1. Field of the Invention
The present invention relates to a liquid storage container comprising a container body including a liquid storage portion for containing liquid therein and an instilling portion for allowing the liquid to flow out of the container in an opened state.
2. Description of the Related Art
An example of the liquid storage container noted above is a medical eyedropper (referred to simply as “eyedropper” hereinafter) for containing medical eyedrops therein for free instillation. As an example of this type of eyedropper, what is called a three-piece type eyedropper is known which includes a main container body in the form of a hollow cylinder having a liquid storage portion for storing the medical liquid therein, an instilling tube attached to the container body, and a cap for sealing the instilling tube to make three components forming a whole eyedropper.
As shown in FIG. 4, what is called a bottle pack eyedropper X is in wide use which includes an integral molding type container A, with an instilling tube 6 and a main container body 10 formed integrally by blow molding or vacuum forming technique, and a cap B screwed or fitted to the container A.
It is also known that the instilling tube has a plug having an instilling opening mounted on a tip end thereof (see Patent Document 1, for example).
As a material of the eyedropper X of this type, a soft thermoplastic resin is used because it is easy to form and so on.
With this type of eyedropper X, when the medical liquid contained in the eyedrops container A shown in FIG. 4 is applied, a barrel 2 of the eyedrops container A (main container body 10) is held by tips of two fingers to keep it in an applying posture where the instilling opening 61a of the eyedrops container A faces an eye to receive the liquid. The barrel 2 is pressed toward an axis of the container while maintaining the applying posture, whereby the medical liquid is instilled and applied from the instilling opening 61a. 
In the above-noted eyedroppers, as the medical liquid is instilled and applied from the instilling opening after the eyedropper is opened, the container will tend to return to the original shape before the liquid is discharged, due to the restoring property of the container per se, and thus ambient air flows into the eyedrops container in a volume corresponding to the medical liquid applied. As this type of construction allowing ambient air to flow in, a construction providing an equalizing valve for taking in ambient air is known (Patent Document 2, for example). With this construction, ambient air can be taken in after the medical liquid is instilled and applied to keep the balance between the pressures inside and outside of the container.
The above-noted construction includes a mounting position for an ambient air intake valve provided adjacent the instilling opening. On the other hand, another construction is also known in which the mounting position for the ambient air intake valve is provided so as to face away from the instilling opening (Patent Document 3, for example).
Patent Document 1: U.M. Publication No. 39-11991 (FIGS. 1 to 2)
Patent Document 2: Patent Application “Kokai” No. 51-146789 (see pages 7 to 8, FIG. 4)
Patent Document 3: U.M. Application “Kokai” No. 1-110147 (see Claims, FIG. 2)
The eyedropper disclosed in Patent Document 2 includes a filter member together with the ambient air intake valve, which can prevent the interior of the liquid storage portion from being contaminated by germs when ambient air is drawn in. However, since the mounting position for the ambient air intake valve and the filter member is provided adjacent the instilling opening, it is necessary to provide the instilling opening, the ambient air intake valve and the filter member in the instilling tube, for example, as a result of which the construction around the instilling opening becomes complicated and the sizes of the ambient air intake valve and the filter member are restricted. On the other hand, with the construction disclosed in Patent Document 3 in which the mounting position for the ambient air intake valve is provided to face away from the instilling opening, the construction adjacent the instilling opening is simplified to facilitate manufacture of the container.
Further, with the eyedropper disclosed in Patent Document 2, the instilling opening is directed downward in time of instillation, and thus the liquid contained in the liquid storage portion will constantly contact the ambient air intake valve as long as such a posture is maintained. Although the ambient air intake valve has a construction of a check valve that allows ambient air to flow into the container while prohibiting the liquid from flowing out of the container, it is preferable from a viewpoint of preventing liquid leakage that the ambient air intake valve does not contact the liquid in time of instillation.
In contrast, the construction of the instilling container disclosed in Patent Document 3 includes the ambient air intake valve provided to face away from the instilling opening to prevent the liquid contained in the liquid storage portion from contacting the ambient air intake valve, which eliminates the chance of the liquid leaking from the ambient air intake valve. However, no filter member is provided, and thus there is a risk of contaminating the interior of the liquid storage portion with germs when ambient air is drawn in.
Also, according to the constructions of these eyedroppers and instilling containers, the instilling opening is in a closed state when the container is in storage or otherwise unused for instillation. In this state, when a pressure is applied to the ambient air intake valve due to a shock or the like and ambient air flows into the liquid container portion through the ambient air intake valve, the pressure within the liquid storage portion is increased. If the instilling opening is opened in time of instillation in this state, the increased pressure is released from the instilling opening, which leads to a chance of the liquid of being discharged forcibly from the liquid storage portion.
In such a case, if the eyedropper is designed for controlling a drop amount of liquid in time of instillation to be a predetermined amount, for example, and if the liquid is discharged forcibly in time of instillation as noted above, it is necessary to carry out the instilling operation again to instill and apply the liquid to the eye in order to compensate for the amount of the liquid dispersed to peripheries of the container. This results in problems that the extra instilling operations are required and the liquid is wasted.
The object of the present invention is to provide a liquid storage container capable of preventing liquid from leaking from an ambient air intake valve and of preventing the interior of a liquid storage portion from being contaminated by germs or the like when ambient air is drawn in, as well as capable of preventing a pressure difference from being produced between inside and outside of the container except in time of instillation.