JPH0929833A - Film for overhead projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide less heat shrinkage, heat resistant flexibility, transparency and antistatic properties and no curl after passing a copying machine by specifying the shrinkage differential value of a specific temperature range, the temperature range of a fine heat absorbing peak appearing before crystal melting by a differential scanning calorimeter, and a film haze. SOLUTION: This film for an overhead projector having a biaxially oriented polyester film has 0.3% or less of heat shrinkage of 30min at 150 deg.C, and always 0.01% or less of a shrinkage differential value dL/dT (L: length, T: temperature) in a temperature range of glass transition point to 200 deg.C in the differential curve of the true shrinkage in the longitudinal direction of the film obtained from the stretching or shrinkage amount at the time of temperature rise or fall by a thermomechanical characteristic tester. The differential heat absorbing peak appearing before the crystal melting by a differential scanning calorimeter is a range of a melting point to (melting point -30 deg.C). Further, the film haze at that time is 10% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overhead projector (hereinafter also abbreviated as OHP) composed of a biaxially stretched (biaxially oriented) polyester film.
Film. More specifically, the heat shrinkage rate is low,
It relates to an OHP film that has excellent heat-softening resistance and transparency, good flatness after passing through a copying machine, printer, printing machine, etc., and has excellent antistatic properties and easy adhesion. It is used.

[0002]

2. Description of the Related Art OHP films have excellent thermal characteristics,
Polyester films with good flatness are often used, but polyester films stretched biaxially in the longitudinal direction and the width direction are particularly preferably used because they have excellent mechanical properties. . Among the polyesters, polyethylene terephthalate (PET)
And polyethylene-2,6-naphthalate (also referred to as PEN) are more preferably used because of their excellent mechanical and thermal properties, and especially because PET is inexpensive.

The biaxially stretched film of polyester improves mechanical properties such as strength by molecular orientation by stretching, but conversely, strain due to stretching remains in the molecular chain, so heat is applied. As a result, the strain of the molecular chain is released and the molecule shrinks, and this heat shrinkability is one of the obstacles for the OHP film.
So, after biaxial stretching, heat treatment (also called heat setting)
The method of releasing the strain of the molecular chain is performed by performing. Generally, the amount of heat shrinkage decreases according to the temperature of this heat treatment, but the strain cannot be completely removed only by this heat treatment, the heat shrinkage remains, and conversely the temperature of the heat treatment is raised too high. Then, there is a problem that the molecular orientation is relaxed and the mechanical properties are deteriorated.

Therefore, in order to remove this residual strain, the rail width of the tenter (width direction stretching device) is tapered (called toe-in, relax, etc.) and slightly contracted in the width direction. , A method of completely removing this residual strain is adopted.

However, with this method, heat shrinkage in the width direction can be removed, but heat shrinkage in the longitudinal direction (machine direction) cannot be removed. Therefore, various methods have been studied from the past as a method for removing the heat shrinkage in the longitudinal direction. For example, as disclosed in Japanese Examined Patent Publication No. 28218/1992, a method has been proposed in which the clip interval of the tenter is gradually narrowed to perform a relaxing process in the longitudinal direction. This way, with mechanical problems,
There is an upper limit to the amount of relaxation, and when the amount of relaxation is increased, there is a problem that the gap between clips before relaxation processing becomes wider, and the difference in physical properties between the clip gripping part and the non-gripping part becomes large. However, there is a problem that the effect of reducing is not sufficient.

[0006] Further, there is a method in which, after the film is once wound, it is slowly unwound and heat-treated in an oven or the like, and at that time, a relaxation treatment is performed by applying a speed difference in the longitudinal direction. . However, this method has a problem that the flatness is deteriorated because the width of the film is not fixed.

Further, as disclosed in Japanese Patent Publication No. 60-226160, there is proposed a method of providing a longitudinal relaxation treatment device by an oven during the film production process. On the other hand, if the treatment temperature is raised, the flatness and mechanical properties of the film are deteriorated, so the temperature cannot be raised so much, and as a result, the heat shrinkage particularly when exposed to a high temperature of 150 ° C or 200 ° C is sufficient. The problem of not being removed occurs,
It was not possible to obtain a sufficiently satisfactory film as an OHP film.

If the OHP film has a low heat shrinkability and at the same time is not excellent in heat softening resistance, it is exposed to a relatively high temperature when used in a copying machine, a printer, a printing machine or the like, and thus has a flatness. It deteriorates, causing curls and partial sagging. Further, even if the antistatic property, the transparency and the easy adhesiveness are lacking, a problem occurs during use. For example, if the antistatic property is lacking, dust and dust will adhere to the film surface, and double feeding will easily occur when the film is transported by a copying machine. If lacking transparency, a clear image will be obtained when projected with OHP. Is not obtained, and lack of easy adhesion causes a problem that the toner baked on the film surface is easily peeled off. However, conventional methods have not been able to obtain an OHP film having all of these properties.

[0009]

Therefore, an object of the present invention is to sufficiently reduce the heat shrinkage, which is the fate of a biaxially stretched film, in the longitudinal direction and the width direction at a low cost, and
Antistatic property without causing problems of transparency, flatness, and deterioration of flatness during transportation in a copying machine due to thermal softening,
An object of the present invention is to provide an OHP film made of a polyester film having excellent adhesiveness and transparency.

[0010]

In order to achieve this object, the OHP film of the present invention has a thermal shrinkage of 0.3% or less at 150 ° C. for 30 minutes, and a thermomechanical property tester (hereinafter,
(Also referred to as TMA) in the differential curve of the true shrinkage amount in the longitudinal direction of the film, which is obtained from the expansion and contraction amount at the time of temperature increase and decrease.
The shrinkage differential value dL / dT (L: length, T: temperature) is always 0. 0 in the range of not less than the glass transition point (Tg) and not more than 200 ° C.
01% / ° C or less, and a differential scanning calorimeter (hereinafter,
A minute endothermic peak (hereinafter also referred to as Tmeta) appearing before crystal melting by DSC) has a melting point (hereinafter, T
m)) or less, (Tm−30) ° C. or more, and a film haze at that time of 10% or less, which is a biaxially oriented polyester film.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The polyester referred to in the present invention is a polymer obtained by polycondensation of a diol and a dicarboxylic acid, and the dicarboxylic acid is represented by terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like. The diol is typified by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol and the like. Specifically, for example, polymethylene terephthalate, polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexanedimethylene terephthalate, polyethylene-2,6-naphthalate and the like can be used. Of course, these polyesters may be homopolymers or copolymers, and as the copolymerization component, for example, diethylene glycol, neopentyl glycol, polyalkylene glycol and other diol components, adipic acid, sebacic acid, phthalic acid, A dicarboxylic acid component such as isophthalic acid or 2,6-naphthalenedicarboxylic acid can be used. In the case of the present invention, polyethylene terephthalate and polyethylene-2,6-naphthalate are particularly preferable from the viewpoint of mechanical strength, heat resistance, chemical resistance, durability and the like.

Further, various additives such as an antioxidant, a crystal nucleating agent, inorganic particles and organic particles may be added to these polyesters. In particular, the inorganic particles and the organic particles are effective for imparting slipperiness to the film surface and improving the handleability of the film.

The biaxially oriented film in the present invention means a longitudinal direction of the film and a direction (width direction) perpendicular to the longitudinal direction.
It is a film in which molecules are oriented. Specifically, a melt-extruded substantially non-oriented film is stretched in the longitudinal direction and then stretched in the width direction, stretched in the width direction and then stretched in the longitudinal direction, or the longitudinal direction and the width. The stretching may be performed in the same direction, or the stretching in the longitudinal direction and the stretching in the width direction may be performed plural times in combination.

In the present invention, the heat shrinkage ratio in 30 minutes at 150 ° C. in the longitudinal and width directions of the film needs to be 0.3% or less, preferably 0.1% or less.
If it exceeds 0.3%, in a machine such as a copying machine, a printer, or a printing machine, a considerable amount of heat may be applied for speeding up, so that the film shrinks during use, curling or partial curling occurs. Defects such as sagging and deterioration of flatness occur. Therefore, it is necessary that the heat shrinkage rate at a high temperature such as 150 ° C. is small.

In the present invention, the Tg of the polyester is 200 or more in the differential curve of the true shrinkage amount in the longitudinal direction of the film, which is obtained from the expansion and contraction amount during temperature increase and decrease by TMA.
In the range of 0 ° C. or less, the contraction amount differential value dL / dT is always 0.
It is necessary to be 01% / ° C. or less. TMA is a device that measures the change in length while raising or lowering the temperature of the furnace at a constant rate by applying no load or constant load to the film set in the electric furnace. The amount of expansion and contraction of the film due to the change can be measured.

Here, the behavior of the biaxially oriented film in the longitudinal direction when the amount of expansion and contraction is measured by TMA will be generally described. When the temperature is raised from room temperature at a constant rate, the film expands due to the thermal expansion of the polymer. This thermal expansion is a reversible behavior and returns to the original length when the temperature decreases. When the temperature is raised, from the vicinity of the glass transition point of the polymer,
In addition to thermal expansion, the strain due to stretching is released and the film begins to shrink. This contraction is an irreversible change that does not return once it has contracted. What is actually measured here is the value obtained by subtracting the thermal expansion from the thermal contraction. Next, when the temperature is raised to a certain temperature and then lowered at a constant rate, reversible thermal expansion causes contraction to return to the original length. FIG. 1 shows a series of these behaviors.

Here, the present inventors have found that it is necessary to separate the above-described reversible stretching behavior and irreversible shrinking behavior in order to reduce the heat shrinkage of the biaxially oriented polyester film, and the following is performed. Was processed. That is,
The above-mentioned measurement curve at the time of temperature rise is a combination of reversible expansion and contraction and irreversible contraction, and the measurement curve at the time of temperature reduction expresses only reversible expansion and contraction. Therefore, the measurement output from the TMA was converted into a digital value via an AD converter, loaded into a computer, and digitized. Here, as shown in FIG. 2, the length of the temperature rising curve and the temperature falling curve at room temperature are
Each value was set to 0, re-expressed, and a process of subtracting the value of the temperature decrease curve from the temperature increase curve was performed. With this process,
The reversible expansion and contraction is erased, and a curve (L) showing only irreversible contraction can be obtained. This curve will be called a true contraction amount curve. Next, this curve is numerically differentiated by the temperature T by the Douglas-Abakian method (for example, written by Hirata, Suda, Takemoto, "Numerical Calculation by PC", published by Asakura Shoten Co., Ltd., page 34), The differential curve (dL / dT) of the true contraction amount was obtained. From this differential curve, it is possible to investigate how much shrinkage is occurring at what temperature. That is, the area surrounded by the horizontal axis (temperature axis) and the differential curve has an irreversible expansion / contraction amount. The detailed methods of these processes will be described later.

The present inventors have set the amount of expansion and contraction of the film as TMA.
In the differential curve of the true shrinkage amount in the longitudinal direction of the film, in order to reduce the heat shrinkage of the biaxially oriented film, the irreversible shrinkage behavior of the film is analyzed by performing the above treatment. , Tg of the polyester or more 2
It has been found that the shrinkage differential value dL / dT needs to be always 0.01% / ° C. or less in the range of 00 ° C. or less. That is, the film produced by the usual method has a first peak of dL / dT between Tg and 150 ° C., and a second film in the region of 150 ° C. or higher, as shown in FIG. Has a peak of. These are both 0.0
This is a large peak exceeding 1% / ° C., which increases heat shrinkage. The present inventors have conducted diligent studies and found a method of setting dL / dT to 0.01% / ° C. or less in the range from Tg to 200 ° C., and a film satisfying such a condition suppresses heat shrinkage to a very low level. I found that I could do it.

Further, in the present invention, T by DSC is used.
It is necessary that meta is in the range of Tm or lower and (Tm-30) ° C or higher, preferably Tm or lower and (Tm-4).
0) C. or higher. This Tmeta is observed as a minute peak at a temperature corresponding to the heat treatment temperature of the film, and is caused by the incomplete portion of the crystal structure formed by the heat treatment melting. As described above, the irreversible shrinkage in the region of 150 ° C. or higher is caused by the residual strain due to stretching, and in order to completely remove this strain, the crystal structure of the film partially melts. The present inventors have found that heat treatment at such a temperature is preferable. For that, Tmeta is T
It is preferably observed in the range of m or less and (Tm−30) ° C. or more.

It should be noted that depending on the orientation state of the film, Tme
In some cases, ta becomes too small to be observed, but in such a case, Tm was taken as the temperature of Tmeta.

Further, in the present invention, the film haze needs to be 10% or less, and preferably,
The haze is 5% or less. Tme in the range as described above
If there is ta, the haze is usually high, but the present inventors have found that the haze depends on the orientation state of molecules before the heat treatment, and the molecular orientation before the heat treatment is 10% or less. I found that I need to be in a proper state. On the other hand, if the haze exceeds 10%, the image becomes blurry and unclear when translucent with OHP or the like, which is not preferable.

Further, in the present invention, it is preferable that the (100) plane crystal size of the film by wide angle X-ray diffraction is 60 angstroms or more and 80 angstroms or less, and the plane orientation coefficient is 0.1 or less. More preferably, the crystal size is 65 angstroms or more, 75
It is angstrom or less and the plane orientation coefficient is 0.07 or less. If the crystal size is less than 60 angstrom, the crystallinity is insufficient, and the film having a plane orientation coefficient of more than 0.1 has a weak molecular orientation. It is difficult to obtain, and there is a problem that curling is likely to occur after being conveyed by a copying machine or the like. Further, in order to obtain a film having a crystal size of more than 80 angstrom, it is necessary to perform heat treatment for a long time, and the heat treatment temperature must be considerably high.
It is impossible to obtain a film having such a crystal size.

In the present invention, it is preferable that the pin insertion temperature in TMA is 115 ° C. or higher and the insertion distance is 8% or less of the film thickness. More preferably, the pin penetration starting temperature is 125 ° C. or higher and the penetration distance is 5% or less of the film thickness. If they are removed from the above, the temperature inside the machine becomes high during transportation in a copying machine or the like, so that the film is deformed due to thermal softening, and thus problems such as deterioration of flatness are likely to occur. In particular, it has recently been found that since the transfer speed of copiers, printers, printing machines, etc., has become faster, considerable heat and pressure is applied, and the flatness deteriorates due to heat shrinkage and deformation due to heat and pressure during use. Therefore, it has been found that it is preferable to have both excellent heat softening resistance.

In the present invention, the applied voltage 100
Surface resistance at 20 ° C and 60% RH at V is 1 × 10
It is preferably ¹¹ Ω / □ or less. Since polyester is hydrophobic, it is extremely easily charged by friction. In particular, if the surface resistance exceeds 1 × 10 ¹¹ Ω / □, it will be double-fed when the film is conveyed by a copying machine, and dust or dirt will easily adhere to the film surface, which may cause the OHP or the like to see through. It is not preferable because the dust and dirt are reflected in the image as a shadow. In order to obtain a film having low surface resistance, an antistatic agent may be added to the extent that transparency and mechanical properties are not impaired. As the antistatic agent, quaternary ammonium salts, amines, imidazolines, amine oxide adducts, polyalkylene glycols,
Sorbitan esters and the like can be used. Among them, for example, in the case of polyalkylene glycol, the molecular weight is preferably about 600 to 20,000, and as such, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol polypropylene glycol copolymer and the like can be used. When adding these, 0% by weight
It is preferable that the amount added is more than 15% by weight. Further, as described later, it is also preferable to coat the film surface with an antistatic resin.

In the present invention, the toner peeling rate in the toner peeling test is preferably 10% or less,
It is more preferably 5% or less. Toner peeling rate is 10
If it exceeds%, the toner burned on the film may be peeled off due to contact with parts inside the machine during transportation by a copying machine, etc., or the toner burned off due to contact with other objects after transportation. Problems such as are likely to occur.

Therefore, in order to obtain a film having good adhesion to toner and the like, it is preferable to laminate easily adhesive polyester on both sides of the film by co-extrusion or coat the easily adhesive resin on the film surface. As the easily adhesive polyester, a polymer containing an ester group obtained by polycondensation from a dicarboxylic acid and a diol component, for example, isophthalic acid as the dicarboxylic acid,
There are adipic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, and the like, and as diols, ethylene glycol, 1,4-butanediol, diethylene glycol, triethylene glycol,
Examples include neopentyl glycol, cyclohexanedimethanol and polyethylene glycol. Further, it may be a copolymer of two or more kinds of dicarboxylic acids or diols, or a copolymer of other monomers or polymers.

As the easily-adhesive resin, it is preferable to use polyurethane, polyester, or acrylic resin as a water-soluble or water-dispersible resin from the viewpoint of not only adhesiveness but also transparency. For example, as the polyurethane, one having at least one of a carboxylic acid group, a sulfonic acid group, and a sulfuric acid half-ester base, in particular, an ammonium salt can be used. In addition, specific examples of polyester include 5-5
-Sulfosodium isophthalic acid 0.5 to 20
Mol% copolymerized polyester or polyethylene glycol, or ethylene oxide, propylene oxide 1 to
It is possible to use one obtained by copolymerizing 30 mol%. Among them, at least one of terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid and adipic acid is used as the acidic component, and ethylene glycol or hexylene glycol, 1,4 is used as the alcohol component.
-When a polyester having at least one of butanediol, diethylene glycol, neopentyl glycol, tetramethylene glycol, and polyethylene glycol and having a water-soluble content at 5% by weight dilution or a viscosity of an aqueous dispersion of 3 to 6 cps is used, It is possible to obtain a film excellent not only in adhesiveness but also in antistatic property. Further, as the acrylic resin, one having an alkyl acrylate or an alkyl methacrylate as a main component can be used.

Next, a method for producing the film of the present invention will be described, but the invention is not limited to such an example. An example in which polyethylene terephthalate is used as the polyester is shown, but conditions such as drying conditions, extrusion conditions, and stretching temperature differ depending on the resin. According to a conventional method, bis-β-hydroxyethyl terephthalate (BH) is obtained by esterification from terephthalic acid and ethylene glycol or transesterification of dimethyl terephthalate and ethylene glycol.
T) was obtained. Next, this BHT was transferred to a polymerization tank and heated to 280 ° C. under vacuum with stirring to proceed the polymerization reaction. Here, the stirring torque was detected, and the reaction was terminated when the predetermined torque was reached. At this time, an antistatic agent may be added to reduce the surface resistance of the film.

The polyethylene terephthalate pellets polymerized as described above were vacuum dried at 180 ° C. for 5 hours, and then
It is supplied to the extruder A heated to a temperature of 270 to 300 ° C. and extruded in a sheet form from the T die. Further, in order to impart easy adhesiveness, after being dried and separately polymerized, the easily adhesive copolymerized polyester is supplied to the extruder B, and the polymer of the extruder B layer becomes both surface layers with a T-die three-layer die. It can also be formed in a sheet shape by stacking it in a B / A / B three-layer structure. At this time, an antistatic agent may be added to the B layer.

The sheet melted as described above is brought into close contact with a drum cooled to a surface temperature of 25 ° C. by electrostatic force and solidified to obtain a molded film in a substantially amorphous state. This film is heated by a heating roll group at 80 to 120 ° C., longitudinally stretched in a single stage or multiple stages by 3 to 6 times in the longitudinal direction, and cooled at a roll group at 20 to 50 ° C. Next, the film is guided to a tenter and, while holding both ends of the film with clips, it is preheated in a hot air atmosphere heated to 80 to 140 ° C. and laterally stretched 3 to 6 times in the width direction. Longitudinal direction,
When the film is stretched in the width direction, the refractive index in the thickness direction is 1. so that the molecular orientation becomes a haze of 10% or less.
Stretching is performed while adjusting the magnification so that it becomes 5 or more. Here, when a film having an antistatic property and an easy-adhesive property is obtained with a coating agent, a uniaxially stretched film obtained by stretching after cooling with a group of longitudinal stretching rolls and then cooling is coated with a predetermined resin dispersed in water. After providing the coating layer containing the agent, it is introduced into a tenter, and while holding both ends of the film with clips, the preheating temperature is increased or the preheating zone is increased, and dehydrated in a sufficient preheating step. To the width direction.

Here, in order to obtain the film of the present invention, first in the longitudinal direction of the film, 150 ° C.
It is necessary to suppress the peak of dL / dT in the above,
As one method for that purpose, there is a method of raising the temperature of the heat treatment to near the melting point of the polyester. That is, the film thus biaxially stretched, low heat shrinkage, flatness,
Heat treatment is performed to impart heat-softening resistance, but in the case of polyethylene terephthalate, (Tm-30) ° C ~
By setting to Tm, performing rapid temperature rise and short time heat treatment,
The characteristics as described above can be obtained. Further, by setting such a heat treatment temperature, the crystallinity of the film is increased, the (100) plane crystal size is large, and the disorder of the molecular orientation is small, and a film having good plane orientation can be obtained. However, if only such a heat treatment temperature is used, dL / d in the range from the glass transition point to 150 ° C.
It is impossible to lower T. That is, by cooling from such a high temperature, the amount of thermal expansion at the time of high temperature reversibly contracts, so that strain is accumulated and the glass transition point becomes 1
The peak of dL / dT appears in the range of 50 ° C. Therefore, in order to suppress this peak, in the step of cooling from the heat treatment of the tenter, it is preferable to apply relaxation in the longitudinal direction so as to absorb the reversible shrinkage component accompanying the cooling. However, if the relaxation treatment is immediately performed from the heat treatment temperature, the relaxation of the molecular orientation becomes large, so that a film having excellent heat softening resistance cannot be obtained. Therefore, in order to control the relaxation of molecular orientation and obtain a film having good heat-softening resistance, it is more preferable to perform a relaxation treatment after cooling under tension to about 200 ° C. after the heat treatment. Various methods are conceivable for this relaxing treatment, but a method of shortening the interval between the clips while gripping the film with the clips of the tenter is particularly preferable in order to maintain the flatness. In addition, the film of the present invention can be obtained by performing a relaxation treatment in the width direction, narrowing the rail width of the tenter if necessary, and gradually cooling to room temperature and winding.

As described above, an antistatic and easily adhesive resin is used as a coating agent, an antistatic agent is added,
It is possible to obtain excellent antistatic property and easy adhesiveness by molding a laminated film of easily adhesive polyester.
In addition, by performing the relaxation treatment, it is possible to control the disorder of the molecular orientation of the film, to obtain a film excellent in low heat shrinkability, flatness, heat softening resistance and transparency, and to obtain an excellent film as an OHP film. It has become possible.

[Evaluation Method of Physical Properties] (1) About 5 mg of Tg, Tmeta, and Tm samples were sampled in an aluminum pan, and a robot DSC: RDC220 manufactured by Seiko Instruments Inc., and a data analysis unit: SSC5200H were used. Temperature rising rate 20
In the process of heating to 300 ° C at ℃ / min,
The Tm was measured. Subsequently, the temperature was maintained at 300 ° C for 5 minutes, followed by rapid cooling with liquid nitrogen, and Tg was measured at a temperature rising rate of 20 ° C / minute. When it was difficult to observe Tmeta associated with the melting peak, the vicinity of the peak was enlarged in the data analysis section and the peak was read. When Tmeta became too small to be observed, Tm was set to Tmeta.

(2) Differential curve of true shrinkage amount by TMA A sample is sampled to have a width of 2 mm, and the test length is 15 mm so that TMA: TM-300 manufactured by Vacuum Riko Co., Ltd.
0 and heating control unit: TA-1500.
Here, the output of the amount of expansion and contraction is drawn on the recorder, and the AD converter manufactured by Canopus Electronics Co., Ltd .: ADX-98
It was installed so as to take in data to a personal computer: PC-9801 manufactured by NEC Corporation via E.
Here, a load of 1 g is applied, the temperature of TMA is increased from room temperature at a temperature increase rate of 10 ° C./minute, and the temperature is increased to 200 ° C., then 10 ° C. /
The temperature was lowered to room temperature in minutes. The amount of expansion / contraction at the time of temperature increase / decrease at this time was loaded into a personal computer every 1 ° C., and this data was loaded into Lotus 1-2-3 spreadsheet software. Using the data on a spreadsheet software, the data at the time of temperature increase and the data at the time of temperature decrease are set to 0% for the amount of expansion and contraction at 30 ° C, and the value at each temperature is the amount of expansion or contraction from 30 ° C. (It is divided by the trial length of 15 mm and multiplied by 100 to display the percentage). L = Lu-Ld (%), where Lu (%) is the amount of expansion / contraction at the time of temperature rise and Ld (%) is the amount of expansion / contraction at the time of temperature decrease.
Was calculated at each temperature, and L was taken as the true shrinkage amount. Next, this L was numerically differentiated by temperature T on spreadsheet software. The numerical differentiation method was performed by the Douglas-Abakian method (for example, Hirata, Suda, Takemoto, "Numerical calculation by personal computer", published by Asakura Shoten Co., Ltd., p. 34). In addition, in L, when a small variation due to noise or the like is large, a moving average of 5 ° C. is obtained, smoothing is performed, and then a differentiation process is performed. Moving average, for example, the value of L in the _{T 1, (T 1 -2)} ~ (T 1 +
2) A method of expressing the average value of L at 5 points up to ° C.

(3) Heat shrinkage rate The sample is sampled in a width of 10 mm and a length of about 250 mm, dots are set at intervals of about 200 mm, and the intervals are accurately measured by a ruler to obtain L ₀ (mm). The sample is treated in an oven heated to 150 ° C. for 30 minutes, allowed to cool at room temperature, and then the point interval is accurately measured again with a ruler to obtain L (mm). Where heat shrinkage =
[(L ₀ −L) / L ₀ ] × 100 (%) was set and the average value of two samples was adopted.

(4) Crystal size Films are laminated in a thickness of about 50 μm or more and used as X-ray diffraction data, and placed in a sample holder of an X-ray diffractometer manufactured by Rigaku Denki Co., Ltd. When the diffraction peak is observed by the reflection method while changing the incident angle of the line, 2θ is about 26.
From the diffraction peak at °, the crystal size D (angstrom) in the direction of the diffraction crystal (100) plane of the same peak was calculated according to Scherrer's formula. D = λ / (B−b) COS θ where B: half width of diffraction peak, b = 0.12 λ: wavelength of Cu Ka line (1.5418 angstrom) θ: peak diffraction angle

(5) Plane Orientation Coefficient As with the measurement of crystal size, a film of about 50 μm
The laminate having the above thickness was used as an X-ray diffraction sample, and the sample was set in a sample holder of an X-ray diffraction device manufactured by Rigaku Denki Co., Ltd.
When the diffraction peak was observed by the reflection method while changing the width direction of the film and the incident angle of X-ray, (10
0), 26 ° corresponding to the diffraction angle 2θ of the following Expression 2, 22.
The diffraction intensities at 5 ° were I ₁ and II ₂ , respectively, and the plane orientation coefficient was calculated from the ratio (II ₂ / I ₁ ).

[0038]

[Equation 2]

(6) Flatness Fuji Xerox Co., Ltd. copier "Vivace50"
0 ”, about 100μ thickness cut into A4 size
The flatness of the m film before and after passing through the copying machine was spread on a table and visually determined as follows. ◯: No curved portion is seen Δ: Three or less curved portions ×: Three or more curved portions

(7) Transparency Haze meter "SEP-H" manufactured by Nippon Seimitsu Optical Co., Ltd.
2 "according to ASTM-D1003-52, the incident light amount, the total light transmission amount, the scattered light amount by the device, the scattered light amount by the device and the test piece are measured, and the total light transmittance (%), the scattered light transmission The rate (%) and the film haze (%) were calculated according to the following formulas. T ₁ : incident light amount T ₂ : total light transmission amount T ₃ : scattered light amount by the device T ₄ : scattered light amount by the test piece of the device T _t : total light transmittance (%) T _d : scattered light transmittance (%)

[0041]

(Equation 3)

Note that T ₃ (T ₂ / T ₁ ) is a correction for diffusion (not by the test piece) by the test apparatus.

(8) Thermal Softening Test TMA: TM-3000 and TA manufactured by Vacuum Riko Co., Ltd.
As shown in FIG. 4, using -1500, a quartz cylinder pedestal 2 having a diameter of 8 mm and a height of 5 mm is placed on the support tube 1,
Place the sample 3 of about 5 x 5 mm on it, and
The metal pin 4 of mφ is set on the detection rod 5, and a load P of 10 g is applied, and the temperature rise rate is 5 ° C./min.
The temperature is increased to obtain a thermal dimension change curve, and as shown in FIG. 5, a tangent line is drawn on the straight line portion including the metal pin and the thermal expansion in the film thickness direction. The pin penetration (softening) start temperature was used, and the value obtained by dividing the dimensional difference at which the thermal dimension curve deviates most from the extension line by the film thickness was defined as the penetration distance. In addition, the softening temperature was set to 200 ° C. or higher when the pin penetration was not observed.

(9) Antistatic property A super insulation resistance meter MODEL-VE40 (manufactured by Kawaguchi Denki Kogyo Co., Ltd.) at an applied voltage of 100 V at 20 ° C. and 60% RH.
The surface resistance was measured.

(10) Easy Adhesion A film having a thickness of about 100 μm cut into A4 size was copied by Fuji Xerox Co., Ltd. "Vivace 50".
After black toner solid printing was performed with “0”, cellophane tape “CT-24” (manufactured by Nichiban Co., Ltd.) was attached to the surface, and a hand roller was used to apply a load of about 5 kg and reciprocate 10 times. Then, the cellophane tape is peeled off in 90 ° direction by hand, and the toner peeling rate is obtained from the peeled area of the peeled portion and the non-peeled portion by an image analyzer ("PIASIV / HDTV" manufactured by Pierce Co., Ltd.). Was calculated.

(11) Refractive index in the thickness direction Using an Abbe refractometer type 4 manufactured by Atago Co., Ltd., a polarizing plate was inserted in the eyepiece section, and one drop of methylene iodide was used as an intermediate liquid in the prism of refractive index. Hang it down, put the sample on it, hang methylene iodide further on it, put a measurement prism with a refractive index of 1.70 on both front and back surfaces of the sample, and measure from the longitudinal direction and the width direction,
The average value of the refractive index in the thickness direction measured from each direction was adopted.

[0047]

EXAMPLES The present invention will be described below based on examples. Example 1 Polyethylene terephthalate (T having an intrinsic viscosity of 0.65)
The pellets (g: 69 ° C.) were vacuum dried at 180 ° C. for 5 hours, then fed to an extruder heated to 270 to 300 ° C., and formed into a sheet by a T die. Further, this film was brought into close contact with a cooling drum having a surface temperature of 25 ° C. by electrostatic force and solidified to obtain an unstretched film.

The unstretched film is heated by a heating roll group at 80 to 100 ° C., longitudinally stretched 3.3 times in the machine direction (MD) in one step, and cooled at a roll group at 20 to 50 ° C. The surface of the stretched film was subjected to electric discharge treatment in air, and the following water-based coating agent was applied.

Acrylic polymer (A): An acrylic polymer (average molecular weight of 500,000) in which 2.5 parts by weight of each of a carboxyl group and a methylol group as a functional group is introduced into methyl methacrylate / ethyl acrylate (50/50) mol%. ) Was used. Sulfonated polystyrene and / or its salt (B): SO
A sulfonated polystyrene having H ⁺ as an X ⁺ ion of a ₂ O ⁻ X ⁺ group and having a molecular weight of about 70,000 was used. (A) /
The weight ratio of (B) was 80/20, and the coating agent was prepared by diluting with water to 6% by weight.

The thickness of the coating agent after biaxial stretching is 0.
Apply with a gravure coater so that the thickness is 07 μm.
It was sufficiently dried in a hot air atmosphere heated to 0 ° C and laterally stretched 3.5 times in the width direction.

The biaxially stretched film is continuously heat-treated at 250 ° C. in a tenter and once cooled to 200 ° C. under tension, and the width of the tenter rail is reduced in a slow cooling section of 200 to 110 ° C. 5% in the direction (TD) and 2% in the longitudinal direction by relaxing the clip interval of the tenter and taking it out from the tenter, trimming the edge parts of both ends of the film and winding it to a thickness of 100 μm.
m was obtained.

The differential curve of the true shrinkage amount in the longitudinal direction of the obtained film is as shown by the characteristic line 6 in FIG. 6, and the physical properties are as shown in Tables 1 and 2. 20 from the glass transition point
In the range up to 0 ° C., no shrinkage peak was observed and a film having a small heat shrinkage rate was obtained. Further, a film having excellent heat resistance and softness, which is excellent in transparency, antistatic property and flatness, and in which softening start temperature and pin penetration is not observed, was obtained. Cut this film into A4 size and copy it from Fuji Xerox Copier Viv
When it was passed through ace500, it was discharged with good flatness without curling or partial slack, and it was also excellent in easy adhesion.

Example 2 A biaxially stretched film which had been longitudinally stretched, coated and transversely stretched in the same manner as in Example 1 was continuously placed in a tenter for 24 hours.
After heat treatment at 0 ° C, the rail width of the tenter was reduced by 5% in the width direction in the slow cooling section of 240 to 110 ° C, and the clip interval of the tenter was reduced by 2% in the longitudinal direction. Take it out from the rear tenter, trim the edges of both ends of the film and wind it up to a thickness of 100 μm.
Was obtained.

The differential curve of the true shrinkage amount in the longitudinal direction of the obtained film is as shown by the characteristic line 7 in FIG. 6, and the physical properties are as shown in Tables 1 and 2. 20 from the glass transition point
As compared with Example 1 in the range up to 0 ° C., a peak was seen near 200 ° C., but it was still a sufficiently small peak. Also, a film with a small heat shrinkage rate was obtained,
Since the relaxation start temperature is high, the disorder of the molecular orientation becomes large, and a decrease in the softening start temperature and a slight increase in pin penetration were observed, but a film with excellent transparency and antistatic properties and good flatness was obtained. It was When this film was cut into A4 size and passed through Fuji Xerox Co., Ltd., Copier Vivace 500, it was discharged in a good flatness state with no curl or partial slack, and was also excellent in easy adhesion. .

Comparative Example 1 A film which has been longitudinally stretched, coated and transversely stretched in the same manner as in Example 1 is subsequently heat-treated at 230 ° C. in a tenter and then cooled to 200 ° C. under tension. Two
In the slow cooling zone of 00 to 110 ° C, the rail width of the tenter is shortened by 5% in the width direction, and the clip interval of the tenter is shortened by 2% in the longitudinal direction. The edge portion of was trimmed and wound up to obtain a biaxially stretched film having a thickness of 100 μm.

The differential curve of the true shrinkage amount in the machine direction of the obtained film is as shown by the characteristic line 8 in FIG. 6, and the physical properties are as shown in Tables 1 and 2. Excellent in transparency and antistatic property, and in the range from glass transition point to 200 ° C,
No peak is observed at 100 to 140 ° C., but a large peak is seen at 170 ° C. or higher. In addition, a decrease in the softening start temperature and an increase in the pin penetration are observed, and the heat shrinkage rate is still large. The flatness could be collected in a relatively good state. When this film was cut into A4 size and passed through a copy machine Vivace 500 manufactured by Fuji Xerox Co., Ltd., the curl was large and a partial slack was generated in the surface, but it was excellent in easy adhesion.

Example 3 In the same manner as in Example 1, a biaxially stretched film which was longitudinally stretched and laterally stretched in a hot air atmosphere of 95 ° C. without coating was continuously heat treated at 250 ° C. in a tenter. And once cooled to 200 ° C. under tension, 200 to 110
Reduce the rail width of the tenter in the slow cooling section at ℃
%, And shorten the tenter clip interval to 2 in the longitudinal direction.
% After relaxing, take out from the tenter, trim the edge parts of both ends of the film and wind it up.
A biaxially stretched film having a thickness of 100 μm was obtained.

The differential curve of the true shrinkage amount in the longitudinal direction of the obtained film is as shown by the characteristic line 9 in FIG. 7, and the physical properties are as shown in Tables 1 and 2. 20 from the glass transition point
In the range up to 0 ° C., no shrinkage peak was observed and a film having a small heat shrinkage rate was obtained. Further, a film having excellent heat resistance and softening property, which is excellent in transparency and flatness and in which softening start temperature and pin penetration is not observed, was obtained, but the film had poorer antistatic property as compared with Example 1. This film is A4
Cut into plates, and copy machine Vivac manufactured by Fuji Xerox Co., Ltd.
When it was passed through e500, it was discharged in a good flatness state in which no curl or partial slack was observed, but the adhesiveness deteriorated.

Example 4 A biaxially stretched film longitudinally stretched, coated and transversely stretched in the same manner as in Example 1 was continuously used in a tenter for 240
After heat treatment at ℃, cool it to 200 ℃ under tension once, and reduce the rail width of the tenter in the slow cooling section of 200 to 110 ℃ to 6% in the width direction. After subjecting the film to a 3% relaxation treatment in the direction, the film was taken out from the tenter, and the edge portions of both ends of the film were trimmed and wound up to obtain a biaxially stretched film having a thickness of 100 μm.

The differential curve of the true shrinkage amount in the longitudinal direction of the obtained film is as shown by the characteristic line 10 in FIG. 7, and the physical properties are as shown in Tables 1 and 2. 200 from the glass transition point
In the range up to ℃, no peak of shrinkage was observed, the heat shrinkage rate was small, the transparency and the antistatic property were excellent, and the film having relatively good flatness was obtained, but it was softened as compared with Example 1. A decrease in onset temperature and an increase in pin habituation were observed. Cut this film into A4 size and copy it with Fuji Xerox Co. V
When it was passed through Ivace 500, some curling and partial slack occurred, but it was excellent in easy adhesion.

COMPARATIVE EXAMPLE 2 A film which had been longitudinally stretched, coated and transversely stretched in the same manner as in Example 1 was continuously heat-treated at 240 ° C. in a tenter and then cooled to 200 ° C. under tension. Two
Reduce the rail width of the tenter in the slow cooling zone of 00 to 110 ° C and perform 5% relaxation treatment in the width direction, take it out from the tenter without performing relaxation treatment in the longitudinal direction and trim the edge parts of both ends of the film. Then, the film was wound up to obtain a biaxially stretched film having a thickness of 100 μm.

The differential curve of the true shrinkage amount in the longitudinal direction of the obtained film is as shown by the characteristic line 11 in FIG. 7, and the physical properties are as shown in Tables 1 and 2. Excellent in transparency and antistatic property.
No peak is observed at 0 ° C. or higher, but in Example 1
A large peak is seen in the vicinity of 100 to 140 ° C. Moreover, the heat shrinkage was large, and a decrease in the softening start temperature and a slight increase in the pin penetration were observed, but flatness could be collected in a good state. When this film was cut into A4 size and passed through a copy machine Vivace 500 manufactured by Fuji Xerox Co., Ltd., the curl was large and a partial slack was generated in the surface, but it was excellent in easy adhesion.

Comparative Example 3 A biaxially stretched film which was longitudinally stretched, coated and transversely stretched in the same manner as in Example 1 was continuously used in a tenter for 250
After heat treatment at ℃, without slowing the width and longitudinal directions after heat treatment, after gradually cooling to 110 ℃, take out from the tenter, trim the edges of both ends of the film and wind it. A 100 μm biaxially stretched film was obtained.

The differential curve of the true shrinkage amount in the longitudinal direction of the obtained film is as shown by the characteristic line 12 in FIG. 8, and the physical properties are as shown in Tables 1 and 2. Excellent in transparency and antistatic property, thermal softening start temperature, pin penetration is not observed, and no peak is observed at 160 ° C or higher in the range from the glass transition point to 200 ° C, but 100 to 140. A large peak was observed near ℃. Further, although the heat shrinkage rate was large, the sample could be collected in a state of good flatness. Cut this film into A4 size and copy it from Fuji Xerox Copier Viv
When it was passed through the ace500, the curl was large, and some of them were jammed in the machine.

Comparative Example 4 In the same manner as in Example 1, the longitudinal stretching ratio was changed to 2.5 times, and the transverse stretching ratio was changed to 2.5 times in a hot air atmosphere of 95 ° C. without coating. The biaxially stretched film thus obtained is then subjected to heat treatment at 250 ° C. in a tenter,
Temporarily cool to 200 ℃ under tension, and reduce the rail width of the tenter by 5% in the width direction in the slow cooling section of 200-110 ℃, and reduce the clip interval of the tenter by 2% in the longitudinal direction. After removing the film from the tenter, trim the edges of both edges of the film and wind it up to a thickness of 1
A biaxially stretched film of 00 μm was obtained.

The differential curve of the true shrinkage amount in the longitudinal direction of the obtained film is as shown by the characteristic line 13 in FIG. 8, and the physical properties are as shown in Tables 1 and 2. 2 from the glass transition point
No peak of shrinkage is seen in the range up to 00 ° C, and
A film having a small heat shrinkage ratio and excellent antistatic properties was obtained, but as compared with Example 1, the molecular orientation was weak, so that the softening initiation temperature was low and an increase in pin penetration was observed. And the transparency and flatness were deteriorated. When this film was cut into A4 size and passed through a copy machine Vivace 500 manufactured by Fuji Xerox Co., Ltd., curling and partial slack were generated, and the adhesiveness was also deteriorated.

[0067]

[Table 1]

[0068]

[Table 2]

[0069]

EFFECT OF THE INVENTION The OHP film of the present invention has a small heat shrinkage ratio, excellent heat softening resistance, transparency and antistatic property, and does not cause curling or partial slack even after passing through a copying machine. It is possible to obtain an OHP film having good flatness and excellent adhesiveness.

[Brief description of drawings]

FIG. 1 is a diagram showing the behavior of thermal expansion and thermal contraction in TMA.

FIG. 2 is a diagram showing a process of obtaining a differential curve of a true shrinkage amount from a TMA measurement curve.

FIG. 3 is a diagram in which a biaxially stretched film produced by a normal method is measured by TMA and converted into a differential curve of a true shrinkage amount.

FIG. 4 is a schematic configuration diagram showing a method for measuring thermal softening property using a thermomechanical property tester.

5 is a characteristic diagram showing an example of thermal softening property obtained by the measurement of FIG.

FIG. 6 is a diagram showing a differential curve of true shrinkage amount by TMA in the machine direction of the films of Examples 1 and 2 and Comparative Example 1.

FIG. 7 is a diagram showing differential curves of true shrinkage amounts of the films of Examples 3 to 4 and Comparative Example 2 in the machine direction by TMA.

FIG. 8 is a diagram showing a differential curve of true shrinkage amount by TMA in the machine direction of the films of Comparative Examples 3 to 4.

[Explanation of symbols]

1 Support Tube 2 Pedestal 3 Sample 4 Metal Pin 5 Detecting Rod P Load 6 Differential Curve of True Shrinkage Amount of TMA in the Machine Direction of Example 1 7 Differential Curve of True Shrinkage Amount of TMA in the Machine Direction of Example 2 8 Differential curve of true shrinkage due to TMA in the machine direction of Comparative Example 9 Differential curve of true shrinkage due to TMA of the machine direction of Example 10 Differential curve of true shrinkage due to TMA in the machine direction of Example 4 11 Differential Curve of True Shrinkage by TMA in Machine Direction of Comparative Example 12 Differential Curve of True Shrinkage by TMA of Machine Direction in Comparative Example 13 Differential of True Shrinkage by TMA in Comparative Example 4 in Machine Direction curve

Claims (6)

[Claims] 1. The heat shrinkage ratio at 30 minutes at 150 ° C. is 0.3%.
In the differential curve of the true shrinkage amount in the longitudinal direction of the film obtained from the expansion / contraction amount at the time of temperature rise / fall by a thermomechanical property tester, the shrinkage amount differential value dL / dT (L: length, T: temperature) is always 0.01% / ° C. or less, and a fine endothermic peak appearing before crystal melting by a differential scanning calorimeter is equal to or lower than melting point,
A film for overhead projector, comprising a biaxially oriented polyester film having a melting point of −30 ° C. or higher and a film haze of 10% or less. 2. The overhead projector film according to claim 1, wherein the pin accelerating start temperature is 115 ° C. or more and the pin accelerating distance is 8% or less of the film thickness in the heat softening test. 3. The overhead projector film according to claim 1, wherein the crystal size of (100) plane by wide-angle X-ray diffraction is 60 angstroms or more and 80 angstroms or less. 4. The equation 1 The film for overhead projector according to any one of claims 1 to 3, wherein the plane orientation coefficient obtained from the X-ray diffraction intensity ratio of the (100) plane is 0.1 or less. 5. An applied voltage of 100 V, 20 ° C., 60% R
The overhead projector film according to claim 1, wherein a surface resistance at H is 1 × 10 ¹¹ Ω / □ or less. 6. The overhead projector film according to claim 1, wherein a toner peeling rate in a toner peeling test is 10% or less.