JP2008310160A - Eyeglasses lens and method for manufacturing eyeglasses lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide eyeglasses lens having no change in the thickness in a rim portion along the periphery and showing preferable appearance. <P>SOLUTION: The eyeglasses lens 1 is provided with a diffraction structure 4 having different pitches in an astigmatic axis X and an intersection axis Y orthogonal to the astigmatic axis X. The diffraction structure 4 comprises a plurality of concentrically formed ellipses. The difference in the radius of curvature between the astigmatic axis X and the intersection axis Y orthogonal to the astigmatic axis X on an astigmatism synthesized plane of the eyeglasses lens 1 can be reduced by the astigmatism given by the diffraction structure 4. Thereby, even when a large astigmatism is imparted to the eyeglasses lens 1 for astigmatism correction, the difference in the thickness in the rim portion of the eyeglasses lens 1 can be decreased. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a spectacle lens that imparts astigmatism and a method of manufacturing the spectacle lens.

Eyeglass lenses that provide astigmatism for astigmatism correction are widely used. Some spectacle lenses use a lens having a surface far from the eye as a rotationally symmetric surface and a surface near the eye as a rotationally asymmetric toric surface. This rotationally asymmetric toric surface is given astigmatism by making the curvatures of curved surfaces in two directions orthogonal to each other different.
In this spectacle lens, in order to increase the degree of astigmatism to be corrected, the difference in curvature between two directions orthogonal to each other is increased, but the thickness of the edge portion of the spectacle lens greatly varies with the difference in curvature. become.

  In eyeglasses, the edge of the lens is attached by a lens frame. When the thickness of the edge portion of the spectacle lens is greatly different, a thin portion where the edge portion of the spectacle lens fits in the frame and a thick portion that protrudes from the frame are generated, and the appearance of the spectacles is impaired.

On the other hand, as a conventional example for correcting aberration, there is a spectacle lens having a diffractive structure (Patent Document 1).
This conventional spectacle lens has a diffractive structure composed of steps that are rotationally symmetric with respect to the optical axis.
This diffractive structure is composed of steps formed on concentric circles, and the pitch of the steps decreases as the distance from the center of the lens increases.

JP 2000-284238 A

However, in the conventional example shown in Patent Document 1, the object to be corrected is chromatic aberration, and astigmatism is not mentioned at all.
That is, in the conventional example shown in Patent Document 1, all the diffractive structures are formed of concentric annular zones with respect to the optical axis, and there is a problem that it cannot cope with correction of astigmatism with locally astigmatism.

  An object of the present invention is to provide a spectacle lens and a method for manufacturing a spectacle lens, in which the thickness of the peripheral portion does not change along the outer periphery and the appearance is good.

Therefore, the spectacle lens of the present invention is a spectacle lens provided with a diffractive structure, and is characterized in that the pitch of the diffractive structure is different between an astigmatic axis and an intersecting axis intersecting the astigmatic axis.
In the invention with this configuration, the difference in the radius of curvature between the astigmatism axis direction on the astigmatism synthesis surface of the lens and the cross axis direction intersecting the astigmatism axis can be reduced by the amount of astigmatism provided by the diffraction structure. Therefore, the difference in the peripheral edge of the lens is reduced, the appearance is improved, and the lens is thin and light.

Here, in the spectacle lens of the present invention, it is preferable that the diffractive structure is composed of a plurality of ellipses formed concentrically.
In the invention of this configuration, the power change between the astigmatism axis and the cross axis becomes smooth, and thus eye fatigue is not caused to the user of the glasses.

The diffractive structure is preferably provided on the object side surface.
In the invention of this configuration, normally, the spherical side surface, aspherical surface, toric surface, and progressive surface may be processed separately on the eyeball side surface. Therefore, if a diffractive structure is provided on the object side surface, the eyeball side surface is processed or not. First, astigmatism can be corrected.

The diffractive structure preferably has a concave lens effect such that a light beam incident in parallel with the optical axis is separated from the optical axis.
In the invention of this configuration, since the concave lens effect is generated by the diffractive structure, a large astigmatism can be imparted. Therefore, the difference in the lens peripheral edge between the astigmatic axis and the cross axis can be further reduced.

The diffractive structure preferably has a plurality of chevron shapes with continuous cross sections, and the pitch of the chevron shape decreases as the distance from the optical axis increases, or the angle of the chevron shape increases with respect to a plane perpendicular to the optical axis.
In the invention with this configuration, it is possible to easily manufacture a spectacle lens that can correct astigmatism by simply forming a predetermined chevron shape on the spectacle lens.

The spectacle lens of the present invention is preferably used for astigmatism correction.
In the invention of this configuration, astigmatism is given to the spectacle lens so as to correct astigmatism.

The diffractive structure is preferably formed on a lens substrate, and a coating layer made of a material having a refractive index different from that of the lens substrate is formed on the diffractive structure formed on the lens substrate.
In the invention of this configuration, since the coating layer is formed on the diffractive structure, the diffractive structure is protected by the coating layer, and the durability of the spectacle lens can be ensured.

The spectacle lens manufacturing method of the present invention is a method for manufacturing a spectacle lens having the above-described configuration, wherein a transfer shape that is reversed to the diffraction structure is formed in a lens mold by lithography, and a lens substrate is formed using the lens mold. It is characterized by manufacturing.
In the invention of this configuration, a transfer shape is formed on the lens mold by a simple technique called lithography, and when the lens is manufactured with the lens mold, the transfer structure is transferred to the spectacle lens itself to easily form the diffraction structure. it can.

Here, in the spectacle lens manufacturing method of the present invention, a spectacle lens blank in which the diffraction structure is provided in advance on the object side surface is prepared, and a spherical surface, an aspheric surface, a toric surface, a progressive surface is provided on the eyeball side surface according to prescription. The structure which processes is preferable.
In the invention of this configuration, since the diffractive structure is previously formed on the object side surface of the spectacle lens blank, the spectacle lens blank can be shared regardless of the prescription.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the structure of the spectacle lens 1 according to the present embodiment will be described with reference to FIGS. This embodiment is for astigmatism correction. FIGS. 1 and 2 are examples in which the spectacle lens 1 is a concave lens, and FIGS. 3 and 4 are examples in which the spectacle lens 1 is a convex lens.
1 and 3 are schematic views of the spectacle lens 1 as viewed from the front. 2 and 4 are cross-sectional views of the spectacle lens 1, wherein (A) is a cross-sectional view showing the whole, and (B) is an enlarged cross-sectional view of a portion indicated by an arrow B in (A). .

In these drawings, the spectacle lens 1 includes a plastic lens substrate 2 and a coating layer 3 provided on the object side surface of the plastic lens substrate 2.
The plastic lens substrate 2 has a diffractive structure 4 formed on the surface facing the coating layer 3, that is, the object side surface, and a toric surface 5 formed on the eyeball side surface. 2 and 4, the left side is the object side, and the right side is the eyeball side. Since FIG. 2 shows a concave lens, the curve of the eyeball side surface of the plastic lens substrate 2 is formed deeper than the curve of the object side surface. Since FIG. 4 shows a convex lens, the curve of the eyeball side surface of the plastic lens substrate 2 is formed shallower than the curve of the object side surface.

The plastic lens substrate 2 is formed of a thermosetting resin. This thermosetting resin is, for example, tetrakis (2,3-epithiopropylthio) tin, tetrakis (2,3-epithiopropylthio) silicon, tetrakis (2,3-epithiopropylthio) having a high refractive index. Examples thereof include thermosetting resins obtained by polymerizing compounds such as zirconium, tetrakis (2,3-epithiopropylthio) germanium, tetrakis (2,3-epithiopropylthio) titanium.
The coating layer 3 is allyl diglycol carbonate or other synthetic resin material and has a refractive index of n1, and this refractive index n1 is not the same as the refractive index n2 of the plastic lens substrate 2.
A primer layer, a hard coat layer, and an antireflection layer (not shown) are formed on the surface of the coating layer 3 as necessary. A known material can be used for these layers.

The diffractive structure 4 has a shape in which a mountain-shaped portion 4A in cross section is continuously formed from the optical axis Z to the peripheral portion.
The pitch of the adjacent mountain-shaped portion 4A is different from the pitch P _{s + c} along the cross axis Y perpendicular to the pitch P _s along the astigmatic axis X and the astigmatic axis X, these pitch _{P s,} P _s + _c Becomes smaller from the portion closer to the optical axis Z toward the lens peripheral edge away from the optical axis Z. Therefore, the plan view of the diffractive structure 4 is a plurality of elliptical annular gratings having the optical axis Z concentric.
The chevron shaped portion 4A constituting the diffractive structure 4 includes a rising surface 4A1 substantially parallel to the optical axis Z and an inclined surface 4A2 formed continuously with the rising surface 4A1.
In order to produce a concave lens effect in which the light beam incident on the diffractive structure 4 in parallel with the optical axis Z is separated from the optical axis Z, the inclined surface 4A2 has an intersection between the vertical line segment and the optical axis Z. It is formed so as to be closer to the object side (left side in FIGS. 2 and 4) than the lens 1.

  Here, the height of the rising surface 4A1 of the chevron shaped portion 4A is the lattice thickness d, and this lattice thickness d is obtained from the following equation 1.

For example, mercury lamp e-line λ ₀ = 546.07 nm (JIS T7330) is used as the reference wavelength.
The material of the coating layer 3 is allyl diglycol carbonate (n ₁ = 1.50), and the plastic lens substrate 2 is a thiourethane resin (Mitsui Chemicals, Inc. MR-8, n ₂ = 1.60). The optical path length difference m given by the diffractive structure 4 is one wavelength (m = 1).
The specific lattice thickness d under the above conditions is d≈5.46 μm.
The material of the coating layer 3 is allyl diglycol carbonate (n ₁ = 1.50), and the plastic lens base 2 is a disulfide resin (Mitsui Chemicals, Inc. MR-174, n ₂ = 1.74). The optical path length difference given by the diffractive structure 4 is one wavelength (m = 1).
The specific lattice thickness d under the above conditions is d≈2.28 μm.

  The radius of the annular zone of the m-th diffractive structure 4 counted from the optical axis Z (the pitch of the diffractive structure 4) can be obtained from the following equation 2. In the formula, f is a focal length.

Here, in consideration of the refractive index n2 of the plastic lens substrate 2 constituting the diffractive structure 4, the radius rm of the _mth diffractive structure annular zone is as shown in Equation 3.

  Accordingly, the pitch of the ring zones of each diffractive structure is as shown in Equation 4.

For example, as an effect of the diffractive structure 4, the pitch when obtaining minus 0.50 diopter in the astigmatic axis X direction and minus 1.00 diopter in the cross axis Y direction (astigmatic axis + 90 °) orthogonal to the astigmatic axis is shown in Table 1. As shown.
P _s : Astigmatic axis direction pitch
P _{s + c} : Pitch in the direction perpendicular to the astigmatic axis λ ₀ = 546.07 nm (mercury lamp e-line as the reference wavelength)
Ax: Astigmatic axis direction Φs: Frequency due to diffractive structure in astigmatic axis direction Φs + c: Frequency due to diffractive structure in direction perpendicular to astigmatic axis Φs = −0.50 diopter, Φs + c = −1.00 diopter

The pitch P _s of the direction of the astigmatic axis X from Table 1, the pitch P _{s + c} in the direction Y orthogonal to the astigmatic axis X is found to differ. Moreover, these pitches P _s and P _{s + c become} smaller from the optical axis Z toward the periphery. Therefore, when the grating thickness d is constant, the angle formed by the inclined surface 4A2 with the optical axis Z increases as it goes toward the peripheral edge.
The “distance from the optical axis of the lens” and the “reciprocal of the pitch at that position” are graphically displayed as shown in FIGS. FIG. 5 is a graph showing the relationship between “the distance from the optical axis of the lens” and “the reciprocal of the pitch at that position” in the astigmatic axis direction, and FIG. 6 shows the “from the optical axis of the lens” in the direction orthogonal to the astigmatic axis. It is a graph which shows the relationship between "distance" and "the reciprocal of the pitch in the position."
Here, the pitch in the direction of the astigmatism axis and the pitch in the direction orthogonal to the astigmatism axis are in the relationship of Formula 5 in each annular zone.

  When connecting the diffraction element in the direction of the astigmatism axis and the diffraction element in the direction orthogonal to the astigmatism axis by an ellipse, the number of the ellipse (ring zone) is m (m = 0, 1, 2,...) The diffractive structure 4 can be expressed by an elliptic equation represented by 6.

Next, a method for manufacturing the spectacle lens 1 having the above-described configuration will be described with reference to FIGS.
[Diffraction structure forming process to lens mold]
As will be described later, a thermosetting resin is injected into a mold 15 having a pair of lens molds 10 to polymerize the plastic lens substrate 2, but diffraction is performed on one lens mold 10 of the pair of lens molds 10. A transfer shape 40 that reverses the structure 4 is formed. Therefore, a photosensitive material is thinly and uniformly applied to the inner surface of the lens mold 10, and the pattern is baked with light and transferred.

[Molding process]
The molding process assembled using the lens mold 10 will be described with reference to FIG.
In FIG. 7, while rotating the pair of lens molds 10 held by the chucks 12 and 13, the tape 14 is wound around the peripheral portions of the pair of lens molds 10, and the tape 14 is wound around the entire peripheral surfaces of the pair of lens molds 10. When it is done, a predetermined position is cut with a cutter (not shown). Thereby, the mold 15 is shape | molded.
In FIG. 7, reference numeral 16 denotes a roll that presses the tape 14 against the peripheral surface of the lens mold 10.

[Plastic polymerization process]
The plastic polymerization process will be described with reference to FIG. FIG. 8 shows a plastic lens manufacturing apparatus.
In FIG. 8, the plastic lens manufacturing apparatus includes a resin injection mechanism 20 that injects a thermosetting resin into the mold 15, and the resin injection mechanism 20 supplies a resin raw material into the mold 15. 21 and a control unit 22 for controlling the amount of the resin raw material to be supplied.
The supply unit 21 is connected to a nozzle 211 for injecting a resin material into the mold 15, a resin material flow pipe 212 having a lower end connected to the base end of the nozzle 211, and an upper end of the resin material flow pipe 212. The amount of the resin raw material supplied from the nozzle 211 is controlled by controlling the opening amount with an injection control valve 214 provided in the resin raw material distribution pipe 212.
The control unit 22 includes a flow rate adjusting unit 221 that controls the injection control valve 214, a sensor 222 that detects that the resin raw material has been injected into the mold 15 to a predetermined position, a sensor 224 that switches the flow rate of the resin raw material, And a control unit main body 223 for receiving the signals from the sensors 222 and 224 and controlling the flow rate adjusting unit 221.

In the plastic lens manufacturing apparatus, a thermosetting resin is injected into the mold 15 by the resin injection mechanism 20. At this time, the liquid level of the thermosetting resin rises with the injection of the resin raw material, but the sensor 224 detects that the liquid level has reached the vicinity of the injection port 14A, and the injection flow rate is gradually reduced. . When the sensor 222 detects that the resin raw material is filled in the mold 15, a signal from the sensor 222 is sent to the control unit 22, and the injection of the resin raw material is stopped. After the resin injection, the injection port 14A is sealed by an appropriate means. When the inlet 14A is sealed, the mold 15 is placed in a furnace and cured by heating.
As a result, the plastic is polymerized and the transfer shape 40 formed on the lens mold 10 is transferred to the plastic lens substrate 2.

[Release process]
In the mold 15 taken out from the furnace, the tape 14 is peeled off from the peripheral surfaces of the pair of lens molds 10, and the pair of lens molds 10 is peeled off to form the plastic lens substrate 2. A diffractive structure 4 is formed on the surface of the plastic lens substrate 2.
[Coating layer forming process]
A coating layer 3 is formed on the surface of the plastic lens substrate 2 on which the diffractive structure 4 is formed. For this purpose, a lens mold (not shown) is arranged facing the surface of the plastic lens substrate 2 on which the diffractive structure 4 is formed, and a synthetic resin for forming the coating layer 3 between the lens mold and the plastic lens substrate 2 is used. Inflow. After the synthetic resin is cured, the lens mold is removed.
[Eyeball side surface formation process]
A spectacle lens blank in which the diffractive structure 4 and the coating layer 3 are provided in advance is prepared, and on the opposite side of the surface on which the diffractive structure 4 of the plastic lens substrate 2 is provided, that is, on the side surface of the eyeball according to the prescription, Machining aspherical surfaces, toric surfaces, and progressive surfaces. This processing step is the same as the conventional one, and is performed, for example, by grinding.
Thereafter, a primer layer, a hard coat layer and an antireflection layer are formed on the surface of the spectacle lens 1 in the same manner as in the prior art.

Therefore, in the present embodiment, the following operational effects can be achieved.
(1) Since the diffractive structure 4 having a different pitch between the astigmatism axis X and the cross axis Y is provided in the spectacle lens 1, it is necessary to increase the difference in curvature between the astigmatism axis and the cross axis in order to give large astigmatism. Therefore, the difference in the thickness of the lens periphery can be reduced. Therefore, even if the frame is attached to the spectacle lens 1, a part of the peripheral edge portion of the spectacle lens 1 does not protrude from the frame, and the appearance of the spectacle lens 1 is improved. In addition, the eyeglass lens 1 itself can be made thinner and lighter.

(2) Since the diffractive structure 4 is composed of a plurality of concentric ellipses, the frequency change between the astigmatic axis X and the cross axis Y becomes smooth. Therefore, even if a user wearing glasses changes his / her line of sight, the eyes will not become tired.
(3) Since the diffractive structure 4 is provided on the object side surface, astigmatism can be imparted regardless of whether or not the eyeball side surface is processed.

(4) When a progressive surface is processed on the side of the eyeball, adjustment force correction by a progressive multifocal lens can be performed together.
(5) Since the diffractive structure 4 is configured to produce a concave lens effect in which a light beam incident in parallel to the optical axis Z is separated from the optical axis, large astigmatism can be efficiently imparted. Therefore, the difference in the thickness of the lens peripheral edge between the astigmatism axis X and the cross axis Y can be further reduced.

(6) The diffractive structure 4 has a plurality of chevron-shaped portions 4A having a continuous cross section, and the pitch between the chevron-shaped portions 4A decreases from the optical axis Z toward the peripheral portion. The spectacle lens 1 capable of correcting astigmatism can be easily manufactured simply by forming the spectacle lens.

(7) Since the diffractive structure 4 is formed on the plastic lens substrate 2 and the coating layer 3 having a refractive index different from that of the plastic lens substrate 2 is formed on the diffractive structure 4 of the plastic lens substrate 2, the plastic lens The diffractive structure 4 formed on the substrate 2 is protected by the coating layer 3, and the durability of the spectacle lens 1 can be ensured.

(8) The transfer shape 40 is formed on the lens mold 10 by a simple technique called lithography, and the transfer shape 40 is transferred when the plastic lens substrate 2 is polymerized using the lens mold 10 to form the diffraction structure 4. did. Therefore, the diffractive structure 4 can be easily formed on the plastic lens substrate 2.

(9) A spectacle lens blank in which the diffractive structure 4 is provided in advance on the object side surface is prepared, and a spherical surface, an aspherical surface, a toric surface, and a progressive surface are processed on the side surface of the eyeball according to the prescription. One part can be shared.

Next, experimental examples will be described in order to confirm the effects of the present embodiment.
Table 2 shows the minimum thickness condition of the spectacle lens 1. Here, CT is the center thickness, and the unit is shown in mm. minEdge is the minimum lens edge thickness and is expressed in mm.

[Example 1]
Example 1 is a case of a negative lens having a negative power as a whole, and corresponds to the spectacle lens 1 of FIGS. 1 and 2.
First, a spherically designed astigmatic lens designed in the same manner as in the prior art will be described. In this spherical design astigmatic lens, a prescription power (S-3.00, C-2.00, Ax180 °) is produced using a plastic lens base material having a lens outer diameter of 50 mm, a base curve of 2.00, and a refractive index of 1.60 (MR-8). . At this time, the plastic lens substrate has a center thickness of 1.300 mm, a minimum lens edge thickness of 2.891 mm, a maximum lens edge thickness of 3.985 mm, and a lens edge thickness difference of 1.094 mm.

On the other hand, in Example 1, S-0.50, C-0.50, and Ax180 ° were obtained as the lens effect by the diffractive structure to reduce the difference in lens shape, particularly the lens edge thickness.
In order to obtain S-0.50, C-0.50, and Ax180 ° as the concave lens effect by the diffractive structure 4, the power of the lens was S-2.50, C-1.50, and Ax180 °. As for the thickness of each part at that time, the lens center thickness was 1.400 mm, the minimum lens edge thickness was 2.723 mm, the maximum lens edge thickness was 3.534 mm, and the lens edge thickness difference was 0.811 mm. That is, the lens edge thickness difference is from 1.094 mm to 0.811 mm, which is decreased by 0.283 mm. The results are shown in Table 3.

Further, the specific shape for obtaining S-0.50, C-0.50, and Ax180 ° as the concave lens effect by the diffractive structure 4 can be approximated as follows. It is desirable to perform precise calculations such as a ray tracing method to optimize the diffraction structure.
Allyl diglycol carbonate (n ₁ = 1.50) is used as a material constituting the coating layer 3 formed on the diffractive structure 4, and the plastic lens substrate 2 is made of Mitsui Chemicals Co., Ltd. MR-8 (thiourethane resin, n ₂ = 1.60). Further, the optical path length difference given by the diffractive structure is one wavelength, and the mercury lamp e-line λ ₀ = 546.07 nm (JIS T7330) is used as the reference wavelength.
In this case, the grating thickness d can be derived from Equation 1. The numerical value is shown in Equation 7.

[Example 2]
Example 2 is a case of a plus lens having a positive power as a whole, and corresponds to the eyeglass lens 1 of FIGS. 3 and 4.
First, a spherically designed astigmatic lens designed in the same manner as in the prior art will be described. In the case of this spherical design astigmatic lens, a prescription power (S + 3.00, C−2.00, Ax180 °) is produced using a lens base material having a lens outer diameter of 50 mm, a base curve of 5.00, and a refractive index of 1.60 (MR-8). . At this time, the plastic lens substrate has a center thickness of 2.800 mm, a minimum lens edge thickness of 1.234 mm, a maximum lens edge thickness of 2.288 mm, and a lens edge thickness difference of 1.054 mm.

On the other hand, in Example 2, S-0.50, C-0.50, and Ax180 ° were obtained as the lens effect by the diffractive structure to reduce the difference in lens shape, particularly the lens edge thickness.
In order to obtain S-0.50, C-0.50, and Ax180 ° as the concave lens effect by the diffractive structure 4, the lens power is S + 3.50, C-1.50, and Ax180 °. At that time, as for the thickness of each part, the lens center thickness was 3.000 mm, the minimum lens edge thickness was 1.174 mm, the maximum lens edge thickness was 1.961 mm, and the lens edge thickness difference was 0.787 mm. In other words, the difference in lens edge thickness decreased from 1.054mm to 0.787mm by 0.267mm. The results are shown in Table 4.

Further, the specific shape for obtaining S-0.50, C-0.50, and Ax180 ° as the concave lens effect by the diffractive structure 4 can be approximated as follows.
Allyl diglycol carbonate (n ₁ = 1.50) is used as a material constituting the coating layer 3 formed on the diffractive structure 4, and the plastic lens substrate 2 is made of Mitsui Chemicals Co., Ltd. MR-8 (thiourethane resin, n ₂ = 1.60). Further, the optical path length difference given by the diffractive structure is one wavelength, and the mercury lamp e-line λ ₀ = 546.07 nm (JIS T7330) is used as the reference wavelength.
In this case, the lattice thickness d is expressed by Equation 7.

[Example 3]
Example 3 is a case of a mixed lens having a positive power on one axis of the lens and a negative power on the other orthogonal axis.
First, a spherically designed astigmatic lens designed in the same manner as in the prior art will be described. In the case of this spherical design astigmatic lens, a prescription power (S + 3.00, C−4.00, Ax180 °) is produced using a lens base material having a lens outer diameter of 50 mm, a base curve of 5.00, and a refractive index of 1.60 (MR-8). . At this time, the plastic lens base material has a center thickness of 2.800 mm, a minimum lens edge thickness of 1.234 mm, a maximum lens edge thickness of 3.366 mm, and a lens edge thickness difference of 2.132 mm.

On the other hand, in Example 3, S-0.50, C-0.50, and Ax180 ° were obtained as the lens effect by the diffractive structure to reduce the difference in lens shape, particularly the lens edge thickness.
In order to obtain S-0.50, C-0.50, and Ax180 ° as the concave lens effect by the diffractive structure 4, the lens power is S + 3.50, C-3.50, and Ax180 °. At that time, as for the thickness of each part, the lens center thickness was 3.000 mm, the minimum lens edge thickness was 1.174 mm, the maximum lens edge thickness was 3.025 mm, and the lens edge thickness difference was 1.851 mm. In other words, the difference in lens edge thickness decreased from 2.132 mm to 1.851 mm, by 0.281 mm. The results are shown in Table 5.

Further, the specific shape for obtaining S−0.50, C−0.50, and Ax180 ° as the lens effect by the diffractive structure can be approximated as follows. Allyl diglycol carbonate (n ₁ = 1.50) is used as a material for coating the diffractive structure, and the plastic lens substrate 2 is MR-8 (thiourethane resin, n ₂ = 1.60). The optical path length difference given by the diffractive structure 4 is one wavelength, and the mercury lamp e-line λ ₀ = 546.07 nm (JIS T7330) is used as the reference wavelength.
In this case, the lattice thickness d is expressed by Equation 7.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the above embodiment, the diffractive structure 4 is composed of a plurality of ellipses formed concentrically. However, in the present invention, a plurality of triangles formed concentrically and a plurality of rectangles formed concentrically are formed. A diffractive structure may be used.
Further, it is not always necessary to provide the coating layer 3.
Further, the substrate may be formed from glass other than plastic, for example.
The method of forming the diffractive structure 4 on the plastic lens substrate 2 is not limited to the method of forming the transfer shape 40 on the lens mold 10 by lithography. For example, the diffractive structure is formed on the lens substrate using a laser. 4 may be formed directly.

  The present invention can be used for spectacle lenses formed of plastic or other materials.

The schematic diagram which looked at the spectacle lens (concave lens) concerning one Embodiment of this invention from the front. (A) is sectional drawing which shows the whole said spectacle lens, (B) is an expanded sectional view of the part shown by the arrow B of (A). The schematic diagram which looked at the spectacle lens (convex lens) concerning one Embodiment of this invention from the front. (A) is sectional drawing which shows the whole said spectacle lens, (B) is an expanded sectional view of the part shown by the arrow B of (A). The graph which shows the relationship between "the distance from the optical axis of a lens" and "the reciprocal of the pitch in the position" in the astigmatic axis direction. The graph which shows the relationship between "the distance from the optical axis of a lens" and "the reciprocal of the pitch in the position" in the direction orthogonal to an astigmatic axis. The perspective view explaining the outline of a mold formation process. The figure explaining the outline of a plastic polymerization process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Eyeglass lens, 2 ... Plastic lens base material, 3 ... Coating layer, 4 ... Diffraction structure, 4A ... Angle-shaped part, 40 ... Transfer shape, 10 ... Lens type

Claims (10)

  A spectacle lens provided with a diffractive structure, wherein a pitch of the diffractive structure is different between an astigmatic axis and an intersecting axis intersecting the astigmatic axis.   The spectacle lens according to claim 1, wherein the diffractive structure is composed of a plurality of ellipses formed concentrically.   3. The spectacle lens according to claim 1, wherein the diffractive structure is provided on a side surface of the object.   4. The spectacle lens according to claim 3, wherein any one of a spherical surface, an aspheric surface, a toric surface, and a progressive surface is processed on a side surface of the eyeball.   5. The spectacle lens according to claim 1, wherein the diffractive structure produces a concave lens effect such that a light beam incident parallel to the optical axis is separated from the optical axis. .   6. The spectacle lens according to claim 5, wherein the diffractive structure has a plurality of chevron shapes with continuous cross sections, and the pitch of the chevron shape decreases as the distance from the optical axis increases, or the inclination of the chevron shape is orthogonal to the optical axis. A spectacle lens that is larger than a plane.   The spectacle lens according to any one of claims 1 to 6, wherein the spectacle lens is used for astigmatism correction.   The spectacle lens according to any one of claims 1 to 7, wherein the diffractive structure is formed on a lens substrate, and the refractive index of the lens substrate and the refractive index are formed on the diffractive structure formed on the lens substrate. A spectacle lens comprising a coating layer made of a different material.   A method for manufacturing a spectacle lens according to any one of claims 1 to 8, wherein a transfer shape reverse to the diffractive structure is formed in a lens mold by lithography, and a lens substrate is formed using the lens mold. A method of manufacturing a spectacle lens, comprising:   10. The method for manufacturing a spectacle lens according to claim 8 or 9, wherein a spectacle lens in which the diffractive structure is provided in advance on the object side surface is prepared, and a spherical surface, an aspheric surface, a toric surface is provided on the eyeball side surface according to prescription. A method for manufacturing a spectacle lens, characterized by processing either a surface or a progressive surface.

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