JPH0262373B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for injection molding a recording medium, such as a video disk, having an opening in the center and a spiral track.

An apparatus for making video disks with a central opening by injection molding is described in US Pat. No. 3,989,436.

In a video disc, if the birefringence values of the information-bearing surface are not uniform, the video disc is unplayable and useless.

It is an object of the present invention to use an annular gate passageway between the runner passageway and an annular forming cavity for forming a video disk to transfer the molten material to the disk in a manner that does not create stress gradients in the injected material. An object of the present invention is to provide an apparatus for producing a video disc recording body having a substantially uniform value of birefringence over the entire information-bearing surface of a video disc member by flowing into an annular molding cavity for molding. .

To achieve the above object, the present invention provides: an annular molding cavity of substantially uniform thickness formed by a first mold part and a second mold part; and a radial center of the annular molding cavity. an annular gate passageway formed by a first mold part and a second mold part and connecting the runner passageway and an annular molding cavity; an injection molding apparatus for injecting molten molding material from a runner passageway through an annular gate passageway into an annular molding cavity to form an optical disk with a central hole formed therein, the first mold part; and at least one of the second mold parts includes a platen having a stamper on the side of the annular molding cavity, and in the at least one mold part having the platen having the stamper, the part forming the annular gate passage The part adjacent to the platen is
The stamper clamping member includes a protruding part that protrudes toward the annular gate passage, and the protruding part includes a clamping part that protrudes toward the stamper and clamps the stamper to the platen; a passage forming part that is continuous with the tightening part and forms a part of the annular gate passage; the passage forming part includes a flow restricting part whose thickness gradually decreases in a radially outward direction; An outlet part that is continuous with the annular molding cavity, has a thickness smaller than that of the annular molding cavity, and opens into the annular molding cavity.

In a preferred embodiment of the invention, the cooling device comprises:
It is calculated to remove from the molding machine the heat generated by injecting molten plastic into the runner passageway and video disc cavity. This cooling prevents stress defects in the finished video disc recording. The absence of stress defects improves the birefringence properties of the finished video disc recording.

In a preferred embodiment of the invention, the first mold half and the second mold half are reciprocatably mounted within the tool. A runner bushing having an opening communicating with the injection nozzle is secured to the platen. A punch with an end aligned with the runner bushing is reciprocatably mounted to the second mold half. When the second mold half is in the closed position, (1) the end of the punch and the opening in the runner bushing define a runner passage, and (2) the first and second mold halves encircle the runner passage. Limit the annular void. The annular cavity and runner passage form a centrally apertured part and runner, respectively, when heating material is injected therein. After the heated injection material has cooled to some extent, the first and second mold halves are moved from the closed position to a position intermediate between the closed and open positions, while the punch is held in place. , cut the runner from the part along the circumference of the end of the punch. The centering die positioning and fixed center stamper clamping portion of the first mold half, into which the punch end enters, acts as the die. Thereafter, the mold halves are separated and the annular cavity is opened while the runner rests on the end of the punch and the part is in contact with the circumferential surface of the end of the punch. After separating the mold halves, the runner release member and part ejection member are actuated to eject the runner and part, respectively, from the end of the punch.

In a preferred embodiment of the invention, a platen assembly is provided having releasable means for centering the stamper and holding the stamper in position against the surface of the platen. The holding means also includes means for allowing the stamper to expand due to the temperature gradient of the heated injection plastic material. The stamper uses heated injection material to
When filling the disc cavity, the injection material expands uniformly on the front side. Additionally, the platen assembly includes a plurality of separate cooling channels that maintain the platen at a uniform temperature across its surface.

In a preferred embodiment of the invention, a center punch is provided to accurately punch a hole in the center of the injection molded video disk member. The center punch is held stationary while the fixed expanding substrate half and the movable half move over the punch stroke to an intermediate position defined by the punch travel limiter.

In a preferred embodiment of the present invention, the first and second
By closing the mold half, an annular runner passageway is formed by it and the end of the punch. The runner passageway includes a first portion defined by the runner butting itself, a portion of the runner bushing,
a second portion defined by a combination of members including an end of the punch and a portion of an inner centering and clamping member.

Hereinafter, the entire injection molding apparatus related to the present invention will be described, and then the annular gate passage connecting the runner passage and the annular molding cavity will be explained.

Figures 1 and 2 show a 375-ton model manufactured by Stokes Division of the Pennwalt Manufacture Company.
Tool 1 used in combination with standard injection molding machine
0 is shown. The tool 10 is used for duplicating video disk recording media having an opening in the center, and includes a stationary mold half (first mold half) 12 and a movable mold half (second mold half) 14. has.
The stationary mold half 12 includes a stationary stationary base plate 16 and a stationary half-expandable base plate 18 that are mounted to a stationary frame member of a standard molding machine (not shown).
A plurality of main guide and support pins are integrally attached to the base plate 16, one of which is shown at 20. The fixed half main guide and support pin bushing are 22
The substrate 18 is reciprocally mounted along with the substrate 16 during the punching process. The punching process partially involves punching the expansion substrate 18 against the fixed plate 16.
This is done by the reciprocating motion of the

The movable mold half 14 is attached to the movable mold half support plate 3
0, it has a movable half-separation plate 32 and a movable half-fixed substrate 34. A mobile semi-fixed substrate 34 is mounted to the frame of a standard injection molding machine (not shown). A standoff plate 32 is attached to a fixed base plate 34 by a plurality of semi-movable standoff bolts, one of which is shown at 36. The bolt 36 is connected to the separation plate 32
are embedded in the spacer plate 32 and provided at uniform intervals along the periphery of the separation plate 32, and are firmly attached to the fixed base plate 34.

A substrate 34 is also attached to the support plate 30 by a plurality of moving half-tightening bolts, one of which is shown at 38. Each tightening bolt 38 passes through the standoff plate 32 as shown by the dashed line 40 and
As shown, it is attached to the support plate 30 by screw engagement. Tightening bolts 38 are provided at uniform intervals along the periphery of the board, and are connected to the support plate 30 and the separation plate 3.
2 and the substrate 34 are firmly fixed. Each bolt 38 is recessed into the base plate 34 and the plate 34
to have a smooth contact surface 43.

A moving half-main support pin bushing is shown at 44 and is supported on support plate 30. A support pin 20 is disposed within the bushing 40 and provides reciprocating movement between the fixed half-fixed base plate 16 and the support plate 30 during punching operations. The support pins 20 also interlock the stationary half-expandable substrate 18 and the movable half-support plate 30 during punching operations. Once the punching is complete, support pin 20 is fully withdrawn from bushing 44 for the remainder of the opening process. In the fully open position, the support pins move stamper 1
44, but the distance shown in FIG.
It is the same distance apart from

The punch plate assembly 50 is comprised of a punch plate assembly clamping plate 52 and a punch plate assembly support plate 54. The punch plate assembly 50 is a movable half-fixed board 3
A plurality of punch plate assembly guide pins supported within 4 and integrally attached to base plate 34
It is attached to it so that it can freely move back and forth. One punch plate assembly guide pin is shown at 55. The punch plate assembly clamp plate bushing is shown at 56 and the punch plate assembly support plate bushing is shown at 58. A guide pin 55 passes through the plates 52,54. The plates 52 and 54 have bushings 56 and 5, respectively.
8, it is attached to the pin 55 so as to be reciprocally movable.

The guide pin 55 enters the movable half support plate 30 as indicated by the dashed line 60.

A plurality of mobile half-support rods 64 are attached to base plate 34 by individual bolts, one of which is shown at 66. Support rods 64 pass through openings in plates 52 and 54, as shown by dashed lines 72 and 74, respectively.

A support rod 64 provides additional support to the rear surface 76 of the support plate 30 during injection of molten material into the video disc cavity.

Referring to FIG. 2, a punch plate stop bar 77 is positioned intermediate the punch plate assembly support plate 54 and the fixed base plate 34. As shown in FIG. This stopper stick is
The punch plate is attached to the base plate 34 by a plurality of stopper bar bolts, one of which is shown at 78. The stopper rod 77 has a circular cross section. Portions of this rod are shown on the left and right sides of FIG. The stopper bar 77 increases the robustness of the tool and allows it to withstand the full force of the closing force of the main ram attached to the injection molding machine. In this regard, it cooperates with the side members 34a of the stationary base plate 34 to withstand the pressure of the ram during the closing portion of the molding operation as well as the closed state. Although the stopper rod 77 has been described as having a circular cross section, it may also be a single plate. If a single plate is used, a large number of such plates are arranged along the periphery of the substrate 34 so that the overall effect of the member 77 uniformly separates the support plate 54 from the substrate 34.

The punch plate assembly support plate 54 has one of the punch plate assemblies 80
With the multiple support plate tightening plate bolts shown in
The punch plate assembly is integrally attached to the clamping plate 52. When the tightening plate 52 is disassembled from the support plate 54,
An assembly of a plurality of main punch plate assembly travel limiters, one of which is shown at 90, can be positioned within an opening 92 in the clamping plate 52. Each main stroke limiter rests on an interface 94 of support plate 54. The process limiter 90 is connected to the support plate 30 and the substrate 18.
It passes through openings 96, 98 provided in the. A process limiter engages substrate 16 at interface 100 .

A plurality of secondary punch plate assembly travel limiters are supported on the punch plate assembly clamping plate 52. One travel limiter is shown at 102 and bolt 10
4 to the plate 52. In Figure 1,
The end face 106 of the secondary punch plate assembly 102 is aligned with the line 1
It is shown separated from the lower surface 107 of the support plate 30 by a distance indicated at 08. This distance 108
, which will be explained in detail later with reference to FIGS. 4 and 5, represents the distance that the support plate 30 moves from the open position to the intermediate position.

The fixed half-fixed substrate 16 is the runner bushing 11
0, this is the runner bushing fixing ring 11
2. It is held in place by 2. The runner bushing 110 has an opening 114 which is connected to one end 115.
The end 117 communicates with the injection nozzle 116 of the injection molding machine, and the other end 117 communicates with the video disk cavity.

One of them is 12 on the fixed half-expansion board 18.
Fixed platen 1 is fixed by a large number of bolts shown in 2.
20 is installed. A stationary platen 120 supports a stationary stamper 124 that is pressed against the stationary platen 120 at its inner radius by centering die positioning and fixed center stamper clamping members 126 and at its outer radius. Fix the outer stamper ring clamping member 1 in place.
It is held by 28. Tightening member 126
The fixed half-expansion substrate 18 and the fixed platen 1
Center tightening member holding bolt 130 passing through 20
is held in place by the The fixed outer stamper ring clamping member is shown in detail in FIG. The relationship between fixed center stamper clamping member 126 and fixed stamper 124 is shown in detail in FIG.

One of them is 142 on the movable half support plate 30.
A large number of bolts as shown in FIG.
0 is attached. A movable platen 140 has a moving stamper 144 which is pressed against the platen 140 at its inner radius by a centering punch locating and moving center stamper clamping member 146 and a moving outer stamper at its outer radius. It is held by a stamper ring clamping member 148.

Both outer ring clamping members 128, 148 are embedded in respective platens 120, 140 and threaded through these platens.
A bolt entering 8 can effectively hold it in place. These bolts provide a fixed connection, but the formation shown schematically on the left edge of the platens 120, 140 provides a releasable connection.

A movable platen 140 is releasably attached to the movable half support plate 30 by a central clamping member fixation assembly 150. Assembly 150 is assembly 15
0, attach the tightening member 146 to the platen 14.
It may have multiple bolts that hold it in place. Bolts in place of assembly 150 are embedded within support plate 30, similar to the arrangement of bolts 142.

A blanching release pin 156 has a blanching release pin base nut 158 that abuts a piston 159 of an air cylinder 160. The center hole punch 162 is connected to the vertical center hole forming punch member 164 and the punch end circumferential surface 1.
67 with a horizontal center hole forming punch member 166. A center hole punch adjustment nut 168 is attached to the lower end 170 of the vertical punch member 164 and abuts the face 94 of the punch plate assembly support plate 54. The horizontal punch member 166 of the center hole punch 162 has an undercut 173, as seen in FIG. 5, on an inner surface 174 forming a portion of the runner area. When injecting molten plastic material, some runner material fills the undercut area. The plastic in the undercut area holds the runners 175 to the punches 162 as the stationary half-expandable substrate 18 is separated from the movable half-support plate 30. The centrally apertured part is shown at 175a.

Air cylinder 160 is bolted to face 180 of assembly support plate 54 by bolts 182. As a design consideration, the cylinder 160 is
It fits within an opening formed in a surface 184 provided in the substrate 34. The air intake passage for cylinder 160 is shown schematically at 186 and the exhaust port is shown schematically at 188.

The operation of the injection molding apparatus will be explained with reference to FIGS. 3 to 6. The basic operation of a standard injection molding machine, which together with other elements of tool 10 constitute the molding apparatus of the present invention, is shown schematically. These basic steps form part of the method of this invention, and the basic elements of the machine that performs these operations also form part of the injection molding apparatus of this invention. These basic operations, as well as the equipment included in a standard injection molding machine, are shown schematically in FIG.

In FIG. 3, the injection molding apparatus is shown in the closed position. This closed position is such that the end face 100 of the main punch plate assembly travel limiter 90 is in the fixed half fixed base plate 1.
partially limited by contact with 6. A secondary punch plate assembly travel limiter 102 is spaced a distance 108 from the surface 76 of the movable half support plate 30. Ejection pin 156 is in the retracted position.
Horizontal portion 166 of punch assembly 162 is in the retracted position. End face 189 of punch assembly 162 and opening 114 in runner bushing 110 define a runner. The first and second mold halves define an annular cavity surrounding the runner passage. This annular cavity and runner passage constitute a centrally opened part 175a and runner 175, respectively, when heating material is injected therein.

A first selective actuation means 190 moves the second mold half 14 between a closed position (FIGS. 1 and 3) and an open position (FIGS. 5 and 6). 1st
The selective actuation means include a piston 191 (FIG. 3) within a cylinder 192. Connecting rod 193
connects piston 191 to substrate 34. Pressurized fluid is pumped into cylinder 192 through fluid valve 194 to move second mold half 14 from a closed position (FIGS. 1 and 3) to an open position (FIGS. 5 and 6). Pressurized fluid is pumped into cylinder 192 via fluid valve 195 to move second mold half 14 from an open position (FIGS. 5 and 6) to a closed position (FIGS. 1 and 3). .

When the first and second mold halves 12, 14 are in the closed position (FIGS. 1 and 3), (a) the punch 162
The end 189 of the mold and the opening 114 in the runner bushing define a runner passage, and (b) the first and second mold halves define an annular cavity surrounding the runner passage. The annular cavity and runner passage form a centrally apertured part 175a and a runner 175, respectively, when heated material is injected therein.

A second selective actuation means causes the second mold half to move from a closed position (Figs. 1 and 3) to a position (4) intermediate between the closed and open positions (Figs. 5 and 6).
In response to the movement of the first mold half 12 along with the second mold half 14. Thus, the annular cavity remains closed while the first and second mold halves are moved from the closed position to the intermediate position. The second selective actuation means includes latch means 197. The latching means includes a fixed base plate 216 attached to the fixed semi-expandable base plate 18 by a plurality of bolts 218. A first latching means 220 is bolted to the fixed semi-fixed base plate 16 by a plurality of bolts 222 . Second latch means 22
4 is bolted to the movable half support plate 30 by a plurality of bolts 226. Although this latch is a standard latch, its mode of operation has been specifically described because it is an integral actuating mechanism in the configuration of this invention. This latch mechanism is a commercially available standard latch manufactured by the Detroit Mold and Engineering Company called the LL-201 "Jiffy Latch."

Briefly, the center of action of the latch is a horizontally disposed pivoting latch member 230 having a pivot pin 232 whose surface 234 is in contact with a locking surface provided on each latch means 220, 224. engage.
In the drawings, the surface 234 and the locking surfaces of the members 220 and 224 are both indicated by the line 234 because all of these members are shown in plan view.
The length of the pivot pin, represented by the length of line 234, is the extent to which the first latch member 220 can be moved relative to and away from the second latch member 224 while the latch remains locked. represents. This distance is represented by the length of line 235 shown in FIG. The latch means 197 holds the stationary half-expandable substrate 18 in place on the movable half-support plate 30 while the stationary half-expandable substrate 18 and the movable half-support plate 30 move a distance represented by the length of line 235 shown in FIG. It acts as if it is pressed down.

FIG. 4 shows the pivot pin 2 in its fully extended position when the first latch member 220 has moved the full distance relative to the second latch member 224.
32 is shown. Latch mechanism 197 keeps the annular cavity closed during movement of the first and second mold halves from the closed position to the intermediate position.

Returning to FIG. 3, the expanded substrate process limiter is comprised of a plurality of bolts, one of which is shown at 240. A shaft portion 242 of the bolt 240 fits into an opening 244 provided in the fixed half-fixed substrate 16 . A head member 245 having shoulders 246 is attached to the shaft portion 24
2 is integrally connected. Stroke limiter 240
is threadedly engaged with the expansion board 18, as shown at 248. A plurality of such process limiters 240 are provided along the periphery of the base plate 16 so that the pivot latch member 232 rotates as the tool moves from the closed position shown in FIG. 3 to the intermediate position shown in FIG. The movement of the fixed substrate 16 with respect to the expansion substrate 18 during this period is restricted.

A third selective actuation means 250 controls the first and second
mold halves 12, 14 in the closed position (Figs. 1 and 3).
The punch assembly 50 is held in place during movement from the intermediate position (Fig. 4) to the intermediate position (Fig. 4). In the intermediate position, the runner 175 is connected to the peripheral surface 1 of the punch end 166.
67, it is completely cut from part 175a. Punch end 16 of punch butting
The part that contains 6 acts as a die. The third selective actuation means 250 consists of a piston 252 that fits into a cylinder 254. The connecting rod 256 is
Piston 252 is connected to punch plate assembly support plate 54 through an opening in substrate 34 defined by surface 257 . Pressurized fluid or air flows through valve 25
8 into the cylinder 254 while the first and second mold halves 12, 14 move from the closed position (FIGS. 1 and 3) to the intermediate position (FIG. 4). The body support plate 54 is fixed in contact with the substrate 16 at an interface 100. After the second mold half 14 reaches the intermediate position (FIG. 4), the punch plate assembly support plate 54 moves with the second mold half 14 from the intermediate position (FIG. 4) to the open position (FIGS. 5 and 4). 6
Go to figure). To this end, valve 258 may be opened to relieve the pressure holding piston 252 against punch plate assembly support plate 54, or pressurized fluid or air may be pumped in through valve 260. Piston 252 is driven to its retracted position.

In FIG. 4, tool 10 is in an intermediate position. The intermediate position includes, in part, expanded substrate travel limiter 240
Shoulder 246 of fixed half fixed substrate 1 at interface 246
It is defined as the position where it contacts 6. First latch member 2
20 has been retracted from the second latch member 224 by a distance represented by line 235, and the pivot pin 232 has been rotated in the direction shown by arrow 270 to its maximum locking position just before opening. Third selective actuation means 25
0 connecting rod 256 contacts face 180 of punch plate assembly support plate 54 to maintain primary punch plate assembly travel limiter 90 in contact with stationary half stationary substrate 16 at interface 100. Third selective actuation means 250
maintains the restrictor 90 in contact with the substrate 16 and pushes the punch assembly 162 into the runner bushing 11.
When held stationary with respect to 0, the fixed half expansion substrate 18 and the movable half support plate 30,
When fluid is pumped into the cylinder 192 of the first actuating means 190 through the valve 194, it moves in the direction indicated by the arrow 272. Horizontal portion 166 of punch 162
A punching action is performed between the centering die locator and fixed center stamper clamping member 126 to cut the runner 175 from the part 175a. The annular portion 274 of part 175a remains attached to runner 175. The portion 274 is the punch 162
This is the portion that is located between and in contact with the end surface 189 of. The runner 175 is held on the end face 189 of the punch by its undercut portion 173;
Part 175a rests on circumferential surface 167 at the end of the punch. Here, the main dividing line 278 shown between the expansion substrate 18 and the support plate 30 illustrates that the two plates are still firmly attached by the second selective actuation means 197. Please note that

The joint movement of the expansion substrate 18 and the support plate 30 means that the surface 76 of the support plate 30 is connected to the secondary punch plate travel limiter 10
surface 106 of travel limiter 240;
46 comes into contact with the fixed substrate 16, the latch means 19
7 is open. Expansion board stroke limiter 2
40 stops the movement of the substrate 16. The actuation means are
The cavity is subsequently opened by continuing to move the second mold half 14, including the punch assembly 50, to the open position shown in FIG.

FIG. 5 shows the mold injection tool 10 in the open position. When in the open position, the shoulder 246 of the expandable substrate travel limiter 240 connects the fixed semi-fixed substrate 16 at the interface 246.
come into contact with. The primary punch plate travel limiter 90 is fully retracted from the base plate 18. Latch member 23
0 has been fully rotated in the direction shown by arrow 270 and pivot pin 232 has disengaged from both upper and lower latch members 220 and 224. The locking surface 280 of the first latch member 220 is connected to the pivot pin 230.
The position where it left is shown. The position in which the locking surface 282 of the second latch member 224 is disengaged from the locking surface 232 of the latch means 197 is shown. Hot water path 1
75 is attached to the end of the ejection pin 156,
It has an annular projection 284 corresponding to the undercut 173. During injection of molten material into the runner passageway and annular cavity, protrusion 284 engages undercut portion 173.
is formed.

The piston 159 of the air cylinder 160 is shown in an extended position so that the ejector pin is pushed out and moves the runner 175 and its annular portion 274 away from the end 189 of the punch 162. By pumping pressurized fluid through valve 186, piston 159 is moved to its forward position.

Once the runner 175 is separated from the part 175a,
The next action to take is to remove the runner from the end of the ejection pin 156.

FIG. 6 shows the tool 10 in its fully open position and the ejection pin 156 in its retracted position. This retracted position directs fluid into valve 188;
This is achieved by moving the piston to the second retracted position shown in FIG. As ejector pin 156 returns to the retracted position in the direction indicated by arrow 286, protrusion 284 engages punch face 189, separating the runner from ejector pin 156, as shown in FIG.

FIG. 9 shows an enlarged view of the portion shown in circle 9 in FIG. A stationary stamper 124 is attached to the stationary platen 120 by a centering die and fingers 126a of a stationary center stamper clamping member 126.

A moving stamper 144 is attached to the movable platen 140 by centering punch positioning and fingers 146a of a moving center stamper clamping member 146. Lower end 1 of runner footing 110
17 is located near the ejection pin 156.
An undercut 173 of the horizontal punch member 166 is provided on the inner surface 174. Assuming that the cavity formed by the members just described is filled with hardened plastic material injected during the injection cycle of the injection molding machine, the runner will be formed as shown at 175, and the annular portion 174 is formed integrally with the runner 175. It is also shown that protrusion 284 is integrally formed with runner 175.

The runner passageway design, which includes an annular sprue passageway 298 disposed intermediate the runner hole 114 and the video disk cavity 306 formed between the stampers 124, 144, ensures that the injected material flows at a uniform velocity. It has been found that it should also have a shape that advances across the stamper surface. To achieve this desired effect, the annular sprue passage 298 has a unique shape and is comprised of a plurality of annular passage sections, each section having an inlet area and an outlet area. The outlet area of one section corresponds to the inlet passage of the next succeeding section.

As shown by bracket 300, an initial annular portion is formed between end face 299 of runner bushing 110 and end face 189 of punch 166. each side 29
9,189 is an angle of 3% with respect to the horizontal. Surface 299 is 3% above horizontal and line 189 is 3% below horizontal. The entrance area of this first section 300 is 110a. The exit area is 110b. The distance between surfaces 299, 189 in the exit region is equal to the thickness of cavity 306. Looking at this figure, it can be seen that the inlet area between 110a and 166a is thicker than the outlet area between points 110b and 166b. That is, a pressure difference exists between regions 110a and 110b.

A second annular portion includes a fixed center stamper clamping member 126 and a moving center stamper clamping member 14.
6, each formed by a portion of the surface 126b and a portion of the surface 146c. This second region is shown in parentheses 302. Surfaces 126b, 146c are separated by a distance equal to the thickness of video disc cavity 306 and are of the same size over their entire length.

The third annular portion of the injection sprue passageway 298 is connected to the fixed center stamper clamping member 126 and the moving center stamper clamping member 1, respectively, as shown in bracket 304.
It is composed of 46 relatively short portions 126c and 146b. The entrance area of the third annular section is
Equal to the thickness of the disc cavity 306, the exit area is smaller than the entrance area.

The fourth annular portion of the annular sprue passageway 298 connects the fixed center stamper clamping member 126 and the moving center stamper clamping member 1, respectively, as shown in bracket 305.
It is formed by portions 126d and 146d of 46. The exit section of the fourth annular section is
This is the inlet nozzle for the disk cavity 306.

In operation, the high-temperature material to be injected into the video disc cavity to form the video disc recording body is passed through the runner passage 1 as a high-temperature melt.
14, then expands circumferentially along runner passageway 114, enters annular sprue passageway 298, and finally enters video disk cavity 306 to reach the outer dimensions of the cavity. This will be explained in more detail with respect to FIG. Molten plastic was later added to the seventh
The injection molding machine is held in a rest position until it solidifies to a certain temperature, as will be described in more detail with reference to FIGS. During the previously described injection cycle, the hot melt enters the entrance region of passage 298 at a higher velocity than when it exits the same passage via the portion indicated by bracket 305. This is the fourth annular part 30
This is because the outlet opening of No. 5 is narrower than the inlet portion of the first annular portion 300. A third annular portion 304 acts as a partial restriction for the flow of molten material. The first and second sections 300, 302 act as pressure reservoirs and distribution headers for the material flow, minimizing disturbances in the material flow and ensuring that the molten plastic is evenly distributed into the video disk cavity 306. I guarantee it will flow. This control of molten material through the restricted portion 304 has the advantage of producing a very round video disc record with an information track very nearly a perfect circle on the video disc record. This control effect in forming both round video disc recordings and tracks that are very close to a perfect circle is only possible with the use of an annular sprue passage.

FIG. 13 shows a graph illustrating the relationship between allowable video disc thickness and birefringence at a certain radius from the center of the runner.
The graph in FIG. 13 is based on the video disc obtained by the injection molding apparatus shown in FIGS. 1 to 12 described above. Curve A in Figure 13
covers the information-carrying side of the video disk surface, and 4
It exhibits a thickness variation of ±2/1000 inch from a nominal value of 4/1000 inch. Curve B shows the change in birefringence in the same area of the disk surface. The change in birefringence is between 2 and 7 nanometers.

In FIG. 14, curve A extends from a nominal value of 44/1000 inches over the information-bearing surface of the video disk surface.
Figure 2 shows unacceptable birefringence of video disc members having thicknesses in the range of +2 to -5/1000 inches. Note that the graph in FIG. 14 is based on a video disc obtained with a conventional injection molding apparatus. Curve B shows the change in birefringence in the same area of the disk surface. This change in birefringence varies from a maximum of 22 nanometers to a minimum of 2 nanometers. It has been found that video disks are useful only when the birefringence of the video disk is substantially uniform across the playing surface. Returning to FIG. 13, the information bearing surface of a video disc is between 55 and 150 millimeters, and the birefringence value varies from a maximum of 7 to a minimum of 2. Experimental studies have shown that a video disc with the characteristics shown in Figure 13 is suitable for playing in a video disc player such as that described in U.S. Pat. No. 3,829,622; It has been found that discs with the characteristics shown do not work satisfactorily with the same player.

FIG. 10 shows an enlarged view of the portion within the circle 10 in FIG. A stationary outer stamper ring clamping member is shown at 128 and a moving outer stamper ring clamping member is shown at 148. A stationary platen holding a stationary stamper 124 is shown at 120. Fixed stamper 124
terminates at a distance from the moving stationary outer stamper ring clamping member 128, as indicated by the length of the bracket 305. For this reason, the stamper 124
can expand outward until contacting ring clamping member 128. Fixed stamper 124
This expansion zone allows the stamper to expand when heated material is injected into the video disc cavity.

The moving stamper 144 is secured to the movable platen 14 by a moving outer stamper ring clamping member 148.
It is held at 0. The fixed stamper 144 is attached to the bracket 3.
Ring clamping member 1 by a distance indicated by 08
It terminates at a point away from 48. Legs 310 of fixed outer stamper ring clamping member 128 hold movable stamper 144 in place while clamping bracket 308 in response to heat from the injected molten material.
The stamper 144 is allowed to expand by a distance indicated by .

When the molten plastic is injected into the video disk cavity, it is important that the video disk have a substantially uniform thickness over the playing area of the video disk, as shown in FIG. If the thickness of the video disc changes by 6/1000 inch, the disc becomes unplayable, as shown in Figure 14. video·
If the thickness of the disc is kept within 2/1000 inches as shown in Figure 13, a playable disc will be obtained. The upper stamper and the lower stamper are connected to the brackets 307, 3
As shown by 08, by making it expandable in the horizontal direction, a playable disc can be obtained. This is because the stamper expands to fill these areas and does not buckle when exposed to the heat of the injected molten plastic material, causing thickness variations in the video disk member. Passage 312
allows ventilation of the video disk cavity during the injection cycle.

The cooling system used in this invention is designed to remove from tool 10 the heat generated by injecting molten plastic into the runner passageway and video disc cavity. This cooling prevents stress defects in the finished video disc recording. The absence of stress defects improves the birefringence properties of the finished video disc recording.

Next, the cooling groove passages will be explained with reference to FIGS. 1, 2, 7, and 8. Referring to FIG. 1 and FIG. 8 together, the runner bushing cooling channel is 350
, having an inlet valve 352 and an outlet valve 354. As seen in FIG.
is spiral-shaped and has four threads per inch, starting from a position near the end 115 of the runner passageway 114,
Extending downwardly toward the end 117 of the runner passageway 114. The spiral then reverses and passes upwardly through the runner bushing and out the outlet valve 354. An O-ring 356 provides a fluid tight connection between the runner bushing cooling channel 350 and the runner bushing retaining ring 112.

In FIG. 8, fixed platen runner area cooling channels 35
7 has an inlet valve 358 and an outlet valve 359. The plurality of spiral turns of the cooling channel 357 are represented in FIG. 8 by a central turn 357a. Fixed platen inner area cooling channel 360
has an inlet valve 362 and an outlet valve 364.
The entry point is at the inner radius and makes a plurality of spiral turns before exiting the outlet valve 364, forming an inner cooling zone for the stationary platen. A fixed platen intercooling channel 370 has an inlet valve 372 and an outlet valve 374. The intermediate zone cooling channel provides a second cooling zone for the fixed platen.

A fixed platen outer area cooling channel 380 has an inlet valve 382 and an outlet valve 384. The fixed platen outer region cooling channels provide yet another cooling area for the fixed platen.

A plurality of cooling zones attached to the mobile mold half 14 are shown in FIGS. 2 and 7. A movable platen punch area cooling channel 390 has an inlet valve 392 and an outlet valve 394. The punch area cooling flow path makes one turn around the punch area, as shown at 390a in FIG.
go out from The hottest parts of tool 10 are the runner and punch area where molten material enters from the injection molding machine.

A movable platen inner area cooling channel 400 has an inlet valve 402 and an outlet valve 404. The movable platen inner region cooling channels make a number of turns along the platen before exiting through the outlet valve 404. The movable platen inner region cooling zone provides another cooling zone for the movable platen. A movable platen intermediate region cooling channel 410 has an inlet valve 412 and an outlet valve 414.
has. The movable platen mid-zone cooling channels provide a further cooling area for the movable platen. The movable platen outer area cooling channel 420 is connected to the inlet valve 422
and an outlet valve 424. The movable platen outer region cooling channel is a cooling area for the movable platen. Any suitable cooling fluid may be used in any one or all cooling zones, including water.

Both the movable platen 140 and the fixed platen 120,
As shown in FIGS. 1 and 2, a plurality of cooling channels described above are constructed. 1 pair of O-rings 36
6,368 are provided to provide a fluid tight connection to the fixed platen runner area cooling channels 357 of the fixed mold half 12. Second pair of O-rings 39
0,392 and a plurality of cooling zones 360, 370, 380 formed in the fixed platen 120.
Allows for a fluid connection to be made. Another set of O-rings 394, 396 are provided to provide a plurality of cooling zones 400,
410 and 420. Another set of O-rings 430, 432 is provided to provide a fluid tight connection to the movable platen punch area cooling channels 390.

To explain FIG. 7, the movable platen 14
0 includes a plurality of lateral cooling channels. A first movable platen lateral cooling channel 440 has an inlet valve 442 and an outlet valve 444. A second movable platen lateral cooling channel 446 has an inlet valve 448 and an outlet valve 450.

To explain FIG. 8, the fixed platen 12
0 has multiple lateral cooling channels. 1st
The fixed platen lateral cooling channel 452 of the inlet valve 4
54 and an outlet valve 456. A second fixed platen lateral cooling channel 458 has an inlet valve 460 and an outlet valve 462.

Since both the formation of a recording body with a spiral track and the punching of the runner that forms the center hole of the recording body are performed in one setting, the spiral track of the recording body Note that a high degree of concentricity is achieved with the central hole. In this setting, the inner surface of the stamper cooperates with the matching surface of the mold to position the stamper very accurately on the mold. The outer surface of the stamper can remain floating as previously described with respect to FIG. Similarly, the circumferential surface of the punch defining the center hole of the record body is positioned very precisely relative to the mating surface of the fixed center stamper clamping member 126. Both the stamper, which forms the spiral track of the record, and the peripheral surface of the punch, which defines the central hole of the record, are very carefully aligned to the mold, so that the spiral track of the record and the circumferential surface of the punch, which defines the central hole of the record, A high degree of concentricity is achieved between the central hole of the

[Brief explanation of drawings]

FIG. 1 is a sectional view taken along line 1--1 in FIG. 7 of an injection molding apparatus for duplicating a recording medium having a central hole and a spiral track according to the invention, and FIG. Therefore, a cross-sectional view similar to FIG. 1, taken along line 2--2 in FIG. 7, and FIGS. 3 to 6 show an injection molding apparatus for duplicating a recording medium having a central opening and a spiral track. is a schematic diagram showing a series of operations performed by the injection molding apparatus shown in FIGS. 1 and 2, FIG. 7 is a plan view of the movable mold half shown in FIG. 1, and FIG. 9 is an enlarged sectional view of the inside of circle 9 in FIG. 1, and FIG. 10 is an inverted plan view of the fixed half of the mold assembly shown in FIG.
11 is an enlarged sectional view of the inside of circle 11 in FIG. 1, FIG. 12 is an enlarged sectional view taken along line 12-12 in FIG. FIG. 14 is a graph showing the change in birefringence value as a result of an unacceptable change in video disk thickness; FIG. Explanation of main symbols, 114: Runway passage, 156:
runner release pin, 162: punch, 175a: parts,
190: selective actuation means; 306: video disk space;

Claims (1)

[Scope of Claims] 1. An annular molding cavity of substantially uniform thickness formed by a first mold part and a second mold part; a runner passageway for injecting molding material; and an annular gate passageway formed by a first mold part and a second mold part and connecting the runner passageway and an annular molding cavity; An injection molding apparatus for injecting molten molding material from a passageway through an annular gate passageway into an annular molding cavity to form an optical disk with a central hole formed therein, comprising: At least one of the mold parts includes a platen having a stamper on the side of the annular molding cavity, and in the at least one mold part including the platen having the stamper, a part of the part forming the annular gate passageway is adjacent to the platen. teeth,
The stamper clamping member includes a protruding part that protrudes toward the annular gate passage, and the protruding part includes a clamping part that protrudes toward the stamper and clamps the stamper to the platen; a passage forming part that is continuous with the tightening part and forms a part of the annular gate passage; the passage forming part includes a flow restricting part whose thickness gradually decreases in a radially outward direction; An injection molding apparatus for an optical disk, characterized in that the apparatus is configured to form an exit part continuous with the annular molding cavity, having a thickness smaller than that of the annular molding cavity, and opening into the annular molding cavity.