JPH0727901A - Lens sheet - Google Patents

Abstract

(57) [Abstract] [Purpose] Excellent adhesion between the lens part and the transparent resin substrate, accurate transfer of the lens type lens pattern, excellent optical characteristics, and lens defects due to entrainment of bubbles etc. Provide an excellent lens sheet that does not have. In a lens sheet in which a lens portion is formed of an active energy ray-curable resin on at least one surface of a transparent resin substrate, the lens portion comprises 10 to 30% by weight of a compound represented by the general formula (1) and a bifunctional compound. 10 to 50% by weight of (meth) acrylic acid ester and the transparent resin substrate at 25 ° C.
A lens sheet obtained by irradiating an active energy ray and curing the mixture containing 40 to 70% by weight of a monofunctional (meth) acrylic acid ester having a weight loss of 10% or more when immersed for 10 hours.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection screen used as a screen of a projection television or a microfilm reader, a condenser lens, a lens sheet such as a Fresnel lens used for stereoscopic photography, a lenticular lens or a prism. More specifically, the present invention relates to a lens sheet in which a lens portion is formed of an active energy ray curable resin on a transparent resin base material.

[0002]

2. Description of the Related Art As a method for manufacturing a lens sheet such as a Fresnel lens or a lenticular lens, a transparent resin material such as an acrylic resin, a polycarbonate resin, a vinyl chloride resin or a styrene resin is used, and these resins are injection molded. There are known a press molding method in which a resin plate and a lens mold are brought into contact with each other and the lens pattern of the lens mold is transferred by heating and pressing the resin plate, and a direct cutting method in which the resin plate is directly cut.

However, in the injection molding method, it is difficult to mold a large-sized molded product, and it can be used only for molding a relatively small-sized molded product. Further, in the press molding method, since the heating and cooling cycle of the resin plate and the molding die takes a long time, a large number of molding dies are required for mass production of the resin molded product, and in order to manufacture a large resin molded product. Costs a huge amount of production equipment. Further, the direct cut method has a problem that it requires a long time for cutting and it is impossible to form a lens having a fine pitch.

Therefore, recently, a method of injecting an active energy ray-curable composition into a lens mold and then irradiating it with an active energy ray to cure the composition has been proposed. In particular, when used as a lens sheet for a projection screen, high luminance and high color rendering properties are required, and a thin lens sheet with improved resolution and few double images is required. As the active energy ray-curable resin that constitutes the lens portion of such a lens sheet, various types of viscosity suitable for production, low odor, low irritation, transparency after curing, surface hardness, adhesiveness with a substrate, etc. Need to meet requirements.

To meet these demands, for example, Japanese Patent Laid-Open No.
No. 7-82018 discloses a sheet in which a radiation-curable resin is used to form an embossed pattern having an uneven pattern on the surface of a substrate film, and as the radiation-curable resin, 70 to 100 parts by weight of urethane acrylate, V-pyrrole or an acrylic monomer. A composition consisting of 30 parts by weight has been proposed. Further, Japanese Patent Application Laid-Open No. 1-192529 discloses a first mold transferability, defoaming property, wettability, and surface curability.
Of the ionizing radiation curable resin is applied to the mold, and then a second ionizing radiation curable resin having adhesiveness to the base film, fluidity, mechanical strength, and transparency is applied, and then the base film is superposed on the ionizing radiation. It has been proposed to use a urethane acrylate resin as the first ionizing radiation curable resin and an epoxy acrylate resin having a viscosity of 1500 mPa · s as the second ionizing radiation curable resin in the lens sheet cured by irradiation with.

[0006]

However, when the content of the urethane acrylate in the active energy ray-curable composition is high, the viscosity of the composition tends to be as high as several hundreds mPa · s or more, so that the lens has a high viscosity. There is a problem that bubbles are apt to be caught during application to the mold, and the caught bubbles remain as defects in the lens. Also,
Those containing an oligomer such as urethane acrylate as a main component also have poor adhesion to the transparent resin substrate and are likely to cause peeling of the lens portion. Further, when a resin having a high viscosity is used, bubbles tend to be involved, which causes a lens defect, and it becomes very difficult to remove the bubbles once entrapped. As described above, in the active energy ray curable resin such as ultraviolet rays used for the lens sheet, the adhesion to the substrate is insufficient, the lens sheet obtained has a lens defect, and the optical characteristics of the lens sheet are There was a problem that it was inferior to.

Therefore, an object of the present invention is to provide a lens sheet having a lens portion which simultaneously satisfies the adhesion to a substrate, the transferability of a lens pattern, the surface hardness and the optical characteristics.

[0008]

SUMMARY OF THE INVENTION The inventors of the present invention have reached the present invention as a result of earnest studies on the active energy ray-curable resin forming the lens section in view of the problems of the above-mentioned prior art. is there. That is, the lens sheet of the present invention is a lens sheet in which a lens portion is formed of an active energy ray-curable resin on at least one surface of a transparent resin substrate, and the lens portion is a compound represented by the following general formula (1) ( A) 10 to 30% by weight and bifunctional (meta)
Acrylic acid ester (B) 10 to 50% by weight, and monofunctional (meth) acrylic acid ester (C) 40 to 40% by weight reduction of 10% or more when the transparent resin substrate is immersed at 25 ° C. for 10 hours. It is characterized in that a mixture containing 70% by weight is irradiated with an active energy ray and cured.

[0009]

[Chemical 2]

(R ₁ is H or CH ₃ , and R ₂ is C (C
H ₃ ) ₂ or CH ₂ and m and n are integers satisfying m + n ≦ 10. In the lens sheet of the present invention, as the compound (A) represented by the general formula (1), a diacrylic acid ester or dimethacrylic acid ester of bisphenol A modified with ethylene oxide, or a diacrylic acid of bisphenol F modified with ethylene oxide is used. It is an ester or dimethacrylic acid ester, and is a diacrylic acid ester or dimethacrylic acid ester having 2 to 10 mol of ethylene oxide added per mol of bisphenol A or bisphenol F. These compounds (A) can be used alone or in combination of two or more kinds.

The compound (A) is contained in the active energy ray-curable composition in the range of 10 to 30% by weight. This is because when the content of the compound (A) is less than 10% by weight, the polymerization shrinkage ratio becomes large and the transferability of the lens pattern is lowered, or the polymerization is rapidly advanced and the lens sheet is apt to be distorted. This is because the refractive index of the lens portion becomes low and it becomes impossible to make the lens sheet thinner.
When the compound (A) is contained in an amount of more than 30% by weight, the viscosity of the active energy ray-curable composition becomes high,
This is because air bubbles are entangled and dull when the coating is spread on the lens mold.

Bifunctional (meth) acrylic acid ester (meaning acrylic acid ester or methacrylic acid ester)
(B) is not particularly limited, but
6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, hydroxypivalin Those having an affinity with the transparent resin substrate such as acid neopentyl glycol diacrylate are particularly preferable from the viewpoint of adhesion to the transparent resin substrate. These compounds can be used alone or in combination of two or more kinds.

The difunctional (meth) acrylic acid ester (B) is contained in the active energy ray-curable composition in an amount of 10 to 5%.
It is contained in the range of 0% by weight. This is bifunctional (meta)
When the content of the acrylic ester (B) is less than 10% by weight, the crosslink density of the active energy ray-curable resin forming the lens portion decreases, and it tends to be difficult to obtain a lens sheet having sufficient surface hardness. This is because there is 50
When it is contained in an amount of more than wt%, the crosslink density of the active energy ray-curable resin forming the lens portion becomes too high and the lens portion becomes brittle, or the adhesiveness between the lens portion and the transparent resin substrate is poor, This is because the refractive index of the lens portion tends to decrease.

The monofunctional (meth) acrylic acid ester (referring to acrylic acid ester or methacrylic acid ester) (C) used in the present invention is obtained by heating a transparent resin substrate at a temperature of 2
The weight loss when immersed for 10 hours at 5 ° C. is 10% or more. By using such a specific monofunctional (meth) acrylic acid ester (C), a transparent resin substrate and a lens can be obtained. The adhesiveness of the part can be improved. Examples of the specific monofunctional (meth) acrylic acid ester (C) include 2-aminoethyl acrylate, N, N-diethylaminoethyl acrylate, N,
N-dimethylaminoethyl acrylate, 2-ethoxyethyl acrylate, 2-ethoxyethyl methacrylate, 2-hydroxyethyl acrylate, phenoxyhydroxyethyl acrylate, phenoxyhydroxyethyl methacrylate, phenoxyethyl acrylate,
Phenoxyethyl methacrylate, phenoxyethylene glycol acrylate, phenoxyethylene glycol methacrylate, polyethylene glycol methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, N-vinylcaprolactam, N-vinylpyrrolidone, and the like, which may be used alone or in combination of two or more. It can be used in combination.

Such a monofunctional (meth) acrylic acid ester (C) is added to the active energy ray-curable composition at 40%.
It is contained in the range of 70 wt%. This is because when the content of the monofunctional (meth) acrylic acid ester (C) is less than 40% by weight, the adhesiveness to the transparent resin substrate is poor, and conversely, when the content exceeds 70% by weight, the lens portion is contained. This is because the rigidity of the sheet tends to decrease.

In the lens sheet of the present invention, if necessary, an active energy ray-curable resin or a thermoplastic resin (D) is added to the above-mentioned components (A) to (C) to obtain an active energy ray-curable composition. It is also possible to adjust the viscosity of the material. Examples of the resin (D) that can be used in the present invention include:
Active energy ray-curable resins such as ethylene acrylate resin, epoxy acrylate resin, unsaturated polyester resin, and high molecular weight polymers such as polymethyl methacrylate, polystyrene, polyethyl methacrylate, and methyl methacrylate-styrene copolymer. .
These active energy ray-curable resins or thermoplastic resins (D) can be added in a range of 50 parts by weight or less based on 100 parts by weight of the total amount of the components (A) to (C). This is because when the active energy ray-curable resin or the thermoplastic resin (D) is added in an amount of more than 50 parts by weight, the viscosity of the active energy ray-curable composition becomes too high and the composition is spread on the lens mold. This is because air bubbles are trapped and dull.

In the present invention, the photoinitiator used with the active energy ray-curable composition comprising the mixture of the components (A) to (D) is not particularly limited as long as it is a commonly used photoinitiator. Although not limited to these, methylbenzoyl formate, 1-hydroxycyclohexyl denenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, etc. are relatively less colored before and after the reaction, It is preferable because the optical characteristics of the lens sheet are not impaired. These photoinitiators can be used alone or in combination of two or more. Further, these photoinitiators are preferably added in the range of 0.1 to 5 parts by weight with respect to 100 parts by weight of the active energy ray-curable composition. This is because if the amount of the photoinitiator added is less than 0.1 parts by weight, the reactivity may be poor and curing may not be achieved. Conversely, if it is added in excess of 5 parts by weight, the lens part may be easily colored, or the reaction may not occur. Is likely to occur suddenly and cause distortion in the lens sheet.

As the transparent resin base material used in the present invention, any kind of material can be used as long as it is a highly transparent material. For example, acrylic resin, polycarbonate resin, styrene resin, polysulfone resin, polyether sulfone. Examples thereof include resins and vinyl chloride resins. Above all, a base material made of an acrylic resin or a polycarbonate resin having a small optical strain is preferable. The thickness of the transparent resin substrate is 0.2 to
A plate-shaped, sheet-shaped, or film-shaped one having a size of about 5 mm can be used.
A sheet-like or film-like substrate having a thickness of about 2 to 1 mm is preferable.

Next, a method for manufacturing the lens sheet of the present invention will be described. First, using a transparent resin substrate and a lens mold made of glass, metal or resin having fine grooves for forming a lens surface on the inner surface, the lens-shaped fine grooves are directed to the inner surface, and the resin transparent substrate and the lens mold are used. Between (A) ~ (D)
An active energy ray-curable composition comprising a mixture of components is interposed. In this case, the active energy ray-curable composition may be applied onto the transparent resin substrate and the lens mold may be brought into contact with the transparent resin substrate, or the active energy ray-curable composition may be applied into the lens mold or spread. After filling by the method of
You may carry out by stacking a transparent resin base material. The peripheral edge seal is usually unnecessary because the voids are minute, but may be sealed with a gasket or the like if necessary.

After the active energy ray-curable composition is filled between the transparent resin base material and the lens mold, pressure is applied from the transparent base material side using a pressure roll or the like to obtain the active energy ray-curable composition. The composition is sufficiently spread in the fine grooves, irradiated with active energy rays such as ultraviolet rays, electron beams, and radiation to polymerize and cure, and then demolded. Incidentally, when the transparent resin substrate is superposed on the lens mold filled with the active energy ray-curable composition, a roller or the like may be used to apply pressure at the same time as superimposing the transparent resin substrates and perform air bleeding. it can. Further, in order to suppress the entrainment of air as much as possible, it is necessary to adjust the viscosity of the active energy ray-curable composition, which is related to the wetting speed of the transparent resin substrate or the lens mold, 10-100mPa
-S is preferable, and it is more preferable to use a low-viscosity active energy ray-curable composition having a viscosity of about 15 to 50 cps in consideration of air entrapment, thickness uniformity, and the like.

To fill the lens mold with the active energy ray-curable composition, first the active energy ray-curable composition is filled only in the fine groove portions of the lens mold, and then the active energy ray-curable composition is cured as much as necessary for lens formation. The mold composition may be filled and the transparent resin substrates may be superposed. Further, in this case, after filling the lens-shaped fine groove portion with the active energy ray-curable composition, an appropriate amount of the active energy ray is irradiated to be in a semi-cured state, and the active energy ray-cured is further cured as necessary for lens formation. The mold composition can also be filled.

[0022]

EXAMPLES Hereinafter, description will be given based on specific examples of the present invention. In the examples, the viscosity was measured using a BL type rotational viscometer (No. 1 rotor manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25 ° C.
The viscosity at was measured. The polymerization shrinkage is the specific gravity (dm) of the active energy ray-curable composition at a temperature of 25 ° C.,
The specific gravity (dp) at a temperature of 25 ° C. of the active energy ray-curing resin after irradiation curing with the active energy ray is measured,
It was calculated based on the polymerization shrinkage rate (%) = (dp-dm) / dp × 100.

Regarding the surface hardness, a resin plate having a thickness of 1 mm was prepared, and Rockwell hardness HR15X was measured under the following measurement conditions using an electric digital twin hardness meter manufactured by Akashi Co., Ltd. in accordance with JIS K7202. Standard load: 3 Kgf Test load: 15 Kgf Test load holding time: 15 seconds Time from test load removal to measurement: 15 seconds Steel ball indenter diameter: 6.35 mm Rockwell hardness calculation formula: HR15X = 130-500
h (h (mm): Difference in indenter penetration depth between two front and rear standard loads) The refractive index was measured using an Appe refractometer (4T, manufactured by Atago Co., Ltd.) by preparing a resin plate having a thickness of 1 mm. For total light transmittance, make a resin plate with a thickness of 1 mm and follow ASTM D1003.
It was measured according to.

Examples 1 to 12, Comparative Examples 1 to 4 Ethylene oxide modified bisphenol A dimethacrylate (NK ester BPE-100 manufactured by Shin-Nakamura Chemical Co., m + n = 2 in the general formula (1)), tripropylene glycol dimethacrylate (TOA) Synthetic Chemical Industry Co., Ltd. Aronix M2
20) and phenoxyethyl acrylate (Viscoat # 192 manufactured by Osaka Organic Chemical Industry Co., Ltd.) were mixed in the mixing ratio shown in Table 1, and further 2-hydroxy-2-methyl-1-phenylpropane-1-as an ultraviolet polymerization initiator. On (Merck Japan Darocur 1173) mixture 100
An ultraviolet curable composition was obtained by adding 2 parts by weight to 1 part by weight. In addition, phenoxyethyl acrylate has a weight loss of 10% when the methacrylic resin plate used as a base material is immersed at a temperature of 25 ° C. for 10 hours.
That is all.

The UV curable composition thus obtained was applied to a thickness of 3 m.
It is spread on a lens mold consisting of a nickel stamper with a Fresnel lens pattern of 800 mm × 600 mm pasted on an iron plate of m, and a methacrylic resin plate with a thickness of 2 mm (Acrylite # 000 manufactured by Mitsubishi Rayon Co., Ltd.) is overlaid on it It was After that, the surplus UV-curable composition is removed by a pressure roll, and UV of 320 to 390 nm is irradiated at an integrated UV irradiation amount of 1000 mJ / cm ² to polymerize and cure the UV-curable composition to be integrated with the methacrylic resin plate. I got a Fresnel lens that became. The obtained Fresnel lens had a lens-shaped lens pattern transferred sufficiently and had a shape as designed.

On the other hand, the above UV-curable composition was poured between two glass cells having a gap of 1 mm, and the amount of 320-
Ultraviolet rays of 390nm is 1000mJ with integrated ultraviolet irradiation amount
/ Cm ² irradiation to polymerize and cure the ultraviolet curable composition to obtain an ultraviolet curable resin plate having a thickness of 1 mm. Polymerization shrinkage, surface hardness, refractive index and total light transmittance were measured using the obtained resin plate, and the results are shown in Table 1.

[0027]

[Table 1]

Comparative Example 5 A Fresnel lens was manufactured in the same manner as in Example 1 except that lauroyl methacrylate (Acryester L manufactured by Mitsubishi Rayon Co., Ltd.) was used instead of phenoxyethyl acrylate. However, a usable Fresnel lens could not be obtained because the lens portion was peeled from the transparent resin substrate in the lens mold peeling step.

Example 13 To 100 parts by weight of the ultraviolet-curable composition used in Example 1, 15 parts by weight of a urethane acrylic resin (Goselac UV-7000B manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added, and the same as in Example 1. A Fresnel lens was obtained by the method. The Fresnel lens obtained had good adhesion between the substrate and the lens portion, had a lens-type lens pattern sufficiently transferred, and had a shape as designed.

Example 14 Fresnel was prepared in the same manner as in Example 1 except that a resin plate (manufactured by Mitsubishi Gas Chemical Co., Inc.) having a thickness of 3 mm and made of a methyl methacrylate-styrene copolymer was used as the transparent resin substrate. Got the lens. The Fresnel lens obtained had good adhesion between the substrate and the lens portion.

Example 15 A Fresnel lens was obtained in the same manner as in Example 1 except that a 0.5 mm-thick polycarbonate film (manufactured by Mitsubishi Rayon Co., Ltd.) was used as the transparent resin substrate. The Fresnel lens obtained had good adhesion between the substrate and the lens portion.

[0032]

EFFECTS OF THE INVENTION Since the present invention has the constitution as described in detail above, it is excellent in the adhesiveness between the lens portion and the transparent resin base material and can accurately transfer the lens type lens pattern. Further, it is possible to provide an excellent lens sheet which has excellent optical characteristics and does not have lens defects due to inclusion of bubbles. Moreover, since the viscosity of the active energy ray-curable composition is in the proper range, it is excellent in handleability and workability in the production of lens sheets.

Claims (2)

[Claims] 1. A lens sheet in which a lens portion is formed of an active energy ray-curable resin on at least one surface of a transparent resin substrate, wherein the lens portion is a compound (A) 10 represented by the following general formula (1): 30% by weight, 10 to 50% by weight of a bifunctional (meth) acrylic acid ester (B), and a monofunctional (10% or more in weight loss when the transparent resin substrate is immersed at 25 ° C. for 10 hours. A lens sheet, which is obtained by irradiating a mixture containing 40 to 70% by weight of a meth) acrylic acid ester (C) with an active energy ray and curing the mixture. [Chemical 1] (R ₁ is H or CH ₃ , R ₂ is C (CH ₃ ) ₂ or CH ₂ , and m and n are integers satisfying m + n ≦ 10.) 2. The lens part is a mixture containing 50 parts by weight or less of an active energy ray-curable resin or a thermoplastic resin (D) per 100 parts by weight of the total amount of the components (A) to (C). The lens sheet according to claim 1, which is obtained by irradiating an active energy ray and curing the same.