JP5163832B2 - Optical element - Google Patents

Description

The present invention relates to an optical element formed by using the forming metal mold.

  When molding an optical element having an optical surface having a staircase-like microstructure such as a diffractive structure, the radius of curvature is large to prevent deviation between the optical transfer surface of the mold and the optical surface of the optical element when the mold is opened. There is a method in which an optical surface that does not have a fine structure is released from one mold first, and then an optical surface that has a small curvature radius and has a fine structure is released from the other mold (for example, Patent Documents). 1).

Japanese Patent Laid-Open No. 2002-200652

  However, in a molding die such as Patent Document 1, an optical surface having a small curvature radius and a fine structure is used as compared with a case where an optical surface having a large curvature radius and no fine structure is released from one mold. When the mold is released from the other mold, the cooling of the optical element is more advanced. Since the resin contracts when the optical element is cooled, the mold release resistance of the optical element increases when the optical surface has a fine structure. Therefore, in the molding die as in Patent Document 1, when the optical surface having a fine structure is released from the other die, the fine structure wall surface of the optical element and the fine structure wall surface of the mold are rubbed strongly. Therefore, there arises a problem that the fine structure of the optical element is deformed.

  For example, as an objective optical element for an optical pickup, a wavelength (780 nm) of a CD (Compact Disc) having a numerical aperture (NA) of 0.45 is collected on a CD optical disc, and a DVD ( CD / DVD dual wavelength compatible optical pickup objective optical element that collects the wavelength (650 nm) of a digital versatile disc on a DVD optical disc, and a wavelength of 0.45 (780 nm) with a numerical aperture (NA) of CD Condensed on an optical disc, the wavelength (650 nm) of DVD with a numerical aperture (NA) of 0.6 is condensed onto the optical disc of DVD, and the wavelength of BD (Blu-ray Disc) with a numerical aperture (NA) of 0.85 There is a CD / DVD / BD 3-wavelength compatible objective optical element for optical pickup that collects (405 nm) on a BD optical disk. Among these, the CD / DVD / BD three-wavelength compatible optical pickup objective optical element has a deeper stepped shape in the fine structure provided in the optical element than the CD / DVD two-wavelength compatible optical pickup objective optical element. Therefore, the CD / DVD / BD 3-wavelength compatible optical pickup objective optical element has a larger release resistance than the CD / DVD 2-wavelength compatible optical pickup objective optical element, and has a fine structure. When releasing the optical surface having, the fine structure of the optical element is more likely to be deformed. Here, the CD / DVD / BD three-wavelength compatible optical pickup objective optical element requires higher molding accuracy and optical performance than the CD / DVD two-wavelength compatible optical pickup objective optical element. It is necessary to further reduce the deformation of the fine structure of the optical element that occurs during the process. Therefore, particularly when molding an optical optical pickup objective optical element such as a CD / DVD / BD 3-wavelength compatible type, the problem of mold release resistance that causes deformation of the fine structure becomes a very large problem.

  Thus, when the fine structure of the optical surface has a deep step shape, the mold release resistance is further increased, and when the optical surface having the fine structure is released, deformation of the fine structure of the optical element is more likely to occur. turn into. When the deformation amount of the fine structure of the optical element is increased, the optical performance of the optical element is degraded. Therefore, the present inventor has now found that the problem of mold release resistance is a very serious problem that cannot be ignored when molding an optical element having a fine structure.

Accordingly, the present invention may be an optical element having a deep level difference in microstructure, to provide an optical element formed by using the forming metal mold that can be difficult to deform the microstructure during the release And

A molding die for molding an optical element according to the present invention is a molding die that molds an optical element by forming a mold space by clamping a first mold and a second mold. The first mold has a first optical transfer surface that forms the first optical surface of the optical element. The first mold is released from the optical element before the second mold, and the second mold is formed of the optical element. A second optical transfer surface forming a second optical surface, holding the optical element when the first mold is released, and the absolute value of the radius of curvature of the first optical transfer surface is the second optical transfer surface; The first optical transfer surface has a step shape forming a diffractive structure, the width of the step shape is X, the height of the step shape is Y, and the following conditional expression 0 .50 ≦ (Y / X) maximum value ≦ 1.0
To meet. Here, (Y / X) is the value of the ratio of the width and height of the step shape.

According to the molding die described above, the first optical transfer surface having the step shape forming the diffractive structure is released from the optical element before the second optical transfer surface, so that the step as in the multi-wavelength compatible optical element is obtained. Even when the shape is a relatively deep range satisfying the maximum value ≦ 1.0 of 0.50 ≦ (Y / X), it is possible to suppress the release resistance due to resin shrinkage due to cooling and solidification during injection molding. . Thereby, the optical element is released from the first mold smoothly with almost no resistance, and the step of the diffraction structure of the optical element, that is, the deformation of the fine shape can be prevented. When (Y / X) is smaller than 0.50, the level difference is small and the above problems hardly occur. On the other hand, a step where (Y / X) exceeds 1.0 is not practical even if the method for producing the optical element of the present invention is used, and transfer deterioration is likely to occur.

Further, the concrete embodiments or aspects, in the molding die, the first optical transfer surface, the optical axis side region disposed toward the optical axis, an outer region arranged outside the optical axis side region having at least the door, the maximum value of the outer region (Y / X) is not smaller than the maximum value of (Y / X) in the optical axis side region. In general, the optical element is cooled and solidified from the outside. Therefore, when a fine structure having a deep step shape is formed in the outer region of the optical element, the mold release resistance is larger than when a fine structure having a deep step shape is formed in the optical axis side region of the optical element. End up. In view of such a problem, in the present invention, focusing on the fact that the optical element is cooled and solidified from the outside, the maximum value of (Y / X) in the outer region is set to the maximum value of (Y / X) in the optical axis side region. By making it smaller than the value, it is possible to relax the mold release resistance applied to the step-shaped wall surface in the outer region at the time of mold release, and to facilitate the mold release from the first mold.

In another aspect, the inner wall surface and the angle between the optical axis of the stepped shape, Ru der angle less formed between an outer wall surface and the optical axis of the stepped shape. In this case, the mold structure is such that the mold release resistance is likely to be relatively large, such that the angle formed between the inner wall surface of the step shape and the optical axis is equal to or smaller than the angle formed between the outer wall surface of the step shape and the optical axis. However, smooth release can be realized by preferentially releasing from the first optical transfer surface having a high release resistance while it is warm.

In another aspect the of et, inner wall surface of the stepped shape, Ru parallel der the optical axis. In this case, the step shape can be, for example, a rectangular shape or an inner blaze shape.

Further, in another aspect the the et, stepped shape, including a rectangular shape. In this case, a multi-level diffraction grating can be formed.

In another aspect the of al, the minimum value of the outer wall surface and the angle between the optical axis of the step shape in the outer region, the minimum value of the outer wall surface and the angle between the optical axis of the step shape in the optical axis side region not larger than. In this case, paying attention to the fact that the optical element is cooled and solidified from the outside, a step in the outside region is made by making the angle of the outside wall surface in the outside region larger than the angle of the outside wall surface in the optical axis side region. The shape has less release resistance due to resin shrinkage than the step shape in the optical axis side region, and can be easily released from the first mold.

In another aspect the of al, the minimum value of the outer wall surface and the angle between the optical axis of the step shape in the outer region, the minimum value of the outer wall surface and the angle between the optical axis of the step shape in the optical axis side region Ru der below. In this case, the mold structure is such that the mold release resistance tends to be relatively large on the outside such that the angle of the outer wall surface in the outer region is equal to or less than the angle of the outer wall surface in the optical axis side region. Smooth release can be realized by preferentially releasing the first optical transfer surface having high resistance while it is warm.

In another aspect the of al, the optical axis side region, a central region disposed toward the optical axis, at least an intermediate region disposed outside the center region, the outer region than the intermediate region at least has a most peripheral area which is arranged outside the maximum value of (Y / X) in the most peripheral area is not smaller than the maximum value of (Y / X) of at least one of the central region and the intermediate region . In this case, paying attention to the fact that the optical element is cooled and solidified from the outside, the maximum value of (Y / X) in the most peripheral region is the maximum value of (Y / X) in at least one of the central region and the intermediate region. By making it smaller than this, it is possible to relieve the mold release resistance applied to the step-shaped wall surface in the outermost peripheral area at the time of mold release, and to facilitate the mold release from the first mold.

In another aspect the of et, a step shape in the central region, and the step shape in the intermediate region, the step shape in the most peripheral area, Ru different respectively. In this case, by having different step shapes in each region, a multiple wavelength compatible optical pickup objective lens can be easily realized, and the diffraction efficiency of the optical element can be improved.

In another aspect the of al, the minimum value of the angle between the outer wall surface and the optical axis of the step shape in the most peripheral area forms the outer wall surface and the optical axis of the step shape in one of the central region and the intermediate region There have larger than the minimum value of the angle. In this case, paying attention to the fact that the optical element cools and solidifies from the outside, the angle of the outer wall surface in the outermost peripheral region is made larger than the angle of the outer wall surface in either the central region or the intermediate region. As a result, the step shape in the outermost peripheral region has less mold release resistance due to resin shrinkage than the step shape in the central region and the intermediate region, and can be easily released from the first mold.

In another aspect the of al, the minimum value of the angle between the outer wall surface and the optical axis of the step shape in the most peripheral area forms the outer wall surface and the optical axis of the step shape in one of the central region and the intermediate region There Ru minimum der following angle. In this case, the mold structure in which the mold release resistance tends to be relatively large on the outside, such that the angle of the outer wall surface in the outermost peripheral region is equal to or smaller than the angle of the outer wall surface in one of the central region and the intermediate region. However, smooth release can be realized by preferentially releasing the first optical transfer surface having a high release resistance while it is warm.

In another aspect the of et, the first mold is a fixed mold, a second mold Ru movable die der.

An optical element according to the present invention is an optical element having a first optical surface and a second optical surface, and the absolute value of the radius of curvature of the first optical surface is greater than the absolute value of the radius of curvature of the second optical surface. The first optical surface is small and has at least a step constituting a diffractive structure in an optical axis side region arranged on the optical axis side and an outer region arranged outside the optical axis side region, and the width of the step Where X is X, the height of the step is Y, and the maximum value of (Y / X) in the outer region is smaller than the maximum value of (Y / X) in the optical axis side region.
Maximum value of (Y / X) on the first optical surface ≦ 1.0
It is characterized by satisfying. In general, the optical element is cooled and solidified from the outside. Therefore, when a fine structure having a deep step shape is formed in the outer region of the optical element, the mold release resistance is larger than when a fine structure having a deep step shape is formed in the optical axis side region of the optical element. End up. In view of such a problem, in the present invention, focusing on the fact that the optical element is cooled and solidified from the outside, the maximum value of (Y / X) in the outer region is set to the maximum value of (Y / X) in the optical axis side region. By making it smaller than the value, the release resistance applied to the step-shaped wall surface in the outer region at the time of release from the first mold can be relaxed, and the release from the first mold can be facilitated.

  In another aspect of the present invention, the optical axis side region has at least a central region disposed on the optical axis side and an intermediate region disposed outside the central region, and the outer region is more than the intermediate region. It has at least the outermost peripheral region arranged outside, and the maximum value of (Y / X) in the outermost peripheral region is smaller than the maximum value of (Y / X) in at least one of the central region and the intermediate region It is characterized by. In this case, paying attention to the fact that the optical element is cooled and solidified from the outside, the maximum value of (Y / X) in the most peripheral region is the maximum value of (Y / X) in at least one of the central region and the intermediate region. Since the release resistance applied to the step-shaped wall surface in the outermost peripheral region at the time of release from the first mold can be relaxed by making it smaller than the first mold, it can be made easier to release from the first mold. Accurate transfer is possible.

In still another aspect of the present invention, the following conditional expression 0.50 ≦ maximum value of (Y / X) in the first optical surface ≦ 1.0
It is characterized by satisfying.
In still another aspect of the present invention, the optical element is a CD / DVD / BD 3-wavelength compatible optical pickup objective optical element.

An optical element manufacturing method for manufacturing an optical element according to the present invention is an optical element manufacturing method in which an optical element is molded by a molding die, and the molding die does not remain in an open state. A first mold and a second mold in which the optical element remains in an open state; the first mold has a first optical transfer surface that forms a first optical surface of the optical element; The mold has a second optical transfer surface that forms the second optical surface of the optical element, and the absolute value of the radius of curvature of the first optical transfer surface is smaller than the absolute value of the radius of curvature of the second optical transfer surface. The first optical transfer surface has a step shape that forms a diffractive structure, where the width of the step shape is X and the height of the step shape is Y. The following conditional expression 0.50 ≦ (Y / X) Maximum value ≦ 1.0
The filled, after the mold opening process, that have a release step of releasing the optical element from the second mold.

According to the above manufacturing method, the first optical transfer surface having the step shape forming the diffractive structure is released from the optical element before the second optical transfer surface, so that the step shape like a multi-wavelength compatible optical element is obtained. Even within a relatively deep range satisfying the maximum value ≦ 1.0 of 0.50 ≦ (Y / X), it is possible to suppress the mold release resistance due to resin shrinkage due to cooling and solidification during injection molding. Thereby, the optical element is released from the first mold smoothly with almost no resistance, and the step of the diffraction structure of the optical element, that is, the deformation of the fine shape can be prevented. When (Y / X) is smaller than 0.50, the level difference is small and the above problems hardly occur. On the other hand, a step where (Y / X) exceeds 1.0 is not practical even if the method for producing the optical element of the present invention is used, and transfer deterioration is likely to occur.

It is a conceptual diagram explaining the shaping die etc. which concern on 1st Embodiment. It is a figure explaining the 1st optical transfer surface of the shaping die concerning a 1st embodiment. It is a figure explaining the optical element shape | molded using the shaping die of FIG. It is a figure explaining the 1st optical transfer surface of the shaping die concerning a 2nd embodiment. It is a figure explaining the 1st optical transfer surface of the shaping die concerning a 3rd embodiment. It is a figure explaining the 1st optical transfer surface of the molding die concerning a 4th embodiment.

[First Embodiment]
With reference to FIG.1 and FIG.2, the shaping die for shape | molding the optical element of this invention is demonstrated. The molding die 100 forms a mold space CV by clamping a fixed die 10 as a first die and a movable die 20 as a second die to form a plastic lens PL as an optical element (see FIG. 3). ). The molding die 100 is incorporated into an injection molding apparatus including the temperature adjusting unit 30, the movable mold driving unit 40, the resin injection unit 50, and the like.

  As shown in FIG. 1, the molding die 100 includes a fixed die 10 and a movable die 20. A mold space CV is formed between the molds 10 and 20 by abutting the movable mold 20 against the fixed mold 10. A gate GP communicating with the mold space CV is formed in a part of the periphery of the mold space CV. The mold space CV is filled with molten resin by the resin injection unit 50 through the gate GP.

  Here, the plastic lens PL molded by the molding die 100 will be described. In FIG. 3, the left side is a side sectional view of the plastic lens PL, and the right side is a conceptual diagram of the first optical surface OL1. The plastic lens PL is a small diffractive refractive compound lens, and is used as an objective lens of an optical pickup device, for example. The plastic lens PL has a center portion OL having an optical function and an annular flange portion FL extending from the center portion OL in the outer diameter direction. The center portion OL has a convex first optical surface OL1 having a small curvature radius and a convex second optical surface OL2 having a large curvature radius. The first optical surface OL1 and the second optical surface OL2 are opposed to each other with a thick and light-transmitting main body interposed therebetween. The flange portion FL has a first flange surface FL1 on the first optical surface OL1 side and a second flange surface FL2 on the second optical surface OL2 side.

  In the central portion OL, the first optical surface OL1 has a step of the diffractive structure, that is, a fine structure in order to be compatible with multiple wavelengths. That is, the plastic lens PL is a three-wavelength compatible optical element corresponding to a short wavelength, high numerical aperture standard, a medium wavelength, medium numerical aperture standard, and a long wavelength, low numerical aperture standard. The fine structure provided on one optical surface OL1 has a shape that allows light collection in conformity with each wavelength. In the example shown in the drawing, the first optical surface OL1 is divided into three concentric regions to correspond to light beams of three wavelengths having different numerical apertures, and a three-wavelength compatible region AR1 and two wavelengths from the inside toward the outside. The compatible area AR2 and the one-wavelength dedicated area AR3 are included. With all these areas AR1, AR2, AR3, for example, the wavelength (405 nm) of a BD (Blu-ray Disc) is condensed with a numerical aperture (NA) of 0.85 to form an optimum spot on the BD optical disc. Further, the wavelength (650 nm) of a DVD (Digital Versatile Disc) is condensed with, for example, a numerical aperture (NA) of 0.6 by the areas AR1 and AR2 excluding the outermost peripheral side away from the optical axis OA, and the optical disk on the DVD To form the optimal spot. At this time, the light flux of DVD wavelength (650 nm) that passes through the optical surface area corresponding to NA 0.6 to NA 0.85 is a flare component that does not contribute to the formation of spots used for recording / reproduction of DVD optical discs. Become. Further, by the area AR1 on the optical axis OA side, for example, the wavelength (780 nm) of a CD (Compact Disc) is condensed with a numerical aperture (NA) of 0.45, and an optimum spot is formed on the CD optical disc. At this time, the light flux of the CD wavelength (780 nm) passing through the region of the optical surface corresponding to NA 0.45 to NA 0.85 is a flare component that does not contribute to the formation of spots used for recording / reproduction of CD optical discs. Become. Note that the specific fine structure of the first optical surface OL1 is a transfer of the fine structure of the first optical transfer surface 11A of the fixed mold 10, which will be described later, and will not be described.

  Returning to FIG. 1, the fixed die 10 has a core die 11 on the center side and an outer peripheral die 12 on the peripheral side. The core mold 11 and the outer peripheral mold 12 are formed of the same steel material, for example, and are integrally fixed to each other. Of the fixed mold 10, the core mold 11 is provided with a ring-shaped diffraction pattern having a fine structure on the side facing the movable mold 20, and has a first optical transfer surface 11 </ b> A that is concave as a whole. 11A of 1st optical transfer surfaces respond | correspond to 1st optical surface OL1 (refer FIG. 3) with a small curvature radius of the plastic lens PL which is a molded article. On the other hand, the first molding surface 12A on the peripheral side formed by the outer peripheral mold 12 corresponds to the first flange surface FL1 (see FIG. 3) around the plastic lens PL.

  Hereinafter, the fine structure of the optical transfer surface 11A will be described in detail with reference to FIG. FIG. 2 is a schematic enlarged view of a side cross section of the first optical transfer surface 11A. As described above, the surface formed by the first optical transfer surface 11A is the first optical surface OL1 of the plastic lens PL.

  The first optical transfer surface 11A has a circular optical axis side region 11C and a ring-shaped outer region 11D so as to be concentric from the optical axis OA side of the first optical transfer surface 11A toward the outer side in the radial direction. Divided. The optical axis side region 11C is further divided into a concentric central region A1 and intermediate region A2 from the center of the first optical transfer surface 11A toward the outer region 11D. The center area A1 corresponds to the three-wavelength compatible area AR1 of the plastic lens PL of FIG. 3, and the intermediate area A2 corresponds to the two-wavelength compatible area AR2. The outer region 11D is the outermost peripheral region A3 and corresponds to the one-wavelength dedicated region AR3 of the plastic lens PL of FIG.

  In order to form a step of the diffractive structure of the plastic lens PL on the first optical transfer surface 11A, a large number of fine step shapes form the optical axis OA in each of the central region A1, the intermediate region A2, and the outermost peripheral region A3. It is formed in a ring shape at the center. When this ring-shaped step shape is viewed as a cross section, the inner wall surface of the concave step shape that causes mold release resistance is parallel to the optical axis OA, and the inner wall surface of the step shape and the optical axis OA are The angles α1 and α3 formed are respectively equal to or less than the angles β1 and β3 formed by the outer wall surface of the step shape and the optical axis OA. Specifically, as can be seen from the figure, in the central region A1 of the first optical transfer surface 11A, the step shape 13A is rectangular, and the inner wall surface 13B of all the step shapes 13A in the region and the optical axis OA. And the angle β1 formed by the outer wall surface 13C of the step shape 13A and the optical axis OA are both 0 degrees and the same. In the most peripheral area A3, the step shape 15A is blazed.

  Here, in the most peripheral region A3, the angle β3 formed by the outer wall surface 15C of each step shape 15A and the optical axis OA may have different values. In the case of a blazed shape, not only in the most peripheral area A3 but also in the area of the central area A1 (similar to the intermediate area A2), the angle β1 (the angle β2 is also the same between the outer wall surfaces and the optical axis OA). ) May have different values. In each stepped shape 15A, the angle α3 formed by the inner wall surface 15B and the optical axis OA is smaller than the angle β3 formed by the outer wall surface 15C and the optical axis OA.

  Further, as can be seen from the figure, the minimum value of the angle β3 formed by the outer wall surface 15C of the step shape 15A and the optical axis OA in the outermost region A3 of the outer region 11D is the central region A1 in the optical axis side region 11C. It is larger than the angle β1 formed by the outer wall surface 13C of the step shape 13A and the optical axis OA. In addition, although illustration is abbreviate | omitted, the level | step difference shape in intermediate | middle area | region A2 is rectangular shape, for example, and the angle which the wall surface inside the level | step difference shape of intermediate | middle area A2 and optical axis OA make | forms is the level | step difference shape of intermediate | middle area A2. Is equal to or smaller than the angle formed by the outer wall surface and the optical axis OA, for example, they are equal to each other. The minimum value of the angle β3 formed by the outer wall surface of the step shape 15A in the most peripheral area A3 and the optical axis OA is larger than the angle formed by the outer wall surface of the step shape in the intermediate area A2 and the optical axis OA. .

In addition, on the first optical transfer surface 11A, the width of the step shape is X, the height of the step shape is Y, and the aspect ratio value (Y / X) of the step shape is the following conditional expression 0.50 ≦ ( Maximum value of Y / X) ≦ 1.0
The step shape of the first optical transfer surface 11A is relatively deep. Such an optical transfer surface having a relatively deep step shape is indispensable for forming a multi-wavelength compatible optical element, specifically, a three-wavelength compatible optical element. Here, the maximum value of the aspect ratio (Y / X) between the width X and the height Y of the step shape in each of the regions 11C and 11D is the maximum value when the step shape has a U-shaped step shape. It is obtained on the basis of the value of the ratio between the width X and the height Y of the U-shaped step shape. For example, as shown in FIG. 2, in the central region A1, the maximum value of (Y / X) is obtained on the basis of the ratio between the width X1 and the height Y1 of the U-shaped step shape UN1. The height Y1 of the U-shaped step shape UN1 is, as shown in FIG. 2, the optical axis OA direction of two wall surfaces parallel to the optical axis OA forming the U-shaped step shape UN1. The height of the wall surface having the higher height is Y1. When the step shape does not have a U-shaped step shape, for example, in the case of a blaze type step shape, the step shape is obtained based on the value of the ratio between the width X and the height Y of the blaze type step shape. For example, as shown in FIG. 2, in the most peripheral area A3, the maximum value of (Y / X) is obtained based on the ratio of the width X3 and the height Y3 of the blaze-shaped step shape UN3.

  As shown in FIG. 2, the step shapes in the regions 11C and 11D, specifically the regions A1 and A3, are different from each other, and the maximum value of (Y / X) in the outermost peripheral region A3 which is the outer region 11D is It is smaller than the maximum value of (Y / X) in the central region A1 of the optical axis side region 11C. Although not shown, the step shape in the intermediate area A2 is, for example, a rectangle, and the maximum value of (Y / X) in the intermediate area A2 is (Y / X) in the most peripheral area A3 in the specific example. It is larger than the maximum value.

  In each of the areas AR1, AR3, etc. of the first optical surface OL1, there are formed steps that are substantially inverted from the step shapes 13A, 15A formed in the areas A1, A3, etc. of the first optical transfer surface 11A.

  Returning to FIG. 1, the movable mold 20 includes a core mold 21 on the center side and an outer peripheral mold 22 on the peripheral side. The core mold 21 and the outer peripheral mold 22 are made of, for example, the same steel material, and the outer peripheral mold 22 supports the core mold 21 from the periphery. Of the movable mold 20, the core mold 21 has a smooth concave second optical transfer surface 21 </ b> A having no step on the side facing the fixed mold 10. The second optical transfer surface 21A corresponds to the second optical surface OL2 (see FIG. 3) having a large curvature radius of the plastic lens PL that is a molded product. On the other hand, the second molding surface 22A on the peripheral side formed by the outer peripheral die 22 corresponds to the second flange surface FL2 (see FIG. 3) around the plastic lens PL.

  In the case of the present embodiment, the core mold 21 functions as a protruding portion, and can reciprocate in the direction of the axis AX while being inserted in a hole 22B provided in the outer peripheral mold 22 slightly apart. After the mold is opened to move the movable mold 20 away from the fixed mold 10, the core mold 21 is moved toward the fixed mold 10 with respect to the outer peripheral mold 22, thereby easily releasing the plastic lens PL remaining on the movable mold 20. Can do.

  Hereinafter, molding of the plastic lens PL using the molding die 100 shown in FIG. 1 will be described. First, the mold is closed by joining the movable mold 20 to the fixed mold 10. By such mold closing, a mold space CV having a shape in which the parting line surface PA1 of the fixed mold 10 and the parting line surface PA2 of the movable mold 20 are closed is formed between the molds 10 and 20.

  Next, molten plastic resin is injected into the mold space CV formed between the molds 10 and 20. That is, the molten plastic resin is introduced into the mold space CV between the molds 10 and 20 through the gate GP, and the mold space CV is filled with the molten plastic resin.

  Next, the molten plastic resin filled in the mold space CV is radiated and cooled. The temperature of the molten plastic resin injected into the mold space CV is usually 200 to 300 ° C., and the optical transfer surfaces 11A and 21A of both molds 10 and 20 held at 100 to 180 ° C. by the temperature adjusting unit 30 are usually used. And when it contacts the molding surfaces 12A and 22A, the molten plastic resin gradually cools and solidifies from the contact surface with the molding die 100.

  Next, using the movable drive unit 40, mold opening for separating the movable mold 20 from the fixed mold 10 is performed while the molten plastic resin is warm. Thereby, the mold release resistance due to the resin shrinkage due to cooling and solidification is suppressed, and even if the first optical transfer surface 11A of the molding die 100 has a relatively deep step shape, the first optical surface of the plastic lens PL. OL1 is smoothly released from the fixed mold 10 with almost no resistance. The mold opening distance for moving the movable mold 20 backward is, for example, about the thickness of the diffraction lens.

  Next, using the movable drive unit 40, the core mold 21 that is a protruding part is moved from the illustrated retracted state housed in the outer peripheral mold 22 to the fixed mold 10 side to the fixed mold 10 side from the second molding surface 22A. Drive to the protruding operating state. As a result, the plastic lens PL in which the resin contraction due to cooling is remarkable can be released from the movable mold 20, that is, separated. In the separated plastic lens PL, as shown in FIG. 3, the first optical surface OL1 is a convex surface having an annular diffraction pattern corresponding to the first optical transfer surface 11A, and the second optical surface OL2 However, it has a smooth convex surface corresponding to the second optical transfer surface 21A. Further, around the plastic lens PL, a flange portion FL is formed corresponding to the molding surfaces 12A and 22A.

  According to the molding die 100 described above, by separating the first optical transfer surface 11A having the step shapes 13A and 15A forming the diffractive structure from the plastic lens PL before the second optical transfer surface 21A, For example, even if the stepped shapes 13A and 15A such as a three-wavelength compatible optical element are in a relatively deep range satisfying the maximum value ≦ 1.0 of 0.50 ≦ (Y / X), the resin by cooling and solidifying at the time of injection molding Release resistance due to shrinkage can be suppressed. Thereby, the plastic lens PL is released from the fixed mold 10 smoothly without any resistance, and the step of the diffractive structure of the plastic lens PL, that is, the deformation of the fine shape can be prevented.

  Further, the maximum value of (Y / X) in the outermost region A3 of the outer region 11D is made smaller than the maximum value of (Y / X) in the central region A1 of the optical axis side region 11C, etc. The mold release resistance applied to the inner wall surface 15B of the step shape 15A in the most peripheral area A3 can be relaxed, and the mold can be more easily released from the fixed mold 10 even if the plastic lens PL is cooled and solidified from the outside.

  Further, the minimum value of the angle β3 formed by the outer wall surface 15C of the step shape 15A and the optical axis OA in the outermost region A3 of the outer region 11D is the outer wall surface of the step shape 13A in the central region A1 of the optical axis side region 11C. By making it larger than the minimum value of the angle β1 formed by 13C and the optical axis OA, the step shape 15A in the most peripheral region A3 has less mold release resistance due to resin contraction than the step shape 13A in the central region A1, and the plastic Even if the lens PL is cooled and solidified from the outside, it can be easily released from the fixed mold 10.

  Example 1

  Table 1 explains the aspect ratio value (Y / X) of the step shape on the first optical transfer surface 11A of FIG. As shown in Table 1, the aspect ratio value (Y1 / X1) of the step shape UN1 in the central region A1 is 0.038 to 0.617. The aspect ratio (Y3 / X3) of the step shape UN3 in the most peripheral area A3 is 0.005 to 0.030. As a result, the maximum value of (Y / X) in the central area A1 is 0.617, and the maximum value of (Y / X) in the most peripheral area A3 is 0.030.

  In summary, on the first optical transfer surface 11A, the maximum value of the aspect ratio (Y / X) of the step shape is 0.617, and the maximum value of 0.50 ≦ (Y / X) ≦ 1. Within the range of 0.0. The maximum value (0.030) of (Y / X) in the outermost region A3 of the outer region 11D is greater than the maximum value (0.617) of (Y / X) in the central region A1 of the optical axis side region 11C. Is also getting smaller.

[Second Embodiment]
Hereinafter, a molding die for molding the optical element according to the second embodiment of the present invention will be described. The molding die according to the second embodiment is a modification of the molding die according to the first embodiment, and portions not particularly described are the same as those in the first embodiment.

  Hereinafter, the fine structure of the optical transfer surface 11A of the molding die 100 according to the second embodiment will be described in detail with reference to FIG.

  On the first optical transfer surface 11A, a large number of fine step shapes for forming steps of the diffractive structure of the plastic lens PL are formed in a ring shape around the optical axis OA. When this ring-shaped step shape is viewed as a cross section, the inner wall surface of the concave step shape that causes mold release resistance is parallel to the optical axis OA, and the inner wall surface of the step shape and the optical axis OA are The angles α1, α2, and α3 formed are equal to or less than the angles β1, β2, and β3 formed by the outer wall surface of the step shape and the optical axis OA, respectively. Specifically, as can be seen from the figure, in the central region A1 of the first optical transfer surface 11A, the step shape 13A is rectangular, and the inner wall surface 13B of all the step shapes 13A in the region and the optical axis OA. And the angle β1 formed by the outer wall surface 13C of the step shape 13A and the optical axis OA are both 0 degrees and the same. Further, in the intermediate region A2, the step shape 14A is rectangular, and an angle α2 formed by the inner wall surface 14B of all the step shapes 14A in the region and the optical axis OA, and the outer wall surface 14C of the step shape 14A The angle β2 formed by the optical axis OA is 0 degree and is the same. Further, in the most peripheral area A3, the step shape 15A is blazed, and in each step shape 15A, the angle α3 formed by the inner wall surface 15B and the optical axis OA is equal to the outer wall surface 15C and the optical axis OA. Is smaller than the angle β3 formed by.

  Further, as can be seen from the figure, the minimum value of the angle β3 formed by the outer wall surface 15C of the step shape 15A and the optical axis OA in the outermost region A3 of the outer region 11D is the central region A1 in the optical axis side region 11C. It is larger than the angle β1 formed by the outer wall surface 13C of the stepped shape 13A and the optical axis OA and the similar angle β2 in the intermediate region A2.

In addition, on the first optical transfer surface 11A, the width of the step shape is X, the height of the step shape is Y, and the aspect ratio value (Y / X) of the step shape is the following conditional expression 0.50 ≦ ( Maximum value of Y / X) ≦ 1.0
The step shape of the first optical transfer surface 11A is relatively deep. Here, the maximum value of the aspect ratio (Y / X) between the width X and the height Y of the step shape in each of the regions 11C and 11D is the maximum value when the step shape has a U-shaped step shape. It is obtained on the basis of the value of the ratio between the width X and the height Y of the U-shaped step shape. For example, as shown in FIG. 4, in the central region A1, the maximum value of (Y / X) is obtained on the basis of the ratio between the width X1 and the height Y1 of the U-shaped step shape UN1. As shown in FIG. 4, the height Y1 of the U-shaped step shape UN1 is the direction of the optical axis OA among two wall surfaces parallel to the optical axis OA forming the U-shaped step shape UN1. The height of the wall surface having the higher height is Y1. In the intermediate region A2, the maximum value of (Y / X) is obtained based on the ratio of the width X2 and the height Y2 of the U-shaped step shape UN2. The height Y2 of the U-shaped step shape UN2 is, as shown in FIG. 4, the direction of the optical axis OA among the two wall surfaces parallel to the optical axis OA forming the U-shaped step shape UN2. The height of the wall with the higher height is Y2. When the step shape does not have a U-shaped step shape, for example, in the case of a blaze type step shape, the step shape is obtained based on the value of the ratio between the width X and the height Y of the blaze type step shape. For example, as shown in FIG. 4, in the most peripheral area A3, the maximum value of (Y / X) is obtained based on the ratio between the width X3 and the height Y3 of the blaze-shaped step shape UN3.

  The step shapes in the regions 11C and 11D, specifically the regions A1, A2 and A3, are different from each other, and the maximum value of (Y / X) in the outermost region A3 of the outer region 11D is the optical axis side. It is smaller than the maximum value of (Y / X) in either one of the central region A1 and the intermediate region A2 of the region 11C.

  In each of the areas AR1, AR2, AR3 of the first optical surface OL1, steps formed by substantially inverting the step shapes 13A, 14A, 15A formed in the areas A1, A2, A3 of the first optical transfer surface 11A are formed. Is done.

  According to the molding die 100 described above, the minimum value of the angle β3 formed by the outer wall surface 15C of the step shape 15A and the optical axis OA in the outermost peripheral region A3 of the outer region 11D is determined as the central region of the optical axis side region 11C. The step shape 15A in the outermost peripheral region A3 is changed from the central region A1 and the intermediate region A3 by increasing the angle β1, β2 between the outer wall surfaces 13C, 14C of the step shape 13A, 14A in the intermediate region A2 and the optical axis OA. The mold release resistance due to resin contraction is smaller than the step shapes 13A and 14A in the region A2, and even when the plastic lens PL is cooled and solidified from the outside, it can be easily released from the fixed mold 10.

  (Example 2)

  Table 2 explains the aspect ratio value (Y / X) of the step shape on the first optical transfer surface 11A of FIG. As shown in Table 2, the aspect ratio value (Y1 / X1) of the step shape UN1 in the central area A1 is 0.006 to 0.090, and the aspect ratio value of the step shape UN2 in the intermediate area A2 (Y2 / X2) is 0.421 to 0.517. The aspect ratio value (Y3 / X3) of the step shape UN3 in the most peripheral area A3 is 0.007 to 0.086. As a result, the maximum value of (Y / X) in the central area A1 is 0.090, the maximum value of (Y / X) in the intermediate area A2 is 0.517, and the maximum value of (Y / X) in the most peripheral area A3. The maximum value is 0.086.

  In summary, in the first optical transfer surface 11A, the maximum value of the aspect ratio (Y / X) of the step shape is 0.517, and the maximum value of 0.50 ≦ (Y / X) ≦ 1. Within the range of 0.0. Further, the maximum value (0.086) of (Y / X) in the outermost peripheral region A3 of the outer region 11D is the maximum value (0.090) of (Y / X) in the central region A1 of the optical axis side region 11C. And, it is smaller than the maximum value (0.517) of (Y / X) in the intermediate region A2 of the optical axis side region 11C.

[Third Embodiment]
Hereinafter, a molding die for molding the optical element according to the third embodiment of the present invention will be described. The molding die of the third embodiment is a modification of the molding die of the first embodiment, and the parts that are not particularly described are the same as those of the first embodiment.

  Hereinafter, the fine structure of the optical transfer surface 11A of the molding die 100 according to the third embodiment will be described in detail with reference to FIG.

  On the first optical transfer surface 11A, a large number of fine step shapes for forming steps of the diffractive structure of the plastic lens PL are formed in a ring shape around the optical axis OA. When this ring-shaped step shape is viewed as a cross section, the inner wall surface of the concave step shape that causes mold release resistance is parallel to the optical axis OA, and the inner wall surface of the step shape and the optical axis OA are The angles α1, α2, and α3 formed are equal to or less than the angles β1, β2, and β3 formed by the outer wall surface of the step shape and the optical axis OA, respectively. Specifically, as can be seen from the figure, in the central region A1 of the first optical transfer surface 11A, the step shape 13A is rectangular, and the angle α1 formed by the inner wall surface 13B of the step shape 13A and the optical axis OA. The angle β1 formed by the outer wall surface 13C of the step shape 13A and the optical axis OA is both 0 degrees and the same. In the intermediate region A2, the step shape 14A is blazed. In each step shape 14A, the angle α2 formed between the inner wall surface 14B and the optical axis OA is determined by the outer wall surface 14C and the optical axis OA. It is smaller than the formed angle β2. Further, in the most peripheral area A3, the step shape 15A is blazed, and in each step shape 15A, the angle α3 formed by the inner wall surface 15B and the optical axis OA is equal to the outer wall surface 15C and the optical axis OA. Is smaller than the angle β3 formed by.

  Further, as can be seen from the figure, the minimum value of the angle β3 formed by the outer wall surface 15C of the step shape 15A and the optical axis OA in the outermost region A3 of the outer region 11D is the central region A1 in the optical axis side region 11C. The angle formed by the outer wall surface 14C of the step shape 14A and the optical axis OA in the intermediate region A2 of the optical axis side region 11C is larger than the angle β1 formed by the outer wall surface 13C of the step shape 13A and the optical axis OA. It is smaller than the minimum value of β2.

In addition, on the first optical transfer surface 11A, the width of the step shape is X, the height of the step shape is Y, and the aspect ratio value (Y / X) of the step shape is the following conditional expression 0.50 ≦ ( Maximum value of Y / X) ≦ 1.0
The step shape of the first optical transfer surface 11A is relatively deep. Here, the maximum value of the aspect ratio (Y / X) between the width X and the height Y of the step shape in each of the regions 11C and 11D is the maximum value when the step shape has a U-shaped step shape. It is obtained on the basis of the value of the ratio between the width X and the height Y of the U-shaped step shape. For example, as shown in FIG. 5, in the central region A1, the maximum value of (Y / X) is obtained based on the ratio of the width X1 and the height Y1 of the U-shaped step shape UN1. As shown in FIG. 5, the height Y1 of the U-shaped step shape UN1 is the direction of the optical axis OA among the two wall surfaces parallel to the optical axis OA forming the U-shaped step shape UN1. The height of the wall surface having the higher height is Y1. When the step shape does not have a U-shaped step shape, for example, in the case of a blaze type step shape, the step shape is obtained based on the value of the ratio between the width X and the height Y of the blaze type step shape. For example, as shown in FIG. 5, in the intermediate region A2, the maximum value of (Y / X) is obtained on the basis of the ratio between the width X2 and the height Y2 of the blaze-shaped step shape UN2. In the outermost peripheral region A3, the maximum value of (Y / X) is obtained based on the ratio between the width X3 and the height Y3 of the blaze-shaped step shape UN3.

  The step shapes in the regions 11C and 11D, specifically the regions A1, A2 and A3, are different from each other, and the maximum value of (Y / X) in the outermost region A3 of the outer region 11D is the optical axis side. It is smaller than the maximum value of (Y / X) in either one of the central region A1 and the intermediate region A2 of the region 11C.

  In each of the areas AR1, AR2, AR3 of the first optical surface OL1, steps formed by substantially inverting the step shapes 13A, 14A, 15A formed in the areas A1, A2, A3 of the first optical transfer surface 11A are formed. Is done.

  According to the molding die 100 described above, the minimum value of the angle β3 formed by the outer wall surface 15C of the step shape 15A and the optical axis OA in the outermost peripheral region A3 of the outer region 11D is determined as the central region of the optical axis side region 11C. The step shape 15A in the outermost peripheral area A3 is released by contraction of the resin more than the step shape 13A in the central area A1 by making it larger than the angle β1 formed by the outer wall surface 13C of the step shape 13A in A1 and the optical axis OA. Even if the resistance is reduced and the plastic lens PL is cooled and solidified from the outside, it can be easily released from the fixed mold 10.

  (Example 3)

  Table 3 explains the aspect ratio value (Y / X) of the step shape on the first optical transfer surface 11A of FIG. As shown in Table 3, the aspect ratio (Y1 / X1) of the step shape UN1 in the central region A1 is 0.110 to 0.957, and the value of the aspect ratio of the step shape UN2 in the intermediate region A2 (Y2 / X2) is 0.039 to 0.112. The aspect ratio value (Y3 / X3) of the step shape UN3 in the most peripheral area A3 is 0.064 to 0.362. As a result, the maximum value of (Y / X) in the central area A1 is 0.957, the maximum value of (Y / X) in the intermediate area A2 is 0.112, and the maximum value of (Y / X) in the most peripheral area A3. The maximum value is 0.362.

  In summary, on the first optical transfer surface 11A, the maximum value of the aspect ratio (Y / X) of the step shape is 0.957, and the maximum value of 0.50 ≦ (Y / X) ≦ 1. Within the range of 0.0. The maximum value (0.362) of (Y / X) in the outermost region A3 of the outer region 11D is larger than the maximum value (0.957) of (Y / X) in the central region A1 of the optical axis side region 11C. Is also getting smaller.

[Fourth Embodiment]
Hereinafter, a molding die for molding the optical element according to the fourth embodiment of the present invention will be described. The molding die according to the fourth embodiment is a modification of the molding die according to the first embodiment, and portions not particularly described are the same as those in the first embodiment.

  Hereinafter, the fine structure of the optical transfer surface 11A of the molding die 100 according to the fourth embodiment will be described in detail with reference to FIG.

  On the first optical transfer surface 11A, a large number of fine step shapes for forming steps of the diffractive structure of the plastic lens PL are formed in a ring shape around the optical axis OA. When this ring-shaped step shape is viewed as a cross section, the inner wall surface of the concave step shape that causes mold release resistance is parallel to the optical axis OA, and the inner wall surface of the step shape and the optical axis OA are The angles α1 and α3 formed are respectively equal to or less than the angles β1 and β3 formed by the outer wall surface of the step shape and the optical axis OA. Specifically, as can be seen from the figure, in the central region A1 of the first optical transfer surface 11A, the step shape 13A is a blazed shape, and the inner wall surface 13B and the optical axis OA are in each step shape 13A. The angle α1 formed is smaller than the angle β1 formed by the outer wall surface 13C and the optical axis OA. In the most peripheral area A3, the step shape 15A is rectangular, and the angle α3 formed by the inner wall surface 15B and the optical axis OA in all the step shapes 15A is 0 degree. The angle β3 formed by the outer wall surface 15C of the step shape 15A and the optical axis OA can take a plurality of different values of 0 degrees or more corresponding to the angle of the base aspheric surface (base surface). That is, the inner angle β1 is equal to or smaller than the outer angle β3.

  As can be seen from FIG. 6, the minimum value of the angle β3 formed by the outer wall surface 15C of the step shape 15A and the optical axis OA in the outermost peripheral region A3 of the outer region 11D is the central region A1 in the optical axis side region 11C. Is smaller than the minimum value of the angle β1 formed by the outer wall surface 13C of the step shape 13A and the optical axis OA. Although not shown, the step shape in the intermediate region A2 is, for example, a blazed shape, and the angle formed between the inner wall surface and the optical axis OA in each step shape in the intermediate region A2 is the outer wall surface. And the angle formed by the optical axis OA. The minimum value of the angle β3 formed by the outer wall surface of the step shape 15A in the most peripheral area A3 and the optical axis OA is smaller than the minimum value of the angle formed by the outer wall surface of the step shape in the intermediate area A2 and the optical axis OA. It has become.

In addition, on the first optical transfer surface 11A, the width of the step shape is X, the height of the step shape is Y, and the aspect ratio value (Y / X) of the step shape is the following conditional expression 0.50 ≦ ( Maximum value of Y / X) ≦ 1.0
The step shape of the first optical transfer surface 11A is relatively deep. Here, the maximum value of the aspect ratio (Y / X) between the width X and the height Y of the step shape in each of the regions 11C and 11D is the maximum value when the step shape has a U-shaped step shape. It is obtained on the basis of the value of the ratio between the width X and the height Y of the U-shaped step shape. For example, as shown in FIG. 6, in the most peripheral area A3, the maximum value of (Y / X) is obtained based on the ratio of the width X3 and the height Y3 of the U-shaped step shape UN3. The height Y3 of the U-shaped step shape UN3 is, as shown in FIG. 6, the direction of the optical axis OA among the two wall surfaces parallel to the optical axis OA forming the U-shaped step shape UN3. The height of the wall surface having the higher height is Y3. When the step shape does not have a U-shaped step shape, for example, in the case of a blaze type step shape, the step shape is obtained based on the value of the ratio between the width X and the height Y of the blaze type step shape. For example, as shown in FIG. 6, in the central region A1, the maximum value of (Y / X) is obtained on the basis of the ratio between the width X1 and the height Y1 of the blaze-type step shape UN1.

  As shown in FIG. 6, the step shapes in the regions 11C and 11D, specifically the regions A1 and A3, are different from each other, and the maximum value of (Y / X) in the outermost peripheral region A3 of the outer region 11D. Is smaller than the maximum value of (Y / X) in the central region A1 of the optical axis side region 11C. Although not shown, the step shape in the intermediate area A2 is, for example, a rectangle, and the maximum value of (Y / X) in the intermediate area A2 is (Y / X) in the most peripheral area A3 in the specific example. It is larger than the maximum value.

  In each of the areas AR1, AR3, etc. of the first optical surface OL1, there are formed steps that are substantially inverted from the step shapes 13A, 15A formed in the areas A1, A3, etc. of the first optical transfer surface 11A.

  According to the molding die 100 described above, the minimum value of the angle β3 formed by the outer wall surface 15C of the step shape 15A and the optical axis OA in the outermost peripheral region A3 of the outer region 11D is the central region of the optical axis side region 11C. The mold structure is such that the mold release resistance tends to be relatively large on the outside, which is smaller than the minimum value of the angle β1 formed by the outer wall surface 13C of the step shape 13A in A1 and the optical axis OA, but the mold release resistance is large. By releasing the first optical transfer surface 11A preferentially while it is warm, smooth release can be realized.

  In the third embodiment, the step shape 13A of the central region A1 may be rectangular. In this case, the minimum value of the angle β3 formed by the outer wall surface 15C of the step shape 15A in the outermost region A3 of the outer region 11D and the optical axis OA is outside the step shape 13A in the central region A1 of the optical axis side region 11C. It becomes 0 degree which is the same as the angle β1 formed by the wall surface 13C of the optical axis OA.

Although the molding die according to the present embodiment has been described above, the molding die for molding the optical element according to the present invention is not limited to the above. For example, in the molding die 100, the plastic lens PL remaining on the movable mold 20 is released by protruding the core mold 21, but the second flange surface FL2 of the plastic lens PL by the protruding pin embedded in the movable mold 20 is used. May protrude from the movable mold 20.

  Moreover, in the said embodiment, the shape of level | step difference shape 13A, 14A, 15A is an illustration, The combination of shapes can also be designed freely within the range of conditions. For example, the same or similar pattern can be formed in the central area A1 and the intermediate area A2 constituting the optical axis side area 11C. Further, all the step shapes in the central area A1, the intermediate area A2, and the most peripheral area may be rectangular or blazed.

DESCRIPTION OF SYMBOLS 100 Molding die 10 Fixed mold 20 Movable mold 30 Temperature control part 40 Movable mold drive part 50 Resin injection part 11A, 21A Optical transfer surface 11C Optical axis side area | region 11D Outer area | region 12A, 22A Molding surface 13A, 14A, 15A Step shape A1 Central area A2 Middle area A3 Most peripheral area CV type space OL Central part OL1, OL2 Optical surface FL Flange part FL1, FL2 Flange surface PL Plastic lens OA Optical axis

Claims (4)

An optical element having a first optical surface and a second optical surface,
The absolute value of the radius of curvature of the first optical surface is smaller than the absolute value of the radius of curvature of the second optical surface;
The first optical surface has at least a step forming a diffractive structure in an optical axis side region disposed on the optical axis side and an outer region disposed outside the optical axis side region,
When the width of the step is X and the height of the step is Y, the maximum value of (Y / X) in the outer region is smaller than the maximum value of (Y / X) in the optical axis side region,
The following conditional expression
Maximum value of (Y / X) on the first optical surface ≦ 1.0
An optical element characterized by satisfying: The optical axis side region has at least a central region arranged on the optical axis side and an intermediate region arranged outside the central region,
The outer region has at least a most peripheral region disposed outside the intermediate region,
2. The maximum value of (Y / X) in the most peripheral region is smaller than the maximum value of (Y / X) in at least one of the central region and the intermediate region. The optical element described. Conditional formula 0.50 ≦ maximum value of (Y / X) in the first optical surface ≦ 1.0
The optical element according to claim 1, wherein:   4. The optical element according to claim 1, wherein the optical element is a CD / DVD / BD 3-wavelength compatible optical pickup objective optical element. 5.