferred fine particles are silica having an average particle diameter of 0.5 to 20 m.

In addition, the solvent in which the polymer polymer, the antistatic agent, the crosslinking agent, and the polyester resin are dissolved is not particularly limited as long as it is a general coating agent, but esters, ketones, aromatic compounds, glycol ether acetates, chlorinated carbon compounds and the like are preferable.

The coating composition of the composition as described above may be applied onto the substrate by various techniques conventionally used. In the present invention, by removing the unnecessary process of applying twice in one-side coating, the coating is applied on at least one side of the polymer substrate by coating one side once in a two-head three-roll reverse coating method. After the drying and heat setting step, the transparent film for an electrophotographic photocopier of the present invention is produced. Drying is preferably performed for 10 seconds to 3 minutes at a temperature of 100 to 140 ??, and heat setting for 6 to 30 seconds at a temperature of 150 to 170 ??. In addition, the coating amount of the image receiving layer is preferably 0.2 to 4.0 g / m 2.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not necessarily limited thereto.

Evaluation of the physical properties of the transparent film for an electrophotographic copier in the present invention was performed by the following method.

1) Toner Adhesion: Copy to Xerox 5026, Xerox Vivace 500 and Canon 3030 to form toner adsorption area on the film surface. If the amount of toner adsorption at this time is referred to as the total adsorption amount, and the amount of remaining toner at the time of adhering and peeling off with a cellophane tape is referred to as the amount of post adsorption, the toner adhesion force is calculated as (post adsorption amount / presorption amount) × 100. The level of toner adhesion measured in this way is evaluated based on the following criteria.

Above 90%: Very good level

50% to 90%: good level

Less than 50%: poor level

2) Haze: Hunter Lab's Colorimeter Model Color QUEST II was measured under conditions defined in ASTM D 1003 before and after radiation. The copier used at this time is Xerox Vivace 500, and the value measured before radiation is called pre-haze and the value measured after radiation is called post-haze.

3) Curling resistance: The film medium copied with Xerox 5026 was placed on a flat plate, the gap between the film and the flat plate was measured, and the maximum gap at that time was evaluated according to the following criteria.

Less than 5mm: good level

5mm or more: poor level

4) Blocking resistance: Four films of 5 cm square samples are made on the film on which the image receiving layer is formed, and the two sheets are overlapped, and the uncoated polyester film of the same size is placed on the upper, middle and lower surfaces thereof. Place it between the glass plates and apply a load of 5 kg and heat it for 30 minutes at 78 °. After cooling for 5 minutes, observe the sample while separating the overlapping sample. That is, if sticking or blocking does not occur between mutually bonded square samples, it is determined that the blocking resistance is good.

5) Surface resistance: Using a Keithley model 617 under the conditions of ASTM D 2597-90 was measured at 23 ± 2 ??, relative humidity 55 ± 5%.

6) Friction Coefficient: Measured at 23 ± 2 ?? and relative humidity of 55 ± 5% using HEIDON-14DR under the conditions of ASTM D 1894-78.

7) Transferability: The number of jams when 100 sheets were copied under various conditions of 23 ± 2 ?? and 55 ± 5% relative humidity was measured. The transferability test was carried out five times to determine the range of jam occurrence sheets.

8) Interlayer Bonding Force: After 1000 hours using Q-PANEL's QU, crosshatch with cutter knife, and then attach and peel cellophane tape on the same surface 5 times. , The presence or absence of the peeling of the image receiving layer was visually observed to determine defect or good.

<Comparative Example 1-4>

To prepare a coating composition as shown in Table 1, and then applied to the reverse coating method on one side of a 100㎛ thick biaxially oriented polyethylene terephthalate film. Subsequently, the transparent film was dried at 140 ° for 42 seconds to form an image receiving layer of 1.5 g / m 2. At this time, citric acid (35% aqueous solution) as an acid catalyst was added to the base film immediately before application. Various physical properties of the prepared transparent film were measured and shown in Table 1.

As can be seen from Table 1, the film produced by Comparative Examples 1-3 did not have any good physical properties in surface resistance, toner adhesion, curling resistance and the like. On the contrary, except that the polyester resin was not added, the film (Comparative Example 4) manufactured by the same method as the present invention had excellent surface resistance, toner adhesion, and curling resistance.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Coating composition (unit: weight ratio) Mixed Solvents ^* 359.3 349.9 350.2 310.0 Circol 836 (acrylic copolymer) - 15.2 13.8 - Acrylic acid-methacrylic acid ester (50% solids) - - - 68.1 Methyl methacrylate-butyl methacrylate copolymer 33.7 - 2.8 3.0 Melamine-formaldehyde resin (80% solids) - 23.2 21.4 6.0 Quaternary amine ethoxylate (90% solids) 6.8 6.8 6.8 6.8 Citric acid - 4.8 4.8 - Properties Surface resistance (Ω / □) - - 1 × 10 ^{14 to} 1 × 10 ¹⁶ 6 × 10 ^{9 to} 5 × 10 ¹¹ Toner adhesion Good Bad Good Good Curling Resistance Bad Good Good Good

* Mixed solvent: methyl ethyl ketone, toluene and oxytol acetate (59:11:11 volume ratio)

Comparative Example 5

Except for using the coating composition as shown in Table 2, a transparent film was prepared in the same manner as in Comparative Example 1-4, and then various physical properties were measured and shown in Table 2.

<Example 1>

Except for using the coating composition as shown in Table 2, a transparent film was prepared in the same manner as in Comparative Example 1-4, and then various physical properties were measured and shown in Table 2.

Comparing the physical properties of the film produced according to the conventional method and the film produced according to the present invention through Table 2, the conventional film (Comparative Example 5) without the addition of the polyester resin is surface resistance, toner adhesion, curling resistance Was good, but the interlayer bonding strength was not good. On the contrary, the film prepared according to the present invention (Example 1) was excellent in surface resistance, toner adhesion, curling resistance as well as interlayer bonding strength.

division Comparative Example 5 Example 1 Coating composition (unit: weight ratio) Mixed Solvents ^* 315.1 315.1 Psychicia 446 (Silica, Fuji Silesian Chemical) 0.12 0.12 Acrylic acid-methacrylic acid ester (50% solids) 56.6 56.6 Methyl methacrylate-butyl methacrylate copolymer 3.1 3.1 Melamine-formaldehyde resin (80% solids) 7.2 7.2 Polyester resin (brand name: SKA-100) - 0.6 Quaternary amine ethoxylate (90% solids) 12.0 12.0 Citric acid 6.0 6.0 Properties Surface resistance (Ω / □) 6 × 10 ^{9 to} 5 × 10 ¹¹ 6 × 10 ^{9 to} 5 × 10 ¹¹ Toner adhesion Good Good Curling Resistance Good Good Interlayer Bonding Force Bad Good

* Mixed solvent: methyl ethyl ketone, toluene and oxytol acetate (59:11:11 volume ratio)

As can be seen from the above, the film produced according to the present invention has excellent surface resistance, toner adhesion, curling resistance, as well as excellent interlayer bonding strength. Therefore, it is suitable for use as an OHP film for an electrophotographic copier.

Claims (13)

A coating composition comprising a polyester base film and a methyl methacrylate-butyl methacrylate copolymer as the thermoplastic polymer, an acrylic acid-methacrylic acid ester polymer as the thermosetting polymer, a crosslinking agent, and an antistatic agent And an image receiving layer, wherein the coating composition has a weight average molecular weight of 18,000 to 23,000, a glass transition temperature of 63 to 67 °, and a softening temperature of 130 to 150 ° in order to improve adhesion between the image receiving layer and the base film. A transparent film for electrophotographic copiers, further comprising a phosphorus polyester resin. The transparent film for electrophotographic photocopier according to claim 1, wherein the polyester is biaxially oriented polyethylene terephthalate. The transparent film for an electrophotographic photocopier according to claim 1, wherein the weight ratio of the methyl methacrylate-butyl methacrylate copolymer and the acrylic acid-methacrylic acid ester is 1:50 to 50: 1. The transparent film for an electrophotographic photocopier according to claim 1, wherein the methyl methacrylate-butyl methacrylate copolymer has a molecular weight of 50,000 to 500,000. The transparent film of claim 1, wherein the crosslinking agent is at least one selected from the group consisting of formaldehyde resin, melamine-formaldehyde resin, urea-formaldehyde resin, isocyanate and blocked isocyanate. The transparent film for electrophotographic copier according to claim 5, wherein the crosslinking agent is a melamine-formaldehyde resin. The transparent film for electrophotographic copier of claim 1, wherein the crosslinking agent is 5 to 60% by weight based on the thermosetting polymer. The transparent film of claim 1, wherein the antistatic agent is at least one selected from the group consisting of ammonium salts, nitrites, and sulfates. The transparent film for electrophotographic copier of claim 8, wherein the antistatic agent is a quaternary fatty acid amine ethoxylate. The transparent film for an electrophotographic copier according to claim 1, wherein the amount of the antistatic agent added is 5 to 40% by weight based on the total resin solid content of the coating composition. The method of claim 1, wherein the coating composition comprises at least one particulate selected from the group consisting of amorphous silica, alumina hydrate, magnesia, wax, fluorinated polymer, polyethylene, polypropylene, polystyrene, polyacrylate and urea-formaldehyde resin. Transparent film for an electrophotographic copier, characterized in that it comprises. 12. The transparent film for electrophotographic copier according to claim 11, wherein the fine particles are 1 to 50 mu m. The transparent film for an electrophotographic photocopier according to claim 1, wherein the coating amount of the image receiving layer on the base film is 0.2 to 4.0 g / m ² .