JP5082274B2 - Sheet molding method - Google Patents

Description

  The present invention relates to a sheet molding method for imparting a curved shape to a sheet for an optical screen, for example, a transmission screen of a projection television.

An optical screen such as a transmissive screen of a projection television is usually constituted by a sheet such as a Fresnel lens sheet, a lenticular lens sheet, or a front panel. In general, a configuration in which a Fresnel lens sheet and a lenticular lens sheet are superposed is employed. In recent years, a configuration in which a front panel is further superposed is employed for the purpose of protecting these lens sheets.
In the above-described optical screen, a phenomenon called “floating” occurs between sheets due to temperature and humidity changes in the installation environment, which may cause problems such as a reduction in image resolution. In order to solve this problem, a method of imparting warpage to the sheet is known for the purpose of improving the adhesion between the sheets.

As a method of imparting warpage to the sheet, a method of extruding the sheet into a curved shape and then heating it on a mold having a curved shape (see Patent Document 1), placing the sheet on a concave curved mold. A method of performing a heat treatment for a specific time at a temperature 5 to 20 ° C. lower than the heat deformation temperature (see Patent Document 2), and placing a sheet heated to a temperature higher than the plastic deformation temperature by infrared rays between the concave warp mold and the convex warp mold A method of cooling while pressing is known (see Patent Document 3).
However, the curved sheet obtained by the conventional method may cause deformation of the attached shape, or the curved shape may be insufficient. In response to the recent demand for higher performance, there is a demand for a sheet molding method capable of obtaining a curved sheet that is sufficiently molded and in which a change in the molded shape is suppressed.
Japanese Patent Laid-Open No. 11-216773 JP 2003-5295 A JP 2004-252292 A

  It is an object of the present invention to provide a sheet molding method for obtaining a curved sheet that is sufficiently molded and in which a change in the molded shape is suppressed.

The present invention relates to a sheet forming method for imparting a curved shape to a sheet mainly composed of a thermoplastic resin. The sheet is placed on a concave curved mold and an infrared heater is used to increase the output of the infrared heater. While gradually changing to a low output, after heating to a temperature in the range of 20 ° C. lower than the thermal deformation temperature of the sheet to the thermal deformation temperature over at least 30 seconds , a convex curved mold is placed on the pair of curved molds A sheet forming method characterized by providing a curved shape while cooling with a sheet interposed therebetween .
In addition, this molding method is preferably applied when the sheet is a surface-treated antiglare plate or when the surface treatment is a hard coat treatment.

  By the method of the present invention, it is possible to obtain a sheet having a curved shape that is sufficiently shaped and in which a change in the shaped shape is suppressed.

  Hereinafter, the present invention will be described in detail. The sheet provided for the method of the present invention is composed of a thermoplastic resin, and usually a sheet mainly composed of a highly transparent thermoplastic resin is used. Examples of the thermoplastic resin include acrylic resins such as methyl methacrylate polymer, methyl methacrylate-methyl acrylate copolymer, methyl methacrylate-styrene copolymer, methyl methacrylate-styrene-butadiene copolymer. Moreover, polycarbonate resin etc. are mentioned and those 2 or more types can also be used as needed. These resins may be rubber reinforced, and various additives such as light diffusing agents, antioxidants, plasticizers, mold release agents, colorants, antistatic agents, ultraviolet absorbers, flame retardants, etc. May be one or more added depending on the purpose.

  The above-mentioned sheet is for constituting an optical screen such as a transmissive screen of a projection television. For example, a sheet-like screen constituting member such as a Fresnel lens sheet, a lenticular lens sheet, and a front panel, and the like are manufactured. For example, a sheet-like base material used as an original plate is used.

  As the Fresnel lens sheet, for example, it may be obtained by cast molding, or may be obtained by imparting a Fresnel lens shape by press molding to a sheet-like substrate obtained by extrusion molding, An ultraviolet curable resin may be cured on the surface of the sheet-like substrate so as to form a Fresnel lens shape.

  Moreover, as the lenticular lens sheet, for example, it may be obtained by extrusion molding or cast molding, or may be a sheet-like base material provided with a lenticular lens shape by press molding, It may be obtained by bonding a film having a lenticular lens shape formed on the surface with an ultraviolet curable resin to a sheet-like substrate.

  Further, the front panel may be obtained by, for example, extrusion molding or cast molding, or may be subjected to surface treatment such as hard coating or low reflection coating.

  Furthermore, surface processing such as a surface mat, a prism, a lenticular lens, and a linear Fresnel lens may be applied to the sheet-like base material (Fresnel lens original plate) and the front panel for the Fresnel lens.

  Further, as the sheet, a sheet having a fine unevenness on the surface and having an antiglare surface can be used. As a method for producing this antiglare sheet, for example, an extrusion roll transfer molding method in which irregularities are formed on the surface of the resin immediately after being extruded into a plate shape from a die in a heated and melted state using a roll having irregularities on the surface, Examples thereof include an injection molding method in which a resin is injected into a mold having irregularities on the inner surface and a casting molding method in which a raw material monomer is polymerized in a cell having irregularities on the inner surface.

  It can also be produced by an extrusion method in which insoluble resin particles are dispersed in a thermoplastic resin to obtain a thermoplastic resin composition, which is heated and extruded from a die in a molten state. The extruded thermoplastic resin composition extruded from a die has fine irregularities formed by insoluble resin particles on the surface thereof, whereby an antiglare substrate surface can be obtained.

  The insoluble resin is a resin particle that can be dispersed in the thermoplastic resin in the form of particles without melting itself even if the thermoplastic resin is heated together with the thermoplastic resin and melted. As the insoluble resin particles, cross-linked particles can be used. Specifically, when MS resin is used as the resin constituting the base material, methyl methacrylate and styrene and a functional group capable of radical polymerization can be used. Examples thereof include those obtained by copolymerizing two or more polyfunctional monomers. The particle diameter of the insoluble resin particles is usually 10 μm or more when sufficient antiglare properties are imparted.

The amount of insoluble resin particles used varies depending on the extrusion conditions, particularly the cooling conditions after extrusion, but is, for example, about 5 to 15 parts by mass per 100 parts by mass of the resin constituting the substrate.
The insoluble resin particles may exist uniformly in the thickness direction of the base material, but the surface layer in which the insoluble resin particles are dispersed and the base material layer that does not contain the insoluble resin particles or has a lower content than the surface layer. Is preferable because it can reduce the amount of insoluble resin particles used. A substrate having such a multilayer structure is produced as a two-layer two-layer board by, for example, a multilayer extrusion molding method in which a thermoplastic resin composition in which insoluble resin particles are dispersed and a thermoplastic resin not containing insoluble resin particles are coextruded. can do.

Further, examples of the sheet include a surface-treated sheet such as a hard coat on one or both sides of the sheet surface.
As the hard coating agent, various types of energy ray curable hard coating agents that are cured by irradiation with energy rays such as ultraviolet rays and various thermosetting hard coating agents that are cured by heating are known. However, for example, when MS resin is used as the resin constituting the base material, it contains a curable compound having an aromatic ring and a (meth) acryloyloxy group in the molecule, and per aromatic ring Hard coating agent containing 3 or more (meth) acryloyloxy groups [Patent Document: Japanese Patent Application Laid-Open No. 2004-1372], curable compound having an alicyclic ring and a (meth) acryloyloxy group in the molecule And a hard coat agent comprising a curable compound having three or more (meth) acryloyloxy groups in the molecule or an oligomer thereof [Patent Document: JP 003-311891 JP] like it is preferably used. The (meth) acryloyloxy group means a methacryloyloxy group or an acryloyloxy group. By applying such a hard coat agent, a surface treatment film can be formed as a hard coat film.

  As the solvent that can be used for the surface treatment, any solvent that can dissolve the surface treatment agent and can be volatilized after coating may be used, for example, methanol, ethanol, 2-propanol, 1-methoxy-2-propanol, 4- Alcohols such as hydroxy-4-methyl-2-pentanone, acetone, 2-butanone, ketones such as 4-methylpentanone, aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate These may be used alone or in combination of two or more. The content of the solvent in the surface treatment liquid is usually about 50% by mass to 80% by mass, preferably about 60% by mass to 70% by mass based on the surface treatment liquid.

  For example, fine particles of a conductive inorganic compound may be dispersed in the surface treatment liquid. The particle diameter of the fine particles is, for example, 0.1 μm or less [Patent Document 1: Japanese Patent Laid-Open No. 2004-1372, Patent Document 2: Japanese Patent Laid-Open No. 2003-311891]. By using a surface treatment liquid in which such fine particles are dispersed, an antistatic surface treatment film is formed, and an antistatic surface-treated antiglare plate can be obtained.

In order to apply the surface treatment liquid to the antiglare surface of the antiglare substrate, for example, a dip coating method in which the entire antiglare substrate is immersed in the surface treatment liquid, a spray that sprays and attaches the surface treatment liquid to the antiglare surface The coating method may be applied by a coating method such as a bar coating method or a roll coating method in which the surface treatment liquid is extended by a bar or roll on the antiglare surface.
The coating amount of the surface treatment liquid may be an amount necessary for forming the target surface treatment film. For example, the surface treatment liquid (C) of about 10 g / m 2 to 25 g / cm 2 may be applied per unit area. .

  Depending on the coating method, an excessive amount of the surface treatment liquid may be applied to the antiglare surface. In this case, the excess amount may be removed. In order to remove the excess, for example, when contact is made by the dip coating method, the antiglare substrate may be pulled up from the surface treatment liquid, and after the pulling up, further compressed air is blown to blow off the excess. May be removed. When contact is made by the spray coating method, the spraying of the surface treatment liquid may be stopped, and after the spraying is stopped, compressed air or the like may be further sprayed to remove the excess. When the coating is applied by the bar coating method or the roll coating method, the surface treatment liquid on the antiglare surface may be further extended by the bar to remove the excess. In this way, by removing the excess surface treatment liquid, an amount of the surface treatment liquid suitable for forming the target surface treatment film can be applied on the antiglare surface.

  The coating temperature may be a temperature at which the surface treatment liquid does not cure and the solvent does not volatilize and can be applied to the surface treatment liquid, and is usually about 0 ° C to 40 ° C.

  After coating, the solvent can be volatilized by drying, and cured as necessary to form the target surface treatment film. In order to volatilize the solvent, a method of air-drying at room temperature as it is, a method of heating and drying, a method of volatilizing under reduced pressure, and the like can be mentioned. The curing method varies depending on the type of the surface treatment agent. When an energy ray curable surface treatment agent is used, it is sufficient to irradiate the energy beam. The intensity and irradiation time of the energy beam are used for the surface treatment used. It is appropriately selected depending on the type of agent and the average film thickness. In addition, when a thermosetting surface treatment agent is used, it may be heated, and the heating time, heating temperature, and the like are appropriately selected depending on the type of surface treatment agent used, the average film thickness, and the like. Curing may be performed after the solvent is volatilized or may be performed simultaneously with the volatilization of the solvent.

FIG. 1 is a schematic view showing an example of a molding apparatus used in the present invention.
The sheet 1 is placed on the concave curved mold 2 that is conveyed by the roller conveyor 8 in the stacking machine 4. The concave curved mold 2 on which the sheet 1 is placed is conveyed to the heating chamber 5 by the roller conveyors 8 and 9, and the sheet 1 is heated by the infrared heater 6. The concave curved mold 2 on which the heated sheet 1 is placed is unloaded from the heating chamber 5 by the roller conveyors 9 and 10, and then the convex curved mold 3 is placed on the concave curved mold 2 on which the sheet 1 is placed. Is lowered, and a curved shape is imparted while cooling by sandwiching the sheet 1 between a pair of curved molds. Thereafter, the convex curved mold 3 is raised, and the concave curved mold 2 on which the sheet 1 with the curved shape is placed is conveyed by the roller conveyors 10 and 11, and the sheet 1 with the curved shape is taken out by the stacking machine 4. .

The sheet is preferably heated with an infrared heater since temperature control is easy and the sheet can be heated uniformly. In particular, those that mainly emit far infrared rays are preferable because they can be heated more quickly and uniformly.
In the heating of the sheet, the sheet is heated to a temperature in the range of about 20 ° C. lower than the heat deformation temperature of the sheet to a temperature substantially equal to the heat deformation temperature (hereinafter sometimes referred to as heating temperature). When the heating temperature of the sheet is lower than the temperature about 20 ° C. lower than the thermal deformation temperature, the provision of the curved shape becomes insufficient, and when the heating temperature exceeds approximately the thermal deformation temperature, the return rate of the attached curved shape increases. The change in the glossiness of the substrate surface, which is an index of antiglare property, is also unfavorable. This temperature is a value obtained by measuring the surface temperature of the sheet using a surface thermometer.
Further, when the temperature is set to the above temperature, it is not preferable to rapidly heat the mold because the molding rate decreases, and in the case of a normal sheet, it takes at least about 30 seconds. This time is up to about 120 seconds. Even if it is long, the effect corresponding to it cannot be obtained.

  When heating, it is preferable to increase the infrared heater output first and decrease the output stepwise. Depending on the capacity of the heater, the position of the heater, etc., for example, the output is 100 to 90% up to 91% of the heating temperature, the output is 90 to 80% and 97% up to 93%. Up to 80% to 70% output, and up to the final 100% temperature, the output is performed with a heating pattern of 70% to 60%.

By heating the sheet to the above temperature on the concave curved mold, the sheet approaches the curved shape of the concave curved mold, but finally the curved shape is sandwiched between the concave curved mold and the convex curved mold while cooling. Is granted.
At this time, it is not necessary to apply a special pressure between the concave curved mold and the convex curved mold, and pressing by the weight of the convex curved mold may be used. Further, the cooling is not necessarily performed by cooling the curved mold, and the sheet is naturally cooled by holding the sheet between the concave curved mold and the convex curved mold for about 3 to 10 minutes, preferably about 4 to 7 minutes. To do.

  The curved shape is a shape in which one direction of the rectangular sheet is curved or a shape in which the whole is curved, and when the arc length is 700 to 800 mm, the arc height is about 20 to 50 mm, but is not limited thereto. It is not a thing.

  Although FIG. 1 shows an example in which one sheet is molded, a plurality of sheets can be placed and molded at once.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

An antistatic hard coat antiglare plate (thermal deformation temperature: 100 ° C.) having a length of 750 mm and a width of 300 mm was used as a sheet to give a curved shape.
Evaluation of the obtained sheet molding was performed by the following method.
(1) Deflection rate (%)
The obtained sheet molding was placed upright, the arc height at that time was measured, and the ratio with respect to the arc height of 35 mm was determined.
(2) Warpage return rate (%)
The obtained molded sheet was annealed (heated in a hot air oven at 80 ° C. for 30 minutes under no load), and then the arc height was measured to obtain the return rate.
Warpage return rate = {[Arc height (after molding) −Arc height (after annealing)] / [Arc height (after molding)]} × 100
(3) 60 ° gloss (gloss)
It measured using the gloss meter [Minolta Co., Ltd. make, "GM-268"].
(4) Glossiness change The average value of the glossiness at four positions of 135 mm, 295 mm, 455 mm and 615 mm from one side in the length 750 mm direction is obtained at a position 90 mm from one side in the 300 mm width direction of the sheet. Thus, the glossiness change (after molding-before molding) and the glossiness change (after annealing-before molding) were determined.

  The antistatic hard coat antiglare plate is made of a copolymer resin of methyl methacrylate (60% by weight) and styrene (40% by weight) (“SUMIPEX HS” manufactured by Sumitomo Chemical Co., Ltd.) with insoluble resin particles [ A substrate (thickness: about 2.1 mm) containing a polymer containing methyl methacrylate and styrene as main components) is converted into dipentaerythritol hexaacrylate [Shin Nakamura Chemical Co., Ltd., “NK Ester A-9530”], 2, 2'-bis (4-acryloyloxydiethoxy) phenylpropane-2-propanol [Kyoeisha Chemical Co., Ltd., "Light Acrylate BP-4EA"], scratch-resistant paint mainly composed of 2-methyl-1-propanol Immersion in an antistatic hard coat paint in which diantimony pentoxide dispersion [Sb2O5, Catalyst Chemical Industry Co., Ltd., "ELECOM PC-14"] was added to And cloth, drying, curing by ultraviolet irradiation, antistatic in the surface hard coat film: is obtained (having a thickness of approximately 5 [mu] m).

The concave curved type and the convex curved type are made of a SUS304 plate having a thickness of 2 mm, the radius of curvature is 2303 mm, the arc length is 800 mm, the arc height at 750 mm is 35 mm, and the sheet length A curved shape only in the 750 mm direction was used. The curved type is such that the plate is supported on the surface by ribs and the thickness is about 50 to 100 mm as a whole.
The above sheet is placed horizontally on the concave curved mold with the surface-treated surface facing up, and a far infrared radiation type quick response heater (manufactured by Asano Seisakusho) (with a surface thermometer) is used in Table 1 from above. Heated under the conditions indicated.
The distance from the heater panel surface to the sheet upper surface was about 180 mm. The heater panel temperature at an output of 100% was set to 600 ° C.

In the heating pattern A, the heater output is 90% until it reaches 91% of the target heating temperature, the heater output is 80% from 91% to 93%, the heater output is 70% from 93% to 97%, and 97%. From 100% to 100% is when the heater output is heated at 60%.
In the heating pattern B, the heater output is 100% until it reaches 91% of the target heating temperature, the heater output is 90% from 91% to 93%, the heater output is 80% from 93% to 97%, 97 From 100% to 100% is when the heater output is heated at 70%.

  After the sheet temperature reached a predetermined temperature, heating was stopped, a convex curved mold was placed on the sheet, the sheet was sandwiched between a pair of curved molds, held for 5 minutes, and naturally cooled to give a curved shape. . The results are shown in Table 1.

  If the heating is higher than the heat deformation temperature, the warping return rate becomes too large, that is, the shape is greatly deformed and the change in glossiness is also unfavorable. In addition, when the heating time to the heating temperature is less than 30 seconds, the warping die rate is lowered because the temperature does not rise uniformly to the lower surface of the sheet.

It is a schematic diagram which shows an example of the shaping | molding processing apparatus used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sheet 2 Concave curve type 3 Convex curve type 4 Stacking machine 5 Heating chamber 6 Infrared heater 7 Stacking machine 8, 9, 10, 11 Roller conveyor

Claims (3)

A sheet forming method that gives a curved shape to a sheet mainly made of thermoplastic resin. The sheet is placed on a concave curved mold, and the output of the infrared heater is stepped from high output to low output by an infrared heater. And at least 30 seconds, the sheet is heated to a temperature in the range of 20 ° C. lower than the heat deformation temperature of the sheet to the heat deformation temperature, and then the convex curved mold is placed between the pair of curved molds. A method for forming a sheet, characterized in that a curved shape is imparted while being cooled in a step. Sheet molding method according to claim 1, wherein the sheet is a surface treated antiglare plate. 3. The sheet molding method according to claim 2, wherein the surface treatment is a hard coat treatment.

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