JPH03100027A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To improve the slip and mold release properties and inhibit the offset by coating a surface of a biaxially oriented polyester film with a coating material comprising an isocyanate resin and a specific silicone to thereby form a resin layer having a surface with a specified offset index. CONSTITUTION:A coating material comprising an isocyanate (e.g. 2,4-tolylene diisocyanate) and (or) a resin having an isocyanate group (e.g. a polyester- hexamethylene diisocyanate copolymer) and a silicone having a sec. and (or) tert. amino group (e.g. an aminated hydroxylated silicone) is applied to at least one surface of a biaxially oriented polyester film to form a resin layer having a surface with an offset index of 30-50dyne/cm. the coated film is useful for an audio cassette tape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a biaxially oriented polyester film. Specifically, the present invention relates to a biaxially oriented polyester film that has excellent slipperiness, mold releasability, and abrasion resistance, and has little set-off.

[Prior Art] Biaxially oriented polyester film has excellent mechanical properties, two-dimensional stability, and heat resistance, so it is used in many applications such as magnetic recording materials, packaging materials, graphic arts materials, and information recording materials. Widely used as a base film.

However, polyester film is used in fields where easy sliding and mold releasability are required, such as preventing sticking of thermal transfer foil in thermal transfer printers, adhesive tenor sheets (friction plates) for audio cassettes, etc.

It is known that a coating layer is provided in back coats for magnetic tapes to provide slipperiness and mold release properties. slipperiness,
As a polyester film imparted with mold releasability, one in which one side of the film is coated with a mixture of an aqueous polymer and a lubricant (Japanese Patent No. 1988-192628) is known.

[Problems to be Solved by the Invention] However, the above-mentioned polyester film that has been given slipperiness and mold release properties has a problem in that the lubricant falls off from the resin layer when it is rolled into a roll due to the addition of a lubricant. (This is called set-off), causing the following problems.

(1) Thermal transfer foil is a thin polyester film with a coloring layer (thermal melting or heat sublimation ink layer) coated on one side, and a hot stick on the other side that causes the thermal head to stick to the foil. ), an anti-hot stick layer is provided. If there is set-off, problems such as repellency of the coloring material and poor adhesion will occur when applying the coloring material layer.

(2) Audio cassette tapes have a retainer sheet (friction plate) attached to the inner surface of the case that stores the tape, and when the tape is running, the side of the tape wound on the reel comes into contact with the retainer sheet. By rotating the reel while rotating, the tape runs smoothly and the tape wound around the reel is not wound unevenly. For this reason, the retainer sheet is required to have easy sliding properties, and the polyester film is provided with an easy slipping layer.

If there is set-off, it will cause problems such as printing defects when printing on the back side of the retainer sheet.

(3) The back coat layer of magnetic tape is also required to have easy sliding properties, but if there is set-off, repellency when applying magnetic material,
The adhesion of the magnetic material to the film decreases, and the magnetic material may peel off.

The present invention eliminates these drawbacks of the prior art and provides a biaxially oriented polyester film that has excellent hot stick prevention properties and less backside transfer.

[Means for Solving the Problems] The present invention provides a biaxially oriented polyester film having a set-off index of 30 dynes/cm on at least one side of the biaxially oriented polyester film.
A film provided with a resin layer having a surface of 50 dyne/cm or less, the resin layer comprising at least an isocyanate and/or a resin having an isocyanate group and a secondary and/or tertiary amine. The film is based on a biaxially oriented polyester film that is coated with a coating material made of silicone.

The term "polyester film" as used herein is a general term for polymers having ester bonds as the main bond chains, and particularly preferred polyesters include polyethylene terephthalate, polyethylene 2.6 naphthalate, polyethylene α, β-bis( 2-chlorophenoxy)ethane 4,4
'-dicarboxylate, polybutylene terephthalate, etc. Among these, polyethylene terephthalate is the most preferable from a comprehensive consideration of quality, economy, etc. Therefore, hereinafter, we will proceed with the description using polyethylene terephthalate as a representative polyester.

Polyethylene terephthalate (hereinafter referred to as PET) in the present invention
It is abbreviated as. ) means 80 mol% or more, preferably 90 mol%
At least 95 mol%, more preferably at least 95 mol%, of the repeating unit is ethylene terephthalate. still,
A portion of the acid component and/or glycol component can be replaced with a third component as described below.

Monoacid component monoisophthalic acid, 2.6-naphthalene dicarboxylic acid, 1.
5-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 44'
- diphenylsulfone dicarboxylic acid, 44'-diphenyl ether dicarboxylic acid, p-β-hydroxyethoxybenzoic acid, adipic acid, azelaic acid, cepatic acid, hexahydroterephthalic acid, hexahydroisophthalic acid,
ε-oxycaproic acid, trimellitic acid, trimesic acid, pyromellitic acid, α,β-bisphenoxyethane-4
, 4'-dicarboxylic acid, α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, etc.

- Glycol components - Propylene glycol, butylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene gellicol, 1.1-cyclohexane dimetatool, 1.4-cyclohexane dimetatool, 2.2-bis(4-β -hydroxyethoxyphenyl)propane,
Bis(4-β-hydroxyethoxyphenyl)sulfone, diethylene glycol, triethylene glycol, pentaerythritol, trimethylolpropane, polyethylene glycol, etc.

PET also contains known additives, such as heat stabilizers, oxidation stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, and release agents. A molding agent, an antistatic agent, a nucleating agent, etc. may be added.

The intrinsic viscosity of PET as described above (measured in orthochlorophenol at 25°C) is preferably 0.40 to 1.20, more preferably 0.50 to 0.80, and even more preferably 0.55. It is in the range of ~0.75 dl/g.

Next, a biaxially oriented polyester film is usually made by stretching an unstretched polyester sheet or film in the longitudinal direction and the width direction, so-called biaxial directions. Refers to a pattern of orientation.

Although the thickness of the polyester film of the present invention is not particularly limited, it is preferably 1 to 30 μm for use in thermal transfer foils and magnetic tapes. More preferably, it is 2 to 15 μm. Also,
For retainer sheets, it is preferably in the range of 15 μm to 100 μm, more preferably 30 μm to 75 μm.
m range.

In the present invention, the set-off index is 30 dyne/cm or more and 50
It is necessary to be within the range of dyne/cm or less.

This range is more preferably 32 dyne/cm or more and 47 dyne/cm or less, and even more preferably 35 dyne/cm.
ne/cm or more and 45 dyne/cm or less. If the set-off index is too small, problems such as repellency, poor adhesion, and poor printing will occur when coating or printing on the back side of this polyester film. On the other hand, if the set-off index is too large, problems such as blocking will occur.

Examples of the isocyanate of the present invention include 4,4'-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate, dicyclohexyl diisocyanate (H-MD I), isophorone diisocyanate), 1.
3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 2,4-tolylene diisocyanate (
TDI), 26-tolidine diisocyanate (T
DI), hydrogenated TDI, 15-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate.

Examples include lysine diisocyanate and tolysine diisocyanate. In the present invention, MDI, TDI.

Hexamethylene diisocyanate is preferred because it can be easily masked with a blocking agent.

The resin having an isocyanate group as used in the present invention refers to a resin obtained by reacting an isocyanate with urethane, polyester, acrylic, epoxy, caprolactone, polycarbonate, polyimide, polyamide, polystyrene, or a copolymer thereof. Furthermore, this resin has unreacted isocyanate groups in an amount ranging from 1 to 70 wt%, preferably from 5 to 50 wt%. If the amount of isocyanate groups is too small, the reactivity will be poor, and if the amount is too large, the stability of the resin will be poor. This resin is produced using polyisocyanate, urethane with hydroxyl groups, polyester, acrylic, and epoxy.

Caprolactone, polycarbonate, polyimide.

It is obtained by reacting polyamide, polystyrene, etc., or a copolymer thereof. For example, urethane acrylate is obtained by reacting a polyol (polyester polyol, polyether polyol, etc.), polyisocyanate, and acrylate having a hydroxyl group. In the present invention, heat resistance.

Urethane, polyester, acrylic and copolymers thereof are preferred from the viewpoint of abrasion resistance.

Blocking agents that mask the isocyanate groups of the isocyanate and/or isocyanate group-containing resin of the present invention include ethyleneimine, lactams, oximes, phenols, acidic sodium sulfite, tertiary alcohols, hydrocyanic acid, aromatic secondary amines, etc. It is. Isocyanate is
Because it is highly reactive, it is stabilized by masking it with a blocking agent, and if necessary, the blocking agent is removed and regenerated. This is especially essential for water-based isocyanates.

Regeneration is achieved by applying heat. In the present invention, blocking agents that are easily removed at low temperatures are preferred, and sodium bisulfite, methyl ethyl ketoxime, and the like are preferred.

The silicone having a secondary and/or tertiary amine of the present invention is a silicone having a secondary and/or tertiary amine added to dimethylsiloxane.
Amino-modified silicone to which -OH groups etc. may be added,
Examples include amino-polyether modified silicone and self-crosslinking amino--OH modified silicone. In the present invention,
Set-off.

Self-crosslinking amino--OH modified silicone having excellent slipperiness and mold releasability is preferred.

The viscosity of the silicone having a secondary and/or tertiary amine of the present invention is not particularly limited, but the viscosity measured at 25°C is 10 centistose (hereinafter centistose is abbreviated as C, S) or more 100,000 c ,s,
The following, preferably 50c, s, or more than 1000
0c, s, or less are preferred. If the viscosity is too low, the slipperiness and mold releasability will not be sufficient (on the other hand, if the viscosity is too high, the slipping property will be insufficient).

Poor mold releasability.

In the present invention, it is particularly preferable that the coating agent made of an isocyanate and/or a resin having an isocyanate group and a silicone having a secondary and/or tertiary amine be water-based. Water-based paints pose no environmental problems when drying, can be used in dryers without explosion-proof equipment, and are easy to handle. Furthermore, in the process of producing a biaxially oriented polyester film, when applying the coating material, it is particularly desirable that the horizontal stretching machine used for drying is not equipped with explosion-proof equipment and is water-based.

In the present invention, a binder can be mixed into the coating material. Binders include polyester, epoxy, polyamide, polyimide, polycarbonate polysulfone, polyvinyl butyral, polyarylate, and polyacrylic ester.

Polymethacrylic acid ester, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, polybutadiene, polyurethane, polyfluoroprene, phenolic resin.

Alkyd resin, glue, natural polymers such as casein, polyethylene glycol, polyvinyl alcohol, methyl cellulose and other cellulose derivatives, urea resin,
Melamine resins, polyester ethers, etc., copolymers of the above, and mixtures thereof can be used.

In the present invention, anti-blocking agents, lubricants, pigments, coloring agents such as dyes, plasticizers, light and heat stabilizers, etc. may be added to the resin layer within a range that does not impair the effects of the present invention. In addition, a basic substance is added to promote the regeneration of the blocking agent.
A known catalyst such as dibutyltin laurylate may also be added to adjust H or to promote the reaction of isocyanate groups.

In the present invention, a surfactant or the like may be added to the coating liquid for the purpose of improving the coating properties on the polyester film.

In the present invention, a resin layer consisting of a resin having an isocyanate and/or an isocyanate group and a silicone having a secondary and/or tertiary amine is provided. When the resin having the amine is 100, the silicone having the secondary and/or tertiary amine is 1 to 20.
0, particularly preferably in the range of 3 to 60. If the amount of silicone containing secondary and/or tertiary amine is too small, slipperiness and mold releasability will be poor; if it is too large, set-off and
Poor wear resistance.

In the present invention, a polyester film is coated with a coating agent made of isocyanate and/or a resin having an isocyanate group and a silicone having a secondary and/or tertiary amine. , a gravure coater, various roll coaters, knife coaters, etc. can be used. Coating on polyester film is
It may be done after biaxial stretching or before stretching.

The aforementioned resin layer provided on the polyester film has 1
It is desirable to undergo heat treatment at 80°C or higher, preferably 200°C or higher for 1 to 10 seconds. By undergoing such a high-temperature thermal history, slipperiness, mold releasability, abrasion resistance, and set-off properties are greatly improved. Such high-temperature heat treatment is extremely difficult with the usual coating method of applying a coating material to a biaxially oriented polyester film and drying it. and is extremely thin,
When exposed to high temperatures of over 180°C, the film shrinks and becomes full of wrinkles.

). Therefore, in the process of producing a biaxially oriented polyester film, it is preferable to apply the above mixture, and then stretch and heat treat it. With this method, 1
High temperature heat treatment of 80° C. or higher, preferably 20,000° C. or higher, can also be carried out without any problems. The thickness of the resin layer applied to the back surface of the film is 0.
It is desirable that the thickness be in the range of 0.01 to 2 μm, preferably 0.02 to 1 μm. If the thickness is too thin, slipperiness, mold releasability, and abrasion resistance will be poor, and if the thickness is to a certain extent, no greater thickness is required.

Next, a specific example of the method for producing a biaxially oriented polyester film of the present invention will be described. PET containing so-called precipitated particles and inorganic fine particles (for example, colloidal silica with an average particle size of 1 μm) precipitated during the polymerization process is dried and melt-extruded according to a conventional method, and the extruded sheet-like melt is cooled and solidified to form an unprocessed material. Make stretched PET film. 80% of this film
It is heated to ~120°C and stretched 2.5 to 5 times in the longitudinal direction to form a uniaxially oriented film. One side of this film is subjected to a corona discharge treatment, and a coating liquid consisting of an aqueous isocyanate and/or resin having an isocyanate group and a silicone having a secondary and/or tertiary amine is applied to this treated side. Next, the coated film is stretched 3 to 4.5 times in the width direction while being heated to 90 to 130°C, bowed, and then introduced into a heat treatment zone at 180 to 240°C to Heat treat for 10 seconds. During this heat treatment, it is better to perform a relaxation treatment of 3 to 12% in the width direction. The heat-treated film is gradually cooled through an intermediate cooling zone, and when it reaches room temperature, it is wound up with a winder to form a mill roll. Next, this mill roll is passed through a slitter to form a film product roll of desired width and length.

When using the film obtained in this way as a heat-sensitive transfer foil, a heat-melting or heat-sublimation coloring material layer is applied to the non-coated side, and if necessary, a top coat layer for mold release is applied on top of it. After that, it is slit to the required width for serial type or line type printers to make thermal transfer foil.

When using as a retainer sheet for audio cassette tape, punch out the film in the specified shape and insert it so that the coated side is in contact with the side of the tape wound on the reel.
Attach it inside the cassette case.

When used as a magnetic tape, a magnetic material is coated on the non-coated side, and then the tape is slit to the required width of a video tape or the like.

[Method for Measuring Properties and Evaluating Effects Methods for measuring properties and evaluating effects in the present invention are as follows.

(1) Average surface roughness (Ra) Measured according to JI 5-BO601-1976.

The cutoff value was 0.25 mm.

(2) Layer a polyester film on the surface with the set-off index coating,
Process at 70° C. for 30 minutes with a load of 50 kg/cm 2 applied. Next, the polyester film was peeled off and the surface tension of the polyester film surface was measured using JISK-6768.
It was used as a set-off index.

(3) Evaluation of set-off of thermal transfer foil A polyester film is placed on the surface provided with the resin layer, and treated at 70° C. for 30 minutes under a load of 50 kg/cm 2 . Next, peel off the polyester film and apply 5 g of heat-melt ink with the following ingredients on the surface of the polyester film.
Melt coating and ink repellency were observed at a coating amount of cm2.

Hot melt ink composition Carbon black: 20 parts by weight Carnagua wax 140 parts by weight Ester wax: 40 parts by weight The judgment criteria are as follows.

No repelling: Good Repelling: Poor (4) Evaluation of set-off of retainer sheet A polyester film is placed on the surface on which the resin layer is provided, and treated at 70° C. for 30 minutes under a load of 50 kg/cm 2 . Next, the polyester film was peeled off, and the surface of the polyester film was painted with magic ink and observed to see if it repelled.

The judgment criteria are as follows.

No repelling: Good Repellent: Defective (5) Evaluation of coatability of resin layer The film-coated surface was visually observed.

No repellency or coating spots: Good Repellency, coating spots: Poor [Example] Example 1. Example 2 Particle size 0. 0.15% by weight of precipitated particles (particles precipitated during the polymerization process) of 5 to 1.5 μm and an average particle size of about 1.5
0.0 μm calcium carbonate particles. P containing 2% by weight
After sufficiently vacuum drying the ET pellets (intrinsic viscosity 0.63 dl/g), they are fed into an extruder, melted and extruded at 280°C, filtered through a 10 μm cut metal sintered filter, and then processed into sheets from a T-shaped nozzle. extrude it into a shape, and the surface temperature of this
It was wound around a cooling drum at 0°C and cooled and solidified. In order to improve the adhesion between the sheet and the surface of the cooling drum, a wire electrode is placed on the sheet side, and this
A DC voltage of 0V was applied. The thus obtained unstretched P
The ET film was heated to 95°C and 3.
It was stretched 5 times to obtain a uniaxially stretched film. One side of this film was subjected to corona discharge treatment, and the water-based paint shown in Table 1 was applied onto the treated surface using a rod coating method. This uniaxially stretched film coated on one side was preheated at 98°C, and then stretched 3°9 times in the width direction while heating to 105°C. Next, this film was introduced into hot air at 225°C, heat-set under tension for 1 second, allowed to shrink by 8% of the original film width in the width direction in the same temperature atmosphere, and then heated again at the same temperature. Tension heat set in an atmosphere for about 1 second,
Next, 180℃.

It was gradually cooled through each zone of 150° C. and 100° C., and finally cooled to room temperature, and then led to a winder and wound up into a mill roll. Next, this mill roll was passed through a slitter to slit the film to a film width of 600 mm to obtain a film product roll. The film thus obtained has a thickness of about 6 μm and has a thickness of about 0.0 μm on one side. A coating layer of 1 μm is applied, and the average roughness of both surfaces is 0.10 μm on the coated surface (measured including the coating layer) and 0.1 μm on the non-coated surface.
It was 12 μm. On the non-coated side of this film, heat sublimation ink with the following composition was applied as a coloring material layer with a dry coating amount of 1 g/
The film was coated so as to have a thickness of lrr, dried, and then slit to an appropriate width to produce a heat-sensitive transfer foil.

Disperse dye KST-B-136: 4 parts by weight (manufactured by Nippon Kayaku) Ethyl hydroxyethyl cellulose 2 6 parts by weight Methyl ethyl ketone: 45 parts by weight Toluene
:45 parts by weight Example 3. Example 4 Example 1 except that the film thickness was 25 μm. A film was obtained in exactly the same manner as in Example 2.

This film was punched out into a predetermined shape, mounted on an audio cassette, and the tape was run. The tape ran smoothly and wound evenly onto the reel.

As shown in Table 1, the set-off properties and coating properties of these films are good within the range of the present invention (Examples 1 to 4).

Comparative example 1. Comparative Example 2 Example 1 and Example 2 except for changing the paint shown in Table 2.
A film was obtained in exactly the same manner.

Comparative example 3. Comparative Example 4 Example 3 and Example 4 except for changing the paint shown in Table 2.
A film was obtained in exactly the same manner. This film was punched out into a predetermined shape, mounted on an audio cassette, and the tape was run. The tape runs while jerking,
It was not wound evenly on the reel.

As shown in Comparative Examples 1 to 4 in Table 2, no film satisfying set-off properties and coatability was obtained.

[Effects of the Invention] The present invention provides a biaxially oriented polyester film containing isocyanate and/or a resin having an isocyanate group and a second
By using a coating material made of silicone containing primary and/or tertiary amines, the stability of the coating material is increased, and by providing a coating film formed by applying this coating material, easy slipping and mold release properties can be achieved. By providing excellent performance in both cases and with little set-off, it has the effect of eliminating the adverse effects caused by transfer on the back side.

According to the present invention, a thermal transfer foil with no coating defects and less set-off can be obtained.

Claims (3)

[Claims] (1) At least one side of the biaxially oriented polyester film has a set-off index of 30 dyne/cm or more and 50 dyne.
/cm or less, the resin layer is at least made of an isocyanate and/or a resin having an isocyanate group, and a silicone having a secondary and/or tertiary amine. A biaxially oriented polyester film characterized by being provided by coating. (2) The biaxially oriented polyester film according to claim 1, wherein the isocyanate and/or the isocyanate group of the isocyanate group-containing resin is masked with a blocking agent. (3) The biaxial coating according to claim 1 or 2, characterized in that the coating material made of isocyanate and/or resin having an isocyanate group and silicone having secondary and/or tertiary amine is water-based. Oriented polyester film.