as can be seen in fig1 , a device 10 for injecting pharmaceutical liquid may be in the form of a single - use syringe 10 . this device 10 is configured to be prefilled , so as to be able to store the pharmaceutical liquid over a relatively long period before injecting it . the device 10 comprises a liquid storage reservoir 12 , which has two opposite ends , namely a proximal end 14 and a distal end 16 . each of the ends 14 , 16 is provided with an orifice 14 a , 16 a . more specifically , the storage reservoir 12 has a tubular shape with circular cross section and has at its proximal end 14 , a flange 18 , and at its distal end 16 , a part intended to receive an added injection needle , introduced into the orifice 16 a . the device 10 is arranged to receive a plunger , similar to the plunger 20 represented in fig2 , slidably mounted in the reservoir 12 so as to be able to exert a pressure on the liquid stored in the reservoir 12 in order to make it pass into the injection needle , by sliding of the liquid in the direction indicated by the arrow 22 . generally the plunger 20 is a generally cylindrical axisymmetric part made of rubber or made from another elastically deformable material , mounted in a leaktight manner in the reservoir 12 so that liquid in the reservoir 12 cannot come out through the proximal end 14 . the reservoir 12 has inner walls arranged in order to allow sliding cooperation with the plunger , in particular that do not generate excessive friction . in this example , the plunger 20 which is in the reservoir 12 is actuated by a plunger rod which passes through the proximal end 14 a , by being pushed by the user &# 39 ; s fingers . the reservoir 12 is defined by a tubular wall 24 , comprising a first plastic layer 26 and a second plastic layer 28 that are superposed . the layers 26 and 28 have a different permeability to gases , very particularly to oxygen and to carbon dioxide . the first layer 26 here forms a barrier against water . its water permeability is less than 0 . 2 g /( m 2 * day * bar ) at 23 ° c . and at a relative humidity ratio of 85 %, preferably less than 0 . 05 g /( m 2 * day * bar ). this first layer 26 comprises a cycloolefin polymer , more specifically a cyclic olefin polymer ( for example cop ) or an ethylene / cyclic olefin copolymer ( for example coc ). this first layer 26 is in direct contact with the pharmaceutical liquid stored in the reservoir 12 , it prevents the liquid from leaving the reservoir 12 and also prevents water found outside of the injection device 10 from being introduced into the reservoir . the second layer 28 forms a barrier against gases , its oxygen permeability is less than 5 cm 3 /( m 2 * day * bar ) at 20 ° c . and at a relative humidity ratio of 65 %, preferably less than 1 cm 3 /( m 2 * day * bar ) at 20 ° c . and at a relative humidity ratio of 65 %. this second layer 28 comprises a material selected from an ethylene / vinyl alcohol copolymer ( evoh ), a polyester or a co - polyester , a polyamide or a co - polyamide , or silicon oxide ( siox ). this second layer 28 is on the outer side with respect to the first layer 26 . it is more impermeable to gases than the first layer 26 . the second layer 28 comprises , in this example , two plastic sublayers superposed on one another and firmly attached to one another . the first sublayer , in contact with the first layer 26 , is referred to as the cohesion layer , it comprises a material that provides cohesion with the first layer 26 , preferably by fusion of material at the surface between this sublayer and the first layer 26 . for example , the first layer 26 comprises a cyclic olefin polymer ( cop ), the cohesion sublayer also comprises a cycloolefin polymer ( cop ), and the other sublayer comprises a material selected from an ethylene / ethylene vinyl alcohol copolymer ( evoh ), a polyester or a co - polyester , a polyamide or a co - polyamide , or silicon oxide ( siox ). optionally , between the two sublayers forming the second layer 28 , an additional sublayer of adhesive may be provided , which is intended to bond the first cohesion sublayer and the other sublayer . according to one particularly advantageous example , provided on top of the second layer 28 is an outer layer , or at the very least a layer that covers other inner layers , the mechanical characteristics of which , such as the tensile modulus , permit an autoclave cycle at 121 ° c ., which thus makes it possible to ensure the resistance of the injection device 10 during a sterilization . according to another example , or in combination with this layer , the mechanical characteristics of which permit an autoclave cycle at 121 ° c ., the second layer 28 is covered with an outer layer that forms a marking support , making it possible to identify the syringe and the liquid stored within . the process for manufacturing the injection device from fig1 will now be described . according to a first way of proceeding , a film , optionally a multilayer film , intended to form the second layer 28 that forms a barrier against gases is firstly inserted into a mold , then a material is injected into the same mold in order to form the first layer 26 . according to another way of proceeding , a material is injected into a mold in order to form the first layer 26 , and once this first layer 26 is molded , a film intended to form the second layer 28 is added around it . fig2 illustrates an injection device 10 having a reservoir with a composition similar to that from fig1 . however , in this example , the device 10 is a medical cartridge , its distal end comprises an added assembly 30 , comprising in this example means 32 for attaching the cartridge to another device , such as an autoinjector , and also a central surface area 34 intended to be pierced by a needle during the autoinjection process . fig3 and 4 illustrate an injection device 10 similar to that from fig1 and different from a syringe , it is in the form of a medical cartridge having , at its distal end , a septum 36 crimped over the rest of the cartridge . alternatively , the element 36 could be a removable cap . it will be noted that the invention is not limited to the embodiments presented above , other embodiments will appear clear to a person skilled in the art . in particular , it is possible to modify the composition of the layers 26 and 28 .
an injection device which is configured to be pre - filled , including a vessel for storing the liquid , having two opposing ends , each provided with an opening , referred to as proximal end and distal end , and arranged to receive a sliding piston in order to exert pressure on the liquid . the vessel includes a wall including at least two vertically adjacent layers , each including vertically adjacent plastic material , the first and second layers having different gas permeability .