JP2007196399A - Mold for molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for molding a concave lens which can suppress the formation of a weld line only by setting the shape of a lens cavity. <P>SOLUTION: A specular piece 14a and a specular piece 14b are arranged to face each other with an imaginary plane including a y-axis and an x-axis crossing rectangularly held between them. The widths in the y-axis direction of the specular piece 14a and the specular piece 14b projected on the imaginary plane are longer than the widths in the x-axis direction. When the maximum distance between the specular piece 14a and the specular piece 14b in a cross-sectional shape by an imaginary plane including the y-axis and a z-axis is D, the maximum distance between the specular piece 14a and the specular piece 14b in a cross-sectional shape by an imaginary plane including the x-axis and the z-axis is D', the minimum distance between the specular piece 14a and the specular piece 14b in the cross-sectional shape by the imaginary plane including the y-axis and the z-axis (= the minimum distance between the specular piece 14a and the specular piece 14b in the cross-sectional shape by the imaginary plane including the x-axis and the z-axis) is d, H=D/d, and H'=D'/d, H>H' and H'>2.5 are satisfied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a molding die, and more particularly to a molding die for molding a concave lens.

  Conventionally, there is an optical element made of glass as an optical element. A glass optical element (for example, a lens) requires high technology and time for polishing to obtain an accurate curved surface, so that mass production does not work and it is expensive.

  On the other hand, resin-made optical elements have been frequently used in recent years. The resin optical element can be mass-produced by injection molding using a mold, and an aspherical curved surface can be easily obtained, and is lightweight. Therefore, it is easy to assemble even a small device.

  An example of the metal mold | die which forms such a resin-made optical element is shown. FIG. 8 (a) is a plan view schematically showing the shape of the cavity of the mold for molding the concave lens, and FIG. 8 (b) is a cross-sectional view taken along the line AA ′ of FIG. 8 (a).

As shown in FIGS. 8A and 8B, the mold includes two mirror pieces 1 and 2 and a gate 4 which face each other. The mirror pieces 1 and 2 are combined with each other to form a lens-shaped cavity 3. Then, molten thermoplastic resin is injected into the cavity 3 from the gate 4. The injected resin is solidified by being cooled. After the resin is solidified, the mirror surface piece on the movable mold side of the mirror surface pieces 1 and 2 moves away from the counterpart mirror surface piece. Then, the molded concave lens is taken out. (For example, refer to Patent Document 1.)
Japanese Unexamined Patent Publication No. 2003-211500 ([Summary], FIGS. 1 and 2)

  By the way, in the concave lens molding die, the distance between the mirror piece 1 and the mirror piece 2 is narrower in the central portion than in the peripheral portion. Therefore, the flow of the resin injected from the gate into the cavity is suppressed in the central portion as compared with the peripheral portion, so that the entire fluidity becomes non-uniform. As a result, when filling of the injected resin is completed, a joint where the resins join together is likely to occur at a position 180 degrees opposite to the gate position.

  9A, 9B, and 9C are diagrams for explaining such a joint. Here, arrows a and a ′ indicate the flow of the resin. First, as shown in FIG. 2A, the resin 5 injected from the gate 4 into the cavity 3 moves faster in the peripheral portion than in the central portion of the cavity 3.

  Then, as shown in FIG. 4B, immediately after the filling of the injected resin is completed, the resins that have flowed from the peripheral portion proceed toward the planned joining point 6. When the resin reaches the junction 6 (when filling is completed), a streak-like boundary line (boundary surface) is formed as shown in FIG. Such a boundary line becomes a joint 7 and remains in the periphery of the lens.

  This seam 7 is commonly called a weld line. This weld line often occurs at a position facing the gate 4 (a position on the opposite side by 180 degrees). Such weld lines often optically cause defective phenomena such as ghosts and flares regardless of whether they are outside the optical effective surface or in the optical effective surface.

  Various molds for suppressing the occurrence of such weld lines have been proposed so far. However, any mold is not preferable because it is complicated to handle and has a complicated structure.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a molding die that can suppress the occurrence of weld lines, particularly a molding die for concave lenses.

  In order to solve the above-mentioned problems, a molding die according to the present invention is a die including a first mirror piece, a second mirror piece, and a gate, and includes a first axis and a second axis that are orthogonal to each other. Of the two axes and the third axis, a plane including the first axis and the second axis is a first virtual plane, and a plane including the first axis and the third axis is a second virtual plane. When the surface including the second axis and the third axis is a third virtual surface, the first mirror surface piece and the second mirror surface piece face each other across the first virtual surface. The outer shape of the first mirror surface piece and the second mirror surface piece arranged and projected onto the first virtual surface (outer shape on the surfaces facing each other) has a width in the first axial direction, 2 is longer than the width in the axial direction of the gate, and the exit of the gate has an angle formed by the normal direction of the exit surface of the exit and the first axial direction. The maximum distance between the first mirror face piece and the second mirror face piece in a cross-sectional shape by the second virtual surface is provided at a position smaller than the angle formed by the first axis and the second axis. D ′ is the maximum distance between the first mirror surface piece and the second mirror surface piece in the cross-sectional shape by the third virtual surface, and the first mirror surface piece and the above in the cross-sectional shape by the second virtual surface Of the minimum distance between the second mirror surface pieces and the minimum distance between the first mirror surface piece and the second mirror surface piece in the cross-sectional shape of the third virtual surface, the smaller minimum distance is d H = D / d and H ′ = D ′ / d, and H> H ′ is satisfied.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the shaping die which can suppress generation | occurrence | production of a weld line, especially the shaping die for negative lenses.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic side cross-sectional view showing a configuration of a mold in the first embodiment.
As shown in FIG. 1, the mold 10 includes a fixed mold 12 and a movable mold 13. Further, the fixed mold 12 and the movable mold 13 are provided with mirror surface pieces 14a (first mirror face pieces) and 14b (second mirror face pieces) in a detachable manner. Each of the specular pieces 14a and 14b is a member for forming an optical element and is a pair of two. In the mold shown in FIG. 1, two pairs of mirror pieces 14a and 14b are provided, but the number of pairs of mirror pieces 14 may be one or three or more.

  A molding surface corresponding to the optical surface shape of an injection molded product (here, a concave lens) is formed at one end of the mirror surface pieces 14a and 14b. The mirror surface pieces 14a and 14b are arranged in such a manner that the molding surfaces face each other. A cavity 16 into which an injection molding resin material (hereinafter simply referred to as a resin material) is injected is formed between the opposing surfaces.

  A sprue (sprue) 17 into which a resin material is injected from the outside is formed at the center of the fixed mold 12. A runner 18 that runs to the sprue 17 is formed at one end of the sprue 17. The runner 18 extends right and left (up and down in the drawing) along the pressing surface 15 of the fixed mold 12 and the movable mold 13. Gates 19 are respectively formed at the left and right ends of the runner 18. The gate 19 is a passage narrower than the runner 18, and is connected to the cavity 16 at the end thereof.

  FIG. 2 is a diagram showing the shape of the cavity 16 of the mold 10 in the present embodiment, and a cross-sectional view is shown on the left (b) and below (c) with the plan view (a) as the center. The shape of the cavity 16 is a shape formed by the facing surfaces when the mirror surface pieces 14a and 14b are opposed to each other. Therefore, the shape of the cavity 16 matches the shape of the lens.

  FIG. 2 shows three axes orthogonal to each other, that is, the x-axis (second axis), the y-axis (first axis), and the z-axis (third axis). Here, as shown in FIG. 2A, the x-axis and the y-axis are axes in the paper plane, and the z-axis is an axis orthogonal to the paper plane. Further, the intersection of the x-axis, y-axis, and z-axis coincides with the center of the cavity 16. In this embodiment, the molding surface of the mirror piece (corresponding to the optical surface of the optical element) has a rotationally symmetric shape, so that the intersection of the x axis, the y axis, and the z axis is located on the rotationally symmetric axis.

  In the mold of the present embodiment, as shown in FIG. 2B or FIG. 2C, the mirror piece 14a and the mirror piece 14b sandwich a virtual plane (first virtual plane) including the y axis and the x axis. Opposed to each other. Here, FIG. 2A is a plan view showing the cavity 16, which is also a diagram in which the mirror surface piece 14a and the mirror surface piece 14b are projected onto the first virtual plane. More specifically, the projected surface is a surface of the mirror piece 14a and the mirror piece 14b on the cavity 16 side. As is clear from FIG. 2A, in the mirror piece 14a in the mold according to the present embodiment, the surface on the cavity 16 side is such that the width W in the y-axis direction is longer than the width W ′ in the x-axis direction. Is formed. Similarly, the mirror piece 14b is also formed with a surface on the cavity 16 side so that W> W '. In the present embodiment, the gate 19 is provided on the y-axis.

  Further, the outer peripheral shape (the outer peripheral shape on the cavity 16 side) of the specular piece 14a and the specular piece 14b has a so-called oval shape as a whole, as shown in FIG. That is, in the outer peripheral shape, the contours of the regions (upper and lower) intersecting with the y axis are arcs, and the contours of the regions (left and right) intersecting with the x axis are straight lines.

  In other words, of the outer peripheral shapes of the first mirror face piece (mirror face piece 14a) and the second mirror face piece (mirror face piece 14b), the shape of the region facing the second axis (x axis) is an arc. It can also be said that there is an area of the outer periphery of the first mirror face piece (mirror face piece 14a) and the second mirror face piece (mirror face piece 14b) facing each other across the first axis (y axis). It can be said that the shape is a straight line.

Further, the cavity 16, that is, the mold according to the present embodiment satisfies the following conditions.
H> H '
Here, H = D / d and H ′ = D ′ / d. D, D ′ and d are as follows.
As shown in FIG. 2B, the maximum distance between the mirror piece 14a and the mirror piece 14b in the cross-sectional shape by the virtual plane (second virtual plane) including the y axis and the z axis is D. Further, as shown in FIG. 2C, the maximum distance between the specular piece 14a and the specular piece 14b in the cross-sectional shape of the virtual plane (third virtual plane) including the x-axis and the z-axis is defined as D ′. Further, the smaller minimum of the minimum distance d1 between the mirror surface piece 14a and the mirror surface piece 14b in the cross-sectional shape by the second virtual surface and the minimum distance d2 between the mirror surface piece 14a and the mirror surface piece 14b in the cross-sectional shape by the third virtual surface. Let the interval be d. In this embodiment, since the shape of the molding surface is rotationally symmetric, d1 = d2. Therefore, d = d1 = d2.

  H and H ′ are thickness deviations, and the larger the value, the greater the difference between the maximum distances D and D ′ and the minimum distance d. In this embodiment, since H> H ′, the thickness deviation in the x-axis direction is small. As described above, the gate 19 is located on the y axis. Therefore, the resin flowing out from the gate 19 is filled in the cavity 16 as shown in FIG.

FIG. 3 is a view showing an inflow state of the resin injected into the cavity 16. The figure shows the state from the initial stage to the middle stage of resin injection at the top and the state at the end of injection at the bottom.
As shown in FIG. 3, the resin 24 injected from the injection port 21 of the gate 19 into the cavity 16 flows in a direction along the y axis. At that time, the resin 24 also spreads in the x-axis direction. However, in this embodiment, since the thickness variation of the cavity 16 in the x-axis direction is relatively small, the entrainment of the inflowing resin as shown in FIG.

  In other words, the flow front of the resin 24 spreading in the x direction travels in the y axis direction in the cavity 16 so as to be aligned in a substantially horizontal line. As a result, even at the end of injection, the resins wound from the left and right as shown in FIG. 8 (b) do not form a junction. Therefore, the resin seam (weld line) as shown in FIG. 8C does not occur.

Thus, in this embodiment, the mold, more specifically the shape of the specular pieces 14a and 14b, can suppress the generation of weld lines during resin filling.
Here, in the above configuration, the exit port 21 of the gate 19 is provided so that the normal direction of the exit surface of the exit port 21 coincides with the y-axis direction, as shown in FIG. . That is, the center of the exit surface of the exit port 21 is located on the y axis. However, the position of the injection port 21 and the normal direction of the surface do not necessarily have to coincide with the y axis. For example, the injection port 21 may be provided at a position where the angle formed by the normal direction of the injection surface and the y-axis direction is smaller than the angle formed by the y-axis direction and the x-axis.

  As an arrangement for suppressing the generation of weld lines, in FIG. 2, the injection port 21 has an angle of deviation from the y-axis of the center 22 of the injection surface in the x-axis direction from the y-axis of the shape of the cavity 16. The width of the extending arc portion 23 is preferably ± 5% or less.

  In addition, it has been stated that the thickness deviation H ′ in the x-axis direction is relatively small. However, it is necessary to test various molds to determine how small the thickness deviation can suppress the generation of weld lines. An injection experiment was conducted and the results were evaluated.

FIG. 4 is a chart evaluating the thickness deviation H ′ in the x-axis direction of various prototype molds and whether or not a weld line is generated after resin is injected into the cavity.
As shown in FIG. 4, when the thickness deviation H ′ in the x-axis direction (gate vertical direction) is less than 2.5, the thickness deviation H in the y-axis direction (gate direction) is 2.5 or more. It has been found that even a meat lens can suppress the occurrence of welds.

  When the above experimental results are combined, it has been found that the resin thickness can be suppressed, that is, the occurrence of welds can be suppressed when the thickness deviation in the x-axis direction is smaller than the thickness deviation in the y-axis direction.

In the above embodiment, the mold for forming the biconcave lens has been described. However, the concave lens capable of suppressing the occurrence of welds is not limited to the biconcave lens.
FIG. 5 is a diagram showing various shapes of a negative lens that can be formed by a mold to which the dimensional condition of the mold of the present invention is applied to suppress the occurrence of welds. This figure shows, from top to bottom, a negative meniscus lens 26 and a plano-concave lens 27, in addition to a biconcave lens 25 molded with the same mold as in FIG.

Even in the case of molding such a concave lens, if the dimensional condition of the mold is set to “H> H ′” and “H ′ <2.5”, the occurrence of welds can be suppressed.
In other words, the mold for forming the biconcave lens 25 has a shape in which the mold region of the first mirror piece (mirror piece 14a) is lower in the periphery than the center. It can be said that the mold area of the mirror piece (mirror piece 14b) has a shape whose periphery is lower than the center.

  Further, in the mold for molding the negative meniscus lens 26, the mold region of the first mirror surface piece has a shape whose periphery is lower than the center, and the mold region of the second mirror surface piece has a shape whose periphery is higher than the center. It can be said.

  Further, in the mold for molding the plano-concave lens 27, the mold region of the first specular piece has a shape whose periphery is lower than the center, and the mold region of the second specular piece has substantially the same height from the center to the periphery. It can be said.

  In the above embodiment, the outer peripheral shape (see the plan view of FIG. 2) of the specular piece 14a and the specular piece 14b projected on the first virtual plane is such that the upper and lower contours intersecting the y-axis each form an arc. Although the left and right contours intersecting with the x-axis each form a straight line and have an oval shape as a whole, the outer peripheral shape of the mirror piece projected onto the first virtual plane is not limited to this. .

  FIG. 6 is a diagram showing various modifications of various molds other than the oval shape that satisfy the conditions “H> H ′” and “H ′ <2.5”. Note that the molds 28 to 30 shown in the figure all have the second axis (x axis) of the outer peripheral shapes of the first mirror face piece (mirror face piece 14a) and the second mirror face piece (mirror face piece 14b). There is no change in the point that the shape of the region facing each other is an arc 31.

  However, the mold 28 has a shape of a region facing each other across the first axis (y-axis) among the outer peripheral shapes of the first mirror face piece (mirror face piece 14a) and the second mirror face piece (mirror face piece 14b). It can be said that it is a curve 32.

  In addition, the mold 29 or 30 is a region in the outer peripheral shape of the first mirror face piece (mirror face piece 14a) and the second mirror face piece (mirror face piece 14b) across the first axis (y axis). It can be said that the shape is a combination of a straight line 33 and a curved line 34.

  In the embodiment, the molding surfaces of the mirror surface pieces 14a and 14b are rotationally symmetric. However, the molding surfaces of the mirror pieces 14a and 14b may be toric surfaces (spherical surfaces / aspheric surfaces) or free-form surfaces.

  Further, the outer shape shown in FIG. 2A may be formed by either one of the specular pieces 14a and 14b. That is, FIG. 7A is a diagram showing a configuration in which the outer shape is determined by the mirror piece 14a. In FIG. 7A, there is no protrusion in the peripheral part of the mirror piece 14b, and it is a flat surface. On the other hand, a projection is formed in the periphery of the mirror piece 14a as in FIG. However, the length of the protrusion is such that when the predetermined cavity shape is formed, the tip thereof is in contact with the peripheral portion of the specular piece 14b. FIG. 7B is a diagram showing a configuration in which the outer shape is determined by the mirror piece 14b.

It is a typical sectional side view which shows the structure of the metal mold | die in 1st Embodiment. It is a figure which shows the shape of the cavity of the metal mold | die in 1st Embodiment to the left and the lower part centering on a top view. It is a figure which shows the inflow state of the resin inject | poured into the cavity in the shape of the two mirror piece of the metal mold | die in 1st Embodiment. It is the chart which evaluated the presence or absence of the weld line generation | occurrence | production after the resin injection | pouring to the cavity of the x-axis direction of the metal mold | die made variously. It is a figure which shows the various shape of the concave lens which can shape | mold with the metal mold | die which applied the dimension conditions of the metal mold | die of this invention, and can suppress generation | occurrence | production of a weld. It is a figure which shows the various modifications of the metal mold | die of various shapes other than the oval shape which satisfy the dimension conditions of the metal mold | die of this invention. (a) A diagram showing a configuration in which the outer shape is determined by the mirror surface piece 14a, and (b) is a diagram showing a configuration in which the outer shape is determined by the mirror surface piece 14b. (a) is a top view which shows simply the shape of the cavity of the mold for the conventional concave lens shaping | molding, (b) is an AA 'cross section arrow view of (a). (a), (b) is a figure explaining the joint which generate | occur | produces at the time of completion of filling of injection resin in the conventional metal mold | die for concave lens shaping | molding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Mirror surface piece 3 Cavity 4 Gate 5 Resin 6 Junction point 7 Joint 10 Mold 12 Fixed mold 13 Movable die 14 Mirror surface piece 15 Pressing surface 16 Cavity (cavity)
17 sprue
18 Runner (runner)
DESCRIPTION OF SYMBOLS 19 Gate 21 Injecting port 22 Outgoing surface center 23 Arc part 24 Resin 25 Biconcave lens 26 Concave meniscus lens 27 Plano-concave lens 28, 29, 30 Various modifications of the mold 31 Arc 32 Curve 33 Straight 34 Curve

Claims (11)

A mold comprising a first mirror piece, a second mirror piece, and a gate,
Of the first axis, the second axis, and the third axis that are orthogonal to each other, a plane including the first axis and the second axis is a first imaginary plane, the first axis, and the third axis. When a surface including an axis is a second virtual surface, and a surface including the second axis and the third axis is a third virtual surface,
The first mirror surface piece and the second mirror surface piece are arranged to face each other across the first virtual surface,
The outer diameter shape of the first specular piece and the second specular piece projected on the first imaginary plane has a width in the first axial direction longer than a width in the second axial direction. And
The exit of the gate is located at a position where the angle formed between the normal direction of the exit surface of the exit and the first axial direction is smaller than the angle formed between the first axis and the second axis. Provided in
The maximum distance between the first mirror surface piece and the second mirror surface piece in the cross-sectional shape by the second virtual surface is D,
D ′ is the maximum distance between the first mirror surface piece and the second mirror surface piece in the cross-sectional shape of the third virtual surface,
The minimum distance between the first mirror surface piece and the second mirror surface piece in the cross-sectional shape by the second virtual surface, and the first mirror surface piece and the second mirror surface piece in the cross-sectional shape by the third virtual surface When the smallest minimum interval between the two is d,
A mold for molding, wherein H = D / d, H ′ = D ′ / d, and H> H ′ is satisfied. A mold that molds a biconcave lens,
The mold region of the first mirror piece has a shape whose periphery is lower than the center,
The mold region of the second specular piece has a shape whose periphery is lower than the center,
The molding die according to claim 1, wherein: A mold for molding negative meniscus lenses,
The mold region of the first specular piece has a shape whose periphery is lower than the center,
The mold region of the second specular piece has a shape whose periphery is higher than the center,
The molding die according to claim 1, wherein: A mold for molding plano-concave lenses,
The mold region of the first mirror piece has a shape whose periphery is lower than the center,
The mold region of the second specular piece has substantially the same height from the center to the periphery,
The molding die according to claim 1, wherein:   The shape of the area | region which opposes across the said 2nd axis | shaft among the outer periphery shape of a said 1st mirror surface piece and a said 2nd mirror surface piece is a circular arc, The any one of Claim 1 to 4 characterized by the above-mentioned. 2. A molding die according to item 1.   The shape of the area | region which opposes across the said 1st axis | shaft among the outer peripheral shape of a said 1st mirror surface piece and a said 2nd mirror surface piece is a straight line, The any one of Claims 1-5 characterized by the above-mentioned. 2. A molding die according to item 1.   The shape of the area | region which opposes on both sides of the said 1st axis | shaft among the outer peripheral shape of a said 1st mirror surface piece and a said 2nd mirror surface piece is a curve, Either of the Claims 1-5 characterized by the above-mentioned. 2. A molding die according to item 1.   The shape of the area | region which opposes on both sides of the said 1st axis | shaft among the outer periphery shape of the said 1st mirror surface piece and the said 2nd mirror surface piece is a combination of a straight line and a curve. The molding die according to any one of 5.   The molding die according to any one of claims 1 to 8, wherein a center of the injection surface is located on the first axis.   The deviation angle of the center of the exit surface from the first axis is ± 5% or less of the width of an arc extending in the second axis direction. The molding die according to any one of the above.   11. The molding die according to claim 1, wherein the H ′ satisfies H ′ <2.5. 11.