JP2007178996A - Lens sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens sheet with good productivity and good dimensional stability at high temperature. <P>SOLUTION: The lens sheet is obtained by forming an optical element on at least one surface of a transparent substrate formed of a polyester resin consisting of diol units 1-80 mol% of which are diol units having a cyclic acetal skeleton and dicarboxylic acid units. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lens sheet used in a liquid crystal display device used as a display of a notebook personal computer, a liquid crystal television or the like, and in particular, a lens sheet using a film made of a polyester resin as a transparent substrate.

  In recent years, color liquid crystal display devices have been widely used in various fields as portable notebook personal computers, desktop personal computer liquid crystal monitors, liquid crystal television or car navigation monitors, mobile phone monitors, and the like. Since the liquid crystal itself is not a self-luminous element, a device that shines light from the back side called a backlight is used. This backlight is composed of a fluorescent tube, a light guide plate, a reflection sheet, a prism sheet, and the like. Among these, the prism sheet is arranged on the light emitting surface of the light guide plate and improves the optical efficiency of the backlight to improve the brightness. For example, an optical device in which prism rows having a triangular cross section are arranged in parallel. An element is a prism sheet formed on a resin surface. In addition, a lens sheet (Fresnel lens sheet) in which an optical element having a Fresnel lens portion formed in a concentric Fresnel lens shape on the resin surface may be used. In some cases, a lens sheet (lenticular lens sheet) in which an optical element having a lenticular lens portion in which a plurality of cylindrical lens rows are formed in parallel is formed on the resin surface is used. The prism sheet, the Fresnel lens sheet, and the lenticular lens sheet are referred to as a lens sheet.

In general, a prism sheet is made by injecting an active energy ray-curable resin into a mold having a predetermined prism pattern, overlaying a transparent substrate thereon, and then irradiating the active energy ray through the transparent substrate. Is obtained by curing. As the transparent substrate, a stretched heat-set polyethylene terephthalate film (O-PET) is often used because of mechanical strength, cost, transparency, and the like (see, for example, Patent Document 1). However, since heat shrinkage may occur due to irradiation heat at the time of curing, it corresponds to a reduction in the amount of irradiation energy, which is one reason why productivity is not improved. In addition, the production of O-PET is complicated and involves many processes such as melt extrusion, stretching, and heat setting (see, for example, Patent Document 2). In addition, O-PET must be thickened from the standpoint of dimensional stability when used in applications exposed to high-temperature environments such as car navigation monitors and mobile phone monitors mounted on vehicles. It has become a hindrance to thinning.
JP-A-10-197702 JP 2004-131728 A

  In view of the above problems, an object of the present invention is to provide a lens sheet having good productivity and high dimensional stability at a high temperature by using a transparent substrate made of a polyester resin having excellent heat resistance.

As a result of intensive studies, the present inventors have found that the transparent substrate is a film formed by melting T-die extrusion method using a polyester resin in which 1 to 80 mol% of diol units are composed of a diol unit having a cyclic acetal skeleton and a dicarboxylic acid unit. It has been found that the above problems can be solved by using a polyester film.
That is, according to the present invention, an optical element is formed on at least one surface of a transparent substrate composed of a polyester resin in which 1 to 80 mol% of diol units are composed of a diol unit having a cyclic acetal skeleton and a dicarboxylic acid unit. This relates to a lens sheet.

  The lens sheet of the present invention uses a polyester resin having a high glass transition temperature as a transparent substrate, so that productivity and dimensional stability at high temperatures are remarkably higher than those of conventional O-PET-based lens sheets. improves.

The present invention relates to a lens in which an optical element is formed on at least one surface of a transparent substrate made of a polyester resin in which 1 to 80 mol% of diol units are composed of a diol unit having a cyclic acetal skeleton and a dicarboxylic acid unit. It relates to the sheet.
The ratio of the diol unit having a cyclic acetal skeleton in the polyester resin used in the present invention is preferably 1 to 80 mol%. By including 1 mol% or more of diol units having a cyclic acetal skeleton, the crystallinity of the polyester resin is lowered and the glass transition temperature is increased at the same time, and the transparent substrate obtained from the resin has improved transparency and heat resistance. To do. In addition, the processability of the transparent substrate is improved, for example, generation of whiskers is suppressed during processing such as cutting and punching. On the other hand, when the ratio of the diol unit having a cyclic acetal skeleton in the polyester resin exceeds 80 mol%, the crystallinity of the polyester resin increases, and the transparency of the obtained transparent substrate may decrease. Therefore, the ratio of the diol unit having a cyclic acetal skeleton is preferably 1 to 80 mol%, more preferably 1 to 60 mol%, more preferably from the viewpoint of heat resistance, transparency and processability of the transparent substrate. 5 to 60 mol%, particularly 15 to 60 mol% is preferable.

または一般式（２）：

で表される化合物に由来する単位が好ましい。一般式（１）と（２）において、Ｒ^１およびＲ^２はそれぞれ独立して、炭素数が１〜１０の脂肪族炭化水素基、炭素数が３〜１０の脂環式炭化水素基、及び炭素数が６〜１０の芳香族炭化水素基からなる群から選ばれる炭化水素基を表す。Ｒ^１およびＲ^２は、メチレン基、エチレン基、プロピレン基、ブチレン基、又はこれらの構造異性体が好ましい。これらの構造異性体としては、例えば、イソプロピレン基、イソブチレン基が例示される。Ｒ^３は炭素数が１〜１０の脂肪族炭化水素基、炭素数が３〜１０の脂環式炭化水素基、及び炭素数が６〜１０の芳香族炭化水素基からなる群から選ばれる炭化水素基を表す。Ｒ^３は、メチル基、エチル基、プロピル基、ブチル基、又はこれらの構造異性体が好ましい。これらの構造異性体としては、例えば、イソプロピル基、イソブチル基が例示される。一般式（１）及び（２）の化合物としては、３，９−ビス（１，１−ジメチル−２−ヒドロキシエチル）−２，４，８，１０−テトラオキサスピロ〔５．５〕ウンデカン、５−メチロール−５−エチル−２−（１，１−ジメチル−２−ヒドロキシエチル）−１，３−ジオキサン等が特に好ましい。 The diol unit having a cyclic acetal skeleton in the diol structural unit of the polyester resin used in the present invention is represented by the general formula (1):

Or general formula (2):

The unit derived from the compound represented by these is preferable. In the general formulas (1) and (2), R ¹ and R ² are each independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, and This represents a hydrocarbon group selected from the group consisting of aromatic hydrocarbon groups having 6 to 10 carbon atoms. R ¹ and R ² are preferably a methylene group, an ethylene group, a propylene group, a butylene group, or a structural isomer thereof. Examples of these structural isomers include an isopropylene group and an isobutylene group. R ³ is a carbon selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, and an aromatic hydrocarbon group having 6 to 10 carbon atoms. Represents a hydrogen group. R ³ is preferably a methyl group, an ethyl group, a propyl group, a butyl group, or a structural isomer thereof. Examples of these structural isomers include isopropyl group and isobutyl group. Examples of the compounds of the general formulas (1) and (2) include 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 5-methylol-5-ethyl-2- (1,1-dimethyl-2-hydroxyethyl) -1,3-dioxane and the like are particularly preferable.

  In addition, the diol constituent unit other than the diol unit having a cyclic acetal skeleton is not particularly limited, but ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol. , Aliphatic diols such as diethylene glycol, propylene glycol and neopentyl glycol; 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-decahydronaphthalenediethanol, 1,3-decahydronaphthalene Methanol, 1,4-decahydronaphthalene diethanol, 1,5-decahydronaphthalene diethanol, 1,6-decahydronaphthalene diethanol, 2,7-decahydronaphthalene diethanol, tetralin dimethanol, norbornane Alicyclic diols such as methanol, tricyclodecane dimethanol and pentacyclododecane dimethanol; polyether compounds such as polyethylene glycol, polypropylene glycol and polybutylene glycol; 4,4 ′-(1-methylethylidene) bisphenol; Bisphenols such as methylene bisphenol (bisphenol F), 4,4′-cyclohexylidene bisphenol (bisphenol Z), 4,4′-sulfonylbisphenol (bisphenol S); alkylene oxide adducts of the bisphenols; hydroquinone, resorcin, Aromatic dihydroxy compounds such as 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenylbenzophenone; Alkylene oxide adducts of the diol units families dihydroxy compounds can be exemplified. Considering the mechanical strength, heat resistance, and availability of diol of the polyester resin, diol units of ethylene glycol, diethylene glycol, trimethylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol are preferred, and ethylene glycol Units are particularly preferred.

  The dicarboxylic acid structural unit of the polyester resin used in the present invention is not particularly limited, but succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, cyclohexane Dicarboxylic acid, decalin dicarboxylic acid, norbornane dicarboxylic acid, tricyclodecane dicarboxylic acid, pentacyclododecanedicarboxylic acid, 3,9-bis (1,1-dimethyl-2-carboxyethyl) -2,4,8,10-tetra Aliphatic dicarboxylic acid units such as oxaspiro [5.5] undecane, 5-carboxy-5-ethyl-2- (1,1-dimethyl-2-carboxyethyl) -1,3-dioxane, dimer acid; terephthalic acid , Isophthalic acid, phthalic acid, 2-methylterephthalic acid, 1,3 For aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, tetralindicarboxylic acid, etc. Examples are derived units. Considering the mechanical strength and heat resistance of the polyester resin, a unit derived from an aromatic dicarboxylic acid is preferable, and considering the availability of the dicarboxylic acid, a unit derived from terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid Is particularly preferred. In addition, the dicarboxylic acid structural unit of a polyester resin may be comprised from 1 type, or may be comprised from 2 or more types.

  Polyester resins include units derived from monoalcohols such as butyl alcohol, hexyl alcohol, octyl alcohol, trimethylolpropane, glycerin, 1 to the extent that the object of the present invention is not impaired in order to adjust melt viscoelasticity, molecular weight, and the like. , 3,5-pentanetriol, units derived from trihydric or higher polyhydric alcohols such as pentaerythritol, monocarboxylic acid units such as benzoic acid, propionic acid and butyric acid, polycarboxylic acids such as trimellitic acid and pyromellitic acid Units derived from oxyacids such as glycolic acid, lactic acid, hydroxybutyric acid, 2-hydroxyisobutyric acid, and hydroxybenzoic acid may be included.

  In view of moldability, heat resistance, mechanical performance, etc., particularly in the polyester resin used in the present invention, the diol unit having a cyclic acetal skeleton is 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4. , 8,10-tetraoxaspiro [5.5] undecane unit, the diol constituent unit other than the diol unit having a cyclic acetal skeleton is an ethylene glycol unit, the dicarboxylic acid constituent unit is a terephthalic acid unit, an isophthalic acid unit, And at least one dicarboxylic acid unit selected from 2,6-naphthalenedicarboxylic acid units. When the dicarboxylic acid structural unit is a 2,6-naphthalenedicarboxylic acid unit, the heat resistance and mechanical performance of the polyester resin are particularly easily improved.

  The intrinsic viscosity of the polyester resin used in the present invention can be appropriately selected according to the molding method and application. In the polyester resin used in the present invention, a range of 0.5 to 1.5 dl / g as measured at 25 ° C. using a mixed solvent of phenol and 1,1,2,2-tetrachloroethane in a mass ratio of 6: 4. It is preferable that it is 0.5-1.2 dl / g, More preferably, it is 0.6-1.0 dl / g. When the intrinsic viscosity is within this range, the polyester resin used in the present invention has an excellent balance between moldability and mechanical performance.

  Although the glass transition temperature of the polyester resin used for this invention can be suitably selected according to a use, it is preferable that it is 85 degreeC or more, More preferably, it is 90 degreeC or more, Especially preferably, it is 94 degreeC or more. When the glass transition temperature is in the above range, the transparent substrate used in the present invention is excellent in heat resistance.

  There is no restriction | limiting in particular in the method of manufacturing the polyester resin used for this invention, The manufacturing method of a conventionally well-known polyester can be applied. Examples thereof include a melt polymerization method such as a transesterification method and a direct esterification method, or a solution polymerization method. In the direct esterification method, after dicarboxylic acid is esterified with a diol having no cyclic acetal skeleton, it may be necessary to react with a diol having a cyclic acetal skeleton after reducing the acid value. Various catalysts such as transesterification catalysts, esterification catalysts, polycondensation catalysts, etc., etherification inhibitors, heat stabilizers, light stabilizers, and other stabilizers used in the production, polymerization regulators, etc., may be those conventionally known. These can be appropriately selected according to the reaction rate, the color tone of the polyester resin, safety, thermal stability, weather resistance, self-elution properties, and the like.

  The polyester resins used in the present invention include antioxidants, light stabilizers, ultraviolet absorbers, plasticizers, extenders, matting agents, drying regulators, antistatic agents, antisettling agents, surfactants, flow improvers. Various additives such as drying oil, waxes, fillers, colorants, reinforcing agents, surface smoothing agents, leveling agents, curing reaction accelerators, thickeners, and molding aids can be added. Resin such as polyolefin resin, polyamide resin, acrylonitrile resin, vinyl chloride resin, vinyl acetate resin, acrylic resin, methacrylic resin, polystyrene, ABS resin, AS resin, polyimide resin, AS resin, polyester resin having no cyclic acetal skeleton Or these oligomers can also be added. These additives, resins, and oligomers may be added at the production stage of a polyester resin having a cyclic acetal skeleton or a polyester resin or polycarbonate resin not having a cyclic acetal skeleton to be blended, or may be added after the production. . Moreover, you may add at the time of shaping | molding.

  Next, the transparent substrate used in the present invention will be described. Examples of the method for producing the transparent substrate include a melt extrusion method using the polyester resin and a solution casting method. The melt extrusion method is preferable from the viewpoint of the balance between economy and the performance of the transparent substrate. In addition, the transparent base material used for this invention does not need to perform an extending | stretching and heat setting process.

  The melt extrusion method will be further described in detail. The transparent substrate used in the present invention can be formed using a conventionally known method. Examples of the melt extrusion method include a T-die extrusion method and an inflation method, and the T-die extrusion method is preferable. As an apparatus for melting the polyester resin, a generally used extruder may be used, and a single-screw extruder or a multi-screw extruder may be used. The extruder may have one or more vents, and may remove moisture, low-molecular substances, etc. from the molten resin by reducing the vents. Moreover, you may provide a metal-mesh filter, a sintered filter, and a gear pump as needed at the front-end | tip or downstream side of an extruder. As the die, a T die, a hanger die, a fish tail die, a stack plate die, or the like can be used.

  The extrusion temperature is preferably 200 to 300 ° C, more preferably 210 to 280 ° C, and particularly preferably 220 to 270 ° C. When extrusion temperature exists in the said range, it is excellent in balance, such as smoothness of the transparent base material obtained, transparency, a color tone, and a mechanical physical property.

  A conventionally known method can be used as a method for cooling the molten resin extruded from the die. In general, it can be cooled by a cooling drum. Since the polyester resin used in the present invention is a substantially amorphous resin, the temperature of the cooling drum can be set widely. The temperature of the cooling drum is preferably 30 ° C above and below the glass transition temperature of the polyester resin, more preferably 20 ° C above and below the glass transition temperature of the polyester resin, and particularly preferably 10 ° C above and below the glass transition temperature of the polyester resin. . It is preferable to control the discharge speed, the take-up speed and the temperature of the cooling drum according to the apparatus so that the dimensional stability at high temperature may deteriorate when it is stretched at the time of molding so that it is not substantially stretched. . It is preferable to anneal the transparent substrate because the dimensional stability at high temperature may be improved. The annealing temperature is 30 ° C. above and below the glass transition temperature of the polyester resin, preferably 20 ° C. above and below the glass transition temperature of the polyester resin, and particularly preferably 10 ° C. above and below the glass transition temperature of the polyester resin.

  The thickness of the transparent substrate used in the present invention can be arbitrarily set according to the required specifications. The required specification is generally 50 to 800 μm, preferably 80 μm or more from the viewpoint of handleability, and preferably 300 μm or less from the viewpoint of thinning the backlight.

  The total light transmittance of the transparent substrate used in the present invention is preferably 85% or more, and more preferably 90% or more. Moreover, it is preferable that a haze is 3% or less, More preferably, it is 2% or less. When these values are in the above range, the performance is sufficient for use as a transparent base material for a lens sheet.

  The transparent base material used in the present invention is an adhesion improving treatment such as an anchor coating on the surface on which the optical element is formed in order to improve the adhesion with the active energy ray-curable resin or thermosetting resin forming the optical element. It is preferable to apply.

Next, the optical element used in the present invention will be described.
As a first aspect of the optical element, a plurality of prism rows having a triangular cross section are formed in parallel on one side or both sides of a transparent substrate. In the case where a plurality of prism rows having a triangular cross section are formed on both surfaces of the transparent substrate, it is preferable that the plurality of prism rows each having a triangular cross section be arranged so as to be orthogonal. The apex angles of the plurality of prism rows having a triangular cross section are appropriately selected according to the directivity characteristics of the light emitted from the light guide so that the front luminance can be sufficiently improved, and are generally in the range of 50 to 150 °. Is preferred. In particular, when the plurality of prism portions having a triangular cross section are disposed on the light guide side in the backlight of the liquid crystal display device, the apex angle of the plurality of prism rows having a triangular cross section is preferably 50 to 75 °. When it is arranged so that a plurality of prism portions having a triangular cross section are on the liquid crystal panel side, it is preferably 80 to 100 °, particularly preferably 90 to 100 °. °. The pitch of the plurality of prism rows having a triangular cross section is preferably 20 to 300 μm, particularly preferably 20 to 120 μm. The refractive index of the plurality of prism portions having a triangular cross section is preferably 1.45 or more, more preferably 1.50 or more, and particularly preferably 1.55 or more. In this case, the lens sheet is used as a prism sheet (see FIG. 1).
As a second aspect of the optical element, there is one having a lenticular lens portion in which a plurality of cylindrical lens rows are formed in parallel. In this case, the lens sheet is used as a lenticular lens sheet, arranged so that cylindrical lenses are arranged in the vertical direction of the liquid crystal display device, and further diffuses the backlight light in the horizontal direction of the display to increase the viewing angle in the horizontal direction of the display. It is possible to control. When the focal length of the cylindrical lens is long, the viewing angle in the left-right direction is limited, and when the focal length is short, the viewing angle is enlarged.
As a third aspect of the optical element, there is one having a Fresnel lens portion formed in a concentric Fresnel lens shape. In this case, the lens sheet is used as a Fresnel lens sheet, and is used to limit the viewing angle of the display and improve the luminance.
In addition, a Fresnel lens sheet and a lenticular lens sheet or prism sheet in which front and back are integrated may be used. In this case, it is produced by forming respective optical elements on both surfaces of the transparent substrate.

The optical element used in the present invention is composed of a thermosetting resin in addition to the active energy ray curable resin as the curable resin, or by directly shaping the optical element on the transparent substrate of the present invention. Composed.
When composed of an active energy ray curable resin, the active energy ray curable resin is generally injected into a mold on which a predetermined optical element pattern is formed, and a transparent base material is superimposed thereon, and then activated through the transparent base material. It is obtained by curing the curable resin by irradiating energy rays. Use of an active energy ray-curable resin for the optical element is preferable from the viewpoint of scratch resistance, handleability, and productivity of the optical element.

  The active energy ray-curable resin for forming the optical element used in the present invention is not particularly limited as long as it is a resin cured with active energy rays such as ultraviolet rays and electron beams. Such an active energy ray-curable resin is generally preferably composed mainly of (A) a monomer or oligomer capable of radical polymerization, (B) an active energy ray-sensitive catalyst, and (C) a heat-sensitive catalyst. It can also be mixed.

(A) is a monomer or oligomer capable of radical polymerization, and these can be used alone or in combination of two or more, but generally it is preferable to use in combination of two or more. (A) determines the optical performance of the optical element, and is preferably selected as appropriate according to the performance required of the lens sheet.
Examples of (A) include aliphatic mono (meth) acrylate, alicyclic mono (meth) acrylate, aromatic mono (meth) acrylate, aromatic skeleton ester di (meth) acrylate, and alicyclic skeleton ester di (meth). Acrylate, aliphatic skeleton ester di (meth) acrylate, polyfunctional (meth) acrylate and other ester type (meth) acrylate, epoxy poly (meth) acrylate, urethane poly (meth) acrylate, polyester poly (meth) acrylate, etc. (Meth) acrylate resins are preferred from the viewpoint of their optical properties.

  (B) is an active energy ray-sensitive catalyst, and is preferably a substance that generates a radical source mainly in response to ultraviolet rays having a wavelength of 200 to 400 nm. For example, benzophenone, benzoin isopropyl ether, methylphenylglyoxylate, 1-hydroxycyclohexylphenyl Examples thereof include carbonyl compounds such as ketone and benzyldimethyl ketal, sulfur compounds, acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and the like. These can be used alone or in combination of two or more.

  The amount of (B) used is 0.005 to 5 parts by weight, preferably 0.02 to 2 parts by weight, based on the active energy ray-curable resin. If the amount of (B) is less than 0.005 parts by weight, the curability may not be sufficient, and if it is 5 parts by weight or more, the deep part curability may be lowered or the color may be easily colored.

(C) is a heat-sensitive catalyst, and an organic peroxide or an azo compound is preferable. Examples of these compounds include benzoyl peroxide, octanoyl peroxide, diisopropyl peroxypercarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, t-butylperoxyisobutyrate as organic peroxides, t-Butylperoxy-2-ethylhexanoate, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile as an azo compound, 2,2′- Examples include azobis (4-methoxy-2,4-dimethylvaleronitrile) and 2,2′-azobis (2-methylbutyronitrile).
The amount of (C) used is 0 to 5 parts by weight, preferably 0.005 to 2 parts by weight, based on the active energy ray-curable resin. When the amount of (C) is 5 parts by weight or more, the mechanical strength of the optical element may be lowered or the color may be easily colored.

  The optical element used in the present invention may contain additives such as an antioxidant, an ultraviolet absorber, a yellowing inhibitor, a bluing agent, a pigment, a diffusing agent, and a fluorescent brightening agent as necessary.

  Next, the performance of the lens sheet of the present invention obtained as described above will be described. The lens sheet of the present invention has good dimensional stability at high temperatures. Specifically, the dimensional change before and after being left for 30 minutes in an environment of 80 ° C. is 0%, and further, the dimensional change before and after being left for 30 minutes in an environment of 100 ° C. is 0%, especially left in an environment of 120 ° C. for 30 minutes. The dimensional change before and after being performed is 0%.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by these examples.

Evaluation methods of the polyester resin, the transparent substrate, and the lens sheet used in this example are as follows.
<Evaluation method of polyester resin>
(1) Ratio of diol unit having cyclic acetal skeleton The ratio of diol unit having a cyclic acetal skeleton in the polyester resin was calculated by ¹ H-NMR measurement. The measuring apparatus used JNM-AL400 by JEOL Co., Ltd., and measured it at 400 MHz. Deuterated chloroform was used as the solvent.
(2) Glass transition temperature As for the glass transition temperature of the polyester resin, DSC / TA-50WS manufactured by Shimadzu Corporation is used, about 10 mg of polyester is put in an aluminum non-sealed container, and the rate of temperature rise in a nitrogen gas (30 ml / min) stream. The sample heated and melted at 280 ° C. at 20 ° C./min was rapidly cooled to obtain a measurement sample. The sample was measured under the same conditions, and the temperature at which the difference between the baselines before and after the transition of the DSC curve changed by 1/2 was taken as the glass transition temperature.
(3) Intrinsic viscosity A sample for measuring the intrinsic viscosity (abbreviated as IV) is 0.5 g of polyester resin dissolved in 120 g of a mixed solvent of phenol and 1,1,2,2-tetrachloroethane (mass ratio = 6: 4). The solution was cooled to 25 ° C. after filtration. The measurement was performed at a temperature of 25 ° C. using a capillary viscometer automatic measuring device SS-300-L1 manufactured by Shibayama Scientific Machinery Co., Ltd.
<Evaluation method of transparent substrate>
(4) Total light transmittance, haze Measured according to JIS-K-7105, ASTM D1003. The transparent substrate was conditioned for 48 hours and then measured in an atmosphere of 23 ° C. and 50% relative humidity. The measuring apparatus used is a fog value measuring apparatus (model: COH-300A) manufactured by Nippon Denshoku Industries Co., Ltd.
<Lens sheet evaluation method>
(5) Dimensional change rate It measured according to JIS-K7133. Write a square of 100 x 100 mm on each of the three lens sheets cut out to approximately 120 x 120 mm, place them in a hot air dryer at a predetermined temperature for 30 minutes, and then follow the rate of dimensional change in the extrusion direction and in the direction perpendicular to the extrusion direction. Calculated by the equation, the average value of the three test pieces was taken as the dimensional change rate in each direction. In the table, the extrusion direction is referred to as MD direction, and the direction perpendicular to the extrusion direction is referred to as TD direction.
Dimensional change rate (%) = {(La−Lb) / La} × 100
La: Distance between lines before putting in hot air dryer (100 mm)
Lb: Spacing between lines after putting in hot air dryer

[Examples 1 to 8]
[Production and evaluation of polyester resin]
The raw material monomers listed in Tables 1 and 2 are charged into a 0.15 cubic meter polyester production apparatus equipped with a packed tower rectification tower, a partial condenser, a full condenser, a cold trap, a stirrer, a heating device, and a nitrogen introduction pipe. In the presence of 0.03 mol% of manganese acetate tetrahydrate with respect to the dicarboxylic acid component, the temperature was raised to 215 ° C. in a nitrogen atmosphere to conduct a transesterification reaction. After the reaction conversion rate of the dicarboxylic acid component is set to 90% or more, 0.02 mol% of antimony (III) oxide and 0.06 mol% of trimethyl phosphate are added to the dicarboxylic acid component, and the temperature and pressure are gradually increased. And finally polycondensation was performed at 270 ° C. and 0.1 kPa or less. The reaction was terminated when an appropriate melt viscosity was reached, and a polyester resin was produced. The evaluation results are shown in Tables 1 and 2.
In addition, the meaning of the abbreviation in a table | surface is as follows.
DMT: dimethyl terephthalate NDCM: 2,6-dimethyl naphthalate DMI: dimethyl isophthalate EG: ethylene glycol SPG: 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10- Tetraoxaspiro [5.5] undecane

[Manufacture and evaluation of transparent substrates]
Polyester resin was melt-extruded at a cylinder temperature of 220-240 ° C., a die temperature of 240 ° C., and a discharge rate of 30 kg / h using a single screw extruder having a screw diameter of 50 mmφ with a vacuum vent and a 550 mm wide coat hanger die. The extruded molten resin was cooled with a first roll set at Tg-10 ° C. and a second roll set at 60 ° C., and was drawn at 12 m / min to produce a transparent substrate having a thickness of 100 μm and a width length of 480 mm. The evaluation results are shown in Tables 1 and 2.

[Production and evaluation of prism sheet (lens sheet (1))]
An optical element pattern (prism pattern) is formed on a 3 mm × 300 mm × 400 mm brass plate conforming to JIS 2804 by cutting parallel prisms with an apex angle of 65 ° and an isosceles triangle at a pitch of 50 μm, followed by Ganizen plating. After a suitable amount of the acrylic ultraviolet curable monomer mixture was injected into the lens mold subjected to the above, a transparent base material cut to a suitable size was superposed while being pressed with a roll. Next, the resin was cured by irradiating ultraviolet rays for 45 seconds from three 6.4 kw ultraviolet lamps (manufactured by Western Quartz) with an irradiation intensity of 80 w / cm arranged above the transparent substrate, and then peeled off (lens sheet ( 1)) was obtained. The evaluation results are shown in Tables 1 and 2. The acrylic ultraviolet curable monomer mixture has the following composition.
Hitachi Chemical FA-321M ... 50% by weight
KAYARADR-604 ... 20% by weight, manufactured by Nippon Kayaku Co., Ltd.
Osaka Organic Chemical Co., Ltd. Biscoat # 192 ... 30% by weight
DAROCURE 1173 (radical photopolymerization initiator) manufactured by Merck & Co., Ltd. 1.5 parts by weight (FA-321M, KAYARADR-604 and biscoat # 192 correspond to (A) a monomer or oligomer capable of radical polymerization. Darocur 1173 corresponds to (B) an active energy ray-sensitive catalyst.)

[Manufacture and evaluation of lenticular lens sheet (lens sheet (2))]
A lenticular in which a plurality of cylindrical lens arrays are formed in parallel by cutting an arc array having a curvature radius of 0.5 mm in parallel at a 0.2 mm pitch on a 3 mm × 300 mm × 400 mm plate made of brass conforming to JIS 2804 (Lens sheet (2)) was obtained in the same manner as the lens sheet (1) using a lens mold on which the lens part was formed and then subjected to Ganizen plating. The evaluation results are shown in Tables 1 and 2.

[Production and evaluation of Fresnel lens sheet (lens sheet (3))]
Lens formed by forming a Fresnel lens part formed in the shape of a concentric Fresnel lens having a focal length of 300 mm and a Fresnel zone pitch of 0.5 mm on a 3 mm x 300 mm x 400 mm plate made of brass conforming to JIS 2804 Using a mold, (lens sheet (3)) was obtained in the same manner as the lens sheet (1). The evaluation results are shown in Tables 1 and 2.

[Manufacture and evaluation of a sheet (lens sheet (4)) with a Fresnel lens on the surface and a lenticular lens on the other surface]
Similarly to the manufacture of the Fresnel lens sheet and the lenticular lens sheet, after forming the Fresnel lens part on the surface of the transparent substrate, the lenticular lens part was formed on the other surface, and the lens sheet (4) was manufactured. . The evaluation results are shown in Tables 1 and 2.

[Manufacture and evaluation of a sheet (lens sheet (5)) in which a Fresnel lens portion is formed on the surface of the sheet and a prism array having an isosceles triangular section is formed on the other surface]
Similar to the manufacture of the Fresnel lens sheet and the prism sheet, after forming the Fresnel lens section on the surface of the transparent substrate, an isosceles triangular prism array is formed on the other surface (lens sheet ( 5)) was manufactured. The evaluation results are shown in Tables 1 and 2.

Example of lens sheet (prism sheet) configuration

Claims (9)

A lens sheet in which an optical element is formed on at least one surface of a transparent substrate made of a polyester resin in which 1 to 80 mol% of a diol unit is composed of a diol unit having a cyclic acetal skeleton and a dicarboxylic acid unit. The diol unit having a cyclic acetal skeleton has the general formula (1):

(In the formula, R ¹ and R ² are each independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, and an aromatic having 6 to 10 carbon atoms. Represents a hydrocarbon group selected from the group consisting of aromatic hydrocarbon groups.)
Or general formula (2):

(In the formula, R ¹ is the same as described above, and R ³ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, and 6 to 10 carbon atoms. Represents a hydrocarbon group selected from the group consisting of aromatic hydrocarbon groups.)
The lens sheet according to claim 1, which is a diol unit derived from a diol represented by: The diol unit having a cyclic acetal skeleton is 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane or 5-methylol-5 The lens sheet according to claim 2, which is a diol unit derived from -ethyl-2- (1,1-dimethyl-2-hydroxyethyl) -1,3-dioxane. The diol unit other than the diol unit having a cyclic acetal skeleton is derived from one or more diols selected from ethylene glycol, diethylene glycol, trimethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol. The lens sheet in any one of -3. The lens sheet according to any one of claims 1 to 4, wherein the dicarboxylic acid unit is derived from one or more dicarboxylic acids selected from terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. The lens sheet according to any one of claims 1 to 5, wherein the optical element is formed of an active energy ray curable resin. The lens sheet according to any one of claims 1 to 6, wherein the optical element has a prism portion in which a plurality of prism rows having a triangular cross section are formed in parallel. The lens sheet according to claim 1, wherein the optical element has a lenticular lens portion in which a plurality of cylindrical lens rows are formed in parallel. The lens sheet according to any one of claims 1 to 6, wherein the optical element has a Fresnel lens portion formed in a concentric Fresnel lens shape.

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