JP3212085B2 - Manufacturing method of lenticular lens sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lenticular lens sheet used as a front screen of a rear projection television in combination with a Fresnel lens, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a front screen of a rear projection television has a parallel convex lens structure for widening a horizontal viewing angle, and contains a light diffusing material for widening a vertical viewing angle. There have been many proposals to further roughen the surface and further improve the light diffusivity. At that time, a transparent plastic such as methacrylic resin was used as the material of the screen, and fine particles having a different refractive index from the base resin were generally used as the light diffusing material.

As a criterion for selecting a light diffusing material, a difference in refractive index between the light diffusing fine particles and the base resin and a particle diameter have been used. For example, in Japanese Patent Application Laid-Open No. 60-139758, crystalline silica, amorphous silica or calcium carbonate having a refractive index difference of 0.02 to 0.1 and a particle size of 10 to 50 .mu. Inorganic transparent fine particles such as aluminum are mixed. or,
In JP-A-60-184559, a polystyrene resin or a polycarbonate resin has a refractive index difference of 0.0.
Proposals have been made, for example, in which crystalline silica having a particle size of 2 to 0.1 and a particle size of 4 to 10 μm is mixed. In addition to this, JP-A-61-4
No. 762, No. 62-17426, Japanese Patent Publication No. 60-216
Many proposals such as No. 62 have been made. The above examples are intended for use in rear projection screens in addition to lighting covers and partition boards, and the combinations of the base resin and the light diffusing material that are specifically described are extremely diverse.

[0004]

However, these methods aim at improving the light diffusivity and do not always take into account the color temperature characteristics for obtaining a screen with a uniform color tone in a rear projection television. Was. Color temperature is a one-dimensional index that represents the color of light radiated from a black body in terms of the temperature of the black body, and is not necessarily an appropriate index for expressing light emitted from a phosphor of a cathode ray tube, but is close to white. It is preferable that the color difference can be simply expressed. The lenticular lens sheet must faithfully distribute the light and color emitted from the rear to the front surface. If the distribution ratio differs depending on the wavelength, the tint looks different, which is not preferable.

[0005] The conventionally proposed light diffusing plate is not always satisfactory from the above viewpoints. The reason seems to be that the conventional light diffusing plate has been mainly developed for use mainly in lighting, display and the like.

An object of the present invention is to provide a lenticular lens sheet used as a front screen of a rear projection television in combination with a Fresnel lens, comprising a base resin,
Manufacture of lenticular lens sheets with excellent color temperature characteristics by combining with substantially transparent fine particles having an appropriate refractive index, average particle diameter and refractive index difference according to wavelength without impairing high light diffusivity. It is to provide a method .

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to achieve the object of the present invention, that is to say that the refractive indices are respectively _NPA and N _PB , average particle size.
Diameter of each _{d A (μm)} and _{d B (μm),}
Refractive index, average particle size and difference in refractive index by wavelength from base resin
Satisfy the following formulas (I), (II) and (III):
Two types of light diffusing properties of substantially transparent A and B
Mixing the substantially transparent plastic having a refractive index N _s microparticles
Melt and extrude the combined resin to give a lens shape
From the parallel convex lens through the engraved roll
Lenticular lens sheet
Lenticular lens sheet . _{(I): 0.02 ≦ | N} S -N PA | ≦ 0.10 0.02 ≦ | N S -N PB | ≦ 0.10 (II): 5 ≦ d A <20 5 ≦ d B <20 (III): (| △ nF _A | − | △ nC _A |) × (| △ nF _B | − | △ nC _B |) <0 (where the refractive indexes N _S , N _PA and N in the above equation)
_PB is the refractive index at the d-line (5893Å), and | △
nF _A | is the F line (48) between the base resin and the light diffusing fine particles A.
61Å), | △ nF _B | is the difference in the refractive index at the F line (4861Å) between the base resin and the light diffusing fine particles B, and | △ nC _A | is the light diffusion between the base resin and | NC _B | is the difference between the refractive index at the C-line (6563 °) and the diffusing fine particles A, and | △ nC _B |
And the difference in the refractive index at the C line (6563 °). )

[0008]

The lenticular lens sheet according to the present invention is used together with a Fresnel lens sheet as a front plate of a rear projection television, and the plastic used for the sheet is methacrylic resin, polystyrene resin, or the like.
MMA-styrene copolymer resin, polycarbonate resin,
A highly transparent resin such as a vinyl chloride resin is used. In particular, a methacrylic resin and a styrene-based resin are preferable because of their high transparency.

The first requirement for the performance of the light diffusing fine particles to be dispersed in the lenticular lens sheet is the difference in refractive index between the fine particles and the base resin. In order to achieve the object of the present invention, it is necessary that the refractive index difference is in the range of 0.02 or more and 0.10 or less. If the refractive index difference is less than 0.02, the vertical directional characteristics of light are small, and the angle range of suitable brightness at the peripheral portion (upper or lower) with respect to the central portion is not preferable. Further, since the diffusion effect is small, a large amount of addition is required, which is not preferable from the viewpoint of economic reasons or mechanical properties. Further, the difference in refractive index is 0.10
If it is larger, it is brighter in the peripheral part (upper or lower in the vertical direction) than in the central part, and the visible angle range is wide, but the change rate of luminance near the front is large and the amount of addition is small. Therefore, stripes called hot bands due to see-through become easy to see, which is not preferable. From the above, it is necessary that the refractive index difference is in the range of 0.02 to 0.10. However, it is preferable that the difference is in the range of about 0.04 to 0.06.

The second requirement for the performance of the light diffusing fine particles is that the average particle diameter d of the fine particles is 5 μm or more and 30 μm or more.
m or less. If the average particle size exceeds 30 μm, a large amount of fine particles is required to obtain a desired diffusion effect, which is not preferable, and the diffusion effect is reduced, and the transparency tends to occur. The average particle size is 5
When the particle size is smaller than μm, the amount of the fine particles is small, but the presence of the fine particles does not have a good effect on the color temperature characteristics and the amount of the fine particles is small, so that the transparency is likely to occur. From the above, the average particle diameter of the light diffusing fine particles is 5 to 3
The range of 0 μm is appropriate, but preferably 10 to 20 μm.
It is desirable that it is about μm.

Next, the third requirement that the light diffusing fine particles should have is a difference in refractive index by wavelength with respect to the base resin. In general, the refractive index of a substance depends on the wavelength of light, and the refractive index of blue light having a short wavelength is larger than that of red light having a long wavelength. F-line (4861 °), d-line (5893 °),
Dispersion value (nF) expressed using the refractive index of line C (6563 °)
-NC) and the number of Abbe (nd-1) / (nF-nC) are known.

In the present invention, attention is paid to the difference in the refractive index difference between the base resin and the fine particles by wavelength, and it is determined that the color temperature characteristic of the lenticular lens sheet is caused by the difference in refractive index by wavelength. It has been found that a lenticular lens sheet having uniform color temperature characteristics can be realized by mixing and dispersing transparent fine particles having different refractive index differences. When mixing and dispersing with one kind of fine particles, even if the refractive index difference Δnd with the base resin is appropriate, the refractive index differences ΔnF and ΔnC for each wavelength are not necessarily appropriate.
In many cases, the color temperature characteristics are inferior. Generally, the refractive index of a substance is caused by its molecular structure, and it is difficult to operate only the refractive index difference for each wavelength without changing the refractive index difference from the base resin.

According to the present invention, even if the refractive index difference by wavelength is not appropriate by itself, and those having inferior color temperature characteristics are combined with each other, they can be used as appropriate fine particles having excellent color temperature characteristics. I found something.

Specifically, the difference in the refractive index for each wavelength is expressed by the following formula (III).
The objective of the present invention can be achieved by mixing fine particles A and B satisfying the first requirement and the second requirement so as to satisfy the above formula (IV). Equation (III) shows the relationship between the refractive index differences of the fine particles A and B by wavelength, and the relationship between ΔnF and ΔnC indicates that one of (ΔnF−ΔnC) is negative. Further, the formula (IV) i.e. _{0.95 ≦ (S A | △ nF} A | + S B | △ nF B |) / (S A
| △ nC _A | + S _B | △ nC _B |) ≦ 1.05 (where S _A is the specific cross-sectional area c of the light diffusing fine particles A)
m ² / g and the addition amount g / kg, and the refractive index difference | △ nd _A | of the light diffusing fine particles A and the base resin, and S _B
Is the product of the specific cross-sectional area cm ² / g and the added amount g / kg of the light diffusing fine particles B and the refractive index difference | △ nd _B | of the light diffusing fine particles B and the base resin, and | △ nF _A | Is the difference in the refractive index between the base resin and the light diffusing fine particles A at the F line (4861 °), and | {nF _B | is the difference in the refractive index between the base resin and the light diffusing fine particles B at the F line (4861 °). And | △ nd _A | is the d of the base resin and the light diffusing fine particles A.
The difference in the refractive index at the line (5893), || nd
_B | is the d-line (5893) between the base resin and the light diffusing fine particles B.
△) is the difference in the refractive index, | ＣnC _A | is the difference in the refractive index at the C line (6563Å) between the base resin and the light diffusing fine particles A, and | △ nC _B | is the light diffusion from the base resin. This is the difference in the refractive index at the C-line (6563 °) from the conductive fine particles B. ) Shows the relationship between the difference in refractive index by wavelength between the fine particles A and B and the base resin, the amount of addition and the specific cross-sectional area, when the ratio of fine particles A and B is in the range of 0.95 to 1.05. The color temperature difference can be made within 1500 k in the vertical direction of 0 to 25 °.

The color temperature difference 1500k is a color temperature difference at which a change in color tone cannot be visually recognized, and is set as a range that does not hinder practical use. However, it is desirable that the color temperature difference be as small as possible, and the color temperature difference can be further reduced by making the value of the formula (IV) closer to 1.0.

In the present invention, when three or more types of light diffusing fine particles are mixed, the relationship between the refractive index difference by wavelength, the amount added, and the specific cross-sectional area was also examined. That is, the present invention provides a refractive index N _S in which light diffusing fine particles are dispersed.
In the lenticular lens sheet made of substantially transparent plastic, the k-th (1 ≦ k ≦ a)
A type of substantially transparent light-diffusing fine particles having a refractive index of N _Pk and an average particle diameter of d _k (μm)
The present invention relates to a lenticular lens sheet using fine particles of ≧ 3) and having a refractive index, an average particle diameter, and a difference in refractive index by wavelength with respect to a base resin satisfying the following formulas (V), (VI) and (VII). (V): 0.02 ≦ | N _S −N _Pk | ≦ 0.10 (VI): 5 ≦ d _k ≦ 30

(Equation 3) (Where S _k is the specific cross-sectional area c of the k-th light diffusing fine particle)
and m ² / g and the amount g / kg, the refractive index difference between the k-th light diffusing fine particles and base resin | is the product of (| | [Delta] nd _k [Delta] nd _k | base resin and k-th light-diffusing This is the difference in refractive index between the particles and the d-line (5893 °).) |
ΔnF _k | and | ΔnC _k | are the differences in refractive index between the base resin and the k-th light diffusing fine particle at the F line (4861 °) and the C line (6563 °), respectively. )

The difference in refractive index between the base resin and the light diffusing fine particles by wavelength indicates that
ΔnF | − | ΔnC |), but at least one of the other types (|
ΔnF | − | ΔnC |), and | ΔnF | and | Δn
It is preferable that the magnitude relationship of C | is reversed.

As described above, it has been found that the color temperature characteristics of a lenticular lens sheet are improved by mixing fine particles having poor color temperature characteristics alone with each other at a certain ratio, and an image having a uniform color tone can be obtained. did.

As the transparent fine particles satisfying the above-mentioned ranges of the refractive index and the average particle diameter, inorganic fine particles (glass beads,
Silica, aluminum hydroxide, etc.) and organic high-molecular fine particles (methyl methacrylate-based cross-linked polymer fine particles, etc.), etc., all of which can be suitably used depending on the refractive index difference from the base resin and the wavelength-dependent refractive index difference. it can

As described above, two or three or more types of light diffusing fine particles are melted and extruded from a resin mixed with a substantially transparent plastic, and are passed in parallel between engraved rolls to give a lens shape. A lenticular lens sheet can be manufactured by using a lenticular lens sheet made of a convex lens.

[0021]

The present invention will be described in detail with reference to the following examples. In the examples and comparative examples, the average particle diameter is a weight median diameter measured by Seishin Micron Photosizer (SKA-5000, Seishin Enterprise Co., Ltd.). The refractive index was measured for each wavelength using an ATAGO precision Atsube refractometer 3T and an ATAGO spectral light source device MM-700. Luminance and color temperature are Minolta Co., Ltd.
And a colorimeter CS-100. To measure the screen gain and color temperature, a lenticular lens sheet was attached to a 50-inch projection television, the luminance in the normal direction was measured from a position at a distance of 1 m, and G ₀ was calculated from a sample with a known gain. . Further, the gain and the color temperature at an angle of 0 to 25 ° in a direction (vertical direction) parallel to the axis of the lenticular lens were determined. The gain and the color temperature at each density and mixing ratio were measured, and the color temperature was evaluated based on the color temperature difference from 0 to 25 °.

Examples 1-4 An MMA-styrene copolymer resin having a refractive index of 1.53 (TX-400-300L, manufactured by Denki Kagaku Kogyo Co., Ltd.) had an average particle size of 1
8.9 μm, glass beads having a refractive index of 1.56 (Toshiba Barotini Co., Ltd. EGB210) and styrene-based crosslinked polymer resin fine particles (SBX-17, Sekisui Plastics Co., Ltd.) have an average particle diameter of 12.3 μm and a refractive index of 1. 59 was mixed and melt-extruded at the ratios shown in Table 1, and passed between rolls engraved to impart a lens shape to obtain a lenticular lens sheet comprising parallel convex lenses. This sheet was mounted on the front of a 50-inch rear projection television, a white signal was projected, and the luminance and color temperature in the direction parallel to the lens axis from the front of the sheet were measured.

As a result, mixing was carried out so that the ratio according to the formula (III) would be 1.0 to 1.05 in relation to the specific cross-sectional area of the fine particles A and B, the added amount, and the difference in refractive index by wavelength with respect to the base resin. Then, the color temperature difference was as small as 200 to 1200 k. In addition, in FIG. 1, Examples 1, 2, 3, and 4
,,.

Examples 5 to 8 In the same manner as in Examples 1 to 4, an MMA-styrene copolymer resin having a refractive index of 1.53 was used instead of styrene-based crosslinked fine particles.
MMA-based crosslinked polymer resin fine particles (Sekisui Plastics Co., Ltd. MB
X-8) A mixture of glass beads (EGB210) having an average particle diameter of 7.9 μm and a refractive index of 1.49 at a ratio shown in Table 1 was melt-extruded to obtain a lenticular lens sheet. This sheet was similarly attached to the front of a 50-inch rear projection television, and the luminance and color temperature at a white signal were measured.

As a result, as in Examples 1-4, (II
When mixed so that the ratio in the formula (I) was 1.0 to 1.05, the color temperature difference was as small as 700 to 1200 k. In addition, in FIG. 1, Examples 5, 6, 7, and 8 respectively correspond to.

Comparative Examples 1-2 MMA-styrene copolymer resin having a refractive index of 1.53 was added to MMA.
The crosslinked polymer resin fine particles (MBX-8) and the styrene crosslinked polymer resin fine particles (SBX-17) were mixed and melt-extruded at the ratio shown in Table 1 to obtain a lenticular lens sheet.
This sheet was similarly attached to the front of a 50-inch rear projection television, and the luminance and color temperature at a white signal were measured.

As a result, in the above two kinds of mixture, (III)
A mixing ratio within the range of 0.95 to 1.05 in the formula could not be obtained, and the color temperature difference was as large as 3000 k or more. In addition, in FIG.
This corresponds to (10).

Comparative Examples 3 and 4 Only glass beads (EGB210) were mixed and extruded with MMA-styrene copolymer resin having a refractive index of 1.53 to obtain a lenticular lens sheet. Repeat this sheet for 5
It was mounted on the front of a 0-inch rear projection television, and the luminance and color temperature of a white signal were measured.

As a result, the ratio in the formula (III) was less than 0.95, and the color temperature difference was as large as -3500 k. In FIG. 1, Comparative Examples 3 and 4 correspond to (11) and (1), respectively.
It corresponds to 2).

Comparative Examples 5 and 6 MMA-styrene copolymer resin having a refractive index of 1.53 was added to MMA.
Only the system-crosslinked polymer resin fine particles (MBX-8) were mixed and melt-extruded to obtain a lenticular lens sheet. This sheet was attached to the front of a 50-inch rear projection television, and the luminance and color temperature of the white signal were measured.

As a result, the ratio in the formula (III) was 1.05 or more, and the color temperature difference was as large as 5000 k. In addition,
In FIG. 1, Comparative Examples 5 and 6 correspond to (13) and (14), respectively.

[0032]

[Table 1]

[0033]

According to the present invention, by combining light diffusing fine particles, it is possible to obtain a screen with a uniform color tone without a color temperature difference in a rear projection television without impairing high diffusion performance. .

[Brief description of the drawings]

FIG. 1 shows the value of ΔK and the value of formula (IV) in Examples and Comparative Examples.
This shows the relationship.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03B 21/62 G02B 5/02 G02B 3/00

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein the refractive indices are N _PA and N _PB , respectively.
Average particle diameter of each _{d A (μm)} and _{d B (μm)}
And substantially transparent A and B having a refractive index, an average particle diameter, and a refractive index difference by wavelength with respect to the base resin satisfying the following formulas (I), (II) and (III). A lenticular lens sheet composed of parallel convex lenses, through which a kind of light diffusing fine particles melt-extrude a resin mixed with a substantially transparent plastic having a refractive index N _s and pass between engraved rolls to give a lens shape; A method for manufacturing a lenticular lens sheet. _{(I): 0.02 ≦ | N} S -N PA | ≦ 0.10 0.02 ≦ | N S -N PB | ≦ 0.10 (II): 5 ≦ d A <20 5 ≦ d B <20 (III): (| △ nF _A | − | △ nC _A |) × (| △ nF _B | − | △ nC _B |) <0, where the refractive indexes N _S , N _PA and N _PB in the above equation
Is the refractive index at the d-line (5893Å), and | △ nF
_A | is the F line (4861) between the base resin and the light diffusing fine particles A.
Å) is the difference in refractive index, | △ nF _B | is the difference in refractive index between the base resin and the light diffusing fine particles B at the F line (4861 拡 散), and | △ nC _A | | NC _B | is the difference between the refractive indices of the base resin and the light diffusing fine particles B at the C line (6563 °). 2. The k-th (where 1 ≦ k ≦ a) light diffusing fine particles have a refractive index of N _Pk and an average particle diameter of d _k (μm).
A kind of substantially transparent a (where a is a number) in which the refractive index, the average particle diameter, and the refractive index difference with respect to the wavelength of the base resin satisfy the following formulas (V), (VI) and (VII). ≧
A lenticular lens sheet comprising parallel convex lenses, wherein the light diffusing fine particles of 3) melt-extrude a resin mixed with a substantially transparent plastic having a refractive index N _s and pass between engraved rolls to impart a lens shape. A method for producing a lenticular lens sheet. (V): 0.02 ≦ | N _S −N _Pk | ≦ 0.10 (VI): 5 ≦ d _k ≦ 30 However, in the refractive index difference by wavelength between the base resin and the light diffusing fine particles, (| ΔnF | − | Δ
nC |), but at least one of the other types (| ΔnF | − |
ΔnC |). S _k is the specific cross-sectional area cm ² / g and the added amount g / kg of the k-th light diffusing fine particle, and k
Index difference between the second light diffusing fine particle and the base resin | Δn
d _k | (| Δnd _k | is the difference in refractive index between the base resin and the k-th light diffusing fine particle at the d-line (5893 °)). | ΔnF _k | and | ΔnC _k | are the F-line (48
61 °) and C-line (6563 °).