JPH02146501A - Highly accurate lenticular lens - Google Patents

Abstract

PURPOSE:To improve the toughness of the lens by consisting the lens of an ultra-high mol. wt. acrylic resin having 300,000 weight average mol. wt., biaxially orienting the resin at >=2 times the stretching magnification by area under >=10kg/cm<2> average orientation release stress and forming the lens to <=0.8mm pitch. CONSTITUTION:The lenticular lens is formed by heating the sheet, which is formed by biaxially stretching the ultra-high mol. wt. acrylic resin having 300,000 weight average mol. wt. to >=2 times stretching magnification by area, to the temp. higher than the glass transition point of the acrylic resin by means of lenticular dies and pressurizing the sheet to compressively mold the sheet so as to substantially obviate the generation of shrinkage, cooling the sheet and taking the sheet out of the dies. The sheet is subjected to a high degree of the biaxial orientation under >=10kg/cm<2> average orientation release stress. The sheet is heated to the high temp. higher by >=20 deg.C than the glass transition point of the resin and is molded under pressurization in order to transfer the surface of the lenticular lens exactly from the die surface. The highly accurate lenticular lens having the high toughness is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Minute Hand] The present invention is a high-definition lenticular lens with excellent optical properties and toughness, and is used in reflective or transmissive high-definition video gloss screens, etc. be done.

[Conventional technology]

Acrylic resins are currently mainly used for lenticular lenses used in video globulation screens and the like, as they require advanced optical properties.

〔Problems to be solved〕

However, in order to accommodate broadcasting such as high-definition television, the pitch of the lenticular lens is required to be reduced.
Inevitably, lenticular lenses are required to be made thinner.

Acrylic resin is the most preferable material for these screens and filters due to its optical properties, but thin sheets of acrylic resin are brittle, and the use of lenses made of thin sheets poses a problem. It is presumed that acrylic resin becomes significantly tougher by being biaxially stretched, and thin lenses that have been biaxially stretched can be used favorably for these purposes. However, in general, when a synthetic resin @ biaxially stretched sheet is sandwiched between a lens mold and compression molded at a high temperature above the glass transition temperature of the resin, the biaxial orientation of the sheet is significantly relaxed, and the stretching effect is significantly reduced. It was generally said that the

The present invention is a high-definition lenticular lens in which biaxial orientation is maintained and the stretching effect is maintained.

[Means and effects for solving the problems] As a result of various studies on molding methods to achieve the above object, the present invention was arrived at.

That is, the present invention is made of an ultra-high molecular weight acrylic resin with a weight average molecular weight of 300,000 or more, an area ratio stretching ratio of 2 times or more, and an average orientation release stress of 1.
Provided is a high-definition lenticular lens that is biaxially oriented at 107G/Cl1l'' or more and has a tightness of 0.8n or less.

The acrylic resin mentioned here is methyl methacrylate (
It is a polymer whose main component is MMA (hereinafter abbreviated as MMA), a copolymer containing Nagibutsu (hereinafter abbreviated as PMMA), a copolymer containing Nagibutsu, and the like to which various blends are added.

A copolymer of copolymer and alkyl acrylate (hereinafter abbreviated as Co (MMA-AA)) can be favorably used as the copolymer. As the alkyl acrylate, 1 to 1 oxts copolymers such as methyl acrylate, ethyl acrylate, brol acrylate, butyl acrylate, and 2-ethylhexyl acrylate can be used favorably. Rabbit Buddha
Heat-resistant acrylic resins such as maleic anhydride-styrene ternary copolymer, Nagibutsu-methyl methacrylic acid, and mido copolymer can also be used satisfactorily. In addition, one or more copolymers of styrene, styrene derivatives, acrylonitrile, methacrylonitrile, acrylic acid, and methacrylic acid can also be used. Additives such as various light diffusing agents can be added to the acrylic resin. As the diffusing agent, fine particles that are transparent and have a refractive index different from that of the acrylic resin can be used. For example, glass, barium sulfate, calcium carbonate, dialkyl sila/polymer, etc. can be used favorably. These light diffusing agents may be uniformly blended into the lenticular lens, or may be unevenly distributed on either one surface side.

The ultra-high molecular weight synthetic resin @ described in the present invention is a polymer having a weight average molecular weight of 300,000 or more, preferably 500,000 or more, more preferably 1,000,000 or more and 1,000,000 or more.
It is one combination of less than 10,000. In a 1@r form with a coulometric average molecular weight of less than 300,000, molecular chains break out during heating9 and orientation relaxation occurs. When the number of molecules exceeds 10 million, the moldability gradually deteriorates. Ultra-high molecular weight acrylic resin can be easily produced using the cell casting method.

The stretching magnification of the biaxially oriented lenticular lens of the present invention is:
It is necessary to have an area ratio of 2 times or more, preferably 3 times or more, 1
It is 0 times or less. If the stretching ratio is less than 2 times, the stretching effect will not appear, and if it is 3 times or more, the impact strength etc. will be greatly improved.

The average orientation release stress (
Hereinafter abbreviated as ORB, a high degree of biaxial orientation of 101C19/1m" or more is applied. More preferably 15 to 4
1F/ffi" OR8. The ORB measurement method is A8
Measured at 160°C in accordance with TMD 1504.

The oriented molecules of the oRsh film and sheet are heated
9. Stress that occurs when trying to return to the original state, and indicates the degree of distribution.

The 2''-axis orientation described herein refers to uniform orientation in two axial directions, and includes slight differences in OR8 and stretching ratio in the two axial directions. A multiaxially oriented sheet that is uniformly oriented in each direction is optically uniform and can be used well in the present invention.A multiaxially oriented sheet is generally included in a biaxially oriented sheet, and the present invention It is also included in the biaxially stretched sheet of the invention.

The lenticular lens of the present invention has a pitch of 0.8 ats.
It is a high-definition lens as shown below, preferably a lens with a depth of 0.611 or less. There are various types of lenticular lenses, but all of the lenticular lenses used in video projection screens etc. can be used. Preferably, the lens is a thin lenticular lens, the thickness is QJ3+m or less, and the pitch is 0.8.
The lens has a thickness of 0.6 mm or less, and more preferably has a thickness of 0.6 mm.
This is a lens with a 0.6111 or less edge. Particularly preferably, it is a thin lens whose front and back surfaces are lenticular lenses.

The lenticular lens of the present invention can be well molded by the following method. That is, a sheet obtained by biaxially stretching an ultra-high molecular weight acrylic resin with an xi average molecular weight of 300,000 or more at an area ratio stretching ratio of 2 times or more is heated to a temperature of 20° C. or more above the glass transition temperature of the acrylic resin using a lenticular mold. It can be molded by compression molding by heating and pressurizing at a high temperature so as not to substantially cause shrinkage, and after cooling, it is taken out from the mold.

In general synthetic resins, when 11 compressed in a mold is heated above the lath transition temperature, the dipolymer chains slip due to molecular movement, V stress relaxation occurs, and the degree of orientation decreases. On the other hand, in ultra-high molecular weight synthetic resins, the polymer chains are sufficiently intertwined, making it difficult for the polymer chains to slip out, and therefore the degree of orientation is unlikely to decrease even when heated above the glass transition temperature. This discovery led to the present invention. It is important to use a biaxially oriented sheet of ultra-high content synthetic resin.

Gitsuchi [1,8JJ, In order to accurately transfer the fine lenticular lens surface shown below from the mold surface, it is necessary to heat and pressure mold at a temperature 20°C higher than the glass transition of the resin. There is. It is preferable to mold by heating at a temperature of preferably 306 C or above and 1 below the decomposition temperature. During compression molding, it is necessary to mold the biaxially stretched sheet without causing substantial shrinkage, so the compressed material is heated in a mold, molded, and cooled before being removed from the mold. .

125°C to 250°C for PMMA biaxially oriented sheets
Compression molding is preferable. Furthermore, in the present invention, compression molding is preferably carried out under vacuum.

Biaxially stretched sheet of ultra-high molecular weight synthetic resin is disclosed in JP-A-60-1
It can be molded by the press stretch molding method shown in No. 90331 or the like. That is, in the method of forming an oriented molded product by compressing a synthetic resin base material in a compression die, 1. Two or more layers of thermoplastic resin base materials are laid together in a non-adhesive manner in a die. @, 2. Make the interface between the inner surface of the die and the surface of the resin base lubricated, 3. Orient the resin base by compressing it at a temperature above the glass transition temperature and below the melting point of the resin base, 46. After cooling, take it out from inside the die. A compression molding method for oriented molded products can be used, in which two or more molded products are obtained by mutually peeling oriented molded products formed from each base material.

Example 1 (Formation of biaxially stretched PMMA sheet) Weight average molecular weight of 2,000,00002 polymerized by cell casting method
am thick PMMA sheet with smooth surface (glass transition temperature 1
05°C) is used as a resin base, 10 sheets of the base are stacked, and a release sheet of polypropylene 2 is placed on the interface of each base.
A 0 μm thick interface sheet was placed, and the 10-ply thick-walled base was vacuum-packed with the above polypropylene sheet to provide a base for pressure @biaxial orientation molding. Apply polydimethylsiloxane to the inner surface of the compression die, and heat the compression die and resin base to 150℃.
The film was heated to , compressed to cause a plug flow, and biaxially oriented with an area ratio of 4 times. After the compression die is cooled and the biaxially oriented molded product is cooled, the molded products are taken out from the compression die, each molded product is peeled off from each other, and the polypropylene is further peeled off to form a smooth surface Q, with an area of 5 gu + thickness. Ten PMMA biaxially oriented sheets with a stretching ratio of 4 times were obtained.

Molded Q, 5gi thick PMMA biaxially oriented sheet O
R8 was 24JC9/α2.

Similarly, a 2n thick sheet of I-methyl acrylate copolymer (methyl acrylate 5 copolymer, glass transition temperature 95°C) with a weight average molecular weight of 130,000 was biaxially stretched to a four times the area ratio, Q, 5ii+ A thick biaxially oriented sheet was obtained.

(Compression molding of Fresnel lens) 0.51 pitch high-definition Fresnel lens mold
0 thickness acrylic resin sheet yal-scissors, entire mold?
After creating a vacuum, the temperature was raised to 11,140°C by applying a compressive force, a high compressive force of 1 kg/2 was applied to the resin sheet, held for 10 minutes, and then cooled to 50°C to form a molded product. Remove from the mold and check the mold surface! We obtained a high-definition Fresnel lens that was fully reproduced.

The following sheet was used as the acrylic resin sheet.

(A)i! A biaxially stretched sheet with an average molecular weight of 2 million, +
B) Biaxially stretched sheet with weight average molecule: bt 130,000,
(C) Non-oriented sheet with mt average molecular weight 130,000, falling weight impact strength of molded Fresnel lens and 0R8t Measurement method shown below, fixed: 5 inch diameter frame height = 0.5 corner, natural fall) : 3/4 inch R During lens molding, the glass transition temperature of PMMA (105°C
Even though the temperature was 35° C. higher than that of lens (A), the lens of (A) had a high OR8, the degree of biaxial orientation was sufficiently maintained, and it exhibited excellent falling weight impact strength.

Example 2 The biaxially stretched sheet (A) with a weight average molecular weight of 2,000,000 shown in Example 1 and the biaxially stretched sheet (B) with a weight average molecular weight of 130,000 were used, and substantially no shrinkage occurred. After heating and compression molding without letting the material cool, the product was taken out from the mold, and the falling weight impact strength was measured, and the results are shown in the table below.

Sheet (4) having a weight average molecular weight of 2 million showed almost no decrease in falling weight impact strength even when heated and compression molded at temperatures above the glass transition temperature. (B) with a weight average molecular weight of 130,000
The falling weight impact strength of the sheet was significantly reduced by heating and compression molding at temperatures above the lath transition temperature, resulting in a brittle sheet close to that of a non-oriented acrylic sheet.

〔Effect of the invention〕

FX and optical display devices become larger on high-definition televisions, etc.
Screens and filters using lenticular lenses used in these display devices also become larger. On the other hand, the lenticular lenses used in these screens and filters have become thinner, and therefore stronger screens and filters are required. By providing fine lenticular thin 2eχ, we can meet the above requirements. It is li plus.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] Made of ultra-high molecular weight acrylic resin with a weight average molecular weight of 300,000 or more, biaxially oriented with an area ratio stretching ratio of 2 times or more, an average orientation release stress of 10 kg/cm^2 or more, and a pitch of 0.8 mm or less. High-definition lenticular lens