JPH0691748A - Syndiotactic polystyrene-based biaxially oriented film for overhead projectors - Google Patents

Abstract

(57) [Summary] [Object] The present invention is a syndiotactic polystyrene biaxially oriented film for an overhead projector, and more specifically, for an overhead projector having excellent transparency, running property, abrasion resistance and heat resistance. The present invention relates to a syndiotactic polystyrene biaxially stretched film. [Structure] A light transmittance is 80% or more, a three-dimensional surface roughness S Δa of at least one surface is 0.004 or more and 0.04 or less, and a heat shrinkage ratio at 150 ° C. is 1% or less, Syndiotactic polystyrene biaxially oriented film for overhead projectors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a syndiotactic polystyrene biaxially stretched film for an overhead projector, more specifically, a syndiotactic overhead projector having excellent transparency, running property, abrasion resistance and heat resistance. The present invention relates to a tic polystyrene biaxially stretched film.

[0002]

2. Description of the Related Art Films for overhead projectors are widely used in lectures and presentations, but most of them use a method of printing an image by PPC copying. Since PPC copying is a method in which toner is transferred to the printing material as a medium and is fused and fixed on a heat roll, the film used for PPC copying requires the highest heat resistance among various overhead projector films. Further, in recent years, printing by a thermal transfer method has been increasing, and in this case, heat resistance is required as in PPC copying.
Further, in order to obtain a bright and easily visible projected image, the light transmittance of the overhead projector must be good. Therefore, a polyethylene terephthalate film having excellent transparency and heat-resistant dimensional stability is used for this purpose. However, heat of about 120 ° C. to 130 ° C. is applied to the film, and the heat shrinks the film, which may cause a dimensional change from the original drawing, and the flatness of the film may be extremely deteriorated. This is especially noticeable when the original drawing is of a large size from B4 to A3 groups. As a result, as a second original drawing for design and drafting, PPC
This is one of the reasons why a film made by copying cannot be used. The syndiotactic polystyrene biaxially stretched film satisfies the requirements for heat resistance and transparency required for the overhead projector film base. However, in the syndiotactic polystyrene biaxially stretched film, if it is simply made transparent, the running property and abrasion resistance during the production and processing of the film will be poor. Also,
When a lubricant is added to improve the running property, the syndiotactic polystyrene-based polymer is fragile even if the running property is improved depending on the lubricant used. The internal haze increases due to the voids generated in the gap, and the transparency as a whole is reduced, or the lubricant in which the voids are generated is scraped off and abrasion resistance is reduced. Furthermore, in order to improve heat resistance, it is necessary to raise the heat setting temperature, but as a result, brittleness increases, and white powder is likely to be generated due to scratches or abrasion during running. As a film having good slipperiness, it is known that inorganic particles are added, the surface roughness Ra is in a specific range, and the coefficient of static friction is limited (JP-A-3-74437).
Further, a film excellent in transparency and heat resistance using a syndiotactic polystyrene biaxially stretched film is known (JP-A-1-316246, JP-A-1-168709, JP-A-2-27).
9731).

[0003]

However, in the above-mentioned conventional film having good slipperiness, the syndiotactic polystyrene biaxially stretched film is large in brittleness, so that it was added in order to improve the slipperiness in the stretching step. Voids were likely to be formed around the lubricant, resulting in poor transparency. Further, due to the occurrence of such voids, the surface of the film is likely to be scraped during the production of the film and the use of the product. On the other hand, in the conventional transparent and heat-resistant film, the tension during running of the film is increased due to the smooth surface, scratches are likely to occur, and heat for further improving heat resistance By increasing the fixing temperature, the brittleness increased and the scraping increased. An object of the present invention is to provide a syndiotactic polystyrene-based biaxially stretched film for an overhead projector, which is excellent in transparency, running property, abrasion resistance and heat resistance.

[0004]

The present invention has a light transmittance of 80.
%, And the three-dimensional surface roughness S Δa of at least one side
Is 0.004 or more and 0.04 or less, and the heat shrinkage ratio at 150 ° C is 1% or less, and is excellent in transparency, and good in running property, wear resistance and heat resistance. A tic polystyrene-based biaxially stretched film is provided. The polystyrene polymer with stereoregularity having a syndiotactic structure used in the present invention has a tacticity of diad (two constitutional units) in which a phenyl group or a substituted phenyl group which is a side chain is quantified by a nuclear magnetic resonance method. It is desirable that the syndiotactic structure is 85% or more, and pentad (5 constitutional units) is 50% or more. Examples of the polystyrene-based polymer include polystyrene, poly (p-, m- or o-methylstyrene), poly (2,4-, 2,5-, 3,4- or 3,5-dimethylstyrene), poly (P-tert-butyl styrene)
Such as poly (alkylstyrene), poly (p-, m- or o-
Poly (halogenated styrene) such as chlorostyrene), poly (p-, m- or o-bromostyrene), poly (p-, m- or o-fluorostyrene), poly (o-methyl-p-fluorostyrene) ), Poly (halogen-substituted alkylstyrenes) such as poly (p-, m- or o-chloromethylstyrene),
Poly (p-, m- or o-methoxystyrene), Poly (p-, m-
Or poly (alkoxystyrene) such as o-ethoxystyrene), poly (carboxyalkylstyrene) such as poly (p-, m- or o-carboxymethylstyrene), poly (alkylether) such as poly (p-vinylbenzylpropyl) Styrene), poly (alkylsilylstyrene) such as poly (p-trimethylsilylstyrene), and further poly (vinylbenzyldimethoxyphosphide).

In the present invention, polystyrene is particularly preferable among the polystyrene polymers. Also,
The polystyrene-based polymer having a syndiotactic structure used in the present invention is not necessarily a single compound, and if the syndiotacticity is within the above range, a polystyrene-based polymer having an atactic structure or an isotactic structure is used. It may be a mixture of, a copolymer and a mixture thereof. The polystyrene-based polymer used in the present invention has a weight average molecular weight of 10,000 or more, more preferably 50,000 or more. When the weight average molecular weight is less than 10,000, it is not possible to obtain a biaxially stretched film having excellent strength and elongation characteristics and heat resistance. The upper limit of the weight average molecular weight is not particularly limited, but if it is 1500,000 or more, breakage may occur due to an increase in stretching tension, which is not preferable.

Further, the syndiotactic polystyrene biaxially stretched film of the present invention can be produced by a known method, for example, a sequential biaxial stretching method in which longitudinal stretching and transverse stretching are carried out in order.
A stretching method such as a transverse / longitudinal / longitudinal stretching method, a longitudinal / lateral / longitudinal stretching method, or a longitudinal / longitudinal / lateral stretching method can be adopted. The syndiotactic polystyrene biaxially stretched film in the present invention may be required to have a film having excellent heat resistance at high temperature, and in that case, in addition to the selection of these stretching methods, the stretching conditions have a great influence. Further, in order to obtain excellent heat resistance such that the heat shrinkage rate at 150 ° C. is 1% or less, it is preferable to perform heat setting treatment, longitudinal relaxation treatment, transverse relaxation treatment and the like. The light transmittance, the three-dimensional surface roughness S Δa, the running property, the wear resistance, and the heat resistance are adjusted by the film forming conditions of the film and the lubricant particles. The type and amount of the lubricant particles are not particularly limited as long as the light transmittance, the three-dimensional surface roughness SΔa, the running property and the wear resistance are within the predetermined ranges, but silica, titanium dioxide, talc, Examples are particles that are inert to syndiotactic polystyrene-based polymers such as metal oxides such as kaolinite, salts of metals such as calcium carbonate, calcium phosphate, and barium sulfate, or particles made of organic polymers. Any one of these lubricants may be used alone, or two or more thereof may be used in combination, but the average particle size of the lubricant used is preferably 0.01 μm or more and 3.5 μm or less, The degree of variation (ratio between standard deviation and average particle size) is preferably 25% or less, and the addition amount is 0.005 with respect to 100% by weight of syndiotactic polystyrene polymer.
It is preferably contained in an amount of not less than 2.0% by weight and not more than 1.0% by weight. In addition, it is preferable that the shape of the lubricant particles includes at least one kind having a surface shape factor of 60% or more. This area shape factor is calculated by the following equation. Area shape factor = (projected cross-sectional area of particle / area of circle circumscribing particle) x 100 (%)

The polystyrene-based polymer used in the present invention may contain, if necessary, known compounds such as antioxidants and antistatic agents blended in appropriate amounts. The blending amount is
10% by weight or less is desirable based on 100% by weight of the polystyrene polymer. If it exceeds 10% by weight, breakage tends to occur during stretching, resulting in poor production stability. Further, the syndiotactic polystyrene biaxially stretched film for overhead projector of the present invention, if necessary, various known functions, for example, antistatic, easy adhesion of toner, easy sliding, running scratch resistance, water-based A coating layer having ink fixing and the like can be provided on the surface. This coating layer may be provided by an in-line coating method performed during film formation or an off-line coating method in which coating is performed again after stretching and heat setting of the film are completed. However, the syndiotactic polystyrene type biaxially stretched film for overhead projector in the present invention has a feature that the adhesiveness with a toner which is usually commercially available is very good, and when the demand for the adhesive strength is very strict. Excluding the above, one coating layer required for the polyethylene terephthalate film currently used can be removed, which is advantageous in terms of cost and transparency.

The syndiotactic polystyrene type biaxially stretched film in the present invention needs to have a light transmittance of 80% or more. More preferably, it is 85% or more.
In addition, in an overhead projector application, it is not preferable that the surface haze and the internal haze (per 100 μm) exceed 10%. Here, the surface haze is 4%
The following is preferable. Furthermore, the syndiotactic polystyrene biaxially stretched film of the present invention needs to have a three-dimensional surface roughness S Δa of at least one surface within a range of 0.004 or more and 0.04 or less. If S Δa is less than 0.004, the running property and wear resistance will be poor, and if it exceeds 0.04, the transparency will be decreased, which is not preferable. The heat shrinkage ratio of the syndiotactic polystyrene biaxially stretched film of the present invention at 150 ° C. is 1% or less, preferably 0.5% or less, more preferably 0.3% or less. If the heat shrinkage ratio at 150 ° C. exceeds 1%, dimensional change from the original drawing may occur when printing the original drawing by PPC copying, or the flatness may deteriorate, which is not preferable. Here, since the abrasion resistance becomes poor when the film is exposed to a high temperature for a long time in order to reduce the heat shrinkage rate, a relaxation treatment is performed after the longitudinal stretching treatment, and the heat setting temperature and time are kept within a certain range, Further, if necessary, it is preferable to perform lateral and / or longitudinal relaxation treatment after the heat setting treatment. Here, the longitudinal relaxation treatment after the longitudinal stretching is performed at a stretching temperature or higher and a cold crystallization temperature or lower so that the film after the longitudinal relaxation treatment has a shrinkage rate of 5% or less at 5% or less. 220 ℃ or more,
It is preferable to perform the treatment at a temperature below the melting point within 30 seconds, preferably within 10 seconds, and the relaxation treatment in the horizontal and vertical directions is preferably performed at a temperature not higher than the maximum temperature of the heat setting treatment so that the flatness is not disturbed. As described above, the present invention can provide an excellent film having transparency, running property, abrasion resistance, and heat resistance required for overhead projector applications.

[0009]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation method of the film is shown below. (1) Light transmittance According to JIS-K6714, the light transmittance of the film was determined with a Poic integrating sphere HTR meter SEP-H2D type manufactured by Nippon Seimitsu Optical Co., Ltd. (2) Three-dimensional surface roughness S Δa Using a stylus-type three-dimensional surface roughness meter (SE-3AK, Kosaka Laboratory Ltd.) on the film surface, needle radius 2 μm, load
Cutoff value of 0 in the longitudinal direction of the film under the condition of 30 mg.
Measured at 25 mm over a measuring length of 1 mm, 5 at 2 μm pitch
It is divided into 00 points, and the height of each point is calculated by 3D roughness analyzer (SPA
-11). The same operation was continuously performed 150 times in the widthwise direction of the film at intervals of 2 μm, that is, over 0.3 mm in the widthwise direction of the film, and the data was taken into the analyzer. Next, S Δa was obtained using an analyzer.

(3) Heat shrinkage rate at 150 ° C. The shrinkage rate of the film in a tension-free state in an atmosphere of 150 ° C. for 30 minutes was determined. (4) Average particle size Lubricant particles were observed with Hitachi Ltd. S-510 scanning electron microscope, the photographed one was enlarged and copied, and the external shape of the lubricant was traced to arbitrarily select 200 particles. Was painted black. This image was measured for the Feret diameter in the horizontal direction of each particle using a Luzex 500 type image analyzer manufactured by Nikole Co., Ltd., and the average value was taken as the average particle diameter. Also,
The degree of variation in particle size was calculated by the following formula. Variability = (standard deviation of particle size / average particle size) x 10
0 (%)

(5) Area shape coefficient 20 particles are arbitrarily selected from the trace image used for measuring the average particle diameter, and the projected cross-sectional area of each particle is measured using the image analysis device used in (4). did. Further, the area of the circle circumscribing these particles was calculated and calculated by the following formula. Area shape factor = (projected cross-sectional area of particle / area of circle circumscribing the particle) x 100 (%) (6) Runability and abrasion resistance of film Slit the film into narrow width and rub it against a metal roll to run At this time, the tension of the tape after passing through the guide roll, the occurrence of scratches and the amount of white powder adhering to the roll were evaluated 5 times in a given supply tension, and the results are shown in the following ranking. Runnability evaluation 1st class; large tension, many scratches 2nd class; tension, slightly large, scratches considerably 3rd class; medium tension, slight scratches 4th class; tension, small, almost no scratches 5th class; small tension, no scratches here If the resulting tensions and scratches have different ranks, the worse rank is used. Abrasion resistance evaluation 1st grade: White powder is very much generated 2nd grade: White powder is often generated 3rd grade: White powder is slightly generated 4th grade: White powder is hardly generated 5th grade: White powder is not generated

(7) PPC Copying Characteristics Using a PPS copying machine (RICOPY FT 6860 manufactured by Ricoh Co., Ltd.), a film of A3 size was actually copied, and the deviation from the original drawing was examined. The copying was performed at the same size. The evaluation result was evaluated in four levels and expressed in the following ranking. 1st grade; blockage occurs and copying is not possible 2nd grade; copying is possible, but there is misalignment on the entire surface 3rd grade: misalignment in part of the copy

Example As a lubricant, silica having an average particle size of 1.7 μm, a degree of variation of 20% and an area shape factor of 80% was used in an amount of 0.5 with respect to 100% by weight of syndiotactic polystyrene (weight average molecular weight 300000).
The polymer chips added with the weight% and the polymer chips without the addition of the lubricant were mixed at a weight ratio of 1: 9, dried, melted at 295 ° C., and extruded from a T-die having a 4000 μm lip gap. A 1150 μm amorphous sheet was obtained by sticking to a chill roll at ℃ by the electrostatic loading method and solidifying by cooling. The amorphous sheet is first preheated to 90 ° C. by a roll, four infrared heaters with a surface temperature of 700 ° C. are further heated, and the film is stretched 3.5 times in the machine direction at a film temperature of 130 ° C. and then a ceramic roll of 130 ° C. 12% longitudinal relaxation between metal rolls at 40 ℃
Preheated to ℃ and stretched transversely at a draw temperature of 120 ℃ 3.3 times,
It was heat-set at 260 ° C for 12 seconds. Then, it was subjected to 3% lateral relaxation treatment at 185 ° C, and further subjected to 2% longitudinal relaxation treatment at 175 ° C. The thickness of the obtained film was 100 μm.

Comparative Example The extrusion speed was changed, the thickness of the amorphous sheet was set to 1000 μm, and in the longitudinal stretching, the film temperature was heated to 103 ° C. by a roll, the film was stretched 3.0 times in the longitudinal direction, and heat set at 270 ° C. Was carried out for 30 seconds, and the same operation as in Example was carried out except that the relaxation treatment after the heat setting treatment was not performed. The thickness of the obtained film was 100 μm.

[0015]

EFFECTS OF THE INVENTION The syndiotactic polystyrene type biaxially stretched film for an overhead projector of the present invention adopts the constitution as set forth in the above-mentioned claims so that the transparency, the running property, the abrasion resistance and the heat resistance can be improved. It can be said that the film is a syndiotactic polystyrene-based biaxially stretched film useful as a film for an overhead projector having excellent properties. In addition, even when copying with a PPC copier, there is almost no deviation from the original drawing due to shrinkage, and there is no deterioration in flatness, so it can be used as a second original drawing for design and drafting. Further, since the adhesiveness with the toner is good, the coating for easy adhesion is unnecessary, and therefore it is excellent in transparency and cost. Thus, the industrial value of the film of the present invention is high.

[0016]

[Table 1]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location B29K 105: 32 B29L 7:00 4F (72) Inventor Tadashi Okuhira 2-1-1 Katata, Otsu City, Shiga Prefecture No. 1 Toyobo Co., Ltd.

Claims (1)

[Claims] 1. A light transmittance of 80% or more, a three-dimensional surface roughness S Δa of at least one surface of 0.004 or more and 0.04 or less, and a heat shrinkage ratio at 150 ° C. of 1% or less. A biaxially stretched syndiotactic polystyrene film for overhead projectors.